Homeostasis and function of regulatory T cells in HIV/SIV infection

CD4+CD25+CD127 regulatory cells play multiple roles in maintaining HIV-1 p24 production in patients on long-term treatment: HIV-1 p24-producing cells and suppression of anti-HIV immunity

BACKGROUND

A major question when attempting to eradicate and treat HIV-1 infection is how to reactivate latent proviruses. Stimulating HIV-1-specific cytolytic T lymphocytes (CTL) has been shown to facilitate the elimination of the latent viral reservoir after viral reactivation. Regulatory T (Treg) cells are known to be capable of lowering both HIV-specific immunoreactions and general immune activation during HIV-1 infection. It was hypothesized that the depletion of Treg cells could increase the HIV-1-specific cytolytic T lymphocyte response and reactivate HIV-1 p24 production.

METHODS

Treg cells were isolated by isolation kit according to the surface marker of Treg cells. Real-time PCR method was used to quantify HIV-1 DNA. P24 antigens in the cell culture supernatant was done by ELISA. Cells activation and HIV specific HIV-1 CD8+ T cells were analyses using a FACSCalibur flow cytometer and CELLQUEST software.

RESULTS

This study included both HIV-infected patients who were antiviral treatment-naïve and patients with sustained viral responses to antiretroviral therapy (ART) for 1 or 5 years. It was found that the HIV-DNA levels in Treg cells were approximately 10-fold higher than those in non-Treg CD4+ cells and that the depletion of Treg cells could enhance the frequency of HIV-1-specific CTL and immune activation after 5 years of effective ART.

CONCLUSIONS

CD4+CD25+CD127 regulatory cells play multiple roles in maintaining HIV-1 p24 production in long-term ART patients. Treg cells may be a target for eliminating the latent HIV reservoir after effective long-term ART.

Increased Regulatory T-Cell Percentage Contributes to Poor CD4(+) Lymphocytes Recovery: A 2-Year Prospective Study After Introduction of Antiretroviral Therapy

Background. The primary aim of this study was to determine the impact of regulatory T cells (Tregs) percentage on immune recovery in human immunodeficiency virus (HIV)-infected patients after antiretroviral therapy introduction.

Methods. A 2-year prospective study was conducted in HIV-1 chronically infected naive patients with CD4 count <500 cells/mm³. Regulatory T cells were identified as CD4⁺CD25^highCD127^low cells among CD4⁺ lymphocytes. Effect of Treg percentage at inclusion on CD4 evolution overtime was analyzed using a mixed-effect Poisson regression for count data.

Results. Fifty-eight patients were included (median CD4 = 293/mm³, median Treg percentage = 6.1%). Percentage of Treg at baseline and CD4 nadir were independently related to the evolution of CD4 absolute value according to time: (1) at any given nadir CD4 count, 1% increase of initial Treg was associated with a 1.9% lower CD4 absolute value at month 24; (2) at any given Treg percentage at baseline, 10 cell/mm³ increase of CD4 nadir was associated with a 2.4% increase of CD4 at month 24; and (3) both effects did not attenuate with time. The effect of Treg at baseline on CD4 evolution was as low as the CD4 nadir was high.

Conclusions. Regulatory T-cell percentage at baseline is a strong independent prognostic factor of immune recovery, particularly among patients with low CD4 nadir.

CD4 T Cells Mediate Both Positive and Negative Regulation of the Immune Response to HIV Infection: Complex Role of T Follicular Helper Cells and Regulatory T Cells in Pathogenesis

HIV-1 infection results in chronic activation of cells in lymphoid tissue, including T cells, B-cells, and myeloid lineage cells. The resulting characteristic hyperplasia is an amalgam of proliferating host immune cells in the adaptive response, increased concentrations of innate response mediators due to viral and bacterial products, and homeostatic responses to inflammation. While it is generally thought that CD4 T cells are greatly depleted, in fact, two types of CD4 T cells appear to be increased, namely, regulatory T cells (Tregs) and T follicular helper cells (Tfh). These cells have opposing roles, but may both be important in the pathogenic process. Whether Tregs are failing in their role to limit lymphocyte activation is unclear, but there is no doubt now that Tfh are associated with B-cell hyperplasia and increased germinal center activity. Antiretroviral therapy may reduce the lymphocyte activation, but not completely, and therefore, there is a need for interventions that selectively enhance normal CD4 function without exacerbating Tfh, B-cell, or Treg dysfunction.

