Regulatory T cells (Treg) and HIV/AIDS: summary of the September 7-8, 2006 workshop

Short- and long-term effects of antiretroviral therapy on peripheral regulatory CD4+/CD25hi/CD127low T lymphocytes in people living with HIV/AIDS

The effect of antiretroviral therapy (ART) on CD4⁺/CD25^hi/CD127^low T lymphocyte changes in people living with HIV/AIDS (PLWHA) is still a matter of debate. From October 2015 to December 2019, peripheral blood from 70 cases of PLWHA were collected for the detection of CD4⁺/CD25^hi/CD127^low T lymphocytes by flow cytometry. Statistical analysis was performed to detect changes of CD4⁺/CD25^hi/CD127^low T lymphocytes in patients with different duration of ART and different treatment effects. We found that the number of CD4⁺/CD25^hi/CD127^low T lymphocytes in ART-naive PLWHA were lower than those in healthy volunteers (10.3±٦.٠ cells/uL vs 31.7±8.0 cells/uL, P < 0.05). CD4⁺/CD25^hi/CD127^low T lymphocyte counts increased to 17.8±٤.٠ cells/uL 6 months post-ART and 25.0±١١.٩ cells/uL 9 months post-ART, respectively (P < 0.05). There was no significant difference in CD4⁺/CD25^hi/CD127^low T lymphocyte counts between PLWHA who reached a complete immune reconstruction after ART and healthy volunteers. The growth of CD4⁺/CD25^hi/CD127^low T lymphocyte counts in patients who had baseline CD4 > 200 cells/uL was greater than those who had baseline CD4 ≤ 200 cells/uL (12.6±٤.٦ cells/uL vs 5.6±٥.٠ cells/uL, P = 0.027). CD4⁺/CD25^hi/CD127^low T lymphocyte counts were positively correlated with CD4⁺ T lymphocyte counts (r = 0.923, P < 0.001) and CD4⁺/CD8⁺ ratio (r = 0.741, P < 0.001), but were negatively correlated with HIV-VL (r = −0.648, P = 0.000). In conclusion, the results of the present study showed that changes in CD4⁺/CD25^hi/CD127^low T lymphocyte counts can be used to assess the effect of ART in PLWHA.

Determinants of vaccine immunogenicity in HIV-infected pregnant women: analysis of B and T cell responses to pandemic H1N1 monovalent vaccine

Influenza infections have high frequency and morbidity in HIV-infected pregnant women, underscoring the importance of vaccine-conferred protection. To identify the factors that determine vaccine immunogenicity in this group, we characterized the relationship of B- and T-cell responses to pandemic H1N1 (pH1N1) vaccine with HIV-associated immunologic and virologic characteristics. pH1N1 and seasonal-H1N1 (sH1N1) antibodies were measured in 119 HIV-infected pregnant women after two double-strength pH1N1 vaccine doses. pH1N1-IgG and IgA B-cell FluoroSpot, pH1N1- and sH1N1-interferon γ (IFNγ) and granzyme B (GrB) T-cell FluoroSpot, and flow cytometric characterization of B- and T-cell subsets were performed in 57 subjects. pH1N1-antibodies increased after vaccination, but less than previously described in healthy adults. pH1N1-IgG memory B cells (Bmem) increased, IFNγ-effector T-cells (Teff) decreased, and IgA Bmem and GrB Teff did not change. pH1N1-antibodies and Teff were significantly correlated with each other and with sH1N1-HAI and Teff, respectively, before and after vaccination. pH1N1-antibody responses to the vaccine significantly increased with high proportions of CD4+, low CD8+ and low CD8+HLADR+CD38+ activated (Tact) cells. pH1N1-IgG Bmem responses increased with high proportions of CD19+CD27+CD21- activated B cells (Bact), high CD8+CD39+ regulatory T cells (Treg), and low CD19+CD27-CD21- exhausted B cells (Bexhaust). IFNγ-Teff responses increased with low HIV plasma RNA, CD8+HLADR+CD38+ Tact, CD4+FoxP3+ Treg and CD19+IL10+ Breg. In conclusion, pre-existing antibody and Teff responses to sH1N1 were associated with increased responses to pH1N1 vaccination in HIV-infected pregnant women suggesting an important role for heterosubtypic immunologic memory. High CD4+% T cells were associated with increased, whereas high HIV replication, Tact and Bexhaust were associated with decreased vaccine immunogenicity. High Treg increased antibody responses but decreased Teff responses to the vaccine. The proportions of immature and transitional B cells did not affect the responses to vaccine. Increased Bact were associated with high Bmem responses to the vaccine.

