Factors Associated With the Control of Viral Replication and Virologic Breakthrough in a Recently Infected HIV-1 Controller

IL-15-dependent immune crosstalk between natural killer cells and dendritic cells in HIV-1 elite controllers

As the principal effector cell population of the innate immune system, natural killer (NK) cells may make critical contributions to natural, immune-mediated control of HIV-1 replication. Using genome-wide assessments of activating and inhibitory chromatin features, we demonstrate here that cytotoxic NK (cNK) cells from elite controllers (ECs) display elevated activating histone modifications at the interleukin 2 (IL-2)/IL-15 receptor β chain and the BCL2 gene loci. These histone changes translate into increased responsiveness of cNK cells to paracrine IL-15 secretion, which coincides with higher levels of IL-15 transcription by myeloid dendritic cells in ECs. The distinct immune crosstalk between these innate immune cell populations results in improved IL-15-dependent cNK cell survival and cytotoxicity, paired with a metabolic profile biased toward IL-15-mediated glycolytic activities. Together, these results suggest that cNK cells from ECs display a programmed IL-15 response signature and support the emerging role of innate immune pathways in natural, drug-free control of HIV-1.

Targeting the HIV reservoir: chimeric antigen receptor therapy for HIV cure

ABSTRACT

Although antiretroviral therapy (ART) can reduce the viral load in the plasma to undetectable levels in human immunodeficiency virus (HIV)-infected individuals, ART alone cannot completely eliminate HIV due to its integration into the host cell genome to form viral reservoirs. To achieve a functional cure for HIV infection, numerous preclinical and clinical studies are underway to develop innovative immunotherapies to eliminate HIV reservoirs in the absence of ART. Early studies have tested adoptive T-cell therapies in HIV-infected individuals, but their effectiveness was limited. In recent years, with the technological progress and great success of chimeric antigen receptor (CAR) therapy in the treatment of hematological malignancies, CAR therapy has gradually shown its advantages in the field of HIV infection. Many studies have identified a variety of HIV-specific CAR structures and types of cytolytic effector cells. Therefore, CAR therapy may be beneficial for enhancing HIV immunity, achieving HIV control, and eliminating HIV reservoirs, gradually becoming a promising strategy for achieving a functional HIV cure. In this review, we provide an overview of the design of anti-HIV CAR proteins, the cell types of anti-HIV CAR (including CAR T cells, CAR natural killer cells, and CAR-encoding hematopoietic stem/progenitor cells), the clinical application of CAR therapy in HIV infection, and the prospects and challenges in anti-HIV CAR therapy for maintaining viral suppression and eliminating HIV reservoirs.

Cohort-Specific Peptide Reagents Broaden Depth and Breadth Estimates of the CD8 T Cell Response to HIV-1 Gag Potential T Cell Epitopes

An effective HIV vaccine will need to stimulate immune responses against the sequence diversity presented in circulating virus strains. In this study, we evaluate breadth and depth estimates of potential T-cell epitopes (PTEs) in transmitted founder virus sequence-derived cohort-specific peptide reagents against reagents representative of consensus and global sequences. CD8 T-cells from twenty-six HIV-1+ PBMC donor samples, obtained at 1-year post estimated date of infection, were evaluated. ELISpot assays compared responses to 15mer consensus (n = 121), multivalent-global (n = 320), and 10mer multivalent cohort-specific (n = 300) PTE peptides, all mapping to the Gag antigen. Responses to 38 consensus, 71 global, and 62 cohort-specific PTEs were confirmed, with sixty percent of common global and cohort-specific PTEs corresponding to consensus sequences. Both global and cohort-specific peptides exhibited broader epitope coverage compared to commonly used consensus reagents, with mean breadth estimates of 3.2 (global), 3.4 (cohort) and 2.2 (consensus) epitopes. Global or cohort peptides each identified unique epitope responses that would not be detected if these peptide pools were used alone. A peptide set designed around specific virologic and immunogenetic characteristics of a target cohort can expand the detection of CD8 T-cell responses to epitopes in circulating viruses, providing a novel way to better define the host response to HIV-1 with implications for vaccine development.

