Plasma levels of bacterial DNA correlate with immune activation and the magnitude of immune restoration in persons with antiretroviral-treated HIV infection

Short Communication: Lack of Effect of Maraviroc Intensification on Blood and Gut Reservoir

We show that intensification of treatment with maraviroc in patients chronically infected with HIV-1 receiving successful long-term antiretroviral therapy was not associated with improvements in HIV-related morbidity, HIV reservoir, microbial translocation, immune activation, or immune exhaustion in either gut or peripheral blood. The measurement of reservoir in both gut and blood longitudinally contributes to a paucity of data in the area.

Marked Enteropathy in an Accelerated Macaque Model of AIDS

Enteropathy in HIV infection is not eliminated with combination antiretroviral therapy and is possibly linked to microbial translocation. We used a rapidly progressing SIV/pigtailed macaque model of HIV to examine enteropathy and microbial translocation. Histologic evidence of intestinal disease was observed in only half of infected macaques during late-stage infection (LSI). Combination antiretroviral therapy initiated during acute infection prevented intestinal disease. In the ileum and colon, enteropathy was associated with increased caspase-3 staining, decreased CD3⁺ T cells, and increased SIV-infected cells. CD3⁺ T cells were preserved in LSI animals without intestinal disease, and levels of CD3 staining in all LSI animals strongly correlated with the number of infected cells in the intestine and plasma viral load. Unexpectedly, there was little evidence of microbial translocation as measured by soluble CD14, soluble CD163, lipopolysaccharide binding protein, and microbial 16s ribosomal DNA. Loss of epithelial integrity indicated by loss of the tight junction protein claudin-3 was not observed during acute infection despite significantly fewer T cells. Claudin-3 was reduced in LSI animals with severe intestinal disease but did not correlate with increased microbial translocation. LSI animals that did not develop intestinal disease had increased T-cell intracytoplasmic antigen 1-positive cytotoxic T lymphocytes, suggesting a robust adaptive cytotoxic T-lymphocyte response may, in part, confer resilience to SIV-induced intestinal damage.

Integrative Analysis of Immunological Data to Explore Chronic Immune T-Cell Activation in Successfully Treated HIV Patients

OBJECTIVES

To unravel the complex relationships between cytomegalovirus-induced-, autoimmune-induced responses, microbial translocation and chronic immune activation (CIA) in successfully treated HIV-infected patients and to explore the mediating role of alpha-interferon in these processes.

DESIGN

Cross-sectional study nested in the ANRS CO3 Aquitaine Cohort, a prospective hospital-based cohort of HIV-1-infected patients in South-Western France.

METHODS

Patients initiated antiretroviral therapy between 2005 and 2008 and were treated with sustained virological suppression for at least two years. CIA was defined by the percentage of HLA-DR+/CD38+ among CD8+T-cells. Integrative analyses were performed using structural equation modelling (SEM).

RESULTS

The main analysis was performed in 57 HLA-A*0201 positive patients, due to availability of percentages of actin-, vimentin-, lamin-specific CD8+T-cells (HLA-A2-restricted tests) to further characterize autoimmune response. Cytomegalovirus-induced response was assessed by Quantiferon and pp-65 ELISPOT. SEM revealed a direct effect of cytomegalovirus-induced response on CIA (standardized estimate βstd = 0.56, p-value = 0.0004). The effect of autoimmune-induced response on CIA was indirect through alpha-interferon pathway, assessed by expression levels of 5 alpha-interferon-stimulated genes ADAR, ISG15, IFIT1, Mx1 and OAS1 (effect of autoimmune response on alpha-interferon: βstd = 0.36, p-value = 0.0401; effect of alpha-interferon on CIA: βstd = 0.39, p-value = 0.0044). There was no direct effect of autoimmune-induced response on CIA (p-value = 0.3169). Microbial translocation as measured by 16SrDNA and sCD14 in plasma was not associated with CIA. Results were consistent in 142 patients in whom cytomegalovirus and auto-immunity responses were measured by Quantiferon and anti-nuclear antibodies, respectively. All analyses performed in HLA-A*0201 positive patients and in the overall population revealed a significant effect of IFN-α latent variable on CIA.

CONCLUSION

The role of cytomegalovirus-induced response on CIA was confirmed as well as the involvement of alpha-interferon on CIA. The indirect effect of auto-immunity response on CIA revealed through the alpha-interferon pathway requires further investigation to confirm the potential role of auto-immunity for CIA in HIV-infected patients.

Impact of probiotic Saccharomyces boulardii on the gut microbiome composition in HIV-treated patients: A double-blind, randomised, placebo-controlled trial

Dysbalance in gut microbiota has been linked to increased microbial translocation, leading to chronic inflammation in HIV-patients, even under effective HAART. Moreover, microbial translocation is associated with insufficient reconstitution of CD4+T cells, and contributes to the pathogenesis of immunologic non-response. In a double-blind, randomised, placebo-controlled trial, we recently showed that, compared to placebo, 12 weeks treatment with probiotic Saccharomyces boulardii significantly reduced plasma levels of bacterial translocation (Lipopolysaccharide-binding protein or LBP) and systemic inflammation (IL-6) in 44 HIV virologically suppressed patients, half of whom (n = 22) had immunologic non-response to antiretroviral therapy (<270 CD4+Tcells/μL despite long-term suppressed viral load). The aim of the present study was to investigate if this beneficial effect of the probiotic Saccharomyces boulardii is due to modified gut microbiome composition, with a decrease of some species associated with higher systemic levels of microbial translocation and inflammation. In this study, we used 16S rDNA gene amplification and parallel sequencing to analyze the probiotic impact on the composition of the gut microbiome (faecal samples) in these 44 patients randomized to receive oral supplementation with probiotic or placebo for 12 weeks. Compared to the placebo group, in individuals treated with probiotic we observed lower concentrations of some gut species, such as those of the Clostridiaceae family, which were correlated with systemic levels of bacterial translocation and inflammation markers. In a sub-study of these patients, we observed significantly higher parameters of microbial translocation (LBP, soluble CD14) and systemic inflammation in immunologic non-responders than in immunologic responders, which was correlated with a relative abundance of specific gut bacterial groups (Lachnospiraceae genus and Proteobacteria). Thus, in this work, we propose a new therapeutic strategy using the probiotic yeast S. boulardii to modify gut microbiome composition. Identifying pro-inflammatory species in the gut microbiome could also be a useful new marker of poor immune response and a new therapeutic target.

Effects of atorvastatin on biomarkers of immune activation, inflammation, and lipids in virologically suppressed, human immunodeficiency virus-1-infected individuals with low-density lipoprotein cholesterol <130 mg/dL (AIDS Clinical Trials Group Study A5275)

BACKGROUND

Persistent immune activation and inflammation in virologically suppressed human immunodeficiency virus (HIV) infection are linked to excess cardiovascular risk.

OBJECTIVE

To evaluate atorvastatin as a strategy to reduce cardiovascular risk.

METHODS

A5275 was a multicenter, prospective, randomized, double-blind, placebo-controlled, cross-over pilot study of atorvastatin (10 mg/day for 4 weeks then 20 mg/day for 16 weeks) with a planned enrollment of 97 HIV-infected participants ≥18 years old, receiving boosted protease inhibitor-based antiretroviral therapy for ≥6 months, with plasma HIV-1 RNAs below limits of quantification ≥180 days, and fasting low-density lipoprotein (LDL) cholesterol ≥70 and <130 mg/dL. Primary endpoints were differences of changes ([week 44-week 24]-[week 20-baseline]) in CD4+ and CD8+ T-lymphocyte activation (% CD38+/DR+) and plasma levels of IL-6 and D-dimer. Arms were compared using the Wilcoxon rank-sum tests and also summarized changes pre-to-post atorvastatin treatment. Analyses were as-treated.

RESULTS

Ninety-eight participants were enrolled at 31 U S sites and 73 completed study treatment. Atorvastatin treatment did not decrease T-lymphocyte or monocyte activation, circulating biomarker levels (interleukin-6, D-dimer, soluble CD14, soluble CD163, monocyte chemoattractant protein-1, interferon-gamma-induced protein-10, high-sensitivity C-reactive protein, CD40L, and P-selectin) or white blood cell Krüppel-like Factor 2/4 messenger RNA levels. Pre-to-post atorvastatin reductions in calculated LDL (-38%), oxidized-LDL (-33%), and lipoprotein-associated phospholipase A2 (-31%) were significant (P < .01).

