New Insights about Treg and Th17 Cells in HIV Infection and Disease Progression

The role of T regulatory cells in the immunopathogenesis of HIV: Clinical implications

Human Immunodeficiency Virus (HIV) infection is among the most challenging issues in the healthcare system, presenting significant financial and hygiene problems with a wide range of clinical manifestations. Despite the hopeful outcomes of Antiretroviral Therapies (ARTs), the current strategies for the treatment of patients with HIV infection have not shown clinical significance for all subjects, which is mainly due to the complexity of the disease. Therefore, the need for collaborative and interdisciplinary research focused on deciphering the multifaceted cellular, and molecular immunopathogenesis of HIV remains essential in the development of innovative and more efficacious therapeutic approaches. T-regulatory (Treg) cells function as suppressors of effector T-cell responses contributing to the inhibition of autoimmune disorders and the limitation of chronic inflammatory diseases. Notably, these cells can play substantial roles in regulating immune responses, immunopathogenesis, viral persistence and disease progression, and affect therapeutic responses in HIV patients. In this review, we aim elucidating the role of T-regulatory cells (Tregs) in the immunopathogenesis of HIV, including immunological fatigue and seroconversion. In particular, the focus of the current study is exploration of novel immunotherapeutic approaches to target HIV or related co-infections.

HIV-Associated Hypertension: Risks, Mechanisms, and Knowledge Gaps

HIV type 1 (HIV-1) is the causative agent of AIDS. Since the start of the epidemic, HIV/AIDS has been responsible for ≈40 million deaths. Additionally, an estimated 39 million people are currently infected with the virus. HIV-1 primarily infects immune cells, such as CD4+ (cluster of differentiation 4+) T lymphocytes (T cells), and as a consequence, the number of CD4+ T cells progressively declines in people living with HIV. Within a span of ≈10 years, HIV-1 infection leads to the systemic failure of the immune system and progression to AIDS. Fortunately, potent antiviral therapy effectively controls HIV-1 infection and prevents AIDS-related deaths. The efficacy of the current antiviral therapy regimens has transformed the outcome of HIV/AIDS from a death sentence to a chronic disease with a prolonged lifespan of people living with HIV. However, antiviral therapy is not curative, is challenged by virus resistance, can be toxic, and, most importantly, requires lifelong adherence. Furthermore, the improved lifespan has resulted in an increased incidence of non-AIDS-related morbidities in people living with HIV including cardiovascular diseases, renal disease, liver disease, bone disease, cancer, and neurological conditions. In this review, we summarize the current state of knowledge of the cardiovascular comorbidities associated with HIV-1 infection, with a particular focus on hypertension. We also discuss the potential mechanisms known to drive HIV-1-associated hypertension and the knowledge gaps in our understanding of this comorbid condition. Finally, we suggest several directions of future research to better understand the factors, pathways, and mechanisms underlying HIV-1-associated hypertension in the post-antiviral therapy era.

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.

Engineered collagen polymeric materials create noninflammatory regenerative microenvironments that avoid classical foreign body responses

The efficacy and longevity of medical implants and devices is largely determined by the host immune response, which extends along a continuum from pro-inflammatory/pro-fibrotic to anti-inflammatory/pro-regenerative. Using a rat subcutaneous implantation model, along with histological and transcriptomics analyses, we characterized the tissue response to a collagen polymeric scaffold fabricated from polymerizable type I oligomeric collagen (Oligomer) in comparison to commercial synthetic and collagen-based products. In contrast to commercial biomaterials, no evidence of an immune-mediated foreign body reaction, fibrosis, or bioresorption was observed with Oligomer scaffolds for beyond 60 days. Oligomer scaffolds were noninflammatory, eliciting minimal innate inflammation and immune cell accumulation similar to sham surgical controls. Genes associated with Th2 and regulatory T cells were instead upregulated, implying a novel pathway to immune tolerance and regenerative remodeling for biomaterials.

The Influence Between C-C Chemokine Receptor 5 Genetic Polymorphisms and the Type-1 Human Immunodeficiency Virus: A 20-Year Review

Acquired immune deficiency syndrome (AIDS) is an infectious disease caused by the types 1 and 2 human immunodeficiency virus (HIV-1 and HIV-2). Clinical outcomes in patients are highly varied and delineated by complex interactions between virus, host, and environment, such as with help of co-receptors, for example, the C-C chemokine receptor 5 (CCR5). This work aimed to describe the scientific evidence relating the influence of CCR5 polymorphisms in association studies for HIV-1 disease susceptibility, severity, and transmissibility. This is a systematic review of the literature on single nucleotide polymorphisms (SNPs) and the deletion [Insertion and Deletion (Indel)] Δ32 of CCR5. The search for articles was based on the ScienceDirect, PubMed, and Coordination for the Improvement of Higher Education Personnel (CAPES) databases for the period between 2001 and 2021. The final sample consisted of 32 articles. ^†SNP rs1799987 is one of the genetic polymorphisms most associated with the criteria of susceptibility and severity of HIV-1, having distinct consequences in genotypic, allelic, and clinical analysis in the variability of investigated populations. As for the transmission character of the disease, the G mutant allele of rs1799987 corresponds to the highest positive association. ^‡Furthermore, the results on Indel Δ32 corroborate the absence and rarity of this variant in some populations. Finally, mitigating the severity of cases, SNPs rs1799988 and rs1800023 obtained significant attribution in individuals in the studied populations. It is shown that the reported polymorphisms express significant influences for the evaluation of diagnostic, therapeutic, and prophylactic measures for HIV-1 having fundamental particularities in the molecular, genetic, and transcriptional aspects of CCR5.

