HIV controllers: how do they tame the virus?

Epiglottitis Strikes Twice: A Case of Adult Recurrent Epiglottitis

Epiglottitis is an uncommon condition in adults, and recurrent episodes are rare. We report a 58-year-old male who had a second episode of epiglottitis nine years after his first. Our patient's immunologic profile obtained during his hospitalization revealed a significantly low absolute cluster of differentiation 4+ (CD4+) T lymphocyte count of 77 cells/mcL and a low immunoglobulin G (IgG) level of 635 mg/dL. Our patient was successfully managed with broad-spectrum antibiotics and corticosteroids. Given the known ability of short-term corticosteroids and acute inflammation's effect on lymphocyte populations, the significance of these laboratory values remains unclear due to our patient's unwillingness to undergo further diagnostic testing following discharge from our facility. We have considered multiple underlying etiologies for our patient's predisposition to developing this rare, recurrent, infectious manifestation; however, the exact cause is yet to be fully elucidated.

Genotypic and Phenotypic Characterization of Replication-Competent HIV-2 Isolated from Controllers and Progressors

Although some individuals with HIV-2 develop severe immunodeficiency and AIDS-related complications, most may never progress to AIDS. Replication-competent HIV-2 isolated from asymptomatic long-term non-progressors (controllers) have lower replication rates than viruses from individuals who progress to AIDS (progressors). To investigate potential retroviral factors that correlate with disease progression in HIV-2, we sequenced the near full-length genomes of replication-competent viruses previously outgrown from controllers and progressors and used phylogeny to seek genotypic correlates of disease progression. We validated the integrity of all open reading frames and used cell-based assays to study the retroviral transcriptional activity of the long terminal repeats (LTRs) and Tat proteins of HIV-2 from controllers and progressors. Overall, we did not identify genotypic defects that may contribute to HIV-2 non-progression. Tat-induced, LTR-mediated transcription was comparable between viruses from controllers and progressors. Our results were obtained from a small number of participants and should be interpreted accordingly. Overall, they suggest that progression may be determined before or during integration of HIV-2.

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.

A role for CD4 + helper cells in HIV control and progression

OBJECTIVE

It remains unclear why HIV persists in most untreated individuals, and why a small minority of individuals can control the virus, either spontaneously or after an early treatment. Striking differences have been discovered between patient cohorts in CD4 + T-cell avidity but not in CD8 + T-cell avidity. The present work has the aim to explain the diverse outcome of infection and identify the key virological and immunological parameters predicting the outcome.

DESIGN AND METHOD

A mathematical model informed by these experiments and taking into account the details of HIV virology is developed.

RESULTS

The model predicts an arms race between viral dissemination and the proliferation of HIV-specific CD4 + helper cells leading to one of two states: a low-viremia state (controller) or a high-viremia state (progressor). Helper CD4 + cells with a higher avidity favor virus control. The parameter segregating spontaneous and posttreatment controllers is the infectivity difference between activated and resting CD4 + T cells. The model is shown to have a better connection to experiment than a previous model based on T-cell 'exhaustion'.

CONCLUSION

Using the model informed by patient data, the timing of antiretroviral therapy can be optimized.

Elite and viremic HIV-1 controllers in West Africa

BACKGROUND

Data on HIV-1 controllers in Africa are scarce. We report the proportion of HIV-1 controllers in a group of adults prospectively monitored with frequent viral load measurements as part of a clinical trial in West Africa.

METHODS

For the Temprano trial, antiretroviral therapy (ART)-naive HIV-1 infected adults with no criteria for starting ART were randomized to start ART immediately or defer ART until the WHO starting criteria were met. Plasma viral load was measured every 6 months. The trial follow-up was 30 months. We considered all Temprano participants randomized to defer ART. Patients with all semestrial viral <2000 copies/ml and still off ART at month 30 were defined as HIV-1 controllers. Controllers with all viral loads <50 copies/ml were defined as elite controllers, the rest as viremic controllers.

RESULTS

Of the 1023 HIV-1-infected adults randomized in the Temprano deferred-ART group, 18 (1.8%) met the criteria for classification as HIV controllers, of whom seven (0.7%) were elite controllers and 11 (1.1%) viremic controllers. The HIV-1 controllers had low peripheral blood mononuclear cell HIV-1 DNA and low inflammatory marker levels. They maintained high CD4+ cell count and percentages and had a low morbidity rate.

DISCUSSION

HIV controllers exist in Africa at a proportion close to that reported elsewhere. They represent a small fraction of all HIV-1-infected patients but raise important questions. Further studies should assess whether starting ART might represent more risk than benefit for some controllers, and where it does, how to identify these patients before they start ART.

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

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

SIV-specific CD8+ T cells are clonotypically distinct across lymphoid and mucosal tissues

CD8+ T cell responses are necessary for immune control of simian immunodeficiency virus (SIV). However, the key parameters that dictate antiviral potency remain elusive, conceivably because most studies to date have been restricted to analyses of circulating CD8+ T cells. We conducted a detailed clonotypic, functional, and phenotypic survey of SIV-specific CD8+ T cells across multiple anatomical sites in chronically infected rhesus macaques with high (>10,000 copies/mL plasma) or low burdens of viral RNA (<10,000 copies/mL plasma). No significant differences in response magnitude were identified across anatomical compartments. Rhesus macaques with low viral loads (VLs) harbored higher frequencies of polyfunctional CXCR5+ SIV-specific CD8+ T cells in various lymphoid tissues and higher proportions of unique Gag-specific CD8+ T cell clonotypes in the mesenteric lymph nodes relative to rhesus macaques with high VLs. In addition, public Gag-specific CD8+ T cell clonotypes were more commonly shared across distinct anatomical sites than the corresponding private clonotypes, which tended to form tissue-specific repertoires, especially in the peripheral blood and the gastrointestinal tract. Collectively, these data suggest that functionality and tissue localization are important determinants of CD8+ T cell-mediated efficacy against SIV.

Cis-regulatory genetic variants in the CCR5 gene and natural HIV-1 control in black South Africans

Studies have investigated CCR5 haplotypes (HHA, HHB, HHC, HHD, HHE, HHF*1, HHF*2, HHG*1, HHG*2), defined by seven 5'UTR single nucleotide polymorphisms (SNPs), CCR2-V64I and CCR5Δ32, in HIV-1 disease. CCR5 cis-regulatory regions were sequenced, CCR2-V64I and CCR5Δ32 genotyped, and compared in HIV-1-infected black South Africans: 71 HIV-1 controllers (23 elite controllers, 37 viraemic controllers (VCs), 11 high viral load long-term non-progressors) and 74 progressors. The HHE haplotype and 3'UTR +2919 T > G SNP heterozygosity were underrepresented in total controllers and VCs vs. progressors (p = .004; p = .007 and p = .002, p_bonferroni = 0.032; p = .004, respectively). Possession of the +2919 T > G SNP (dominant mode) was associated with HIV-1 progression (controllers vs. progressors: p = .001, p_bonferroni = 0.016). The +2919 T > G SNP is in linkage disequilibrium (LD; r² = 0.73) with two 5'UTR SNPs (-2459G > A and -2135 T > C; r² = 1: 5'UTR-2SNP-hap). The 5'UTR-2SNP-hap was lower in total controllers and VCs vs. progressors (p = .003, p_bonferroni = 0.048; p = .01, respectively). Results suggest -2459G > A, -2135 T > C, and + 2919 T > G as key CCR5 variants in HIV-1 control.

