Antiretroviral therapy transformed HIV from a nearly uniform death sentence into a manageable chronic condition by blocking new rounds of infection. Yet the therapy does nothing to the proviral DNA already stitched into the genomes of long-lived host cells. As soon as treatment lapses, the reservoir seeds rapid viral rebound. Understanding why particular infected clones persist for years, while others decay, has therefore become one of the most consequential questions in HIV research, and the new findings suggest the answer lies partly in the immune environment the reservoir cells inhabit rather than in the virus alone.

Natural killer cells are innate lymphocytes that patrol the body and kill stressed or infected cells without requiring the antigen-specific recognition that defines T and B lymphocytes. Their activity is governed by a delicate balance of activating and inhibitory receptors. KIR2DL1 is an inhibitory killer-cell immunoglobulin-like receptor that recognizes specific HLA class I molecules, the same surface proteins that HIV-exposed cells display. The education model of NK cell biology holds that a developing NK cell calibrates its functional competence through interactions between its inhibitory receptors and self-HLA; a KIR2DL1-positive NK cell in an individual carrying the corresponding HLA ligand becomes ‘educated,’ or licensed, to respond vigorously when that ligand is lost or altered, as frequently happens during viral infection.

The study demonstrates that these education states are not a fleeting influence but leave durable imprints on the reservoir. By examining cells from people who had spent years, in some cases many years, on suppressive antiretroviral regimens, the researchers found that proviruses surviving over the long term were not distributed randomly across the infected cell population. Instead, their persistence correlated with features of the innate immune landscape, indicating that some infected cells had been preferentially spared or eliminated depending on how the NK cell compartment of that individual had been trained.

This reframes the reservoir as an active participant in a prolonged evolutionary standoff with the immune system. Cells harboring intact, replication-competent proviruses that somehow avoid NK-mediated killing gain a survival advantage and expand, sometimes through clonal proliferation, over years of therapy. Cells that present vulnerabilities to educated NK cells are progressively culled. The result is a reservoir sculpted by immune pressure, analogous in some respects to how antigen escape shapes the evolution of the virus in untreated infection, but operating here through germline-encoded innate receptors rather than clonal adaptive recognition.

The technical achievement underlying these conclusions is considerable. Single-cell approaches now allow researchers to connect proviral sequence, integration site, transcriptional state, and surface phenotype in the same individual cell, converting what was once a population-level average into a high-resolution map of reservoir heterogeneity. Combined with deep characterization of NK cell receptor repertoires and their HLA ligands in each study participant, such methods make it possible to ask which immune configurations leave measurable signatures on which reservoir lineages, and the study deployed precisely this integrative strategy across cohorts on long-term therapy.

The clinical implications are potentially far-reaching. Current cure strategies aim to ‘shock and kill’ the reservoir, using latency-reversing agents to force latent proviruses into expression so that immune or pharmacological effectors can destroy the exposed cells. If KIR2DL1-educated NK cells already exert selection pressure on the reservoir, then the efficiency of such interventions may depend heavily on whether the killing arm of the strategy is matched to the individual’s NK cell education status and HLA type. A shock-and-kill regimen delivered to a person whose NK cells are poorly licensed against their own reservoir cells might flush virus into the open without achieving meaningful depletion.

This line of thinking points toward precision immunotherapies for HIV. Just as cancer immunotherapy increasingly considers the tumor microenvironment and the patient’s innate immune competence, curative interventions for HIV may need to account for innate immune imprints. Engaging NK cells deliberately, through bispecific killer-cell engagers, cytokine modulation, or engineered NK products, could in principle tip the standoff in favor of the host. Conversely, therapies that inadvertently impair NK education or function might relax selection pressure and allow reservoir clones to expand unchecked during what was assumed to be stable suppression.

The findings also resonate with a broader shift in virology: the recognition that innate immunity is not merely a rapid first response but a long-lived determinant of infection outcomes. Trained immunity, NK cell memory-like behavior, and receptor education all illustrate that innate cells carry histories. In chronic infections treated for years with suppressive drugs, those histories accumulate and leave fingerprints on the surviving pathogen population. HIV, the most intensively studied persistent human virus, now appears to bear such fingerprints in its reservoir.

