Conditional lethal mutants of rabbitpox virus: I. Isolation of host cell-dependent and temperature-dependent mutants

Growth of a cloned stock of rabbitpox virus in the presence of the mutagens 5-bromodeoxyuridine and 2-aminopurine resulted in a reduced yield of infectious virus. Temperature- and host-dependent mutants could be detected in these yields. Methods were devised for the large-scale isolation of both types of conditional lethal mutants and for enriching the yield of temperature-sensitive mutants by the use of the viral inhibitor isatin β-thiosemicarbazone.