IDENTIFICATION OF MENGO-VIRUS T-HELPER CELL EPITOPES

To identify Mengo virus-specific T cell epitopes in mice (the natural host for the virus), lymph node cells were obtained from BALB/c (H-2(d )) mice, previously immunized with u.v.-inactivated virus, and stimula ted in vitro with each of 116 overlapping peptides (10 to 18 residues long) covering the entire capsid coding region (834 amino acids). T ce ll epitopes were defined on the basis of specific peptide-induced lymp hocyte proliferation. Where proliferation occurred, immunological char acterization showed that it was the CD4(+) T helper (T,) cell subpopul ation that was responsible for the Mengo virus-specific response. Surp risingly, no Mengo virus T-h cell epitopes were found in capsid protei n VP1 or VP4. Six peptides in VP2 (residues 1 to 15, 99 to 108, 118 to 132, 133 to 147, 227 to 236 and 247 to 256) identified the positions of separate T-h cell epitopes, and two overlapping peptides (residues 173 to 182 and 178 to 192) defined an additional T-h cell immunogenic sequence. Three individual peptides in VP3 (residues 46 to 58, 136 to 150 and 198 to 212) and two overlapping peptides (residues 1 to 15 and 11 to 20) also represent T-h cell epitopes. Similar assays with C57BL /6 (M-2(b)) and SJL/J (H-2(s)) mice showed that the pattern of recogni tion of these peptides was H-2 restricted. Each of the previously iden tified sites of B cell antigenicity in VP2 and VP3 are associated with one T-h epitope. Comparison of the experimentally determined T-h epit opes with potential T cell epitopes identified by several predictive s trategies revealed only a low correlation between authentic and predic ted epitopes.