Department of Animal, Dairy and Veterinary Sciences, Utah State University, Logan, Utah, USA.
Montana Biotechnology Center, University of Montana, Missoula, Montana, USA.
J Virol. 2021 Jun 24;95(14):e0039721. doi: 10.1128/JVI.00397-21.
Live-attenuated virus vaccines are highly effective in preventing viral disease but carry intrinsic risks of residual virulence and reversion to pathogenicity. The classically derived Candid#1 virus protects seasonal field workers in Argentina against zoonotic infection by Junín virus (JUNV) but is not approved in the United States, in part due to the potential for reversion at the attenuating locus, a phenylalanine-to-isoleucine substitution at position 427 in the GP2 subunit of the GPC envelope glycoprotein. Previously, we demonstrated facile reversion of recombinant Candid#1 (rCan) in cell culture and identified an epistatic interaction between the attenuating I427 and a secondary K33S mutation in the stable signal peptide (SSP) subunit of GPC that imposes an evolutionary barrier to reversion. The magnitude of this genetic barrier is manifest in our repeated failures to rescue the hypothetical revertant virus. In this study, we show that K33S rCan is safe and attenuated in guinea pigs and capable of eliciting potent virus-neutralizing antibodies. Immunized animals are fully protected against lethal challenge with virulent JUNV. In addition, we employed a more permissive model of infection in neonatal mice to investigate genetic reversion. RNA sequence analysis of the recovered virus identified revertant viruses in pups inoculated with the parental rCan virus and none in mice receiving K33S rCan ( < 0.0001). Taken together, our findings support the further development of K33S rCan as a safe second-generation JUNV vaccine. Our most successful vaccines comprise weakened strains of virus that initiate a limited and benign infection in immunized persons. The live-attenuated Candid#1 strain of Junín virus (JUNV) was developed to protect field workers in Argentina from rodent-borne hemorrhagic fever but is not licensed in the United States, in part due to the likelihood of genetic reversion to virulence. A single-amino-acid change in the GPC envelope glycoprotein of the virus is responsible for attenuation, and a single nucleotide change may regenerate the pathogenic virus. Here, we take advantage of a unique genetic interaction between GPC subunits to design a mutant Candid#1 virus that establishes an evolutionary barrier to reversion. The mutant virus (K33S rCan) is fully attenuated and protects immunized guinea pigs against lethal JUNV infection. We find no instances of reversion in mice inoculated with K33S rCan. This work supports the further development of K33S rCan as a second-generation JUNV vaccine.
活病毒疫苗在预防病毒病方面非常有效，但存在残余毒力和回复致病性的内在风险。经典衍生的 Candid#1 病毒可保护阿根廷季节性野外工作者免受 Junín 病毒 (JUNV) 的动物源性感染，但未在美国获得批准，部分原因是在减弱的位置存在回复的潜在风险，即在 GPC 包膜糖蛋白 GP2 亚单位中第 427 位的苯丙氨酸到异亮氨酸取代。以前，我们证明了重组 Candid#1(rCan) 在细胞培养中容易回复，并鉴定了在 GPC 稳定信号肽 (SSP) 亚单位中与减弱的 I427 相互作用的上位性，这对回复施加了进化障碍。这种遗传障碍的大小表现在我们反复未能挽救假设的回复病毒上。在这项研究中，我们表明 K33S rCan 在豚鼠中是安全和减毒的，并能够引发有效的病毒中和抗体。免疫动物完全免受致命性强毒 JUNV 攻击的保护。此外，我们在新生小鼠中采用了更宽松的感染模型来研究遗传回复。从接种亲本 rCan 病毒的幼鼠中回收的病毒的 RNA 序列分析表明，在接受 K33S rCan 的小鼠中没有发现回复病毒（<0.0001）。总之，我们的研究结果支持进一步开发 K33S rCan 作为安全的第二代 JUNV 疫苗。我们最成功的疫苗包括减毒病毒株，这些病毒株在免疫人群中引发有限且良性的感染。Junín 病毒 (JUNV) 的活减毒 Candid#1 株被开发用于保护阿根廷的野外工作者免受啮齿动物传播的出血热的侵害，但未在美国获得许可，部分原因是存在向毒力回复的可能性。病毒包膜糖蛋白 GPC 中的单个氨基酸变化负责衰减，单个核苷酸变化可能使致病性病毒再生。在这里，我们利用 GPC 亚基之间的独特遗传相互作用来设计一种突变 Candid#1 病毒，该病毒建立了回复的进化障碍。突变病毒 (K33S rCan) 完全减毒，可保护免疫豚鼠免受致命 JUNV 感染。我们没有发现接种 K33S rCan 的小鼠中存在回复的情况。这项工作支持进一步开发 K33S rCan 作为第二代 JUNV 疫苗。
