Fig. 5

Genetic landscape of NA in PR8 and PR8^PB1(S216G) viruses. a After being reverse-genetically recovered, PR8 and PR8^PB1(S216G) viruses were synchronized at passage 5, and successively amplified during nine additional passages. Nucleotides 523–921 (amino acids 189–321) were deep-sequenced, and the NA mutations were plotted as mutation counts per million reads versus nucleotide position. Both viruses appeared to establish their own unique genetic landscapes after five serial passages, and yet no NA mutations associated with oseltamivir resistance were detected from either virus. b Identification of unique NA mutations in PR8 and PR8^PB1(S216G) at passage 5, as compared to their parental viruses at passage 1. In PR8, 16 unique mutations were identified at passage 5, whereas 11 unique mutations were detected in PR8^PB1(S216G) at passage 5