Table 3. Antibody responses and protection of offspring when mothers were immunized via the IP route and their offspring via the IN route^a.

Mothers	Vaccine dosage for offspring (μg)	Ab titers in offspring (log2)b			Lung virus titers (log10 TCID50) b	Survival offspring/tested offspring
		Serum IgG Ab		sIgA Ab
		Prime	Boost	Boost
Immunized	0.1	11.33±0.58	10.00±0.00c,d	1.68±0.58	14.20±0.34c,d	0/9c
	1.0	11.75±0.50	14.33±0.58c,d	2.00±0.00	2.72±0.54c,d	9/9 d
	5.0	13.33±0.58	14.00±1.0c,d	2.67±0.58	2.67±0.34c,d	9/9d
	unimmunized	11.75±0.50	10.30±0.50	Undetected	13.83±0.44d	0/9
Unimmunized	0.1	13.50±0.58	15.00±0.82d	1.50±0.50	5.00±1.00d	9/9d
	1.0	13.75±0.50	17.33±0.58d	2.33±0.58	Undetectedd	9/9d
	5.0	15.75+0.50	19.33±0.58d	3.33±0.58	Undetectedd	9/9d
	unimmunized	<1	<1	<1	18.33±0.58	0/9

^a Female mice were immunized twice at a 3 week interval with the inactivated vaccine through the IP route. The offspring were immunized through the IN route at 1 and 4 weeks of age. One week after the booster, the offspring were challenged with a lethal dose (40 LD₅₀) of A/Chicken/Henan/12/2004 (H5N1). Serum samples were collected from the offspring 3 weeks after the primary immunization and 1 week after the booster, and nasal washes were collected 3 days after the challenge. Serum IgG and sIgA Ab titers were measured by ELISA. Lungs were removed from three mice in each group 3 days after challenge for virus titration by the standard MDCK assay. Survival rates of the mice were determined 3 weeks after the challenge.

^b Values represent the mean ± S.D. of each group.

^c Significant difference (p <0.05) compared with the same dosage group of offspring without MDAs.

^d Significant difference (p <0.05) compared with the negative control.