Secretory antibody response to respiratory syncytial virus infection.

The secretory antibody response to primary and secondary infection with respiratory syncytial virus (RSV) in Igg, IgM and 11S IgA immunoglobulin classes was determined using an indirect immunofluorescence antibody technique. Nasopharyngeal secretions were collected after naturally acquired primary or secondary infection with RSV. Immunoglobulin A responses to RSV were significantly greater in infants older than 6 months of age at the time of infection than in younger infants. Reinfection with RSV resulted in enhanced antibody production in all three immunoglobulin classes, and virus-specific antibody persisted for longer periods after secondary infection. Repeated immunizations with live RSV vaccine may be necessary for the development of immunity to severe illness.