The number of CCR5 expressing CD4+ T lymphocytes is lower in HIV-infected long-term non-progressors with viral control compared to normal progressors: a cross-sectional study

A germ-free humanized mouse model shows the contribution of resident microbiota to human-specific pathogen infection

Germ-free (GF) mice, which are depleted of their resident microbiota, are the gold standard for exploring the role of the microbiome in health and disease; however, they are of limited value in the study of human-specific pathogens because they do not support their replication. Here, we develop GF mice systemically reconstituted with human immune cells and use them to evaluate the role of the resident microbiome in the acquisition, replication and pathogenesis of two human-specific pathogens, Epstein-Barr virus (EBV) and human immunodeficiency virus (HIV). Comparison with conventional (CV) humanized mice showed that resident microbiota enhance the establishment of EBV infection and EBV-induced tumorigenesis and increase mucosal HIV acquisition and replication. HIV RNA levels were higher in plasma and tissues of CV humanized mice compared with GF humanized mice. The frequency of CCR5+ CD4+ T cells throughout the intestine was also higher in CV humanized mice, indicating that resident microbiota govern levels of HIV target cells. Thus, resident microbiota promote the acquisition and pathogenesis of two clinically relevant human-specific pathogens.

Astrocytes: Role in pathogenesis and effect of commonly misused drugs in the HIV infected brain

The roles of astrocytes as reservoirs and producers of a subset of viral proteins in the HIV infected brain have been studied extensively as a key to understanding HIV-associated neurocognitive disorders (HAND). However, their comprehensive role in the context of intersecting substance use and neurocircuitry of the reward pathway and HAND has yet to be fully explained. Use of methamphetamines, cocaine, or opioids in the context of HIV infection have been shown to lead to a faster progression of HAND. Glutamatergic, dopaminergic, and GABAergic systems are implicated in the development of HAND-induced cognitive impairments. A thorough review of scientific literature exploring the variety of mechanisms in which these drugs exert their effects on the HIV brain and astrocytes has revealed marked areas of convergence in overexcitation leading to increased drug-seeking behavior, inflammation, apoptosis, and irreversible neurotoxicity. The present review investigates astrocytes, the neural pathways, and mechanisms of drug disruption that ultimately play a larger holistic role in terms of HIV progression and drug use. There are opportunities for future research, therapeutic intervention, and preventive strategies to diminish HAND in the subset population of patients with HIV and substance use disorder.

Reduced CCR5 expression among Uganda HIV controllers

BACKGROUND

Several mechanisms including reduced CCR5 expression, protective HLA, viral restriction factors, broadly neutralizing antibodies, and more efficient T-cell responses, have been reported to account for HIV control among HIV controllers. However, no one mechanism universally accounts for HIV control among all controllers. In this study we determined whether reduced CCR5 expression accounts for HIV control among Ugandan HIV controllers. We determined CCR5 expression among Ugandan HIV controllers compared with treated HIV non-controllers through ex-vivo characterization of CD4 + T cells isolated from archived PBMCs collected from the two distinct groups.

RESULTS

The percentage of CCR5 + CD4 + T cells was similar between HIV controllers and treated HIV non-controllers (ECs vs. NCs, P = 0.6010; VCs vs. NCs, P = 0.0702) but T cells from controllers had significantly reduced CCR5 expression on their cell surface (ECs vs. NCs, P = 0.0210; VCs vs. NCs, P = 0.0312). Furthermore, we identified rs1799987 SNP among a subset of HIV controllers, a mutation previously reported to reduce CCR5 expression. In stark contrast, we identified the rs41469351 SNP to be common among HIV non-controllers. This SNP has previously been shown to be associated with increased perinatal HIV transmission, vaginal shedding of HIV-infected cells and increased risk of death.

CONCLUSION

CCR5 has a non-redundant role in HIV control among Ugandan HIV controllers. HIV controllers maintain high CD4 + T cells despite being ART naïve partly because their CD4 + T cells have significantly reduced CCR5 densities.

