GROWTH-CONTROL OF INFLUENZA-A VIRUS BY M1 PROTEIN - ANALYSIS OF TRANSFECTANT VIRUSES CARRYING THE CHIMERIC M-GENE

Analysis of fast-growing reassortants (AWM viruses) of influenza A vir us produced by mixed infection with a fast-growing WSN strain and a sl owly growing Aichi strain indicated that the M gene plays a role in th e regulation of virus growth rate at an early step of infection (J. Ya suda, T. Toyoda, M. Nakayama, and A. Ishihama, Arch. Virol. 133:283-29 4, 1993). To determine which of the two M gene products, M1 or M2, is responsible for the growth rate control, one recombinant WSN virus (CW A) clone possessing a chimeric M gene (WSN M1-Aichi M2) was generated by using an improved reverse genetics and transfection system. The rec ombinant CWA virus retained the phenotype of both large plaque formati on and early onset of virus growth. This indicates that the WSN M1 pro tein is responsible for rapid virus growth.