CONCLUSION

In virologically suppressed individuals with HIV infection, atorvastatin did not significantly decrease levels of soluble or cellular biomarkers of immune activation and inflammation but resulted in robust reductions in LDL cholesterol, oxLDL, and lipoprotein-associated phospholipase A2, biomarkers associated with cardiovascular risk.

Effect of Antiretroviral Therapy on the Memory and Activation Profiles of B Cells in HIV-Infected African Women

Human immunodeficiency virus infection induces a wide range of effects in B cells, including skewed memory cell differentiation, compromised B cell function, and hypergammaglobulinemia. However, data on the extent to which these B cell abnormalities can be reversed by antiretroviral therapy (ART) are limited. To investigate the effect of ART on B cells, the activation (CD86) and differentiation (IgD, CD27, and CD38) profiles of B cells were measured longitudinally in 19 HIV-infected individuals before (median, 2 mo) and after ART initiation (median, 12 mo) and compared with 19 age-matched HIV-uninfected individuals using flow cytometry. Twelve months of ART restored the typical distribution of B cell subsets, increasing the proportion of naive B cells (CD27^-IgD⁺CD38^-) and concomitantly decreasing the immature transitional (CD27^-IgD⁺CD38⁺), unswitched memory (CD27⁺IgD⁺CD38^-), switched memory (CD27⁺IgD^-CD38^- or CD27^-IgD^-CD38^-), and plasmablast (CD27⁺IgD^-CD38^high) subsets. However, B cell activation was only partially normalized post-ART, with the frequency of activated B cells (CD86⁺CD40⁺) reduced compared with pre-ART levels (p = 0.0001), but remaining significantly higher compared with HIV-uninfected individuals (p = 0.0001). Interestingly, unlike for T cell activation profiles, the extent of B cell activation prior to ART did not correlate with HIV plasma viral load, but positively associated with plasma sCD14 levels (p = 0.01, r = 0.58). Overall, ART partially normalizes the skewed B cell profiles induced by HIV, with some activation persisting. Understanding the effects of HIV on B cell dysfunction and restoration following ART may provide important insights into the mechanisms of HIV pathogenesis.

Chronic distress and the vulnerable host: a new target for HIV treatment and prevention?

Pathologic stress (distress) disturbs immune, cardiovascular, metabolic, and behavioral homeostasis. Individuals living with HIV and those at risk are vulnerable to stress disorders. Corticotropin-releasing hormone (CRH) is critical in neuroendocrine immune regulation. CRH, a neuropeptide, is distributed in the central and peripheral nervous systems and acts principally on CRH receptor type 1 (CRHR1). CRH in the brain modulates neuropsychiatric disorders. CRH and stress modulation of immunity is two-pronged; there is a direct action on hypothalamic-pituitary-adrenal secretion of glucocorticoids and through immune organ sympathetic innervation. CRH is a central and systemic proinflammatory cytokine. Glucocorticoids and their receptors have gene regulatory actions on viral replication and cause central and systemic immune suppression. CRH and stress activation contributes to central nervous system (CNS) viral entry important in HIV-associated neurocognitive disorders and HIV-associated dementia. CNS CRH overproduction short-circuits reward, executive, and emotional control, leading to addiction, cognitive impairment, and psychiatric comorbidity. CRHR1 is an important therapeutic target for medication development. CRHR1 antagonist clinical trials have focused on psychiatric disorders with little attention paid to neuroendocrine immune disorders. Studies of those with HIV and those at risk show that concurrent stress-related disorders contribute to higher morbidity and mortality; stress-related conditions, addiction, immune dysfunction, and comorbid psychiatric illness all increase HIV transmission. Neuropsychiatric disease, chronic inflammation, and substance abuse are endemic, and chronic distress is a pathologic factor. It is being understood that stress and CRH are fundamental to neuroendocrine immunity; therapeutic interventions with existing and novel agents hold promise for restoring homeostasis, reducing morbidity and mortality for those with HIV and possibly reducing future disease transmission.

Stimulation of PBMC and Monocyte-Derived Macrophages via Toll-Like Receptor Activates Innate Immune Pathways in HIV-Infected Patients on Virally Suppressive Combination Antiretroviral Therapy

In HIV-infected, combination antiretroviral therapy (cART)-treated patients, immune activation and microbial translocation persist and associate with inadequate CD4 recovery and morbidity/mortality. We analyzed whether alterations in the toll-like receptor (TLR) pathway could be responsible for the immune hyperactivation seen in these patients. PBMC/monocyte-derived macrophages (MDMs) of 28 HIV+ untreated and 35 cART-treated patients with HIV-RNA < 40 cp/mL [20 Full Responders (FRs): CD4 ≥ 350; 15 Immunological Non-Responders (INRs): CD4 < 350], as well as of 16 healthy controls were stimulated with a panel of TLR agonists. We measured: CD4/CD8/CD14/CD38/HLA-DR/Ki67/AnnexinV/CD69/TLR4/8 (Flow Cytometry); PBMC expression of 84 TLR pathway genes (qPCR); PBMC/MDM cytokine release (Multiplex); and plasma lipopolysaccharide (LPS)/sCD14 (LAL/ELISA). PBMC/MDM from cART patients responded weakly to LPS stimulation but released high amounts of pro-inflammatory cytokines. MDM from these patients were characterized by a reduced expression of HLA-DR+ MDM and failed to expand activated HLA-DR+ CD38+ T-lymphocytes. PBMC/MDM from cART patients responded more robustly to ssRNA stimulation; this resulted in a significant expansion of activated CD38 + CD8 and the release of amounts of pro-inflammatory cytokines comparable to those seen in untreated viremic patients. Despite greater constitutive TLR pathway gene expression, PBMC from INRs seemed to upregulate only type I IFN genes following TLR stimulation, whereas PBMC from full responders showed a broader response. Systemic exposure to microbial antigens drives immune activation during cART by triggering TLRs. Bacterial stimulation modifies MDM function/pro-inflammatory profile in cART patients without affecting T-lymphocytes; this suggests translocating bacteria as selective stimulus to chronic innate activation during cART. High constitutive TLR activation is seen in patients lacking CD4 recovery, suggesting an exhausted immune milieu, anergic to further antigen encounters.

Serious Non-AIDS Events: Therapeutic Targets of Immune Activation and Chronic Inflammation in HIV Infection

In the antiretroviral therapy (ART) era, serious non-AIDS events (SNAEs) have become the major causes of morbidity and mortality in HIV-infected persons. Early ART initiation has the strongest evidence for reducing SNAEs and mortality. Biomarkers of immune activation, inflammation and coagulopathy do not fully normalize despite virologic suppression and persistent immune activation is an important contributor to SNAEs. A number of strategies aimed to reduce persistent immune activation including ART intensification to reduce residual viremia; treatment of co-infections to reduce chronic antigen stimulation; the use of anti-inflammatory agents, reducing microbial translocation as well as interventions to improve immune recovery through cytokine administration and reducing lymphoid tissue fibrosis, have been investigated. To date, there is little conclusive evidence on which strategies beyond treatment of hepatitis B and C co-infections and reducing cardiovascular risk factors will result in clinical benefits in patients already on ART with viral suppression. The use of statins seems to show early promise and larger clinical trials are underway to confirm their efficacy. At this stage, clinical care of HIV-infected patients should therefore focus on early diagnosis and prompt ART initiation, treatment of active co-infections and the aggressive management of co-morbidities until further data are available.

Increased Immune Activation and Exhaustion in HIV-infected Youth

BACKGROUND

Immune activation and exhaustion drive several comorbidities and disease progression in HIV-infected adults; however, they are not well studied in HIV-infected youth. Thus, this study sought to examine levels of immune activation and exhaustion in this population, investigate associated HIV- and non-HIV-related variables and compare results with a matched healthy control group.

METHODS

HIV-infected youth 8-25 years of age on stable antiretroviral therapy with an HIV-1 RNA level <1000 copies/mL were enrolled, along with matched healthy controls. We measured T-cell and monocyte immune activation and exhaustion markers in cryopreserved peripheral blood mononuclear cell and plasma samples.

RESULTS

A total of 136 subjects (80 HIV+: 66% male; 91% black) were enrolled. Markers of CD4+ and CD8+ T-cell activation were higher in the HIV-infected group versus controls [mean % CD4+CD38+HLA-DR+ and CD8+CD38+HLA-DR+ = 2.2 versus 1.5 (P=0.002) and 4.9 versus 2.2 (P<0.0001), respectively], as were exhausted CD4+ and CD8+ T-cells [mean % CD4+CD38+HLA-DR+PD-1+ and CD8+CD38+HLA-DR+PD-1+ = 1.0 versus 0.5 (P<0.0001) and 1.6 versus 0.7 (P<0.0001), respectively]. There were no differences in proportions of inflammatory or patrolling monocytes between groups (P>0.05); however, soluble CD14 was higher in HIV-infected compared with controls (1.6 versus 1.4 µg/mL; P=0.01). Current CD4 count, low-density lipoprotein cholesterol and age were the variables most associated with CD4+ and CD8+ T-cell activation.

