Regulatory T Cells As Potential Targets for HIV Cure Research

Immunometabolism of Tregs: mechanisms, adaptability, and therapeutic implications in diseases

Immunometabolism is an emerging field that explores the intricate interplay between immune cells and metabolism. Regulatory T cells (Tregs), which maintain immune homeostasis in immunometabolism, play crucial regulatory roles. The activation, differentiation, and function of Tregs are influenced by various metabolic pathways, such as the Mammalian targets of rapamycin (mTOR) pathway and glycolysis. Correspondingly, activated Tregs can reciprocally impact these metabolic pathways. Tregs also possess robust adaptive capabilities, thus enabling them to adapt to various microenvironments, including the tumor microenvironment (TME). The complex mechanisms of Tregs in metabolic diseases are intriguing, particularly in conditions like MASLD, where Tregs are significantly upregulated and contribute to fibrosis, while in diabetes, systemic lupus erythematosus (SLE), and rheumatoid arthritis (RA), they show downregulation and reduced anti-inflammatory capacity. These phenomena suggest that the differentiation and function of Tregs are influenced by the metabolic environment, and imbalances in either can lead to the development of metabolic diseases. Thus, moderate differentiation and inhibitory capacity of Tregs are critical for maintaining immune system balance. Given the unique immunoregulatory abilities of Tregs, the development of targeted therapeutic drugs may position them as novel targets in immunotherapy. This could contribute to restoring immune system balance, resolving metabolic dysregulation, and fostering innovation and progress in immunotherapy.

Exploring potential associations between the human microbiota and reservoir of latent HIV

BACKGROUND

The rapid establishment and persistence of latent HIV-1 reservoirs is one of the main obstacles towards an HIV cure. While antiretroviral therapy supresses viral replication, it does not eradicate the latent reservoir of HIV-1-infected cells. Recent evidence suggests that the human microbiome, particularly the gut microbiome, may have the potential to modulate the HIV-1 reservoir. However, literature is limited and the exact mechanisms underlying the role of the microbiome in HIV immunity and potential regulation of the viral reservoir remain poorly understood.

RESULTS

Here, we review updated knowledge on the associations between the human microbiome and HIV reservoir across different anatomical sites, including the gut, the lungs and blood. We provide an overview of the predominant taxa associated with prominent microbiome changes in the context of HIV infection. Based on the current evidence, we summarize the main study findings, with specific focus on consistent bacterial and related byproduct associations. Specifically, we address the contribution of immune activation and inflammatory signatures on HIV-1 persistence. Furthermore, we discuss possible scenarios by which bacterial-associated inflammatory mediators, related metabolites and host immune signatures may modulate the HIV reservoir size. Finally, we speculate on potential implications of microbiome-based therapeutics for future HIV-1 cure strategies, highlighting challenges and limitations inherent in this research field.

CONCLUSIONS

Despite recent advances, this review underscores the need for further research to deepen the understanding of the complex interplay between the human microbiome and HIV reservoir. Further integrative multi-omics assessments and functional studies are crucial to test the outlined hypothesis and to identify potential therapeutic targets ultimately able to achieve an effective cure for HIV.

The nexus between Leishmania & HIV: Debilitating host immunity and Hastening Comorbid disease burden

The scintillating association between Leishmania and HIV has contributed exceptionally towards expansion of Visceral Leishmaniasis (VL) with Acquired Immunodeficiency Syndrome (AIDS). The co-infection poses a grievous threat to elimination of VL and containment of Human Immunodeficiency Virus (HIV). When coinfected, Leishmania and HIV complement each other's proliferation and survival by inducing immunesenescence, T cell fatigue and exhaustion. Antigen presentation is lost, co-stimulatory molecules are diminished whereas co-inhibitory molecules such as CTLA-4, TIGIT, LAG-3 etc. are upregulated to ensure a Th2-baised immune environment. As a consequence, Leishmania-HIV coinfection causes poor outcomes, inflates the spread of Leishmania parasites, enhances the severity of side-effects to drugs, as well as escalate the probability of treatment failure and mortality. What makes control extremely strenuous is that there are frequent episodes of VL relapse with no prognostic markers, no standard immunophenotype(s) and appearance of atypical clinical symptoms. Thus, a standard therapeutic regimen has been difficult to develop and treatment is majorly dependent upon a combination of liposomal Amphotericin B and Miltefosine, a therapy that is expensive and capable of causing drastic side-effects in recipients. As World Health Organization is committed to eliminate both VL and HIV in due course of future, the existing therapeutic interventions require advancements to grapple and overcome this hazardous co-infection. In this context, an overview of HIV-VL co-infection, immunopathology of HIV and Leishmania co-inhabitance, available therapeutic options and their limitations in the treatment of co-infection are discussed in-depth.

Spatial technologies to evaluate the HIV-1 reservoir and its microenvironment in the lymph node

The presence of the HIV-1 reservoir, a group of immune cells that contain intact, integrated, and replication-competent proviruses, is a major challenge to cure HIV-1. HIV-1 reservoir cells are largely unaffected by the cytopathic effects of viruses, antiviral immune responses, or antiretroviral therapy (ART). The HIV-1 reservoir is seeded early during HIV-1 infection and augmented during active viral replication. CD4+ T cells are the primary target for HIV-1 infection, and recent studies suggest that memory T follicular helper cells within the lymph node, more precisely in the B cell follicle, harbor integrated provirus, which contribute to viral rebound upon ART discontinuation. The B cell follicle, more specifically the germinal center, possesses a unique environment because of its distinct property of being partly immune privileged, potentially allowing HIV-1-infected cells within the lymph nodes to be protected from CD8+ T cells. This modified immune response in the germinal center of the follicle is potentially explained by the exclusion of CD8+ T cells and the presence of T regulatory cells at the junction of the follicle and extrafollicular region. The proviral makeup of HIV-1-infected cells is similar in lymph nodes and blood, suggesting trafficking between these compartments. Little is known about the cell-to-cell interactions, microenvironment of HIV-1-infected cells in the follicle, and trafficking between the lymph node follicle and other body compartments. Applying a spatiotemporal approach that integrates genomics, transcriptomics, and proteomics to investigate the HIV-1 reservoir and its neighboring cells in the lymph node has promising potential for informing HIV-1 cure efforts.

Advanced Therapies for Human Immunodeficiency Virus

Human Immunodeficiency Virus (HIV) remains a significant global health challenge with approximately 38 million people currently having the virus worldwide. Despite advances in treatment development, the virus persists in the human population and still leads to new infections. The virus has a powerful ability to mutate and hide from the human immune system in reservoirs of the body. Current standard treatment with antiretroviral therapy effectively controls viral replication but requires lifelong adherence and does not eradicate the virus. This review explores the potential of Advanced Therapy Medicinal Products as novel therapeutic approaches to HIV, including cell therapy, immunisation strategies and gene therapy. Cell therapy, particularly chimeric antigen receptor T cell therapy, shows promise in preclinical studies for targeting and eliminating HIV-infected cells. Immunisation therapies, such as broadly neutralising antibodies are being investigated to control viral replication and reduce reservoirs. Despite setbacks in recent trials, vaccines remain a promising avenue for HIV therapy development. Gene therapy using technologies like CRISPR/Cas9 aims to modify cells to resist HIV infection or eliminate infected cells. Challenges such as off-target effects, delivery efficiency and ethical considerations persist in gene therapy for HIV. Future directions require further research to assess the safety and efficacy of emerging therapies in clinical trials. Combined approaches may be necessary to achieve complete elimination of the HIV reservoir. Overall, advanced therapies offer new hope for advancing HIV treatment and moving closer to a cure.

