Safety, immunogenicity and effect on viral rebound of HTI vaccines in early treated HIV-1 infection: a randomized, placebo-controlled phase 1 trial

Post-intervention control in HIV immunotherapy trials

PURPOSE OF REVIEW

While post-treatment control following interruption of standard-of-care antiretroviral therapy (ART) is well described, post-intervention control following immunotherapy in HIV cure-related clinical trials is less well understood. We provide an overview of recent studies that have identified post-intervention controllers and review the mechanisms that may drive this biologically important phenotype.

RECENT FINDINGS

Post-intervention controllers have been identified in recent immunotherapy trials testing broadly neutralizing antibodies, immune modulators, modified T cells, checkpoint inhibitors, and gene therapy administered individually or in combination. Currently, there is substantial variability in how each trial defines post-intervention control, as well as in how the mechanisms underlying such control are evaluated. Such mechanisms include ongoing activity of both exogenous and autologous antibodies, as well as changes in HIV-specific T cell function.

SUMMARY

While no therapeutic strategy to date has succeeded in definitively inducing HIV control, many studies have identified at least a small number of post-intervention controllers. The field would benefit from a standardized approach to defining and reporting this phenotype, as well as standardization in the approach to assessment of how it is achieved. Such efforts would allow for comparisons across clinical trials and could help accelerate efforts toward an HIV cure.

Biotech's role in advancing HIV vaccine development

HIV vaccine development has been hindered by significant challenges over four decades. Despite persistent efforts, all efficacy trials to date have yielded disappointing results. This has pushed the field back to the discovery phase and created uncertainty about the future involvement of large pharmaceutical companies. Currently, the HIV vaccine landscape is dominated by startup biotech firms, which face a complex array of obstacles. These include evolving HIV prevention methods, waning interest in vaccine research, and difficulties securing sustainable funding. This viewpoint explores the challenges faced by these biotech companies and the support mechanisms necessary for their continued involvement in HIV vaccine development. By leveraging insights from both pharmaceutical and biotech sectors, we propose a multi-faceted approach that includes enhanced communication, fostering innovation, and implementing strategic funding models.

Safety and immunogenicity of the ChAdOx1-MVA-vectored conserved mosaic HIVconsvX candidate T-cell vaccines in HIV-CORE 005.2, an open-label, dose-escalation, first-in-human, phase 1 trial in adults living without HIV-1 in the UK

BACKGROUND

An HIV-1 vaccine is long overdue. Although vaccine research focuses on the induction of broadly neutralising antibodies, challenging infections such as HIV-1 could require parallel induction of protective T cells. It is important to recognise that not all T cells contribute to protection equally. Previously, we developed a T-cell immunogen-based bivalent mosaic vaccine, HIVconsvX, delivered by vaccine vectors ChAdOx1 and modified vaccinia Ankara. In this study, we tested the HIVconsvX vaccine regimen for the first time in humans. Other ongoing trials will assess the contribution of the vaccine-induced killer T cells to the control of HIV-1.

METHODS

HIV-CORE 005.2 was an open-label, dose-escalation, first-in-human, phase 1 trial done at the Centre for Clinical Vaccinology and Tropical Medicine, University of Oxford, Oxford, UK. Eligible participants were healthy volunteers aged 18-65 years living without HIV-1 and at a low likelihood of acquiring it. Because it was the first administration of ChAdOx1.tHIVconsv1 (C1) to humans, participants were assigned stepwise to two groups. Volunteer group 1 received a low dose of C1 on enrolment. Following a satisfactory safety review 7 days after vaccination, volunteer group 2 received a full dose of C1 boosted by vaccines MVA.tHIVconsv3 (M3) and MVA.tHIVconsv4 (M4) 4 weeks later in regimen C1-M3M4 and were followed up until day 140. Focusing on the full vaccine doses in group 2, the primary outcome was the local and systemic safety of the vaccine. The secondary outcome was the frequency and breadth of epitope recognition by vaccine-induced T cells determined by IFN-γ ELISPOT assay using peripheral blood mononuclear cells (PBMC) at peak (1 and 2 weeks after the M3M4 boost) and at the end of the study, assessed against volunteer's pre-vaccination levels. The HIV-CORE 005.2 trial is registered at ClinicalTrials.gov (NCT04586673) and is closed.

FINDINGS

Between July 3, 2021, and Aug 3, 2022, 13 participants were recruited and assigned to group 1 (n=3) and group 2 (n=10). Low-dose C1 was safe and well tolerated in group 1, and all three vaccine components were well tolerated in volunteer group 2. There were no serious adverse events. Local and systemic reactogenicities were consistent with intramuscular needle administration of immunogenic substances. All volunteers responded, and their vaccine-elicited T-cell frequencies peaked at a median of 4433 (IQR 2750-5820) IFN-γ spot-forming units per 106 PBMC and recognised a median of 9 (IQR 9-10) peptide pools out of 10, indicating that the responses were broadly specific and each vaccine recipient targeted at least nine epitopes on HIV-1. These frequencies were 7·4 times lower by day 140 (ie, 3 months later). T cells proliferated upon antigen re-exposure and displayed multiple effector functions, recognised variant epitopes, and inhibited HIV-1 from the four major global clades A, B, C, and D.

