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

Gut microbiome and cardiometabolic comorbidities in people living with HIV

BACKGROUND

Despite modern antiretroviral therapy (ART), people living with HIV (PLWH) have increased relative risk of inflammatory-driven comorbidities, including cardiovascular disease (CVD). The gut microbiome could be one of several driving factors, along with traditional risk factors and HIV-related risk factors such as coinfections, ART toxicity, and past immunodeficiency.

RESULTS

PLWH have an altered gut microbiome, even after adjustment for known confounding factors including sexual preference. The HIV-related microbiome has been associated with cardiometabolic comorbidities, and shares features with CVD-related microbiota profiles, in particular reduced capacity for short-chain fatty acid (SCFA) generation. Substantial inter-individual variation has so far been an obstacle for applying microbiota profiles for risk stratification. This review covers updated knowledge and recent advances in our understanding of the gut microbiome and comorbidities in PLWH, with specific focus on cardiometabolic comorbidities and inflammation. It covers a comprehensive overview of HIV-related and comorbidity-related dysbiosis, microbial translocation, and microbiota-derived metabolites. It also contains recent data from studies in PLWH on circulating metabolites related to comorbidities and underlying gut microbiota alterations, including circulating levels of the SCFA propionate, the histidine-analogue imidazole propionate, and the protective metabolite indole-3-propionic acid.

CONCLUSIONS

Despite recent advances, the gut microbiome and related metabolites are not yet established as biomarkers or therapeutic targets. The review gives directions for future research needed to advance the field into clinical practice, including promises and pitfalls for precision medicine. Video Abstract.

Suppressor T helper type 17 cell responses in intestinal transplant recipients with allograft rejection

BACKGROUND

Intestinal transplant (ITx) rejection is associated with memory T helper type 17 cell (Th17) infiltration of grafted tissues. Modulation of Th17 effector cell response is facilitated by T regulatory (Treg) cells, but a phenotypic characterization of this process is lacking in the context of allograft rejection.

METHODS

Flow cytometry was performed to examine the expression of surface receptors, cytokines, and transcription factors in Th17 and Treg cells in ITx control (n = 34) and rejection patients (n = 23). To elucidate key pathways guiding the rejection biology, we utilized RNA sequencing (RNAseq) and assessed epigenetic stability through pyrosequencing of the Treg-specific demethylated region (TSDR).

RESULTS

We found that intestinal allograft rejection is characterized by Treg cellular infiltrates, which are polarized toward Th17-type chemokine receptor, ROR-γt transcription factor expression, and cytokine production. These Treg cell subsets have maintained epigenetic stability, as defined by FoxP3-TSDR methylation status, but displayed upregulation of functional Treg and purinergic signaling genes by RNAseq analysis such as CD39, in keeping with suppressor Th17 properties.

CONCLUSION

We show that ITx rejection is associated with increased polarized cells that express a Th17-like phenotype concurrent with regulatory purinergic markers.

High-parameter phenotypic characterization reveals a subset of human Th17 cells that preferentially produce IL-17 against M. tuberculosis antigen

Background

Interleukin-17-producing CD4 T cells contribute to the control of Mycobacterium tuberculosis (Mtb) infection in humans; whether infection with human immunodeficiency virus (HIV) disproportionately affects distinct Th17-cell subsets that respond to Mtb is incompletely defined.

Methods

We performed high-definition characterization of circulating Mtb-specific Th17 cells by spectral flow cytometry in people with latent TB and treated HIV (HIV-ART). We also measured kynurenine pathway activity by liquid chromatography-mass spectrometry (LC/MS) on plasma and tested the hypothesis that tryptophan catabolism influences Th17-cell frequencies in this context.

Results

We identified two subsets of Th17 cells: subset 1 defined as CD4+Vα7.2-CD161+CD26+and subset 2 defined as CD4+Vα7.2-CCR6+CXCR3-cells of which subset 1 was significantly reduced in latent tuberculosis infection (LTBI) with HIV-ART, yet Mtb-responsive IL-17-producing CD4 T cells were preserved; we found that IL-17-producing CD4 T cells dominate the response to Mtb antigen but not cytomegalovirus (CMV) antigen or staphylococcal enterotoxin B (SEB), and tryptophan catabolism negatively correlates with both subset 1 and subset 2 Th17-cell frequencies.

Conclusions

We found differential effects of ART-suppressed HIV on distinct subsets of Th17 cells, that IL-17-producing CD4 T cells dominate responses to Mtb but not CMV antigen or SEB, and that kynurenine pathway activity is associated with decreases of circulating Th17 cells that may contribute to tuberculosis immunity.

High-parameter phenotypic characterization reveals a subset of human Th17 cells that preferentially produce IL17 against M. tuberculosis antigen

Background

Interleukin 17 producing CD4 T cells contribute to the control of Mycobacterium tuberculosis (Mtb) infection in humans; whether infection with Human Immunodeficiency Virus (HIV) disproportionately affects distinct Th17 cell subsets that respond to Mtb is incompletely defined.

Methods

We performed high-definition characterization of circulating Mtb-specific Th17 cells by spectral flow cytometry in people with latent TB and treated HIV (HIV-ART). We also measured kynurenine pathway activity by LC/MS on plasma and tested the hypothesis that tryptophan catabolism influences Th17 cell frequencies in this context.

Results

We identified two subsets of Th17 cells: subset 1 defined as CD4+Vα7.2-CD161+CD26+ and subset 2 defined as CD4+Vα7.2-CCR6+CXCR3- cells of which subset 1 was significantly reduced in LTBI with HIV-ART, yet Mtb-responsive IL17-producing CD4 T cells were preserved; we found that IL17-producing CD4 T cells dominate the response to Mtb antigen but not CMV antigen or staphylococcal enterotoxin B (SEB); and tryptophan catabolism negatively correlates with both subset 1 and subset 2 Th17 cell frequencies.

Conclusions

We found differential effects of ART-suppressed HIV on distinct subsets of Th17 cells, that IL17-producing CD4 T cells dominate responses to Mtb but not CMV antigen or SEB, and that kynurenine pathway activity is associated with decreases of circulating Th17 cells that may contribute to tuberculosis immunity.

Current Advances in Graft-versus-host Disease After Intestinal Transplantation

Graft-versus-host disease (GvHD) remains a potentially fatal complication following intestinal transplant (ITx). Over the past decade, advances in the understanding of the pathophysiology of this complex immunological phenomenon have led to the reassessment of the host systemic immune response and have created a gateway for novel preventive and therapeutic strategies. Although sufficient evidence dictates the use of corticosteroids as a first-line option, the treatment for refractory disease remains contentious and lacks a standardized therapeutic approach. Timely diagnosis remains crucial, and the advent of chimerism detection and immunological biomarkers have transformed the identification, prognostication, and potential for survival after GvHD in ITx. The objectives of the following review aim to discuss the clinical and diagnostic features, pathophysiology, advances in immune biomarkers, as well as therapeutic opportunities in the prevention and treatment of GvHD in ITx.

