Success and failure of the cellular immune response against HIV-1

RPLP1 restricts HIV-1 transcription by disrupting C/EBPβ binding to the LTR

Long-term non-progressors (LTNPs) of HIV-1 infection may provide important insights into mechanisms involved in viral control and pathogenesis. Here, our results suggest that the ribosomal protein lateral stalk subunit P1 (RPLP1) is expressed at higher levels in LTNPs compared to regular progressors (RPs). Functionally, RPLP1 inhibits transcription of clade B HIV-1 strains by occupying the C/EBPβ binding sites in the viral long terminal repeat (LTR). This interaction requires the α-helixes 2 and 4 domains of RPLP1 and is evaded by HIV-1 group M subtype C and group N, O and P strains that do not require C/EBPβ for transcription. We further demonstrate that HIV-1-induced translocation of RPLP1 from the cytoplasm to the nucleus is essential for antiviral activity. Finally, knock-down of RPLP1 promotes reactivation of latent HIV-1 proviruses. Thus, RPLP1 may play a role in the maintenance of HIV-1 latency and resistance to RPLP1 restriction may contribute to the effective spread of clade C HIV-1 strains.

Impact of predicted HLA class I immunopeptidome on viral reservoir in a cohort of people living with HIV in Italy

The class I HLA genotype has been widely recognized as a factor influencing HIV disease progression in treatment-naïve subjects. However, little is known regarding its role in HIV disease course and how it influences the size of the viral reservoir once anti-retroviral therapy (ART) is started. Here, leveraging on cutting-edge bioinformatic tools, we explored the relationship between HLA class I and the HIV reservoir in a cohort of 90 people living with HIV (PLWH) undergoing ART and who achieved viral suppression. Analysis of HLA allele distribution among patients with high and low HIV reservoir allowed us to document a predominant role of HLA-B and -C genes in regulating the size of HIV reservoir. We then focused on the analysis of HIV antigen (Ag) repertoire, by investigating immunogenetic parameters such as the degree of homozygosity, HLA evolutionary distance and Ag load. In particular, we used two different bioinformatic algorithms, NetMHCpan and MixMHCpred, to predict HLA presentation of immunogenic HIV-derived peptides and identified HLA-B*57:01 and HLA-B*58:01 among the highest ranking HLAs in terms of total load, suggesting that their previously reported protective role against HIV disease progression might be linked to a more effective viral recognition and presentation to Cytotoxic T lymphocytes (CTLs). Further, we speculated that some peptide-HLA complexes, including those produced by the interaction between HLA-B*27 and the HIV Gag protein, might be particularly relevant for the efficient regulation of HIV replication and containment of the HIV reservoir. Last, we provide evidence of a possible synergistic effect between the CCR5 ∆32 mutation and Ag load in controlling HIV reservoir.

HIV vaccines induce CD8+ T cells with low antigen receptor sensitivity

Current HIV vaccines designed to stimulate CD8+ T cells have failed to induce immunologic control upon infection. The functions of vaccine-induced HIV-specific CD8+ T cells were investigated here in detail. Cytotoxic capacity was significantly lower than in HIV controllers and was not a consequence of low frequency or unaccumulated functional cytotoxic proteins. Low cytotoxic capacity was attributable to impaired degranulation in response to the low antigen levels present on HIV-infected targets. The vaccine-induced T cell receptor (TCR) repertoire was polyclonal and transduction of these TCRs conferred the same reduced functions. These results define a mechanism accounting for poor antiviral activity induced by these vaccines and suggest that an effective CD8+ T cell response may require a vaccination strategy that drives further TCR clonal selection.

HIV-1-specific T-cell responses and exhaustion profiles in people with HIV after switching to dual therapy vs. maintaining triple therapy based on integrase inhibitors

BACKGROUND

Dual therapy (DT) has shown comparable results to triple therapy (TT) in efficacy and other immunological aspects. However, there are still some concerns about DT, including several immunological features. Therefore, we evaluated whether HIV-1-specific memory T-cell responses and exhaustion phenotypes are adversely influenced after simplification to DT.

METHODS

HIV-1-specific CD4+ and CD8+ T-cell responses were assessed by intracellular cytokine and degranulation marker staining, and polyfunctionality indexes after stimulation with a Gag peptide pool. Exhaustion phenotypes were evaluated by PD-1, TIM-3, and LAG-3 expression in CD4+ and CD8+ T cells.

RESULTS

Forty participants in the TRIDUAL trial (ClinicalTrials.gov: NCT03447873) who were randomized to continue integrase inhibitor-based TT (n = 20) or to switch to DT (dolutegravir or darunavir/cobicistat plus lamivudine) (n = 20). After 96 weeks, the magnitude of CD4+ and CD8+ T-cell responses was similar in both treatment arms (p = 0.221 and p = 0.602, respectively). The CD4+ polyfunctionality index decreased in the TT arm (p = 0.013) and remained stable in the DT arm, while the polyfunctionality of CD8+ T cells was unchanged in both arms. There was a significant decrease in the expression of PD-1, TIM-3, and the co-expression of PD-1+TIM-3+LAG-3+, and PD-1 +TIM-3 + in both CD4+ and CD8+ T cells. However, the decrease in the expression of exhaustion markers did not improve HIV-1-specific T-cell responses.

CONCLUSIONS

Our results suggest that simplification to DT does not negatively influence the HIV-1-specific T-cell response or the exhaustion phenotype after 96 weeks of follow-up.

Proviral location affects cognate peptide-induced virus production and immune recognition of HIV-1-infected T cell clones

BACKGROUNDHIV-1-infected CD4+ T cells contribute to latent reservoir persistence by proliferating while avoiding immune recognition. Integration features of intact proviruses in elite controllers (ECs) and people on long-term therapy suggest that proviruses in specific chromosomal locations can evade immune surveillance. However, direct evidence of this mechanism is missing.METHODSIn this case report, we characterized integration sites and full genome sequences of expanded T cell clones in an EC before and after chemoradiation. We identified the cognate peptide of infected clones to investigate cell proliferation and virus production induced by T cell activation, and susceptibility to autologous CD8+ T cells.RESULTSThe proviral landscape was dominated by 2 large clones with replication-competent proviruses integrated into zinc finger (ZNF) genes (ZNF470 and ZNF721) in locations previously associated with deeper latency. A third nearly intact provirus, with a stop codon in Pol, was integrated into an intergenic site. Upon stimulation with cognate Gag peptides, infected clones proliferated extensively and produced virus, but the provirus in ZNF721 was 200-fold less inducible. While autologous CD8+ T cells decreased the proliferation of cells carrying the intergenic provirus, they had no effect on cells with the provirus in the ZNF721 gene.CONCLUSIONSWe provide direct evidence that upon activation of infected clones by cognate antigen, the lower inducibility of intact proviruses in ZNF genes can result in immune evasion and persistence.FUNDINGOffice of the NIH Director and National Institute of Dental & Craniofacial Research; NIAID, NIH; Johns Hopkins University Center for AIDS Research.

Impact of early antiretroviral therapy, early life immunity and immune sex differences on HIV disease and posttreatment control in children

PURPOSE OF REVIEW

To review recent insights into the factors affecting HIV disease progression in children living with HIV, contrasting outcomes: following early ART initiation with those in natural, antiretroviral therapy (ART)-naive infection; in children versus adults; and in female individuals versus male individuals.