INTERPRETATION

These results inform and support a programme of clinical evaluations of the HIVconsvX T-cell vaccines together with other cutting-edge tools for HIV-1 cure and prevention such as latency reactivating agents, passively infused combinations of broadly neutralising antibodies, and active Env-based vaccines or immunomodulators.

FUNDING

EU Horizon 2020 Research and Innovation programme, Medical Research Council and Foreign Commonwealth and Development Office Concordat agreement, European and Developing Countries Clinical Trials Partnership, National Institute for Health Research Oxford Biomedical Research Centre, and IAVI.

Enhancing broadly neutralising antibody suppression of HIV by immune modulation and vaccination

Although HIV infection can be managed with antiretroviral drugs, there is no cure and therapy has to be taken for life. Recent successes in animal models with HIV-specific broadly neutralising antibodies (bNAbs) have led to long-term virological remission and even possible cures in some cases. This has resulted in substantial investment in human studies to explore bNAbs as a curative intervention for HIV infection. Emerging data are encouraging, but suggest that combinations of bNAbs with other immunomodulatory agents may be needed to induce and sustain long-term viral control. As a result, a number of clinical trials are currently underway exploring these combinations. If successful, the impact for the millions of people living with HIV could be substantial. Here, we review the background to the use of bNAbs in the search for an HIV cure and how different adjunctive agents might be used together to enhance their efficacy.

Host genetic and immune factors drive evasion of HIV-1 pathogenesis in viremic non-progressors

BACKGROUND

Viremic non-progressors (VNPs) represent an exceptional and uncommon subset of people with HIV-1, characterized by the remarkable preservation of normal CD4+ T cell counts despite uncontrolled viral replication-a trait reminiscent of natural hosts of simian immunodeficiency virus. The mechanisms orchestrating evasion from HIV-1 pathogenesis in human VNPs remain elusive, primarily due to the absence of integrative studies.

METHODS

We implemented a novel single-cell and multiomics approach to comprehensively characterize viral, genomic, transcriptomic, and metabolomic factors driving this exceedingly rare disease phenotype in 16 VNPs and 29 HIV+ progressors.

FINDINGS

Genetic predisposition to the VNP phenotype was evidenced by a higher prevalence of CCR5Δ32 heterozygosity, which was associated with lower levels of CCR5 expression and a lower frequency of infected cells in peripheral circulation. We also observed reduced levels of plasma markers of intestinal disruption and attenuated interferon responses in VNPs. These factors potentially drive the other phenotypic traits of immune preservation in this population, including the unaltered tryptophan metabolic profile, reduced activation of cytotoxic lymphocytes, and reduced bystander CD4+ T cell apoptosis.

CONCLUSIONS

In summary, our comprehensive analysis identified intricate factors collectively associated with the unique immunovirological equilibrium in VNPs, shedding light on potential avenues for therapeutic exploration in managing HIV pathogenesis.

FUNDING

The work was supported by funding from the Spanish Ministry of Science and Innovation and the National Institutes of Health (NIH).

Low prevalence of HIV in the northern Cameroon: contribution of some AIDS restriction genes and potential implications for gene therapy

Background

HIV infection and its progression to AIDS depend on several factors including host genetic factors. The immunological mechanisms of host resistance to HIV infection greatly influence the prevalence of HIV in a given region. Worldwide, Cameroon not exempted, the frequency of AIDS-associated genes varies and may influence this prevalence. The North and Far North Regions of Cameroon have had the lowest HIV prevalence in the country for many years despite risky behaviors associated with their customs and habits. In this work, we seek to explore the contribution of host genes to the HIV low prevalence in these regions.

Methodology

Five genes variants previously described as HIV AIDS related were studied. These genes are: CCR5Δ32, CCR5promoter59029G, CCR2-64I, SDF1-3'A and Trim5α(R136Q). A total of 384 consented participants were included in this study. The HIV serological status was confirmed using national algorithm. Genomic DNA was extracted from the buffy coats and used for genotyping. The results obtained were compiled in Excel 2016, Epi Info 7.1 and snpStats software and Chi two tests allowed us to compare the frequencies of the AIDS related alleles in the North with those in other Regions of Cameroon and to measure the impact of these ARGs on protection against HIV.

Results

The frequency of protective alleles CCR5Δ32, CCR5promoter59029G, CCR2-64I, SDF1-3'A and Trim5α(R136Q) was the allelic frequencies should be expressed as percentages i.e. 0.52%; 37.56%; 36.46%; 25.19% and 69.33%. These allelic frequencies exhibited a significant difference when compared to those obtained in other regions of Cameroon (p < 0.01). Protective alleles were predominant in the Northern region compared to others and were associated with resistance to HIV [(p < 0.0001); OR = 2.02 CI, 95%].

Conclusion

The higher frequency of HIV-protective alleles in the northern regions may be a contributing factor to the lower prevalence of HIV. Nevertheless, this should be reinforced by other preventive and surveillance methods to guarantee the sustained low prevalence. HIV can develop resistance through the process of mutation, but the host targets themselves are genetically stable. The study of these host genetic restriction factors is of great value in the design of a practical cure for HIV infection or an effective vaccine.