Patients Recovering from Severe COVID-19 Develop a Polyfunctional Antigen-Specific CD4+ T Cell Response

Specific T cells are crucial to control SARS-CoV-2 infection, avoid reinfection and confer protection after vaccination. We have studied patients with severe or moderate COVID-19 pneumonia, compared to patients who recovered from a severe or moderate infection that had occurred about 4 months before the analyses. In all these subjects, we assessed the polyfunctionality of virus-specific CD4+ and CD8+ T cells by quantifying cytokine production after in vitro stimulation with different SARS-CoV-2 peptide pools covering different proteins (M, N and S). In particular, we quantified the percentage of CD4+ and CD8+ T cells simultaneously producing interferon-γ, tumor necrosis factor, interleukin (IL)-2, IL-17, granzyme B, and expressing CD107a. Recovered patients who experienced a severe disease display high proportions of antigen-specific CD4+ T cells producing Th1 and Th17 cytokines and are characterized by polyfunctional SARS-CoV-2-specific CD4+ T cells. A similar profile was found in patients experiencing a moderate form of COVID-19 pneumonia. No main differences in polyfunctionality were observed among the CD8+ T cell compartments, even if the proportion of responding cells was higher during the infection. The identification of those functional cell subsets that might influence protection can thus help in better understanding the complexity of immune response to SARS-CoV-2.

An Overview of Autophagy in Hematopoietic Stem Cell Transplantation

Autophagy is a fundamental homeostatic process crucial for cellular adaptation in response to metabolic stress. Autophagy exerts its effect through degrading intracellular components and recycling them to produce macromolecular precursors and energy. This physiological process contributes to cellular development, maintenance of cellular/tissue homeostasis, immune system regulation, and human disease. Allogeneic hematopoietic stem cell transplantation (HSCT) is the only preferred therapy for most bone marrow-derived cancers. Unfortunately, HSCT can result in several serious and sometimes untreatable conditions due to graft-versus-host disease (GVHD), graft failure, and infection. These are the major cause of morbidity and mortality in patients receiving the transplant. During the last decade, autophagy has gained a considerable understanding of its role in various diseases and cellular processes. In light of recent research, it has been confirmed that autophagy plays a crucial role in the survival and function of hematopoietic stem cells (HSCs), T-cell differentiation, antigen presentation, and responsiveness to cytokine stimulation. Despite the importance of these events to HSCT, the role of autophagy in HSCT as a whole remains relatively ambiguous. As a result of the growing use of autophagy-modulating agents in the clinic, it is imperative to understand how autophagy functions in allogeneic HSCT. The purpose of this literature review is to elucidate the established and implicated roles of autophagy in HSCT, identifying this pathway as a potential therapeutic target for improving transplant outcomes.

Altered Expression of ACE2 and Co-receptors of SARS-CoV-2 in the Gut Mucosa of the SIV Model of HIV/AIDS

The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection, the cause of the COVID-19 pandemic, is initiated by its binding to the ACE2 receptor and other co-receptors on mucosal epithelial cells. Variable outcomes of the infection and disease severity can be influenced by pre-existing risk factors. Human immunodeficiency virus (HIV), the cause of AIDS, targets the gut mucosal immune system and impairs epithelial barriers and mucosal immunity. We sought to determine the impact and mechanisms of pre-existing HIV infection increasing mucosal vulnerability to SARS-CoV-2 infection and disease. We investigated changes in the expression of ACE2 and other SARS-CoV-2 receptors and related pathways in virally inflamed gut by using the SIV infected rhesus macaque model of HIV/AIDS. Immunohistochemical analysis showed sustained/enhanced ACE2 expression in the gut epithelium of SIV infected animals compared to uninfected controls. Gut mucosal transcriptomic analysis demonstrated enhanced expression of host factors that support SARS-CoV-2 entry, replication, and infection. Metabolomic analysis of gut luminal contents revealed the impact of SIV infection as demonstrated by impaired mitochondrial function and decreased immune response, which render the host more vulnerable to other pathogens. In summary, SIV infection resulted in sustained or increased ACE2 expression in an inflamed and immune-impaired gut mucosal microenvironment. Collectively, these mucosal changes increase the susceptibility to SARS-CoV-2 infection and disease severity and result in ineffective viral clearance. Our study highlights the use of the SIV model of AIDS to fill the knowledge gap of the enteric mechanisms of co-infections as risk factors for poor disease outcomes, generation of new viral variants and immune escape in COVID-19.

Peripheral blood CD4+CCR6+ compartment differentiates HIV-1 infected or seropositive elite controllers from long-term successfully treated individuals

HIV-1 infection induces a chronic inflammatory environment not restored by suppressive antiretroviral therapy (ART). As of today, the effect of viral suppression and immune reconstitution in people living with HIV-1 (PLWH) has been well described but not completely understood. Herein, we show how PLWH who naturally control the virus (PLWH_EC) have a reduced proportion of CD4⁺CCR6⁺ and CD8⁺CCR6⁺ cells compared to PLWH on suppressive ART (PLWH_ART) and HIV-1 negative controls (HC). Expression of CCR2 was reduced on both CD4⁺, CD8⁺ and classical monocytes in PLWH_EC compared to PLWH_ART and HC. Longer suppressive therapy, measured in the same patients, decreased number of cells expressing CCR2 on all monocytic cell populations while expression on CD8⁺ T cells increased. Furthermore, the CD4⁺CCR6⁺/CCR6^- cells exhibited a unique proteomic profile with a modulated energy metabolism in PLWH_EC compared to PLWH_ART independent of CCR6 status. The CD4⁺CCR6⁺ cells also showed an enrichment in proteins involved in apoptosis and p53 signalling in PLWH_EC compared to PLWH_ART, indicative of increased sensitivity towards cell death mechanisms. Collectively, this data shows how PLWH_EC have a unique chemokine receptor profile that may aid in facilitating natural control of HIV-1 infection.