Kopycinski J, Gilmour J, Kumar S, Muthu M, Subramaniam S, Swaminathan S, Prasad Tripathy S, Luke HE. Induction and maintenance of bi-functional (IFN-γ + IL-2+ and IL-2+ TNF-α+) T cell responses by DNA prime MVA boosted subtype C prophylactic vaccine tested in a Phase I trial in India

Effective vaccine design relies on accurate knowledge of protection against a pathogen, so as to be able to induce relevant and effective protective responses against it. An ideal Human Immunodeficiency virus (HIV) vaccine should induce humoral as well as cellular immune responses to prevent initial infection of host cells or limit early events of viral dissemination. A Phase I HIV-1 prophylactic vaccine trial sponsored by the International AIDS Vaccine Initiative (IAVI) was conducted in India in 2009.The trial tested a HIV-1 subtype C vaccine in a prime-boost regimen, comprising of a DNA prime (ADVAX) and Modified Vaccine Ankara (MVA) (TBC-M4) boost. The trial reported that the vaccine regimen was safe, well tolerated, and resulted in enhancement of HIV-specific immune responses. However, preliminary immunological studies were limited to vaccine-induced IFN-γ responses against the Env and Gag peptides. The present study is a retrospective study to characterize in detail the nature of the vaccine-induced cell mediated immune responses among volunteers, using Peripheral Blood Mononuclear Cells (PBMC) that were archived during the trial. ELISpot was used to measure IFN-γ responses and polyfunctional T cells were analyzed by intracellular multicolor flow cytometry. It was observed that DNA priming and MVA boosting induced Env and Gag specific bi-functional and multi-functional CD4⁺ and CD8⁺ T cells expressing IFN-γ, TNF-α and IL-2. The heterologous prime-boost regimen appeared to be slightly superior to the homologous prime-boost regimen in inducing favorable cell mediated immune responses. These results suggest that an in-depth analysis of vaccine-induced cellular immune response can aid in the identification of correlates of an effective immunogenic response, and inform future design of HIV vaccines.

A child with perinatal HIV infection and long-term sustained virological control following antiretroviral treatment cessation

Understanding HIV remission in rare individuals who initiated antiretroviral therapy (ART) soon after infection and then discontinued, may inform HIV cure interventions. Here we describe features of virus and host of a perinatally HIV-1 infected child with long-term sustained virological control. The child received early limited ART in the Children with HIV Early antiRetroviral therapy (CHER) trial. At age 9.5 years, diagnostic tests for HIV are negative and the child has characteristics similar to uninfected children that include a high CD4:CD8 ratio, low T cell activation and low CCR5 expression. Virus persistence (HIV-1 DNA and plasma RNA) is confirmed with sensitive methods, but replication-competent virus is not detected. The child has weak HIV-specific antibody and T cell responses. Furthermore, we determine his HLA and KIR genotypes. This case aids in understanding post-treatment control and may help design of future intervention strategies.

Some perinatally HIV infected children who have received early antiretroviral therapy (ART) show long-term sustained virological control after ART cessation. Here the authors describe a case who, at age 9.5 years, shows normal CD4:CD8 T cell ratios and has no detectable levels of replication-competent virus.

Elevated Expression of miR-19b Enhances CD8+ T Cell Function by Targeting PTEN in HIV Infected Long Term Non-progressors With Sustained Viral Suppression

Human immunodeficiency virus (HIV)-infected long-term non-progressors (LTNPs) are of particular importance because of their unique disease progression characteristics. Defined by the maintenance of normal CD4⁺T cells after more than 8 years of infection, these LTNPs are heterogeneous. Some LTNPs exhibit ongoing viral production, while others do not and are able to control viral production. The underlying basis for this heterogeneity has not been clearly elucidated. In this study, the miRNA expression profiles of LTNPs were assessed. The levels of microRNA-19b (miR-19b) were found to be significantly increased in peripheral blood mononuclear cells of LTNPs with lower rather than higher viral load. We made clear that miR-19b may regulate CD8⁺T cell functions in HIV infection, which has not been addressed before. Overexpression of miR-19b promoted CD8⁺T cell proliferation, as well as interferon-γ and granzyme B expression, while inhibiting CD8⁺T cells apoptosis induced by anti-CD3/CD28 stimulation. The target of miR-19b was found to be the "phosphatase and tensin homolog", which regulates CD8⁺T cells function during HIV infections. Furthermore, we found that miR-19b can directly inhibit viral production in in-vitro HIV infected T cells. These results highlight the importance of miR-19b to control viral levels, which facilitate an understanding of human immunodeficiency virus pathogenesis and provide potential targets for improved immune intervention.

Dynamics in HIV-DNA levels over time in HIV controllers

INTRODUCTION

HIV controllers (HIC) maintain viraemia at low levels without antiretroviral treatment and have small HIV reservoirs. Nevertheless, they are heterogeneous regarding their risk of infection progression. The study of reservoirs can help elucidate this control. This study aimed to explore the factors implicated in the pathogenesis of HIV infection that are potentially associated with HIV reservoirs and their dynamics in HIC.

METHODS

Individuals living with HIV included in the ANRS-CODEX cohort with at least two HIV-DNA measurements between 2009 and 2016 were selected. The total HIV-DNA levels had been quantified prospectively from blood samples. Mixed-effect linear models estimated the HIV-DNA dynamics over time.

RESULTS

The median (interquartile range (IQR)) HIV-DNA level was 1.5 (1.3 to 1.9) log copies/million peripheral blood mononuclear cells at inclusion (n = 202 individuals). These low levels showed heterogeneity among HIC. Lower levels were then associated with the protective HLA-B*27/B*57 alleles and/or lower HIV-RNA level at inclusion, negative hepatitis C virus serology, lower HIV-suppressive capacity of specific CD8 T cells and lower levels of immune activation and inflammation. Interestingly, mathematical modelling of the dynamics of HIV-DNA over time (840 measurements) showed that the number of infected cells decreased in 46% of HIC (follow-up: 47.6 months) and increased in 54% of HIC. A multivariate analysis indicated that HLA-B*27/B*57 alleles, a low level of HIV-RNA and a low level of HIV-DNA at inclusion were markers independently associated with this decrease.

CONCLUSIONS

These results offer new insights into the mechanisms of long-term control in HIC. In half of HIC, the decrease in HIV-DNA level could be linked to tighter viral control and progressive loss of infected cells. These findings allow the identification of HIC with a low risk of progression who may not need treatment.

Human Immunodeficiency Virus Type-1 Elite Controllers Maintain Low Co-Expression of Inhibitory Receptors on CD4+ T Cells

Human immunodeficiency virus type-1 (HIV-1) elite controllers (ELCs) represent a unique population that control viral replication in the absence of antiretroviral therapy (cART). It is well established that expression of multiple inhibitory receptors on CD8+ T cells is associated with HIV-1 disease progression. However, whether reduced co-expression of inhibitory receptors on CD4+ T cells is linked to natural viral control and slow HIV-1 disease progression remains undefined. Here, we report on the expression pattern of numerous measurable inhibitory receptors, associated with T cell exhaustion (programmed cell death-1, CTLA-4, and TIGIT), on different CD4+ T cell memory populations in ELCs and HIV-infected subjects with or without long-term cART. We found that the co-expression pattern of inhibitory receptors was significantly reduced in ELCs compared with HIV-1 cART-treated and viremic subjects, and similar to healthy controls. Markers associated with T cell exhaustion varied among different memory CD4+ T cell subsets and highest levels were found mainly on transitional memory T cells. CD4+ T cells co-expressing all inhibitory markers were positively correlated to T cell activation (CD38+ HLA-DR+) as well as the transcription factors Helios and FoxP3. Finally, clinical parameters such as CD4 count, HIV-1 viral load, and the CD4/CD8 ratio all showed significant associations with CD4+ T cell exhaustion. We demonstrate that ELCs are able to maintain lower levels of CD4+ T cell exhaustion despite years of ongoing viral replication compared with successfully cART-treated subjects. Our findings suggest that ELCs harbor a “healthy” state of inhibitory receptor expression on CD4+ T cells that might play part in maintenance of their control status.

