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

我们的主要疫苗平台是基于重组水疱性口炎病毒(RVSVs)，这是一种减毒活疫苗方法。多年来，我们已经产生了几个表达所有埃博拉病毒物种的代表性分离株的糖蛋白(GP)的rVSV：苏丹埃博拉病毒、扎伊尔埃博拉病毒(EBOV)、塔森林埃博拉病毒、本迪布乔埃博拉病毒(BDBV)和雷斯顿埃博拉病毒(RESTV)。此外，我们还构建了表达马尔堡病毒(Marburg Virus，MARV)两个分离株(Musoke和安哥拉株)的rVSVs。所有疫苗载体在细胞培养中都有广泛的特征，它们的保护效果至少在动物模型(啮齿动物、非人灵长类动物)中进行了评估，主要针对同源挑战。为了应对西非埃博拉疫情，rVSV-EBOV被快速追踪，并被证明对人类是安全的和免疫原性的。在西非启动了rVSV-EBOV的人类II期和III期临床试验。RVSV-EBOV目前正用于刚果民主共和国东北部正在爆发的埃博拉疫情。(在Suder等人的报告中总结。HUM疫苗免疫其他2018年)。 不同丝状病毒物种之间的交叉保护是一个重要的考虑因素，因为撒哈拉以南非洲的特有区域可能会重叠。然而，这似乎很难实现，因为相对较高的遗传变异性，因此不同物种和属的病毒之间的交叉保护性免疫反应有限。在解决这个问题的第一次尝试中，我们以前使用了与三个混合疫苗载体的单次注射方案，并展示了对三个同源病毒物种的完全保护(Geisbert等人。J Virol，2009)。我们还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-EBOV)免疫后的交叉保护，并展示了对异源病毒(BDBV)攻击的部分交叉保护(Falzarano等人)。J Infect Dis 2011)。这表明，基于单价rVSV的疫苗对新出现的丝状病毒物种可能是有用的；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包括多种免疫原来增强免疫反应。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接近的挑战病毒物种的情况下提供部分交叉保护。 如上所述，克服这一限制的一种方法是使用混合的单价rVSV疫苗载体，它提供了更广泛的保护，以抵御同源和部分保护，以抵御某些异源挑战。如果需要，可以立即实施此方法。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。在一项对仓鼠的概念验证研究中，证实了使用同时表达ZEBOV GP和ANDV糖蛋白的单个rVSV载体对ZEBOV和ANDV(ANDV)攻击具有保护作用(Tsuda等人)。J Infect Dis 2011)。这些数据表明，使用双价rVSV载体是一种可行的针对多种病原体的疫苗接种方法。 EBOV GP为重要的免疫细胞提供靶向，如单核/巨噬细胞和树突状细胞。利用这一有利的靶向，我们已经产生了更多的二价rVSV疫苗，以证明通过EBOV GP增强免疫的概念(Prescott等人，疫苗2015)。我们已经开发了表达Nipah病毒糖蛋白(G和F)(De Buysscher等人2014年疫苗；De Wit等人，未发表)、寨卡病毒Prem和E蛋白(Emanuel等人。SCI Rep 2018)、流感血凝素(H5)(Furuyama等人，在修订中)以及Kyasanur森林病病毒的Prem和E蛋白(Bhatia等人，未发表)。在所有情况下，我们都可以在各自的动物模型中表现出完全或几乎完全的保护作用，以抵御同源挑战。我们推测，由于良好的免疫细胞靶向性，基于rVSV-EBOV的疫苗载体将显示出更强的保护作用。根据这一概念，我们最近开发了一种表达拉萨病毒糖蛋白(GP)的rVSV-EBOV载体；动物疗效测试正在进行中。 为了优化rVSV-EBOV载体对外来抗原的免疫应答，我们构建了携带EBOV GP的载体，其粘蛋白样结构域以及粘蛋白样和糖帽结构域被删除。这些载体将维持EBOV GP驱动的细胞靶向，但由于EBOV GP蛋白的主要抗原区已被去除，因此应该显示对EBOV GP的免疫反应减少。我们目前正在组织培养和动物模型中鉴定和评估这些新的rVSV-EBOV载体。 最近，我们评估了rVSV-RESTV作为疫苗载体在一个牲畜物种中的应用。在攻毒前7天，用rVSV-RESTV单针免疫约克夏杂交仔猪。在这种新的动物疾病模型中，疫苗提供了66%的疾病保护。计划进行进一步的研究，以优化疫苗管理以提高疫苗效力(Haddock等人，未发表)。 总体而言，该项目已显示出希望，并应继续下去，因为rVSV方法已证明对紧急疫苗接种有效。病媒可在短时间内产生(1-2个月)，疫苗产品可在几个月内(6-9个月)上市。因此，这个平台有潜力使我们有能力应对新出现的传染病。

Our main vaccine platform is based on recombinant vesicular stomatitis virus (rVSVs), a live-attenuate vaccine approach. Over the years we have generated several rVSVs expressing the glycoproteins (GP) of representative isolates of all ebolavirus species: Sudan ebolavirus, Zaire ebolavirus (EBOV), Ta Forest ebolavirus, Bundibugyo ebolavirus (BDBV) and Reston ebolavirus (RESTV). Additionally, we generated rVSVs expressing the GPs of two isolates of Marburg virus (MARV), Musoke and Angola. All vaccine vectors have been extensively characterized in cell culture and their protective efficacy has been evaluated at least in animal models (rodents, nonhuman primates) largely against homologous challenges. In response to the West African Ebola epidemic, rVSV-EBOV was fast-tracked and shown to be safe and immunogenic in humans. Human phase II and III clinical trials with rVSV-EBOV were initiated in West Africa. rVSV-EBOV is currently being used in the ongoing Ebola outbreak in the northeastern Democratic Republic of the Congo. (summarized in Suder et al. Hum Vaccin Immunother 2018). Cross-protection among the different filovirus species is an important consideration as endemicity zones may overlap in Sub-Saharan Africa. This, however, seems difficult to achieve due to relatively high genetic variability and therefore limited cross-protective immune responses among viruses of different species and genera. In a first attempt to address this issue, we previously used a single-injection protocol with three blended vaccine vectors and demonstrated complete protection against challenge with the three homologous virus species (Geisbert et al. J Virol 2009). We