Host Immunity to Mycobacterium tuberculosis Infection Is Similar in Simian Immunodeficiency Virus (SIV)-Infected, Antiretroviral Therapy-Treated and SIV-Naïve Juvenile Macaques

Pre-existing HIV infection increases tuberculosis (TB) risk in children. Antiretroviral therapy (ART) reduces, but does not abolish, this risk in children with HIV. The immunologic mechanisms involved in TB progression in both HIV-naive and HIV-infected children have not been explored. Much of our current understanding is based on human studies in adults and adult animal models. In this study, we sought to model childhood HIV/Mycobacterium tuberculosis (Mtb) coinfection in the setting of ART and characterize T cells during TB progression. Macaques equivalent to 4 to 8 year-old children were intravenously infected with SIVmac239M, treated with ART 3 months later, and coinfected with Mtb 3 months after initiating ART. SIV-naive macaques were similarly infected with Mtb alone. TB pathology and total Mtb burden did not differ between SIV-infected, ART-treated and SIV-naive macaques, although lung Mtb burden was lower in SIV-infected, ART-treated macaques. No major differences in frequencies of CD4+ and CD8+ T cells and unconventional T cell subsets (Vγ9+ γδ T cells, MAIT cells, and NKT cells) in airways were observed between SIV-infected, ART-treated and SIV-naive macaques over the course of Mtb infection, with the exception of CCR5+ CD4+ and CD8+ T cells which were slightly lower. CD4+ and CD8+ T cell frequencies did not differ in the lung granulomas. Immune checkpoint marker levels were similar, although ki-67 levels in CD8+ T cells were elevated. Thus, ART treatment of juvenile macaques, 3 months after SIV infection, resulted in similar progression of Mtb and T cell responses compared to Mtb in SIV-naive macaques.

People with HIV have higher percentages of circulating CCR5+ CD8+ T cells and lower percentages of CCR5+ regulatory T cells

CCR5 is the main HIV co-receptor. We aimed to (1) compare CCR5 expression on immune cells between people living with HIV (PLHIV) using combination antiretroviral therapy (cART) and HIV-uninfected controls, (2) relate CCR5 expression to viral reservoir size and (3) assess determinants of CCR5 expression. This cross-sectional study included 209 PLHIV and 323 controls. Percentages of CCR5+ cells (%) and CCR5 mean fluorescence intensity assessed by flow cytometry in monocytes and lymphocyte subsets were correlated to host factors, HIV-1 cell-associated (CA)-RNA and CA-DNA, plasma inflammation markers and metabolites. Metabolic pathways were identified. PLHIV displayed higher percentages of CCR5+ monocytes and several CD8+ T cell subsets, but lower percentages of CCR5+ naive CD4+ T cells and regulatory T cells (Tregs). HIV-1 CA-DNA and CA-RNA correlated positively with percentages of CCR5+ lymphocytes. Metabolome analysis revealed three pathways involved in energy metabolism associated with percentage of CCR5+ CD8+ T cells in PLHIV. Our results indicate that CCR5 is differently expressed on various circulating immune cells in PLHIV. Hence, cell-trafficking of CD8+ T cells and Tregs may be altered in PLHIV. Associations between energy pathways and percentage of CCR5+ CD8+ T cells in PLHIV suggest higher energy demand of these cells in PLHIV.

Targeted Immuno-Antiretroviral to Promote Dual Protection against HIV: A Proof-of-Concept Study

The C-C motif chemokine receptor-5 (CCR5) expression on the T-cell surface is the prime barrier to HIV/AIDS eradication, as it promotes both active human immunodeficiency virus (HIV)-infection and latency; however, antiretrovirals (ARVs) suppress plasma viral loads to non-detectable levels. Keeping this in mind, we strategically designed a targeted ARVs-loaded nanoformulation that targets CCR5 expressing T-cells (e.g., CD4+ cells). Conceptually, CCR5-blocking and targeted ARV delivery would be a dual protection strategy to prevent HIV infection. For targeting CCR5+ T-cells, the nanoformulation was surface conjugated with anti-CCR5 monoclonal antibodies (CCR5 mAb) and loaded with dolutegravir+tenofovir alafenamide (D+T) ARVs to block HIV replication. The result demonstrated that the targeted-ARV nanoparticle’s multimeric CCR5 binding property improved its antigen-binding affinity, prolonged receptor binding, and ARV intracellular retention. Further, nanoformulation demonstrated high binding affinity to CCR5 expressing CD4+ cells, monocytes, and other CCR5+ T-cells. Finally, the short-term pre-exposure prophylaxis study demonstrated that prolonged CCR5 blockage and ARV presence further induced a “protective immune phenotype” with a boosted T-helper (Th), temporary memory (TM), and effector (E) sub-population. The proof-of-concept study that the targeted-ARV nanoformulation dual-action mechanism could provide a multifactorial solution toward achieving HIV “functional cure”.

