Pneumococcal conjugate vaccines overcome splenic dependency of antibody response to pneumococcal polysaccharides

Protection against infectious with Streptococcus pneumoniae depends on the presence of antibodies against capsular polysaccharides that facilitate pha gocytosis. Asplenic patients are at increased risk for pneumococcal infecti ons, since both phagocytosis and the initiation of the antibody response to polysaccharides take place in the spleen. Therefore, vaccination with pneu mococcal polysaccharide vaccines is recommended prior to splenectomy, which , as in the case of trauma, is not always feasible. We show that in rats, v accination with a pneumococcal conjugate vaccine can induce good antibody r esponses even after splenectomy, particularly after a second dose. The sple en remains necessary for a fast, primary response to (blood-borne) polysacc harides, even when they are presented in a conjugated form. Coadministratio n of a conjugate vaccine with additional nonconjugated polysaccharides of o ther serotypes did not improve the response to the nonconjugated polysaccha rides. We conclude that pneumococcal conjugate vaccines can be of value in protecting asplenic or hyposplenic patients against pneumococcal infections .