Therapeutic efficacy of combined active and passive immunization in ART-suppressed, SHIV-infected rhesus macaques.

The latent viral reservoir is the critical barrier for developing an HIV-1 cure. Previous studies have shown that therapeutic vaccination or broadly neutralizing antibody (bNAb) administration, together with a Toll-like receptor 7 (TLR7) agonist, enhanced virologic control or delayed viral rebound, respectively, following discontinuation of antiretroviral therapy (ART) in SIV- or SHIV-infected rhesus macaques. Here we show that the combination of active and passive immunization with vesatolimod may lead to higher rates of post-ART virologic control compared to either approach alone. Therapeutic Ad26/MVA vaccination and PGT121 administration together with TLR7 stimulation with vesatolimod resulted in 70% post-ART virologic control in SHIV-SF162P3-infected rhesus macaques. These data suggest the potential of combining active and passive immunization targeting different immunologic mechanisms as an HIV-1 cure strategy.

Safety and antiviral activity of triple combination broadly neutralizing monoclonal antibody therapy against HIV-1: a phase 1 clinical trial.

HIV-1 therapy with single or dual broadly neutralizing antibodies (bNAbs) has shown viral escape, indicating that at least a triple bNAb therapy may be needed for robust suppression of viremia. We performed a two-part study consisting of a single-center, randomized, double-blind, dose-escalation, placebo-controlled first-in-human trial of the HIV-1 V2-glycan-specific antibody PGDM1400 alone or in combination with the V3-glycan-specific antibody PGT121 in 24 adults without HIV in part 1, as well as a multi-center, open-label trial of the combination of PGDM1400, PGT121 and the CD4-binding-site antibody VRC07-523LS in five viremic adults living with HIV not on antiretroviral therapy (ART) in part 2 ( NCT03205917 ). The primary endpoints were safety, tolerability and pharmacokinetics for both parts and antiviral activity among viremic adults living with HIV and not on ART for part 2 of the study. The secondary endpoints were changes in CD4+ T cell counts and development of HIV-1 sequence variations associated with PGDM1400, PGT121 and VRC07-523LS resistance in part 2. Intravenously administered PGDM1400 was safe and well-tolerated at doses up to 30 mg kg-1 and when given in combination with PGT121 and VRC07-523LS. A single intravenous infusion of 20 mg kg-1 of each of the three antibodies reduced plasma HIV RNA levels in viremic individuals by a maximum mean of 2.04 log10 copies per ml; however, viral rebound occurred in all participants within a median of 20 days after nadir. Rebound viruses demonstrated partial to complete resistance to PGDM1400 and PGT121 in vitro, whereas susceptibility to VRC07-523LS was preserved. Viral rebound occurred despite mean VRC07-523LS serum concentrations of 93 µg ml-1. The trial met the pre-specified endpoints. Our data suggest that future bNAb combinations likely need to achieve broad antiviral activity, while also maintaining high serum concentrations, to mediate viral control.

Characterization of Elite Suppressors Cell-Associated HIV-1 mRNA at Baseline and with T Cell Activation

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Objective: Elite Controllers or Suppressors (ES) are patients who control HIV replication without antiretroviral therapy. In this study, we compared baseline and inducible HIV-1 mRNA levels in CD4+ T cells from ES and chronic progressors (CPs) receiving suppressive antiretroviral therapy. Methods: We quantified basal levels of cell associated HIV-1 mRNA in CD4+ T cells isolated from CPs and ES. Additionally, we measured the fold upregulation of intracellular HIV-mRNA after stimulation of CD4+ T cells with phorbol 12-myristate 13-acetate (PMA) and ionomycin, and quantified the amount of HIV-mRNA levels released into culture supernatant. Results: ES have significantly less cell associated HIV-mRNA per 5x106 cells (p = 0.003); 8 of 10 CPs had quantifiable HIV-1 mRNA at baseline, whereas this was present in only 2 of 10 ES. Upon stimulation with PMA and ionomycin, 4 of 5 CPs and 7 of 9 ES showed increased cell associated HIV-mRNA. Interestingly, released HIV-1 mRNA could be detected in supernatants of CD4+ T cells stimulated with PMA/ionomycin from 5 of 8 ES. Conclusion: Our results demonstrate that while the baseline levels of cell associated HIV-1 mRNA are significantly lower in ES compared to CPs, stimulation of CD4+ T cells results in a comparable relative upregulation of viral transcription.

