Development of a founder-based CMV vaccine to interrupt Ebola virus transmission

描述（由申请方提供）：埃博拉病毒（EBOV）是丝状病毒科的一种阴性单链RNA病毒，被列为NIAID A类病原体。该项目的长期目标是开发基于巨细胞病毒（CMV）的疫苗，以干扰野生类人猿种群中的EBOV传播。近年来，西非严重EBOV相关出血热的人间暴发一直在增加，导致高发病率和死亡率，死亡率接近90%1。人类的自然宿主和传播方式尚未确定，但蝙蝠和类人猿（大猩猩和黑猩猩）似乎在传播中发挥了作用。在啮齿动物和非人灵长类动物（NHP）模型中已显示出保护免受EBOV的候选疫苗都不具有从初始疫苗接受者有效传播到群体的其他成员的能力1，7-16。因此，群体免疫要求大多数人接种疫苗。这种无法传播的情况在将EBOV疫苗瞄准无法接触的西非巨猿种群时造成了困难。使用表达EBOV抗原的基于CMV的载体的疫苗可能对于这种难以接近的野生种群是理想的。CMV具有显著的再感染和通过人群传播的能力，而不管先前的CMV免疫力如何17 -19。基于CMV的疫苗也是高度免疫原性的17，20-24。在我们的策略中，对“创始人”进行疫苗接种将首先在人群中传播疫苗，从而消除对所有个体进行免疫接种的需要。CMV也是垂直传播的，因此基于CMV的疫苗可以提供预防EBOV传播的永久解决方案。CMV很可能在野生大猩猩和黑猩猩中普遍存在25 -27。基于CMV的疫苗仅仅代表了一种良性的、普遍存在的病毒的感染，不同之处仅在于表达EBOV衍生的抗原。EBOV作为五种抗原性不同的物种存在。我们建议构建基于CMV的载体，分别表达EBOV糖蛋白（GP）（体液免疫应答的主要但高度可变的靶标）和EBOV核蛋白（NP）（含有多个T细胞表位的更高度保守的蛋白质）。靶向GP和NP两者可以诱导异源（交叉EBOV物种）以及同源保护。这项初步研究旨在建立基于创始人的EBOV疫苗的原则，非常适合R21资助。在小鼠中用MCMV建立“原理验证”将支持R 01应用以评估在NHP模型中由表达GP和NP的基于恒河猴CMV的载体提供的保护，其中还可以评估交叉保护水平。具体目标1：将在体外构建和表征分别表达EBOV GP或NP的两种鼠CMV（MCMV）载体构建体（分别命名为MCMV/EBOV-GP和-NP）。具体目标2：将确定MCMV/EBOV载体在小鼠中诱导和维持EBOV GP和NP特异性体液和T细胞应答的能力。具体目标3：将确定MCMV/EBOV载体在小鼠模型中保护免受小鼠适应性EBOV攻击的能力。 公共卫生相关性：埃博拉病毒（EBOV）是一种NIAID A类病原体，可在西非流行地区引起致命性出血热暴发。爆发的频率一直在上升，加上意外和故意释放到非流行国家的可能性，使EBOV成为一个主要的健康问题。该项目的长期目标是开发基于巨细胞病毒（CMV）的疫苗，以干扰野生类人猿种群中的EBOV传播，从而阻断EBOV传播给人类的传染渠道。

DESCRIPTION (provided by applicant): Ebola virus (EBOV) is a negative single-stranded RNA virus of the filovirus family that is listed as a NIAID Category A agent. The long-term aim of this project is to develop cytomegalovirus (CMV)-based vaccines to interfere with EBOV transmission in wild Great Ape populations. Human outbreaks of severe EBOV-associated hemorrhagic fever in Western Africa have been increasing in recent years, resulting in high morbidity and mortality with a death rate approaching 90%1. The natural reservoir and mode of transmission to humans is not defined, however bats and Great Apes (gorillas and chimpanzees) appear to play a role in transmission. None of the vaccine candidates that have been shown to protect against EBOV in rodent and non-human primate (NHP) models have the ability to spread efficiently from initial vaccine recipients to other members of the population1,7-16. Thus, population immunization requires that most individuals are vaccinated. This inability to disseminate poses difficulties when targeting EBOV vaccines to inaccessible Western African Great Ape populations. A vaccine using CMV-based vectors expressing EBOV antigens may be ideal for such inaccessible wild populations. CMV possesses the remarkable ability to re-infect and disseminate through the population regardless of prior CMV immunity17-19. CMV-based vaccines are also highly immunogenic17,20-24. In our strategy, vaccination of 'founders' would initially spread the vaccine through the population, eliminating the need for immunization of all individuals. CMV is also transmitted vertically, thus a CMV-based vaccine could afford a permanent solution to preventing EBOV transmission. CMV is most likely ubiquitous in wild gorillas and chimpanzees25-27. A CMV-based vaccine merely represents infection with a benign, ubiquitous virus, differing only by expression of EBOV-derived antigens. EBOV exists as five antigenically distinct species. We propose to construct CMV-based vectors individually expressing EBOV glycoprotein (GP) (a major, but highly variable target of the humoral immune response) and EBOV nucleoprotein (NP) (a more highly conserved protein containing multiple T cell epitopes). Targeting both GP and NP may induce heterologous (cross-EBOV species) as well as homologous protection. This initial study to establish the principle of a founder-based vaccine for EBOV is ideally suited to R21 funding. Establishment of 'proof-of-principle' with MCMV in mice will support an R01 application to assess protection afforded by GP and NP-expressing rhesus CMV-based vectors in the NHP model, wherein levels of cross-protection can also be assessed. Specific Aim 1: will construct and characterize in vitro two murine CMV (MCMV) vector constructs individually expressing either EBOV GP or NP (designated MCMV/EBOV-GP and -NP, respectively). Specific Aim 2: will determine the ability of MCMV/EBOV vectors to induce and maintain an EBOV GP and NP-specific humoral and T cell response in mice. Specific Aim 3: will determine the capacity of MCMV/EBOV vectors to protect against mouse-adapted EBOV challenge in a mouse model. PUBLIC HEALTH RELEVANCE: Ebola virus (EBOV) is a NIAID Category A agent that causes outbreaks of lethal haemorrhagic fever in endemic areas of Western Africa. The frequency of outbreaks has been on the rise, which combined with the potential for accidental and deliberate release into non-endemic nations, makes EBOV a major health concern. The long-term aim of this project is to develop cytomegalovirus (CMV)-based vaccines to interfere with EBOV transmission in wild Great Ape populations, and thereby block this infectious conduit for EBOV transmission to Man.