The central paradox is that rotavirus vaccines are given orally, which means they must replicate in the infant intestine to stimulate immunity. Live attenuated vaccine viruses are swallowed, infect cells lining the small intestine, and mimic a natural infection without causing disease. This replication triggers both antibodies and local T cell responses at the mucosal surface, the front line of defense against a virus that attacks the gut. Any factor that interferes with vaccine virus replication therefore blunts the immune response. In high-income countries, vaccine take is robust: most infants seroconvert, developing measurable antibody responses after two or three doses. In many parts of Africa and Asia, by contrast, the same or similar vaccine formulations induce protective responses in a substantially smaller fraction of recipients, leaving a large proportion of children vulnerable to severe disease despite being fully vaccinated.

One of the best-documented explanations involves maternal antibodies. Pregnant women transfer immunoglobulin G across the placenta, arming newborns with passive immunity against pathogens they have encountered. Mothers also pass antibodies to their infants through breast milk, particularly secretory immunoglobulin A, which coats the intestinal lining. These maternal antibodies can neutralize vaccine virus in the infant gut before it has a chance to infect enough cells to prime the immune system. The review highlights that this interference may be exacerbated in low- and middle-income countries for two reasons. First, women in high-transmission settings have experienced more natural rotavirus infections over their lifetimes, so they carry higher circulating and mucosal antibody levels to pass on. Second, breastfeeding practices differ: prolonged and exclusive breastfeeding, which carries many other benefits, means infants continue receiving antibody-rich milk throughout the vaccination window, sustaining the inhibitory pressure on oral vaccine replication.

The evidence for maternal antibody interference is not merely circumstantial. Studies have correlated higher titers of transplacentally acquired antibodies and breast milk antibody concentrations with reduced vaccine immunogenicity, and some trials have explored delaying vaccination or manipulating feeding around the time of dosing to see whether responses improve. The relationship is complex, because breast milk also contains other bioactive components, including antimicrobial proteins and factors that shape the developing gut microbiome, so the net effect of breastfeeding on vaccine performance is not uniformly negative. Nevertheless, the review argues that in settings where both maternal antibody levels and breastfeeding duration are high, passive immunity represents a significant and underappreciated barrier to successful oral vaccination, one that helps explain why infants in the highest-burden countries respond least well to the current vaccines.

Beyond maternal antibodies, the overall health of the infant gut emerges as a decisive factor. Malnutrition, widespread in many resource-limited regions, impairs the immune system in multiple ways, reducing the capacity of intestinal immune cells to respond to stimulation and compromising the structural integrity of the gut barrier. Environmental enteric dysfunction, a chronic inflammatory condition of the small intestine common among children in settings with poor sanitation and repeated microbial exposure, flattens the villi that absorb nutrients and alters the cellular landscape that vaccine viruses must infect. A gut in this state is a hostile environment for an attenuated live vaccine: inflammation accelerates the turnover of intestinal epithelial cells, shortening the window in which vaccine virus can replicate, and the damaged mucosa mounts aberrant immune responses that fail to generate durable protection against rotavirus.

The gut microbiome adds another layer of complexity. The trillions of microbes colonizing the infant intestine do not merely coexist with the immune system; they actively train it. Early-life microbial colonization influences the development of mucosal lymphoid tissue, the balance of inflammatory and regulatory responses, and even the expression of antiviral genes in epithelial cells. Disruption of this microbial community, through malnutrition, antibiotic exposure, recurrent infections or poor sanitation, can leave the gut immune system poorly calibrated for responding to an oral vaccine. The review emphasizes that the relative contributions of malnutrition, microbiome disruption and environmental enteric dysfunction vary by geography, so no single intervention will correct the problem everywhere. In one region, nutritional supplementation may be the dominant lever; in another, sanitation and microbial restoration may matter more.

Competition from other oral vaccines and concurrent enteric infections provides further interference, and both are more prevalent in resource-limited settings. The oral poliovirus vaccine, given on schedules that often overlap with rotavirus vaccination, replicates in the same intestinal niche and can interfere with rotavirus vaccine take, an interaction documented in trials where the two vaccines were co-administered. Meanwhile, infants in high-burden environments are frequently infected with other enteric pathogens, including bacteria, parasites and other viruses, at the very time they are being immunized. These co-infections can crowd out vaccine virus, provoke inflammatory responses that disrupt mucosal immunity, or redirect the immune system’s attention away from rotavirus. The cumulative effect is that an infant in a low-income setting may face a gauntlet of biological obstacles to oral vaccination that an infant in a wealthy country rarely encounters.

Host genetics introduces a less obvious but increasingly well-supported variable. Rotavirus entry into intestinal cells depends on histo-blood group antigens, carbohydrate structures on the cell surface whose synthesis is governed by fucosyltransferase genes. Different human populations carry different frequencies of polymorphisms in these genes, and these variants determine which histo-blood group antigens an individual’s gut expresses. Because particular rotavirus strains, and by extension particular vaccine strains, show preferences for certain antigen types, an infant’s genotype can influence how readily the vaccine virus infects intestinal cells and stimulates immunity. The review highlights that these genetic differences across populations further modulate vaccine immunogenicity, adding a layer of biological variation that cannot be addressed through delivery or nutrition alone and that may partly explain geographic patterns of vaccine failure.

A crucial theme running through the review is that none of these factors acts in isolation. Maternal antibodies, nutritional status, microbiome composition, environmental enteric dysfunction, co-infections, co-vaccinations and host genetics interact to shape the gut environment and collectively limit oral vaccine replication. A malnourished infant in a high-transmission setting may simultaneously face high maternal antibody levels, a dysbiotic microbiome, an inflamed intestine, competing enteric infections and a genotype less permissive to the vaccine strain. The result is a multiplicative, not merely additive, reduction in vaccine effectiveness. This systems-level view reframes the problem: rather than searching for a single silver bullet, researchers and public health programs must consider how multiple determinants converge in specific populations and design interventions accordingly.

The path forward, the authors argue, requires context-specific strategies that combine several approaches. Optimized vaccine scheduling, including adjustments to the timing and number of doses relative to breastfeeding patterns and co-vaccinations, could reduce interference in some settings. Nutritional interventions and microbiome-targeted therapies may restore the gut environment to a state more conducive to oral vaccine replication. Ultimately, however, the review points toward the development of novel vaccine platforms capable of overcoming the unique immunological challenges of low- and middle-income countries, whether through injectable formulations that bypass the gut’s inhibitory environment, engineered vaccine strains resistant to neutralization, or adjuvanted approaches that strengthen mucosal responses. Closing the rotavirus vaccine equity gap is not only a scientific challenge but a moral imperative, given that the children least protected by current vaccines are those at greatest risk of dying from the disease the vaccines were designed to prevent.

Subject of Research: Determinants of variable rotavirus vaccine effectiveness across global settings

Article Title: Why does rotavirus vaccine effectiveness vary around the globe?

Article References: Why does rotavirus vaccine effectiveness vary around the globe?. (n.d.). https://doi.org/10.1371/journal.ppat.1014670

Image Credits: AI Generated

DOI: 10.1371/journal.ppat.1014670

Keywords: rotavirus, vaccine effectiveness, maternal antibodies, gut microbiome, environmental enteric dysfunction, malnutrition, oral poliovirus vaccine, histo-blood group antigens, fucosyltransferase, low- and middle-income countries, mucosal immunity, PLOS Pathogens

The significance of the finding lies in what it says about evolutionary history. Immunoglobulin M is the most ancient and widely distributed antibody class in jawed vertebrates, playing a central role both in circulating humoral immunity and in mucosal defense. Yet its architecture has shifted considerably over hundreds of millions of years. In mammals, IgM circulates as a pentamer or hexamer of antibody units, and the J-chain acts as a molecular linchpin that both stabilizes the polymer and provides the docking site recognized by pIgR. When pIgR binds a J-chain-containing IgM polymer on the basolateral surface of an epithelial cell, the receptor-antibody complex is internalized, shuttled across the cell, and released at the mucosal surface, where the receptor’s extracellular portion remains attached as the secretory component. That pathway, in the mammalian version, is strictly J-chain dependent.

Teleost fish complicate this tidy picture. Their IgM is not a pentamer but a tetramer, assembled from four antibody units, and earlier work had established that teleost IgM and pIgR can still interact even though the fish joining chain does not appear to mediate the recognition in the way it does in mammals. How a receptor could recognize a polymeric antibody without the accessory chain that mammalian systems rely on remained an open question, and it is precisely this question that the Zhejiang team set out to answer using structural biology and biochemical characterization of the two proteins.

