Institute of Virology, Justus Liebig University Giessen, Germany.
Institute of Virology and Immunology (IVI), Bern and Mittelhäusern, Switzerland.
J Virol. 2023 Jul 27;97(7):e0196422. doi: 10.1128/jvi.01964-22. Epub 2023 Jun 26.
Porcine epidemic diarrhea virus is a swine pathogen that has been responsible for significant animal and economic losses worldwide in recent years. In this manuscript, we report the generation of a reverse genetics system C(RGS) for the highly virulent US PEDV strain Minnesota (PEDV-MN; GenBank accession number KF468752), which was based on the assembly and cloning of synthetic DNA, using vaccinia virus as a cloning vector. Viral rescue was only possible following the substitution of 2 nucleotides within the 5'UTR and 2 additional nucleotides within the spike gene, based on the sequence of the cell culture-adapted strains. Besides displaying a highly pathogenic phenotype in newborn piglets, in comparison with the parental virus, the rescued recombinant PEDV-MN was used to confirm that the PEDV spike gene has an important role in PEDV virulence and that the impact of an intact PEDV ORF3 on viral pathogenicity is modest. Moreover, a chimeric virus with a TGEV spike gene in the PEDV backbone generated with RGS was able to replicate efficiently and could be readily transmitted between piglets. Although this chimeric virus did not cause severe disease upon the initial infection of piglets, there was evidence of increasing pathogenicity upon transmission to contact piglets. The RGS described in this study constitutes a powerful tool with which to study PEDV pathogenesis and can be used to generate vaccines against porcine enteric coronaviruses. PEDV is a swine pathogen that is responsible for significant animal and economic losses worldwide. Highly pathogenic variants can lead to a mortality rate of up to 100% in newborn piglets. The generation of a reverse genetics system for a highly virulent PEDV strain originating from the United States is an important step in phenotypically characterizing PEDV. The synthetic PEDV mirrored the authentic isolate and displayed a highly pathogenic phenotype in newborn piglets. With this system, it was possible to characterize potential viral virulence factors. Our data revealed that an accessory gene (ORF3) has a limited impact on pathogenicity. However, as it is also now known for many coronaviruses, the PEDV spike gene is one of the main determinants of pathogenicity. Finally, we show that the spike gene of another porcine coronavirus, namely, TGEV, can be accommodated in the PEDV genome background, suggesting that similar viruses can emerge in the field via recombination.
猪流行性腹泻病毒是一种猪病原体,近年来在全球范围内造成了重大动物和经济损失。在本手稿中,我们报告了一种基于痘苗病毒作为克隆载体的合成 DNA 组装和克隆,为高度毒力的美国 PEDV 株明尼苏达州(PEDV-MN;GenBank 登录号 KF468752)生成反向遗传学系统 C(RGS)。基于细胞培养适应株的序列,只有在 5'UTR 内替换 2 个核苷酸和 Spike 基因内另外 2 个核苷酸后,才能进行病毒拯救。与亲本病毒相比,拯救的重组 PEDV-MN 不仅表现出高致病性表型,还证实了 PEDV Spike 基因在 PEDV 毒力中具有重要作用,并且完整的 PEDV ORF3 对病毒致病性的影响适度。此外,使用 RGS 生成的具有 TGEV Spike 基因的 PEDV 骨架嵌合病毒能够有效地复制,并能够在仔猪之间容易传播。尽管这种嵌合病毒在仔猪初次感染时不会引起严重疾病,但在传播给接触仔猪时,有证据表明其致病性增加。本研究中描述的 RGS 构成了研究 PEDV 发病机制的有力工具,并可用于生成针对猪肠冠状病毒的疫苗。PEDV 是一种在全球范围内导致重大动物和经济损失的猪病原体。高致病性变体可导致新生仔猪的死亡率高达 100%。生成源自美国的高度毒力 PEDV 株的反向遗传学系统是表型表征 PEDV 的重要步骤。合成的 PEDV 与真实分离株相匹配,并在新生仔猪中表现出高致病性表型。通过该系统,可以对潜在的病毒毒力因子进行特征描述。我们的数据表明,一个辅助基因(ORF3)对致病性的影响有限。然而,正如许多冠状病毒现在也已知的那样,PEDV Spike 基因是致病性的主要决定因素之一。最后,我们表明,另一种猪冠状病毒,即 TGEV 的 Spike 基因可以容纳在 PEDV 基因组背景中,这表明通过重组,类似的病毒可以在野外出现。