have also performed another proof-of-concept study, in which we evaluated cross-protection following immunization with a single vaccine vector (rVSV-EBOV) and demonstrated partial cross-protection against challenge with a heterologous virus species (BDBV) (Falzarano et al. J Infect Dis 2011). This demonstrates that monovalent rVSV-based vaccines may be useful against a newly emerging filovirus 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. Overall, we can conclude that single monovalent rVSV vaccine vectors can provide partial cross-protection in cases of challenge virus species that are genetically more closely related. As mentioned above, one approach to overcome this limitation is the use of blended monovalent rVSV vaccine vectors, which provide broader protection against homologous and partial protection against certain heterologous challenges. This approach can be immediately implemented if needed. Another approach to overcome the limitations in cross-protection is the use of multivalent rVSV vaccine vectors. In a proof-of-concept study in hamsters protection against ZEBOV and Andes virus (ANDV) challenge was demonstrated using a single rVSV vector expressing both the ZEBOV GP and the ANDV glycoprotein (Tsuda et al. J Infect Dis 2011). This data showed that the use of bivalent rVSV vectors is a feasible approach to vaccination against multiple pathogens. EBOV GP provides targeting to important immune cells such as monocytes/macrophages and dendritic cells. Using this favorable targeting, we have generated further bivalent rVSV vaccines to proof the concept of immune enhancement through EBOV GP (Prescott et al., Vaccine 2015). We have developed rVSV-EBOV vectors expressing the Nipah virus glycoproteins (G and F) (de Buysscher et al Vaccine 2014; de wit et al., unpublished), the Zika virus preM and E proteins (Emanuel et al. Sci Rep 2018), the influenza hemagglutinin (H5) (Furuyama et al., in revision) and the preM and E proteins of Kyasanur Forest Disease virus (Bhatia et al., unpublished). In all cases we could demonstrate complete or nearly complete protection against homologous challenge in respective animal models. We postulate that vaccine vectors based on rVSV-EBOV will show enhanced protection due to favorable immune cell targeting. Following this concept, we recently have generated a rVSV-EBOV vector expressing the Lassa virus glycoprotein (GP); efficacy testing in animals is ongoing. To optimize the rVSV-EBOV vector for immune responses directed to a foreign antigen we have generated vectors carrying an EBOV GP deleted for its mucin-like domain as well as the mucin-like and glycan cap domains. These vectors will maintain the EBOV GP-driven cell targeting but are supposed to show reduced immune responses to EBOV GP as the main antigenic regions of the protein have been removed. We are currently characterizing and evaluating these new rVSV-EBOV vectors in tissue culture and animal models. Recently, we have evaluated rVSV-RESTV as a vaccine vector in a livestock species. Young Yorkshire cross pigs were immunized with a single shot of rVSV-RESTV 7 days prior to challenge. The vaccine provided 66% protection from disease in this new animal disease model. Further studies are planned to optimize vaccine administration to increase vaccine efficacy (Haddock et al., unpublished). Overall, this project has shown promise and should be continued as the rVSV approach has demonstrated efficacy for emergency vaccination. Vectors can be generated in a short period of time (1-2 months) and a vaccine product can be available in several months (6-9 months). Thus, this platform has potential for our response capabilities to counteract emerging infectious diseases.