Post-Infectious Autoimmunity in the Central (CNS) and Peripheral (PNS) Nervous Systems: An African Perspective

The direct impact and sequelae of infections in children and adults result in significant morbidity and mortality especially when they involve the central (CNS) or peripheral nervous system (PNS). The historical understanding of the pathophysiology has been mostly focused on the direct impact of the various pathogens through neural tissue invasion. However, with the better understanding of neuroimmunology, there is a rapidly growing realization of the contribution of the innate and adaptive host immune responses in the pathogenesis of many CNS and PNS diseases. The balance between the protective and pathologic sequelae of immunity is fragile and can easily be tipped towards harm for the host. The matter of immune privilege and surveillance of the CNS/PNS compartments and the role of the blood-brain barrier (BBB) and blood nerve barrier (BNB) makes this even more complex. Our understanding of the pathogenesis of many post-infectious manifestations of various microbial agents remains elusive, especially in the diverse African setting. Our exploration and better understanding of the neuroimmunology of some of the infectious diseases that we encounter in the continent will go a long way into helping us to improve their management and therefore lessen the burden. Africa is diverse and uniquely poised because of the mix of the classic, well described, autoimmune disease entities and the specifically "tropical" conditions. This review explores the current understanding of some of the para- and post-infectious autoimmune manifestations of CNS and PNS diseases in the African context. We highlight the clinical presentations, diagnosis and treatment of these neurological disorders and underscore the knowledge gaps and perspectives for future research using disease models of conditions that we see in the continent, some of which are not uniquely African and, where relevant, include discussion of the proposed mechanisms underlying pathogen-induced autoimmunity. This review covers the following conditions as models and highlight those in which a relationship with COVID-19 infection has been reported: a) Acute Necrotizing Encephalopathy; b) Measles-associated encephalopathies; c) Human Immunodeficiency Virus (HIV) neuroimmune disorders, and particularly the difficulties associated with classical post-infectious autoimmune disorders such as the Guillain-Barré syndrome in the context of HIV and other infections. Finally, we describe NMDA-R encephalitis, which can be post-HSV encephalitis, summarise other antibody-mediated CNS diseases and describe myasthenia gravis as the classic antibody-mediated disease but with special features in Africa.

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.

CRISPR/Cas9-Mediated Insertion of HIV Long Terminal Repeat within BACH2 Promotes Expansion of T Regulatory-like Cells

One key barrier to curative therapies for HIV is the limited understanding of HIV persistence. HIV provirus integration sites (ISs) within BACH2 are common, and almost all sites mapped to date are located upstream of the start codon in the same transcriptional orientation as the gene. These unique features suggest the possibility of insertional mutagenesis at this location. Using CRISPR/Cas9-based homology-directed repair in primary human CD4+ T cells, we directly modeled the effects of HIV integration within BACH2 Integration of the HIV long terminal repeat (LTR) and major splice donor increased BACH2 mRNA and protein levels, altered gene expression, and promoted selective outgrowth of an activated, proliferative, and T regulatory-like cell population. In contrast, introduction of the HIV-LTR alone or an HIV-LTR-major splice donor construct into STAT5B, a second common HIV IS, had no functional impact. Thus, HIV LTR-driven BACH2 expression modulates T cell programming and leads to cellular outgrowth and unique phenotypic changes, findings that support a direct role for IS-dependent HIV-1 persistence.

Preterm Birth in Women With HIV: The Role of the Placenta

Maternal HIV infection is associated with an increased risk of preterm birth (PTB). However, the mechanisms underlying this increased risk in women with HIV remain poorly understood. In this regard, it is well-established that labor is an inflammatory process and premature activation of the pro-inflammatory signals (associated with labor) can result in preterm labor which can subsequently lead to PTB. HIV infection is known to cause severe immune dysregulation within its host characterized by altered immune profiles, chronic inflammation and eventually, the progressive failure of the immune system. The human placenta comprises different immune cell subsets, some of which play an important role during pregnancy including participating in the inflammatory processes that accompany labor. It is therefore plausible that HIV/antiretroviral therapy (ART)-associated immune dysregulation within the placental microenvironment may underlie the increased risk of PTB reported in women with HIV. Here, we review evidence from studies that point toward the placental origin of spontaneous PTB and discuss possible ways maternal HIV infection and/or ART could increase this risk. We focus on key cellular players in the maternal decidua including natural killer cells, CD4+ T cells including CD4+ regulatory T cells, CD8+ T cells as well as macrophages.

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.

Endometriotic Peritoneal Fluid Stimulates Recruitment of CD4+CD25highFOXP3+ Treg Cells

Endometriosis is a common gynecological disorder characterized by the presence of endometrial-like tissue outside the uterus. The disease is associated with disturbed local and systemic immunity. It has been reported that the proportion of CD4⁺CD25^highFOXP3⁺ Treg cells may be significantly increased in the peritoneal fluid of patients with endometriosis. Therefore, the aim of our study was to investigate whether the proportions of Treg cells in the peritoneal cavity of patients with endometriosis are related to the chemotactic and stimulatory activity of the local peritoneal milieu. The peritoneal fluid was collected from 13 women with ovarian endometriosis and 12 control women without the disease. T cell populations were analyzed by flow cytometry, cytokines and chemokines were evaluated using the cytometric bead kit, and cell chemotaxis was studied by cell migration assay. We confirmed that the proportions of Treg cells are increased in the peritoneal fluid of women with endometriosis as compared to the control women. Endometriosis was also associated with elevated concentrations of IL-6, IL-10, and TGF-β1/2 as well as CCL20, CXCL8, CXCL9, and CXCL10. We did not reveal any changes in the proportion of peritoneal Th17 cells and concentrations of IL-17A. Peritoneal Treg cells positively correlated with concentrations of TGF-β, IL-10, and CCL20. Endometriotic peritoneal fluid stimulated chemotaxis of both CD4⁺ and Treg cells. This chemotactic activity positively correlated with concentrations of CCL20. CCL20 stimulated the migration of Treg cells, and the chemotactic activity of the endometriotic peritoneal fluid was inhibited by neutralizing anti-CCL20 antibodies. These results imply that increased proportions of the peritoneal Treg cells in women with endometriosis may result from attraction and activation by local chemokines and cytokines, especially CCL20 and TGF-β. Since Treg cells contribute to the immunopathogenesis of endometriosis, their chemotaxis and activation may be considered as a target for therapeutic intervention.

