CAP: Trivalent Filovirus Vaccine for Pre- and Post-Exposure Vaccination

我们已经开发了表达所有种类的埃博拉病毒代表性分离株的糖蛋白(GP)的rVSVs：苏丹埃博拉病毒(Sebov)、扎伊尔埃博拉病毒(ZEBOV)、科特迪瓦埃博拉病毒(CIEBOV)、本迪布乔埃博拉病毒(Bebov)和雷斯顿埃博拉病毒(ReBOV)。此外，我们还构建了表达马尔堡病毒两个分离物的rVSV：维多利亚湖马尔堡病毒分离株Musoke(MARVmus)和安哥拉分离株(MARVang)。主要是rVSV/ZEBOVgp、rVSV/SEBOVgp和rVSV/MARVmusgp疫苗载体已经在细胞培养中得到了广泛的特征，并在动物模型中针对同源挑战评估了它们的保护效果(Hoenen等人)。2012年；法尔扎拉诺和费尔德曼，2013年)。最近，我们证实了rVSV/BEBOVgp和rVSV/MARVangGP在非人类灵长类动物(HAP)中对同源攻击(PLoS Negl trop Dis，修订版)的保护作用。 为了破译rVSV疫苗载体对ZEBOV的保护机制，我们能够在NHP中证明针对病毒抗原的抗体发挥关键作用(Marzi等人，2013年)。正在进行的工作是研究rVSV疫苗载体对Marv的保护机制。明确保护机制(S)和相关(S)将是将该平台转移到临床试验的里程碑。 不同的埃博拉病毒物种之间甚至马尔堡病毒之间的交叉保护是一个重要的考虑因素，但由于遗传和抗原的变异性相对较高，特别是在属之间，而且在单一属内的物种之间，以及即使在物种之间普遍缺乏交叉保护抗体，因此很难实现这一点。在这方面，我们以前曾对包括rVSV/SEBOVgp、rVSV/ZEBOVgp和rVSV/MARVmusGP在内的混合疫苗进行了一次注射方案的概念验证研究，以确定是否可以开发出针对中部非洲流行的四种人类致病性丝状病毒的交叉保护性疫苗。在用MARVmus、Sebov、ZEBOV和CIEBOV免疫四周后进行攻击，从而对同源挑战和异源挑战(CIEBOV)产生保护，表明交叉保护疫苗是可行的(Hoenen等人)。2012年；法尔扎拉诺和费尔德曼，2013年)。最近，我们进行了另一项概念验证研究，在该研究中，我们评估了单一疫苗载体(rVSV/ZEBOVgp或rVSV/CIEBOVgp)免疫后的交叉保护。单独接种rVSV/ZEBOVgp可提供交叉保护(75%的存活率)以抵御随后的异种Bebov攻击，而rVSV/CIEBOVgp接种则没有保护作用。这表明，基于单价rVSV的疫苗可能对新出现的物种有用；然而，跨物种的异源保护仍然具有挑战性，可能取决于通过加强免疫或通过纳入多种免疫原来增强免疫反应(Hoenen等人)。2012年；法尔扎拉诺和费尔德曼，2013年)。总体而言，我们可以得出结论，单价rVSV疫苗载体可以在基因上更密切相关的挑战病毒情况下提供部分交叉保护。克服这一限制的一种方法是使用混合的单价rVSV疫苗载体，它针对同源挑战提供了更广泛的交叉保护，对某些异源挑战提供了部分保护。 克服交叉保护局限性的另一种方法是使用多价rVSV疫苗载体。在一项概念验证研究中，在叙利亚仓鼠模型中，使用同时表达ZEBOVgp和ANDV糖蛋白的单个rVSV载体证明了对ZEBOV和ANDV的保护作用。这些数据表明，双价rVSV载体是一种可行的针对多种病原体的疫苗接种方法。此外，这项研究证明叙利亚仓鼠是研究rVSV介导的保护的适当模型(Hoenen等人。2012年；法尔扎拉诺和费尔德曼，2013年)。 基于上述结果，在过去的一个财政年度，我们已经产生了表达两种或三种不同丝状病毒GP的二价和三价rVSV载体，其中一种作为跨膜蛋白(取代VSV糖蛋白)，以及一种或两种作为可溶性蛋白，在载体复制过程中将被分泌。这些重组疫苗病毒的恢复和体外鉴定正在进行中。最初将使用啮齿动物模型，主要是叙利亚仓鼠，对这些媒介进行效力测试。最有希望的疫苗载体将在非人灵长类动物模型中用于丝状病毒感染的有效性测试。

We have developed rVSVs expressing the glycoproteins (GP) of representative isolates of all species of Ebola virus: Sudan ebolavirus (SEBOV), Zaire ebolavirus (ZEBOV), Cote d'Ivoire ebolavirus (CIEBOV), Bundibugyo ebolavirus (BEBOV) and Reston ebolavirus (REBOV). Additionally, we generated rVSVs expressing the GPs of two isolates of Marburg virus: Lake Victoria marburgvirus isolate Musoke (MARVmus) and Angola (MARVang). Mainly the rVSV/ZEBOVgp, rVSV/SEBOVgp and rVSV/MARVmusGP vaccine vectors have been extensively characterized in cell culture and their protective efficacy has been evaluated in animal models against homologous challenges (Hoenen et al. 2012; Falzarano & Feldmann, 2013). Recently, we were able to demonstrate the protective efficacy of rVSV/BEBOVgp and rVSV/MARVangGP against homologous challenge in nonhuman primates (NHPs) (PLoS Negl Trop Dis, in revision). In an effort to decipher the mechanism of protection of the rVSV vaccine vector against ZEBOV, we were able to demonstrate in NHPs that antibodies specific to the viral antigen play a critical role (Marzi et al., 2013). Ongoing work is investigating the mechanism of protection of the rVSV vaccine vector against MARV. Defining the mechanism(s) and correlate(s) of protection will be milestones for moving the platform into clinical trials. Cross-protection among the different Ebola virus species and even Marburg virus is an important consideration and has been difficult to achieve