The research team set out to address a persistent gap in the VZV literature. While numerous studies have characterized how VZV infects neurons, neural stem cells, and astrocytes, the role of microglia—the central innate immune defenders of the brain—had never been systematically examined. Because VZV lacks a suitable animal model, the investigators turned to in vitro systems, comparing the behavior of wild-type VZV strain YC01, isolated from a shingles patient, with the live-attenuated vaccine strain MAV/06 across multiple cellular platforms. These included the HMC3 and HIM human microglial cell lines, the monocytic THP1 line, and, critically, human embryonic stem cell-derived microglia (ESC-MG), a model that closely mimics authentic brain microglia in surface markers and gene expression.

The first surprise came from replication assays. Using quantitative PCR to track viral gene expression—measuring immediate-early genes ORF4 and ORF63 and the early gene ORF54—the researchers found that both microglial cell lines supported VZV gene expression and protein production, with the wild-type strain replicating somewhat more efficiently than the vaccine strain. Immunoblotting and confocal microscopy confirmed that viral glycoprotein E, the most abundant protein of VZV, accumulated in infected cells in a time-dependent manner. Notably, cell viability remained largely intact during the early stages of infection, suggesting that the virus was establishing itself in microglia without immediately killing its host cells. Flow cytometry revealed that YC01-infected microglia markedly upregulated CD45 and CD68, markers of microglial activation and phagocytic activity, and showed enhanced uptake of latex beads and apoptotic cells—signs of a functionally activated, yet potentially exploited, immune cell.

To understand the molecular consequences of infection at scale, the team performed bulk RNA sequencing of infected cells. The results were striking: YC01 infection produced a distinct transcriptional signature characterized by robust induction of antiviral innate immunity genes, including retinoic acid-inducible gene I (RIG-I), melanoma differentiation-associated protein 5 (MDA5), IFN-stimulated gene 15 (ISG15), IP-10, and 2′-5′-oligoadenylate synthetase 1 (OAS1). In contrast, the attenuated MAV strain elicited gene expression profiles nearly indistinguishable from mock-infected controls. In the ESC-MG model, this divergence was even more pronounced. Wild-type VZV triggered not only inflammatory and antiviral programs but also a shift toward a disease-associated microglia phenotype, with upregulation of genes such as APOE, TYROBP, and TMEM119 that have been linked to dysfunctional microglia in neurodegenerative contexts. Morphologically, YC01-infected ESC-MG underwent dramatic changes—soma enlargement and a shift toward an amoeboid shape, with three-dimensional analysis revealing increased surface area but reduced filament length, hallmarks of activated microglia—while MAV-infected cells maintained their homeostatic branching.

The inflammatory consequences were equally dramatic. YC01-infected microglia secreted elevated levels of proinflammatory cytokines and chemokines, including IL-6, IL-8, IP-10, and MCP-1/2, as confirmed by ELISA, Luminex multiplex assays, and cytokine antibody arrays. Intriguingly, the team traced part of this inflammatory drive to ORF62, the immediate-early 62 protein of VZV. Twelve of the twenty-four non-synonymous mutations that distinguish the vaccine strain from wild-type virus reside in ORF62. When the researchers expressed wild-type or mutant ORF62 in microglia, the wild-type version drove substantially higher NF-κB and IP-10 promoter activity, fuller nuclear translocation of the p65 subunit of NF-κB, and greater secretion of IL-6, IL-8, IL-1β, and TNF-α upon stimulation. This suggests that mutations acquired during vaccine attenuation dampen the virus’s capacity to provoke inflammation in microglia, providing a mechanistic window into why wild-type and vaccine strains behave so differently in the brain’s immune compartment.

Perhaps the most consequential discovery involved MARCO, the macrophage receptor with collagenous structure. This class A scavenger receptor, traditionally known for bacterial defense, emerged as one of the most highly upregulated genes—more than sixfold—in YC01-infected ESC-MG. Recognizing that other viruses, including herpes simplex virus 1, vaccinia virus, and adenovirus, exploit MARCO for entry, the team hypothesized a similar role for VZV. A series of elegant binding experiments confirmed the suspicion: purified recombinant MARCO bound to VZV glycoprotein E in a dose-dependent manner in an ELISA-based assay, while showing no interaction with glycoprotein B. Confocal microscopy of cells co-expressing MARCO and gE revealed strong membrane colocalization, but this was lost when the C-terminal scavenger receptor cysteine-rich (SRCR) domain of MARCO was deleted. Co-immunoprecipitation experiments cemented the finding that the SRCR domain is essential for the MARCO–gE interaction.

