CHARACTERIZATION OF THE L(D)-RESTRICTED CYTOTOXIC T-LYMPHOCYTE EPITOPE IN THE MOUSE HEPATITIS-VIRUS NUCLEOCAPSID PROTEIN

The mouse hepatitis virus (MHV) JHM strain (JHMV) produces primary dem yelination in the central nervous system associated with acute encepha lomyelitis. Humoral and cellular immune responses both participate in controlling the development of chronic MHV-induced demyelination. A su bset of the CD8+ cytotoxic T lymphocytes (CTL) induced by immunization of BALB/c (H-2d) mice with JHMV is specific for the viral nucleocapsi d protein. This CTL population recognizes an epitope located within th e carboxy-terminal 149 amino acids in association with the L(d) class I molecule (S. A. Stohlman, S. Kyuwa, M. Cohen, C. Bergmann, J. P. Pol o, J. Yeh, R. Anthony, and J. G. Keck, Virology 189:217-224, 1992). Us ing a panel of vaccinia virus recombinants expressing truncated forms of the nucleocapsid protein and a series of overlapping synthetic pept ides, we mapped the response to 15 amino acids. This sequence, encompa ssing the MHV epitope, contains the L(d)-specific binding motif. The p redicted 9-mer peptide (residues 318 to 326: APTAGAFFF) was sufficient and highly active in sensitizing target cells for CTL recognition whe n either added exogenously or synthesized intracellularly. Cross-react ivity of JHMV nucleocapsid protein-specific CTL with six other MHV str ains indicated that natural sequence variations within the 9-mer epito pe are tolerated in positions 4 and 5, whereas all other amino acids a re conserved. These data define a novel 9-mer L(d)-restricted CTL epit ope which represents the first MHV CTL epitope. Characterization of th is epitope provides a molecular basis to study the role of nucleocapsi d protein-specific CTL in the clearance of JHMV from the central nervo us system.