Engagement of CD43 enhances human immunodeficiency virus type 1 transcriptional activity and virus production that is induced upon TCR/CD3 stimulation

Human immunodeficiency virus type 1 (HIV-1) transcriptional activity is regulated by several cytokines and T cell activators. CD43 (sialophorin) is a sialoglycoprotein expressed on the surface of a wide variety of blood cells including T lymphocytes. Several studies have shown that CD43 ligation induces proliferation and activation of human T lymphocytes. We were thus interested in defining whether CD43-mediated signaling events can modulate the life cycle of HIV-1. We demonstrate here that CD43 cross-linking potentiates HIV-1 promoter-driven activity and virus production that is seen following the engagement of the T-cell receptor (TCR)-CD3 complex. This effect is independent of the CD28 co-stimulatory molecule and is mediated by both NF-kappaB and NFAT transcription factors. A number of signal transducers known to be involved in the TCR/CD3-dependent signal transduction pathway, including p56(lck), p36(lat), and SLP-76, as well as capacitative entry of calcium, are crucial for the noticed CD43 co-stimulatory effect. Calcium mobilization studies indicate that a synergy is occurring between CD43- and TCR/CD3-mediated signaling events leading to an augmented calcium release. These data suggest that CD43 can be seen as a co-stimulatory cell surface constituent that can modulate HIV-1 expression in T lymphocytes.