Effect of maternal antibodies on influenza virus-specific immune response elicited by inactivated virus and naked DNA

While vaccines are effective in adults, they are less successful in newborn s and infants. Neonatal unresponsiveness to vaccines could be owing to imma turity of lymphocytes and/or to inhibition by maternal antibodies. Unrespon siveness of newborn to vaccines can be overcame by genetic immunization. In the present study we investigated the effect of maternal antibodies on the anti-influenza virus protective response in progeny born to dams immunized with plasmid containing the hemagglutinin gene or UV-inactivated virus. Th e effect of maternal antibodies was studied in plasmid immunized F1 mice bo rn to BALB/c dams, previously immunized with virus or plasmid and crossed w ith C57BL/6 males, as well as in offspring born to BALB/c dams immunized wi th plasmid and then immunized with UV-inactivated WSN virus. We have found that the inhibition period of the anti-HA antibody response in offspring bo rn to dams immunized with DNA is shorter than that of offspring born to dam s immunized with virus. Furthermore, there is a persistent inhibitory effec t on B cells from offspring born to dams immunized with virus or injected w ith antiviral monoclonal antibodies (MoAb), after the decline of maternal a ntibody titers. The analysis of the haemagglutinin-specific clonotype react ivity pattern of offspring born to dams immunized with inactivated influenz a virus or with a plasmid showed that clonotypes producing antibodies speci fic for the immunizing virus strain were predominant in offspring born to d ams immunized with DNA compared to those born to dams immunized with virus. Maternal antibodies do not affect cell-mediated immunity. These findings m ight be used to design efficient vaccination schedules for newborns and inf ants.