Functionally, MARCO proved to be a genuine proviral factor. Overexpression of full-length MARCO in HMC3 cells significantly elevated expression of VZV ORF4, ORF54, and ORF63 following infection, whereas the SRCR-deleted variant failed to provide the same enhancement. Blocking MARCO with a specific antibody, competing it out with the scavenger receptor ligand polyinosinic acid, or knocking it down with siRNA each significantly suppressed viral gene expression; siRNA treatment reduced VZV gE protein levels by roughly seventy percent. CRISPR-Cas9-generated MARCO-knockout HMC3 cells showed markedly reduced early viral gene transcription compared with wild-type controls, and MARCO knockdown in MeWo cells reduced both viral protein expression and infectious titers as measured by plaque assay. Together, these experiments demonstrate that MARCO facilitates VZV uptake, entry, and replication in microglia, positioning it as a key viral exploitation target.

But MARCO’s role did not end at viral entry. Prior work had established that the SRCR domain of MARCO enhances NF-κB activity through interaction with toll-like receptor 2, and that VZV activates inflammatory cytokines in monocytes and macrophages via TLR2. Co-immunoprecipitation confirmed a physical association between full-length MARCO and TLR2, and luciferase reporter assays in HEK293T cells showed that increasing amounts of MARCO co-transfected with TLR2 produced a dose-dependent enhancement of NF-κB promoter activity. Co-expression of MARCO and TLR2 significantly amplified NF-κB activation in response to both VZV gE and TNF-α. In actual microglia, overexpression of MARCO and TLR2 drove higher IL-6 and IL-8 secretion during VZV infection, while MARCO siRNA had the opposite effect. The picture that emerges is one of a two-pronged exploitation: VZV uses MARCO as a receptor to gain entry, and the gE-bound MARCO then cooperates with TLR2 to supercharge inflammatory signaling, converting the brain’s first line of defense into an engine of neuroinflammation.

The final piece of the puzzle addressed what this means for neurons. The researchers differentiated human embryonic stem cells into sensory neurons enriched for nociceptors—the pain-sensing cells of the dorsal root ganglia—and exposed them to conditioned medium from VZV-infected microglia. The results were compelling. Neuroblastoma cells treated with the infected-microglia secretome showed increased propidium iodide uptake, elevated reactive oxygen species production, and Fluoro-Jade C staining consistent with degeneration. In the ESC-derived sensory neurons, the microglial secretome markedly increased expression of Nav1.8, the nociceptor-specific sodium channel encoded by SCN10A, along with calcitonin gene-related peptide, a neuropeptide central to pain signaling. Crucially, calcium imaging with Fluo-4 AM revealed that conditioned medium from VZV-infected microglia triggered robust calcium influx—a readout of nociceptor activation—while medium from MARCO-knockout infected microglia produced only a modest increase. This establishes a plausible mechanistic chain linking microglial MARCO to the neuropathic pain that so often follows shingles, potentially including the chronic, debilitating post-herpetic neuralgia seen in elderly patients.

The findings carry implications that extend well beyond VZV biology. Growing epidemiological evidence, including natural-experiment studies of shingles vaccination, has suggested that vaccination against herpes zoster reduces the risk of dementia, hinting at a role for VZV-induced neuroinflammation in neurodegenerative processes. By demonstrating that VZV-infected microglia adopt a disease-associated phenotype, secrete a potent inflammatory cocktail, and can amplify nociceptor activity in sensory neurons, this study provides a cellular framework for how the virus might contribute to long-term neurological complications. It also highlights MARCO as a druggable node: blocking its interaction with viral gE or its cooperation with TLR2 could, in principle, simultaneously limit viral spread in the brain and dampen the inflammatory cascade that drives pain and neuronal injury. As the authors note, with VZV vaccines still absent from the national immunization programs of many countries and VZV-associated diseases remaining prevalent worldwide, understanding the molecular choreography between this ancient virus and the brain’s immune sentinels has never been more urgent.

SARS-CoV-2’s ability to propagate unabated hinges on intricate viral-host interactions and immune dysregulation, notably the cytokine storm, which often dictates disease severity and patient outcomes. Contemporary antiviral agents primarily focus on viral polymerase and spike protein targets, but emerging drug resistance and variant-associated escape mechanisms necessitate alternative approaches. The papain-like protease (PLpro) of SARS-CoV-2 represents a less conventional, yet highly druggable target essential for viral polyprotein processing and antagonism of host innate immunity.

