Abstract
Tuberculosis has emerged as an epidemic, extended by the large number of individuals infected with human immunodeficiency virus type 1 (HIV- 1). The major goal of this study was to determine whether the mycobacterial cell wall component mannose-capped lipoarabinomannan (ManLAM) of Mycobacterium tuberculosis (M. tuberculosis) could activate transcription of HIV-1 in T cells with the use of an in vitro cell culture system. These experiments are of prime importance considering that CD4-expressing T lymphocytes represent the major virus reservoir in the peripheral blood of infected individuals. Using the 1G5 cell line harbouring the luciferase reporter gene under the control of the HIV-1 LTR, it was first found that culture protein filtrates (CFP) from M. tuberculosis or purified ManLAM could activate HIV-1 LTR-dependent gene expression unlike similarly prepared CFP extracts devoid of ManLAM. The implication of protein tyrosine kinase(s), protein kinase A and/or protein kinase C was highlighted by the abrogation of the ManLAM- mediated activation of HIV-1 LTR-driven gene expression using herbimycin A and H7. It was also determined, using electrophoresis mobility shift assays, that M. tuberculosis ManLAM led to the nuclear translocation of the transcription factor NF-kappaB. M. tuberculosis ManLAM resulted in clear induction of the luciferase gene placed under the control of the wild-type, but not the kappaB-mutated, HIV-1 LTR region. Finally, the ManLAM-mediated activation of HIV-1 LTR transcription was found to be independent of the autocrine or paracrine action of endogenous TNF-alpha. The results suggest that M. tuberculosis can upregulate HIV-1 expression in T cells and could thus have the potential to influence the pathogenesis of HIV-1 infection.