PspA: A Potential Pneumococcal Vaccine Component

PspA：一种潜在的肺炎球菌疫苗成分

• 批准号: 7924405
• 负责人: David E Briles
• 金额: $ 5.24万
• 依托单位: UNIVERSITY OF ALABAMA AT BIRMINGHAM
• 依托单位国家: 美国
• 财政年份: 2009
• 资助国家: 美国
• 起止时间: 2009-09-22 至 2010-08-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/7924405
• 关键词: Abbreviations; Address; Adherence; Affect; Alabama; Amino Acids; Antibodies; Antibody-mediated protection; Antigens; Binding; Biological Assay; Blood; C57BL/6 Mouse; Cell Wall; Cholera Toxin; Cholera Toxin Protomer B; Choline; Clinical Research; Coiled-Coil Domain; Colony-forming units; Complement; Complement component C1; Conjugate Vaccines; Data; Deposition; Development; Disease; Dose; Epitopes; Erythrocytes; Evolution; Fluorescence; Grant; Host resistance; Human; Immune; Immune Sera; Immunity; Immunization; In Vitro; Infection; Intravenous; Investigation; Knock-out; Lactoferrin; Measurable; Mediating; Membrane Proteins; Mus; Myosin ATPase; N-terminal; Nervousness; Paper; Pathogenesis; Peer Review; Peptides; Phagocytosis; Phase; Phase I Clinical Trials; Pneumococcal vaccine; Polysaccharides; Proline; Proline-Rich Domain; Protein C; Proteins; Publications; Role; Safety; Sepsis; Serum; Streptococcus pneumoniae; Streptococcus pneumoniae plY protein; Surface; Techniques; Temperature; Testing; Text; Transgenic Organisms; Universities; Vaccine Clinical Trial; Vaccines; Virulence; apolactoferrin; bactericide; base; capsule; clinically relevant; cost; efficacy trial; extracellular; granulocyte; immune phagocytosis; immunogenicity; in vitro Assay; in vivo; intraperitoneal; killings; neutrophil; pneumococcal surface protein A; preclinical study; prevent; public health relevance; research study; subcutaneous; vaccine candidate

DESCRIPTION (provided by applicant): Pneumococcal surface protein A (PspA) is a leading vaccine candidate to protect against Streptococcus pneumoniae (Sp) infections. This grant addresses issues critical to defining the mechanisms of action of PspA and antibody (Ab) to PspA. This information is important to our understanding of the pathogenesis of Sp and to the potential use of PspA as a component of a common-protein vaccine. The proposed experiments constitute some of the last pre-clinical studies needed prior to renewed human trials with PspA. New and existing information about the mechanism of action of both PspA and Ab to PspA will be used to develop and test the relevance of in vitro surrogate assays for in vivo protection mediated by Ab to PspA. Relevant surrogate assays are needed to evaluate immune sera from phase I and II human safety and immunogenicity trials. The information gained will provide a scientific basis for decisions about whether the much more expensive phase III efficacy trials should be conducted. PspA can inhibit C' activation and surface deposition on Sp. Ab to PspA can enhance C' deposition on Sp. Our studies should also reveal the mechanism by which PspA blocks C' activation. In studies that will include transgenic and KO mice, we will evaluate the effects of Ab to PspA on phagocytosis, immune adherence, and blood clearance of Sp. PspA also keeps apolactoferrin from killing Sp by neutralizing lactoferrin and its cationic peptide lactoferricin. Ab to PspA prevents the PspA-lactoferrin interaction and, thus, enhances apolactoferrin's ability to kill Sp. We will use a lactoferrin KO mouse to help determine if these effects have in vivo relevance. We will also determine if PspA can also prevent killing by other cationic peptides. We will use a panel of MAb to different domains and epitopes of PspA and paired pre-and post-immune (anti- PspA) human sera to help us determine which of the our mechanistic assays of protection with Ab to PspA are best able to predict the ability of the same MAb to passively protect mice from infection. The results obtained will allow us to identify both those mechanisms that are critical for in vivo protection and in vitro assays that will best serve as in vitro surrogates of in vivo protection mediated by antibodies to PspA. Finally, the proposal includes an expanded investigation of our observation that immunization with the proline-rich (PR) domain of PspA can elicit protection against infection. This finding may turn out to be extremely important to the use of PspA as a vaccine because of a prior observation that some Ab to the protection-eliciting coiled coil (CC) domain of PspA can react with denatured myosin at room temperature. Although there is no compelling reason to believe that this observation has clinical relevance, it has caused nervousness on the part of for-profit vaccine companies. If, as we expect, immunization with the PR domain is broadly efficacious and cross- protective, the PR domain will not only provide a means of circumventing the theoretical worries about the CC domain but will also be a more effective immunogen. PUBLIC HEALTH RELEVANCE: This application describes pre-clinical studies to determine the virulence mechanisms of Streptococcus pneumoniae protein PspA and the protective action of antibody elicited to it. This information is critical to understand the role of PspA in pathogenesis and to our development herein of in vitro surrogate assays of the in vivo protection mediated by Ab to PspA. These surrogate assays are needed to guide the development of clinical vaccine trials from phase I through phase III. A protein vaccine against S. pneumoniae is important because of the high complexity and cost of the polysaccharide-protein conjugate vaccine and the rapid evolution of pneumococci to evade the capsule-type-specific protection elicited by the conjugate vaccine.