The Application Potential of the Regulation of Tregs Function by Irisin in the Prevention and Treatment of Immune-Related Diseases

Irisin is a muscle factor induced by exercise, generated through the proteolytic cleavage of the membrane protein fibronectin type III domain-containing protein 5 (FNDC-5). Numerous studies have shown that irisin plays a significant role in regulating glucose and lipid metabolism, inhibiting oxidative stress, reducing systemic inflammatory responses, and providing neuroprotection. Additionally, irisin can exert immunomodulatory functions by regulating regulatory T cells (Tregs). Tregs are a highly differentiated subset of mature T cells that play a key role in maintaining self-immune homeostasis and are closely related to infections, inflammation, immune-related diseases, and tumors. Irisin exerts persistent positive effects on Treg cell functions through various mechanisms, including regulating Treg cell differentiation and proliferation, improving their function, modulating the balance of immune cells, increasing the production of anti-inflammatory cytokines, and enhancing metabolic functions, thereby helping to maintain immune homeostasis and prevent immune-related diseases. As an important myokine, irisin interacts with receptors on the cell membrane, activating multiple intracellular signaling pathways to regulate cell metabolism, proliferation, and function. Although the specific receptor for irisin has not been fully identified, integrins are considered potential receptors. Irisin activates various signaling pathways, including AMPK, MAPK, and PI3K/Akt, through integrin receptors, thereby exerting multiple biological effects. These research findings provide important clues for understanding the mechanisms of irisin's action and theoretical basis for its potential applications in metabolic diseases and immunomodulation. This article reviews the relationship between irisin and Tregs, as well as the research progress of irisin in immune-related diseases such as multiple sclerosis, myasthenia gravis, acquired immune deficiency syndrome, type 1 diabetes, sepsis, and rheumatoid arthritis. Studies have revealed that irisin plays an important role in immune regulation by improving the function of Tregs, suggesting its potential application value in the treatment of immune-related diseases.

The Complex Dysregulations of CD4 T Cell Subtypes in HIV Infection

Human immunodeficiency virus (HIV) infection remains an important global public health problem. About 40 million people are infected with HIV, and this infection caused about 630,000 deaths in 2022. The hallmark of HIV infection is the depletion of CD4+ T helper lymphocytes (Th cells). There are at least seven different Th subtypes, and not all are the main targets of HIV. Moreover, the effect of the virus in a specific subtype can be completely different from that of the others. Although the most compromised Th subtype in HIV infection is Th17, HIV can induce important dysregulations in other subtypes, such as follicular Th (Tfh) cells and regulatory Th cells (Treg cells or Tregs). Several studies have shown that HIV can induce an increase in the immunosuppressive activity of Tregs without causing a significant reduction in their numbers, at least in the early phase of infection. The increased activity of this Th subtype seems to play an important role in determining the immunodeficiency status of HIV-infected patients, and Tregs may represent a new target for innovative anti-HIV therapies, including the so-called "Kick and Kill" therapeutic method whose goal is the complete elimination of the virus and the healing of HIV infection. In this review, we report the most important findings on the effects of HIV on different CD4+ T cell subtypes, the molecular mechanisms by which the virus impairs the functions of these cells, and the implications for new anti-HIV therapeutic strategies.

Immunogenetic Profile Associated with Patients Living with HIV-1 and Epstein-Barr Virus (EBV) in the Brazilian Amazon Region

Viral coinfection among HIV-positive patients, coupled with the development of AIDS, remains a major public health problem. The synergism between the presence of HIV and other viruses has consequences in relation to changes in the severity of the infection, as well as changes in the natural course of both infections. Several polymorphisms present in genes that encode cytokines have a relevant influence on their transcription and consequently on the production of such immunological molecules. The present study evaluated the influence of SNPs located in the promoter regions of genes encoding the cytokines INF-ɣ, TNF, IL-6, IL-4, and IL-2, as well as their respective plasma concentrations, in patients infected with HIV and/or EBV in the state of Pará. Additionally, this study described the epidemiological profile and compared CD4+ and CD8+ T lymphocyte counts among the groups studied. The associative analysis between the SNPs and plasma cytokine concentrations in different groups showed statistical relevance for three polymorphisms: rs2069762 (IL2), where the GG genotype demonstrated higher IL-2 levels in HIV mono-infected individuals; rs2243250 (IL4), where the CT genotype showed higher IL-4 levels in the control group; and rs2069705 (IFNG), where the TT genotype showed higher IFN-γ levels in the coinfected group. Regarding SNP associations with CD4+/CD8+ counts, significant findings were observed in HIV mono-infected individuals: the rs2069705 (IFNG) polymorphism was linked to higher CD4+ counts with the CT genotype, and rs1799964 (TNF) was associated with higher CD8+ counts with the CC genotype. Therefore, this study provides evidence that the rs2069705 (IFNG) SNP is associated with elevated IFN-γ levels, which may have pathogenic consequences, as depletion of this cytokine is concerning for people living with HIV due to its antiviral properties.

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

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

Pattern and Prevalence of Intestinal Helminthiasis among Human Immunodeficiency Virus-Infected Children at the University of Nigeria Teaching Hospital, Ituku-Ozalla, Enugu State

BACKGROUND

Children infected with the human immunodeficiency virus (HIV) may be more prone to helminthic infestation because they have depleted immunity, which increases their susceptibility to infection and infestations, even with minimally pathogenic organisms such as helminths.

AIM

The prevalence and pattern of intestinal helminthiasis among children living with HIV attending the University of Nigeria Teaching Hospital (UNTH), Ituku-Ozalla, Enugu.

PATIENTS AND METHODS

A cross-sectional study in which 70 HIV-infected children were consecutively recruited from the Pediatric HIV clinic and matched for age and sex with 70 children recruited from the children outpatient clinic (CHOP) of UNTH Ituku-Ozalla. Stool samples of study participants were collected and analyzed using the Kato-Katz method and subsequently examined under the microscope for helminths' eggs and larvae. The worm intensity was determined using the theoretical analytic sensitivity (TAS) of 24 eggs per gram (EPG) to obtain the number of eggs per gram of feces. The CD4+ count, which describes the severity of immunosuppression in HIV-positive children was determined using the PARTEC Cyflow counter for the CD4+ lymphocyte count, whereas HIV screening was performed using the rapid diagnostic tests for HIV (Determine, Statpack and Unigold). Data were analyzed using IBM SPSS.

RESULTS

The prevalence of intestinal helminthiasis among HIV-infected and non-infected children was 27.1% and 12.9%, respectively (P = 0.038). HIV-positive children were more likely to have intestinal helminthiasis than HIV-negative children (odds ratio [OR] =2.525, 95% confidence interval [CI]: 1.052-6.063). Ascaris lumbricoides was the predominant helminthic species in both HIV-infected and non-infected groups; however, there was no statistical significance between intestinal helminthic species and HIV status (P = 0.655) but the severity of intestinal helminthiasis was significantly associated with decreasing CD4+ count (P = 0.028). The risk factors for intestinal helminthic infestation examined were similar in both HIV-positive and HIV-negative children (P > 0.05).

CONCLUSION

There was a significantly higher prevalence of helminthic infestation among HIV-infected children compared to their HIV-negative counterparts. The severity of intestinal helminthiasis was significantly associated with decreasing CD4+ count.

Regulation of Immune Homeostasis, Inflammation, and HIV Persistence by the Microbiome, Short-Chain Fatty Acids, and Bile Acids

Despite antiretroviral therapy (ART), people living with human immunodeficiency virus (HIV) (PLWH) continue to experience chronic inflammation and immune dysfunction, which drives the persistence of latent HIV and prevalence of clinical comorbidities. Elucidating the mechanisms that lead to suboptimal immunity is necessary for developing therapeutics that improve the quality of life of PLWH. Although previous studies have found associations between gut dysbiosis and immune dysfunction, the cellular/molecular cascades implicated in the manifestation of aberrant immune responses downstream of microbial perturbations in PLWH are incompletely understood. Recent literature has highlighted that two abundant metabolite families, short-chain fatty acids (SCFAs) and bile acids (BAs), play a crucial role in shaping immunity. These metabolites can be produced and/or modified by bacterial species that make up the gut microbiota and may serve as the causal link between changes to the gut microbiome, chronic inflammation, and immune dysfunction in PLWH. In this review, we discuss our current understanding of the role of the microbiome on HIV acquisition and latent HIV persistence despite ART. Further, we describe cellular/molecular cascades downstream of SCFAs and BAs that drive innate or adaptive immune responses responsible for promoting latent HIV persistence in PLWH. This knowledge can be used to advance HIV cure efforts.

