Vaccine potential of the proline-rich domain of pneumococcal surface protein A

 描述（由申请方提供）：预防中耳炎、非并发性肺炎和脑膜炎需要非荚膜型特异性的疫苗溶液。肺炎球菌表面蛋白PspA在小鼠中对肺炎、菌血症、定植和致命性脓毒症具有保护作用。PspA在FDA批准的安全性（I期）试验中（1998年，2002年，2010年和2012-14年）。这些试验显示没有安全性问题，并且针对PspA引发的人抗体（Ab）保护小鼠免于致命的脓毒症。纯化的rPspA的人体试验（1998、2002和2010）检查了由PspA的N末端处的~300个aa α-螺旋结构域（aHD）引起的保护。aHD是可变的;在疫苗中可能需要多达三种不同的aHD来覆盖所有SP中PspA的多样性。我们最近已经表明，~80个氨基酸的富含脯氨酸的结构域（PRD）也增强了针对脓毒症的保护。PRD结构域存在于所有PspA中。每个PRD含有1至5个不同的6-10个AA重复序列。我们有保护性单克隆抗体（mAb），这些短重复序列之一，并保守的22个氨基酸的非脯氨酸封闭（NBP）序列，目前在约50%的PRD。然而，缺少这些表位中的任一个的PRD仍然可以引起交叉保护，表明存在额外的保护性表位。我们已经在人血清中发现了针对四种PRD重复序列的Ab。我们将创建广泛的交叉反应rPRD包括其所有共同的保护引发表位。开发高度交叉保护的PRD免疫原是重要的，因为将PspA转移到3期疗效试验中的一些延迟是由于担心aHD中的变异性， 结构可以允许Sp围绕PspA aHD疫苗进化。PRD将提供覆盖所有PspA的第二组表位。我们将确定rPRD可以取代或增强aHD引起的针对所有相关荚膜类型的Sp菌株的交叉保护的程度。目标1.鉴定PRD中在小鼠、兔和人中具有免疫原性的主要保护诱导重复序列，并使用此信息构建预期具有广泛交叉保护性的候选rPRD。目标2。在小鼠脓毒症、局灶性肺炎和定植模型中评价由目标1中构建的rPRD免疫原引起的交叉保护。比较PRD、aHD和PRD+aHD引起对不同种属的保护的能力。PspA结构的变异与荚膜类型在遗传或功能上无关。因此，长期以来人们一直认为，观察到的抗PspA抗体对少数小鼠毒力荚膜类型的保护作用将适用于非小鼠毒力荚膜类型的Sp。为了检查针对所有相关荚膜类型的侵袭性菌株的保护，我们将：1）使用我们的体外功能测定，2）使用局灶性肺炎，其在小鼠中由比脓毒症多得多的荚膜类型引起，和3）使用宿主炎症相关分子暂时增强通常不是小鼠毒性的荚膜类型的侵袭性临床IPD分离株的毒性。目标3。确定PRD的Ab是否可以增强Sp上的C'沉积并增强杀菌肽对Sp的杀伤。抗PspA的aHD抗体通过这两种机制发挥作用。

 DESCRIPTION (provided by applicant): Protection against otitis media, non-complicated pneumonia, and meningitis requires a vaccine solution that is not capsular type-specific. The pneumococcal surface protein PspA elicits protection in mice against pneumonia, bacteremia, colonization, and fatal sepsis. PspA was in FDA-approved safety (phase 1) trials (1998, 2002, 2010, and 2012-14). These trials revealed no safety problems, and the human antibody (Ab) elicited to PspA protected mice from fatal sepsis. The human trials of purified rPspA (1998, 2002, and 2010) examined protection elicited by the ~300 aa a-helical domain (aHD) at the N-terminal end of PspA. The aHD is variable; up to three different aHD may be required in a vaccine to cover the diversity of PspA in all Sp. We have recently shown that the ~80 aa proline-rich domain (PRD) also elicits protection against sepsis. The PRD domain is found in all PspAs. Each PRD contains 1 to 5 different 6-10 AA repeat sequences. We have protective monoclonal antibody (mAb) to one of these short repeat sequences and to a conserved 22 aa non-proline block (NBP) sequence, present in ~50% of PRD. However, a PRD lacking either of these epitopes could still elicit cross-protection, indicating the existence of additional protective epitopes. We have already found Ab to four of the PRD repeat sequences in human sera. We will create broadly cross-reactive rPRD by including all of its common protection-eliciting epitopes. Developing a highly cross-protective PRD immunogen is important because some of the delay in moving PspA into phase 3 efficacy trials is due to concern that variability in the aHD structure may allow Sp to evolve around a PspA aHD vaccine. The PRD will provide a second set of epitopes with which to cover all PspAs. We will determine the degree to which rPRD can replace, or augment, the cross-protection elicited by the aHD against Sp strains of all relevant capsular types. Aim1. Identify major protection-eliciting repeats in PRD that are immunogenic in mice, rabbits, and humans and use this information to construct candidate rPRD expected to be broadly cross-protective. Aim2. Evaluate cross- protection elicited by the rPRD immunogens constructed in Aim 1 in mouse sepsis, focal pneumonia, and colonization models. Compare the ability of PRD, aHD, and PRD+aHD to elicit protection against diverse Sp. Variations in PspA structure are not genetically or functionally related to capsule type. Thus, it has long been assumed that the protection observed against the few mouse-virulent capsule types with Ab to PspA would hold for Sp of non-mouse virulent capsular types. To examine protection against invasive strains of all relevant capsular types we will: 1) use our in vitro functional assay, 2) ue focal pneumonia which is caused in the mouse by many more capsular types than sepsis, and 3) use host inflammation-associated molecules to temporarily enhance the virulence of invasive clinical IPD isolates of capsular types that are not normally mouse-virulent. Aim3. Determine whether Ab to PRD can enhance C' deposition on Sp and enhance the killing of Sp by bactericidal peptides. Ab to the aHD of PspA functions by both of these mechanisms.