OPTIMAL LYMPHOCYTIC CHORIOMENINGITIS VIRUS SEQUENCES RESTRICTED BY H-2D(B) MAJOR HISTOCOMPATIBILITY COMPLEX CLASS-I MOLECULES AND PRESENTEDTO CYTOTOXIC T-LYMPHOCYTES

Infection with lymphocytic choriomeningitis virus induces the generati on of CD8(+) cytotoxic T lymphocytes (CTL). In the H-2(b) mouse, this cellular immune response is directed against three viral structural ep itopes (GP1, GP2, and NP) presented by the major histocompatibility co mplex (MHC) class I H-2D(b) molecules. This study was undertaken to de lineate which sequence of each of these three epitopes is optimal for MHC binding and CTL recognition. The first step was to synthesize the relevant peptides truncated at the N or C terminus and flanking the cr ucial H-2D(b)-anchoring Asn residue in position 5. These peptides were then tested (i) for their binding properties in two H-2D(b)-specific assays with viable cells (upregulation of H-2D(b) expression on the su rface of RMA-S cells and competition against the D-b-restricted peptid e I-125-gp276-286 on T2-D-b cells) and (ii) for their abilities to sen sitize H-2(b) target cells for CTL lysis in vitro. For optimal antigen ic presentation, all three epitopes required the MHC-anchoring Asn res idue at position 5 of their sequences. The results clearly and unambig uously delineated optimal lengths for two of the epitopes and two opti ons for the third. NP appeared as a conventional 9-amino-acid (aa)-lon g peptide, np396-404 (FQPQNGQFI). GP2 was defined as a longer peptide (11 aa), gp276-286 (SGVENPGGYCL). Characterization of the GPI epitope was more complex: the 9-aa-long peptide gp33-41 (KAVYNFATC) and the ca rboxyl-extended 11-aa-long peptide gp33-43 (KAVYNFATCGI) were both est ablished as possible optimal sequences depending on the cell line used to test binding and lysis.