Temperature-sensitive mutants of influenza virus: VI. Transfer of ts lesions from the Asian subtype of influenza a virus (H2N2) to the Hong Kong subtype (H3N2)

Temperature-sensitive genetic lesions were transferred from the ts-1 (H2N2) and ts-2 (H2N2) mutants of influenza A virus to wild-type influenza A (H3N2) virus by genetic reassortment. The ts-2 (H3N2) recombinants appeared to be homogeneous and did not undergo recombination with one another, suggesting that the original ts-2 mutant of influenza A (H2N2) contained a ts lesion(s) on only one RNA segment of its genome. In contrast the ts-1 (H3N2) recombinants fell into three phenotypic subsets which differed in degree of temperature sensitivity. Initially, the three subsets of ts-1 (H3N2) recombinants were thought to represent distinct complementation-recombination groups. However, complementation-recombination between the three subsets of ts-1 (H3N2) recombinants subsets was variable. Subsequent study indicated that mutants in each of the three subsets shared one ts lesion and two of the subsets shared an additional ts lesion. The mechanism whereby viruses of the three subsets which share one or two ts lesions, and nevertheless undergo apparent complementation-recombination on occasion is not understood.