Céline Didier

The Th17/Treg Ratio, IL-1RA and sCD14 Levels in Primary HIV Infection Predict the T-cell Activation Set Point in the Absence of Systemic Microbial Translocation

Impairment of the intestinal barrier and subsequent microbial translocation (MT) may be involved in chronic immune activation, which plays a central role in HIV pathogenesis. Th17 cells are critical to prevent MT. The aim of the study was to investigate, in patients with primary HIV infection (PHI), the early relationship between the Th17/Treg ratio, monocyte activation and MT and their impact on the T-cell activation set point, which is known to predict disease progression. 27 patients with early PHI were included in a prospective longitudinal study and followed-up for 6 months. At baseline, the Th17/Treg ratio strongly negatively correlated with the proportion of activated CD8 T cells expressing CD38/HLA-DR or Ki-67. Also, the Th17/Treg ratio was negatively related to viral load and plasma levels of sCD14 and IL-1RA, two markers of monocyte activation. In untreated patients, the Th17/Treg ratio at baseline negatively correlated with CD8 T-cell activation at month 6 defining the T-cell activation set point (% HLA-DR+CD38+ and %Ki-67+). Soluble CD14 and IL-1RA plasma levels also predicted the T-cell activation set point. Levels of I-FABP, a marker of mucosal damages, were similar to healthy controls at baseline but increased at month 6. No decrease in anti-endotoxin core antibody (EndoCAb) and no peptidoglycan were detected during PHI. In addition, 16S rDNA was only detected at low levels in 2 out 27 patients at baseline and in one additional patient at M6. Altogether, data support the hypothesis that T-cell and monocyte activation in PHI are not primarily driven by systemic MT but rather by viral replication. Moreover, the “innate immune set point” defined by the early levels of sCD14 and IL-1RA might be powerful early surrogate markers for disease progression and should be considered for use in clinical practice.

Relationship between regulatory T cells and immune activation in human immunodeficiency virus-infected patients interrupting antiretroviral therapy.

Persistent immune activation plays a central role in driving Human Immunodeficiency Virus (HIV) disease progression. Whether CD4+CD25+ regulatory T cells (Tregs) are harmful by suppressing HIV-specific immune responses and/or beneficial through a decrease in immune activation remains debatable. We analysed the relationship between proportion and number of regulatory T cells (Tregs) and immune activation in HIV-infected patients interrupting an effective antiretroviral therapy (ART). Twenty-five patients were included in a substudy of a prospective multicenter trial of treatment interruption (TI) (ANRS 116). Proportions and numbers of Tregs and the proportion of activated CD4 and CD8 T cells were assessed at baseline and month 12 (M12) of TI. Specific anti-HIV CD4 and CD8 responses were investigated at baseline and M12. Non parametric univariate analyses and multivariate linear regression models were conducted. At baseline, the proportion of Tregs negatively correlated with the proportion of HLA-DR+CD8+T cells (r = −0.519). Following TI, the proportion of Tregs increased from 6.3% to 7.2% (p = 0.029); absolute numbers of Tregs decreased. The increase in the proportion of HLA-DR+CD38+CD8+T cells was significantly related to the increase in proportion of Tregs (p = 0.031). At M12, the proportion of Tregs did not negatively correlate with CD8 T-cell activation. Nevertheless, Tregs retain a suppressive function since depletion of Treg-containing CD4+CD25+ cells led to an increase in lymphoproliferative responses in most patients studied. Our data suggest that Tregs are efficient in controlling residual immune activation in patients with ART-mediated viral suppression. However, the insufficient increase in the proportion and/or the decrease in the absolute number of Tregs result in a failure to control immune activation following TI. Trial Registration ClinicalTrials.gov NCT00118677

The CD85j + NK Cell Subset Potently Controls HIV-1 Replication in Autologous Dendritic Cells

Natural killer (NK) cells and dendritic cells (DC) are thought to play critical roles in the first phases of HIV infection. In this study, we examined changes in the NK cell repertoire and functions occurring in response to early interaction with HIV-infected DC, using an autologous in vitro NK/DC coculture system. We show that NK cell interaction with HIV-1-infected autologous monocyte-derived DC (MDDC) modulates NK receptor expression. In particular, expression of the CD85j receptor on NK cells was strongly down-regulated upon coculture with HIV-1-infected MDDC. We demonstrate that CD85j+ NK cells exert potent control of HIV-1 replication in single-round and productively HIV-1-infected MDDC, whereas CD85j− NK cells induce a modest and transient decrease of HIV-1 replication. HIV-1 suppression in MDCC by CD85j+ NK cells required cell-to-cell contact and did not appear mediated by cytotoxicity or by soluble factors. HIV-1 inhibition was abolished when NK-MDDC interaction through the CD85j receptor was blocked with a recombinant CD85j molecule, whereas inhibition was only slightly counteracted by blocking HLA class I molecules, which are known CD85j ligands. After masking HLA class I molecules with specific antibodies, a fraction of HIV-1 infected MDDC was still strongly stained by a recombinant CD85j protein. These results suggest that CD85j+ NK cell inhibition of HIV-1 replication in MDDC is mainly mediated by CD85j interaction with an unknown ligand (distinct from HLA class I molecules) preferentially expressed on HIV-1-infected MDDC.

