PavB is a surface-exposed adhesin of Streptococcus pneumoniae contributing to nasopharyngeal colonization and airways infections

Summary The genomic analysis of Streptococcus pneumoniae strains identified the Pneumococcal adherence and virulence factor B (PavB), whose repetitive sequences, designated Streptococcal Surface REpeats (SSURE), interact with human fibronectin. Here, we showed the gene in all tested pneumococci and identified that the observed differences in the molecular mass of PavB rely on the number of repeats, ranging from five to nine SSURE. PavB inter- acted with fibronectin and plasminogen in a dose- dependent manner as shown by using various SSURE peptides. In addition, we identified PavB as coloniza- tion factor. Mice infected intranasally with DpavB pneumococci showed significantly increased sur- vival times compared with wild-type bacteria. Impor- tantly, the pavB-mutant showed a delay in transmigration to the lungs as observed in real-time using bioluminescent pneumococci and decreased colonization rates in a nasopharyngeal carriage model. In co-infection experiments the wild-type out- competed the pavB-mutant and infections of epithe- lial cells demonstrated that PavB contributes to adherence to host cell. Blocking experiments sug- gested a function of PavB as adhesin, which was confirmed by direct binding of SSURE peptides to host cells. Finally, PavB may represent a new vaccine candidate as SSURE peptides reacted with human sera. Taken together, PavB is a surface-exposed adhesin, which contributes to pneumococcal coloni- zation and infections of the respiratory airways.