A Therapeutic Vaccine for Chronic Hepatitis B

描述（由申请方提供）：本提案旨在评估使用重组病毒样颗粒（VLP）引发中和抗体的可行性， 作为慢性HBV感染的候选免疫治疗剂的与B型肝炎病毒（HBV）抗原反应的初始CD 4 + T细胞。为此，我们从HBV包膜Pre-S1区域确定了8个中和B细胞表位，这些表位将被整合并插入到HBV核心蛋白的物种变体上，即土拨鼠肝炎核心抗原（WHcAg）。选择Pre-S1 B细胞表位是因为它们在HBV病毒粒子上优先表达。WHO估计超过3.6亿人慢性感染HBV，约20- 40%的人将发展为严重并发症，如肝硬化、肝功能衰竭和肝细胞癌。尽管安全有效的HBV预防性疫苗已经存在了20多年，但HBV感染仍然是一个主要的健康问题（每年超过5000万例HBV感染），并且不存在有效的慢性感染治疗方法。抗病毒药物改善了慢性HBV的治疗选择，但由于HBV复制的重新激活，其疗效仍然有限 停药后。基于疫苗的免疫疗法已被建议作为可能的单一疗法或作为与抗病毒药物的联合疗法。然而，免疫耐受阻止了治疗性疫苗功效。为了克服HBV慢性携带者免疫耐受的障碍，我们选择了与HBcAg同源性约66-68%的WHcAg作为疫苗载体。WHcAg和HBcAg在B细胞水平上没有交叉反应性，并且对于我们的目的同样重要的是，在CD 4 + T细胞水平上仅部分交叉反应性。因此，特异于WHcAg独特T细胞位点的CD 4 + T细胞将为抗PreS 1抗体产生提供同源T-B细胞帮助，并且不会被免疫耐受性削减。事实上，在对HBcAg耐受的HBcAg-Tg小鼠中的初步研究中，用杂合WHcAg-PreS 1 VLP免疫在野生型和HBcAg-Tg小鼠中产生等同的高滴度抗PreS 1抗体。具体而言，在目标1中，我们提出将8个Ag-PreS 1中和B细胞表位整合到WHcAg VLP载体上，并基于组装、产率、稳定性和免疫原性优化构建体，并且将在HBV复制的转基因（Tg）小鼠模型中评价基于VLP的候选疫苗的治疗功效。在目标2中，将继续进行WHcAg-PreS 1疫苗的临床前开发，包括cGMP生产和药理学/毒理学研究。

DESCRIPTION (provided by applicant): The objective of this proposal is to assess the feasibility of using recombinant virus-like- particles (VLPs) to elicit neutralizing antibodies and prime CD4+ T cells reactive with hepatitis B viral (HBV) antigens as candidate immunotherapeutics for chronic HBV infection. For this purpose, we have defined 8 neutralizing B cell epitopes from the HBV envelope Pre-S1 region, which will be consolidated and inserted onto a species variant of the HBV core protein, namely the woodchuck hepatitis core antigen(WHcAg). Pre-S1 B cell epitopes were chosen because of their preferential expression on HBV virions. The WHO estimates that more than 360 million individuals are chronically infected with HBV and approximately 20- 40% will develop serious complication such as cirrhosis, liver failure and hepatocellular carcinoma. Although a safe and efficacious preventative vaccine for HBV has been available for over 20years, HBV infections continue (with more than 50 million HBV infections per year) to be a major health problem and no effective treatments for chronic infection exist. Antiviral drugs have improved the therapeutic options for chronic HBV, but, their efficacy remains limited due to reactivation of HBV replication upon drug withdrawal. Vaccine-based immunotherapy has been suggested as a possible monotherapy or as a combination therapy with antiviral drugs. However, immune tolerance has prevented therapeutic vaccine efficacy. To circumvent the obstacle of immune tolerance in HBV chronic carriers, we have chosen the WHcAg, which is approximately 66-68% homologous with the HBcAg, as a vaccine carrier. The WHcAg and the HBcAg are not crossreactive at the B cell level and, just as importantly for our purposes, are only partially crossreactive at the CD4+ T cel level. Therefore, CD4+ T cells specific for WHcAg-unique T cell sites will provide cognate T-B cell help for anti- PreS1 antibody production and will not be curtailed by immune tolerance. In fact, in preliminary studies in HBcAg-Tg mice, which are tolerant to HBcAg, immunization with hybrid WHcAg- PreS1 VLPs elicits equivalent high titer anti- PreS1 antibodies in wildtype and HBcAg-Tg mice. Specifically, in Aim 1 we propose to consolidate 8 HBsAg-PreS1 neutralizing B cell epitopes onto the WHcAg VLP carrier and optimize the constructs based on assembly, yield, stability and immunogenicity and the therapeutic efficacy of the VLP-based vaccine candidates will be evaluated in a transgenic (Tg) mouse model of HBV replication. In Aim 2 preclinical development of the WHcAg-PreS1 vaccine will be pursued including cGMP manufacturing and pharm/tox studies.