TABLE 2.

Infectivity and replication of A/Leningrad/134/17/57 parent virus, its rg counterparts, and H5N1 reassortants in mice

Virus	MID50a (log10 PFU)			Vaccine virus doseb (log10 PFU)	Mean virus titer atc:
					3 dpi			6 dpi
	Nasal turbinate	Lung	Total		Nasal turbinate	Lung	Braind	Nasal turbinate	Lung	Braind
caLen17	3.32	≥5.0	3.32	5.80	3.6 ± 0.1	1.0 ± 0.6	<0.6	2.8 ± 0.4	<0.6	<0.6
caLen17-rg	3.5	≥5.5	3.50	5.98	3.4 ± 0.2	2.0 ± 0.1	<0.6	2.5 ± 0.5	0.8 ± 0.5	<0.6
Len134	2.68	1.83	1.83	4.31	3.4 ± 1.1	5.1 ± 0.2	<0.6	1.6 ± 0.8	3.8 ± 0.2	<0.6
Len134-rg	3.37	2.62	2.62	5.10	3.8 ± 0.4	3.1 ± 0.2e	<0.6	1.2 ± 0.2	2.6 ± 0.5e	<0.6
caEG-Len17rg	2.17	≥5.0	2.17	4.65	2.7 ± 0.4	0.7 ± 0.2	<0.6	0.9 ± 0.2	<0.6	<0.6
caVN-Len17rg	2.37	3.37	2.37	4.85	3.4 ± 0.4	1.1 ± 0.3	<0.6	3.1 ± 0.9	0.7 ± 0.3	<0.6
VN-Len134rg	2.62	0.83	0.83	3.31	2.5 ± 1.8	5.1 ± 0.2	<0.6	0.6 ± 0.0	4.6 ± 0.3	<0.6

^aTo determine MID₅₀, groups of 5 mice were infected with 10¹ to 10⁵ PFU of each virus. Three days later, mice were euthanized and lung and nasal turbinates were collected and titrated by plaque assay in MDCK cells (limit of detection was 0.6 log₁₀ PFU/ml). MID₅₀ values were separately calculated based on virus detection in lung and nasal turbinates. Total MID₅₀ value was calculated based on virus detection in any organ of the mice.

^bInfectious virus dose (in log₁₀ PFU) used to inoculate groups of eight mice with the equivalent of 300 MID₅₀s of each virus in a volume of 50 μl per mouse.

^cNasal turbinates, lung, and brains were collected from four mice at 3 dpi and four mice at 6 dpi and titrated by plaque assay in MDCK cells. The virus titers are expressed as the mean log₁₀ PFU/ml ± standard deviation from four mice per group (limit of detection was 0.6 log₁₀). Tissues in which no virus was detected were given a value of 0.6 log₁₀ to calculate the mean titer.

^dNo virus was detected in the brain tissues of mice from any of the groups.

^eP < 0.05 compared to Len134 virus.