The first surprise concerns the architecture of the receptor itself. Mammalian pIgR is a multi-domain protein, with its extracellular region built from several immunoglobulin-like domains that cooperate to capture polymeric ligands. Teleost pIgR, by contrast, is a stripped-down version comprising only two immunoglobulin-like domains, designated D1 and D2. The researchers showed that this minimal two-domain receptor nevertheless binds directly and specifically to the Cμ4 domain of tetrameric IgM, the constant-region domain that in mammalian systems forms part of the J-chain-dependent recognition surface. Both D1 and D2 contribute to the interaction, meaning that the compact fish receptor uses its entire extracellular apparatus to grip the antibody.

The second and arguably more striking surprise is the stoichiometry of the complex. In mammals, one pIgR molecule engages one IgM polymer in a one-to-one relationship, a monovalent engagement that reflects the single J-chain-dependent docking site on the antibody. The new analyses reveal an unconventional two-to-one arrangement in teleosts: a single IgM tetramer simultaneously engages two pIgR molecules. This multivalent engagement means the fish antibody can be gripped by two receptors at once, a configuration that sharply contrasts with the monovalent mammalian complex and suggests that the ancestral transport system operated with a different geometric logic than the one that evolved later in tetrapods.

Perhaps the most subtle discovery is that the two receptor molecules bound to one IgM tetramer are not interchangeable in the details of their contacts. The two pIgR molecules attach to the tetramer in an approximately symmetrical overall arrangement, occupying equivalent positions on the antibody scaffold. However, when the researchers examined which amino acids actually mediate each interaction, they found that the key residues involved are not entirely identical between the two binding sites. One pIgR molecule relies more heavily on its D1 domain to hold onto the IgM tetramer, while the other depends more on its D2 domain. In other words, the apparent symmetry of the complex conceals an asymmetry at the level of individual atomic contacts, with each receptor exploiting a different portion of its small two-domain toolkit.

This kind of asymmetric multivalency has interesting mechanistic implications. A two-to-one complex in which each receptor uses a different domain-dominant binding mode would be expected to have distinctive avidity properties compared with a one-to-one interaction. Multivalent engagement can increase the overall stability of a complex through avidity effects, because both receptors must disengage simultaneously for the antibody to be released. At the same time, the fact that the two sites use partially distinct residue sets implies a degree of functional specialization within the complex, hinting that the teleost system may fine-tune binding through contributions that are distributed unevenly across the receptor’s two domains rather than concentrated in a single dominant interface.

Placed in an evolutionary frame, the findings sketch a plausible trajectory for how mucosal antibody transport evolved. The teleost mechanism, which dispenses with the J-chain and achieves recognition through direct contacts between a minimal two-domain receptor and the Cμ4 region of a tetrameric IgM, looks like a primordial solution to the transport problem. As vertebrates diversified, the system appears to have been remodeled: the antibody polymerization state changed, the J-chain became an essential adaptor, and the receptor expanded and refined its domain architecture so that a single receptor molecule could recognize a single polymer in a strictly J-chain-dependent fashion. The contrast between the multivalent, J-chain-independent teleost complex and the monovalent, J-chain-dependent mammalian complex therefore delineates two evolutionary endpoints of the same biological function, with the fish system preserving what the authors describe as a primordial interaction mechanism.

The work also carries practical weight beyond evolutionary theory. Teleost fish are enormously important in aquaculture, and mucosal immunity determines how farmed fish resist pathogens at the gill, gut and skin surfaces, the primary entry points for many aquatic pathogens. Understanding precisely how IgM is moved across epithelial barriers in fish could inform vaccine design and disease-control strategies in aquaculture, where mucosal antibody delivery is a key determinant of protective immunity. Moreover, because the Cμ4 domain and the pIgR binding interface are conserved in broad outline across vertebrates, defining the atomic contacts in the fish system may illuminate features of the mammalian interaction that are difficult to isolate when the J-chain dominates the picture.

Technically, the study combined structural analysis with biochemical validation to reach its conclusions, mapping the binding interface to the Cμ4 domain, demonstrating the participation of both D1 and D2, and establishing the two-to-one stoichiometry and the domain-dominant asymmetry of the two bound receptors. The research was supported by the National Natural Science Foundation of China under grant number 32102824, and the article was published open access, received on 30 March 2026, accepted on 1 October 2026 and published on 9 October 2026. By resolving how a minimal receptor grips a tetrameric antibody without the accessory chain that mammals deem indispensable, the study adds a missing chapter to the story of mucosal antibody evolution, showing that the elegant J-chain-dependent system of mammals is not the only way, and probably not the original way, that vertebrates armed their mucosal surfaces with antibody.

Subject of Research: J-chain-independent interaction between teleost pIgR and IgM and its implications for mucosal antibody evolution

Article Title: Interaction mechanism between teleost pIgR and IgM provides new insights on mucosal antibody evolution

Article References: Yang, S., Zhao, L., Ren, H., Ma, Y., Huang, M., & Fei, H. (2026). Interaction mechanism between teleost pIgR and IgM provides new insights on mucosal antibody evolution. Cellular and Molecular Life Sciences. https://doi.org/10.1007/s00018-026-06478-6

Image Credits: AI Generated

DOI: 10.1007/s00018-026-06478-6

Keywords: immunoglobulin M, polymeric immunoglobulin receptor, teleost, joining chain, mucosal immunity, Cμ4 domain, protein structure, stoichiometry, evolution, antibody transport, secretory immunity, aquaculture

The scale of the psychological burden was the study’s first headline finding. Using standardized psychometric assessments, the researchers determined that 90.4 percent of the 637 undergraduates surveyed experienced moderate-to-high perceived stress. That figure is remarkable even for a population assumed to be under pressure, and it suggests that stress among university students is not an occasional complaint of exam season but a near-universal condition of contemporary student life. Perceived stress, as measured in the study, reflects how overwhelmed and out of control individuals feel about the demands placed on them, and it is a well-established predictor of downstream mental health problems including anxiety and depression.

Crucially, the psychological data did not exist in isolation. The researchers found that higher perceived stress correlated significantly with two of the most common complaints among students: fatigue and poor sleep. Stress levels correlated with fatigue at a correlation coefficient of 0.41 and with poor sleep quality at 0.35, both statistically significant at the p < 0.01 level. In practical terms, students who felt more stressed were also markedly more exhausted and slept worse—creating a feedback loop in which stress degrades sleep, and degraded sleep, in turn, erodes the physical and cognitive resources needed to cope with stress.

To understand what these subjective reports look like in the body, the team conducted a second, laboratory-based component of the study. They recruited 33 participants representing high-stress and low-stress profiles and performed diurnal biomarker profiling—that is, they measured stress-related molecules in saliva across the day rather than at a single snapshot in time. This approach matters because many physiological stress systems follow daily rhythms, and a single measurement can miss the pattern of dysregulation that distinguishes a chronically stressed individual from a well-rested one.

Saliva proved to be a surprisingly rich medium for this detective work. Among the molecules measured was alpha-amylase, an enzyme released by salivary glands under the control of the sympathetic nervous system—the branch of the autonomic nervous system responsible for the fight-or-flight response. Students in the high-stress group showed elevated alpha-amylase, a signature of sympathetic activation, indicating that their bodies were effectively idling in a state of heightened alertness even during ordinary daily activities.

The hormone cortisol, the classic chemical messenger of the hypothalamic-pituitary-adrenal axis, told a more nuanced story. Rather than a simple elevation, the high-stress students displayed altered diurnal cortisol patterns, which the researchers interpret as dysregulation of the HPA axis—the central hormonal machinery that mobilizes the body’s response to stress. A healthy cortisol rhythm rises sharply after waking and declines through the day; flattening or distorting that curve is one of the most consistent biological hallmarks of chronic stress, and its presence here suggests that the students’ stress had become embedded in their physiology rather than remaining a purely subjective experience.

Perhaps the most unexpected finding concerned melatonin, the hormone that signals darkness to the body and orchestrates the onset of sleep. High-stress students showed elevated melatonin, which the researchers read as a marker of circadian disruption. The interpretation is subtle: chronically stressed individuals often experience mistimed or fragmented circadian signaling, and abnormal melatonin dynamics fit with the poor sleep quality reported in the survey data. Together, the cortisol and melatonin findings paint a picture of students whose internal clocks—normally precise coordinators of sleep, wakefulness, and hormone release—had been knocked out of alignment by sustained psychological pressure.