Mathematical modeling indicates that regulatory inhibition of CD8+ T cell cytotoxicity can limit efficacy of IL-15 immunotherapy in cases of high pre-treatment SIV viral load

Immunotherapeutic cytokines can activate immune cells against cancers and chronic infections. N-803 is an IL-15 superagonist that expands CD8+ T cells and increases their cytotoxicity. N-803 also temporarily reduced viral load in a limited subset of non-human primates infected with simian immunodeficiency virus (SIV), a model of HIV. However, viral suppression has not been observed in all SIV cohorts and may depend on pre-treatment viral load and the corresponding effects on CD8+ T cells. Starting from an existing mechanistic mathematical model of N-803 immunotherapy of SIV, we develop a model that includes activation of SIV-specific and non-SIV-specific CD8+ T cells by antigen, inflammation, and N-803. Also included is a regulatory counter-response that inhibits CD8+ T cell proliferation and function, representing the effects of immune checkpoint molecules and immunosuppressive cells. We simultaneously calibrate the model to two separate SIV cohorts. The first cohort had low viral loads prior to treatment (≈3-4 log viral RNA copy equivalents (CEQ)/mL), and N-803 treatment transiently suppressed viral load. The second had higher pre-treatment viral loads (≈5-7 log CEQ/mL) and saw no consistent virus suppression with N-803. The mathematical model can replicate the viral and CD8+ T cell dynamics of both cohorts based on different pre-treatment viral loads and different levels of regulatory inhibition of CD8+ T cells due to those viral loads (i.e. initial conditions of model). Our predictions are validated by additional data from these and other SIV cohorts. While both cohorts had high numbers of activated SIV-specific CD8+ T cells in simulations, viral suppression was precluded in the high viral load cohort due to elevated inhibition of cytotoxicity. Thus, we mathematically demonstrate how the pre-treatment viral load can influence immunotherapeutic efficacy, highlighting the in vivo conditions and combination therapies that could maximize efficacy and improve treatment outcomes.

T cell activation is insufficient to drive SIV disease progression

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

Impact of in vitro HIV infection on human thymic regulatory T cell differentiation

Background

The differentiation and function of immunosuppressive regulatory T cells (Tregs) is dictated by the master transcription factor FoxP3. During HIV infection, there is an increase in Treg frequencies in the peripheral blood and lymphoid tissues. This accentuates immune dysfunction and disease progression. Expression of FoxP3 by thymic Tregs (tTregs) is partially controlled by TGF-β. This cytokine also contributes to Treg development in the peripheral blood and lymphoid tissues. Although TGF-β mediates lymphoid tissue fibrosis and peripheral Treg differentiation in HIV-infected individuals, its role in the induction and maintenance of Tregs within the thymus during HIV infection remains unclear.

Methods

Thymocytes were isolated from fresh human thymic tissues obtained from pediatric patients undergoing cardiac surgery. Infection by both R5- and X4-tropic HIV-1 strains and TGF-β treatment of human thymocytes was performed in an in vitro co-culture model with OP9-DL1 cells expressing Notch ligand delta-like 1 without T cell receptor (TCR) activation.

Results

Despite high expression of CCR5 and CXCR4 by tTregs, FoxP3 +  CD3highCD8- thymocytes were much less prone to in vitro infection with R5- and X4-tropic HIV strains compared to FoxP3-CD3highCD8- thymocytes. As expected, CD3highCD4+ thymocytes, when treated with TGF-β1, upregulated CD127 and this treatment resulted in increased FoxP3 expression and Treg differentiation, but did not affect the rate of HIV infection. FoxP3 expression and Treg frequencies remained unchanged following in vitro HIV infection alone or in combination with TGF-β1.

Conclusion

FoxP3 expression and tTreg differentiation is not affected by in vitro HIV infection alone or the combination of in vitro HIV infection and TGF-β treatment.

Changes in the balance of Th17/Treg cells and oxidative stress markers in patients with HIV‑associated pulmonary tuberculosis who develop IRIS

Tuberculosis (TB) is the most common opportunistic infection in patients with acquired immunodeficiency syndrome (AIDS) caused by human immunodeficiency virus (HIV) infection and is one of the primary causes of death from AIDS. The increased accessibility to highly active antiretroviral therapy (HAART) has significantly improved the clinical outcome of patients with HIV infection. However, following ART, rapid restoration of the immune system leads to immune reconstitution inflammatory syndrome (IRIS). Oxidative stress and innate immunity play a role in TB-associated IRIS (TB-IRIS). The present study investigated the changes that occur in oxidative stress markers and T helper (Th)17/regulatory T (Treg) cell balance and their significance in IRIS patients with HIV-associated pulmonary TB. A total of 316 patients with HIV-associated pulmonary TB were treated with HAART and followed up regularly for 12 weeks. Those who developed IRIS were included in the IRIS group (n=60), while the remaining patients were included in the non-IRIS group (n=256). The changes in plasma oxidative stress markers superoxide dismutase (SOD) and malondialdehyde (MDA) were detected with the ELISA, and the ratio of Th17 to Treg cells in whole blood were analyzed before and after treatment through the flow cytometric assay. Following treatment, MDA and Th17 cells levels were significantly increased while SOD and Treg cells levels were decreased in the IRIS group (P<0.05) compared with before treatment. In the non-IRIS group, a non-significant decrease was observed in SOD levels (P>0.05), while the MDA levels significantly decreased compared with before treatment (P<0.05) and the Th17 and Treg cells levels were both significantly increased (P<0.05). After treatment, compared with the non-IRIS group, the IRIS group showed a significant increase in MDA and Th17 cells and decrease in SOD and Treg cells levels (P<0.05). In addition, Th17 cells levels were positively correlated with MDA but negatively correlated with SOD levels. Treg levels were negatively correlated with MDA and positively correlated with SOD levels (P<0.05). The area under the curve values of serum MDA and SOD, Th17 and Treg levels predicting the occurrence of IRIS were 0.738, 0.883, 0.722 and 0.719, respectively (P<0.05). These results indicated that the above parameters have certain diagnostic value for the occurrence of IRIS. The occurrence of IRIS in patients with HIV-associated pulmonary TB may be associated with oxidative stress and Th17/Treg cell imbalance.

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.

Identification of prognostic and predictive biomarkers in high-dimensional data with PPLasso

In clinical trials, identification of prognostic and predictive biomarkers has became essential to precision medicine. Prognostic biomarkers can be useful for the prevention of the occurrence of the disease, and predictive biomarkers can be used to identify patients with potential benefit from the treatment. Previous researches were mainly focused on clinical characteristics, and the use of genomic data in such an area is hardly studied. A new method is required to simultaneously select prognostic and predictive biomarkers in high dimensional genomic data where biomarkers are highly correlated. We propose a novel approach called PPLasso, that integrates prognostic and predictive effects into one statistical model. PPLasso also takes into account the correlations between biomarkers that can alter the biomarker selection accuracy. Our method consists in transforming the design matrix to remove the correlations between the biomarkers before applying the generalized Lasso. In a comprehensive numerical evaluation, we show that PPLasso outperforms the traditional Lasso and other extensions on both prognostic and predictive biomarker identification in various scenarios. Finally, our method is applied to publicly available transcriptomic and proteomic data.

CPHEN-014: Comprehensive phenotyping of mouse regulatory T cells relevant to viral infections

Regulatory T (Treg) cells are a specialized subpopulation of CD4⁺ T cells that enforce peripheral immune tolerance. Treg cells act to suppress exuberant immune responses, limit inflammation, and promote tissue repair, thereby maintaining homeostasis and tolerance to self-antigens and those of the commensal microbial flora. Treg cells are characterized by the expression of the master regulator Foxp3, which plays a major role in Treg cells development and function. Under inflammatory conditions, Foxp3⁺ Treg cells may acquire effector T cell programs that modify their phenotype and function, reflecting their plasticity. During microbial infections, Treg cells act to limit the immunopathology triggered by the host immune response to pathogens albeit at the potential risk of pathogen persistence. In this review, we will discuss the influence of Treg cells on the outcome of viral infection and will give an overview of the Treg phenotype at steady-state and in inflammatory conditions.

Follicular regulatory T cells eliminate HIV-1-infected follicular helper T cells in an IL-2 concentration dependent manner

Follicular helper CD4+ T cells (TFH) are highly permissive to HIV and major foci of virus expression in both untreated and treated infection. Follicular regulatory CD4+ T cells (TFR) limit TFH numbers and function in vitro and in vivo. We evaluated the hypothesis that TFR suppress HIV replication in TFH using a well-established model of ex vivo HIV infection that employs tonsil cells from HIV uninfected individuals spinoculated with CXCR4- and CCR5-tropic HIV-GFP reporter viruses. Both CXCR4 and CCR5-tropic HIV replication were reduced in TFH cultured with TFR as compared to controls. Blocking antibodies to CD39, CTLA-4, IL-10, and TGF-beta failed to reverse suppression of HIV replication by TFR, and there were no sex differences in TFR suppressive activity. TFR reduced viability of TFH and even more so reduced HIV infected TFH as assessed by total and integrated HIV DNA. Exogenous IL-2 enhanced TFH viability and particularly numbers of GFP+ TFH in a concentration dependent manner. TFR reduced productively infected TFH at low and moderate IL-2 concentrations, and this was associated with decreases in extracellular IL-2. Both IL-2 expressing cells and larger numbers of FoxP3+CD4+ cells were detected in follicles and germinal centers of lymph nodes of people living with HIV. TFR may deplete TFH in vivo through restriction of IL-2 and thereby contribute to decay of HIV expressing cells in B cell follicles during HIV infection.