Concurrently, RIPK1, a crucial signaling mediator in host cells, orchestrates inflammatory cascades and necroptosis pathways, which are implicated in the hyperinflammatory responses characterizing severe COVID-19 cases. Viral exploitation of RIPK1 not only facilitates viral replication but accelerates cytokine storms, aggravating pulmonary damage. Thus, RIPK1 stands as a promising host-directed therapeutic target that could mitigate inflammation and viral load concomitantly.

The research team employed robust high-throughput screening methodologies to discover potent and selective small-molecule inhibitors against both PLpro and RIPK1. Their efforts culminated in the identification of two lead compounds, SHY1643 targeting PLpro and QY1892 targeting RIPK1. These inhibitors exhibit high specificity and favorable pharmacokinetic profiles, critical parameters for advancing preclinical development.

In in vivo studies using a SARS-CoV-2-infected mouse model, administration of SHY1643 and QY1892 individually resulted in significant, yet moderate, reductions in viral titers and inflammatory cytokines. Remarkably, combined treatment with these inhibitors produced a synergistic therapeutic effect, dramatically diminishing viral loads and attenuating cytokine release syndrome, thereby preventing severe lung pathology. This synergistic efficacy underlines the therapeutic advantage of simultaneously modulating viral enzymatic activity and host inflammatory pathways.

Mechanistically, SHY1643 inhibits PLpro by competitively binding to its catalytic domain, thereby obstructing viral polyprotein cleavage and impairing viral replication. QY1892’s inhibitory action on RIPK1 curtails kinase-mediated signaling pathways responsible for propagating pro-inflammatory cytokine production and programmed necrosis, which are hallmarks of severe systemic inflammation in COVID-19. The dual blockade of viral replication and host inflammation presents a compelling case for combination therapy.

This study’s insights address an unmet clinical need for effective treatments that circumvent the limitations of existing antivirals and immunosuppressants. The robust preclinical data offer a proof-of-concept that dual targeting of viral and host factors can yield superior therapeutic benefits. Moreover, the selective nature of the inhibitors minimizes off-target effects, potentially translating into favorable safety profiles for future clinical trials.

The discovery pipeline integrating high-throughput screening, structural biology, and in vivo validation exemplifies a multidisciplinary approach in antiviral drug development. Such methodologies enable rapid identification and optimization of lead compounds with desirable pharmacodynamics and pharmacokinetics against emerging infectious diseases. The PLpro and RIPK1 inhibitors described represent promising candidates for further medicinal chemistry refinement and regulatory evaluation.

Importantly, the study emphasizes that viral proteases like PLpro constitute underexplored antiviral targets that complement established modalities focusing on polymerases or spike proteins. Meanwhile, targeting host molecules such as RIPK1 leverages the host-pathogen interface to temper deleterious immune responses without directly exerting selective pressure on the virus, thereby reducing the likelihood of resistance development.

While the findings are promising, challenges remain in translating these preclinical successes into clinical practice. Pharmacological characterization, dosage optimization, and comprehensive safety assessments in larger animal models and human subjects will be essential. Additionally, evaluating efficacy across diverse SARS-CoV-2 variants and in patients with varying disease severities will determine the clinical utility of this combination therapy.

Looking forward, the dual-inhibitor strategy delineated by this research holds potential not only for COVID-19 but also for other viral diseases where host inflammation exacerbates disease progression. It underscores the paradigm shift towards combination therapies that simultaneously target virus and host factors, heralding a new era in antiviral treatment design.

In summary, this groundbreaking study by Shan and colleagues marks a significant advance in COVID-19 therapeutics by demonstrating that concurrent inhibition of SARS-CoV-2 PLpro and host RIPK1 synergistically reduces viral replication and cytokine-mediated inflammation. This novel combination therapy approach offers a promising avenue to mitigate severe COVID-19 outcomes and enriches the antiviral arsenal against this relentless pandemic.

Subject of Research: Discovery and preclinical evaluation of synergistic inhibitors targeting SARS-CoV-2 PLpro and host RIPK1 for COVID-19 therapy.