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

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

Targeting CCR5 as a Component of an HIV-1 Therapeutic Strategy

Globally, human immunodeficiency virus type 1 (HIV-1) infection is a major health burden for which successful therapeutic options are still being investigated. Challenges facing current drugs that are part of the established life-long antiretroviral therapy (ART) include toxicity, development of drug resistant HIV-1 strains, the cost of treatment, and the inability to eradicate the provirus from infected cells. For these reasons, novel anti-HIV-1 therapeutics that can prevent or eliminate disease progression including the onset of the acquired immunodeficiency syndrome (AIDS) are needed. While development of HIV-1 vaccination has also been challenging, recent advancements demonstrate that infection of HIV-1-susceptible cells can be prevented in individuals living with HIV-1, by targeting C-C chemokine receptor type 5 (CCR5). CCR5 serves many functions in the human immune response and is a co-receptor utilized by HIV-1 for entry into immune cells. Therapeutics targeting CCR5 generally involve gene editing techniques including CRISPR, CCR5 blockade using antibodies or antagonists, or combinations of both. Here we review the efficacy of these approaches and discuss the potential of their use in the clinic as novel ART-independent therapies for HIV-1 infection.

Naive infection predicts reservoir diversity and is a formidable hurdle to HIV eradication

Historically, naive cells have been considered inconsequential to HIV persistence. Here, we compared the contributions of naive and memory cells to the reservoirs of individuals with a spectrum of reservoir sizes and variable immunological control. We performed proviral sequencing of approximately 6000 proviruses from cellular subsets of 5 elite controllers (ECs) off antiretroviral therapy (ART) and 5 chronic progressors (CPs) on ART. The levels of naive infection were barely detectable in ECs and approximately 300-fold lower compared with those in CPs. Moreover, the ratio of infected naive to memory cells was significantly lower in ECs. Overall, the naive infection level increased as reservoir size increased, such that naive cells were a major contributor to the intact reservoir of CPs, whose reservoirs were generally very diverse. In contrast, the reservoirs of ECs were dominated by proviral clones. Critically, the fraction of proviral clones increased with cell differentiation, with naive infection predicting reservoir diversity. Longitudinal sequencing revealed that the reservoir of ECs was less dynamic compared with that of CPs. Naive cells play a critical role in HIV persistence. Their infection level predicts reservoir size and diversity. Moreover, the diminishing diversity of the reservoir as cellular subsets mature suggests that naive T cells repopulate the memory compartment and that direct infection of naive T cells occurs in vivo.

HIV co-receptor-tropism: cellular and molecular events behind the enigmatic co-receptor switching

Recognition of cell-surface receptors and co-receptors is a crucial molecular event towards the establishment of HIV infection. HIV exists as several variants that differentially recognize the principal co-receptors, CCR5 and CXCR4, in different cell types, known as HIV co-receptor-tropism. The relative levels of these variants dynamically adjust to the changing host selection pressures to infect a vast repertoire of cells in a stage-specific manner. HIV infection sets in through immune cells such as dendritic cells, macrophages, and T-lymphocytes in the acute stage, while a wide range of other cells, including astrocytes, glial cells, B-lymphocytes, and epithelial cells, are infected during chronic stages. A change in tropism occurs during the transition from acute to a chronic phase, termed as co-receptor switching marked by a change in disease severity. The cellular and molecular events leading to co-receptor switching are poorly understood. This review aims to collate our present understanding of the dynamics of HIV co-receptor-tropism vis-à-vis host and viral factors, highlighting the cellular and molecular events involved therein. We present the possible correlations between virus entry, cell tropism, and co-receptor switching, speculating its consequences on disease progression, and proposing new scientific pursuits to help in an in-depth understanding of HIV biology.

