HIV control: Is getting there the same as staying there?

Autovaccination revisited: potential to boost antiviral immunity and facilitate HIV-1 cure/remission in children

PURPOSE OF REVIEW

To review the concept of autovaccination as a strategy to boost anti-HIV-1 immunity and improve immune control, especially as a means to facilitate cure/remission in paediatric HIV-1 infection, where effective interventions in clinical testing remain limited compared to adults.

RECENT FINDINGS

Early autovaccination studies, conducted 15-25 years ago, suggested potential immunological benefits from exposure to autologous virus in both children and adults, specifically when antiretroviral therapy (ART) was initiated during acute infection. More recent work in nonhuman primates (NHPs) has shown that early ART initiation can significantly reduce the viral setpoint following treatment interruption, primarily through CD8 + T-cell responses, and prevent early immune escape - a phenomenon commonly observed in ART-naive acute infections. Additionally, NHP studies indicate that multiple, short analytical treatment interruptions (ATIs) can delay viral rebound and further lower the viral setpoint via enhanced CD8 + T-cell responses.

SUMMARY

Recent studies in NHP support the potential for autovaccination via short ATIs to enhance antiviral immunity and improve immune control of HIV-1. With well tolerated, well monitored ATI protocols, autovaccination could be a valuable approach to facilitating cure/remission in children living with HIV (LWH), in whom very early-ART initiation and early-life immunity are associated with low viral reservoirs and high cure/remission potential.

Exploitation of Unconventional CD8 T-Cell Responses Induced by Engineered Cytomegaloviruses for the Development of an HIV-1 Vaccine

After four decades of intensive research, traditional vaccination strategies for HIV-1 remain ineffective due to HIV-1's extraordinary genetic diversity and complex immune evasion mechanisms. Cytomegaloviruses (CMV) have emerged as a novel type of vaccine vector with unique advantages due to CMV persistence and immunogenicity. Rhesus macaques vaccinated with molecular clone 68-1 of RhCMV (RhCMV68-1) engineered to express simian immunodeficiency virus (SIV) immunogens elicited an unconventional major histocompatibility complex class Ib allele E (MHC-E)-restricted CD8+ T-cell response, which consistently protected over half of the animals against a highly pathogenic SIV challenge. The RhCMV68-1.SIV-induced responses mediated a post-infection replication arrest of the challenge virus and eventually cleared it from the body. These observations in rhesus macaques opened a possibility that MHC-E-restricted CD8+ T-cells could achieve similar control of HIV-1 in humans. The potentially game-changing advantage of the human CMV (HCMV)-based vaccines is that they would induce protective CD8+ T-cells persisting at the sites of entry that would be insensitive to HIV-1 evasion. In the RhCMV68-1-protected rhesus macaques, MHC-E molecules and their peptide cargo utilise complex regulatory mechanisms and unique transport patterns, and researchers study these to guide human vaccine development. However, CMVs are highly species-adapted viruses and it is yet to be shown whether the success of RhCMV68-1 can be translated into an HCMV ortholog for humans. Despite some safety concerns regarding using HCMV as a vaccine vector in humans, there is a vision of immune programming of HCMV to induce pathogen-tailored CD8+ T-cells effective against HIV-1 and other life-threatening diseases.

Advances in the mathematical modeling of posttreatment control of HIV-1

PURPOSE OF REVIEW

Several new intervention strategies have shown significant improvements over antiretroviral therapy (ART) in eliciting lasting posttreatment control (PTC) of HIV-1. Advances in mathematical modelling have offered mechanistic insights into PTC and the workings of these interventions. We review these advances.

RECENT FINDINGS

Broadly neutralizing antibody (bNAb)-based therapies have shown large increases over ART in the frequency and the duration of PTC elicited. Early viral dynamics models of PTC with ART have been advanced to elucidate the underlying mechanisms, including the role of CD8+ T cells. These models characterize PTC as an alternative set-point, with low viral load, and predict routes to achieving it. Large-scale omic datasets have offered new insights into viral and host factors associated with PTC. Correspondingly, new classes of models, including those using learning techniques, have helped exploit these datasets and deduce causal links underlying the associations. Models have also offered insights into therapies that either target the proviral reservoir, modulate immune responses, or both, assessing their translatability.

SUMMARY

Advances in mathematical modeling have helped better characterize PTC, elucidated and quantified mechanisms with which interventions elicit it, and informed translational efforts.

Single-cell analyses reveal that monocyte gene expression profiles influence HIV-1 reservoir size in acutely treated cohorts

Elimination of latent HIV-1 is a major goal of AIDS research but the host factors determining the size of these reservoirs are poorly understood. Here, we investigated whether differences in host gene expression modulate the size of the HIV-1 reservoir during suppressive ART. Peripheral blood mononuclear cells (PBMC) from fourteen individuals initiating ART during acute infection who demonstrated effective viral suppression but varying magnitude of total HIV-1 DNA were characterized by single-cell RNA sequencing (scRNA-seq). Differentially expressed genes and enriched pathways demonstrated increased monocyte activity in participants with undetectable HIV-1 reservoirs. IL1B expression in CD14+ monocytes showed the greatest fold difference. The inverse association of IL1B with reservoir size was validated in an independent cohort comprised of 38 participants with different genetic backgrounds and HIV-1 subtype infections, and further confirmed with intact proviral DNA assay (IPDA®) measurements of intact HIV-1 proviruses in a subset of the samples. Modeling interactions with cell population frequencies showed that monocyte IL1B expression associated inversely with reservoir size in the context of higher frequencies of central memory CD4+ T cells, implicating an indirect effect of IL1B via the cell type well established to be a reservoir for persistent HIV-1. Signatures consisting of co-expressed genes including IL1B were highly enriched in the "TNFα signaling via NF-κB" geneset. Functional analyses in cell culture revealed that IL1B activates NF-κB, thereby promoting productive HIV-1 infection while simultaneously suppressing viral spread, suggesting a natural latency reversing activity to deplete the reservoir in ART treated individuals. Altogether, unbiased high throughput scRNA-seq analyses revealed that monocyte IL1B variation could decrease HIV-1 proviral reservoirs in individuals initiating ART during acute infection.

Acute-phase innate immune responses in SIVmac239-infected Mamu-B*08+ Indian rhesus macaques may contribute to the establishment of elite control

Introduction

Spontaneous control of chronic-phase HIV/SIV viremia is often associated with the expression of specific MHC class I allotypes. HIV/SIV-specific CD8+ cytotoxic T lymphocytes (CTLs) restricted by these MHC class I allotypes appear to be critical for viremic control. Establishment of the elite controller (EC) phenotype is predictable in SIVmac239-infected Indian rhesus macaques (RMs), with approximately 50% of Mamu-B*08+ RMs and 20% of Mamu-B*17+ RMs becoming ECs. Despite extensive characterization of EC-associated CTLs in HIV/SIV-infected individuals, the precise mechanistic basis of elite control remains unknown. Because EC and non-EC viral load trajectories begin diverging by day 14 post-infection, we hypothesized that hyperacute innate immune responses may contribute to viremic control.

Methods

To gain insight into the immunological factors involved in the determination of EC status, we vaccinated 16 Mamu-B*08+ RMs with Vif and Nef to elicit EC-associated CTLs, then subjected these 16 vaccinees and an additional 16 unvaccinated Mamu-B*08+ controls to repeated intrarectal SIVmac239 challenges. We then performed whole-blood transcriptomic analysis of all 32 SIVmac239-infected Mamu-B*08+ RMs and eight SIVmac239-infected Mamu-B*08 - RMs during the first 14 days of infection.

Results

Vaccination did not provide protection against acquisition, but peak and setpoint viremia were significantly lower in vaccinees relative to controls. We did not identify any meaningful correlations between vaccine-induced CTL parameters and SIVmac239 acquisition rate or chronic-phase viral loads. Ultimately, 13 of 16 vaccinees (81%) and 7 of 16 controls (44%) became ECs (viremia ≤ 10,000 vRNA copies/mL plasma for ≥ 4 weeks). We identified subsets of immunomodulatory genes differentially expressed (DE) between RM groupings based on vaccination status, EC status, and MHC class I genotype. These DE genes function in multiple innate immune processes, including the complement system, cytokine/chemokine signaling, pattern recognition receptors, and interferon-mediated responses.

Discussion

A striking difference in the kinetics of differential gene expression among our RM groups suggests that Mamu-B*08-associated elite control is characterized by a robust, rapid innate immune response that quickly resolves. These findings indicate that, despite the association between MHC class I genotype and elite control, innate immune factors in hyperacute SIV infection preceding CTL response development may facilitate the establishment of the EC phenotype.

Sustained aviremia despite anti-retroviral therapy non-adherence in male children after in utero HIV transmission

After sporadic reports of post-treatment control of HIV in children who initiated combination anti-retroviral therapy (cART) early, we prospectively studied 284 very-early-cART-treated children from KwaZulu-Natal, South Africa, after vertical HIV transmission to assess control of viremia. Eighty-four percent of the children achieved aviremia on cART, but aviremia persisting to 36 or more months was observed in only 32%. We observed that male infants have lower baseline plasma viral loads (P = 0.01). Unexpectedly, a subset (n = 5) of males maintained aviremia despite unscheduled complete discontinuation of cART lasting 3-10 months (n = 4) or intermittent cART adherence during 17-month loss to follow-up (n = 1). We further observed, in vertically transmitted viruses, a negative correlation between type I interferon (IFN-I) resistance and viral replication capacity (VRC) (P < 0.0001) that was markedly stronger for males than for females (r = -0.51 versus r = -0.07 for IFN-α). Although viruses transmitted to male fetuses were more IFN-I sensitive and of higher VRC than those transmitted to females in the full cohort (P < 0.0001 and P = 0.0003, respectively), the viruses transmitted to the five males maintaining cART-free aviremia had significantly lower replication capacity (P < 0.0001). These data suggest that viremic control can occur in some infants with in utero-acquired HIV infection after early cART initiation and may be associated with innate immune sex differences.