RECENT FINDINGS

Early life immune polarization and several factors associated with mother-to-child transmission of HIV result in an ineffective HIV-specific CD8+ T-cell response and rapid disease progression in most children living with HIV. However, the same factors result in low immune activation and antiviral efficacy mediated mainly through natural killer cell responses in children and are central features of posttreatment control. By contrast, rapid activation of the immune system and generation of a broad HIV-specific CD8+ T-cell response in adults, especially in the context of 'protective' HLA class I molecules, are associated with superior disease outcomes in ART-naive infection but not with posttreatment control. The higher levels of immune activation in female individuals versus male individuals from intrauterine life onwards increase HIV infection susceptibility in females in utero and may favour ART-naive disease outcomes rather than posttreatment control.

SUMMARY

Early-life immunity and factors associated with mother-to-child transmission typically result in rapid HIV disease progression in ART-naive infection but favour posttreatment control in children following early ART initiation.

HIV specific CD8+ TRM-like cells in tonsils express exhaustive signatures in the absence of natural HIV control

Lymphoid tissues are an important HIV reservoir site that persists in the face of antiretroviral therapy and natural immunity. Targeting these reservoirs by harnessing the antiviral activity of local tissue-resident memory (TRM) CD8+ T-cells is of great interest, but limited data exist on TRM-like cells within lymph nodes of people living with HIV (PLWH). Here, we studied tonsil CD8+ T-cells obtained from PLWH and uninfected controls from South Africa. We show that these cells are preferentially located outside the germinal centers (GCs), the main reservoir site for HIV, and display a low cytolytic and a transcriptionally TRM-like profile distinct from blood CD8+ T-cells. In PLWH, CD8+ TRM-like cells are expanded and adopt a more cytolytic, activated, and exhausted phenotype not reversed by antiretroviral therapy (ART). This phenotype was enhanced in HIV-specific CD8+ T-cells from tonsils compared to matched blood suggesting a higher antigen burden in tonsils. Single-cell transcriptional and clonotype resolution showed that these HIV-specific CD8+ T-cells in the tonsils express heterogeneous signatures of T-cell activation, clonal expansion, and exhaustion ex-vivo. Interestingly, this signature was absent in a natural HIV controller, who expressed lower PD-1 and CXCR5 levels and reduced transcriptional evidence of T-cell activation, exhaustion, and cytolytic activity. These data provide important insights into lymphoid tissue-derived HIV-specific CD8+ TRM-like phenotypes in settings of HIV remission and highlight their potential for immunotherapy and targeting of the HIV reservoirs.

CD8 + T-cell responses in HIV controllers: potential implications for novel HIV remission strategies

PURPOSE OF REVIEW

Immunological studies of spontaneous HIV and simian virus (SIV) controllers have identified virus-specific CD8 +  T cells as a key immune mechanism of viral control. The purpose of this review is to consider how knowledge about the mechanisms that are associated with CD8 +  T cell control of HIV/SIV in natural infection can be harnessed in HIV remission strategies.

RECENT FINDINGS

We discuss characteristics of CD8 +  T-cell responses that may be critical for suppressing HIV replication in spontaneous controllers comprising HIV antigen recognition including specific human leukocyte antigen types, broadly cross-reactive T cell receptors and epitope targeting, enhanced expansion and antiviral functions, and localization of virus-specific T cells near sites of reservoir persistence. We also discuss the need to better understand the timing of CD8 +  T-cell responses associated with viral control of HIV/SIV during acute infection and after treatment interruption as well as the mechanisms by which HIV/SIV-specific CD8 +  T cells coordinate with other immune responses to achieve control.

SUMMARY

We propose implications as to how this knowledge from natural infection can be applied in the design and evaluation of CD8 +  T-cell-based remission strategies and offer questions to consider as these strategies target distinct CD8 +  T-cell-dependent mechanisms of viral control.

Combination anti-HIV antibodies provide sustained virological suppression

Antiretroviral therapy is highly effective in suppressing human immunodeficiency virus (HIV)1. However, eradication of the virus in individuals with HIV has not been possible to date2. Given that HIV suppression requires life-long antiretroviral therapy, predominantly on a daily basis, there is a need to develop clinically effective alternatives that use long-acting antiviral agents to inhibit viral replication3. Here we report the results of a two-component clinical trial involving the passive transfer of two HIV-specific broadly neutralizing monoclonal antibodies, 3BNC117 and 10-1074. The first component was a randomized, double-blind, placebo-controlled trial that enrolled participants who initiated antiretroviral therapy during the acute/early phase of HIV infection. The second component was an open-label single-arm trial that enrolled individuals with viraemic control who were naive to antiretroviral therapy. Up to 8 infusions of 3BNC117 and 10-1074, administered over a period of 24 weeks, were well tolerated without any serious adverse events related to the infusions. Compared with the placebo, the combination broadly neutralizing monoclonal antibodies maintained complete suppression of plasma viraemia (for up to 43 weeks) after analytical treatment interruption, provided that no antibody-resistant HIV was detected at the baseline in the study participants. Similarly, potent HIV suppression was seen in the antiretroviral-therapy-naive study participants with viraemia carrying sensitive virus at the baseline. Our data demonstrate that combination therapy with broadly neutralizing monoclonal antibodies can provide long-term virological suppression without antiretroviral therapy in individuals with HIV, and our experience offers guidance for future clinical trials involving next-generation antibodies with long half-lives.

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 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.

Epitope length variants balance protective immune responses and viral escape in HIV-1 infection

Cytotoxic T lymphocyte (CTL) and natural killer (NK) cell responses to a single optimal 10-mer epitope (KK10) in the human immunodeficiency virus type-1 (HIV-1) protein p24Gag are associated with enhanced immune control in patients expressing human leukocyte antigen (HLA)-B∗27:05. We find that proteasomal activity generates multiple length variants of KK10 (4-14 amino acids), which bind TAP and HLA-B∗27:05. However, only epitope forms ≥8 amino acids evoke peptide length-specific and cross-reactive CTL responses. Structural analyses reveal that all epitope forms bind HLA-B∗27:05 via a conserved N-terminal motif, and competition experiments show that the truncated epitope forms outcompete immunogenic epitope forms for binding to HLA-B∗27:05. Common viral escape mutations abolish (L136M) or impair (R132K) production of KK10 and longer epitope forms. Peptide length influences how well the inhibitory NK cell receptor KIR3DL1 binds HLA-B∗27:05 peptide complexes and how intraepitope mutations affect this interaction. These results identify a viral escape mechanism from CTL and NK responses based on differential antigen processing and peptide competition.

Human lymph node immune dynamics as driver of vaccine efficacy: an understudied aspect of immune responses

INTRODUCTION

During the last century, changes in hygiene, sanitation, and the advent of childhood vaccination have resulted in profound reductions in mortality from infectious diseases. Despite this success, infectious diseases remain an enigmatic public health threat, where effective vaccines for influenza, human immunodeficiency virus (HIV), tuberculosis, and malaria, among others remain elusive.

AREA COVERED

In addition to the immune evasion tactics employed by complex pathogens, our understanding of immunopathogenesis and the development of effective vaccines is also complexified by the inherent variability of human immune responses. Lymph nodes (LNs) are the anatomical sites where B cell responses develop. An important, but understudied component of immune response complexity is variation in LN immune dynamics and in particular variation in germinal center follicular helper T cells (Tfh) and B cells which can be impacted by genetic variation, aging, the microbiome and chronic infection.

EXPERT OPINION

This review describes the contribution of genetic variation, aging, microbiome and chronic infection on LN immune dynamics and associated Tfh responses and offers perspective on how inclusion of LN immune subset and cytoarchitecture analyses, along with peripheral blood biomarkers can supplement systems vaccinology or immunology approaches for the development of vaccines or other interventions to prevent infectious diseases.