NK Cells, Monocytes and Macrophages in HIV-1 Control: Impact of Innate Immune Responses

Rapid and synchronized responses of innate immune cells are an integral part of managing viral spread in acute virus infections. In human immunodeficiency virus type 1 (HIV-1) infection, increased immune control has been associated with the expression of certain natural killer (NK) cell receptors. Further, immune activation of monocytes/macrophages and the presence of specific cytokines was linked to low levels of HIV-1 replication. In addition to the intrinsic antiviral capabilities of NK cells and monocytes/macrophages, interaction between these cell types has been shown to substantially enhance NK cell function in the context of viral infections. This review discusses the involvement of NK cells and monocytes/macrophages in the effective control of HIV-1 and highlights aspects of innate immune crosstalk in viral infections that may be of relevance to HIV-1 infection.

Evaluation of CCR5-Δ32 mutation and HIV-1 surveillance drug-resistance mutations in peripheral blood mononuclear cells of long-term non progressors of HIV-1-infected individuals

Aim: This study aimed to evaluate chemokine receptor 5 delta 32 (CCR5-Δ32) mutation and HIV-1 surveillance drug-resistance mutations (SDRMs) in peripheral blood mononuclear cells of long-term non progressors (LTNPs) of HIV-1-infected individuals. Materials and methods: This research was performed on 197 treatment-naive HIV-1-infected patients. After follow-up, it was determined that 15 (7.6%) of these people were LTNPs. The PCR assay was performed to identify the CCR5 genotype and HIV-1 SDRMs. Results: One (6.7%) of the LTNPs was heterozygous (wt/Δ32) for the CCR5 delta 32 (CCR5Δ32). However, none of the individuals was homozygous for this mutation (Δ32/Δ32). Moreover, none of the LTNPs showed HIV-1 SDRMs. The CRF35-AD subtype was the most dominant subtype, with a percentage of 93.3%. Conclusion: Iranian elite controllers are negative for CCR5-delta 32 homozygous genotype and drug resistance against antiretroviral drugs.

The New Kid on the Block: HLA-C, a Key Regulator of Natural Killer Cells in Viral Immunity

The human leukocyte antigen system (HLA) is a cluster of highly polymorphic genes essential for the proper function of the immune system, and it has been associated with a wide range of diseases. HLA class I molecules present intracellular host- and pathogen-derived peptides to effector cells of the immune system, inducing immune tolerance in healthy conditions or triggering effective immune responses in pathological situations. HLA-C is the most recently evolved HLA class I molecule, only present in humans and great apes. Differentiating from its older siblings, HLA-A and HLA-B, HLA-C exhibits distinctive features in its expression and interaction partners. HLA-C serves as a natural ligand for multiple members of the killer-cell immunoglobulin-like receptor (KIR) family, which are predominately expressed by natural killer (NK) cells. NK cells are crucial for the early control of viral infections and accumulating evidence indicates that interactions between HLA-C and its respective KIR receptors determine the outcome and progression of viral infections. In this review, we focus on the unique role of HLA-C in regulating NK cell functions and its consequences in the setting of viral infections.

Evolution of Serum Acute-Phase Glycoproteins Assessed by 1H-NMR in HIV Elite Controllers

Elite controllers (ECs) are an exceptional group of people living with HIV (PLWH) who maintain undetectable viral loads (VLs) despite not being on antiretroviral therapy (ART). However, this phenotype is heterogeneous, with some of these subjects losing virological control over time. In this longitudinal retrospective study, serum acute-phase glycoprotein profile assessed by proton nuclear magnetic resonance (¹H-NMR) was determined in 11 transient controllers (TCs) who spontaneously lost virological control and 11 persistent controllers (PCs) who persistently maintained virological control over time. Both PCs and TCs showed similar acute-phase glycoprotein profiles, even when TCs lost the virological control (GlycB, p = 0.824 and GlycA, p = 0.710), and the serum acute-phase glycoprotein signature in PCs did not differ from that in HIV-negative subjects (GlycB, p = 0.151 and GlycA, p = 0.243). Differences in serum glycoproteins A and B were significant only in ECs compared to HIV-typical progressors (TPs) with < 100 CD4+ T-cells (p < 0.001). ¹H-NMR acute-phase glycoprotein profile does not distinguish TCs form PCs before the loss of viral control. ECs maintain a low-grade inflammatory state compared to TPs. PCs revealed a closer serum signature to HIV-negative subjects, reaffirming this phenotype as a closer model of functional control of HIV.

