Table 3.
Protection against a lethal influenza virus challenge in offspring immunized with DNA vaccine born to the mothers immunized with inactivated vaccinea
| Serum IgG titersb in offspring | |||||||
| Dose (μg) of Inactivated vaccine for female mice | Plasmid for offspring | ELISA (2n)c | NI assay (2n)c | Lung virus titersb (log10 TCID50) | Survival offspring/Tested offspring (3 weeks) | ||
| 21 days after primary immunization | 7 days after booster | 21 days after primary immunization | 7 days after booster | ||||
| 1.00 | 30 μg HA | 14.8 ± 0.50 | 13.3 ± 0.30 | 3.3 ± 0.35* | 3/6 | ||
| 0.10 | 30 μg HA | 11.7 ± 0.50 | 12.5 ± 0.60 | 3.8 ± 0.23* | 3/7 | ||
| 0.01 | 30 μg HA | 11.3 ± 0.60 | 13.0 ± 0.00 | 3.0 ± 0.71* | 6/7* | ||
| 1.00 | 30 μg NA | 4.3 ± 0.60 | 7.0 ± 1.00 | 1.9 ± 0.58* | 7/7* | ||
| 0.10 | 30 μg NA | 3.7 ± 0.60 | 7.2 ± 0.80 | 1.5 ± 0.24* | 7/7* | ||
| 0.01 | 30 μg NA | 4.3 ± 0.60 | 8.0 ± 1.00 | 0.9 ± 0.83* | 6/6* | ||
| Unimmunized | Unimmunized | <1 | <1 | <3 | <3 | 5.3 ± 0.35 | 0/7 |
a Female mice were immunized twice, 3 weeks apart, with various doses of inactivated vaccine. The offspring were immunized with 30 μg HA or 30 μg NA at ages of 1 and 4 weeks respectively. Serum samples from offspring were collected 3 weeks after primary immunization and 1 week after booster. The anti-HA antibody titers were measured by ELISA. The anti-NA antibody titers were measured by NI assay. 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)