Profound loss of intestinal Tregs in acutely SIV-infected neonatal macaques

Impairment of the intestinal mucosal immune system is an early feature of HIV-infected children. Most infected children exhibit clinical gastrointestinal symptoms at some stage of infection, and persistent diarrhea is a marker for rapid disease progression. It is known that Tregs are especially important in mediating intestinal immune homeostasis and that loss of this subset may result in intestinal inflammation and associated clinical signs. Large numbers of FoxP3(+) T cells were found in all tissues in newborn macaques, which coexpressed high levels of CD25 and CD4, indicating that they were Tregs. Moreover, neonates had much greater percentages of Tregs in intestinal tissues compared with peripheral lymphoid tissues. After SIV infection, a significant loss of Tregs was detected in the intestine compared with age-matched normal infants. Finally, SIV-infected FoxP3(+) T cells were detected in tissues in neonates as early as 7 SIV dpi. These results demonstrate that Tregs constitute a significant fraction of CD4(+) T cells in neonatal intestinal tissues and that an early, profound loss of Tregs occurs in acute SIV infection, which may contribute to the intestinal disorders associated with neonatal HIV infection.

Defective IL-17- and IL-22-dependent mucosal host response to Candida albicans determines susceptibility to oral candidiasis in mice expressing the HIV-1 transgene

BACKGROUND

The tissue-signaling cytokines IL-17 and IL-22 are critical to host defense against oral Candida albicans infection, by their induction of oral antimicrobial peptide expression and recruitment of neutrophils. Mucosal Th17 cells which produce these cytokines are preferentially depleted in HIV-infected patients. Here, we tested the hypothesis that defective IL-17- and IL-22-dependent host responses to C. albicans determine the phenotype of susceptibility to oropharyngeal candidiasis (OPC) in transgenic (Tg) mice expressing HIV-1.

RESULTS

Naïve CD4+ T-cells and the differentiated Th1, Th2, Th17, Th1Th17 and Treg lineages were all profoundly depleted in cervical lymph nodes (CLNs) of these Tg mice. However, naive CD4+ cells from Tg mice maintained the capacity to differentiate into these lineages in response to polarizing cytokines in vitro. Expression of Il17, Il22, S100a8 and Ccl20 was enhanced in oral mucosal tissue of non-Tg, but not of Tg mice, after oral infection with C. albicans. Treatment of infected Tg mice with the combination of IL-17 and IL-22, but not IL-17 or Il-22 alone, significantly reduced oral burdens of C. albicans and abundance of Candida hyphae in the epithelium of tongues of infected Tg mice, and restored the ability of the Tg mice to up-regulate expression of S100a8 and Ccl20 in response to C. albicans infection.

CONCLUSIONS

These findings demonstrate that defective IL-17- and IL-22-dependent induction of innate mucosal immunity to C. albicans is central to the phenotype of susceptibility to OPC in these HIV transgenic mice.

Association between discordant immunological response to highly active anti-retroviral therapy, regulatory T cell percentage, immune cell activation and very low-level viraemia in HIV-infected patients

The mechanisms sustaining the absence of complete immune recovery in HIV-infected patients upon long-term effective highly active anti-retroviral therapy (HAART) remain elusive. Immune activation, regulatory T cells (T(regs)) or very low-level viraemia (VLLV) have been alternatively suspected, but rarely investigated simultaneously. We performed a cross-sectional study in HIV-infected aviraemic subjects (mean duration of HAART: 12 years) to concomitantly assess parameters associated independently with inadequate immunological response. Patients were classified as complete immunological responders (cIR, n = 48) and inadequate immunological responders (iIR, n = 39), depending on the CD4(+) T cell count (> or < 500/mm(3)). Clinical and virological data (including very low-level viraemia) were collected. In parallel, immunophenotyping of CD4(+) lymphocytes, including T(reg) subsets, and CD8(+) T cells was performed. Percentages of activated CD4(+) T cells, T(regs), effector T(regs) and terminal effector T(regs) were found to be significantly elevated in iIR. Neither the percentage of activated CD8(+) T cells nor VLLV were found to be associated with iIR. In the multivariate analysis, nadir of CD4(+) T cell count and percentage of T(regs) were the only two parameters associated independently with iIR [odds ratio (OR) = 2·339, P = 0·001, and OR = 0·803, P = 0·041]. We present here the largest study investigating simultaneously the immune response to long-term HAART, activation of CD4(+) and CD8(+) T cells, T(reg) percentages and very low-level viraemia. Causative interactions between T(regs) and CD4(+) T cells should now be explored prospectively in a large patients cohort.

