Rational Approach to Optimize Immune Potency of DNA Vaccines

描述（由申请人提供）：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，没有任何预防人类寄生虫感染的疫苗，研制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，疟疾感染造成近100万人死亡。基于针对疟原虫性阶段的抗原的疫苗为减少疟疾传播提供了一种直接途径。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。在这一R21申请中，我们建议使用一种特性良好的疟疾候选疫苗Pfs25作为模型免疫原，评估修饰DNA疫苗的有效性和安全性的细胞、分子和免疫相关因素。DNA疫苗诱导良好的初始免疫反应；然而，在大型哺乳动物中，它们需要异源促进，例如。辅助蛋白维持功能性抗体滴度。DNA疫苗免疫原性差可能是由于一种免疫现象引起的，这种免疫现象被描述为T细胞衰竭或功能障碍，这是由活化T细胞中的程序性死亡1 （PD-1）受体和抗原提呈细胞上的PD-L1的上调引起的。我们建议通过在DNA疫苗中添加新的RNAi序列（旨在敲低PD-L1）来验证这一假设，并期望DNA疫苗的免疫原性得到增强，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。特定目标2的研究将通过体内评价修饰DNA疫苗的效力和相关的TFH细胞反应提供原理证明。这些研究将有助于更好地了解DNA疫苗免疫原性有效性和安全性的细胞和分子相关性，并为在广泛范围内更深入地研究疫苗开发提供基础。

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.