DIFFERENTIAL REGULATION OF HIV-1 FUSION COFACTOR EXPRESSION BY CD28 COSTIMULATION OF CD4(-CELLS() T)

Activation of CD4(+) T lymphocytes from human immunodeficiency virus-t ype 1 (HIV-1)-infected donors with immobilized antibodies to CD3 and C D28 induces a virus-resistant state. This effect is specific for macro phage-tropic HIV-I, Transcripts encoding CXCR4/Fusin, the fusion cofac tor used by T cell line-tropic isolates, were abundant in CD3/CD28-sti mulated cells, but transcripts encoding CCR5, the fusion cofactor used by macrophage-tropic viruses, were not detectable. Thus, CD3/CD28 cos timulation induces an HIV-1-resistant phenotype similar to that seen i n some highly exposed and HIV-uninfected individuals.