So-Yon Lim, Jina Lee, Christa E Osuna, Pratik Vikhe, Dane R Schalk, Elsa Chen, Emily Fray, Mithra Kumar, Nancy Schultz-Darken, Eva Rakasz, Saverio Capuano, Ruby A Ladd, Hwi Min Gil, David T Evans, Emily K Jeng, Michael Seaman, Malcolm Martin, Christiaan Van Dorp, Alan S Perelson, Hing C Wong, Janet D Siliciano, Robert Siliciano
8 min
Eliminating the latent HIV-1 viral reservoir—the population of cells harboring replication-competent virus—remains the primary barrier to a clinical cure. Current antiretroviral therapy (ART) effectively suppresses active replication but cannot clear this latent reservoir. The authors of this study investigated whether a combination of N-803 (an IL-15 superagonist that activates NK and CD8+ T cells) and broadly neutralizing antibodies (bNAbs) could facilitate immune-mediated control of the virus even after ART is discontinued.
Researchers conducted two studies using a total of 36 rhesus macaques infected with the pathogenic SHIV-AD8 virus. After stabilizing the infection with daily ART, the monkeys were treated with N-803 alone, bNAbs alone, or a combination of both. Following a period of treatment, ART was withdrawn to monitor for viral rebound. The researchers tracked immune cell activation (particularly CD8+ T cells), changes in the viral reservoir, and the durability of viral suppression after treatment cessation. They further confirmed the role of CD8+ T cells through in vivo depletion experiments.
The combination of N-803 and bNAbs demonstrated a clear synergistic effect. While N-803 administration alone induced transient viremia and immune activation, it did not lead to sustained control after ART discontinuation. However, in approximately 70% of the animals treated with the combination therapy, researchers observed long-term viral control despite the presence of the viral reservoir. This control was not due to a massive reduction in the reservoir size, but rather a functional reprogramming of CD8+ T cells that allowed the immune system to suppress viral rebound. Depletion of CD8+ cells confirmed that these cells were essential for maintaining the aviremic state.
These results provide a proof-of-concept that a functional cure—where the body controls the virus without medication—does not necessarily require the complete eradication of every infected cell. By enhancing the quality of the existing CD8+ T cell response through this dual-agent strategy, it may be possible to induce durable remission in individuals living with HIV.
The eradication of the viral reservoir represents the major obstacle to the development of a clinical cure for established HIV-1 infection. Here, we demonstrate that the administration of N-803 (brand name Anktiva) and broadly neutralizing antibodies (bNAbs) results in sustained viral control after discontinuation of antiretroviral therapy (ART) in simian-human AD8 (SHIV-AD8)–infected, ART-suppressed rhesus macaques. N-803+bNAbs treatment induced immune activation and transient viremia but only limited reductions in the SHIV reservoir. Upon ART discontinuation, viral rebound occurred in all animals, which was followed by durable control in approximately 70% of all N-803+bNAb–treated macaques. Viral control was correlated with the reprogramming of CD8 + T cells by N-803+bNAb synergy. Thus, complete eradication of the replication-competent viral reservoir is likely not a prerequisite for the induction of sustained remission after discontinuation of ART. , Editor’s summary Although antiretroviral therapy (ART) effectively manages HIV infection by inhibiting the ability of the virus to replicate, it cannot completely eradicate the latent viral reservoir, frustrating the ultimate clinical goal of a functional cure. Lim et al . used broadly neutralizing antibodies against the HIV-1 envelope, along with a soluble interleukin-15 superagonist that activates and expands natural killer and CD8 + T cells, to treat rhesus macaques infected with SIV-HIV chimeric virus after the discontinuation of ART. This combined superagonist-antibody treatment induced long-term viral control in more than 70% of infected animals primarily through enhanced CD8 + T cell responses, suggesting that the complete eradication of the HIV reservoir may not be needed for sustained remission after discontinuation of ART. —Seth Thomas Scanlon , A combination therapy–induced vaccinal effect can induce long-term remission from SHIV infection after ART discontinuation.
Alex: Across both experiments, there were 36 animals. The first compared the stimulant alone, an antibody alone, their combination, and a vehicle control. Animals had been suppressed on antiviral drugs for roughly a year before the experimental treatment began.
Sam: Keeping the drugs in place seems central. What happened when they stimulated immunity during that suppression?
