Recombination between snowhoe hare and La Crosse bunyaviruses.

We have previously reported heterologous genetic recombination resulting from crosses involving temperature-sensitive (ts) mutants of La Crosse (LAC) group II and snowshoe hare (SSH) group I ts mutants (J. Gentsch, L. R. Wynne, J. P. Clewley, R. E. Shope, and D. H. L. Bishop, J. Virol. 24:893-902, 1977). From those crosses two reassortant viruses having the large/medium/small viral RNA segment genotypes of SSH/LAC/SSH and SSH/LAC/LAC were obtained. In this study it has been found that the reciprocal cross (SSH group II x LAC group I ts mutants) has not yielded the expected LAC/SSH/SSH or LAC/SSH/LAC reassortant viruses. The backcross of a SSH/LAC/SSH group II ts mutant with a LAC group I ts mutant has produced a new reassortant virus, LAC/LAC/SSH, whereas the backcross of SSH/LAC/LAC group I ts mutants with SSH group II ts mutants gave another reassortant, SSH/SSH/LAC. Backcross analyses of LAC/LAC/SSH group I ts mutants with Group II ts mutants of SSH have not yielded the expected LAC/SSH/SSH reassortant virus, nor have backcrosses of SSH/SSH/LAC group II ts mutants with group I ts mutants of LAC virus yielded the expected LAC/SSH/LAC reassortant. Possible reasons why certain reassortant viruses are not produced are discussed. A procedure to screen SSH-LAC reassortant viruses which differ in their virion N polypeptides is described.