Malaria Vaccine Adjuvant Immunogenicity and Safety

描述（由申请人提供）：在这份R21申请中，我们建议使用一种特性良好的疟疾候选疫苗作为模型免疫原，评估纳米颗粒制剂的有效性和安全性的细胞、分子和免疫相关因素。一种基于Pfs25蛋白的针对疟原虫性阶段的疫苗提供了一种减少疟疾传播的直接方法。在恶性疟原虫中，红细胞内配子细胞阶段产生的Pfs230和Pfs48/45蛋白以及在蚊子阶段合子发育为卵母细胞期间表达的Pfs25蛋白代表了传播阻断抗体的既定靶抗原。识别这些蛋白中特定构象表位的抗体是疟原虫在蚊子中的传染性的有效阻断剂。我们最近成功地在大肠杆菌中重组表达和纯化了重新折叠的Pfs25，这是第一次在接近天然构象的情况下。实验佐剂中纯化的蛋白（rPfs25）在小鼠体内具有很强的免疫原性。需要开发更好和更安全的佐剂和给药方法，以便最终适用于人类。纳米颗粒作为安全有效的疫苗佐剂正迅速获得人们的认可。我们建议开发Pfs25纳米颗粒制剂（目标1），并评估近交系和远交系小鼠的功能性免疫反应（目标3）。我们还建议研究疫苗注射部位与免疫反应相关的宿主基因表达变化，以获得pfs25纳米颗粒疫苗功效的机制（Aim 2）。最后，还建议研究相关的疫苗安全参数（Aim 4）。这些研究将更好地了解纳米颗粒制剂免疫原性功效和安全性的细胞和分子相关性，并为更深入的疫苗开发研究提供基础。

DESCRIPTION (provided by applicant): In this R21 application we propose to assess cellular, molecular and immune correlates of efficacy and safety of nanoparticle formulations using a well characterized malaria vaccine candidate as a model immunogen. A vaccine based on Pfs25 protein targeting the sexual stages of the parasite provides a direct approach to reduce malaria transmission. In Plasmodium falciparum, Pfs230 and Pfs48/45 proteins produced within the intra-erythrocytic gametocyte stages and Pfs25, expressed during the mosquito stage development of zygote into ookinete, represent well established target antigens of transmission-blocking antibodies. Antibodies recognizing specific conformational epitopes in these proteins are potent blockers of infectivity of malaria parasites in the mosquito. We have recently succeeded in recombinant expression and purification of re-folded Pfs25, for the first time in near native conformation, in E. coli. The purified protein (rPfs25) in experimental adjuvants elicited strong immunogenicity in mice. Better and safer adjuvants and delivery methods need to be developed for eventual human applicability. Nanoparticles are fast gaining acceptability as safe and effective vaccine adjuvants. We propose to develop Pfs25 - nanoparticle formulations (Aim 1) and evaluate functional immune response in inbred and outbred mice (Aim 3). We also propose to study the immune response-related host gene expression changes at the site of vaccine injection to gain mechanistic insights of Pfs25-nanoparticle vaccine efficacy (Aim 2). Finally studies are also proposed to investigate relevant vaccine safety parameters (Aim 4). These studies will provide better understanding of cellular and molecular correlates of immunogenic efficacy and safety of nanoparticle formulations, and also provide the basis for more in depth studies on vaccine development, in general. PUBLIC HEALTH RELEVANCE: Malaria parasites are responsible for nearly 300 million infections globally resulting in nearly a million deaths annually. Vaccines are urgently needed to control and eliminate the disease. The proposed research will focus on the development of a vaccine to stop transmission and help with the ultimate goal of malaria elimination.