Role of novel choline binding proteins in virulence of Streptococcus pneumoniae

The choline binding proteins (CBPs) are a family of surface proteins noncov alently bound to the phosphorylcholine moiety of the cell wall of Streptoco ccus pneumoniae by a conserved choline binding domain. Six new members of t his family were identified, and these six plus two recently described cell wall hydrolases, LytB and LytC, were characterized for their roles in virul ence. CBP-deficient mutants were constructed and tested for adherence to eu karyotic cells, colonization of the rat nasopharynx, and ability to cause s epsis, Five CBP mutants, CbpD, CbpE, CbpG, LytB, and LytC, showed significa ntly reduced colonization of the nasopharynx. For CbpE and -G this was attr ibutable to a decreased ability to adhere to human cells. CbpG, a putative serine protease, also played a role in sepsis, the first observation of a p neumococcal virulence determinant strongly operative both on the mucosal su rface and in the bloodstream.