CONCLUSIONS

CD4+ and CD8+ T-cell immune activation and exhaustion are higher in HIV-infected youth compared with matched controls, while monocyte subpopulations are not altered despite a high soluble CD14 level. The clinical significance of the increased immune activation and exhaustion should be further explored.

Microbial Translocation and Inflammation Occur in Hyperacute Immunodeficiency Virus Infection and Compromise Host Control of Virus Replication

Within the first three weeks of human immunodeficiency virus (HIV) infection, virus replication peaks in peripheral blood. Despite the critical, causal role of virus replication in determining transmissibility and kinetics of progression to acquired immune deficiency syndrome (AIDS), there is limited understanding of the conditions required to transform the small localized transmitted founder virus population into a large and heterogeneous systemic infection. Here we show that during the hyperacute "pre-peak" phase of simian immunodeficiency virus (SIV) infection in macaques, high levels of microbial DNA transiently translocate into peripheral blood. This, heretofore unappreciated, hyperacute-phase microbial translocation was accompanied by sustained reduction of lipopolysaccharide (LPS)-specific antibody titer, intestinal permeability, increased abundance of CD4+CCR5+ T cell targets of virus replication, and T cell activation. To test whether increasing gastrointestinal permeability to cause microbial translocation would amplify viremia, we treated two SIV-infected macaque 'elite controllers' with a short-course of dextran sulfate sodium (DSS)-stimulating a transient increase in microbial translocation and a prolonged recrudescent viremia. Altogether, our data implicates translocating microbes as amplifiers of immunodeficiency virus replication that effectively undermine the host's capacity to contain infection.

Immune Activation at Sites of HIV/TB Co-Infection Contributes to the Pathogenesis of HIV-1 Disease

Systemic immune activation is critical to the pathogenesis of HIV-1 disease, and is accentuated in HIV/TB co-infected patients. The contribution of immune activation at sites of HIV/TB co-infection to viral activity, CD4 T cell count, and productive HIV-1 infection remain unclear. In this study, we measured markers of immune activation both in pleural fluid and plasma, and in T cells in pleural fluid mononuclear cell (PFMC) and peripheral blood mononuclear cell (PBMC) in HIV/TB co-infected subjects. The relationship between soluble and T cell activation markers with viral load in pleural fluid and blood CD4 T cell count were assessed. The T cell phenotype and activation status of HIV-1 p24 + T cells in PFMC and PBMC from HIV/TB patients were determined. We found that T cell and macrophage-specific and non-specific soluble markers of immune activation, sCD27, sCD163, IL1Ra, and sCD14, were higher in pleural fluid as compared to plasma from HIV/TB co-infected subjects, and higher as compared to pleural fluid from TB mono-infected subjects. Intestinal fatty acid-binding protein, a marker of intestinal tract damage, in plasma from HIV/TB co-infected patients was not different than that in HIV+ subjects. Expression of HLADR and CD38 double positive (HLADR/CD38) on CD4 T cells, and CD69+ on CD8 T cells correlated with pleural fluid viral load, and inversely with blood CD4 T cell count. Higher expression of HLADR/CD38 and CCR5 on CD4 T cells, and HLADR/CD38 and CD69 on CD8 T cells in PFMC were limited to effector memory populations. HIV-1 p24+ CD8 negative (includes CD4 + and double negative T cells) effector memory T cells in PFMC had higher expression of HLADR/CD38, Ki67, and CCR5 compared to HIV-1 p24- CD8 negative PFMC. Cumulatively, these data indicate that sites of HIV/TB co-infection are the source of intense immune activation.

Strategies to limit immune-activation in HIV patients

INTRODUCTION

Antiretroviral treatment of HIV infection reduces, but does not eliminate, viral replication and down modulates immune activation. The persistence of low level HIV replication in the host, nevertheless, drives a smouldering degree of immune activation that is observed throughout the natural history of disease and is the main driving force sustaining morbidity and mortality. Areas covered: Early start of antiretroviral therapy (ART) and intensive management of behavioural risk factors are possible but, at best, marginally successful ways to manage immune activation. We review alternative, possible strategies to reduce immune activation in HIV infection including timing of ART initiation and ART intensification to reduce HIV residual viremia; switch of ART to newer molecules with reduced toxicity; use of anti inflammatory/immunomodulatory agents and, finally, interventions aimed at modifying the composition of the microbiota. Expert commentary: Current therapeutic strategies to limit immune activation are only marginally successful. Because HIV eradication is currently impossible, intensive studies are needed to determine if and how immune activation can be silenced in HIV infection.

Microbial translocation and microbiome dysbiosis in HIV-associated immune activation

PURPOSE OF REVIEW

This article describes the mechanisms and consequences of both microbial translocation and microbial dysbiosis in HIV infection.

RECENT FINDINGS

Microbes in HIV are likely playing a large role in contributing to HIV pathogenesis, morbidities and mortality. Two major disruptions to microbial systems in HIV infection include microbial translocation and microbiome dysbiosis. Microbial translocation occurs when the bacteria (or bacterial products) that should be in the lumen of the intestine translocate across the tight epithelial barrier into systemic circulation, where they contribute to inflammation and pathogenesis. This is associated with poorer health outcomes in HIV-infected individuals. In addition, microbial populations in the gastrointestinal tract are also altered after HIV infection, resulting in microbiome dysbiosis, which further exacerbates microbial translocation, epithelial barrier disruption, inflammation and mucosal immune functioning.

SUMMARY

Altered microbial regulation in HIV infection can lead to poor health outcomes, and understanding the mechanisms underlying microbial dysbiosis and translocation may result in novel pathways for therapeutic interventions.

Sex differences in HIV-1-mediated immunopathology

PURPOSE OF REVIEW

The article reviews our current knowledge regarding the role of sex and sex hormones in regulating innate immune responses to viral infections, which may account for the described sex differences in immunity to HIV-1.

RECENT FINDINGS

Prominent sex differences exist in various infectious and autoimmune diseases. Biological mechanisms underlying these differences include the modulation of immunological pathways by sex hormones and gene dosage effects of immunomodulatory genes encoded by the X chromosome. During HIV-1 infections, women have been shown to present with lower viral load levels in primary infection, although their progression to AIDS is faster in comparison with men when accounting for viral load levels in chronic infection. HIV-1-infected women furthermore tend to have higher levels of immune activation and interferon-stimulated gene expression in comparison with men for the same viral load, which has been associated to innate sensing of HIV-1 by Toll-like receptor 7 and the consequent interferon-α production by plasmacytoid dendritic cells.

SUMMARY

Improvement in understanding the mechanisms associated with sex differences in HIV-1-mediated immunopathology will be critical to take sex differences into consideration when designing experimental and clinical studies in HIV-1-infected populations.

Casp8p41: The Protean Mediator of Death in CD4 T-cells that Replicate HIV

HIV cure is now the focus of intense research after Timothy Ray Brown (the Berlin patient) set the precedent of being the first and only person cured. A major barrier to achieving this goal on a meaningful scale is an elimination of the latent reservoir, which is thought to comprise CD4-positive cells that harbor integrated, replication-competent HIV provirus. These cells do not express viral proteins, are indistinguishable from uninfected CD4 cells, and are thought to be responsible for HIV viral rebound—that occurs within weeks of combination anti retroviral therapy (cART) interruption. Modalities to engineer transcriptional stimulation (reactivation) of this dormant integrated HIV provirus, leading to expression of cytotoxic viral proteins, are thought to be a specific way to eradicate the latently infected CD4 pool and are becoming increasingly relevant in the era of HIV cure. HIV protease is one such protein produced after HIV reactivation that cleaves procaspase-8 to generate a novel protein Casp8p41. Casp8p41 then binds to the BH3 domain of BAK, leading to BAK oligomerization, mitochondrial depolarization, and apoptosis. In central memory T cells (TCMs) from HIV-infected patients, an elevated Bcl-2/procaspase-8 ratio was observed, and Casp8p41 binding to Bcl-2 was associated with a lack of reactivation-induced cell death. This was reversed by priming cells with a specific Bcl-2 antagonist prior to reactivation, resulting in increased cell death and decreased HIV DNA in a Casp8p41-dependent pathway. This review describes the biology, clinical relevance, and implications of Casp8p41 for a potential cure.

