Vaccine and therapeutic antibodies against Group A Streptococcus

描述（由申请人提供）：A群链球菌（GAS）是一种主要的人类病原体，可引起多种疾病，包括较轻的咽炎和严重的侵袭性感染，如坏死性筋膜炎。不幸的是，没有获得许可的GAS疫苗，严重的侵袭性感染很难用常规抗生素治疗。该项目的目标是开发一种GAS疾病的候选疫苗和保护性单克隆抗体，为未来开发治疗严重侵袭性感染的免疫疗法提供基础。学术界和工业界几十年来的努力表明，由于序列变异或保护性抗原的保护能力有限，任何已测试的候选疫苗都不足以成为广泛有效的GAS疫苗。作为解决GAS疫苗开发和治疗问题的新策略，我们将同时针对GAS分泌酯酶（指定为SsE）和链溶素S （SLS）进行研究。sse基因是坏死性筋膜炎小鼠模型中高毒力血清型M1菌株的毒力和传播所必需的。SsE主动和被动免疫对小鼠皮下气体感染和细菌在皮下扩散具有显著的保护作用。我们的初步数据表明sse基因也是小鼠鼻内感染中GAS毒力和咽喉定植所必需的。SsE基因是抑制中性粒细胞募集所必需的。这些发现表明SsE参与了GAS的先天免疫逃避，是一个重要的毒力因子和保护性抗原。然而，SsE对某些临床菌株并不是一个足够的保护性抗原。我们的初步数据表明，SsE和SLS在高毒力M3血清型小鼠皮下感染中协同作用，阻断中性粒细胞功能，SLS对GAS毒力和喉咙定植至关重要。已知抗体可以针对SLS的肽成分SagA的c端片段产生，并中和SLS的溶血活性。我们假设我们可以基于SsE和SagA开发一种有效的、广泛的GAS疫苗。我们还假设单克隆抗体（mab）可以中和SsE和SLS的活性，用于治疗严重的GAS感染。我们将在Aim 1中使用小鼠鼻内和皮下感染模型来测试基于SsE和SagA的疫苗制剂对GAS感染的有效性。在Aim 2中，我们将生成SsE-和saga特异性的抑制单抗，并测试抑制单抗是否能保护小鼠免受被动免疫中皮下GAS感染。该项目有可能导致开发针对气体疾病的广泛疫苗和治疗严重气体感染的抗体疗法。

DESCRIPTION (provided by applicant): Group A Streptococcus (GAS) is a major human pathogen that causes a variety of diseases, including relatively mild pharyngitis and severe invasive infections, such as necrotizing fasciitis. Unfortunately, there is no licensed GAS vaccine, and severe invasive infections are difficult to treat with conventional antibiotics. The goals of this project are to develop a candidate vaccine for GAS diseases and protective monoclonal antibodies for future development of immunotherapy to treat severe invasive infections. The endeavors of several decades made by academic and industrial communities have demonstrated that any of the vaccine candidates tested yet is not sufficient for a broad, efficacious GAS vaccine due to sequence variation or limited capacity of protection of protective antigens. As a new strategy to tackle the problems in development of GAS vaccine and treatment, we will target both the secreted esterase of GAS (designated SsE) and streptolysin S (SLS). The sse gene is required for the virulence and dissemination of a hypervirulent serotype M1 strain in a mouse model of necrotizing fasciitis. Active and passive immunizations with SsE significantly protects mice against subcutaneous GAS infection and bacterial spreading in the subcutis. Our preliminary data shows that the sse gene is also required for GAS virulence and throat colonization in intranasal infection of mice. The SsE gene is required for inhibition of neutrophil recruitment. These findings indicate that SsE is involved in the innate immune evasion by GAS and is a critical virulence factor and protective antigen. However, SsE is not a sufficiently protective antigen for some clinical strains. Our preliminary data suggest that SsE and SLS function in tandem to block neutrophil functions in subcutaneous infection of mice with a hypervirulent serotype M3 strain and that SLS is critical for GAS virulence and throat colonization. It is known that antibodies can be raised against the C-terminal fragment of SagA, the peptide component of SLS, and neutralize the hemolytic activity of SLS. We hypothesize that we can develop an efficacious, broad GAS vaccine based on SsE and SagA. We also hypothesize that monoclonal antibodies (mAbs) neutralizing the activity of SsE and SLS can be used to treat severe GAS infections. We will test the efficacy of SsE and SagA -based vaccine formulations against GAS infections using mouse models of intranasal and subcutaneous infections in Aim 1. In Aim 2, we will generate SsE- and SagA-specific inhibitory mAbs and test whether inhibitory mAbs protect mice against subcutaneous GAS infection in passive immunization. The project has the potential to lead to the development of a broad vaccine against GAS diseases and an antibody therapy to treat severe GAS infections. PUBLIC HEALTH RELEVANCE: Medical significance: Group A Streptococcus (GAS) is a major cause of acute pharyngitis and severe invasive infections in humans. Unfortunately, no licensed GAS vaccine is available, and severe invasive GAS infections are difficult to treat. This project will test the potential of two virulence factors as the targets for the development of a ne GAS vaccine and generation of protective monoclonal antibodies. If realized, the findings may lead to the further development of a broad, efficacious vaccine against GAS diseases and an immunotherapy against severe GAS infections.