Idiopathic CD4+ T-cell lymphocytopenia is associated with impaired membrane expression of the chemokine receptor CXCR4

Idiopathic CD4(+) T-cell lymphocytopenia (ICL) is a rare acquired T-cell immunodeficiency of unknown pathogenic basis. Six adults with ICL who developed opportunistic infections were investigated using extensive immunophenotyping analysis and functional evaluation of the chemokine receptor CXCR4. For all 6 patients studied, a profound defect in CXCR4 expression was detected at the surface of CD4(+) T lymphocytes, in association with an abnormal intracellular accumulation of CXCR4 and of its natural ligand, the chemokine CXCL12. For all patients studied, CD4(+) T-cell chemotactic response toward CXCL12 was decreased, whereas sensitivity to CXCL8 was preserved. CXCR4 recovery after ligand-induced endocytosis was impaired in ICL CD4(+) T cells. Upon in vitro addition of interleukin-2 (IL-2), membrane expression of CXCR4 returned to normal levels in 5 of 6 patients, whereas intracellular accumulation of CXCR4 and CXCL12 disappeared. Upon therapeutic administration of IL-2, CD4(+) T-cell count and membrane CXCR4 expression and function improved over time in 3 of 4 patients treated. Therefore, our data indicate that ICL is associated with defective surface expression of CXCR4, which may be reversed by IL-2.

Level of double negative T cells, which produce TGF-β and IL-10, predicts CD8 T-cell activation in primary HIV-1 infection.

Objective:Persistent immune activation plays a central role in the pathogenesis of HIV disease. Besides natural regulatory T cells (nTregs), ‘double negative’ T cells shown to exhibit regulatory properties could be involved in the control of harmful immune activation. The aim of this study was to analyze, in patients with primary HIV infection (PHI), the relationship between CD4+CD25+CD127lowFoxP3+ nTregs or CD3+CD4−CD8− double negative T cells and systemic immune activation. Design:A prospective longitudinal study of patients with early PHI. Methods:Twenty-five patients were included. Relationships between frequency of Treg subsets and T-cell activation, assessed on fresh peripheral blood mononuclear cells, were analyzed using nonparametric tests. Cytokine production by double negative T cells was assessed following anti-CD3/anti-CD28 stimulation. Results:No relationship was found between T-cell activation and frequencies of nTregs. In contrast, a strong negative relationship was found at baseline between the proportion of double negative T cells and the proportion of activated CD8 T cells coexpressing CD38 and HLA-DR (P = 0.005) or expressing Ki-67 (P = 0.002). In addition, the frequency of double negative T cells at baseline negatively correlated with the frequency of HLA-DR+CD38+CD8+ T cells at month 6, defining the immune activation set point (P = 0.031). High proportions of stimulated double negative T cells were found to produce the immunosuppressive cytokines transforming growth factor-&bgr;1 and/or IL-10. Conclusion:The proportion of double negative T cells at baseline was found to be predictive of the immune activation set point. Our data strongly suggest that double negative T cells may control immune activation in PHI. This effect might be mediated through the production of TGF-&bgr;1/IL-10 known to downmodulate immune activation.

S100A9 protein is a novel ligand for the CD85j receptor and its interaction is implicated in the control of HIV-1 replication by NK cells

BackgroundThe reportedly broad expression of CD85j across different immune cell types suggests an importance for this molecule in the human immune system. Previous reports have shown that this receptor interacts with several HLA class-I molecules, as well as with some viral proteins. We have demonstrated that the subset of CD85j + Natural Killer (NK) cells efficiently controls human immunodeficiency virus type 1 (HIV-1) replication in monocyte-derived dendritic cells (MDDC) in vitro and this led us to hypothesize that the CD85j + NK cell-mediated anti-HIV activity in MDDC is specifically dependent on the interaction between the CD85j receptor and unknown non-HLA class-I ligand(s).ResultsIn this study, we focused our efforts on the identification of these non-described ligands for CD85j. We found that the CD85j receptor interacts with a calcium-binding proteins of the S100 family; namely, S100A9. We further demonstrated that HIV-1 infection of MDDC induces a modulation of S100A9 expression on surface of the MDDC, which potentially influences the anti-HIV-1 activity of human NK cells through a mechanism involving CD85j ligation. Additionally, we showed that stimulation of NK cells with exogenous S100A9 enhances the control of HIV-1 infection in CD4+ T cells.ConclusionsOur data show that S100A9 protein, through ligation with CD85j, can stimulate the anti-HIV-1 activity of NK cells.

