ROLE OF HIV-1 NEF EXPRESSION IN ACTIVATION PATHWAYS IN CD4-CELLS( T)

The role of the human immunodeficiency virus (HIV-1) Nef protein in T cell activation pathways was investigated using a Jurkat CD4(+) cell l ine stably transfected with a Nef expression vector. Secretion of IL-2 and TNF-alpha, surface expression of IL-2R, and DNA-binding activity of NF-kappa B and AP-1 (Fos/Jun) complex in response to phorbol myrist ate acetate, TNF-alpha, or immobilized antibodies to CD3 were monitore d. These parameters were not modified by Nef expression in Jurkat cell s, whereas stimulation with the same stimuli resulted in partial inhib ition of LTR activation in Nef(+) Jurkat cells. This inhibition was no t mediated through Nef phosphorylation on Thr-15 or GTP-binding activi ty because mutations in critical sites did not alter this inhibition. Analysis of truncated LTRs confirmed that inhibition of LTR activation was not mediated through NF-kappa B-binding activity but through the region containing the negative responding elements (NREs). These resul ts suggest that Nef downmodulates LTR activation without significantly inhibiting the capacity of T cells to respond to immunological activa tions.