O-polysaccharide (OPS)-IpaB Conjugate Vaccine to Prevent Shigellosis

研究综述 志贺氏菌在全球范围内造成很高的痢疾负担。5岁以下儿童，尤其是蹒跚学步儿童 2-3岁，生活在缺乏清洁水和卫生设施的贫困地区的儿童受到的影响最大。重复 感染会导致终生健康损害和残疾。志贺氏菌也会在工业化地区引发疫情 在许多国家(日托中心和医疗机构)，由于其多重耐药性，是一个严重的威胁。 目前还没有批准的疫苗。大多数现有的候选人依赖于对志贺氏菌O抗原的免疫，这种抗原 是血清型特异的(有4种和50个致泻性志贺氏菌血清型)。志贺氏菌O-多糖 (OP)结合物(如SF2a-TT15和Flexyn2a)是临床上最先进的。这些疫苗是有限的 他们使用无关的(非志贺氏菌)蛋白作为载体。SF2a-TT15使用破伤风类毒素，它包含在 许多疫苗接种给目标年龄的儿童，并已知会抑制对其他疫苗的反应 组件。Flexyn2a使用REPA作为载体，但在最近的一项挑战研究中效果不佳(未满足 研究终点)。早期的S.sonnei OPS-REPA对年龄较大的儿童有效，但对蹒跚学步的儿童(目标年龄)无效。 为了回应RFA-AI-22-037，马里兰大学(UMB)与Vaxcell合作，提议 用A型志贺菌IPAB研制双价(福氏2a志贺菌和宋内氏志贺菌)OPS结合疫苗 作为载体，在所有志贺氏菌中高度保守的分泌蛋白。IPAB是例外的 免疫原性，是一种广为人知的保护性抗原；血清免疫球蛋白(IgG1)水平和IPAB抗体功能 在受控的人类挑战研究中发现与疾病减少呈正相关。 第一次，我们用Vaxcell的 无细胞蛋白表达系统。IPAB通过Vaxcell的位点与S.flex 2a和S.sonnei OPS偶联。 特定的共轭技术。小鼠两次肌肉注射明矾后的S.flex 2a OPS-IPAB 相隔28天，激发了强大的免疫反应，并对S.flex 2a(同源)提供了78%的保护 对宋内氏志贺氏菌(异源)致死性肺志贺菌攻击有56%的抵抗率。福氏沙门氏菌疫苗免疫效果观察 与白喉类毒素突变体CRM197接合的S.flex 2a OPS相比，2a的表达水平较高。 该提案包括三个目标，以优化工艺开发、配方和扩大生产 S.flex 2a-和S.sonnei OPS-IPAB结合物(目标1)，评价两种疫苗的免疫原性和疫苗效力 动物模型：小鼠(肺感染)和豚鼠(直肠结肠炎感染)(目标2)，并鉴定免疫 通过被动转移实验和一套体外实验与保护性免疫相关的操作员 功能分析(目标3)。双价志贺氏菌-OPS-IPAB疫苗预计耐受性良好，并具有 比现有疫苗具有更强的保护能力。 UMB和Vaxcell拥有独特的互补专业知识。该项目的成功完成将为 疫苗进入cGMP生产并启动人体研究。

RESEARCH SUMMARY Shigella causes a high burden of dysentery globally. Children younger than 5 years of age, particularly toddlers 2-3 years old, living in impoverished areas lacking clean water and sanitation are the most affected. Repeated infection results in lifelong health impairment and disability. Shigella also causes outbreaks in industrialized countries (daycare centers and medical institutions) and is a serious threat due to its multi-drug resistance. There is no approved vaccine. Most of the existing candidates rely on immunity to the Shigella O-antigen, which is serotype-specific (there are 4 species and >50 diarrheagenic Shigella serotypes). Shigella O-polysaccharide (OPS) conjugates (e.g., SF2a-TT15 and Flexyn2a) are the most clinically advanced. These vaccines are limited in their use of irrelevant (non-Shigella) proteins as carriers. SF2a-TT15 uses tetanus toxoid, which is included in many vaccines given to children of the target age and is known to suppress responses to other vaccine components. Flexyn2a uses rEPA as carrier but had modest efficacy in a recent challenge study (did not meet study endpoints). An earlier S. sonnei OPS-rEPA was effective in older children but not in toddlers (target age). In response to RFA-AI-22-037, the University of Maryland (UMB), in partnership with Vaxcyte, proposes to develop a bivalent (Shigella flexneri 2a and Shigella sonnei) OPS conjugate vaccine using Shigella IpaB, a Type III secretion protein that is highly conserved among all Shigella spp., as carrier. IpaB is exceptionally immunogenic and is a known broadly protective antigen; serum IgG (IgG1) levels and IpaB antibody function were found to be positively associated with reduced disease in controlled human challenge studies. For the first time, we have produced soluble, immunoreactive IpaB at a high (industrial) yield using Vaxcyte’s cell-free protein expression system. IpaB is conjugated to S. flex 2a and S. sonnei OPS using Vaxcyte’s site- specific conjugation technology. S. flex 2a OPS-IpaB given to mice intramuscularly with Alum on two occasions 28 days apart, elicited robust immune responses and afforded 78% protection against S. flex 2a (homologous) and 56% against S. sonnei (heterologous) lethal pulmonary Shigella challenge. Vaccine efficacy against S. flex 2a was higher as compared with S. flex 2a OPS-conjugated to CRM197 (a diphtheria toxoid mutant). This proposal consists of three aims to optimize process development, formulation, and scale-up production of S. flex 2a- and S. sonnei OPS-IpaB conjugates (Aim 1), evaluate the immunogenicity and vaccine efficacy in two animal models: mice (pulmonary challenge) and guinea pigs (rectocolitis infection) (Aim 2), and identify immune operatives associated with protective immunity through passive transfer experiments and a suite of in vitro functional assays (Aim 3). A bivalent Shigella-OPS-IpaB vaccine is expected to be well tolerated and to have enhanced protective capacity than existing vaccines. UMB and Vaxcyte have unique complementary expertise. Successful completion of this project will prepare the vaccine to enter cGMP manufacturing and initiate human studies.