IL-27 induces IFN/STAT1-dependent genes and enhances function of TIGIT+ HIVGag-specific T cells

HIV-specific T cells have diminished effector function and fail to control/eliminate the virus. IL-27, a member of the IL-6/IL-12 cytokine superfamily has been shown to inhibit HIV replication. However, whether or not IL-27 can enhance HIV-specific T cell function is largely unknown. In the present manuscript, we investigated the role of IL-27 signaling in human T cells by evaluating the global transcriptional changes related to the function of HIV-specific T cells. We found that T cells from people living with HIV (PLWH), expressed higher levels of STAT1 leading to enhanced STAT1 activation upon IL-27 stimulation. Observed IL-27 induced transcriptional changes were associated with IFN/STAT1-dependent pathways in CD4 and CD8 T cells. Importantly, IL-27 dependent modulation of T-bet expression promoted IFNγ secretion by TIGIT+HIVGag-specific T cells. This new immunomodulatory effect of IL-27 on HIV-specific T cell function suggests its potential therapeutic use in cure strategies.

Why the HIV Reservoir Never Runs Dry: Clonal Expansion and the Characteristics of HIV-Infected Cells Challenge Strategies to Cure and Control HIV Infection

Antiretroviral therapy (ART) effectively reduces cycles of viral replication but does not target proviral populations in cells that persist for prolonged periods and that can undergo clonal expansion. Consequently, chronic human immunodeficiency virus (HIV) infection is sustained during ART by a reservoir of long-lived latently infected cells and their progeny. This proviral landscape undergoes change over time on ART. One of the forces driving change in the landscape is the clonal expansion of infected CD4 T cells, which presents a key obstacle to HIV eradication. Potential mechanisms of clonal expansion include general immune activation, antigenic stimulation, homeostatic proliferation, and provirus-driven clonal expansion, each of which likely contributes in varying, and largely unmeasured, amounts to maintaining the reservoir. The role of clinical events, such as infections or neoplasms, in driving these mechanisms remains uncertain, but characterizing these forces may shed light on approaches to effectively eradicate HIV. A limited number of individuals have been cured of HIV infection in the setting of bone marrow transplant; information from these and other studies may identify the means to eradicate or control the virus without ART. In this review, we describe the mechanisms of HIV-1 persistence and clonal expansion, along with the attempts to modify these factors as part of reservoir reduction and cure strategies.

New Approaches to Multi-Parametric HIV-1 Genetics Using Multiple Displacement Amplification: Determining the What, How, and Where of the HIV-1 Reservoir

Development of potential HIV-1 curative interventions requires accurate characterization of the proviral reservoir, defined as host-integrated viral DNA genomes that drive rebound of viremia upon halting ART (antiretroviral therapy). Evaluation of such interventions necessitates methods capable of pinpointing the rare, genetically intact, replication-competent proviruses within a background of defective proviruses. This evaluation can be achieved by identifying the distinct integration sites of intact proviruses within host genomes and monitoring the dynamics of these proviruses and host cell lineages over longitudinal sampling. Until recently, molecular genetic approaches at the single proviral level have been generally limited to one of a few metrics, such as proviral genome sequence/intactness, host-proviral integration site, or replication competency. New approaches, taking advantage of MDA (multiple displacement amplification) for WGA (whole genome amplification), have enabled multiparametric proviral characterization at the single-genome level, including proviral genome sequence, host-proviral integration site, and phenotypic characterization of the host cell lineage, such as CD4 memory subset and antigen specificity. In this review, we will examine the workflow of MDA-augmented molecular genetic approaches to study the HIV-1 reservoir, highlighting technical advantages and flexibility. We focus on a collection of recent studies in which investigators have used these approaches to comprehensively characterize intact and defective proviruses from donors on ART, investigate mechanisms of elite control, and define cell lineage identity and antigen specificity of infected CD4+ T cell clones. The highlighted studies exemplify how these approaches and their future iterations will be key in defining the targets and evaluating the impacts of HIV curative interventions.

Functional impairment of HIV-specific CD8+ T cells precedes aborted spontaneous control of viremia

Spontaneous control of HIV infection has been repeatedly linked to antiviral CD8+ T cells but is not always permanent. To address mechanisms of durable and aborted control of viremia, we evaluated immunologic and virologic parameters longitudinally among 34 HIV-infected subjects with differential outcomes. Despite sustained recognition of autologous virus, HIV-specific proliferative and cytolytic T cell effector functions became selectively and intrinsically impaired prior to aborted control. Longitudinal transcriptomic profiling of functionally impaired HIV-specific CD8+ T cells revealed altered expression of genes related to activation, cytokine-mediated signaling, and cell cycle regulation, including increased expression of the antiproliferative transcription factor KLF2 but not of genes associated with canonical exhaustion. Lymphoid HIV-specific CD8+ T cells also exhibited poor functionality during aborted control relative to durable control. Our results identify selective functional impairment of HIV-specific CD8+ T cells as prognostic of impending aborted HIV control, with implications for clinical monitoring and immunotherapeutic strategies.

Depressive Disorders in HIV/AIDS: A Clinically Focused Narrative Review

After participating in this activity, learners should be better able to:• Assess strategies for diagnosing depressive disorders in patients with human immunodeficiency virus/acquired immunodeficiency syndrome (HIV/AIDS)• Identify factors that contribute to the development of depressive disorders in HIV/AIDS• Evaluate strategies for managing depressive disorders in HIV/AIDS ABSTRACT: Depressive disorders and human immunodeficiency virus/acquired immunodeficiency syndrome (HIV/AIDS) are associated with major socioeconomic burdens. The negative impact of depressive disorders on HIV/AIDS is well known, including on treatment outcomes. Unfortunately, depressive disorders are underdiagnosed and undertreated in seropositive persons. This review summarizes clinically useful information on depressive disorders in HIV/AIDS. More specifically, we address assessment, differential diagnosis, contributing factors, management, and common challenges in the treatment of depressive disorders in seropositive individuals. Assessment and diagnosis of depression may be challenging in seropositive persons because of several biopsychosocial particularities associated with HIV/AIDS. One of the difficulties is the overlap between depression and HIV/AIDS symptoms, particularly in individuals with advanced AIDS, requiring consideration of a broad differential diagnosis. Several factors related to HIV/AIDS status contribute to the higher rates of depressive disorders, including infectious-immunological, psychosocial, and exogenous factors. The treatment of depressive disorders in HIV/AIDS involves three groups of interventions: (1) pharmacological interventions, (2) psychotherapeutic interventions, and (3) management of other contributing factors. Challenges in management include poor adherence to treatment and the risk of suicide. We provide evidence-based recommendations to improve assessment and management of depressive disorders in seropositive persons.

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.

SARS-CoV-2 Portrayed against HIV: Contrary Viral Strategies in Similar Disguise

SARS-CoV-2 and HIV are zoonotic viruses that rapidly reached pandemic scale, causing global losses and fear. The COVID-19 and AIDS pandemics ignited massive efforts worldwide to develop antiviral strategies and characterize viral architectures, biological and immunological properties, and clinical outcomes. Although both viruses have a comparable appearance as enveloped viruses with positive-stranded RNA and envelope spikes mediating cellular entry, the entry process, downstream biological and immunological pathways, clinical outcomes, and disease courses are strikingly different. This review provides a systemic comparison of both viruses' structural and functional characteristics, delineating their distinct strategies for efficient spread.

Humanized Mice for the Evaluation of Novel HIV-1 Therapies

With the discovery of antiretroviral therapy, HIV-1 infection has transitioned into a manageable but chronic illness, which requires lifelong treatment. Nevertheless, complete eradication of the virus has still eluded us. This is partly due to the virus’s ability to remain in a dormant state in tissue reservoirs, ‘hidden’ from the host’s immune system. Also, the high mutation rate of HIV-1 results in escape mutations in response to many therapeutics. Regardless, the development of novel cures for HIV-1 continues to move forward with a range of approaches from immunotherapy to gene editing. However, to evaluate in vivo pathogenesis and the efficacy and safety of therapeutic approaches, a suitable animal model is necessary. To this end, the humanized mouse was developed by McCune in 1988 and has continued to be improved on over the past 30 years. Here, we review the variety of humanized mouse models that have been utilized through the years and describe their specific contribution in translating HIV-1 cure strategies to the clinic.

