Passive immunity for arbovirus infection: II. Quantitative aspects of naturally and artificially acquired protection in mice for Japanese (B) encephalitis virus

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  • 1 Department of Epidemiology and Microbiology, Graduate School of Public Health, University of Pittsburgh, Pittsburgh, Pennsylvania 15261
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In an effort to obtain quantitative data applicable to man which could not reasonably be obtained directly, a series of experiments was carried out in mice. Progeny mice, whose mothers were immunized with various combinations of live and inactivated Japanese encephalitis (JBE) virus vaccines, were resistant to intraperitoneal challenge with JBE virus, relative to control mice. The basis of protection appeared to be maternal antibody, which by indirect evidence was of the IgG class. Protection and serum antibody levels in the progeny declined as the mice increased in size and age. Protection was directly proportional to the level of neutralizing antibody. This relationship could be duplicated by inoculating normal weanling mice with immune serum from other vaccinated mother mice. The presence of naturally or artificially acquired maternal antibody in progeny, in addition to protecting them against JBE virus challenge, also reduced the amount of new antibody they synthesized following injection of JBE virus. The amount of the reduction was a function of neutralizing antibody concentration at the time of challenge. When maternal antibody was nearly depleted, the antibody response in JBE-challenged progeny of immune mothers approached that of progeny of non-immunized mothers. By the methods employed, no major reproducible sex differences were observed either in sensitivity to virus or antibody response. The applicability of these results to man is discussed