Impact of CD4 and CD8 dynamics and viral rebounds on loss of virological control in HIV controllers

Objective

HIV controllers (HICs) spontaneously maintain HIV viral replication at low level without antiretroviral therapy (ART), a small number of whom will eventually lose this ability to control HIV viremia. The objective was to identify factors associated with loss of virological control.

Methods

HICs were identified in COHERE on the basis of ≥5 consecutive viral loads (VL) ≤500 copies/mL over ≥1 year whilst ART-naive, with the last VL ≤500 copies/mL measured ≥5 years after HIV diagnosis. Loss of virological control was defined as 2 consecutive VL >2000 copies/mL. Duration of HIV control was described using cumulative incidence method, considering loss of virological control, ART initiation and death during virological control as competing outcomes. Factors associated with loss of virological control were identified using Cox models. CD4 and CD8 dynamics were described using mixed-effect linear models.

Results

We identified 1067 HICs; 86 lost virological control, 293 initiated ART, and 13 died during virological control. Six years after confirmation of HIC status, the probability of losing virological control, initiating ART and dying were 13%, 37%, and 2%. Current lower CD4/CD8 ratio and a history of transient viral rebounds were associated with an increased risk of losing virological control. CD4 declined and CD8 increased before loss of virological control, and before viral rebounds.

Discussion

Expansion of CD8 and decline of CD4 during HIV control may result from repeated low-level viremia. Our findings suggest that in addition to superinfection, other mechanisms, such as low grade viral replication, can lead to loss of virological control in HICs.

A Subset of Extreme Human Immunodeficiency Virus (HIV) Controllers Is Characterized by a Small HIV Blood Reservoir and a Weak T-Cell Activation Level

Background

Human immunodeficiency virus controllers (HICs) form a heterogeneous group of patients with regard to formal definitions, immunologic characteristics, and changes over time in viral load.

Patients and Methods

The HICs with undetectable viral load ([uHICs] ie, for whom a viral load had never been detected with routine assays; n = 52) were compared with 178 HICs with blips during the follow up (bHICs). Clinical characteristics, ultrasensitive HIV-ribonucleic acid (RNA) and HIV-deoxyribonucleic acid (DNA) loads, HIV1-Western blot profiles, and immune parameters were analyzed.

Results

Relative to bHICs, uHICs had significantly lower ultrasensitive plasma HIV-RNA loads (P < .0001) and HIV-DNA levels in peripheral blood mononuclear cells (P = .0004), higher CD4⁺ T-cell count (P = .04) at enrollment, and lower T-cell activation levels. Between diagnosis and inclusion in the cohort, the CD4⁺ T-cell count had not changed in uHICs but had significantly decreased in bHICs. Twenty-one percent of the uHICs lacked specific anti-HIV immunoglobulin G antibodies, and these individuals also had very low levels of HIV-DNA. Half of the uHICs had a protective human leukocyte antigen (HLA) allele (-B57/58/B27), a weak CD8⁺ T-cell response, and very small HIV-DNA reservoir.

Conclusions

We suggest that an interesting HIC phenotype combines protective HLA alleles, low level of HIV blood reservoirs, and reduced immune activation. Prospective studies aimed at evaluating the benefit of combined antiretroviral therapy in HICs might take into account the identification of uHICs and bHICs.

Role of CD8+ T Cells in the Selection of HIV-1 Immune Escape Mutations

Human immunodeficiency virus type-1 (HIV-1) infection represents one of the biggest public health problems worldwide. The immune response, mainly the effector mechanisms mediated by CD8⁺ T cells, induces the selection of mutations that allows the virus to escape the immune control. These mutations are generally selected within CD8⁺ T cell epitopes restricted to human leukocyte antigen class I (HLA-I), leading to a decrease in the presentation and recognition of the epitope, decreasing the activation of CD8⁺ T cells. However, these mutations may also affect cellular processing of the peptide or recognition by the T cell receptor. Escape mutations often carry a negative impact in viral fitness that is partially or totally compensated by the selection of compensatory mutations. The selection of either escape mutations or compensatory mutations may negatively affect the course of the infection. In addition, these mutations are a major barrier for the development of new therapeutic strategies focused on the induction of specific CD8⁺ T cell responses.

Preservation of Lymphopoietic Potential and Virus Suppressive Capacity by CD8+ T Cells in HIV-2-Infected Controllers

Compared with HIV-1, HIV-2 infection is characterized by a larger proportion of slow or nonprogressors. A better understanding of HIV-2 pathogenesis should open new therapeutic avenues to establish control of HIV-1 replication in infected patients. In this study, we studied the production of CD8(+) T cells and their capacity for viral control in HIV-2 controllers from the French ANRS CO5 HIV-2 cohort. HIV-2 controllers display a robust capacity to support long-term renewal of the CD8(+) T cell compartment by preserving immune resources, including hematopoietic progenitors and thymic activity, which could contribute to the long-term maintenance of the CD8(+) T cell response and the avoidance of premature immune aging. Our data support the presence of HIV-2 Gag-specific CD8(+) T cells that display an early memory differentiation phenotype and robust effector potential in HIV-2 controllers. Accordingly, to our knowledge, we show for the first time that HIV-2 controllers possess CD8(+) T cells that show an unusually strong capacity to suppress HIV-2 infection in autologous CD4(+) T cells ex vivo, an ability that likely depends on the preservation of host immune resources. This effective and durable antiviral response probably participates in a virtuous circle, during which controlled viral replication permits the preservation of potent immune functions, thus preventing HIV-2 disease progression.

Effects of neutralizing antibodies on escape from CD8+ T-cell responses in HIV-1 infection

Despite substantial advances in our knowledge of immune responses against HIV-1 and of its evolution within the host, it remains unclear why control of the virus eventually breaks down. Here, we present a new theoretical framework for the infection dynamics of HIV-1 that combines antibody and CD8⁺ T-cell responses, notably taking into account their different lifespans. Several apparent paradoxes in HIV pathogenesis and genetics of host susceptibility can be reconciled within this framework by assigning a crucial role to antibody responses in the control of viraemia. We argue that, although escape from or progressive loss of quality of CD8⁺ T-cell responses can accelerate disease progression, the underlying cause of the breakdown of virus control is the loss of antibody induction due to depletion of CD4⁺ T cells. Furthermore, strong antibody responses can prevent CD8⁺ T-cell escape from occurring for an extended period, even in the presence of highly efficacious CD8⁺ T-cell responses.

Type I interferons in viral control and immune regulation

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IFN-I signaling has recently been shown to contribute to viral immune pathologies.

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Elevated IFN-I signatures are found in persistent virus infections in multiple species.

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Blocking IFN-I signaling reduces immune system activation, regulatory molecule expression.

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Inhibiting IFN-I signaling promotes hastened control of persistent LCMV infection.

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Targeting IFN-I signaling during viral infection may treat a range of viral diseases.