The alveolar microenvironment of patients infected with human immunodeficiency virus does not modify alveolar macrophage interactions with Streptococcus pneumoniae

We tested the hypothesis that HIV infection results in activation of alveolar macrophages and that this might be associated with impaired defense against pneumococcus. We compared alveolar macrophages and lymphocytes in 131 bronchoalveolar lavage samples from HIV-infected and healthy controls using inflammatory gene microarrays, flow cytometry, real-time PCR, and enzyme-linked immunosorbent assay (ELISA) to determine the pattern of macrophage activation associated with HIV infection and the effect of this activation on defense against pneumococcus. We used gamma interferon (IFN-γ) priming to mimic the cellular milieu in HIV-infected lungs. InnateDB and BioLayout 3D were used to analyze the interactions of the upregulated genes. Alveolar macrophages from HIV-infected adults showed increased gene expression and cytokine production in a classical pattern. Bronchoalveolar lavage from HIV-infected subjects showed excess CD8(+) lymphocytes with activated phenotype. Toll-like receptor 4 (TLR4) expression was increased in macrophages from HIV-infected subjects, but function was similar between the groups; lung lavage fluid did not inhibit TLR function in transfected HeLa cells. Alveolar macrophages from HIV-infected subjects showed normal binding and internalization of opsonized pneumococci, with or without IFN-γ priming. Alveolar macrophages from HIV-infected subjects showed classical activation compared to that of healthy controls, but this does not alter macrophage interactions with pneumococci.

Thoughts on intervention in HIV/AIDS with traditional Chinese medicine

HIV/AIDS has become a worldwide pandemic and highly active antiretroviral therapy (HAART) is the only generally recognized effective therapy at present. However, various unresolvable problems appear with the widespread use of HAART. Traditional Chinese Medicine shows good efficacy for intervention in HIV/AIDS and could become an effective treatment option.

Factors influencing T cell activation and programmed death 1 expression in HIV-infected children

Immune activation is the best marker of HIV disease progression in both adults and children. However, the factors that drive immune activation in HIV-infected children remain incompletely understood and may differ from those in adults. Immune activation was investigated in a cohort of 93 untreated HIV-infected children, of median age 10.8 years, and 37 HIV-uninfected children. CD8(+) T cell activation, which was higher in HIV-infected than HIV-uninfected children (p<0.001), did not correlate with viral load (R=-0.03, p=0.838). Similarly, programmed death 1 (PD-1) expression on CD8(+) T cells, which was higher in HIV-infected children than HIV-uninfected children (p<0.001), was not associated with viral load (R=0.11, p=0.40), but correlated with CD8 activation (R=0.41, p=0.002). Both CD8 activation and PD-1 expression were partially driven by the magnitude of the HIV-specific CD8(+) T cell response. CD3(+)CD4(+)CD25(hi)FoxP3(+) regulatory T cells (Tregs) were depleted in HIV-infected, compared to HIV-uninfected, children [median 1.0% (IQR 0.6, 1.9) vs. 2.6% (IQR 1.7, 3.2) CD3 cells; p<0.001]. Depletion was associated with increased CD8 activation (R=-0.27, p=0.068), suggesting that the decline in Tregs may allow immune activation to increase. Taken together, immune activation and PD-1 upregulation in children are not directly driven by viral load but may be influenced by the magnitude of the immune response to HIV itself, and to the depletion of Tregs that occurs during HIV infection. Further understanding of the factors that drive immune activation in children is critical to developing future therapeutic strategies in this population.

