Comparative Studies of Wild-Type and 'Cold-Mutant' (Temperature Sensitive) Influenza Viruses: Genealogy of the Matrix (M) and Non-structural (NS) Proteins in Recombinant Cold-Adapted H3N2 Viruses

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Abstract
The matrix (M) protein of the H2N2 virus A/Ann Arbor/6/60 may be distinguished from M protein of several H3N2 viruses and A/New Jersey/76 (Hsw1N1) by SDS [sodium dodecyl sulfate] acrylamide gel electrophoresis using a discontinuous buffer system. The smallest RNA (RNA 8) of the A/Ann Arbor/6/60 virus may be distinguished from RNA 8 of several H3N2 viruses by acrylamide gel electrophoresis in 3% or 3.6% gels in the absence of urea, if electrophoresis is done at 30-35.degree. C or 20.degree. C, respectively. Ten clones of conditionally-lethal temperature-sensitive (ts) mutants were studied, which derived their cold-adaption and ts genes from mutant A/Ann Arbor/6/60, and their hemagglutinin from the H3N2 virus A/Scotland/840/74. Each clone derived its M protein from A/Ann Arbor/6/60 mutant, and its RNA 8 from A/Scotland/840/74. The only assignment of genes 7 and 8 consistent with these findings for the recombinants is that in each parent virus (and in the recombinants) gene 7 codes for M protein, and gene 8 for NS [non-structural] protein. The biologically important ts lesions in the A/Ann Arbor/6/60 mutant parent are apparently not present in the NS gene. Besides the recombinants of A/Ann Arbor/6/60 and A/Scotland/840/74, 5 independent ts/cold-adapted recombinants of A/Ann Arbor/6/60 mutant with H3N2 and HSW1N1 wild-type viruses were examined, and all contained the M protein of the A/Ann Arbor/6/60 mutant parent. Thus, the M protein may be at least partially responsible for the cold-adaptation and/or ts properties of the A/Ann Arbor/6/60 mutant and the recombinants.