Monitoring cellular immune markers in HIV infection: from activation to exhaustion

The role of IFN-γ production during retroviral infections: an important cytokine involved in chronic inflammation and pathogenesis

Interferon-gamma (IFN-γ) plays a crucial role in viral infections by preventing viral replication and in the promotion of innate and adaptive immune responses. However, IFN-gamma can exert distinct effects in different persistent viral infections. The long-term overproduction of IFN-γ in retroviral infections, such as the human immunodeficiency virus (HIV), human T-lymphotropic virus type 1 (HTLV-1), and human endogenous retroviruses (HERVs), resulting in inflammation, may cause neuronal damage. This review is provocative about the role of IFN-γ during persistent retroviral infections and its relationship with the causation of some neurological disorders that are important for public health.

Differential upregulations of SMAC and LAMIN B levels in the buffy coat of HIV associated preeclamptic women

OBJECTIVE

To assess HIV positivity as an apoptotic confounding variable in pregnancies complicated by preeclampsia.

METHODS AND MATERIALS

Using a Bio-plex Multiplex Immunoassay, Smac and Lamin B concentrations (ng/ml) were analyzed in a buffy coat collected from 128 pregnant women attending a large regional hospital in Durban, South Africa. Study groups consisted of Normotensive and Preeclamptic pregnant women stratified according to their HIV status. All HIV positive groups received highly active antiretroviral therapy (HAART).

RESULTS

Our findings showed significant (p < .05) upregulation in the levels of both SMAC and LAMIN B in the HIV positive patients and a concomitant downregulation of the same apoptotic makers were observed in preeclampsia regardless of HIV status.

CONCLUSIONS

These results could be associated with the fact that apoptosis promotes deregulation of mitochondrial dynamics, contributing to the associated severe obstetric events observed in pregnancies among HIV-infected women on HAART.

Heightened resistance to host type 1 interferons characterizes HIV-1 at transmission and after antiretroviral therapy interruption

Type 1 interferons (IFN-I) are potent innate antiviral effectors that constrain HIV-1 transmission. However, harnessing these cytokines for HIV-1 cure strategies has been hampered by an incomplete understanding of their antiviral activities at later stages of infection. Here, we characterized the IFN-I sensitivity of 500 clonally derived HIV-1 isolates from the plasma and CD4+ T cells of 26 individuals sampled longitudinally after transmission or after antiretroviral therapy (ART) and analytical treatment interruption. We determined the concentration of IFNα2 and IFNβ that reduced viral replication in vitro by 50% (IC50) and found consistent changes in the sensitivity of HIV-1 to IFN-I inhibition both across individuals and over time. Resistance of HIV-1 isolates to IFN-I was uniformly high during acute infection, decreased in all individuals in the first year after infection, was reacquired concomitant with CD4+ T cell loss, and remained elevated in individuals with accelerated disease. HIV-1 isolates obtained by viral outgrowth during suppressive ART were relatively IFN-I sensitive, resembling viruses circulating just before ART initiation. However, viruses that rebounded after treatment interruption displayed the highest degree of IFNα2 and IFNβ resistance observed at any time during the infection course. These findings indicate a dynamic interplay between host innate responses and the evolving HIV-1 quasispecies, with the relative contribution of IFN-I to HIV-1 control affected by both ART and analytical treatment interruption. Although elevated at transmission, host innate pressures are the highest during viral rebound, limiting the viruses that successfully become reactivated from latency to those that are IFN-I resistant.

Innate immune mechanisms to oral pathogens in oral mucosa of HIV-infected individuals

A crucial aspect of mucosal HIV transmission is the interaction between HIV, the local environmental milieu and immune cells. The oral mucosa comprises many host cell types including epithelial cells, CD4 + T cells, dendritic cells and monocytes/macrophages, as well as a diverse microbiome predominantly comprising bacterial species. While the oral epithelium is one of the first sites exposed to HIV through oral-genital contact and nursing infants, it is largely thought to be resistant to HIV transmission via mechanisms that are still unclear. HIV-1 infection is also associated with predisposition to secondary infections, such as tuberculosis, and other diseases including cancer. This review addresses the following questions that were discussed at the 8th World Workshop on Oral Health and Disease in AIDS held in Bali, Indonesia, 13 September –15 September 2019: (a) How does HIV infection affect epithelial cell signalling? (b) How does HIV infection affect the production of cytokines and other innate antimicrobial factors, (c) How is the mucosal distribution and function of immune cells altered in HIV infection? (d) How do T cells affect HIV (oral) pathogenesis and cancer? (e) How does HIV infection lead to susceptibility to TB infections?