HIV Vaccine Development at a Crossroads: New B and T Cell Approaches

Despite rigorous scientific efforts over the forty years since the onset of the global HIV pandemic, a safe and effective HIV-1 vaccine remains elusive. The challenges of HIV vaccine development have proven immense, in large part due to the tremendous sequence diversity of HIV and its ability to escape from antiviral adaptive immune responses. In recent years, several phase 3 efficacy trials have been conducted, testing a similar hypothesis, e.g., that non-neutralizing antibodies and classical cellular immune responses could prevent HIV-1 acquisition. These studies were not successful. As a result, the field has now pivoted to bold novel approaches, including sequential immunization strategies to drive the generation of broadly neutralizing antibodies and human CMV-vectored vaccines to elicit MHC-E-restricted CD8+ T cell responses. Many of these vaccine candidates are now in phase 1 trials, with early promising results.

The impact of analytical treatment interruptions and trial interventions on time to viral re-suppression in people living with HIV restarting ART in cure-related clinical studies: a systematic review and meta-analysis

INTRODUCTION

To assess the effectiveness of novel HIV curative strategies, "cure" trials require periods of closely monitored antiretroviral therapy (ART) analytical treatment interruptions (ATIs). We performed a systematic review and meta-analysis to identify the impact of ATI with or without novel therapeutics in cure-related studies on the time to viral re-suppression following ART restart.

METHODS

Medline, Embase and Web of Science databases were searched for human studies involving ATIs from 1 January 2015 till 22 April 2024. The primary outcome was time to first viral re-suppression (plasma HIV viral load [VL] <50 copies/ml) stratified by receipt of interventional drug with ATI (IA) or ATI-only groups. Random-effects proportional meta-analysis and multivariable Cox proportional hazards analysis were performed using R.

RESULTS

Of 1073 studies screened, 13 were included that met the inclusion criteria with VL data available after restarting ART (n = 213 participants). There was no difference between time to viral suppression in IA or ATI-only cohorts (p = 0.22). For 87% of participants, viral suppression within 12 weeks of ART restart was achieved, and all eventually had at least one VL <50 copies/ml during follow-up. After adjusting for covariables, while participants in the IA cohort were associated with less rapid suppression (adjusted hazard ratio [aHR] 0.61, 95% CI 0.40-0.94, p = 0.026), other factors include greater log VL at ART restart (aHR 0.56, 95% CI 0.46-0.68, p<0.001), duration since HIV diagnosis (aHR 0.93, 95% CI 0.89-0.96) and longer intervals between HIV VL monitoring (aHR 0.66, 95% CI 0.59-0.74, p<0.001). However, the use of integrase inhibitors was associated with more rapid viral suppression (aHR 1.74, 95% CI 1.16-2.59).

DISCUSSION

When designing studies involving ATIs, information on time to viral re-suppression after restarting ART is important to share with participants, and should be regularly monitored and reported, to assess the impact and safety of specific trial interventions in ATI studies.

CONCLUSIONS

The majority of participants achieved viral suppression after restarting ART in ATI studies. ART regimens containing integrase inhibitors and frequent VL monitoring should be offered for people restarting ART after ATI studies to ensure rapid re-suppression.

Arenavirus-Based Vectors Generate Robust SIV Immunity in Non-Human Primates

Arenavirus-based vectors are being investigated as therapeutic vaccine candidates with the potential to elicit robust CD8 T-cell responses. We compared the immunogenicity of replicating (artPICV and artLCMV) and non-replicating (rPICV and rLCMV) arenavirus-based vectors expressing simian immunodeficiency virus (SIV) Gag and Envelope (Env) immunogens in treatment-naïve non-human primates. Heterologous regimens with non-replicating and replicating vectors elicited more robust SIV IFN-γ responses than a homologous regimen, and replicating vectors elicited significantly higher cellular immunogenicity than non-replicating vectors. The heterologous regimen elicited high anti-Env antibody titers when administered intravenously, with replicating vectors inducing significantly higher titers than non-replicating vectors. Intramuscular immunization resulted in more durable antibody responses than intravenous immunization for both vector platforms, with no difference between the replicating and non-replicating vectors. Overall, both replicating and non-replicating arenavirus vectors generated robust T- and B-cell-mediated immunity to SIV antigens in treatment-naïve non-human primates, supporting further evaluation of these vectors in a clinical setting for HIV therapy.

Immune targeting of HIV-1 reservoir cells: a path to elimination strategies and cure

Successful approaches for eradication or cure of HIV-1 infection are likely to include immunological mechanisms, but remarkably little is known about how human immune responses can recognize and interact with the few HIV-1-infected cells that harbour genome-intact viral DNA, persist long term despite antiretroviral therapy and represent the main barrier to a cure. For a long time regarded as being completely shielded from host immune responses due to viral latency, these cells do, on closer examination with single-cell analytic techniques, display discrete footprints of immune selection, implying that human immune responses may be able to effectively engage and target at least some of these cells. The failure to eliminate rebound-competent virally infected cells in the majority of persons likely reflects the evolution of a highly selected pool of reservoir cells that are effectively camouflaged from immune recognition or rely on sophisticated approaches for resisting immune-mediated killing. Understanding the fine-tuned interplay between host immune responses and viral reservoir cells will help to design improved interventions that exploit the immunological vulnerabilities of HIV-1 reservoir cells.

