Temperature-sensitive mutants of influenza A virus. XI. Transfer of ts lesions in the Hong Kong/68-ts-1 [a] virus to the influenza A/Udorn/72 wild type.

The presence of the temperature-sensitive (ts) lesions of complementation-recombination groups 1 and 5 in the Hong Kong/68-ts-1[A] virus was confirmed by genetic analysis of ts recombinants of the Hong Kong/68-ts-1[A] virus and a Udorn/72 wild-type virus. Three classes of Udorn/72-ts recombinants were found. One class possessed both ts genes of the Hong Kong/68-ts-1[A] parent, a second class possessed the ts lesion characteristic of group 1, and a third class possessed the ts lesion of group 5. The Hong Kong/68-ts-1[A] parent and the Udorn/72-ts recombinants exhibited a 10,000-fold or greater restriction of replication in the lungs of hamsters than did the homologous wild-type virus. All isolates from the lungs and nasal turbinates of recipients of two of the four Udorn/72-ts-1[A] recombinants contained only ts virus. These two properties, restricted replication and genetic stability after replication in vivo, suggest that the Udorn/72-ts-1[A] recombinants should be considered for evaluation as vaccines for use in humans.