POSITIVE SELECTION OF HIV-1 CYTOTOXIC T-LYMPHOCYTE ESCAPE VARIANTS DURING PRIMARY INFECTION

Cytotoxic T lymphocytes (CTLs) are thought to play a crucial role in t he termination of the acute primary HIV-1 syndrome, but clear evidence for this presumption has been lacking, Here we demonstrate positive s election of HIV-1 proviral sequences encoding variants within a CTL ep itope in Nef, a gene product critical for viral pathogenicity, during and after seroconversion, These positively selected HIV-1 variants car ried epitope sequence changes that either diminished or escaped CTL re cognition, Other proviruses had mutations that abolished the Nef epito pe altogether, These results provide clear evidence that CTLs exert se lection pressure on the viral population in acute HIV-1 infection.