RNA recombination of coronaviruses: localization of neutralizing epitopes and neuropathogenic determinants on the carboxyl terminus of peplomers.

Murine coronaviruses undergo RNA recombination at a very high frequency. We have obtained a series of recombinant viruses using neutralizing monoclonal antibodies in conjunction with temperature-sensitive markers. All of the recombinants obtained have a crossover within gene C, which encodes the peplomer protein of the virus. The genetic structure of these recombinants suggests that the antigenic regions recognized by these neutralizing monoclonal antibodies are localized on the carboxyl-terminal one-third of the peplomer protein. Since the two monoclonal antibodies used are also associated with the critical determinants of virus neuropathogenicity, we conclude that both the neutralizing antibody binding sites and determinants of pathogenicity are localized at the carboxyl-terminal one-third of the peplomer. The variation of crossover sites in different recombinant viruses also allowed precise mapping of additional antigenic sites. RNA recombination thus presents a powerful genetic tool, and the carboxyl-terminal localization of the biological functions of peplomers suggests a distinct conformation of these viral membrane proteins.