Immunologic Control of HIV-1: What Have We Learned and Can We Induce It?

PURPOSE OF REVIEW

A large amount of data now exists on the virus-specific immune response associated with spontaneous or induced immunologic control of lentiviruses. This review focuses on how the current understanding of HIV-specific immunity might be leveraged into induction of immunologic control and what further research is needed to accomplish this goal.

RECENT FINDINGS

During chronic infection, the function most robustly associated with immunologic control of HIV-1 is CD8⁺ T cell cytotoxic capacity. This function has proven difficult to restore in HIV-specific CD8⁺ T cells of chronically infected progressors in vitro and in vivo. However, progress has been made in inducing an effective CD8⁺ T cell response prior to lentiviral infection in the macaque model and during acute lentiviral infection in non-human primates. Further study will likely accelerate the ability to induce an effective CD8⁺ T cell response as part of prophylactic or therapeutic strategies.

Vulnerable targets in HIV-1 Pol for attenuation-based vaccine design

Identification of viral immune escape mutations that compromise HIV's ability to replicate may aid rational attenuation-based vaccine design. Previously we reported amino acids associated with altered viral replication capacity (RC) from a sequence-function analysis of 487 patient-derived RT-integrase sequences. In this study, site-directed mutagenesis experiments were performed to validate the effect of these mutations on RC. Viral reverse transcripts were measured by quantitative PCR and structural modelling was performed to gain further insight into the effect of reverse transcriptase (RT) mutations on reverse transcription. RT-integrase variants in or flanking cytotoxic T cell epitopes in the RT palm (158S), RT thumb (241I and 257V) and integrase catalytic core domain (124N) were confirmed to significantly reduce RC. RT mutants showed a delayed initiation of viral DNA synthesis. Structural models provide insight into how these attenuating RT mutations may affect amino acid interactions in the helix clamp, primer grip and catalytic site regions.

Quantifying the clonality and dynamics of the within-host HIV-1 latent reservoir

Among people living with human immunodeficiency virus type 1 (HIV-1), the long-term persistence of a population of cells carrying transcriptionally silent integrated viral DNA (provirus) remains the primary barrier to developing an effective cure. Ongoing cell division via proliferation is generally considered to be the driving force behind the persistence of this latent HIV-1 reservoir. The contribution of this mechanism (clonal expansion) is supported by the observation that proviral sequences sampled from the reservoir are often identical. This outcome is quantified as the ‘clonality’ of the sample population, e.g. the fraction of provirus sequences observed more than once. However, clonality as a quantitative measure is inconsistently defined and its statistical properties are not well understood. In this Reflections article, we use mathematical and phylogenetic frameworks to formally examine the inherent problems of using clonality to characterize the dynamics and proviral composition of the reservoir. We describe how clonality is not adequate for this task due to the inherent complexity of how infected cells are ‘labeled’ by proviral sequences—the outcome of a sampling process from the evolutionary history of active viral replication before treatment—as well as variation in cell birth and death rates among lineages and over time. Lastly, we outline potential directions in statistical and phylogenetic research to address these issues.

Effect of antiretroviral therapy initiation time and baseline CD4+ cell counts on AIDS-related mortality among former plasma donors in China: a 21-year retrospective cohort study

Background

The conventional survival analysis model on HIV/AIDS prognosis is the Cox proportional hazard model, which deals with only one event type, death, regardless of the cause. Few studies have used a competing risk model to evaluate the predictors of AIDS-related mortality.

Objective

To estimate the influence of antiretroviral therapy (ART) initiation time and baseline CD4⁺ cell counts on acquired immunodeficiency syndrome (AIDS)-related death among former plasma donors.

Methods

A retrospective cohort study was conducted involving 11,905 human immunodeficiency virus (HIV) or AIDS patients in a high-risk area of Henan province in China between 1995 and 2016. Demographic and clinical data were collected. Sub-distribution hazard ratios (sHRs) for AIDS-related mortality with baseline CD4⁺ cell counts and ART initiation time were determined using a competing risk model.

Results

Patients who initiated ART within 90 days of HIV/AIDS diagnosis (sHR: 0.24, 95% CI: 0.22–0.27) or had baseline CD4⁺ counts of >500 cells/μL (sHR: 0.23, 95% CI: 0.19–0.28) were associated with lower AIDS-related mortality risk. Patients with ART initiation time >1 year but CD4⁺ counts >350 cells/μL (sHR: 4.42, 95% CI: 3.30–5.91) had a higher AIDS-related mortality risk than those with ART initiation time >90 days but CD4⁺ counts ≤350 cells/μL (sHR: 4.33, 95% CI: 3.58–5.23).

Conclusions

Our results demonstrate that patients with high CD4⁺ cell counts and late ART had a 9% higher risk of AIDS-related death than those with low CD4⁺ cell counts and early ART. This study confirms the great significance of immediate ART initiation among former plasma donor HIV patients in China.

The gift of a lifetime: analysis of HIV at autopsy

Currently, the incidence of HIV infection exceeds the death rate from HIV, and as a result, the prevalence of individuals living with the infection continues to increase. A critical limitation preventing the development of curative strategies is the lack of knowledge regarding mechanisms that allow HIV-infected cells to persist in individuals during combination antiviral therapy (ART). In this issue of the JCI, Chaillon and coworkers assessed HIV-infected cells from various anatomic compartments obtained through a rapid autopsy program of individuals undergoing long-term ART. This study, made possible with strong community collaboration, provides new insights on the potential locations of reservoirs of HIV-infected cells that persist during therapy.

Prolonged Posttreatment Virologic Control and Complete Seroreversion After Advanced Human Immunodeficiency Virus-1 Infection

Background

Possible human immunodeficiency virus (HIV)-1 clearance has rarely been reported. In this study, we describe a unique case of an HIV-positive, combination antiretroviral therapy (cART)-experienced woman with prior acquired immunodeficiency syndrome (AIDS) who has not experienced viral rebound for over 12 years since discontinuing cART.

Methods

Leukapheresis, colonoscopy, and lymph node excision were performed for detailed examination of virologic (including HIV reservoir) and immunologic features. Comparisons were made with chronically infected patients and healthy controls.

Results

No HIV-specific antibodies were detected in serum. Plasma HIV ribonucleic acid (RNA) levels were <0.2 copies/mL, and, except for low-frequency HIV deoxyribonucleic acid (DNA)⁺ cells in lymph node tissue (1 copy/3 × 10⁶ cells), HIV antigen could not be detected by quantitative virus outgrowth (<0.0025 infectious units/10⁶ CD4⁺ T cells) or by most measurements of HIV RNA or DNA in blood, lymph node, or gut-associated mononuclear cells. Human immunodeficiency virus-specific T-cell responses were detectable but low. Brain imaging revealed a prior biopsy site and persistent white matter disease since 1996. Human immunodeficiency virus DNA⁺ cells in the 1996 brain biopsy specimen confirmed her identity and initial HIV diagnosis.

Conclusions

This represents the first report of complete seroreversion, prolonged posttreatment virus suppression, a profoundly small HIV reservoir, and persistent HIV-specific T cells in an adult with prior AIDS.

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.