Japanese Kampo Medicine Juzentaihoto Improves Antiviral Cellular Immunity in Tumour-Bearing Hosts

Global and antigen-independent immunosuppression by growing tumours can cause life-threating damage when concurrent with an infection in tumour-bearing hosts. In the present study, we investigated whether the oral administration of the Japanese traditional herbal (Kampo) medicine, juzentaihoto (JTT), plays a role in the improvement of antiviral cellular immunity in tumour-bearing hosts. Female BALB/c mice subcutaneously injected with murine colorectal cancer CT26 cells fed a control or JTT diet were inoculated with recombinant vaccinia virus expressing human immunodeficiency virus-1 glycoprotein 160 (vSC25). At 7 days postinfection, anti-vSC25 cellular immunity was evaluated by measuring the abundance of splenic virus-specific CD8⁺ T cells. JTT had no impact on CT26 tumour growth in vivo. Surprisingly, JTT augmented anti-vSC25 cellular immunity in CT26-bearing mice. Depletion of either CD25⁺ regulatory T (Treg) cells or myeloid-derived suppressor cells (MDSCs) also enhanced anti-vSC25 cellular immunity in tumour-bearing mice but had no therapeutic benefit against tumour growth. However, JTT had no impact on the abundance of these immunosuppressive cells. Overall, our data indicates that JTT contributes to the improvement of anti-vSC25 cellular immunity in tumour-bearing hosts possibly via a mechanism independent of CD25⁺ Treg cells and MDSCs, suggesting that this Kampo medicine can act as a promising antiviral adjuvant in an immunosuppressive state caused by tumours.

Challenges and Opportunities of Therapies Targeting Early Life Immunity for Pediatric HIV Cure

Early initiation of antiretroviral therapy (ART) significantly improves clinical outcomes and reduces mortality of infants/children living with HIV. However, the ability of infected cells to establish latent viral reservoirs shortly after infection and to persist during long-term ART remains a major barrier to cure. In addition, while early ART treatment of infants living with HIV can limit the size of the virus reservoir, it can also blunt HIV-specific immune responses and does not mediate clearance of latently infected viral reservoirs. Thus, adjunctive immune-based therapies that are geared towards limiting the establishment of the virus reservoir and/or mediating the clearance of persistent reservoirs are of interest for their potential to achieve viral remission in the setting of pediatric HIV. Because of the differences between the early life and adult immune systems, these interventions may need to be tailored to the pediatric settings. Understanding the attributes and specificities of the early life immune milieu that are likely to impact the virus reservoir is important to guide the development of pediatric-specific immune-based interventions towards viral remission and cure. In this review, we compare the immune profiles of pediatric and adult HIV elite controllers, discuss the characteristics of cellular and anatomic HIV reservoirs in pediatric populations, and highlight the potential values of current cure strategies using immune-based therapies for long-term viral remission in the absence of ART in children living with HIV.

The role of CD101-expressing CD4 T cells in HIV/SIV pathogenesis and persistence

Despite the advent of effective antiretroviral therapy (ART), human immunodeficiency virus (HIV) continues to pose major challenges, with extensive pathogenesis during acute and chronic infection prior to ART initiation and continued persistence in a reservoir of infected CD4 T cells during long-term ART. CD101 has recently been characterized to play an important role in CD4 Treg potency. Using the simian immunodeficiency virus (SIV) model of HIV infection in rhesus macaques, we characterized the role and kinetics of CD101+ CD4 T cells in longitudinal SIV infection. Phenotypic analyses and single-cell RNAseq profiling revealed that CD101 marked CD4 Tregs with high immunosuppressive potential, distinct from CD101- Tregs, and these cells also were ideal target cells for HIV/SIV infection, with higher expression of CCR5 and α4β7 in the gut mucosa. Notably, during acute SIV infection, CD101+ CD4 T cells were preferentially depleted across all CD4 subsets when compared with their CD101- counterpart, with a pronounced reduction within the Treg compartment, as well as significant depletion in mucosal tissue. Depletion of CD101+ CD4 was associated with increased viral burden in plasma and gut and elevated levels of inflammatory cytokines. While restored during long-term ART, the reconstituted CD101+ CD4 T cells display a phenotypic profile with high expression of inhibitory receptors (including PD-1 and CTLA-4), immunsuppressive cytokine production, and high levels of Ki-67, consistent with potential for homeostatic proliferation. Both the depletion of CD101+ cells and phenotypic profile of these cells found in the SIV model were confirmed in people with HIV on ART. Overall, these data suggest an important role for CD101-expressing CD4 T cells at all stages of HIV/SIV infection and a potential rationale for targeting CD101 to limit HIV pathogenesis and persistence, particularly at mucosal sites.

Changes to the Simian Immunodeficiency Virus (SIV) Reservoir and Enhanced SIV-Specific Responses in a Rhesus Macaque Model of Functional Cure after Serial Rounds of Romidepsin Administrations

HIV persistence requires lifelong antiretroviral therapy (ART), calling for a cure. The histone deacetylase inhibitor, romidepsin, is used in the "shock and kill" approach with the goal of reactivating virus and subsequently clearing infected cells through cell-mediated immune responses. We tested serial and double infusions of romidepsin in a rhesus macaque (RM) model of SIV functional cure, which controls virus without ART. Off ART, romidepsin reactivated SIV in all RMs. Subsequent infusions resulted in diminished reactivation, and two RMs did not reactivate the virus after the second or third infusions. Therefore, those two RMs received CD8-depleting antibody to assess the replication competence of the residual reservoir. The remaining RMs received double infusions, i.e., two doses separated by 48-h. Double infusions were well tolerated, induced immune activation, and effectively reactivated SIV. Although reactivation was gradually diminished, cell-associated viral DNA was minimally changed, and viral outgrowth occurred in 4/5 RMs. In the RM which did not reactivate after CD8 depletion, viral outgrowth was not detected in peripheral blood mononuclear cells (PBMC)-derived CD4+ cells. The frequency of SIV-specific CD8+ T cells increased after romidepsin administration, and the increased SIV-specific immune responses were associated, although not statistically, with the diminished reactivation. Thus, our data showing sequential decreases in viral reactivation with repeated romidepsin administrations with all RMs and absence of viral reactivation after CD8+ T-cell depletion in one animal suggest that, in the context of healthy immune responses, romidepsin affected the inducible viral reservoir and gradually increased immune-mediated viral control. Given the disparities between the results of romidepsin administration to ART-suppressed SIVmac239-infected RMs and HIV-infected normal progressors compared to our immune-healthy model, our data suggest that improving immune function for greater SIV-specific responses should be the starting point of HIV cure strategies. IMPORTANCE HIV cure is sought after due to the prevalence of comorbidities that occur in persons with HIV. One of the most investigated HIV cure strategies is the "shock and kill" approach. Our study investigated the use of romidepsin, a histone deacetylase (HDAC) inhibitor, in our rhesus macaque model of functional cure, which allows for better resolution of viral reactivation due to the lack of antiretroviral therapy. We found that repeated rounds of romidepsin resulted in gradually diminished viral reactivation. One animal inevitably lacked replication-competent virus in the blood. With the accompanying enhancement of the SIV-specific immune response, our data suggest that there is a reduction of the viral reservoir in one animal by the cell-mediated immune response. With the differences observed between our model and persons living with HIV (PWH) treated with romidepsin, specifically in the context of a healthy immune system in our model, our data thereby indicate the importance of restoring the immune system for cure strategies.

Altered mucosal immunity in HIV-positive colon adenoma: decreased CD4+ T cell infiltration is correlated with nadir but not current CD4+ T cell blood counts

BACKGROUND

People living with HIV (PLWH) face greater risks of developing non-AIDS-defining cancers (NADCs) than the general population; however, the underlying mechanisms remain elusive. The tumor microenvironment plays a significant role in the carcinogenesis of colorectal cancer (CRC), an NADC. We studied this carcinogenesis in PLWH by determining inflammatory phenotypes and assessing PD-1/PD-L1 expression in premalignant CRC stages of colon adenomas in HIV-positive and HIV-negative patients.

