Dysregulation of M segment gene expression contributes to influenza A virus host restriction
Fig 3
pH1N1 influenza A virus M segment confers efficient replication and transmission of PR8-based virus among guinea pigs.
Groups of four guinea pigs were inoculated with 10 PFU of each avian M-encoding virus or NL09 M-encoding virus, as indicated. (A) Virus replication in nasal wash was measured by plaque titration at days 2, 4, 6, and 8 post-infection and the area under the curve was calculated. Graphs show mean AUC with SD for three experiments. All avian M-encoding viruses exhibited lower levels of growth in vivo than the isogenic virus possessing the NL09 M segment. The replication differences between avian M and NL09 M-based viruses were statistically significant, whereas those among avian M-based viruses were not. Statistical significance was evaluated using an unpaired, two-tailed Student’s t-test. (B) To assess transmission, each inoculated guinea pig was treated as an independent biological sample. The pH1N1 M segment conferred efficient transmission to naïve animals that were contact exposed (7/9 transmissions; 78%). In contrast, significantly poorer (12%), or no transmission was observed from guinea pigs infected with PR8 avian M viruses to naïve cage mates. Statistical significance of transmission differences were evaluated using an unpaired, two-tailed Student’s t-test.