HIV disease: fallout from a mucosal catastrophe?

Immune mechanisms in the pathophysiology of hypertension

Hypertension is a leading risk factor for morbidity and mortality worldwide. Despite current anti-hypertensive therapies, most individuals with hypertension fail to achieve adequate blood pressure control. Moreover, even with adequate control, a residual risk of cardiovascular events and associated organ damage remains. These findings suggest that current treatment modalities are not addressing a key element of the underlying pathology. Emerging evidence implicates immune cells as key mediators in the development and progression of hypertension. In this Review, we discuss our current understanding of the diverse roles of innate and adaptive immune cells in hypertension, highlighting key findings from human and rodent studies. We explore mechanisms by which these immune cells promote hypertensive pathophysiology, shedding light on their multifaceted involvement. In addition, we highlight advances in our understanding of autoimmunity, HIV and immune checkpoints that provide valuable insight into mechanisms of chronic and dysregulated inflammation in hypertension.

Neuroimmune cell interactions and chronic infections in oral cancers

Inflammation is a process that is associated with the activation of distal immunosuppressive pathways that have evolved to restore homeostasis and prevent excessive tissue destruction. However, long-term immunosuppression resulting from systemic and local inflammation that may stem from dysbiosis, infections, or aging poses a higher risk for cancers. Cancer incidence and progression dramatically increase with chronic infections including HIV infection. Thus, studies on pro-tumorigenic effects of microbial stimulants from resident microbiota and infections in the context of inflammation are needed and underway. Here, we discuss chronic infections and potential neuro-immune interactions that could establish immunomodulatory programs permissive for tumor growth and progression.

Making a Monkey out of Human Immunodeficiency Virus/Simian Immunodeficiency Virus Pathogenesis: Immune Cell Depletion Experiments as a Tool to Understand the Immune Correlates of Protection and Pathogenicity in HIV Infection

Understanding the underlying mechanisms of HIV pathogenesis is critical for designing successful HIV vaccines and cure strategies. However, achieving this goal is complicated by the virus's direct interactions with immune cells, the induction of persistent reservoirs in the immune system cells, and multiple strategies developed by the virus for immune evasion. Meanwhile, HIV and SIV infections induce a pandysfunction of the immune cell populations, making it difficult to untangle the various concurrent mechanisms of HIV pathogenesis. Over the years, one of the most successful approaches for dissecting the immune correlates of protection in HIV/SIV infection has been the in vivo depletion of various immune cell populations and assessment of the impact of these depletions on the outcome of infection in non-human primate models. Here, we present a detailed analysis of the strategies and results of manipulating SIV pathogenesis through in vivo depletions of key immune cells populations. Although each of these methods has its limitations, they have all contributed to our understanding of key pathogenic pathways in HIV/SIV infection.

Landscape of gut mucosal immune cells showed gap of follicular or memory B cells into plasma cells in immunological non-responders

BACKGROUND

The gut is an important site for human immunodeficiency virus (HIV) infection and immune responses. The role of gut mucosal immune cells in immune restoration in patients infected with HIV undergoing antiretroviral therapy remains unclear.

METHODS

Ileocytes, including 54 475 immune cells, were obtained from colonoscopic biopsies of five HIV-negative controls, nine immunological responders (IRs), and three immunological non-responders (INRs) and were analyzed using single-cell RNA sequencing. Immunohistochemical assays were performed for validation. The 16S rRNA gene was amplified using PCR in faecal samples to analyze faecal microbiota. Flow cytometry was used to analyze CD4+ T-cell counts and the activation of T cells.

RESULTS

This study presents a global transcriptomic profile of the gut mucosal immune cells in patients infected with HIV. Compared with the IRs, the INRs exhibited a lower proportion of gut plasma cells, especially the IGKC+IgA+ plasma cell subpopulation. IGKC+IgA+ plasma cells were negatively associated with enriched f. Prevotellaceae the INRs and negatively correlated with the overactivation of T cells, but they were positively correlated with CD4+ T-cell counts. The INRs exhibited a higher proportion of B cells than the IRs. Follicular and memory B cells were significantly higher in the INRs. Reduced potential was observed in the differentiation of follicular or memory B cells into gut plasma cells in INRs. In addition, the receptor-ligand pairs CD74_MIF and CD74_COPA of memory B/ follicular helper T cells were significantly reduced in the INRs, which may hinder the differentiation of memory and follicular B cells into plasma cells.

CONCLUSIONS

Our study shows that plasma cells are dysregulated in INRs and provides an extensive resource for deciphering the immune pathogenesis of HIV in INRs.

KEY POINTS

An investigation was carried out at the single-cell-level to analyze gut mucosal immune cells alterations in PLWH after ART. B cells were significantly increased and plasma cells were significantly decreased in the INRs compared to the IRs and NCs. There are gaps in the transition from gut follicular or memory B cellsinto plasma cells in INRs.

T cell activation is insufficient to drive SIV disease progression

Resolution of T cell activation and inflammation is a key determinant of the lack of SIV disease progression in African green monkeys (AGMs). Although frequently considered together, T cell activation occurs in response to viral stimulation of acquired immunity, while inflammation reflects innate immune responses to mucosal injury. We dissociated T cell activation from inflammation through regulatory T cell (Treg) depletion with Ontak (interleukin-2 coupled with diphtheria toxin) during early SIV infection of AGMs. This intervention abolished control of T cell immune activation beyond the transition from acute to chronic infection. Ontak had no effect on gut barrier integrity, microbial translocation, inflammation, and hypercoagulation, despite increasing T cell activation. Ontak administration increased macrophage counts yet decreased their activation. Persistent T cell activation influenced SIV pathogenesis, shifting the ramp-up in viral replication to earlier time points, prolonging the high levels of replication, and delaying CD4+ T cell restoration yet without any clinical or biological sign of disease progression in Treg-depleted AGMs. Thus, by inducing T cell activation without damaging mucosal barrier integrity, we showed that systemic T cell activation per se is not sufficient to drive disease progression, which suggests that control of systemic inflammation (likely through maintenance of gut integrity) is the key determinant of lack of disease progression in natural hosts of SIVs.

Macromolecule Translocation across the Intestinal Mucosa of HIV-Infected Patients by Transcytosis and through Apoptotic Leaks

Based on indirect evidence, increased mucosal translocation of gut-derived microbial macromolecules has been proposed as an important pathomechanism in HIV infection. Here, we quantified macromolecule translocation across intestinal mucosa from treatment-naive HIV-infected patients, HIV-infected patients treated by combination antiretroviral therapy, and HIV-negative controls and analyzed the translocation pathways involved. Macromolecule permeability was quantified by FITC-Dextran 4000 (FD4) and horseradish peroxidase (HRP) flux measurements. Translocation pathways were addressed using cold inhibition experiments. Tight junction proteins were characterized by immunoblotting. Epithelial apoptosis was quantified and translocation pathways were further characterized by flux studies in T84 cell monolayers using inducers and inhibitors of apoptosis and endocytosis. In duodenal mucosa of untreated but not treated HIV-infected patients, FD4 and HRP permeabilities were more than a 4-fold increase compared to the HIV-negative controls. Duodenal macromolecule permeability was partially temperature-dependent and associated with epithelial apoptosis without altered expression of the analyzed tight junction proteins. In T84 monolayers, apoptosis induction increased, and both apoptosis and endocytosis inhibitors reduced macromolecule permeability. Using quantitative analysis, we demonstrate the increased macromolecule permeability of the intestinal mucosa in untreated HIV-infected patients. Combining structural and mechanistic studies, we identified two pathways of increased macromolecule translocation in HIV infection: transcytosis and passage through apoptotic leaks.

The Rapid interaction: a qualitative study of provider approaches to implementing Rapid ART

BACKGROUND

Offering antiretroviral therapy (ART) to patients directly following an HIV diagnosis ("Rapid ART") improves clinical outcomes and is feasible and acceptable for patients and providers. Despite this, implementation of Rapid ART is not yet standard practice in the USA. Structural-level implementation guidance is available, but research at the individual provider level that explores the patient-provider interaction itself remains scarce. The Consolidated Framework for Implementation Research (CFIR) provides a nuanced guide to investigating the less visible, more social elements of implementation like the knowledge and feelings of people, and the influences of culture and resources on individual approaches.

METHODS

We conducted a multi-site qualitative study, exploring intervention commonalities across three HIV clinic environments: an HIV primary care clinic; an HIV/STI testing, treatment, and prevention clinic; and a large federally qualified health center (FQHC). Qualitative data were gathered from 27 provider informants-Rapid ART program staff and clinicians-using an interview guide developed using the CFIR. An experienced qualitative team conducted a comprehensive thematic analysis and identified cross-cutting themes in how providers approach and engage in the Rapid interaction, as well as longer-form narratives from providers that describe more fully what this interaction looks like for them.

RESULTS

Three main themes represent the range and content of individual provider approaches to the Rapid interaction: (1) patient-centeredness; (2) emotional support and partnership; and (3) correcting misperceptions about HIV. Each theme encompassed both conceptual approaches to offering Rapid ART and concrete examples of messaging to the patient that providers used in the Rapid interaction. We describe and show examples of these themes, offer key take-aways for implementation, and provide expanded narratives of providers' personal approaches to the Rapid interaction.

