v-src oncogene-specific carboxy-terminal peptide is immunoprotective against Rous sarcoma growth in chickens with MHC class I allele B-F12.

B(12) haplotype of the inbred chicken line CB (B12/B12) contains, like the bulk of chicken MHC(B) haplotypes, only a single dominantly expressed class I molecule (B-F). The peptide binding motifs for this major B-F12 molecule in chickens of Rous sarcoma regressor line CB (B12/B12) have been determined. Using stringent and relaxed motifs, several peptides were found in the v-src molecule of the PR-RSV-C, but most of these peptides are identical with that of endogenous c-src. Only the v-src C-tail peptide(517-524) (LPACVLEV) contains critical anchor amino acids (valine at positions 5 and 8) and shows a sequence different from the corresponding c-src peptide. This v-src C-tail peptide up-regulates expression of the B-F12 class I molecule on PBL, as assessed by FACS analysis, and stimulates T cell proliferation in a [3H]thymidine uptake assay. A protective effect of the immune response to LPACVLEV against RSV challenge was demonstrated in CB (B12/B12) chickens immunised with peptides encapsulated in liposomes.