Oral Vaccination Approaches for Anti-SHIV Immunity

We modified a Sabin Oral Poliovirus Vaccine (OPV) vector to permit secretion of the antigens of interest with the goal of improving anti-HIV Env humoral responses in a SHIV mucosal immunization composed of DNA and recombinant OPVs. We evaluated stimulation of systemic and mucosal cell-mediated and humoral immunity in Rhesus macaques by two regimens, both involving a prime with a SHIVBG505 DNA construct producing non-infectious particles formulated in lipid nanoparticles, administered in the oral cavity, and two different viral vector boostings, administered in the oral cavity and intestinally. Group 1 was boosted with rMVA-SHIVBG505, expressing SIV Gag/Pol and HIVBG505 Env. Group 2 was boosted with a SHIVBG505-OPV vaccine including a non-secreting SIVmac239CA-p6-OPV, expressing Gag CA, NC and p6 proteins, and a HIVBG505C1-V2-OPV, secreting the C1-V2 fragment of HIV EnvBG505, recognized by the broadly neutralizing antibody PG16. A time course analysis of anti-SHIV Gag and Env CD4+ and CD8+ T-cell responses in PBMC and in lymph node, rectal, and vaginal MNC was carried out. Both regimens stimulated significant cell-mediated responses in all compartments, with SHIVBG505-OPV immunization stimulating more significant levels of responses than rMVA- SHIVBG505. Boolean analysis of these responses revealed predominantly monofunctional responses with multifunctional responses also present in all tissues. Stimulation of antibody responses was disappointing in both groups with negative anti-SHIV IgG in plasma, and IgA in salivary, rectal and vaginal secretions being restricted to a few animals. After repeated rectal challenge with SHIVBG505, two Group 1 animals remained uninfected at challenge termination. No significant differences were observed in post-infection viral loads between groups. After the acute phase decline, CD4+ T cell percentages returned to normal levels in vaccinated as well as control animals. However, when compared to controls, vaccinate groups had more significant preservation of PBMC and rectal MNC Th17/Treg ratios, considered the strongest surrogate marker of progression to AIDS. We conclude that the vaccine platforms used in this study are insufficient to stimulate significant humoral immunity at the tested doses and schedule but sufficient to stimulate significant mucosal and systemic cell-mediated immunity, impacting the preservation of key Th17 CD4+ T cells in blood and rectal mucosa.

Expansion of GARP-Expressing CD4+CD25-FoxP3+ T Cells and SATB1 Association with Activation and Coagulation in Immune Compromised HIV-1-Infected Individuals in South Africa

Although antiretroviral treatment lowers the burden of human immunodeficiency virus (HIV)-related disease, it does not always result in immunological recovery. This manifests as persistent chronic inflammation, immune activation or exhaustion that can promote the onset of co-morbidities. As the exact function of regulatory T (Treg) cells in HIV remains unclear, this cross-sectional study investigated three expression markers (Forkhead box protein P3 [FOXP3], glycoprotein A repetitions predominant [GARP], special AT-rich sequence binding protein 1 [SATB1]) and compared their expansion between CD4⁺CD25^- and CD4⁺CD25⁺⁺ T cells. Age-matched study subjects were recruited (Western Cape, South Africa) and sub-divided: HIV-negative subjects (n = 12), HIV-positive naïve treated (n = 22), HIV-positive treated based on CD4 count cells/µL (CD4 > 500 and CD4 < 500) (n = 34) and HIV-treated based on viral load (VL) copies/mL (VL < 1000 and VL > 1000) (n = 34). Markers of immune activation (CD38) and coagulation (CD142) on T cells (CD8) were assessed by flow cytometry together with FOXP3, GARP and SATB1 expression on CD4⁺CD25^- and CD4⁺CD25⁺⁺ T cells. Plasma levels of interleukin-10 (IL-10; anti-inflammatory marker), IL-6 (inflammatory marker) and D-dimer (coagulation marker) were assessed. This study revealed three major findings in immuno-compromised patients with virological failure (CD4 < 500; VL > 1000): (1) the expansion of the unconventional Treg cell subset (CD4⁺CD25^-FOXP3⁺) is linked with disease progression markers; (2) increased GARP expression in the CD4⁺CD25^- and CD4⁺CD25⁺⁺ subsets; and (3) the identification of a strong link between CD4⁺CD25^-SATB1⁺ cells and markers of immune activation (CD8⁺CD38⁺) and coagulation (CD8⁺CD142⁺ and D-dimer).

Propolis antiviral and immunomodulatory activity: a review and perspectives for COVID-19 treatment

OBJECTIVES

Viral outbreaks are a frequent concern for humans. A great variety of drugs has been used to treat viral diseases, which are not always safe and effective and may induce adverse effects, indicating the need for new antiviral drugs extracted from natural sources. Propolis is a bee-made product exhibiting many biological properties. An overview of viruses, antiviral immunity, propolis safety and its immunomodulatory and antiviral action is reported, as well as perspectives for coronavirus disease 2019 (COVID-19) treatment. PubMed platform was used for data collection, searching for the keywords "propolis", "virus", "antiviral", "antimicrobial" and "coronavirus".

KEY FINDINGS

Propolis is safe and exerts antiviral and immunomodulatory activity; however, clinical trials should investigate its effects on individuals with viral diseases, in combination or not with antiviral drugs or vaccines.

SUMMARY

Regarding COVID-19, the effects of propolis should be investigated directly on the virus in vitro or on infected individuals alone or in combination with antiviral drugs, due to its immunomodulatory and anti-inflammatory action. Propolis administration simultaneously with vaccines should be analyzed, due to its adjuvant properties, to enhance the individuals' immune response. The search for therapeutic targets may be useful to find out how propolis can help to control COVID-19.

The role of Th17 cells in viral infections

The present review provides an overview of recent advances regarding the function of Th17 cells and their produced cytokines in the progression of viral diseases. Viral infections alone do not lead to virus-induced malignancies, as both genetic and host safety factors are also involved in the occurrence of malignancies. Acquired immune responses, through the differentiation of Th17 cells, form the novel components of the Th17 cell pathway when reacting with viral infections all the way from the beginning to its final stages. As a result, instead of inducing the right immune responses, these events lead to the suppression of the immune system. In fact, the responses from Th17 cells during persistent viral infections causes chronic inflammation through the production of IL-17 and other cytokines which provide a favorable environment for tumor growth and its development. Additionally, during the past decade, these cells have been understood to be involved in tumor progression and metastasis. However, further research is required to understand Th17 cells' immune mechanisms in the vast variety of viral diseases. This review aims to determine the roles and effects of the immune system, especially Th17 cells, in the progression of viral diseases; which can be highly beneficial for the diagnosis and treatment of these infections.