Type 1 interferons (IFN-I) exert pleiotropic biological effects during viral infections, all which contribute to balancing virus control and immune pathology. Despite extensive antiviral functions that subdue virus replication, recent studies demonstrate pathogenic and pro-viral roles for IFN-I signaling during acute and persistent virus infection. IFN-I signaling can promote morbidity and mortality through induction of aberrant inflammatory responses during acute viral infection. In contrast, IFN-I signaling during persistent viral infection supports immune suppression, lymphoid tissue disorganization and CD4 T cell dysfunction. Systematic characterization of the cellular populations and intricacies of IFN-I signaling that promote pathology or immune suppression during acute and persistent viral infections, respectively, should inform the development of treatments and modalities to control viral associated pathologies.

Pleiotropic Roles of Type 1 Interferons in Antiviral Immune Responses

Since Isaac's and Lindenmann's seminal experiments over 50 years ago demonstrating a soluble factor generated from heat killed virus-stimulated chicken embryos could inhibit live influenza virus replication, the term interferon has been synonymous with inhibition of virus replication. While the antiviral properties of type 1 interferon (IFN-I) are undeniable, recent studies have reported expanding and somewhat unexpected roles of IFN-I signaling during both acute and persistent viral infections. IFN-I signaling can promote morbidity and mortality through induction of aberrant inflammatory responses and recruitment of inflammatory innate immune cell populations during acute respiratory viral infections. During persistent viral infection, IFN-I signaling promotes containment of early viral replication/dissemination, however, also initiates and maintains immune suppression, lymphoid tissue disorganization, and CD4 T cell dysfunction through modulation of multiple immune cell populations. Finally, new data are emerging illuminating how specific IFN-I species regulate immune pathology and suppression during acute and persistent viral infections, respectively. Systematic characterization of the cellular populations that produce IFN-I, how the timing of IFN-I induction and intricacies of subtype specific IFN-I signaling promote pathology or immune suppression during acute and persistent viral infections should inform the development of treatments and modalities to control viral associated pathologies.

Immunologic and Virologic Progression in HIV Controllers: The Role of Viral "Blips" and Immune Activation in the ANRS CO21 CODEX Study

Some HIV controllers (HICs) experience CD4+T cell count loss and/or lose their ability to control HIV. In this study, we investigated the rate of immunologic and/or virologic progression (ImmP/VirP) and its determinants in the ANRS CO21/CODEX cohort. Immunologic progression was defined as a lasting fall in CD4+T cell count below 350/mm(3) or more than 200/mm(3) with a baseline count below 600/mm(3). Virologic progression was defined as a HIV viral load (VL) above 2000 copies/mL on two consecutive determinations. Clinical characteristics, immune activation, ultrasensitive HIV VL and total HIV DNA were analyzed. Disease progression was observed in 15 of the 217 patients followed up between 2009 and 2013 (ImmP, n = 10; VirP, n = 5). Progressors had higher ultrasensitive HIV RNA levels at inclusion (i.e. 1-2 years before progression) than non-progressors. ImmP had also lower CD4+T cell nadir and CD4+T cell count at inclusion, and VirP had higher HIV DNA levels in blood. T cell activation and IP10 levels at inclusion were significantly higher in ImmP than in non-progressors. In summary, the lasting loss of CD4+T cells, residual HIV replication and basal levels of immune activation appear to be major determinants of progression in HICs. These factors should be considered for adjusting their follow-up.

Prolonged Antiretroviral Therapy Preserves HIV-1-Specific CD8 T Cells with Stem Cell-Like Properties

HIV-1-specific CD8 T cells can influence HIV-1 disease progression during untreated HIV-1 infection, but the functional and phenotypic properties of HIV-1-specific CD8 T cells in individuals treated with suppressive antiretroviral therapy remain less well understood. Here we show that a subgroup of HIV-1-specific CD8 T cells with stem cell-like properties, termed T memory stem cells (TSCM cells), is enriched in patients receiving suppressive antiretroviral therapy compared with their levels in untreated progressors or controllers. In addition, a prolonged duration of antiretroviral therapy was associated with a progressive increase in the relative proportions of these stem cell-like HIV-1-specific CD8 T cells. Interestingly, the proportions of HIV-1-specific CD8 TSCM cells and total HIV-1-specific CD8 TSCM cells were associated with the CD4 T cell counts during treatment with antiretroviral therapy but not with CD4 T cell counts, viral loads, or immune activation parameters in untreated patients, including controllers. HIV-1-specific CD8 TSCM cells had increased abilities to secrete interleukin-2 in response to viral antigen, while secretion of gamma interferon (IFN-γ) was more limited in comparison to alternative HIV-1-specific CD8 T cell subsets; however, only proportions of IFN-γ-secreting HIV-1-specific CD8 TSCM cells were associated with CD4 T cell counts during antiretroviral therapy. Together, these data suggest that HIV-1-specific CD8 TSCM cells represent a long-lasting component of the cellular immune response to HIV-1 that persists in an antigen-independent fashion during antiretroviral therapy but seems unable to survive and expand under conditions of ongoing viral replication during untreated infection.

IMPORTANCE

Memory CD8 T cells that imitate the functional properties of stem cells to maintain lifelong cellular immunity have been hypothesized for many years, but only recently have such cells, termed T memory stem cells (TSCM cells), been physically identified and isolated in humans, mice, and nonhuman primates. Here, we investigated whether cellular immune responses against HIV-1 include such T memory stem cells. Our data show that HIV-1-specific CD8 T memory stem cells are detectable during all stages of HIV-1 infection but occur most visibly at times of prolonged viral antigen suppression by antiretroviral combination therapy. These cells may therefore be particularly relevant for designing antiviral immune defense strategies against the residual reservoir of HIV-1-infected cells that persists despite treatment and leads to viral rebound upon treatment discontinuation.

The diffuse infiltrative lymphocytosis syndrome (DILS). A comprehensive review

The Diffuse Infiltrative Lymphocytosis Syndrome (DILS) is a rare multisystemic syndrome described in HIV-infected patients. It is characterised by CD8(+) T-cell lymphocytosis associated with a CD8(+) T-cell infiltration of multiple organs. DILS is usually seen in uncontrolled or untreated HIV infection but can also manifest itself independently of CD4(+) T-cell counts. The syndrome may present as a Sjögren-like disease that generally associates sicca signs with bilateral parotiditis, lymphadenopathy, and extraglandular organ involvement. The latter may affect the lungs, nervous system, liver, kidneys, and digestive tract. Anomalies of the respiratory system are often identified as lymphocytic interstitial pneumonia. Facial nerve palsy, aseptic meningitis or polyneuropathy are among the more frequent neurological features. Hepatic lymphocytic infiltration, lymphocytic interstitial nephropathy and digestive tract lymphocytic infiltration account for more rarely noted complications. Sicca syndrome, organomegaly and/or organ dysfunction associated with polyclonal CD8(+) T-cell organ-infiltration are greatly suggestive of DILS in people living with HIV. Labial salivary gland biopsy is therefore helpful when the focus score is equal or greater than 1 (or Chisholm Score ≥ 3). Primary Sjögren syndrome, chronic HCV or HTLV1 infection, graft versus host disease, IgG4-related disease, and immune reconstitution inflammatory syndrome are among the differential diagnoses that need to be considered. Treatment consists in highly active anti-retroviral therapy (HAART), which is usually effective in resolving clinical signs and symptoms. Steroids, however, may also be occasionally required when organ infiltration does not respond to HAART. This review should provide an insight into this rare entity complicating the course of HIV infection.