Initiation of Antiretroviral Therapy Differentially Influences Genital and Systemic Immune Activation in HIV-Infected Women

Antiretroviral therapy (ART) has significantly improved the quality of life of HIV-infected individuals: reducing plasma viremia, restoring CD4⁺ T cell numbers, and correcting imbalances in blood memory T cell subsets. While ART improves immune correlates at mucosal sites, including the lower female genital tract (FGT), ART initiation has been associated with reactivation of common FGT infections. We investigated the effect of ART on immune activation and inflammation in the genital tract. We measured blood and genital T cell activation, proliferation, and immunosenescence (CD38, HLADR, Ki67, CD127, and CD57), and cytokine levels in women on ART for ∼7 years (cross-sectional analysis) or initiating ART (immediately before and 1 month after). Effector memory T cells predominated in blood and FGT during chronic infection, irrespective of ART status. In women initiating ART, 1 month was insufficient for T cell reconstitution, or alterations in T cell subset distribution, despite both plasma and genital viral loads decreasing to undetectable levels in most participants. Initiating ART was accompanied by a decline in plasma IP-10 that correlated with decreased blood CD38 expression in blood (p = .0204) but not in the FGT. The reduction in plasma (but not genital) cytokine levels due to ART initiation was dependent on their concentrations before treatment. While T cell activation decreased significantly in blood (CD4: p = .032; CD8: p = .0137), activation levels remained similar in the genital tract despite 1 month of treatment. Overall, the decrease in cellular activation and inflammation seen in blood with ART initiation was not evident in the FGT.

Serum Tryptophan-Derived Quinolinate and Indole-3-Acetate Are Associated With Carotid Intima-Media Thickness and its Evolution in HIV-Infected Treated Adults

Background

HIV-infected individuals undergoing effective antiretroviral therapy (ART) present an increased risk of atherosclerotic cardiovascular disease. We identified serum metabolites associated with carotid intima-media thickness (c-IMT) and its evolution.

Methods

One hundred forty-three hydrophilic serum metabolites were measured by ultraperformance liquid chromatography coupled with high-resolution mass spectrometry in 49 HIV+ ART+, 48 HIV+ ART-naïve and 50 HIV-negative, age-matched, never-smoking male triads. Metabolites differentially altered between groups ("features") were defined as having a Benjamini-Hochberg-adjusted P value <.05 from a t test and >0.25 log₂ absolute mean fold change in metabolite levels. c-IMT was measured across 12 sites at inclusion in all individuals and at the carotid artery (cca) after a median of 5.1 years in 32 HIV+ ART+ individuals. The difference in c-IMT (cross-sectional analysis) and slope of cca-IMT regression/progression per year (longitudinal analysis) for each log₁₀ (area) increase in metabolite level were estimated with linear regression.

Results

Compared with HIV-, metabolite features of HIV+ ART+ were increased N6,N6,N6-trimethyl-L-lysine and decreased ferulate and 5-hydroxy-L-tryptophan, whereas features of HIV+ ART-naïve were increased malate, kynurenine, 2-oxoglutarate, and indole-3-acetate and decreased succinate and 5-hydroxy-L-tryptophan. In HIV+ ART+ individuals, quinolinate and/or indole-3-acetate were positively associated with c-IMT (P < .03), cca-IMT (P < .03), and cca-IMT progression (P < .008). These associations were not observed in HIV+ ART-naïve or HIV-negative individuals. In HIV+ ART+ individuals, the metabolites xanthosine and uridine, from nucleotide metabolism, and g-butyrobetaine, from lysine/dietary choline degradation, were also positively or negatively associated with c-IMT and/or cca-IMT (all P < .01), but not its evolution.

Conclusions

In these highly selected HIV-positive ART-controlled males, 2 novel metabolites derived from tryptophan catabolism, indole-3-acetate and quinolinate, were associated with c-IMT and its progression.

