Brucella Iron Metabolism in Host Macrophages

描述(由申请人提供)：长时间停留在宿主巨噬细胞的吞噬小室对布鲁氏菌的能力至关重要。制造疾病。在这种环境下，布鲁氏菌必须抵抗缺铁。流产杆菌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降解和清除受损细胞释放的血红蛋白和血红素中的中心作用，血红素可能是布鲁氏菌在宿主吞噬细胞内停留的重要铁源。两个基因位点(命名为bhuA和bhuTUV)被预测与利用血红素作为铁源有关，并且对一个bhuA突变体的初步鉴定表明，该血红素转运体在小鼠的毒力中起着关键作用。因此，本申请中概述的研究的具体目的是：a)确认我们指定为BUT、U和V的基因的产物与BobA一起在流产杆菌2308中形成功能上的血红素转运体；b)在小鼠模型中确定BhoA和BuTUV对B.bortus 2308的毒力的相对贡献；以及c)确定B.bortus 2308中bhuA和bhuTUV对铁和血红素的响应调节的性质。拟议的研究应该会增加我们对布鲁氏菌所使用的机制的基本了解。以及其他细胞内病原体，以满足其对宿主中铁的生理需求。他们还应该更好地确定血红素和含血红素的化合物作为这种环境中微生物病原体的铁源的重要性。此外，这些研究应该提供对布鲁氏菌用来预防铁中毒的调节机制的洞察，这可能不同于其他依赖铁摄取调节因子(Fur)活性的革兰氏阴性细菌所使用的调节机制。拟议的研究具有公共卫生相关性，因为它们可能提供适合作为新的活疫苗候选进行测试的减毒细菌菌株。虽然布鲁氏菌属。布鲁氏菌是重要的人畜共患病病原体和潜在的生物恐怖分子，目前还没有安全有效的疫苗来预防人类布鲁氏菌病，许多研究表明，目前活的减毒布鲁氏菌株为这种疫苗的开发提供了最大的希望。

DESCRIPTION (provided by applicant): 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 V work together with BhuA to form a functional heme transporter in B. abortus 2308; b) to determine the relative contributions of BhuA and BhuTUV to the virulence of B. 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.