Preclinical Evaluation of a Novel TALEN Targeting CCR5 Confirms Efficacy and Safety in Conferring Resistance to HIV-1 Infection

Therapies to treat patients infected with human immunodeficiency virus (HIV) aim at preventing viral replication but fail to eliminate the virus. Although transplantation of allogeneic CCR5Δ32 homozygous stem cell grafts provided a cure for a few patients, this approach is not considered a general therapeutic strategy because of potential side effects. Conversely, gene editing to disrupt the C-C chemokine receptor type 5 (CCR5) locus, which encodes the major HIV coreceptor, has shown to confer resistance to CCR5-tropic HIV strains. Here, an engineered transcription activator-like effector nuclease (TALEN) that enables efficient CCR5 editing in hematopoietic cells is presented. After transferring TALEN-encoding mRNA into primary CD4+ T cells, up to 89% of CCR5 alleles are disrupted. Genotyping confirms the genetic stability of the CCR5-edited cells, and genome-wide off-target analyses established the absence of relevant mutagenic events. When challenging the edited T cells with CCR5-tropic HIV, protection in a dose-dependent manner is observed. Functional assessments reveal no significant differences between edited and control cells in terms of proliferation and their ability to secrete cytokines upon exogenous stimuli. In conclusion, a highly active and specific TALEN to disrupt CCR5 is successfully engineered, paving the way for its clinical application in hematopoietic stem cell grafts.

Canonical Wnts Mediate CD8+ T Cell Noncytolytic Anti-HIV-1 Activity and Correlate with HIV-1 Clinical Status

CD8⁺ T cells do not rely solely on cytotoxic functions for significant HIV control. Moreover, the noncytotoxic CD8⁺ T cell antiviral response is a primary mediator of natural HIV control such as that seen in HIV elite controllers and long-term nonprogressors that does not require combined antiretroviral therapy. In this study, we investigated the biological factors contributing to the noncytotoxic control of HIV replication mediated by primary human CD8⁺ T cells. We report that canonical Wnt signaling inhibits HIV transcription in an MHC-independent, noncytotoxic manner and that mediators of this pathway correlate with HIV controller clinical status. We show that CD8⁺ T cells express all 19 Wnts and CD8⁺ T cell-conditioned medium (CM) induced canonical Wnt signaling in infected recipient cells while simultaneously inhibiting HIV transcription. Antagonizing canonical Wnt activity in CD8⁺ T cell CM resulted in increased HIV transcription in infected cells. Further, Wnt2b expression was upregulated in HIV controllers versus viremic patients, and in vitro depletion of Wnt2b and/or Wnt9b from CD8⁺ CM reversed HIV inhibitory activity. Finally, plasma concentration of Dkk-1, an antagonist of canonical Wnt signaling, was higher in viremic patients with lower CD4 counts. This study demonstrates that canonical Wnt signaling inhibits HIV and significantly correlates with HIV controller status.

CCR5 attenuates neutrophilic airway inflammation exacerbated by infection with rhinovirus

Human rhinovirus (hRV) is the most common cause of asthma exacerbation characterized by clinical and pathophysiological heterogeneity. Steroid-sensitive, Th2 type-eosinophilic asthma has been somewhat studied, but hRV-induced neutrophilic asthma exacerbation is poorly understood. Here, CCR5 was found to play a role in attenuating neutrophilic airway inflammation in hRV-induced asthma exacerbation using chicken ovalbumin (OVA)-based model. CCR5 deficiency resulted in exacerbated neutrophilic asthmatic responses in airways following hRV infection. CCR5-deficient mice showed enhanced mucus expression and altered expression of tight junction proteins in lung tissues. CCR5-deficient mice were also manifested with influx of CD45⁺CD11b⁺Siglec-F⁺Gr-1⁺ neutrophils, along with enhanced production of IL-17A, IFN-γ, IL-6, IL-1β cytokines in inflamed tissues. In contrast, CCR5-deficient mice elicited down-regulation of Th2-related cytokine proteins following hRV infection. More interestingly, the lack of CCR5 altered the equilibrium of CD4⁺FoxP3⁺ Tregs and IL-17⁺CD4⁺ Th17 in inflamed tissues. CCR5-deficient mice showed increased frequency and absolute number of IL-17-producing CD4⁺ Th17 cells in lung tissues compared to wild-type mice, whereas the reduced infiltration of CD4⁺FoxP3⁺ Treg cells was observed. CCR5 deficiency resulted in the skewed production of Th17 and Th1 cytokines in lymph nodes and lungs upon OVA stimulation. Likewise, CCR5-deficient mice showed enhanced expression of Th17-inducing cytokines (IL-1β, IL-6, and TNF-α) in lung tissues. These results imply that CCR5 deficiency facilitates Th17 airway inflammation during hRV-induced asthma exacerbation, along with suppressing Th2 responses. Furthermore, our results suggest that CCR5 attenuates hRV-induced neutrophilic airway inflammation through conserving the equilibrium of CD4⁺Foxp3⁺ Treg cells and IL-17⁺CD4⁺ Th17 cells in hRV-induced asthma exacerbation.

