Altered CD4+ T cell homing to the gut impairs mucosal immune reconstitution in treated HIV-infected individuals

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.

The Th17 Lineage: From Barrier Surfaces Homeostasis to Autoimmunity, Cancer, and HIV-1 Pathogenesis

The T helper 17 (Th17) cells represent a subset of CD4+ T-cells with unique effector functions, developmental plasticity, and stem-cell features. Th17 cells bridge innate and adaptive immunity against fungal and bacterial infections at skin and mucosal barrier surfaces. Although Th17 cells have been extensively studied in the context of autoimmunity, their role in various other pathologies is underexplored and remains an area of open investigation. This review summarizes the history of Th17 cell discovery and the current knowledge relative to the beneficial role of Th17 cells in maintaining mucosal immunity homeostasis. We further discuss the concept of Th17 pathogenicity in the context of autoimmunity, cancer, and HIV infection, and we review the most recent discoveries on molecular mechanisms regulating HIV replication/persistence in pathogenic Th17 cells. Finally, we stress the need for novel fundamental research discovery-based Th17-specific therapeutic interventions to treat pathogenic conditions associated with Th17 abnormalities, including HIV infection.

The effect of plasma auto-IgGs on CD4+ T cell apoptosis and recovery in HIV-infected patients under antiretroviral therapy

Although effective antiretroviral therapy (ART) suppresses HIV viral replication, prevents AIDS-related complications, and prolongs life, a proportion of patients fails to restore the patients' CD4⁺ T cell number to the level of healthy individuals. Increased mortality and morbidity have been observed in these patients. In the current study, we have investigated the role of auto-IgGs in CD4⁺ T cell apoptosis and recovery in a cross-sectional study. All HIV⁺ subjects were on viral-suppressive ART treatment with a different degree of CD4⁺ T cell reconstitution. Total auto-IgG binding on CD4⁺ T cell surfaces and its associated apoptosis and CD4⁺ T cell recovery were analyzed by flow cytometry ex vivo. Total IgGs from plasma were tested for their binding capacities to CD4⁺ T cell surfaces and their mediation to CD4⁺ T cell death through NK cell cytotoxicity in vitro. HIV⁺ subjects had increased surface binding of auto-IgGs on CD4⁺ T cells compared with healthy controls, and IgG binding was associated with elevated CD4⁺ T cell apoptosis in HIV⁺ subjects but not in healthy controls. Plasma IgGs from HIV⁺ subjects bound to CD4⁺ T cells and induced cell apoptosis through NK cytotoxicity in vitro. Soluble CD4 (sCD4) preincubation prevented NK cell-mediated CD4⁺ T cell death. Our results suggest that plasma autoantibodies may play a role in some HIV⁺ patients with poor CD4⁺ T cell recovery under viral-suppressive ART.

HIV-TB co-infection: mechanisms that drive reactivation of Mycobacterium tuberculosis in HIV infection

HIV infection predisposes the host to tuberculosis by impairing the hosts' immune system principally by killing and altering CD4 T-cell function. How HIV infection disrupts CD4 T-cell function, which specifically compromises host immunity to Mycobacterium tuberculosis, is poorly understood and is a critical roadblock in developing better vaccine- or immune-based strategies to control and monitor TB in HIV-infected subjects. This review considers key pathways that are altered in HIV-infected subjects that impair anti-TB immunity.

Probiotic supplementation promotes a reduction in T-cell activation, an increase in Th17 frequencies, and a recovery of intestinal epithelium integrity and mitochondrial morphology in ART-treated HIV-1-positive patients

INTRODUCTION

HIV infection is characterized by a persistent immune activation associated to a compromised gut barrier immunity and alterations in the profile of the fecal flora linked with the progression of inflammatory symptoms. The effects of high concentration multistrain probiotic (Vivomixx®, Viale del Policlinico 155, Rome, Italy in EU; Visbiome®, Dupont, Madison, Wisconsin in USA) on several aspects of intestinal immunity in ART-experienced HIV-1 patients was evaluated.

METHODS

A sub-study of a longitudinal pilot study was performed in HIV-1 patients who received the probiotic supplement twice a day for 6 months (T6). T-cell activation and CD4+ and CD8+ T-cell subsets expressing IFNγ (Th1, Tc1) or IL-17A (Th17, Tc17) were stained by cytoflorimetric analysis. Histological and immunohistochemical analyses were performed on intestinal biopsies while enterocytes apoptosis index was determined by TUNEL assay.

RESULTS

A reduction in the frequencies of CD4+ and CD8+ T-cell subsets, expressing CD38+ , HLA-DR+ , or both, and an increase in the percentage of Th17 cell subsets, especially those with central or effector memory phenotype, was recorded in the peripheral blood and in gut-associated lymphoid tissue (GALT) after probiotic intervention. Conversely, Tc1 and Tc17 levels remained substantially unchanged at T6, while Th1 cell subsets increase in the GALT. Probiotic supplementation was also associated to a recovery of the integrity of the gut epithelial barrier, a reduction of both intraepithelial lymphocytes density and enterocyte apoptosis and, an improvement of mitochondrial morphology sustained in part by a modulation of heat shock protein 60.

CONCLUSIONS

These findings highlight the potential beneficial effects of probiotic supplementation for the reconstitution of physical and immunological integrity of the mucosal intestinal barrier in ART-treated HIV-1-positive patients.

Brief Report: A High Rate of β7+ Gut-Homing Lymphocytes in HIV-Infected Immunological Nonresponders is Associated With Poor CD4 T-Cell Recovery During Suppressive HAART

Supplemental Digital Content is Available in the Text.

Objective:

Correlation between GALT homing markers on lymphocytes and the low blood CD4 T-cell reconstitution in immunological nonresponders (INRs) has been studied.

Design:

Thirty-one INRs, 19 immunological responders (IRs), and 12 noninfected controls were enrolled in this study. INRs were defined by an undetectable plasma viral load RNA less than 40 copies per milliliter and CD4⁺ T-cell count <500 cells per cubic milliliter in at least 3 years.

Methods:

A complete peripheral and mucosal lymphocyte immunophenotyping was performed on these patients with a focus on the CCR9, CCR6, and α4β7 gut-homing markers.

Results:

A highly significant upregulation of α4β7 on INRs peripheral lymphocytes compared with that of IRs has been observed. This upregulation impacts different lymphocyte subsets namely CD4⁺, CD8⁺, and B lymphocytes. The frequency of β7⁺ Th17 and Treg cells are increased compared with IRs and healthy controls. The frequency of β7⁺ CD8⁺ T cells in the blood is negatively correlated with integrated proviral DNA in rectal lymphoid cells in contrast to β7⁺ CD4⁺ T cells associated with HIV integration.

Conclusions:

Alteration of lymphocyte homing abilities would have deleterious effects on GALT reconstitution and could participate to HIV reservoir constitution. These results emphasize the great interest to consider α4β7-targeted therapy in INR patients to block homing of lymphocytes and/or to directly impair gp120-α4β7 interactions.

HIV-1 selectively targets gut-homing CCR6+CD4+ T cells via mTOR-dependent mechanisms

Gut-associated lymphoid tissues are enriched in CCR6+ Th17-polarized CD4+ T cells that contribute to HIV-1 persistence during antiretroviral therapy (ART). This raises the need for Th17-targeted immunotherapies. In an effort to identify mechanisms governing HIV-1 permissiveness/persistence in gut-homing Th17 cells, we analyzed the transcriptome of CCR6+ versus CCR6- T cells exposed to the gut-homing inducer retinoic acid (RA) and performed functional validations in colon biopsies of HIV-infected individuals receiving ART (HIV+ART). Although both CCR6+ and CCR6- T cells acquired gut-homing markers upon RA exposure, the modulation of unique sets of genes coincided with preferential HIV-1 replication in RA-treated CCR6+ T cells. This molecular signature included the upregulation of HIV-dependency factors acting at entry/postentry levels, such as the CCR5 and PI3K/Akt/mTORC1 signaling pathways. Of note, mTOR expression/phosphorylation was distinctively induced by RA in CCR6+ T cells. Consistently, mTOR inhibitors counteracted the effect of RA on HIV replication in vitro and viral reactivation in CD4+ T cells from HIV+ART individuals via postentry mechanisms independent of CCR5. Finally, CCR6+ versus CCR6- T cells infiltrating the colons of HIV+ART individuals expressed unique molecular signatures, including higher levels of CCR5, integrin β7, and mTOR phosphorylation. Together, our results identify mTOR as a druggable key regulator of HIV permissiveness in gut-homing CCR6+ T cells.

