Immunosuppression of the antibody response to respiratory syncytial virus (RSV) by pre-existing serum antibodies: partial prevention by topical infection of the respiratory tract with vaccinia virus-RSV recombinants.

Immunization strategies to prevent respiratory syncytial virus (RSV) disease will involve immunization of infants less than 2 months of age who possess maternally derived RSV antibodies. Vaccinia-RSV recombinant viruses are useful tools for defining parameters important in immunization against RSV and also are being considered as live virus vaccines for use in humans. Previous studies demonstrated that passively acquired RSV antibodies can suppress the immune response and the protective efficacy of vaccinia-RSV recombinants administered by the intradermal route. The present study demonstrates that the suppressive effects of passively acquired antibody on immunity induced by intradermally administered vaccinia-RSV recombinants in cotton rats can be partially overcome by administration of the recombinants by the intranasal route.