Antiviral capacity of the early CD8 T-cell response is predictive of natural control of SIV infection: Learning in vivo dynamics using ex vivo data

While most individuals suffer progressive disease following HIV infection, a small fraction spontaneously controls the infection. Although CD8 T-cells have been implicated in this natural control, their mechanistic roles are yet to be established. Here, we combined mathematical modeling and analysis of previously published data from 16 SIV-infected macaques, of which 12 were natural controllers, to elucidate the role of CD8 T-cells in natural control. For each macaque, we considered, in addition to the canonical in vivo plasma viral load and SIV DNA data, longitudinal ex vivo measurements of the virus suppressive capacity of CD8 T-cells. Available mathematical models do not allow analysis of such combined in vivo-ex vivo datasets. We explicitly modeled the ex vivo assay, derived analytical approximations that link the ex vivo measurements with the in vivo effector function of CD8-T cells, and integrated them with an in vivo model of virus dynamics, thus developing a new learning framework that enabled the analysis. Our model fit the data well and estimated the recruitment rate and/or maximal killing rate of CD8 T-cells to be up to 2-fold higher in controllers than non-controllers (p = 0.013). Importantly, the cumulative suppressive capacity of CD8 T-cells over the first 4-6 weeks of infection was associated with virus control (Spearman's ρ = -0.51; p = 0.05). Thus, our analysis identified the early cumulative suppressive capacity of CD8 T-cells as a predictor of natural control. Furthermore, simulating a large virtual population, our model quantified the minimum capacity of this early CD8 T-cell response necessary for long-term control. Our study presents new, quantitative insights into the role of CD8 T-cells in the natural control of HIV infection and has implications for remission strategies.

Modelling HIV-1 control and remission

Remarkable advances are being made in developing interventions for eliciting long-term remission of HIV-1 infection. The success of these interventions will obviate the need for lifelong antiretroviral therapy, the current standard-of-care, and benefit the millions living today with HIV-1. Mathematical modelling has made significant contributions to these efforts. It has helped elucidate the possible mechanistic origins of natural and post-treatment control, deduced potential pathways of the loss of such control, quantified the effects of interventions, and developed frameworks for their rational optimization. Yet, several important questions remain, posing challenges to the translation of these promising interventions. Here, we survey the recent advances in the mathematical modelling of HIV-1 control and remission, highlight their contributions, and discuss potential avenues for future developments.

Low unspliced cell-associated HIV RNA in early treated adolescents living with HIV on long suppressive ART

Introduction

Initiation of antiretroviral treatment (ART) in patients early after HIV-infection and long-term suppression leads to low or undetectable levels of HIV RNA and cell-associated (CA) HIV DNA and RNA. Both CA-DNA and CA-RNA, overestimate the size of the HIV reservoir but CA-RNA as well as p24/cell-free viral RNA can be indicators of residual viral replication. This study describes HIV RNA amounts and levels of cytokines/soluble markers in 40 well-suppressed adolescents who initiated ART early in life and investigated which viral markers may be informative as endpoints in cure clinical trials within this population.

Methods

Forty adolescents perinatally infected with HIV on suppressive ART for >5 years were enrolled in the CARMA study. HIV DNA and total or unspliced CA-RNA in PBMCs were analyzed by qPCR/RT-qPCR and dPCR/RT-dPCR. Cell-free HIV was determined using an ultrasensitive viral load (US-VL) assay. Plasma markers and p24 were analyzed by digital ELISA and correlations between total and unspliced HIV RNA and clinical markers, including age at ART, Western Blot score, levels of cytokines/inflammation markers or HIV CA-DNA, were tested.

Results

CA-RNA was detected in two thirds of the participants and was comparable in RT-qPCR and RT-dPCR. Adolescents with undetectable CA-RNA showed significantly lower HIV DNA compared to individuals with detectable CA-RNA. Undetectable unspliced CA-RNA was positively associated with age at ART initiation and Western Blot score. We found that a higher concentration of TNF-α was predictive of higher CA-DNA and CA-RNA. Other clinical characteristics like US-VL, time to suppression, or percent CD4+ T-lymphocytes were not predictive of the CA-RNA in this cross-sectional study.

Conclusions

Low CA-DNA after long-term suppressive ART is associated with lower CA-RNA, in concordance with other reports. Patients with low CA-RNA levels in combination with low CA-DNA and low Western Blot scores should be further investigated to characterize candidates for treatment interruption trials. Unspliced CA-RNA warrants further investigation as a marker that can be prioritized in paediatric clinical trials where the sample volume can be a significant limitation.

Early antiretroviral therapy favors post-treatment SIV control associated with the expansion of enhanced memory CD8+ T-cells

HIV remission can be achieved in some people, called post-treatment HIV controllers, after antiretroviral treatment discontinuation. Treatment initiation close to the time of infection was suggested to favor post-treatment control, but the circumstances and mechanisms leading to this outcome remain unclear. Here we evaluate the impact of early (week 4) vs. late (week 24 post-infection) treatment initiation in SIVmac251-infected male cynomolgus macaques receiving 2 years of therapy before analytical treatment interruption. We show that early treatment strongly promotes post-treatment control, which is not related to a lower frequency of infected cells at treatment interruption. Rather, early treatment favors the development of long-term memory CD8+ T cells with enhanced proliferative and SIV suppressive capacity that are able to mediate a robust secondary-like response upon viral rebound. Our model allows us to formally demonstrate a link between treatment initiation during primary infection and the promotion of post-treatment control and provides results that may guide the development of new immunotherapies for HIV remission.

Multiplex interrogation of the NK cell signalome reveals global downregulation of CD16 signaling during lentivirus infection through an IL-18/ADAM17-dependent mechanism

Despite their importance, natural killer (NK) cell responses are frequently dysfunctional during human immunodeficiency virus-1 (HIV-1) and simian immunodeficiency virus (SIV) infections, even irrespective of antiretroviral therapies, with poorly understood underlying mechanisms. NK cell surface receptor modulation in lentivirus infection has been extensively studied, but a deeper interrogation of complex cell signaling is mostly absent, largely due to the absence of any comprehensive NK cell signaling assay. To fill this knowledge gap, we developed a novel multiplex signaling analysis to broadly assess NK cell signaling. Using this assay, we elucidated that NK cells exhibit global signaling reduction from CD16 both in people living with HIV-1 (PLWH) and SIV-infected rhesus macaques. Intriguingly, antiretroviral treatment did not fully restore diminished CD16 signaling in NK cells from PLWH. As a putative mechanism, we demonstrated that NK cells increased surface ADAM17 expression via elevated plasma IL-18 levels during HIV-1 infection, which in turn reduced surface CD16 downregulation. We also illustrated that CD16 expression and signaling can be restored by ADAM17 perturbation. In summary, our multiplex NK cell signaling analysis delineated unique NK cell signaling perturbations specific to lentiviral infections, resulting in their dysfunction. Our analysis also provides mechanisms that will inform the restoration of dysregulated NK cell functions, offering potential insights for the development of new NK cell-based immunotherapeutics for HIV-1 disease.

Factors associated with post-treatment control of viral load in HIV-infected patients: a systematic review and meta-analysis

OBJECTIVES

This study aimed to investigate the factors associated with maintenance of viral suppression after antiretroviral therapy (ART) discontinuation.

METHODS

Databases were searched for studies published between January 01, 2011, and July 01, 2022, that correlated the time of virus rebound with treatment interruption (TI). The corresponding data were extracted from these studies. A fixed-effects model was used to calculate pooled estimates.

RESULTS

Thirty-one studies were included in this analysis. Results showed that patients who started ART during acute or early infection had longer viral control than those who started ART during chronic infection. It has been reported that some broadly neutralizing HIV-1-specific antibodies can significantly prolong viral inhibition. The study also found that approximately 7.2% of patients achieved post-treatment control (PTC) approximately a year after TI.

CONCLUSION

ART initiation in the acute or early phases can delay viral rebound after TI. Cell-associated HIV RNA and HIV DNA have been difficult to prove as able to predict viral rebound time. Many vaccines and antibodies have also been shown to be effective in prolonging viral control in people without PTC, and more research is needed to develop alternative ART therapies that can effectively inhibit or even eliminate HIV.

Preservation of antigen-specific responses in cryopreserved CD4+ and CD8+ T cells expanded with IL-2 and IL-7

Objectives

We sought to develop medium throughput standard operating procedures for screening cryopreserved human peripheral blood mononuclear cells (PBMCs) for CD4⁺ and CD8⁺ T cell responses to potential autoantigens.