The loss of CCR6+ and CD161+ CD4+ T-cell homeostasis contributes to disease progression in SIV-infected rhesus macaques

Although previous studies have shown that CD4+ T cells expressing CCR6 and CD161 are depleted from blood during HIV infection, the mechanisms underlying their loss remain unclear. In this study, we investigated how the homeostasis of CCR6+ and CD161+ CD4+ T cells contributes to SIV disease progression and the mechanisms responsible for their loss from circulation. By comparing SIV infection in rhesus macaques (RMs) and natural host sooty mangabeys (SMs), we found that the loss of CCR6+ and CD161+ CD4+ T cells from circulation is a distinguishing feature of progressive SIV infection in RMs. Furthermore, while viral infection critically contributes to the loss of CD161+CCR6-CD4+ T cells, a redistribution of CCR6+CD161- and CCR6+CD161+CD4+ T cells from the blood to the rectal mucosa is a chief mechanism for their loss during SIV infection. Finally, we provide evidence that the accumulation of CCR6+CD4+ T cells in the mucosa is damaging to the host by demonstrating their reduction from this site following initiation of antiretroviral therapy in SIV-infected RMs and their lack of accumulation in SIV-infected SMs. These data emphasize the importance of maintaining CCR6+ and CD161+ CD4+ T-cell homeostasis, particularly in the mucosa, to prevent disease progression during pathogenic HIV/SIV infection.

Genome-wide association study of HIV-associated neurocognitive disorder (HAND): A CHARTER group study

HIV-associated neurocognitive disorder (HAND) often complicates HIV infection despite combination antiretroviral therapy (ART) and may be influenced by host genomics. We performed a genome-wide association study (GWAS) of HAND in 1,050 CNS HIV Anti-Retroviral Therapy Effects Research (CHARTER) Study participants. All participants underwent standardized, comprehensive neurocognitive, and neuromedical assessments to determine if they had cognitive impairment as assessed by the Global Deficit Score (GDS), and individuals with comorbidities that could confound diagnosis of HAND were excluded. Neurocognitive outcomes included GDS-defined neurocognitive impairment (NCI; binary GDS, 366 cases with GDS ≥ 0.5 and 684 controls with GDS < 0.5, and GDS as a continuous variable) and Frascati HAND definitions that incorporate assessment of functional impairment by self-report and performance-based criteria. Genotype data were obtained using the Affymetrix Human SNP Array 6.0 platform. Multivariable logistic or linear regression-based association tests were performed for GDS-defined NCI and HAND. GWAS results did not reveal SNPs meeting the genome-wide significance threshold (5.0 × 10-8 ) for GDS-defined NCI or HAND. For binary GDS, the most significant SNPs were rs6542826 (P = 8.1 × 10-7 ) and rs11681615 (1.2 × 10-6 ), both located on chromosome 2 in SH3RF3. The most significant SNP for continuous GDS was rs11157436 (P = 1.3 × 10-7 ) on chromosome 14 in the T-cell-receptor alpha locus; three other SNPs in this gene were also associated with binary GDS (P ≤ 2.9 × 10-6 ). This GWAS, conducted among ART-era participants from a single cohort with robust neurological phenotyping, suggests roles for several biologically plausible loci in HAND that deserve further exploration. © 2017 Wiley Periodicals, Inc.

HIV Persistence in Gut-Associated Lymphoid Tissues: Pharmacological Challenges and Opportunities

An increasing amount of evidence suggests that HIV replication persists in gut-associated lymphoid tissues (GALT), despite treatment with combination antiretroviral therapy (cART). Residual replication in this compartment may propagate infection at other sites in the body and contribute to sustained immune dysregulation and delayed immune recovery. Therefore, it is important to focus efforts on eliminating residual replication at this site. There are several challenges to accomplishing this goal, including low antiretroviral (ARV) exposure at specific tissue locations within GALT, which might be overcome by using the tools of clinical pharmacology. Here, we summarize the evidence for GALT as a site of residual HIV replication, highlight the consequences of persistent infection in tissues, identify current pharmacologic knowledge of drug exposure in GALT, define the challenges that hinder eradication from this site, and propose several avenues for pharmacologic intervention.

Increased Natural Killer Cell Activation in HIV-Infected Immunologic Non-Responders Correlates with CD4+ T Cell Recovery after Antiretroviral Therapy and Viral Suppression

The role of natural killer (NK) cell function in HIV disease especially in the setting of long-term antiretroviral therapy (ART) and viral suppression is not fully understood. In the current study, we have investigated NK cell activation in healthy controls and aviremic ART-treated HIV+ subjects with different degrees of immune restoration. We performed a cross sectional study in 12 healthy controls and 24 aviremic ART-treated HIV-infected subjects including 13 HIV+ subjects with CD4+ T cells above 500 cells/μL defined as "immunologic responders" and 11 HIV+ subjects with CD4+ T cells below 350 cells/μL defined as "immunologic non-responders". We analyzed NK cell number, subset, and activation by expression of CD107a and NKG2D and co-expression of CD38 and HLA-DR. NK cell-mediated cytotoxicity against uninfected CD4+ T cells was tested in vitro. We found that NK cell absolute number, percentage of NK cells, and percentage of NK cell subsets were similar in the three study groups. The increased NK cell activation was found predominantly in CD56dimCD16+ subset of immunologic non-responders but not immunologic responders compared to healthy controls. The activation of NK cells was inversely correlated with the peripheral CD4+ T cell count in HIV+ subjects, even after controlling for chronic T cell activation, sex, and age, potential contributors for CD4+ T cell counts in HIV disease. Interestingly, NK cells from immunologic non-responders mediated cytotoxicity against uninfected CD4+ T cells ex vivo. NK cells may play a role in blunted CD4+ T cell recovery in ART-treated HIV disease.

HIV persists in CCR6+CD4+ T cells from colon and blood during antiretroviral therapy

OBJECTIVES

The objective of this article is to investigate the contribution of colon and blood CD4 T-cell subsets expressing the chemokine receptor CCR6 to HIV persistence during antiretroviral therapy.

DESIGN

Matched sigmoid biopsies and blood samples (n = 13) as well as leukapheresis (n = 20) were collected from chronically HIV-infected individuals receiving antiretroviral therapy. Subsets of CD4 T cells with distinct differentiation/polarization profiles were identified using surface markers as follows: memory (TM, CD45RA), central memory (TCM; CD45RACCR7), effector (TEM/TM; CD45RACCR7), Th17 (CCR6CCR4), Th1Th17 (CCR6CXCR3), Th1 (CCR6CXCR3), and Th2 (CCR6CCR4).

METHODS

We used polychromatic flow cytometry for cell sorting, nested real-time PCR for HIV DNA quantification, ELISA and flow cytometry for HIV p24 quantification. HIV reactivation was induced by TCR triggering in the presence/absence of all-trans retinoic acid.

RESULTS

Compared with blood, the frequency of CCR6 TM was higher in the colon. In both colon and blood compartments, CCR6 TM were significantly enriched in HIV DNA when compared with their CCR6 counterparts (n = 13). In blood, integrated HIV DNA levels were significantly enriched in CCR6 versus CCR6 TCM of four of five individuals and CCR6 versus CCR6 TEM of three of five individuals. Among blood TCM, Th17 and Th1Th17 contributed the most to the pool of cells harboring integrated HIV DNA despite their reduced frequency compared with Th2, which were infected the least. HIV reactivation was induced by TCR triggering and/or retinoic acid exposure at higher levels in CCR6 versus CCR6 TM, TCM, and TEM.

CONCLUSION

CCR6 is a marker for colon and blood CD4 T cells enriched for replication-competent HIV DNA. Novel eradication strategies should target HIV persistence in CCR6CD4 T cells from various anatomic sites.

Impairment of CCR6+ and CXCR3+ Th Cell Migration in HIV-1 Infection Is Rescued by Modulating Actin Polymerization

CD4+ T cell repopulation of the gut is rarely achieved in HIV-1-infected individuals who are receiving clinically effective antiretroviral therapy. Alterations in the integrity of the mucosal barrier have been indicated as a cause for chronic immune activation and disease progression. In this study, we present evidence that persistent immune activation causes impairment of lymphocytes to respond to chemotactic stimuli, thus preventing their trafficking from the blood stream to peripheral organs. CCR6+ and CXCR3+ Th cells accumulate in the blood of aviremic HIV-1-infected patients on long-term antiretroviral therapy, and their frequency in the circulation positively correlates to levels of soluble CD14 in plasma, a marker of chronic immune activation. Th cells show an impaired response to chemotactic stimuli both in humans and in the pathogenic model of SIV infection, and this defect is due to hyperactivation of cofilin and inefficient actin polymerization. Taking advantage of a murine model of chronic immune activation, we demonstrate that cytoskeleton remodeling, induced by okadaic acid, restores lymphocyte migration in response to chemokines, both in vitro and in vivo. This study calls for novel pharmacological approaches in those pathological conditions characterized by persistent immune activation and loss of trafficking of T cell subsets to niches that sustain their maturation and activities.

