Rapid Development of Vaccines for Emerging Viruses

虽然ZIKV在美洲的爆发已经消退，但在怀孕期间暴露于ZIKV的母亲所生的婴儿中存在先天性Zika综合征的持续风险。目前还没有获得许可的疫苗或治疗方法来对抗ZIKV感染。由于对ZIKV疫苗的迫切需求，以及在当前疫情中证明有效性的时间有限，我们专注于开发一种可以快速生产并可以使用遗传技术轻松修饰的DNA疫苗。第一代DNA疫苗是基于先前在西尼罗河病毒上的成功。我们设计并评价了两种在转染后产生亚病毒颗粒（SVP）的前导DNA疫苗候选物。 第一候选物（VRC 5283）表达来自ZIKV法属波利尼西亚2014菌株的prM和E蛋白。 另一种（VRC 5288）是ZIKV/JEV嵌合体病毒，并且被设计为用来自ZIKV的相应区域交换的最后98个氨基酸（包含来自JEV的跨膜结构域和茎结构域），这已被证明改善其他黄病毒的SVP分泌。用这些构建体免疫在小鼠和恒河猴中产生稳健的中和抗体应答。 两剂表达寨卡病毒prM和E蛋白的候选DNA疫苗在寨卡病毒攻击后保护了18只恒河猴中的17只免于病毒血症。 这种保护与血清中和活性相关。 单剂量DNA疫苗并不能完全预防感染，但显著降低了寨卡病毒攻击恒河猴的病毒血症水平。 随后，我们通过进行剂量递减研究来继续研究这两种DNA疫苗，以确定保护的中和抗体阈值和保护的相关性。 此外，我们还与多个小组合作，帮助开发替代ZIKV疫苗，包括基于mRNA的疫苗和减毒活疫苗。 尼帕病毒（NiV）在动物宿主中传播，并在印度和东南亚的人类中引起零星爆发。 NiV通过呼吸道途径传播，但可以发展成高度致命的神经系统疾病。目前还没有针对尼帕病毒的许可疫苗或治疗方法，尽管目前正在开发用于尼帕病毒的G蛋白疫苗和来自相关亨德拉病毒的mAb。 我们已经开始使用基于结构的设计来稳定融合蛋白在其融合前的确认，以用作疫苗免疫原。 在建立G抗体作为亨德拉病毒保护相关物的基础上，我们还开发了寡聚G蛋白疫苗和表达Pre-F和G蛋白的嵌合疫苗。 这些疫苗在蛋白质和mRNA平台中具有高度免疫原性，表达这些抗原的mRNA疫苗目前正在雪貂攻击模型中进行评估，并正在向临床试验测试迈进。我们正在采取同样的方法来开发针对其他副粘病毒（麻疹和腮腺炎）的亚单位和基因疫苗，并正在动物模型中评估候选疫苗。 肠道病毒D 68在儿科人群中引起一年两次的呼吸道疾病，并与急性氟脲嘧啶（AFM）的爆发有时间关系。 我们已经开始努力开发表达EV-D 68结构蛋白的VLP疫苗。 我们已经证明了B1亚型VLP的免疫原性和B3和A2亚型病毒的交叉中和。我们正在继续开发免疫缺陷AG 129小鼠和小鼠适应B3和A2亚型病毒的攻击模型，以评估VLP引发的免疫应答的功效。我们的目标是应用该项目的知识开发一个肠道病毒疫苗平台，可用于针对相关肠道病毒的疫苗。

While the outbreak of ZIKV in the Americas has subsided, there is an ongoing risk of congenital Zika syndrome in babies born to mothers exposed to ZIKV during pregnancy. There is no licensed vaccine or treatment to combat ZIKV infection. Because of the urgent need for a ZIKV vaccine, and a finite time in which efficacy could be demonstrated in the current outbreak, we focused on developing a DNA vaccine which can be rapidly produced and can easily modified using genetic techniques. The first generation DNA vaccines are based on prior success in West Nile Virus. We designed and evaluated two lead DNA vaccine candidates which produce subviral particles (SVP) after transfection. The first candidate (VRC5283) expresses the prM and E proteins from the ZIKV French Polynesia 2014 strain. The other (VRC5288) is a ZIKV/JEV chimera virus and was designed with the final 98 amino acids of (comprising the transmembrane and stem domains from JEV) swapped for the corresponding regions from ZIKV which has been demonstrated to improve SVP secretion for other flaviviruses. Immunization with these constructs generated robust neutralizing antibody responses in mice and rhesus macaques. Two doses of DNA vaccine candidates expressing the prM and E proteins of Zika virus protected 17 out of 18 rhesus macaques from viremia after Zika virus challenge. This protection was correlated with serum neutralizing activity. A single dose of DNA vaccine did not completely prevent infection, but significantly reduced the level of viremia in Zika virus challenged rhesus macaques. Subsequently, we have continued to study the two DNA vaccines by performing dose de-escalation studies to determine the neutralizing antibody threshold of protection, and correlates of protection. Additionally, we have collaborated with multiple groups to help develop alternative ZIKV vaccines, including mRNA-based and live-attenuated vaccines. Nipah Virus (NiV) circulates in animal reservoirs and has caused sporadic outbreaks in humans in India and South East Asia. NiV is transmitted by the respiratory route, but can develop into a highly fatal neurologic disease. There is no licensed vaccine or treatment for NiV, although a G protein vaccine, and mAb from the related Hendra virus are currently being developed for Nipah. We have begun to use structure-based design to stabilize the fusion protein in its prefusion confirmation to use as a vaccine immunogen. Based on the establishment of G antibodies as a correlate of protection for Hendra virus, we also developed oligomeric G protein vaccines and chimeric vaccine that expresses the Pre-F and G protein. These vaccines are highly immunogenic in the protein and mRNA platforms and mRNA vaccines expressing these antigens are currently being evaluated in a ferret challenge model and advancing toward clinical trial testing. We are taking the same approach to develop subunit and gene-based vaccines for other paramyxoviruses (measles and mumps), and are evaluating candidates in animal models. Enterovirus D68 causes biannual respiratory illnesses in pediatric populations, and has been temporally related to outbreaks of acute flacid myelitis (AFM). We have begun efforts to develop a VLP vaccine that expresses the structural proteins of EV-D68. We have demonstrated immunogenicity of B1 subclade VLP and cross-neutralization of B3 and A2 subclade viruses. We are continuing to develop challenge models in immunodeficient AG129 mice, and mouse adapting B3 and A2 subclade viruses to evaluate the efficacy of VLP-elicited immune responses. We aim to apply the knowledge from this project to develop an enterovirus vaccine platform that can be used for vaccines against related enteroviruses.