Molecular basis and intervention of Staphylococcus aureus agglutination

描述(申请人提供)：金黄色葡萄球菌，人类皮肤和鼻孔的共生菌，也是一种侵袭性病原体，经常导致皮肤和软组织感染、菌血症和败血症。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败血症患者的年存活率不到50%。金黄色葡萄球菌是已知的唯一一种凝结血浆并与血液中的纤维蛋白电缆凝集的细菌。我们在这里表明，这种凝集表型是基于三个基因(CoA、VWB、clfA)的分泌性产物以及几个非分泌性基因产物。我们提出了一个新的模型，其中金黄色葡萄球菌的凝集涉及葡萄凝血酶(CoA，vWBP)组装的纤维蛋白电缆的形成，这些电缆由聚集因子A(ClfA)覆盖在葡萄球菌表面，并由因子XIII交联。我们假设金黄色葡萄球菌凝集提供了逃避吞噬细胞杀死的途径。此外，vWBP介导的von Willebrand因子(VWF)的募集为内皮细胞提供了一条系绳，并支持细菌从血管系统出来，从而促进金黄色葡萄球菌传播到器官组织，在那里金黄色葡萄球菌作为细菌群落复制，受到免疫细胞的保护。这一关键的毒力策略可能会被单抗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。初步工作表明，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体(与凝血酶原、纤维蛋白原、纤维连接蛋白和凝血因子XIII)，专门用于形成交联的纤维蛋白电缆。葡萄球菌凝集涉及到功能性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介导的锚定在细菌细胞壁被膜(SrtA)之前修饰ClfA。除了遗传功能丧失的分析，我们还将通过在表皮葡萄球菌中表达基因来重建体外和体内的凝集作用，表皮葡萄球菌是一种条件致病菌，不能凝集或形成离散的脓肿病变。针对纯化的CoA、vWBP或ClfA的单抗和小分子抑制剂正被用于扰乱葡萄球菌的体外和体内凝集，并在金黄色葡萄球菌败血症的小鼠模型中进行保护或治疗试验。

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 that S. aureus agglutination provides for escape from phagocytic killing. Further, vWbp-mediated recruitment of von Willebrand Factor (vWF) provides a tether for endothelial cells and supports bacterial traffic out of the vasculature thereby promoting S. aureus dissemination to organ tissues 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 purifie 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.