Measuring the Success of HIV-1 Cure Strategies

HIV-1 eradication strategies aim to achieve viral remission in the absence of antiretroviral therapy (ART). The development of an HIV-1 cure remains challenging due to the latent reservoir (LR): long-lived CD4 T cells that harbor transcriptionally silent HIV-1 provirus. The LR is stable despite years of suppressive ART and is the source of rebound viremia following therapy interruption. Cure strategies such as "shock and kill" aim to eliminate or reduce the LR by reversing latency, exposing the infected cells to clearance via the immune response or the viral cytopathic effect. Alternative strategies include therapeutic vaccination, which aims to prime the immune response to facilitate control of the virus in the absence of ART. Despite promising advances, these strategies have been unable to significantly reduce the LR or increase the time to viral rebound but have provided invaluable insight in the field of HIV-1 eradication. The development and assessment of an HIV-1 cure requires robust assays that can measure the LR with sufficient sensitivity to detect changes that may occur following treatment. The viral outgrowth assay (VOA) is considered the gold standard method for LR quantification due to its ability to distinguish intact and defective provirus. However, the VOA is time consuming and resource intensive, therefore several alternative assays have been developed to bridge the gap between practicality and accuracy. Whilst a cure for HIV-1 infection remains elusive, recent advances in our understanding of the LR and methods for its eradication have offered renewed hope regarding achieving ART free viral remission.

HIV-1 elite controllers present a high frequency of activated regulatory T and Th17 cells

HIV-1 infection is characterized by generalized deregulation of the immune system, resulting in increased chronic immune activation. However, some individuals called HIV controllers (HICs) present spontaneous control of viral replication and have a more preserved immune system. Among HICs, discordant results have been observed regarding immune activation and the frequency of different T cell subsets, including Treg and Th17 cells. We evaluated T cell immune activation, differentiation and regulatory profiles in two groups of HICs—elite controllers (ECs) and viremic controllers (VCs)—and compared them to those of cART-treated individuals (cART) and HIV-1-negative (HIV-neg) individuals. ECs demonstrated similar levels of activated CD4⁺ and CD8⁺ T cells in comparison to HIV-neg, while cART and VCs showed elevated T cell activation. CD4⁺ T cell subset analyses showed differences only for transitional memory T cell frequency between the EC and HIV-neg groups. However, VC individuals showed higher frequencies of terminally differentiated, naïve, and stem cell memory T cells and lower frequencies of transitional memory and central memory T cells compared to the HIV-neg group. Among CD8⁺ T cell subsets, ECs presented higher frequencies of stem cell memory T cells, while VCs presented higher frequencies of terminally differentiated T cells compared to the HIV-neg group. HICs showed lower frequencies of total Treg cells compared to the HIV-neg and cART groups. ECs also presented higher frequencies of activated and a lower frequency of resting Treg cells than the HIV-neg and cART groups. Furthermore, we observed a high frequency of Th17 cells in ECs and high Th17/Treg ratios in both HIC groups. Our data showed that ECs had low levels of activated T cells and a high frequency of activated Treg and Th17 cells, which could restrict chronic immune activation and be indicative of a preserved mucosal response in these individuals.

Targeting FOXP3 complex ensemble in drug discovery

Forkhead Box P3 (FOXP3) is a key transcriptional regulator of regulatory T cells (Tregs), especially for its function of immune suppression. The special immune suppression function of Tregs plays an important role in maintaining immune homeostasis, and is related to several diseases including cancer, and autoimmune diseases. At the same time, FOXP3 takes a place in a large transcriptional complex, whose stability and functions can be controlled by various post-translational modification. More and more researches have suggested that targeting FOXP3 or its partners might be a feasible solution to immunotherapy. In this review, we focus on the transcription factor FOXP3 in Tregs, Treg functions in diseases and the FOXP3 targets.

The Role of Natural Killer Cells and Regulatory T Cells While Aging with Human Immunodeficiency Virus

Combined antiretroviral therapy (cART) has increased the quality of life of people living with HIV (PLHIV). Consequently, the number of PLHIV >50 years is increasing worldwide. Patients on cART are known to remain in a proinflammatory state. The latter is linked to the development of non-AIDS-related chronic conditions. Although the number of aging PLHIV is increasing, the effect of HIV infection on the process of aging is not fully understood. Understanding the complexity of aging with HIV by investigating the effect of the latter on different components of the innate and adaptive immune systems is important to reduce the impact of these comorbid conditions and improve the quality of life of PLHIV. The role of killer immunoglobulin receptors (KIRs), expressed on the surface of natural killer (NK) cells, and their human leukocyte antigen (HLA) ligands in the clearance, susceptibility to or disease progression following HIV infection is well established. However, data on the effect of KIR-HLA interaction in aging HIV-infected population and the development of non-AIDS-related comorbid conditions are lacking. Moreover, conflicting data exist on the role of regulatory T cells (Tregs) during HIV infection. The purpose of this review is to advance the current knowledge on the role of NK cells and Tregs while aging with HIV infection.

Correlation of High Interleukin 17A and Interleukin 6 Levels with High Virus Load Among Subtype C HIV-infected, Antiretroviral Therapy-naive Zimbabwean Patients: A Cross-sectional Study

Introduction:

In response to the human immunodeficiency virus (HIV) infection, activated immune cells produce several cytokines that alter the immune response and HIV disease progression. We quantified Th1/Th2/Th17 cytokines in an antiretroviral therapy naïve (ART) cohort to investigate their correlation with traditional markers of HIV disease progression; CD4+ T-lymphocytes and virus load (VL).

Methods:

We enrolled 247 HIV-infected ART-naïve participants into the study. CD4+ T- and CD8+ T-lymphocytes were enumerated using flow cytometry. VL was quantified using the Cavidi ExaVirTM Load assay. IL-2, IL-4, IL-6, IL-10, IL-17A, TNF-α, and IFN-γ levels were quantified using the BD Cytometric Bead Array Human Th1/Th2/Th17 cytokine assay. The Kendall’s rank correlation coefficient was used to determine the correlation between log10 transformed data for cytokine levels and CD4+ T- and CD8+ T-lymphocytes, CD4/CD8 ratio, and VL.