Substantial questions remain. The relationship between KIR2DL1 education and reservoir persistence will need to be validated across larger and more diverse cohorts, since KIR and HLA genotype distributions vary substantially across populations, and HIV epidemiology is concentrated in regions where such genetic diversity is greatest. Whether innate selection can be therapeutically harnessed to shrink the reservoir, or only to shape it, is unresolved. But the conceptual contribution is clear: the latent HIV reservoir is not hidden from the immune system in any absolute sense. It has been living under innate immune surveillance all along, and the cells that persist during long-term antiretroviral therapy are, in part, the survivors of that surveillance. Any credible path to a cure will have to reckon with the imprints that this ancient arm of immunity has already left on the virus’s last refuge.

Subject of Research: The influence of KIR2DL1-educated natural killer cells on the persistence of latent HIV-1 reservoir cells during long-term antiretroviral therapy.

Article Title: Innate immune imprints shape HIV-1 reservoir cell persistence during long-term antiretroviral therapy

Article References: Tan, T. S., Sun, W., Gao, C., Viard, M., Walters, L. C., Lancien, M., Yuki, Y., Van, T. N., Casquero, C., Guo, X., Hoh, R., Haas, D. W., Michael, N., Kirk, G. D., Yendewa, G., Gandhi, R. T., Kassaye, S. G., Tien, P. C., Walker, B. D., … Lichterfeld, M. (2026). Innate immune imprints shape HIV-1 reservoir cell persistence during long-term antiretroviral therapy. Nature Immunology. https://doi.org/10.1038/s41590-026-02637-w

Image Credits: AI Generated

DOI: 10.1038/s41590-026-02637-w

Keywords: HIV-1, viral reservoir, natural killer cells, KIR2DL1, NK cell education, antiretroviral therapy, viral latency, innate immunity, HIV cure research, Nature Immunology, immunotherapy, proviral persistence

Published in Nature Microbiology, the study tested a regimen combining standard antiretroviral therapy, broadly neutralizing antibodies and leronlimab, an experimental monoclonal antibody that blocks the CCR5 receptor used by many HIV strains to enter immune cells. The treatment was administered to infant macaques shortly after infection and continued for several weeks. According to the researchers, the combination limited the formation of viral reservoirs and achieved results that none of the individual treatments had produced on its own.

The findings remain preclinical and do not demonstrate that HIV can currently be permanently cleared in human newborns. However, they address a central obstacle in HIV medicine: the virus can integrate its genetic material into the DNA of infected cells soon after exposure, creating latent reservoirs that are largely invisible to both the immune system and conventional antiretroviral drugs. Once these reservoirs are established, stopping therapy can allow the virus to rebound. Preventing or sharply reducing reservoir seeding during the earliest phase of infection could therefore be more effective than attempting to eliminate a mature reservoir later.

The study was led by Jonah Sacha, a professor and chief of pathobiology and immunology at OHSU’s Oregon National Primate Research Center and Vaccine and Gene Therapy Institute, and Nancy Haigwood, a virologist and immunologist who has spent decades studying HIV antibodies. The experiments involved researchers and animals from both the Oregon and California national primate research centers. The infant macaque model was used because the animals share important anatomical, immunological and virological characteristics with humans, while allowing scientists to examine the earliest events following infection in a controlled setting.

Each component of the regimen was designed to interrupt a different stage of HIV’s spread. Antiretroviral drugs suppress viral replication by targeting enzymes and other processes required for the production of new virus particles. Broadly neutralizing antibodies, or bNAbs, bind to vulnerable regions on the viral surface and can block infection by multiple HIV variants. They may also help recruit immune cells to remove antibody-coated virus and infected cells. Leronlimab adds a third layer of protection by binding to CCR5, a chemokine receptor on the surface of many immune cells that HIV uses as a coreceptor during entry.