On the translocation of bacteria and their lipopolysaccharides between blood and peripheral locations in chronic, inflammatory diseases: the central roles of LPS and LPS-induced cell death

We have recently highlighted (and added to) the considerable evidence that blood can contain dormant bacteria. By definition, such bacteria may be resuscitated (and thus proliferate). This may occur under conditions that lead to or exacerbate chronic, inflammatory diseases that are normally considered to lack a microbial component. Bacterial cell wall components, such as the endotoxin lipopolysaccharide (LPS) of Gram-negative strains, are well known as potent inflammatory agents, but should normally be cleared. Thus, their continuing production and replenishment from dormant bacterial reservoirs provides an easy explanation for the continuing, low-grade inflammation (and inflammatory cytokine production) that is characteristic of many such diseases. Although experimental conditions and determinants have varied considerably between investigators, we summarise the evidence that in a great many circumstances LPS can play a central role in all of these processes, including in particular cell death processes that permit translocation between the gut, blood and other tissues. Such localised cell death processes might also contribute strongly to the specific diseases of interest. The bacterial requirement for free iron explains the strong co-existence in these diseases of iron dysregulation, LPS production, and inflammation. Overall this analysis provides an integrative picture, with significant predictive power, that is able to link these processes via the centrality of a dormant blood microbiome that can resuscitate and shed cell wall components.

Polymorphisms in the CD14 and TLR4 genes independently predict CD4+ T-cell recovery in HIV-infected individuals on antiretroviral therapy

BACKGROUND

Chronic HIV infection leads to marked depletion of CD4 T cells in the gastrointestinal tract and increased microbial translocation measured by an increase in circulating lipopolysaccharide (LPS) levels. Here, we hypothesized that single-nucleotide polymorphisms (SNPs) in genes encoding the Toll-like receptor 4 (TLR4) and CD14, the principal receptors for LPS, were associated with CD4 T-cell recovery postantiretroviral therapy (ART).

METHODS

Prospective study of predominantly white HIV-infected participants receiving suppressive ART for at least 12 months. We analysed the CD14 SNPs C-260T and the TLR4 SNPs A+896G, C+1196T. We also determined the levels of LPS and soluble CD14 in plasma samples collected pre-ART and post-ART initiation. CD4 T-cell recovery was assessed by linear mixed models.

RESULTS

Following ART, individuals with a TT genotype compared with a CT or CC genotype for CD14 C-260T SNP showed higher levels of soluble CD14 (P = 0.008 and 0.003, respectively). The CC genotype for the CD14 C-260T SNP, compared with CT or TT, and the TLR4 SNP (AC/GT), compared with the homozygous genotype (AA/CC), were both independently associated with enhanced long-term CD4 T-cell recovery (>3 months; P < 0.001).

CONCLUSION

Polymorphisms in CD14 and TLR4 are independently associated with long-term CD4 T-cell recovery in HIV-infected individuals post-ART.

Endotoxemia-menace, marker, or mistake?

Endotoxemia is in its scientific ascendancy. Never has blood-borne, Gram-negative bacterial endotoxin (LPS) been invoked in the pathogenesis of so many diseases-not only as a trigger for septic shock, once its most cited role, but also as a contributor to atherosclerosis, obesity, chronic fatigue, metabolic syndrome, and many other conditions. Finding elevated plasma endotoxin levels has been essential supporting evidence for each of these links, yet the assays used to detect and quantitate endotoxin have important limitations. This article describes several assays for endotoxin in plasma, reviews what they do and do not measure, and discusses why LPS heterogeneity, LPS trafficking pathways, and host LPS inactivation mechanisms should be considered when interpreting endotoxin assay results.

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.

Humoral Dysregulation Associated with Increased Systemic Inflammation among Injection Heroin Users

Background

Injection drug use is a growing major public health concern. Injection drug users (IDUs) have a higher incidence of co-morbidities including HIV, Hepatitis, and other infections. An effective humoral response is critical for optimal homeostasis and protection from infection; however, the impact of injection heroin use on humoral immunity is poorly understood. We hypothesized that IDUs have altered B cell and antibody profiles.

Methods and Findings

A comprehensive systems biology-based cross-sectional assessment of 130 peripheral blood B cell flow cytometry- and plasma- based features was performed on HIV-/Hepatitis C-, active heroin IDUs who participated in a syringe exchange program (n = 19) and healthy control subjects (n = 19). The IDU group had substantial polydrug use, with 89% reporting cocaine injection within the preceding month. IDUs exhibited a significant, 2-fold increase in total B cells compared to healthy subjects, which was associated with increased activated B cell subsets. Although plasma total IgG titers were similar between groups, IDUs had significantly higher IgG3 and IgG4, suggestive of chronic B cell activation. Total IgM was also increased in IDUs, as well as HIV Envelope-specific IgM, suggestive of increased HIV exposure. IDUs exhibited numerous features suggestive of systemic inflammation, including significantly increased plasma sCD40L, TNF-α, TGF-α, IL-8, and ceramide metabolites. Machine learning multivariate analysis distilled a set of 10 features that classified samples based on group with absolute accuracy.

Conclusions

These results demonstrate broad alterations in the steady-state humoral profile of IDUs that are associated with increased systemic inflammation. Such dysregulation may impact the ability of IDUs to generate optimal responses to vaccination and infection, or lead to increased risk for inflammation-related co-morbidities, and should be considered when developing immune-based interventions for this growing population.

IL-15 promotes activation and expansion of CD8+ T cells in HIV-1 infection

In HIV-1-infected patients, increased numbers of circulating CD8+ T cells are linked to increased risk of morbidity and mortality. Here, we identified a bystander mechanism that promotes CD8 T cell activation and expansion in untreated HIV-1-infected patients. Compared with healthy controls, untreated HIV-1-infected patients have an increased population of proliferating, granzyme B+, CD8+ T cells in circulation. Vβ expression and deep sequencing of CDR3 revealed that in untreated HIV-1 infection, cycling memory CD8 T cells possess a broad T cell repertoire that reflects the repertoire of the resting population. This suggests that cycling is driven by bystander activation, rather than specific antigen exposure. Treatment of peripheral blood mononuclear cells with IL-15 induced a cycling, granzyme B+ phenotype in CD8+ T cells. Moreover, elevated IL-15 expression in the lymph nodes of untreated HIV-1-infected patients correlated with circulating CD8+ T cell counts and was normalized in these patients following antiretroviral therapy. Together, these results suggest that IL-15 drives bystander activation of CD8+ T cells, which predicts disease progression in untreated HIV-1-infected patients and suggests that elevated IL-15 may also drive CD8+ T cell expansion that is linked to increased morbidity and mortality in treated patients.

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.

Inflammation, immune activation, and cardiovascular disease in HIV

Cardiovascular disease is one of the leading causes of morbidity and mortality in people living with HIV. Several epidemiological studies have shown an increased risk of myocardial infarction and stroke compared to uninfected controls. Although traditional risk factors contribute to this increased risk of cardiovascular disease, HIV-specific mechanisms likely also play a role. Systemic inflammation has been linked to cardiovascular disease in several populations suffering from chronic inflammation, including people living with HIV. Although antiretroviral therapy reduces immune activation, levels of inflammatory markers remain elevated compared to uninfected controls. The causes of this sustained immune response are likely multifactorial and incompletely understood. In this review, we summarize the evidence describing the relationship between inflammation and cardiovascular disease and discuss potential anti-inflammatory treatment options for cardiometabolic disease in people living with HIV.

The Link Between Inflammatory Disorders and Coronary Heart Disease: a Look at Recent Studies and Novel Drugs in Development

Inflammation is a critical component in the development of coronary heart disease (CHD), specifically in the process of atherogenesis. Human translational and preclinical studies have demonstrated that inflammation contributes to the development, sustainment, and progression of atherosclerosis, and epidemiological studies demonstrate that human diseases associated with increased systemic inflammation increase the risk of CHD-related events. Therefore, over the last decade, multiple clinical studies were designed to target the inflammatory cascade in order to reduce the risk of CHD and to identify which populations may benefit from these preventative treatment strategies. This review briefly summarizes inflammation as a risk factor in atherosclerosis, human disease states associated with accelerated atherosclerosis, and current treatment strategies for CHD targeting the inflammatory cascade.