Results:

The median CD4+ T- and CD8+ T-lymphocyte counts were 458 cells/µL (IQR:405-556) and 776 cells/µL (IQR:581-1064), respectively. The median CD4/CD8 ratio was 0.6 (IQR: 0.45-0.86). The median VL was log103.3.copies/mL (IQR:2.74-3.93). Low CD4+ T-lymphocyte counts (p=0.010) and CD4/CD8 ratio (p=0.044) were significantly correlated with high VL. There was no significant correlation of cytokine levels with CD4+ T-, CD8+ T-lymphocyte counts and CD4/CD8 ratio. However, high levels of IL-17A (p=0.012) and IL-6 (p=0.034) were significantly correlated with high VL.

Conclusion:

Our study contributes to the little knowledge available on the role of cytokine profiles in the immune response to subtype C HIV infection.

Immunological Changes in Monocyte Subsets and Their Association With Foxp3+ Regulatory T Cells in HIV-1-Infected Individuals With Syphilis: A Brief Research Report

The incidence of syphilis has increased dramatically in men who have sex with men (MSM), especially those with HIV-1 infection. Treponema pallidum and HIV-1 are bidirectionally synergistic, accelerating disease progression reciprocally in co-infected individuals. We have shown that monocytes have different effects on T helper cells at different stages of HIV-1 infection. However, the immunological changes in the three monocyte subsets and in regulatory T cells (Tregs), and the associations between these cell types during syphilis infection among HIV-1-infected MSM remain unclear. Herein, we used cell staining methods to explore changes in monocyte subsets and Tregs and any associations between these cells. We found that the frequency of classical monocytes was higher in the rapid plasma reagin (RPR⁺) group than in the healthy controls (HCs) and the chronic HIV-1 infection (CHI) plus RPR⁺ (CHI&RPR⁺) group. The frequencies of Foxp3⁺CD25⁺CD45RA⁺ and Foxp3⁺Helios⁺CD45RA⁺ Tregs were significantly higher in the RPR⁺, CHI, and CHI&RPR⁺ groups than in HCs, whereas the frequency of CD45RA⁺ Tregs was lower in the CHI&RPR⁺ group than in CHI group. The frequencies of Foxp3⁺CD25⁺CD45RO⁺ and Foxp3⁺Helios⁺CD45RO⁺ Tregs were lower in the RPR⁺, CHI, and CHI&RPR⁺ groups than in HCs. The frequency of intermediate monocytes was inversely correlated with the frequency of CD45RA⁺ Tregs and positively correlated with the frequency of CD45RO⁺ Tregs. These results demonstrate for the first time that intermediate monocytes control the differentiation of Treg subsets in Treponema pallidum/HIV-1 co-infections. These findings provide new insights into an immunological mechanism involving monocytes/Tregs in HIV-infected individuals with syphilis.

Impact of HIV-ART on the restoration of Th17 and Treg cells in blood and female genital mucosa

The aim of this study was to evaluate the effectiveness of antiretroviral treatment (ART) on the proportion and functions of Th17 and Treg cells in peripheral blood and female genital tract (FGT) respectively. To this aim, samples from 41 HIV-neg, 33 HIV+ ART-naïve and 32 HIV+ ART+ subjects were obtained. In peripheral blood, altered Th17 and Th17/Treg proportions were normalized in HIV+ ART+, but certain abnormal Treg and activated T-cell proportions were still observed. In FGT, abnormal patterns of secretion for Th17-related cytokines were observed in cervical mononuclear cells (CMCs) from HIV+ women, even in those from HIV+ ART+, compared to the HIV-neg group. Moreover, these altered patterns of secretion were associated with diminished levels of CXCL5 and CXCL1 chemokines and with an immunoregulatory skew in the CCL17/CCL20 ratio in ectocervix samples of these women. Finally, ART did not restore proportions of Th17-precursor cells with gut-homing potential in PBMCs, and positive correlations between these cells and the levels of IL-17F and IL-21 production by CMCs may suggest that a better homing of these cells to the intestine could also imply a better restoration of these cells in the female genital tract. These results indicate that antiretroviral treatment did not restore Th17-related immune functions completely at the female mucosal level.

Human Immunodeficiency Virus Infection: Spectrum of Rheumatic Manifestations

Emerging and reemerging viral infections have been a characteristic feature of the past several decades, with HIV infection being the most important example of an emergent viral infection. To date, the status of a considerable proportion of HIV/AIDS patients has changed from a near-fatal disorder secondary to opportunistic infections to a chronic disease in which a variety of co-morbid conditions have become prevalent and relevant. Arthralgia and myalgias are the most common symptoms. The rate of spondyloarthritis varies according to the geographic area, genetic and mode of transmission. Most RA and SLE patients might go into remission after the development of AIDS, but also there are patients that continue with active disease. Prevalence of DILS is highest among African Americans in less advanced stages. PAN is clinically less aggressive and peripheral neuropathy is the most common clinical manifestation. Anti-phospholipid syndrome (APS), systemic sclerosis and poly-dermatomyositis are uncommon. After the introduction of combination antiretroviral therapy (cART), a decline of spondyloarthritis disorders and of DILS and development of new syndromes such as IRIS, osteoporosis and avascular bone necrosis have occurred. The treatment of patients with rheumatic diseases and HIV infection remains a challenge.

Impact of schistosome infection on long-term HIV/AIDS outcomes

Background

Africa bears the burden of approximately 70% of global HIV infections and 90% of global schistosome infections. We sought to investigate the impact of schistosome infection at the time of HIV-1 seroconversion on the speed of HIV-1 disease progression, as measured by the outcome CD4+ T-cell (CD4) counts <350 cells/μL and/or death. We hypothesized that people who had been infected with Schistosoma spp. at the time they acquired HIV-1 infection would have impaired antiviral immune response, thus leading them to progress twice as fast to a CD4 count less than 350 cells/μL or death than would people who had been free of schistosomes at time of HIV-1 seroconversion.