HIV-1 infection impairs regulatory T-cell suppressive capacity on a per-cell basis

The impact of CD4+ regulatory T cells (Tregs) on human immunodeficiency virus type 1 (HIV-1) pathogenesis remains incompletely understood. Although it has been shown that Tregs can be infected with HIV-1, the consequences of infection on a per-cell basis are still unknown. In vitro HIV-GFP infected and noninfected Tregs were isolated by flow-based cell-sorting to investigate Treg suppressive capacity and gene expression profiles. Our data show that HIV-1-infected Tregs were significantly less suppressive than noninfected Tregs and demonstrated down-regulation of genes critical to Treg function. This impaired function may have detrimental consequences for the control of generalized immune activation and accelerate HIV disease progression.

Epigenetic modification of FOXP3 in patients with chronic HIV infection

OBJECTIVES

HIV-1 modulates host cell epigenetic machinery to control its own replication and induce immune suppression. HIV-1 infection leads to activation of T regulatory cell (T(reg)), but the mechanism underlying this immune modulation is unclear. T(reg) plays a prominent role in gut-mucosal immune tolerance by restraining excessive effector T-cell responses, a mechanism that is known to be disturbed in chronic HIV-1 infection. DNA methylation plays a major role in T(reg) lineage commitment and immune homeostasis, which may be regulated by HIV. To investigate the mechanisms of aberrant methylation of the T(reg) marker FOXP3 in HIV-1 infection, we evaluated the expression pattern of methylation-related enzymes and its correlation to FOXP3 methylation.

METHODS

FOXP3 promoter methylation in the colon mucosa and peripheral blood from HIV-infected patients and control subjects was measured using Pyrosequencing. Gene expression pattern of DNA methylation enzymes in the colon mucosa was investigated by Microarray and quantitative reverse transcriptase-polymerase chain reaction analysis in the same subjects.

RESULTS

FOXP3 promoter was significantly (P ≤ 0.0001) demethylated in HIV-infected patients compared with control subjects in both tissues. Expression of DNA methyltransferase 1 (DNAMT1), DNA methyltransferase 1-associated protein 1(DMAP1), methyltransferase-like 7B (METTL7B), and methyltransferase-like 10 (METTL10) were significantly down regulated in HIV-infected patients compared with controls and had a significant positive correlation to FOXP3 promoter methylation.

CONCLUSIONS

We present evidence suggesting that altered methylation pattern of FOXP3 and accordingly higher T(reg) frequency in gut mucosa of HIV-infected patients may be because of aberrant methylation processing in HIV.

Regulatory T cells expanded from HIV-1-infected individuals maintain phenotype, TCR repertoire and suppressive capacity

While modulation of regulatory T cell (Treg) function and adoptive Treg transfer are being explored as therapeutic modalities in the context of autoimmune diseases, transplantation and cancer, their role in HIV-1 pathogenesis remains less well defined. Controversy persists regarding their beneficial or detrimental effects in HIV-1 disease, which warrants further detailed exploration. Our objectives were to investigate if functional CD4⁺ Tregs can be isolated and expanded from HIV-1-infected individuals for experimental or potential future therapeutic use and to determine phenotype and suppressive capacity of expanded Tregs from HIV-1 positive blood and tissue. Tregs and conventional T cell controls were isolated from blood and gut-associated lymphoid tissue of individuals with HIV-1 infection and healthy donors using flow-based cell-sorting. The phenotype of expanded Tregs was assessed by flow-cytometry and quantitative PCR. T-cell receptor ß-chain (TCR-β) repertoire diversity was investigated by deep sequencing. Flow-based T-cell proliferation and chromium release cytotoxicity assays were used to determine Treg suppressive function. Tregs from HIV-1 positive individuals, including infants, were successfully expanded from PBMC and GALT. Expanded Tregs expressed high levels of FOXP3, CTLA4, CD39 and HELIOS and exhibited a highly demethylated TSDR (Treg-specific demethylated region), characteristic of Treg lineage. The TCRß repertoire was maintained following Treg expansion and expanded Tregs remained highly suppressive in vitro. Our data demonstrate that Tregs can be expanded from blood and tissue compartments of HIV-1+ donors with preservation of Treg phenotype, function and TCR repertoire. These results are highly relevant for the investigation of potential future therapeutic use, as currently investigated for other disease states and hold great promise for detailed studies on the role of Tregs in HIV-1 infection.

