Summary:To examine the effects ofMycobacterium tuberculosison human immunodeficiency virus type 1 (HIV-1) expression, the monocytoid cell line U1 containing integrated provirus was incubated with the H37Ra strain ofM. tuberculosis.This resulted in heightened expression of virus in supernatant that was partially inhibited by antibody to tumor necrosis factor-α (TNF-α). Purified protein derivative (PPD) prepared fromM. tuberculosisalso could activate HIV expression, and this was less affected by anti-TNF antibody. PPD could activate the HIV promoter in both U937, the monocytoid cell line from which U1 was derived, and Jurkat, a CD4+lymphoid line. Activation was abolished by mutations in the nuclear factor (NF)-kB binding domains. Jurkat cells transfected with a plasmid construct linking 8 NF-kB binding domains to the chloramphenicol acetyltransferase (CAT) gene showed increased activity of the reporter gene after activation with PPD. Transcriptional activation of HIV expression by mycobacteria and mycobacterial products may enhance propagation of HIV in monocytoid and lymphoid cells. This may result in accelerated HIV disease progression in persons coinfected withM. tuberculasis.