Methods and principal findings

We conducted a longitudinal study in Tanzania from 2006 to 2017 using stored blood spot samples, demographic surveillance and sero-survey data from the community, and a review of clinical charts. A competing risk analysis was performed to look at the difference in time to reaching CD4 counts < 350 cells/μL and/or death in HIV-1-infected people who were infected versus not infected with Schistosoma spp. at time of HIV-1 seroconversion. We found an 82% reduction in risk of reaching the outcome in seroconverters who had been infected with Schistosoma (subHazard Ratio = 0.18[0.068,0.50], p = 0.001) after adjusting for age, occupation, clinic attendance and time-dependent covariates.

Conclusions

Our study demonstrates that people with schistosome infection at the time of HIV-seroconversion develop adverse HIV outcomes more slowly than those without. The findings are contrary to our original hypothesis. Our current longitudinal findings suggest complex interactions between HIV-1 and schistosome co-infections that may be modulated over time. We urge new immunological studies to investigate the long-term impact of schistosome infection on HIV-1 viral load and CD4 counts as well as related immunologic pathways.

Several studies had shown that people infected with schistosome parasites were at risk of getting HIV and that they may have higher HIV viral concentrations in their blood as well. The authors explored the impact of the parasite on HIV disease after infection, expecting that people co-infected with the parasite at time of HIV-infection would develop worse HIV outcomes than people who did not have the parasite. HIV seroconverters were identified among a large cohort tested regularly for HIV in northwest Tanzania and were followed-up in clinics to determine their CD4 + T-cells counts and mortality. The seroconverters’ stored blood samples were tested for infection with the parasite and outcomes were compared between seroconverters who were and were not infected with the parasites at the time that they became HIV-infected. The authors surprisingly found that people with the parasite experienced fewer negative outcomes of HIV than people who did not have the parasite. To the investigators’ knowledge, this is the first longitudinal study to find this result. Long-term immunological changes may explain this protective effect and more studies are recommended to explore this research question.

Effects of Th17 cells and IL-17 in the progression of cervical carcinogenesis with high-risk human papillomavirus infection

The existence of Th17 cells and IL‐17 was recently shown in several types of infectious diseases, but their distribution and functions in cervical lesions with high‐risk human papillomavirus (HPV) infection have not been fully elucidated. In this study, the frequency of Th17 cells in peripheral blood samples obtained from 28 cervical squamous cell carcinoma patients, 26 CIN1 patients, 30 CIN2 patients, 29 CIN3 patients, 25 high‐risk HPV‐infected women with normal cervical cytology, and 30 healthy controls was determined by flow cytometry. Besides, the levels of IL‐17 in peripheral blood samples as well as in supernatant of cervical tissue homogenate were assessed by enzyme‐linked immunosorbent assay (ELISA) simultaneously. We found that during the disease progression of cervical lesions, the proportion of Th17 cells in the total CD4⁺ cells showed a gradually increased tendency compared with the controls (P < 0.05). Moreover, levels of IL‐17 in serum and supernatant of cervical tissue homogenate showed the same tendency as the proportion of Th17 cells (P < 0.05). When compared in pairs, the levels of IL‐17 in supernatant differed significantly among the study groups and the control group (P < 0.05), but no significant difference was observed in serum (P > 0.05). In conclusions, the results indicate that Th17 cells and IL‐17 may play a role of immune enhancement in the infection of high‐risk HPV especially in the cervical microenvironment, which contribute to the disease progression of its associated cervical lesions.

High CXCL10/IP-10 levels are a hallmark in the clinical evolution of the HIV infection

The aim of this study was to investigate the modulation of plasma CXCL10, CCL20, CCL22, CCL2, CCL17 and CCL24 levels in HIV-positive patients grouped according to extreme phenotypes of progression to AIDS, and at different stages of HIV infection. HIV-positive individuals with extreme phenotypes of AIDS progression (n=58) at different clinical stages (chronic individuals, both pre-HAART and under-HAART) and HIV-negative controls (n=20) were evaluated. Additionally, HIV-positive individuals that initiated HAART with >350CD4⁺T-cells/mm³ were compared with those who initiated treatment with <350CD4⁺T-cells/mm³. Plasma levels of six chemokines were quantified by a Luminex assay. Higher CXCL10 levels were observed in individuals immediately before their CD4⁺T-cell levels were indicative for HAART (pre-HAART), independently of their progressor status, i.e. slow (SPs) or rapid progressors (RPs). SPs pre-HAART showed higher CXCL10 levels compared to elite controllers and RPs under HAART (p_c=0.009 and p_c=0.007, respectively). CXCL10 levels were higher in SPs HAART CD4<350 (initiated HAART with <350 CD4⁺T-cells) when compared with SPs HAART CD4>350 (initiated HAART with >350 CD4⁺T-cells) (1096 vs. 360.33pg/mL, p=0.0101). Normalisation of CXCL10 levels seems to depend on the CD4⁺T-cell nadir at HAART initiation. CCL20 levels were higher in chronic SPs, SPs pre-HAART, SPs HAART and RPs HAART compared with the HIV-negative controls, indicating persistent CCL20 expression. In conclusion, our results indicate that CXCL10 levels are a hallmark in the clinical evolution of HIV infection. However, our results must be verified in a study evaluating a larger number of AIDS progressors.

Engineering hematopoietic stem cells toward a functional cure of human immunodeficiency virus infection

The battle with human immunodeficiency virus (HIV) has been ongoing for more than 30 years, and although progress has been made, there are still significant challenges remaining. A few unique features render HIV to be one of the toughest viruses to conquer in the modern medicine era, such as the ability to target the host immune system, persist by integrating into the host genome and adapt to a hostile environment such as a single anti-HIV medication by continuously evolving. The finding of combination anti-retroviral therapy (cART) about 2 decades ago has transformed the treatment options for HIV-infected patients and significantly improved patient outcomes. However, finding an HIV cure has proven to be extremely challenging with the only known exception being the so-called "Berlin patient," whose immune system was replaced by stem cell transplants from a donor missing one of HIV's key co-receptors (CCR5). The broad application of this approach is limited by the requirement of an HLA-matched donor who is also homozygous for the rare CCR5 delta32 deletion. On the other hand, the Berlin patient provided the proof of concept of a potential cure for HIV using HIV-resistant hematopoietic stem cells (HSCs), revitalizing the hope to find an HIV cure that is broadly applicable. Here we will review strategies and recent attempts to engineer HIV-resistant HSCs as a path to an HIV cure.