Phenotype Alterations in Regulatory T-Cell Subsets in Primary HIV Infection and Identification of Tr1-like Cells as the Main Interleukin 10–Producing CD4+ T Cells

BACKGROUND Conventional regulatory T cells (Tregs) can suppress human immunodeficiency virus type 1 (HIV-1)-specific immune responses but cannot control immune activation in primary HIV infection. Here, we characterized Treg subsets, using recently defined phenotypic delineation, and analyzed the relative contribution of cell subsets to the production of immunosuppressive cytokines in primary HIV infection. METHODS In a longitudinal prospective study, ex vivo phenotyping of fresh peripheral blood mononuclear cells from patients with primary HIV infection was performed at baseline and month 6 of follow-up to characterize Treg subsets, immune activation, and cytokine production in isolated CD4(+) T cells. RESULTS The frequency of CD4(+)CD25(+)CD127(low) Tregs and the distribution between the naive, memory, and activated/memory Treg subsets was similar in patients and healthy donors. However, Tregs from patients with primary HIV infection showed peculiar phenotypic profiles, such as elevated FoxP3, ICOS, and CTLA-4 expression, with CTLA-4 expression strikingly increased in all Treg subsets both at baseline and month 6 of follow-up. The great majority of interleukin 10 (IL-10)-producing CD4(+) T cells were FoxP3(neg) (ie, Tr1-like cells). In contrast to conventional Tregs, Tr1-like cells were inversely correlated with immune activation and not associated with lower effector T-cell responses. CONCLUSION FoxP3(neg) Tr1-like cells-major contributors to IL-10 production-may have a beneficial role by controlling immune activation in early HIV infection.

T-cell activation positively correlates with cell-associated HIV-DNA level in viremic patients with primary or chronic HIV-1 infection.

We investigated the relationship between the size of blood HIV reservoirs and T-cell activation in patients with primary HIV infection (PHI) and chronic HIV infection (CHI) before and after antiretroviral therapy (ART) interruption. Levels of T-cell activation strongly positively correlated with HIV-DNA levels in viremic PHI and CHI patients. In ART-treated CHI patients, residual immune activation was not associated with HIV-DNA levels. Interestingly, early levels of HIV-DNA in PHI predicted the extent of residual T-cell proliferation under ART.

Naive T Lymphocytes and Recent Thymic Emigrants Are Associated With HIV-1 Disease History in French Adolescents and Young Adults Infected in the Perinatal Period: The ANRS-EP38-IMMIP Study

BACKGROUND Children born at the start of the human immunodeficiency virus (HIV) epidemic and infected during the perinatal period are now young adults living with the virus. Naive T-lymphocyte restoration is essential for the maintenance of a diverse T-cell receptor repertoire and for immunity to pathogens. METHODS The ANRS-EP38-IMMIP study included 93 patients infected with HIV type 1 (HIV-1) during the perinatal period. Naive CD4 (CD4N) and CD8 (CD8N) T lymphocytes and CD4 recent thymic emigrants (CD4RTE) were quantified in the peripheral blood by flow cytometry. Wilcoxon tests, Pearson correlation coefficients, and linear regressions were used to study their associations with HIV disease parameters. RESULTS Median CD4N, CD8N, and CD4RTE percentages were 56% (interquartile range [IQR], 44-64), 31% (IQR, 22-44), and 79% (IQR, 74-83), respectively. The three T-lymphocyte subsets were positively correlated with CD4 T-cell count. Patients aviremic at the time of the study tended to have a lower CD4N percentage (55% vs 58%; P = .10), a significantly higher CD8N percentage (39% vs 22%; P < .0001), and a significantly lower CD4RTE percentage (77% vs 81%; P = .003) than viremic patients. In aviremic patients, CD4N percentages were positively associated with cumulative viremia over the last 10 years (r = 0.335; P = .01) and were significantly higher in patients harboring X4R5 viruses than in those harboring R5 viruses (61% vs 44%; P = .001). CONCLUSIONS After at least 15 years of HIV infection, perinatally infected youths had preserved CD4N and CD4RTE levels. This persistence of high levels of thymic activity potentially compensating for the deleterious effects of current and past HIV replication is remarkable.

In untreated HIV-1-infected children, PBMC-associated HIV DNA levels and cell-free HIV RNA levels are correlated to distinct T-lymphocyte populations.

Background:Clinical studies support biologically independent roles of cell-free HIV particles and HIV-infected cells in disease progression. The associations between the level of infected cells and immune markers have been poorly studied, particularly in perinatally infected children. Objective:We tested the hypothesis that independent roles of cell-free virus and infected cells in HIV pathogenesis should be revealed by different associations between each of them and specific immune markers. Methods:Levels of HIV RNA and DNA, HIV-specific CD8 T lymphocytes, activated and naive/memory T lymphocytes were determined in 44 untreated HIV-1-infected children. Pearson partial correlation coefficients were used to assess associations between the variables. Results:Here we provide new information, by showing a direct correlation between the percentages of CD4+HLA-DR+ lymphocytes and HIV DNA levels. Furthermore, higher HIV-specific CD8 T-lymphocyte frequencies were associated with lower HIV DNA levels. In contrast, CD8+38+ lymphocytes and memory CD4 lymphocytes were correlated only to the HIV RNA level. All correlations were independent of age and CD4 depletion. Conclusions:Several immune markers were correlated to either the HIV RNA or the HIV DNA level, but never to both of them, supporting the concept that cell-free virus and infected cells play different roles in HIV-1 immunopathogenesis.