Role of Pertussis Toxin in Bordetella pertussis infection

描述（由申请人提供）：百日咳博德泰拉是一种感染人类呼吸道的革兰氏阴性细菌病原体，导致严重的阵发性咳嗽疾病，即百日咳，对婴儿来说是致命的。这种病原体用来建立感染和致病的机制仍然相对模糊。此外，尽管已经在体外对几种假定的百日咳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百日咳毒素（PT）在百日咳引起的呼吸道感染中所起的作用。PT是一种仅由百日咳病原体产生的外毒素，可以使培养的多种哺乳动物细胞中毒，但其在百日咳感染中的作用在很大程度上是未知的。通过在小鼠鼻内感染模型中比较野生型菌株（WT）和编码PT基因缺失的突变株（deltaPT），我们初步获得了PT在百日咳B.百日咳在呼吸道定植中起重要早期作用的数据。与deltaPT感染相比，至少有三种不同的免疫反应（早期肺中性粒细胞募集，呼吸道早期细胞因子和趋化因子产生，血清抗体反应）对WT感染似乎受到抑制。因此，我们假设PT的一个重要作用是抑制百日咳的抗菌免疫反应，从而建立感染和随后的疾病发病机制。为了验证这一假设，我们提出了四个具体目标：(1)确定抑制中性粒细胞向肺募集的机制；(2)利用化学和基因改造的小鼠确定PT活性的相关靶点；(3)确定PT是否抑制百日咳感染后肺抗体和T细胞反应；(4)确定百日咳感染后PT免疫抑制是否会增加对继发感染的易感性。阐明PT在百日咳感染中的具体作用将增加我们对这种有机体致病机制的理解，并可能导致对抗百日咳感染和疾病的新治疗方法。

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.