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

• Published in: Archives of virology 1977, Vol.55 (3), p.233-246
• Main Authors: Spring, S B, Maassab, H F, Kendal, A P, Murphy, B R, Chanock, R M
• Format: Article
• Language: English
• Subjects: Animals; Cold Temperature; Cricetinae; Culture Techniques; Genetic Complementation Test; Genetic Variation; Influenza A virus - genetics; Influenza A virus - growth & development; Influenza Vaccines; Lung - microbiology; Mutation; Phenotype; Recombination, Genetic; Turbinates - microbiology; Vaccines, Attenuated; Virus Replication
• ISSN: 0304-8608
• DOI: 10.1007/BF01319909

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.