Anti-Autolysin Passive Immunity for MRSA Osteomyelitis

描述（由申请人提供）：最近，耐甲氧西林金黄色葡萄球菌（MRSA）已经超过HIV成为美国最致命的病原体，每年造成超过10万人死亡。在骨科，MRSA骨髓炎（OM）已成为患者护理中最关心的问题，尽管手术技术的改进和积极的抗生素预防已经将大多数手术的感染率降低到不到1-5%。为了更好地了解OM建立过程中的病原体-宿主相互作用，开发新的干预措施和有效的诊断方法，我们开发了一种新的植入物相关OM的小鼠模型，其中不锈钢针涂覆金黄色葡萄球菌并经皮通过胫骨干骺端植入。这导致在第9天发生高度可复制的骨溶解感染，三周内骨折，与临床外固定钉周围的OM非常相似。此外，我们还建立了实时定量pcr （RTQ-PCR）来测定感染骨组织中nuc基因的拷贝数，精确到~100拷贝；以及体内生物发光成像，纵向定量细菌负荷。我们利用该模型克隆了自溶素的氨基葡萄糖酶亚基作为免疫优势抗原，并证明了其作为活疫苗的潜力。然而，由于这种疫苗的目标人群是免疫功能低下或老年患者，Codevax LLC已经开始开发一种被动免疫，可以在手术前给予高风险患者。

DESCRIPTION (provided by applicant): Recently methicillin resistant Staphylococcus aureus (MRSA) has surpased HIV as the most deadly pathogen in the United States, accounting for over 100,000 deaths per year. In Orthopaedics, MRSA osteomyelitis (OM) has become the greatest concern in patient care, desite the fact that improvements in surgical technique and aggressive antibiotic prophylaxis have decreased the infection rate for most procedures to less than 1-5%. In order to better understand pathogen-host interactions during the establishment of OM, develop new interventions and an effective diagnostic, we have developed a novel murine model of implant- associated OM in which a stainless steel pin is coated with S. aureus and implanted transcortically through the tibial metaphysis. This leads to a highly reproducible infection with osteolysis by day 9, fractures within three weeks, and closely resembles clinical OM around an external fixation pin. Furthermore, we have developed real time quantitative-PCR (RTQ-PCR) to determine nuc gene copy number in infected bone tissue, which is accurate to ~100 copies; and in vivo bioluminescence imaging to quantify the bacterial load longitudinally. We used this model to clone the glucosaminidase subunit of autolysin as an immuno-dominant antigen and demonstrated its potential as an active vaccine. However, as the target populations for this vaccine are immuno-compromised or elderly patients, Codevax LLC has initiated development of a passive immunization that can be given to high-risk patients prior to surgery. Currently, the company has 13 monoclonal antibodies against glucosaminidase that it needs to screen to derive a primary, secondary and tertiary candidate for clinical trials based on their ability to: 1) bind an epitope within a highly concerned domain (100%amino acid identity of all know S. aureus strains) with high affinity (<10-9M; 2); 2) mediate enzyme inhibition, cytostasis or cytolysis of the bacteria in vitro; and 3) significantly protect mice from implant associated OM. Here we propose the pivotal experiments to test these mAbs accordingly, and derive the candidates to be developed as the first passive immunization for MRSA. PUBLIC HEALTH RELEVANCE: Anti-Autolysin Passive Immunity for MRSA Osteomyelitis Methicillin resistant Staphylococcus aureus (MRSA) has surpased HIV as the most deadly pathogen in the United States, accounting for over 100,000 deaths per year. In Orthopaedics, MRSA osteomyelitis (OM) has become the greatest concern in patient care. To address this need, Codevax, Inc. aims to develop the first passive immunization to prevent MRSA infections in patients undergoing total joint replacement surgery.