A Blood Immunological Signature of Subclinical Coronary Artery Atherosclerosis in People Living with HIV-1 Receiving Antiretroviral Therapy

Cardiovascular disease (CVD) remains an important co-morbidity in people living with HIV-1 (PLWH) receiving antiretroviral therapy (ART). Our previous studies performed on the Canadian HIV/Aging Cohort Study (CHACS) (>40 years-old; Framingham Risk Score (FRS) >5%), revealed a 2-3-fold increase in non-calcified coronary artery atherosclerosis (CAA) plaque burden, measured by Computed tomography angiography scan (CTAScan) as total (TPV) and low attenuated plaque volume (LAPV) in ART-treated PLWH (HIV+) versus uninfected controls (HIV-). In an effort to identify novel correlates of subclinical CAA, markers of intestinal damage (sCD14, LBP, FABP2); cell trafficking/inflammation (CCL20, CX3CL1, MIF, CCL25); subsets of Th17-polarized and regulatory (Tregs) CD4 + T-cells, classical/intermediate/non-classical monocytes, and myeloid/plasmacytoid dendritic cells, were studied in relationship with HIV and TPV/LAPV status. The TPV detection/values coincided with higher plasma sCD14, FABP2, CCL20, MIF, CX3CL1 and triglyceride levels, lower Th17/Treg ratios, and classical monocyte expansion. Among HIV + , TPV + versus TPV - exhibited lower Th17 frequencies, reduced Th17/Treg ratios, higher frequencies of non-classical CCR9 low HLADR high monocyte, and increased plasma fibrinogen levels. Finally, Th17/Treg ratios and non-classical CCR9 low HLADR high monocyte frequencies remained associated with TPV/LAPV after adjusting for FRS and HIV/ART duration in a logistic regression model. These findings point to Th17 paucity and non-classical monocyte abundance as novel immunological correlates of subclinical CAA that may fuel the CVD risk in ART-treated PLWH.

Zinc finger protein 189 promotes the differentiation of lamina propria T helper 17.1 cells in dextran sulfate sodium-induced colitis

The factors regulating the heterogeneity of interleukin-17A (IL-17A)-expressing CD4⁺ T cells in inflammatory bowel diseases remain unclear. In the current study, we characterised the expression and function of zinc finger protein 189 (ZFP189) in a murine colitis model. Mice were given dextran sulphate sodium to induce acute colitis. Flow cytometry was applied to recognise and enrich Th17 and Th17.1 cells based on the expression of IL-17A, interferon-γ (IFN-γ), C-X-C motif chemokine receptor 3 (CXCR3), and C-C motif chemokine receptor 4 (CCR4). The expression of ZFP189 in Th17 and Th17.1 cells was determined by Immunoblotting. Lentivirus-mediated ZFP189 knockdown was conducted to evaluate the effect of ZFP189 on the differentiation of Th17 and Th17.1 cells. The adoptive transfer was performed to analyse the pathogenicity of Th17.1 cells in vivo. We found that ZFP189 was mildly up-regulated in IL-17A-expressing CD4⁺ T cells in colonic lamina propria. Lamina propria Th17.1 cells expressed higher ZFP189 than Th17 cells. In vitro ZFP189 knockdown in CD4⁺ T cells did not impact Th17 cell differentiation but suppressed Th17.1 cell differentiation, as evidenced by lower T-box expressed in T cells (T-bet) and IFN-γ. When adoptively transferred into mice, ZFP189-deficient Th17.1 cells produced fewer IFN-γ, tumour necrosis factor-alpha (TNF-α), and granulocyte-macrophage colony-stimulating factor (GM-CSF) than ZFP189-expressing Th17.1 cells. Moreover, ZFP189-deficient Th17.1 cells induced less severe colitis than ZFP189-expressing Th17.1 cells, as evidenced by less body weight loss, a lower disease activity index, and a lower colon histological score. In summary, ZFP189 acts as a positive regulator of the differentiation and pathogenicity of lamina propria Th17.1 cells in colitis.

HIV-1-Host Interaction in Gut-Associated Lymphoid Tissue (GALT): Effects on Local Environment and Comorbidities

HIV-1 replication in the gastrointestinal (GI) tract causes severe CD4+ T-cell depletion and disruption of the protective epithelial barrier in the intestinal mucosa, causing microbial translocation, the main driver of inflammation and immune activation, even in people living with HIV (PLWH) taking antiretroviral drug therapy. The higher levels of HIV DNA in the gut compared to the blood highlight the importance of the gut as a viral reservoir. CD4+ T-cell subsets in the gut differ in phenotypic characteristics and differentiation status from the ones in other tissues or in peripheral blood, and little is still known about the mechanisms by which the persistence of HIV is maintained at this anatomical site. This review aims to describe the interaction with key subsets of CD4+ T cells in the intestinal mucosa targeted by HIV-1 and the role of gut microbiome and its metabolites in HIV-associated systemic inflammation and immune activation that are crucial in the pathogenesis of HIV infection and related comorbidities.

Identification of aryl hydrocarbon receptor as a barrier to HIV-1 infection and outgrowth in CD4+ T cells

The aryl hydrocarbon receptor (AhR) regulates Th17-polarized CD4+ T cell functions, but its role in HIV-1 replication/outgrowth remains unknown. Genetic (CRISPR-Cas9) and pharmacological inhibition reveal AhR as a barrier to HIV-1 replication in T cell receptor (TCR)-activated CD4+ T cells in vitro. In single-round vesicular stomatitis virus (VSV)-G-pseudotyped HIV-1 infection, AhR blockade increases the efficacy of early/late reverse transcription and subsequently facilitated integration/translation. Moreover, AhR blockade boosts viral outgrowth in CD4+ T cells of people living with HIV-1 (PLWH) receiving antiretroviral therapy (ART). Finally, RNA sequencing reveals genes/pathways downregulated by AhR blockade in CD4+ T cells of ART-treated PLWH, including HIV-1 interactors and gut-homing molecules with AhR-responsive elements in their promoters. Among them, HIC1, a repressor of Tat-mediated HIV-1 transcription and a tissue-residency master regulator, is identified by chromatin immunoprecipitation as a direct AhR target. Thus, AhR governs a T cell transcriptional program controlling viral replication/outgrowth and tissue residency/recirculation, supporting the use of AhR inhibitors in "shock and kill" HIV-1 remission/cure strategies.

The Imbalance Between Intestinal Th17 and Treg Cells Is Associated with an Incomplete Immune Reconstitution During Long-Term Antiretroviral Therapy in Patients with HIV

Studies assessing the gut mucosal immune balance in HIV-infected patients using intestinal samples are scarce. In this study, we used intestinal mucosal specimens from the ileocecal region of seven immunological nonresponders (INRs), nine immunological responders (IRs), and six HIV-negative controls. We investigated T helper 17 (Th17) and T regulatory (Treg) cell counts and their ratio, zonula occludens-1 (ZO-1), intestinal fatty acid-binding protein (I-FABP), tumor necrosis factor-α, CD4+ T cell counts, HIV DNA, and cell-associated HIV RNA. The results showed that INRs had lower Th17 and higher Treg cell counts than IR, resulting in a significant difference in the Th17/Treg ratio between IRs and INRs. In addition, INRs had lower ZO-1 and higher I-FABP levels than IRs. The Th17/Treg ratio was positively associated with ZO-1 and negatively associated with I-FABP levels. There was a positive correlation between Th17/Treg ratio and CD4+ T cell counts and a negative correlation between the Th17/Treg ratio and HIV DNA in the intestine. Our study suggests that the imbalance of Th17/Treg in the intestine is a characteristic of incomplete immune reconstitution to antiretroviral therapy and is associated with intestinal damage.

HIV/Mtb Co-Infection: From the Amplification of Disease Pathogenesis to an “Emerging Syndemic”

Human immunodeficiency virus (HIV) and Mycobacterium tuberculosis (Mtb) are pathogens responsible for millions of new infections each year; together, they cause high morbidity and mortality worldwide. In addition, late-stage HIV infection increases the risk of developing tuberculosis (TB) by a factor of 20 in latently infected people, and even patients with controlled HIV infection on antiretroviral therapy (ART) have a fourfold increased risk of developing TB. Conversely, Mtb infection exacerbates HIV pathogenesis and increases the rate of AIDS progression. In this review, we discuss this reciprocal amplification of HIV/Mtb coinfection and how they influence each other’s pathogenesis. Elucidating the infectious cofactors that impact on pathogenesis may open doors for the design of new potential therapeutic strategies to control disease progression, especially in contexts where vaccines or the sterile clearance of pathogens are not effectively available.

