A five-residue HIV envelope helper T cell determinant: Does this peptide-MHC interaction leave the binding groove half empty?

Abstract

High-resolution structures have revealed major pockets in the MHC class II peptide binding groove within a region designated P1-P9. The region can accommodate 9-mer peptides, consistent with the observation that minimal core helper T (Th) cell determinants are usually eight or nine residues in size. Here we describe mouse Th cell hybridomas that are specific for a core peptide of only five residues (NPIIL) in the HIV envelope glycoprotein. Effective Th cell stimulation requires that these MHC class II Iab-presented peptides contain amino acids flanking the minimal pentamer, but the flanking residues may be located on either the N or C terminus. To explain these findings, we suggest that mini..