CONCLUSIONS

Exploration of provider-level approaches to Rapid ART implementation, as carried out in the patient-provider Rapid interaction, contributes a critical layer of evidence for wider implementation. It is our hope that, together with existing research showing positive outcomes and core components of systems-level implementation, these findings add to an instructive body of findings that facilitates the implementation of Rapid ART as an enhanced model of HIV care.

Plasma metabolomics by nuclear magnetic resonance reveals biomarkers and metabolic pathways associated with the control of HIV-1 infection/progression

How the human body reacts to the exposure of HIV-1 is an important research goal. Frequently, HIV exposure leads to infection, but some individuals show natural resistance to this infection; they are known as HIV-1-exposed but seronegative (HESN). Others, although infected but without antiretroviral therapy, control HIV-1 replication and progression to AIDS; they are named controllers, maintaining low viral levels and an adequate count of CD4+ T lymphocytes. Biological mechanisms explaining these phenomena are not precise. In this context, metabolomics emerges as a method to find metabolites in response to pathophysiological stimuli, which can help to establish mechanisms of natural resistance to HIV-1 infection and its progression. We conducted a cross-sectional study including 30 HESN, 14 HIV-1 progressors, 14 controllers and 30 healthy controls. Plasma samples (directly and deproteinized) were analyzed through Nuclear Magnetic Resonance (NMR) metabolomics to find biomarkers and altered metabolic pathways. The metabolic profile analysis of progressors, controllers and HESN demonstrated significant differences with healthy controls when a discriminant analysis (PLS-DA) was applied. In the discriminant models, 13 metabolites associated with HESN, 14 with progressors and 12 with controllers were identified, which presented statistically significant mean differences with healthy controls. In progressors, the metabolites were related to high energy expenditure (creatinine), mood disorders (tyrosine) and immune activation (lipoproteins), phenomena typical of the natural course of the infection. In controllers, they were related to an inflammation-modulating profile (glutamate and pyruvate) and a better adaptive immune system response (acetate) associated with resistance to progression. In the HESN group, with anti-inflammatory (lactate and phosphocholine) and virucidal (lactate) effects which constitute a protective profile in the sexual transmission of HIV. Concerning the significant metabolites of each group, we identified 24 genes involved in HIV-1 replication or virus proteins that were all altered in progressors but only partially in controllers and HESN. In summary, our results indicate that exposure to HIV-1 in HESN, as well as infection in progressors and controllers, affects the metabolism of individuals and that this affectation can be determined using NMR metabolomics.

The role of extracellular ATP and P2X receptors in the pathogenesis of HIV-1

Human Immunodeficiency Virus Type 1 (HIV-1) causes a chronic, incurable infection associated with chronic inflammation despite virologic suppression on antiretroviral therapy (ART). This chronic inflammation underlies significant comorbidities, including cardiovascular disease, neurocognition decline, and malignancies. The mechanisms of chronic inflammation have been attributed, in part, to the role of extracellular ATP and P2X-type purinergic receptors that sense damaged or dying cells and undergo signaling responses to activate inflammation and immunomodulation. This review describes the current literature on the role of extracellular ATP and P2X receptors in HIV-1 pathogenesis, describing the known intersection with the HIV-1 life cycle in mediating immunopathogenesis and neuronal disease. The literature supports key roles for this signaling mechanism in cell-to-cell communication and in activating transcriptional changes that impact the inflammatory state leading to disease progression. Future studies must characterize the numerous functions of ATP and P2X receptors in HIV-1 pathogenesis to inform future therapeutic targeting.

Combination Antiretroviral Therapy and Immunophenotype of Feline Immunodeficiency Virus

Feline Immunodeficiency Virus (FIV) causes progressive immune dysfunction in cats similar to human immunodeficiency virus (HIV) in humans. Although combination antiretroviral therapy (cART) is effective against HIV, there is no definitive therapy to improve clinical outcomes in cats with FIV. This study therefore evaluated pharmacokinetics and clinical outcomes of cART (2.5 mg/kg Dolutegravir; 20 mg/kg Tenofovir; 40 mg/kg Emtricitabine) in FIV-infected domestic cats. Specific pathogen free cats were experimentally infected with FIV and administered either cART or placebo treatments (n = 6 each) for 18 weeks, while n = 6 naïve uninfected cats served as controls. Blood, saliva, and fine needle aspirates from mandibular lymph nodes were collected to quantify viral and proviral loads via digital droplet PCR and to assess lymphocyte immunophenotypes by flow cytometry. cART improved blood dyscrasias in FIV-infected cats, which normalized by week 16, while placebo cats remained neutropenic, although no significant difference in viremia was observed in the blood or saliva. cART-treated cats exhibited a Th2 immunophenotype with increasing proportions of CD4+CCR4+ cells compared to placebo cats, and cART restored Th17 cells compared to placebo-treated cats. Of the cART drugs, dolutegravir was the most stable and long-lasting. These findings provide a critical insight into novel cART formulations in FIV-infected cats and highlight their role as a potential animal model to evaluate the impact of cART on lentiviral infection and immune dysregulation.

Inflammasomes as mediators of inflammation in HIV-1 infection

Human immunodeficiency virus type 1 (HIV-1) infection is a chronic disease without a known cure. The advent of effective antiretroviral therapy (ART) has enabled people with HIV (PWH) to have significantly prolonged life expectancies. As a result, morbidity and mortality associated with HIV-1 infection have declined considerably. However, these individuals experience chronic systemic inflammation whose multifaceted etiology is associated with other numerous comorbidities. Inflammasomes are vital mediators that contribute to inflammatory signaling in HIV-1 infection. Here, we provide an overview of the inflammatory pathway that underlies HIV-1 infection, explicitly highlighting the role of the NLRP3 inflammasome. We also delineate the current literature on inflammasomes and the therapeutic targeting strategies aimed at the NLRP3 inflammasome to moderate HIV-1 infection-associated inflammation. Here we describe the NLRP3 inflammasome as a key pathway in developing novel therapeutic targets to block HIV-1 replication and HIV-1-associated inflammatory signaling. Controlling the inflammatory pathways is critical in alleviating the morbidities and mortality associated with chronic HIV-1 infection in PWH.

Cardiovascular disease and risk assessment in people living with HIV: Current practices and novel perspectives

Human immunodeficiency virus (HIV) infection represents a major cardiovascular risk factor, and the cumulative cardiovascular disease (CVD) burden among aging people living with HIV (PLWH) constitutes a leading cause of morbidity and mortality. To date, CVD risk assessment in PLWH remains challenging. Therefore, it is necessary to evaluate and stratify the cardiovascular risk in PLWH with appropriate screening and risk assessment tools and protocols to correctly identify which patients are at a higher risk for CVD and will benefit most from prevention measures and timely management. This review aims to accumulate the current evidence on the association between HIV infection and CVD, as well as the risk factors contributing to CVD in PLWH. Furthermore, considering the need for cardiovascular risk assessment in daily clinical practice, the purpose of this review is also to report the current practices and novel perspectives in cardiovascular risk assessment of PLWH and provide further insights into the development and implementation of appropriate CVD risk stratification and treatment strategies, particularly in countries with high HIV burden and limited resources.

Relevance of biomarkers indicating gut damage and microbial translocation in people living with HIV

The intestinal barrier has the daunting task of allowing nutrient absorption while limiting the entry of microbial products into the systemic circulation. HIV infection disrupts the intestinal barrier and increases intestinal permeability, leading to microbial product translocation. Convergent evidence has shown that gut damage and an enhanced level of microbial translocation contribute to the enhanced immune activation, the risk of non-AIDS comorbidity, and mortality in people living with HIV (PLWH). Gut biopsy procedures are invasive, and are not appropriate or feasible in large populations, even though they are the gold standard for intestinal barrier investigation. Thus, validated biomarkers that measure the degree of intestinal barrier damage and microbial translocation are needed in PLWH. Hematological biomarkers represent an objective indication of specific medical conditions and/or their severity, and should be able to be measured accurately and reproducibly via easily available and standardized blood tests. Several plasma biomarkers of intestinal damage, i.e., intestinal fatty acid-binding protein (I-FABP), zonulin, and regenerating islet-derived protein-3α (REG3α), and biomarkers of microbial translocation, such as lipopolysaccharide (LPS) and (1,3)-β-D-Glucan (BDG) have been used as markers of risk for developing non-AIDS comorbidities in cross sectional analyses and clinical trials, including those aiming at repair of gut damage. In this review, we critically discuss the value of different biomarkers for the estimation of gut permeability levels, paving the way towards developing validated diagnostic and therapeutic strategies to repair gut epithelial damage and to improve overall disease outcomes in PLWH.

