Homology, similarity, and identity in peptide epitope immunodefinition.
- Darja Kanduc
- Journal of peptide science : an official…
We have previously unravelled the striking SLWDQ pentapeptide identity between HIV-1 env gp120 and the CD4 molecule. We show here that this pentapeptide is required for the functioning of the co-stimulatory MHC-CD4 signal in T4-cell activation since it suppresses antigen-induced T-cell proliferation. Moreover, concerning the MHC class II counterpart, the LNGQEETGVVSTN sequence which strongly inhibits T-cell immune activation is likely to be part of the functional site of the molecule. Interestingly the MHC/gp120 homology described by Young overlaps this MHC region. We further report that the gp120 SLWDQ peptide triggers an immune reaction which is both humoral (anti-SLWDQ antibodies) and cellular (CTLs against autologous targets carrying the pentapeptide) in HIV-1 infected individuals. Finally, anti-SLWDQ antibodies from patients sera purified by column chromatography strongly inhibit antigen-induced immune T-cell activation. This result led us to postulate that these antibodies found in high titers in HIV-1 infected individuals could contribute to set up the progressive systemic immune T-cell suppression characterizing AIDS.