Development of a Recombinant Tetravalent Dengue Vaccine Based on a Subunit Envelo

描述（由申请人提供）：登革热对全球超过25亿人构成重大威胁，目前尚无获得许可的疫苗。有效和安全的疫苗需要对所有四种血清型登革热病毒（DENV-1至-4）有平衡的免疫反应，因为不同血清型登革热病毒的连续感染可导致危及生命的登革出血热或登革休克综合征。减毒活疫苗或基于嵌合病毒的疫苗很有希望，但由于干扰，它们存在衰减不足或免疫反应不平衡的问题。虽然干扰可以通过12个月的免疫计划来克服，但这一计划使得疫苗不适合需要快速发展免疫力的接受者。此外，与17D相关的安全问题可能限制其在免疫功能低下的个体、儿童或老年人中的使用。基于我们临床验证的疫苗平台，我们开发了一系列黄病毒疫苗，分为三种格式，不同的是抗原附着在鞭毛蛋白（一种TLR5配体）上的位置。这些候选疫苗

DESCRIPTION (provided by applicant): Dengue disease poses a significant threat to over 2.5 billion people worldwide and currently, no licensed vaccine is available. An effective and safe vaccine requires a balanced immune response to all four serotypes of dengue viruses (DENV-1 to -4) because sequential infection by different dengue virus serotypes can lead to life-threatening dengue hemorrhagic fever or dengue shock syndrome. Live attenuated or chimeric virus-based vaccines are promising but they struggle with inadequate attenuation or an imbalanced immune response due to interference. While interference can be overcome by a 12-month immunization schedule, this schedule renders the vaccine unsuitable for recipients requiring rapid development of immunity. Additionally, safety concerns associated with 17D may limit its use in immunocompromised individuals, children or elderly. We have developed a series of flavivirus vaccines based on our clinically proven vaccine platform in three formats, which differ in the site of antigen attachment to the flagellin (a TLR5 ligand). These vaccine candidates can be efficiently produced and elicit protective levels of neutralizing antibodies to both dengue serotypes. TLR signaling triggers an innate immune cascade that enhances antigen uptake and presentation, and facilitates induction of adaptive immune response, thereby eliminating the need for adjuvants typically used in subunit vaccines. Flagellin contains of four distinct domains (D0, D1, D2, and D3) where D1 contains the TLR5 binding site. Antigens can be fused to the C-terminus in the C-term format, in place of D3 in the R3 format, or to both positions in two copies in the R3.2x formats. Among the three, the R3.2x format was found to be the safest and the most immunogenic in Phase I trials of influenza vaccine. To develop flavivirus vaccines, we initially fused the domain III of the envelope (EIII) to the C-terminus of the flagellin. We have demonstrated that monovalent West Nile and DENV-2 vaccine candidates based on the flagellin-EIII fusion induce potent antibody responses and are efficacious in mouse challenge models. We have subsequently generated flagellin-EIII dengue vaccines in various formats, and have identified R3.2x as the lead format for use in a tetravalent vaccine candidate in mice and non-human primates (NHP). Based on recent findings of neutralizing epitopes of human polyclonal and monoclonal antibodies, we have generated backup subunit flagellin-E vaccines that include major neutralizing epitopes in the domains III and I of the E protein (EIEIII) as well as the EI/EII junction region. We here propose to optimize the lead TDV formulation (dose level and component ratio) in immunogenicity studies in mice, and then to optimize the fermentation conditions and purification process for those candidates. We will next evaluate the immunogenicity and efficacy of the lead TDV in NHP DENV challenge models, followed by evaluation of dose range using a well-established rabbit reactogenicity model as well as formulation development. We will demonstrate that the tetravalent vaccine induces durable, balanced immune responses that are capable of neutralizing a broad spectrum of strains and genotypes of each serotype, and provides protection against all four DENV serotypes in mouse and monkey models. Once the lead candidates are locked we will develop a liquid formulation suitable for 4 ¿C storage for at least one year. Further, we will confirm a safe and effective window of the TDV candidate to guide the dose selection in the subsequent GLP rabbit toxicity study as well as dose escalating study in phase I trial. The positive outcome of this study will be a solid step towards the successful development of a safer, cheaper, and effective vaccine, which can be used to prevent DENV-associated diseases. Lastly, VaxInnate's rapid and low cost bacteria-based manufacturing can easily be transferred to endemic countries as demonstrated by a recent successful process transfer of the 2009 H1N1 pandemic vaccine.