Quality and kinetics of the antibody response in mice after three different low-dose influenza virus vaccination strategies

Abstract

The threat of a new influenza pandemic has led to renewed interest in dose-sparing vaccination strategies such as intradermal immunization and the use of adjuvanted vaccines. In this study we compared the quality and kinetics of the serum antibody response elicited in mice after one or two immunizations with a split influenza A (H3N2) virus, using three different low-dose vaccination strategies. The mice were divided into four groups, receiving either a low-dose vaccine (3 microg hemagglutinin [HA]) intradermally or intramuscularly with or without aluminum adjuvant or the normal human vaccine dose (15 microg HA) intramuscularly. Sera were collected weekly after vaccination and tested in the hemagglutination inhibition, virus neutralization, and enzyme-linked immunosorbent assays. The antibody responses induced after intradermal or intramuscular low-dose vaccinations were similar and lower than those observed after the human vaccine dose. However, low-dose adjuvanted vaccine elicited a serum antibody response comparable to that elicited by the human dose, although the second immunization did not result in any increase in cross-reactive hemagglutination inhibition antibodies, and the peak serum antibody response was observed 1 week later than in the other vaccination groups. Our murine data suggest that the low-dose intradermal route does not show any obvious advantage over the low-dose intramuscular route in inducing a serum antibody response and that none of the low-dose vaccination strategies is as effective as intramuscular vaccination with the normal human dose. However, the low-dose aluminum-adjuvanted vaccine could present a feasible alternative in case of limited vaccine supply.

FIG. 1.

The kinetics of the HI antibody response induced after vaccination with A/Panama/2007/99 (H3N2) vaccine. The HI titers are presented as the geometric mean titers (GMT) from mice vaccinated i.d. with 3 μg HA (blue), i.m. with 3 μg HA (yellow), i.m. with 3 μg HA adjuvanted with 60 μg aluminum hydroxide (red), or i.m. with 15 μg HA (green). The number of animals in each group is shown in Table 1.

FIG. 2.

VN antibody titers elicited after vaccination with A/Panama/2007/99 (H3N2) vaccine. VN titers 3 weeks after the first (open bars) and second (filled bars) vaccinations are presented as mean titers ± standard errors of the means for all the vaccination groups (22 to 24 mice in each group after the first dose and 12 mice in each group after the second vaccination). An asterisk indicates a statistically significant difference (P ≤ 0.05) between the indicated paired groups.

FIG. 3.

Cross-reactive HI antibody titers induced after vaccination with A/Panama/2007/99 (H3N2) vaccine. Cross-reactive HI titers against the A/Sydney/05/97 (H3N2) and the A/New York/155/04 (H3N2) strains were measured in sera from all sacrificed mice (10 to 12 mice in each group) 3 weeks after the first (open bars) and second (filled bars) vaccinations. The HI titers against the vaccine strain A/Panama/2007/99 (H3N2) are also presented for reference purposes (22 to 24 mice in each group after the first dose and 12 mice in each group after the second vaccination). Results are presented as geometric mean titers (GMT), and the error bars represent the 95% confidence intervals. An asterisk indicates a statistically significant difference (P ≤ 0.05) between the indicated paired groups for the homologous A/Panama vaccine strain.