A randomized case-control study of dynamic changes in peripheral blood Th17/Treg cell balance and interleukin-17 levels in highly active antiretroviral-treated HIV type 1/AIDS patients

Our objective was to dynamically observe changes in peripheral blood Th17, Treg cells, and interleukin (IL)-17 levels in HIV-1/AIDS patients before and after highly active antiretroviral therapy (HAART). The study design consisted of a randomized case-controlled study. A total of 33 HIV-1/AIDS patients were chosen to receive a HAART regimen and 30 healthy volunteers were assigned as controls. Peripheral blood Th17 and Treg cells were measured by flow cytometry before or 6 and 12 months after HAART therapy. The plasma IL-17 level was determined by ELISA. The percentage of Th17 cells to total CD4(+) cells was 1.2 ± 0.37% in HIV/AIDS patients before treatment, which was significantly lower than that in uninfected controls (4.7 ± 1.43%). After HAART therapy for 6 or 12 months, the Th17 percentage increased to 2.5 ± 1.03% and 3.7±1.56%, respectively. The percentage of Treg cells to CD4(+) cells is 9.16 ± 3.33% in HIV/AIDS patients, which was significantly elevated compared to controls (4.43 ± 0.97%). HAART therapy for 6 and 12 months significantly decreased Treg cell percentage (7.19 ± 2.91% and 5.53 ± 1.88%, respectively). Interestingly, the ratio of Th17/Treg cells was significantly decreased in HIV/AIDS patients before treatment, while HAART treatment partially normalized the Th17/Treg ratio. IL-17 levels were 5.3 ± 2.5 and 17.7 ± 6.60 pg/ml in HIV/AIDS patients and controls, respectively; the HAART regimen increased the IL-17 level to 7.7 ± 2.4 and 10.4 ± 3.1 pg/ml at 6 and 12 months, respectively. The percentage of Th17 cells correlated with IL-17 level, but both negatively correlated with viral load before treatment, whereas the percentage of Treg cells positively correlated with viral load before HAART therapy. The imbalance of peripheral blood Th17 and Treg cells may play a crucial role in the pathogenesis of AIDS. HAART can restore the balance of Th17 and Treg cells as well as the IL-17 level, which may gradually rebuild the immune equilibrium in HIV/AIDS patients.

Immune correlates of herpes zoster in HIV-infected children and youth

To identify immunologic factors that modulate the risk of herpes zoster (HZ), we compared varicella-zoster virus (VZV)-specific and nonspecific T-cell subpopulations of 47 HIV-infected children before they developed HZ with those of 141 VZV-positive HZ-negative matched controls. Compared with controls, HZ cases had lower VZV-specific CD8(+) CD107a(+) cell percentages independently of CD4(+) percentages or HIV loads, suggesting that VZV-specific cytotoxic T cells are protective against HZ. In contrast, high nonspecific regulatory and activated T cells were associated with an increased risk of HZ.

Reduced immunogenicity of influenza vaccines in HIV-infected compared with uninfected pregnant women is associated with regulatory T cells

OBJECTIVES

To evaluate the immunogenicity of influenza vaccines in HIV-infected pregnant women and the factors that may determine this response.

DESIGN

Prospective, single-site study of HIV-infected and uninfected women.

METHODS

Pregnant women had the following immunologic measurements at vaccination, 6 weeks after immunization, and 12 weeks after delivery: hemagglutination inhibition (HAI) antibody titers, lymphocyte proliferation (LPA), interferon-γ enzyme-linked immunospot (ELISPOT), and polychromatic flow cytometric enumeration of influenza-specific effector and regulatory T cells.

RESULTS

At vaccination, demographic and gestational characteristics did not differ significantly between the 20 HIV-infected and 18 uninfected participants. Prevaccination HAI geometric mean titers (GMTs) against all strains of influenza in the vaccines were similar between the two groups. Antibody responses to vaccination measured by GMT or four-fold titer increase were significantly lower in HIV-infected compared with uninfected pregnant women for influenza A strains. Antibody responses to influenza B were equally low in the two groups of participants. There were no significant LPA or ELISPOT responses to vaccination in either group. LPA results were significantly lower in HIV-infected compared with uninfected women at all time points, but ELISPOT were not. Influenza-specific regulatory CD4(+)FoxP3(+)% and CD4(+)IL10(+)% increased after vaccination in both groups, but significantly more in HIV-infected compared with uninfected pregnant women. Higher influenza-specific CD4(+)FoxP3(+)% postvaccination correlated with lower antibody responses to the vaccine and lower LPA results.

CONCLUSIONS

Influenza vaccines have reduced immunogenicity in HIV-infected compared with uninfected pregnant women. In HIV-infected women, increased regulatory CD4(+)FoxP3(+)% may attenuate the immunogenicity of vaccines.

