Peripheral T follicular helper Cells Make a Difference in HIV Reservoir Size between Elite Controllers and Patients on Successful cART

Transcriptomic crosstalk between viral and host factors drives aberrant homeostasis of T-cell proliferation and cell death in HIV-infected immunological non-responders

BACKGROUND

Immunological non-responders (INRs) among people living with HIV have inherently higher mortality and morbidity rates. The underlying immunological mechanisms whereby failure of immune reconstitution occurs in INRs require elucidation.

METHOD

HIV-1 DNA and HIV-1 cell-associated RNA (CA-HIV RNA) quantifications were conducted via RT-qPCR. Transcriptome sequencing (RNA-seq), bioinformatics, and biological verifications were performed to discern the crosstalk between host and viral factors. Flow cytometry was employed to analyze cellular activation, proliferation, and death.

RESULTS

HIV-1 DNA and CA-HIV RNA levels were observed to be significantly higher in INRs compared to immunological responders (IRs). Evaluation of CD4/CD8 ratios showed a significantly negative correlation with HIV-1 DNA in IRs, but not in INRs. Bioinformatics analyses and biological verifications showed IRF7/INF-α regulated antiviral response was intensified in INRs. PBMCs of INRs expressed significantly more HIV integrase-mRNA (p31) than IRs. Resting (CD4+CD69- T-cells) and activated (CD4+CD69+ T-cells) HIV-1 reservoir harboring cells were significantly higher in INRs, with the co-occurrence of significantly higher cellular proliferation and cell death in CD4+ T-cells of INRs.

CONCLUSION

In INRs, the systematic crosstalk between the HIV-1 reservoir and host cells tends to maintain a persistent antiviral response-associated inflammatory environment, which drives aberrant cellular activation, proliferation, and death of CD4+ T-cells.

Challenges and Opportunities of Therapies Targeting Early Life Immunity for Pediatric HIV Cure

Early initiation of antiretroviral therapy (ART) significantly improves clinical outcomes and reduces mortality of infants/children living with HIV. However, the ability of infected cells to establish latent viral reservoirs shortly after infection and to persist during long-term ART remains a major barrier to cure. In addition, while early ART treatment of infants living with HIV can limit the size of the virus reservoir, it can also blunt HIV-specific immune responses and does not mediate clearance of latently infected viral reservoirs. Thus, adjunctive immune-based therapies that are geared towards limiting the establishment of the virus reservoir and/or mediating the clearance of persistent reservoirs are of interest for their potential to achieve viral remission in the setting of pediatric HIV. Because of the differences between the early life and adult immune systems, these interventions may need to be tailored to the pediatric settings. Understanding the attributes and specificities of the early life immune milieu that are likely to impact the virus reservoir is important to guide the development of pediatric-specific immune-based interventions towards viral remission and cure. In this review, we compare the immune profiles of pediatric and adult HIV elite controllers, discuss the characteristics of cellular and anatomic HIV reservoirs in pediatric populations, and highlight the potential values of current cure strategies using immune-based therapies for long-term viral remission in the absence of ART in children living with HIV.

Accuracy of real-time PCR and digital PCR for the monitoring of total HIV DNA under prolonged antiretroviral therapy

Total HIV DNA is a standard marker to monitor the HIV reservoir in people living with HIV. We investigated HIV DNA quantification accuracy by a real-time PCR kit (qPCR) and digital PCR (dPCR) method within the same set of primers and probes. Among 48 aviremic patients followed for up to 7 years with qPCR, the mean coefficient of variation of total HIV DNA between two successive measurements was 77% (± 0.42log₁₀ HIVDNA copies/10⁶ PBMC). The total HIV DNA quantified by the two PCR methods has a high correlation (0.99 and 0.83, for 8E5 and PLHIV samples, respectively), but we observed better repeatability and reproducibility of the dPCR compared to the qPCR (CV of 11.9% vs. 24.7% for qPCR, p-value = 0.024). Furthermore, we highlighted a decay of the number of HIV copies in the 8E5 cell line qPCR standard over time (from 0.73 to 0.43 copies per cell), contributing to variations of HIV DNA results in patients whose HIV reservoir should be theoretically stabilized. Our study highlighted that absolute quantification of total HIV DNA by dPCR allows more accurate monitoring of the HIV reservoir than qPCR in patients under prolonged antiretroviral therapy.