Analysis of the dysregulation between regulatory B and T cells (Breg and Treg) in human immunodeficiency virus (HIV)-infected patients

This study examines the relationship between regulatory B (Breg) and T (Treg) compartments, which play crucial roles in the maintenance of immune homeostasis in the context of HIV. Using flow cytometry, the phenotypes of different Breg and Treg subsets from HIV-infected and healthy individuals were analyzed, along with the suppressive capacity of Breg. Peripheral blood samples of thirteen HIV+ treatment-naïve individuals, fourteen treated-HIV+ individuals with undetectable viral load and twelve healthy individuals were analyzed. The absolute counts of Breg and Treg subsets were decreased in HIV+ treatment-naïve individuals in comparison to treated-HIV+ and healthy individuals. Interestingly, correlations between Breg subsets (CD24hiCD27+ and PD-L1+ B cells) and IL-10-producing Breg observed in healthy individuals were lost in HIV+ treatment-naïve individuals. However, a correlation between frequencies of CD24hiCD38hi or TIM-1+-Breg subsets and Treg was observed in HIV+ treatment-naïve individuals and not in healthy individuals. Therefore, we hypothesized that various Breg subsets might have different functions during B and T-cell homeostasis during HIV-1 infection. In parallel, stimulated Breg from HIV-infected treatment-naïve individuals presented a decreased ability to suppress CD4+ T-cell proliferation in comparison to the stimulated Breg from treated-HIV+ or healthy individuals. We demonstrate a dysregulation between Breg and Treg subsets in HIV-infected individuals, which might participate in the hyper-activation and exhaustion of the immune system that occurs in such patients.

Type I IFN signaling blockade by a PASylated antagonist during chronic SIV infection suppresses specific inflammatory pathways but does not alter T cell activation or virus replication

Chronic activation of the immune system in HIV infection is one of the strongest predictors of morbidity and mortality. As such, approaches that reduce immune activation have received considerable interest. Previously, we demonstrated that administration of a type I interferon receptor antagonist (IFN-1ant) during acute SIV infection of rhesus macaques results in increased virus replication and accelerated disease progression. Here, we administered a long half-life PASylated IFN-1ant to ART-treated and ART-naïve macaques during chronic SIV infection and measured expression of interferon stimulated genes (ISG) by RNA sequencing, plasma viremia, plasma cytokines, T cell activation and exhaustion as well as cell-associated virus in CD4 T cell subsets sorted from peripheral blood and lymph nodes. Our study shows that IFN-1ant administration in both ART-suppressed and ART-untreated chronically SIV-infected animals successfully results in reduction of IFN-I-mediated inflammation as defined by reduced expression of ISGs but had no effect on plasma levels of IL-1β, IL-1ra, IL-6 and IL-8. Unlike in acute SIV infection, we observed no significant increase in plasma viremia up to 25 weeks after IFN-1ant administration or up to 15 weeks after ART interruption. Likewise, cell-associated virus measured by SIV gag DNA copies was similar between IFN-1ant and placebo groups. In addition, evaluation of T cell activation and exhaustion by surface expression of CD38, HLA-DR, Ki67, LAG-3, PD-1 and TIGIT, as well as transcriptome analysis showed no effect of IFN-I blockade. Thus, our data show that blocking IFN-I signaling during chronic SIV infection suppresses IFN-I-related inflammatory pathways without increasing virus replication, and thus may constitute a safe therapeutic intervention in chronic HIV infection.

Differentiation and Function of Follicular CD8 T Cells During Human Immunodeficiency Virus Infection

The combination antiretroviral therapeutic (cART) regime effectively suppresses human immunodeficiency virus (HIV) replication and prevents progression to acquired immunodeficiency diseases. However, cART is not a cure, and viral rebound will occur immediately after treatment is interrupted largely due to the long-term presence of an HIV reservoir that is composed of latently infected target cells that maintain a quiescent state or persistently produce infectious viruses. CD4 T cells that reside in B-cell follicles within lymphoid tissues, called follicular helper T cells (TFH), have been identified as a major HIV reservoir. Due to their specialized anatomical structure, HIV-specific CD8 T cells are largely insulated from this TFH reservoir. It is increasingly clear that the elimination of TFH reservoirs is a key step toward a functional cure for HIV infection. Recently, several studies have suggested that a fraction of HIV-specific CD8 T cells can differentiate into a CXCR5-expressing subset, which are able to migrate into B-cell follicles and inhibit viral replication. In this review, we discuss the differentiation and functions of this newly identified CD8 T-cell subset and propose potential strategies for purging TFH HIV reservoirs by utilizing this unique population.