The immune system, too, bore visible marks. Salivary immunoglobulin A and lysozyme, two frontline components of mucosal immunity that defend the mouth and throat against pathogens, were both elevated in the high-stress group. Mucosal immune activation of this kind is consistent with the body mounting a low-grade defensive posture under chronic stress, a state that in the long run can paradoxically impair immune effectiveness. The researchers also uncovered a striking degree of coordination between the nervous and immune systems: alpha-amylase and lysozyme levels were coupled across participants, with a correlation coefficient of 0.52, significant at p < 0.001. This coupling, the authors suggest, reflects neuro-immune coordination—the idea that the sympathetic nervous system and mucosal immunity do not operate independently but respond in tandem to the body’s stress state.

Taken together, the two components of the study demonstrate that salivary biomarker profiles are associated with perceived stress in ways that span multiple physiological systems simultaneously. The value of this integrated approach lies precisely in its breadth: while cortisol alone has been studied extensively in student populations, few investigations have examined neuroendocrine, immune, and circadian markers side by side in the same individuals. By doing so, the study shows that chronic stress in students is not a single-hormone phenomenon but a whole-body pattern involving sympathetic arousal, hormonal dysregulation, circadian disturbance, and immune activation, all detectable in a noninvasive bodily fluid that can be collected without needles or clinical settings.

The authors are careful about what the study can and cannot establish. As a cross-sectional design, it captures associations at a single point in time and cannot prove that stress causes the biomarker changes, nor that the biomarker patterns drive the fatigue and sleep problems students reported. The researchers explicitly flag sleep quality and fatigue as warranting further investigation as potential intervention targets in future longitudinal studies—work that would follow students over time to see whether improving sleep, for example, normalizes stress physiology. Even so, the findings carry an urgent public health message. With stress-related mental health disorders recognized globally as a major concern, and with more than 90 percent of surveyed students reporting moderate-to-high stress, the study suggests that universities are confronting not merely a wellness issue but a measurable physiological burden—one written in cortisol curves, melatonin rhythms, and immune molecules, and readable in a few milliliters of saliva.

Subject of Research: Salivary biomarkers of stress, sleep quality, and circadian disruption in college students

Article Title: The hidden burden of college life: Stress, sleep, and salivary biomarkers in students—A cross-sectional study

Article References: The hidden burden of college life: Stress, sleep, and salivary biomarkers in students—A cross-sectional study. (n.d.). https://doi.org/10.1371/journal.pmen.0000717

Image Credits: AI Generated

DOI: 10.1371/journal.pmen.0000717

Keywords: perceived stress, college students, cortisol, alpha-amylase, melatonin, salivary biomarkers, sleep quality, fatigue, HPA axis, circadian rhythm, mucosal immunity, immunoglobulin A

The research focuses on a family of CD4-positive helper T cells known as Th17 cells, which have occupied an ambiguous position in cystic fibrosis immunology for over a decade. Elevated levels of interleukin-17, the signature cytokine of this lineage, were initially interpreted as a hallmark of pathology, since IL-17 drives neutrophil recruitment and tissue-destructive inflammation. Later work complicated that picture by showing that Th17 cells are functionally heterogeneous. Conventional Th17 cells, which co-produce IL-17 alongside the anti-inflammatory cytokine IL-10 and the epithelial-supporting IL-22, actually promote mucosal homeostasis and barrier integrity. By contrast, a distinct pro-inflammatory population, termed Th1/17 for its co-expression of interferon-gamma and IL-17 in the absence of IL-10, has been implicated in chronic inflammatory diseases ranging from multiple sclerosis to Crohn’s disease. Which of these faces Th17 presents in the cystic fibrosis lung remained an open question.

To resolve it, the team analysed T cells isolated from explanted lungs and blood of people with cystic fibrosis, alongside non-CF lung tissue and healthy donor blood. Using high-dimensional flow cytometry and unsupervised clustering based on chemokine receptor expression, they identified two pathogenic subsets, CCR5-positive Th1/17 cells and pro-inflammatory CCR5-positive Th17 cells, that were markedly enriched in cystic fibrosis lungs compared with both patient blood and non-CF lungs. Critically, this enrichment was not a general feature of the disease. The pathogenic subsets expanded selectively in lungs chronically colonized by Pseudomonas aeruginosa, irrespective of whether other pathogens such as Staphylococcus aureus were also present. In Pseudomonas-negative patients, protective conventional Th17 cells predominated instead, pointing to the bacterium itself as the upstream driver of the pathological shift.

The functional consequences of this shift were striking. In an air-liquid interface model of primary human bronchial epithelium, a laboratory system that recapitulates the differentiated, ciliated airway lining, activated Th1/17 and pro-inflammatory Th17 cells caused extensive disruption of epithelial integrity. Immunofluorescence staining for zonula occludens-1, a core component of tight junctions, revealed discontinuous, fragmented junctional patterns in cultures exposed to these subsets, while conventional Th17 cells left the barrier largely intact. Quantitative artificial intelligence-assisted image analysis confirmed the selective loss of junctional continuity. The pathogenic subsets also provoked a significantly stronger inflammatory response from epithelial cells, which released elevated amounts of cytokines and chemokines including IL-8, IL-6, CCL20 and RANTES, molecules that in turn recruit further immune cells to the airway wall.

Transcriptomic profiling by RNA sequencing deepened the picture. Pulmonary Th1/17 and pro-inflammatory Th17 cells from Pseudomonas-infected cystic fibrosis lungs displayed a distinctive signature of 210 upregulated and 40 downregulated genes compared with the same subsets in blood and non-CF lungs. Gene set enrichment analysis showed that lung-resident pathogenic cells upregulated 21 pathways linked to bacterial response, inflammation and tissue remodelling, with high-ranking genes including PPARG, CEBPD and IRAK2, transcriptional regulators known to shape Th17 differentiation and function. Peripheral counterparts of the same subsets showed a largely repressed programme, indicating that the lung environment itself actively reconfigures these cells rather than merely recruiting pre-formed effectors from the circulation.

T cell receptor sequencing added a crucial layer of evidence. The researchers found a significant expansion of private clonotypes, receptor sequences unique to individual patients, within cystic fibrosis lungs, accounting for 45.8 percent of the Th1/17 repertoire compared with roughly 22 percent in non-CF lungs. Among the most expanded clonotypes, some were shared between Th1/17 and pro-inflammatory Th17 cells but minimally represented in Th1 or conventional Th17 populations, suggesting a common antigenic experience driving functional convergence. Partial overlap between the receptor repertoires of pathogenic subsets and conventional Th17 cells, but not Th1 cells, provided a molecular fingerprint of lineage relationships that the team then tested experimentally.

That experimental work centred on dendritic cells, the antigen-presenting sentinels that instruct T cell fate. The team exposed human monocyte-derived dendritic cells to 26 clinical Pseudomonas aeruginosa strains isolated longitudinally from Danish cystic fibrosis patients, spanning early isolates taken at disease onset and late isolates collected after years of chronic colonization. Late strains were internalized more efficiently and persisted longer inside dendritic cells than the reference laboratory strain PAO1. More importantly, clinical isolates skewed the dendritic cell cytokine output toward a polarizing cocktail of IL-1β and IL-23, the two cytokines known to drive interferon-gamma-producing Th17 differentiation, while relatively suppressing IL-12, the canonical Th1-polarizing signal. IL-1β secretion correlated with intracellular bacterial persistence, and clinical strains also triggered strong release of CCL20, the chemokine that recruits CCR6-positive Th17 cells to sites of infection.

In antigen-specific co-culture assays, the researchers then demonstrated that conventional Th17 cells, not Th1 cells, are the precursors of the pathogenic populations. After ten days of co-culture with Pseudomonas-infected dendritic cells, sorted conventional Th17 cells acquired robust interferon-gamma and IL-17 co-expression, whereas Th1 cells never converted. Unexpectedly, early clinical isolates lacking the classic adaptations of chronic infection, such as reduced motility and biofilm formation, were at least as effective as late isolates at inducing this conversion, and some strains exceeded the levels seen with PAO1. The reprogramming extended to transcription factors: converted cells upregulated C/EBPδ and PPARγ, and in some cases BATF3, mirroring the profile of lung-resident pathogenic Th17 cells from patients. This indicates that the immunostimulatory virulence determinants responsible are present from the earliest stages of colonization and retained throughout bacterial adaptation to the cystic fibrosis lung.