The researchers describe the combined effect as complementary rather than simply additive. Antiretroviral therapy reduces the amount of virus being produced, while neutralizing antibodies can capture or disable virus circulating in the bloodstream. CCR5 blockade then makes susceptible immune cells less accessible to viral entry. This layered approach may be particularly powerful during the first days of infection, when HIV is spreading rapidly from initial sites of exposure and beginning to populate tissues that can later serve as long-lived reservoirs.

The precise biological mechanism behind the apparent clearance is not yet fully understood. The investigators reported that the treatment prevented or greatly restricted reservoir seeding in the infant macaques, but further work will be needed to determine whether all replication-competent virus was eliminated or whether residual virus remained below the limits of detection. Studies will also need to establish how long protection lasts, whether the result can be reproduced with different viral strains and treatment doses, and whether the therapy remains effective when administration is delayed beyond the first 72 hours.

The timing question is especially important for clinical use. Newborns exposed to HIV may not be identified immediately, and the circumstances of exposure vary widely. The researchers plan to investigate whether the combination can work when given one or two weeks after infection rather than within three days. They also want to determine whether the approach could benefit adults who have recently acquired HIV, when viral reservoirs may still be relatively limited. Any human application would require carefully designed clinical trials, beginning with studies of safety, dosing, immune effects and viral rebound after treatment interruption.

Antiretroviral therapy is already approved for human use, while bNAbs and leronlimab are being evaluated separately in clinical research. Leronlimab’s development has included efforts to use CCR5 blockade as a way to prevent HIV entry into immune cells, but blocking CCR5 alone has not been sufficient to eradicate established infection. The new study suggests that its greatest potential may lie in combination therapy administered immediately after exposure, before the virus has fully entrenched itself in the body.

The researchers emphasize that the work represents a possible strategy, not an available cure. HIV continues to cause hundreds of thousands of deaths globally each year, and access to lifelong treatment remains uneven. A safe, single-course intervention for newborns could substantially reduce the burden of pediatric HIV, particularly in settings where continuous treatment is difficult to maintain. The study was supported by several National Institutes of Health institutes and programs. OHSU disclosed that Sacha and co-author Scott Hansen have significant financial interests in CytoDyn, a company that may have a commercial interest in the research and related technology.

Subject of Research: Infant macaque model of HIV; implications for newborn HIV infection

Article Title: Combination therapy with broadly neutralizing antibodies, antiretroviral therapy and CCR5 blockade limits viral reservoir seeding in infant macaque model of HIV

News Publication Date: 10-Aug-2026

Web References: OHSU research announcement: https://news.ohsu.edu/; DOI: https://doi.org/10.1038/s41564-026-02444-x

References: Nature Microbiology, DOI: 10.1038/s41564-026-02444-x

Keywords: HIV, AIDS, newborn infection, infant macaques, viral reservoirs, broadly neutralizing antibodies, antiretroviral therapy, leronlimab, CCR5 blockade, HIV cure research, viral suppression, infectious disease, virology

Building on this foundation, a pioneering scientific collaboration co-led by Dr. Lishomwa Ndhlovu at Weill Cornell Medicine and Dr. Jonah Sacha at Oregon Health & Science University has now gained significant momentum. Recently awarded an NIH MERIT Award, their ambitious research program aims to unravel the biological and immunological mechanisms responsible for the eradication of HIV in patients who have undergone similar stem cell transplants. With approximately $8.2 million in funding guaranteed over an initial five years, with a potential extension up to ten, this endeavor represents a vital step forward in translating rare cure cases into scalable therapeutic strategies.

The crux of their research hinges on understanding why such transplants led to complete viral clearance in some patients but failed in others, despite the uniformity of the procedure. Bone marrow transplantation, although a potential cure, remains a burdensome intervention with considerable risks including graft-versus-host disease, severe immunosuppression, and life-threatening complications. As Dr. Ndhlovu emphasizes, the group’s focus is on deciphering the immune responses that mediate viral eradication in those few exceptional survivors, to inform the design of less invasive, broadly applicable immunotherapies against HIV.

