Intranasal Immunization of Mice to Avoid Interference of Maternal Antibody against H5N1 Infection

Maternally-derived antibodies (MDAs) can protect offspring against influenza virus infection but may also inhibit active immune responses. To overcome MDA-mediated inhibition, active immunization of offspring with an inactivated H5N1 whole-virion vaccine under the influence of MDAs was explored in mice. Female mice were vaccinated twice via the intraperitoneal (IP) or intranasal (IN) route with the vaccine prior to mating. One week after birth, the offspring were immunized twice via the IP or IN route with the same vaccine and then challenged with a lethal dose of a highly homologous virus strain. The results showed that, no matter which immunization route (IP or IN) was used for mothers, the presence of MDAs severely interfered with the active immune response of the offspring when the offspring were immunized via the IP route. Only via the IN immunization route did the offspring overcome the MDA interference. These results suggest that intranasal immunization could be a suitable inoculation route for offspring to overcome MDA interference in the defense against highly pathogenic H5N1 virus infection. This study may provide references for human and animal vaccination to overcome MDA-induced inhibition.