The study thereby rewrites a long-standing paradigm. Adaptive immune dysfunction in cystic fibrosis was widely assumed to emerge only in late-stage disease, but the new data show that Pseudomonas aeruginosa can corrupt protective Th17 immunity from the moment it establishes infection, creating a self-sustaining immunopathological loop in which reprogrammed T cells damage the epithelium, epithelial cells release chemokines that recruit more Th17 cells, and the resulting inflammation further impairs bacterial clearance. The findings carry direct therapeutic implications. IL-1 receptor blockade with anakinra has already been shown to mitigate Pseudomonas-driven airway inflammation in cystic fibrosis, and IL-23 inhibitors are clinically established in other chronic inflammatory diseases, although safety concerns about prolonged IL-1β blockade and the need to preserve protective mucosal immunity remain. The authors caution that their lung cohort reflects advanced disease and that the specific bacterial or host antigens driving the T cell skewing are still unknown. Even so, selectively depleting Th1/17 and pro-inflammatory Th17 cells, or blocking their generation from conventional Th17 precursors, now stands as a credible precision immunomodulatory strategy, one that could address the inflammation that persists even in patients receiving CFTR modulator therapy.

Subject of Research: Pseudomonas aeruginosa-driven reprogramming of Th17 cells in cystic fibrosis lung immunopathology

Article Title: Pseudomonas aeruginosa induces the generation of pathogenic IFNγ+Th17 cells that promote lung damage and chronic inflammation in cystic fibrosis

Article References: Dusetti, I., Conte, G., Chiara, M., Puccio, S., Guidone, D., Ricciardelli, E., Cibella, J., Ronzio, M., Dolfini, D., Rossi, E., Landini, P., Ascagni, M., Orlandi, R., Damarco, F., Palleschi, A., Gramegna, A., Blasi, F., Lugli, E., Galietta, L. J., … Paroni, M. (2026). Pseudomonas aeruginosa induces the generation of pathogenic IFNγ+Th17 cells that promote lung damage and chronic inflammation in cystic fibrosis. Nature Microbiology. https://doi.org/10.1038/s41564-026-02469-2

Image Credits: AI Generated

DOI: 10.1038/s41564-026-02469-2

Keywords: cystic fibrosis, Pseudomonas aeruginosa, Th17 cells, interferon-gamma, dendritic cells, IL-23, IL-1β, epithelial barrier, T cell receptor, mucosal immunity, chronic inflammation, immunotherapy

The team used Citrobacter rodentium, a mouse pathogen closely related to the human diarrheal bacteria enteropathogenic and enterohemorrhagic Escherichia coli. These attaching and effacing pathogens colonize the apical surface of intestinal epithelial cells and deploy a type III secretion system, a molecular syringe that injects bacterial effector proteins directly into the host cell cytosol. Crucially, the bacteria never enter the cell as intact organisms; only the injected proteins breach the epithelial barrier. The researchers asked whether this distinction matters immunologically, and the answer proved to be dramatic.

To track a defined immune response, the investigators engineered isogenic C. rodentium strains carrying the same model CD4 T cell epitope, the lymphocytic choriomeningitis virus gp66-80 peptide recognized by SMARTA T cells, fused to different bacterial carrier proteins. Intimin, an outer membrane adhesin, kept the epitope on the bacterial surface. Tir, a translocated receptor, placed it in the epithelial apical membrane. NleA distributed it diffusely through the host cytosol, and EspZ concentrated it in cytosolic clusters beneath attached bacteria. All strains retained wild-type virulence, ensuring that epitope insertion did not compromise bacterial fitness.

When naive SMARTA T cells were transferred into infected mice, the results were striking. Antigens confined to the bacterial surface or the epithelial membrane failed to drive responses beyond background levels, whereas cytosolically delivered antigens triggered robust clonal expansion. NleA-gp66 and EspZ-gp66 induced 28-fold and 47-fold greater accumulation of antigen-specific T cells in the colon, respectively, compared with intimin-gp66. Antigen abundance could not explain the disparity: Tir was the most abundantly secreted protein yet elicited a minimal response, while the poorly expressed EspZ drove the strongest reaction. Compartmentalization, not dose, emerged as the critical determinant of immunogenicity.

The investigators then isolated translocation as the sole variable by comparing full-length EspZ with a truncated variant lacking its type III secretion signal, so that the identical protein and epitope differed only in access to the host cytosol. The bifurcation was even more pronounced: full-length EspZ generated more than a 100-fold increase in mucosal antigen-specific T cells at the peak of the response. This difference held across all infected tissues and time points, establishing that cytosolic delivery alone accounts for the greatest divergence in the clonal CD4 T cell response to bacterial antigen.

Mapping the geography of the response revealed that immunity to C. rodentium is initiated in the cecum, where the bacterium first colonizes a highly focal region near the cecal patch, a gut-associated lymphoid structure. Fluorescence in situ hybridization showed bacteria clustered at the cecal apex, and T cell priming occurred predominantly in the cecum-draining distal mesenteric lymph node before effector cells spread to the distal colon. The weak response to bacterially associated antigen was evident at every site, ruling out differences in priming location as an explanation for the muted reaction to noncytosolic antigens.

The most consequential finding concerned memory. Weeks after bacterial clearance, cytosolic antigens had driven the majority of antigen-specific CD4 T cells into a tissue-resident memory phenotype, marked by CD69 and CD103 expression, whereas noncytosolic antigens left memory cells largely confined to gut-associated lymphoid tissue. Light-sheet fluorescence microscopy of intact, optically cleared colons showed that nearly 69 percent of memory T cells responding to injected antigen occupied the epithelial compartment, a density roughly threefold higher than in lymphoid structures and ninefold higher than the lamina propria. In mice lacking epithelial MHC class II, mucosal memory cells were reduced more than 20-fold, and intraepithelial residency was virtually abolished.

Single-cell RNA sequencing of more than half a million cells exposed the bidirectional dialogue underlying this programming. Epithelial MHC class II expression peaked during infection and persisted long after pathogen clearance, sustaining MHC-class-II-dependent contacts with resident memory T cells, a finding confirmed by LIPSTIC intercellular labeling, which marked about 79 percent of intraepithelial CD4 memory cells as actively engaged with epithelial cells. Interferon-gamma signaling dominated the transcriptional response of epithelial cells receiving T cell help, while ligand-receptor analysis identified MHC class II-CD4 interactions as the dominant epithelial-T cell axis, supplemented by CXCL16-CXCR6 and IL-7 and IL-15 pathways that support tissue residency and survival. Without epithelial antigen presentation, memory differentiation defaulted toward a central memory-like transcriptional program, with reduced expression of residency and effector genes such as Itgae, Ifng and Gzma and increased activity of plasticity-associated factors including Tcf7 and Bach2.

The functional payoff was demonstrated in a heterologous rechallenge experiment. Mice primed with cytosolic antigen-expressing C. rodentium were later challenged with Salmonella Typhimurium engineered to inject the same epitope into epithelial cells via its own secretion system. Primed mice showed significantly lower cecal bacterial burdens, complete survival through the observation window compared with 50 percent mortality in controls, and more than tenfold greater recovery of interferon-gamma-producing memory T cells. The authors conclude that nonprofessional antigen-presenting epithelial cells are central regulators of CD4 T cell memory fate, deploying protective residents precisely where reinfection will be encountered. The findings suggest that vaccines targeting antigens to the cytosol of intestinal epithelial cells could markedly enhance barrier-protective mucosal immunity, while offering new angles for modulating pathological memory in chronic inflammatory disease.

Subject of Research: How intestinal epithelial cell presentation of cytosol-delivered bacterial antigens programs mucosal CD4 tissue-resident memory T cell formation

Article Title: Barrier immune memory is programmed by intestinal epithelial cell presentation of cytosol-delivered bacterial antigens

Article References: Wilson, C. G., Acharya, M. P., Karsch, L., Duck, L. W., Twumasi-Ankrah, N., Wang, Y., Shen, H., Frey, B. F., McKee, A. R., Oza, V. H., Harbour, S. N., Nagaoka-Kamata, Y., Singer, J. R., Hatton, R. D., Moffitt, J., Gunzer, M., Zindl, C. L., & Weaver, C. T. (2026). Barrier immune memory is programmed by intestinal epithelial cell presentation of cytosol-delivered bacterial antigens. Nature Immunology, 27(10), 2117-2133. https://doi.org/10.1038/s41590-026-02656-7

Image Credits: AI Generated

DOI: 10.1038/s41590-026-02656-7

Keywords: intestinal epithelial cells, antigen presentation, CD4 T cells, tissue-resident memory, Citrobacter rodentium, type III secretion system, MHC class II, mucosal immunology, immune memory, barrier immunity, vaccine design, single-cell RNA sequencing

IgA is the most abundantly produced antibody in the human body, secreted in staggering quantities across mucosal surfaces every day. In the gut, it binds to bacteria, archaea, and other residents, coating some microbes heavily while leaving others untouched. This selective binding is thought to influence which organisms persist, where they localize, and how they interact with the host epithelium. Despite decades of work in mucosal immunology, however, IgA targeting has rarely been treated as a formal, quantitative dimension of microbiome analysis. Standard metagenomic studies measure abundance and diversity; they do not ask how actively the immune system is engaging each species. The new work sets out to close that gap.