Gut Homing CD4+ and CD8+ T-Cell Frequencies in HIV Infected Individuals on Antiretroviral Treatment

The depletion of mucosal CD4+ T-cells occurs early in HIV infection and despite years on antiretroviral treatment (ART), this population never reconstitutes to pre-HIV infection levels. In an effort to understand the effect of ART initiation and different ART regimens on the reconstitution of mucosal T cells within the gut associated lymphoid tissue (GALT), we quantified the frequency of CD4+ and CD8+ T cells expressing the gut homing receptors CCR9 and β7 in peripheral blood (PB) of HIV infected individuals naive to ART and treated individuals on both short-term (less than a year) and long-term ART (more than 2 years). We found that the gut homing CD4+ T cells were depleted in ART-naive individuals and increased after ART initiation but levels were not comparable to HIV uninfected individuals. Gut homing CD4+ T cell activation decreased after ART initiation whilst gut homing CD8+ T cell activation remained elevated in ART experienced individuals, especially in those individuals taking protease inhibitors. Our findings provide new insights into the effects of ART initiation and ART regimens on the frequency and immune status of gut homing CD4+ and CD8+ T cells.

Preferential loss of gut-homing α4β7 CD4+ T cells and their circulating functional subsets in acute HIV-1 infection

Preferential infection and depletion of gut-homing α4β7 CD4+ T cells in the blood are observed in chronic HIV/SIV infection. The dynamic change in gut-homing α4β7 CD4+ T cells and their functional subsets during the acute stages of HIV-1 infection are less documented. Therefore, we conducted a cohort study to investigate whether acute HIV-1 infection induced abnormalities in gut-homing α4β7 CD4+ T cells and their functional subsets. We examined the frequency, absolute number, and functionality of gut-homing α4β7 CD4+ T cells in 26 acute HIV-1-infected patients compared with 20 healthy individuals. We found that circulating gut-homing α4β7 CD4+ T cells were preferentially depleted during acute HIV-1 infection and were positively correlated with absolute CD4+ T-cell count in blood. Notably, Th17 and Th1 cell subsets of gut-homing CD4+ T cells were also decreased, which resulted in an imbalance of T helper cells (Th1):regulatory T cells (Treg) and Treg:Th17 ratios. Gut-homing Th17 and Th1 cells were also positively correlated with the absolute number of total CD4+ T cells and gut-homing CD4+ T cells. The gut-homing Treg:Th17 ratio was inversely correlated with the CD4+ T-cell count. Taken together, the analyses of our acute HIV-1 cohort demonstrate that gut-homing α4β7 CD4+ T cells and their functional subsets were profoundly depleted during acute HIV-1 infection, which may have resulted in the persistent loss of circulating CD4+ T cells and an imbalance of Th1:Treg and Treg:Th17 ratios and contribute to HIV-1 disease pathogenesis.

CCR6(-) regulatory T cells blunt the restoration of gut Th17 cells along the CCR6-CCL20 axis in treated HIV-1-infected individuals

The gut CD4(+) T cells, particularly the T helper type 17 (Th17) subset, are not completely restored in most HIV-1-infected individuals despite combined antiretroviral therapy, when initiated at the chronic phase of infection. We show here that the CCR6-CCL20 chemotactic axis is altered, with reduced CCL20 production by small intestine epithelial cells in treated HIV-1-infected individuals. This leads to impaired CCR6(+)CD4(+) T-cell homing, particularly Th17 cells, to the small intestine mucosa. In contrast, the frequency of gut FoxP3(+) T regulatory (Treg) cells, specifically the CCR6(-) subset, was increased. The resulting imbalance in the Th17/CCR6(-) Treg ratio and the associated shift from interleukin (IL)-17 to IL-10 and transforming growth factor-β (TGF-β) blunts CCL20 production by enterocytes, perpetuating a negative feedback for the recruitment of CCR6(+)CD4(+) T cells to the small intestine in treated HIV-1-infected individuals.

Elevated Basal Pre-infection CXCL10 in Plasma and in the Small Intestine after Infection Are Associated with More Rapid HIV/SIV Disease Onset

Elevated blood CXCL10/IP-10 levels during primary HIV-1 infection (PHI) were described as an independent marker of rapid disease onset, more robust than peak viremia or CD4 cell nadir. IP-10 enhances the recruitment of CXCR3+ cells, which include major HIV-target cells, raising the question if it promotes the establishment of viral reservoirs. We analyzed data from four cohorts of HIV+ patients, allowing us to study IP-10 levels before infection (Amsterdam cohort), as well as during controlled and uncontrolled viremia (ANRS cohorts). We also addressed IP-10 expression levels with regards to lymphoid tissues (LT) and blood viral reservoirs in patients and non-human primates. Pre-existing elevated IP-10 levels but not sCD63 associated with rapid CD4 T-cell loss upon HIV-1 infection. During PHI, IP-10 levels and to a lesser level IL-18 correlated with cell-associated HIV DNA, while 26 other inflammatory soluble markers did not. IP-10 levels tended to differ between HIV controllers with detectable and undetectable viremia. IP-10 was increased in SIV-exposed aviremic macaques with detectable SIV DNA in tissues. IP-10 mRNA was produced at higher levels in the small intestine than in colon or rectum. Jejunal IP-10+ cells corresponded to numerous small and round CD68neg cells as well as to macrophages. Blood IP-10 response negatively correlated with RORC (Th17 marker) gene expression in the small intestine. CXCR3 expression was higher on memory CD4+ T cells than any other immune cells. CD4 T cells from chronically infected animals expressed extremely high levels of intra-cellular CXCR3 suggesting internalization after ligand recognition. Elevated systemic IP-10 levels before infection associated with rapid disease progression. Systemic IP-10 during PHI correlated with HIV DNA. IP-10 production was regionalized in the intestine during early SIV infection and CD68+ and CD68neg haematopoietic cells in the small intestine appeared to be the major source of IP-10.

Chronic immune activation is a hallmark of HIV infection and contributes in multiple ways to HIV persistence. Here, we gained insights on the association between a pro-inflammatory chemokine, CXCL10/IP-10 and HIV infection in four cohorts of HIV+ individuals, studied at distinct stages of infection (before, primary and chronic stage with spontaneous- and treatment-controlled infection). We further analyzed pathogenic and non-pathogenic SIV infections to address IP-10 levels and the presence of infected cells in tissues (lymph nodes, small and large intestine). We found that elevated systemic IP-10 levels before HIV-1 infection associate with a more rapid disease progression. During primary infection, IP-10 in blood strongly correlated with the amount of infected cells in blood. The animal model showed that IP-10 expression was regionalized in the intestine and highest in the small intestine. Studies of aviremic animals suggest that high IP-10 is indicative of viral replication in lymphoid tissues. Haematopoietic cells rather than epithelial/endothelial cells mainly contributed to the IP-10 production in small intestine (jejunum). The receptor of IP-10 was highly expressed on memory CD4+ T cells, i.e. major target cells for the virus. This study contributes to our understanding of the establishment of HIV reservoirs and why IP-10 associates with HIV/AIDS.

A Summary of the First HIV Microbiome Workshop 2015

The role of microbiota in the pathogenesis of HIV infection has become the subject of intense research in recent years. A rapidly growing amount of data suggest that microbial dysbiosis-in the gut or the genital tract-can influence HIV transmission and/or disease progression; however, a deeper understanding of the mechanisms involved is lacking. To better understand the relationship between the microbiome and HIV infection, investigators from a wide variety of disciplines, including those working in basic and clinical HIV studies, cardiovascular disease, reproductive health, and bioinformatics, gathered at the first International Workshop on Microbiome in HIV Pathogenesis, Prevention and Treatment, at NIH on 7 and 8 April, 2015.

Impact of early cART in the gut during acute HIV infection

Early after HIV infection there is substantial depletion of CD4+ T cells in the gastrointestinal (GI) tract lamina propria (LP), with associated epithelial barrier damage, leading to microbial translocation and systemic inflammation and immune activation. In this study, we analyzed these early events in the GI tract in a cohort of Thai acute HIV-infected patients and determined the effect of early combination antiretroviral treatment (cART). HIV-uninfected and chronically and acutely HIV-infected patients at different Fiebig stages (I-V) underwent colonic biopsies and then received cART. Immunohistochemistry and quantitative image analysis were performed on cross-sectional and longitudinal colon biopsy specimens (day 0 to week 96) to measure GI tract damage (infiltration of polymorphonuclear cells), inflammation (M×1, TNF-α), immune activation (Ki-67), and the CD4+ T cell population in the LP. The magnitude of GI tract damage, immune activation, and inflammation was significantly increased, with significantly depleted CD4+ T cells in the LP in all acutely infected groups prior to cART compared with HIV-uninfected control participants. While most patients treated during acute infection resolved GI tract inflammation and immune activation back to baseline levels after 24 weeks of cART, most acutely infected participants did not restore their CD4+ T cells after 96 weeks of cART.

