York Joanne, Nunberg Jack H
Montana Biotechnology Center, University of Montana, Missoula, Montana, USA.
Montana Biotechnology Center, University of Montana, Missoula, Montana, USA
J Virol. 2017 Dec 14;92(1). doi: 10.1128/JVI.01682-17. Print 2018 Jan 1.
The Candid#1 strain of Junín virus was developed using a conventional attenuation strategy of serial passage in nonhost animals and cultured cells. The live-attenuated Candid#1 vaccine is used in Argentina to protect at-risk individuals against Argentine hemorrhagic fever, but it has not been licensed in the United States. Recent studies have revealed that Candid#1 attenuation is entirely dependent on a phenylalanine-to-isoleucine substitution at position 427 in the fusion subunit (GP2) of the viral envelope glycoprotein complex (GPC), thereby raising concerns regarding the potential for reversion to virulence. In this study, we report the identification and characterization of an intragenic epistatic interaction between the attenuating F427I mutation in GP2 and a lysine-to-serine mutation at position 33 in the stable signal peptide (SSP) subunit of GPC, and we demonstrate the utility of this interaction in creating an evolutionary barrier against reversion to the pathogenic genotype. In the presence of the wild-type F427 residue, the K33S mutation abrogates the ability of ectopically expressed GPC to mediate membrane fusion at endosomal pH. This defect is rescued by the attenuating F427I mutation. We show that the recombinant Candid#1 (rCan) virus bearing K33S GPC is viable and retains its attenuated genotype under cell culture conditions that readily select for reversion in the parental rCan virus. If back-mutation to F427 offers an accessible pathway to increase fitness in rCan, reversion in K33S-GPC rCan is likely to be lethal. The epistatic interaction between K33S and F427I thus may minimize the likelihood of reversion and enhance safety in a second-generation Candid#1 vaccine. The live-attenuated Candid#1 vaccine strain of Junín virus is used to protect against Argentine hemorrhagic fever. Recent findings that a single missense mutation in the viral envelope glycoprotein complex (GPC) is responsible for attenuation raise the prospect of facile reversion to pathogenicity. Here, we characterize a genetic interaction between GPC subunits that evolutionarily forces retention of the attenuating mutation. By incorporating this secondary mutation into Candid#1 GPC, we hope to minimize the likelihood of reversion and enhance safety in a second-generation Candid#1 vaccine. A similar approach may guide the design of live-attenuated vaccines against Lassa and other arenaviral hemorrhagic fevers.
胡宁病毒的Candid#1株是采用在非宿主动物和培养细胞中连续传代的传统减毒策略培育而成。减毒活疫苗Candid#1在阿根廷用于保护高危个体预防阿根廷出血热，但尚未在美国获得许可。最近的研究表明，Candid#1的减毒完全依赖于病毒包膜糖蛋白复合物（GPC）融合亚基（GP2）第427位苯丙氨酸到异亮氨酸的替换，这引发了对其毒力回复可能性的担忧。在本研究中，我们报告了在GP2中减毒的F427I突变与GPC稳定信号肽（SSP）亚基第33位赖氨酸到丝氨酸突变之间的基因内上位性相互作用的鉴定和表征，并证明了这种相互作用在创建针对致病基因型回复的进化屏障中的作用。在野生型F427残基存在的情况下，K33S突变消除了异位表达的GPC在内体pH值下介导膜融合的能力。这种缺陷通过减毒的F427I突变得以挽救。我们表明，携带K33S GPC的重组Candid#1（rCan）病毒是可行的，并且在易于选择亲代rCan病毒回复的细胞培养条件下保留其减毒基因型。如果回突变为F427提供了一条增加rCan适应性的途径，那么K33S - GPC rCan中的回复可能是致命的。因此，K33S和F427I之间的上位性相互作用可能会降低回复的可能性，并提高第二代Candid#1疫苗的安全性。胡宁病毒的减毒活疫苗Candid#1株用于预防阿根廷出血热。最近的研究发现病毒包膜糖蛋白复合物（GPC）中的单个错义突变导致减毒，这增加了轻易回复至致病性的可能性。在这里，我们表征了GPC亚基之间的遗传相互作用，这种相互作用在进化上迫使减毒突变得以保留。通过将这种二次突变纳入Candid#1 GPC，我们希望降低回复的可能性，并提高第二代Candid#1疫苗的安全性。类似的方法可能会指导针对拉沙热和其他沙粒病毒出血热的减毒活疫苗的设计。
