COTTER LAB

Erich is currently using his science skills in Boston, but when he was in the lab, he studied FIM and FHA. Bordetella fimbria (FIM) are generally considered to be adhesins despite a lack of supporting experimental evidence for Bordetella pertussis and evidence suggesting fimbria are unnecessary for adherence of Bordetella bronchiseptica to mammalian cell lines. Using B. bronchiseptica and mice, we developed an in vivo adherence assay using bronchoalveolar lavage to recover non-adherent bacteria from the lower respiratory tract one hours post-inoculation. This assay revealed that fimbria and filamentous hemagglutinin (FHA) both function as necessary adhesins and that they mediate adherence specifically to respiratory epithelium. Using a mouse model of bacterial persistence, we showed that FIM-deficient B. bronchiseptica induced a more robust inflammatory response than wild-type bacteria, suggesting that fimbria allow B. bronchiseptica to suppress the innate immune response to infection, similar to what we have previously shown for mice inoculated with FHA-deficient bacteria. To determine bacterial localization, we incubated lung sections with serum from a rabbit chronically infected with WT B. bronchiseptica and an anti-rabbit secondary antibody conjugated to alkaline phosphatase. These analyses indicated that fimbria are required for attachment to airway epithelium, as bacteria lacking fimbria localized to the alveoli, while FHA-deficient bacteria localized to airways. Bacteria unable to produce both fimbria and FHA localized to alveoli and also caused increased inflammation and histopathology identical to that caused by FIM-deficient bacteria, demonstrating that lack of fimbria is epistatic to lack of FHA. Co-inoculation experiments provided evidence that wild-type B. bronchisepticasuppresses inflammation locally within the respiratory tract and that both FHA and fimbria are required for defense against host-mediated clearance. Altogether, our data suggest that fimbria-mediated adherence to airway epithelium is a critical first step in Bordetella infection that allows FHA-dependent interactions to mediate tight adherence, suppression of inflammation and resistance to inflammatory cell clearance.