Enteropathy and gut dysbiosis as obstacles to achieve immune recovery in undetectable people with HIV: a clinical view of evidence, successes, and projections

Immune performance following antiretroviral therapy initiation varies among patients. Despite achieving viral undetectability, a subgroup of patients fails to restore CD4+ T-cell counts during follow-up, which exposes them to non-AIDS defining comorbidities and increased mortality. Unfortunately, its mechanisms are incompletely understood, and no specific treatment is available. In this review, we address some of the pathophysiological aspects of the poor immune response from a translational perspective, with emphasis in the interaction between gut microbiome, intestinal epithelial dysfunction, and immune system, and we also discuss some studies attempting to improve immune performance by intervening in this vicious cycle.

Relationship between Hypoxic and Immune Pathways Activation in the Progression of Neuroinflammation: Role of HIF-1α and Th17 Cells

Neuroinflammation is a common event in degenerative diseases of the central and peripheral nervous system, triggered by alterations in the immune system or inflammatory cascade. The pathophysiology of these disorders is multifactorial, whereby the therapy available has low clinical efficacy. This review propounds the relationship between the deregulation of T helper cells and hypoxia, mainly Th17 and HIF-1α molecular pathways, events that are involved in the occurrence of the neuroinflammation. The clinical expression of neuroinflammation is included in prevalent pathologies such as multiple sclerosis, Guillain-Barré syndrome, and Alzheimer's disease, among others. In addition, therapeutic targets are analyzed in relation to the pathways that induced neuroinflammation.

Immuno-metabolic control of the balance between Th17-polarized and regulatory T-cells during HIV infection

Th17-polarized CD4⁺ effector T-cells together with their immunosuppressive regulatory T-cell (Treg) counterparts, with transcriptional profiles governed by the lineage transcription factors RORγt/RORC2 and FOXP3, respectively, are important gatekeepers at mucosal interfaces. Alterations in the Th17/Treg ratios, due to the rapid depletion of Th17 cells and increased Treg frequencies, are a hallmark of both HIV and SIV infections and a marker of disease progression. The shift in Th17/Treg balance, in favor of increased Treg frequencies, contributes to gut mucosal permeability, immune dysfunction, and microbial translocation, subsequently leading to chronic immune activation/inflammation and disease progression. Of particular interest, Th17 cells and Tregs share developmental routes, with changes in the Th17 versus Treg fate decision influencing the pro-inflammatory versus anti-inflammatory responses. The differentiation and function of Th17 cells and Tregs rely on independent yet complementary metabolic pathways. Several pathways have been described in the literature to be involved in Th17 versus Treg polarization, including 1) the activity of ectonucleotidases CD39/CD73; 2) the increase in TGF-β1 production; 3) a hypoxic environment, and subsequent upregulation in hypoxia-inducible factor-1α (HIF-1α); 4) the increased mTOR activity and glycolysis induction; 5) the lipid metabolism, including fatty acid synthesis, fatty acids oxidation, cholesterol synthesis, and lipid storage, which are regulated by the AMPK, mevalonate and PPARγ pathways; and 6) the tryptophan catabolism. These metabolic pathways are understudied in the context of HIV-1 infection. The purpose of this review is to summarize the current knowledge on metabolic pathways that are dysregulated during HIV-1 infection and their impact on Th17/Treg balance.

The Double Game Played by Th17 Cells in Infection: Host Defense and Immunopathology

T-helper 17 (Th17) cells represent a subpopulation of CD4+ T lymphocytes that play an essential role in defense against pathogens. Th17 cells are distinguished from Th1 and Th2 cells by their ability to produce members of the interleukin-17 (IL-17) family, namely IL-17A and IL-17F. IL-17 in turn induces several target cells to synthesize and release cytokines, chemokines, and metalloproteinases, thereby amplifying the inflammatory cascade. Th17 cells reside predominantly in the lamina propria of the mucosa. Their main physiological function is to maintain the integrity of the mucosal barrier against the aggression of infectious agents. However, in an appropriate inflammatory microenvironment, Th17 cells can transform into immunopathogenic cells, giving rise to inflammatory and autoimmune diseases. This review aims to analyze the complex mechanisms through which the interaction between Th17 and pathogens can be on the one hand favorable to the host by protecting it from infectious agents, and on the other hand harmful, potentially generating autoimmune reactions and tissue damage.

Mucosal microbiotas and their role in stem cell transplantation

Mucosal microbiotas and their role in stem cell transplantation. Patients with hematological disorders such as leukemia often undergo allogeneic hematopoietic stem cell transplantation, and thereby receive stem cells from a donor for curation of disease. This procedure also involves immunosuppressive and antimicrobial treatments that disturb the important interactions between the microbiota and the immune system, especially at mucosal sites. After transplantation, bacterial diversity decreases together with a depletion of Clostridia, and shifts toward predominance of Proteobacteria. Infectious and inflammatory complications, such as graft-versus-host disease, also interfere with patient recovery. This review collects and contextualizes current knowledge of the role of mucosal microbiotas at different body sites in stem cell transplantation, proposes underlying mechanisms, and discusses potential clinical value of bacterial markers for improved treatment strategies.

Neglected mycobiome in HIV infection: Alterations, common fungal diseases and antifungal immunity

Human immunodeficiency virus (HIV) infection might have effects on both the human bacteriome and mycobiome. Although many studies have focused on alteration of the bacteriome in HIV infection, only a handful of studies have also characterized the composition of the mycobiome in HIV-infected individuals. Studies have shown that compromised immunity in HIV infection might contribute to the development of opportunistic fungal infections. Despite effective antiretroviral therapy (ART), opportunistic fungal infections continue to be a major cause of HIV-related mortality. Human immune responses are known to play a critical role in controlling fungal infections. However, the effect of HIV infection on innate and adaptive antifungal immunity remains unclear. Here, we review recent advances in understanding of the fungal microbiota composition and common fungal diseases in the setting of HIV. Moreover, we discuss innate and adaptive antifungal immunity in HIV infection.

Features of Peripheral Blood Th-Cell Subset Composition and Serum Cytokine Level in Patients with Activity-Driven Ankylosing Spondylitis

Th cells may exhibit pathological activity depending on the regulatory and functional signals sensed under a wide range of immunopathological conditions, including ankylosing spondylitis (AS). The relationship between Th cells and cytokines is important for diagnoses and for determining treatment. Accordingly, the aim of this study was to investigate the relationship between Th-cell subset composition and serum cytokine profile for patients with activity-driven AS. In our study, patients were divided into two groups according to disease activity: low-activity AS (ASDAS-CRP < 2.1) and high-activity AS (ASDAS-CRP > 2.1). The peripheral blood Th cell subset composition was studied by flow cytometry. Using multiplex analysis, serum cytokine levels were quantified and investigated. It was found that only patients with high-activity AS had reduced central memory (CM) Th1 cells (p = 0.035) but elevated numbers of CM (p = 0.014) and effector memory (EM) Th2 cells (p < 0.001). However, no activity-driven change in the Th17 cell subset composition was observed in AS patients. Moreover, low-AS activity patients had increased numbers of Tfh17 EM cells (p < 0.001), whereas high-AS activity was associated with elevated Tfh2 EM level (p = 0.031). The serum cytokine profiles in AS patients demonstrated that cues stimulating cellular immunity were increased, but patients with high-AS activity reveled increased IL-5 level (p = 0.017). Analyzing the data obtained from AS patients allowed us to conclude that Th cell subset differentiation was mainly affected during the CM stage and characterized the IL-23/IL-17 regulatory axis, whereas increased humoral immunity was observed in the high-AS activity group.