Intestinal Fatty Acid Binding Protein (I-FABP) as a Prognostic Marker in Critically Ill COVID-19 Patients

Gastrointestinal symptoms are common in critically ill COVID-19 patients. There is currently no generally recognized method of assessing gastrointestinal injury in unconscious or sedated intensive care unit (ICU) patients. I-FABP (intestinal fatty acid binding protein) and citrulline have previously been studied as potential biomarkers of enterocyte damage in various gastrointestinal tract diseases, and changes in the levels of these markers may reflect intestinal wall damage in COVID-19. Patients with critical COVID-19, with diagnosed sepsis, or septic shock requiring ICU treatment were included in the study. Blood samples for citrulline and I-FABP were taken daily from day 1 to 5. I-FABP levels were significantly higher in patients who eventually died from COVID-19 than in survivors, and the optimal I-FABP cut-off point for predicting 28-day mortality was 668.57 pg/mL (sensitivity 0.739, specificity 0.765). Plasma levels of I-FABP, but not citrulline, were associated with significantly higher mortality and appeared to be a predictor of poor outcome in multivariate logistic regression analysis. In conclusion, I-FABP seems to be an effective prognostic marker in critically ill COVID-19 patients. Assessing mortality risk based on intestinal markers may be helpful in making clinical decisions regarding the management of intestinal injury, imaging diagnostics, and potential surgical interventions.

Inflammatory and immune markers in HIV-infected older adults on long-term antiretroviral therapy: Persistent elevation of sCD14 and of proinflammatory effector memory T cells

HIV-positive patients whose viral loads are successfully controlled by active antiretroviral therapy (ART) show no clinical signs of AIDS. However, their lifespan is shorter compared with individuals with no HIV infection and they prematurely exhibit a multitude of chronic diseases typically associated with advanced age. It was hypothesized that immune system aging may correlate with, and provide useful biomarkers for, this premature loss of healthspan in HIV-positive subjects. Here, we tested whether the immune correlates of aging, including cell numbers and phenotypes, inflammatory status, and control of human cytomegalovirus (hCMV) in HIV-positive subjects on long-term successful ART (HIV+) may reveal increased "immunological age" compared with HIV-negative, age-matched cohort (HIV-) in participants between 50 and 69 years of age. Specifically, we expected that younger HIV+ subjects may immunologically resemble older individuals without HIV. We found no evidence to support this hypothesis. While T cells from HIV+ participants displayed differential expression in several differentiation and/or inhibitory/exhaustion markers in different T cell subpopulations, aging by a decade did not pronounce these changes. Similarly, while the HIV+ participants exhibited higher T cell responses and elevated inflammatory marker levels in plasma, indicative of chronic inflammation, this trait was not age-sensitive. We did find differences in immune control of hCMV, and, more importantly, a sustained elevation of sCD14 and of proinflammatory CD4 and CD8 T cell responses across age groups, pointing towards uncontrolled inflammation as a factor in reduced healthspan in successfully treated older HIV+ patients.

I've looked at gut from both sides now: Gastrointestinal tract involvement in the pathogenesis of SARS-CoV-2 and HIV/SIV infections

The lumen of the gastrointestinal (GI) tract contains an incredibly diverse and extensive collection of microorganisms that can directly stimulate the immune system. There are significant data to demonstrate that the spatial localization of the microbiome can impact viral disease pathogenesis. Here we discuss recent studies that have investigated causes and consequences of GI tract pathologies in HIV, SIV, and SARS-CoV-2 infections with HIV and SIV initiating GI pathology from the basal side and SARS-CoV-2 from the luminal side. Both these infections result in alterations of the intestinal barrier, leading to microbial translocation, persistent inflammation, and T-cell immune activation. GI tract damage is one of the major contributors to multisystem inflammatory syndrome in SARS-CoV-2-infected individuals and to the incomplete immune restoration in HIV-infected subjects, even in those with robust viral control with antiretroviral therapy. While the causes of GI tract pathologies differ between these virus families, therapeutic interventions to reduce microbial translocation-induced inflammation and improve the integrity of the GI tract may improve the prognoses of infected individuals.

Diagnostic Accuracy of Therapeutic Drug Monitoring During Tuberculosis Treatment

Tuberculosis (TB) patients co-infected with human immunodeficiency virus (HIV) are more likely to have low blood concentrations of the first-line anti-TB drugs (associated with poor outcomes). Therapeutic drug monitoring (TDM) is recommended for certain TB patient populations at increased risk for a poor outcome. Our objective was to estimate the diagnostic accuracy of a 2-hour TDM serum sample for the first-line anti-TB drugs among HIV/TB patients, and evaluate the information gained by an additional 6-hour sample. We created a virtual (n = 1,000) HIV/TB patient population and performed pharmacokinetic (PK) simulations using published population models for isoniazid, rifampin, pyrazinamide, and ethambutol. We performed receiver-operating-characteristic (ROC) analysis to compare the diagnostic performance of a single 2-hour serum sample with samples obtained at 2- and 6-hours post-dosing. The sensitivity of a single 2-hour serum concentration to identify HIV/TB patients with adequate serum exposures was lowest for rifampin (54.9%, 95% CI 50.79-59.41%) and highest for ethambutol (70.8%, 95% CI 66.06-72.61%) for C_max targets. Diagnostic accuracy of a single 2-hour serum sample for the AUC_0-24 target was highest for isoniazid (93%, 95% CI 90.9-94.1%) and lowest for pyrazinamide (66.3%, 95% CI 62.6-70.0%). In summary, the diagnostic performance of TDM for C_max and AUC_0-24 targets demonstrated variability across the first-line anti-TB drugs. The addition of a 6-hour serum sample lead to the highest statistically significant improvement (p < 0.001) and highest increase in diagnostic accuracy (area under the ROC curve) for rifampin for C_max and AUC. The other first-line drugs had modest/negligible increases in diagnostic accuracy. This article is protected by copyright. All rights reserved.

CXCR3 Expression Pattern on CD4+ T Cells and IP-10 Levels with Regard to the HIV-1 Reservoir in the Gut-Associated Lymphatic Tissue

(1) Background: The gut-associated lymphatic tissue (GALT) represents the largest lymphoid organ, and is considered to be the largest HIV reservoir. The exact size of the GALT reservoir remains unclear. Several markers, such as the chemokine receptor CXCR3 and its pro-inflammatory ligand IP-10, have been proposed to define the size of HIV reservoirs in the peripheral blood (PB). However, little is known about the role of CXCR3 and IP-10 within the GALT. (2) Methods: We compared the CXCR3 expression, IP-10 levels, and cell-associated HIV DNA of distinct memory CD4+ T cell subsets from the terminal ileum (TI), PB and rectum (RE) of 18 HIV+ patients with antiretroviral therapy (ART), 6 HIV+ treatment-naive patients and 16 healthy controls. (3) Results: While the relative distributions of CD4+ T cell subsets were similar in PB, TI and RE, HIV DNA and CXCR3 expression were markedly increased and IP-10 levels were decreased in TI when compared to PB. No significant correlation was found between the CXCR3 expression and memory CD4+ T cell subsets, IP-10 levels and the HIV DNA amounts measured in PB, TI or RE. (4) Conclusions: During a chronic HIV-1 infection, neither CXCR3 nor IP-10 are indicative of the size of the viral reservoir in the GALT (TI and RE).

Characterization of human IgM and IgG repertoires in individuals with chronic HIV-1 infection

Advancements in high-throughput sequencing (HTS) of antibody repertoires (Ig-Seq) have unprecedentedly improved our ability to characterize the antibody repertoires on a large scale. However, currently, only a few studies explored the influence of chronic HIV-1 infection on human antibody repertoires and many of them reached contradictory conclusions, possibly limited by inadequate sequencing depth and throughput. To better understand how HIV-1 infection would impact humoral immune system, in this study, we systematically analyzed the differences between the IgM (HIV-IgM) and IgG (HIV-IgG) heavy chain repertoires of HIV-1 infected patients, as well as between antibody repertoires of HIV-1 patients and healthy donors (HH). Notably, the public unique clones accounted for only a negligible proportion between the HIV-IgM and HIV-IgG repertoires libraries, and the diversity of unique clones in HIV-IgG remarkably reduced. In aspect of somatic mutation rates of CDR1 and CDR2, the HIV-IgG repertoire was higher than HIV-IgM. Besides, the average length of CDR3 region in HIV-IgM was significant longer than that in the HH repertoire, presumably caused by the great number of novel VDJ rearrangement patterns, especially a massive use of IGHJ6. Moreover, some of the B cell clonotypes had numerous clones, and somatic variants were detected within the clonotype lineage in HIV-IgG, indicating HIV-1 neutralizing activities. The in-depth characterization of HIV-IgG and HIV-IgM repertoires enriches our knowledge in the profound effect of HIV-1 infection on human antibody repertoires and may have practical value for the discovery of therapeutic antibodies.

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Ultra-deep sequencing of both IgM and IgG repertoires in chronic HIV-1 infection.

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VDJ gene rearrangement patterns can be dramatically changed by HIV-1 infection.

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Multiple mechanisms cause the high complexity of HIV-1-experienced antibodies.

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Discovery of promising neutralizing HIV-1 antibodies from antibody repertoires.