Antigenic Restimulation of Virus-Specific Memory CD8+ T Cells Requires Days of Lytic Protein Accumulation for Maximal Cytotoxic Capacity

In various infections or vaccinations of mice or humans, reports of the persistence and the requirements for restimulation of the cytotoxic mediators granzyme B (GrB) and perforin (PRF) in CD8+ T cells have yielded disparate results. In this study, we examined the kinetics of PRF and GrB mRNA and protein expression after stimulation and associated changes in cytotoxic capacity in virus-specific memory cells in detail. In patients with controlled HIV or cleared respiratory syncytial virus (RSV) or influenza virus infections, all virus-specific CD8+ T cells expressed low PRF levels without restimulation. Following stimulation, they displayed similarly delayed kinetics for lytic protein expression, with significant increases occurring by days 1 to 3 before peaking on days 4 to 6. These increases were strongly correlated with, but were not dependent upon, proliferation. Incremental changes in PRF and GrB percent expression and mean fluorescence intensity (MFI) were highly correlated with increases in HIV-specific cytotoxicity. mRNA levels in HIV-specific CD8+ T-cells exhibited delayed kinetics after stimulation as with protein expression, peaking on day 5. In contrast to GrB, PRF mRNA transcripts were little changed over 5 days of stimulation (94-fold versus 2.8-fold, respectively), consistent with posttranscriptional regulation. Changes in expression of some microRNAs, including miR-17, miR-150, and miR-155, suggested that microRNAs might play a significant role in regulation of PRF expression. Therefore, under conditions of extremely low or absent antigen levels, memory virus-specific CD8+ T cells require prolonged stimulation over days to achieve maximal lytic protein expression and cytotoxic capacity.IMPORTANCE Antigen-specific CD8+ T cells play a major role in controlling most virus infections, primarily by perforin (PRF)- and granzyme B (GrB)-mediated apoptosis. There is considerable controversy regarding whether PRF is constitutively expressed, rapidly increased similarly to a cytokine, or delayed in its expression with more prolonged stimulation in virus-specific memory CD8+ T cells. In this study, the degree of cytotoxic capacity of virus-specific memory CD8+ T cells was directly proportional to the content of lytic molecules, which required antigenic stimulation over several days for maximal levels. This appeared to be modulated by increases in GrB transcription and microRNA-mediated posttranscriptional regulation of PRF expression. Clarifying the requirements for maximal cytotoxic capacity is critical to understanding how viral clearance might be mediated by memory cells and what functions should be induced by vaccines and immunotherapies.

Distinct viral reservoirs in individuals with spontaneous control of HIV-1

Sustained, drug-free control of HIV-1 replication is naturally achieved in less than 0.5% of infected individuals (here termed 'elite controllers'), despite the presence of a replication-competent viral reservoir1. Inducing such an ability to spontaneously maintain undetectable plasma viraemia is a major objective of HIV-1 cure research, but the characteristics of proviral reservoirs in elite controllers remain to be determined. Here, using next-generation sequencing of near-full-length single HIV-1 genomes and corresponding chromosomal integration sites, we show that the proviral reservoirs of elite controllers frequently consist of oligoclonal to near-monoclonal clusters of intact proviral sequences. In contrast to individuals treated with long-term antiretroviral therapy, intact proviral sequences from elite controllers were integrated at highly distinct sites in the human genome and were preferentially located in centromeric satellite DNA or in Krüppel-associated box domain-containing zinc finger genes on chromosome 19, both of which are associated with heterochromatin features. Moreover, the integration sites of intact proviral sequences from elite controllers showed an increased distance to transcriptional start sites and accessible chromatin of the host genome and were enriched in repressive chromatin marks. These data suggest that a distinct configuration of the proviral reservoir represents a structural correlate of natural viral control, and that the quality, rather than the quantity, of viral reservoirs can be an important distinguishing feature for a functional cure of HIV-1 infection. Moreover, in one elite controller, we were unable to detect intact proviral sequences despite analysing more than 1.5 billion peripheral blood mononuclear cells, which raises the possibility that a sterilizing cure of HIV-1 infection, which has previously been observed only following allogeneic haematopoietic stem cell transplantation2,3, may be feasible in rare instances.

The Role of Immunomodulatory Receptors in the Pathogenesis of HIV Infection: A Therapeutic Opportunity for HIV Cure?

Immune activation is the hallmark of HIV infection and plays a role in the pathogenesis of the disease. In the context of suppressed HIV RNA replication by combination antiretroviral therapy (cART), there remains immune activation which is associated to the HIV reservoirs. Persistent virus contributes to a sustained inflammatory environment promoting accumulation of "activated/exhausted" T cells with diminished effector function. These T cells show increased expression of immunomodulatory receptors including Programmed cell death protein (PD1), Cytotoxic T Lymphocyte Associated Protein 4 (CTLA4), Lymphocyte activation gene 3 (LAG3), T cell immunoglobulin and ITIM domain (TIGIT), T cell immunoglobulin and mucin domain containing 3 (TIM3) among others. More importantly, recent reports had demonstrated that, HIV infected T cells express checkpoint receptors, contributing to their survival and promoting maintenance of the viral reservoir. Therapeutic strategies are focused on viral reservoir elimination and/or those to achieve sustained cART-free virologic remission. In this review, we will discuss the immunological basis and the latest advances of the use of checkpoint inhibitors to treat HIV infection.

Some Aspects of CD8+ T-Cell Exhaustion Are Associated With Altered T-Cell Mitochondrial Features and ROS Content in HIV Infection

BACKGROUND

Reversing or preventing T-cell exhaustion is an important treatment goal in the context of HIV disease; however, the mechanisms that regulate HIV-specific CD8 T-cell exhaustion are incompletely understood. Since mitochondrial mass (MM), mitochondrial membrane potential (MMP), and cellular reactive oxygen species (ROS) content are altered in exhausted CD8 T cells in other settings, we hypothesized that similar lesions may arise in HIV infection.

METHODS

We sampled cryopreserved peripheral blood mononuclear cells from HIV-uninfected (n = 10) and HIV-infected participants with varying levels and mechanisms of viral control: viremic (VL > 2000 copies/mL; n = 8) or aviremic (VL < 40 copies/mL) due to antiretroviral therapy (n = 11) or natural control (n = 9). We characterized the MM, MMP, and ROS content of bulk CD8 T cells and MHC class I tetramer+ HIV-specific CD8 T cells by flow cytometry.

RESULTS

We observed higher MM, MMP, and ROS content across bulk effector-memory CD8 T-cell subsets in HIV-infected compared with HIV-uninfected participants. Among HIV-specific CD8 T cells, these features did not vary by the extent or mechanism of viral control but were significantly altered in cells displaying characteristics associated with exhaustion (eg, high PD-1 expression, low CD127 expression, and impaired proliferative capacity).

CONCLUSIONS

While we did not find that control of HIV replication in vivo correlates with the CD8 T-cell MM, MMP, or ROS content, we did find that some features of CD8 T-cell exhaustion are associated with alterations in mitochondrial state. Our findings support further studies to probe the relationship between mitochondrial dynamics and CD8 T-cell functionality in HIV infection.