Functional role of mucosal-associated invariant T cells in HIV infection

MAIT cells represent an evolutionarily conserved, MR1-restricted, innate-like cell subset that express high levels of CD161; have a canonical semi-invariant TCR iVα7.2; and may have an important role in mucosal immunity against various bacterial and fungal pathogens. Mature MAIT cells are CD161(hi)PLZF(hi)IL-18Rα(+)iVα7.2(+)γδ-CD3(+)CD8(+) T cells and occur in the peripheral blood, liver, and mucosa of humans. MAIT cells are activated by a metabolic precursor of riboflavin synthesis presented by MR1 and, therefore, respond to many bacteria and some fungi. Despite their broad antibacterial properties, their functional role in persistent viral infections is poorly understood. Although there is an increasing line of evidence portraying the depletion of MAIT cells in HIV disease, the magnitude and the potential mechanisms underlying such depletion remain unclear. Recent studies suggest that MAIT cells are vulnerable to immune exhaustion as a consequence of HIV and hepatitis C virus infections and HIV/tuberculosis coinfections. HIV infection also appears to cause functional depletion of MAIT cells resulting from abnormal expression of T-bet and EOMES, and effective ART is unable to completely salvage functional MAIT cell loss. Depletion and exhaustion of peripheral MAIT cells may affect mucosal immunity and could increase susceptibility to opportunistic infections during HIV infection. Here, we review some of the important mechanisms associated with depletion and functional loss of MAIT cells and also suggest potential immunotherapeutic strategies to restore MAIT cell functions, including the use of IL-7 to restore effector functions in HIV disease.

Novel relationships of markers of monocyte activation and endothelial dysfunction with pulmonary dysfunction in HIV-infected persons

OBJECTIVE

Chronic obstructive pulmonary disease is a common comorbidity in HIV, with prevalence and severity of disease incompletely explained by risk factors such as smoking and age. Unique HIV-associated factors, including microbial translocation, monocyte activation, and endothelial dysfunction, have been described in other comorbidities, but have not been investigated in relation to pulmonary abnormalities in HIV. This study assessed the relationship of these pathologic processes to pulmonary function in HIV-infected and uninfected individuals and determined if relationships were unique to HIV.

DESIGN

Longitudinal observational study.

METHODS

Total 274 participants completed pulmonary function testing. Markers of inflammation (IL-6, IL-8, and TNFα), microbial translocation (lipopolysaccharide, sCD14), monocyte activation (sCD163, sCD14, and IL-2 receptor), and endothelial dysfunction (endothelin-1) were measured at baseline. Cross-sectional and longitudinal analyses were performed, adjusting for pertinent covariates.

RESULTS

In HIV-infected individuals, higher IL-6 and endothelin-1 associated with worse forced expiratory volume in one second (FEV1) percentage-predicted, and higher sCD163 associated with worse FEV1/forced vital capacity. IL-6, TNFα, lipopolysaccharide, sCD163, IL-2 receptor, and endothelin-1 associated with diffusing impairment. sCD163 and endothelin-1 interacted with HIV status in relationship to pulmonary function. In HIV-infected individuals only, baseline endothelin-1 was associated with lower FEV1, and sCD163 and endothelin-1 were associated with lower diffusing capacity during follow-up.

CONCLUSION

Circulating markers of HIV-associated humoral abnormalities are associated with airflow obstruction and diffusing impairment and baseline measures of monocyte activation and endothelial dysfunction associate with lower pulmonary function over time in HIV-infected persons. These findings suggest mechanisms of the disproportionate burden of chronic obstructive pulmonary disease in HIV-infected persons.

Impaired gut junctional complexes feature late-treated individuals with suboptimal CD4+ T-cell recovery upon virologically suppressive combination antiretroviral therapy

OBJECTIVE

HIV-infected individuals with incomplete CD4⁺ T-cell recovery upon combination antiretroviral therapy (cART) display high levels of immune activation and microbial translocation. However, whether a link exists between gut damage and poor immunological reconstitution remains unknown.

DESIGN

Cross-sectional study of the gastrointestinal tract in late cART-treated HIV-infected individuals: 15 immunological nonresponders (CD4⁺ <350 cells/μl and/or delta CD4⁺ change from baseline <30%); 15 full responders (CD4⁺ >350 cells/μl and/or delta CD4⁺ change from baseline >30%).

METHODS

We assessed gut structure (junctional complex proteins in ileum and colon) and function (small intestine permeability/damage and microbial translocation parameters). The composition of the fecal microbiome and the size of the HIV reservoir in the gut and peripheral blood were investigated as possible mechanisms underlying mucosal impairment.

RESULTS

Markers of intestinal permeability, damage, systemic inflammation, and microbial translocation were comparable in all study individuals, yet the expression of junctional complex proteins in gut biopsies was significantly lower in HIV-infected patients with incomplete CD4⁺ restoration and negatively correlated with markers of CD4⁺ reconstitution. Electron microscopy revealed dilated intercellular spaces in individuals lacking immunological response to cART, yet not in patients displaying CD4⁺ T-cell recovery. Analysis of the fecal microbiome revealed an overall outgrowth of Bacteroides-Prevotella spp. with no differences according to CD4⁺ T-cell reconstitution. Interestingly, HIV reservoirs in peripheral CD4⁺ T cells and intestinal tissue negatively correlated with immune recovery.

CONCLUSION

These observations establish gut damage and the size of the HIV reservoir as features of deficient immunological response to cART and provide new elements for interventional strategies in this setting.

Optimal vitamin D plasma levels are associated with lower bacterial DNA translocation in HIV/hepatitis c virus coinfected patients

OBJECTIVE

Vitamin D has been linked to the immune response modulation and the integrity of the intestinal mucosal barrier. Therefore, vitamin D might be involved in bacterial translocation related to HIV infection. Our major aim was to analyze the association between plasma levels of 25-hydroxy-vitamin D [25(OH)D] and bacterial 16S ribosomal DNA (bactDNA) in 120 HIV/hepatitis c virus (HCV) coinfected patients.

DESIGN

Cross-sectional study.

METHODS

Plasma 25(OH)D levels were quantified by enzyme immunoassay. The vitamin D status was defined as deficient (<25 nmol/l), insufficient (25-74 nmol/l), and optimal (≥75 nmol/l) plasma levels. Plasma bactDNA levels were measured by quantitative real-time PCR. For bactDNA levels the cutoffs used were as follows: low [<p25th (46 copies/μl)], moderate [p25th to p50th (78 copies/μl)], high [p50th to p75th (159 copies/μl)], and very high (>p75th).

RESULTS

Eighteen (15%) patients had 25(OH)D deficiency, 93 (77.5%) had insufficiency and nine (7.5%) had 25(OH)D optimal values. The bactDNA levels were lower in patients with 25(OH)D at least 75 nmol/l [37 copies/μl] than in patients with 25(OH)D insufficiency [84.2 copies/μl; P = 0.042]. Conversely, low bactDNA levels (<p25th) were found in 66.7% of patients with 25(OH)D optimal levels, whereas bactDNA levels above p25th were found only in 11.1% of them (P = 0.029). The plasma 25(OH)D not less than 75 nmol/l was associated with low bactDNA levels (<p25th) [adjusted OR = 8.13 (95% confidence interval = 1.82; 36.67); P = 0.006)]. The patients with optimal vitamin D status [25(OH)D ≥75 nmol/l] had lower plasma levels of CCL7 (P = 0.047) and basic fibroblast growth factor (P = 0.042).

CONCLUSION

The optimal vitamin D status was associated with low bacterial translocation and inflammation in HIV/HCV coinfected patients.

Gut barrier structure, mucosal immunity and intestinal microbiota in the pathogenesis and treatment of HIV infection

Over the past 10 years, extensive work has been carried out in the field of microbial translocation in HIV infection, ranging from studies on its clinical significance to investigations on its pathogenic features. In the present work, we review the most recent findings on this phenomenon, focusing on the predictive role of microbial translocation in HIV-related morbidity and mortality, the mechanisms by which it arises and potential therapeutic approaches. From a clinical perspective, current work has shown that markers of microbial translocation may be useful in predicting clinical events in untreated HIV infection, while conflicting data exist on their role in cART-experienced subjects, possibly due to the inclusion of extremely varied patient populations in cohort studies. Results from studies addressing the pathogenesis of microbial translocation have improved our knowledge of the damage of the gastrointestinal epithelial barrier occurring in HIV infection. However, the extent to which mucosal impairment translates directly to increased gastrointestinal permeability remains an open issue. In this respect, novel work has established a role for IL-17 and IL-22-secreting T cell populations in limiting microbial translocation and systemic T-cell activation/inflammation, thus representing a possible target of immune-therapeutic interventions shown to be promising in the animal model. Further, recent reports have not only confirmed the presence of a dysbiotic intestinal community in the course of HIV infection but have also shown that it may be linked to mucosal damage, microbial translocation and peripheral immune activation. Importantly, technical advances have also shed light on the metabolic activity of gut microbes, highlighting the need for novel therapeutic approaches to correct the function, as well as the composition, of the gastrointestinal microbiota.