Reduction of death receptor 5 expression and apoptosis of CD4+ T cells from HIV controllers

TNF-related apoptosis ligand (TRAIL) induces apoptosis of HIV-1-exposed CD4 T cells expressing the death receptor 5 (DR5) in vitro and has been associated with reduced CD4 T cell number in viremic HIV-1-infected patients. Alterations of the TRAIL/DR5 apoptotic pathway could be involved in the absence of massive CD4 T cell depletion in HIV-1-infected controllers (HIC). We studied here apoptosis of CD4 T cells from HIV-infected progressors and controllers. Reduced apoptosis of CD4 T cells from HIC was observed upon HIV stimulation. This lower apoptosis correlated with a deficiency of DR5 cell surface expression by CD4 T cells upon HIV-1 stimulation. The significant lower apoptosis observed in CD4 T cells after HIV exposure, associated with lower expression of membrane DR5 could explain the better survival of HIV-specific CD4 T cells from HIV controllers. The levels of DR5 cell surface expression on CD4 T cells could represent a new prognostic marker.

A correlate of HIV-1 control consisting of both innate and adaptive immune parameters best predicts viral load by multivariable analysis in HIV-1 infected viremic controllers and chronically-infected non-controllers

HIV-1 infected viremic controllers maintain durable viral suppression below 2000 copies viral RNA/ml without anti-retroviral therapy (ART), and the immunological factor(s) associated with host control in presence of low but detectable viral replication are of considerable interest. Here, we utilized a multivariable analysis to identify which innate and adaptive immune parameters best correlated with viral control utilizing a cohort of viremic controllers (median 704 viral RNA/ml) and non-controllers (median 21,932 viral RNA/ml) that were matched for similar CD4⁺ T cell counts in the absence of ART. We observed that HIV-1 Gag-specific CD8⁺ T cell responses were preferentially targeted over Pol-specific responses in viremic controllers (p = 0.0137), while Pol-specific responses were positively associated with viral load (rho = 0.7753, p = 0.0001, n = 23). Viremic controllers exhibited significantly higher NK and plasmacytoid dendritic cells (pDC) frequency as well as retained expression of the NK CD16 receptor and strong target cell-induced NK cell IFN-gamma production compared to non-controllers (p<0.05). Despite differences in innate and adaptive immune function however, both viremic controllers (p<0.05) and non-controller subjects (p<0.001) exhibited significantly increased CD8⁺ T cell activation and spontaneous NK cell degranulation compared to uninfected donors. Overall, we identified that a combination of innate (pDC frequency) and adaptive (Pol-specific CD8⁺ T cell responses) immune parameters best predicted viral load (R² = 0.5864, p = 0.0021, n = 17) by a multivariable analysis. Together, this data indicates that preferential Gag-specific over Pol-specific CD8⁺ T cell responses along with a retention of functional innate subsets best predict host control over viral replication in HIV-1 infected viremic controllers compared to chronically-infected non-controllers.

Elevated IP10 levels are associated with immune activation and low CD4⁺ T-cell counts in HIV controller patients

BACKGROUND

Although HIV controllers (HICs) achieve long-term control of viremia in the absence of antiretroviral therapy (ART), they display marked immune activation. The levels of inflammatory biomarkers in HICs and the biomarkers' relationships with immunologic and virologic status have yet to be fully characterized.

DESIGN

A cohort study.

METHODS

Plasma levels of seven biomarkers [tumor necrosis factor (TNF)α, interleukin (IL)6, IL10, interferon gamma-induced protein 10 (IP10), monocyte chemoattractant protein-1 (MCP1), soluble CD14 (sCD14), soluble CD163 (sCD163)] were compared in 70 HICs, 33 HIV-1-infected, treatment-naive noncontrollers (viremic patients), 30 ART-treated patients and 40 healthy donors. In HICs, we investigated the interplay between biomarkers, cell activation and the CD4⁺ T-cell count.

RESULTS

HICs had higher levels of IP10, TNFα and sCD14 than healthy donors did (P < 0.01 for each). Also, TNFα and sCD14 levels of the HICs were similar to those measured in viremic and ART-treated patients. However, the levels of IL6 and IL10 were significantly lower in HICs than in viremic or ART-treated patients. In HICs, only IP10 levels differed significantly from those in both healthy donors and viremic patients, and were positively correlated with the expression of CD8⁺ and CD4⁺ T-cell activation markers. The IP10 levels of HICs were still elevated 12 and 24 months after the initial assay. Lastly, IP10 levels at enrollment were negatively correlated with the CD4⁺ T-cell count at enrollment and 12 months later.

CONCLUSION

HICs display a number of inflammatory features associated with persistent T-cell immune activation.

Blunted response to combination antiretroviral therapy in HIV elite controllers: an international HIV controller collaboration

Objective

HIV “elite controllers” (ECs) spontaneously control viral load, but some eventually require combination antiretroviral treatment (cART), due to a loss of viral control or a decline in CD4 T-cell counts. Here we studied the CD4 T-cell count dynamics after cART initiation among 34 ECs followed in U.S. and European cohorts, by comparison with chronically viremic patients (VIRs).

Methods

ECs were defined as patients with at least ≥5 viral load (VL) measurements below 400 copies/mL during at least a 5-year period despite never receiving ART and were selected from the French ANRS CO18 cohort, the U.S. SCOPE cohort, the International HIV Controllers study and the European CASCADE collaboration. VIRs were selected from the ANRS COPANA cohort of recently-diagnosed (<1 year) ART-naïve HIV-1-infected adults. CD4 T-cell count dynamics after cART initiation in both groups were modelled with piecewise mixed linear models.

Results

After cART initiation, CD4 T-cell counts showed a biphasic rise in VIRs with: an initial rapid increase during the first 3 months (+0.63/month), followed by +0.19/month. This first rapid phase was not observed in ECs, in whom the CD4Tc count increased steadily, at a rate similar to that of the second phase observed in VIRs. After cART initiation at a CD4 T-cell count of 300/mm³, the estimated mean CD4 T-cell gain during the first 12 months was 139/mm³ in VIRs and 80/mm³ in ECs (p = 0.048).

Conclusions

cART increases CD4 T-cell counts in elite controllers, albeit less markedly than in other patients.

T-cell therapies for HIV

Antiretroviral therapy has improved the quality of life for HIV(+) individuals but efficacy requires strict adherence and treatment is not curative. Recently, the use of T cells as therapeutic agents has been in the spotlight in the settings of post-transplant opportunistic infections and cancer. Whether T-cell therapy can be harnessed for treating HIV remains to be determined but there are a few studies that seek to answer that question. Infusion of ex vivo-expanded HIV-specific T cells showed limited efficacy but no adverse events. Genetically modified T cells expressing CD4 chimeric antigen receptors have recently been shown to have persistence that outperforms chimeric antigen receptors used for cancers. Although the results have not yet been published for many clinical studies using T cells for HIV, preclinical studies and the clinical data that are available highlight the potential for T-cell therapy to decrease or eliminate HIV patients' dependency on antiretroviral therapy.

Natural history of HIV-control since seroconversion

OBJECTIVES

HIV-controllers spontaneously maintain HIV viremia at an undetectable level. We aimed to describe the delay to control from seroconversion, the duration of control, and risk factors for losing control.

METHODS

HIV-controllers were identified from a pooled dataset of 24 seroconverter cohorts from Europe, Australia, and Canada (CASCADE). HIV-controllers had at least five consecutive viral loads less than 400/500 copies/ml, while antiretroviral therapy naive, for at least 5 years after seroconversion. End of control was defined as two consecutive viral loads above 2000 copies/ml. Duration of control was described using Kaplan-Meier estimates; factors associated with duration of control were identified using a Cox model. CD4⁺ cell count evolution during control was described using a mixed model.

