Isolation, Identification, and Evaluation of the Pathogenicity of a Porcine Enterovirus G Isolated From China

Abstract

Enterovirus G (EV-G) infects porcine populations worldwide and the infections are generally asymptomatic, with the insertion of the papain-like cysteine protease gene (PLCP) increasing the potential public health threats. However, the genetic and pathogenic characteristics of EV-G itself are not fully understood as yet. In the present study, one EV-G strain, named CH/17GXQZ/2017, was isolated and purified from piglets with diarrheic symptoms from the Guangxi Province, China. This strain produced stable cytopathic effects on Marc-145 cells with a titer of 5 × 106 PFU/mL. The spherical enterovirus particles with diameters of 25–30 nm were observed by using transmission electron microscopy. The whole genome sequence of the CH/17GXQZ/2017 strain consists of 7,364 nucleotides, and the phylogenetic tree based on the amino acid sequences of VP1 indicated this strain was clustered to the G1 genotype. Seven-day-old piglets were inoculated orally with the CH/17GXQZ/2017 strain in order to evaluate its pathogenicity. Although none of the infected piglets died during the experiment, clinical neurological symptoms were observed manifesting as mild hyperemia and Nissl bodies vacuolization in the cerebrum. In addition, the infection with the CH/17GXQZ/2017 strain decelerated the weight gain of suckling piglets significantly. This study demonstrates that CH/17GXQZ/2017 is pathogenic to neonatal piglets and advance knowledge on the biological characteristics, evolution and pathogenicity of EV-G.

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

“…Therefore, it cannot be concluded that EV-G infection will cause skin symptoms in pigs. In this study, a recombinant EV-G strain (EV-G/YN23/2022) carrying a PLCP gene was isolated from the fecal samples of pigs with diarrhea, and the regression infection experiment showed that EV-G/YN23/2022 could induce typical skin lesions in pigs (Figure 4D); this is inconsistent with previous reports [21,22]. Considering that the virus strain (CH/17GXQZ/2017) used in the research of Xue et al [22] was non-PLCP-inserted EV-G, and the fact that only the 3D gene was sequenced for the strains (CH-PW12 and CH-PW20) in another report [21], we speculate that the PLCP-inserted EV-G share the potential to induce skin lesions in piglets.…”

“…In this study, a recombinant EV-G strain (EV-G/YN23/2022) carrying a PLCP gene was isolated from the fecal samples of pigs with diarrhea, and the regression infection experiment showed that EV-G/YN23/2022 could induce typical skin lesions in pigs (Figure 4D); this is inconsistent with previous reports [21,22]. Considering that the virus strain (CH/17GXQZ/2017) used in the research of Xue et al [22] was non-PLCP-inserted EV-G, and the fact that only the 3D gene was sequenced for the strains (CH-PW12 and CH-PW20) in another report [21], we speculate that the PLCP-inserted EV-G share the potential to induce skin lesions in piglets. Admittedly, we cannot rule out that the clinical symptoms were more obvious and induced by the artificial high-dose inoculations when compared to natural infections; therefore, further detailed research should be carried out to confirm this speculation.…”

“…EV-G/YN23/2022 propagated effectively and caused strong CPEs in BHK-21, Marc-145, PK-15, ST, and SIEC cells (Figure 1A), which is in agreement with the reports that EV-Gs could propagate in BHK-21, Vero, ST, and Marc-145 cells [1,22,24,54]. The growth curves of EV-G/YN23/2022 showed that the virus propagated the most rapidly in SIEC cells and reached a peak (7.2 × 10 6 PFU/mL) at 48 hpi (Figure 1C), which was higher than the virus titers for the other cell lines (Figure 1C).…”

Metagenomic analysis of endemic viruses in oral secretions from Chinese pigs

“…Alignment of the sequences among the EV strains revealed EV‐G (86%–96%). EV‐G is prevalent and widespread in the general pig population in middle and eastern China, and infections tend to occur early, usually within the first week after birth (Mi et al., 2021).…”

Phylogenetic and Spatiotemporal Analyses of Porcine Epidemic Diarrhea Virus in Guangxi, China during 2017–2022

“…A total of 110 partial S1 gene sequences from Guangxi (including 12 strains obtained from the Genbank database shown in the Supplementary Table S1 ) were aligned by using the MEGA version 7.0 program [ 26 ]. A maximum likelihood tree was reconstructed using the IQ-TREE software, implemented by the TN + F + R3 model with 1000 bootstrap replicates [ 27 ].…”