The team’s central methodological innovation is the Species Immune Engagement Score, abbreviated IM-score. Rather than relying on IgA binding alone, the score integrates three distinct features for each microbial taxon: the intensity of IgA binding to that organism, its abundance in the community, and its prevalence across individuals in a cohort. The logic is that a microbe only registers as immunologically engaged if it is both recognized by antibodies and consistently present at meaningful levels across a population — a design intended to separate genuine, reproducible immune targeting from transient binding events or artifacts of low-abundance detection. The result is a per-species numerical measure of how hard the immune system is working against each resident of the gut.

When the researchers applied IM-score across three geographically distinct human cohorts, a striking pattern emerged: a conserved set of IgA-targeted gut microbes appeared across all three populations. This set included well-characterized commensal bacteria such as Coprococcus comes, a species frequently associated with short-chain fatty acid production, as well as poorly characterized taxa such as an Oscillospiraceae species designated SGB15216, which has no established functional profile in the literature. The implication is that immunological relevance and scientific characterization have diverged — some of the microbes the immune system engages most actively are precisely the ones microbiome research has paid the least attention to.

To move from individual species to community-level organization, the team aggregated IM-score values into a second metric, the Immunologically Engaged Gut Microbiota Index, or IMG-index. Where IM-score describes how strongly the immune system targets a single taxon, IMG-index summarizes the overall state of IgA-mediated engagement across the entire community. Conceptually, the index functions as a readout of how coherently the immune system is surveying the gut: a high, structured engagement pattern suggests an organized surveillance program, while fragmentation suggests the immune system’s relationship with the microbiota has been disrupted.

The clinical test case was early multiple sclerosis, a disease in which gut microbiome alterations have been repeatedly reported but mechanistically remain murky. Applying the new framework to people with early-stage disease, the researchers found a profound fragmentation of IgA-mediated immune engagement, particularly affecting short-chain fatty acid-producing bacteria and the dominant archaeal lineage in the gut. This is a notable finding because short-chain fatty acids are central players in immune regulation and gut-brain signaling, and their producing organisms have been implicated in MS-associated inflammation before. Crucially, the authors report that these fragmentation patterns are not captured by standard diversity or compositional metrics — meaning a conventional metagenomic analysis could look at the same samples and miss the immune-level disruption entirely.

The sensitivity of IMG-index extended beyond cross-sectional differences. The researchers tracked the index through fecal microbiota transplantation, a therapeutic intervention increasingly studied for its potential to reshape disease-associated microbiomes, and found that it registered changes following the procedure. The index also fluctuated with disease activity, suggesting it is not a static marker of diagnosis but a dynamic measure that responds as the immune-microbiota relationship shifts. Taken together, these observations position IMG-index as a candidate monitoring tool — one that could, in principle, track both disease-associated alterations and responses to microbiome-directed therapies over time.

Technically, the framework rests on the combination of IgA-seq-style binding measurements with deep metagenomic sequencing, allowing the team to quantify antibody coating and species identity simultaneously. The authors also report robustness analyses showing that the immune engagement metrics hold up under alternative feature-weighting schemes, and that the findings extend to the level of metagenome-assembled genomes, not just reference species. Importantly, the team has released an R package, IMGI, that computes both scores, lowering the barrier for other groups to apply the framework to their own cohorts. The authors note a pending patent application related to immunomodulatory scoring for personalized medicine, though they state it did not influence the study’s design or interpretation.

The conceptual payoff of the study may ultimately matter more than any single clinical result. By demonstrating that IgA targeting is conserved across populations, disrupted in a defined neurological disease, and responsive to intervention, the work establishes antibody-mediated surveillance as a quantifiable organizing axis of gut microbiota structure — a third dimension alongside taxonomy and function. It reframes the microbiome not as a free-floating ecological community but as one continuously curated by the host immune system, with that curation itself carrying diagnostic and prognostic information. If the findings replicate broadly, microbiome studies of the future may routinely report immune engagement alongside abundance, and diseases currently studied through compositional lenses may be re-examined through the antibody layer that has been coating the data all along.

There are, of course, caveats inherent to any observational framework of this kind. IgA binding reflects immune recognition, but the causal direction of the relationship — whether antibodies actively shape community structure, or simply mirror it — remains an open question that the correlational data cannot fully resolve. The multiple sclerosis findings come from early-stage disease and specific cohorts, and the index’s performance as a longitudinal biomarker will need validation in larger, prospective studies before it can inform clinical decisions. Still, the study provides something the field has lacked: a standardized, reproducible, and openly implemented way to measure the immune-microbiota interface. For a discipline that has spent fifteen years cataloguing microbial residents, the message is that the landlord’s fingerprints are everywhere — and now they can finally be counted.

Subject of Research: IgA-mediated immune surveillance as a quantitative organizing axis of gut microbiota structure in health and early multiple sclerosis

Article Title: Antibody-mediated immune surveillance as an organizing axis of gut microbiota structure

Article References: Nthuku, S., Sterlin, D., Pons, N., Parizot, C., Larsen, M., Rastetter, A., Marie, Y., Vicart, S., Maillart, E., Papeix, C., Gorochov, G., & Imamovic, L. (2026). Antibody-mediated immune surveillance as an organizing axis of gut microbiota structure. Microbiome. https://doi.org/10.1186/s40168-026-02542-2

Image Credits: AI Generated

DOI: 10.1186/s40168-026-02542-2

Keywords: gut microbiota, immunoglobulin A, IgA-seq, immune surveillance, mucosal immunity, microbiome, multiple sclerosis, short-chain fatty acids, fecal microbiota transplantation, host-microbe interactions, metagenomics, Coprococcus comes

Redox chemistry—the continuous shuttling of electrons between molecules—is one of the most fundamental processes in biology. Inside cells, redox state governs everything from enzyme activity to gene expression, and elaborate protein networks keep it tightly controlled. What happens outside cells, in the extracellular space, has been far harder to study, particularly in invertebrates. For filter-feeding animals like oysters, whose mucosal surfaces are in permanent contact with a shifting microbial world, the question is not academic. Their mucus is simultaneously a habitat for commensal bacteria, a first line of defense against pathogens, and a chemical environment whose composition could plausibly reshape all of these functions at once.

To probe this environment, the team characterized the mucosal proteome of Magallana gigas, the Pacific oyster, and compared it with proteins found in the animal’s plasma. The comparison revealed that mucus is not simply diluted blood plasma; it carries its own distinctive protein signature, enriched for enzymes involved in redox regulation. Among these were thioredoxin and glutaredoxin, two evolutionarily ancient protein families whose members catalyze the reduction and oxidation of disulfide bonds—the covalent bridges formed between pairs of cysteine amino acids in proteins. When the researchers challenged oysters with pathogens, including the bacterium Vibrio ZJ51 and the devastating virus OsHV-1, expression of these redox regulators in mucus rose significantly, hinting that the extracellular redox machinery is not a passive background feature but something the animal actively deploys during infection.

The centerpiece of the study is a mucosa-specific defensin the authors named Mg-Defm. Defensins are small, cysteine-rich antimicrobial peptides found across much of the animal kingdom, and bivalves possess their own branch of this family. Mg-Defm carries conserved cysteine residues that form intramolecular disulfide bonds, giving the peptide a defined three-dimensional fold. What makes the new work striking is the demonstration that this fold is not merely structural decoration. When the researchers treated Mg-Defm with dithiothreitol, or DTT, a chemical agent that reduces disulfide bonds back to free cysteine pairs, the peptide underwent measurable conformational changes consistent with bond reduction. Its shape shifted—and so did its function.

That functional shift was dramatic. Reduced Mg-Defm showed a five- to six-fold increase in bactericidal activity against Vibrio species compared with its oxidized counterpart. In other words, the redox state of the peptide itself appears to modulate how lethal it is to bacteria. This finding reframes defensin regulation in an invertebrate context. Rather than relying solely on producing more or less of the peptide, the oyster may be able to tune the activity of molecules already deployed in its mucus simply by altering the extracellular redox environment around them. The authors propose that the multiple redox regulators upregulated during infection could collectively form an extracellular switch that activates Mg-Defm when pathogens appear.

The corollary is equally consequential. If redox state controls antimicrobial activity, then disturbing that state should disturb the microbial community. The researchers tested this in two ways: through genuine pathogenic infection and through chemically induced reduction of the mucosal environment using DTT. Both interventions triggered profound microbial dysbiosis—a collapse of the normal balance of the mucosal microbiome. That a purely chemical perturbation, without any living pathogen involved, could destabilize the microbial community underscores how sensitive the system is to redox chemistry. It suggests that the oyster’s resident microbes live within a redox window maintained by the host, and that pushing the chemistry outside that window reshapes who can thrive on the mucosal surface.

