Assessment of the Immunogenicity and Protective Efficacy of a Multiagent DNA Vacc

描述（由申请人提供）：埃博拉病毒（EBOV）和马尔堡病毒（MARV）是NIAID A类病原体，可在人类和非人类灵长类动物中引起严重出血热，死亡率高达90%。目前还没有获得许可的疫苗来预防这些病毒引起的疾病。最近用重组水疱性口炎病毒（VSV）或腺病毒载体EBOV或MARV疫苗在非人灵长类动物中引发保护性免疫的成功表明，可以开发出有效的疫苗。尽管取得了令人鼓舞的结果，但人们对这些疫苗平台在人类中的使用提出了担忧。重组腺病毒疫苗存在复制缺陷；因此，需要非常高的剂量来诱导保护性免疫。更重要的是，由于腺病毒是常见的人类病原体，大多数人都有预先存在的免疫力，这极大地干扰了载体诱导对重组基因产物的免疫反应的能力。除了自然存在的预先存在的免疫力外，重组腺病毒载体的广泛使用使疫苗开发领域复杂化，因为接种疫苗后诱导的载体抗体会抑制对采用类似递送策略的独立疫苗的反应。相比之下，VSV载体是一种通常不会感染人类的活病毒疫苗；然而，它是一种人类病原体，人们对其使用的安全性提出了重大关切。相比之下，DNA疫苗在许多人体临床试验中已被证明是安全的，并且不存在载体免疫的可能性。虽然DNA疫苗在人体中缺乏足够的效力，但体内电穿孔递送系统的发展有可能解决这一缺点。所要求的资金不仅将促进研制安全有效的埃博拉病毒和马尔堡病毒联合疫苗的进展，而且还将推动开发一种疫苗交付平台，该平台有能力满足生物防御领域所需的许多性能属性，即一种易于制造、具有足够效力的稳定疫苗，在很少的免疫接种后就能提供针对多种病原体的保护功效。因此，提出的研究直接解决了本次征集的目标。本研究的具体目的是：(1)通过对两种病毒的GP基因进行密码子优化，构建两种EBOV和两株MARV的改良DNA疫苗；(2)比较不同剂量的DNA候选疫苗经肌内或皮内电穿孔给药小鼠时的免疫原性；(3)评价和比较电穿孔免疫小鼠后DNA联合疫苗与单株疫苗的保护效果；(4)证明EBOV和MARV DNA联合疫苗在非人灵长类动物中的免疫原性和保护效果。

DESCRIPTION (provided by applicant): Ebola (EBOV) and Marburg (MARV) viruses are NIAID Category A pathogens and cause severe hemorrhagic fevers in humans and nonhuman primates with mortalities as high as 90%. There are currently no licensed vaccines for preventing disease caused by these viruses. Recent successes in eliciting protective immunity in nonhuman primates with recombinant vesicular stomatitis virus (VSV) or adenovirus- vectored EBOV or MARV vaccines suggest that effective vaccines can be developed. Despite the promising results, concerns have been raised about the use of these vaccine platforms in humans. The recombinant adenovirus vaccines are replication deficient; thus, very high doses are needed to induce protective immunity. More importantly, because adenoviruses are common human pathogens, most humans have pre- existing immunity, which greatly interferes with the ability of the vector to induce an immune response to the recombinant gene product. In addition to naturally occurring preexisting immunity, the broad use of recombinant adenovirus vectors complicates the field of vaccine development because vector antibodies induced as the result of vaccination would suppress the responses to an independent vaccine utilizing a similar delivery strategy. In contrast, the VSV vector is a live virus vaccine that does not commonly infect humans; however, it is a human pathogen and significant safety concerns about its use have been raised. By comparison, DNA vaccines have been proven safe in many human clinical trials and there is no possibility of vector immunity. While DNA vaccines have lacked sufficient potency in humans, the development of in vivo electroporation delivery systems has the potential to address this shortcoming. The requested funding will not only facilitate progress toward safe and effective combination vaccines for Ebola (EBOV) and Marburg (MARV) viruses, but will also advance the development of a vaccine delivery platform that has the capacity to address many of the performance attributes desired in the field of biodefense, namely a readily manufactured, stable vaccine with sufficient potency to provide protective efficacy against multiple pathogens after few immunizations. As such, the research proposed directly addresses the goals of this solicitation. Specific aims of the research are to: (1) Generate improved DNA vaccine constructs for two species of EBOV and two strains of MARV through codon-optimization of the GP genes of each virus; (2) Compare the immunogenicity of the individual DNA vaccine candidates when delivered to mice in various dosages using electroporation via intramuscular or intradermal routes; (3) Evaluate and compare the protective efficacy of combined vs. individual DNA vaccines in mice after immunization by electroporation; (4) Demonstrate the immunogenicity and protective efficacy of combined EBOV and MARV DNA vaccines in non-human primates.