due to relatively high genetic and antigenic variability among genera in particular, but also among species within a single genus, and the general lack of cross-protective antibodies even among species. In this regard we have previously performed a proof-of-concept study using a single-injection protocol with a blended vaccine including rVSV/SEBOVgp, rVSV/ZEBOVgp and rVSV/MARVmusGP to see if a cross-protective vaccine could be developed against four human pathogenic filoviruses endemic in Central Africa. Challenge was performed four weeks after immunization with MARVmus, SEBOV, ZEBOV and CIEBOV resulting in protection against homologous challenges as well as a heterologous challenge (CIEBOV) indicating that cross-protective vaccines are feasible (Hoenen et al. 2012; Falzarano & Feldmann, 2013). More recently, we have performed another proof-of-concept study in which we evaluated cross-protection following immunization with a single vaccine vector (rVSV/ZEBOVgp or rVSV/CIEBOVgp). A single vaccination with the rVSV/ZEBOVgp provided cross-protection (75% survival) against a subsequent heterologous BEBOV challenge, whereas vaccination with the rVSV/CIEBOVgp resulted in no protection. This demonstrates that monovalent rVSV-based vaccines may be useful against a newly emerging species; however, heterologous protection across species remains challenging and may depend on enhancing the immune responses either through booster immunizations or through the inclusion of multiple immunogens (Hoenen et al. 2012; Falzarano & Feldmann, 2013). Overall, we can conclude that single monovalent rVSV vaccine vectors can provide partial cross-protection in cases of challenge viruses that are genetically more closely related. One approach to overcome this limitation is the use of blended monovalent rVSV vaccine vectors, which provide broader cross-protection against homologous and partial protection against certain heterologous challenges. Another approach to overcome the limitations in cross-protection is the use of multivalent rVSV vaccine vectors. In a proof-of-concept study protection against ZEBOV and Andes virus (ANDV) was demonstrated using a single rVSV vector expressing both the ZEBOVgp and ANDV glycoprotein in the Syrian hamster model. This data showed that bivalent rVSV vectors are a feasible approach to vaccination against multiple pathogens. Further, this study demonstrated that the Syrian hamster is an adequate model to study rVSV-mediated protection (Hoenen et al. 2012; Falzarano & Feldmann, 2013). Based on the results described above, we have in the past fiscal year generated bivalent and trivalent rVSV vectors expressing two or three different filovirus GPs, one as a transmembrane protein (replacing the VSV glycoprotein) and one or two as soluble proteins that will be secreted during vector replication. Recovery of these recombinant vaccine viruses and in vitro characterization are ongoing. Efficacy testing of these vectors will be performed initially using rodent models, mainly the Syrian hamster. The most promising vaccine vectors will be moved into efficacy testing in the nonhuman primate model for filovirus infections.