Molecular Biology and Diversification of Human Retroviruses

Studies of retroviruses have led to many extraordinary discoveries that have advanced our understanding of not only human diseases, but also molecular biology as a whole. The most recognizable human retrovirus, human immunodeficiency virus type 1 (HIV-1), is the causative agent of the global AIDS epidemic and has been extensively studied. Other human retroviruses, such as human immunodeficiency virus type 2 (HIV-2) and human T-cell leukemia virus type 1 (HTLV-1), have received less attention, and many of the assumptions about the replication and biology of these viruses are based on knowledge of HIV-1. Existing comparative studies on human retroviruses, however, have revealed that key differences between these viruses exist that affect evolution, diversification, and potentially pathogenicity. In this review, we examine current insights on disparities in the replication of pathogenic human retroviruses, with a particular focus on the determinants of structural and genetic diversity amongst HIVs and HTLV.

Robust HIV-specific CD4+ and CD8+ T-cell responses distinguish elite control in adolescents living with HIV from viremic nonprogressors

BACKGROUND

Elite controllers are therapy-naive individuals living with HIV capable of spontaneous control of plasma viraemia for at least a year. Although viremic nonprogressors are more common in vertical HIV-infection than in adults' infection, elite control has been rarely characterized in the pediatric population.

DESIGN

We analyzed the T-cell immunophenotype and the HIV-specific response by flow cytometry in four pediatric elite controllers (PECs) compared with age-matched nonprogressors (PNPs), progressors and HIV-exposed uninfected (HEUs) adolescents.

RESULTS

PECs T-cell populations had lower immune activation and exhaustion levels when compared with progressors, reflected by a more sustained and preserved effector function. The HIV-specific T-cell responses among PECs were characterized by high-frequency Gag-specific CD4+ T-cell activity, and markedly more polyfunctional Gag-specific CD8+ activity, compared with PNPs and progressors. These findings were consistently observed even in the absence of protective HLA-I molecules such as HLA-B∗27/57/81.

CONCLUSION

Pediatric elite control is normally achieved after years of infection, and low immune activation in PNPs precedes the increasing ability of CD8+ T-cell responses to achieve immune control of viraemia over the course of childhood, whereas in adults, high immune activation in acute infection predicts subsequent CD8+ T-cell mediated immune control of viremia, and in adult elite controllers, low immune activation is therefore the consequence of the rapid CD8+ T-cell mediated immune control generated after acute infection. This distinct strategy adopted by PECs may help identify pathways that facilitate remission in posttreatment controllers, in whom protective HLA-I molecules are not the main factor.

Human Immunodeficiency Virus Persistence in the Spleen: Opportunities for Pharmacologic Intervention

The persistence of HIV in the spleen, despite combination antiretroviral therapy, is not well understood. Sustained immune dysregulation and delayed immune recovery, in addition to immune cell exhaustion, may contribute to persistence of infection in the spleen. Eliminating HIV from this secondary lymphoid organ will require a thorough understanding of antiretroviral (ARV) pharmacology in the spleen, which has been minimally investigated. Low ARV exposure within the spleen may hinder the achievement of a functional or sterilizing cure if cells are not protected from HIV infection. In this study, we provide an overview of the anatomy and physiology of the spleen, review the evidence of the spleen as a site for persistence of HIV, discuss the consequences of persistence of HIV in the spleen, address challenges to eradicating HIV in the spleen, and examine opportunities for future curative efforts.

Interleukin-21 in Viral Infections

Interleukin (IL)-21 is a cytokine that affects the differentiation and function of lymphoid and myeloid cells and regulates both innate and adaptive immune responses. In addition to regulating the immune response to tumor and viral infections, IL-21 also has a profound effect on the development of autoimmune and inflammatory diseases. IL-21 is produced mainly from CD4⁺ T cells-in particular, follicular helper T (Tfh) cells-which have a great influence on the regulation of antibody production. It is also an important cytokine for the activation of CD8⁺ T cells, and its role in recovering the function of CD8⁺ T cells exhausted by chronic microbial infections and cancer has been clarified. Thus, IL-21 plays an extremely important role in viral infections, especially chronic viral infections. In this review, I will introduce the findings to date on how IL-21 is involved in some typical viral infections and the potential of treating viral diseases with IL-21.