HIV long-term non-progressors elite controllers: an interplay between host, immune and viral factors

There is a rare group of HIV-1-infected individuals who show permanent control of clinical progression for over 10 years, maintain CD4+ cells >500 μl and have undetectable viral loads; they are designated long-term non-progressors elite controllers (LTNPs ECs). Multiple studies have demonstrated the necessary contribution of at least two of host, immune and viral factors to the LTNP phenotype. This group of individuals is not homogenous because of the different involvement of these factors. We will review the role of each of these and their combinations to the LTNP EC phenotype. LTNP EC individuals offer an opportunity for the investigation into the mechanisms for the spontaneous control of HIV infection.

Whole Exome Sequencing of HIV-1 long-term non-progressors identifies rare variants in genes encoding innate immune sensors and signaling molecules

Common CCR5-∆32 and HLA alleles only explain a minority of the HIV long-term non-progressor (LTNP) and elite controller (EC) phenotypes. To identify rare genetic variants contributing to the slow disease progression phenotypes, we performed whole exome sequencing (WES) on seven LTNPs and four ECs. HLA and CCR5 allele status, total HIV DNA reservoir size, as well as variant-related functional differences between the ECs, LTNPs, and eleven age- and gender-matched HIV-infected non-controllers on antiretroviral therapy (NCARTs) were investigated. Several rare variants were identified in genes involved in innate immune sensing, CD4-dependent infectivity, HIV trafficking, and HIV transcription mainly within the LTNP group. ECs and LTNPs had a significantly lower HIV reservoir compared to NCARTs. Furthermore, three LTNPs with variants affecting HIV nuclear import showed integrated HIV DNA levels below detection limit after in vitro infection. HIV slow progressors with variants in the TLR and NOD2 pathways showed reduced pro-inflammatory responses compared to matched controls. Low-range plasma levels of fibronectin was observed in a LTNP harboring two FN1 variants. Taken together, this study identified rare variants in LTNPs as well as in one EC, which may contribute to understanding of HIV pathogenesis and these slow progressor phenotypes, especially in individuals without protecting CCR5-∆32 and HLA alleles.

CCR5 Revisited: How Mechanisms of HIV Entry Govern AIDS Pathogenesis

The chemokine receptor CCR5 has been the focus of intensive studies since its role as a coreceptor for HIV entry was discovered in 1996. These studies lead to the development of small molecular drugs targeting CCR5, with maraviroc becoming in 2007 the first clinically approved chemokine receptor inhibitor. More recently, the apparent HIV cure in a patient transplanted with hematopoietic stem cells devoid of functional CCR5 rekindled the interest for inactivating CCR5 through gene therapy and pharmacological approaches. Fundamental research on CCR5 has also been boosted by key advances in the field of G-protein coupled receptor research, with the realization that CCR5 adopts a variety of conformations, and that only a subset of these conformations may be targeted by chemokine ligands. In addition, recent genetic and pathogenesis studies have emphasized the central role of CCR5 expression levels in determining the risk of HIV and SIV acquisition and disease progression. In this article, we propose to review the key properties of CCR5 that account for its central role in HIV pathogenesis, with a focus on mechanisms that regulate CCR5 expression, conformation, and interaction with HIV envelope glycoproteins.

Higher expression of human telomerase reverse transcriptase in productively-infected CD4 cells possibly indicates a mechanism for persistence of the virus in HIV infection

Mechanisms involved in survival of productively-infected memory CD4+cells after initial antigenic stimulation and their subsequent reversion to the resting state are critical for the development of a predominant replication-competent HIV reservoir. These mechanisms may also counter their elimination after HIV reactivation through latency-reversing agents (LRA). Thus, their evaluation is critical when using an appropriate HIV latency model that recapitulates the predominant replication-competent HIV reservoir to develop strategies for HIV eradication. The model for evaluating the possible survival mechanisms after T cell receptor (TCR) stimulation was developed by infecting memory CD4+cells with an HIV-1C primary isolate and cytokine secretion and gene expression patterns determined. Infected cells showed compromised functionality as evident from 6.8-fold lower secretion of IL-2 than from uninfected control cells. After TCR stimulation, the infected cells showed significantly higher fold increases in CD27 and CCR5 and smaller increases in CD5 mRNA over baseline values. Because CD27 expression may influence telomerase activity through AKT phosphorylation, CD27, human telomerase reverse transcriptase (hTERT) and pAKT expression in productively-infected cells from HIV-infected patients was evaluated by flow cytometry. HIV harbored in memory CD4+ cells was reactivated by HIV-1 envelope peptides, which have been shown to act as effective LRA. P24+CD4+cell showed significantly higher expression of CD27, hTERT and pAKT than P24-CD4+cells. These findings indicate compromised functionality of HIV-infected cells after TCR stimulation, which may interfere with their elimination by the immune system. They also indicate that pAKT and hTERT induction are possible survival mechanisms of productively-infected CD4+cells.

