THE FLAVIVIRUS NONSTRUCTURAL PROTEIN NS3 IS A DOMINANT SOURCE OF CYTOTOXIC T-CELL PEPTIDE DETERMINANTS

Vaccinia virus recombinants encoding regions of the Murray Valley ence phalitis virus (MVE) genome, which together cover the entire viral cod ing region, were employed to identify the MVE protein which is the dom inant source of CD8(+), cytotoxic, T cell antigenic determinant(s) pre sented by the mouse H-2K(k) major histocompatibility antigen. MVE and West Nile virus-immune, H-2(k)-restricted, effector cells recognized p eptides derived from the MVE nonstructural polyprotein segment, and in this region the immunodominant determinant mapped to protein NS3. Int erestingly, mapping of cytotoxic T cell antigenic determinants of othe r flaviviruses also identified the NS3 protein as the dominant source of antigenic peptides (A. B. Hill, A. Mullbacher, C. Parrish, G. Coia, E. G. Westaway, and R. V. Blanden, 1999, J. Gen. Virol. 73, 1115-1123 ; A. L. Rothman, I. Kurane, C.-J. Lai, M. Bray, a. Falgout, R. Men, an d F. A Ennis, 1993, J. Virol. 67, 801-806). Using an allele-specific p eptide motif for H-2K(k), we predicted 12 peptides in the MVE NS3 prot ein as ligands for the restriction element and identified three peptid es which were recognized in association with H-2K(k) by MVE-immune cyt otoxic T cells. We also examined the effect of proteolytic processing in the MVE nonstructural polyprotein segment mediated by the viral pro teinase NS3 on antigen processing and presentation of the MVE H-2K(k)- restricted T cell determinant. Processing of the MVE polyprotein by th e viral proteinase did not markedly influence the availability of this peptide determinant. (C) 1994 Academic Press, Inc