First Identification and Pathogenicity Evaluation of an EV-G17 Strain Carrying a Torovirus Papain-like Cysteine Protease (PLCP) Gene in China

Abstract

Enterovirus G (EV-G) is prevalent in pig populations worldwide, and a total of 20 genotypes (G1 to G20) have been confirmed. Recently, recombinant EV-Gs carrying the papain-like cysteine protease (PLCP) gene of porcine torovirus have been isolated or detected, while their pathogenicity is poorly understood. In this study, an EV-G17-PLCP strain, ‘EV-G/YN23/2022’, was isolated from the feces of pigs with diarrhea, and the virus replicated robustly in numerous cell lines. The isolate showed the highest complete genome nucleotide (87.5%) and polyprotein amino acid (96.6%) identity in relation to the G17 strain ‘IShi-Ya4’ (LC549655), and a possible recombination event was detected at the 708 and 3383 positions in the EV-G/YN23/2022 genome. EV-G/YN23/2022 was nonlethal to piglets, but mild diarrhea, transient fever, typical skin lesions, and weight gain deceleration were observed. The virus replicated efficiently in multiple organs, and the pathological lesions were mainly located in the small intestine. All the challenged piglets showed seroconversion for EV-G/YN23/2022 at 6 to 9 days post-inoculation (dpi), and the neutralization antibody peaked at 15 dpi. The mRNA expression levels of IL-6, IL-18, IFN-α, IFN-β, and ISG-15 in the peripheral blood mononuclear cells (PBMCs) were significantly up-regulated during viral infection. This is the first documentation of the isolation and pathogenicity evaluation of the EV-G17-PLCP strain in China. The results may advance our understanding of the evolution characteristics and pathogenesis of EV-G-PLCP.

First Detection of Recombinant Enterovirus G Carrying a Torovirus Papain-like cysteine protease Gene from India

“…Recently, two types of EV-G variants arising from recombination of G1, G2, G8, G10, G12, G17 genotypes and papain-like cysteine protease sequence (PLCP) from torovirus are reported (Li et al, 2023) sequences was detected in Japanese pig faeces (Imai et al, 2019). The PLCP gene present in ORF1 of torovirus serves as protease to cleave viral ORF1a and ORF1b polyproteins to nonstructural proteins (Mielech et al, 2014).…”

“…The EV-G currently includes 20 genotypes, which undergo intragenotypic and intergenotypic recombination or cross-order recombination between EV-G (Picornavirales), and torovirus (family Coronaviridae and order Nidovirales) (Muslin et al, 2015). Recently, two types of EV-G variants arising from recombination of G1, G2, G8, G10, G12, G17 genotypes and papain-like cysteine protease sequence (PLCP) from torovirus are reported (Li et al, 2023). The type 1 recombinant have insertion sequence at 2C-3A junction and detected from fecal samples of porcine diarrhea cases in USA, Belgium, Germany, South Korea (Bunke et al, 2018; Knutson et al, 2017; Shang et al, 2017; Conceição-Neto et al, 2017; Lee & Lee, 2019), while from asymptomatic and diarrheic pigs in Japan (Tsuchiaka et al, 2018).…”

“…Another way the virulence of EV-G is influenced by the acquisition of foreign innate immune antagonist, torovirus PLCP. Additionally, experimental proven pathogenic potential of G1-PLCP genotype (Mi et al, 2021), the capacity of EV-G-PLCP to infect cell lines from diverse origins (Li et al, 2023) and non-homologous recombination between EV-G (picornavirus) and torovirus (coronavirus) highlights their potential to cross species barriers.…”