Th17 CD4+ T-Cell as a Preferential Target for HIV Reservoirs

Among CD4+ T-cells, T helper 17 (Th17) cells play a sentinel role in the defense against bacterial/fungal pathogens at mucosal barriers. However, Th17 cells are also highly susceptible to HIV-1 infection and are rapidly depleted from gut mucosal sites, causing an imbalance of the Th17/Treg ratio and impairing cytokines production. Consequently, damage to the gut mucosal barrier leads to an enhanced microbial translocation and systemic inflammation, a hallmark of HIV-1 disease progression. Th17 cells’ expression of mucosal homing receptors (CCR6 and α4β7), as well as HIV receptors and co-receptors (CD4, α4β7, CCR5, and CXCR4), contributes to susceptibility to HIV infection. The up-regulation of numerous intracellular factors facilitating HIV production, alongside the downregulation of factors inhibiting HIV, helps to explain the frequency of HIV DNA within Th17 cells. Th17 cells harbor long-lived viral reservoirs in people living with HIV (PLWH) receiving antiretroviral therapy (ART). Moreover, cell longevity and the proliferation of a fraction of Th17 CD4 T cells allow HIV reservoirs to be maintained in ART patients.

So Pathogenic or So What?-A Brief Overview of SIV Pathogenesis with an Emphasis on Cure Research

HIV infection requires lifelong antiretroviral therapy (ART) to control disease progression. Although ART has greatly extended the life expectancy of persons living with HIV (PWH), PWH nonetheless suffer from an increase in AIDS-related and non-AIDS related comorbidities resulting from HIV pathogenesis. Thus, an HIV cure is imperative to improve the quality of life of PWH. In this review, we discuss the origins of various SIV strains utilized in cure and comorbidity research as well as their respective animal species used. We briefly detail the life cycle of HIV and describe the pathogenesis of HIV/SIV and the integral role of chronic immune activation and inflammation on disease progression and comorbidities, with comparisons between pathogenic infections and nonpathogenic infections that occur in natural hosts of SIVs. We further discuss the various HIV cure strategies being explored with an emphasis on immunological therapies and "shock and kill".

HIV pre-exposure prophylaxis and sexually transmitted infections: intersection and opportunity

Pre-exposure prophylaxis (PrEP) has revolutionized HIV prevention, but PrEP does not protect against other sexually transmitted infections (STIs). Rates of STIs are rising worldwide, with notably high incidences among PrEP-using men who have sex with men in high-income countries; in low-income and middle-income countries, data are sparse, but results from a limited number of studies among African women initiating and taking PrEP have shown high STI prevalence and incidence. Efforts aimed at markedly reducing HIV in populations worldwide include a major focus on increasing PrEP use, along with improving HIV testing and treatment in order to eliminate HIV transmission. Together, these efforts could augment continued expansion of the global STI epidemic, but they could alternatively create an opportunity to improve STI control, including the development of comprehensive sexual health programmes and research to develop new STI prevention strategies. The introduction of PrEP globally has been characterized by challenges and many successes, and its role as part of a range of robust strategies to reduce HIV infections is clear. Looking ahead, understanding rising rates of curable STIs and their relationship to HIV prevention, and considering the future directions for synergies in PrEP and STI prevention will be integral to improving sexual health.

Attenuated Negative Feedback in Monocyte-Derived Macrophages From Persons Living With HIV: A Role for IKAROS

Persons living with HIV (PLWH) are at higher risk of developing secondary illnesses than their uninfected counterparts, suggestive of a dysfunctional immune system in these individuals. Upon exposure to pathogens, monocytes undergo epigenetic remodeling that results in either a trained or a tolerant phenotype, characterized by hyper-responsiveness or hypo-responsiveness to secondary stimuli, respectively. We utilized CD14⁺ monocytes from virally suppressed PLWH and healthy controls for in vitro analysis following polarization of these cells toward a pro-inflammatory monocyte-derived macrophage (MDM) phenotype. We found that in PLWH-derived MDMs, pro-inflammatory signals (TNFA, IL6, IL1B, miR-155-5p, and IDO1) dominate over negative feedback signals (NCOR2, GSN, MSC, BIN1, and miR-146a-5p), favoring an abnormally trained phenotype. The mechanism of this reduction in negative feedback involves the attenuated expression of IKZF1, a transcription factor required for de novo synthesis of RELA during LPS-induced inflammatory responses. Furthermore, restoring IKZF1 expression in PLWH-MDMs partially reinstated expression of negative regulators of inflammation and lowered the expression of pro-inflammatory cytokines. Overall, this mechanism may provide a link between dysfunctional immune responses and susceptibility to co-morbidities in PLWH with low or undetectable viral load.

Th17 cell master transcription factor RORC2 regulates HIV-1 gene expression and viral outgrowth

HIV-1 infects CD4 T cells, and, among these, T helper 17 (Th17) cells are known to be particularly permissive for virus replication. The infection of Th17 cells is critical for AIDS pathogenesis and viral persistence. It is, however, not clear why these cells are highly permissive to HIV-1. We found that Th17 cell permissiveness depends on the expression of the hormone receptor RORC2, which is the master transcriptional regulator of Th17 cell differentiation. We identify RORC2 as a cell-specific host-dependency factor that can be targeted by small molecules. Our results suggest that RORC2 may be a cell-specific target to mitigate the loss of Th17 cells as a consequence of their preferential HIV-1 infection.

Among CD4⁺ T cells, T helper 17 (Th17) cells are particularly susceptible to HIV-1 infection and are depleted from mucosal sites, which causes damage to the gut barrier, resulting in a microbial translocation-induced systemic inflammation, a hallmark of disease progression. Furthermore, a proportion of latently infected Th17 cells persist long term in the gastrointestinal lymphatic tract where a low-level HIV-1 transcription is observed. This residual viremia contributes to chronic immune activation. Thus, Th17 cells are key players in HIV pathogenesis and viral persistence. It is, however, unclear why these cells are highly susceptible to HIV-1 infection. Th17 cell differentiation depends on the expression of the master transcriptional regulator RORC2, a retinoic acid-related nuclear hormone receptor that regulates specific transcriptional programs by binding to promoter/enhancer DNA. Here, we report that RORC2 is a key host cofactor for HIV replication in Th17 cells. We found that specific inhibitors that bind to the RORC2 ligand-binding domain reduced HIV replication in CD4⁺ T cells. The depletion of RORC2 inhibited HIV-1 infection, whereas its overexpression enhanced it. RORC2 was also found to promote HIV-1 gene expression by binding to the nuclear receptor responsive element in the HIV-1 long terminal repeats (LTR). In treated HIV-1 patients, RORC2⁺ CD4 T cells contained more proviral DNA than RORC2⁻ cells. Pharmacological inhibition of RORC2 potently reduced HIV-1 outgrowth in CD4⁺ T cells from antiretroviral-treated patients. Altogether, these results provide an explanation as to why Th17 cells are highly susceptible to HIV-1 infection and suggest that RORC2 may be a cell-specific target for HIV-1 therapy.

IL-17A reprograms intestinal epithelial cells to facilitate HIV-1 replication and outgrowth in CD4+ T cells

The crosstalk between intestinal epithelial cells (IECs) and Th17-polarized CD4⁺ T cells is critical for mucosal homeostasis, with HIV-1 causing significant alterations in people living with HIV (PLWH) despite antiretroviral therapy (ART). In a model of IEC and T cell co-cultures, we investigated the effects of IL-17A, the Th17 hallmark cytokine, on IEC ability to promote de novo HIV infection and viral reservoir reactivation. Our results demonstrate that IL-17A acts in synergy with TNF to boost IEC production of CCL20, a Th17-attractant chemokine, and promote HIV trans-infection of CD4⁺ T cells and viral outgrowth from reservoir cells of ART-treated PLWH. Importantly, the Illumina RNA-sequencing revealed an IL-17A-mediated pro-inflammatory and pro-viral molecular signature, including a decreased expression of type I interferon (IFN-I)-induced HIV restriction factors. These findings point to the deleterious features of IL-17A and raise awareness for caution when designing therapies aimed at restoring the paucity of mucosal Th17 cells in ART-treated PLWH.

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IL-17A acts in synergy with TNF to enhance CCL20 production in IEC exposed to HIV

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IL-17A/TNF-activated IEC efficiently promote HIV trans-infection of CD4⁺ T cells

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IL-17A reprograms IEC to boost HIV outgrowth from CD4⁺ T cells of ART-treated PLWH

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IL-17A decreases the expression of IFN-I-induced HIV restriction factors in IEC

A Tale of Two Viruses: Immunological Insights Into HCV/HIV Coinfection

Nearly 2.3 million individuals worldwide are coinfected with human immunodeficiency virus (HIV) and hepatitis C virus (HCV). Odds of HCV infection are six times higher in people living with HIV (PLWH) compared to their HIV-negative counterparts, with the highest prevalence among people who inject drugs (PWID) and men who have sex with men (MSM). HIV coinfection has a detrimental impact on the natural history of HCV, including higher rates of HCV persistence following acute infection, higher viral loads, and accelerated progression of liver fibrosis and development of end-stage liver disease compared to HCV monoinfection. Similarly, it has been reported that HCV coinfection impacts HIV disease progression in PLWH receiving anti-retroviral therapies (ART) where HCV coinfection negatively affects the homeostasis of CD4⁺ T cell counts and facilitates HIV replication and viral reservoir persistence. While ART does not cure HIV, direct acting antivirals (DAA) can now achieve HCV cure in nearly 95% of coinfected individuals. However, little is known about how HCV cure and the subsequent resolution of liver inflammation influence systemic immune activation, immune reconstitution and the latent HIV reservoir. In this review, we will summarize the current knowledge regarding the pathogenesis of HIV/HCV coinfection, the effects of HCV coinfection on HIV disease progression in the context of ART, the impact of HIV on HCV-associated liver morbidity, and the consequences of DAA-mediated HCV cure on immune reconstitution and HIV reservoir persistence in coinfected patients.