RESULTS

Of 9896 eligible seroconverters, we identified 140 (1.4%) HIV-controllers, the largest database of HIV-controllers followed from seroconversion. For 64 with viral load measured within 24 months from seroconversion, median delay to control was 16.7 (interquartile range: 7.8-37.9) months. Probability of maintaining control 20 years after seroconversion was 0.74 [95% confidence interval (CI): 0.64-0.85]. Occurrence of blips followed by return to undetectability did not increase the risk of loss of control [hazard ratio: 0.81 (95% CI: 0.10-6.70)]. However, CD4⁺ cell loss during control was significantly accelerated in individuals with blips.

CONCLUSION

In most individuals, control occurred rapidly after seroconversion; however, more than 3 years were required to achieve control in 25% of HIV-controllers. Control may be sustained even when CD4⁺ cell levels are below 500 cells/μl, opening important new perspectives to understand the physiopathology underlying control.

Persistent LCMV infection is controlled by blockade of type I interferon signaling

During persistent viral infections, chronic immune activation, negative immune regulator expression, an elevated interferon signature, and lymphoid tissue destruction correlate with disease progression. We demonstrated that blockade of type I interferon (IFN-I) signaling using an IFN-I receptor neutralizing antibody reduced immune system activation, decreased expression of negative immune regulatory molecules, and restored lymphoid architecture in mice persistently infected with lymphocytic choriomeningitis virus. IFN-I blockade before and after establishment of persistent virus infection resulted in enhanced virus clearance and was CD4 T cell-dependent. Hence, we demonstrate a direct causal link between IFN-I signaling, immune activation, negative immune regulator expression, lymphoid tissue disorganization, and virus persistence. Our results suggest that therapies targeting IFN-I may help control persistent virus infections.

Dendritic Cells in HIV-1 and HCV Infection: Can They Help Win the Battle?

Persistent infections with human immunodeficiency virus type 1 (HIV-1) and hepatitis C virus (HCV) are a major cause of morbidity and mortality worldwide. As sentinels of our immune system, dendritic cells (DCs) play a central role in initiating and regulating a potent antiviral immune response. Recent advances in our understanding of the role of DCs during HIV-1 and HCV infection have provided crucial insights into the mechanisms employed by these viruses to impair DC functions in order to evade an effective immune response against them. Modulation of the immunological synapse between DC and T-cell, as well as dysregulation of the crosstalk between DCs and natural killer (NK) cells, are emerging as two crucial mechanisms. This review focuses on understanding the interaction of HIV-1 and HCV with DCs not only to understand the immunopathogenesis of chronic HIV-1 and HCV infection, but also to explore the possibilities of DC-based immunotherapeutic approaches against them. Host genetic makeup is known to play major roles in infection outcome and rate of disease progression, as well as response to anti-viral therapy in both HIV-1 and HCV-infected individuals. Therefore, we highlight the genetic variations that can potentially affect DC functions, especially in the setting of chronic viral infection. Altogether, we address if DCs’ potential as critical effectors of antiviral immune response could indeed be utilized to combat chronic infection with HIV-1 and HCV.

Antibodies attenuate the capacity of dendritic cells to stimulate HIV-specific cytotoxic T lymphocytes

BACKGROUND

Control of HIV is suggested to depend on potent effector functions of the virus-specific CD8(+) T-cell response. Antigen opsonization can modulate the capture of antigen, its presentation, and the priming of specific CD8(+) T-cell responses.

OBJECTIVE

We have previously shown that opsonization of retroviruses acts as an endogenous adjuvant for dendritic cell (DC)-mediated induction of specific cytotoxic T lymphocytes (CTLs). However, in some HIV-positive subjects, high levels of antibodies and low levels of complement fragments coat the HIV surface.

METHODS

Therefore we analyzed the effect of IgG opsonization on the antigen-presenting capacity of DCs by using CD8(+) T-cell proliferation assays after repeated prime boosting, by measuring the antiviral activity against HIV-infected autologous CD4(+) T cells, and by determining IFN-γ secretion from HIV-specific CTL clones.

RESULTS

We find that DCs exposed to IgG-opsonized HIV significantly decreased the HIV-specific CD8(+) T-cell response compared with the earlier described efficient CD8(+) T-cell activation induced by DCs loaded with complement-opsonized HIV. DCs exposed to HIV bearing high surface IgG levels after incubation in plasma from HIV-infected subjects acted as weak stimulators for HIV-specific CTL clones. In contrast, HIV opsonized with plasma from patients exhibiting high complement and low IgG deposition on the viral surface favored significantly higher activation of HIV-specific CD8(+) T-cell clones.

CONCLUSION

Our ex vivo and in vitro observations provide the first evidence that IgG opsonization of HIV is associated with a decreased CTL-stimulatory capacity of DCs.

The split personality of regulatory T cells in HIV infection

Natural regulatory T cells (Tregs) participate in responses to various chronic infections including HIV. HIV infection is associated with a progressive CD4 lymphopenia and defective HIV-specific CD8 responses known to play a key role in the control of viral replication. Persistent immune activation is a hallmark of HIV infection and is involved in disease progression independent of viral load. The consequences of Treg expansion, observed in HIV infection, could be either beneficial, by suppressing generalized T-cell activation, or detrimental, by weakening HIV-specific responses and thus contributing to viral persistence. The resulting balance between Tregs contrasting outcomes might have critical implications in pathogenesis. Topics covered in this review include HIV-induced alterations of Tregs, Treg cell dynamics in blood and tissues, Treg-suppressive function, and the relationship between Tregs and immune activation. This review also provides a focus on the role of CD39(+) Tregs and other regulatory cell subsets. All these issues will be explored in different situations including acute and chronic infection, antiretroviral treatment-mediated viral control, and spontaneous viral control. Results must be interpreted with regard to both the Treg definition used in context and to the setting of the disease in an attempt to draw clearer conclusions from the apparently conflicting results.

Early HLA-B*57-restricted CD8+ T lymphocyte responses predict HIV-1 disease progression

Although HLA-B*57 (B57) is associated with slow progression to disease following HIV-1 infection, B57 heterozygotes display a wide spectrum of outcomes, including rapid progression, viremic slow progression, and elite control. Efforts to identify differences between B57-positive (B57(+)) slow progressors and B57(+) rapid progressors have largely focused on cytotoxic T lymphocyte (CTL) phenotypes and specificities during chronic stages of infection. Although CTL responses in the early months of infection are likely to be the most important for the long-term rate of HIV-1 disease progression, few data on the early CTL responses of eventual slow progressors have been available. Utilizing the Multicenter AIDS Cohort Study (MACS), we retrospectively examined the early HIV-1-specific CTL responses of 14 B57(+) individuals whose time to development of disease ranged from 3.5 years to longer than 25 years after infection. In general, a greater breadth of targeting of epitopes from structural proteins, especially Gag, as well as of highly conserved epitopes from any HIV-1 protein, correlated with longer times until disease. The single elite controller in the cohort was an outlier on several correlations of CTL targeting and time until disease, consistent with reports that elite control is typically not achieved solely by protective HLA-mediated CTLs. When targeting of individual epitopes was analyzed, we found that early CTL responses to the IW9 (ISPRTLNAW) epitope of Gag, while generally subdominant, correlated with delayed progression to disease. This is the first study to identify early CTL responses to IW9 as a correlate of protection in persons with HLA-B*57.

