Virulence factors involved in B. pertussis survival in intracellular niches

LAMBERTI YA; ALVAREZ HAYES J; RODRIGUEZ ME

Puerto Madryn

Congreso; XLVI Reunión Anual Sociedad Argentina de Investigación en Bioquímica y Biología Molecular; 2010

SAIB

Previous studies of our group have shown that B. pertussis(Bp), the etiologic agent of whooping cough, is able to survive and replicate inside human macrophages. The goal of this study was to gain a first insight into the virulence factors involved in Bp survival inside the immune cell. In this approach we investigated the ability of a virulent strain, avirulent mutants, and mutants deficient in specific virulence factors to enter and survive intracellularly in human macrophages in vitro. Confocal studies and Polymyxin B protection assays shown that among Bp virulence factors adenylate cyclase toxin (CyaA), previously described as involved in actin polimerization inhibition, is required to preclude Bp?containig vacuoles to undergo phagolysosome biogenesis which eventually leads to the bacterial survival within the first hours of infection. However, at longer times (48h of infection) neither CyaA nor other virulent factor seem relevant for bacterial suvival and duplication inside the macrophage. Accordingly, by comparing gene expression of infecting bacteria and bacteria that has been inside the macrophage for up to 48h using semi-quantitative RT-PCR we found that cyaA was downregulated in bacteria inside the cell suggesting that Bp modulates its expression once inside the macrophage. These results indicate that Bp undergoes an adaptative response to survive inside the cell.