PSPA, A PROTECTION-ELICITING PNEUMOCOCCAL PROTEIN - IMMUNOGENICITY OFISOLATED NATIVE PSPA IN MICE

PspA is a surface exposed virulence factor of S. pneumoniae that can e licit protective immunity to pneumococcal sepsis in mice. It can be re leased from pneumococci by washing them with a solution containing 2% choline chloride, by growing pneumococci in media containing 1.2% chol ine chloride, or by growing pneumococci in media in which the choline has been replaced by ethanolamine. Our results indicate that PspA is t he major protection-eliciting antigen in each of these preparations. T wo injections of less than or equal to 1 mu g of native PspA purified by use of a choline-Sepharose column are highly immunogenic in BALB/c and CBA/N mice, and even in the absence of adjuvant can elicit protect ion against otherwise fatal sepsis with 100 times the LD(50) of S. pne umoniae. Fragments comprising the N-terminal 115 and 245 amino acids o f PspA were able to elicit protection but only in the presence of comp lete Freund's adjuvant (CFA). In the absence of CFA the 245 amino acid fragment was less than 1/100 as immunogenic as native PspA. Copyright (C) Elsevier Science Ltd.