How elite controllers and posttreatment controllers inform our search for an HIV-1 cure

A small percentage of people living with HIV-1 can control viral replication without antiretroviral therapy (ART). These patients are called elite controllers (ECs) if they are able to maintain viral suppression without initiating ART and posttreatment controllers (PTCs) if they control HIV replication after ART has been discontinued. Both types of controllers may serve as a model of a functional cure for HIV-1 but the mechanisms responsible for viral control have not been fully elucidated. In this review, we highlight key lessons that have been learned so far in the study of ECs and PTCs and their implications for HIV cure research.

Viral reservoirs in elite controllers of HIV-1 infection: Implications for HIV cure strategies

Elite controllers are HIV-1 positive subjects who control viral replication without antiretroviral therapy. Many of these subjects have replication-competent virus and thus represent a model of a functional cure. Peripheral CD4+ T cells in these subjects have small reservoirs with a low frequency of intact proviruses. Furthermore, recent studies suggest that many of these intact proviruses are disproportionally integrated at sites that have limited transcriptional activity raising the possibility that replication-competent viruses do not replicate because they are in a “blocked and locked” state. However, this feature is probably a consequence rather than a cause of elite control. Additionally, evolution of plasma virus has been detected in many elites suggesting that there continues to be ongoing viral replication in other compartments. While exceptional elite controllers with very limited viral reservoirs have recently been described, more work is needed to determine whether these patients have achieved a sterilizing cure.

In vivo Effects of Romidepsin on T-Cell Activation, Apoptosis and Function in the BCN02 HIV-1 Kick&Kill Clinical Trial

Romidepsin (RMD) is a well-characterized histone deacetylase inhibitor approved for the treatment of cutaneous T-cell lymphoma. in vitro and in vivo studies have demonstrated that it is able to induce HIV-1 gene expression in latently infected CD4⁺ T cells from HIV-1⁺ individuals on suppressive antiretroviral therapy. However, in vitro experiments suggested that RMD could also impair T-cell functionality, particularly of activated T cells. Thus, the usefulness of RMD in HIV-1 kick&kill strategies, that aim to enhance the immune system elimination of infected cells after inducing HIV-1 viral reactivation, may be limited. In order to address whether the in vitro observations are replicated in vivo, we determined the effects of RMD on the total and HIV-1-specific T-cell populations in longitudinal samples from the BCN02 kick&kill clinical trial (NCT02616874). BCN02 was a proof-of-concept study in 15 early treated HIV-1⁺ individuals that combined MVA.HIVconsv vaccination with three weekly infusions of RMD given as a latency reversing agent. Our results show that RMD induced a transient increase in the frequency of apoptotic T cells and an enhanced activation of vaccine-induced T cells. Although RMD reduced the number of vaccine-elicited T cells secreting multiple cytokines, viral suppressive capacity of CD8⁺ T cells was preserved over the RMD treatment. These observations have important implications for the design of effective kick&kill strategies for the HIV-1 cure.

Combined Effects of HLA-B*57/5801 Elite Suppressor CD8+ T Cells and NK Cells on HIV-1 Replication

Elite controllers or suppressors (ES) are HIV-1 infected individuals who maintain undetectable viral loads without anti-retroviral therapy. The HLA-B*57 allele is overrepresented in ES suggesting a role for HIV-specific CD8+ T cells in immune control. Natural killer (NK) cells also play a role in controlling viral replication, and genetic studies demonstrate that specific combinations of killer cell immunoglobulin-like receptor (KIR) alleles and HLA subtypes including HLA-B*57 correlate with delayed progression to AIDS. While prior studies have shown that both HIV-specific CD8+ T cells and NK cells can inhibit viral replication in vitro, the interaction between these two effector cells has not been studied. We performed in vitro suppression assays using CD8+ T cells and NK cells from HLA-B*57 ES either alone or in combination with each other. We found no evidence of antagonism or synergy between the CD8+ T cells and NK cells, suggesting that they have independent mechanisms of inhibition in vitro. Our data has implications for combined immunotherapy with CD8+ T cells and NK cells in HIV cure strategies.

Proteomic Profile Associated With Loss of Spontaneous Human Immunodeficiency Virus Type 1 Elite Control

BACKGROUND

Elite controllers (ECs) spontaneously control plasma human immunodeficiency virus type 1 (HIV-1) RNA without antiretroviral therapy. However, 25% lose virological control over time. The aim of this work was to study the proteomic profile that preceded this loss of virological control to identify potential biomarkers.

