Improved Brucella Vaccine Strains

o -多糖是布鲁氏菌的主要免疫原和主要毒力决定因素。在缺乏o -多糖的情况下，经典的布鲁氏菌不会引起疾病，并能迅速从宿主体内清除。来自体外模型系统的数据似乎不那么具有决定性。尽管大多数证据表明粗糙突变体对巨噬细胞杀微生物杀灭机制保持抗性，但一些结果表明，相当大的复制能力可能被对早期杀伤机制的敏感性增加所掩盖。然而，也有报道称细胞毒性细胞死亡（CCD）是由“噬细胞”特异性的粗糙突变体感染引起的。CCD伴有肿瘤坏死因子（TNFa）和一氧化氮（NO）水平的升高，巨噬细胞的检查显示，暴露于粗糙生物的巨噬细胞中核因子κ B （nf - κ B）的核募集，这些细胞留在被光滑生物感染的细胞的细胞质中。越来越多的人认为，布鲁氏菌与宿主细胞之间的相互作用可能部分由布鲁氏菌表面的脂多糖（LPS）控制或改变。

O-polysaccharide is both the dominant immunogen and a major virulence determinant of Brucella spp. In the absence of O-polysaccharide classical Brucella species do not cause disease, and are rapidly cleared from :he host. Data from in vitro model systems appears less decisive. Although most evidence suggests rough mutants retain resistance to macrophage microbicidal killing mechanisms, some results suggest considerable replicative ability that may be masked by increased sensitivity to early killing mechanisms. However, there are also reports of cytotoxic cell death (CCD) induced by infection with rough mutants that is specific for "nacrophages. CCD is accompanied by elevated levels of tumor necrosis factor (TNFa), and nitric oxide (NO) and examination of macrophages revealed nuclear recruitment of nuclear factor kappa B (NF-kappaB) in macrophages exposed to rough organisms that remained in the cytoplasm of cells infected with smooth organisms. There is an increasing consensus that interaction between Brucella and the host cell may be in part controlled or altered by lipopolysaccharide (LPS) on the surface of Brucella. Our long-range goal is to identify the genes required for intracellular survival of Brucella. The objectives of !his application are to determine the contribution of O-polysaccharide in establishing a successful infection through its interaction with macrophages. Our central hypothesis is that O-polysaccharide is an essential element in the interaction between Brucella and host macrophages and enhances survival by evading or altering the innate immune response. The rationale for the proposed research is that understanding the interactions between smooth organisms and the host cell to elicit proper uptake and survival will enhance understanding of the mechanisms resulting in persistence and disease and provide information for the development of improved vaccines or treatments to enhance clearance of infections. We are particularly well prepared to study this interaction because we have established a Brucella mefitensis mutant bank and in vitro and in vivo models of infection and have the capacity to examine Brucella macrophage interaction at the cellular level and in animals models of infection using molecular, genomic and bioinformatic approaches.