Immune targeting of PD-1(hi) expressing cells during and after antiretroviral therapy in SIV-infected rhesus macaques

High-level T cell expression of PD-1 during SIV infection is correlated with impaired proliferation and function. We evaluated the phenotype and distribution of T cells and Tregs during antiretroviral therapy plus PD-1 modulation (using a B7-DC-Ig fusion protein) and post-ART. Chronically SIV-infected rhesus macaques received: 11 weeks of ART (Group A); 11 weeks of ART plus B7-DC-Ig (Group B); 11 weeks of ART plus B7-DC-Ig, then 12 weeks of B7-DC-Ig alone (Group C). Continuous B7-DC-Ig treatment (Group C) decreased rebound viremia post-ART compared to pre-ART levels, associated with decreased PD-1(hi) expressing T cells and Tregs in PBMCs, and PD-1(hi) Tregs in lymph nodes. It transiently decreased expression of Ki67 and α4β7 in PBMC CD4(+) and CD8(+) Tregs for up to 8 weeks post-ART and maintained Ag-specific T-cell responses at low levels. Continued immune modulation targeting PD-1(hi) cells during and post-ART helps maintain lower viremia, keeps a favorable T cell/Treg repertoire and modulates antigen-specific responses.

CD4+ T-cell activation impairs serogroup C Neisseria meningitis vaccine response in HIV-infected children

OBJECTIVE

To investigate the influence of CD4 T-cell activation and regulatory populations in HIV-infected children antibody response to vaccination with a conjugate C polysaccharide vaccine.

DESIGN

CD4 T-cell activation was evaluated by expression of CD38, HLA-DR and CCR5 molecules. Regulatory CD4 T cells (TReg) were characterized as FoxP3CD127CD25 and inducer T cells (TInd) as CD4FoxP3CD25CD39.

METHODS

All patients (n = 36) were HIV-vertically infected, aged 2-17 years-old and were vaccinated with one vaccine injection. Blood samples were obtained before and after immunization to determine bactericidal antibody titers (SBA), CD4 T-cell activation and frequency of TReg and TInd subsets (multiparametric flow cytometry).

RESULTS

Children not-responding (n = 18) to MenC vaccine expressed higher frequency of activated CD4 T cells (HLA-DRCD38CCR5) than responders (n = 18), both before and after vaccination (P < 0.05). A significant higher frequency of TReg was detected in responders compared with nonresponders (P = 0.0001). We also detected an inverse correlation between CD4DRCD38CCR5 (P = 0.01) or CD4DRCD38 (P = 0.02) T cells and TReg cell frequency after vaccination. CD4 T-cell activation negatively correlated (P = 0.006) with postvaccination SBA titers but a positive correlation (P = 0.0001) was detected between TReg cells and SBA. TReg and TInd subsets were inversely correlated (P = 0.04).

CONCLUSION

Our findings suggest that higher CD4 T-cell activation leads to poor vaccine response in children living with HIV, which may be associated with a TReg/TInd disequilibrium.

T Cell Transcription Factors and Their Impact on HIV Expression

By targeting CD4⁺ effector T cells, HIV has a dramatic impact on the depletion, expansion and function of the different polarized T cell subsets. The maturation of T cell lineages is in part driven by intrinsic transcription factors that potentially influence how efficiently HIV replicates. In this review, we explore whether transcription factors that are required for polarizing T cells influence HIV replication. In particular, we examine provirus transcription as well as the establishment and maintenance of HIV latency. Furthermore, it is suggested these factors may provide novel cell-specific therapeutic strategies for targeting the HIV latent reservoir.