Antiretroviral Therapy Dampens Mucosal CD4+ T Lamina Propria Lymphocytes Immune Activation in Long-Term Treated People Living with HIV-1

HIV infection is characterized by a severe deterioration of an immune cell-mediated response due to a progressive loss of CD4⁺ T cells from gastrointestinal tract, with a preferential loss of IL-17 producing Th cells (Th17), a specific CD4⁺ T cells subset specialized in maintaining mucosal integrity and antimicrobial inflammatory responses. To address the effectiveness of antiretroviral therapy (ART) in reducing chronic immunological dysfunction and immune activation of intestinal mucosa, we conducted a cross-sectional observational study comparing total IFN-γ-expressing (Th1) and IL-17-expressing (Th17) frequencies of CD4⁺ T lamina propria lymphocytes (LPLs) and their immune activation status between 11 male ART-naïve and 11 male long-term ART-treated people living with HIV-1 (PLWH) who underwent colonoscopy and retrograde ileoscopy for biopsies collection. Flow cytometry for surface and intracellular staining was performed. Long-term ART-treated PLWH showed lower levels of CD38⁺ and/or HLA-DR⁺ LPLs compared to ART-naïve PLWH. Frequencies of Th1 and Th17 LPLs did not differ between the two groups. Despite ART failing to restore the Th1 and Th17 levels within the gut mucosa, it is effective in increasing overall CD4⁺ T LPLs frequencies and reducing mucosal immune activation.

Perspectives on Non-BLT Humanized Mouse Models for Studying HIV Pathogenesis and Therapy

A variety of humanized mice, which are reconstituted only with human hematopoietic stem cells (HSC) or with fetal thymus and HSCs, have been developed and widely utilized as in vivo animal models of HIV-1 infection. The models represent some aspects of HIV-mediated pathogenesis in humans and are useful for the evaluation of therapeutic regimens. However, there are several limitations in these models, including their incomplete immune responses and poor distribution of human cells to the secondary lymphoid tissues. These limitations are common in many humanized mouse models and are critical issues that need to be addressed. As distinct defects exist in each model, we need to be cautious about the experimental design and interpretation of the outcomes obtained using humanized mice. Considering this point, we mainly characterize the current conventional humanized mouse reconstituted only with HSCs and describe past achievements in this area, as well as the potential contributions of the humanized mouse models for the study of HIV pathogenesis and therapy. We also discuss the use of various technologies to solve the current problems. Humanized mice will contribute not only to the pre-clinical evaluation of anti-HIV regimens, but also to a deeper understanding of basic aspects of HIV biology.

A network of immune and microbial modifications underlies viral persistence in the gastrointestinal tract

Many pathogens subvert intestinal immunity to persist within the gastrointestinal tract (GIT); yet, the underlying mechanisms that enable sanctuary specifically in this reservoir are unclear. Using mass cytometry and network analysis, we demonstrate that chronic LCMV infection of the GIT leads to dysregulated microbial composition, a cascade of metabolic alterations, increased susceptibility to GI disease, and a system-wide recalibration of immune composition that defines viral persistence. Chronic infection led to outgrowth of activated Tbet–expressing T reg cell populations unique to the GIT and the rapid erosion of pathogen-specific CD8 tissue-resident memory T cells. Mechanistically, T reg cells and coinhibitory receptors maintained long-term viral sanctuary within the GIT, and their targeting reactivated T cells and eliminated this viral reservoir. Thus, our data provide a high-dimensional definition of the mechanisms of immune regulation that chronic viruses implement to exploit the unique microenvironment of the GIT and identify T reg cells as key modulators of viral persistence in the intestinal tract.

Dimethyl Fumarate, an Approved Multiple Sclerosis Treatment, Reduces Brain Oxidative Stress in SIV-Infected Rhesus Macaques: Potential Therapeutic Repurposing for HIV Neuroprotection

Dimethyl fumarate (DMF), an antioxidant/anti-inflammatory drug approved for the treatment of multiple sclerosis, induces antioxidant enzymes, in part through transcriptional upregulation. We hypothesized that DMF administration to simian immunodeficiency virus (SIV)-infected rhesus macaques would induce antioxidant enzyme expression and reduce oxidative injury and inflammation throughout the brain. Nine SIV-infected, CD8⁺-T-lymphocyte-depleted rhesus macaques were studied. Five received oral DMF prior to the SIV infection and through to the necropsy day. Protein expression was analyzed in 11 brain regions, as well as the thymus, liver, and spleen, using Western blot and immunohistochemistry for antioxidant, inflammatory, and neuronal proteins. Additionally, oxidative stress was determined in brain sections using immunohistochemistry (8-OHdG, 3NT) and optical redox imaging of oxidized flavoproteins containing flavin adenine dinucleotide (Fp) and reduced nicotinamide adenine dinucleotide (NADH). The DMF treatment was associated with no changes in virus replication; higher expressions of the antioxidant enzymes NQO1, GPX1, and HO-1 in the brain and PRDX1 and HO-2 in the spleen; lower levels of 8-OHdG and 3NT; a lower optical redox ratio. The DMF treatment was also associated with increased expressions of cell-adhesion molecules (VCAM-1, ICAM-1) and no changes in HLA-DR, CD68, GFAP, NFL, or synaptic proteins. The concordantly increased brain antioxidant enzyme expressions and reduced oxidative stress in DMF-treated SIV-infected macaques suggest that DMF could limit oxidative stress throughout the brain through effective induction of the endogenous antioxidant response. We propose that DMF could potentially induce neuroprotective brain responses in persons living with HIV.

Early Colorectal Responses to HIV-1 and Modulation by Antiretroviral Drugs

Innate responses during acute HIV infection correlate with disease progression and pathogenesis. However, limited information is available about the events occurring during the first hours of infection in the mucosal sites of transmission. With an ex vivo HIV-1 challenge model of human colorectal tissue we assessed the mucosal responses induced by R5- and X4-tropic HIV-1 isolates in the first 24 h of exposure. Microscopy studies demonstrated virus penetration of up to 39 μm into the lamina propia within 6 h of inoculation. A rapid, 6 h post-challenge, increase in the level of secretion of inflammatory cytokines, chemokines, interferon- γ (IFN-γ), and granulocyte-macrophage colony-stimulating factor (GM-CSF) was observed following exposure to R5- or X4-tropic isolates. This profile persisted at the later time point measured of 24 h. However, exposure to the X4-tropic isolate tested induced greater changes at the proteomic and transcriptomic levels than the R5-tropic. The X4-isolate induced greater levels of CCR5 ligands (RANTES, MIP-1α and MIP-1β) secretion than R5-HIV-1. Potential drugs candidates for colorectal microbicides, including entry, fusion or reverse transcriptase inhibitors demonstrated differential capacity to modulate these responses. Our findings indicate that in colorectal tissue, inflammatory responses and a Th1 cytokine profile are induced in the first 24 h following viral exposure.

Long-Term Suppressive cART Is Not Sufficient to Restore Intestinal Permeability and Gut Microbiota Compositional Changes

Background: We explored the long-term effects of cART on markers of gut damage, microbial translocation, and paired gut/blood microbiota composition, with a focus on the role exerted by different drug classes.

Methods: We enrolled 41 cART naïve HIV-infected subjects, undergoing blood and fecal sampling prior to cART (T0) and after 12 (T12) and 24 (T24) months of therapy. Fifteen HIV-uninfected individuals were enrolled as controls. We analyzed: (i) T-cell homeostasis (flow cytometry); (ii) microbial translocation (sCD14, EndoCab, 16S rDNA); (iii) intestinal permeability and damage markers (LAC/MAN, I-FABP, fecal calprotectin); (iv) plasma and fecal microbiota composition (alpha- and beta-diversity, relative abundance); (v) functional metagenome predictions (PICRUSt).

Results: Twelve and twenty four-month successful cART resulted in a rise in EndoCAb (p = 0.0001) and I-FABP (p = 0.039) vis-à-vis stable 16S rDNA, sCD14, calprotectin and LAC/MAN, along with reduced immune activation in the periphery. Furthermore, cART did not lead to substantial modifications of microbial composition in both plasma and feces and metabolic metagenome predictions. The stratification according to cART regimens revealed a feeble effect on microbiota composition in patients on NNRTI-based or INSTI-based regimens, but not PI-based regimens.

Conclusions: We hereby show that 24 months of viro-immunological effective cART, while containing peripheral hyperactivation, exerts only minor effects on the gastrointestinal tract. Persistent alteration of plasma markers indicative of gut structural and functional impairment seemingly parallels enduring fecal dysbiosis, irrespective of drug classes, with no effect on metabolic metagenome predictions.

