IDENTIFICATION OF D-B-RESTRICTED AND K-B-RESTRICTED SUBDOMINANT CYTOTOXIC T-CELL RESPONSES IN LYMPHOCYTIC CHORIOMENINGITIS VIRUS-INFECTED MICE

Antiviral cytotoxic T-cells are critical for control of lymphoctytic c horiomeningitis virus (LCMV) infection in mice. In H-2(b) mice, the an tiviral response is directed against three D-b-restricted epitopes in the viral nucleoprotein (NP396-404) and glycoprotein (GP276-286 and GP 33-41). Our present data revealed a clear hierarchy among these three epitopes, in which NP396-404 is immunodominant, followed by GP33-41 an d GP276-286, respectively. In order to identify additional CTL epitope s in the LCMV nucleoprotein and glycoprotein, we used the motifs for D -b-and K-b-binding peptides, combined with MHC class I-binding assays. Out of 23 D-b motif-fitting peptides, we identified 4 D-b binders, on e of which (GP92-101) turned out to be a new CTL epitope. Among 28 K-b motif-fitting peptides, 12 bound K-b, and one of these (NP205-212) wa s a CTL epitope. Both newly identified CTL peptides were recognized by LCMV-immune splenocytes after secondary in vitro stimulation. Both pe ptides bound their MHC class I molecules with intermediate affinity (4 70 and 170 nM for GP92-101 and NP205-212, respectively). Responses aga inst these peptides were weaker than the responses against the three m ajor epitopes. None of the high affinity binders were new epitopes, su ggesting that high affinity binders are either immunodominant epiitope s or no epitopes at all. Thus, analysis of 51 K-b and D-b motif-fittin g peptides yielded 2 new, subdominant epitopes. Immunization of C57BL/ 6 mice with these peptides, or with vaccinia virus recombinants expres sing these epitopes as minigenes, protected against chronic LCMV infec tion, demonstrating that immunization with subdominant epitopes can co nfer protection against chronic viral infection. (C) 1998 Academic Pre ss.