Major influence of CD4 count at the initiation of cART on viral and immunological reservoir constitution in HIV-1 infected patients

Background

A persistent immune activation is observed in gut during HIV-1 infection, which is not completely reversed by a combined antiretroviral therapy (cART). The impact of the time of cART initiation may highly influence the size of the viral reservoir and the ratio of CD4⁺/CD8⁺ T cells in the gut. In this study, we analyzed the characteristics of HIV rectal reservoir of long-term treated patients, regarding their blood CD4⁺ T cells count at the time of cART initiation.

Results

Twenty-four consenting men were enrolled: 9 exhibiting a CD4⁺ T cells count >350/mm³ (“high-level CD4 group”) and 15 < 350/mm³ (“low-level CD4 group”) in blood, at the start of cART. An immunophenotypical analysis of T and B cells subpopulations was performed in blood and rectal biopsies. HIV cell-associated DNA loads and qualitative intra-cellular RNA were determined in both compartments. The ratio of CD4⁺/CD8⁺ T cells was significantly decreased in the blood but not in the rectum of the “low-level CD4 group” of patients. The alteration in β7⁺ CD4⁺ T cells homing was higher in this group and was correlated to a low ratio of CD4⁺/CD8⁺ T cells in blood. An initiation of cART in men exhibiting a low-level CD4 count was also associated with an alteration of B cells maturation. HIV blood and gut DNA reservoirs were significantly lower in the “high-level CD4 group” of men. A high HIV DNA level was associated to a detectable intracellular HIV RNA in rectum.

Conclusions

An early initiation of cART could significantly preserve gut immunity and limit the viral reservoir constitution.

Electronic supplementary material

The online version of this article (doi:10.1186/s12977-016-0278-5) contains supplementary material, which is available to authorized users.

Mucosal Regulatory T Cells and T Helper 17 Cells in HIV-Associated Immune Activation

Residual mucosal inflammation along with chronic systemic immune activation is an important feature in individuals infected with human immunodeficiency virus (HIV), and has been linked to a wide range of co-morbidities, including malignancy, opportunistic infections, immunopathology, and cardiovascular complications. Although combined antiretroviral therapy (cART) can reduce plasma viral loads to undetectable levels, reservoirs of virus persist, and increased mortality is associated with immune dysbiosis in mucosal lymphoid tissues. Immune-based therapies are pursued with the goal of improving CD4⁺ T-cell restoration, as well as reducing chronic immune activation in cART-treated patients. However, the majority of research on immune activation has been derived from analysis of circulating T cells. How immune cell alterations in mucosal tissues contribute to HIV immune dysregulation and the associated risk of non-infectious chronic complications is less studied. Given the significant differences between mucosal T cells and circulating T cells, and the immediate interactions of mucosal T cells with the microbiome, more attention should be devoted to mucosal immune cells and their contribution to systemic immune activation in HIV-infected individuals. Here, we will focus on mucosal immune cells with a specific emphasis on CD4⁺ T lymphocytes, such as T helper 17 cells and CD4⁺Foxp3⁺ regulatory T cells (T_regs), which play crucial roles in maintaining mucosal barrier integrity and preventing inflammation, respectively. We hypothesize that pro-inflammatory milieu in cART-treated patients with immune activation significantly contributes to enhanced loss of Th17 cells and increased frequency of dysregulated T_regs in the mucosa, which in turn may exacerbate immune dysfunction in HIV-infected patients. We also present initial evidence to support this hypothesis. A better comprehension of how pro-inflammatory milieu impacts these two types of cells in the mucosa will shed light on mucosal immune dysfunction and HIV reservoirs, and lead to novel ways to restore immune functions in HIV⁺ patients.

Sequential Dysfunction and Progressive Depletion of Candida albicans-Specific CD4 T Cell Response in HIV-1 Infection

Loss of immune control over opportunistic infections can occur at different stages of HIV-1 (HIV) disease, among which mucosal candidiasis caused by the fungal pathogen Candida albicans (C. albicans) is one of the early and common manifestations in HIV-infected human subjects. The underlying immunological basis is not well defined. We have previously shown that compared to cytomegalovirus (CMV)-specific CD4 cells, C. albicans-specific CD4 T cells are highly permissive to HIV in vitro. Here, based on an antiretroviral treatment (ART) naïve HIV infection cohort (RV21), we investigated longitudinally the impact of HIV on C. albicans- and CMV-specific CD4 T-cell immunity in vivo. We found a sequential dysfunction and preferential depletion for C. albicans-specific CD4 T cell response during progressive HIV infection. Compared to Th1 (IFN-γ, MIP-1β) functional subsets, the Th17 functional subsets (IL-17, IL-22) of C. albicans-specific CD4 T cells were more permissive to HIV in vitro and impaired earlier in HIV-infected subjects. Infection history analysis showed that C. albicans-specific CD4 T cells were more susceptible to HIV in vivo, harboring modestly but significantly higher levels of HIV DNA, than CMV-specific CD4 T cells. Longitudinal analysis of HIV-infected individuals with ongoing CD4 depletion demonstrated that C. albicans-specific CD4 T-cell response was preferentially and progressively depleted. Taken together, these data suggest a potential mechanism for earlier loss of immune control over mucosal candidiasis in HIV-infected patients and provide new insights into pathogen-specific immune failure in AIDS pathogenesis.

HIV infection is closely associated with enhanced host susceptibility to various opportunistic infections (OIs), among which mucosal candidiasis caused by the fungal pathogen Candida albicans (C. albicans) is an early and common manifestation. Even in the era of effective ART, mucosal candidiasis is still a clinically relevant presentation in HIV-infected patients. The underlying mechanisms are not well defined. CD4-mediated immunity is the major host defense mechanism against C. albicans. We here investigated a group of ART naïve, HIV-infected human subjects and examined longitudinally the impact of HIV on C. albicans-specific CD4 T-cell immunity as compared to CD4 T-cell immunity specific for CMV, another opportunistic pathogen that usually does not cause active disease in early HIV infection. We found that C. albicans-specific CD4 T cells were more susceptible to HIV in vivo and were preferentially depleted in progressive HIV-infected individuals as compared to CMV-specific CD4 T cells. Of importance, we also found that in these HIV-infected subjects C. albicans-specific CD4 T cell response manifested a sequential dysfunction with earlier impairment of Th17, but not Th1, functions. Our study suggests an immunological basis that helps explain the earlier and more common onsets of mucosal candidiasis in progressive HIV-infected patients.

Cell-to-Cell Spread of HIV and Viral Pathogenesis

Human immunodeficiency virus type 1 (HIV-1) gives rise to a chronic infection that progressively depletes CD4(+) T lymphocytes. CD4(+) T lymphocytes play a central coordinating role in adaptive cellular and humoral immune responses, and to do so they migrate and interact within lymphoid compartments and at effector sites to mount immune responses. While cell-free virus serves as an excellent prognostic indicator for patient survival, interactions of infected T cells or virus-scavenging immune cells with uninfected T cells can greatly enhance viral spread. HIV can induce interactions between infected and uninfected T cells that are triggered by cell surface expression of viral Env, which serves as a cell adhesion molecule that interacts with CD4 on the target cell, before it acts as the viral membrane fusion protein. These interactions are called virological synapses and promote replication in the face of selective pressure of humoral immune responses and antiretroviral therapy. Other infection-enhancing cell-cell interactions occur between virus-concentrating antigen-presenting cells and recipient T cells, called infectious synapses. The exact roles that these cell-cell interactions play in each stage of infection, from viral acquisition, systemic dissemination, to chronic persistence are still being determined. Infection-promoting immune cell interactions are likely to contribute to viral persistence and enhance the ability of HIV-1 to evade adaptive immune responses.

Chemokine receptor patterns in lymphocytes mirror metastatic spreading in melanoma

Melanoma prognosis is dictated by tumor-infiltrating lymphocytes, the migratory and functional behavior of which is guided by chemokine or cytokine gradients. Here, we retrospectively analyzed the expression patterns of 9 homing receptors (CCR/CXCR) in naive and memory CD4+ and CD8+ T lymphocytes in 57 patients with metastatic melanoma (MMel) with various sites of metastases to evaluate whether T cell CCR/CXCR expression correlates with intratumoral accumulation, metastatic progression, and/or overall survival (OS). Homing receptor expression on lymphocytes strongly correlated with MMel dissemination. Loss of CCR6 or CXCR3, but not cutaneous lymphocyte antigen (CLA), on circulating T cell subsets was associated with skin or lymph node metastases, loss of CXCR4, CXCR5, and CCR9 corresponded with lung involvement, and a rise in CCR10 or CD103 was associated with widespread dissemination. High frequencies of CD8+CCR9+ naive T cells correlated with prolonged OS, while neutralizing the CCR9/CCL25 axis in mice stimulated tumor progression. The expansion of CLA-expressing effector memory CD8+ T cells in response to a single administration of CTLA4 blockade predicted disease control at 3 months in 47 patients with MMel. Thus, specific CCR/CXCR expression patterns on circulating T lymphocytes may guide potential diagnostic and therapeutic approaches.

