Vaccine and therapeutic antibodies against Group A Streptococcus

描述(申请人提供)：A组链球菌(GAS)是一种主要的人类病原体，可导致多种疾病，包括相对轻微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传统的抗生素治疗。该项目的目标是开发一种针对GAS疾病的候选疫苗和保护性单抗，为未来治疗严重侵袭性感染的免疫疗法的发展奠定基础。学术界和工业界几十年的努力表明，由于序列变异或保护性抗原保护能力有限，目前测试的任何候选疫苗都不足以成为广泛有效的气体疫苗。作为应对GAS疫苗和治疗发展问题的新策略，我们将同时针对GAS分泌酯酶(简称SSE)和链球菌溶血素S(SLS)。在坏死性筋膜炎小鼠模型中，SSE基因是超强毒力血清型M1毒株的毒力和传播所必需的。SSE的主动和被动免疫显著保护小鼠免受皮下气体感染和皮下细菌传播。我们的初步数据表明，SSE基因也是小鼠鼻内感染GAS毒力和咽部定植所必需的。SSE基因是抑制中性粒细胞募集所必需的。这些结果表明，SSE参与了GAS的先天免疫逃避，是一种重要的毒力因子和保护性抗原。然而，SSE对于一些临床菌株来说并不是一个足够的保护性抗原。我们的初步数据表明，在超强毒力M3型小鼠的皮下感染中，SSE和SLS共同发挥作用，阻断中性粒细胞的功能，而SLS对毒力和喉部定植至关重要。已知针对SLS的多肽成分SAGA的C末端片段可以产生抗体，并中和SLS的溶血活性。我们假设我们可以开发一种基于SSE和SAGA的有效、广泛的GAS疫苗。我们还假设，中和SSE和SLS活性的单抗可用于治疗严重的GAS感染。在目标1中，我们将使用鼻腔和皮下感染的小鼠模型来测试SSE和SAGA疫苗制剂对GAS感染的有效性。在目标2中，我们将产生SSE和SAGA特异性的抑制性单抗，并测试抑制性单抗在被动免疫中是否能保护小鼠免受皮下GAS感染。该项目有可能导致开发一种针对气体疾病的广泛疫苗和一种治疗严重气体感染的抗体疗法。 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，严重的侵袭性气体感染很难治疗。该项目将测试两种毒力因子作为开发新城疫毒气疫苗和产生保护性单抗的目标的潜力。如果实现，这些发现可能会导致进一步开发针对气体疾病的广泛、有效的疫苗，以及针对严重气体感染的免疫疗法。

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.