PHOSPHATASE AS A VIRULENCE FACTOR IN Q FEVER

贝氏柯克斯体是引起人类Q热的立克次体， 专性细胞内细菌。 偶尔，急性疾病是 其次是危及生命的慢性心内膜炎，但没有 持续有效的治疗。 这项研究的长期目标是 是发现生物化学/分子机制， 贝氏梭菌在吞噬细胞吞噬溶酶体中的存活 其他宿主细胞 初步研究显示， 具有显著的酸性磷酸酶活性， 负责抑制人类中性粒细胞的氧化爆发;这 表明该酶可能是一个主要的毒力决定因子。 磷酸酶已被证明发生在或接近表面的 利什曼原虫前鞭毛体和米氏军团菌， 与C burnetii有亲缘关系。 磷酸酶抑制 氧化爆发和伴随产生的有毒超氧阴离子， 吞噬人类嗜中性粒细胞;这可能占，在很大程度上， 这些寄生虫在吞噬细胞中的生存。 具体目标 拟议的研究是：（一）表征生物化学和 最近发现的周质贝氏疟原虫的生物物理特性 酸性磷酸酶;（ii）克隆和表征酸性磷酸酶基因 使用可用的基因库;（iii）检查酶对 人中性粒细胞 初步证据显示， 部分纯化的贝氏梭菌酸性磷酸酶抑制氧化 人中性粒细胞爆发;这将用纯化的 磷酸酶。 酶的作用位点和机制将是 研究了 无论磷酸酶是否从 寄生虫在感染过程中将被确定。 这些目标 将提供一种酶的基本信息， 在阻止宿主细胞的能力，以安装一个响应对 入侵和居住的寄生虫。 实现这些目标将导致 为了更好地了解寄生虫的能力， 宿主在入侵期间的防御和随后的生存， 在吞噬细胞和其他宿主细胞内增殖。 这样的知识 制定有效发展战略的关键 治疗/预防Q热的药物和疫苗，包括生命- 有心内膜炎的危险

Coxiella burnetii, the rickettsial agent of Q fever in humans, is an obligate intracellular bacterium. Occasionally, acute disease is followed by life-threatening chronic endocarditis for which there is no consistently effective treatment. The long-term goal of this research is to discover the biochemical/molecular mechanisms that account for survival of C burnetii in the phagolysosomes of phagocytic cells and other host cells. Preliminary studies have revealed that the organism possesses significant acid phosphatase activity and that it may be responsible for inhibiting the oxidative burst in human neutrophils; this indicates that the enzyme may be a major virulence determinant. Phosphatases have been shown to occur at or near the surface of Leishmania promastigotes and Legionella micdadei, a bacterium that is phylogenetically related to C burnetii. The phosphatases inhibit the oxidative burst and concomitant production of toxic superoxide anion by phagocytosing human neutrophils; this probably accounts, in large part, for the survival of these parasites within phagocytes. The specific aims of the proposed research are to: (i) characterize the biochemical and biophysical properties of the recently discovered periplasmic C burnetii acid phosphatase; (ii) clone and characterize the acid phosphatase gene using available gene banks; (iii) examine the effect of the enzyme on human neutrophils. Preliminary evidence strongly indicates that partially purified C burnetii acid phosphatase inhibits the oxidative burst of human neutrophils; this will be verified with purified phosphatase. The site and mechanism of action of the enzyme will be investigated. Whether or not the phosphatase is released from the parasite during the infection process will be determined. These aims will provide basic information about an enzyme which may play a key role in blocking the host cell's capacity to mount a response against the invading and resident parasites. Attainment of these goals will result in a better understanding of the parasite's capacity to circumvent the host's defenses during invasion of and subsequent survival and proliferation within phagocytes and other host cells. Such knowledge is essential for devising strategies for the development of efficacious drugs and vaccines for treating/preventing Q fever, including life- threatening endocarditis.