Oral Typhoid Vaccination With Live-Attenuated Salmonella Typhi Strain Ty21a Generates Ty21a-Responsive and Heterologous Influenza Virus-Responsive CD4+ and CD8+ T Cells at the Human Intestinal Mucosa

Background. Oral vaccination with live-attenuated Salmonella Typhi strain Ty21a is modestly efficacious, but the mechanisms of protection are currently unknown. While humoral and cellular immune responses are well described in peripheral blood, the cellular response at the intestinal mucosa has never been directly assessed.

Methods. We vaccinated healthy adults with Ty21a and assessed humoral and cellular immunity in vaccinated volunteers and controls after 18 days. Immunoglobulin levels were assessed in peripheral blood by an enzyme-linked immunosorbent assay. Cellular responses were assessed in peripheral blood and at the duodenal and colonic mucosa by flow cytometry.

Results. We demonstrate the generation of Ty21a-responsive and heterologous influenza virus–responsive CD4⁺ and CD8⁺ T cells at the duodenal mucosa. All duodenal responses were consistently correlated, and no responses were observed at the colonic mucosa. Peripheral anti-lipopolysaccharide immunoglobulin G and immunoglobulin A responses were significantly correlated with duodenal responses. The assessment of integrin β₇ expression intensity among peripheral and duodenal T-cell subsets revealed varied capacities for mucosal homing and residence.

Conclusions. The breadth of duodenal cellular responses was not reflected peripherally. The direct evaluation of mucosal immune defense may yield functional correlates of protection and could provide insight into mechanisms that may be manipulated to enhance vaccine immunogenicity.

The effect of timing of antiretroviral therapy on CD4+ T-cell reconstitution in the intestine of HIV-infected patients

Whether and to what extent gut mucosal CD4(+) T cells of HIV-infected patients can be restored by combination antiretroviral therapy (cART) is not yet fully resolved. We studied absolute numbers, differentiation, and activation of mucosal CD4(+) T cells at different stages of HIV infection and assessed the effect of timing of cART initiation on this cell population. Mucosal CD4(+) T-cell numbers were severely reduced at all stages of chronic infection, but normal in patients with acute infection. In patients with initiation of cART during chronic HIV infection, mucosal CD4(+) T cells restored to less than half of the numbers in controls. However, in patients who initiated cART during acute HIV infection, mucosal CD4(+) T-cell numbers were fully preserved and markers of microbial translocation and inflammation reversed to normal. The proportion of mucosal effector memory CD4(+) T cells normalized only if cART was initiated at >350 CD4(+) T cells per μl blood but not with delayed treatment. In conclusion, mucosal CD4(+) T-cell numbers can be preserved if cART is initiated in acute HIV infection. In chronically HIV-infected patients, early cART improves mucosal CD4(+) T-cell differentiation but cannot prevent the persistent lack of total CD4(+) T cells.

Identification of novel HIV-1 dependency factors in primary CCR4(+)CCR6(+)Th17 cells via a genome-wide transcriptional approach

BACKGROUND

The HIV-1 infection is characterized by profound CD4(+) T cell destruction and a marked Th17 dysfunction at the mucosal level. Viral suppressive antiretroviral therapy restores Th1 but not Th17 cells. Although several key HIV dependency factors (HDF) were identified in the past years via genome-wide siRNA screens in cell lines, molecular determinants of HIV permissiveness in primary Th17 cells remain to be elucidated.

RESULTS

In an effort to orient Th17-targeted reconstitution strategies, we investigated molecular mechanisms of HIV permissiveness in Th17 cells. Genome-wide transcriptional profiling in memory CD4(+) T-cell subsets enriched in cells exhibiting Th17 (CCR4(+)CCR6(+)), Th1 (CXCR3(+)CCR6(-)), Th2 (CCR4(+)CCR6(-)), and Th1Th17 (CXCR3(+)CCR6(+)) features revealed remarkable transcriptional differences between Th17 and Th1 subsets. The HIV-DNA integration was superior in Th17 versus Th1 upon exposure to both wild-type and VSV-G-pseudotyped HIV; this indicates that post-entry mechanisms contribute to viral replication in Th17. Transcripts significantly enriched in Th17 versus Th1 were previously associated with the regulation of TCR signaling (ZAP-70, Lck, and CD96) and Th17 polarization (RORγt, ARNTL, PTPN13, and RUNX1). A meta-analysis using the NCBI HIV Interaction Database revealed a set of Th17-specific HIV dependency factors (HDFs): PARG, PAK2, KLF2, ITGB7, PTEN, ATG16L1, Alix/AIP1/PDCD6IP, LGALS3, JAK1, TRIM8, MALT1, FOXO3, ARNTL/BMAL1, ABCB1/MDR1, TNFSF13B/BAFF, and CDKN1B. Functional studies demonstrated an increased ability of Th17 versus Th1 cells to respond to TCR triggering in terms of NF-κB nuclear translocation/DNA-binding activity and proliferation. Finally, RNA interference studies identified MAP3K4 and PTPN13 as two novel Th17-specific HDFs.

CONCLUSIONS

The transcriptional program of Th17 cells includes molecules regulating HIV replication at multiple post-entry steps that may represent potential targets for novel therapies aimed at protecting Th17 cells from infection and subsequent depletion in HIV-infected subjects.

Gut commensal microbes do not represent a dominant antigenic source for continuous CD4+ T-cell activation during HIV-1 infection

Chronic immune activation is a hallmark of HIV-1 infection; specifically, the activation of T cells has predictive value for progression to AIDS. The majority of hyperactivated T cells are not HIV-specific and their antigenic specificities remain poorly understood. Translocation of gut luminal microbial products to systemic sites contributes to chronic immune activation during HIV-1 infection, but how it affects (TCR-dependent) immune activation remains elusive. We hypothesized that gut luminal antigens foster activation of CD4(+) T cells with specificities for commensal bacterial antigens, thereby contributing to the pool of activated CD4(+) T cells in the circulation of HIV-1 infected individuals. To test this hypothesis, we quantified the frequencies of gut microbe-specific CD4(+) T cells by cytokine production upon restimulation with selected gut commensal microbial antigens. Contrary to our hypothesis, we did not observe increased but rather decreased frequencies of gut microbe-specific CD4(+) T cells in HIV-1 infected individuals compared to healthy controls. We conclude that the increased activation status of circulating CD4(+) T cells in HIV-1 infected individuals is not driven by CD4(+) T cells with specificities for commensal bacterial antigens.

[Targeting and role of α4β7 integrin in the pathophysiology of IBD and HIV infection]

Integrins are a large family of heterodimeric cell adhesion molecules that are key regulators in multiple biological functions. They orchestrate cell-cell and cell-extracellular matrix (ECM) adhesive interactions from embryonic development to mature tissue function, and are thus involved in cell migration, proliferation, differentiation, and survival. As such, they are also involved in human diseases, such as thrombotic diseases, inflammation, cancer, fibrosis and infectious diseases. Integrins are exciting pharmacological targets because they are exposed on the cell surface. Indeed, several compounds have been developed that block integrins function, and five have been approved as therapeutic drugs for use in clinic. This review will detail the role of α4β7, an integrin of particular relevance for mucosal diseases such as IBD (inflammatory bowel disease) and also, as reported more recently, HIV infection.

Effect of Probiotic Supplement on Cytokine Levels in HIV-Infected Individuals: A Preliminary Study

Inflammation persists in patients infected with HIV. Reduction of inflammatory cytokines and microbial translocation might be one way that this could be managed. Purpose: The anti-inflammatory properties of certain probiotic strains prompted us to investigate whether a probiotic could reduce the inflammatory index of HIV-infected patients. Methods: The study involved 30 HIV+ males on antiretroviral therapy, who were given one bottle of fermented milk Yakult Light^® containing Lactobacillus casei Shirota (LcS) twice a day for four weeks. Results: The probiotic LcS was associated with an increase of T lymphocytes and a significant increase of CD56+ cells (p = 0.04). There was also a significant decrease of mRNA levels of TGFβ, IL-10 and IL-12 (p < 0.001) and IL-1β expression (p < 0.001) and an increase of serum IL-23 (p = 0.03). In addition, decreased inflammation and cardiovascular risk were observed, as shown by a reduction of cystatin C (p < 0.001). Conclusions: These data provide preliminary evidence that probiotic supplementation may modulate certain immunological parameters and some of the cytokines that were analyzed. Thus, we propose that LcS may be an inexpensive and practical strategy to support the immune function of HIV+ patients.

Probiotics Reduce Inflammation in Antiretroviral Treated, HIV-Infected Individuals: Results of the "Probio-HIV" Clinical Trial

Background

HIV infection results in damage to the gastrointestinal (GI) tract, microbial translocation and immune activation. These are not completely normalized with combined antiretroviral therapy (cART). Moreover, increate morbidity and mortality of cART-treated HIV-infected individuals is associated with inflammation.