Methods

Dendritic cells were loaded with a peptide cocktail from ubiquitous viruses or full-length viral protein antigens and cocultured with autologous T cells. We measured expression of surface activation markers on T cells by flow cytometry and cytometry by time of flight 24-72 h later. We tested responses among T cells freshly isolated from healthy control PBMCs, cryopreserved T cells, and T cells derived from a variety of T cell expansion protocols. We also compared the transcriptional profile of CD8⁺ T cells rested with interleukin (IL)7 for 48 h after 1) initial thawing, 2) expansion, and 3) secondary cryopreservation/thawing of expanded cells. To generate competent antigen presenting cells from PBMCs, we promoted differentiation of PBMCs into dendritic cells with granulocyte macrophage colony stimulating factor and IL-4.

Results

We observed robust dendritic cell differentiation from human PBMCs treated with 50 ng/mL GM-CSF and 20 ng/mL IL-4 in as little as 3 days. Dendritic cell purity was substantially increased by magnetically enriching for CD14⁺ monocytes prior to differentiation. We also measured antigen-dependent T cell activation in DC-T cell cocultures. However, polyclonal expansion of T cells with anti-CD3/antiCD28 abolished antigen-dependent upregulation of CD69 in our assay despite minimal transcriptional differences between rested CD8⁺ T cells before and after expansion. Furthermore, resting these expanded T cells in IL-2, IL-7 or IL-15 did not restore the antigen dependent responses. In contrast, T cells that were initially expanded with IL-2 + IL-7 rather than plate bound anti-CD3 + anti-CD28 retained responsiveness to antigen stimulation and these responses strongly correlated with responses measured at initial thawing.

Significance

While screening techniques for potential pathological autoantibodies have come a long way, comparable full-length protein target assays for screening patient T cells at medium throughput are noticeably lacking due to technical hurdles. Here we advance techniques that should have broad applicability to translational studies investigating cell mediated immunity in infectious or autoimmune diseases. Future studies are aimed at investigating possible CD8⁺ T cell autoantigens in MS and other CNS autoimmune diseases.

Morphine suppresses peripheral responses and transforms brain myeloid gene expression to favor neuropathogenesis in SIV infection

The twin pandemics of opioid abuse and HIV infection can have devastating effects on physiological systems, including on the brain. Our previous work found that morphine increased the viral reservoir in the brains of treated SIV-infected macaques. In this study, we investigated the interaction of morphine and SIV to identify novel host-specific targets using a multimodal approach. We probed systemic parameters and performed single-cell examination of the targets for infection in the brain, microglia and macrophages. Morphine treatment created an immunosuppressive environment, blunting initial responses to infection, which persisted during antiretroviral treatment. Antiretroviral drug concentrations and penetration into the cerebrospinal fluid and brain were unchanged by morphine treatment. Interestingly, the transcriptional signature of both microglia and brain macrophages was transformed to one of a neurodegenerative phenotype. Notably, the expression of osteopontin, a pleiotropic cytokine, was significantly elevated in microglia. This was especially notable in the white matter, which is also dually affected by HIV and opioids. Increased osteopontin expression was linked to numerous HIV neuropathogenic mechanisms, including those that can maintain a viral reservoir. The opioid morphine is detrimental to SIV/HIV infection, especially in the brain.

Long-term antiretroviral therapy mitigates mortality and morbidity independent of HIV tropism: 18 years follow-up in a women's cohort

OBJECTIVE

CXCR4 (X4)-tropic HIV-1 was found previously to herald CD4 + cell depletion and disease progression in individuals who were antiretroviral-naive or took combination antiretroviral therapy (cART) for less than 5 years. We updated this finding by investigating whether the deleterious effect of X4-tropic strains is mitigated by long-term cART.

DESIGN

We examined morbidity and mortality in relation to HIV-1 tropism and cART in 529 participants followed up to 18 years in the Women's Interagency HIV Study; 91% were women of color.

METHODS

Plasma-derived HIV-1 tropism was determined genotypically.

RESULTS

We categorized participants according to the number of visits reported on cART after initiation. Group 1: three or less visits, 74% of these participants reporting no cART; group 2: at least four visits and less than 70% of visits on cART; group 3: at least 70% of visits on cART. AIDS mortality rates for participants in each group with X4 virus compared with those with R5 virus exclusively were, respectively: 62 vs. 40% ( P  = 0.0088); 23% vs. 22% [nonsignificant (NS)]; 7% vs. 14% (NS). Kaplan-Meier curves showed accelerated progression to AIDS death or AIDS-defining illness in participants with three or less cART visits and X4 viruses ( P  = 0.0028) but no difference in progression rates stratified by tropism in other groups. Logistic regression found that HIV-1 suppression for at least 10 semiannual visits (≥5 years total) mitigated X4 tropism's deleterious effect on mortality, controlling for maximal viral load, and CD4 + nadir.

CONCLUSION

Long-term cART markedly mitigated the deleterious effect of X4 viruses on AIDS morbidity and mortality. Mitigation was correlated with duration of viral suppression, supporting HIV-1 suppression as a crucial goal.

Antiretroviral therapy restores the homeostatic state of microglia in SIV-infected rhesus macaques

Microglia and macrophages are essential for homeostatic maintenance and innate immune response in the brain. They are the first line of defense against infections such as HIV/SIV in the brain. However, they are susceptible to infection and function as viral reservoirs even under effective viral suppression. While current antiretroviral regimens successfully suppress viremia and improve quality of life and lifespan, neurologic complications persist and are in part attributed to activated microglia. We sought to test the hypothesis that brain microglia return to a more homeostatic-like state when viremia is suppressed by combination antiretroviral therapy. Using the SIV-rhesus macaque model, we combined single-cell RNA sequencing, bioinformatics, and pathway analysis to compare gene expression profiles of brain myeloid cells under 4 conditions: uninfected, SIV infected, SIV infected with cART suppression, and SIV encephalitis (SIVE). Our study reveals greater myeloid diversity and an elevated proinflammatory state are associated with untreated SIV infection compared with uninfected animals. The development of encephalitis and suppression of viremia both reduced myeloid diversity. However, they had converse effects on the activation state of microglia and inflammation. Notably, suggestive of a restoration of a homeostatic state in microglia, gene expression and activation of pathways related to inflammation and immune response in cART-suppressed monkeys were most similar to that in uninfected monkeys. Untreated SIV infection shared characteristics, especially in brain macrophages to SIVE, with SIVE showing dramatic inflammation. In support of our hypothesis, our study demonstrates that cART indeed restores this key component of the brain's homeostatic state. Summary: ScRNA-seq of rhesus monkey microglia reveals clusters of cells in activated states in the setting of SIV infection, which is primarily reversed by suppressing viremia with combination antiretroviral therapy.

Elite controllers long-term non progressors present improved survival and slower disease progression

Different phenotypes exhibiting no evidences of disease progression have been described in ART-naïve HIV-1 positive individuals. Long-term non progressors (LTNP) and elite controllers (EC) are low frequent examples of immunological and virological control in HIV-1 positive subjects, respectively. The combination of both phenotypes is even less frequent and studied despite being considered as models of HIV-1 functional cure. A multicenter, prospective study in retrospect including clinical and epidemiological data collected from 313 LTNP of 21 Spanish hospitals was carried out. LTNPs maintaining CD4+ T cell counts over 500 cells/µl and viral loads (VL) under 10,000 copies/mL for at least 10 years in the absence of antiretroviral therapy were followed for a median of 20.8 years (IQR = 15.6–25.5). A 52.1% were considered EC (undetectable VL) and LTNP (EC-LTNP) and a total of 171 (54.8%) and 42 (13.5%) out of the 313 participants maintained LTNP status for at least 20 and 30 years, respectively. EC-LTNP showed lower CD4+ T cell count loss (9.9 vs 24.2 cells/µl/year), higher CD4/CD8 ratio (0.01 vs − 0.09 in ratio), and lesser VL increase (no increase vs 197.2 copies/mL/year) compared with LTNPs with detectable VL (vLTNP). Survival probabilities for all-cause mortality at 30 years from HIV + diagnosis were 0.90 for EC-LTNP and 0.70 for vLTNP (p = 2.0 × 10⁻³), and EC-LTNP phenotype was the only factor associated with better survival in multivariate analyses (HR = 0.28; 95% CI 0.10–0.79). The probability to preserve LTNP status at 30 years was 0.51 for EC-LTNP and 0.18 for vLTNP (p < 2.2 × 10⁻¹⁶). Risk factors associated to the loss of LTNP status was: higher age at diagnosis and the increase of VL, whereas the increase of CD4+ T cell counts and CD4/CD8 ratio, the initial EC-LTNP phenotype and HCV coinfection were protective factors. EC-LTNP phenotype was associated with improved survival and slower disease progression compared with other phenotypes of LTNP. EC-LTNP individuals represent one of the most favorable phenotypes of immune activation against HIV-1 found in nature and, therefore, are strong candidates to be considered a model of functional cure of HIV-1 infection.

Towards a molecular profile of antiretroviral therapy-free HIV remission

PURPOSE OF REVIEW

To summarize the current status and highlight recent findings on predictive biomarkers for posttreatment HIV control (PTC) and virological remission. While historically, many studies focused on virological markers, there is an increasing tendency to enter immune and metabolic factors into the equation.

RECENT FINDINGS

On the virological side, several groups reported that cell-associated HIV RNA could predict time to viral rebound. Recent data hints at the possible importance of the genic location and chromatin context of the integrated provirus, although these factors still need to be assessed in relation to PTC and virological remission. Evidence from immunological studies highlighted innate and humoral immunity as important factors for prolonged HIV remission. Interestingly, novel metabolic markers have emerged, which offer additional angles to our understanding of latency and viral rebound.