The interleukin-6/interleukin-23/T helper 17-axis as a driver of neuro-immune toxicity in the major neurocognitive psychosis or deficit schizophrenia: A precision nomothetic psychiatry analysis

BACKGROUND

Schizophrenia and especially deficit schizophrenia (DSCZ) are characterized by increased activity of neuroimmunotoxic pathways and a generalized cognitive decline (G-CoDe). There is no data on whether the interleukin (IL)-6/IL-23/T helper 17 (IL-6/IL-23/Th17)-axis is more associated with DSCZ than with non-deficit schizophrenia (NDSCZ) and whether changes in this axis are associated with the G-CoDe and the phenome (a factor extracted from all symptom domains) of schizophrenia.

METHODS

This study included 45 DSCZ and 45 NDSCZ patients and 40 controls and delineated whether the IL-6/IL-23/Th17 axis, trace elements (copper, zinc) and ions (magnesium, calcium) are associated with DSCZ, the G-CoDe and the schizophrenia phenome.

RESULTS

Increased plasma IL-23 and IL-6 levels were associated with Th17 upregulation, assessed as a latent vector (LV) extracted from IL-17, IL-21, IL-22, and TNF-α. The IL-6/IL-23/Th17-axis score, as assessed by an LV extracted from IL-23, IL-6, and the Th17 LV, was significantly higher in DSCZ than in NDSCZ and controls. We discovered that 70.7% of the variance in the phenome was explained by the IL-6/IL-23/Th17-axis (positively) and the G-CoDe and IL-10 (both inversely); and that 54.6% of the variance in the G-CoDe was explained by the IL-6/IL-23/Th17 scores (inversely) and magnesium, copper, calcium, and zinc (all positively).

CONCLUSION

The pathogenic IL-6/IL-23/Th17-axis contributes to the generalized neurocognitive deficit and the phenome of schizophrenia, especially that of DSCZ, due to its key role in peripheral inflammation and neuroinflammation and its consequent immunotoxic effects on neuronal circuits. These clinical impairments are more prominent in subjects with lowered IL-10, magnesium, calcium, and zinc.

Identification and Characterization of Epithelial Cell-Derived Dense Bodies Produced upon Cytomegalovirus Infection

Dense bodies (DB) are complex, noninfectious particles produced during CMVinfection containing envelope and tegument proteins that may be ideal candidates as vaccines. Although DB were previously described in fibroblasts, no evidence of DB formation has been shown after propagating CMV in epithelial cells. In the present study, both fibroblast MRC-5 and epithelial ARPE-19 cells were used to study DB production during CMV infection. We demonstrate the formation of epithelial cell-derived DB, mostly located as cytoplasmic inclusions in the perinuclear area of the infected cell. DB were gradient-purified, and the nature of the viral particles was confirmed using CMV-specific immunelabeling. Epithelial cell-derived DB had higher density and more homogeneous size (200-300 nm) compared to fibroblast-derived DB (100-600 nm).In agreement with previous results characterizing DB from CMV-infected fibroblasts, the pp65 tegument protein was predominant in the epithelial cell-derived DB. Our results also suggest that epithelial cells had more CMV capsids in the cytoplasm and had spherical bodies compatible with nucleus condensation (pyknosis) in cells undergoing apoptosis that were not detected in MRC-5 infected cells at the tested time post-infection. Our results demonstrate the formation of DB in CMV-infected ARPE-19 epithelial cells that may be suitable candidate to develop a multiprotein vaccine with antigenic properties similar to that of the virions while not including the viral genome.

Targeting Th17 cells in HIV-1 remission/cure interventions

Since the discovery of HIV-1, progress has been made in deciphering the viral replication cycle and mechanisms of host-pathogen interactions that has facilitated the implementation of effective antiretroviral therapies (ARTs). Major barriers to HIV-1 remission/cure include the persistence of viral reservoirs (VRs) in long-lived CD4⁺ T cells, residual viral transcription, and lack of mucosal immunity restoration during ART, which together fuel systemic inflammation. Recently, T helper (Th)17-polarized cells were identified as major contributors to the pool of transcriptionally/translationally competent VRs. In this review, we discuss the functional features of Th17 cells that were elucidated by fundamental immunology studies in the context of autoimmunity. We also highlight recent discoveries supporting the possibility of extrapolating this knowledge toward the identification of new putative Th17-targeted HIV-1 remission/cure strategies.

CAR-T Cell Performance: How to Improve Their Persistence?

Adoptive cell therapy with T cells reprogrammed to express chimeric antigen receptors (CAR-T cells) has been highly successful in patients with hematological neoplasms. However, its therapeutic benefits have been limited in solid tumor cases. Even those patients who respond to this immunotherapy remain at risk of relapse due to the short-term persistence or non-expansion of CAR-T cells; moreover, the hostile tumor microenvironment (TME) leads to the dysfunction of these cells after reinfusion. Some research has shown that, in adoptive T-cell therapies, the presence of less differentiated T-cell subsets within the infusion product is associated with better clinical outcomes. Naive and memory T cells persist longer and exhibit greater antitumor activity than effector T cells. Therefore, new methods are being studied to overcome the limitations of this therapy to generate CAR-T cells with these ideal phenotypes. In this paper, we review the characteristics of T-cell subsets and their implications in the clinical outcomes of adoptive therapy with CAR-T cells. In addition, we describe some strategies developed to overcome the reduced persistence of CAR T-cells and alternatives to improve this therapy by increasing the expansion ability and longevity of modified T cells. These methods include cell culture optimization, incorporating homeostatic cytokines during the expansion phase of manufacturing, modulation of CAR-T cell metabolism, manipulating signaling pathways involved in T-cell differentiation, and strategies related to CAR construct designs.

Genetic Associations and Differential mRNA Expression Levels of Host Genes Suggest a Viral Trigger for Endemic Pemphigus Foliaceus

The long search for the environmental trigger of the endemic pemphigus foliaceus (EPF, fogo selvagem) has not yet resulted in any tangible findings. Here, we searched for genetic associations and the differential expression of host genes involved in early viral infections and innate antiviral defense. Genetic variants could alter the structure, expression sites, or levels of the gene products, impacting their functions. By analyzing 3063 variants of 166 candidate genes in 227 EPF patients and 194 controls, we found 12 variants within 11 genes associated with differential susceptibility (p < 0.005) to EPF. The products of genes TRIM5, TPCN2, EIF4E, EIF4E3, NUP37, NUP50, NUP88, TPR, USP15, IRF8, and JAK1 are involved in different mechanisms of viral control, for example, the regulation of viral entry into the host cell or recognition of viral nucleic acids and proteins. Only two of nine variants were also associated in an independent German cohort of sporadic PF (75 patients, 150 controls), aligning with our hypothesis that antiviral host genes play a major role in EPF due to a specific virus−human interaction in the endemic region. Moreover, CCL5, P4HB, and APOBEC3G mRNA levels were increased (p < 0.001) in CD4+ T lymphocytes of EPF patients. Because there is limited or no evidence that these genes are involved in autoimmunity, their crucial role in antiviral responses and the associations that we observed support the hypothesis of a viral trigger for EPF, presumably a still unnoticed flavivirus. This work opens new frontiers in searching for the trigger of EPF, with the potential to advance translational research that aims for disease prevention and treatment.

