PROTECTIVE IMMUNITY IN MACAQUES VACCINATED WITH LIVE ATTENUATED, RECOMBINANT, AND SUBUNIT MEASLES-VACCINES IN THE PRESENCE OF PASSIVELY ACQUIRED ANTIBODIES

The presence of maternal antibodies is one of the main causes of measl es vaccine failure. To evaluate the interference of passively acquired antibodies with vaccine efficacy, macaques (n = 16) were vaccinated w ith live attenuated measles vaccine in the presence or absence of pass ively acquired measles virus-specific monkey serum antibodies. As litt le as 0.1 IU of virus-neutralizing antibody/mL of serum abrogated the induction of specific serum IgM, IgG, and virus-neutralizing antibodie s. This effect was also demonstrated in monkeys vaccinated with live r ecombinant vaccinia virus expressing the hemagglutinin and fusion prot eins of measles virus but not in monkeys vaccinated with the same prot eins incorporated into immune-stimulating complexes. All of the monkey s vaccinated in the presence of virus-neutralizing antibodies (n = 9) were still largely protected from intratracheal challenge with wild ty pe virus. This protection is probably mediated by the observed specifi c T lymphocyte responses.