One of the distinctions of this research is its comprehensive analysis of immune function drawn from a unique cohort of individuals who have undergone stem cell transplantation for hematologic malignancies. These participants, including some like Marc Franke, Adam Castillejo, and Paul Edmonds—who have bravely shared their journeys—have contributed invaluable clinical samples and insights. Crucially, all these individuals have ceased antiretroviral therapy without viral rebound, constituting a functional cure, a testament to the profound immune reconstitution they experienced.

Central to the investigative approach are state-of-the-art immunological assays and molecular profiling methods designed to interrogate the cellular and humoral arms of the immune system. By evaluating the landscape of T-cell responses, natural killer cell activity, and the presence or absence of viral reservoirs, the researchers strive to pinpoint the particular immune signatures associated with HIV eradication. Such granular mechanistic data are expected to shed light on the interplay between host immunity, viral persistence, and the unique features of donor-derived hematopoietic cells.

Complementary to human studies, the research leverages innovative preclinical models to replicate and validate findings. At Weill Cornell, a sophisticated humanized mouse model equipped with HIV-infected human immune cells allows dissection of immune cell functions in vivo, offering dynamic insights into viral clearance processes. Meanwhile, Dr. Sacha and his team at Oregon Health & Science University have engineered a non-human primate model closely mimicking human immune reconstitution following stem cell transplantation, successfully reproducing virus-clearing phenomena. These platforms provide critical translational bridges from bench to bedside.

The ultimate vision driving this endeavor is the development of a novel immunotherapy capable of selectively targeting and eliminating HIV-infected cells without the need for risky bone marrow transplantation. By harnessing the immune mechanisms elucidated through their studies, the investigators hope to engineer targeted cell-based or molecular treatments that can replicate the ‘cure effect’ safely and effectively in a wider population of people living with HIV.

This research undertaking not only advances scientific understanding but also embodies the spirit of human resilience and altruism. Participants like Adam Castillejo, who became the second person publicly declared cured of HIV after Brown, actively engage as advocates and collaborators. Their willingness to contribute to science underscores an ethical commitment to leverage personal experiences for global health impact. Castillejo, now a Global HIV Ambassador, envisions this collaboration as pivotal in extinguishing the AIDS pandemic.

Furthermore, the study holds significant implications for immunology and infectious disease fields at large. An in-depth characterization of immune system recalibration post-transplant may reveal novel pathways applicable to other viral infections and malignancies. By dissecting how donor hematopoietic cells remodel immunity and confer resistance to HIV, scientists can better understand immune plasticity, tolerance, and memory in contexts of chronic infection.

While the research journey is fraught with complexity, the stakes are tremendous. As participant Paul Edmonds, living with HIV for over thirty years prior to his transplant, expresses, the hope is that these investigations will yield therapies that eradicate the virus indefinitely. The intersection of cutting-edge cellular biology, immunotherapy, and translational medicine in this study exemplifies the innovative drive needed to confront one of humanity’s most enduring viral scourges.

In summary, the NIH MERIT Award-supported project spearheaded by Drs. Ndhlovu and Sacha represents a strategic and multidisciplinary approach to unlock the mysteries underlying the rare phenomenon of HIV cure following stem cell transplantation. By meticulously dissecting immune correlates of viral clearance and validating them in robust animal models, this research aspires to catalyze development of safe, effective, and scalable curative immunotherapies. The collaboration offers an inspiring blueprint of hope emerging from scientific rigor and human courage.

Subject of Research: HIV cure mechanisms following stem cell transplantation and development of immunotherapy to eradicate HIV.

Article Title: Not provided.

News Publication Date: Not provided.

Web References:

• Timothy Ray Brown cure report: https://www.liebertpub.com/doi/10.1089/aid.2014.0224
• HIV-free patient study: https://pubmed.ncbi.nlm.nih.gov/39484913/
• Non-human primate model detailed study: https://www.cell.com/immunity/fulltext/S1074-7613(23)00216-9?_returnURL=https%3A%2F%2Flinkinghub.elsevier.com%2Fretrieve%2Fpii%2FS1074761323002169%3Fshowall%3Dtrue

References: Not provided.

Image Credits: Dr. Lishomwa Ndhlovu

Keywords: HIV research; Human immunodeficiency virus; Stem cells; Cancer