The Role of the Oral Immune System in Oropharyngeal Candidiasis-Facilitated Invasion and Dissemination of Staphylococcus aureus

Candida albicans and Staphylococcus aureus account for most invasive fungal and bacterial bloodstream infections (BSIs), respectively. However, the initial point of invasion responsible for S. aureus BSIs is often unclear. Recently, C. albicans has been proposed to mediate S. aureus invasion of immunocompromised hosts during co-colonization of oral mucosal surfaces. The status of the oral immune system crucially contributes to this process in two distinct ways: firstly, by allowing invasive C. albicans growth during dysfunction of extra-epithelial immunity, and secondly following invasion by some remaining function of intra-epithelial immunity. Immunocompromised individuals at risk of developing invasive oral C. albicans infections could, therefore, also be at risk of contracting concordant S. aureus BSIs. Considering the crucial contribution of both oral immune function and dysfunction, the aim of this review is to provide an overview of relevant aspects of intra and extra-epithelial oral immunity and discuss predominant immune deficiencies expected to facilitate C. albicans induced S. aureus BSIs.

HIV Infection and Spread between Th17 Cells

HIV mainly targets CD4+ T cells, from which Th17 cells represent a major cell type, permissive, and are capable of supporting intracellular replication at mucosal sites. Th17 cells possess well-described dual roles, while being central to maintaining gut integrity, these may induce inflammation and contribute to autoimmune disorders; however, Th17 cells’ antiviral function in HIV infection is not completely understood. Th17 cells are star players to HIV-1 pathogenesis and a potential target to prevent or decrease HIV transmission. HIV-1 can be spread among permissive cells via direct cell-to-cell and/or cell-free infection. The debate on which mode of transmission is more efficient is still ongoing without a concrete conclusion yet. Most assessments of virus transmission analyzing either cell-to-cell or cell-free modes use in vitro systems; however, the actual interactions and conditions in vivo are not fully understood. The fact that infected breast milk, semen, and vaginal secretions contain a mix of both cell-free viral particles and infected cells presents an argument for the probability of HIV taking advantage of both modes of transmission to spread. Here, we review important insights and recent findings about the role of Th17 cells during HIV pathogenesis in mucosal surfaces, and the mechanisms of HIV-1 infection spread among T cells in tissues.

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.

Aging With Grace for People Living With HIV: Strategies to Overcome Leaky Gut and Cytomegalovirus Coinfection

ABSTRACT

The intestinal epithelial layer acts as a mechanical and functional barrier between the intraluminal microbiota and the immunologically active submucosa. A progressive loss of gut barrier function (leaky gut) leads to enhanced translocation of microbial products, which in turn contributes as endotoxins to inflammaging. Th17 T cell represents the main immune sentinels in the gut epithelium, preventing aggression from commensal and pathogenic microbes. As HIV infection deeply affects gut Th17 function and increases gut permeability, microbial translocation occurs at high level in people living with HIV (PLWH) and has been associated with the development of non-AIDS comorbidities. Although the inflammatory role of endotoxins like lipopolysaccharide produced by Gram-negative bacteria is well-established, fungal products such as β-D-glucan emerge as new contributors. In addition, PLWH are more frequently infected with cytomegalovirus (CMV) than the general population. CMV infection is a well-described accelerator of immune aging, through the induction of expansion of dysfunctional CD8 T-cells as well as through enhancement of gut microbial translocation. We critically review immune mechanisms related to bacterial and fungal translocation, with a focus on the contribution of CMV coinfection in PLWH. Improving gut barrier dysfunction, microbial composition, and reducing microbial translocation constitute emerging strategies for the prevention and treatment of HIV-associated inflammation and may be relevant for age-related inflammatory conditions.

Involvement of Th1Th17 Cell Subpopulations in the Immune Responses of Mothers Who Gave Birth to Children with Congenital Zika Syndrome (CZS)

High levels of T helper 17 cell (Th17)-related cytokines have been shown in acute Zika virus (ZIKV) infection. We hypothesized that the high levels of Th17-related cytokines, associated with a regulatory environment during pregnancy, create a favorable milieu for the differentiation of CD4+Th17 cells. We present data from a cross-sectional study on mothers who confirmed ZIKV infection by qRT-PCR and their children. We also recruited non-pregnant women infected with ZIKV in the same period. ZIKV infection occurred between 2015 and 2017. We collected samples for this study between 2018 and 2019, years after the initial infection. We highlight that, after in vitro stimulation with ZIKV CD4 megapool (ZIKV MP), we found a lower frequency of IL-17-producing CD4+ T cells (Th17), especially in the mothers, confirmed by the decrease in IL-17 production in the supernatant. However, a higher frequency of CD4+ IL-17+ IFN-γ+ T cells (Th1Th17) responding to the ZIKV MP was observed in the cells of the mothers and children but not in those of the non-pregnant women. Our data indicate that the priming of CD4 T cells of the Th1Th17 phenotype occurred preferentially in the mothers who gave birth to children with CZS and in the children.

Interleukine-17 Modulates Neurogenesis and Behavior Following Exposure to Trauma in Mice

Post-traumatic stress disorder (PTSD) is a psychiatric disorder accompanied by deficits in cognitive and social skills. Adult hippocampal neurogenesis is a lifelong phenomenon, with new neurons being formed in the granular cell layer of the dentate gyrus. Impaired neurogenesis is associated with multiple behavioral disorders including Alzheimer's disease and schizophrenia. PTSD patients often present hippocampal atrophy and animal models clearly present impaired neurogenesis. Previous studies on PTSD patients demonstrated elevated levels of Th17 cells and plasma levels of the pro-inflammatory cytokine interleukin-17A (IL-17A). Since IL-17A can impair neurogenesis in mice, we thus hypothesized that decreasing the serum levels of IL-17A will increase hippocampal neurogenesis and alleviate symptoms in a murine model of PTSD. Surprisingly, our results showed that attempting to neutralize IL-17A with an antibody resulted in increased serum levels of IL-17A, while targeting IL-23, the upstream regulator of IL-17, did lower the levels of IL-17A in trauma-exposed mice. As expected, increased levels of serum IL-17A (in anti-IL-17A treated mice) resulted in impaired neurogenesis, reflected by reduced number of proliferating Ki67⁺ neural progenitors and newly formed DCX⁺ neurons, which was correlated with increased expression of Hes1. Nevertheless, increased maturation was noted by the expression of Slit2 and Ache. In contrast, treatment with anti-IL-23 indeed resulted in increased neurogenesis. Behaviorally, both treatments did not affect trauma-related freezing behavior but did affect trauma-related social deficits. Unexpectedly, increased levels of serum IL-17A (in anti-IL-17A treated mice) prevented social deficits in trauma-exposed mice while anti-IL-23 exacerbated these deficits. We thus conclude that IL-17 is involved in regulating neurogenesis following exposure to stress but may be important in maintaining social behavior.

Flow Cytometry Sorting of Memory CCR6+CD4+ T-Cells for HIV Reservoir Quantification

Antiretroviral therapy (ART) has transformed the deadly human immunodeficiency virus type I (HIV-1) epidemic into a manageable chronic condition. Current ART is not curative and treatment interruption leads to viral rebound in people living with HIV-1 (PLWH). The main cause of viral rebound is the persistence of HIV reservoirs in long-lived memory CD4⁺ T cells. Accurate techniques to identify and quantify viral reservoirs are required to monitor therapeutic approaches designed to cure HIV infection. Th17-polarized CD4⁺ T cells are located at mucosal sites of HIV entry and are preferentially targeted for infection and viral reservoir persistence. They constitute an important reservoir in both blood and colon. In this chapter we describe a step-by-step flow cytometry-based protocol to isolate a fraction of Th17-enriched cells from PBMC based on their expression of the Th17 surface marker CCR6. The isolation of memory CCR6⁺CD4⁺ T cells allows subsequent PCR/RT-PCR-based HIV DNA/RNA quantifications, as well as their culture for quantitative viral outgrowth assays (QVOA). This method can be adapted for the isolation of CCR6⁺CD4⁺ T cells from peripheral tissues, such as the colon.