Anionic Carbosilane Dendrimers Destabilize the GP120-CD4 Complex Blocking HIV-1 Entry and Cell to Cell Fusion

Cell-to-cell transmission is the most effective pathway for the spread of human immunodeficiency virus (HIV-1). Infected cells expose virus-encoded fusion proteins on their surface as a consequence of HIV-1 replicative cycle that interacts with noninfected cells through CD4 receptor and CXCR4 coreceptor leading to the formation of giant multinucleated cells known as syncytia. Our group previously described the potent activity of dendrimers against CCR5-tropic viruses. Nevertheless, the study of G1-S4, G2-S16, and G3-S16 dendrimers in the context of X4-HIV-1 tropic cell-cell fusion referred to syncytium formation remains still unknown. These dendrimers showed a suitable biocompatibility in all cell lines studied and our results demonstrated that anionic carbosilane dendrimers G1-S4, G2-S16, and G3-S16 significantly inhibit the X4-HIV-1 infection, as well as syncytia formation, in a dose dependent manner. We also demonstrated that G2-S16 and G1-S4 significantly reduced syncytia formation in HIV-1 Env-mediated cell-to-cell fusion model. Molecular modeling and in silico models showed that G2-S16 dendrimer interfered with gp120-CD4 complex and demonstrated its potential use for a treatment.

HIV as a Cause of Immune Activation and Immunosenescence

Systemic immune activation has emerged as an essential component of the immunopathogenesis of HIV. It not only leads to faster disease progression, but also to accelerated decline of overall immune competence. HIV-associated immune activation is characterized by an increase in proinflammatory mediators, dysfunctional T regulatory cells, and a pattern of T-cell-senescent phenotypes similar to those seen in the elderly. These changes predispose HIV-infected persons to comorbid conditions that have been linked to immunosenescence and inflamm-ageing, such as atherosclerosis and cardiovascular disease, neurodegeneration, and cancer. In the antiretroviral treatment era, development of such non-AIDS-defining, age-related comorbidities is a major cause of morbidity and mortality. Treatment strategies aimed at curtailing persistent immune activation and inflammation may help prevent the development of these conditions. At present, the most effective strategy appears to be early antiretroviral treatment initiation. No other treatment interventions have been found effective in large-scale clinical trials, and no adjunctive treatment is currently recommended in international HIV treatment guidelines. This article reviews the role of systemic immune activation in the immunopathogenesis of HIV infection, its causes and the clinical implications linked to immunosenescence in adults, and the therapeutic interventions that have been investigated.

Humanized mouse models of latent HIV infection

Antiretroviral therapy can efficiently control HIV viral replication, resulting in low viral loads and sustained CD4⁺ T cell counts in HIV-infected persons. However, fast viral rebound occurs in most infected persons when therapy is interrupted. The principal component of persistent infection is a latent but replication-competent HIV reservoir. The long half-life of this reservoir is a major barrier to cure, and its elimination is the target of important research efforts. Animal models that can recapitulate this aspect of human infection are needed to examine the HIV reservoir in tissues in vivo, and to test eradication strategies. In this review, we will summarize recent studies using humanized mouse models to examine different aspects of the viral reservoir.

Targeting type I interferon-mediated activation restores immune function in chronic HIV infection

Chronic immune activation, immunosuppression, and T cell exhaustion are hallmarks of HIV infection, yet the mechanisms driving these processes are unclear. Chronic activation can be a driving force in immune exhaustion, and type I interferons (IFN-I) are emerging as critical components underlying ongoing activation in HIV infection. Here, we have tested the effect of blocking IFN-I signaling on T cell responses and virus replication in a murine model of chronic HIV infection. Using HIV-infected humanized mice, we demonstrated that in vivo blockade of IFN-I signaling during chronic HIV infection diminished HIV-driven immune activation, decreased T cell exhaustion marker expression, restored HIV-specific CD8 T cell function, and led to decreased viral replication. Antiretroviral therapy (ART) in combination with IFN-I blockade accelerated viral suppression, further decreased viral loads, and reduced the persistently infected HIV reservoir compared with ART treatment alone. Our data suggest that blocking IFN-I signaling in conjunction with ART treatment can restore immune function and may reduce viral reservoirs during chronic HIV infection, providing validation for IFN-I blockade as a potential therapy for HIV infection.

Decay of ccc-DNA marks persistence of intrahepatic viral DNA synthesis under tenofovir in HIV-HBV co-infected patients

BACKGROUND & AIMS

In the presence of highly-potent antivirals, persistence of hepatitis B virus (HBV) is most well-characterized by covalently-closed circular DNA (cccDNA) and total intrahepatic DNA (IH-DNA). We sought to determine how antiviral therapy could affect their levels during human immunodeficiency virus (HIV)-HBV co-infection.

METHODS

Sixty co-infected patients from a well-defined cohort with ⩾1 liver biopsy were studied. HBV cccDNA and total IH-DNA were extracted from biopsies and quantified by real-time PCR. Factors associated with intrahepatic viral load were determined using mixed-effect linear regression and half-life viral kinetics during reconstructed follow-up using non-linear exponential decay models.