SUMMARY

Facilitating PTC and virological remission remain top priorities for the HIV cure research. We advocate for clear and precise definitions for both phenomena in order to avoid misconceptions and to strengthen the conclusions that can be drawn. As no one-size-fits-all marker has emerged yet, more biomarkers are on the horizon, and viral rebound is a complex and heterogeneous process, it is likely that a combination of various biomarkers in cohesion will be necessary for a more accurate prediction of antiretroviral therapy-free HIV remission.

A Dynamic Interplay of Circulating Extracellular Vesicles and Galectin-1 Reprograms Viral Latency during HIV-1 Infection

Combined Antiretroviral therapy (cART) suppresses HIV replication but fails to eradicate the virus, which persists in a small pool of long-lived latently infected cells. Immune activation and residual inflammation during cART are considered to contribute to viral persistence. Galectins, a family of β-galactoside-binding proteins, play central roles in host-pathogen interactions and inflammatory responses. Depending on their structure, glycan binding specificities and/or formation of distinct multivalent signaling complexes, different members of this family can complement, synergize, or oppose the function of others. Here, we identify a regulatory circuit, mediated by galectin-1 (Gal-1)–glycan interactions, that promotes reversal of HIV-1 latency in infected T cells. We found elevated levels of circulating Gal-1 in plasma from HIV-1-infected individuals, which correlated both with inflammatory markers and the transcriptional activity of the reservoir, as determined by unspliced-RNA (US-RNA) copy number. Proinflammatory extracellular vesicles (EVs) isolated from the plasma of HIV-infected individuals induced Gal-1 secretion by macrophages. Extracellularly, Gal-1 interacted with latently infected resting primary CD4⁺ T cells and J-LAT cells in a glycan-dependent manner and reversed HIV latency via activation of the nuclear factor κB (NF-κB). Furthermore, CD4⁺ T cells isolated from HIV-infected individuals showed increased HIV-1 transcriptional activity when exposed to Gal-1. Thus, by modulating reservoir dynamics, EV-driven Gal-1 secretion by macrophages links inflammation with HIV-1 persistence in cART-treated individuals.

Approach to the management of paediatric HIV spontaneous controllers

Paediatric HIV spontaneous controllers (HSCs) are a unique and understudied population with potential to inform alternative treatment options for patients living with HIV. As HSCs are so rare and often not recognised prior to antiretroviral treatment (ART) initiation, it can be difficult for clinicians to optimally manage this group. We describe the diagnosis, history and management of three paediatric HSCs, two girls and a boy who were followed for 2, 1.25 and 10.4 years, respectively, before starting ART. All had low but detectable viral loads throughout follow-up but mostly marginally low CD4:CD8 ratios. The reason for starting ART in all was a gradual tendency to poorer virological control. This case series should assist in recognising paediatric HSCs. Clinical dilemmas arising in the management of paediatric HSCs include arriving at a correct HIV-positive diagnosis, correct diagnosis as an HSC, as well as whether to initiate ART. Decision-making for initiation of ART in paediatric HSCs should be individualised. Factors supporting ART initiation in these patients included increased frequency of viral load blips, increasing detectable viral load, CD4 percentage and CD4:CD8 ratio. Other factors included Hepatitis C serology and highly sensitive C-reactive protein. All three patients ultimately required ART, which supports universal initiation of ART in paediatric HSCs, but further research is required.

Learning to Be Elite: Lessons From HIV-1 Controllers and Animal Models on Trained Innate Immunity and Virus Suppression

Although antiretroviral therapy (ART) has drastically changed the lives of people living with human immunodeficiency virus-1 (HIV-1), long-term treatment has been associated with a vast array of comorbidities. Therefore, a cure for HIV-1 remains the best option to globally eradicate HIV-1/acquired immunodeficiency syndrome (AIDS). However, development of strategies to achieve complete eradication of HIV-1 has been extremely challenging. Thus, the control of HIV-1 replication by the host immune system, namely functional cure, has long been studied as an alternative approach for HIV-1 cure. HIV-1 elite controllers (ECs) are rare individuals who naturally maintain undetectable HIV-1 replication levels in the absence of ART and whose immune repertoire might be a desirable blueprint for a functional cure. While the role(s) played by distinct human leukocyte antigen (HLA) expression and CD8+ T cell responses expressing cognate ligands in controlling HIV-1 has been widely characterized in ECs, the innate immune phenotype has been decidedly understudied. Comparably, in animal models such as HIV-1-infected humanized mice and simian Immunodeficiency Virus (SIV)-infected non-human primates (NHP), viremic control is known to be associated with specific major histocompatibility complex (MHC) alleles and CD8+ T cell activity, but the innate immune response remains incompletely characterized. Notably, recent work demonstrating the existence of trained innate immunity may provide new complementary approaches to achieve an HIV-1 cure. Herein, we review the known characteristics of innate immune responses in ECs and available animal models, identify gaps of knowledge regarding responses by adaptive or trained innate immune cells, and speculate on potential strategies to induce EC-like responses in HIV-1 non-controllers.

The Characteristics of the HIV-1 Env Glycoprotein Are Linked With Viral Pathogenesis

The understanding of HIV-1 pathogenesis and clinical progression is incomplete due to the variable contribution of host, immune, and viral factors. The involvement of viral factors has been investigated in extreme clinical phenotypes from rapid progressors to long-term non-progressors (LTNPs). Among HIV-1 proteins, the envelope glycoprotein complex (Env) has been concentrated on in many studies for its important role in the immune response and in the first steps of viral replication. In this study, we analyzed the contribution of 41 Envs from 24 patients with different clinical progression rates and viral loads (VLs), LTNP-Elite Controllers (LTNP-ECs); Viremic LTNPs (vLTNPs), and non-controller individuals contemporary to LTNPs or recent, named Old and Modern progressors. We studied the Env expression, the fusion and cell-to-cell transfer capacities, as well as viral infectivity. The sequence and phylogenetic analysis of Envs were also performed. In every functional characteristic, the Envs from subjects with viral control (LTNP-ECs and vLTNPs) showed significant lower performance compared to those from the progressor individuals (Old and Modern). Regarding sequence analysis, the variable loops of the gp120 subunit of the Env (i.e., V2, V4, and mainly V5) of the progressor individuals showed longer and more glycosylated sequences than controller subjects. Therefore, HIV-1 Envs from virus of patients presenting viremic control and the non-progressor clinical phenotype showed poor viral functions and shorter sequences, whereas functional Envs were associated with virus of patients lacking virological control and with progressor clinical phenotypes. These correlations support the role of Env genotypic and phenotypic characteristics in the in vivo HIV-1 infection and pathogenesis.

Transmitted HIV-1 is more virulent in heterosexual individuals than men-who-have-sex-with-men

Transmission bottlenecks introduce selection pressures on HIV-1 that vary with the mode of transmission. Recent studies on small cohorts have suggested that stronger selection pressures lead to fitter transmitted/founder (T/F) strains. Manifestations of this selection bias at the population level have remained elusive. Here, we analysed early CD4 cell count measurements reported from ∼340,000 infected heterosexual individuals (HET) and men-who-have-sex-with-men (MSM), across geographies, ethnicities and calendar years. The reduction in CD4 counts early in infection is reflective of the virulence of T/F strains. MSM and HET use predominant modes of transmission, namely, anal and penile-vaginal, with among the largest differences in the selection pressures at transmission across modes. Further, in most geographies, the groups show little inter-mixing, allowing for the differential selection bias to be sustained and amplified. We found that the early reduction in CD4 counts was consistently greater in HET than MSM (P<0.05). To account for inherent variations in baseline CD4 counts, we constructed a metric to quantify the extent of progression to AIDS as the ratio of the reduction in measured CD4 counts from baseline and the reduction associated with AIDS. We found that this progression corresponding to the early CD4 measurements was ∼68% for MSM and ∼87% for HET on average (P<10⁻⁴; Cohen’s d, d_s = 0.36), reflecting the more severe disease caused by T/F strains in HET than MSM at the population level. Interestingly, the set-point viral load was not different between the groups (d_s<0.12), suggesting that MSM were more tolerant and not more resistant to their T/F strains than HET. This difference remained when we controlled for confounding factors using multivariable regression. We concluded that the different selection pressures at transmission have resulted in more virulent T/F strains in HET than MSM. These findings have implications for our understanding of HIV-1 pathogenesis, evolution, and epidemiology.

HIV-1 encounters a key bottleneck at the time of its transmission from one individual to another. This transmission bottleneck can differ between modes of transmission. The stronger this bottleneck is, the more fit the virus has to be to be successfully transmitted. Accordingly, the transmitted/founder (T/F) strains of HIV-1 may have different fitness in risk groups that use different modes of transmission. While studies on small cohorts do support this notion, observations of the manifestations of this differential selection bias at the population level have been lacking. Here, we examined reported early CD4 count measurements from ∼340,000 HET and MSM, across geographies, ethnicities, and calendar years. Early CD4 counts are a measure of the severity of the infection due to T/F strains. HET and MSM transmit predominantly via penile-vaginal and anal modes, respectively, and do not inter-mix significantly. Remarkably, we found that HET consistently had lower early CD4 counts than MSM. This difference could not be attributed to potential confounding factors, such as set-point viral load. The difference thus provided evidence that T/F strains had evolved to be more virulent in HET than MSM at the population level. Intervention strategies may benefit from accounting for this difference between risk groups.

