Alveolar T-helper 17 responses to streptococcus pneumoniae are preserved in ART-untreated and treated HIV-infected Malawian adults.

Objective: We explored if HIV infection is associated with impaired T-Helper 17 responses against Streptococcus pneumoniae in the lung.

Methods: We recruited 30 HIV-uninfected healthy controls, 23 asymptomatic HIV-infected adults not on ART, and 40 asymptomatic HIV-infected adults on ART (Median time 3.5yrs), in whom we collected bronchoalveolar lavage fluid. We measured alveolar CD4 T cell immune responses following stimulation with pneumococcal cell culture supernatant using flow cytometry-based intracellular cytokine staining.

Results: We found that the proportion of alveolar CD4 T cells producing IL-17A following stimulation with pneumococcal cell culture supernatant (CCS) was similar between HIV-uninfected controls and ART-naïve HIV-infected adults (0.10% vs. 0.14%; p = 0.9273). In contrast, the proportion and relative absolute counts of CD4 T cells producing IL-17A in response to pneumococcal CCS were higher in ART-treated HIV-infected adults compared HIV-uninfected controls (0.22% vs. 0.10%, p = 0.0166; 5420 vs. 1902 cells/100 ml BAL fluid; p = 0.0519). The increase in relative absolute numbers of IL-17A-producing alveolar CD4 T cells in ART-treated individuals was not correlated with the peripheral blood CD4 T cell count (r=-0.1876, p = 0.1785).

Conclusion: Alveolar Th17 responses against S. pneumoniae are preserved in HIV-infected adults. This suggests that there are other alternative mechanisms that are altered in HIV-infected individuals that render them more susceptible to pneumococcal pneumonia.