Production of HIV-1 Env-specific antibodies mediating innate immune functions depends on cognate IL-21- secreting CD4+ T cells

Antibodies with a functional Fc region were previously associated with protection from HIV-1 acquisition and spontaneous suppression of viral replication. Unlike broadly neutralizing antibodies, they are not restricted to neutralizing epitopes and do not require unconventional structural traits to exert their antiviral activity. They, therefore, develop earlier after infection and can be detected in the majority of cases. The conditions under which these antibodies are generated, however, remain largely unknown. Here we demonstrate that the generation of HIV-1 Env-specific antibodies facilitating Fc-dependent innate immune responses, including neutrophil phagocytosis (ADNP), complement deposition (ADCD), and NK cell activation, likely depends on help provided by CD4+ T and peripheral T follicular helper (pTfh) cells secreting IL-21. Other proteins, including CD40L, IFNγ, and IL-4/13, involved in crosstalk between B and T cells were linked to the production of antibodies with functional Fc region but only when co-expressed with IL-21. As a potential source of these antibodies, we identified a subset of Env-specific memory B cells known to be expanded in chronic HIV-1 infection. The frequency and level of Blimp-1 expression in Env-specific tissue-like memory B cells (TLM) correlated with the functional CD4+ T cell subsets associated with robust antibody-dependent innate responses. Thus, our data suggest a mechanism responsible for the generation of antibodies with functional Fc region in chronically HIV-1 infected individuals that is based on CD4+ T cell-induced activation of memory B cells.Importance To develop a vaccine or immunotherapy that would cure the HIV-1 infection it is important to identify helper T cells able to mount an efficient antibody response. Here, we demonstrate that the generation of HIV-1 Env-specific antibodies facilitating antibody-dependent innate immune responses likely depends on Env-specific IL-21-secreting CD4+ T and peripheral T follicular helper cells.

Towards a Functional Cure of HIV-1: Insight Into the Chromatin Landscape of the Provirus

Despite potent combination antiretroviral therapy, HIV-1 infection persists due to irreversible integration of the virus in long-living cells of the immune system. The main focus of HIV-1 cure strategies has been on HIV-1 eradication, yet without great success so far. Therefore, HIV-1 remission or a functional cure, whereby the virus is silenced rather than eradicated, is considered as an alternative strategy. Elite controllers, individuals who spontaneously control HIV-1, may point us the way toward a functional HIV-1 cure. In order to achieve such a cure, a profound understanding of the mechanisms controlling HIV-1 expression and silencing is needed. In recent years, evidence has grown that the site of integration as well as the chromatin landscape surrounding the integration site affects the transcriptional state of the provirus. Still, at present, the impact of integration site selection on the establishment and maintenance of the HIV-1 reservoirs remains poorly understood. The discovery of LEDGF/p75 as a binding partner of HIV-1 integrase has led to a better understanding of integration site selection. LEDGF/p75 is one of the important determinants of integration site selection and targets integration toward active genes. In this review, we will provide an overview of the most important determinants of integration site selection. Secondly, we will discuss the chromatin landscape at the integration site and its implications on HIV-1 gene expression and silencing. Finally, we will discuss how interventions that affect integration site selection or modifications of the chromatin could yield a functional cure of HIV-1 infection.

HIV-DNA content in pTfh cells is associated with residual viremia in elite controllers

OBJECTIVE

The source of residual HIV viremia is highly debated and its potential relationship with the HIV reservoir has not been clarified. Herein, we analysed the cell-associated HIV-DNA content in two important cell compartments of the HIV reservoir, resting CD4+ T memory (Trm) and peripheral T follicular helper (pTfh) cells, and the association with the residual HIV viremia in individuals with spontaneous HIV replication control (elite controllers, EC group) and in individuals with antiretroviral therapy (ART)-mediated HIV replication control (cART group).

DESIGN

A cross-sectional study.

