Zhang Shizhen, Green Nicole M, Sitkiewicz Izabela, Lefebvre Rance B, Musser James M
Center for Molecular and Translational Human Infectious Diseases Research, The Methodist Hospital Research Institute, The Methodist Hospital, B154, 6565 Fannin St., Houston, TX 77030, USA.
Infect Immun. 2006 Jul;74(7):4200-13. doi: 10.1128/IAI.00493-06.
Group A Streptococcus (GAS) is a gram-positive human bacterial pathogen that causes infections ranging in severity from pharyngitis to life-threatening invasive disease, such as necrotizing fasciitis. Serotype M28 strains are consistently isolated from invasive infections, particularly puerperal sepsis, a severe infection that occurs during or after childbirth. We recently sequenced the genome of a serotype M28 GAS strain and discovered a novel 37.4-kb foreign genetic element designated region of difference 2 (RD2). RD2 is similar in gene content and organization to genomic islands found in group B streptococci (GBS), the major cause of neonatal infections. RD2 encodes seven proteins with conventional gram-positive secretion signal sequences, six of which have not been characterized. Herein, we report that one of these six proteins (M28_Spy1325; Spy1325) is a member of the antigen I/II family of cell surface-anchored molecules produced by oral streptococci. PCR and DNA sequence analysis found that Spy1325 is very well conserved in GAS strains of distinct M protein serotypes. As assessed by real-time TaqMan quantitative PCR, the Spy1325 gene was expressed in vitro, and Spy1325 protein was present in culture supernatants and on the GAS cell surface. Western immunoblotting and enzyme-linked immunosorbent assays indicated that Spy1325 was produced by GAS in infected mice and humans. Importantly, the immunization of mice with recombinant Spy1325 fragments conferred protection against GAS-mediated mortality. Similar to other antigen I/II proteins, recombinant Spy1325 bound purified human salivary agglutinin glycoprotein. Spy1325 may represent a shared virulence factor among GAS, GBS, and oral streptococci.
A 群链球菌（GAS）是一种革兰氏阳性人类细菌病原体，可引起从咽炎到危及生命的侵袭性疾病（如坏死性筋膜炎）等严重程度不等的感染。M28 血清型菌株一直从侵袭性感染中分离出来，尤其是产褥期败血症，这是一种在分娩期间或之后发生的严重感染。我们最近对一株 M28 血清型 GAS 菌株的基因组进行了测序，发现了一个新的 37.4 kb 外源遗传元件，命名为差异区域 2（RD2）。RD2 在基因含量和组织上与 B 群链球菌（GBS，新生儿感染的主要原因）中的基因组岛相似。RD2 编码七种具有传统革兰氏阳性分泌信号序列的蛋白质，其中六种尚未得到表征。在此，我们报告这六种蛋白质之一（M28_Spy1325；Spy1325）是口腔链球菌产生的细胞表面锚定分子抗原 I/II 家族的成员。PCR 和 DNA 序列分析发现 Spy1325 在不同 M 蛋白血清型的 GAS 菌株中非常保守。通过实时 TaqMan 定量 PCR 评估，Spy1325 基因在体外表达，Spy1325 蛋白存在于培养上清液和 GAS 细胞表面。Western 免疫印迹和酶联免疫吸附测定表明 Spy1325 由感染小鼠和人类的 GAS 产生。重要的是，用重组 Spy1325 片段免疫小鼠可提供针对 GAS 介导的死亡的保护。与其他抗原 I/II 蛋白类似，重组 Spy1325 结合纯化的人唾液凝集素糖蛋白。Spy1325 可能代表 GAS、GBS 和口腔链球菌之间共有的毒力因子。