RESULTS

At biopsy, 35 (58.3%) patients were hepatitis B "e" antigen (HBeAg)-positive and 33 (55.0%) had detectable plasma HBV-DNA (median=4.58log10IU/ml, IQR=2.95-7.43). Overall, median cccDNA was -0.95log10copies/cell (IQR=-1.70, -0.17) and total IH-DNA was 0.27log10copies/cell (IQR=-0.39, 2.00). In multivariable analysis, significantly lower levels of cccDNA and total IH-DNA were observed in patients with HBeAg-negative serology, nadir CD4(+) cell counts >250/mm(3), and longer cumulative TDF-duration, but not lamivudine- or adefovir-duration. In post-hoc analysis using reconstructed TDF-duration (median 29.6months, IQR=15.0-36.1, n=31), average half-life of cccDNA was estimated at 9.2months (HBeAg-positive=8.6, HBeAg-negative=26.2) and total IH DNA at 5.8months (HBeAg-positive=1.3, HBeAg-negative=13.6). Intrahepatic viral loads remained detectable for all patients, even with prolonged TDF-exposure.

CONCLUSIONS

In co-infection, TDF-use is associated with lower levels of HBV replication intermediates and cccDNA. Slow decay of intrahepatic viral loads underscores that TDF is unable to completely block intracellular viral DNA synthesis, which possibly accounts for continuous replenishment of the cccDNA pool.

LAY SUMMARY

Chronic hepatitis B virus (HBV) is a persistent infection, while the only real way of knowing the extent of this persistence is through measuring levels of virus in the liver. In this study, we examine levels of HBV in the liver among patients with both HBV and human immunodeficiency virus, or HIV, infection. It would appear that the currently available medication, namely "tenofovir", works well to decrease virus levels in the liver, but it remains at low levels despite long periods of treatment.

Chronic Hepatitis C Virus Infection and the Proinflammatory Effects of Injection Drug Use

BACKGROUND

 Chronic inflammation, as defined by persistent immune activation, is associated with adverse clinical outcomes. People who inject drugs (PWID) have evidence of persistent immune activation. Here, in a cohort of PWID with or without hepatitis C virus (HCV) infection, we sought to dissect out the contribution of chronic HCV infection (common in PWID) from the effects of injection drug use itself.

METHODS

 Four groups of study volunteers were recruited: group 1 comprised active PWID; group 2, individuals who ceased injecting drugs 1-2 months before recruitment; group 3, individuals who ceased injecting drugs 3-4 months before recruitment; and group 4, healthy volunteers. Soluble and cell-associated markers of immune activation were quantified.

RESULTS

 HCV-viremic PWID have elevated levels of immune activation when compared to healthy volunteers. Cessation of injection drug use results in a decline in immune activation in the absence of HCV viremia, while HCV-viremic individuals who previously were PWID continue to harbor elevated levels of immune activation, as defined by increased levels of soluble CD14 and tumor necrosis factor α and by the presence of CD38⁺HLA-DR⁺ CD4⁺ and CD8⁺ T cells.

CONCLUSIONS

 Immune activation, a well-defined surrogate of poor clinical outcome that is elevated in PWID, can regress to normal levels in former injection drug users who are HCV aviremic. Therefore, enhanced harm-reduction efforts should incorporate aggressive treatment of HCV infection.

CLINICAL TRIALS REGISTRATION

 NCT01831284.

Type I and Type II Interferon Coordinately Regulate Suppressive Dendritic Cell Fate and Function during Viral Persistence

Persistent viral infections are simultaneously associated with chronic inflammation and highly potent immunosuppressive programs mediated by IL-10 and PDL1 that attenuate antiviral T cell responses. Inhibiting these suppressive signals enhances T cell function to control persistent infection; yet, the underlying signals and mechanisms that program immunosuppressive cell fates and functions are not well understood. Herein, we use lymphocytic choriomeningitis virus infection (LCMV) to demonstrate that the induction and functional programming of immunosuppressive dendritic cells (DCs) during viral persistence are separable mechanisms programmed by factors primarily considered pro-inflammatory. IFNγ first induces the de novo development of naive monocytes into DCs with immunosuppressive potential. Type I interferon (IFN-I) then directly targets these newly generated DCs to program their potent T cell immunosuppressive functions while simultaneously inhibiting conventional DCs with T cell stimulating capacity. These mechanisms of monocyte conversion are constant throughout persistent infection, establishing a system to continuously interpret and shape the immunologic environment. MyD88 signaling was required for the differentiation of suppressive DCs, whereas inhibition of stimulatory DCs was dependent on MAVS signaling, demonstrating a bifurcation in the pathogen recognition pathways that promote distinct elements of IFN-I mediated immunosuppression. Further, a similar suppressive DC origin and differentiation was also observed in Mycobacterium tuberculosis infection, HIV infection and cancer. Ultimately, targeting the underlying mechanisms that induce immunosuppression could simultaneously prevent multiple suppressive signals to further restore T cell function and control persistent infections.