METHODS

Seventeen chronically HIV-infected patients with suppressed HIV replication were included. Cell-associated HIV-DNA was measured by ultrasensitive digital-droplet-PCR in purified Trm and pTfh cells. Residual HIV plasma viremia was quantified using a single-copy assay with a sensitivity of 0.3 HIV-RNA copies/ml.

RESULTS

A significant and positive correlation was demonstrated between HIV-DNA levels in pTfh cells and residual plasma viral load (rpVL) (rho = 0.928, P = 0.008) in HIV-positive elite controllers, but not in HIV-positive treated patients, despite the lower levels of cell-associated HIV-DNA found in elite controllers compared with cART patients in pTfh cells [176 (77-882) vs. 608 (361-860) copies/million cells, respectively; P = 0.05].

CONCLUSION

This association suggests that pTfh cells could have an important contribution to persistent viremia in elite controllers. This could be the consequence of a more limited control of HIV replication in elite controllers with higher transcriptional activity of HIV in pTfh cells of elite controllers than that in cART patients.

TFH Cells Induced by Vaccination and Following SIV Challenge Support Env-Specific Humoral Immunity in the Rectal-Genital Tract and Circulation of Female Rhesus Macaques

T follicular helper (T_FH) cells are pivotal in lymph node (LN) germinal center (GC) B cell affinity maturation. Circulating CXCR5⁺ CD4⁺ T (cT_FH) cells have supported memory B cell activation and broadly neutralizing antibodies in HIV controllers. We investigated the contribution of LN SIV-specific T_FH and cT_FH cells to Env-specific humoral immunity in female rhesus macaques following a mucosal Ad5hr-SIV recombinant priming and SIV gp120 intramuscular boosting vaccine regimen and following SIV vaginal challenge. T_FH and B cells were characterized by flow cytometry. B cell help was evaluated in T_FH-B cell co-cultures and by real-time PCR. Vaccination induced Env-specific T_FH and Env-specific memory (ESM) B cells in LNs. LN Env-specific T_FH cells post-priming and GC ESM B cells post-boosting correlated with rectal Env-specific IgA titers, and GC B cells at the same timepoints correlated with vaginal Env-specific IgG titers. Vaccination expanded cT_FH cell responses, including CD25⁺ Env-specific cT_FH cells that correlated negatively with vaginal Env-specific IgG titers but positively with rectal Env-specific IgA titers. Although cT_FH cells post-2^nd boost positively correlated with viral-loads following SIV challenge, cT_FH cells of SIV-infected and protected macaques supported maturation of circulating B cells into plasma cells and IgA release in co-culture. Additionally, cT_FH cells of naïve macaques promoted upregulation of genes associated with B cell proliferation, BCR engagement, plasma cell maturation, and antibody production, highlighting the role of cT_FH cells in blood B cell maturation. Vaccine-induced LN T_FH and GC B cells supported anti-viral mucosal immunity while cT_FH cells provided B cell help in the periphery during immunization and after SIV challenge. Induction of T_FH responses in blood and secondary lymphoid organs is likely desirable for protective efficacy of HIV vaccines.

Human Immunodeficiency Virus 1 (HIV-1): Viral Latency, the Reservoir, and the Cure

An estimated 37 million people globally suffer from Human Immunodeficiency Virus-1 (HIV-1) infection with 1.7 million newly acquired infections occurring on average each year. Although crucial advances in combined antiretroviral therapy (ART) over the last two decades have transformed an HIV-1 diagnosis into a tolerable and controlled condition, enabling over 20 million people living with HIV-1 to enjoy healthy and productive lives, no cure or vaccine yet exists. Developing a successful cure strategy will require a firm understanding of how viral latency is established and how a persistent and long-lived latent is generated. The latent reservoir remains the primary obstacle for cure development and most putative cure strategies proposed fundamentally address its eradication or permanent suppression.

