Brucella Iron Metabolism in Host Macrophages

长时间滞留在宿主巨噬细胞的吞噬小体隔间是关键的能力 布鲁氏菌属制造疾病。在这种环境下，布鲁氏菌必须抵抗缺铁。胡麻B. 流产儿2308在体外可以利用血红素作为铁源。由于巨噬细胞在 红细胞的降解和从受损细胞释放的血红蛋白和血红素的清除， 在布鲁氏菌的胞内停留期间，血红素可能是布鲁氏菌的重要铁源 宿主吞噬细胞。两个遗传基因座(指定为bhuA和bhuTUV)，其产物被预测为 已经在流产杆菌2308中确定了参与利用血红素作为铁源的因素，并初步确定了 对一个流产杆菌bhuA突变体的鉴定表明，这种血红素转运蛋白在 小鼠的致命性。因此，本申请书中概述的研究的具体目的是a)确认 我们被指定为布特、U和V的基因的产物与布A一起工作形成 6.流产者2308中的功能性血红素转运体；b)确定Hb A和Hb A的相对贡献 在小鼠模型中对6.流产2308的毒力；以及c)定义铁的性质-和 BhuA和bhuTUV在流产杆菌2308中对血红素反应的调节。建议的研究应 增加我们对布鲁氏菌所用机制的基本了解。和其他细胞内 病原体满足其对寄主中铁的生理需求。他们还应该更好地界定 在这一环境中，作为微生物病原体铁源的血红素和含血红素化合物。 此外，这些研究应能深入了解布鲁氏菌的调控机制。 预防铁中毒，这可能不同于其他依赖于 铁摄取调节剂(Fur)的活性。拟议的研究具有公共卫生相关性，因为 他们可能会提供适合作为新的活疫苗候选进行测试的减毒菌株。虽然 布鲁氏菌属。是重要的人畜共患病病原体和潜在的生物恐怖主义病原体，目前没有 安全有效的疫苗预防人类布鲁氏菌病，许多研究表明，活的， 目前，减毒布鲁氏菌株为这种疫苗的开发提供了最大的希望。

Prolonged residence in the phagosomal compartment of host macrophages is critical to the ability of the Brucella spp. to produce disease. Within this environment, the brucellae must resist iron deprivation. B. abortus 2308 can utilize heme as an iron source in vitro. Due to the central role of macrophages in the degradation of erythrocytes and the scavenging of hemoglobin and heme released from damaged cells, heme may represent an important iron source for the brucellae during their intracellular residence in these host phagocytes. Two genetic loci (designated bhuA and bhuTUV) whose products are predicted to be involved in the utilization of heme as an iron source have been identified in B. abortus 2308 and preliminary characterization of a B. abortus bhuA mutant suggests that this heme transporter plays a critical role in virulence in mice. Consequently, the specific aims of the studies outlined in this application are a) to confirm that the products of the genes that we have designated as bhuT, U and Vwork together with BhuA to form a functional heme transporter in 6. abortus 2308; b) to determine the relative contributions of BhuA and BhuTUV to the virulence of 6. abortus 2308 in the mouse model; and c) to define the nature of the iron- and heme-responsive regulation of bhuA and bhuTUV in the B. abortus 2308. The proposed studies should increase our basic understanding of the mechanisms employed by the Brucella spp. and other intracellular pathogens to meet their physiologic need for iron in the host. They should also better define the importance of heme and heme-containing compounds as iron sources for microbial pathogens within this environment. In addition, these studies should provide insight into the regulatory mechanisms employed by the brucellae to prevent iron toxicity, which may be different from those used by other Gram-negative bacteria that rely on the activity of the ferric uptake regulator (Fur). The proposed studies have public health relevance because they may provide attenuated bacterial strains suitable for testing as novel, live vaccine candidates. Although the Brucella spp. are important zoonotic pathogens and potential bioterrorism agents, there is presently no safe and effective vaccine to prevent human brucellosis, and numerous studies have shown that live, attenuated Brucella strains presently offer the greatest promise for the development of such a vaccine.