SYSTEMATIC IDENTIFICATION OF H-2 K-D BINDING PEPTIDES AND INDUCTION OF PEPTIDE-SPECIFIC CTL

Most peptides with putative MHC I restricted sequence motifs do not bi nd to the corresponding MHC I nor induce cytolytic T cells. There exis t additional constraints which limit peptide binding and immunogenicit y. To identify immunogenic peptides in novel protein sequences, it wil l be necessary to first evaluate peptide binding to MHC I. In this stu dy, a soluble single chain fusion protein SC-K-d was used to evaluate potential K-d binding peptides from the sequences of mouse mammary tum or virus gag and env proteins. A total of 27 peptides were identified which displayed the reported K-d restricted motif. Of the 27 peptides, six demonstrated strong to moderate binding to SC-K-d. The strongest binding peptides expressed tyrosine or phenylalanine at position 2 and leucine at the C-terminus. The capability of MMTV peptides to induce CTL corresponds to their SC-K-d binding activity. Of the six peptides that demonstrated moderate to strong binding, five induced CTL in BALB /c mice. These peptides induced CTL after 1-3 in vivo immunizations fo llowed by 5 day in vitro stimulation. Furthermore, a single in vitro s timulation of naive lymphocytes with strong-binding G425 was sufficien t to induce significant CTL activity. Weak or non-binding peptides did not induce CTL. Therefore, peptide binding to SC-K-d is a predictive indicator of CTL inducing activity.