METHODS

We obtained polyp specimens from 22 HIV-positive and 61 HIV-negative participants treated with colonoscopy and polyp excision. We analyzed adenomas from 33 HIV-positive and 99 HIV-negative patients by immunohistochemistry using anti-CD4, anti-CD8, anti-FoxP3, and anti-CD163 antibodies. Additionally, we analyzed the expression levels of immune checkpoint proteins. We also evaluated the correlation between cell infiltration and blood cell counts.

RESULTS

HIV-positive participants had fewer infiltrating CD4⁺ T cells than HIV-negative participants (p = 0.0016). However, no statistical differences were observed in infiltrating CD8⁺ and FoxP3⁺ T cells and CD163⁺ macrophages. Moreover, epithelial cells did not express PD-1 or PD-L1. Notably, CD4⁺ T cell infiltration correlated with nadir blood CD4⁺ T cell counts (p <  0.05) but not with current blood CD4⁺ T cell counts.

CONCLUSION

Immune surveillance dysfunction owing to decreased CD4⁺ T cell infiltration in colon adenomas might be involved in colon carcinogenesis in HIV-positive individuals. Collectively, since the nadir blood CD4⁺ T cell count is strongly correlated with CD4⁺ T cell infiltration, it could facilitate efficient follow-up and enable treatment strategies for HIV-positive patients with colon adenomas.

An exploration of how broadly neutralizing antibodies might induce HIV remission: the 'vaccinal' effect

PURPOSE OF REVIEW

Broadly neutralizing antibodies (bNAbs) are a potential new therapeutic strategy to treat HIV infection. This review explores possible mechanisms of action of bNAbs and summarizes the current evidence supporting their immunomodulatory properties, which might lead to sustained virological remission - the 'vaccinal effect'.

RECENT FINDINGS

Antiretroviral therapy (ART) is required to confer lasting HIV suppression; stopping ART almost invariably leads to HIV recrudescence from a persistent pool of virally infected cells - the HIV reservoir. HIV-specific broadly neutralizing antibodies (bNAbs) may confer viral control after ART cessation predominantly through blockade of viral entry into uninfected target cells. In some human and animal studies, HIV bNAbs also conferred lasting viral suppression after therapeutic bNAb plasma levels had declined. Immune-modulatory mechanisms have been postulated to underlie this observation - the 'vaccinal effect'. Hypothesized mechanisms include the formation of immune complexes between bNAbs and HIV envelope protein, thereby enhancing antigen presentation and uptake by immune cells, with boosted adaptive immune responses subsequently controlling the HIV reservoir.

SUMMARY

There is emerging evidence for potent antiviral efficacy of bNAb therapy. Whether bNAbs can induce sustained viral suppression after dropping below therapeutic levels remains controversial. Mechanistic data from on-going and future clinical trials will help answer these questions.

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.

Influence of dietary supplementation of short-chain fatty acid sodium propionate in people living with HIV (PLHIV)

BACKGROUND

Non-AIDS associated chronic diseases in HIV+ patients have been on the rise since the advent of antiretroviral therapy. Especially cardiovascular diseases and disruption in the gastrointestinal tract have limited health-related quality of life (QoL). Several of those complications have been associated with chronic systemic inflammation. Short chain fatty-acids (SCFA), with propionate as one of the major compounds, have been described as an important link between gut microbiota and the immune system, defining the pro- and the anti-inflammatory milieu through direct and indirect regulation of T-cell homeostasis. The effects of dietary supplementation of sodium propionate (SP) in people living with HIV (PLHIV) have not yet been investigated prior to this study.

OBJECTIVES

To investigate the impact of SP uptake among PLHIV and its relevance to improve QoL, the study aimed to investigate metabolic, immunological, microbiome and patient-reported QoL related changes post SP-supplementation with follow up.  METHODS: A prospective, non-randomized, controlled, monocentric interventional study was conducted in WIR, Center for Sexual Health and Medicine, in Bochum, Germany. 32 HIV+ patients with unaltered ART-regimen in the last three months were included. Participants were given SP for a duration of 12 weeks in the form of daily oral supplementation and were additionally followed-up for another 12 weeks.

RESULTS

The supplementation of SP was well tolerated. We found an improvement in lipid profiles and long-term blood glucose levels. A decrease in pro-inflammatory cytokines and a depletion of effector T-Cells was observed. Regulatory T-Cells and IL-10 decreased. Furthermore, changes in taxonomic composition of the microbiome during follow-up were observed and improvement of items of self-reported life-quality assessment.  CONCLUSION: Taken together, the beneficial impact of SP in PLHIV reflects its potential in improving metabolic parameters and modulating pro-inflammatory immune responses. Thus possibly reducing the risk of cardiovascular disorders and facilitating long-term improvement of the gut flora.

Immune checkpoint blockade in HIV

Antiretroviral therapy (ART) has dramatically improved life expectancy for people with HIV (PWH) and helps to restore immune function but is not curative and must be taken lifelong. Achieving long term control of HIV in the absence of ART will likely require potent T cell function, but chronic HIV infection is associated with immune exhaustion that persists even on ART. This is driven by elevated expression of immune checkpoints that provide negative signalling to T cells. In individuals with cancer, immune checkpoint blockade augments tumour-directed T-cell responses resulting in significant clinical cures. There is therefore high interest if ICB can contribute to HIV cure or remission by reversing HIV-latency and/or drive recovery of HIV-specific T-cells. We here review recent evidence on the role of immune checkpoints in persistent HIV infection and discuss the potential for employing immune checkpoint blockade as a therapeutic approach to target HIV persistence on ART.

Functional evaluation of immunoregulatory molecules HLA-G, galectin-1, and IL-10 in people living with HIV

OBJECTIVES

Investigate polymorphisms and expressions of human leukocyte antigen-G (HLA-G), galectin-1 (Gal-1), and interleukin-10 (IL-10) in people living with HIV (PLHIV) with and without comorbidities to help understanding the mechanisms involved in triggering these disorders in PLHIV and in their prognosis.

DESIGN

Here we evaluated the potential correlation between the genetic polymorphism and/or protein levels of HLA-G, Gal-1, and IL-10 with and without comorbidities of PLHIV.

METHODS

Two hundred HIV patients under antiretroviral treatment (83 with comorbidities and 117 without comorbidities) and 200 healthy individuals (controls) were genotyped, using PCR, for HLA-G 14-base pair polymorphism located at the 3' untranslated region in exon 8 insertion/insertion (Ins/Ins: low HLA-G expression) or deletion/deletion (Del/Del: high HLA-G expression). Soluble levels of HLA-G (sHLA-G), Gal-1, and IL-10 were quantified by enzyme-linked immunosorbet assay.

RESULTS

HIV patients without comorbidities exhibited higher frequency of 14-base pair Del/Del genotype than HIV patients with comorbidities. As expected, HIV patients Ins/Ins with and without comorbidities produced less sHLA-G than controls. However, HIV patients Del/Del with comorbidities expressed sHLA-G more than controls and HIV patients Del/Del without comorbidities. Interestingly, patients that showed low levels sHLA-G, and presence of comorbidities, exhibited high Gal-1 serum levels. However, an increase in soluble levels of IL-10 in PLHIV was observed when compared to controls, especially in the PLHIV group without comorbidities suggesting, a protective role of IL-10 in the development of comorbidities.

CONCLUSIONS

These data suggested that the high expression of sHLA-G and IL-10 or Gal-1 could be associated and could be associated with the development or not of comorbidities in PLHIV.

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

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

Mitochondrial Exhaustion of Memory CD4 T-Cells in Treated HIV-1 Infection

People living with HIV (PLWH) who are immune non-responders (INR) to therapy are unable to restore their CD4 T-cell count and remain at great risk of morbidity and mortality. Here the mitochondrial defects that characterize memory CD4 T-cells in INR and causes of this mitochondrial exhaustion are reviewed. This review also describes the various reagents used to induce the expression of the peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PGC1α), the master regulator of mitochondrial biogenesis, which can restore mitochondria fitness and CD4 T-cell proliferation in INR. Due to sustained heightened inflammation in INR, the mitochondrial network is unable to be rejuvenated and requires attenuation of mediators of inflammation to rescue mitochondria and CD4 T-cell counts in INR.