Low CCR5 expression protects HIV-specific CD4+ T cells of elite controllers from viral entry

HIV elite controllers maintain a population of CD4 + T cells endowed with high avidity for Gag antigens and potent effector functions. How these HIV-specific cells avoid infection and depletion upon encounter with the virus remains incompletely understood. Ex vivo characterization of single Gag-specific CD4 + T cells reveals an advanced Th1 differentiation pattern in controllers, except for the CCR5 marker, which is downregulated compared to specific cells of treated patients. Accordingly, controller specific CD4 + T cells show decreased susceptibility to CCR5-dependent HIV entry. Two controllers carried biallelic mutations impairing CCR5 surface expression, indicating that in rare cases CCR5 downregulation can have a direct genetic cause. Increased expression of β-chemokine ligands upon high-avidity antigen/TCR interactions contributes to autocrine CCR5 downregulation in controllers without CCR5 mutations. These findings suggest that genetic and functional regulation of the primary HIV coreceptor CCR5 play a key role in promoting natural HIV control.

Viral, inflammatory, and reservoir characteristics of posttreatment controllers

PURPOSE OF REVIEW

To provide an overview of studies to date that have identified posttreatment controllers (PTCs) and to explore current evidence around clinical characteristics, immune effector function, and inflammatory and viral reservoir characteristics that may underlie the control mechanism.

RECENT FINDINGS

PTCs are broadly defined as individuals capable of maintaining control of HIV replication after cessation of antiretroviral therapy (ART). While starting ART early after HIV infection is associated with PTC, genetic disposition or CD8+ T-cell function do not appear to explain this phenomenon, but these features have not been exhaustively analyzed in PTCs. A lower frequency of latently infected cells prior to stopping ART has been associated with achieving PTC, including a lower level of intact HIV DNA, but more studies are needed to map the genetic location, epigenetic characteristics, and tissue distribution of the intact HIV reservoir in PTCs.

SUMMARY

Current studies are small and heterogeneous and there is a significant need to agree on a uniform definition of PTC. Many aspects of PTC are still unexplored including whether specific features of genetic disposition, immune effector functions, and/or viral reservoir characteristics play a role in PTC. A large multisite international cohort study could aide in providing the important insights needed to fully understand PTC.

A Tale of Two Viruses: Immunological Insights Into HCV/HIV Coinfection

Nearly 2.3 million individuals worldwide are coinfected with human immunodeficiency virus (HIV) and hepatitis C virus (HCV). Odds of HCV infection are six times higher in people living with HIV (PLWH) compared to their HIV-negative counterparts, with the highest prevalence among people who inject drugs (PWID) and men who have sex with men (MSM). HIV coinfection has a detrimental impact on the natural history of HCV, including higher rates of HCV persistence following acute infection, higher viral loads, and accelerated progression of liver fibrosis and development of end-stage liver disease compared to HCV monoinfection. Similarly, it has been reported that HCV coinfection impacts HIV disease progression in PLWH receiving anti-retroviral therapies (ART) where HCV coinfection negatively affects the homeostasis of CD4⁺ T cell counts and facilitates HIV replication and viral reservoir persistence. While ART does not cure HIV, direct acting antivirals (DAA) can now achieve HCV cure in nearly 95% of coinfected individuals. However, little is known about how HCV cure and the subsequent resolution of liver inflammation influence systemic immune activation, immune reconstitution and the latent HIV reservoir. In this review, we will summarize the current knowledge regarding the pathogenesis of HIV/HCV coinfection, the effects of HCV coinfection on HIV disease progression in the context of ART, the impact of HIV on HCV-associated liver morbidity, and the consequences of DAA-mediated HCV cure on immune reconstitution and HIV reservoir persistence in coinfected patients.

Elite controllers: A heterogeneous group of HIV-infected patients

The exceptional group of ECs has been of great help, and will continue to provide invaluable insight with regard to reach a potential functional cure of HIV. However, there is no consensus on the immune correlates associated to this EC phenotype which preclude reaching a potential functional cure of HIV. The existing literature studying this population of individuals has indeed revealed that they are a very heterogeneous group regarding virological, immunological, and even clinical characteristics, and that among ECs only a very small proportion are homogeneous in terms of maintaining virological and immunological control in the long term (the so-called long-term elite controllers, LTECs). Thus, it is of pivotal relevance to identify the LTECs subjects and use them as the right model to redefine immune correlates of a truly functional cure. This review summarizes the evidence of the heterogeneity of HIV elite controllers (ECs) subjects in terms of virological, immunological and clinical outcomes, and the implications of this phenomenon to adequately consider this EC phenotype as the right model of a functional cure.

The TLR7 agonist vesatolimod induced a modest delay in viral rebound in HIV controllers after cessation of antiretroviral therapy

Toll-like receptor 7 (TLR7) agonists, in combination with other therapies, can induce sustained control of simian-human immunodeficiency virus (SHIV) or simian immunodeficiency virus (SIV) in nonhuman primates. Here, we report the results of a randomized, double-blind, placebo-controlled phase 1b clinical trial of an oral TLR7 agonist, vesatolimod, in HIV-1-infected controllers on antiretroviral therapy (ART). We randomized participants 2:1 to receive vesatolimod (n = 17) or placebo (n = 8) once every other week for a total of 10 doses while continuing on ART. ART was then interrupted, and the time to viral rebound was analyzed using the Kaplan-Meier method. Vesatolimod was associated with induction of immune cell activation, decreases in intact proviral DNA during ART, and a modest increase in time to rebound after ART was interrupted. The delayed viral rebound was predicted by the lower intact proviral DNA at the end of vesatolimod treatment (13 days after the final dose). Inferred pathway analysis suggested increased dendritic cell and natural killer cell cross-talk and an increase in cytotoxicity potential after vesatolimod dosing. Larger clinical studies will be necessary to assess the efficacy of vesatolimod-based combination therapies aimed at long-term control of HIV infection.

Immunogenetic determinants of heterosexual HIV-1 transmission: key findings and lessons from two distinct African cohorts

Immunogenetic studies in the past three decades have uncovered a broad range of human genetic factors that seem to influence heterosexual HIV-1 transmission in one way or another. In our own work that jointly evaluated both genetic and nongenetic factors in two African cohorts of cohabiting, HIV-1-discordant couples (donor and recipient pairs) at risk of transmission during quarterly follow-up intervals, relatively consistent findings have been seen with three loci (IL19, HLA-A, and HLA-B), although the effect size (i.e., odds ratio or hazards ratio) of each specific variant was quite modest. These studies offered two critical lessons that should benefit future research on sexually transmitted infections. First, in donor partners, immunogenetic factors (e.g., HLA-B*57 and HLA-A*36:01) that operate directly through HIV-1 viral load or indirectly through genital coinfections are equally important. Second, thousands of single-nucleotide polymorphisms previously recognized as "causal" factors for human autoimmune disorders did not appear to make much difference, which is somewhat puzzling as these variants are predicted or known to influence the expression of many immune response genes. Replicating these observations in additional cohorts is no longer feasible as the field has shifted its focus to early diagnosis, universal treatment, and active management of comorbidities.

Incoming HIV virion-derived Gag Spacer Peptide 2 (p1) is a target of effective CD8+ T cell antiviral responses

Persistence of HIV through integration into host DNA in CD4+ T cells presents a major barrier to virus eradication. Viral integration may be curtailed when CD8+ T cells are triggered to kill infected CD4+ T cells through recognition of histocompatibility leukocyte antigen (HLA) class I-bound peptides derived from incoming virions. However, this has been reported only in individuals with "beneficial" HLA alleles that are associated with superior HIV control. Through interrogation of the pre-integration immunopeptidome, we obtain proof of early presentation of a virion-derived HLA-A∗02:01-restricted epitope, FLGKIWPSH (FH9), located in Gag Spacer Peptide 2 (SP2). FH9-specific CD8+ T cell responses are detectable in individuals with primary HIV infection and eliminate HIV-infected CD4+ T cells prior to virus production in vitro. Our data show that non-beneficial HLA class I alleles can elicit an effective antiviral response through early presentation of HIV virion-derived epitopes and also demonstrate the importance of SP2 as an immune target.

The Interplay of HIV and Autophagy in Early Infection

HIV/AIDS is still a global threat despite the notable efforts made by the scientific and health communities to understand viral infection, to design new drugs or to improve existing ones, as well as to develop advanced therapies and vaccine designs for functional cure and viral eradication. The identification and analysis of HIV-1 positive individuals that naturally control viral replication in the absence of antiretroviral treatment has provided clues about cellular processes that could interact with viral proteins and RNA and define subsequent viral replication and clinical progression. This is the case of autophagy, a degradative process that not only maintains cell homeostasis by recycling misfolded/old cellular elements to obtain nutrients, but is also relevant in the innate and adaptive immunity against viruses, such as HIV-1. Several studies suggest that early steps of HIV-1 infection, such as virus binding to CD4 or membrane fusion, allow the virus to modulate autophagy pathways preparing cells to be permissive for viral infection. Confirming this interplay, strategies based on autophagy modulation are able to inhibit early steps of HIV-1 infection. Moreover, autophagy dysregulation in late steps of the HIV-1 replication cycle may promote autophagic cell-death of CD4⁺ T cells or control of HIV-1 latency, likely contributing to disease progression and HIV persistence in infected individuals. In this scenario, understanding the molecular mechanisms underlying HIV/autophagy interplay may contribute to the development of new strategies to control HIV-1 replication. Therefore, the aim of this review is to summarize the knowledge of the interplay between autophagy and the early events of HIV-1 infection, and how autophagy modulation could impair or benefit HIV-1 infection and persistence, impacting viral pathogenesis, immune control of viral replication, and clinical progression of HIV-1 infected patients.