Normalization of FoxP3(+) regulatory T cells in response to effective antiretroviral therapy

Regulatory T cells (Tregs) blunt uncontrolled immune responses. In advanced human immunodeficiency virus (HIV) infection, the total number of Tregs is decreased, but the proportion of T cells with a regulatory phenotype is highly variable. We studied CD4(+)CD25(+)FoxP3(+) T cells from patients successfully treated with combination antiretroviral therapy (ART). The proportion of CD4(+)CD25(+)FoxP3(+) cells transiently increased and then decreased from a median of 13% at baseline to 5.1% at 48 weeks, similar to values in normal subjects. These data suggest that with effective therapy, the regulatory cell numbers normalize, and that the inflammatory signals driving their production may also abate.

Regulatory T cells in HIV infection: who's suppressing what?

The role of regulatory T cells (Treg) in HIV pathogenesis is not fully elucidated. Persistent antigens such as HIV are believed to promote the expansion and activation of antigen-specific Treg, and several reports have described beneficial and detrimental roles for Treg in HIV pathogenesis. These apparently contradictory observations may arise from imprecision in enumerating Treg and the lack of definition of Treg subsets. New markers allowing more precise identification and purification of Treg for functional studies have been described recently, and these may open avenues for efficient isolation of pure, homogenous populations of human Treg.

In vivo depletion of CD4(+)CD25(hi) regulatory T cells is associated with improved antiviral responses in cats chronically infected with feline immunodeficiency virus

Regulatory T (Treg) cells are activated and suppress immune responses during infection, and are characterized as CD4(+)CD25(hi)FOXP3(+). Ex vivo studies demonstrate that Treg cells potentially suppress anti-HIV-1 T cell responses. Lentivirus-induced CD4(+)CD25(hi) Treg cells were first described in feline immunodeficiency virus (FIV)-infected cats. In the present study we demonstrate that anti-feline CD25 monoclonal antibody (mAb) therapy depletes Treg cells in FIV-infected cats for 4 weeks and does not exacerbate viral replication or proinflammatory cytokine production. Significant FIV-specific immune responses are revealed in Treg cell-depleted cats. These anti-FIV effector cells exist prior to Treg cell depletion and are not expanded while Treg cells are depleted. Importantly, cats receiving the Treg cell-depleting mAb are able to produce a robust humoral response to new antigen. We propose that short-term in vivo Treg cell depletion during chronic HIV-1 infection could provide a window of opportunity for therapeutic vaccination in individuals with controlled viral replication.

Regulatory function of cytomegalovirus-specific CD4+CD27-CD28- T cells

CMV infection is characterized by high of frequencies of CD27-CD28- T cells. Here we demonstrate that CMV-specific CD4+CD27-CD28- cells are regulatory T cells (TR). CD4+CD27-CD28- cells sorted from CMV-stimulated PBMC of CMV-seropositive donors inhibited de novo CMV-specific proliferation of autologous PBMC in a dose-dependent fashion. Compared with the entire CMV-stimulated CD4+ T-cell population, higher proportions of CD4+CD27-CD28- TR expressed FoxP3, TGFbeta, granzyme B, perforin, GITR and PD-1, lower proportions expressed CD127 and PD1-L and similar proportions expressed CD25, CTLA4, Fas-L and GITR-L. CMV-CD4+CD27-CD28- TR expanded in response to IL-2, but not to CMV antigenic restimulation. The anti-proliferative effect of CMV-CD4+CD27-CD28- TR significantly decreased after granzyme B or TGFbeta inhibition. The CMV-CD4+CD27-CD28- TR of HIV-infected and uninfected donors had similar phenotypes and anti-proliferative potency, but HIV-infected individuals had higher proportions of CMV-CD4+CD27-CD28- TR. The CMV-CD4+CD27-CD28- TR may contribute to the downregulation of CMV-specific and nonspecific immune responses of CMV-infected individuals.

Mucosal immunity to HIV: a review of recent literature

PURPOSE OF REVIEW

This review summarizes recent literature in the field of mucosal immunology as it applies to HIV transmission and pathogenesis.

RECENT FINDINGS

Pertinent recent findings include elucidation of the role of mucosal antigen-presenting cells and retinoic acid in imprinting a gut-homing phenotype on antigen-specific T and B cells, and the identification of Th17 and T regulatory cells as key modulators of the balance between tolerance and inflammation in mucosal tissues.