Persistent virus infections induce host derived immunosuppressive factors that attenuate the immune response and prevent control of infection. Although the mechanisms of T cell exhaustion are being defined, we know surprisingly little about the underlying mechanisms that induce the immunosuppressive state and the origin and functional programming of the cells that deliver these signals to the T cells. We recently demonstrated that type I interferon (IFN-I) signaling was responsible for many of the immune dysfunctions associated with persistent virus infection and in particular the induced expression of the suppressive factors IL-10 and PDL1 by dendritic cells (DCs). Yet, mechanistically how IFN-I signaling specifically generates and programs cells to become immunosuppressive is still unknown. Herein, we define the underlying mechanisms of IFN-I mediated immunosuppression and establish that the induction of factors and the generation of the DCs that express them are separable events integrally reliant on additional inflammatory factors. Further, we demonstrate a similar derivation of the suppressive DCs that emerge in other diseases associated with prolonged inflammation and immunosuppression, specifically in HIV infection, Mycobacterium tuberculosis, and cancer, indicating a conserved origin of immunosuppression and suggesting that targeting the pathways that underlie expression of immunosuppressive cells and factors could be beneficial to treat multiple chronic diseases.

Role of Regulatory T Cells and Inhibitory Molecules in the Development of Immune Exhaustion During Human Immunodeficiency Virus Type 1 Infection

One of the key hallmarks of chronic human immunodeficiency virus type 1 (HIV-1) infection is the persistent immune activation triggered since early stages of the infection, followed by the development of an exhaustion phenomena, which leads to the inability of immune cells to respond appropriately to the virus and other pathogens, constituting the acquired immunodeficiency syndrome (AIDS); this exhausting state is characterized by a loss of effector functions of immune cells such as proliferation, production of cytokine, as well as cytotoxic potential and it has been attributable to an increased response of regulatory T cells and recently also to the expression in different cell populations of inhibitory molecules, such as programmed death receptor-1 (PD-1), cytotoxic T lymphocyte antigen-4 (CTLA-4), T cell immunoglobulin-3 (Tim-3), and lymphocyte activation gene-3 (LAG-3). The importance of these molecules relies on the possibility to restore the immune response once these molecules are blocked, constituting a potential therapeutic target for treatment during HIV infection. In this regard, we explored the available data evaluating the functional role of Treg cells and inhibitory molecules during the infection in both blood and gut-associated lymphoid tissue (GALT) and their contribution to the development of immune exhaustion and progression to AIDS, as well as their therapeutic potential.

Out-of-Sequence Signal 3 Paralyzes Primary CD4(+) T-Cell-Dependent Immunity

Primary T cell activation involves the integration of three distinct signals delivered in sequence: (1) antigen recognition, (2) costimulation, and (3) cytokine-mediated differentiation and expansion. Strong immunostimulatory events such as immunotherapy or infection induce profound cytokine release causing "bystander" T cell activation, thereby increasing the potential for autoreactivity and need for control. We show that during strong stimulation, a profound suppression of primary CD4(+) T-cell-mediated immune responses ensued and was observed across preclinical models and patients undergoing high-dose interleukin-2 (IL-2) therapy. This suppression targeted naive CD4(+) but not CD8(+) T cells and was mediated through transient suppressor of cytokine signaling-3 (SOCS3) inhibition of the STAT5b transcription factor signaling pathway. These events resulted in complete paralysis of primary CD4(+) T cell activation, affecting memory generation and induction of autoimmunity as well as impaired viral clearance. These data highlight the critical regulation of naive CD4(+) T cells during inflammatory conditions.