The immunogenicity of an HIV-1 Gag conserved element DNA vaccine in people with HIV and receiving antiretroviral therapy

OBJECTIVE

The primary objective of the study was to assess the immunogenicity of an HIV-1 Gag conserved element DNA vaccine (p24CE DNA) in people with HIV (PWH) receiving suppressive antiretroviral therapy (ART).

DESIGN

AIDS Clinical Trials Group A5369 was a phase I/IIa, randomized, double-blind, placebo-controlled study of PWH receiving ART with plasma HIV-1 RNA less than 50 copies/ml, current CD4 + T-cell counts greater than 500 cells/μl, and nadir CD4 + T-cell counts greater than 350 cells/μl.

METHODS

The study enrolled 45 participants randomized 2 : 1 : 1 to receive p24CE DNA vaccine at weeks 0 and 4, followed by p24CE DNA admixed with full-length p55 Gag DNA vaccine at weeks 12 and 24 (arm A); full-length p55 Gag DNA vaccine at weeks 0, 4, 12, and 24 (arm B); or placebo at weeks 0, 4, 12, and 24 (arm C). The active and placebo vaccines were administered by intramuscular electroporation.

RESULTS

There was a modest, but significantly greater increase in the number of conserved elements recognized by CD4 + and/or CD8 + T cells in arm A compared with arm C ( P  = 0.014). The percentage of participants with an increased number of conserved elements recognized by T cells was also highest in arm A (8/18, 44.4%) vs. arm C (0/10, 0.0%) ( P  = 0.025). There were no significant differences between treatment groups in the change in magnitude of responses to total conserved elements.

CONCLUSION

A DNA-delivered HIV-1 Gag conserved element vaccine boosted by a combination of this vaccine with a full-length p55 Gag DNA vaccine induced a new conserved element-directed cellular immune response in approximately half the treated PWH on ART.

Strategies to target the central nervous system HIV reservoir

PURPOSE OF THE REVIEW

The central nervous system (CNS) is an hotspot for HIV persistence and may be a major obstacle to overcome for curative strategies. The peculiar anatomical, tissular and cellular characteristics of the HIV reservoir in the CNS may need to be specifically addressed to achieve a long-term HIV control without ART. In this review, we will discuss the critical challenges that currently explored curative strategies may face in crossing the blood-brain barrier (BBB), targeting latent HIV in brain-resident myeloid reservoirs, and eliminating the virus without eliciting dangerous neurological adverse events.

RECENT FINDINGS

Latency reversing agents (LRA), broadly neutralizing monoclonal antibodies (bNabs), chimeric antigen receptor (CAR) T-cells, and adeno-associated virus 9-vectored gene-therapies cross the BBB with varying efficiency. Although brain penetration is poor for bNAbs, viral vectors for in vivo gene-editing, certain LRAs, and CAR T-cells may reach the cerebral compartment more efficiently. All these approaches, however, may encounter difficulties in eliminating HIV-infected perivascular macrophages and microglia. Safety, including local neurological adverse effects, may also be a concern, especially if high doses are required to achieve optimal brain penetration and efficient brain cell targeting.

SUMMARY

Targeting the CNS remains a potential problem for the currently investigated HIV curing strategies. In vivo evidence on CNS effectiveness is limited for most of the investigated strategies, and additional studies should be focused on evaluating the interplay between the cerebral HIV reservoir and treatment aiming to achieve an ART-free cure.

Impact of Recombinant VSV-HIV Prime, DNA-Boost Vaccine Candidates on Immunogenicity and Viremia on SHIV-Infected Rhesus Macaques

Currently, no effective vaccine to prevent human immunodeficiency virus (HIV) infection is available, and various platforms are being examined. The vesicular stomatitis virus (VSV) vaccine vehicle can induce robust humoral and cell-mediated immune responses, making it a suitable candidate for the development of an HIV vaccine. Here, we analyze the protective immunological impacts of recombinant VSV vaccine vectors that express chimeric HIV Envelope proteins (Env) in rhesus macaques. To improve the immunogenicity of these VSV-HIV Env vaccine candidates, we generated chimeric Envs containing the transmembrane and cytoplasmic tail of the simian immunodeficiency virus (SIV), which increases surface Env on the particle. Additionally, the Ebola virus glycoprotein was added to the VSV-HIV vaccine particles to divert tropism from CD4 T cells and enhance their replications both in vitro and in vivo. Animals were boosted with DNA constructs that encoded matching antigens. Vaccinated animals developed non-neutralizing antibody responses against both the HIV Env and the Ebola virus glycoprotein (EBOV GP) as well as systemic memory T-cell activation. However, these responses were not associated with observable protection against simian-HIV (SHIV) infection following repeated high-dose intra-rectal SHIV SF162p3 challenges.

Harnessing immune cells to eliminate HIV reservoirs

PURPOSE OF REVIEW

Despite decades of insights about how CD8 + T cells and natural killer (NK) cells contribute to natural control of infection, additional hurdles (mutational escape from cellular immunity, sequence diversity, and hard-to-access tissue reservoirs) will need to be overcome to develop a cure. In this review, we highlight recent findings of novel mechanisms of antiviral cellular immunity and discuss current strategies for therapeutic deisgn.