Methods

In order to enhance GI tract immunity, we recruited and treated 20 HIV-infected humans with cART supplemented with probiotics and followed inflammation and immunological parameters (clinical trial number NCT02164344). 11 HIV seronegative subjects were included as control group. The enumeration of CD4+, CD8+, CD38+ and HLA-DR+ lymphocytes were evaluated on peripheral blood; HIV-RNA levels, sCD14, d-dimer, C-reactive protein (CRP) high sensitivity C-reactive protein (hsCRP), IL-6 and Lipopolysaccharide Binding Protein (LBP) were assayed on plasma.

Results

We observe that cART does not normalize the levels of immune activation in HIV positive patients anyway inflammation and markers of microbial translocation were significantly reduced with probiotic supplementation. Patients show a clear and statistically significant reduction in the levels of immune activation on CD4 T-lymphocytes, for both markers CD38 and HLA-DR and their simultaneous expression, LBP and hsCRP plasma levels after probiotic diet supplementation settling to values comparable to controls.

Conclusions

Supplementing cART with probiotics in HIV-infected individuals may improve GI tract immunity and there by mitigate inflammatory sequelae, ultimately improving prognosis.

Trial Registration

ClinicalTrials.gov NCT02164344

Impact of HIV infection and smoking on lung immunity and related disorders

HIV-infected persons not only have higher rates of smoking than the general population, but are also unusually vulnerable to the associated adverse health effects, both infective and noninfective in origin. Indeed, in the setting of well-organised care and availability of highly active antiretroviral therapy, HIV-infected smokers lose more life-years to smoking than to HIV infection per se, presenting a major challenge to healthcare providers. Not surprisingly, the respiratory system is particularly susceptible to the damaging interactive chronic inflammatory and immunosuppressive effects of HIV and smoking, intensifying the risk of the development of opportunistic infections, as well as lung cancer and obstructive lung disorders. The impact of smoking on the immunopathogenesis and frequencies of these respiratory conditions in the setting of HIV infection, as well as on the efficacy of antiretroviral therapy, represent the primary focus of this review.

The role of serum I-FABP concentration in assessment of small intestine mucosa among HIV-infected patients

Objectives:

The intestinal fatty acid binding protein (I-FABP) is a useful marker in the assessment of damages and inflammation to the small intestinal mucosa. We have investigated the influence of HIV infections and antiretroviral treatment on the small intestine mucosa aided by the evaluation of I-FABP concentration levels.

Methods:

We included in the study: 31 HIV-infected patients with antiretroviral therapy (ART) treatment (T), 32 HIV-infected patients not treated with ART (NT), and 18 healthy volunteers as a control group. The concentrations of I-FABP were measured in serum using a sandwich enzyme immunoassay kit: Human I-FABP.

Results:

The median level of I-FABP in the serum of HIV-infected patients was 2.10 ± 2.56 ng/mL and did not significantly differ between T and NT (2.32 ± 2.69 ng/mL vs. 1.89 ± 2.45 ng/mL). However, the I-FABP serum level was significantly higher in HIV-infected patients when compared to the group control (2.10 ± 2.56 ng/mL vs. 1.26 ± 1.18 ng/mL; P = 0.048). We recorded a correlation for treated HIV-infected patients between Viral load and I-FABP serum level (r = −0.66; P <0.05).

Conclusions:

Elevated serum I-FABP level in HIV-infected patients confirm that HIV causes damage to the intestinal mucosa. I-FAB is a useful marker in the assessment of intestinal damage in HIV-infected patients.

The Gut Microbiota Regulates Intestinal CD4 T Cells Expressing RORγt and Controls Metabolic Disease

A high-fat diet (HFD) induces metabolic disease and low-grade metabolic inflammation in response to changes in the intestinal microbiota through as-yet-unknown mechanisms. Here, we show that a HFD-derived ileum microbiota is responsible for a decrease in Th17 cells of the lamina propria in axenic colonized mice. The HFD also changed the expression profiles of intestinal antigen-presenting cells and their ability to generate Th17 cells in vitro. Consistent with these data, the metabolic phenotype was mimicked in RORγt-deficient mice, which lack IL17 and IL22 function, and in the adoptive transfer experiment of T cells from RORγt-deficient mice into Rag1-deficient mice. We conclude that the microbiota of the ileum regulates Th17 cell homeostasis in the small intestine and determines the outcome of metabolic disease.

Altered metabolism of gut microbiota contributes to chronic immune activation in HIV-infected individuals

Altered interplay between gut mucosa and microbiota during treated HIV infection may possibly contribute to increased bacterial translocation and chronic immune activation, both of which are predictors of morbidity and mortality. Although a dysbiotic gut microbiota has recently been reported in HIV+ individuals, the metagenome gene pool associated with HIV infection remains unknown. The aim of this study is to characterize the functional gene content of gut microbiota in HIV+ patients and to define the metabolic pathways of this bacterial community, which is potentially associated with immune dysfunction. We determined systemic markers of innate and adaptive immunity in a cohort of HIV-infected individuals on successful antiretroviral therapy without comorbidities and in healthy non-HIV-infected subjects. Metagenome sequencing revealed an altered functional profile, with enrichment of the genes involved in various pathogenic processes, lipopolysaccharide biosynthesis, bacterial translocation, and other inflammatory pathways. In contrast, we observed depletion of genes involved in amino acid metabolism and energy processes. Bayesian networks showed significant interactions between the bacterial community, their altered metabolic pathways, and systemic markers of immune dysfunction. This study reveals altered metabolic activity of microbiota and provides novel insight into the potential host-microbiota interactions driving the sustained inflammatory state in successfully treated HIV-infected patients.

Low expression of activation marker CD69 and chemokine receptors CCR5 and CXCR3 on memory T cells after 2009 H1N1 influenza A antigen stimulation in vitro following H1N1 vaccination of HIV-infected individuals

Unlike well-studied antibody responses to pandemic 2009 H1N1 influenza A virus vaccines in human immunodeficiency virus-infected (HIV+) individuals, less well understood are cell-mediated immune (CMI) responses to this antigen in this susceptible population. We investigated such influenza-specific CMI responses in 61 HIV+ individuals and in 20 HIV-negative (HIV-) healthy controls. Each was vaccinated with a single licensed dose of inactivated, split-virion vaccine comprised of the influenza A/California/7/2009 (H1N1) virus-like strain. Cells collected just prior to vaccination and at 1 and 3 months afterwards were stimulated in vitro with dialyzed vaccine antigen and assayed by flow cytometry for cytokines TNF-α, IFN-γ, IL-2, and IL-10, for degranulation marker CD107a, as well as phenotypes of memory T-cell subpopulations. Comparable increases of cytokine-producing and CD107a-expressing T cells were observed in both HIV+ subjects and healthy HIV-controls. However, by 3 months post-vaccination, in vitro antigen stimulation of peripheral blood mononuclear cells induced greater expansion in controls of both CD4 and CD8 central memory and effector memory T cells, as well as higher expression of the activation marker CD69 and chemokine receptors CCR5 and CXCR3 than in HIV+ subjects. We concluded CD4+ and CD8+ memory T cells produce cytokines at comparable levels in both groups, whereas the expression after in vitro stimulation of molecules critical for cell migration to infection sites are lower in the HIV+ than in comparable controls. Further immunization strategies against influenza are needed to improve the CMI responses in people living with HIV.

HIV therapeutic vaccines: moving towards a functional cure

Anti-viral T-cell and B-cell responses play a crucial role in suppressing HIV and SIV replication during chronic infection. However, these infections are rarely controlled by the host immune response, and most infected individuals need lifelong antiretroviral therapy (ART). Recent advances in our understanding of how anti-HIV immune responses are elicited and regulated prompted a surge of interest in harnessing these responses to reduce the HIV 'residual disease' that is present in ART-treated HIV-infected individuals. Novel approaches that are currently explored include both conventional therapeutic vaccines (i.e., active immunization strategies using HIV-derived immunogens) as well as the use of checkpoint blockers such as anti-PD-1 antibodies. These approaches appear promising as key components of complex therapeutic strategies aimed at curing HIV infection.

Impaired Th17 polarization of phenotypically naive CD4(+) T-cells during chronic HIV-1 infection and potential restoration with early ART

Background

Depletion of mucosal Th17 cells during HIV/SIV infections is a major cause for microbial translocation, chronic immune activation, and disease progression. Mechanisms contributing to Th17 deficit are not fully elucidated. Here we investigated alterations in the Th17 polarization potential of naive-like CD4⁺ T-cells, depletion of Th17-commited subsets during HIV pathogenesis, and Th17 restoration in response to antiretroviral therapy (ART).