Innate immunity in the control of HIV/AIDS: recent advances and open questions

From the publication of the first AIDS issue onwards, major advances have been made in the field of innate immunity during HIV infection. Innate immunity can be defined as the first and unspecific lines of defense constitutively present and ready to be mobilized upon infection. Although a large body of literature adamantly highlights that innate immunity is a critical weapon of defense against HIV and its simian parents (simian immunodeficiency virus, SIV), innate immunity is still underexplored. Focusing on innate immunity may open new paths for the development of innovative therapeutics and vaccine strategies against HIV. Understanding innate immunity may shed light on the natural protection occurring in rare HIV-1-infected individuals who control their infection. This review focuses on innate mechanisms sensing HIV-1 entry and controlling HIV-1 infection, as well as promoting inflammation and shaping adaptive immunity.

The colocalization potential of HIV-specific CD8+ and CD4+ T-cells is mediated by integrin β7 but not CCR6 and regulated by retinoic acid

CD4⁺ T-cells from gut-associated lymphoid tissues (GALT) are major targets for HIV-1 infection. Recruitment of excess effector CD8⁺ T-cells in the proximity of target cells is critical for the control of viral replication. Here, we investigated the colocalization potential of HIV-specific CD8⁺ and CD4⁺ T-cells into the GALT and explored the role of retinoic acid (RA) in regulating this process in a cohort of HIV-infected subjects with slow disease progression. The expression of the gut-homing molecules integrin β7, CCR6, and CXCR3 was identified as a “signature” for HIV-specific but not CMV-specific CD4⁺ T-cells thus providing a new explanation for their enhanced permissiveness to infection in vivo. HIV-specific CD8⁺ T-cells also expressed high levels of integrin β7 and CXCR3; however CCR6 was detected at superior levels on HIV-specific CD4⁺versus CD8⁺ T-cells. All trans RA (ATRA) upregulated the expression of integrin β7 but not CCR6 on HIV-specific T-cells. Together, these results suggest that HIV-specific CD8⁺ T-cells may colocalize in excess with CD4⁺ T-cells into the GALT via integrin β7 and CXCR3, but not via CCR6. Considering our previous findings that CCR6⁺CD4⁺ T-cells are major cellular targets for HIV-DNA integration in vivo, a limited ability of CD8⁺ T-cells to migrate in the vicinity of CCR6⁺CD4⁺ T-cells may facilitate HIV replication and dissemination at mucosal sites.

Gene array studies in HIV-1 infection

HIV-1-infected individuals exhibit remarkable variation in the onset of disease. Virus replication and disease progression depend on host cellular transcription and gene regulation in virus-specific target cells. Both viral and host factors are implicated in this differential regulation. Gene arrays and transcriptome analyses might shed light on why some infected individuals remain asymptomatic while others progress rapidly to AIDS. Here we review developments in HIV research using gene array technologies and the unifying concepts that have emerged from these studies. Gene set enrichment analysis has revealed gene signatures linked to disease progression involving pathways related to metabolism, apoptosis, cell-cycle dysregulation, and T-cell signaling. Macrophages contain anti-apoptotic signatures. Also, HIV-1 regulates previously under-emphasized cholesterol biosynthesis and energy production pathways. Notably, cellular pathways linked to a subset of HIV-infected individuals known as non-progressors contribute to survival and anti-viral responses.

CD4 T-cell regeneration in HIV-1 elite controllers

BACKGROUND

Elite controllers spontaneously control HIV-1 replication, which in many cases is associated with preservation of normal CD4 T-cell counts. However, a subset of elite controllers has progressive CD4 T-cell losses despite undetectable viral loads, for reasons that remain undefined. Here, we assessed mechanisms of CD4 T-cell homeostasis in elite controllers with progressive vs. nonprogressive HIV-1 disease courses.

METHODS

Flow cytometry assays were used to determine the proliferation, activation and apoptosis levels of naive T cells in elite controllers with high or low CD4 T-cell counts and reference cohorts of HIV-1-negative and HAART-treated persons. Thymic output was measured by single-joint T-cell receptor excision circle (sjTREC)/β T-cell receptor excision circle (βTREC) ratios, and the frequency of circulating recent thymic emigrants was flow cytometrically determined by surface expression of protein tyrosine kinase 7.

RESULTS

Proportions of naive T cells in elite controllers were severely reduced and closely resemble those of HIV-1 patients with progressive disease. Despite reductions in naive T cells, most elite controllers were able to maintain normal total CD4 T-cell counts by preservation of uncompromised thymic function in conjunction with extrathymic processes that led to elevated levels of circulating recent thymic emigrants. In contrast, elite controllers with low CD4 T-cell counts had reduced thymic output that mirrored thymic dysfunction during untreated progressive HIV-1 infection.

CONCLUSION

These results indicate that both thymic and extrathymic mechanisms contribute to CD4 T-cell maintenance in elite controllers and support the idea that CD4 T-cell homeostasis and control of viral replication are distinct but frequently coinciding processes.

Delayed-type hypersensitivity responses to HIV Gag p24 relate to clinical outcome after peptide-based therapeutic immunization for chronic HIV infection

Therapeutic immunization in chronic HIV infection aims to induce durable, HIV-specific immune responses capable of controlling disease progression, but immunological correlates of clinical efficacy are poorly defined. We have previously immunized 38 patients with a mixture of four short Gag p24-like conserved peptides (Vacc-4x) targeting skin dendritic cells. Antiretroviral treatment (ART) was initially stopped after completed immunizations and resumed post-protocol during regular clinical follow-up according to current guidelines. Four years after enrolment, Vacc-4x-specific cellular responses were evaluated in vivo by delayed-type hypersensitivity (DTH) skin test, and in vitro by a T-cell proliferation assay. Kaplan-Meier product-limit estimates were used to analyse time until ART was resumed. Peptide-specific cellular immune responses induced by Vacc-4x had persisted 4 years after the last immunization in terms of unchanged DTH independent of ART and detectable proliferative T-cell responses which correlated to the native peptides (R = 0.73, p = 0.01). Circulating bifunctional (IFN-γ and IL-10) Vacc-4x-specific T-cell clones were detected in 43% of patients. Subjects with the strongest post-immunization DTH responses appeared to start ART later compared with DTH low responders (p = 0.07). These data suggest that DTH responses should be further evaluated as a new and convenient tool for predicting clinical efficacy in trials testing therapeutic immunizations.

Virus-host interactions in HIV pathogenesis: directions for therapy

The challenge of controlling HIV infection involves an understanding of the heterogeneity of the virus, its wide cellular host range, its primary routes of transmission, and the immunologic and intrinsic cellular factors that can prevent its transmission and replication. Identification of HIV-infected individuals who have survived more than 10 years without signs of the infection and without therapy encourages studies examining the natural mechanisms for resistance to infection and disease. Within the immune system, emphasis should be given to the innate or natural response that appears within minutes of the infection and offers the optimal time for controlling HIV. All these parameters in HIV pathogenesis underline the information needed to develop optimal anti-HIV therapies and an effective AIDS vaccine.

Coming of age: reconstruction of heterosexual HIV-1 transmission in human ex vivo organ culture systems

Heterosexual transmission of human immunodeficiency virus-1 (HIV-1), from men to women, involves exposure to infectious HIV-1 in semen. Therefore, the cellular and molecular processes that underlie HIV-1 transmission are closely interconnected with fundamental principles of human reproductive biology. Human ex vivo organ culture systems allow experimental reconstruction of HIV-1 transmission, using human semen and premenopausal cervicovaginal mucosal tissue, with specific emphasis on the progression from exposure to development of primary HIV-1 infection. Clearly, an isolated piece of human tissue cannot duplicate the full complexity of events in natural infections, but with correct observation of conventional medical and ethical standards, there is no opportunity to study HIV-1 exposure and primary infection in young women. Human mucosal organ cultures allow direct study of HIV-1 infection in a reproducible format while retaining major elements of complexity and variability that typify community-based HIV-1 transmission. Experimental manipulation of human mucosal tissue both allows and requires acquisition of new insights into basic processes of human mucosal immunology. Expanding from the current foundations, we believe that human organ cultures will become increasingly prominent in experimental studies of HIV-1 transmission and continuing efforts to prevent HIV-1 infection at human mucosal surfaces.