RECENT FINDINGS

Of note are the apparent converging roles of viral antigen-specific MHC-E-restricted CD8 + T cells and NK cells, interleukin (IL)-15 biologics to boost cytotoxicity, and broadly neutralizing antibodies in their native form or as anitbody fragments to neutralize virus and engage cellular immunity, respectively. Finally, renewed interest in myeloid cells as relevant viral reservoirs is an encouraging sign for designing inclusive therapeutic strategies.

SUMMARY

Several studies have shown promise in many preclinical models of disease, including simian immunodeficiency virus (SIV)/SHIV infection in nonhuman primates and HIV infection in humanized mice. However, each model comes with its own limitations and may not fully predict human responses. We eagerly await the results of clinical trails assessing the efficacy of these strategies to achieve reductions in viral reservoirs, delay viral rebound, or ultimately elicit immune based control of infection without combination antiretroviral therapy (cART).

A follow-up study: 6-year cART-free virologic control of rhesus macaques after PD-1-based DNA vaccination against pathogenic SHIVSF162P3CN challenge

IMPORTANCE

Efficient strategies for HIV-1 cART-free virologic control are critical for ending the AIDS pandemic. The essential role of effector-memory CD8+ T cells in controlling viremia and eliminating virus-infected cells has made them a promising target for vaccine development. It has been previously reported that PD-1-based DNA vaccination was effective in inducing polyfunctional effector-memory CD8+ T cells for AIDS virus control for 2 years in rhesus monkeys. This follow-up study extends the findings and shows that a viremia-free period of over 6 years was detected in two monkeys immunized with PD-1-based DNA vaccine against pathogenic SHIVSF162P3CN infection in the absence of antiretroviral therapy. Long-term vaccine-induced memory T cell responses were detected. Our results warrant the clinical trials of PD-1-based DNA vaccines for achieving HIV-1 cART-free virologic control used either alone or in combination with other biomedical interventions.

Immunogenic arenavirus vector SIV vaccine reduces setpoint viral load in SIV-challenged rhesus monkeys

HIV affects more than 38 million people worldwide. Although HIV can be effectively treated by lifelong combination antiretroviral therapy, only a handful of patients have been cured. Therapeutic vaccines that induce robust de novo immune responses targeting HIV proteins and latent reservoirs will likely be integral for functional HIV cure. Our study shows that immunization of naïve rhesus macaques with arenavirus-derived vaccine vectors encoding simian immunodeficiency virus (SIVSME543 Gag, Env, and Pol) immunogens is safe, immunogenic, and efficacious. Immunization induced robust SIV-specific CD8+ and CD4+ T-cell responses with expanded cellular breadth, polyfunctionality, and Env-binding antibodies with antibody-dependent cellular cytotoxicity. Vaccinated animals had significant reductions in median SIV viral load (1.45-log10 copies/mL) after SIVMAC251 challenge compared with placebo. Peak viral control correlated with the breadth of Gag-specific T cells and tier 1 neutralizing antibodies. These results support clinical investigation of arenavirus-based vectors as a central component of therapeutic vaccination for HIV cure.

Generating and measuring effective vaccine-elicited HIV-specific CD8 + T cell responses

PURPOSE OF REVIEW

There is growing consensus that eliciting CD8 + T cells in addition to antibodies may be required for an effective HIV vaccine for both prevention and cure. Here, we review key qualities of vaccine-elicited CD8 + T cells as well as major CD8 + T cell-based delivery platforms used in recent HIV vaccine clinical trials.

RECENT FINDINGS

Much progress has been made in improving HIV immunogen design and delivery platforms to optimize CD8 + T cell responses. With regards to viral vectors, recent trials have tested newer chimp and human adenovirus vectors as well as a CMV vector. DNA vaccine immunogenicity has been increased by delivering the vaccines by electroporation and together with adjuvants as well as administering them as part of a heterologous regimen. In preclinical models, self-amplifying RNA vaccines can generate durable tissue-based CD8 + T cells. While it may be beneficial for HIV vaccines to recapitulate the functional and phenotypic features of HIV-specific CD8 + T cells isolated from elite controllers, most of these features are not routinely measured in HIV vaccine clinical trials.

SUMMARY

Identifying a vaccine capable of generating durable T cell responses that target mutationally vulnerable epitopes and that can rapidly intercept infecting or rebounding virus remains a challenge for HIV. Comprehensive assessment of HIV vaccine-elicited CD8 + T cells, as well as comparisons between different vaccine platforms, will be critical to advance our understanding of how to design better CD8 + T cell-based vaccines for HIV.

'Immunization during ART and ATI for HIV-1 vaccine discovery/development'

PURPOSE OF REVIEW

Explore whether immunization with germline-targeting Env immunogens during ART, followed by ATI, leads to the identification of viral envelope glycoproteins (Envs) that promote and guide the full maturation of broadly neutralizing antibody responses.