Compromised Gut Associated Lymphoid Tissue is a Risk Factor for Postoperative Septic Complications in HIV-Seropositive Trauma Patients

Background

The gut associated lymphoid tissue (GALT) is an important part of the immune system and compromised in HIV treatment-naïve as well as in HIV-seropositive patients on antiretroviral treatment (ART) due to HIV-induced changes. The influence of the impaired GALT on the postoperative complication rate after surgery for penetrating abdominal trauma has not been investigated and the hypothesis that the HIV-induced changes of the GALT contribute to septic complications postoperatively was tested.

Material and methods

This prospective study included patients who required a small bowel resection due to abdominal gunshot wounds. A bowel specimen was obtained in the index operation, and the T-lymphocytic quantity in the specimen was analyzed via immunohistochemistry to scrutinize whether these lymphocyte numbers had an impact on the postoperative outcome. Septic and postoperative complications were documented during the in-hospital course and the first month after discharge.

Results

In total, 62 patients were included in the study of which 38 patients were HIV-seronegative and 24 were HIV-seropositive. HIV-seropositive patients had a significantly lower quantity of CD4 + T cells in the GALT compared to the HIV-seronegative patients (p = 0.0001), which was also associated with a significantly higher rate of septic complications in the postoperative course. In the HIV-seropositive group, no significant differences were detected for T-lymphocytic quantity in the GALT between the HIV-treatment naïve and antiretroviral treatment groups.

Conclusion

The compromised GALT in HIV-seropositive patients may predispose these patients to postoperative septic complications. Antiretroviral therapy does not result in an adequate immune reconstitution in this tissue.

Lipopolysaccharide induces platelet activation in HIV patients: the role of different viral load patterns

OBJECTIVES

This study aimed to assess whether gut-derived lipopolysaccharide (LPS) could affect platelet function in HIV-1 patients with residual viral load.

METHODS

In 23 HIV-1 patients on effective antiretroviral treatment, 10 treatment-naïve HIV-1 subjects and 20 healthy subjects (HS), LPS, zonulin, markers of platelet activation and oxidative stress were evaluated. In vitro, platelets from HS were exposed to plasma from HIV-1-infected treated and untreated patients.

RESULTS

Compared with HS, LPS was higher in treated and treatment-naïve subjects with HIV-1 (7.7 ± 2.9, 80.9 ± 13.7 and 75.3 ± 22.6 pg/mL, P < 0.001 vs. HS) as well as serum zonulin (1.3 ± 0.5, 6.1 ± 1.5 and 5.3 ± 1.7 ng/mL, P < 0.001 vs. HS). LPS and zonulin were correlated in HIV patients (Spearman correlation coefficient (rS) = 0.73, P < 0.0001). Levels of soluble CD40 ligand (sCD40L), soluble P-selectin (sP-selectin) and thromboxane B₂ (TxB₂ ) were higher in HIV-1-treated and treatment-naïve subjects compared with HS as well as NADPH oxidase 2 (NOX2) activation and hydrogen peroxide (H₂ O₂ ) production. In vitro, sCD40L, sP-selectin and TxB₂ production, NOX2 activation and p47^phox phosphorylation were higher in platelets exposed to plasma from HIV-1 patients with different viral load compared with the exposure to plasma from HS. This effect was blunted in platelets pre-treated with TLR4 or TLR7 inhibitors.

CONCLUSIONS

Low-grade endotoxaemia and persistent viraemia increase platelet function with a mechanism mediated by NOX2 in patients with HIV-1 infection.

Regulation of Gut Microbiota on Immune Reconstitution in Patients With Acquired Immunodeficiency Syndrome

Human immunodeficiency virus type 1 (HIV-1) infection of CD4⁺ T cells in the gut plays an insidious role in acquired immunodeficiency syndrome (AIDS) pathogenesis. Host immune function is closely related to gut microbiota. Changes in the gut microbiota cause a different immune response. Previous studies revealed that HIV-1 infection caused changes in gut microbiota, which induced immune deficiency. HIV-1 infection results in an abnormal composition and function of the gut microbiota, which may disrupt the intestinal epithelial barrier and microbial translocation, leading to long-term immune activation, including inflammation and metabolic disorders. At the same time, an abnormal gut microbiota also hinders the effect of antiviral therapy and affects the immune reconstruction of patients. However, studies on the impact of the gut microbiota on immune reconstitution in patients with HIV/AIDS are still limited. In this review, we focus on changes in the gut microbiota caused by HIV infection, as well as the impact and regulation of the gut microbiota on immune function and immune reconstitution, while we also discuss the potential impact of probiotics/prebiotics and fecal microbiota transplantation (FMT) on immune reconstitution.

CNS Macrophages and Infant Infections

The central nervous system (CNS) harbors its own immune system composed of microglia in the parenchyma and CNS-associated macrophages (CAMs) in the perivascular space, leptomeninges, dura mater, and choroid plexus. Recent advances in understanding the CNS resident immune cells gave new insights into development, maturation and function of its immune guard. Microglia and CAMs undergo essential steps of differentiation and maturation triggered by environmental factors as well as intrinsic transcriptional programs throughout embryonic and postnatal development. These shaping steps allow the macrophages to adapt to their specific physiological function as first line of defense of the CNS and its interfaces. During infancy, the CNS might be targeted by a plethora of different pathogens which can cause severe tissue damage with potentially long reaching defects. Therefore, an efficient immune response of infant CNS macrophages is required even at these early stages to clear the infections but may also lead to detrimental consequences for the developing CNS. Here, we highlight the recent knowledge of the infant CNS immune system during embryonic and postnatal infections and the consequences for the developing CNS.

Interrogating the recognition landscape of a conserved HIV-specific TCR reveals distinct bacterial peptide cross-reactivity

T cell cross-reactivity ensures that diverse pathogen-derived epitopes encountered during a lifetime are recognized by the available TCR repertoire. A feature of cross-reactivity where previous exposure to one microbe can alter immunity to subsequent, non-related pathogens has been mainly explored for viruses. Yet cross-reactivity to additional microbes is important to consider, especially in HIV infection where gut-intestinal barrier dysfunction could facilitate T cell exposure to commensal/pathogenic microbes. Here we evaluated the cross-reactivity of a ‘public’, HIV-specific, CD8 T cell-derived TCR (AGA1 TCR) using MHC class I yeast display technology. Via screening of MHC-restricted libraries comprising ~2×10⁸ sequence-diverse peptides, AGA1 TCR specificity was mapped to a central peptide di-motif. Using the top TCR-enriched library peptides to probe the non-redundant protein database, bacterial peptides that elicited functional responses by AGA1-expressing T cells were identified. The possibility that in context-specific settings, MHC class I proteins presenting microbial peptides influence virus-specific T cell populations in vivo is discussed.

NLRP3 Inflammasome Signaling as a Link Between HIV-1 Infection and Atherosclerotic Cardiovascular Disease

36.9 million people worldwide are living with HIV-1. The disease remains incurable and HIV-infected patients have increased risk of atherosclerosis. Inflammation is a key driver of atherosclerosis, but no targeted molecular therapies have been developed to reduce cardiovascular risk in people with HIV-1 (PWH). While the mechanism is unknown, there are several important inflammatory signaling events that are implicated in the development of chronic inflammation in PWH and in the inflammatory changes that lead to atherosclerosis. Here we describe the pro-inflammatory state of HIV-1 infection that leads to increased risk of cardiovascular disease, the role of the NLR Family Pyrin Domain Containing 3 (NLRP3) inflammasome in HIV-1 infection, the role of the NLRP3 inflammasome in cardiovascular disease (CVD), and outline a model whereby HIV-1 infection can lead to atherosclerotic disease through NLRP3 inflammasome activation. Our discussion highlights the literature supporting HIV-1 infection as a stimulator of the NLRP3 inflammasome as a driver of atherosclerosis.

Parallel studies of mucosal immunity in the reproductive and gastrointestinal mucosa of HIV-infected women

PROBLEM

The effects of HIV on the gastrointestinal tract (GIT), including CD4 depletion, epithelial disruption, and collagen deposition, are well documented and only partially reversed by combination antiretroviral therapy (cART). However, the effects of HIV on the female reproductive tract (FRT) are poorly understood, and most studies have focused on ectocervix and vagina without assessing the upper tract. Here, we investigated CD4⁺ T-cell frequency, phenotype, and HIV-specific T-cell responses in the endocervix and endometrium of HIV-infected women, comparing these tissues to the GIT.

METHOD OF STUDY

Mucosal samples and blood were obtained from 18 women: four who were HIV-positive and not on cART for at least 3 years prior to sampling, including two natural controllers (viral load [VL] undetectable and CD4 >350); nine women on cART with low to undetectable VL; and five HIV-uninfected women. Mucosal samples included terminal ileum, sigmoid colon, endocervical cytobrush, endocervical curettage, and endometrial biopsy. T-cell frequency, phenotypes, and HIV-specific T-cell responses were analyzed by multiparameter flow cytometry.

