Heme Acquisition in Group A Streptococcus

描述（申请人提供）：溶血性化脓性链球菌，俗称A群链球菌（GAS），是一种重要的人类病原体，可引起咽炎、蜂窝织炎、猩红热、坏死性膜炎、中毒性休克综合征、急性风湿热、风湿性心脏病、肾小球肾炎等。GAS感染的发病机制是由大量的毒力因子介导的，这使得GAS疾病的有效免疫治疗控制极其困难。许多细菌病原体的铁获取系统是关键的毒力因素。它们在毒力、保守的抗原性和表面暴露方面的作用使它们成为有吸引力的候选疫苗。GAS可以将铁从血红蛋白中分离出来，血红素被认为是体内GAS的主要铁来源。然而，我们对GAS中血红素获取的机制知之甚少。最近，我们发现了一种新的由GAS产生的血红素相关细胞表面蛋白（命名为Shp1）。shp 1基因与8个连续的下游基因共转录，包括spy1795、spy1794和spy1793，它们编码革兰氏阴性菌中参与铁摄取的ABC转运体组分的同源物。我的初步结果表明，假定的GAS转运体的脂蛋白成分（Spy1795，指定为Shp2）也与血红素结合。拟议的研究将调查sht位点（包含shp1和shp2）是否编码GAS中血红素获取机制，以及sht是否为GAS毒力所必需。我计划利用生化和遗传方法以及感染模型来确定血红素获得在GAS发病机制中的作用，以实现以下具体目标。

DESCRIPTION (provided by applicant): Hemolytic Streptococcus pyogenes, commonly referred as Group A Streptococcus (GAS), is an important human pathogen causing pharyngitis, cellulitis, scarlet fever, necrotizing fasciitis, toxic shock syndrome, acute rheumatic fever, rheumatic heart disease, and glomerulonephritis. The pathogenesis of GAS infection is mediated by an abundance of virulence factors which make effective immunotherapeutic control of GAS diseases extremely difficult. Iron acquisition systems of many bacterial pathogens are key virulence factors. Their role in virulence, conserved antigenicity, and surface exposure make them attractive vaccine candidates. GAS can sequester iron from hemoglobin and heme is thought to be the primary iron source for GAS in vivo. However, little is known about the machinery for heme acquisition in GAS. Recently, we identified a novel heme-associated cell-surface protein (designated Shp1) made by GAS. The shp 1 gene is co-transcribed with 8 contiguous downstream genes, including spy1795, spy1794, and spy1793 encoding homologues of the components of ABC transporters involved in iron uptake in Gramnegative bacteria. My preliminary results suggest that the lipoprotein component (Spy1795, designated Shp2) of the GAS putative transporter also binds heme. The proposed studies will investigate whether the sht locus (containing shp1 and shp2) encodes the machinery for heme acquisition in GAS and if sht is required for GAS virulence. I plan to achieve the following specific aims using biochemical and genetic approaches and infection models to define the role of heme acquisition in GAS pathogenesis. Aim 1. Determine whether recombinant Shp2 binds heme Aim 2. Elucidate if the sht locus encodes a transporter system for heme acquisition Aim 3. Investigate whether the disruption of shp1 and/or shp2 attenuates GAS virulence The study will advance our understanding of the mechanism of heme acquisition in GAS and may identify new potential GAS vaccine candidate(s).