Cross-protection among pneumococcal serotypes within serogroups was measured in the chinchilla otitis media (OM) model because several serotypes that cause OM in children are closely related biochemically. Chinchillas were given tetravalent vaccine composed of pneumococcal capsular polysaccharides (PS; types 6B, 14, 19F, 23F) conjugated to an outer membrane protein complex, and 89% to 96% developed a ≥2-fold serum IgG rise against vaccine PS. Vaccine efficacy was tested by inoculating middle ear hypotympanic bullae with Streptococcus pneumoniae types 6B, 6A, 19F, or 19A. OM severity in the vaccinated groups challenged with types 6B, 6A, and 19F but not 19A was significantly better than in the respective placebo groups. Culture-positive pneumococcal OM occurred in 38%, 62%, 0, and 78% of vaccinated chinchillas challenged with types 6B, 6A, 19F, and 19A, respectively, but in 88% of type 6B- and 100% of type 6A-, 19A-, and 19F-challenged placebo chinchillas.
Bibliographical noteFunding Information:
Received 10 April 1995; revised 8 September 1995. Presented in part: Second Extraordinary International Symposium of Recent Advances in Otitis Media, Oita, Japan, 31 March to 3 April 1993; Association for Research in Otolaryngology, St. Petersburg, Florida, 5-9 February 1995. The use of laboratory animals in this research conformed with University of Minnesota Regents' Policies and Procedures for Animal Care and Usage, US Public Health Service Policy on Humane Care and Use of Laboratory Animals, and the Animal Welfare Act (public law 89-144 as amended). Animals received food and water ad libitum under the care of University of Minnesota Research Animal Resources staff. Grant support: Merck Research Laboratories. Reprints or correspondence: Dr. G. Scott Giebink, Box 296 UMHC, 420 Delaware St. SE, Minneapolis, MN 55455.