Article Title: Discovery of SARS-CoV-2 PLpro inhibitors and RIPK1 inhibitors with synergistic antiviral efficacy in a mouse COVID-19 model

News Publication Date: Not specified

Web References:

• Journal homepage: http://www.imm.ac.cn/
• Chinese Pharmaceutical Association: http://www.cpa.org.cn/Index.html
• Article DOI: http://dx.doi.org/10.1016/j.apsb.2025.09.026
• Acta Pharmaceutica Sinica B on ScienceDirect: https://www.sciencedirect.com/journal/acta-pharmaceutica-sinica-b

References:
Hengyue Shan, Yuzheng Zhou, Ying Qin, Taijie Guo, Xiao Zhang, Huaijiang Xiang, Qinyang He, Chen Shi, Dekang Li, Jingli Liu, Chunting Qi, Shi Chen, Jiajia Dong, Gang Xu, Ying Li, Zheng Zhang, Li Tan, Acta Pharmaceutica Sinica B, Volume 16, Issue 1, 2026, Pages 387-405.

Keywords: SARS-CoV-2, COVID-19, PLpro, RIPK1, Infectious diseases, Cytokine storm, Small molecule inhibitors, Combination therapy.

The significance of viruses in both environmental and health contexts cannot be overstated. Increasingly, researchers are recognizing viruses not merely as agents of disease but as fascinating components of ecosystems that can shape biological interactions in profound ways. This special issue will delve into various aspects of viral research, encouraging authors to provide thorough reviews that encompass a broad spectrum of topics, including viral evolution, host-virus interactions, and the role of viruses in ecology.

The editors encourage submissions that reflect innovative methodologies or novel discoveries in virology. This is a unique opportunity for researchers to share insights derived from their investigations into viral mechanics, their interactions with host organisms, and emerging antiviral strategies. Submissions will be evaluated based on their scientific merit and contribution to the knowledge base surrounding viral phenomena.

Review articles are particularly sought after, as they offer a synthesis of existing knowledge while identifying gaps in research that could lead to future discoveries. Authors are invited to draw from a diverse range of studies, integrating findings from molecular biology, genomics, and ecological studies to present a holistic view of current understanding in virology. The reviewers will look for manuscripts that provide depth and clarity while facilitating the exploration of unexplored territories in viral studies.

In light of the recent global events influenced by viral pathogens, and the continuous evolution of viral diseases, the need for comprehensive reviews in this domain has never been more pressing. Through the special issue, contributors will be able to highlight the latest advancements in virology, address contemporary challenges in public health, and contribute to a better understanding of viral dynamics in various ecosystems.

The editors are dedicated to assembling a collection that not only showcases high-caliber research but also engages the scientific community in meaningful dialogue regarding future directions in viral research. They encourage authors to consider the broader implications of their work beyond the laboratory, connecting their findings to real-world applications in healthcare and environmental management.

This special issue represents a promising avenue for researchers eager to disseminate their findings to a wider audience. It serves as an opportunity to foster collaboration across disciplines and disciplines and engender discussions about the potential benefits and threats posed by viruses. By soliciting contributions from myriad researchers, the editors seek to create a rich tapestry of insights that reflects the current state of viral research and future trajectories.

As the submission deadline of June 2025 approaches, potential authors are urged to prepare their manuscripts diligently. Contributors are asked to adhere to submission guidelines that will be provided, ensuring a smooth review process for all parties involved. There is no doubt that the contributions assembled in this special issue will hold significant value for practitioners, researchers, and policymakers alike, potentially paving the way for new breakthroughs and collaborative efforts.

In conclusion, this call for papers signifies an invaluable opportunity for scientists to showcase their inventions and insights while collectively pushing the boundaries of what is known about viruses. With the guidance of seasoned experts Yong-Bok Lee and Seung-Hyun Jeong, this special issue is poised to become a cornerstone reference point for current and future research in virology. The broader scientific community is encouraged to participate in this endeavor, capitalizing on the chance to significantly impact how viruses are understood and managed across various domains.

For those ready to join this exciting academic initiative, further details can be expected in the coming months, including specific formatting guidelines and key topics of interest. As the field of viral research evolves, so too does the imperative for comprehensive and thoughtful scholarship. Now is the time for researchers to add their voices to this critical conversation.

Subject of Research: Viral Research and its Implications

Article Title: Comprehensive Review on the Dynamics of Viruses in Health and Ecosystems

Article References:

Image Credits: AI Generated

DOI:

Keywords: Viral Research, Virology, Host-Virus Interactions, Viral Evolution, Antiviral Strategies, Ecosystems, Infectious Diseases.

