Coutte Loic, Alonso Sylvie, Reveneau Nathalie, Willery Eve, Quatannens Brigitte, Locht Camille, Jacob-Dubuisson Francoise
INSERM U447, Institut National de Sante et la Recherche Medical Institut de Biologie de Lille, Institut Pasteur de Lille, 1 rue Calmette, 59019 Lille Cedex, France.
J Exp Med. 2003 Mar 17;197(6):735-42. doi: 10.1084/jem.20021153. Epub 2003 Mar 10.
Pathogen attachment is a crucial early step in mucosal infections. This step is mediated by important virulence factors called adhesins. To exert these functions, adhesins are typically surface-exposed, although, surprisingly, some are also released into the extracellular milieu, the relevance of which has previously not been studied. To address the role of adhesin release in pathogenesis, we used Bordetella pertussis as a model, since its major adhesin, filamentous hemagglutinin (FHA), partitions between the bacterial surface and the extracellular milieu. FHA release depends on its maturation by the specific B. pertussis protease SphB1. We constructed SphB1-deficient mutants and found that they were strongly affected in their ability to colonize the mouse respiratory tract, although they adhered even better to host cells in vitro than their wild-type parent strain. The defect in colonization could be overcome by prior nasal instillation of purified FHA or by coinfection with FHA-releasing B. pertussis strains, but not with SphB1-producing FHA-deficient strains, ruling out a nonspecific effect of SphB1. These results indicate that the release of FHA is important for colonization, as it may facilitate the dispersal of bacteria from microcolonies and the binding to new sites in the respiratory tract.
病原体附着是黏膜感染关键的早期步骤。这一步骤由称为黏附素的重要毒力因子介导。为发挥这些功能，黏附素通常暴露于表面，不过令人惊讶的是，有些黏附素也会释放到细胞外环境中，其相关性此前尚未得到研究。为了探讨黏附素释放在发病机制中的作用，我们以百日咳博德特氏菌为模型，因为其主要黏附素丝状血凝素（FHA）在细菌表面和细胞外环境之间分布。FHA的释放取决于百日咳博德特氏菌特异性蛋白酶SphB1对其的成熟作用。我们构建了SphB1缺陷型突变体，发现它们在定殖于小鼠呼吸道的能力上受到严重影响，尽管它们在体外比野生型亲本菌株更能有效地黏附宿主细胞。通过预先经鼻滴注纯化的FHA或与释放FHA的百日咳博德特氏菌菌株共感染可以克服定殖缺陷，但与产生SphB1的FHA缺陷型菌株共感染则不能，这排除了SphB1的非特异性作用。这些结果表明，FHA的释放对定殖很重要，因为它可能有助于细菌从微菌落中扩散并与呼吸道中的新位点结合。