Results

Peripheral blood CD4⁺ T-cells expressing a naive-like phenotype (CD45RA⁺CCR7⁺) from chronically HIV-infected subjects receiving ART (CI on ART; median CD4 counts 592 cells/μl; viral load: <50 HIV-RNA copies/ml; time since infection: 156 months) compared to uninfected controls (HIV-) were impaired in their survival and Th17 polarization potential in vitro. In HIV- controls, IL-17A-producing cells mainly originated from naive-like T-cells with a regulatory phenotype (nTregs: CD25^highCD127⁻FoxP3⁺) and from CD25⁺CD127⁺FoxP3⁻ cells (DP, double positive). Th17-polarized conventional naive CD4⁺ T-cells (nT: CD25⁻CD127⁺FoxP3⁻) also produced IL17A, but at lower frequency compared to nTregs and DP. In CI on ART subjects, the frequency/counts of nTreg and DP were significantly diminished compared to HIV- controls, and this paucity was further associated with decreased proportions of memory T-cells producing IL-17A and expressing Th17 markers (CCR6⁺CD26⁺CD161⁺, mTh17). nTregs and DP compared to nT cells harbored superior levels of integrated/non-integrated HIV-DNA in CI on ART subjects, suggesting that permissiveness to integrative/abortive infection contributes to impaired survival and Th17 polarization of lineage-committed cells. A cross-sectional study in CI on ART subjects revealed that nTregs, DP and mTh17 counts were negatively correlated with the time post-infection ART was initiated and positively correlated with nadir CD4 counts. Finally, a longitudinal analysis in a HIV primary infection cohort demonstrated a tendency for increased nTreg, DP, and mTh17 counts with ART initiation during the first year of infection.

Conclusions

These results support a model in which the paucity of phenotypically naive nTregs and DP cells, caused by integrative/abortive HIV infection and/or other mechanisms, contributes to Th17 deficiency in HIV-infected subjects. Early ART initiation, treatment intensification with integrase inhibitors, and/or other alternative interventions aimed at preserving/restoring the pool of cells prone to acquire Th17 functions may significantly improve mucosal immunity in HIV-infected subjects.

Electronic supplementary material

The online version of this article (doi:10.1186/s12977-015-0164-6) contains supplementary material, which is available to authorized users.

Site-specific differences in T cell frequencies and phenotypes in the blood and gut of HIV-uninfected and ART-treated HIV+ adults

Gastrointestinal T lymphocytes are critical for mucosal immunity and HIV pathogenesis, yet little is known about normal T cell numbers and phenotypes in different regions of the gut, or the degree to which ART can restore levels to those of HIV-uninfected individuals. To investigate these questions, we measured T cell frequencies and markers of memory, activation, anergy, and homing in the blood, ileum, and rectum of HIV- and ART-suppressed HIV+ adults. In HIV- individuals, T cell frequencies and phenotypes differed significantly between sites. Compared to HIV- adults, HIV+ adults had lower absolute CD4+T cell counts in the ileal lamina propria and lower relative CD4+T cell counts in the blood and ileum. In the gut, HIV+ adults had a higher proportion of CD38+ CD4+T cells, a lower proportion of terminally-differentiated effector cells, and, in the rectum, a higher proportion of CTLA-4+ CD4+T cells. In HIV+ individuals, relative CD4+T cell numbers in the ileum correlated with the proportion of CTLA-4+ CD4+T cells, whereas in the rectum, they tended to correlate with the proportion of circulating CD4+T cells expressing α4β7 or CCR6. Mechanisms of T cell reconstitution may differ throughout the gut, with homing contributing more in the rectum while ileal reconstitution is associated with mucosal CD4+T cell anergy.

Effects of HIV-1 Tat on enteric neuropathogenesis

The gastrointestinal (GI) tract presents a major site of immune modulation by HIV, resulting in significant morbidity. Most GI processes affected during HIV infection are regulated by the enteric nervous system. HIV has been identified in GI histologic specimens in up to 40% of patients, and the presence of viral proteins, including the trans-activator of transcription (Tat), has been reported in the gut indicating that HIV itself may be an indirect gut pathogen. Little is known of how Tat affects the enteric nervous system. Here we investigated the effects of the Tat protein on enteric neuronal excitability, proinflammatory cytokine release, and its overall effect on GI motility. Direct application of Tat (100 nm) increased the number of action potentials and reduced the threshold for action potential initiation in isolated myenteric neurons. This effect persisted in neurons pretreated with Tat for 3 d (19 of 20) and in neurons isolated from Tat(+) (Tat-expressing) transgenic mice. Tat increased sodium channel isoforms Nav1.7 and Nav1.8 levels. This increase was accompanied by an increase in sodium current density and a leftward shift in the sodium channel activation voltage. RANTES, IL-6, and IL-1β, but not TNF-α, were enhanced by Tat. Intestinal transit and cecal water content were also significantly higher in Tat(+) transgenic mice than Tat(-) littermates (controls). Together, these findings show that Tat has a direct and persistent effect on enteric neuronal excitability, and together with its effect on proinflammatory cytokines, regulates gut motility, thereby contributing to GI dysmotilities reported in HIV patients.

Influence of immune activation and inflammatory response on cardiovascular risk associated with the human immunodeficiency virus

Patients infected with the human immunodeficiency virus (HIV) have an increased cardiovascular risk. Although initially this increased risk was attributed to metabolic alterations associated with antiretroviral treatment, in recent years, the attention has been focused on the HIV disease itself. Inflammation, immune system activation, and endothelial dysfunction facilitated by HIV infection have been identified as key factors in the development and progression of atherosclerosis. In this review, we describe the epidemiology and pathogenesis of cardiovascular disease in patients with HIV infection and summarize the latest knowledge on the relationship between traditional and novel inflammatory, immune activation, and endothelial dysfunction biomarkers on the cardiovascular risk associated with HIV infection.

Binding of HIV-1 virions to α4β 7 expressing cells and impact of antagonizing α4β 7 on HIV-1 infection of primary CD4+ T cells

HIV-1 envelope glycoprotein is reported to interact with α4β7, an integrin mediating the homing of lymphocytes to gut-associated lymphoid tissue, but the significance of α4β7 in HIV-1 infection remains controversial. Here, using HIV-1 strain BaL, the gp120 of which was previously shown to be capable of interacting with α4β7, we demonstrated that α4β7 can mediate the binding of whole HIV-1 virions to α4β7-expressing transfectants. We further constructed a cell line stably expressing α4β7 and confirmed the α4β7-mediated HIV-1 binding. In primary lymphocytes with activated α4β7 expression, we also observed significant virus binding which can be inhibited by an anti-α4β7 antibody. Moreover, we investigated the impact of antagonizing α4β7 on HIV-1 infection of primary CD4(+) T cells. In α4β7-activated CD4(+) T cells, both anti-α4β7 antibodies and introduction of short-hairpin RNAs specifically targeting α4β7 resulted in a decreased HIV-1 infection. Our findings indicate that α4β7 may serve as an attachment factor at least for some HIV-1 strains. The established approach provides a promising means for the investigation of other viral strains to understand the potential roles of α4β7 in HIV-1 infection.

CD161+ MAIT cells are severely reduced in peripheral blood and lymph nodes of HIV-infected individuals independently of disease progression

Mucosal-associated invariant T (MAIT) cells are characterized by the combined expression of the semi-invariant T cell receptor (TCR) Vα7.2, the lectin receptor CD161, as well as IL-18R, and play an important role in antibacterial host defense of the gut. The current study characterized CD161⁺ MAIT and CD161^–TCRVα7.2⁺ T cell subsets within a large cohort of HIV patients with emphasis on patients with slow disease progression and elite controllers. Mononuclear cells from blood and lymph node samples as well as plasma from 63 patients and 26 healthy donors were analyzed by multicolor flow cytometry and ELISA for IL-18, sCD14 and sCD163. Additionally, MAIT cells were analyzed after in vitro stimulation with different cytokines and/or fixed E.coli. Reduced numbers of CD161⁺ MAIT cells during HIV infection were detectable in the blood and lymph nodes of all patient groups, including elite controllers. CD161⁺ MAIT cell numbers did not recover even after successful antiretroviral treatment. The loss of CD161⁺ MAIT cells was correlated with higher levels of MAIT cell activation; an increased frequency of the CD161^–TCRVα7.2⁺T cell subset in HIV infection was observed. In vitro stimulation of MAIT cells with IL-18 and IL-12, IL-7 and fixed E.coli also resulted in a rapid and additive reduction of the MAIT cell frequency defined by CD161, IL-18R and CCR6. In summary, the irreversible reduction of the CD161⁺ MAIT cell subset seems to be an early event in HIV infection that is independent of later stages of the disease. This loss appears to be at least partially due to the distinctive vulnerability of MAIT cells to the pronounced stimulation by microbial products and cytokines during HIV-infection.

Reconstitution of intestinal CD4 and Th17 T cells in antiretroviral therapy suppressed HIV-infected subjects: implication for residual immune activation from the results of a clinical trial

Introduction

During HIV infection the severe depletion of intestinal CD4⁺ T-cells is associated with microbial translocation, systemic immune activation, and disease progression. This study examined intestinal and peripheral CD4⁺ T-cell subsets reconstitution under combined antiretroviral therapy (cART), and systemic immune activation markers.