Connexin channels modulation in pathophysiology and treatment of immune and inflammatory disorders

Connexin-mediated intercellular communication mechanisms include bidirectional cell-to-cell coupling by gap junctions and release/influx of molecules by hemichannels. These intercellular communications have relevant roles in numerous immune system activities. Here, we review the current knowledge about the function of connexin channels, mainly those formed by connexin-43, on immunity and inflammation. Focusing on those evidence that support the design and development of therapeutic tools to modulate connexin expression and/or channel activities with treatment potential for infections, wounds, cancer, and other inflammatory conditions.

Myeloid-derived suppressor cells and the pathogenesis of human immunodeficiency virus infection

There are several mechanisms by which human immunodeficiency virus (HIV) can mediate immune dysfunction and exhaustion during the course of infection. Chronic immune activation, after HIV infection, seems to be a key driving force of such unwanted consequences, which in turn worsens the pathological status. In such cases, the immune system is programmed to initiate responses that counteract unwanted immune activation, for example through the expansion of myeloid-derived suppressor cells (MDSCs). Although the expansion of immune suppressor cells in the setting of systemic chronic immune activation, in theory, is expected to contain immune activation, HIV infection is still associated with a remarkably high level of biomarkers of immune activation. Paradoxically, the expansion of immune suppressor cells during HIV infection can suppress potent anti-viral immune responses, which in turn contribute to viral persistence and disease progression. This indicates that HIV hijacks not only immune activation but also the immune regulatory responses to its advantage. In this work, we aim to pave the way to comprehend how such unwanted expansion of MDSCs could participate in the pathology of acute/primary and chronic HIV infection in humans, as well as simian immunodeficiency virus infection in rhesus macaques, according to the available literature.

Dynamics and epigenetic signature of regulatory T-cells following antiretroviral therapy initiation in acute HIV infection

BACKGROUND

HIV infection promotes the expansion of immunosuppressive regulatory T-cells (Tregs), contributing to immune dysfunction, tissue fibrosis and disease progression. Early antiretroviral treatment (ART) upon HIV infection improves CD4 count and decreases immune activation. However, Treg dynamics and their epigenetic regulation following early ART initiation remain understudied.

METHODS

Treg subsets were characterized by flow cytometry in 103 individuals, including untreated HIV-infected participants in acute and chronic phases, ART-treated in early infection, elite controllers (ECs), immunological controllers (ICs), and HIV-uninfected controls. The methylation status of six regulatory regions of the foxp3 gene was assessed using MiSeq technology.

FINDINGS

Total Treg frequency increased overtime during HIV infection, which was normalized in early ART recipients. Tregs in untreated individuals expressed higher levels of activation and immunosuppressive markers (CD39, and LAP(TGF-β1)), which remained unchanged following early ART. Expression of gut migration markers (CCR9, Integrin-β7) by Tregs was elevated during untreated HIV infection, while they declined with the duration of ART but not upon early ART initiation. Notably, gut-homing Tregs expressing LAP(TGF-β1) and CD39 remained higher despite early treatment. Additionally, the increase in LAP(TGF-β1)⁺ Tregs overtime were consistent with higher demethylation of conserved non-coding sequence (CNS)-1 in the foxp3 gene. Remarkably, LAP(TGF-β1)-expressing Tregs in ECs were significantly higher than in uninfected subjects, while the markers of Treg activation and gut migration were not different.

INTERPRETATION

Early ART initiation was unable to control the levels of immunosuppressive Treg subsets and their gut migration potential, which could ultimately contribute to gut tissue fibrosis and HIV disease progression.

FUNDING

This study was funded by the Canadian Institutes of Health Research (CIHR, grant MOP 142294) and in part by the AIDS and Infectious Diseases Network of the Réseau SIDA et maladies infectieuses du Fonds de recherche du Québec-Santé (FRQ-S).

Temporal and spatial characterization of negative regulatory T cells in HIV-infected/AIDS patients raises new diagnostic markers and therapeutic strategies

Background

Negative regulatory T cells (Tregs) not only deplete effector T cells but also inhibit the clearance of HIV during infection, which may allow Tregs to be used as informative diagnostic markers. To facilitate both diagnosis and treatment, a thorough understanding of these regulators by characterizing them on temporal and spatial scales is strongly required.

Methods

Hundred HIV‐infected/AIDS patients, including 87 males, with an average age of 35.8 years, as well as 20 healthy controls, were enrolled. Flow cytometry was used to analyze CD3+T cells, CD4+T cells, and CD8+T cells to evaluate the immune status of the participants. Then, a group of representative negative regulatory T cells, including CD4+PD‐1+T cells, CD4+PD‐1^highT cells, CD8+PD‐1+T cells, and CD4+CD25^high Tregs was also analyzed to explore their effects on disease progression and intercorrelation.

Results

The percentages of CD4⁺PD‐1⁺T cells and CD4⁺CD25^highTregs increased in patients with the same ultrahigh significance. Temporally, the patients with both intermediate‐stage and late‐stage disease had higher percentages of CD4⁺PD‐1⁺T cells; however, the percentage of CD4⁺CD25^highTregs only increased in the patients with late‐stage disease. In addition, CD4⁺PD‐1⁺T cells but not CD4⁺CD25^highTregs were negatively correlated with the absolute CD4⁺T cell count. Spatially, no correlations between CD4⁺PD‐1⁺T cells and CD4⁺CD25^highTregs were observed, which suggests these Tregs function differently during immunosuppression.

Conclusions

This study characterized negative regulatory T cells in HIV‐infected/AIDS patients at both temporal and spatial scales and found that CD4⁺CD25⁺Tregs and CD4⁺PD‐1⁺T cells could be used as potential diagnostic markers for identifying different disease stages and monitoring disease progression.

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).

Host-directed Therapy: A New Arsenal to Come

The emergence of drug-resistant strains among the variety of pathogens worsens the situation in today's scenario. In such a situation, a very heavy demand for developing the new antibiotics has arisen, but unfortunately, very limited success has been achieved in this arena till now. Infectious diseases usually make their impression in the form of severe pathology. Intracellular pathogens use the host's cell machinery for their survival. They alter the gene expression of several host's pathways and endorse to shut down the cell's innate defense pathway like apoptosis and autophagy. Intracellular pathogens are co-evolved with hosts and have a striking ability to manipulate the host's factors. They also mimic the host molecules and secrete them to prevent the host's proper immune response against them for their survival. Intracellular pathogens in chronic diseases create excessive inflammation. This excessive inflammation manifests in pathology. Host directed therapy could be alternative medicine in this situation; it targets the host factors, and abrogates the replication and persistence of pathogens inside the cell. It also provokes the anti-microbial immune response against the pathogen and reduces the exacerbation by enhancing the healing process to the site of pathology. HDT targets the host's factor involved in a certain pathway that ultimately targets the pathogen life cycle and helps in eradication of the pathogen. In such a scenario, HDT could also play a significant role in the treatment of drugsensitive as well with drug resistance strains because it targets the host's factors, which favors the pathogen survival inside the cell.

The Hitchhiker Guide to CD4+ T-Cell Depletion in Lentiviral Infection. A Critical Review of the Dynamics of the CD4+ T Cells in SIV and HIV Infection

CD4⁺ T-cell depletion is pathognomonic for AIDS in both HIV and simian immunodeficiency virus (SIV) infections. It occurs early, is massive at mucosal sites, and is not entirely reverted by antiretroviral therapy (ART), particularly if initiated when T-cell functions are compromised. HIV/SIV infect and kill activated CCR5-expressing memory and effector CD4⁺ T-cells from the intestinal lamina propria. Acute CD4⁺ T-cell depletion is substantial in progressive, nonprogressive and controlled infections. Clinical outcome is predicted by the mucosal CD4⁺ T-cell recovery during chronic infection, with no recovery occurring in rapid progressors, and partial, transient recovery, the degree of which depends on the virus control, in normal and long-term progressors. The nonprogressive infection of African nonhuman primate SIV hosts is characterized by partial mucosal CD4⁺ T-cell restoration, despite high viral replication. Complete, albeit very slow, recovery of mucosal CD4+ T-cells occurs in controllers. Early ART does not prevent acute mucosal CD4⁺ T-cell depletion, yet it greatly improves their restoration, sometimes to preinfection levels. Comparative studies of the different models of SIV infection support a critical role of immune activation/inflammation (IA/INFL), in addition to viral replication, in CD4⁺ T-cell depletion, with immune restoration occurring only when these parameters are kept at bay. CD4⁺ T-cell depletion is persistent, and the recovery is very slow, even when both the virus and IA/INFL are completely controlled. Nevertheless, partial mucosal CD4⁺ T-cell recovery is sufficient for a healthy life in natural hosts. Cell death and loss of CD4⁺ T-cell subsets critical for gut health contribute to mucosal inflammation and enteropathy, which weaken the mucosal barrier, leading to microbial translocation, a major driver of IA/INFL. In turn, IA/INFL trigger CD4⁺ T-cells to become either viral targets or apoptotic, fueling their loss. CD4⁺ T-cell depletion also drives opportunistic infections, cancers, and comorbidities. It is thus critical to preserve CD4⁺ T cells (through early ART) during HIV/SIV infection. Even in early-treated subjects, residual IA/INFL can persist, preventing/delaying CD4⁺ T-cell restoration. New therapeutic strategies limiting mucosal pathology, microbial translocation and IA/INFL, to improve CD4⁺ T-cell recovery and the overall HIV prognosis are needed, and SIV models are extensively used to this goal.

