Identification of a conserved universal Th epitope in HIV-1 reverse transcriptase that is processed and presented to HIV-specific CD4(+) T cells by at least four unrelated HLA-DR molecules

CD4(+) Th cells play an important role in the induction and maintenance of specific T cell immunity. Indications for a protective role of CD4(+) T cel ls against HIV-1 infection were found in subjects who were able to control HIV-1 viremia as well as in highly HIV-1-exposed, yet seronegative, individ uals, This study describes the identification of an HIV-1-specific Th epito pe that exhibits high affinity binding as well as high immunogenicity in th e context of at least four different HLA-DR molecules that together cover 5 0-60% of the Caucasian, Oriental, and Negroid populations. This HIV-1 rever se transcriptase-derived peptide (RT171-190) is highly conserved among diff erent HIV-1 isolates. Importantly, stimulation of PBL cultures from HIV-1 s eronegative donors with this peptide resulted in Th1-type lymphocytes capab le of efficient recognition of HIV-1-pulsed APCs, Taken together, these dat a indicate that peptide RT171-190 constitutes an attractive component of va ccines aiming at induction or enhancement of HIV-1-specific T cell immunity .