Transcriptional signature of resting-memory CD4 T cells differentiates spontaneous from treatment-induced HIV control

The HIV reservoir is the main barrier to eradicating HIV infection, and resting memory CD4 T (Trm) cells are one of the most relevant cellular component harboring latent proviruses. This is the first study analyzing the transcriptional profile of Trm cells, in two well-characterized groups of HIV patients with distinct mechanisms of viral replication control (spontaneous versus treatment-induced). We use a systems biology approach to unravel subtle but important differences in the molecular mechanisms operating at the cellular level that could be associated with the host's ability to control virus replication and persistence. Despite the absence of significant differences in the transcriptome of Trm cells between Elite Controllers (ECs) and cART-treated (TX) patients at the single gene level, we found 353 gene ontology (GO) categories upregulated in EC compared with TX. Our results suggest the existence of mechanisms at two different levels: first boosting both adaptive and innate immune responses, and second promoting active viral replication and halting HIV latency in the Trm cell compartment of ECs as compared with TX patients. These differences in the transcriptional profile of Trm cells could be involved in the lower HIV reservoir observed in ECs compared with TX individuals, although mechanistic studies are needed to confirm this hypothesis. Combining transcriptome analysis and systems biology methods is likely to provide important findings to help us in the design of therapeutic strategies aimed at purging the HIV reservoir. KEY MESSAGES: HIV-elite controllers have the lowest HIV-DNA content in resting memory CD4 T cells. HIV-ECs show a particular transcriptional profile in resting memory CD4 T cells. Molecular mechanisms of enhanced adaptative and innate immune response in HIV-ECs. High viral replication and low viral latency establishment associate to the EC status.

Follicular T-cell subsets in HIV infection: recent advances in pathogenesis research

PURPOSE OF REVIEW

T cells within B-cell follicles of secondary lymphoid tissues play key roles in HIV immunopathogenesis. This review highlights recent findings and identifies gaps in current knowledge.

RECENT FINDINGS

B-cell follicles are major sites of virus replication and demonstrate significant impairments in the generation of humoral immunity in HIV infection. Follicular T helper cells (Tfh), follicular T regulatory cells (Tfr) and follicular CD8 T cells (fCD8) play key roles in HIV immunopathogenesis. Tfh and more recently Tfr are highly permissive to HIV, and may serve as reservoirs of HIV in treated infection. Virus-specific CD8 T cells are less abundant in B-cell follicles than extrafollicular regions, but their effector mechanisms remain an area of significant controversy. Impairments in Tfh likely contribute to impaired humoral immunity and potential mechanisms include B-cell counter-regulatory mechanisms, Tfr suppression and diminished repertoire breadth. A better understanding of the roles of Tfh, Tfr and fCD8 in HIV immunopathogenesis is critical to the development of effective HIV vaccines and cure strategies.

SUMMARY

Tfh, Tfr and fCD8 contribute to HIV persistence and impaired humoral immunity. A better understanding of their roles could facilitate vaccine development and HIV cure strategies.

Elite suppressors have low frequencies of intact HIV-1 proviral DNA

: Elite controllers or suppressors control viral replication without antiretroviral therapy. We used the intact proviral DNA assay to approximate the size of the inducible latent reservoir in elite suppressors and found that, while the median frequency of both total and intact proviral DNA was markedly lower than the frequencies seen in chronic progressors on antiretroviral therapy there was no significant difference in the ratio of intact to total proviral DNA between elite suppressors and chronic progressors.

Quantification of Viral RNA and DNA Positive Cells in Tissues From Simian Immunodeficiency Virus/Simian Human Immunodeficiency Virus Infected Controller and Progressor Rhesus Macaques

Eradication of human immunodeficiency virus 1 (HIV-1) from an infected individual cannot be achieved using current antiretroviral therapy (ART) regimens. Viral reservoirs established in early infection remain unaffected by ART and are able to replenish systemic infection upon treatment interruption. Simian immunodeficiency virus (SIV) infected macaque models are useful for studying HIV pathogenesis, treatments, and persistent viral reservoirs. Here, we used the SIV macaque model to examine and quantify RNA and DNA positive cells in tissues from macaques that control viral replication (controllers) and those that have persistently high plasma viremia (progressors). A positive correlation was detected between tissue RNA+ cells and plasma viral load in both mesenteric lymph node (LN) and spleen. Similarly, a positive correlation also observed between DNA+ cells and plasma viral load in ileum and jejunum. Controllers had a lower frequency of both RNA and DNA+ cells in several tissues compared to progressors. However, DNA+ cells were prevalent in mesenteric LN, inguinal LN, colon, midbrain, and bone marrow tissues in both controller and progressors. Organized lymphoid tissues of LNs, spleen, and intestine were found as the major tissues positive for virus. Viral RNA and DNA positive cells were detected in brain and thymus in macaques with high plasma viremia and SIV-encephalitis. Both T cells and macrophages were shown to be infected in several tissues, indicating vaccines and ART should be specifically designed to protect these cells in organized lymphoid tissues. These results indicate ART should target infected cells in secondary lymphoid organs to reduce both productively and latently infected cells.

