Distinct cytokine and regulatory T cell profile at pleural sites of dual HIV/tuberculosis infection compared to that in the systemic circulation

Abstract

Pleural tuberculosis (TB) remains a common presentation of Mycobacterium tuberculosis (MTB) infection in HIV/TB dually infected subjects, and both cellular and acellular components of the pleural milieu promote HIV-1 replication; however, they remain uncharacterized. Using cytokine array of pleural fluid and real-time reverse transcription-polymerase chain reaction (RT-PCR) and immunophenotype analysis, pleural fluid mononuclear cells (PFMC) were compared to systemic counterparts [i.e. plasma and peripheral blood mononuclear cells (PBMC)]. Significant increases in pleural fluid cytokines compared to plasma were limited to interleukin (IL)-6, IL-8, interferon (IFN)-γ and transforming growth factor (TGF)-β, and did not include other T helper type 1 (Th1) (IL-2, IL-15), Th2 or Th17 cytokines. Patterns and levels of cytokines were indistinguishable between pleural fluid from HIV/TB and TB patients. Forkhead box P3 (FoxP3) mRNA in PFMC was increased significantly and correlated highly with levels of IL-6 and IL-8, less with TGF-β, and not with IFN-γ. Among CD4 T cells, FoxP3-reactive CD25(hi) were increased in HIV/TB dually infected subjects compared to their PBMC, and up to 15% of FoxP3(+) CD25(hi) CD4 T cells were positive for IL-8 by intracellular staining. These data implicate a dominant effect of MTB infection (compared to HIV-1) at pleural sites of dual HIV/TB infection on the local infectious milieu, that include IL-6, IL-8, IFN-γ and TGF-β and regulatory T cells (T(reg) ). A correlation in expansion of T(reg) with proinflammatory cytokines (IL-6 and IL-8) in pleural fluid was shown. T(reg) themselves may promote the inflammatory cytokine milieu through IL-8.