Control theory helps to resolve the measles paradox

Measles virus (MV) is a highly contagious respiratory morbillivirus that results in many disabilities and deaths. A crucial challenge in studying MV infection is to understand the so-called 'measles paradox'-the progression of the infection to severe immunosuppression before clearance of acute viremia, which is also observed in canine distemper virus (CDV) infection. However, a lack of models that match in vivo data has restricted our understanding of this complex and counter-intuitive phenomenon. Recently, progress was made in the development of a model that fits data from acute measles infection in rhesus macaques. This progress motivates our investigations to gain additional insights from this model into the control mechanisms underlying the paradox. In this paper, we investigated analytical conditions determining the control and robustness of viral clearance for MV and CDV, to untangle complex feedback mechanisms underlying the dynamics of acute infections in their natural hosts. We applied control theory to this model to help resolve the measles paradox. We showed that immunosuppression is important to control and clear the virus. We also showed under which conditions T-cell killing becomes the primary mechanism for immunosuppression and viral clearance. Furthermore, we characterized robustness properties of T-cell immunity to explain similarities and differences in the control of MV and CDV. Together, our results are consistent with experimental data, advance understanding of control mechanisms of viral clearance across morbilliviruses, and will help inform the development of effective treatments. Further the analysis methods and results have the potential to advance understanding of immune system responses to a range of viral infections such as COVID-19.

A "Drug-Dependent" Immune System Can Compromise Protection against Infection: The Relationships between Psychostimulants and HIV

Psychostimulant use is a major comorbidity in people living with HIV, which was initially explained by them adopting risky behaviors that facilitate HIV transmission. However, the effects of drug use on the immune system might also influence this phenomenon. Psychostimulants act on peripheral immune cells even before they reach the central nervous system (CNS) and their effects on immunity are likely to influence HIV infection. Beyond their canonical activities, classic neurotransmitters and neuromodulators are expressed by peripheral immune cells (e.g., dopamine and enkephalins), which display immunomodulatory properties and could be influenced by psychostimulants. Immune receptors, like Toll-like receptors (TLRs) on microglia, are modulated by cocaine and amphetamine exposure. Since peripheral immunocytes also express TLRs, they may be similarly affected by psychostimulants. In this review, we will summarize how psychostimulants are currently thought to influence peripheral immunity, mainly focusing on catecholamines, enkephalins and TLR4, and shed light on how these drugs might affect HIV infection. We will try to shift from the classic CNS perspective and adopt a more holistic view, addressing the potential impact of psychostimulants on the peripheral immune system and how their systemic effects could influence HIV infection.

Predicting Post-treatment HIV Remission: Does Size of the Viral Reservoir Matter?

Combination antiretroviral therapy (ART) suppresses human immunodeficiency virus (HIV) replication and improves immune function. However, due to the persistence of long-lived HIV reservoirs, therapy interruption almost inevitably leads to a fast viral rebound. A small percentage of individuals who are able to control HIV replication for extended periods after therapy interruption are of particular interest because they may represent a model of long-term HIV remission without ART. These individuals are characterized by a limited viral reservoir and low reservoir measures can predict post-treatment HIV remission. However, most individuals with a low reservoir still experience fast viral rebound. In this Perspective, we discuss the possible reasons behind this and propose to develop an integral profile, composed of viral and host biomarkers, that could allow the accurate prediction of post-treatment HIV remission. We also propose to incorporate information on the chromatin context of the proviral integration sites into the characterization of the HIV reservoir, as this likely influences the reactivation capacity of latent proviruses and, together with the actual number of intact proviruses, contributes to the replication competence of the reservoir.

PLA2G1B is involved in CD4 anergy and CD4 lymphopenia in HIV-infected patients

The precise mechanism leading to profound immunodeficiency of HIV-infected patients is still only partially understood. Here, we show that more than 80% of CD4+ T cells from HIV-infected patients have morphological abnormalities. Their membranes exhibited numerous large abnormal membrane microdomains (aMMDs), which trap and inactivate physiological receptors, such as that for IL-7. In patient plasma, we identified phospholipase A2 group IB (PLA2G1B) as the key molecule responsible for the formation of aMMDs. At physiological concentrations, PLA2G1B synergized with the HIV gp41 envelope protein, which appears to be a driver that targets PLA2G1B to the CD4+ T cell surface. The PLA2G1B/gp41 pair induced CD4+ T cell unresponsiveness (anergy). At high concentrations in vitro, PLA2G1B acted alone, independently of gp41, and inhibited the IL-2, IL-4, and IL-7 responses, as well as TCR-mediated activation and proliferation, of CD4+ T cells. PLA2G1B also decreased CD4+ T cell survival in vitro, likely playing a role in CD4 lymphopenia in conjunction with its induced IL-7 receptor defects. The effects on CD4+ T cell anergy could be blocked by a PLA2G1B-specific neutralizing mAb in vitro and in vivo. The PLA2G1B/gp41 pair constitutes what we believe is a new mechanism of immune dysfunction and a compelling target for boosting immune responses in HIV-infected patients.

The role of CD8 T cells in controlling HIV beyond the antigen-specific face

OBJECTIVES

Understanding the determinants of HIV immune control is important for seeking viable HIV prevention, treatment and curative strategies. The antigen-specific roles of CD8 T cells in controlling primary HIV infection have been well documented, but their abilities to control the latent HIV reservoir is less well studied.

METHODS

The scientific literature on this issue was searched on PubMed.

RESULTS

Recent reports have demonstrated that CD8 T cells are also involved in the control of viral replication in HIV-infected individuals receiving antiretroviral therapy (ART). However, based on accumulating evidence, the antiviral role of CD8 T cells in ART patients may not be achieved via an antigen-specific manner as HIV-specific CD8 T cells can sense, but not effectively eliminate, cells harbouring intact provirus without first being activated. Our recent study indicated that virtual memory CD8 T cells, a semi-differentiated component of CD8 T cells, may be involved in the mechanism restraining the HIV DNA reservoir in ART patients.

CONCLUSIONS

In this review, we summarize recent findings on the role of CD8 T cells in controlling HIV, highlighting differences between conventional antigen-specific and innate-like CD8 T cells. A better understanding of the roles of CD8 T cells during HIV infection should benefit the informed design of immune-based treatment strategies.

Pre-existing resistance in the latent reservoir can compromise VRC01 therapy during chronic HIV-1 infection

Passive immunization with broadly neutralizing antibodies (bNAbs) of HIV-1 appears a promising strategy for eliciting long-term HIV-1 remission. When administered concomitantly with the cessation of antiretroviral therapy (ART) to patients with established viremic control, bNAb therapy is expected to prolong remission. Surprisingly, in clinical trials on chronic HIV-1 patients, the bNAb VRC01 failed to prolong remission substantially. Identifying the cause of this failure is important for improving VRC01-based therapies and unraveling potential vulnerabilities of other bNAbs. In the trials, viremia resurged rapidly in most patients despite suppressive VRC01 concentrations in circulation, suggesting that VRC01 resistance was the likely cause of failure. ART swiftly halts viral replication, precluding the development of resistance during ART. If resistance were to emerge post ART, virological breakthrough would have taken longer than without VRC01 therapy. We hypothesized therefore that VRC01-resistant strains must have been formed before ART initiation, survived ART in latently infected cells, and been activated during VRC01 therapy, causing treatment failure. Current assays preclude testing this hypothesis experimentally. We developed a mathematical model based on the hypothesis and challenged it with available clinical data. The model integrated within-host HIV-1 evolution, stochastic latency reactivation, and viral dynamics with multiple-dose VRC01 pharmacokinetics. The model predicted that single but not higher VRC01-resistant mutants would pre-exist in the latent reservoir. We constructed a virtual patient population that parsimoniously recapitulated inter-patient variations. Model predictions with this population quantitatively captured data of VRC01 failure from clinical trials, presenting strong evidence supporting the hypothesis. We attributed VRC01 failure to single-mutant VRC01-resistant proviruses in the latent reservoir triggering viral recrudescence, particularly when VRC01 was at trough levels. Pre-existing resistant proviruses in the latent reservoir may similarly compromise other bNAbs. Our study provides a framework for designing bNAb-based therapeutic protocols that would avert such failure and maximize HIV-1 remission.

Antiretroviral therapy (ART) can control but not eradicate HIV-1. Stopping ART leads to rapid viral resurgence and progressive disease. ART is therefore administered lifelong. Tremendous efforts are ongoing to devise strategies that will enable stopping ART and yet prevent viral resurgence. One such strategy involves the administration of broadly neutralizing antibodies (bNAbs) of HIV-1 at the time of stopping ART. This strategy is expected to delay if not prevent viral resurgence. Surprisingly, treatment with VRC01, a potent bNAb, resulted in hardly any improvement in viral remission. In this study, we elucidate the cause of this failure. We hypothesized that VRC01-resistant strains may pre-exist in latently infected cells, which are unaffected by ART. They can thus outlast ART and get reactivated, triggering VRC01 failure. We built a detailed mathematical model based on this hypothesis and showed that it quantitatively captured observations of VRC01 failure in clinical trials on chronic HIV-1 patients. Our study thus identifies a potential vulnerability of bNAbs, namely, bNAb-resistant strains pre-existing in latently infected cells. Our model offers a framework for predicting bNAb-based treatment protocols that would preclude failure due to pre-existing resistance and maximally prolong remission.

