Vaccination with hemagglutinin or neuraminidase DNA protects BALB/c mice against influenza virus infection in presence of maternal antibody

Table 1 Influence of maternal antibodies on protective effect of offspring immunized with the same inactivated vaccine as their mothers^a

Dose (μg)		Serum IgG titers^b in offspring ELISA (2ⁿ)^c		Lung virus titers^b (log₁₀ TCID₅₀)	Survival offspring/Tested offspring (3 weeks)
Female mice	Offspring	21 days after primary immunization	7 days after booster
1.00	1.00	14.8 ± 0.50	13.3 ± 0.30	3.7±0.00	0/7
0.10	0.10	13.8 ± 0.90	11.5 ± 0.60	4.7 ± 0.23	0/7
0.01	0.01	9.7 ± 0.60	11.3 ± 0.50	4.8 ± 0.71	0/7
Unimmunized	1.00	14.3 ± 0.60	16.7 ± 0.60	ND*	7/7*
Unimmunized	0.10	12.7 ± 0.60	16.0 ± 1.00	3.4 ± 0.54*	6/6*
Unimmunized	0.01	11.3 ± 0.50	13.0 ± 0.00	3.4 ± 0.54*	5/6*
Unimmunized	Unimmunized	<1	<1	5.4 ± 0.10	0/7

^a The female mice were immunized twice, 3 weeks apart, with various doses of inactivated vaccine. The offspring were immunized at ages of 1 and 4 weeks, respectively, with the same vaccine as their mothers. Serum samples from offspring were collected 3 weeks after primary immunization and 1 week after booster. The serum antibody titers were measured by ELISA. One week after booster, the offspring were challenged with a lethal dose of A/PR/8/34 (20 × LD₅₀). Lungs were taken out from at least three mice in each group 3 days after challenge for virus titration by standard MDCK assay. Survival rates of mice were measured 3 weeks after challenge.
^b Values represent mean ± S.D. of each group.
^c The serum samples were diluted 2-fold serially and "n" represents the dilution factor.
* Significant difference (p < 0.05). ND: virus not detected

ISSN: 1471-2334