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Regulatory effects of matrix protein variations on influenza virus growth
J Yasuda1, T Toyoda, M Nakayama
1Department of Molecular Genetics, National Institute of Genetics, Shizuoka, Japan.
Abstract:
Influenza virus A/WSN/33 forms large plaques (> 3 mm diameter) on MDCK cells whereas A/Aichi/2/68 forms only small plaques (< 1 mm diameter). Fast growing reassortants (AWM), isolated by mixed infection of MDCK cells with these two virus strains in the presence of anti-WSN antibodies, all carried the M gene from WSN. On MDCK cells, these reassortants produced progeny viruses as rapidly as did WSN, and the virus yield was as high as Aichi. The fast-growing reassortants overcame the growth inhibitory effect of lignins. Pulse-labeling experiments at various times after virus infection showed that the reassortant AWM started to synthesize viral proteins earlier than Aichi. Taken together, we conclude that upon infecting MDCK cells, the reassortant viruses advance rapidly into the growth cycle, thereby leading to an elevated level of progeny viruses in the early period of infection. Possible mechanisms of the M gene involvement in the determination of virus growth rate are discussed, in connection with multiple functions of the M proteins.
Insights
Influenza virus reassortants with the M gene from A/WSN/33 showed faster replication and higher progeny yields in MDCK cells. This M gene segment is crucial for rapid viral growth cycle advancement and overcoming growth inhibition.
Area of Science:
- Virology
- Molecular Biology
Background:
- Influenza A virus strains exhibit distinct plaque morphologies and growth characteristics on Madin-Darby Canine Kidney (MDCK) cells.
- A/WSN/33 forms large plaques, while A/Aichi/2/68 forms small plaques.
Purpose of the Study:
- To investigate the genetic basis for differential growth rates and plaque sizes of influenza A virus strains.
- To identify the gene segment responsible for rapid viral replication and high progeny yield.
Main Methods:
- Isolation of reassortant influenza viruses (AWM) from mixed infections of MDCK cells with A/WSN/33 and A/Aichi/2/68 strains.
- Characterization of reassortant growth kinetics, viral protein synthesis, and plaque formation on MDCK cells.
- Analysis of gene content in fast-growing reassortants.
Main Results:
- All fast-growing reassortants (AWM) possessed the M gene segment from the A/WSN/33 strain.
- Reassortant AWM exhibited rapid progeny virus production and high virus yields, comparable to A/WSN/33 and A/Aichi/2/68 respectively.
- Reassortant AWM initiated viral protein synthesis earlier than A/Aichi/2/68, indicating accelerated entry into the viral growth cycle.
- Fast-growing reassortants demonstrated the ability to overcome growth inhibitory effects of lignins.
Conclusions:
- The M gene segment of influenza A virus plays a critical role in determining viral growth rate and replication efficiency in MDCK cells.
- The M gene influences the speed of entry into the viral growth cycle, leading to increased early-stage progeny virus production.
- The M protein's multiple functions may contribute to its role in regulating influenza virus growth rate.