Cold adapted variants of influenza A. II. Comparison of the genetic and biological properties of ts mutants and recombinants of the cold adapted A/AA/6/60 strain.
The genetic and biological properties of 13 recombinant influenza A clones derived at 25 degrees C from the A/AA/6/60-cold variant (by crosses with 4 different wild type strains) were compared with a set of 5-FU induced ts-mutants. The 5-FU mutants had previously been placed into 7 complementation-recombination groups; the A/AA/6/60-cold parent (PI-7) and the 12 cold recombinant clones which were ts were shown to share a lesion with only one of these groups. The parental strain and 5 recombinant clones were evaluated for replication in the lungs and nasal turbinates of hamsters. Each virus appeared to be attenuated; genetic stability correlated with the level of viral replication in the hamster lung, i.e., viruses which grew best showed a tendency to revert to the ts+ phenotype. Characterization of the ts+ revertants for the presence of the cold adaptation property revealed that these viruses exhibited a spectrum of cold adaptation properties. Two viruses, PI-7 (the parental cold variant) and the CR6 recombinant (A/Queensland/6/72) did not revert in either the lungs or nasal turbinates of hamsters.
D000818:Animals; D003080:Cold Temperature; D006224:Cricetinae; D046508:Culture Techniques; D005816:Genetic Complementation Test; D014644:Genetic Variation; D009980:Influenza A virus / Q000235:genetics* / Q000254:growth & development; D007252:Influenza Vaccines; D008168:Lung / Q000382:microbiology; D009154:Mutation; D010641:Phenotype; D011995:Recombination, Genetic; D014420:Turbinates / Q000382:microbiology; D014613:Vaccines, Attenuated; D014779:Virus Replication
D007252:Influenza Vaccines; D014613:Vaccines, Attenuated