For aquaculture, the implications are hard to ignore. The Pacific oyster is one of the most widely farmed animals in the world’s oceans, and its industry suffers recurrent, sometimes catastrophic losses to OsHV-1 and Vibrio infections. If extracellular redox state genuinely gates antimicrobial defenses, it offers a new dimension to consider in breeding programs, disease diagnostics, and husbandry. Redox markers in mucus could potentially serve as early indicators of infection or stress, and interventions that stabilize the mucosal redox environment might help preserve microbiome homeostasis during vulnerable periods. The study’s authors are careful to frame their conclusions as proposing a potential role for extracellular redox regulation rather than proving a complete mechanistic pathway, but the framework they outline gives the field a concrete and testable model.

The work also speaks to a broader question in immunology: how did animals defend themselves before adaptive immunity evolved? Invertebrates depend entirely on innate mechanisms—physical barriers, pattern-recognition receptors, and antimicrobial effectors like defensins. The idea that these effectors can be regulated post-secretion, by the redox chemistry of the surrounding fluid rather than by the cell that made them, adds a layer of sophistication to innate immunity that is easy to overlook. It also raises evolutionary questions. Disulfide-rich antimicrobial peptides are ancient, and redox-sensitive regulation of protein activity is equally so. The convergence of the two in a molluscan mucus layer hints that extracellular redox control may be a general and underappreciated principle of mucosal defense, one that vertebrates may share in their own mucus-covered surfaces.

Methodologically, the study illustrates the value of looking at mucus as an organ of sorts in its own right. By cataloging the mucosal proteome separately from plasma, the researchers could identify which redox enzymes are actually deployed at the host–microbe interface rather than inferring from whole-animal data. The combination of proteomics, expression analysis after pathogen challenge, biochemical characterization of a purified defensin, and microbiome profiling under both infectious and chemical perturbation gives the redox-switch hypothesis multiple independent lines of support. Supplementary analyses, including evolutionary comparisons of bivalve defensins and sequence alignments across species, situate Mg-Defm within the larger family of cysteine-rich antimicrobial peptides and reinforce that its disulfide architecture is conserved.

Many questions remain. The precise enzymes that reduce or oxidize Mg-Defm in living mucus, the kinetics of the switch during a natural infection, and the identity of the microbial taxa most sensitive to redox-driven dysbiosis all await direct demonstration. The authors themselves note that the upregulated redox regulators possibly form the extracellular switch, and that infection may alter the mucosal redox microenvironment in a way that modulates Mg-Defm activity—language that appropriately marks the model as a proposal grounded in strong correlative and biochemical evidence. Even so, the study opens a genuinely new window onto how a soft-bodied animal with no antibodies manages to coexist with a dense and dangerous microbial world. The answer, it seems, may be written in the oxidation state of its mucus—a chemical dial that the oyster can turn when pathogens arrive, and one that keeps its microscopic tenants in check when they do not.

Subject of Research: Extracellular redox regulation of mucosal antimicrobial defensins and microbiota homeostasis in the Pacific oyster

Article Title: Extracellular redox regulation in Pacific oyster mucosal immunity and microbiota homeostasis

Article References: Mao, F., Song, J., Jin, X., Wong, N.-K., Wu, S., Kawsar, M. A., Xiao, S., Xiang, Z., Yu, Z., & Zhang, Y. (2026). Extracellular redox regulation in Pacific oyster mucosal immunity and microbiota homeostasis. BMC Biology. https://doi.org/10.1186/s12915-026-02751-z

Image Credits: AI Generated

DOI: 10.1186/s12915-026-02751-z

Keywords: Pacific oyster, Magallana gigas, redox regulation, mucosal immunity, defensin, Mg-Defm, thioredoxin, glutaredoxin, microbiome, Vibrio, OsHV-1, antimicrobial peptide

The central problem the review confronts is one of fidelity. Traditional animal models of inflammatory bowel disease, for example, rely on chemically induced colitis in rodents, which captures only fragments of the human condition and often fails to predict how patients will respond to drugs. Population-based analyses of the global burden of digestive diseases across 204 countries, and systematic assessments of lifetime gastrointestinal cancer risks across 185 countries, underscore how large the unmet clinical need is. At the same time, statistics on clinical drug development suggest that roughly ninety percent of programmes fail, a figure that many in the field attribute in part to the poor predictive power of preclinical models. The translational gap between animal efficacy data and human outcomes has become one of the most cited justifications for developing human-relevant in vitro systems.

Microphysiological systems address that gap by reconstructing the architecture and dynamics of human tissue at miniature scale. Organoids are self-organising three-dimensional cultures derived from adult stem cells or induced pluripotent stem cells, and they can recapitulate the cellular diversity of the epithelium from which they originate, including absorptive enterocytes, goblet cells, Paneth cells, enteroendocrine cells and tuft cells. Organ-on-a-chip devices go a step further by embedding such cultures within microfluidic channels where engineers can control fluid shear stress, apply cyclic mechanical deformation that mimics peristalsis, maintain anaerobic conditions compatible with obligate gut anaerobes, and co-culture the epithelium with immune cells, fibroblasts, endothelial cells and living microbiomes. The combination of cellular, spatial and mechanical fidelity is what distinguishes these platforms from static cultures.

The review traces the evolution of these technologies from early proof-of-concept devices to today’s increasingly sophisticated models. Landmark studies demonstrated that a human gut-on-a-chip could sustain intestinal bacterial overgrowth and inflammation under controlled flow and deformation, and that a microfluidic interface could model the human–microbe boundary directly. Subsequent work achieved something once thought impossible outside the body: culturing a complex human gut microbiome under anaerobic conditions within an intestine-on-a-chip, allowing investigators to observe host–microbiome crosstalk in real time. In parallel, scaffold-guided organoid morphogenesis produced homeostatic mini-intestines with villus-like architecture, while automated microcavity arrays brought high-throughput organoid culture within reach, addressing one of the field’s persistent scalability problems.

Applications across the length of the gastrointestinal tract now form a substantial body of evidence. In the oral cavity, gingival tissue models have been developed that sustain inflammation and recovery over multi-week experiments, capturing crevicular fluid flow and host–oral microbiome interactions relevant to periodontitis, a condition whose immune cell networks are otherwise difficult to study in isolation. In the oesophagus, organ chips have been used to model epithelial–stromal interactions in Barrett’s oesophagus, the premalignant condition that precedes oesophageal adenocarcinoma, while oesophageal organoid cultures have revealed functional interplay between Notch signalling and inflammatory cytokines and have recapitulated the heterogeneity of oesophageal adenocarcinoma for clonality studies and precision therapeutics. Patient-derived oesophageal adenocarcinoma organ chips are now being positioned as platforms for functional precision oncology.

In the stomach, bioinspired stomach-on-a-chip devices reproduce luminal flow and peristaltic-like motility, and organoid-based microphysiological systems have been engineered to recapitulate the dynamic mucosal defence mechanisms of the gastric lining. A particularly striking recent advance involves Helicobacter pylori, the bacterium responsible for most peptic ulcers and a major risk factor for gastric cancer. Accessible homeostatic gastric organoids have revealed cell-type-specific host–pathogen interactions during infection, and multi-regional gastric assembloids have enabled functional parietal cell maturation and patient-specific modelling of antral foveolar hyperplasia. Because H. pylori deregulates T and B cell signalling to achieve immune evasion, models that pair human epithelium with immune components are especially valuable for dissecting how infection progresses toward metaplasia and malignancy.

The small intestine and colon have seen perhaps the most intense model-building activity. Primary human small intestine-on-a-chip platforms built from biopsy-derived organoids, and induced pluripotent stem cell-derived intestine chips containing self-organising epithelial, mesenchymal and neural cells, have expanded the repertoire of available systems. Nutritional deficiency induced in an intestine-on-a-chip has recapitulated the injury hallmarks of environmental enteric dysfunction, a condition affecting children in low-resource settings that is nearly impossible to model in animals. In celiac disease research, a human autoimmune organoid model revealed a role for interleukin-7 in the disease process, while complementary work has shown that gliadin-dependent unfolded protein responses directly trigger transglutaminase expression, pro-inflammatory cytokine release, permeability dysregulation and reduced CFTR expression in patient epithelial cells.