Identification of heterogeneous subsets of aortic interleukin-17A-expressing CD4+ T cells in atherosclerotic mice

Objectives: T helper 17 (Th17) cells are involved in the inflammatory response of atherosclerosis. However, their heterogeneity in the atherosclerotic aorta remains elusive. This study was designed to identify aortic Th17 subsets. Methods: The surface markers and transcription factors of aortic interleukin-17A (IL-17A)-expressing T cells were determined by flow cytometry in an ApoE-deficient mouse atherosclerotic model. Viable aortic IL-17A-expressing T cell subsets were isolated by flow cytometry on the basis of surface markers, followed by characterizing their transcription factors by either flow cytometry or real-time RT-PCR. The effect of aortic IL-17A-expressing T cell subsets on aortic endothelial cells was determined in vitro. Results: C-X-C Motif Chemokine Receptor 3 (CXCR3), interleukin-17 receptor E (IL-17RE), CD200, and C-C Motif Chemokine Receptor 4 (CCR4) marked three subsets of aortic IL-17A-expressing T cells: CXCR3⁺IL-17RE^lowCD200⁺CCR4^- T cells expressing T-box protein expressed in T cells (T-bet) and interferon-gamma (IFN-γ), CXCR3⁺IL-17RE^lowCD200⁺CCR4⁺ T cells expressing T-bet but fewer IFN-γ, and CXCR3⁻IL-17RE^highCD200⁺CCR4⁺ T cells expressing very low T-bet and no IFN-γ. Based on these markers, viable aortic Th17 cells, Th17.1 cells, and transitional Th17.1 cells were identified. Both Th17.1 cells and transitional Th17.1 cells were more proliferative than Th17 cells. Compared with Th17 cells, Th17.1 cells plus transitional Th17.1 cells induced higher expression of C-X-C motif chemokine ligand 1 (CXCL1), C-C motif chemokine ligand 2 (CCL2), C-X-C motif chemokine 5 (CXCL5), and granulocyte-macrophage colony-stimulating factor (GM-CSF) in aortic endothelial cells. Conclusion: IL-17A-expressing CD4⁺ T cells were heterogeneous in atherosclerotic aortas.

Effects of Recombinant IL-35-BCG on Treg/Th17 Cell Imbalance and Inflammatory Response in Asthmatic Newborn Mice Induced by RSV

Treg/Th17 cell imbalance and inflammatory response may occur in neonatal asthma. IL-35 and BCG have inhibitory effects on inflammatory responses in diseases. However, studies on neonatal asthma after combination of the two have not been reported so far. A respiratory syncytial virus (RSV)-induced neonatal asthma model was first developed in newborn mice. Pathological sections of lung tissue of asthmatic mice were observed by HE staining. Masson staining was used to observe the lung tissue and to compare the deposition of collagen fibers under bronchial epithelium in model mice. The expression of cytokines in serum was detected by ELISA. Giemsa staining analyzed each cell in bronchoalveolar lavage fluid (BALF). Flow cytometry was used to detect the differentiation and development of Treg and Th17 subgroups in BALF. The expression levels of inflammation-related factors were detected by RT-qPCR. Western blot was used to detect the expression of JNK pathway-related proteins. Recombinant IL-35-BCG improved the pathological response of asthmatic mice; inhibited the expression of IgE in serum, neutrophils, macrophages, and eosinophils in BALF; and increased the expression of lymphocytes. In addition, recombinant IL-35-BCG significantly inhibited Th17 differentiation, promoted Treg cell differentiation, and inhibited the expression of inflammatory factors in lung tissue homogenates, thereby reducing allergic airway inflammation. This process might be achieved by inhibiting the JNK signaling pathway. Recombinant IL-35-BCG can regulate Treg/Th17 cell imbalance and inflammatory response in asthmatic newborn mice induced by RSV through JNK signaling pathway, suggesting a new path to neonatal asthma treatment.

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

Relationship between Th17 immune response and cancer

Cancer is the second leading cause of death worldwide and epidemiological projections predict growing cancer mortality rates in the next decades. Cancer has a close relationship with the immune system and, although Th17 cells are known to play roles in the immune response against microorganisms and in autoimmunity, studies have emphasized their roles in cancer pathogenesis. The Th17 immune response profile is involved in several types of cancer including urogenital, respiratory, gastrointestinal, and skin cancers. This type of immune response exerts pro and antitumor functions through several mechanisms, depending on the context of each tumor, including the protumor angiogenesis and exhaustion of T cells and the antitumor recruitment of T cells and neutrophils to the tumor microenvironment. Among other factors, the paradoxical behavior of Th17 cells in this setting has been attributed to its plasticity potential, which makes possible their conversion into other types of T cells such as Th17/Treg and Th17/Th1 cells. Interleukin (IL)-17 stands out among Th17-related cytokines since it modulates pathways and interacts with other cell profiles in the tumor microenvironment, which allow Th17 cells to prevail in tumors. Moreover, the IL-17 is able to mediate pro and antitumor processes that influence the development and progression of various cancers, being associated with variable clinical outcomes. The understanding of the relationship between the Th17 immune response and cancer as well as the singularities of carcinogenic processes in each type of tumor is crucial for the identification of new therapeutic targets.

Transcriptomic effects of rs4845604, an IBD and allergy-associated RORC variant, in stimulated ex vivo CD4+ T cells

RORγt is an isoform of RORC, preferentially expressed in Th17 cells, that functions as a critical regulator of type 3 immunity. As murine Th17-driven inflammatory disease models were greatly diminished in RORC knock-out mice, this receptor was prioritised as an attractive therapeutic target for the treatment of several autoimmune diseases. Human genetic studies indicate a significant contributory role for RORC in several human disease conditions. Furthermore, genome-wide association studies (GWAS) report a significant association between inflammatory bowel disease (IBD) and the RORC regulatory variant rs4845604. To investigate if the rs4845604 variant may affect CD4⁺ T cell differentiation events, naïve CD4⁺ T cells were isolated from eighteen healthy subjects homozygous for the rs4845604 minor (A) or major (G) allele). Isolated cells from each subject were differentiated into distinct T cell lineages by culturing in either T cell maintenance medium or Th17 driving medium conditions for six days in the presence of an RORC inverse agonist (to prevent constitutive receptor activity) or an inactive diastereomer (control). Our proof of concept study indicated that genotype had no significant effect on the mean number of naïve CD4 T cells isolated, nor the frequency of Th1-like and Th17-like cells following six days of culture in any of the four culture conditions. Analysis of the derived RNA-seq count data identified genotype-driven transcriptional effects in each of the four culture conditions. Subsequent pathway enrichment analysis of these profiles reported perturbation of metabolic signalling networks, with the potential to affect the cellular detoxification response. This investigation reveals that rs4845604 genotype is associated with transcriptional effects in CD4⁺ T cells that may perturb immune and metabolic pathways. Most significantly, the rs4845604 GG, IBD risk associated, genotype may be associated with a differential detoxification response. This observation justifies further investigation in a larger cohort of both healthy and IBD-affected individuals.