HIV infection of human regulatory T cells downregulates Foxp3 expression by increasing DNMT3b levels and DNA methylation in the FOXP3 gene

OBJECTIVE

Regulatory T cells (Tregs) play an important role in infections modulating host immune responses and avoiding overreactive immunity. The mechanisms underlying their action in HIV-infected patients have not been well established. HIV can infect Treg, but little is known about the effects of the infection on Treg phenotype and function. The objective of this study was to investigate whether in-vitro HIV infection modifies the phenotype and suppressive capacity of Treg cells.

DESIGN

Because Treg cells are a subset of CD4 T cells, HIV infection could produce alterations in the phenotype and methylation pattern of Treg disturbing the functionality of these cells.

METHODS

Isolated Treg cells from healthy volunteers were cultured in the presence of HIV-1, and phenotype, methylation pattern of FOXP3 locus, cytokine secretion profile and suppressive function of infected Treg were analysed in comparison with noninfected Treg.

RESULTS

We demonstrate that HIV-1 directly infects Treg and deregulates the function and the phenotype that define these cells. HIV infection downregulates the Foxp3 expression in Treg, which is followed by the loss of suppressive capacity and alterations in cytokine secretion pattern, with decreased production of transforming growth factor-beta (TGF-β) and an increased production of interleukin (IL)-4. Foxp3 downregulation in HIV-infected Treg was related to an increase in the expression of DNA methyltransferase3b (DNMT3b) associated with higher methylation of CpG sites in the FOXP3 locus.

CONCLUSION

These findings are pivotal to our understanding of the role of Treg in HIV infection and indicate that regulatory function could be seriously impaired in HIV-infected patients contributing to the immune hyperactivation.

Boosters of a therapeutic HIV-1 vaccine induce divergent T cell responses related to regulatory mechanisms

Therapeutic human immunodeficiency virus (HIV) vaccines aim to reduce disease progression by inducing HIV-specific T cells. Vacc-4x are peptides derived from conserved domains within HIV-1 p24 Gag. Previously, Vacc-4x induced T cell responses in 90% of patients which were associated with reduced viral loads. Here we evaluate the effects of Vacc-4x boosters on T cell immunity and immune regulation seven years after primary immunization. Twenty-five patients on effective antiretroviral therapy received two Vacc-4x doses four weeks apart and were followed for 16 weeks. Vacc-4x T cell responses were measured by proliferation (CFSE), INF-γ, CD107a, Granzyme B, Delayed-Type Hypersensitivity test (DTH) and cytokines and chemokines (Luminex). Functional regulation of Vacc-4x-specific T cell proliferation was estimated in vitro using anti-IL-10 and anti-TGF-ß monoclonal antibodies. Vacc-4x-specific CD8(+) T cell proliferation increased in 80% after either the first (64%) or second (16%) booster. Only 40% remained responders after two boosters with permanently increased Vacc-4x-specific proliferative responses (p=0.005) and improved CD8(+) T cell degranulation, IFN-γ production and DTH. At baseline, responders had higher CD8(+) T cell degranulation (p=0.05) and CD4(+) INF-γ production (p=0.01), whereas non-responders had higher production of proinflammatory TNF-α, IL-1α and IL-1ß (p<0.045) and regulatory IL-10 (p=0.07). Notably, IL-10 and TGF-ß mediated downregulation of Vacc-4x-specific CD8(+) T cell proliferation increased only in non-responders (p<0.001). Downregulation during the study correlated to higher PD-1 expression on Vacc-4x-specific CD8(+) T cells (r=0.44, p=0.037), but was inversely correlated to changes in Vacc4x-specific CD8(+) T cell proliferation (r=-0.52, p=0.012). These findings show that Vacc-4x boosters can improve T cell responses in selected patients, but also induce vaccine-specific downregulation of T cell responses in others. Broad surveillance of T cell functions during immunization may help to individualize boosting, where assessment of vaccine-related immune regulation should be further explored as a potential new parameter.

CD4⁺CD73⁺ T cells are associated with lower T-cell activation and C reactive protein levels and are depleted in HIV-1 infection regardless of viral suppression

BACKGROUND

The role of the adenosine (ADO) suppression pathway, specifically CD39-expressing and CD73-expressing CD4⁺ T cells in HIV-1 infection is unclear.

