Pertactin Is Required forBordetellaSpecies To Resist Neutrophil-Mediated Clearance

Abstract

Pertactin (PRN) is an autotransporter protein produced by all members of theBordetella bronchisepticacluster, which includesB. pertussis,B. parapertussis, andB. bronchiseptica. It is a primary component of acellular pertussis vaccines, and anti-PRN antibody titers correlate with protection.In vitrostudies have suggested that PRN functions as an adhesin and that an RGD motif located in the center of the passenger domain is important for this function. Two regions of PRN that contain sequence repeats (region 1 [R1] and R2) show polymorphisms among strains and have been implicated in vaccine-driven evolution. We investigated the role of PRN in pathogenesis usingB. bronchisepticaand natural-host animal models. A Δprnmutant did not differ from wild-typeB. bronchisepticain its ability to adhere to epithelial and macrophage-like cellsin vitroor to establish respiratory infection in rats but was cleared much faster than wild-type bacteria in a mouse lung inflammation model. Unlike wild-typeB. bronchiseptica, the Δprnmutant was unable to cause a lethal infection in SCID-Bg mice, but, like wild-type bacteria, it was lethal for neutropenic mice. These results suggest that PRN plays a critical role in allowingBordetellato resist neutrophil-mediated clearance. Mutants producing PRN proteins in which the RGD motif was replaced with RGE or in which R1 and R2 were deleted were indistinguishable from wild-type bacteria in all assays, suggesting that these sequences do not contribute to PRN function.