Successful vaccine-induced seroconversion by single-dose immunization in the presence of measles virus-specific maternal antibodies

In humans, maternal antibodies inhibit successful immunization against meas les, because they interfere with vaccine-induced seroconversion, We have in vestigated this problem using the cotton rat model (Sigmodon hispidus). As in humans, passively transferred antibodies inhibit the induction of measle s virus (MV)-neutralizing antibodies and protection after immunization with MV, In contrast, a recombinant vesicular stomatitis virus (VSV) expressing the MV hemagglutinin (VSV-H) induces high titers of neutralizing antibodie s to MV in the presence of MV-specific antibodies. The induction of neutral izing antibodies increased with increasing virus dose, and all doses gave g ood protection from subsequent challenge with MV. Induction of antibodies b y VSV-H was observed in the presence of passively transferred human or cott on rat antibodies, which were used as the models of maternal antibodies. Be cause RN hemagglutinin is not a functional part of the VSV-H envelope, MV-s pecific antibodies only slightly inhibit VSV-R replication in vitro. This d issociation of function and antigenicity is probably key to the induction o f a neutralizing antibody in the presence of a maternal antibody.