The interferon-induced proteins with tetratricopeptide repeats (IFITs) have long been recognized as crucial effectors of the cell’s innate antiviral defense. These proteins rapidly accumulate in response to interferon signaling triggered by viral infection. Despite previous knowledge of their broad antiviral activities, the precise molecular determinants governing IFIT specificity have remained somewhat elusive. The current research sheds light on an intricate partnership between IFIT2 and IFIT3, revealing how their cooperative binding confers an ability to preferentially bind viral mRNAs characterized by short 5’ UTRs, thereby curtailing the production of viral proteins at the very first step: translation initiation.

Viral mRNAs often exhibit 5’ untranslated regions that differ substantially from cellular mRNAs. These regions are not translated into proteins but play critical roles in regulating translation efficiency. Many viruses possess notably short 5’ UTRs, a trait that facilitates rapid production of viral proteins upon infection but simultaneously presents a diagnostic marker for cellular recognition. Through a combination of biochemical and structural investigations, the authors demonstrate that the IFIT2–IFIT3 complex exploits this trait by specifically recognizing the short 5’ UTRs as a viral signature, a mechanism that effectively discriminates self from non-self RNA.

This selective interaction orchestrated by IFIT2 and IFIT3 impedes the recruitment of key components of the translation initiation machinery to viral mRNAs. More precisely, the complex disrupts the assembly of the eukaryotic initiation factor 4F (eIF4F) complex and prevents ribosome loading onto viral mRNAs. Consequently, translation initiation is blocked, stalling viral protein synthesis and limiting viral replication in infected cells. This mode of action offers a potent defense strategy that targets a vulnerability shared across numerous viral families, potentially providing broad-spectrum antiviral capabilities.

The study’s utilization of in vitro translation assays combined with ribosome profiling techniques reveals a striking inhibition pattern that underscores the dependency of IFIT2–IFIT3-mediated repression on 5’ UTR length. Viral transcripts featuring short 5’ UTRs exhibited significant decreases in ribosome occupancy and protein output when the IFIT complex was active. In contrast, cellular mRNAs with longer 5’ UTRs were largely spared. Such selectivity minimizes collateral damage to the host’s own gene expression program, an elegant solution that preserves cellular homeostasis while mounting an effective antiviral attack.

Intriguingly, the researchers elucidate that IFIT3 serves as a stabilizing partner that enhances the binding affinity of IFIT2 toward viral mRNA substrates. The assembly of the heterodimeric IFIT2–IFIT3 complex constitutes a conformational assembly that optimizes RNA binding surfaces and interaction dynamics. These structural rearrangements enable the complex to finely tune its binding specificity and translate molecular recognition into a functional blockade of viral mRNA translation.

The implication of these findings extends beyond fundamental virology, potentially impacting the development of novel antiviral therapeutics. By mimicking or enhancing the IFIT2–IFIT3 interaction with viral mRNAs, it may be possible to design small molecules or biologics that selectively stifle viral translation without compromising host protein synthesis. Such strategies could offer an innovative approach in combating viruses that currently evade or resist classical antiviral drugs.

Given that many emerging viral pathogens employ short 5’ UTRs in their genomic and subgenomic RNAs, this newly characterized immune pathway represents a crucial hurdle that viruses must overcome to achieve successful replication. Future investigations may explore whether mutations that lengthen or otherwise alter viral 5’ UTRs can serve as viral escape mechanisms but at the cost of replicative fitness, thus highlighting a potential evolutionary trade-off shaped by host antiviral pressures.

Moreover, the study invites a reevaluation of the broader IFIT protein family’s roles in antiviral immunity. It is plausible that different IFIT heterocomplexes may recognize distinct RNA features beyond 5’ UTR length, adding layers of specificity and redundancy to the innate immune landscape. The molecular principles uncovered herein may serve as a template for dissecting other such interactions, broadening the horizon of translational control in viral infections.

Importantly, the findings delineate a critical temporal window during infection wherein the IFIT2–IFIT3 complex executes its antiviral function. Interferon induction leads to rapid protein accumulation, swiftly intercepting viral mRNAs before extensive protein synthesis occurs. This early intervention underscores the significance of host defenses that act at the interface of RNA recognition and translation, a frontline barrier preventing the establishment of infection.

The integration of interdisciplinary methods, ranging from high-resolution structural biology to live-cell imaging and transcriptomic profiling, fortifies the robustness of the conclusions drawn. Such comprehensive approaches exemplify the future of molecular virology research, wherein combined technological advances unravel the nuanced interplay between host and pathogen.

The advances reported in this paper underscore an emerging paradigm: antiviral immunity is not solely about recognition and degradation of viral genomes but also involves a nuanced regulation of viral gene expression at the translational level. This refinement allows host cells to apply selective pressure on the viral life cycle with remarkable precision.