METHODS

Plasma samples from ECs who spontaneously lost virological control (transient controllers [TCs]), at 2 years and 1 year before the loss of control, were compared with a control group of ECs who persistently maintained virological control during the same follow-up period (persistent controllers [PCs]). Comparative plasma shotgun proteomics was performed with tandem mass tag (TMT) isobaric tag labeling and nanoflow liquid chromatography coupled to Orbitrap mass spectrometry.

RESULTS

Eighteen proteins exhibited differences comparing PC and preloss TC timepoints. These proteins were involved in proinflammatory mechanisms, and some of them play a role in HIV-1 replication and pathogenesis and interact with structural viral proteins. Coagulation factor XI, α-1-antichymotrypsin, ficolin-2, 14-3-3 protein, and galectin-3-binding protein were considered potential biomarkers.

CONCLUSIONS

The proteomic signature associated with the spontaneous loss of virological control was characterized by higher levels of inflammation, transendothelial migration, and coagulation. Galectin-3 binding protein could be considered as potential biomarker for the prediction of virological progression and as therapeutic target in ECs.

Elite controllers and lessons learned for HIV-1 cure

Following the success of HIV-1 antiviral treatment that maintains undetectable levels of viral replication and lack of clinical progression, the design of an HIV-1 cure for patients became the next objective. The success of the treated individuals together with the identification of subjects that spontaneously control the clinical progression for long periods, such as long-term non-progressors (LTNPs) and particularly LTNP Elite Controllers (LTNP EC) have shed hope for the feasibility of a potential cure. Although a successful cure has not been attained yet, these patients have provided critical information on the mechanisms involved in the clinical control such as host genetic factors, as well as strong immune responses against the virus. Less attention has been paid to virological factors, particularly the association of the genetic variability and the control of viral infection. Considering all these studies, it has become clear that a combination of several host, immune and viral factors is needed to attain control of the viral replication control and the non-progressor clinical phenotype. Because this control can be reached through different combinations of factors, this group of individuals is not homogenous. As HIV-1 cure has been shown to be extremely difficult to achieve, a more feasible objective is the functional cure of the viral infection. After the analysis of multiple studies on the mechanisms of control in LTNP EC, we found subjects with various host protective factors and prolonged viral control. These subjects present a complete lack of evolution after more than 20-30 years of infection, stable levels of CD4+ cells (>400-500 cells/μl), a strong immune response, and no signs of clinical progression. We propose that individuals with these characteristics could have attained a functional cure of the HIV-1 infection.

Optimizing intracellular signaling domains for CAR NK cells in HIV immunotherapy: a comprehensive review

Natural killer (NK) cells are innate immune lymphocytes with a key role in host defense against HIV infection. Recent advances in chimeric antigen receptors (CARs) have made NK cells a prime target for expressing recombinant receptors capable of redirecting NK cytotoxic functions towards HIV-infected cells. In this review, we discuss the role of NK cells in HIV and the mechanisms of actions of HIV-targeting CAR strategies. Furthermore, we also review NK cells signal transduction and its application to CAR NK cell strategies to develop new combinations of CAR intracellular domains and to improve CAR NK signaling and cytotoxic functions.

Identification of NK Cell Subpopulations That Differentiate HIV-Infected Subject Cohorts with Diverse Levels of Virus Control

HIV infection is controlled immunologically in a small subset of infected individuals without antiretroviral therapy (ART), though the mechanism of control is unclear. CD8⁺ T cells are a critical component of HIV control in many immunological controllers. NK cells are also believed to have a role in controlling HIV infection, though their role is less well characterized. We used mass cytometry to simultaneously measure the levels of expression of 24 surface markers on peripheral NK cells from HIV-infected subjects with various degrees of HIV natural control; we then used machine learning to identify NK cell subpopulations that differentiate HIV controllers from noncontrollers. Using CITRUS (cluster identification, characterization, and regression), we identified 3 NK cell subpopulations that differentiated subjects with chronic HIV viremia (viremic noncontrollers [VNC]) from individuals with undetectable HIV viremia without ART (elite controllers [EC]). In a parallel approach, we identified 11 NK cell subpopulations that differentiated HIV-infected subject groups using k-means clustering after dimensionality reduction by t-neighbor stochastic neighbor embedding (tSNE) or linear discriminant analysis (LDA). Among these additional 11 subpopulations, the frequencies of 5 correlated with HIV DNA levels; importantly, significance was retained in 2 subpopulations in analyses that included only cohorts without detectable viremia. By comparing the surface marker expression patterns of all identified subpopulations, we revealed that the CD11b⁺ CD57^- CD161⁺ Siglec-7⁺ subpopulation of CD56^dim CD16⁺ NK cells are more abundant in EC and HIV-negative controls than in VNC and that the frequency of these cells correlated with HIV DNA levels. We hypothesize that this population may have a role in immunological control of HIV infection.IMPORTANCE HIV infection results in the establishment of a stable reservoir of latently infected cells; ART is usually required to keep viral replication under control and disease progression at bay, though a small subset of HIV-infected subjects can control HIV infection without ART through immunological mechanisms. In this study, we sought to identify subpopulations of NK cells that may be involved in the natural immunological control of HIV infection. We used mass cytometry to measure surface marker expression on peripheral NK cells. Using two distinct semisupervised machine learning approaches, we identified a CD11b⁺ CD57^- CD161⁺ Siglec-7⁺ subpopulation of CD56^dim CD16⁺ NK cells that differentiates HIV controllers from noncontrollers. These cells can be sorted out for future functional studies to assess their potential role in the immunological control of HIV infection.