METHODS

We evaluated the frequency and numbers of CD4⁺CD39⁺ and CD4⁺CD73⁺ T cells, activated T cells, and plasma C reactive protein (CRP) levels in 36 HIV-1-positive individuals and 10 normal controls (NC). Low-level plasma viremia was evaluated using single copy assay. Mass spectrometry was used to measure hydrolysis of ATP by ectoenzyme-expressing CD4⁺ T cells, whereas cyclic adenosine monophosphate (cAMP) levels were measured using enzyme immunoassay. Suppression of T-cell function by exogenous ADO and CD4⁺CD73⁺ T cells was tested by flow cytometry.

RESULTS

CD39 and CD73 are expressed in different CD4⁺ T-cell subsets. CD4⁺CD73⁺ T cells do not express CD25 and FOXP3, and their frequency and numbers were lower in HIV-1-positive individuals regardless of virologic suppression (P=0.005 and P<0.001, respectively). CD4⁺CD73⁺ numbers inversely correlated with CD4⁺CD38⁺DR⁺ (P=0.002), CD8⁺CD38⁺DR⁺ T-cell frequency (P=0.05), and plasma CRP levels (P=0.01). Both subsets are required for hydrolysis of exogenous ATP to ADO and can increase CD4⁺ T-cell cAMP levels when incubated with exogenous ATP. Low-level viremia did not correlate with activated T-cell frequency. In vitro, ADO suppressed T-cell activation and cytokine expression. CD4⁺CD7⁺ T cells suppressed T-cell proliferation only in the presence of exogenous 5'-AMP.

CONCLUSION

The ADO-producing CD4⁺CD73⁺ subset of T cells is depleted in HIV-1-positive individuals regardless of viral suppression and may play a key role in controlling HIV-1-associated immune activation.

New tools to expand regulatory T cells from HIV-1-infected individuals

CD4+ Regulatory T cells (Tregs) are potent immune modulators and serve an important function in human immune homeostasis. Depletion of Tregs has led to measurable increases in antigen-specific T cell responses in vaccine settings for cancer and infectious pathogens. However, their role in HIV-1 immuno-pathogenesis remains controversial, as they could either serve to suppress deleterious HIV-1-associated immune activation and thus slow HIV-1 disease progression or alternatively suppress HIV-1-specific immunity and thereby promote virus spread. Understanding and modulating Treg function in the context of HIV-1 could lead to potential new strategies for immunotherapy or HIV vaccines. However, important open questions remain on their role in the context of HIV-1 infection, which needs to be carefully studied. Representing roughly 5% of human CD4+ T cells in the peripheral blood, studying the Treg population has proven to be difficult, especially in HIV-1 infected individuals where HIV-1-associated CD4 T cell and with that Treg depletion occurs. The characterization of regulatory T cells in individuals with advanced HIV-1 disease or tissue samples, for which only very small biological samples can be obtained, is therefore extremely challenging. We propose a technical solution to overcome these limitations using isolation and expansion of Tregs from HIV-1-positive individuals. Here we describe an easy and robust method to successfully expand Tregs isolated from HIV-1-infected individuals in vitro. Flow-sorted CD3(+)CD4(+)CD25(+)CD127(low) Tregs were stimulated with anti-CD3/anti-CD28 coated beads and cultured in the presence of IL-2. The expanded Tregs expressed high levels of FOXP3, CTLA4 and HELIOS compared to conventional T cells and were shown to be highly suppressive. Easier access to large numbers of Tregs will allow researchers to address important questions concerning their role in HIV-1 immunopathogenesis. We believe answering these questions may provide useful insight for the development of an effective HIV-1 vaccine.

CD4 T cell responses in latent and chronic viral infections

The spectrum of tasks which is fulfilled by CD4 T cells in the setting of viral infections is large, ranging from support of CD8 T cells and humoral immunity to exertion of direct antiviral effector functions. While our knowledge about the differentiation pathways, plasticity, and memory of CD4 T cell responses upon acute infections or immunizations has significantly increased during the past years, much less is still known about CD4 T cell differentiation and their beneficial or pathological functions during persistent viral infections. In this review we summarize current knowledge about the differentiation, direct or indirect antiviral effector functions, and the regulation of virus-specific CD4 T cells in the setting of persistent latent or active chronic viral infections with a particular emphasis on herpes virus infections for the former and chronic lymphocytic choriomeningitis virus infection for the latter.