Inflammatory bowel disease and colorectal cancer receive the most detailed treatment in the review, reflecting both their clinical weight and the maturity of the modelling effort. A newly reported human inflammatory bowel disease-on-a-chip can model disease progression, cancer initiation and even sex-specific effects, addressing a dimension of gastrointestinal physiology that has long been underappreciated. Gut–liver physiomimetic systems have exposed paradoxical effects of short-chain fatty acids on inflammation, and macrophage-augmented intestinal organoids now model virus–host interactions in enteric viral disease. On the cancer side, colorectal cancer organoids have been interrogated by multi-omics to identify mediators of progression following SMAD4 inactivation, oncogenic signalling has been linked to specific differentiation states, and colon tumour organoids have been enabled to undergo peristalsis on microfluidic chips. Microfluidic co-culture models from the review’s own authors examine colonocyte–microbiota interactions and the interplay between dietary fibre, macrophages and colonocytes in colorectal cancer, connecting diet — a known modulator of carcinogenesis — to tumour biology in a controlled setting.

The authors are candid about what these systems still cannot do. Complexity remains a limiting factor: most chips contain a fraction of the cell types present in real mucosa, and the full immune compartment, the enteric nervous system and the spatially organised microbiota of the gut wall are only partially represented. Translation from device to clinic is still early, and scalability — producing enough replicate, standardised tissues for industrial drug screening — continues to challenge the field. Radiation injury studies in gut-on-a-chip platforms illustrate both the promise and the difficulty: such models reproduce cell death patterns and allow countermeasure drug testing, but correlating chip-scale dosimetry with clinical radiotherapy remains an open problem. Interconnected multi-organ systems that link gut chips to liver, brain or vascular modules through robotic fluidic coupling point toward a future in which the gut–liver and microbiota–gut–brain axes can be studied pharmacokinetically, but these assemblies add engineering complexity of their own.

The trajectory the review sketches is nonetheless ambitious. Emerging directions include bioprinted patient-derived organoid arrays that capture both intrinsic and extrinsic tumour features for personalised medicine, artificial intelligence applied to microbiome research and to the analysis of spatially resolved transcriptomics, intelligent intestine-on-a-chip devices that screen probiotics automatically, and organoid platforms for studying ageing signatures in the intestinal epithelium. The authors argue that by bridging microengineering innovation with clinical gastroenterology, next-generation human-relevant models can inform mechanistic discovery, guide targeted therapeutic development and support precision medicine in gastrointestinal disease. For a field in which most patients with inflammatory bowel disease still cycle through therapies by trial and error, and in which gastrointestinal cancers remain among the leading causes of cancer death worldwide, the prospect of testing drugs on miniature replicas of a patient’s own diseased tissue represents one of the most consequential shifts in preclinical medicine now underway.

Subject of Research: Microphysiological systems, including organoids and organ-on-a-chip devices, for modelling human gastrointestinal diseases

Article Title: Microphysiological models of human gastrointestinal diseases

Article References: Peñarete-Acosta, D., Noe, P., Kellogg, T., Li, S., Radolf, J. D., Hyams, J. S., & Jalili, S. (2026). Microphysiological models of human gastrointestinal diseases. Nature Biomedical Engineering. https://doi.org/10.1038/s41551-026-01805-5

Image Credits: AI Generated

DOI: 10.1038/s41551-026-01805-5

Keywords: organoids, organ-on-a-chip, gastrointestinal disease, inflammatory bowel disease, colorectal cancer, gut microbiome, microphysiological systems, Helicobacter pylori, precision medicine, biomedical engineering, mucosal immunity, drug development

The proposal, published in the journal Discover Biotechnology, builds on a growing body of work in plant-derived edible vaccines. The idea is deceptively simple: genetically engineer a plant to produce an antigen, a harmless fragment of a pathogen that the immune system can learn to recognize, and then have people or animals eat the plant tissue. When the antigen reaches the gut, it encounters the gut-associated lymphoid tissue, or GALT, a dense network of immune cells that guards one of the body’s main entry points for pathogens. Studies in both mice and humans have shown that plant-derived antigens delivered orally can stimulate antigen-specific mucosal IgA antibodies as well as serum IgG, the systemic antibody class measured after conventional immunization. That dual response matters, because mucosal immunity is the first line of defense against the respiratory and intestinal infections that cause enormous global disease burden.

Plant-based delivery also solves some stubborn engineering problems. The plant cell wall acts as a natural capsule, shielding antigenic proteins from the acidic environment of the stomach so they survive long enough to reach immune tissue. Even more striking, freeze-dried plant material expressing vaccine antigens has been shown to maintain antigen integrity at ambient temperatures, eliminating the need for refrigeration during storage and transport. For regions where electricity is unreliable and cold-chain logistics are prohibitively expensive, a vaccine that can sit on a shelf as dried powder is a fundamentally different proposition from one that must be kept chilled at every step.

Among the many plants tested as vaccine factories, duckweeds—tiny aquatic flowering plants of the family Lemnaceae—stand out. They pack protein at up to 40 percent of their dry weight, grow at remarkable speed on inexpensive byproduct substrates, and, crucially for vaccine consistency, are so small and anatomically uniform that antigen levels should be even between individual plants. That uniformity addresses one of the biggest weaknesses of edible vaccines in general: dosage. When a vaccine is eaten, the amount of antigen consumed can vary depending on which part of the plant is eaten and how much, leading to inconsistent immune responses. Researchers are countering this with genetic engineering strategies that drive uniform antigen expression in specific tissues, and duckweed’s near-homogeneous body plan gives it a natural head start.

The evidence in animal models is encouraging. Duckweed engineered to express Interleukin-17B has been used as a mucosal adjuvant against infectious bronchitis virus in chickens. When the M2e peptide of the H5N1 avian influenza virus—a sequence so conserved it appears across essentially all influenza strains—was expressed in duckweed and fed to mice, the animals produced anti-M2e antibodies detectable in blood serum. And in an aquaculture demonstration, zebrafish fed transgenic duckweed carrying the LamB antigen from Vibrio alginolyticus were protected against fish vibriosis: when challenged with five times the lethal dose of the pathogen, 63 percent of the vaccinated fish survived, compared with complete mortality in the unvaccinated control group.

So why has no one scaled this up? The answer lies in duckweed’s biology. Because the plants are aquatic, they need vast expanses of water to grow, and in water-scarce regions that requirement can outweigh the benefits of the vaccine itself. Artificial ponds would have to be built, consuming capital and competing with agriculture and urban development for land. Open-air ponds are also vulnerable to contamination by microalgae and fungi, which can render entire batches unusable and impose heavy financial losses. Finally, harvesting delicate, millimeter-scale plants is logistically awkward, and ponds are often located far from the end users, forcing complex delivery chains that erode the cost advantages that made duckweed attractive in the first place.

The research team’s answer is a vertical farming and recirculation system. Instead of spreading duckweed across horizontal ponds, the design stacks multiple layers of cultivation trays, with the liquid medium held at a shallow depth of roughly five centimeters—enough for duckweed, which floats at the surface, to thrive. Water is pumped to the top tray and flows gravitationally through the lower trays back to a reserve basin at the bottom, continuously recirculating and dramatically cutting water use. According to the authors, this vertical arrangement could raise production yield per unit area by a factor of ten to twenty compared with conventional cultivation. Biomass is collected with a filtration-based harvester that returns the supernatant to the basin, minimizing waste.

Vertical farms have a well-known Achilles’ heel: trays lower in the stack are shaded by those above. The proposed solution is elegantly mechanical. The trays would be made of transparent material and mounted on retractable mechanisms along both horizontal axes, with a programmable algorithm adjusting the retraction amplitude and frequency in response to real-time light sensors, so each layer of duckweed gets its optimal share of sunlight. Solar panels integrated into the structure would help offset the energy costs of pumping and automation. The team also proposes siting these systems on livestock and poultry farms, where animal wastewater could serve as the growth medium—turning a disposal problem into a nutrient source while the duckweed simultaneously purifies the water. Settling ponds can reduce turbidity and microbial load in the wastewater before use, and prior studies indicate that duckweed grown on wastewater does not suffer unsafe microbial contamination. Because the system is enclosed, it also limits environmental contamination and gene flow, aligning with global biosafety regulations; regular monitoring for heavy metals in the waste streams would be needed, with quality control applied across the value chain to meet Good Manufacturing Practice standards.

The envisioned value chain runs from molecular bioengineering to the dinner bowl. A gene encoding a pathogenic antigen is introduced into duckweed, the transformed plants are cultivated at scale in the retractable vertical trays, and the harvested biomass is dried and ground into a powder that can be mixed into food or feed—immunizing and nourishing the consumer at the same time. The capital costs of such a system, especially when fitted with solar panels, sensors, and automated retraction, exceed those of traditional greenhouse production, but they are far lower than bioreactor-based manufacturing, and operating expenses can be trimmed by optimizing light regimes. The authors argue that high yields and low downstream processing costs could give the approach a decisive edge in overall unit economics, with lighting costs and protein yield as the two variables that will ultimately determine competitiveness.