Restriction of HIV-1 replication in macrophages and CD4+ T cells from HIV controllers

How HIV controllers (HICs) maintain undetectable viremia without therapy is unknown. The strong CD8(+) T-cell HIV suppressive capacity found in many, but not all, HICs may contribute to long-lasting viral control. However, other earlier defense mechanisms may be involved. Here, we examined intrinsic HIC cell resistance to HIV-1 infection. After in vitro challenge, monocyte-derived macrophages and anti-CD3-activated CD4(+) T cells from HICs showed low HIV-1 susceptibility. CD4 T-cell resistance was independent of HIV-1 coreceptors and affected also SIVmac infection. CD4(+) T cells from HICs expressed ex vivo higher levels of p21(Waf1/Cip1), which has been involved in the control of HIV-1 replication, than cells from control subjects. However, HIV restriction in anti-CD3-activated CD4(+) T cells and macrophages was not associated with p21 expression. Restriction inhibited accumulation of reverse transcripts, leading to reduction of HIV-1 integrated proviruses. The block could be overcome by high viral inocula, suggesting the action of a saturable mechanism. Importantly, cell-associated HIV-1 DNA load was extremely low in HICs and correlated with CD4(+) T-cell permissiveness to infection. These results point to a contribution of intrinsic cell resistance to the control of infection and the containment of viral reservoir in HICs.

CD4 dynamics over a 15 year-period among HIV controllers enrolled in the ANRS French observatory

Background

There are few large published studies of HIV controllers with long-term undetectable viral load (VL). We describe the characteristics and outcomes of 81 French HIV controllers.

Methods and Results

HIV controllers were defined as asymptomatic, antiretroviral-naïve persons infected ≥10 years previously, with HIV-RNA <400 copies/mL in >90% of plasma samples. All available CD4 and VL values were collected at enrolment. Mixed-effect linear models were used to analyze CD4 cell count slopes since diagnosis. HIV controllers represented 0.31% of all patients managed in French hospitals. Patients infected through intravenous drug use were overrepresented (31%) and homosexual men were underrepresented (26% of men) relative to the ANRS SEROCO cohort of subjects diagnosed during the same period. HIV controllers whose VL values were always below the detection limit of the assays were compared with those who had rare “blips” (<50% of VL values above the detection limit) or frequent blips (>50% of VL values above the detection limit). Estimated CD4 cell counts at HIV diagnosis were similar in the three groups. CD4 cell counts remained stable after HIV diagnosis in the “no blip” group, while they fell significantly in the two other groups (−0.26√CD4 and −0.28√CD4/mm³/year in the rare and frequent blip groups, respectively). No clinical, immunological or virological progression was observed in the no blip group, while 3 immunological and/or virological events and 4 cancers were observed in the blip subgroups.

Conclusions

Viral blips in HIV controllers are associated with a significant decline in CD4 T cells and may be associated with an increased risk of pathological events, possibly owing to chronic inflammation/immune activation.

CD4+ T cells from elite controllers resist HIV-1 infection by selective upregulation of p21

Elite controllers represent a unique group of HIV-1-infected persons with undetectable HIV-1 replication in the absence of antiretroviral therapy. However, the mechanisms contributing to effective viral immune defense in these patients remain unclear. Here, we show that compared with HIV-1 progressors and HIV-1-negative persons, CD4+ T cells from elite controllers are less susceptible to HIV-1 infection. This partial resistance to HIV-1 infection involved less effective reverse transcription and mRNA transcription from proviral DNA and was associated with strong and selective upregulation of the cyclin-dependent kinase inhibitor p21 (also known as cip-1 and waf-1). Experimental blockade of p21 in CD4+ T cells from elite controllers resulted in a marked increase of viral reverse transcripts and mRNA production and led to higher enzymatic activities of cyclin-dependent kinase 9 (CDK9), which serves as a transcriptional coactivator of HIV-1 gene expression. This suggests that p21 acts as a barrier against HIV-1 infection in CD4+ T cells from elite controllers by inhibiting a cyclin-dependent kinase required for effective HIV-1 replication. These data demonstrate a mechanism of host resistance to HIV-1 in elite controllers and may open novel perspectives for clinical strategies to prevent or treat HIV-1 infection.

Simian immunodeficiency virus-induced changes in T cell cytokine responses in cynomolgus macaques with latent Mycobacterium tuberculosis infection are associated with timing of reactivation

Understanding the early immunologic events accompanying reactivated tuberculosis (TB) in HIV-infected individuals may yield insight into causes of reactivation and improve treatment modalities. We used the cynomolgus macaque (Macaca fascicularis) model of HIV-Mycobacterium tuberculosis coinfection to investigate the dynamics of multifunctional T cell responses and granuloma T cell phenotypes in reactivated TB. CD4(+) and CD8(+) T cells expressing Th1 cytokines (IFN-γ, IL-2, TNF) and Th2 cytokines (IL-4 and IL-10) were followed from latent M. tuberculosis infection to reactivation after coinfection with a pathogenic SIV. Coinfected animals experienced increased Th1 cytokine responses to M. tuberculosis Ags above the latent-response baseline 3-5 wk post-SIV infection that corresponded with peak plasma viremia. Th2 cytokine expression was not Ag specific, but strong, transient IL-4 expression was noted 4-7 wk post-SIV infection. Animals reactivating <17 wk post-SIV infection had significantly more multifunctional CD4(+) T cells 3-5 wk post-SIV infection and more Th2-polarized and fewer Th0-, Th1-polarized CD8(+) T cells during weeks 1-10 post-SIV infection than animals reactivating >26 wk post-SIV infection. Granuloma T cells included Th0-, Th1-, and Th2-polarized phenotypes but were particularly rich in cytolytic (CD107(+)) T cells. When combined with the changes in peripheral blood T cells, these factors indicate that events during acute HIV infection are likely to include distortions in proinflammatory and anti-inflammatory T cell responses within the granuloma that have significant effects on reactivation of latent TB. Moreover, it appears that mycobacteria-specific multifunctional T cells are better correlates of Ag load (i.e., disease status) than of protection.

Transcriptional profiling of CD4 T cells identifies distinct subgroups of HIV-1 elite controllers

Human immunodeficiency virus type 1 (HIV-1) elite controllers maintain undetectable levels of viral replication in the absence of antiretroviral therapy (ART), but their underlying immunological and virological characteristics may vary. Here, we used a whole-genome transcriptional profiling approach to characterize gene expression signatures of CD4 T cells from an unselected cohort of elite controllers. The transcriptional profiles for the majority of elite controllers were similar to those of ART-treated patients but different from those of HIV-1-negative persons. Yet, a smaller proportion of elite controllers showed an alternative gene expression pattern that was indistinguishable from that of HIV-1-negative persons but different from that of highly active antiretroviral therapy (HAART)-treated individuals. Elite controllers with the latter gene expression signature had significantly higher CD4 T cell counts and lower levels of HIV-1-specific CD8(+) T cell responses but did not significantly differ from other elite controllers in terms of HLA class I alleles, HIV-1 viral loads determined by ultrasensitive single-copy PCR assays, or chemokine receptor polymorphisms. Thus, these data identify a specific subgroup of elite controllers whose immunological and gene expression characteristics approximate those of HIV-1-negative persons.