Human immunodeficiency virus-associated changes in signal transduction

It is well established that the activation of T lymphocytes by mitogen/antigen is accompanied by a rise in intracellular free calcium ([Ca2+]i), changes in membrane potential, metabolism of inositol phospholipid, and activation of protein kinase C. These early events of signal transduction culminate in late events of lymphocyte activation, namely, DNA synthesis, lymphokine production, and cellular proliferation. In this study we examined the effect of human immunodeficiency virus (HIV) on changes in membrane potential and [Ca2+]i levels. The membrane potentials were markedly decreased (depolarized) in T cell lines infected with HIV (H9/HTLV IIIb) and did not respond normally to phytohemagglutinin (PHA) or anti-T3 (anti-CD3) monoclonal antibody compared to uninfected H9 cell line. The basal [Ca2+]i levels in H9/HTLV IIIb cells were increased in comparison to those in H9 cells; however, there was very little further increase in [Ca2+]i in H9/HTLV IIIb cells following activation with PHA or anti-T3 monoclonal antibody. This is in contrast to a significant rise in [Ca2+]i in H9 cells following similar stimulation. These data demonstrate abnormalities in the plasma membrane potential and [Ca2+]i levels in chronically infected T cells with HIV. These abnormalities in signal transduction of the T-cell activation pathway could be responsible for T-cell dysfunction in patients with HIV infection.