Vaccine and therapeutic antibodies against Group A Streptococcus

描述（由申请人提供）：A组链球菌（GAS）是一种主要的人类病原体，可引起多种疾病，包括相对轻度的咽炎和严重的侵袭性感染，如坏死性筋膜炎。不幸的是，目前还没有获得许可的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GAS疾病的候选疫苗和保护性单克隆抗体，用于未来开发治疗严重侵袭性感染的免疫疗法。学术界和工业界几十年来的努力已经证明，由于序列变异或保护性抗原的保护能力有限，所测试的任何疫苗候选物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分泌的酯酶（命名为SsE）和链球菌溶血素S（SLS）。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。用SsE主动和被动免疫显著保护小鼠免受皮下GAS感染和皮下组织中的细菌传播。我们的初步数据表明，sse基因也需要GAS毒力和咽喉定植在小鼠鼻内感染。SsE基因是抑制中性粒细胞募集所必需的。这些结果表明，SsE参与了GAS的天然免疫逃避，是一种重要的毒力因子和保护性抗原。然而，SsE对于某些临床菌株不是足够的保护性抗原。我们的初步数据表明，SsE和SLS功能串联阻断中性粒细胞的功能，在皮下感染的小鼠与高毒力血清型M3菌株和SLS是至关重要的气体毒力和咽喉定植。已知可以产生针对佐贺的C末端片段（SLS的肽组分）的抗体，并且中和SLS的溶血活性。我们假设，我们可以开发一种有效的，广泛的GAS疫苗的基础上SsE和佐贺。我们还假设中和SsE和SLS活性的单克隆抗体（mAb）可用于治疗严重的GAS感染。我们将在目标1中使用鼻内和皮下感染的小鼠模型测试基于SsE和佐贺的疫苗制剂针对GAS感染的功效。在目的2中，我们将产生SsE和SagA特异性抑制性mAb，并测试抑制性mAb是否在被动免疫中保护小鼠免受皮下GAS感染。该项目有可能导致开发针对GAS疾病的广泛疫苗和治疗严重GAS感染的抗体疗法。 公共卫生相关性：医学意义：A组链球菌（GAS）是人类急性咽炎和严重侵袭性感染的主要原因。不幸的是，没有获得许可的GAS疫苗，严重的侵袭性GAS感染是难以治疗的。该项目将测试两个毒力因子的潜力，作为开发新GAS疫苗和产生保护性单克隆抗体的目标。如果实现，这些发现可能会导致进一步开发针对GAS疾病的广泛有效的疫苗和针对严重GAS感染的免疫疗法。

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.