Amino acid substitutions involved in the adaptation of a novel highly pathogenic H5N2 avian influenza virus in mice

Table 2 Viral titer of wild-type and mouse-adapted H5N2 avian influenza viruses in tissue

Virus	Days post-infection	Virus titers in organs of mice (log10 EID₅₀/mL) no. virus-positive mice/no. tested mice (mean titer ± SD)
Virus	Days post-infection	Lung	Spleen	Kidney	Liver	Brain	Heart
Wild-type virus (WT-6DK19)	3	3/3(4.0 ± 0)	1/3(2.0 ± 0)	1/3(2.0 ± 0)	3/3(1.5 ± 0.5)	2/3(2.5 ± 0.5)	3/3(1.5 ± 0.5)
	6	3/3(4.5 ± 0.5)	2/3(2.0 ± 0.0)	3/3(2.0 ± 0)	2/3(2.0 ± 0)	3/3(1.5 ± 0.5)	3/3(2.0 ± 0)
	9	3/3(3.5 ± 0)	2/3(2.0 ± 0.0)	0/3	2/3(1.0 ± 0)	3/3(1.5 ± 0.5)	3/3(2.0 ± 0)
Mouse-adapted virus (MA-6DK19)	3	3/3(5.5 ± 0.5)	3/3(2.5 ± 0.5)	3/3(3.0 ± 0)	3/3(2.5 ± 0.5)	3/3(2.5 ± 0.5)	3/3(3.0 ± 0)
	6	ND	ND	ND	ND	ND	ND
	9	ND	ND	ND	ND	ND	ND

Fifteen (15) mice/group were inoculated intranasally with 10^6.0 EID₅₀ of either the wild-type (WT-6DK19) or mouse-adapted (MA-6DK19) viruses in a 50 μL volume. Three mice per group were sacrificed at 3, 6, or 9 dpi and the lung, brain, heart, kidney, spleen, and liver tissues were collected. The viral titer in each tissue was determined in embryonated chicken eggs by the Reed and Muench method. Values represent mean ± SD. ND: Not determined. None of mice infected with MA-6DK19 survived past 5 dpi

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