Statin modulation of monocyte phenotype and function: implications for HIV-1-associated neurocognitive disorders

HIV-1-associated neurocognitive disorder (HAND) remains a persistent problem despite antiretroviral therapy (ART), largely a result of continued inflammation in the periphery and the brain and neurotoxin release from activated myeloid cells in the CNS. CD14+CD16+ inflammatory monocytes, expanded in HIV infection, play a central role in the pathogenesis of HAND and have parallels with monocyte-dependent inflammatory mechanisms in atherosclerosis. Statins, through their HMG-CoA reductase inhibitor activity, have pleiotropic immunomodulatory properties that contribute to their benefit in atherosclerosis beyond lipid lowering. Here, we investigated whether statins would modulate the monocyte phenotype and function associated with HIV-1 neuropathogenesis. Treatment ex vivo with simvastatin and atorvastatin reduced the proportion of CD16+ monocytes in peripheral blood mononuclear cells, as well as in purified monocytes, especially CD14++CD16+ "intermediate" monocytes most closely associated with neurocognitive disease. Statin treatment also markedly reduced expression of CD163, which is also linked to HAND pathogenesis. Finally, simvastatin inhibited production of monocyte chemoattractant protein-1 (MCP-1) and other inflammatory cytokines following LPS stimulation and reduced monocyte chemotaxis in response to MCP-1, a major driver of myeloid cell accumulation in the CNS in HAND. Together, these findings suggest that statin drugs may be useful to prevent or reduce HAND in HIV-1-infected subjects on ART with persistent monocyte activation and inflammation.

Proinflammatory isoforms of IL-32 as novel and robust biomarkers for control failure in HIV-infected slow progressors

HIV-infected slow progressors (SP) represent a heterogeneous group of subjects who spontaneously control HIV infection without treatment for several years while showing moderate signs of disease progression. Under conditions that remain poorly understood, a subgroup of these subjects experience failure of spontaneous immunological and virological control. Here we determined the frequency of SP subjects who showed loss of HIV control within our Canadian Cohort of HIV(+) Slow Progressors and identified the proinflammatory cytokine IL-32 as a robust biomarker for control failure. Plasmatic levels of the proinflammatory isoforms of IL-32 (mainly β and γ) at earlier clinic visits positively correlated with the decline of CD4 T-cell counts, increased viral load, lower CD4/CD8 ratio and levels of inflammatory markers (sCD14 and IL-6) at later clinic visits. We present here a proof-of-concept for the use of IL-32 as a predictive biomarker for disease progression in SP subjects and identify IL-32 as a potential therapeutic target.

A Novel Microbiome Therapeutic Increases Gut Microbial Diversity and Prevents Recurrent Clostridium difficile Infection

BACKGROUND

Patients with recurrent Clostridium difficile infection (CDI) have a ≥60% risk of relapse, as conventional therapies do not address the underlying gastrointestinal dysbiosis. This exploratory study evaluated the safety and efficacy of bacterial spores for preventing recurrent CDI.

METHODS

Stool specimens from healthy donors were treated with ethanol to eliminate pathogens. The resulting spores were fractionated and encapsulated for oral delivery as SER-109. Following their response to standard-of-care antibiotics, patients in cohort 1 were treated with SER-109 on 2 consecutive days (geometric mean dose, 1.7 × 10(9) spores), and those in cohort 2 were treated on 1 day (geometric mean dose, 1.1 × 10(8) spores). The primary efficacy end point was absence of C. difficile-positive diarrhea during an 8-week follow-up period. Microbiome alterations were assessed.

RESULTS

Thirty patients (median age, 66.5 years; 67% female) were enrolled, and 26 (86.7%) met the primary efficacy end point. Three patients with early, self-limiting C. difficile-positive diarrhea did not require antibiotics and tested negative for C. difficile at 8 weeks; thus, 96.7% (29 of 30) achieved clinical resolution. In parallel, gut microbiota rapidly diversified, with durable engraftment of spores and no outgrowth of non-spore-forming bacteria found after SER-109 treatment. Adverse events included mild diarrhea, abdominal pain, and nausea.

CONCLUSIONS

SER-109 successfully prevented CDI and had a favorable safety profile, supporting a novel microbiome-based intervention as a potential therapy for recurrent CDI.

Short Communication: Immune Activation Is Present in HIV-1-Exposed Seronegative Individuals and Is Independent of Microbial Translocation

Analyses of immune activation in HIV-exposed seronegative individuals (HESN) yielded discrepant results. To clarify this issue we performed an extensive investigation of immune parameters in HESN and, in particular, we analyzed in these individuals the possible presence of microbial translocation, the most widely accepted reason driving immune activation in HIV-infected patients. Results showed that immune activation, a skewing of T lymphocyte maturation, and increased responsiveness to lipopolysaccharide (LPS) characterize the HESN phenotype; this is not driven by alterations of the gastrointestinal barrier and microbial translocation. The activation state seen in HESN may influence the induction of stronger adaptive antiviral immune responses and may represent a virus exposure-induced innate immune protective phenotype against HIV.

Gut epithelial barrier dysfunction in human immunodeficiency virus-hepatitis C virus coinfected patients: Influence on innate and acquired immunity

Even in cases where viral replication has been controlled by antiretroviral therapy for long periods of time, human immunodeficiency virus (HIV)-infected patients have several non-acquired immunodeficiency syndrome (AIDS) related co-morbidities, including liver disease, cardiovascular disease and neurocognitive decline, which have a clear impact on survival. It has been considered that persistent innate and acquired immune activation contributes to the pathogenesis of these non-AIDS related diseases. Immune activation has been related with several conditions, remarkably with the bacterial translocation related with the intestinal barrier damage by the HIV or by hepatitis C virus (HCV)-related liver cirrhosis. Consequently, increased morbidity and mortality must be expected in HIV-HCV coinfected patients. Disrupted gut barrier lead to an increased passage of microbial products and to an activation of the mucosal immune system and secretion of inflammatory mediators, which in turn might increase barrier dysfunction. In the present review, the intestinal barrier structure, measures of intestinal barrier dysfunction and the modifications of them in HIV monoinfection and in HIV-HCV coinfection will be considered. Both pathogenesis and the consequences for the progression of liver disease secondary to gut microbial fragment leakage and immune activation will be assessed.

Effects of Prednisolone on Disease Progression in Antiretroviral-Untreated HIV Infection: A 2-Year Randomized, Double-Blind Placebo-Controlled Clinical Trial

BACKGROUND

HIV-disease progression correlates with immune activation. Here we investigated whether corticosteroid treatment can attenuate HIV disease progression in antiretroviral-untreated patients.

METHODS

Double-blind, placebo-controlled randomized clinical trial including 326 HIV-patients in a resource-limited setting in Tanzania (clinicaltrials.gov NCT01299948). Inclusion criteria were a CD4 count above 300 cells/μl, the absence of AIDS-defining symptoms and an ART-naïve therapy status. Study participants received 5 mg prednisolone per day or placebo for 2 years. Primary endpoint was time to progression to an AIDS-defining condition or to a CD4-count below 200 cells/μl.

RESULTS

No significant change in progression towards the primary endpoint was observed in the intent-to-treat (ITT) analysis (19 cases with prednisolone versus 28 cases with placebo, p = 0.1407). In a per-protocol (PP)-analysis, 13 versus 24 study participants progressed to the primary study endpoint (p = 0.0741). Secondary endpoints: Prednisolone-treatment decreased immune activation (sCD14, suPAR, CD38/HLA-DR/CD8+) and increased CD4-counts (+77.42 ± 5.70 cells/μl compared to -37.42 ± 10.77 cells/μl under placebo, p < 0.0001). Treatment with prednisolone was associated with a 3.2-fold increase in HIV viral load (p < 0.0001). In a post-hoc analysis stratifying for sex, females treated with prednisolone progressed significantly slower to the primary study endpoint than females treated with placebo (ITT-analysis: 11 versus 21 cases, p = 0.0567; PP-analysis: 5 versus 18 cases, p = 0.0051): No changes in disease progression were observed in men.

