A Therapeutic Vaccine for Chronic Hepatitis B

描述(申请人提供)：这项建议的目的是评估使用重组病毒样颗粒(VLP)来诱导中和抗体和 主要的CD4+T细胞与乙肝病毒(乙肝)抗原反应作为慢性乙肝病毒感染的候选免疫疗法。为此，我们定义了8个来自乙肝病毒包膜Pre-S1区的中和B细胞表位，它们将被整合并插入到乙肝核心蛋白的一个物种变体上，即土拨鼠肝炎核心抗原(WHcAg)。Pre-S1B细胞表位因其在乙肝病毒粒子上的优势而被选择。世界卫生组织估计，超过3.6亿人慢性感染乙肝病毒，大约20%-40%的人将出现严重的并发症，如肝硬变、肝功能衰竭和肝细胞癌。尽管一种安全有效的乙肝预防性疫苗已经问世20多年了，但乙肝病毒感染(每年有5000多万人感染)仍然是一个主要的健康问题，而且没有有效的慢性感染治疗方法。抗病毒药物已经改善了慢性乙肝的治疗选择，但由于乙肝病毒复制的重新激活，其疗效仍然有限。 在戒毒后。基于疫苗的免疫疗法被认为是一种可能的单一疗法，或者作为抗病毒药物的联合疗法。然而，免疫耐受阻碍了治疗性疫苗的疗效。为了克服慢性携带者的免疫耐受障碍，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，对我们来说同样重要的是，在CD4+T细胞水平上只有部分交叉反应。因此，针对WHcAg特有T细胞位点的CD4+T细胞将为抗PreS1抗体的产生提供同源T-B细胞帮助，并且不会因免疫耐受而受到抑制。事实上，在对HBcAg耐受的HBcAg-TG小鼠的初步研究中，WHcAg-preS1 VLP杂交免疫在野生型和HBcAg-TG小鼠中诱导了同等高滴度的抗PreS1抗体。具体地说，在目标1中，我们建议将8个HBs Ag-preS1中和B细胞表位整合到WHcAg VLP载体上，并根据组装、产量、稳定性和免疫原性对构建进行优化，基于VLP的候选疫苗的治疗效果将在乙肝病毒复制的转基因(TG)小鼠模型中进行评估。在目标2中，将继续进行WHcAg-preS1疫苗的临床前开发，包括cGMP的制造和PHARM/TOX的研究。

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.