Methods

This longitudinal single-arm pilot study evaluates CD4⁺ T cells, including Th1 and Th17, in gut and blood and soluble markers for inflammation in HIV-infected individuals before (M0) and after eight (M8) months of cART. From January 2010 to December 2011, 10 HIV-1 naïve patients were screened and 9 enrolled. Blood and gut CD4⁺ T-cells subsets and cellular immune activation were determined by flow-cytometry and plasma soluble CD14 by ELISA. CD4⁺ Th17 cells were detected in gut biopsies by immunohistochemistry. Microbial translocation was measured by limulus-amebocyte-lysate assay to detect bacterial lipopolysaccharide (LPS) and PCR Real Time to detect plasma bacterial 16S rDNA.

Results

Eight months of cART increased intestinal CD4⁺ and Th17 cells and reduced levels of T-cell activation and proliferation. The magnitude of intestinal CD4⁺ T-cell reconstitution correlated with the reduction of plasma LPS. Importantly, the magnitude of Th17 cells reconstitution correlated directly with blood CD4⁺ T-cell recovery.

Conclusion

Short-term antiretroviral therapy resulted in a significant increase in the levels of total and Th17 CD4⁺ T-cells in the gut mucosa and in decline of T-cell activation. The observation that pre-treatment levels of CD4⁺ and of CD8⁺ T-cell activation are predictors of the magnitude of Th17 cell reconstitution following cART provides further rationale for an early initiation of cART in HIV-infected individuals.

Trial Registration

ClinicalTrials.gov NCT02097381

Mucosal addressin cell adhesion molecule-1 of rhesus macaques: molecular cloning, expression, and alteration after viral infection

BACKGROUND

Mucosal addressin cell adhesion molecule-1 (MAdCAM-1), a member of the immunoglobulin superfamily, is essential for gut-specific homing of leukocytes; however, it has not been well characterized in rhesus macaques.

AIMS

To obtain the complete nucleotide sequence of rhesus macaque MAdCAM-1 cDNA and determine its distribution in gut-associated lymphoid tissues (GALT) and its alteration in duodenal mucosa after simian/human immunodeficiency virus (SHIV) infection.

METHODS

MAdCAM-1 cDNA was cloned from the colon mucosa of a rhesus macaque by 3'- and 5'-RACE. The distribution and abundance of MAdCAM-1 mRNA in the GALT were examined by nested and real-time RT-PCR. The alterations of MAdCAM-1 mRNA levels in SHIV-infected duodenal mucosa were determined by real-time RT-PCR.

RESULTS

The nucleotide sequence of rhesus macaque MAdCAM-1 cDNA (1,503 bp nucleotides) including the 5'- and 3'-untranslated regions was obtained. The coding region (1,086 bp) showed 87.56% and the Ig-like domain 1, 2 and TM + cytoplasmic domains showed >93% nucleotide sequence identity to that of humans. Like humans, rhesus macaques lacked MAdCAM-1 IgA1-like domain, which could be a common feature for all primates appeared later during vertebrate evolution. Two species of MAdCAM-1 mRNA were detected and high-level transcripts were observed primarily in the GALT. The full-length MAdCAM-1 expressed in vitro could bind to human α4β7. MAdCAM-1 mRNA levels were statistically significantly reduced in SHIV-infected duodenal mucosa.

CONCLUSIONS

These data provided a basis for using rhesus macaques in pathological and therapeutic studies on leukocyte homing related diseases such as inflammatory bowel disease and HIV/AIDS.

Progressive proximal-to-distal reduction in expression of the tight junction complex in colonic epithelium of virally-suppressed HIV+ individuals

Effective antiretroviral therapy (ART) dramatically reduces AIDS-related complications, yet the life expectancy of long-term ART-treated HIV-infected patients remains shortened compared to that of uninfected controls, due to increased risk of non-AIDS related morbidities. Many propose that these complications result from translocated microbial products from the gut that stimulate systemic inflammation--a consequence of increased intestinal paracellular permeability that persists in this population. Concurrent intestinal immunodeficiency and structural barrier deterioration are postulated to drive microbial translocation, and direct evidence of intestinal epithelial breakdown has been reported in untreated pathogenic SIV infection of rhesus macaques. To assess and characterize the extent of epithelial cell damage in virally-suppressed HIV-infected patients, we analyzed intestinal biopsy tissues for changes in the epithelium at the cellular and molecular level. The intestinal epithelium in the HIV gut is grossly intact, exhibiting no decreases in the relative abundance and packing of intestinal epithelial cells. We found no evidence for structural and subcellular localization changes in intestinal epithelial tight junctions (TJ), but observed significant decreases in the colonic, but not terminal ileal, transcript levels of TJ components in the HIV+ cohort. This result is confirmed by a reduction in TJ proteins in the descending colon of HIV+ patients. In the HIV+ cohort, colonic TJ transcript levels progressively decreased along the proximal-to-distal axis. In contrast, expression levels of the same TJ transcripts stayed unchanged, or progressively increased, from the proximal-to-distal gut in the healthy controls. Non-TJ intestinal epithelial cell-specific mRNAs reveal differing patterns of HIV-associated transcriptional alteration, arguing for an overall change in intestinal epithelial transcriptional regulation in the HIV colon. These findings suggest that persistent intestinal epithelial dysregulation involving a reduction in TJ expression is a mechanism driving increases in colonic permeability and microbial translocation in the ART-treated HIV-infected patient, and a possible immunopathogenic factor for non-AIDS related complications.

M cell-targeting strategy facilitates mucosal immune response and enhances protection against CVB3-induced viral myocarditis elicited by chitosan-DNA vaccine

Efficient delivery of antigen to mucosal associated lymphoid tissue is a first and critical step for successful induction of mucosal immunity by vaccines. Considering its potential transcytotic capability, M cell has become a more and more attractive target for mucosal vaccines. In this research, we designed an M cell-targeting strategy by which mucosal delivery system chitosan (CS) was endowed with M cell-targeting ability via conjugating with a CPE30 peptide, C terminal 30 amino acids of clostridium perfringens enterotoxin (CPE), and then evaluated its immune-enhancing ability in the context of coxsackievirus B3 (CVB3)-specific mucosal vaccine consisting of CS and a plasmid encoding CVB3 predominant antigen VP1. It had shown that similar to CS-pVP1, M cell-targeting CPE30-CS-pVP1 vaccine appeared a uniform spherical shape with about 300 nm diameter and +22 mV zeta potential, and could efficiently protect DNA from DNase I digestion. Mice were orally immunized with 4 doses of CPE30-CS-pVP1 containing 50 μg pVP1 at 2-week intervals and challenged with CVB3 4 weeks after the last immunization. Compared with CS-pVP1 vaccine, CPE30-CS-pVP1 vaccine had no obvious impact on CVB3-specific serum IgG level and splenic T cell immune responses, but significantly increased specific fecal SIgA level and augmented mucosal T cell immune responses. Consequently, much milder myocarditis and lower viral load were witnessed in CPE30-CS-pVP1 immunized group. The enhanced immunogenicity and immunoprotection were associated with the M cell-targeting ability of CPE30-CS-pVP1 which improved its mucosal uptake and transcytosis. Our findings indicated that CPE30-CS-pVP1 may represent a novel prophylactic vaccine against CVB3-induced myocarditis, and this M cell-targeting strategy indeed could be applied as a promising and universal platform for mucosal vaccine development.

Immune activation is associated with increased gut microbial translocation in treatment-naive, HIV-infected children in a resource-limited setting

BACKGROUND

Gut damage resulting in microbial translocation (MT) is considered a major cause of immune activation (IA) in HIV infection, but data in children are limited, particularly in the absence of antiretroviral therapy.

METHODS

Sixty perinatally HIV-infected, antiretroviral therapy-naive children, aged 2-12 years, were evaluated for plasma levels of lipopolysaccharide, DNA sequences encoding bacterial 16 second ribosomal DNA (16S rDNA) and soluble CD14 concurrently with markers of CD4 and CD8 T-cell IA and immune exhaustion (IE), CD4 counts, and plasma viral load. At study entry, participants were classified into immune categories (ICs): IC1 (CD4% > 25), IC2 (CD4% 15-25), and IC3 (CD4% < 15). Age-matched HIV-uninfected children served as controls. Data were evaluated at study entry and at 12 months.

RESULTS

Levels of MT, IA, and IE were increased in patients as compared with controls, were highest in patients in IC3 group, and did not change over 12 months. MT products lipopolysaccharide and 16S rDNA correlated with each other and each correlated with plasma viral load, soluble CD14, and T-cell IA and IE. There was a correlation of IA with IE. CD4 counts and percentage were inversely correlated with MT products and underlying CD4 activation.

CONCLUSIONS

In a natural history cohort of HIV-infected children not on therapy, MT was more pronounced in the most severely immunocompromised patients and was associated with IA. Strategies to reduce MT may help to reduce IA and prevent CD4 depletion.