Effects of active immunization with a pneumococcal surface protein (PspA) and of locally applied antibodies in experimental otitis media.

An experimental rat model for Streptococcus pneumoniae otitis media was used to investigate passive protection by anti-type 3 capsular antibodies and effects of immunization with pneumococcal surface protein A (PspA). Anti-type 3 antibodies instilled into the middle ear reduced purulent otitis media as compared to control animals (p = 0.015). Secondly, after immunization with PspA, the right middle ear was inoculated with S. pneumoniae type 6A in a dose calibrated to induce purulent otitis media. There was an anti-PspA antibody response in all rats immunized and a reduction in signs of purulent otitis media as compared to control animals (p = 0.026). Thus, purulent (acute) otitis media can be reduced by local application of antibodies in the middle ear and also by immunization with a non-type-specific pneumococcal protein, PspA.