Role of Pertussis Toxin in Bordetella pertussis infection

描述(申请人提供)：百日咳杆菌是一种革兰氏阴性细菌病原体，可感染人类呼吸道，导致一种名为百日咳的严重阵发性咳嗽，可能会导致婴儿死亡。这种病原体用来建立感染和引起疾病的机制仍然相对不清楚。此外，尽管在体外已经对几种可能的百日咳杆菌毒力因子的结构和功能进行了广泛的表征，但这些因子在宿主-病原体相互作用中促进感染和疾病的作用尚不清楚。该项目的总体目标是确定其中一种因子百日咳毒素(PT)在百日咳杆菌呼吸道感染中所起的作用。百日咳杆菌是一种由百日咳杆菌产生的外毒素，可在培养的多种哺乳动物细胞中中毒，但其在百日咳杆菌感染中的作用在很大程度上尚不清楚。在小鼠鼻内感染模型中，通过比较野生型菌株(WT)和突变菌株(DeltaPT)编码PT基因的缺失，我们获得了PT在百日咳杆菌呼吸道定植中起重要和早期作用的初步数据。与感染deltaPT后相比，感染WT后至少有三种不同的免疫反应(肺部早期中性粒细胞募集、呼吸道早期细胞因子和趋化因子产生以及血清抗体反应)似乎受到抑制。因此，我们假设PT的一个重要作用是抑制百日咳杆菌的抗菌免疫反应，使感染与后续疾病的发病机制建立起来。为了验证这一假说，我们提出了四个具体目标：(1)确定抑制中性粒细胞向肺部募集的机制；(2)利用化学和遗传改变的小鼠确定PT活性的相关靶点；(3)确定PT是否抑制百日咳杆菌感染后的肺抗体和T细胞反应；以及(4)确定百日咳杆菌感染后PT的免疫抑制是否增加了继发感染的易感性。阐明PT在百日咳杆菌感染过程中的具体作用将有助于我们更好地了解百日咳杆菌的致病机制，并可能导致抗击百日咳感染和疾病的新的治疗方法。

DESCRIPTION (provided by applicant): Bordetella pertussis is a gram-negative bacterial pathogen that infects the human respiratory tract, leading to a severe paroxysmal coughing disease known as whooping cough that can be fatal in infants. The mechanisms that this pathogen employs to establish an infection and cause disease are still relatively obscure. In addition, although there has been extensive characterization in vitro of the structure and function of several putative B. pertussis virulence factors, the roles that these factors play in the host-pathogen interaction to promote infection and disease are poorly understood. The overall goal of this project is to determine the role that one of these factors, pertussis toxin (PT), plays in respiratory tract infection by B. pertussis. PT is an exotoxin produced exclusively by this pathogen and can intoxicate a wide range of mammalian cells in culture, but its role in B. pertussis infection is largely unknown. By comparing a wild type strain (WT) to a mutant strain (deltaPT) with a deletion of the genes encoding PT in a mouse intranasal infection model, we have preliminary data that PT plays an important and early role in colonization of the respiratory tract by B. pertussis. At least three different immune responses (early neutrophil recruitment to the lungs, early cytokine and chemokine production in the respiratory tract, and serum antibody responses) to infection with WT appear to be suppressed relative to those after infection with deltaPT. Therefore, we hypothesize that an important role of PT is to suppress the antibacterial immune responses to B. pertussis, allowing establishment of the infection with subsequent disease pathogenesis. To test this hypothesis we propose four specific aims: (1) to determine the mechanism of inhibition of neutrophil recruitment to the lungs; (2) to determine the relevant targets of PT activity using chemically- and genetically-altered mice; (3) to determine whether PT suppresses lung antibody and T cell responses after B. pertussis infection; and (4) to determine whether immunosuppression by PT after B. pertussis infection enhances susceptibility to secondary infections. Elucidation of the specific roles of PT during B. pertussis infection will increase our understanding of the pathogenic mechanisms of this organism, and may lead to novel therapeutic approaches to combat pertussis infection and disease.