SUMMARY

Mucosal surfaces of the body serve as the major portal of entry for HIV. These tissues also house a majority of the body's lymphocytes, including the CD4 T-cells that are the major cellular target for HIV infection. Elucidating mucosal immune responses is critical to our understanding of the host-pathogen relationship for two reasons: first, mucosal barriers are defended by a range of innate and adaptive defenses that might be exploited to develop effective vaccines or microbicides; second, adaptive immune responses in mucosal lymphoid tissues might serve to limit viral replication, decreasing the host's viral burden as well as reducing the likelihood of sexual transmission to a naïve host.

The absence of CD4+ T cell count recovery despite receipt of virologically suppressive highly active antiretroviral therapy: clinical risk, immunological gaps, and therapeutic options

Up to 30% of human immunodeficiency virus (HIV)-infected patients who are receiving long-term highly active antiretroviral therapy do not exhibit a marked increase in the CD4(+) T cell count, despite achieving complete suppression of the HIV load. These patients are referred to as "immunological nonresponders." When treating immunological nonresponders, the practicing clinician has several questions, including questions about the clinical risk associated with persistent immunodeficiency and about possible approaches to treatment that would provide clinical and immunological benefits. However, tentative answers to these questions require investigations of the mechanisms that underlie the lack of immune recovery, because only the deepest comprehension of the immunological gaps underlying functional defects will allow administration of highly targeted and efficacious treatment strategies. The aim of our review is to provide a thorough assessment of the clinical implications of a lack of increase in the CD4(+) T cell count in immunological nonresponders, to examine the immunological gaps limiting recovery of the CD4(+) T cell count, and to note possible therapeutic avenues, which may offer clinicians guidance regarding how to most efficaciously treat these critical patients.

Mucosal T-cell responses to HIV: responding at the front lines

Mucosal surfaces of the body serve as the major portal of entry for human immunodeficiency virus (HIV). These tissues also house a majority of the body's lymphocytes, including the CD4(+) T cells that are the major cellular target for HIV infection. Mucosal surfaces are defended by innate and adaptive immune mechanisms, including secreted antibodies and CD8(+) cytotoxic T cells (CTL). CTL in mucosal lymphoid tissues may serve to limit viral replication, decreasing the host's viral burden as well as reducing the likelihood of sexual transmission to a naïve host. This review summarizes recent literature on HIV-specific T-cell responses in mucosal tissues, with an emphasis on the gastrointestinal tract.

Regulatory T cells in HIV infection: who's suppressing what?

The role of regulatory T cells (Treg) in HIV pathogenesis is not fully elucidated. Persistent antigens, such as HIV, are believed to promote the expansion and activation of antigen-specific Treg, and several reports have described beneficial and detrimental roles for Treg in HIV pathogenesis. These apparently contradictory observations may arise from imprecision in enumerating Treg and the lack of definition of Treg subsets. New markers allowing more precise identification and purification of Treg for functional studies have been described recently, and these may open avenues for efficient isolation of pure, homogenous populations of human Treg.

Antiviral NK cell responses in HIV infection: II. viral strategies for evasion and lessons for immunotherapy and vaccination

As is the case in other viral infections, humans respond to HIV infection by activating their NK cells. However, the virus uses several strategies to neutralize and evade the host's NK cell responses. Consequently, it is not surprising that NK cell functions become compromised in HIV-infected individuals in early stages of the infection. The compromised NK cell functions also adversely affect several aspects of the host's antiviral adaptive immune responses. Researchers have made significant progress in understanding how HIV counters NK cell responses of the host. This knowledge has opened new avenues for immunotherapy and vaccination against this infection. In the first part of this review article, we gave an overview of our current knowledge of NK cell biology and discussed how the genes encoding NK cell receptors and their ligands determine innate genetic resistance/susceptibilty of humans against HIV infections and AIDS. In this second part, we discuss NK cell responses, viral strategies to counter these responses, and finally, their implications for anti-HIV immunotherapy and vaccination.

Improving defences at the portal of HIV entry: mucosal and innate immunity

The authors discuss the key scientific issues in mucosal and innate immunity related to immune protection against HIV infection.