Identification of a cytotoxic T-cell epitope on the recombinant nucleocapsid proteins of rinderpest and Peste des petits ruminants viruses presented as assembled nucleocapsids

The nucleocapsid protein (N) of morbilliviruses is not only a major structu ral protein but also the most abundant protein made in infected cells. We o verexpressed the N proteins of Rinderpest virus and Paste des petits rumina nts virus in E. coil, which assemble into nucleocapsids in the absence of v iral RNA that resemble nucleocapsids made in the virus-infected cells. Empl oying these assembled structures resembling subviral particles, we studied the induction of both the antibody response and the cytotoxic T-lymphocyte (CTL) response in a murine model (BALB/c). A single dose of the purified re combinant nucleocapsids of both viruses in the absence of an adjuvant induc es a strong CTL response. The CTLs generated are antigen specific and cross -reactive with respect to each virus and, furthermore, this CTL response is MHC class I restricted. Based on the prediction for H-2(d)-restricted T-ce ll motifs we tested the lysis of transfected P815 (H-2(d)) cells expressing a nine amino acid potential CTL epitope, by splenic T cells in vitro resti mulated with bacterially expressed RPV or PPRV N proteins. We extended our study to the bovine system both to analyze the immunogenicity of these reco mbinant proteins in the natural hosts and to show that PBMC from cattle vac cinated with Rinderpest vaccine proliferate in vitro, in response to restim ulation with soluble nucleocapsid proteins. Furthermore, the murine CTL epi tope functions in the bovine system as a cytotoxic T-cell epitope. This seq uence, which is conserved in the N proteins of morbilliviruses, conforms we ll to the predicted algorithm for some of the most common BoLA CTL antigeni c peptides. (C) 2001 Academic Press.