Tuberculosis and HIV Coinfection

Tuberculosis (TB) and human immunodeficiency virus/acquired immunodeficiency syndrome (HIV/AIDS) constitute the main burden of infectious disease in resource-limited countries. In the individual host, the two pathogens, Mycobacterium tuberculosis and HIV, potentiate one another, accelerating the deterioration of immunological functions. In high-burden settings, HIV coinfection is the most important risk factor for developing active TB, which increases the susceptibility to primary infection or reinfection and also the risk of TB reactivation for patients with latent TB. M. tuberculosis infection also has a negative impact on the immune response to HIV, accelerating the progression from HIV infection to AIDS. The clinical management of HIV-associated TB includes the integration of effective anti-TB treatment, use of concurrent antiretroviral therapy (ART), prevention of HIV-related comorbidities, management of drug cytotoxicity, and prevention/treatment of immune reconstitution inflammatory syndrome (IRIS).

The evaluation of platelet function in HIV infected, asymptomatic treatment-naïve individuals using flow cytometry

INTRODUCTION

Human immunodeficiency virus (HIV) induces inflammation and platelet activation. People living with HIV are at increased risk of thrombotic events. Activated platelets link inflammation with thrombosis. However platelet function in HIV remains unclear. P-selectin (CD62P), a marker of platelet activation, and platelet glycoprotein GPIV (CD36) a marker of platelet aggregation, can be measured using flow cytometry. We raise a hypothesis that HIV alters the signalling pathways involved in normal platelet function. We evaluated platelet function in HIV using a whole blood platelet flow cytometry based assay.

MATERIALS AND METHODS

Fifty-eight antiretroviral therapy naïve HIV infected and 38 HIV negative individuals were recruited in a clinic in Cape Town. Platelet surface CD36 and CD62P were measured using flow cytometry. These were then correlated with CD4 count, viral load and %CD38 on CD8+ T-cells. Platelet function was evaluated using adenosine diphosphate, arachidonic acid and collagen at varying concentrations.

RESULTS

The HIV group showed increased levels of %CD62P (median 5.51[3.03- 10.11] vs. Control group 2.14[0.19 - 3.59], p<0.0001. This correlated with Viral load (r=0.336, P=0.008). The HIV group also showed increased levels of platelet %CD36 21.93[11.03-44.92] vs. Control 16.15[2.24-25.37], p=0.0087) which correlated with viral load (r=0.398, p=0.024). The HIV group showed a hyper response to AA and collagen at various concentrations. Notably, the HIV group only showed a hyper response to ADP at a maximal concentration of 20 μM (median CD62P MFI, 1.91[1.64-4.95] vs. Control 1.75[1.45-2.44] p=0.0279.

CONCLUSION

The measurement of platelet function using flow cytometry is a rapid technique for the evaluation of platelet signalling pathways that may be modified in HIV infected individuals.

Peptide-MHC multimer-based monitoring of CD8 T-cells in HIV-1 infection and AIDS vaccine development

The use of MHC multimers allows precise and direct detecting and analyzing of antigen-specific T-cell populations and provides new opportunities to characterize T-cell responses in humans and animals. MHC-multimers enable us to enumerate specific T-cells targeting to viral, tumor and vaccine antigens with exceptional sensitivity and specificity. In the field of HIV/SIV immunology, this technique provides valuable information about the frequencies of HIV- and SIV-specific CD8(+) cytotoxic T lymphocytes (CTLs) in different tissues and sites of infection, AIDS progression, and pathogenesis. Peptide-MHC multimer technology remains a very sensitive tool in detecting virus-specific T -cells for evaluation of the immunogenicity of vaccines against HIV-1 in preclinical trials. Moreover, it helps to understand how immune responses are formed following vaccination in the dynamics from priming point until T-cell memory is matured. Here we review a diversity of peptide-MHC class I multimer applications for fundamental immunological studies in different aspects of HIV/SIV infection and vaccine development.

HIV-1 Tat protein induces PD-L1 (B7-H1) expression on dendritic cells through tumor necrosis factor alpha- and toll-like receptor 4-mediated mechanisms