RECENT FINDINGS

The HIV-1 envelope glycoprotein (Env) does not efficiently engage the germline precursors of broadly neutralizing antibodies (bnAbs). However, Env-derived proteins specifically designed to precisely do that, have been recently developed. These 'germline-targeting' Env immunogens activate naïve B cells that express the germline precursors of bnAbs but by themselves cannot guide their maturation towards their broadly neutralizing forms. This requires sequential immunizations with heterologous sets of Envs. These 'booster' Envs are currently unknown.

SUMMARY

Combining germline-targeting Env immunization approaches during ART with ATI could lead to the identification of natural Envs that are responsible for the maturation of broadly neutralizing antibody responses during infection. Such Envs could then serve as booster immunogens to guide the maturation of glBCRs that have become activated by germline-targeting immunogens in uninfected subjects.

Vaccination with an HIV T-Cell Immunogen (HTI) Using DNA Primes Followed by a ChAdOx1-MVA Boost Is Immunogenic in Gut Microbiota-Depleted Mice despite Low IL-22 Serum Levels

Despite the important role of gut microbiota in the maturation of the immune system, little is known about its impact on the development of T-cell responses to vaccination. Here, we immunized C57BL/6 mice with a prime-boost regimen using DNA plasmid, the Chimpanzee Adenovirus, and the modified Vaccinia Ankara virus expressing a candidate HIV T-cell immunogen and compared the T-cell responses between individuals with an intact or antibiotic-depleted microbiota. Overall, the depletion of the gut microbiota did not result in significant differences in the magnitude or breadth of the immunogen-specific IFNγ T-cell response after vaccination. However, we observed marked changes in the serum levels of four cytokines after vaccinating microbiota-depleted animals, particularly a significant reduction in IL-22 levels. Interestingly, the level of IL-22 in serum correlated with the abundance of Roseburia in the large intestine of mice in the mock and vaccinated groups with intact microbiota. This short-chain fatty acid (SCFA)-producing bacterium was significantly reduced in the vaccinated, microbiota-depleted group. Therefore, our results indicate that, although microbiota depletion reduces serum levels of IL-22, the powerful vaccine regime used could have overcome the impact of microbiota depletion on IFNγ-producing T-cell responses.

Therapeutic vaccination following early antiretroviral therapy elicits highly functional T cell responses against conserved HIV-1 regions

'Kick and kill' cure strategies aim to induce HIV protein expression in latently infected cells (kick), and thus trigger their elimination by cytolytic T cells (kill). In the Research in Viral Eradication of HIV Reservoirs trial (NCT02336074), people diagnosed with primary HIV infection received immediate antiretroviral therapy (ART) and were randomised 24 weeks later to either a latency-reversing agent, vorinostat, together with ChAdV63.HIVconsv and MVA.HIVconsv vaccines, or ART alone. This intervention conferred no reduction in HIV-1 reservoir size over ART alone, despite boosting virus-specific CD4+ and CD8+ T cells. The effects of the intervention were examined at the cellular level in the two trial arms using unbiased computational analysis of polyfunctional scores. This showed that the frequency and polyfunctionality of virus-specific CD4+ and CD8+ T cell populations were significantly increased over 12 weeks post-vaccination, compared to the ART-only arm. HIV-specific IL-2-secreting CD8+ T cells also expanded significantly in the intervention arm and were correlated with antiviral activity against heterologous HIV in vitro. Therapeutic vaccination during ART commenced in primary infection can induce functional T cell responses that are phenotypically similar to those of HIV controllers. Analytical therapy interruption may help determine their ability to control HIV in vivo.

Higher HIV-1 Env gp120-Specific Antibody-Dependent Cellular Cytotoxicity (ADCC) Activity Is Associated with Lower Levels of Defective HIV-1 Provirus

A cure for HIV-1 (HIV) remains unrealized due to a reservoir of latently infected cells that persist during antiretroviral therapy (ART), with reservoir size associated with adverse health outcomes and inversely with time to viral rebound upon ART cessation. Once established during ART, the HIV reservoir decays minimally over time; thus, understanding factors that impact the size of the HIV reservoir near its establishment is key to improving the health of people living with HIV and for the development of novel cure strategies. Yet, to date, few correlates of HIV reservoir size have been identified, particularly in pediatric populations. Here, we employed a cross-subtype intact proviral DNA assay (CS-IPDA) to quantify HIV provirus between one- and two-years post-ART initiation in a cohort of Kenyan children (n = 72), which had a median of 99 intact (range: 0-2469), 1340 defective (range: 172-3.84 × 104), and 1729 total (range: 178-5.11 × 104) HIV proviral copies per one million T cells. Additionally, pre-ART plasma was tested for HIV Env-specific antibody-dependent cellular cytotoxicity (ADCC) activity. We found that pre-ART gp120-specific ADCC activity inversely correlated with defective provirus levels (n = 68, r = -0.285, p = 0.0214) but not the intact reservoir (n = 68, r = -0.0321, p-value = 0.800). Pre-ART gp41-specific ADCC did not significantly correlate with either proviral population (n = 68; intact: r = -0.0512, p-value = 0.686; defective: r = -0.109, p-value = 0.389). This suggests specific host immune factors prior to ART initiation can impact proviruses that persist during ART.