Reactivation Kinetics of HIV-1 and Susceptibility of Reactivated Latently Infected CD4+ T Cells to HIV-1-Specific CD8+ T Cells.

UNLABELLED: The "shock and kill" model of human immunodeficiency virus type 1 (HIV-1) eradication involves the induction of transcription of HIV-1 genes in latently infected CD4(+) T cells, followed by the elimination of these infected CD4(+) T cells by CD8(+) T cells or other effector cells. CD8(+) T cells may also be needed to control the spread of new infection if residual infected cells are present at the time combination antiretroviral therapy (cART) is discontinued. In order to determine the time frame needed for CD8(+) T cells to effectively prevent the spread of HIV-1 infection, we examined the kinetics of HIV transcription and virus release in latently infected cells reactivated ex vivo. Isolated resting, primary CD4(+) T cells from HIV-positive (HIV+) subjects on suppressive regimens were found to upregulate cell-associated HIV-1 mRNA within 1 h of stimulation and produce extracellular virus as early as 6 h poststimulation. In spite of the rapid kinetics of virus production, we show that CD8(+) T cells from 2 out of 4 viremic controllers were capable of effectively eliminating reactivated autologous CD4(+) cells that upregulate cell-associated HIV-1 mRNA. The results have implications for devising strategies to prevent rebound viremia due to reactivation of rare latently infected cells that persist after potentially curative therapy. IMPORTANCE: A prominent HIV-1 cure strategy termed "shock and kill" involves the induction of HIV-1 transcription in latently infected CD4(+) T cells with the goal of elimination of these cells by either the cytotoxic T lymphocyte response or other immune cell subsets. However, the cytotoxic T cell response may also be required after curative treatment if residual latently infected cells remain. The kinetics of HIV-1 reactivation indicate rapid upregulation of cell-associated HIV-1 mRNA and a 5-h window between transcription and virus release. Thus, HIV-specific CD8(+) T cell responses likely have a very short time frame to eliminate residual latently infected CD4(+) T cells that become reactivated after discontinuation of antiretroviral therapy following potentially curative treatment strategies.

Comparative analysis of the capacity of elite suppressor CD4+ and CD8+ T cells to inhibit HIV-1 replication in monocyte-derived macrophages.

UNLABELLED: Elite controllers or suppressors (ESs) are HIV-1-infected individuals who are able to maintain viral loads below the limit of detection of clinical assays without antiretroviral therapy. The mechanisms of virologic control are not fully understood, but ESs have been shown to have a more effective CD8+ T cell response to infected CD4+ T cells than chronic progressors (CPs). While macrophages are another cell type productively infected by HIV-1, few studies have examined the ability of primary effector T cells to suppress HIV-1 replication in these target cells. Here, we compared the ability of unstimulated primary CD4+ and CD8+ effector T cells to suppress viral replication in monocyte-derived macrophages (MDMs) in ESs and CPs. While CD4+ effector T cells were capable of inhibiting viral replication in MDMs, the magnitude of this response was not significantly different between ESs and CPs. In contrast, the CD8+ T cells from ESs were significantly more effective than those from CPs at inhibiting viral replication in MDMs. The CD4+ T cell response was partially mediated by soluble factors, while the CD8+ T cell response required cell-to-cell interaction. Our results suggest that the individual contributions of various effector cells should be considered in rational vaccine design and in ongoing eradication efforts. IMPORTANCE: Elite suppressors are individuals capable of maintaining low-level viremia in HIV-1 infection without antiretroviral drugs. Their T cell responses have been implicated in eliminating infected CD4+ T cells, and as such, elite suppressors may represent a model of a functional cure of HIV-1 infection. Here, we sought to determine whether the suppressive T cell responses against infected CD4+ T cells also apply to infected macrophages by comparing the responses of elite suppressors and HIV-1-positive individuals on highly active antiretroviral therapy (HAART). Our results show that the CD8+ cells but not CD4+ T cells from elite suppressors have a response against infected macrophages superior to the response of CD8+ cells from patients on HAART. Our results suggest that the induction of a CD8+ T cell response effective against infected macrophages is an outcome to consider in rational vaccine design.