Novel genetic associations and gene-gene interactions of chemokine receptor and chemokine genetic polymorphisms in HIV/AIDS

OBJECTIVE

To investigate the influence of candidate polymorphisms on chemokine receptor/ligand genes on HIV infection and AIDS progression (HIV/AIDS).

DESIGN

Fifteen polymorphisms of the CCR3, CCR4, CCR5, CCR6, CCR8, CXCR3, CXCR6, CCL20, CCL22 and CXCL10 genes were analysed in 206 HIV-positive patients classified as rapid progressors (n = 40), or nonrapid progressors (n = 166), and in 294 HIV-seronegative patients.

METHODS

The polymorphisms were genotyped using minisequencing. Genetic models were tested using binomial logistic regression; nonparametric multifactor dimensionality reduction (MDR) was used to detect gene-gene interactions.

RESULTS

The CCR3 rs3091250 [TT, adjusted odds ratio (AOR): 2.147, 95% confidence interval (CI) 1.076-4.287, P = 0.030], CCR8 rs2853699 (GC/CC, AOR: 1.577, 95% CI 1.049-2.371, P = 0.029), CXCL10 rs56061981 (CT/TT, AOR: 1.819, 95% CI 1.074-3.081, P = 0.026) and CCL22 rs4359426 (CA/AA, AOR: 1.887, 95% CI 1.021-3.487, P = 0.043) polymorphisms were associated with susceptibility to HIV infection. The CCL20 rs13034664 (CC, OR: 0.214, 95% CI 0.063-0.730, P = 0.014) and CCL22 rs4359426 (CA/AA, OR: 2.685, 95% CI 1.128-6.392, P = 0.026) variants were associated with rapid progression to AIDS. In MDR analyses revealed that the CXCL10 rs56061981 and CCL22 rs4359426 combination was the best model, with 57% accuracy (P = 0.008) for predicting susceptibility to HIV infection.

CONCLUSION

Our results provide new insights into the influence of candidate chemokine receptor/ligand polymorphisms and significant evidence for gene-gene interactions on HIV/AIDS susceptibility.

Yin and yang of interleukin-17 in host immunity to infection

The interleukin-17 (IL-17) family cytokines, such as IL-17A and IL-17F, play important protective roles in host immune response to a variety of infections such as bacterial, fungal, parasitic, and viral. The IL-17R signaling and downstream pathways mediate induction of proinflammatory molecules which participate in control of these pathogens. However, the production of IL-17 can also mediate pathology and inflammation associated with infections. In this review, we will discuss the yin-and-yang roles of IL-17 in host immunity to pathogens.

IFN-γ Attenuates Spontaneous Lymphocyte Proliferation by Fuelling Regulatory T Cells in HIV-1-Infected Patients

HIV infection is characterized by a high degree of immune activation. It has an impact on CD4 cell count and populations' distribution and function. T regulatory cells (Tregs) were found to play a controversial role in the course of infection because of their beneficial effect on the degree of immune activation and unfavorable influence on the antigen-specific responses. The goal of the present work was to study the relationship among interferon-γ (IFN-γ), spontaneous lymphocyte proliferation, and regulatory T cells in HIV patients receiving therapy. Three lymphocyte populations, isolated after a stepwise magnetic separation from 17 individuals, were investigated-peripheral blood lymphocytes, CD4⁺CD45RA^- (CD4⁺TM), and CD4⁺CD45RA^-CD25^- (TMCD25depl.) cells. The spontaneous, phytohemagglutinin (PHA) and HIV-1p24Ag-stimulated IFN-γ production and the spontaneous lymphocyte proliferation were evaluated. The potential of Tregs to establish a productive infection was determined by measurement of free HIV-1p24 antigen. Two types of constellations among subsets were found. In the first one (in 11 subjects), the spontaneous INF-γ inversely correlated with the spontaneous proliferation in all fractions (r = -0.9, p < 0.001). Conversely, in the second group (six subjects), no associations between the selected parameters were observed. The overall increase in p24-stimulated IFN-γ from TMCD25depl. cells was weak. Four samples: one in Tregs and three in TMCD25depl. cells were positive for the free p24 antigen. No association with the CD4⁺ T cell count, percentage of Tregs, and stage of infection was determined. In conclusion, our results demonstrate that IFN-γ could impact the proliferative capacity of non-Treg cells by fuelling Tregs. Furthermore, Tregs may control the spontaneous lymphocyte proliferation, but are less powerful in the suppression of Ag-specific IFN-γ production from non-Treg lymphocytes. The direct viral influence on Treg functions should be also considered.

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

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

Glucose Metabolism in T Cells and Monocytes: New Perspectives in HIV Pathogenesis

Activation of the immune system occurs in response to the recognition of foreign antigens and receipt of optimal stimulatory signals by immune cells, a process that requires energy. Energy is also needed to support cellular growth, differentiation, proliferation, and effector functions of immune cells. In HIV-infected individuals, persistent viral replication, together with inflammatory stimuli contributes to chronic immune activation and oxidative stress. These conditions remain even in subjects with sustained virologic suppression on antiretroviral therapy. Here we highlight recent studies demonstrating the importance of metabolic pathways, particularly those involving glucose metabolism, in differentiation and maintenance of the activation states of T cells and monocytes. We also discuss how changes in the metabolic status of these cells may contribute to ongoing immune activation and inflammation in HIV- infected persons and how this may contribute to disease progression, establishment and persistence of the HIV reservoir, and the development of co-morbidities. We provide evidence that other viruses such as Epstein-Barr and Flu virus also disrupt the metabolic machinery of their host cells. Finally, we discuss how redox signaling mediated by oxidative stress may regulate metabolic responses in T cells and monocytes during HIV infection.