RNA recombination of coronavirus.

We have previously shown that Mouse hepatitis virus (MHV) can undergo RNA-RNA recombination at a very high frequency (S. Makino, et al., J. Virol. 57, 729-737, 1986). To better define the mechanism of RNA recombination, we have performed additional crosses involving different MHV strains. We have obtained recombinant viruses with multiple cross-overs. The isolation of such recombinants further indicates the high frequency of coronavirus RNA recombination. By using cell fusion as a selection marker, we have also obtained recombinants between MHV-2 and A59 strains. Some of these recombinants have cross-overs in the 3'-end genes of the genome, thus demonstrating that recombination could occur along the entire genome. Finally, we have obtained recombinants by selecting with neutralizing monoclonal antibodies. These recombinants have cross-overs within gene C which encodes the peplomer protein. The genetic structure of these recombinants allowed us to determine the important domains of the peplomer proteins.