Alex: The stimulant activated T cells and natural killer cells, another antiviral immune population. It also produced brief episodes of detectable virus in the blood. Those episodes generally subsided before the next dose, despite continued antiviral treatment.
Sam: So the treatment was exposing some virus while stimulating immune cells. Did the authors show that this trained a better antiviral response?
Alex: They found evidence consistent with that, but the proposed training mechanism remains a hypothesis. One possibility is that antibodies bind the newly available virus. Those complexes could help other immune cells present viral material and strengthen the T-cell response.
Sam: Before we get to that mechanism, how do we know later control wasn't simply the infused antibodies still working?
Alex: They monitored antibody clearance and waited for washout before stopping antiviral drugs. All animals then rebounded, with no significant difference in time to rebound between groups. The benefit was later control, not preventing that initial return.
Sam: How many animals reached that later control, and what was the comparison?
Alex: In the first experiment, three of five combination-treated animals developed durable control, with a lower eventual viral level than controls. Neither treatment alone showed the combination's pattern of enhanced suppression in the authors' modeling analysis. The investigators then ran a second experiment using the stimulant with two antibodies instead of one.
Sam: Did that second experiment reproduce the result?
Alex: Six of eight combination-treated animals achieved sustained control after a brief rebound and some fluctuating low-level virus. Compared with vehicle controls, treated animals had significantly lower eventual viral levels and lower total viral burden. Control developed by about day eighty after drug withdrawal and persisted through follow-up.
Sam: That gives the result another experimental test, but the antibody regimen changed. We can't treat it as a clean comparison of one antibody against two.
Alex: We can't. Pooled across experiments, nine of thirteen combination-treated animals controlled the virus. That's about seventy percent, but these are small groups with different regimens, not an estimate of how often this would work in people.
Sam: The central claim depends on hidden virus remaining. How thoroughly did they look for it?
Alex: They sampled blood and lymph nodes, and attempted measurements in gut tissue. In the second experiment, intact viral DNA was largely unchanged in blood cells. It declined modestly in lymph nodes, while gut samples yielded too little material for that assay.
Sam: So this isn't evidence that the reservoir was untouched everywhere. It's evidence that control occurred without its complete removal.
Alex: That's the distinction. The first experiment also found little overall change in integrated viral DNA in blood and lymph nodes. Gut measurements were variable, and the authors acknowledged possible sampling inconsistency. Their conclusion is sustained remission despite a persisting reservoir, not eradication.
Sam: How did they test whether immune cells were actively holding that remaining virus down?
Alex: They temporarily depleted CD8-positive lymphocytes in animals that had achieved control. Virus rapidly surged back. As those cells recovered, the treated animals suppressed virus again, whereas controls remained viremic, meaning virus remained detectable in their blood.
Sam: That is a useful intervention, but does depletion isolate the T cells specifically?
Alex: Not by itself. The depletion also affects natural killer cells. The stronger case for T cells comes from combining that result with separate tests of their function outside the animals.
Sam: What did those separate tests show that the depletion couldn't?
Alex: The researchers mixed infected cells with purified CD8-positive T cells from the same animal. Cells collected before treatment suppressed virus weakly. Cells collected later from treatment responders suppressed it much more strongly, while responders also showed enhanced production of molecules involved in antiviral activity.
Sam: So the evidence converges: control breaks when the cell population is depleted, and isolated T cells become better suppressors.
Alex: That supports a central role for those cells. The researchers also found limited antibody-dependent killing activity after antibody washout, and low natural neutralizing responses in both groups. Those results make continuing antibody activity a less persuasive explanation, without proving every step of the proposed immune-training mechanism.
Sam: For someone deciding whether to read this closely, where does the evidence end?
Alex: It ends with a controlled macaque model and finite follow-up, not demonstrated HIV remission in people. The authors explicitly acknowledge differences between these infections. I find the converging experiments persuasive within this model, but the small groups cannot establish human efficacy or identify the best regimen.
Sam: Who should read the full document, and where should they start?
Alex: Researchers working on HIV remission, therapeutic antibodies, or antiviral T cells should read it closely. Start with the treatment comparisons and the sections on correlates of viral control. Then read the vaccinal-effect section, separating the measured T-cell changes from the proposed antibody-assisted training mechanism. For everyone else: controlling the remaining virus may matter as much as removing it.
Sam: Thanks for listening.