HIV-2 as a model to identify a functional HIV cure

Two HIV virus types exist: HIV-1 is pandemic and aggressive, whereas HIV-2 is confined mainly to West Africa and less pathogenic. Despite the fact that it has been almost 40 years since the discovery of AIDS, there is still no cure or vaccine against HIV. Consequently, the concepts of functional vaccines and cures that aim to limit HIV disease progression and spread by persistent control of viral replication without life-long treatment have been suggested as more feasible options to control the HIV pandemic. To identify virus-host mechanisms that could be targeted for functional cure development, researchers have focused on a small fraction of HIV-1 infected individuals that control their infection spontaneously, so-called elite controllers. However, these efforts have not been able to unravel the key mechanisms of the infection control. This is partly due to lack in statistical power since only 0.15% of HIV-1 infected individuals are natural elite controllers. The proportion of long-term viral control is larger in HIV-2 infection compared with HIV-1 infection. We therefore present the idea of using HIV-2 as a model for finding a functional cure against HIV. Understanding the key differences between HIV-1 and HIV-2 infections, and the cross-reactive effects in HIV-1/HIV-2 dual-infection could provide novel insights in developing functional HIV cures and vaccines.

Barriers and strategies to achieve a cure for HIV

9 years since the report of a cure for HIV after C-C chemokine receptor type 5 Δ32 stem cell transplantation, no other case of HIV cure has been reported, despite much research. However, substantial progress has been made in understanding the biology of the latent HIV reservoir, and in measuring the amount of virus that persists after antiretroviral therapy (ART) with increasingly sophisticated approaches. This knowledge is being translated into a long pipeline of clinical trials seeking to reduce viral persistence in participants on suppressive treatment and ultimately to allow safe cessation of ART. In this Review, we discuss the main barriers preventing the development of an HIV cure, methods used to measure HIV persistence in individuals on ART, clinical strategies that aim to cure HIV, and future directions for studies in the field of HIV cure research.

Phylogenies in ART: HIV reservoirs, HIV latency and drug resistance

Combination antiretroviral therapy (ART) has significantly reduced the morbidity and mortality resulting from HIV infection. ART is, however, unable to eradicate HIV, which persists latently in several cell types and tissues. Phylogenetic analyses suggested that the proliferation of cells infected before ART initiation is mainly responsible for residual viremia, although controversy still exists. Conversely, it is widely accepted that drug resistance mutations (DRMs) do not appear during ART in patients with suppressed viral loads. Studies based on sequence clustering have in fact indicated that, at least in developed countries, HIV-infected ART-naive patients are the major source of drug-resistant viruses. Analysis of longitudinally sampled sequences have also shown that DRMs have variable fitness costs, which are strongly influenced by the viral genetic background.

Cat and Mouse: HIV Transcription in Latency, Immune Evasion and Cure/Remission Strategies

There is broad scientific and societal consensus that finding a cure for HIV infection must be pursued. The major barrier to achieving a cure for HIV/AIDS is the capacity of the HIV virus to avoid both immune surveillance and current antiretroviral therapy (ART) by rapidly establishing latently infected cell populations, termed latent reservoirs. Here, we provide an overview of the rapidly evolving field of HIV cure/remission research, highlighting recent progress and ongoing challenges in the understanding of HIV reservoirs, the role of HIV transcription in latency and immune evasion. We review the major approaches towards a cure that are currently being explored and further argue that small molecules that inhibit HIV transcription, and therefore uncouple HIV gene expression from signals sent by the host immune response, might be a particularly promising approach to attain a cure or remission. We emphasize that a better understanding of the game of "cat and mouse" between the host immune system and the HIV virus is a crucial knowledge gap to be filled in both cure and vaccine research.