As viral pandemics and epidemics continue to pose grave threats to global health, fundamental insights into innate antiviral mechanisms remain essential. The delineation of the IFIT2–IFIT3 complex’s targeting of short 5’ UTR viral mRNAs not only deepens mechanistic understanding but may pave the way to novel antiviral strategies aimed at a critical and conserved aspect of viral biology.

In conclusion, the elegant characterization of the IFIT2–IFIT3 antiviral complex highlights a highly sophisticated form of innate immune defense that exploits the molecular idiosyncrasies of viral mRNAs. By harnessing selective translation inhibition, this complex represents a formidable barrier against viral replication, adding a vital piece to the puzzle of host-pathogen interactions. Continued exploration of such mechanisms promises to enrich antiviral therapeutic landscapes and fortify preparedness against future viral outbreaks.

Subject of Research: Antiviral mechanisms of the IFIT2–IFIT3 complex targeting viral mRNAs via recognition of short 5’ untranslated regions.

Article Title: The IFIT2–IFIT3 antiviral complex targets short 5’ untranslated regions on viral mRNAs for translation inhibition.

Article References:
Glasner, D.R., Todd, C., Cook, B. et al. The IFIT2–IFIT3 antiviral complex targets short 5’ untranslated regions on viral mRNAs for translation inhibition. Nat Microbiol (2025). https://doi.org/10.1038/s41564-025-02138-w

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ZBP1 is a cytosolic sensor known to bind nucleic acids adopting the rare left-handed Z-conformation, particularly Z-RNA, facilitating programmed cell death pathways to counteract infection. Until now, viral RNAs were presumed to be the principal ligands triggering this pathway in HSV-1 and IAV infections. The current study, however, demonstrates that endogenous cellular transcripts are the primary ZBP1 activators under these conditions. This discovery was made possible by meticulous genome-wide mapping which pinpointed the source of these Z-RNAs within intergenic endogenous retroelements (EREs) nestled inside aberrantly elongated 3’ extensions of host mRNAs.

These findings hinge on the viral manipulation of host cell transcription termination. Specifically, both HSV-1 and IAV disrupt the function of Cleavage and Polyadenylation Specificity Factor (CPSF), a critical mediator of pre-mRNA 3’ end processing. The viral proteins ICP27 in HSV-1 and NS1 in IAV were shown to incapacitate CPSF, leading to a phenomenon termed Disruption of Transcription Termination (DoTT). DoTT results in extended nascent transcripts containing aberrantly long 3’ untranslated regions (UTRs) that encompass repetitive retroelement sequences capable of assuming the Z-RNA conformation. These extended transcripts accumulate extensively, providing the substrate for ZBP1 binding and activation.

Intriguingly, when scientists investigated mutant strains of HSV-1 and IAV lacking ICP27 or NS1, the viral proteins responsible for CPSF inhibition, the usual accumulation of host cell Z-RNAs was noticeably absent. This absence correlated directly with a marked reduction in ZBP1 activation and downstream cell death signaling. This causal relationship robustly underscores the critical role of DoTT-mediated transcripts in evoking host antiviral defense, rather than viral RNA species serving as the primary triggers.

Further reinforcing this model, experimental overexpression of either ICP27 or NS1 alone in uninfected cells recapitulated the phenomenon observed during viral infection. These manipulations elicited the accumulation of cellular Z-RNAs and consequent activation of ZBP1, mimicking infection-induced responses. Additionally, pharmacological inhibition of CPSF independently induced the same cascade, highlighting the sufficiency of transcription termination disruption in generating ZBP1 ligands.

The implications of these discoveries extend beyond mere mechanistic insights, shedding light on a sophisticated antiviral strategy employed by host cells. By converting viral-mediated transcriptional dysregulation into a distress signal, cells utilize ZBP1-mediated cell death as a barrier to limit viral spread. This cell death serves both to eliminate compromised cells and to alert neighboring cells to the presence of viral invasion.

Moreover, the localization of these host-derived Z-RNAs within endogenous retroelements underscores a fascinating cross-talk between transposable elements and innate immunity. Historically considered genomic parasites, EREs here emerge as critical platforms in the host antiviral arsenal, their sequences exploited to produce unique nucleic acid structures that activate immune sensors when dysregulated.