描述（由申请方提供）：肺炎球菌表面蛋白A（PspA）是预防肺炎链球菌（Sp）感染的主要候选疫苗。该资助解决了定义PspA和PspA抗体（Ab）作用机制的关键问题。这一信息对于我们理解Sp的发病机制和PspA作为普通蛋白疫苗的组分的潜在用途是重要的。拟议的实验构成了PspA重新进行人体试验之前所需的最后一批临床前研究。关于PspA和Ab对PspA的作用机制的新的和现有的信息将用于开发和测试用于由Ab介导的体内保护的体外替代测定的相关性。需要相关替代试验来评价I期和II期人体安全性和免疫原性试验的免疫血清。获得的信息将为决定是否应该进行更昂贵的III期疗效试验提供科学依据。PspA抑制C'活化和表面沉积，抗PspA抗体可增强C'在Sp上的沉积，本研究还揭示了PspA阻断C'活化的机制。在包括转基因和KO小鼠的研究中，我们将评估抗PspA抗体对SP的吞噬作用、免疫粘附和血液清除的影响。PspA还通过中和乳铁蛋白及其阳离子肽乳铁蛋白肽来阻止脱铁乳铁蛋白杀死SP。抗体PspA防止PspA-乳铁蛋白相互作用，因此，增强脱铁乳铁蛋白的能力，杀死SP。我们将使用乳铁蛋白KO小鼠，以帮助确定这些影响是否有体内相关性。我们还将确定PspA是否也可以防止其他阳离子肽的杀伤。我们将使用针对PspA的不同结构域和表位的一组MAb以及配对的免疫前和免疫后（抗PspA）人血清来帮助我们确定我们的针对PspA的Ab保护的机制测定中的哪一个最能够预测相同MAb被动保护小鼠免受感染的能力。所获得的结果将使我们能够鉴定对于体内保护和体外测定都至关重要的那些机制，所述体外测定将最好地充当由针对PspA的抗体介导的体内保护的体外替代物。最后，该提案包括对我们观察到的用PspA的富含脯氨酸（PR）结构域免疫可以引起对感染的保护的扩大调查。这一发现可能对PspA作为疫苗的使用极其重要，因为之前观察到PspA的保护性卷曲螺旋（CC）结构域的一些Ab可以在室温下与变性肌球蛋白发生反应。虽然没有令人信服的理由相信这一观察结果具有临床意义，但它引起了营利性疫苗公司的紧张。如果如我们所期望的，用PR结构域免疫广泛有效且具有交叉保护性，则PR结构域将不仅提供规避关于CC结构域的理论担忧的手段，而且将是更有效的免疫原。公共卫生相关性：本申请描述了确定肺炎链球菌蛋白PspA的毒力机制和针对其引发的抗体的保护作用的临床前研究。该信息对于理解PspA在发病机制中的作用以及我们在此开发由Ab介导的针对PspA的体内保护的体外替代测定是至关重要的。需要这些替代试验来指导疫苗临床试验从I期到III期的发展。抗S.由于多糖-蛋白质缀合物疫苗的高复杂性和成本以及肺炎球菌的快速进化以逃避缀合物疫苗引起的胶囊型特异性保护，因此肺炎球菌的免疫是重要的。