Pharmacokinetics and Immunological Effects of Romidepsin in Rhesus Macaques

HIV/SIV persistence in latent reservoirs requires lifelong antiretroviral treatment and calls for effective cure strategies. Romidepsin (RMD), a histone deacetylase inhibitor, was reported to reactivate HIV/SIV from reservoirs in virus-suppressed individuals. We characterized in detail the pharmacokinetics and safety profile of RMD in three SIV-naïve rhesus macaques which received two rounds of treatment. In plasma, RMD mean terminal half-life was 15.3 h. In comparison, RMD mean terminal half-life was much longer in tissues: 110 h in the lymph nodes (LNs) and 28 h in gastrointestinal tract. RMD administration was accompanied by transient liver and systemic toxicity. Isoflurane anesthesia induced near-immediate transient lymphopenia, which was further exacerbated and extended with the extensive immune modifications by RMD. The effect of RMD on circulating immune cells was complex: (i) slight increase in lymphocyte death rates; (ii) transient, robust increase in neutrophils; (iii) massive downregulation of lymphocyte surface markers; (iv) important migration of CD3⁺ T cells to the gut and LNs; and (v) hindrance to CD8⁺ T cell functionality, yet without reaching significance. Our results show that, in contrast to transient plasma concentrations, RMD has a long-term presence in tissues, with multiple immunomodulatory effects and minimal to moderate kidney, liver, and lymphocyte toxicities. As such, we concluded that RMD can be used for “shock and kill” approaches, preferentially in combination with other latency reversal agents or cytotoxic T lymphocyte boosting strategies with consideration taken for adverse effects.

Near normalization of peripheral blood markers in HIV-infected patients on long-term suppressive antiretroviral therapy: a case-control study

OBJECTIVE

To explore the differences in peripheral blood markers between HIV well controlled patients on long-term suppressive antiretroviral therapy (HIV-group) and age-matched healthy controls, to evaluate the benefits of virological suppression in those patients.

METHODS

We performed a case-control study in 22 individuals in the HIV-group and 14 in the healthy control-group. RNA-seq analysis was performed from peripheral blood mononuclear cells. Peripheral blood T-cell subsets were evaluated by flow cytometry and plasma biomarkers by immunoassays. All P values were corrected by the false discovery rate (q values).

RESULTS

Only the serine/arginine repetitive matrix 4 gene, which is involved in alternative RNA splicing events, was differentially expressed between HIV and healthy control groups (q value ≤0.05 and fold-change ≥2). However, 147 differentially expressed genes were found with a more relaxed threshold (P value ≤0.05 and fold-change ≥1.5), of which 67 genes with values of variable importance in projection at least one were selected for pathway analysis. We found that six ribosomal genes represented significant ribosome-related pathways, all of them downregulated in the HIV-group, which may be a strategy to facilitate viral production. T cells subset and plasma biomarkers did not show significant differences after false discovery rate correction (q value >0.05), but a noncorrected analysis showed higher values of regulatory CD4 T cells (CD4CD25CD127), MCP-1, and sVEGF-R1 in the HIV-group (P value ≤0.05).

CONCLUSION

T-cell subsets, plasma biomarkers, and gene expression were close to normalization in HIV-infected patients on long-term suppressive combination antiretroviral therapy compared with healthy controls. However, residual alterations remain, mainly at the gene expression, which still reveals the impact of HIV infection in these patients.

Immunology of EBV-Related Lymphoproliferative Disease in HIV-Positive Individuals

Epstein-Bar virus (EBV) can directly cause lymphoproliferative disease (LPD), including AIDS-defining lymphomas such as Burkitt’s lymphoma and other non-Hodgkin lymphomas (NHL), as well as human immunodeficiency virus (HIV)-related Hodgkin lymphoma (HL). The prevalence of EBV in HL and NHL is elevated in HIV-positive individuals compared with the general population. Rates of incidence of AIDS-defining cancers have been declining in HIV-infected individuals since initiation of combination anti-retroviral therapy (cART) use in 1996. However, HIV-infected persons remain at an increased risk of cancers related to infections with oncogenic viruses. Proposed pathogenic mechanisms of HIV-related cancers include decreased immune surveillance, decreased ability to suppress infection-related oncogenic processes and a state of chronic inflammation marked by alteration of the cytokine profile and expanded numbers of cytotoxic T lymphocytes with down-regulated co-stimulatory molecules and increased expression of markers of senescence in the setting of treated HIV infection. Here we discuss the cooperation of EBV-infected B cell- and environment-associated factors that may contribute to EBV-related lymphomagenesis in HIV-infected individuals. Environment-derived lymphomagenic factors include impaired host adaptive and innate immune surveillance, cytokine dysregulation and a pro-inflammatory state observed in the setting of chronic, cART-treated HIV infection. B cell factors include distinctive EBV latency patterns and host protein expression in HIV-associated LPD, as well as B cell-stimulating factors derived from HIV infection. We review the future directions for expanding therapeutic approaches in targeting the viral and immune components of EBV LPD pathogenesis.

Nonhuman Primate Testing of the Impact of Different Regulatory T Cell Depletion Strategies on Reactivation and Clearance of Latent Simian Immunodeficiency Virus

Regulatory T cells (Tregs) may be key contributors to the HIV/SIV latent reservoir, since they harbor high levels of HIV/SIV; reverse CD4⁺ T cell immune activation status, increasing the pool of resting CD4⁺ T cells; and impair CD8⁺ T cell function, favoring HIV persistence. We tested the hypothesis that Treg depletion is a valid intervention toward an HIV cure by depleted Tregs in 14 rhesus macaque (RM) controllers infected with SIVsab, the virus that naturally infects sabaeus monkeys, through different strategies: administration of an anti-CCR4 immunotoxin, two doses of an anti-CD25 immunotoxin (interleukin-2 with diphtheria toxin [IL-2-DT]), or two combinations of both. All of these treatments resulted in significant depletion of the circulating Tregs (>70%) and their partial depletion in the gut (25%) and lymph nodes (>50%). The fractions of CD4⁺ T cells expressing K_i -67 increased up to 80% in experiments containing IL-2-DT and only 30% in anti-CCR4-treated RMs, paralleled by increases in the inflammatory cytokines. In the absence of ART, plasma virus rebounded to 10³ vRNA copies/ml by day 10 after IL-2-DT administration. A large but transient boost of the SIV-specific CD8⁺ T cell responses occurred in IL-2-DT-treated RMs. Such increases were minimal in the RMs receiving anti-CCR4-based regimens. Five RMs received IL-2-DT on ART, but treatment was discontinued because of high toxicity and lymphopenia. As such, while all treatments depleted a significant proportion of Tregs, the side effects in the presence of ART prevent their clinical use and call for different Treg depletion approaches. Thus, based on our data, Treg targeting as a strategy for HIV cure cannot be discarded.IMPORTANCE Regulatory T cells (Tregs) can decisively contribute to the establishment and persistence of the HIV reservoir, since they harbor high levels of HIV/SIV, increase the pool of resting CD4⁺ T cells by reversing their immune activation status, and impair CD8⁺ T cell function, favoring HIV persistence. We tested multiple Treg depletion strategies and showed that all of them are at least partially successful in depleting Tregs. As such, Treg depletion appears to be a valid intervention toward an HIV cure, reducing the size of the reservoir, reactivating the virus, and boosting cell-mediated immune responses. Yet, when Treg depletion was attempted in ART-suppressed animals, the treatment had to be discontinued due to high toxicity and lymphopenia. Therefore, while Treg targeting as a strategy for HIV cure cannot be discarded, the methodology for Treg depletion has to be revisited.