Significant hurdles remain before duckweed vaccines reach the main course. Purification steps are still required before the material can be used as a vaccine, and the regulatory pathway for an edible, plant-grown immunization is uncharted territory in most jurisdictions. Yet the convergence of advances in plant biotechnology—improved promoter optimization, enhanced expression systems, and synthetic biology tools—with a cultivation system designed for scale suggests that the gap between laboratory proof and global health impact may finally be closable. If powdered duckweed vaccines can be grown beside the farms and villages that need them, stored without refrigeration, and eaten rather than injected, one of medicine’s oldest tools could take on one of its most persistent inequities.

Subject of Research: Vertical farming of transgenic duckweed for scalable production of edible vaccines

Article Title: Vertical farming of duckweed: advancing edible vaccine production for global health

Article References: Grieš, M., Rosputinský, M., Mećava, M., & del Valle, A. C. (2025). Vertical farming of duckweed: advancing edible vaccine production for global health. Discover Biotechnology, 2(1), Article 14. https://doi.org/10.1007/s44340-025-00018-x

Image Credits: AI Generated

DOI: 10.1007/s44340-025-00018-x

Keywords: duckweed, edible vaccines, vertical farming, mucosal immunity, transgenic plants, Lemnaceae, cold chain, wastewater, antigen expression, global health, plant biotechnology, aquaculture

The research, led by Ethan Gough and Soumya Basu of the Department of International Health at the Johns Hopkins Bloomberg School of Public Health, together with senior author Subhra Chakraborty and colleagues, drew on stool samples and immune measurements from 27 adult volunteers who participated in a controlled clinical trial. Each volunteer received two doses of ACE527, a live attenuated oral ETEC vaccine candidate, and was subsequently challenged with the virulent ETEC strain H10407, a well-characterized isolate that has long served as a benchmark strain in human challenge studies of enteric vaccines. The trial was registered under ClinicalTrials.gov identifier NCT01060748, and the microbiome analysis was approved by the Johns Hopkins University Institutional Review Board under protocol IRB 20100221.

To characterize the bacterial communities living in the participants’ intestines, the team performed 16S ribosomal RNA sequencing on stool samples collected during the trial. This technique amplifies and sequences a molecular marker present in all bacteria, allowing researchers to identify which microbial taxa are present and in what relative abundances, without needing to culture the organisms in the laboratory. From these data the investigators computed two standard measures of community structure: alpha diversity, which captures how many species are present and how evenly distributed they are within a single sample, and beta diversity, which measures how similar or different microbial communities are between individuals or across time points.

The immune outcomes of interest were drawn from enzyme-linked immunosorbent assay measurements of antibody responses directed against two key ETEC antigens: the B subunit of heat-labile toxin, known as LTB, and colonization factor antigen I, or CFA/I, a surface structure the bacteria use to adhere to the intestinal lining. Antibodies were quantified both in serum, reflecting systemic immunity, and in the antibody-in-lymphocyte-supernatant assay, or ALS, which captures antibodies secreted by circulating plasmablasts and serves as a surrogate for mucosal immune activation in the gut. Both IgG and IgA classes were measured, with IgA of particular interest because it is the dominant antibody isotype at mucosal surfaces and is widely regarded as a correlate of protection against intestinal pathogens.

The statistical analysis went well beyond simple comparisons. The team used regression models to link individual bacterial taxa to immune readouts, applied the Microbiome Regression-Based Kernel Association Test, known as MiRKAT, to test whether overall community composition predicted immune responses, and employed a relaxed least absolute shrinkage and selection operator, or LASSO, approach to identify parsimonious sets of taxa associated with protection. Protection itself was assessed clinically, based on whether volunteers developed severe diarrhea and on whether ETEC could be detected as colonizing the gut after the challenge with H10407.

One of the clearest signals emerged from the alpha diversity analysis. Volunteers with higher inverse-Simpson diversity, a metric that increases both with the number of species present and with their evenness, tended to mount weaker ALS IgA responses against both LTB and CFA/I. In other words, a more diverse gut community was associated with a blunted mucosal antibody response to the vaccine. This finding is intriguing because it runs counter to the common assumption that greater microbial diversity is inherently beneficial; in the specific context of oral live attenuated vaccine immunogenicity, a densely populated and diverse intestinal ecosystem may compete with the vaccine strain or modulate innate immune signaling in ways that dampen the antigen-specific response.

Beta diversity told a different story. The overall composition of the gut community, considered as a whole, correlated with increased serum anti-CFA/I IgA, suggesting that the identity of the microbes present, rather than simply their number, shapes the systemic arm of the antibody response. At the level of individual taxa, the vaccination series was associated with a measurable increase, on the order of 25 to 30 percent, in the relative abundance of several groups, including the Eubacterium brachy group, members of Family XIII AD3011, and Actinomyces. Whether these shifts represent a direct effect of vaccine colonization on the ecosystem or an indirect consequence of the immune activation that vaccination triggers remains an open question, but the consistency of the direction of change across participants suggests a reproducible vaccine-microbiome interaction.

Perhaps the most consequential findings concerned specific bacterial families whose abundance tracked with protection. Members of Anaerovoraceae, Peptostreptococcaceae, Oscillospiraceae, and Veillonellaceae were associated with enhanced immune responses and, importantly, with protection against severe diarrhea and against ETEC colonization following the challenge. In contrast, several other groups, including Ruminococcaceae, Sutterellaceae, Coriobacteria, Clostridia, and Actinobacteria, showed antagonistic associations, being linked in the opposite direction with immune outcomes or protection. These antagonistic taxa are not necessarily harmful in their own right; the associations are statistical relationships that require mechanistic follow-up. Nonetheless, the pattern suggests that the interplay between a person’s resident microbiota and an oral vaccine is not uniform across the microbial community but instead involves specific lineages that either support or hinder the generation of protective immunity.

The implications for vaccine development are considerable. Oral live attenuated vaccines must survive passage through the stomach, establish limited replication in the intestine, and present their antigens to the gut-associated lymphoid tissue, and every one of those steps occurs in the context of a complex microbial ecosystem that can facilitate or obstruct them. If the microbiome modulates take of the vaccine strain, the magnitude of mucosal IgA responses, or the likelihood of sterilizing protection after exposure to wild-type bacteria, then microbiome status may help explain a long-standing puzzle in ETEC vaccine research: why candidate vaccines that perform reasonably well in controlled human challenge studies among adults in industrialized settings often show weaker immunogenicity and efficacy when tested in infants and young children in endemic countries, whose gut communities differ markedly from those of the trial volunteers in Baltimore.

The authors emphasize that the study, funded by the National Institute of Allergy and Infectious Diseases through grants R01AI153399 and R56AI168316 and additionally supported by the PATH agreement GAT.1371-05689-CTA, is an early step in a longer research program. With 27 participants, the analysis is necessarily exploratory, and associations identified through sequencing and regression modeling will need to be validated in larger and more diverse cohorts, ideally including populations in ETEC-endemic regions where the public health burden is greatest. Still, the work offers a concrete roadmap: specific taxonomic markers, measurable by inexpensive 16S sequencing, could eventually help researchers stratify volunteers in vaccine trials, stratify risk in endemic populations, or even guide the rational use of microbiome-directed adjuncts such as targeted prebiotics to maximize the protective potential of future ETEC vaccines. As enteric vaccine science matures, it appears increasingly clear that the answer to whether a vaccine works may lie not only in the vaccine itself but in the trillions of microbes with which it shares the intestine.

Subject of Research: How gut microbiota composition influences immune responses and protection following oral ETEC vaccination and challenge

Article Title: Influence of gut microbiota on immune responses and protection in volunteers receiving the live attenuated oral ETEC vaccine ACE527 followed by virulent ETEC H10407 challenge

Article References: Gough, E., Basu, S., Brubaker, J., DeNeraing, B., Sack, D., Bourgeois, A. L., Walker, R., Harro, C. D., & Chakraborty, S. (2026). Influence of gut microbiota on immune responses and protection in volunteers receiving the live attenuated oral ETEC vaccine ACE527 followed by virulent ETEC H10407 challenge. Gut Pathogens. https://doi.org/10.1186/s13099-026-00878-6

Image Credits: AI Generated

DOI: 10.1186/s13099-026-00878-6

Keywords: ETEC, gut microbiota, ACE527 vaccine, H10407 challenge, IgA response, mucosal immunity, 16S rRNA sequencing, diarrhea, vaccine immunogenicity, microbiome diversity, Influence, microbiota