These findings bear significance for therapeutic strategies targeting virus-host interactions. Since ICP27 and NS1 function to subvert CPSF and, by extension, host mRNA processing, drugs modulating CPSF activity or stabilizing transcription termination fidelity could push viral infections into regimes favoring robust ZBP1 activation and subsequent viral clearance. Conversely, modulating ZBP1 signaling might offer pathways to curtail tissue damage arising from excessive cell death in viral diseases.

The delineation of DoTT-generated cellular Z-RNAs as bona fide ZBP1 ligands signifies a paradigm shift in understanding intracellular sensing of viral infections. This pivot from viral RNA-focused models to recognizing self-derived nucleic acid triggers reflects the dynamic co-evolution of viruses and their hosts, where cellular defense strategies capitalize on the perturbations viruses introduce into fundamental biological processes.

Beyond HSV-1 and IAV, it remains an open question whether other viral pathogens inducing transcriptional perturbations similarly exploit this mechanism to trigger ZBP1 activation. Future investigations could expand this framework, providing a broader map of host defense tactics mediated by transcriptional anomalies and nucleic acid structural motifs.

In sum, this study offers compelling evidence that disruption of host transcription termination by viral pathogens induces accumulation of cellular Z-RNAs embedded within elongated mRNAs. These cellular Z-RNAs act as potent triggers for ZBP1 activation, leading to programmed cell death as an antiviral strategy. This sophisticated interplay highlights the intricate molecular arms race at the interface of viral offense and host defense, illuminating new avenues for research and treatment in viral pathogenesis.

Subject of Research: Virus-host interactions focusing on the role of host cell Z-RNAs in activating ZBP1 during HSV-1 and Influenza A virus infections.

Article Title: Host cell Z-RNAs activate ZBP1 during virus infections.

Article References:
Yin, C., Fedorov, A., Guo, H. et al. Host cell Z-RNAs activate ZBP1 during virus infections. Nature (2025). https://doi.org/10.1038/s41586-025-09705-5

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APOBEC proteins serve as formidable viral restriction factors by catalyzing cytosine-to-uracil deamination on single-stranded viral DNA, incurring hypermutation and disruption of viral genomes. Among these proteins, APOBEC1, primarily known for its role in RNA editing, has recently been implicated in DNA editing that restricts HSV-1 replication. This antiviral function is premised on introducing uracil bases into the viral DNA, thereby targeting the genome for degradation or error-prone replication that compromises infectivity. While the APOBEC response is a critical aspect of the innate immune landscape confronting HSV-1 infections, how HSV-1 circumvents such cellular defences to establish lytic infection and cause lethal encephalitis has remained elusive.

In the new study using human carcinoma HEp-2 cells and controlled murine models, researchers elucidated the key role of HSV-1’s uracil-DNA glycosylase enzyme that is instrumental not only for viral DNA repair but also for viral immune evasion. Uracil-DNA glycosylase catalyzes the excision of uracil residues from DNA, a critical step in the base excision repair pathway that maintains genome integrity. Importantly, HSV-1 encodes a viral homolog of UNG that uniquely functions to remove uracil bases introduced by APOBEC1 editing on its DNA genomes during infection. This viral UNG activity counteracts detrimental editing inflicted by APOBEC1, effectively shielding HSV-1 genomes and facilitating productive viral replication.

The research team uncovered that phosphorylation of HSV-1 UNG is a prerequisite for its enzymatic activation and subsequent antiviral immune evasion functions. Phosphorylation, a common post-translational modification, dynamically regulates protein function and interaction networks. Mutating key phosphorylation sites on the viral UNG drastically impaired its ability to counter APOBEC1-mediated DNA editing. These mutant HSV-1 strains exhibited heightened susceptibility to APOBEC1’s antiviral activity and consequently showed reduced replication capacities within the central nervous system of infected mice.

Furthermore, the presence of host Apobec1 drastically influenced pathological outcomes during encephalitis caused by HSV-1 harboring defective UNG phosphorylation sites. Mice genetically competent for Apobec1 expression displayed more favorable disease courses when infected with these phosphorylation-deficient HSV-1 mutants, underscoring the pivotal role of APOBEC1 as a protective host factor. This phenomenon highlights a critical molecular axis between viral UNG-mediated DNA repair and host APOBEC1-driven intrinsic immunity in defining viral pathogenesis within the brain.

