A 16-amino acid peptide of respiratory syncytial virus 1A protein contains two overlapping T cell-stimulating sites distinguishable by class II MHC restriction elements.

The 1A protein of respiratory syncytial (RS) virus is a small, 64-amino acid hydrophobic protein expressed in infected cells. We previously showed that the C-terminal domain of 1A contained a site for stimulation of RS virus-reactive Th lymphocytes in BALB/c and SJL/J mice. In this report we modeled a series of overlapping synthetic peptides of the 1A protein and we present evidence to suggest that the C-terminal domain of the 1A protein contains not one, but two, Th lymphocyte-stimulating sites. Although these sites are extensively overlapping they can be distinguished on the basis of presentation by distinct class II restriction elements of the murine MHC. Additionally, we present evidence to suggest that a 16-amino acid synthetic peptide which contains both of these T cell sites can stimulate T cell activity in mice of multiple different class II MHC haplotypes, perhaps representing a potential lead for designing a "universal" T cell stimulator.