RESULTS

T-cell activation, measured by CD38/HLA-DR co-expression, remained significantly elevated in endometrium following cART, but was lower in gastrointestinal tissues. HIV-specific CD8⁺ T-cell responses were detected in ileum, colon, and endometrial tissues of women both on and off cART, and were of higher magnitude on those not on cART.

CONCLUSION

Our findings reveal differences in CD4⁺ T-cell frequencies, immune activation, and HIV-specific T-cell responses between the gastrointestinal and reproductive tracts, and highlight differences between HIV controllers and women on cART.

Mapping the extent of heterogeneity of human CCR5+ CD4+ T cells in peripheral blood and lymph nodes

BACKGROUND

CD4 T cells that express the chemokine receptor, CCR5, are the most important target of HIV-1 infection, but their functions, phenotypes and anatomical locations are poorly understood. We aimed to use multiparameter flow cytometry to better define the full breadth of these cells.

METHODS

High-parameter fluorescence flow and mass cytometry were optimized to analyse subsets of CCR5 memory CD4 T cells, including CD25CD127 Tregs, CXCR3CCR6- Th1-like, CCR6CD161CXCR3- Th17-like, integrins α4ß7 gut-homing, CCR4 skin-homing, CD62L lymph node-homing, CD38HLA-DR activated cells, and CD27-CD28- cytotoxic T lymphocytes, in a total of 22 samples of peripheral blood, ultrasound-guided fine needle biopsies of lymph nodes and excised tonsils. CCR5 antigen-specific CD4 T cells were studied using the OX40 flow-based assay.

RESULTS

10-20% of CCR5 memory CD4 T cells were Tregs, 10-30% were gut-homing, 10-30% were skin-homing, 20-40% were lymph node-homing, 20-50% were Th1-like and 20-40% were Th17-like cells. Up to 30% were cytotoxic T lymphocytes in CMV-seropositive donors, including cells that were either CCR5Granzyme K or CCR5Granzyme B. When all possible phenotypes were exhaustively analysed, more than 150 different functional and trafficking subsets of CCR5 CD4 T cells were seen. Moreover, a small population of resident CD69Granzyme KCCR5 CD4 T cells was found in lymphoid tissues. CMV- and Mycobacterium tuberculosis-specific CD4 T cells were predominantly CCR5.

CONCLUSION

These results reveal for the first time the prodigious heterogeneity of function and trafficking of CCR5 CD4 T cells in blood and in lymphoid tissue, with significant implications for rational approaches to prophylaxis for HIV-1 infection and for purging of the HIV-1 reservoir in those participants already infected.

Purinergic Receptors: Elucidating the Role of these Immune Mediators in HIV-1 Fusion

Purinergic receptors are inflammatory mediators activated by extracellular nucleotides released by dying or injured cells. Several studies have described an important role for these receptors in HIV-1 entry, particularly regarding their activity on HIV-1 viral membrane fusion. Several reports identify purinergic receptor antagonists that inhibit HIV-1 membrane fusion; these drugs are suspected to act through antagonizing Env-chemokine receptor interactions. They also appear to abrogate activity of downstream mediators that potentiate activation of the NLRP3 inflammasome pathway. Here we review the literature on purinergic receptors, the drugs that inhibit their function, and the evidence implicating these receptors in HIV-1 entry.

Macrophage HIV-1 Gene Expression and Delay Resolution of Inflammation in HIV-Tg Mice

While antiretroviral therapy increases the longevity of people living with HIV (PLWH), about 30% of this population suffers from three or more concurrent comorbidities, whose mechanisms are not well understood. Chronic activation and dysfunction of the immune system could be one potential cause of these comorbidities. We recently demonstrated reduced macrophage infiltration and delayed resolution of inflammation in the lungs of HIV-transgenic mice. Additionally, trans-endothelial migration of HIV-positive macrophages was reduced in vitro. Here, we analyze macrophages’ response to LPS challenge in the kidney and peritoneum of HIV-Tg mice. In contrast to the lung infiltration, renal and peritoneal macrophage infiltrations were similar in WT and HIV-Tg mice. Higher levels of HIV-1 gene expression were detected in lung macrophages compared to peritoneal macrophages. In peritoneal macrophages, HIV-1 gene expression was increased when they were cultured at 21% O₂ compared to 5% O₂, inversely correlating with reduced trans-endothelial migration at higher oxygen levels in vitro. The resolution of macrophage infiltration was reduced in both the lung and the peritoneal cavity of HIV-Tg mice. Taken together, our study described the organ-specific alteration of macrophage dynamics in HIV-Tg mice. The delayed resolution of macrophage infiltration might constitute a risk factor for the development of multiple comorbidities in PLWH.

African green monkeys avoid SIV disease progression by preventing intestinal dysfunction and maintaining mucosal barrier integrity

Unlike HIV infection, SIV infection is generally nonpathogenic in natural hosts, such as African green monkeys (AGMs), despite life-long high viral replication. Lack of disease progression was reportedly based on the ability of SIV-infected AGMs to prevent gut dysfunction, avoiding microbial translocation and the associated systemic immune activation and chronic inflammation. Yet, the maintenance of gut integrity has never been documented, and the mechanism(s) by which gut integrity is preserved are unknown. We sought to investigate the early events of SIV infection in AGMs, specifically examining the impact of SIVsab infection on the gut mucosa. Twenty-nine adult male AGMs were intrarectally infected with SIVsab92018 and serially sacrificed at well-defined stages of SIV infection, preramp-up (1-3 days post-infection (dpi)), ramp-up (4-6 dpi), peak viremia (9-12 dpi), and early chronic SIV infection (46-55 dpi), to assess the levels of immune activation, apoptosis, epithelial damage and microbial translocation in the GI tract and peripheral lymph nodes. Tissue viral loads, plasma cytokines and plasma markers of gut dysfunction were also measured throughout the course of early infection. While a strong, but transient, interferon-based inflammatory response was observed, the levels of plasma markers linked to enteropathy did not increase. Accordingly, no significant increases in apoptosis of either mucosal enterocytes or lymphocytes, and no damage to the mucosal epithelium were documented during early SIVsab infection of AGMs. These findings were supported by RNAseq of the gut tissue, which found no significant alterations in gene expression that would indicate microbial translocation. Thus, for the first time, we confirmed that gut epithelial integrity is preserved, with no evidence of microbial translocation, in AGMs throughout early SIVsab infection. This might protect AGMs from developing intestinal dysfunction and the subsequent chronic inflammation that drives both HIV disease progression and HIV-associated comorbidities.

Protective HLA alleles are associated with reduced LPS levels in acute HIV infection with implications for immune activation and pathogenesis

Despite extensive research on the mechanisms of HLA-mediated immune control of HIV-1 pathogenesis, it is clear that much remains to be discovered, as exemplified by protective HLA alleles like HLA-B*81 which are associated with profound protection from CD4+ T cell decline without robust control of early plasma viremia. Here, we report on additional HLA class I (B*1401, B*57, B*5801, as well as B*81), and HLA class II (DQB1*02 and DRB1*15) alleles that display discordant virological and immunological phenotypes in a Zambian early infection cohort. HLA class I alleles of this nature were also associated with enhanced immune responses to conserved epitopes in Gag. Furthermore, these HLA class I alleles were associated with reduced levels of lipopolysaccharide (LPS) in the plasma during acute infection. Elevated LPS levels measured early in infection predicted accelerated CD4+ T cell decline, as well as immune activation and exhaustion. Taken together, these data suggest novel mechanisms for HLA-mediated immune control of HIV-1 pathogenesis that do not necessarily involve significant control of early viremia and point to microbial translocation as a direct driver of HIV-1 pathogenesis rather than simply a consequence.

During acute HIV infection, there exists a complex interplay between the host immune response and the virus, and the balance of these interactions dramatically affects disease trajectory in infected individuals. Variations in Human Leukocyte Antigen (HLA) alleles dictate the potency of the cellular immune response to HIV, and certain well-studied alleles (HLA-B*57, B*27) are associated with control of HIV viremia. However, though plasma viral load is indicative of disease progression, the number of CD4+ T cells in the blood is a better measurement of disease severity. Through analysis of a large Zambian acute infection cohort, we identified HLA alleles that were associated with protection for CD4+ T cell loss, without dramatic affect on early plasma viremia. We further link these favorable HLA alleles to reduction in a well-known contributor to HIV pathogenesis, the presence of microbial products in the blood, which is indicative of damage to the gastrointestinal tract, a process which accelerates disease progression in HIV infected individuals. Ultimately, these results suggest a new mechanism by which the cellular immune response can combat HIV-associated pathogenesis, and further highlight the contribution of gut damage and microbial translocation to accelerating disease progression, even at early stages in HIV infection.