To explore potential therapeutic avenues, the investigators employed a strategy to inhibit viral UNG function by deploying an adeno-associated virus (AAV) vector engineered to express uracil glycosylase inhibitor (UGI), a potent suppressor of UNG activity. Treatment with this UNG inhibitor conferred pronounced protection in wild-type HSV-1-infected mice, significantly attenuating the severity of encephalitis and preventing lethal outcomes. This intervention effectively disrupted HSV-1’s capability to evade APOBEC1-mediated immunity, reinforcing the therapeutic potential of targeting viral DNA repair machinery to combat neurovirulent HSV-1 infections.

These findings consolidate the role of HSV-1 uracil-DNA glycosylase as a central viral factor enabling viral genomes to escape intrinsic antiviral restriction mechanisms orchestrated by APOBEC1. The study offers a refined molecular understanding of viral-host dynamics in the central nervous system, revealing how HSV-1 strategically capitalizes on protein phosphorylation to activate UNG and thwart host DNA editing defenses. Such mechanistic insights stir new hopes for innovative therapeutic interventions designed to tip the balance of infection in favor of the host and reduce the enormous neuropathological burden caused by HSV-1 encephalitis.

Beyond immediate clinical implications, this research enriches our broader comprehension of viral genome survival strategies against host-imposed hypermutation defenses. Viral adaptations involving genome maintenance enzymes such as UNG signify an evolutionary arms race between pathogen and host immune surveillance, wherein viruses continuously refine countermeasures against innate editing and repair catalysts. Understanding these processes at the biochemical and molecular levels might illuminate similar immune evasion tactics in other DNA viruses and inspire pan-viral antiviral targets.

The study’s use of both in vitro human cell systems and in vivo murine models provides compelling evidence aligning molecular phenomena with disease phenotypes. The translational relevance is profound, as it bridges previously scarce knowledge gaps regarding HSV-1’s evasion of APOBEC-driven intrinsic immunity within the brain milieu—a sanctuary site where immune access is tightly regulated and viral clearance presents unique challenges. These results emphasize the necessity to dig deeper into phosphorylation-dependent viral protein regulation as a potent modulator of pathogenesis.

Moreover, the therapeutic concept of utilizing viral vectors delivering inhibitors targeting viral DNA repair enzymes presents a novel modality that bypasses direct viral targeting, potentially circumventing resistance mechanisms linked to conventional antivirals. The ability to augment intrinsic immunity by blocking viral counter-defense enzymes introduces a paradigm-shifting approach that may have wide applicability across multiple viral infections characterized by similar immune escape strategies.

While the biochemical link between phosphorylation and UNG enzymatic activity emerges clearly, future studies are warranted to decode the upstream kinases involved, their signaling triggers, and temporal regulation throughout infection. Deciphering these phosphorylation networks could identify additional molecular nodes susceptible to pharmacological interference. Likewise, probing APOBEC1 regulation, nuclear localization, and potential interaction partners during HSV-1 infection will deepen holistic comprehension of intrinsic immunity within neuronal environments.

In sum, this seminal research uncovers a sophisticated viral immune evasion mechanism whereby HSV-1 phosphorylates and activates its uracil-DNA glycosylase enzyme to neutralize APOBEC1-mediated DNA editing. This dynamic interplay not only underpins viral genome integrity and survival amid host intrinsic antimicrobial pressures but also governs neuropathogenic outcomes during encephalitis. Pharmacologically blocking this viral glycosylase restores the antiviral efficacy of APOBEC1, revealing a promising therapeutic strategy to mitigate the devastating effects of HSV-1 infection in the central nervous system.

As viral encephalitis continues to exact a heavy toll globally, delineating mechanisms of host-pathogen conflict at the molecular level is imperative. The intersection of viral DNA repair enzymology, host APOBEC antiviral activity, and post-translational modifications characterized in this work represent a frontier in neurovirology and antiviral research. Harnessing such insights will undoubtedly accelerate the quest for durable treatments and improved prognoses for patients afflicted by HSV-1 encephalitis.

Subject of Research: The study investigates the molecular mechanism by which herpes simplex virus 1 (HSV-1) evades APOBEC1-mediated intrinsic antiviral immunity in the central nervous system via phosphorylation-dependent activation of the viral uracil-DNA glycosylase enzyme.

Article Title: Herpes simplex virus 1 evades APOBEC1-mediated immunity via its uracil-DNA glycosylase in mice.

Article References:
Kato, A., Harima, H., Tsunekawa, Y. et al. Herpes simplex virus 1 evades APOBEC1-mediated immunity via its uracil-DNA glycosylase in mice. Nat Microbiol (2025). https://doi.org/10.1038/s41564-025-02026-3

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