HIV-Associated Interactions Between Oral Microbiota and Mucosal Immune Cells: Knowledge Gaps and Future Directions

Even with sustained use of antiretroviral therapy (ART), HIV-infected individuals have an increased risk of systemic comorbid conditions and oral pathologies, including opportunistic infections, oral mucosal inflammation, and gingival and periodontal diseases. The immune-mediated mechanisms that drive this increased risk, in the context of sustained viral suppression, are unclear. HIV infection, even when controlled, alters microbial communities contributing to a chronic low-grade inflammatory state that underlies these non-HIV co-morbidities. The higher prevalence of dental caries, and mucosal and periodontal inflammation reported in HIV-infected individuals on ART is often associated with differentially abundant oral microbial communities, possibly leading to a heightened susceptibility to inflammation. This mini-review highlights current gaps in knowledge regarding the microbe-mediated oral mucosal immunity with HIV infection while discussing opportunities for future research investigations and implementation of novel approaches to elucidate these gaps. Interventions targeting both inflammation and microbial diversity are needed to mitigate oral inflammation-related comorbidities, particularly in HIV-infected individuals. More broadly, additional research is needed to bolster general models of microbiome-mediated chronic immune activation and aid the development of precise microbiota-targeted interventions to reverse or mitigate adverse outcomes.

Overt IL-32 isoform expression at intestinal level during HIV-1 infection is negatively regulated by IL-17A

OBJECTIVES

Untreated HIV infection was previously associated with IL-32 overexpression in gut/intestinal epithelial cells (IEC). Here, we explored IL-32 isoform expression in the colon of people with HIV (PWH) receiving antiretroviral therapy (ART) and IL-32 triggers/modulators in IEC.

DESIGN

Sigmoid colon biopsies (SCB) and blood were collected from ART-treated PWH (HIV + ART; n = 17; mean age: 56 years; CD4+ cell counts: 679 cells/μl; time on ART: 72 months) and age-matched HIV-uninfected controls (HIVneg; n = 5). The IEC line HT-29 was used for mechanistic studies.

METHODS

Cells from SCB and blood were isolated by enzymatic digestion and/or gradient centrifugation. HT-29 cells were exposed to TLR1-9 agonists, TNF-α, IL-17A and HIV. IL-32α/β/γ/D/ε/θ and IL-17A mRNA levels were quantified by real-time RT-PCR. IL-32 protein levels were quantified by ELISA.

RESULTS

IL-32β/γ/ε isoform transcripts were detectable in the blood and SCB, with IL-32β mRNA levels being predominantly expressed in both compartments and at significantly higher levels in HIV + ART compared to HIVneg. IL-17A transcripts were only detectable in SCB, with increased IL-17A levels in HIVneg compared with HIV + ART and negatively correlated with IL-32β mRNA levels. IL-32β/γ/ε isoform mRNA were detected in HT-29 cells upon exposure to TNF-α, Poly I:C (TLR3 agonist), Flagellin (TLR-5 agonist) and HIV. IL-17A significantly decreased both IL-32 β/γ/ε mRNA and cell-associated IL-32 protein levels induced upon TNF-α and Poly I:C triggering.

CONCLUSION

We document IL-32 isoforms abundant in the colon of ART-treated PWH and reveal the capacity of the Th17 hallmark cytokine IL-17A to attenuate IL-32 overexpression in a model of inflamed IEC.

Environmental Pollutants, Mucosal Barriers, and Pathogen Susceptibility; The Case for Aflatoxin B1 as a Risk Factor for HIV Transmission and Pathogenesis

HIV transmission risk is dependent on the infectivity of the HIV+ partner and personal susceptibility risk factors of the HIV- partner. The mucosal barrier, as the internal gatekeeper between environment and self, concentrates and modulates the internalization of ingested pathogens and pollutants. In this review, we summarize the localized effects of HIV and dietary toxin aflatoxin B1 (AFB1), a common pollutant in high HIV burden regions, e.g., at the mucosal barrier, and evidence for pollutant-viral interactions. We compiled literature on HIV and AFB1 geographic occurrences, mechanisms of action, related co-exposures, personal risk factors, and HIV key determinants of health. AFB1 exposure and HIV sexual transmission hotspots geographically co-localize in many low-income countries. AFB1 distributes to sexual mucosal tissues generating inflammation, microbiome changes and a reduction of mucosal barrier integrity, effects that are risk factors for increasing HIV susceptibility. AFB1 exposure has a positive correlation to HIV viral load, a risk factor for increasing the infectivity of the HIV+ partner. The AFB1 exposure and metabolism generates inflammation that recruits HIV susceptible cells and generates chemokine/cytokine activation in tissues exposed to HIV. Although circumstantial, the available evidence makes a compelling case for studies of AFB1 exposure as a risk factor for HIV transmission, and a modifiable new component for combination HIV prevention efforts.

Propolis increases Foxp3 expression and lymphocyte proliferation in HIV-infected people: A randomized, double blind, parallel-group and placebo-controlled study

HIV infection and the prolonged use of antiretroviral therapy (ART) contribute to persistent inflammation and immune deregulation in people living with HIV/AIDS (PLWHA). Propolis is a bee product with plenty of biological properties, including immunomodulatory and anti-inflammatory action. This work aimed to evaluate possible changes in the immune/inflammatory response in PLWHA under ART after propolis intake. Asymptomatic PLWHA were double-blindly randomized into parallel groups receiving propolis (500 mg/day, n = 20) for 3 months or placebo (n = 20). Plasma cytokines (TNF-α, IL-2, IL-4, IL-6, IL-10 and IL17) were evaluated by cytometric bead array; cytokine production by PBMC (IFN-γ, IL-5, IL-17, IL-10, IL-1β, IL-18, and IL-33) was assessed by ELISA; gene expression (T-bet, GATA-3, RORγt and Foxp3) was determined by RT-qPCR, and cell proliferation was analysed by flow cytometry using CFSE staining. The average of gender, age, CD4⁺/CD8⁺ T cell count, time of diagnosis and treatment were similar in both groups. No differences were observed in cytokine levels nor in inflammasome activation. However, Pearson's correlation showed that IL-10 was directly correlated to CD4⁺ T cell count and inversely to IFN-γ after treatment with propolis. Foxp3 expression and lymphocyte proliferation increased in the propolis group. Data suggested that daily propolis consumption may improve the immune response and decrease the inflammatory status in asymptomatic PLWHA under ART.

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.

MiR-22 regulated T cell differentiation and hepatocellular carcinoma growth by directly targeting Jarid2

MiR-22 has been demonstrated to inhibits tumor growth in several cancers. However, its function in the tumor microenvironment is still unclear, especially for T cell differentiation. Here, miR-22 expression in the circulating T cells from hepatocellular carcinoma (HCC) patients and healthy controls was analyzed with quantitative polymerase chain reaction (qPCR). Diethylnitrosamine (DEN)/phenobarbital (PB)-mediated primary HCC and Hepa1-6 subcutaneous tumor mouse models were established and subjected to lenti-miR-22 injection. Mice immunoreconstituted with miR-22-overexpressing T cells were employed to investigate the antitumor effect of miR-22 in mice. Luciferase assay, immunofluorescent staining, in vitro Th17 cell differentiation assay, and rescue experiments were employed to investigate the mechanism underlying the miR-22-mediated regulation of Th17 cell differentiation and liver tumor growth. Results confirmed the dramatic downregulation of miR-22 expression in malignant tissues and circulating T cells from patients with HCC. MiR-22 expression correlated with good prognosis of patients. Overexpression of miR-22 impaired the DEN/PB-induced primary HCC formation and the growth of Hepa1-6 subcutaneous tumors by promoting Th17 differentiation. Injection of miR-22-overexpressing T cells in irradiated mice resulted in the inhibition of Hepa1-6 subcutaneous tumor growth via Th17 differentiation promotion. MiR-22 could directly bind to Jarid2, which played an important role during the miR-22-mediated regulation of Th17 differentiation. Taken together, our study expands the understanding of miR-22 function and provides a therapy target for HCC.

Th17 Cells in Viral Infections-Friend or Foe?