Prevention, treatment and cure of HIV infection

The development of antiretroviral therapy for the prevention and treatment of HIV infection has been marked by a series of remarkable successes. However, the efforts to develop a vaccine have largely failed, and efforts to discover a cure are only now beginning to gain traction. In this Review, we describe recent progress on all fronts - pre-exposure prophylaxis, vaccines, treatment and cure - and we discuss the unmet needs, both current and in the coming years. We describe the emerging arsenal of drugs, biologics and strategies that will hopefully address these needs. Although HIV research has largely been siloed in the past, this is changing, as the emerging research agenda is marked by multiple cross-discipline synergies and collaborations. As the limitations of antiretroviral drugs as a means to truly end the epidemic are becoming more apparent, there is a great need for continued efforts to develop an effective preventative vaccine and a scalable cure, both of which remain formidable challenges.

Features of functional and dysfunctional CD8+ T cells to guide HIV vaccine development

PURPOSE OF REVIEW

CD8+ T cell responses are a key component of the host immune response to human immunodeficiency virus (HIV) but vary significantly across individuals with distinct clinical outcomes. These differences help inform the qualitative features of HIV-specific CD8+ T cells that we should aim to induce by vaccination.

RECENT FINDINGS

We review previous and more recent findings on the features of dysfunctional and functional CD8+ T cell responses that develop in individuals with uncontrolled and controlled HIV infection, with particular emphasis on proliferation, cytotoxic effector function, epitope specificity, and responses in lymph nodes. We also discuss the implications of these findings for both prophylactic and therapeutic T cell vaccine development within the context of T cell vaccine trials.

SUMMARY

The induction of HIV specific CD8+ T cell responses is an important goal of ongoing vaccine efforts. Emerging data on the key features of CD8+ T cell responses that distinguish individuals who spontaneously control from those with progressive disease continues to provide key guidance.

Combined intranasal and intramuscular parainfluenza 5-, simian adenovirus ChAdOx1- and poxvirus MVA-vectored vaccines induce synergistically HIV-1-specific T cells in the mucosa

Introduction

The primary goal of this work is to broaden and enhance the options for induction of protective CD8⁺ T cells against HIV-1 and respiratory pathogens.

Methods

We explored the advantages of the parainfluenza virus 5 (PIV5) vector for delivery of pathogen-derived transgenes alone and in combination with the in-human potent regimen of simian adenovirus ChAdOx1 prime-poxvirus MVA boost delivering bi-valent mosaic of HIV-1 conserved regions designated HIVconsvX.

Results

We showed in BALB/c mice that the PIV5 vector expressing the HIVconsvX immunogens could be readily incorporated with the other two vaccine modalities into a single regimen and that for specific vector combinations, mucosal CD8⁺ T-cell induction was enhanced synergistically by a combination of the intranasal and intramuscular routes of administration.

Discussion

Encouraging safety and immunogenicity data from phase 1 human trials of ChAdOx1- and MVA-vectored vaccines for HIV-1, and PIV5-vectored vaccines for SARS-CoV-2 and respiratory syncytial virus pave the way for combining these vectors for HIV-1 and other indications in humans.

Elevated glutamate impedes anti-HIV-1 CD8 + T cell responses in HIV-1-infected individuals on antiretroviral therapy

CD8 + T cells are essential for long-lasting HIV-1 control and have been harnessed to develop therapeutic and preventive approaches for people living with HIV-1 (PLWH). HIV-1 infection induces marked metabolic alterations. However, it is unclear whether these changes affect the anti-HIV function of CD8 + T cells. Here, we show that PLWH exhibit higher levels of plasma glutamate than healthy controls. In PLWH, glutamate levels positively correlate with HIV-1 reservoir and negatively correlate with the anti-HIV function of CD8 + T cells. Single-cell metabolic modeling reveals glutamate metabolism is surprisingly robust in virtual memory CD8 + T cells (TVM). We further confirmed that glutamate inhibits TVM cells function via the mTORC1 pathway in vitro. Our findings reveal an association between metabolic plasticity and CD8 + T cell-mediated HIV control, suggesting that glutamate metabolism can be exploited as a therapeutic target for the reversion of anti-HIV CD8 + T cell function in PLWH.

Clinical trials aimed at HIV cure or remission: new pathways and lessons learned

INTRODUCTION

The main barrier to finding a cure against HIV is the latent HIV reservoir, which persists in people living with HIV (PLWH) despite antiretroviral treatment (ART). Here, we discuss recent findings from interventional studies using mono- and combination therapies aimed at enhancing immune-mediated killing of the virus with or without activating HIV from latency.

AREAS COVERED

We discuss latency reversal agents (LRAs), broadly neutralizing antibodies, immunomodulatory therapies, and studies aimed at inducing apoptosis.

EXPERT OPINION

The landscape of clinical trials for HIV cure and remission has evolved considerably over the past 10 years. Several novel interventions such as immune checkpoint inhibitors, therapeutic vaccines, and broadly neutralizing antibodies have been tested either alone or in combination with LRAs but studies have so far not shown a meaningful impact on the frequency of latently infected cells. Immunomodulatory therapies could work differently in the setting of antigen expression, that is, during active viremia, and timing of interventions could therefore, be key to future therapeutic success. Lessons learned from clinical trials aimed at HIV cure indicate that while we are still far from reaching a complete eradication cure of HIV, clinical interventions capable of inducing enhanced control of HIV replication in the absence of ART might be a more feasible goal.

