Human Immunodeficiency Virus Infection Abolishes CD4-dependent Activation of ZAP-70 by Inhibition of p56lck

: The effect of early human immunodeficiency virus-1 infection in vitro on proximal signal transduction events in primary peripheral blood lymphocytes was investigated with respect to CD4-mediated costimulation of CD3/T cell-receptor signalling. Tyrosine phosphorylation profiles induced by CD4 and CD3 + CD4 ligation were profoundly abrogated in virally infected cells, although CD4 receptor expression remained intact during early infection. Furthermore, the association of the tyrosine kinase p56lck with the CD4 receptor was reduced in virally infected cells. The downmodulation of CD4-mediated CD3 signalling coincided with the subsequent inhibition of the activity and tyrosine phosphorylation of the downstream kinase ZAP-70 in virally infected cells. The observed virally mediated cosignalling defects during early infection may account for the inhibition of distal signal events and thus contribute to HIV pathogenesis, such as reduced immune response to antigenic exposure, anergy, and apoptosis.