Adoptive lymphocyte transfer to an HIV-infected progressor from an elite controller

BACKGROUNDHIV-infected patients with poor virologic control and multidrug-resistant virus have limited therapeutic options. The current study was undertaken to evaluate the safety, immunologic effects, and antiviral activity of peripheral lymphocytes transferred from an elite controller, whose immune system is able to control viral replication without antiretroviral medications, to an HLA-B*2705-matched progressor.METHODSApproximately 22 billion cells were collected from an elite controller by lymphapheresis and infused within 6 hours into a recipient with a preinfusion CD4+ T cell count of 10 cells/μL (1%) and HIV plasma viral load of 114,993 copies/mL.RESULTSDonor cells were cleared from the recipient's peripheral blood by day 8. A transient decrease in viral load to 58,421 (day 3) was followed by a rebound to 702,972 (day 6) before returning to baseline values by day 8. The decreased viral load was temporally associated with peak levels of donor T cells, including CD8+ T cells that had high levels of expression of Ki67, perforin, and granzyme B. Notably, recipient CD8+ T cells also showed increased expression of these markers, especially in HIV-specific tetramer-positive cells.CONCLUSIONThese results suggest that the adoptive transfer of lymphocytes from an HIV-infected elite controller to an HIV-infected patient with progressive disease may be able to perturb the immune system of the recipient in both positive and negative ways.TRIAL REGISTRATIONClinicalTrials.gov NCT00559416.FUNDINGIntramural Research Programs of the US NIH Clinical Center and the National Institute of Allergy and Infectious Diseases (NIAID); the National Cancer Institute.

ART in HIV-Positive Persons With Low Pretreatment Viremia: Results From the START Trial

BACKGROUND

The benefit of immediate antiretroviral therapy (ART) at CD4 >500 cells/μL was established in the Strategic Timing of Antiretroviral Treatment (START) study. The benefits and risks of immediate ART in participants with low pretreatment viremia, including virologic suppressors, were further assessed.

SETTING

Randomized prospective international study.

METHODS

START participants with enrollment viremia <3000 c/mL were included. We compared clinical outcomes (grade 4 adverse events, hospitalizations, or death), plasma viremia, CD4 counts, and changes in biomarkers in immediate versus deferred ART groups.

RESULTS

Participants (N = 1134 including 93 with viremia ≤50 c/mL) had a median age of 37 years, 40% were women, and median CD4 was 713 cells/µL. Ninety-seven percent in the immediate and 29% in the deferred arm initiated ART at a median of 6 and 699 days, respectively. Clinical outcomes were experienced in 64 versus 61 patients in immediate and deferred arms (hazard ratio 1.10, 95% confidence interval: 0.77 to 1.56). The CD4 count difference was 125 cells/µL at 12 and 235 cells/µL at 36 months higher in the immediate versus deferred groups. D-dimer and VCAM levels decreased, and C-reactive protein increased, in the immediate arm at month 8. No significant changes in CD4 counts or biomarkers were observed in persons who maintained spontaneous virologic suppression.

CONCLUSIONS

START participants with low enrollment viremia experienced higher CD4 counts, greater proportion with suppressed viremia, and decreases in D-dimer levels on immediate ART despite the lack of difference in serious clinical outcomes. These data support immediate ART in people with low viremia, although equipoise remains for suppressors.

Immune Control of HIV

The human immunodeficiency virus (HIV) infection of the immune cells expressing the cluster of differentiation 4 cell surface glycoprotein (CD4⁺ cells) causes progressive decline of the immune system and leads to the acquired immunodeficiency syndrome (AIDS). The ongoing global HIV/AIDS pandemic has already claimed over 35 million lives. Even after 37 years into the epidemic, neither a cure is available for the 37 million people living with HIV (PLHIV) nor is a vaccine discovered to avert the millions of new HIV infections that continue to occur each year. If left untreated, HIV infection typically progresses to AIDS and, ultimately, causes death in a majority of PLHIV. The recommended combination antiretroviral therapy (cART) suppresses virus replication and viremia, prevents or delays progression to AIDS, reduces transmission rates, and lowers HIV-associated mortality and morbidity. However, because cART does not eliminate HIV, and an enduring pool of infected resting memory CD4⁺ T cells (latent HIV reservoir) is established early on, any interruption to cART leads to a relapse of viremia and disease progression. Hence, strict adherence to a life-long cART regimen is mandatory for managing HIV infection in PLHIV. The HIV-1-specific cytotoxic T cells expressing the CD8 glycoprotein (CD8⁺ CTL) limit the virus replication in vivo by recognizing the viral antigens presented by human leukocyte antigen (HLA) class I molecules on the infected cell surface and killing those cells. Nevertheless, CTLs fail to durably control HIV-1 replication and disease progression in the absence of cART. Intriguingly, <1% of cART-naive HIV-infected individuals called elite controllers/HIV controllers (HCs) exhibit the core features that define a HIV-1 "functional cure" outcome in the absence of cART: durable viral suppression to below the limit of detection, long-term non-progression to AIDS, and absence of viral transmission. Robust HIV-1-specific CTL responses and prevalence of protective HLA alleles associated with enduring HIV-1 control have been linked to the HC phenotype. An understanding of the molecular mechanisms underlying the CTL-mediated suppression of HIV-1 replication and disease progression in HCs carrying specific protective HLA alleles may yield promising insights towards advancing the research on HIV cure and prophylactic HIV vaccine.

Quantifying Anti-HIV Envelope-Specific Antibodies in Plasma from HIV Infected Individuals

Quantifying HIV Envelope (Env)-specific antibodies in HIV⁺ plasma is useful for interpreting antibody dependent cellular cytotoxicity assay results. HIV Env, the only viral protein expressed on the surface of infected cells, has a native trimeric closed conformation on cells infected with wild-type HIV. However, CD4⁺ uninfected bystander cells in HIV⁺ cell cultures bind gp120 shed from HIV⁺ cells exposing CD4-induced epitopes normally hidden in native Env. We used flow-cytometry based assays to quantify antibodies in HIV⁺ plasma specific for native trimeric Env or gp120/CD4 conjugates using CEM.NKr.CCR5 (CEM) cells infected with HIV (iCEM) or coated with recombinant gp120 (cCEM), as a surrogate for gp120⁺ HIV^- bystander cells. Results from both assays were compared to those of a plate-based ELISA to monomeric gp120. The levels of Env-specific antibodies to cCEM and iCEM, measured by flow cytometry, and to gp120 by ELISA were positively correlated. More antibodies in HIV⁺ plasma recognized the gp120 conformation exposed on cCEM than on iCEM. Comparisons of plasma from untreated progressors, treated progressors, and elite controllers revealed that antibodies to Env epitopes were the lowest in treated progressors. Plasma from elite controllers and untreated progressors had similarly high levels of Env-specific antibodies, despite elite controllers having undetectable HIV viral loads, while untreated progressors maintained high viral loads.

Identification and characterization of HIV-specific resident memory CD8+ T cells in human lymphoid tissue

Current paradigms of CD8⁺ T cell-mediated protection in HIV infection center almost exclusively on studies of peripheral blood, which is thought to provide a window into immune activity at the predominant sites of viral replication in lymphoid tissues (LTs). Through extensive comparison of blood, thoracic duct lymph (TDL), and LTs in different species, we show that many LT memory CD8⁺ T cells bear phenotypic, transcriptional, and epigenetic signatures of resident memory T cells (T_RMs). Unlike their circulating counterparts in blood or TDL, most of the total and follicular HIV-specific CD8⁺ T cells in LTs also resemble T_RMs Moreover, high frequencies of HIV-specific CD8⁺ T_RMs with skewed clonotypic profiles relative to matched blood samples are present in LTs of individuals who spontaneously control HIV replication in the absence of antiretroviral therapy (elite controllers). Single-cell RNA sequencing analysis confirmed that HIV-specific T_RMs are enriched for effector-related immune genes and signatures compared with HIV-specific non-T_RMs in elite controllers. Together, these data indicate that previous studies in blood have largely failed to capture the major component of HIV-specific CD8⁺ T cell responses resident within LTs.