Association of Viral Persistence and Atherosclerosis in Adults With Treated HIV Infection

IMPORTANCE

Persons living with HIV (PLWH) have increased risk for cardiovascular disease, and inflammation is thought to contribute to this excess risk. Production of HIV during otherwise effective antiretroviral therapy (ART) has been associated with inflammation.

OBJECTIVE

To determine whether higher levels of viral persistence are associated with atherosclerosis as assessed by changes in carotid artery intima-media thickness (IMT) over time.

DESIGN, SETTING, AND PARTICIPANTS

In this cohort study, intima-media thickness, a validated marker of atherosclerosis, was assessed over time in a cohort of treated PLWH with viral suppression. Cell-associated HIV DNA and RNA and change in IMT, adjusted for demographics, cardiovascular risk factors, and HIV-related factors, were examined, as well as which factors were associated with viral persistence. One hundred fifty-two PLWH with undetectable viral loads for at least 6 months before study enrollment were recruited from HIV clinics affiliated with 2 hospitals in San Francisco, California, from January 1, 2003, to December 31, 2012. Data were analyzed from February 7, 2018, to May 12, 2020.

EXPOSURES

Cell-associated HIV RNA and DNA were measured using enriched CD4+ T cells from cryopreserved peripheral blood mononuclear cells.

MAIN OUTCOMES AND MEASURES

Carotid IMT was measured at baseline and the last visit, with a mean (SD) follow-up of 4.2 (2.7) years, using high-resolution B mode ultrasonography. The main study outcomes were baseline IMT, annual IMT progression, and incident plaque, defined as a focal region of carotid IMT of greater than 1.5 mm.

RESULTS

The analysis included 152 PLWH (140 [92.1%] male; median age, 48.5 [interquartile range {IQR}, 43.3-53.7] years). Older age, smoking, medications for hypertension, higher low-density lipoprotein levels, and higher interleukin 6 levels were associated with higher baseline mean IMT, whereas cell-associated HIV DNA (estimate, -0.07% [95% CI, -6.1% to 6.4%]; P = .98), and HIV RNA levels (estimate, -0.8% [95% CI, -5.9% to 4.4%]; P = .75) were not. Levels of HIV RNA (0.017 [95% CI, 0.000-0.034] mm/y; P = .047) and HIV DNA (0.022 [95% CI, 0.001-0.044] mm/y; P = .042) were significantly associated with annual carotid artery IMT progression in unadjusted models only. Both HIV RNA (incidence risk ratio [IRR], 3.05 [95% CI, 1.49-6.27] per IQR; P = .002) and HIV DNA (IRR, 3.15 [95% CI, 1.51-6.57] per IQR; P = .002) were significantly associated with incident plaque, which remained significant after adjusting for demographics, cardiovascular risk factors, and HIV-related factors (IRR for HIV RNA, 4.05 [95% CI, 1.44-11.36] per IQR [P = .008]; IRR for HIV DNA, 3.35 [95% CI, 1.22-9.19] per IQR [P = .02]). Higher C-reactive protein levels were associated with higher cell-associated HIV RNA (estimate, 20.7% [95% CI, 0.9%-44.4%] per doubling; P = .04), whereas higher soluble CD14 levels were associated with HIV DNA (estimate, 18.6% [95% CI, 3.5%-35.8%] per 10% increase; P = .01). Higher soluble CD163 levels were associated with a higher HIV RNA:DNA ratio (difference, 63.8% [95% CI, 3.5%-159.4%]; P = .04).

CONCLUSIONS AND RELEVANCE

These findings suggest that measurements of viral persistence in treated HIV disease are independently associated with incident carotid plaque development. The size and transcriptional activity of the HIV reservoir may be important contributors to HIV-associated atherosclerosis.

Immunological approaches to HIV cure

Combination antiretroviral therapy (ART) to treat human immunodeficiency virus (HIV) infection has proven remarkably successful - for those who can access and afford it - yet HIV infection persists indefinitely in a reservoir of cells, despite effective ART and despite host antiviral immune responses. An HIV cure is therefore the next aspirational goal and challenge, though approaches differ in their objectives - with 'functional cures' aiming for durable viral control in the absence of ART, and 'sterilizing cures' aiming for the more difficult to realize objective of complete viral eradication. Mechanisms of HIV persistence, including viral latency, anatomical sequestration, suboptimal immune functioning, reservoir replenishment, target cell-intrinsic immune resistance, and, potentially, target cell distraction of immune effectors, likely need to be overcome in order to achieve a cure. A small fraction of people living with HIV (PLWH) naturally control infection via immune-mediated mechanisms, however, providing both sound rationale and optimism that an immunological approach to cure is possible. Herein we review up to date knowledge and emerging evidence on: the mechanisms contributing to HIV persistence, as well as potential strategies to overcome these barriers; promising immunological approaches to achieve viral control and elimination of reservoir-harboring cells, including harnessing adaptive immune responses to HIV and engineered therapies, as well as enhancers of their functions and of complementary innate immune functioning; and combination strategies that are most likely to succeed. Ultimately, a cure must be safe, effective, durable, and, eventually, scalable in order to be widely acceptable and available.

Protective Immune Responses Elicited by Deglycosylated Live-Attenuated Simian Immunodeficiency Virus Vaccine Are Associated with IL-15 Effector Functions

Deglycosylated, live-attenuated SIV vaccines elicited protective immune responses against heterologous SIVsmE543-3, which differs from the vaccine strain SIVmac239 to levels similar to those across HIV-1 clades. Two thirds of the vaccinees contained the chronic SIVsmE543-3 infection (controllers), whereas one third did not (noncontrollers). In this study, we investigated immune correlates of heterologous challenge control in rhesus macaques of Burmese origin. Because depletion of CD8⁺ cells in the controllers by administration of anti-CD8α Ab abrogated the control of viral replication, CD8⁺ cells were required for the protective immune response. However, classical SIV-specific CD8⁺ T cells did not account for the protective immune response in all controllers. Instead, IL-15-responding CD8α⁺ cells, including CD8⁺ T and NK cells, were significantly higher in the controllers than those in the noncontrollers, before and after vaccination with deglycosylated SIV. It is well established that IL-15 signal transduction occurs through "trans-presentation" in which IL-15 complexed with IL-15Rα on monocytes, macrophages, and dendritic cells binds to IL-15 Rβ/γ expressed on CD8⁺ T and NK cells. Accordingly, levels of IL-15 stimulation were strongly affected by the depletion of monocytes from PBMCs, implying key roles of innate immune cells. These results suggest that intrinsic IL-15 responsiveness may dictate the outcome of protective responses and may lead to optimized formulations of future broadly protective HIV vaccines.

A Trispecific Anti-HIV Chimeric Antigen Receptor Containing the CCR5 N-Terminal Region

Anti-HIV chimeric antigen receptors (CARs) promote direct killing of infected cells, thus offering a therapeutic approach aimed at durable suppression of infection emerging from viral reservoirs. CD4-based CARs represent a favored option, since they target the essential conserved primary receptor binding site on the HIV envelope glycoprotein (Env). We have previously shown that adding a second Env-binding moiety, such as the carbohydrate recognition domain of human mannose-binding lectin (MBL) that recognizes the highly conserved oligomannose patch on gp120, increases CAR potency in an in vitro HIV suppression assay; moreover it reduces the undesired capacity for the CD4 of the CAR molecule to act as an entry receptor, thereby rendering CAR-expressing CD8⁺ T cells susceptible to infection. Here, we further improve the bispecific CD4-MBL CAR by adding a third targeting moiety against a distinct conserved Env determinant, i.e. a polypeptide sequence derived from the N-terminus of the HIV coreceptor CCR5. The trispecific CD4-MBL-R5Nt CAR displays enhanced in vitro anti-HIV potency compared to the CD4-MBL CAR, as well as undetectable HIV entry receptor activity. The high anti-HIV potency of the CD4-MBL-R5Nt CAR, coupled with its all-human composition and absence of immunogenic variable regions associated with antibody-based CARs, offer promise for the trispecific construct in therapeutic approaches seeking durable drug-free HIV remission.

