A bile salt hydrolase of Brucella abortus contributes to the establishment of a successful infection through the oral route in mice

DELPINO, M. V.; MARCHESINI, M. I.; ESTEIN, S.; DIEGO JOSE COMERCI; CASSATARO, J.; FOSSATI, C. A.; BALDI, P. C.

INFECTION AND IMMUNITY

ASM Press

Año: 2007 vol. 75 p. 299 - 305

0019-9567

Choloylglycine hydrolase (CGH), a bile salt hydrolase, has been annotated in all the available genomes of Brucella species. We obtained the Brucella CGH in recombinant form and demonstrated in vitro its capacity to cleave glycocholate into glycine and cholate. B. abortus 2308 (wild-type) and its isogenic Äcgh deletion mutant exhibited a similar growth in trypticsoy broth in the absence of bile. In contrast, the growth of the Äcgh mutant was notably impaired by both 5% and 10% bile, and mean CFU/ml at 18 h of culture were five-fold and twelve-fold lower, respectively, than those of the wild-type strain. Bile resistance of the complemented mutant was similar to that of the wild-type strain. In mice infected through the intragastric route, splenic infection was significantly lower at 5, 10 and 15 days p.i. in animals infected with the Äcgh mutant than in those infected with the wild-type strain. Mice immunized intragastrically with recombinant CGH mixed with cholera toxin (CGH/CT)developed a specific mucosal humoral (IgG and IgA) and cellular (IL-2) immune response.Fifteen days after challenge by the same route with live B. abortus 2308, splenic CFU countswere ten-fold lower in mice immunized with CGH/CT than in mice immunized with CT orPBS. This study shows that CGH confers Brucella the ability to resist the antimicrobial actionof bile salts. The results also suggest that oral immunization with selected antigens mayprotect the host from orally-acquired Brucella infection.