Analysis of the TCR Repertoire in HIV-Exposed but Uninfected Infants

Maternal human immunodeficiency virus (HIV) infection has been shown to leave profound and lasting impacts on the HIV-exposed uninfected (HEU) infant, including increased mortality and morbidity, immunological changes, and developmental delays compared to their HIV-unexposed (HU) counterparts. Exposure to HIV or antiretroviral therapy may influence immune development, which could increase morbidity and mortality. However, a direct link between the increased mortality and morbidity and the infant's immune system has not been identified. To provide a global picture of the neonatal T cell repertoire in HEU versus HU infants, the diversity of the T cell receptor beta chain (TRB) expressed in cord blood samples from HEU infants was determined using next-generation sequencing and compared to healthy (HU) infants collected from the same community. While the TRB repertoire of HU infants was broadly diverse, in line with the expected idea of a naïve T cell repertoire, samples of HEU infants showed a significantly reduced TRB diversity. This study is the first to demonstrate differences in TRB diversity between HEU and HU cord blood samples and provides evidence that maternal HIV, in the absence of transmission, influences the adaptive immune system of the unborn child.

The effect of pyridostigmine on small intestinal bacterial overgrowth (SIBO) and plasma inflammatory biomarkers in HIV-associated autonomic neuropathies

Small intestinal bacterial overgrowth (SIBO) is common among patients with HIV-associated autonomic neuropathies (HIV-AN) and may be associated with increased bacterial translocation and elevated plasma inflammatory biomarkers. Pyridostigmine is an acetylcholinesterase inhibitor which has been used to augment autonomic signaling. We sought preliminary evidence as to whether pyridostigmine could improve proximal gastrointestinal motility, reduce SIBO, reduce plasma sCD14 (a marker of macrophage activation and indirect measure of translocation), and reduce the inflammatory cytokines IL-6 and TNFα in patients with HIV-AN. Fifteen participants with well-controlled HIV, HIV-AN, and SIBO were treated with 8 weeks of pyridostigmine (30 mg PO TID). Glucose breath testing for SIBO, gastric emptying studies (GES) to assess motility, plasma sCD14, IL-6, and TNFα, and gastrointestinal autonomic symptoms were compared before and after treatment. Thirteen participants (87%) experienced an improvement in SIBO following pyridostigmine treatment; with an average improvement of 50% (p = 0.016). There was no change in gastrointestinal motility; however, only two participants met GES criteria for gastroparesis at baseline. TNFα and sCD14 levels declined by 12% (p = 0.004) and 19% (p = 0.015), respectively; there was no significant change in IL-6 or gastrointestinal symptoms. Pyridostigmine may ameliorate SIBO and reduce levels of sCD14 and TNFα in patients with HIV-AN. Larger placebo-controlled studies are needed to definitively delineate how HIV-AN affects gastrointestinal motility, SIBO, and systemic inflammation in HIV, and whether treatment improves clinical outcomes.

Effect of HIV on the Frequency and Number of Mycobacterium tuberculosis-Specific CD4+ T Cells in Blood and Airways During Latent M. tuberculosis Infection

Human immunodeficiency virus type 1 (HIV) infection substantially increases the risk of developing tuberculosis. There is extensive depletion of Mycobacterium tuberculosis-specific CD4+ T cells in blood during early HIV infection, but little is known about responses in the lungs at this stage. Given that mucosal organs are a principal target for HIV-mediated CD4+ T-cell destruction, we investigated M. tuberculosis-specific responses in bronchoalveolar lavage (BAL) from persons with latent M. tuberculosis infection and untreated HIV coinfection with preserved CD4+ T-cell counts. M. tuberculosis-specific CD4+ T-cell cytokine (interferon γ, tumor necrosis factor α, and interleukin 2) responses were discordant in frequency and function between BAL and blood. Responses in BAL were 15-fold lower in HIV-infected persons as compared to uninfected persons (P = .048), whereas blood responses were 2-fold lower (P = .006). However, an increase in T cells in the airways in HIV-infected persons resulted in the overall number of M. tuberculosis-specific CD4+ T cells in BAL being similar. Our study highlights the important insights gained from studying M. tuberculosis immunity at the site of disease during HIV infection.

Low level expression of the Mitochondrial Antiviral Signaling protein (MAVS) associated with long-term nonprogression in SIV-infected rhesus macaques

BACKGROUND

Abnormally increased immune activation is one of the main pathological features of acquired immunodeficiency syndrome (AIDS). This study aimed to determine whether long-term nonprogression (LTNP) suppresses the upregulation of immune activation and to elucidate the mechanisms whereby the LTNP state is maintained.

METHODS

For this study we selected 4 rhesus macaques(RMs) infected with simian immunodeficiency virus (SIV) that were long-term nonprogressors (LTNP); for comparison we chose 4 healthy RMs that were seronegative for SIV (hereafter referred to as the Control group), and 4 progressing infection (Progressive group) SIV RMs. We observed these animals for 6 months without intervention and explored the immunological and pathological differences among the 3 groups. A series of immune activation and inflammation markers-such as C- C chemokine receptor type 5 (CCR5), beta 2- microglobulin (β2-MG), Human Leukocyte Antigen - antigen D Related (HLA-DR), CD38, the levels of microbial translocation (LPS -binding protein), and MAVS-and histological features were monitored during this period.

RESULTS

Both SIV RNA and SIV DNA in the plasma and lymph nodes (LNs) of the LTNP group were at significantly lower levels than those of the Progressive group (P < 0.05). The CD4/CD8 ratio and CD4 cell count and proportion in the LTNP group were between those of the Progressive and Control groups (P < 0.05): that is, they were higher than in the Progressive group and lower than in the Control group. The LTNP macaques manifested slow progression and decreased immune activation and inflammation; they also had lower levels of CCR5, LPS-binding protein, and β2-MG than the Progressive RMs (P < 0.05). Activation of LTNP in both CD4+ and CD8+ T cells was significantly lower than in the Progressive group and closer to that in the Control group. The histological features of the LTNP macaques were also closer to those of the Control group, even though they had been infected with SIV 4 years earlier. These data point to low viral replication in the LTNP macaques but it is not static. The expression of MAVS in peripheral blood and LNs was lower in the LTNP group than that in the Progressive group (P < 0.01), and MAVS was positively correlated with SIV DNA in LNs (P < 0.05). This may reflect the low activation of T lymphocytes. It was speculated that MAVS may be the link between innate and acquired antiviral immunity in SIV infection.

CONCLUSIONS

The LTNP RMs in our study were in a relatively stable state of low activation and inflammation, some biological progression with no disease events. This may have been associated with their low levels of the mitochondrial antiviral signaling protein (MAVS).

[Causes of T lymphocyte activation in HIV-infected patients coinfected with hepatitis C virus]

AIM

To establish the causes of T lymphocyte activation in human immunodeficiency virus (HIV)-infected patients coinfected with hepatitis C (HCV) who are adherent to their antiretroviral therapy regimen and interferon untreated.

SUBJECTS AND METHODS

Examinations were made in 62 people who were HIV+HCV-positive (n=21), HIV+HCV-negative (n=21), and noninfected volunteers (n=20). The activation (CD38+HLA-DR+) and proliferation (Ki-67+) of CD4+ and CD8+ T lymphocytes were estimated. The blood concentration of intestinal fatty acid-binding protein (I-FABP) was determined.

RESULTS

The proportion of activated cells among the CD4+ T lymphocytes was equal in the HIV+HCV-positive and HIV+HCV-negative groups. But these indicators were statistically significantly higher than those in the controls (HIV- HCV-). CD8+ T cell activation was greater in the HIV/HCV-coinfected patients than that in the other groups and that was higher in the HIV monoinfected than in the noninfected. The blood I-FABP concentrations were elevated in the HIV+HCV-positive and HIV+HCV groups compared with those in the HIV-HCV-negative group, but these did not differ among themselves. In the HIV+HCV-negative patients, CD4+ and CD8+ T cell activation directly and statistically significantly correlated with blood I-FABP levels. In the HIV+HCV-positive group, this correlation remained only for CD4+ T lymphocytes. CD8+ T cell activation in HIV/HCV-coinfected patients was unrelated to I-FABP concentrations.

CONCLUSION

The increased activation of CD4+ and CD8+ T lymphocytes in HIV monoinfection was found to be associated with intestinal epithelial destruction and unrelated to cell division processes. In HIV/HCV coinfection, the activated state of CD4+ T cells is determined by both the level of proliferative processes and impairment of the intestinal barrier and that of CD8+ T cells is only by proliferation.

Combating the HIV reservoirs

Impressive advances have been made in the treatment and management of HIV-1 infected individuals. Combination antiretroviral therapy (cART) has turned HIV-1 infection from an almost invariable deadly infectious disease, to a lifelong manageable infectious disease. However, a cure or vaccine has not been forthcoming. A major problem in HIV-1 infection is the persistent and latently infected cellular and tissue reservoirs. One of these reservoirs is the Gut Associated Lymphoid tissue (GALT), which has been the research focus of our group. Our group and others have shown that HIV-1 evolves differently in different parts of the gastro intestinal tract, which also appears to affect the development of antiretroviral drug resistance. The GALT is not the only reservoir. HIV-1 continues to persist and evolve in various other cell and tissue reservoirs despite intense and apparent successful antiretroviral therapy. Moreover, drug resistance mutations remain prevalent under therapy and successful viral suppression. In addition to finding a vaccine, the research on combating and eradicating the HIV-1 viral reservoirs has also been an important focus of HIV-1 cure strategies. We will discuss some of the research findings on reservoirs in the context of some of the HIV-1 cure approaches.