COMPARISON OF THE PSPA SEQUENCE FROM STREPTOCOCCUS-PNEUMONIAE EF5668 TO THE PREVIOUSLY IDENTIFIED PSPA SEQUENCE FROM STRAIN RX1 AND ABILITYOF PSPA FROM EF5668 TO ELICIT PROTECTION AGAINST PNEUMOCOCCI OF DIFFERENT CAPSULAR TYPES

PspA (pneumococcal surface protein A) is a serologically varied virule nce factor of Streptococcus pneumoniae. In mite, PspA has been shown t o elicit an antibody response that protects against fatal challenge wi th encapsulated S. pneumoniae, and the protection-eliciting residues h ave been mapped to the alpha-helical N-terminal half of the protein. T o date, a published DNA sequence for pspA is available only for S. pne umoniae Rx1, a laboratory strain. PspA/EF5668 (EF5668 indicates the st rain of origin of the PspA) is serologically distinct from PspA/Rx1, S equencing of the gene encoding PspA/EF5668 revealed 71% identity with that of PspA/Rx1. The greatest amount of divergence between the two pr oteins was seen in their cu-helical portions, which are surface expose d and probably under selective pressure to diversify serologically. In spite of the diversity within the alpha-helical regions of PspAs, we have observed that recombinant PspA (rPspA)/EF5668, like rPspA/Rx1, ca n elicit cross-protection against pneumococci of different capsular an d PspA serological types.