Mechanisms of Abrupt Loss of Virus Control in a Cohort of Previous HIV Controllers

Elite and viremic HIV controllers are able to control their HIV infection and maintain undetectable or low-level viremia in the absence of antiretroviral treatment. Despite extensive studies, the immune factors responsible for such exclusive control remain poorly defined. We identified a cohort of 14 HIV controllers that suffered an abrupt loss of HIV control (LoC) to investigate possible mechanisms and virological and immunological events related to the sudden loss of control. The in-depth analysis of these subjects involved the study of cell tropism of circulating virus, evidence for HIV superinfection, cellular immune responses to HIV, as well as an examination of viral adaptation to host immunity by Gag sequencing. Our data demonstrate that a poor capacity of T cells to mediate in vitro viral suppression, even in the context of protective HLA alleles, predicts a loss of viral control. In addition, the data suggest that inefficient viral control may be explained by an increase of CD8 T-cell activation and exhaustion before LoC. Furthermore, we detected a switch from C5- to X4-tropic viruses in 4 individuals after loss of control, suggesting that tropism shift might also contribute to disease progression in HIV controllers. The significantly reduced inhibition of in vitro viral replication and increased expression of activation and exhaustion markers preceding the abrupt loss of viral control may help identify untreated HIV controllers that are at risk of losing control and may offer a useful tool for monitoring individuals during treatment interruption phases in therapeutic vaccine trials.IMPORTANCE A few individuals can control HIV infection without the need for antiretroviral treatment and are referred to as HIV controllers. We have studied HIV controllers who suddenly lose this ability and present with high in vivo viral replication and decays in their CD4+ T-cell counts to identify potential immune and virological factors that were responsible for initial virus control. We identify in vitro-determined reductions in the ability of CD8 T cells to suppress viral control and the presence of PD-1-expressing CD8+ T cells with a naive immune phenotype as potential predictors of in vivo loss of virus control. The findings could be important for the clinical management of HIV controller individuals, and it may offer an important tool to anticipate viral rebound in individuals in clinical studies that include combination antiretroviral therapy (cART) treatment interruptions and which, if not treated quickly, could pose a significant risk to the trial participants.

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

In this brief review and perspective, we address the question of whether the immune responses that bring about immune control of acute HIV infection are the same as, or distinct from, those that maintain long-term viral suppression once control of viremia has been achieved. To this end, we describe the natural history of elite and post-treatment control, noting the lack of data regarding what happens acutely. We review the evidence suggesting that the two clinical phenotypes may differ in terms of the mechanisms required to achieve and maintain control, as well as the level of inflammation that persists once a steady state is achieved. We then describe the evidence from longitudinal studies of controllers who fail and studies of biologic sex (male versus female), age (children versus adults), and simian immunodeficiency virus (SIV) (pathogenic/experimental versus nonpathogenic/natural infection). Collectively, these studies demonstrate that the battle between the inflammatory and anti-inflammatory pathways during acute infection has long-term consequences, both for the degree to which control is maintained and the health of the individual. Potent and stringent control of HIV may be required acutely, but once control is established, the chronic inflammatory response can be detrimental. Interventional approaches designed to bring about HIV cure and/or remission should be nuanced accordingly.