The Role of Immunomodulatory Receptors in the Pathogenesis of HIV Infection: A Therapeutic Opportunity for HIV Cure?

Immune activation is the hallmark of HIV infection and plays a role in the pathogenesis of the disease. In the context of suppressed HIV RNA replication by combination antiretroviral therapy (cART), there remains immune activation which is associated to the HIV reservoirs. Persistent virus contributes to a sustained inflammatory environment promoting accumulation of "activated/exhausted" T cells with diminished effector function. These T cells show increased expression of immunomodulatory receptors including Programmed cell death protein (PD1), Cytotoxic T Lymphocyte Associated Protein 4 (CTLA4), Lymphocyte activation gene 3 (LAG3), T cell immunoglobulin and ITIM domain (TIGIT), T cell immunoglobulin and mucin domain containing 3 (TIM3) among others. More importantly, recent reports had demonstrated that, HIV infected T cells express checkpoint receptors, contributing to their survival and promoting maintenance of the viral reservoir. Therapeutic strategies are focused on viral reservoir elimination and/or those to achieve sustained cART-free virologic remission. In this review, we will discuss the immunological basis and the latest advances of the use of checkpoint inhibitors to treat HIV infection.

Harnessing regulatory T cell neuroprotective activities for treatment of neurodegenerative disorders

Emerging evidence demonstrates that adaptive immunity influences the pathobiology of neurodegenerative disorders. Misfolded aggregated self-proteins can break immune tolerance leading to the induction of autoreactive effector T cells (Teffs) with associated decreases in anti-inflammatory neuroprotective regulatory T cells (Tregs). An imbalance between Teffs and Tregs leads to microglial activation, inflammation and neuronal injury. The cascade of such a disordered immunity includes the drainage of the aggregated protein antigens into cervical lymph nodes serving to amplify effector immune responses. Both preclinical and clinical studies demonstrate transformation of this altered immunity for therapeutic gain. We posit that the signs and symptoms of common neurodegenerative disorders such as Alzheimer's and Parkinson's diseases, amyotrophic lateral sclerosis, and stroke can be attenuated by boosting Treg activities.

Plasmacytoid Dendritic Cells as Cell-Based Therapeutics: A Novel Immunotherapy to Treat Human Immunodeficiency Virus Infection?

Dendritic cells (DCs) play a critical role in mediating innate and adaptive immune responses. Since their discovery in the late 1970's, DCs have been recognized as the most potent antigen-presenting cells (APCs). DCs have a superior capacity for acquiring, processing, and presenting antigens to T cells and they express costimulatory or coinhibitory molecules that determine immune activation or anergy. For these reasons, cell-based therapeutic approaches using DCs have been explored in cancer and infectious diseases but with limited success. In humans, DCs are divided into heterogeneous subsets with distinct characteristics. Two major subsets are CD11c⁺ myeloid (m)DCs and CD11c⁻ plasmacytoid (p)DCs. pDCs are different from mDCs and play an essential role in the innate immune system via the production of type I interferons (IFN). However, pDCs are also able to take-up antigens and effectively cross present them. Given the rarity of pDCs in blood and technical difficulties in obtaining them from human blood samples, the understanding of human pDC biology and their potential in immunotherapeutic approaches (e.g. cell-based vaccines) is limited. However, due to the recent advancements in cell culturing systems that allow for the generation of functional pDCs from CD34⁺ hematopoietic stem and progenitor cells (HSPC), studying pDCs has become easier. In this mini-review, we hypothesize about the use of pDCs as a cell-based therapy to treat HIV by enhancing anti-HIV-immune responses of the adaptive immune system and enhancing the anti-viral responses of the innate immune system. Additionally, we discuss obstacles to overcome before this approach becomes clinically applicable.

The Binary Classification Of Chronic Diseases

Acute diseases start with an insult and end when insult disappears. If the trauma induces an immune reaction (which happens in most cases), this reaction must be terminated with some type of resolution mechanism, when the cause of the trauma ceases. Chronicity develops if insult is permanent or if the resolution mechanism is defective. Another way to reach disease chronicity is a positive feedback loop, whereby the immune reaction activates an internal, insult-like reaction. A distinction between chronic states characterized by a persistent, low suppressive effect and those characterized by a persistent, high suppressive effect of regulatory T cells (Treg), is proposed. This two-class division represents two ways to reach chronicity: (a) by maintaining inflammatory reaction long after insult disappears ("low Treg"), or (b) by suppressing inflammatory reaction prior to the disappearance of insult ("high Treg"). This two-class division may explain the strong association between certain pathogens and cancer, on one hand, and between several other pathogens and autoimmunity, on the other hand. The weak association between autoimmune diseases and HIV infection and the relatively weak association between autoimmune diseases and cancer may be elucidated as well. In addition, the model rationalizes why immune-modulating drugs, which are effective in cancer, are also effective in "high Treg" viral infections, while corticosteroids, which are generally effective in autoimmune diseases, are also effective in other "low Treg" diseases (such as asthma, atopic dermatitis, and "low Treg" infections) but are not effective in solid malignancies and "high Treg" infections. Moreover, the model expounds why certain bacteria inhibit tumor growth and why these very bacteria induce autoimmune diseases.

High-fat diet exacerbates SIV pathogenesis and accelerates disease progression

Consuming a high-fat diet (HFD) is a risk factor for obesity and diabetes; both of these diseases are also associated with systemic inflammation, similar to HIV infection. A HFD induces intestinal dysbiosis and impairs liver function and coagulation, with a potential negative impact on HIV/SIV pathogenesis. We administered a HFD rich in saturated fats and cholesterol to nonpathogenic (African green monkeys) and pathogenic (pigtailed macaques) SIV hosts. The HFD had a negative impact on SIV disease progression in both species. Thus, increased cell-associated SIV DNA and RNA occurred in the HFD-receiving nonhuman primates, indicating a potential reservoir expansion. The HFD induced prominent immune cell infiltration in the adipose tissue, an important SIV reservoir, and heightened systemic immune activation and inflammation, altering the intestinal immune environment and triggering gut damage and microbial translocation. Furthermore, HFD altered lipid metabolism and HDL oxidation and also induced liver steatosis and fibrosis. These metabolic disturbances triggered incipient atherosclerosis and heightened cardiovascular risk in the SIV-infected HFD-receiving nonhuman primates. Our study demonstrates that dietary intake has a discernable impact on the natural history of HIV/SIV infections and suggests that dietary changes can be used as adjuvant approaches for HIV-infected subjects, to reduce inflammation and the risk of non-AIDS comorbidities and possibly other infectious diseases.

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.

Expression of CD39 Is Correlated With HIV DNA Levels in Naïve Tregs in Chronically Infected ART Naïve Patients

Background: Treg cells represent important viral reservoirs during chronic HIV infection. CD39 is closely involved in Treg-mediated immunosuppressive effects. However, CD39 expression on nTregs and mTregs and a relationship with HIV DNA levels during HIV infection is still unclear. In this study, we analyzed the distribution of HIV DNA in Treg subsets and the association between HIV DNA and CD39 expression on Treg subsets. Methods: Sixty-two HIV-infected patients with different HIV stages and 14 uninfected individuals were enrolled. nTregs (CD4⁺CD25⁺CD127^lowCD45RO^-) and mTregs (CD4⁺CD25⁺CD127^lowCD45RO⁺) were isolated by magnetic selection and flow cytometric sorting. HIV DNA was quantified by real-time polymerase chain reaction (PCR). CD39 expression on nTregs and mTregs was analyzed by flow cytometry. Results: Higher levels of HIV DNA were detected in mTregs than those in nTregs during chronic HIV infection. The frequency of CD39⁺ nTregs and HIV DNA levels in nTregs were increased in patients with advanced HIV infection. Furthermore, HIV DNA levels in nTregs correlated positively with CD39⁺ nTreg frequency. CD39⁺ nTreg frequency was also increased in immune non-responders. Conclusions: mTregs and nTregs are both important reservoirs of virus during chronic HIV infection and HIV DNA levels increase in nTregs in patients with advanced HIV infection. We observed increased frequency of CD39⁺ nTregs and HIV DNA levels in nTregs in patients with advanced HIV infection. HIV DNA levels in nTregs correlated positively with CD39⁺ nTreg frequency.