Improving HIV Outgrowth by Optimizing Cell-Culture Conditions and Supplementing With all-trans Retinoic Acid

The persistence of replication-competent HIV reservoirs in people living with HIV (PLWH) receiving antiretroviral therapy (ART) is a barrier to cure. Therefore, their accurate quantification is essential for evaluating the efficacy of new therapeutic interventions and orienting the decision to interrupt ART. Quantitative viral outgrowth assays (QVOAs) represent the "gold standard" for measuring the size of replication-competent HIV reservoirs. However, they require large numbers of cells and are technically challenging. This justifies the need for the development of novel simplified methods adapted for small biological samples. Herein, we sought to simplify the viral outgrowth procedure (VOP) by (i) using memory CD4⁺ T-cells, documented to be enriched in HIV reservoirs (ii) optimizing cell-culture conditions, and (iii) supplementing with all-trans retinoic acid (ATRA), a positive regulator of HIV replication. Memory CD4⁺ T-cells were sorted from the peripheral blood of ART-treated (HIV+ART; n = 14) and untreated (HIV+; n = 5) PLWH. The VOP was first performed with one original replicate of 1 × 10⁶ cells/well in 48-well plates. Cells were stimulated via CD3/CD28 for 3 days, washed to remove residual CD3/CD28 Abs, split every 3 days for optimal cell density, and cultured in the presence or the absence of ATRA for 12 days. Soluble and intracellular HIV-p24 levels were quantified by ELISA and flow cytometry, respectively. Optimal cell-culture density achieved by splitting improved HIV outgrowth detection. ATRA promoted superior/accelerated detection of replication-competent HIV in all HIV+ART individuals tested, including those with low/undetectable viral outgrowth in the absence of ATRA. Finally, this VOP was used to design a simplified ATRA-based QVOA by including 4 and 6 original replicates of 1 × 10⁶ cells/well in 48-well plates and 2 × 10⁵ cells/well in 96-well plates, respectively. Consistently, the number of infectious units per million cells (IUPM) was significantly increased in the presence of ATRA. In conclusion, we demonstrate that memory CD4⁺ T-cell splitting for optimal density in culture and ATRA supplementation significantly improved the efficacy of HIV outgrowth in a simplified ATRA-based QVOA performed in the absence of feeder/target cells or indicator cell lines.

HIGH-FREQUENCY failure of combination antiretroviral therapy in paediatric HIV infection is associated with unmet maternal needs causing maternal NON-ADHERENCE

BACKGROUND

Early combination antiretroviral therapy (cART) reduces the size of the viral reservoir in paediatric and adult HIV infection. Very early-treated children may have higher cure/remission potential.

METHODS

In an observational study of 151 in utero (IU)-infected infants in KwaZulu-Natal, South Africa, whose treatment adhered strictly to national guidelines, 76 infants diagnosed via point-of-care (PoC) testing initiated cART at a median of 26 h (IQR 18-38) and 75 infants diagnosed via standard-of-care (SoC) laboratory-based testing initiated cART at 10 days (IQR 8-13). We analysed mortality, time to suppression of viraemia, and maintenance of aviraemia over the first 2 years of life.

FINDINGS

Baseline plasma viral loads were low (median 8000 copies per mL), with 12% of infants having undetectable viraemia pre-cART initiation. However, barely one-third (37%) of children achieved suppression of viraemia by 6 months that was maintained to >12 months. 24% had died or were lost to follow up by 6 months. Infant mortality was 9.3%. The high-frequency virological failure in IU-infected infants was associated not with transmitted or acquired drug-resistant mutations but with cART non-adherence (plasma cART undetectable/subtherapeutic, p<0.0001) and with concurrent maternal cART failure (OR 15.0, 95%CI 5.6-39.6; p<0.0001). High-frequency virological failure was observed in PoC- and SoC-tested groups of children.

INTERPRETATION

The success of early infant testing and cART initiation strategies is severely limited by subsequent cART non-adherence in HIV-infected children. Although there are practical challenges to administering paediatric cART formulations, these are overcome by mothers who themselves are cART-adherent. These findings point to the ongoing obligation to address the unmet needs of the mothers. Eliminating the particular barriers preventing adequate treatment for these vulnerable women and infants need to be prioritised in order to achieve durable suppression of viraemia on cART, let alone HIV cure/remission, in HIV-infected children.

FUNDING

Wellcome Trust, National Institutes of Health.

Improving Vaccine-Induced Immunity: Can Baseline Predict Outcome?

Immune signatures measured at baseline and immediately prior to vaccination may predict the immune response to vaccination. Such pre-vaccine assessment might allow not only population-based, but also more personalized vaccination strategies (‘precision vaccination’). If baseline immune signatures are predictive, the underlying mechanism they reflect may also determine vaccination outcome. Thus, baseline signatures might contribute to identifying interventional targets to be modulated prior to vaccination in order to improve vaccination responses. This concept has the potential to transform vaccination strategies and usher in a new approach to improve global health.

Extensive baseline variability in immune responses (e.g., antibody titers) among individuals in given populations is increasingly being appreciated as a major contributor to vaccine response heterogeneity.

The concept of ‘baseline may predict outcome’ has recently been reported for human influenza virus, yellow fever virus, and hepatitis B virus, as well as malaria vaccination. This concept might also apply to other vaccines.

The ability to predict who might respond to immunization (and to what extent) might offer avenues for optimization of current vaccination strategies.

We posit that this simple concept might be useful and significant for vaccine design: if ‘baseline determines outcome, then altering baseline prior to vaccination could alter outcome’.

This approach could potentially lead to tailored (precision) vaccines ensuring that the majority, or all individuals vaccinated, respond by eliciting a protective immune response (i.e., devoid of non-responder individuals). Presumably, this approach might also allow the administration of fewer vaccine doses, potentially arriving at one vaccine dose only.

Virtual memory CD8+ T cells restrain the viral reservoir in HIV-1-infected patients with antiretroviral therapy through derepressing KIR-mediated inhibition

The viral reservoir is the major hurdle in developing and establishing an HIV cure. Understanding factors affecting the size and decay of this reservoir is crucial for the development of therapeutic strategies. Recent work highlighted that CD8+ T cells are involved in the control of viral replication in ART-treated HIV-1-infected individuals, but how CD8+ T cells sense and restrict the HIV reservoir are not fully understood. Here, we demonstrate that a population of unconventional CD45RA+, PanKIR+, and/or NKG2A+ virtual memory CD8+ T cells (T_VM cells), which confer rapid and robust protective immunity against pathogens, plays an important role in restraining the HIV DNA reservoir in HIV-1-infected patients with effective ART. In patients undergoing ART, T_VM cells negatively correlate with HIV DNA and positively correlate with circulating IFN-α2 and IL-15. Moreover, T_VM cells constitutively express high levels of cytotoxic granule components, including granzyme B, perforin and granulysin, and demonstrate the capability to control HIV replication through both cytolytic and noncytolytic mechanisms. Furthermore, by using an ex vivo system, we showed that HIV reactivation is effectively suppressed by T_VM cells through KIR-mediated recognition. This study suggests that T_VM cells are a promising target to predict posttreatment virological control and to design immune-based interventions to reduce the reservoir size in ART-treated HIV-1-infected individuals.

Cerebrospinal fluid soluble CD30 elevation despite suppressive antiretroviral therapy in individuals living with HIV-1

OBJECTIVES

The aim of this study was to assess soluble CD30 (sCD30), a protein that colocalises with HIV-1 RNA and DNA in lymphoid cells and tissues, in cerebrospinal fluid (CSF) as a marker of HIV-1 infection in the central nervous system (CNS).

METHODS

This was a cross-sectional study using archived samples from two clinical cohorts. Soluble CD30 concentrations were measured in paired CSF and plasma from untreated viraemic individuals (n=52), individuals on suppressive antiretroviral therapy (ART) (n=33), HIV-1 controllers (n=10), participants with CSF HIV-1 'escape' (n=11) and controls without HIV-1 infection (n=16). Nonparametric tests were used to compare levels across groups and evaluate correlations with HIV-1 RNA, CSF neurofilament light chain protein (NFL) and neopterin.

RESULTS

Compared with controls (median 30 ng/mL, interquartile range [IRQ] 23-50), plasma sCD30 levels were elevated in viraemic participants (75 ng/mL, 52-116; P<0.001), but not in those on suppressive ART (38 ng/mL, 32-62). In contrast, CSF sCD30 levels were elevated in ART-suppressed individuals (34 ng/mL, 19-46; P=0.001) and in those with CSF 'escape' (33 ng/mL, 27-40; P=0.004) compared with controls (18 ng/mL, 11-23), but not in untreated viraemic individuals. No association was observed between CSF sCD30 and plasma HIV-1 RNA, concurrent or nadir CD4+ T cell count, duration of infection or plasma sCD30. CSF sCD30 correlated with CSF NFL (r=0.34, P=0.001).

CONCLUSIONS

In contrast to plasma, sCD30 levels are elevated in the CSF of individuals with HIV-1 infection who are on suppressive ART. Elevated levels of sCD30 in the CSF may be an indicator of persistent CNS HIV-1 infection, although the mechanism underlying this elevation warrants further investigation.

Reduce and Control: A Combinatorial Strategy for Achieving Sustained HIV Remissions in the Absence of Antiretroviral Therapy

Human immunodeficiency virus (HIV-1) indefinitely persists, despite effective antiretroviral therapy (ART), within a small pool of latently infected cells. These cells often display markers of immunologic memory and harbor both replication-competent and -incompetent proviruses at approximately a 1:100 ratio. Although complete HIV eradication is a highly desirable goal, this likely represents a bridge too far for our current and foreseeable technologies. A more tractable goal involves engineering a sustained viral remission in the absence of ART––a “functional cure.” In this setting, HIV remains detectable during remission, but the size of the reservoir is small and the residual virus is effectively controlled by an engineered immune response or other intervention. Biological precedence for such an approach is found in the post-treatment controllers (PTCs), a rare group of HIV-infected individuals who, following ART withdrawal, do not experience viral rebound. PTCs are characterized by a small reservoir, greatly reduced inflammation, and the presence of a poorly understood immune response that limits viral rebound. Our goal is to devise a safe and effective means for replicating durable post-treatment control on a global scale. This requires devising methods to reduce the size of the reservoir and to control replication of this residual virus. In the following sections, we will review many of the approaches and tools that likely will be important for implementing such a “reduce and control” strategy and for achieving a PTC-like sustained HIV remission in the absence of ART.