Correlation of amino acid residues in the M1 and M2 proteins of influenza virus with high yielding properties.

The ability of influenza A viruses to replicate to high titer in the allantoic sac of the chicken embryo has been mapped to the matrix protein gene (RNA 7). Because influenza A/WSN/33 (H1N1) virus grows poorly in this host but contains a matrix protein gene with a sequence similar to sequences from viruses that grow well in eggs, we derived a single gene reassortant containing only the M gene from A/WSN/33 (H1N1) in a background of the other 7 RNA segments from A/Philippines/2/82 (H3N2) (a low yielding virus, hy-). This reassortant replicated 10 times better than the A/WSN parent itself, indicating that the high yielding (hy+) phenotype of the A/WSN/33 M gene may be suppressed by one of the other genes of A/WSN/33. Comparison of M gene sequences between hy+ (including A/WSN/33) and hy- strains allowed us to correlate specific amino acid positions in M1 and M2 proteins with the growth properties of influenza viruses.