Epidemiology and interactions of Human Immunodeficiency Virus - 1 and Schistosoma mansoni in sub-Saharan Africa

Human Immunodeficiency Virus-1/AIDS and Schistosoma mansoni are widespread in sub-Saharan Africa and co-infection occurs commonly. Since the early 1990s, it has been suggested that the two infections may interact and potentiate the effects of each other within co-infected human hosts. Indeed, S. mansoni infection has been suggested to be a risk factor for HIV transmission and progression in Africa. If so, it would follow that mass deworming could have beneficial effects on HIV-1 transmission dynamics. The epidemiology of HIV in African countries is changing, shifting from urban to rural areas where the prevalence of Schistosoma mansoni is high and public health services are deficient. On the other side, the consequent pathogenesis of HIV-1/S. mansoni co-infection remains unknown. Here we give an account of the epidemiology of HIV-1 and S. mansoni, discuss co-infection and possible biological causal relationships between the two infections, and the potential impact of praziquantel treatment on HIV-1 viral loads, CD4+ counts and CD4+/CD8+ ratio. Our review of the available literature indicates that there is evidence to support the hypothesis that S. mansoni infections can influence the replication of the HIV-1, cell-to-cell transmission, as well as increase HIV progression as measured by reduced CD4+ T lymphocytes counts. If so, then deworming of HIV positive individuals living in endemic areas may impact on HIV-1 viral loads and CD4+ T lymphocyte counts.

T cell activation but not polyfunctionality after primary HIV infection predicts control of viral load and length of the time without therapy

Objective

Immune changes occurring after primary HIV infection (PHI) have a pivotal relevance. Our objective was to characterize the polyfunctionality of immune response triggered by PHI, and to characterize immune activation and regulatory T cells, correlating such features to disease progression.

Patients and Methods

We followed 11 patients experiencing PHI for 4 years. By polychromatic flow cytometry, we studied every month, for the first 6 months, T lymphocyte polyfunctionality after cell stimulation with peptides derived from HIV-1 gag and nef. Tregs were identified by flow cytometry, and T cell activation studied by CD38 and HLA-DR expression.

Results

An increase of anti-gag and anti-nef CD8+ specific T cells was observed 3 months after PHI; however, truly polyfunctional T cells, also able to produce IL-2, were never found. No gross changes in Tregs were present. T lymphocyte activation was maximal 1 and 2 months after PHI, and significantly decreased in the following period. The level of activation two months after PHI was strictly correlated to the plasma viral load 1 year after infection, and significantly influenced the length of period without therapy. Indeed, 80% of patients with less than the median value of activated CD8+ (15.5%) or CD4+ (0.9%) T cells remained free of therapy for >46 months, while all patients over the median value had to start treatment within 26 months.

Conclusions

T cell activation after PHI, more than T cell polyfunctionality or Tregs, is a predictive marker for the control of viral load and for the time required to start treatment.

Regulatory T cells in HIV infection: can immunotherapy regulate the regulator?

Regulatory T cells (Tregs) have a dominant role in self-tolerance and control of autoimmune diseases. These cells also play a pivotal role in chronic viral infections and cancer by limiting immune activation and specific immune response. The role of Tregs in HIV pathogenesis remains poorly understood as their function, changes according to the phases of infection. Tregs can suppress anti-HIV specific responses and conversely can have a beneficial role by reducing the deleterious impact of immune activation. We review the frequency, function and homing potential of Tregs in the blood and lymphoid tissues as well as their interaction with dendritic cells in the context of HIV infection. We also examine the new insights generated by recombinant IL-2 and IL-7 clinical trials in HIV-infected adults, including the immunomodulatory effects of Tregs. Based on their detrimental role in limiting anti-HIV responses, we propose Tregs as potential targets for immunotherapeutic strategies aimed at decreasing Tregs frequency and/or immunosuppressive function. However, such approaches require a better understanding of the time upon infection when interfering with Treg function may not cause a deleterious state of hyperimmune activation.