H. ducreyi Pathogenesis (DltA, DsrA and variants)

杜克雷嗜血杆菌（Haemophilus ducreyi）是引起生殖器溃疡性疾病软下疳（chancroid）的病原体，在全球多个地区是一个重要的公共卫生问题。在非洲、亚洲和其他发展中国家，它是异性性传播艾滋病毒的一个重要辅助因素。控制软下疳，使用有效的疫苗，适当管理，可能会减少艾滋病毒的传播。我们建议研究的相互作用H。ducreyi与宿主细胞、细胞外基质组分（ECM）和血清蛋白的结合。对大多数病原微生物来说，附着于宿主细胞是感染过程中关键的第一步。附着后，抵抗正常人血清抗体和补体杀菌活性的能力是第二个重要的毒力因子。我的实验室已经鉴定出两种外膜蛋白，DsrA和DltA，它们对H. ducreyi。此外，DsrA和可能的DltA是H的重要配体。ducreyi附着于皮肤细胞和ECM。DsrA突变体在人类和动物感染模型中是无毒的，但尚不清楚这种无毒性是否是 因为不能附着或抵抗血清的杀菌作用。对DsrA和DltA的深入研究，包括了解它们在血清中的作用机制， 阻力我们将鉴定血清抗性、角质形成细胞和ECM附着所需的DsrA区域/残基以及表面暴露的DsrA区域/残基。将构建dsrA的突变体，其具有血清抗性但不能附着于角质形成细胞和/或宿主ECM。我们将确定这样的突变体在人类感染模型中是否具有感染性。本实验将阐明体外和体内附着研究的明显差异。DltA是一种在结构和功能上与蓖麻毒素β链相关的凝集素;两者都对含乳糖的糖蛋白具有特异性。DltA与蓖麻毒素的相似性表明，DltA与蓖麻毒素一样，是一种粘附素。我们将测试DltA介导与宿主细胞和ECM附着的能力。这些研究对于更好地理解软下疳的发病机制是重要的，并将在几个方面促进疫苗的开发。

Haemophilus ducreyi, the etiologic agent of the genital ulcer disease chancroid, is a significant public health problem in several regions worldwide. In Africa, Asia and other developing countries, it is an important co-factor for the heterosexual transmission of HIV. Control of chancroid, using an effective vaccine that is properly administered, would likely reduce HIV transmission. We propose studies on the interaction of H. ducreyi with host cells, extracellular matrix components (ECMs) and serum proteins. Attachment to host cells is a critical first step in the infectious process for most pathogenic microbes. After attachment, the ability to resist the bactericidal activity of normal human serum antibody and complement is a second important virulence factor. My lab has identified two outer membrane proteins, DsrA and DltA, that are critical for expression of serum resistance in H. ducreyi. Furthermore, DsrA and possibly DltA, are important ligands for H. ducreyi attchment to skin cells and ECMs. DsrA mutants are avirulent in human and animal models of infection, but it is not known whether this avirulence is due to the inability to attach or to resist the bactericidal action of serum. Detailed studies will be undertaken on DsrA and DltA, including understanding their mechanisms of serum resistance. We will identify regions/residues of DsrA that are required for serum resistance, keratinocyte and ECM attachment and those that are surface-exposed. Mutants of dsrA will be constructed which are serum resistant but are unable to attach to keratinoctyes and/or host ECMs. We will determine whether one such mutant is infectious in the humans model of infection. This experiment will clarify the apparent discrepancy of in vitro and in vivo attachment studies. DltA is a lectin structurally and functionally related to the ricin Beta chain; both are specfic for lactose containing glycoproteins. The similarity of DltA to ricin suggest that like ricin, DltA is an adhesin. We will test the ability of DltA to mediate attachment to host cells and ECMs. These studies are important for better understanding of chancroid pathogenesis and will facilitate vaccine development in several aspects.