Chronic human immunodeficiency virus type 1 (HIV-1) infection is associated with induction of T-cell coinhibitory pathways. However, the mechanisms by which HIV-1 induces upregulation of coinhibitory molecules remain to be fully elucidated. The aim of the present study was to determine whether and how HIV-1 Tat protein, an immunosuppressive viral factor, induces the PD-1/PD-L1 coinhibitory pathway on human dendritic cells (DCs). We found that treatment of DCs with whole HIV-1 Tat protein significantly upregulated the level of expression of PD-L1. This PD-L1 upregulation was observed in monocyte-derived dendritic cells (MoDCs) obtained from either uninfected or HIV-1-infected patients as well as in primary myeloid DCs from HIV-negative donors. In contrast, no effect on the expression of PD-L2 or PD-1 molecules was detected. The induction of PD-L1 on MoDCs by HIV-1 Tat (i) occurred in dose- and time-dependent manners, (ii) was mediated by the N-terminal 1-45 fragment of Tat, (iii) did not require direct cell-cell contact but appeared rather to be mediated by soluble factor(s), (iv) was abrogated following neutralization of tumor necrosis factor alpha (TNF-α) or blocking of Toll-like receptor 4 (TLR4), (v) was absent in TLR4-knockoout (KO) mice but could be restored following incubation with Tat-conditioned medium from wild-type DCs, (vi) impaired the capacity of MoDCs to functionally stimulate T cells, and (vii) was not reversed functionally following PD-1/PD-L1 pathway blockade, suggesting the implication of other Tat-mediated coinhibitory pathways. Our results demonstrate that HIV-1 Tat protein upregulates PD-L1 expression on MoDCs through TNF-α- and TLR4-mediated mechanisms, functionally compromising the ability of DCs to stimulate T cells. The findings offer a novel potential molecular target for the development of an anti-HIV-1 treatment.

IMPORTANCE

The objective of this study was to investigate the effect of human immunodeficiency virus type 1 (HIV-1) Tat on the PD-1/PD-L1 coinhibitory pathway on human monocyte-derived dendritic cells (MoDCs). We found that treatment of MoDCs from either healthy or HIV-1-infected patients with HIV-1 Tat protein stimulated the expression of PD-L1. We demonstrate that this stimulation was mediated through an indirect mechanism, involving tumor necrosis factor alpha (TNF-α) and Toll-like receptor 4 (TLR4) pathways, and resulted in compromised ability of Tat-treated MoDCs to functionally stimulate T-cell proliferation.

Glycoproteomic analysis identifies human glycoproteins secreted from HIV latently infected T cells and reveals their presence in HIV+ plasma

Glycoproteins secreted into plasma from T cells infected with human immunodeficiency virus (HIV) latent infection may provide insight into understanding the host response to HIV infection in vivo. Glycoproteomics, which evaluates the level of the glycoproteome, remains a novel approach to study this host response to HIV. In order to identify human glycoproteins secreted from T cells with latent HIV infection, the medium from cultured HIV replication-competent T cells was compared with the medium from cultured parental A3.01 cells via solid phase extraction of glycopeptides (SPEG) and high-performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS). Using these methods, 59 human glycoproteins were identified as having significantly different abundance levels between the media from these two cell lines. The relevance of these 59 proteins to HIV infection in vivo was assessed in plasma from HIV+ and HIV- subjects. Comparison between T cell and plasma revealed that six glycoproteins (galectin-3-binding protein, L-selectin, neogenin, adenosine deaminase CECR1, ICOS ligand and phospholipid transfer protein) were significantly elevated in the HIV+ T cells and plasma studies. These findings suggest that the response of T cells harboring latent HIV infection contributed, in part, to the glycoprotein changes in HIV+ plasma. These proteins, once validated, could provide insight into host-HIV interaction.

Networking at the level of host immunity: immune cell interactions during persistent viral infections

Persistent viral infections are the result of a series of connected events that culminate in diminished immunity and the inability to eliminate infection. By building our understanding of how distinct components of the immune system function both individually and collectively in productive versus abortive responses, new potential therapeutic targets can be developed to overcome immune dysfunction and thus fight persistent infections. Using lymphocytic choriomeningitis virus (LCMV) as a model of a persistent virus infection and drawing parallels to persistent human viral infections such as human immunodeficiency virus (HIV) and hepatitis C virus (HCV), we describe the cellular relationships and interactions that determine the outcome of initial infection and highlight immune targets for therapeutic intervention to prevent or treat persistent infections. Ultimately, these findings will further our understanding of the immunologic basis of persistent viral infection and likely lead to strategies to treat human viral infections.

Decoding the complexity of type I interferon to treat persistent viral infections

Type I interferons (IFN-I) are a broad family of cytokines that are central to the innate immune response. These proteins have long been appreciated for the critical roles they play in restraining viral infections and shaping antiviral immune responses. However, in recent years there has been increased awareness of the immunosuppressive actions of these proteins as well. Although there are many current therapeutic applications to manipulate IFN-I pathways, we have limited understanding of the mechanisms by which these therapies are actually functioning. In this review, we highlight the diversity and temporal impact of IFN-I signaling, discuss the current therapeutic uses of IFN-I, and explore the strategy of blocking IFN-I to alleviate immune dysfunction in persistent virus infections.