Defining Kinetic Properties of HIV-Specific CD8⁺ T-Cell Responses in Acute Infection

Multiple lines of evidence indicate that CD8 + T cells are important in the control of HIV-1 (HIV) replication. However, CD8 + T cells induced by natural infection cannot eliminate the virus or reduce viral loads to acceptably low levels in most infected individuals. Understanding the basic quantitative features of CD8 + T-cell responses induced during HIV infection may therefore inform us about the limits that HIV vaccines, which aim to induce protective CD8 + T-cell responses, must exceed. Using previously published experimental data from a cohort of HIV-infected individuals with sampling times from acute to chronic infection we defined the quantitative properties of CD8 + T-cell responses to the whole HIV proteome. In contrast with a commonly held view, we found that the relative number of HIV-specific CD8 + T-cell responses (response breadth) changed little over the course of infection (first 400 days post-infection), with moderate but statistically significant changes occurring only during the first 35 symptomatic days. This challenges the idea that a change in the T-cell response breadth over time is responsible for the slow speed of viral escape from CD8 + T cells in the chronic infection. The breadth of HIV-specific CD8 + T-cell responses was not correlated with the average viral load for our small cohort of patients. Metrics of relative immunodominance of HIV-specific CD8 + T-cell responses such as Shannon entropy or the Evenness index were also not significantly correlated with the average viral load. Our mathematical-model-driven analysis suggested extremely slow expansion kinetics for the majority of HIV-specific CD8 + T-cell responses and the presence of intra- and interclonal competition between multiple CD8 + T-cell responses; such competition may limit the magnitude of CD8 + T-cell responses, specific to different epitopes, and the overall number of T-cell responses induced by vaccination. Further understanding of mechanisms underlying interactions between the virus and virus-specific CD8 + T-cell response will be instrumental in determining which T-cell-based vaccines will induce T-cell responses providing durable protection against HIV infection.

Interferon Alpha Enhances NK Cell Function and the Suppressive Capacity of HIV-Specific CD8+ T Cells

Current shock-and-kill strategies for the eradication of the HIV-1 reservoir have resulted in blips of viremia but not in a decrease in the size of the latent reservoir in patients on suppressive antiretroviral therapy (ART). This discrepancy could potentially be explained by an inability of the immune system to kill HIV-1-infected cells following the reversal of latency. Furthermore, some studies have suggested that certain latency-reversing agents (LRAs) may inhibit CD8⁺ T cell and natural killer (NK) cell responses. In this study, we tested the hypothesis that alpha interferon (IFN-α) could improve the function of NK cells from chronic progressors (CP) on ART. We show here that IFN-α treatment enhanced cytokine secretion, polyfunctionality, degranulation, and the cytotoxic potential of NK cells from healthy donors (HD) and CP. We also show that this cytokine enhanced the viral suppressive capacity of NK cells from HD and elite controllers or suppressors. Furthermore, IFN-α enhanced global CP CD8⁺ T cell cytokine responses and the suppressive capacity of ES CD8⁺ T cells. Our data suggest that IFN-α treatment may potentially be used as an immunomodulatory agent in HIV-1 cure strategies.IMPORTANCE Data suggest that HIV⁺ individuals unable to control infection fail to do so due to impaired cytokine production and/cytotoxic effector cell function. Consequently, the success of cure agendas such as the shock-and-kill strategy will probably depend on enhancing patient effector cell function. In this regard, NK cells are of particular interest since they complement the function of CD8⁺ T cells. Here, we demonstrate the ability of short-course alpha interferon (IFN-α) treatments to effectively enhance such effector functions in chronic progressor NK cells without inhibiting their general CD8⁺ T cell function. These results point to the possibility of exploring such short-course IFN-α treatments for the enhancement of effector cell function in HIV⁺ patients in future cure strategies.

Does B Cell Follicle Exclusion of CD8+ T Cells Make Lymph Nodes Sanctuaries of HIV Replication?

As we learn more about the HIV latent reservoir, we continue to discover that the viral reservoir is more complicated than just a pool of infected resting memory CD4+ T cells in peripheral blood. Evidence increasingly points to both certain tissues and certain types of cells as potential viral reservoirs. T follicular helper cells (T_FH) are prime targets of HIV infection-this creates a sanctuary for infected cells because CD8+ T cells generally do not enter lymph node follicles unless they express CXCR5, and are not as effective at killing infected CD4+ T cells as peripheral CD8+ T cells. In this review, we summarize the current state of research on T_FH cell infection in peripheral lymphoid tissues and focus on the question of whether CD8+ T cell exclusion from B cell follicles is responsible, at least in part, for establishing secondary lymphoid tissue B cell follicles as an anatomic site of HIV transcription and replication.

Naturally Derived Anti-HIV Polysaccharide Peptide (PSP) Triggers a Toll-Like Receptor 4-Dependent Antiviral Immune Response

Aim

Intense interest remains in the identification of compounds to reduce human immunodeficiency virus type 1 (HIV-1) replication. Coriolus versicolor's polysaccharide peptide (PSP) has been demonstrated to possess immunomodulatory properties with the ability to activate an innate immune response through Toll-like receptor 4 (TLR4) showing insignificant toxicity. This study sought to determine the potential use of PSP as an anti-HIV agent and whether its antiviral immune response was TLR4 dependent.

Materials and Methods

HIV-1 p24 and anti-HIV chemokine release was assessed in HIV-positive (HIV+) THP1 cells and validated in HIV+ peripheral blood mononuclear cells (PBMCs), to determine PSP antiviral activity. The involvement of TLR4 activation in PSP anti-HIV activity was evaluated by inhibition.

Results

PSP showed a promising potential as an anti-HIV agent, by downregulating viral replication and promoting the upregulation of specific antiviral chemokines (RANTES, MIP-1α/β, and SDF-1α) known to block HIV-1 coreceptors in THP1 cells and human PBMCs. PSP produced a 61% viral inhibition after PSP treatment in HIV-1-infected THP1 cells. Additionally, PSP upregulated the expression of TLR4 and TLR4 inhibition led to countereffects in chemokine expression and HIV-1 replication.

Conclusion

Taken together, these findings put forward the first evidence that PSP exerts an anti-HIV activity mediated by TLR4 and key antiviral chemokines. Elucidating these new molecular mediators may reveal additional drug targets and open novel therapeutic avenues for HIV-1 infection.

DNA immunization site determines the level of gene expression and the magnitude, but not the type of the induced immune response

Optimization of DNA vaccine delivery improves the potency of the immune response and is crucial to clinical success. Here, we inquired how such optimization impacts the magnitude of the response, its specificity and type. BALB/c mice were DNA-immunized with two model immunogens, HIV-1 protease and reverse transcriptase by intramuscular or intradermal injections with electroporation. DNA immunogens were co-delivered with DNA encoding luciferase. Delivery and expression were monitored by in vivo bioluminescence imaging (BLI). The endpoint immune responses were assessed by IFN-γ/IL-2 FluoroSpot, multiparametric flow cytometry and antibody ELISA. Expression and immunogenicity were compared in relation to the delivery route. Regardless of the route, protease generated mainly IFN-γ, and reverse transcriptase, IL-2 and antibody response. BLI of mice immunized with protease- or reverse transcriptase/reporter plasmid mixtures, demonstrated significant loss of luminescence over time. The rate of decline of luminescence strongly correlated with the magnitude of immunogen-specific response, and depended on the immunogenicity profile and the immunization route. In vitro and in vivo BLI-based assays demonstrated that intradermal delivery strongly improved the immunogenicity of protease, and to a lesser extent, of reverse transcriptase. Immune response polarization and epitope hierarchy were not affected. Thus, by changing delivery/immunogen expression sites, it is possible to modulate the magnitude, but not the type or fine specificity of the induced immune response.