CONCLUSIONS

This study could not detect any significant effects of prednisolone on disease progression in antiretroviral-untreated HIV infection within the intent-to-treat population. However, significant effects were observed on CD4 counts, immune activation and HIV viral load. This study contributes to a better understanding of the role of immune activation in the pathogenesis of HIV infection.

TRIAL REGISTRATION

ClinicalTrials.gov NCT01299948.

Enhancement of HIV-1 infection and intestinal CD4+ T cell depletion ex vivo by gut microbes altered during chronic HIV-1 infection

BACKGROUND

Early HIV-1 infection is characterized by high levels of HIV-1 replication and substantial CD4 T cell depletion in the intestinal mucosa, intestinal epithelial barrier breakdown, and microbial translocation. HIV-1-induced disruption of intestinal homeostasis has also been associated with changes in the intestinal microbiome that are linked to mucosal and systemic immune activation. In this study, we investigated the impact of representative bacterial species that were altered in the colonic mucosa of viremic HIV-1 infected individuals (HIV-altered mucosal bacteria; HAMB) on intestinal CD4 T cell function, infection by HIV-1, and survival in vitro. Lamina propria (LP) mononuclear cells were infected with CCR5-tropic HIV-1BaL or mock infected, exposed to high (3 gram-negative) or low (2 gram-positive) abundance HAMB or control gram-negative Escherichia coli and levels of productive HIV-1 infection and CD4 T cell depletion assessed. HAMB-associated changes in LP CD4 T cell activation, proliferation and HIV-1 co-receptor expression were also evaluated.

RESULTS

The majority of HAMB increased HIV-1 infection and depletion of LP CD4 T cells, but gram-negative HAMB enhanced CD4 T cell infection to a greater degree than gram-positive HAMB. Most gram-negative HAMB enhanced T cell infection to levels similar to that induced by gram-negative E. coli despite lower induction of T cell activation and proliferation by HAMB. Both gram-negative HAMB and E. coli significantly increased expression of HIV-1 co-receptor CCR5 on LP CD4 T cells. Lipopolysaccharide, a gram-negative bacteria cell wall component, up-regulated CCR5 expression on LP CD4 T cells whereas gram-positive cell wall lipoteichoic acid did not. Upregulation of CCR5 by gram-negative HAMB was largely abrogated in CD4 T cell-enriched cultures suggesting an indirect mode of stimulation.

CONCLUSIONS

Gram-negative commensal bacteria that are altered in abundance in the colonic mucosa of HIV-1 infected individuals have the capacity to enhance CCR5-tropic HIV-1 productive infection and depletion of LP CD4 T cells in vitro. Enhanced infection appears to be primarily mediated indirectly through increased expression of CCR5 on LP CD4 T cells without concomitant large scale T cell activation. This represents a novel mechanism potentially linking intestinal dysbiosis to HIV-1 mucosal pathogenesis.

Key differences in B cell activation patterns and immune correlates among treated HIV-infected patients versus healthy controls following influenza vaccination

BACKGROUND

There is increasing recognition of the role of B cell dysfunction in HIV pathogenesis, but little is known about how these perturbations may influence responses to vaccinations.

METHODS

Healthy controls (n=16) and antiretroviral therapy (ART)-treated aviremic HIV-infected subjects (n=26) receiving standard-of-care annual influenza vaccinations were enrolled in the present study. Total bacterial 16S rDNA levels were assessed by quantitative polymerase chain reactions in plasma. Serologic responses were characterized by ELISA, hemagglutination inhibition assay (HI), and microneutralization, and cell-mediated responses were assessed by ELISPOT (antigen-specific IgG+ antibody-secreting cells (ASCs)) and flow cytometry at pre-vaccination (D0), day 7-10 (D7) and day 14-21 (D14) post-vaccination.

RESULTS

Decreased peripheral CD4+ T cell absolute counts and increased frequencies of cycling and apoptotic B cells were found at baseline in HIV-infected subjects relative to healthy controls. In healthy controls, post-vaccination neutralizing activities were related to the frequencies of vaccine-mediated apoptosis and cycling of B cells, but not to CD4+ T cell counts. In patients, both baseline and post-vaccination neutralizing activities were directly correlated with plasma level of bacterial 16S rDNA. However, overall vaccine responses including antibody titers and fold changes were comparable or greater in HIV-infected subjects relative to healthy controls.

CONCLUSION

B cell function correlates with measures of recall humoral immunity in response to seasonal influenza vaccination in healthy controls but not in ART-treated patients.

Naturally Occurring Subclinical Endotoxemia in Humans Alters Adaptive and Innate Immune Functions through Reduced MAPK and Increased STAT1 Phosphorylation

Multiple studies have shown correlates of immune activation with microbial translocation and plasma LPS during HIV infection. It is unclear whether this activation is due to LPS, residual viral replication, or both. Few studies have addressed the effects of persistent in vivo levels of LPS on specific immune functions in humans in the absence of chronic viral infection or pathological settings such as sepsis. We previously reported on a cohort of HIV-negative men with subclinical endotoxemia linked to alterations in CD4/CD8 T cell ratio and plasma cytokine levels. This HIV-negative cohort allowed us to assess cellular immune functions in the context of different subclinical plasma LPS levels ex vivo without confounding viral effects. By comparing two samples of differing plasma LPS levels from each individual, we now show that subclinical levels of plasma LPS in vivo significantly alter T cell proliferative capacity, monocyte cytokine release, and HLA-DR expression, and induce TLR cross-tolerance by decreased phosphorylation of MAPK pathway components. Using this human in vivo model of subclinical endotoxemia, we furthermore show that plasma LPS leads to constitutive activation of STAT1 through autocrine cytokine signaling, suggesting that subclinical endotoxemia in healthy individuals might lead to significant changes in immune function that have thus far not been appreciated.

CD4+ T cell-dependent and CD4+ T cell-independent cytokine-chemokine network changes in the immune responses of HIV-infected individuals

A vital defect in the immune systems of HIV-infected individuals is the loss of CD4(+) T cells, resulting in impaired immune responses. We hypothesized that there were CD4(+) T cell-dependent and CD4(+) T cell-independent alterations in the immune responses of HIV-1(+) individuals. To test this, we analyzed the secretion of cytokines and chemokines from stimulated peripheral blood mononuclear cell (PBMC) populations from HIV(+) donors, healthy donors, and healthy donors with CD4(+) T cells experimentally depleted. Multivariate analyses of 16 cytokines and chemokines at 6 and 72 hours after three stimuli (antibody-coated beads to stimulate T cells and R848 or lipopolysaccharide to stimulate innate immune cells) enabled integrative analysis of secreted profiles. Two major effects in HIV(+) PBMCs were not reproduced upon depletion of CD4(+) T cells in healthy PBMCs: (i) HIV(+) PBMCs maintained T cell-associated secreted profiles after T cell stimulation; (ii) HIV(+) PBMCs showed impaired interferon-γ (IFN-γ) secretion early after innate stimulation. These changes arose from hyperactive T cells and debilitated natural killer (NK) cell, respectively. Modeling and experiments showed that early IFN-γ secretion predicted later differences in secreted profiles in vitro. This effect was recapitulated in healthy PBMCs by blocking the IFN-γ receptor. Thus, we identified a critical deficiency in NK cell responses of HIV-infected individuals, independent of CD4(+) T cell depletion, which directs secreted profiles. Our findings illustrate a broad approach for identifying key disease-associated nodes in a multicellular, multivariate signaling network.

Intestinal tract and acquired immunodeficiency syndrome

The intestinal tract is closely associated with the transmission, disease progression and the prevention and control of acquired immune deficiency syndrome (AIDS). It has been noticed early in AIDS research that a large percent of AIDS patients presented abnormalities in their intestinal tract, such as diarrhea. Now it is known that the intestinal tract has close and complex relationships with AIDS: (1) the intestinal tract is directly involved in the transmission of human immunodeficiency virus-1 (HIV-1); (2) the damage of the intestinal barrier of HIV/AIDS patients directly promotes AIDS disease progression; and (3) most importantly, the intestinal tract is an important target for the treatment and prevention of HIV/AIDS. The author has previously reviewed the progress in understanding the roles of the intestinal tract in HIV-1 infection and the changes of the intestinal tract after HIV-1 infection. In the current review, I discuss the progress in understanding the roles of the damage of the intestinal mucosal immune system in AIDS disease progression, and the potential application value of the restoration of intestinal mucosal immunity in the treatment of AIDS.

