Erasmus Jesse H, Seymour Robert L, Kaelber Jason T, Kim Dal Y, Leal Grace, Sherman Michael B, Frolov Ilya, Chiu Wah, Weaver Scott C, Nasar Farooq
Institute for Human Infections and Immunity, Center for Tropical Diseases, and Department of Microbiology and Immunology, Center for Structural Biology and Molecular Biophysics, Department of Biochemistry and Molecular Biology University of Texas Medical Branch, Galveston, Texas, USA.
National Center for Macromolecular Imaging, Verna and Marrs McLean Department of Biochemistry and Molecular Biology, and Department of Molecular Virology and Microbiology, Baylor College of Medicine, Houston, Texas, USA.
J Virol. 2018 Jan 30;92(4). doi: 10.1128/JVI.01274-17. Print 2018 Feb 15.
Most alphaviruses are mosquito borne and exhibit a broad host range, infecting many different vertebrates, including birds, rodents, equids, humans, and nonhuman primates. Recently, a host-restricted, mosquito-borne alphavirus, Eilat virus (EILV), was described with an inability to infect vertebrate cells based on defective attachment and/or entry, as well as a lack of genomic RNA replication. We investigated the utilization of EILV recombinant technology as a vaccine platform against eastern (EEEV) and Venezuelan equine encephalitis viruses (VEEV), two important pathogens of humans and domesticated animals. EILV chimeras containing structural proteins of EEEV or VEEV were engineered and successfully rescued in cells. Cryo-electron microscopy reconstructions at 8 and 11 Å of EILV/VEEV and EILV/EEEV, respectively, showed virion and glycoprotein spike structures similar to those of VEEV-TC83 and other alphaviruses. The chimeras were unable to replicate in vertebrate cell lines or in brains of newborn mice when injected intracranially. Histopathologic examinations of the brain tissues showed no evidence of pathological lesions and were indistinguishable from those of mock-infected animals. A single-dose immunization of either monovalent or multivalent EILV chimera(s) generated neutralizing antibody responses and protected animals against lethal challenge 70 days later. Lastly, a single dose of monovalent EILV chimeras generated protective responses as early as day 1 postvaccination and partial or complete protection by day 6. These data demonstrate the safety, immunogenicity, and efficacy of novel insect-specific EILV-based chimeras as potential EEEV and VEEV vaccines. Mostly in the last decade, insect-specific viruses have been discovered in several arbovirus families. However, most of these viruses are not well studied and largely have been ignored. We explored the use of the mosquito-specific alphavirus EILV as an alphavirus vaccine platform in well-established disease models for eastern (EEE) and Venezuelan equine encephalitis (VEE). EILV-based chimeras replicated to high titers in a mosquito cell line yet retained their host range restriction in vertebrates both and In addition, the chimeras generated immune responses that were higher than those of other human and/or equine vaccines. These findings indicate the feasibility of producing a safe, efficacious, mono- or multivalent vaccine against the encephalitic alphaviruses VEEV and EEEV. Lastly, these data demonstrate how host-restricted, insect-specific viruses can be engineered to develop vaccines against related pathogenic arboviruses that cause severe disease in humans and domesticated animals.
大多数甲病毒由蚊子传播，宿主范围广泛，可感染许多不同的脊椎动物，包括鸟类、啮齿动物、马科动物、人类和非人类灵长类动物。最近，一种宿主受限、由蚊子传播的甲病毒——埃拉特病毒（EILV）被发现，它由于附着和/或进入缺陷以及缺乏基因组RNA复制而无法感染脊椎动物细胞。我们研究了利用EILV重组技术作为针对东部马脑炎病毒（EEEV）和委内瑞拉马脑炎病毒（VEEV）的疫苗平台，这两种病毒是人类和家畜的重要病原体。构建了含有EEEV或VEEV结构蛋白的EILV嵌合体，并在细胞中成功拯救出来。分别在8 Å和11 Å分辨率下对EILV/VEEV和EILV/EEEV进行冷冻电子显微镜重建，结果显示病毒粒子和糖蛋白刺突结构与VEEV-TC83及其他甲病毒相似。这些嵌合体在脊椎动物细胞系中或经颅内注射到新生小鼠脑中后无法复制。对脑组织的组织病理学检查未发现病理损伤迹象，与 mock 感染动物的脑组织无异。单剂量接种单价或多价EILV嵌合体可产生中和抗体反应，并在70天后保护动物免受致死性攻击。最后，单剂量的单价EILV嵌合体在接种后第1天就产生了保护性反应，到第6天可提供部分或完全保护。这些数据证明了新型昆虫特异性EILV嵌合体作为潜在的EEEV和VEEV疫苗的安全性、免疫原性和有效性。主要在过去十年中，在几个虫媒病毒科中发现了昆虫特异性病毒。然而，这些病毒大多未得到充分研究，在很大程度上被忽视了。我们在成熟的东部马脑炎（EEE）和委内瑞拉马脑炎（VEE）疾病模型中探索了利用蚊子特异性甲病毒EILV作为甲病毒疫苗平台。基于EILV 的嵌合体在蚊子细胞系中复制至高滴度，但在脊椎动物中仍保留其宿主范围限制。此外，这些嵌合体产生的免疫反应高于其他人类和/或马用疫苗。这些发现表明生产针对脑炎甲病毒VEEV和EEEV的安全、有效、单价或多价疫苗是可行的。最后，这些数据证明了如何对宿主受限的昆虫特异性病毒进行改造，以开发针对在人类和家畜中引起严重疾病的相关致病性虫媒病毒的疫苗。