High-Sequence Diversity and Rapid Virus Turnover Contribute to Higher Rates of Coreceptor Switching in Treatment-Experienced Subjects with HIV-1 Viremia

Coreceptor switching from CCR5 to CXCR4 is common during chronic HIV-1 infection, but is even more common in individuals who have failed antiretroviral therapy (ART). Prior studies have suggested rapid mutation and/or recombination of HIV-1 envelope (env) genes during coreceptor switching. We compared the functional and genotypic changes in env of viruses from viremic subjects who had failed ART just before and after coreceptor switching and compared those to viruses from matched subjects without coreceptor switching. Analysis of multiple unique functional env clones from each subject revealed extensive diversity at both sample time points and rapid diversification of sequences during the 4-month interval in viruses from both 9 subjects with coreceptor switching and 15 control subjects. Only two subjects had envs with evidence of recombination. Three findings distinguished env clones from subjects with coreceptor switching from controls: (1) lower entry efficiency via CCR5; (2) longer V1/V2 regions; and (3), lower nadir CD4 T cell counts during prior years of infection. Most of these subjects harbored virus with lower replicative capacity associated with protease (PR) and/or reverse transcriptase inhibitor resistance mutations, and the extensive diversification tended to lead either to improved entry efficiency via CCR5 or the gain of entry function via CXCR4. These results suggest that R5X4 or X4 variants emerge from a diverse, low-fitness landscape shaped by chronic infection, multiple ART resistance mutations, the availability of target cells, and reduced entry efficiency via CCR5.

Establishment and Reversal of HIV-1 Latency in Naive and Central Memory CD4+ T Cells In Vitro

The latent HIV-1 reservoir primarily resides in resting CD4(+) T cells which are a heterogeneous population composed of both naive (TN) and memory cells. In HIV-1-infected individuals, viral DNA has been detected in both naive and memory CD4(+) T cell subsets although the frequency of HIV-1 DNA is typically higher in memory cells, particularly in the central memory (TCM) cell subset. TN and TCM cells are distinct cell populations distinguished by many phenotypic and physiological differences. In this study, we used a primary cell model of HIV-1 latency that utilizes direct infection of highly purified TN and TCM cells to address differences in the establishment and reversal of HIV-1 latency. Consistent with what is seen in vivo, we found that HIV-1 infected TN cells less efficiently than TCM cells. However, when the infected TN cells were treated with latency-reversing agents, including anti-CD3/CD28 antibodies, phorbol myristate acetate/phytohemagglutinin, and prostratin, as much (if not more) extracellular virion-associated HIV-1 RNA was produced per infected TN cell as per infected TCM cell. There were no major differences in the genomic distribution of HIV-1 integration sites between TN and TCM cells that accounted for these observed differences. We observed decay of the latent HIV-1 cells in both T cell subsets after exposure to each of the latency-reversing agents. Collectively, these data highlight significant differences in the establishment and reversal of HIV-1 latency in TN and TCM CD4(+) T cells and suggest that each subset should be independently studied in preclinical and clinical studies.

IMPORTANCE

The latent HIV-1 reservoir is frequently described as residing within resting memory CD4(+) T cells. This is largely due to the consistent finding that memory CD4(+) T cells, specifically the central (TCM) and transitional memory compartments, harbor the highest levels of HIV-1 DNA in individuals on suppressive therapy. This has yielded little research into the contribution of CD4(+) naive T (TN) cells to the latent reservoir. In this study, we show that although TN cells harbor significantly lower levels of HIV-1 DNA, following latency reversal, they produced as many virions as did the TCM cells (if not more virions). This suggests that latently infected TN cells may be a major source of virus following treatment interruption or failure. These findings highlight the need for a better understanding of the establishment and reversal of HIV-1 latency in TN cells in evaluating therapeutic approaches to eliminate the latent reservoir.