A novel defective recombinant porcine enterovirus G virus carrying a porcine torovirus papain-like cysteine protease gene and a putative anti-apoptosis gene in place of viral structural protein genes

Abstract

35Enterovirus G (EV-G) belongs to the family of Picornaviridae. Two types of recombinant porcine 36 EV-Gs carrying papain-like cysteine protease (PLCP) gene of porcine torovirus, a virus in 37 Coronaviridae, are reported. Type 1 recombinant EV-Gs are detected in pig feces in Japan, USA, 38 and Belgium and carry the PLPC gene at the junction site of 2C/3A genes, while PLPC gene 39 replaces the viral structural genes in type 2 recombinant EV-G detected in pig feces in a Chinese 40 farm. We identified a novel type 2 recombinant EV-G carrying the PLCP gene with flanking 41 sequences in place of the viral structural genes in pig feces in Japan. The ~0.3 kb-long upstream 42 flanking sequence had no sequence homology with any proteins deposited in GenBank, while the 43 downstream ~0.9 kb-long flanking sequence included a domain having high amino acid sequence 44 homology with a baculoviral inhibitor of apoptosis repeat superfamily. The pig feces, where the 45 novel type 2 recombinant EV-G was detected, also carried type 1 recombinant EV-G. Although the 46 phylogenetic analysis suggested that these two recombinant EV-Gs have independently evolved, 47 type 1 recombinant EV-G might have served as a helper virus by providing viral structural proteins 48 for dissemination of the type 2 recombinant EV-G. 49 50

A novel spike subunit 1‐based enzyme‐linked immunosorbent assay reveals widespread porcine torovirus infection in eastern China

“…The sequence of PToV‐ZJU39 reported in the current work is only the sixth complete PToV genome sequence to have been reported thus far, which greatly limits our exploration of the origin and evolution of PToV. Inter‐order recombination between ToV (order Nidovirales ) and the order Picornavirales was recently discovered in different geographical locations (Imai et al., 2019; Ito et al., 2016; Knutson et al., 2017; Lee & Lee, 2019; Shang et al., 2017; Smits et al., 2003; Wang et al., 2018), which further supports the idea that PToVs are common in swine populations globally, along with other enteric pathogens.…”

“…Recently, PToV has received increasing attention due to evidence of inter‐order recombination between PToV and porcine enterovirus G (EV‐G; order Picornavirales ) in different geographical locations. Porcine EV‐G genomes were detected with an insertion of PToV papain‐like cysteine protease gene at the 2C/3A junction in the faeces of diarrhoeal pigs from farms in the United States, Belgium, Japan, China and South Korea (Conceicao‐Neto et al., 2017; Imai et al., 2019; Knutson et al., 2017; Lee & Lee, 2019; Shang et al., 2017; Wang et al., 2018).…”

Novel recombinant porcine enterovirus G viruses lacking structural proteins are maintained in pig farms in Japan

“…Previous studies, including ours, have reported the presence of recombinant type 1 EV-G in many different countries worldwide [6,8,15,17,20,35,40,42]. Type 1 recombinant EV-G has an insertion of a papain-like cysteine protease (PLCP) gene of the porcine torovirus genome at the 2C-3A junction sites [40].…”

“…In addition to type 1 recombinant EV-Gs, type 2 recombinant EV-G genomes that carry an insertion of a torovirus PLCP gene with long flanking genes (unique region 1 [Un1] and unique region 2 [Un2]), in place of viral structural genes have been reported [15]. Amino acid alignment indicated that the biological functions of the PLCP of most type 2 recombinant EV-Gs may be similar to those of the PLCP of type 1 recombinant EV-Gs [15].…”

Recent Progress in Torovirus Molecular Biology

“…Their HE, which is related to haemagglutinin-esterase-fusion (HEF) protein of influenza C, and PDE are thought to have been independently obtained from these ancestors by heterologous recombination events ( Figure 2 ) [ 92 ]. Remarkably, heterologous recombination between ToV and picornavirus has been discovered recently in many countries; a ToV-like PL pro gene is inserted into the porcine enterovirus G (EV-G) genome at the 2C/3A junction [ 93 , 94 , 95 , 96 , 97 ] or completely replaces a viral structural gene up to the VP1/2A junction [ 98 , 99 ] ( Figure 3 c), suggesting that ToV-like PL pro benefits the growth of EV-G.…”