Opportunities for CAR-T Cell Immunotherapy in HIV Cure

Chimeric antigen receptor (CAR) technology is having a huge impact in the blood malignancy field and is becoming a well-established therapy for many types of leukaemia. In recent decades, efforts have been made to demonstrate that CAR-T cells have potential as a therapy to achieve a sterilizing cure for human immunodeficiency virus (HIV) infection. However, translation of this technology to the HIV scenario has not been easy, as many challenges have appeared along the way that hinder the consolidation of CAR-T cells as a putative therapy. Here, we review the origin and development of CAR-T cells, describe the advantages of CAR-T cell therapy in comparison with other therapies, and describe the major obstacles currently faced regarding application of this technology in the HIV field, specifically, viral escape, CAR-T cell infectivity, and accessibility to hidden reservoirs. Nonetheless, promising results in successfully tackling some of these issues that have been obtained in clinical trials suggest a bright future for CAR-T cells as a consolidated therapy.

Highlights from the Tenth International Workshop on HIV Persistence during Therapy, December 13-16, 2022, Miami, Florida-USA

The International Workshop on HIV Persistence during Therapy provides a forum in which HIV/AIDS researchers gather to share the latest research findings related to viral reservoirs and cure. The Tenth Workshop, which was attended by over 400 delegates, extended over 4 days and comprised eight sessions covering topics from the basic science of viral persistence to therapeutic approaches to HIV cure. Furthermore, satellite sessions on the first day of the Conference featuring cure research endeavours being pursued by the Bill and Melinda Gates Foundation as well as those being coordinated under the National Institutes of Health Martin Delaney Collaboratory program, provided important updates on research advances being made in these initiatives. As with previous conferences, the International Workshop on HIV Persistence during Therapy is primarily abstract-driven with only one invited talk for each of the sessions. This format, therefore, increases the number of presentations from early-stage investigators. Furthermore, presentations by Community representatives illustrated approaches to creating cure research literacy with effective messaging for the Community. The following article offers a synopsis of the meeting sessions. Due to space constraints, some presentations may have only been briefly discussed. Nevertheless, the Workshop abstracts can be found online (https://www/sciencedirect.com/journal/journal-of-virus-eradication/vol/8/suppl/S).

XCR1+ DCs are critical for T cell-mediated immunotherapy of chronic viral infections

The contribution of cross-presenting XCR1+ dendritic cells (DCs) and SIRPα+ DCs in maintaining T cell function during exhaustion and immunotherapeutic interventions of chronic infections remains poorly characterized. Using the mouse model of chronic LCMV infection, we found that XCR1+ DCs are more resistant to infection and highly activated compared with SIRPα+ DCs. Exploiting XCR1+ DCs via Flt3L-mediated expansion or XCR1-targeted vaccination notably reinvigorates CD8+ T cells and improves virus control. Upon PD-L1 blockade, XCR1+ DCs are not required for the proliferative burst of progenitor exhausted CD8+ T (TPEX) cells but are indispensable to sustain the functionality of exhausted CD8+ T (TEX) cells. Combining anti-PD-L1 therapy with increased frequency of XCR1+ DCs improves functionality of TPEX and TEX subsets, while increase of SIRPα+ DCs dampened their proliferation. Together, this demonstrates that XCR1+ DCs are crucial for the success of checkpoint inhibitor-based therapies through differential activation of exhausted CD8+ T cell subsets.

Vaccination with an HIV T-cell immunogen induces alterations in the mouse gut microbiota

The gut microbiota is emerging as a crucial factor modulating vaccine responses; however, few studies have investigated if vaccines, in turn, can alter the microbiota and to what extent such changes may improve vaccine efficacy. To understand the effect of T-cell vaccination on the gut microbiome, we administered an HIV-1 T-cell immunogen (HTI arm) or PBS (control, Mock arm) to C57Bl/6 mice following a heterologous prime-boost scheme. The longitudinal dynamics of the mice gut microbiota was characterized by 16 S ribosomal RNA sequencing in fecal samples collected from cages, as well as from three gut sections (cecum, small and large intestine). Serum and spleen cells were obtained at the last time point of the study to assess immune correlates using IFNγ ELISPOT and cytokine Luminex^® assays. Compared with Mock, HTI-vaccinated mice were enriched in Clostridiales genera (Eubacterium xylanophilum group, Roseburia and Ruminococcus) known as primary contributors of anti-inflammatory metabolites, such as short-chain fatty acids. Such shift was observed after the first HTI dose and remained throughout the study follow-up (18 weeks). However, the enriched Clostridiales genera were different between feces and gut sections. The abundance of bacteria enriched in vaccinated animals positively correlated with HTI-specific T-cell responses and a set of pro-inflammatory cytokines, such as IL-6. This longitudinal analysis indicates that, in mice, T-cell vaccination may promote an increase in gut bacteria known to produce anti-inflammatory molecules, which in turn correlate with proinflammatory cytokines, suggesting an adaptation of the gut microbial milieu to T-cell-induced systemic inflammation.