CD32 Expression is not Associated to HIV-DNA content in CD4 cell subsets of individuals with Different Levels of HIV Control

A recent study has pointed out to CD32a as a potential biomarker of HIV-persistent CD4 cells. We have characterized the level and phenotype of CD32+ cells contained in different subsets of CD4 T-cells and its potential correlation with level of total HIV-DNA in thirty HIV patients (10 typical progressors naïve for cART, 10 cART-suppressed patients, and 10 elite controllers). Total HIV-DNA was quantified in different subsets of CD4 T-cells: Trm and pTfh cells. Level and immunephenotype of CD32+ cells were analyzed in these same subsets by flow cytometry. CD32 expression in Trm and pTfh subsets was similar in the different groups, and there was no significant correlation between the level of total HIV-DNA and the level of CD32 expression in these subsets. However, total HIV-DNA level was correlated with expression of CD127 (rho = -0.46, p = 0.043) and of CCR6 (rho = -0.418, p = 0.027) on CD32+ cells. Our results do not support CD32 as a biomarker of total HIV-DNA content. However, analyzing the expression of certain markers by CD32+ cells could improve the utility of this marker in the clinical setting, prompting the necessity of further studies to both validate our results and to explore the potential utility of certain markers expressed by CD32+ cells.

Understanding the CD8 T-cell response in natural HIV control

HIV-infected individuals who maintain control of virus without antiretroviral therapy (ART) are called HIV controllers. The immune responses of these individuals suppress HIV viral replication to low levels or, in the case of elite controllers, to undetectable levels. Although some research indicates a role for inferior virulence of the infecting viral strain in natural control, perhaps by way of defective Nef protein function, we find that the majority of research in HIV controllers highlights CD8 T cells as the main suppressor of viral replication. The most convincing evidence for this argument lies in the strong correlation between certain HLA-I alleles, especially B*57, and HIV control status, a finding that has been replicated by many groups. However, natural control can also occur in individuals lacking these specific HLA alleles, and our understanding of what constitutes an effective CD8 T-cell response remains an incomplete picture. Recent research has broadened our understanding of natural HIV control by illustrating the interactions between different immune cells, including innate immune effectors and antigen-presenting cells. For many years, the immune responses of the natural HIV controllers have been studied for clues on how to achieve functional cure in the rest of the HIV-infected population. The goal of a future functional cure to HIV is one where HIV-infected individuals’ immune responses are able to suppress virus long-term without requiring ART. This review highlights recent advances in our understanding of how HIV controllers’ natural immune responses are able to suppress virus.

Peering into the HIV reservoir

The main obstacle to HIV eradication is the establishment of a long-term persistent HIV reservoir. Although several therapeutic approaches have been developed to reduce and eventually eliminate the HIV reservoir, only a few have achieved promising results. A better knowledge of the mechanisms involved in the establishment and maintenance of HIV reservoir is of utmost relevance for the design of new therapeutic strategies aimed at purging it with the ultimate goal of achieving HIV eradication or alternatively a functional cure. In this regard, it is also important to take a close look into the cellular HIV reservoirs other than resting memory CD4 T-cells with key roles in reservoir maintenance that have been recently described. Unraveling the special characteristics of these HIV cellular compartments could aid us in designing new therapeutic strategies to deplete the latent HIV reservoir.

Deciphering natural control of HIV-1: A valuable strategy to achieve antiretroviral therapy termination

Antiretroviral therapy (ART) has dramatically reduced HIV-1-associated morbidity and mortality, and has transformed HIV-1 infection into a manageable chronic condition by suppressing viral replication. However, despite recent patient care improvements, ART still fails to cure HIV-1 infection due to the inability to counteract immune defects and metabolic disturbances that are associated with residual inflammation alongside viral persistence. Life-long drug administration also results in multiple side-effects in patients including lipodystrophy and insulin resistance. Thus, it is critical to find new ways to reduce the length of treatment and facilitate the termination of ART, for example by boosting protective immunity. The rare ability of some individuals to naturally control HIV-1 infection despite residual inflammation could be exploited to identify molecular mechanisms involved in host protection that may function as potential therapeutic targets. In this review, we highlight evidence illustrating the molecular and metabolic advantages of HIV-1 controllers over ART treated patients that contribute to the maintenance of effective antiviral immunity.