Higher Levels of Peripheral Th17 T CD4+ Cells Are Associated With Immunological Non Response in HIV-Infected Patients Under Effective ART
Th17 T CD4+ lymphocytes have an important function in maintaining mucosal integrity, preventing microbial translocation and are known to be potent inducers of tissue inflammation.1,2 Th17 lymphocytes are preferentially depleted in the gastrointestinal mucosa during chronic SIV/HIV infection, and their frequency and function in the gut are only partially restored under antiretroviral therapy (ART).3 A quantitative and qualitative loss of Th17 in colonrectum occurs early during acute HIV infection, starting from Fiebig stage III.4 It is still not known if gastrointestinal Th17 lymphocytes are lost during HIV infection because of direct virus infection or as a consequence of HIV-associated inflammation and immune activation.2,3,5 A negative correlation between peripheral levels of Th17 and HIV plasma viremia has been previously shown,6 but contradictory results are present in the literature concerning Th17 lymphocytes levels and function after HIV infection.5–8 The interplay between Th17 lymphocytes and immune reconstitution after the introduction of ART, in particular, is still poorly understood.
We performed quantitative analyses on peripheral Th17 CD4 T lymphocytes in HIV-infected and ART-treated patients in whom stable virological suppression was achieved. A cross-sectional single-site study enrolling HIV-infected patients on ART for ≥24 months and with plasma HIV-RNA <50 copies/mL for ≥12 months was designed to this end. Patients with ≤350 CD4+ lymphocytes/μL were defined as immunological nonresponders (INRs), whereas patients with ≥500 CD4+ lymphocytes/μL were defined as immunological responders (IRs). Current opportunistic AIDS-related diseases, hepatitis B virus or hepatitis C virus coinfection, chronic inflammatory disorders, or ongoing immunosuppressive therapy were exclusion criteria to avoid confounding variables. The study was approved by the Ethic Commitee of Monza Brianza on May 29, 2014, and all participants gave written informed consent. Assays were performed on fresh samples obtained for this study. Immunophenotypic analyses (human leucocyte antigen-DRII+CD4+ and CD38+CD8+) were performed by flow citometry on unstimulated peripheral blood mononuclear cells (PBMCs). Peripheral Th17 T CD4+ lymphocytes were defined by the coexpression of RORγT+/IL17-A+/CD4+ and were analyzed by flow citometry either in unstimulated cell cultures, or after stimulation with aldrithiol-2 (AT2)-HIV-1BaL–treated virions (300 ng/mL) or lipopolysaccharide (LPS) (1 μg/mL). Microbial translocation markers (LPS and sCD14) were evaluated as well in plasma by ELISA assay. All statistical analyses were performed using SPSS version 13.0 software package (SPSS Inc, Chicago, IL). Differences between INR and IR patient groups were assessed using Student t-test (continuous variables) and χ2 test or Fisher exact test (categorical variables). Correlations analyses between Th17 T CD4+ lymphocytes (either unstimulated or stimulated) and absolute CD4+ T cell count were performed using Spearman rank coefficient. A multivariate linear regression model was also used to investigate a potential independent association between immunological nonresponse and Th17 CD4+ T lymphocytes levels, after adjustment for age, past AIDS events, and CD4 nadir. A 2-tailed P value <0.05 was considered to be statistically significant.
Thirty-nine HIV-infected patients (22 IRs and 17 INRs) were enrolled in the study. The two groups did not differ by sex (male: 72.7% IRs and 82.4% INRs), epidemiology (heterosexual: 50% IRs and 58.8% INRs; homosexual: 23.7% IRs and 20.8% INRs; unknown: 27.3% IRs and 17.6% INRs), ethnic group (white: 86.4% IRs and 82.4% INRs), median time from HIV diagnosis (years: 9.3 IRs and 10.2 INRs), median time from ART initiation (years: 7.7 IRs and 10.2 INRs), median time with HIV-RNA <50 copies/mL (months: 53.7 IRs and 59 INRs), median time from last regimen initiation (months: 48.5 IRs and 16.8 INRs), and current antiretroviral regimens (NRTI: 90.9% IRs and 94.1% INRs; NNRTI: 54.5% IRs and 41.2% INRs; PI: 27.3% IRs and 35.3% INRs; InSTI: 27.3% IRs and 41.2% INRs).