Targeting the Latent Reservoir for HIV-1

Antiretroviral therapy can effectively block HIV-1 replication and prevent or reverse immunodeficiency in HIV-1-infected individuals. However, viral replication resumes within weeks of treatment interruption. The major barrier to a cure is a small pool of resting memory CD4+ T cells that harbor latent HIV-1 proviruses. This latent reservoir is now the focus of an intense international research effort. We describe how the reservoir is established, challenges involved in eliminating it, and pharmacologic and immunologic strategies for targeting this reservoir. The development of a successful cure strategy will most likely require understanding the mechanisms that maintain HIV-1 proviruses in a latent state and pathways that drive the proliferation of infected cells, which slows reservoir decay. In addition, a cure will require the development of effective immunologic approaches to eliminating infected cells. There is renewed optimism about the prospect of a cure, and the interventions discussed here could pave the way.

T cell receptors for the HIV KK10 epitope from patients with differential immunologic control are functionally indistinguishable

HIV controllers (HCs) are individuals who can naturally control HIV infection, partially due to potent HIV-specific CD8+ T cell responses. Here, we examined the hypothesis that superior function of CD8+ T cells from HCs is encoded by their T cell receptors (TCRs). We compared the functional properties of immunodominant HIV-specific TCRs obtained from HLA-B*2705 HCs and chronic progressors (CPs) following expression in primary T cells. T cells transduced with TCRs from HCs and CPs showed equivalent induction of epitope-specific cytotoxicity, cytokine secretion, and antigen-binding properties. Transduced T cells comparably, albeit modestly, also suppressed HIV infection in vitro and in humanized mice. We also performed extensive molecular dynamics simulations that provided a structural basis for similarities in cytotoxicity and epitope cross-reactivity. These results demonstrate that the differential abilities of HIV-specific CD8+ T cells from HCs and CPs are not genetically encoded in the TCRs alone and must depend on additional factors.

Innovative Approaches to Improve Anti-Infective Vaccine Efficacy

Safe and efficacious vaccines are arguably the most successful medical interventions of all time. Yet the ongoing discovery of new pathogens, along with emergence of antibiotic-resistant pathogens and a burgeoning population at risk of such infections, imposes unprecedented public health challenges. To meet these challenges, innovative strategies to discover and develop new or improved anti-infective vaccines are necessary. These approaches must intersect the most meaningful insights into protective immunity and advanced technologies with capabilities to deliver immunogens for optimal immune protection. This goal is considered through several recent advances in host-pathogen relationships, conceptual strides in vaccinology, and emerging technologies. Given a clear and growing risk of pandemic disease should the threat of infection go unmet, developing vaccines that optimize protective immunity against high-priority and antibiotic-resistant pathogens represents an urgent and unifying imperative.

Neutralizing Antibodies Against a Specific Human Immunodeficiency Virus gp41 Epitope are Associated With Long-term Non-progressor Status

Antibodies (Abs) play a central role in human immunodeficiency virus (HIV) protection due to their multiple functional inhibitory activities. W614A-3S Abs recognize a specific form of a highly conserved motif of the gp41 envelope protein and can elicit viral neutralization to protect CD4+ T cells. Here, we describe in detail the neutralizing profile of W614A-3S Abs in untreated long-term non-progressor (LTNP) HIV-infected patients. W614A-3S Abs were detected in 23.5% (16/68) of untreated LTNP patients compared with <5% (5/104) of HIV-1 progressor patients. The W614A-3S Abs had efficient neutralizing activity that inhibited transmitted founder primary viruses and exhibited Fc-mediated inhibitory functions at low concentrations in primary monocyte-derived macrophages. The neutralizing capacity of W614A-3S Abs was inversely correlated with viral load (r=-0.9013; p<0.0001), viral DNA (r=-0.7696; p=0.0005) and was associated the preservation of high CD4+ T-cell counts and T-cell responses. This study demonstrates that W614A-3S neutralizing Abs may confer a crucial advantage to LTNP patients. These results provide insights for both pathophysiological research and the development of vaccine strategies.

Expression of complete SIV p27 Gag and HIV gp120 engineered outer domains targeted by broadly neutralizing antibodies in live rubella vectors

Infection with HIV or SIV often elicits a potent immune response to viral antigens. This includes T cells and antibodies specific for Gag and Env antigens. In contrast, when given as a vaccine, the same antigens have been weak immunogens, unable to elicit antibodies with comparable titer, durability, or neutralizing activity. We have used the live attenuated rubella vaccine strain RA27/3 as a viral vector to express HIV and SIV antigens. By mimicking an HIV infection, these vectors could elicit stronger and more durable immunity to HIV antigens. The vectors are based on the licensed rubella vaccine strain, which has demonstrated safety and potency in millions of children. One or two doses protect for life against rubella infection. The question was whether rubella vectors could similarly enhance the immunogenicity of a foreign vaccine insert. We have previously reported that rubella vectors can express small protein antigens in vitro and in vivo, where they elicit a strong immune response to the vaccine insert. The vectors have now expressed larger vaccine inserts that include epitope-rich fragments of the Gag matrix and capsid proteins (aa 41-211) or the complete p27 capsid protein with p2 (aa 136-381). These vectors have elicited a robust and durable immune response to Gag in rhesus macaques. This size range also encompasses the engineered outer domain (eOD) of HIV envelope gp120 (172 amino acids). The rubella/eOD-GT6 and GT8 vectors stably expressed glycoproteins that bind germline precursors and mature forms of VRC01-class broadly neutralizing antibodies. These vectors potentially could be used as part of a sequential immunization strategy to initiate the production of broadly neutralizing antibodies.

Accurate predictions of population-level changes in sequence and structural properties of HIV-1 Env using a volatility-controlled diffusion model

The envelope glycoproteins (Envs) of HIV-1 continuously evolve in the host by random mutations and recombination events. The resulting diversity of Env variants circulating in the population and their continuing diversification process limit the efficacy of AIDS vaccines. We examined the historic changes in Env sequence and structural features (measured by integrity of epitopes on the Env trimer) in a geographically defined population in the United States. As expected, many Env features were relatively conserved during the 1980s. From this state, some features diversified whereas others remained conserved across the years. We sought to identify “clues” to predict the observed historic diversification patterns. Comparison of viruses that cocirculate in patients at any given time revealed that each feature of Env (sequence or structural) exists at a defined level of variance. The in-host variance of each feature is highly conserved among individuals but can vary between different HIV-1 clades. We designate this property “volatility” and apply it to model evolution of features as a linear diffusion process that progresses with increasing genetic distance. Volatilities of different features are highly correlated with their divergence in longitudinally monitored patients. Volatilities of features also correlate highly with their population-level diversification. Using volatility indices measured from a small number of patient samples, we accurately predict the population diversity that developed for each feature over the course of 30 years. Amino acid variants that evolved at key antigenic sites are also predicted well. Therefore, small “fluctuations” in feature values measured in isolated patient samples accurately describe their potential for population-level diversification. These tools will likely contribute to the design of population-targeted AIDS vaccines by effectively capturing the diversity of currently circulating strains and addressing properties of variants expected to appear in the future.

HIV-1 is the causative agent of the global AIDS pandemic. The envelope glycoproteins (Envs) of HIV-1 constitute a primary target for antibody-based vaccines. However, the diversity of Envs in the population limits the potential efficacy of this approach. Accurate estimates of the range of variants that currently infect patients and those expected to appear in the future will likely contribute to the design of population-targeted immunogens. We found that different properties (features) of Env have different propensities for small “fluctuations” in their values among viruses that infect patients at any given time point. This propensity of each feature for in-host variance, which we designate “volatility”, is conserved among patients. We apply this parameter to model the evolution of features (in patients and population) as a diffusion process driven by their “diffusion coefficients” (volatilities). Using volatilities measured from a few patient samples from the 1980s, we accurately predict properties of viruses that evolved in the population over the course of 30 years. The diffusion-based model described here efficiently captures evolution of phenotypes in biological systems controlled by a dominant random component.