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P66 is a Borrelia burgdorferi surface protein with ?? integrin binding and channel forming activities. In this study, the role of P66 in mammalian and tick infection was examined. B.?burgdorferi?p66 strains were not infectious in wild-type, TLR2?/?- or MyD88?/?-deficient mice. Strains with p66 restored to the chromosome restored near wild-type infectivity, while complementation with p66 on a shuttle vector did not restore infectivity. ?p66 mutants are cleared quickly from the site of inoculation, but analyses of cytokine expression and cellular infiltrates at the site of inoculation did not reveal a specific mechanism of clearance. The defect in these mutants cannot be attributed to nutrient limitation or an inability to adapt to the host environment in vivo as ?p66 bacteria were able to survive as well as wild type in dialysis membrane chambers in the rat peritoneum. ?p66 bacteria were able to survive in ticks through the larva to nymph moult, but were non-infectious in mice when delivered by tick bite. Independent lines of evidence do not support any increased susceptibility of the ?p66 strains to factors in mammalian blood. This study is the first to define a B.?burgdorferi adhesin as essential for mammalian, but not tick infection.
© 2012 Blackwell Publishing Ltd.