Result: Sequence analysis of the NS1 genes of 42 mouse-adapted clones identified two groups of variants MA20-B, -C and -D as well as MA-51, -52 and -53 (Table 1) that possessed the F103L and M106I mutations respectively and thus were convergent with highly pathogenic H5N1 IAV isolated from humans in Hong Kong in 1997 (A/Hong Kong/156/97-like viruses).

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Result: The NS1 mutants showed an increased extent of alveolar tissue infection with larger foci in the lungs that was more pronounced in the singl

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Result: The growth was also more persistent at 7 dpi with >2 logs increased lung titer due to the presence of F103L + M106I mutations (P < 0.05) (Figure 6b).

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