Tuberculosis specific responses following therapy for TB: Impact of HIV co-infection

- HIV + TB + subjects have higher immune activation compared to TB + subjects.
- Coinfected subjects had lower numbers of TB-specific CD4 + T cells at baseline.
- Plasma IFNγ levels were not significantly different between groups.
- Similar in-vitro proliferation to TB antigens is present in HIV + TB + and TB + subjects.

Characterizing perturbations in the immune response to tuberculosis in HIV can develop insights into the pathogenesis of coinfection. HIV + TB + and TB monoinfected (TB +) subjects recruited from clinics in Bamako prior to initiation of TB treatment were evaluated at time-points following initiation of therapy. Flow cytometry assessed CD4 +/CD8 + T cell subsets and activation markers CD38/HLA-DR. Antigen specific responses to TB proteins were assessed by intracellular cytokine detection and proliferation. HIV + TB + subjects had significantly higher markers of immune activation in the CD4 + and CD8 + T cells compared to TB + subjects. HIV + TB + had lower numbers of TB-specific CD4 + T cells at baseline. Plasma IFNγ levels were similar between HIV + TB + and TB + subjects. No differences were observed in in-vitro proliferative capacity to TB antigens between HIV + TB + and TB + subjects. Subjects with HIV + TB + coinfection demonstrate in vivo expansion of TB-specific CD4 + T cells. Immunodeficiency associated with CD4 + T cell depletion may be less significant compared to immunosuppression associated with HIV viremia or untreated TB infection.