The new temperature-sensitive mutation PA-F35S for developing recombinant avian live attenuated H5N1 influenza vaccine

Table 1 Pathogenicity and growth property of recombinant viruses in chickens and mice

Viruses	IVPI	Virus replication in chickens^#(log₁₀EID₅₀/ml ± SE)						MLD₅₀ (log₁₀EID₅₀ /50 μl)	Virus replication in mice^&(log₁₀EID₅₀/ml ± SE)
		Day 3			Day 5
		Trachea	Cloacal	Lungs	Trachea	Cloacal	Lungs		Day 3	Day 6
C4/W1	0.8	4/4* (3.9 ± 0.4)	4/4 (2.4 ± 0.5)	4/4 (3.5 ± 0.2)	4/4 (5.4 ± 0.2)	3/4 (3.3 ± 0.3)	4/4 (4.7 ± 0.6)	6.5	3/3* (4.6 ± 0.2)	3/3 (3.3 ± 0.3)
ts-C4/W1	0	0/4	0/4	0/4	0/4	0/4	0/4	>8.0	2/3 (1.6 ± 0.1)	0/3
C4/W1-PA(F35S)	0	4/4 (1.8 ± 0.3)	0/4	0/4	0/4	0/4	0/4	>8.0	3/3 (3.4 ± 0.3)	2/3 (2.5 ± 0.1)

Note: IVPI, intravenous pathogenicity index; MLD₅₀, 50% mouse lethal dose; EID₅₀, 50% egg infectious dose; SE, standard errors.
^# Groups of chickens were inoculated intranasally with 0.2 ml 10⁶ EID₅₀ of the indicated viruses. At 3 and 5 days post-inoculation, viral titers in tracheal swabs, cloacal swabs and lungs were determined by testing their EID₅₀ at 37°C, values are the means ± standard errors.
^&Groups of mice were inoculated intranasally with 50 μl 10⁶ EID₅₀ of the indicated viruses. At 3 and 6 days post-inoculation, viral titers in lungs were determined by testing their EID₅₀ at 37°C, values are the means ± standard errors.
^* NO. of chickens or mice with detectable virus/total chickens or mice used.