Plasmatic Levels of IL-18, IP-10, and Activated CD8+ T Cells Are Potential Biomarkers to Identify HIV-1 Elite Controllers With a True Functional Cure Profile

Elite controllers (ECs) are rare individuals able to naturally control HIV-1 replication below the detection limit of viral load (VL) commercial assays. It is unclear, however, whether ECs might be considered a natural model of a functional cure because some studies have noted CD4⁺ T cell depletion and disease progression associated with abnormally high levels of immune activation and/or inflammation in this group. Here, we propose the use of immunological parameters to identify HIV-1 ECs that could represent the best model of a functional cure. We compared plasma levels of six inflammatory biomarkers (IP-10, IL-18, sCD163, sCD14, CRP, and IL-6) and percentages of activated CD8⁺ T cells (CD38⁺HLA-DR⁺) between 15 ECs [8 with persistent undetectable viremia (persistent elite controllers) and 7 with occasional viral blips (ebbing elite controllers)], 13 viremic controllers (VCs—plasma VL between 51 and 2,000 RNA copies/mL), and 18 HIV-1 infected patients in combined antiretroviral therapy, with suppressed viremia, and 18 HIV-uninfected controls (HIV-neg). The two groups of ECs presented inflammation and activation profiles similar to HIV-neg individuals, and there was no evidence of CD4⁺ T cell decline over time. VCs, by contrast, had higher levels of IL-18, IP-10, and CRP and a lower CD4/CD8 ratio than that of HIV-neg (P < 0.05). Plasma levels of IL-18 and IP-10 correlated positively with CD8⁺ T cell activation and negatively with both CD4/CD8 and CD4% in HIV-1 controllers. These results suggest that most ECs, defined using stringent criteria in relation to the cutoff level of viremia (≤50 copies/mL) and a minimum follow-up time of >5 years, show no evidence of persistent inflammation or immune activation. This study further suggests that plasmatic levels of IL-18/IP-10 combined with the frequency of CD8⁺CD38⁺HLA-DR⁺ T cells can be important biomarkers to identify models of a functional cure among HIV-1 ECs.

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.

Factors Leading to the Loss of Natural Elite Control of HIV-1 Infection

HIV-1 elite controllers (EC) maintain undetectable viral loads (VL) in the absence of antiretroviral treatment. However, these subjects have heterogeneous clinical outcomes, including a proportion that loses HIV-1 control over time. In this work, we compared, in a longitudinal design, transient EC, analyzed before and after the loss of virological control, with persistent EC. The aim was to identify factors leading to the loss of natural virological control of HIV-1 infection with a longitudinal retrospective study design. Gag-specific T-cell responses were assessed by in vitro intracellular polycytokine production quantified by flow cytometry. Viral diversity determinations and sequence dating were performed in proviral DNA by PCR amplification at limiting dilution of env and gag genes. The expression profile of 70 serum cytokines and chemokines was assessed by multiplex immunoassays. We identified transient EC as subjects with low Gag-specific T-cell polyfunctionality, high viral diversity, and high proinflammatory cytokine levels before the loss of control. Gag-specific T-cell polyfunctionality was inversely associated with viral diversity in transient controllers before the loss of control (r = -0.8; P = 0.02). RANTES was a potential biomarker of transient control. This study identified virological and immunological factors, including inflammatory biomarkers associated with two different phenotypes within EC. These results may allow a more accurate definition of EC, which could help in better clinical management of these individuals and in the development of future curative approaches.IMPORTANCE There is a rare group of HIV-infected patients who have the extraordinary capacity to maintain undetectable viral load levels in the absence of antiretroviral treatment, the so-called HIV-1 elite controllers (EC). However, there is a proportion within these subjects that eventually loses this capability. In this work, we found differences in virological and immune factors, including soluble inflammatory biomarkers, between subjects with persistent control of viral replication and EC that will lose virological control. The identification of these factors could be a key point for a right medical care of those EC who are going to lose natural control of viral replication and for the design of future immunotherapeutic strategies using as a model the natural persistent control of HIV infection.

The Antiviral Immune Response and Its Impact on the HIV-1 Reservoir

Latently infected resting memory CD4⁺ T cells represent a major barrier to HIV-1 eradication. Studies have shown that it will not be possible to cure HIV-1 infection unless these cells are eliminated. Latently infected cells probably do not express viral antigens and thus may not be susceptible to the HIV-1 specific immune response, nevertheless the size and composition of the reservoir is influenced by the immune system. In this chapter, we review the different components of the HIV-1 specific immune response and discuss how the immune system can be harnessed to eradicate the virus.