Gut-Associated Plasmacytoid Dendritic Cells Display an Immature Phenotype and Upregulated Granzyme B in Subjects with HIV/AIDS

Plasmacytoid dendritic cells (pDCs) in the periphery of subjects with human immunodeficiency virus (HIV)/acquired immunodeficiency syndrome (AIDS) decrease over time, and the fate of these cells has been the subject of ongoing investigation. Previous studies using animal models as well as studies with humans suggest that these cells may redistribute to the gut. Other studies using animal models propose that the periphery pDCs are depleted and gut is repopulated with naive pDCs from the bone marrow. In the present study, we utilized immunohistochemistry to survey duodenum biopsies of subjects with HIV/AIDS and controls. We observed that subjects with HIV/AIDS had increased infiltration of Ki-67⁺/CD303⁺ pDCs, a phenotype consistent with bone marrow-derived pre-pDCs. In contrast, Ki-67⁺/CD303⁺ pDCs were not observed in control biopsies. We additionally observed that gut-associated pDCs in HIV/AIDS cases upregulate the proapoptotic enzyme granzyme B; however, no granzyme B was observed in the pDCs of control biopsies. Our data are consistent with reports in animal models that suggest periphery pDCs are depleted by exhaustion and that naive pDCs egress from the bone marrow and ultimately infiltrate the gut mucosa. Additionally, our observation of granzyme B upregulation in naive pDCs may identify a contributing factor to the gut pathology associated with HIV infection.

Dysregulated B-cell TLR2 expression and elevated regulatory B-cell frequency precede the diagnosis of AIDS-related non-Hodgkin lymphoma

OBJECTIVES

In antiretroviral therapy (ART)-treated patients, to determine if AIDS-related non-Hodgkin lymphoma (AIDS-NHL) is preceded by: elevated frequency of potentially malignant abnormal activated/germinal center-like B cells, elevated serum prevalence of B-cell stimulatory Toll-like receptor (TLR) ligands resulting from HIV infection-associated microbial translocation, dysregulated B-cell TLR expression/signaling, and perturbations in the frequency of immunoregulatory cells.

DESIGN

A case-control study nested with a cohort study of HIV-infected women.

METHODS

Prediagnostic AIDS-NHL cases (n = 12, collected 1-12 months before diagnosis) and controls (n = 42) from the Women's Interagency HIV Study cohort, were matched for HIV and ART status, age, race, and CD4 lymphocyte count. Serum levels of TLR ligands, the prevalence of malignancy-associated abnormal activated/germinal center-like (CD19CD10CD71CD86AID) B cells, TLR2 expression on B cells, expression of TLR2-modulating micro-RNA, and the frequency of regulatory T and B cells were assessed.

RESULTS

Diagnosis of AIDS-NHL was preceded by a significantly elevated frequency of activated/germinal center-like CD19CD10CD71CD86AID B cells (P = 0.0072), elevated serum prevalence of the TLR2 ligand, and significantly elevated B-cell TLR2 expression (P = 0.0015), positively correlating with the frequency of activated/germinal center-like B cells (rho = 0.7273, P = 0.0144). In cases, a purified subset of activated/germinal center-like B cells exhibited decreased expression of microRNAs that modulate TLR2 signaling, including miR-21, 146a, 146b, and 155. Finally, cases also exhibited significantly elevated frequencies of antitumor immunity inhibitory regulatory B cells (P = 0.0024), but not regulatory T cells.

CONCLUSIONS

Our findings suggest that increased microbial translocation and dysregulated TLR expression/signaling, coupled with an elevated frequency of regulatory B cells, precede the diagnosis of AIDS-NHL in HIV-infected ART-treated patients.

Cutting Edge: Hematopoietic Stem Cell Expansion and Common Lymphoid Progenitor Depletion Require Hematopoietic-Derived, Cell-Autonomous TLR4 in a Model of Chronic Endotoxin

Hematopoietic stem and progenitors cells (HSPCs) are activated through TLR4 in vitro. However, it remains unclear whether in vivo TLR4 sensing by HSPCs occurs directly or via other cell intermediates. In this study, we examined the cellular mechanisms underlying murine hematopoietic stem cell (HSC) expansion and common lymphoid progenitor (CLP) depletion in a model of chronic low-dose LPS. Using adoptive-transfer approaches, we show that HSC and CLP sensitivity to chronic LPS depends on hematopoietic-derived, cell subset-autonomous TLR4. Like murine progenitors, human HSPCs are activated by TLR4 in vitro. Using humanized mice, a preclinical model relevant to human physiology, we show that persistent endotoxin increases the frequency of Ki-67(+) HSCs and severely depletes CLPs and B precursors. Together, our findings show that murine HSPCs directly respond to endotoxin in vivo and that persistent LPS, a feature of several diseases of global health significance, impairs human lymphopoiesis.

Inflammatory Markers Related to Microbial Translocation Among HIV-Infected Pregnant Women: A Risk Factor of Preterm Delivery

BACKGROUND

This study was performed to assess the role of lipopolysaccharide modulators as a marker of microbial translocation among human immunodeficiency virus (HIV)-infected women during pregnancy and to evaluate their association with preterm delivery.

METHODS

The study had a prospective cohort design and was performed at the Hospital Clínic in Barcelona, Spain. Thirty-six pregnant women with and 36 without HIV infection, matched on the basis of age and parity, were included. Maternal blood samples were obtained during the first trimester, during the third trimester, and at delivery. Levels of soluble CD14 (sCD14), human lipopolysaccharide-binding protein (LBP), immunoglobulin M endotoxin core antibodies to lipopolysaccharide (EndoCAb), and interleukin 6 (IL-6) were determined. Fetal cord blood levels of sCD14, LBP, and IL-6 were determined. Results were compared between groups.

RESULTS

First trimester sCD14 and LBP levels and third trimester sCD14 levels were significantly higher in the HIV-infected group. HIV-infected women with preterm births and spontaneous preterm births had significantly increased levels of sCD14 throughout pregnancy and significantly increased levels of LBP during the first trimester, compared with HIV-infected women with delivery at term or with HIV-negative women. On multivariate analysis, an independent association was observed between first trimester sCD14 levels and preterm delivery among HIV-infected women.

CONCLUSIONS

This is the first study to assess inflammatory markers related to microbial translocation during pregnancy among HIV-infected women. Higher levels of sCD14 and LBP were observed in HIV-infected pregnant women and were associated with preterm delivery.

Differential Reduction in Monocyte Activation and Vascular Inflammation With Integrase Inhibitor-Based Initial Antiretroviral Therapy Among HIV-Infected Individuals

BACKGROUND

Little is known about how different antiretrovirals effect inflammation and monocyte activation in human immunodeficiency virus (HIV) infection.

METHODS

We examined plasma specimens obtained during a randomized, double-blinded trial in antiretroviral therapy (ART)-naive HIV-infected adults which compared the efficacy of elvitegravir/cobicistat/emtricitabine/tenofovir disoproxil fumarate (EVG/c/FTC/TDF) with that of efavirenz/emtricitabine/tenofovir disoproxil fumarate (EFV/FTC/TDF). From a random sample achieving an HIV type 1 RNA load of <50 copies/mL by week 48, changes over 24 and 48 weeks in levels of biomarkers of monocyte activation (soluble CD14 [sCD14] and soluble CD163 [sCD163]), systemic inflammation (soluble tumor necrosis factor α receptor I [sTNF-RI], interleukin 6 [IL-6], and high-sensitivity C-reactive protein [hsCRP]), and vascular inflammation (lipoprotein-associated phospholipase A2 [Lp-PLA2]) were compared. Multivariable linear regression was used.

RESULTS

A total of 200 participants were included. Significant differences favoring EVG/c/FTC/TDF were noted for changes in sCD14, hsCRP, and Lp-PLA2 levels. Factors independently associated with a larger decrease in the sCD14 level included random assignment to receive EVG/c/FTC/TDF, higher baseline sCD14 level, and larger decreases in hsCRP and sCD163 levels; factors associated with a larger Lp-PLA2 decrease included higher baseline Lp-PLA2 and IL-6 levels, smaller increases in total cholesterol and triglycerides levels, a larger decrease in the sCD14 level, and a smaller decrease in the sCD163 level.

CONCLUSIONS

EVG/c/FTC/TDF led to greater decreases in sCD14, hsCRP, and Lp-PLA2 levels, compared with EFV/FTC/TDF. Randomization group independently predicted the change in sCD14 level, and changes in monocyte activation independently predicted the change in Lp-PLA2 level. There appears to be a more favorable effect of the integrase inhibitor EVG over efavirenz on immune activation, which may affect vascular inflammation.