Molecular basis and intervention of Staphylococcus aureus agglutination

描述（由申请人提供）：金黄色葡萄球菌是人体皮肤和鼻腔的共生菌，也是一种侵袭性病原体，是皮肤和软组织感染、菌血症和败血症的常见原因。许多临床分离株对常用抗生素具有耐药性，这些菌株统称为耐甲氧西林金黄色葡萄球菌（MRSA）。MRSA脓毒症患者的年生存率低于50%。金黄色葡萄球菌是已知的唯一能使血浆凝固并与血液中的纤维蛋白电缆凝集的细菌病原体。我们在这里表明，这种凝集表型是基于三个基因（coa, vwb, clfA）的分泌产物以及几个非分泌基因产物。我们提出了一种新的模型，其中金黄色葡萄球菌凝集涉及葡萄凝血酶（Coa, vWbp）组装的纤维蛋白电缆的形成，该纤维蛋白电缆由葡萄球菌表面的聚集因子a （ClfA）覆盖，并由因子XIII交联。我们进一步假设，金黄色葡萄球菌凝集提供逃避吞噬细胞的杀伤，并促进离散脓肿病变的形成，在那里葡萄球菌作为一个细菌群落复制，保护免疫细胞。这种关键的毒力策略可能被单克隆抗体和小分子抑制剂干扰，以预防或治疗金黄色葡萄球菌败血症。初步研究表明，金黄色葡萄球菌Coa和vWbp分别与宿主凝血酶原结合，在人血浆中形成多蛋白复合物（与凝血酶原、纤维蛋白原、纤维连接蛋白和因子XIII），致力于形成交联的纤维蛋白电缆。葡萄球菌凝集涉及功能性ClfA的表面展示，这需要几个基因产物[aggABCD，（葡萄球菌凝集基因）]，这些基因产物似乎在排序酶a介导的细菌细胞壁包膜锚定（srtA）之前修饰ClfA。除了基因功能丧失分析，我们还会

DESCRIPTION (provided by applicant): Staphylococcus aureus, a commensal of the human skin and nares, is also an invasive pathogen and frequent cause of skin and soft tissue infections, bacteremia and sepsis. Many clinical isolates are resistant against commonly used antibiotics and these strains are collectively referred to as methicillin-resistant S. aureus (MRSA). The annual survival rate of patients with MRSA sepsis is less than 50%. S. aureus is the only bacterial pathogen known to coagulate plasma and to agglutinate with fibrin cables in blood. We show here that this agglutination phenotype is based on the secreted products from three genes (coa, vwb, clfA) as well as several non-secreted gene products. We propose a new model whereby S. aureus agglutination involves the formation of staphylothrombin (Coa, vWbp)-assembled fibrin cables, which are capped by clumping factor A (ClfA) on the staphylococcal surface and crosslinked by factor XIII. We hypothesize further that S. aureus agglutination provides for escape from phagocytic killing and promotes the formation of discrete abscess lesions, where staphylococci replicate as a bacterial community, protected from immune cells. This key virulence strategy may be perturbed with monoclonal antibodies and small molecule inhibitors to either prevent or treat S. aureus sepsis. Preliminary work demonstrated that S. aureus Coa and vWbp each associate with host prothrombin to form multi-protein complexes in human plasma (with prothrombin, fibrinogen, fibronectin and factor XIII) dedicated to the formation of cross-linked fibrin cables. Staphylococcal agglutination involves the surface display of functional ClfA, which requires several gene products [aggABCD, (staphylococcal agglutination genes)] that appear to modify ClfA prior to sortase A-mediated anchoring in the bacterial cell wall envelope (srtA). In addition to genetic loss-of-function analysis, we will also reconstitute agglutination in vitro from purified components and in vivo by expressing genes in Staphylococcus epidermidis, an opportunistic pathogen that cannot agglutinate or form discrete abscess lesions. Monoclonal antibodies (mAbs) -isolated against purified Coa, vWbp or ClfA- and small molecule inhibitors are being used to perturb staphylococcal agglutination in vitro and in vivo and examined for the provision of protection or therapy in a mouse model of S. aureus sepsis.