Th17 cells are recognized as indispensable in inducing protective immunity against bacteria and fungi, as they promote the integrity of mucosal epithelial barriers. It is believed that Th17 cells also play a central role in the induction of autoimmune diseases. Recent advances have evaluated Th17 effector functions during viral infections, including their critical role in the production and induction of pro-inflammatory cytokines and in the recruitment and activation of other immune cells. Thus, Th17 is involved in the induction both of pathogenicity and immunoprotective mechanisms seen in the host's immune response against viruses. However, certain Th17 cells can also modulate immune responses, since they can secrete immunosuppressive factors, such as IL-10; these cells are called non-pathogenic Th17 cells. Here, we present a brief review of Th17 cells and highlight their involvement in some virus infections. We cover these notions by highlighting the role of Th17 cells in regulating the protective and pathogenic immune response in the context of viral infections. In addition, we will be describing myocarditis and multiple sclerosis as examples of immune diseases triggered by viral infections, in which we will discuss further the roles of Th17 cells in the induction of tissue damage.

Preinvasive Colorectal Lesions of African Americans Display an Immunosuppressive Signature Compared to Caucasian Americans

Background

African Americans (AAs) have higher colorectal cancer (CRC) incidence and mortality rate than Caucasian Americans (CAs). Recent studies suggest that immune responses within CRCs contribute to the disparities. If racially distinct immune signatures are present in the early phases of carcinogenesis, they could be used to develop interventions to prevent or slow disease.

Methods

We selected a convenience sample of 95 patients (48 CAs, 47 AAs) with preinvasive colorectal adenomas from the surgical pathology laboratory at the Medical University of South Carolina. Using immunofluorescent-conjugated antibodies on tissue slides from the lesions, we quantified specific immune cell populations: mast cells (CD117⁺), Th17 cells (CD4⁺RORC⁺), and NK cell ligand (MICA/B) and inflammatory cytokines, including IL-6, IL-17A, and IFN-γ. We compared the mean density counts (MDCs) and density rate ratios (RR) and 95% CI of immune markers between AAs to CAs using negative binomial regression analysis. We adjusted our models for age, sex, clinicopathologic characteristics (histology, location, dysplasia), and batch.

Results

We observed no racial differences in age or sex at the baseline endoscopic exam. AAs compared to CAs had a higher prevalence of proximal adenomas (66% vs. 40%) and a lower prevalence of rectal adenomas (11% vs. 23%) (p =0.04) but no other differences in pathologic characteristics. In age, sex, and batch adjusted models, AAs vs. CAs had lower RRs for cells labeled with IFNγ (RR 0.50 (95% CI 0.32-0.81); p=0.004) and NK cell ligand (RR 0.67 (0.43-1.04); p=0.07). In models adjusted for age, sex, and clinicopathologic variables, AAs had reduced RRs relative to CAs for CD4 (p=0.02), NK cell ligands (p=0.01), Th17 (p=0.005), mast cells (p=0.04) and IFN-γ (p< 0.0001).

Conclusions

Overall, the lower RRs in AAs vs. CAs suggests reduced effector response capacity and an immunosuppressive (‘cold’) tumor environment. Our results also highlight the importance of colonic location of adenoma in influencing these differences; the reduced immune responses in AAs relative to CAs may indicate impaired immune surveillance in early carcinogenesis. Future studies are needed to understand the role of risk factors (such as obesity) in influencing differences in immune responses by race.

A case report of disseminated verrucosis secondary to ustekinumab in a patient with Crohn's disease

Ustekinumab is a biologic agent with Food and Drug Administration approval for the treatment of moderate-to-severe plaque psoriasis, psoriatic arthritis, ulcerative colitis, and Crohn’s disease. It functions to inhibit the p40 subunit common to both interleukin-12 and interleukin-23. These pro-inflammatory cytokines are implicated in autoinflammatory and autoimmune disorders, but they also play an important role in cell-mediated immunity against viral, bacterial, and fungal pathogens. Therefore, antagonism of interleukin-12 and interleukin-23 by ustekinumab may increase the risk of human papillomavirus infection or reactivation which can lead to the development of verrucae. To the best of our knowledge, there is only one published report of disseminated verrucosis secondary to ustekinumab treatment for psoriasis. Here, we present the first case report of ustekinumab-induced disseminated verrucosis occurring in the setting of treatment for Crohn’s disease.

LILAC pilot study: Effects of metformin on mTOR activation and HIV reservoir persistence during antiretroviral therapy

BACKGROUND

Chronic inflammation and residual HIV transcription persist in people living with HIV (PLWH) receiving antiretroviral therapy (ART), thus increasing the risk of developing non-AIDS co-morbidities. The mechanistic target of rapamycin (mTOR) is a key regulator of cellular metabolism and HIV transcription, and therefore represents an interesting novel therapeutic target.

METHODS

The LILAC pilot clinical trial, performed on non-diabetic ART-treated PLWH with CD4⁺/CD8⁺ T-cell ratios <0.8, evaluated the effects of metformin (12 weeks oral administration; 500-850 mg twice daily), an indirect mTOR inhibitor, on the dynamics of immunological/virological markers and changes in mTOR activation/phosphorylation in blood collected at Baseline, Week 12, and 12 weeks after metformin discontinuation (Week 24) and sigmoid colon biopsies (SCB) collected at Baseline and Week 12.

FINDINGS

CD4⁺ T-cell counts, CD4⁺/CD8⁺ T-cell ratios, plasma markers of inflammation/gut damage, as well as levels of cell-associated integrated HIV-DNA and HIV-RNA, and transcriptionally-inducible HIV reservoirs, underwent minor variations in the blood in response to metformin. The highest levels of mTOR activation/phosphorylation were observed in SCB at Baseline. Consistently, metformin significantly decreased CD4⁺ T-cell infiltration in the colon, as well as mTOR activation/phosphorylation, especially in CD4⁺ T-cells expressing the Th17 marker CCR6. Also, metformin decreased the HIV-RNA/HIV-DNA ratios, a surrogate marker of viral transcription, in colon-infiltrating CD4⁺ T-cells of 8/13 participants.

INTERPRETATION

These results are consistent with the fact that metformin preferentially acts on the intestine and that mTOR activation/phosphorylation selectively occurs in colon-infiltrating CCR6⁺CD4⁺ T-cells. Future randomized clinical trials should evaluate the benefits of long-term metformin supplementation of ART.

Rejection of intestinal allotransplants is driven by memory T helper type 17 immunity and responds to infliximab

Intestinal transplantation (ITx) can be life-saving for patients with advanced intestinal failure experiencing complications of parenteral nutrition. New surgical techniques and conventional immunosuppression have enabled some success, but outcomes post-ITx remain disappointing. Refractory cellular immune responses, immunosuppression-linked infections, and posttransplant malignancies have precluded widespread ITx application. To shed light on the dynamics of ITx allograft rejection and treatment resistance, peripheral blood samples and intestinal allograft biopsies from 51 ITx patients with severe rejection, alongside 37 stable controls, were analyzed using immunohistochemistry, polychromatic flow cytometry, and reverse transcription-PCR. Our findings inform both immunomonitoring and treatment. In terms of immunomonitoring, we found that while ITx rejection is associated with proinflammatory and activated effector memory T cells in the blood, evidence of treatment efficacy can only be found in the allograft itself, meaning that blood-based monitoring may be insufficient. In terms of treatment, we found that the prominence of intra-graft memory TNF-α and IL-17 double-positive T helper type 17 (Th17) cells is a leading feature of refractory rejection. Anti-TNF-α therapies appear to provide novel and safer treatment strategies for refractory ITx rejection; with responses in 14 of 14 patients. Clinical protocols targeting TNF-α, IL-17, and Th17 warrant further testing.