Rational Approach to Optimize Immune Potency of DNA Vaccines

描述(申请人提供)：疫苗为控制由病毒和细菌病原体引起的传染病提供了最具成本效益的工具。然而，目前还没有针对任何人类寄生虫感染的疫苗，开发有效的疟疾疫苗仍然是一个未实现的目标。在全球每年约3亿临床病例中，疟疾感染导致近100万人死亡。针对寄生虫性阶段的基于抗原的疫苗提供了减少疟疾传播的直接方法。识别这些蛋白质中特定构象表位的抗体是蚊子体内疟疾寄生虫传染性的强有力的阻断剂。在R21的这一应用中，我们建议使用具有良好特性的疟疾候选疫苗Pfs25作为模型免疫原来评估修改后的DNA疫苗的有效性和安全性的细胞、分子和免疫相关性。DNA疫苗诱导了良好的初始免疫反应；然而，在较大的哺乳动物中，它们需要异源增强，例如。佐剂蛋白，以维持功能性抗体效价。DNA疫苗的免疫原性差可能是由于活化的T细胞上的程序性死亡1(PD-1)受体和抗原提呈细胞上的PD-L1受体上调而导致的T细胞衰竭或功能障碍。我们建议通过在DNA疫苗中添加新的RNAi序列(旨在击倒PD-L1)来检验这一假设，并期望DNA疫苗的免疫原性增强，反映在更高的滴度和更持久的抗体反应中。我们将通过追求以下具体目标来检验我们的假设。在具体目标1中，我们将开发能够沉默PD-L1并在同一细胞内表达疫苗抗原的DNA疫苗。针对特定目标2的研究将通过体内评估改良DNA疫苗的效力和相关的TFH细胞反应来提供原则证明。这些研究将更好地了解DNA疫苗免疫原性有效性和安全性的细胞和分子相关性，并为更深入地研究广泛的疫苗开发提供基础。

DESCRIPTION (provided by applicant): Vaccines have provided the most cost-effective tool to control infectious diseases caused by viral and bacterial pathogens. However, there are no vaccines against any human parasitic infections and the development of an effective malaria vaccine remains an unachieved goal. Malaria infections account for nearly a million deaths out of ~ 300 million clinical cases globally on an annual basis. Vaccines based on antigens targeting the sexual stages of the parasite provide a direct approach to reduce malaria transmission. Antibodies recognizing specific conformational epitopes in these proteins are potent blockers of infectivity of malaria parasites in the mosquito. In this R21 application we propose to assess cellular, molecular and immune correlates of efficacy and safety of modified DNA vaccines using a well characterized malaria vaccine candidate, Pfs25, as a model immunogen. DNA vaccines induce a good initial immune response; however, in larger mammals they require heterologous boosting, eg. adjuvanted proteins to sustain functional antibody titers. Poor immunogenicity of DNA vaccines could result from an immune phenomenon described as T cell exhaustion or dysfunction resulting from upregulation of the programmed death 1 (PD-1) receptor in activated T cells and PD-L1 on antigen presenting cells. We propose to test this hypothesis through the novel addition of an RNAi sequence (designed to knockdown PD-L1) to a DNA vaccine and expect enhanced immunogenicity of DNA vaccines reflected in higher titer and longer lasting antibody responses. We will test our hypothesis by pursuing the following specific aims. In specific aim 1 we will develop DNA vaccines capable of silencing PD-L1 and expressing vaccine antigen within the same cell. Studies in specific aim 2 will provide a proof-of-principle through in vivo evaluation of potency of modified DNA vaccines and associated TFH cell responses. These studies will provide a better understanding of the cellular and molecular correlates of immunogenic efficacy and safety of DNA vaccines, and also provide the basis for more in depth studies on vaccine development across a broad spectrum.