Molecular characterization and pathogenicity evaluation of enterovirus G isolated from diarrheic piglets

Four enterovirus G (EV-G) strains were isolated from diarrheic piglets that were negative for common swine enteric viruses. The spherical enterovirus particles of roughly 30-nm diameter were observed under transmission electron microscopy by using plaque-purified enterovirus. The complete genome sequence analysis revealed that each of four enteroviruses contained a papain-like cysteine protease (PLCP) gene between the 2C and 3A junction regions of the viral genome. This insertion encoded a predicted protease similar to the PLCP of porcine torovirus. The phylogenetic analysis based on complete genome with and without PLCP gene revealed that the four isolated EV-G strains were grouped together with global enterovirus G1-PLCP strains, and more closely related to EV-G/PLCP strains previously detected in China, Japan, and Korea (90.3%-92.2% similarities based on nucleotides). The cell susceptibility test demonstrated that the isolated EV-G could infect and replicate in cell lines from various host species. Furthermore, pathogenicity evaluation showed that the isolated EV-Gs induced mild diarrhea, pyrexia, and reduced body weight in infected piglets. The epidemiological investigation revealed a high prevalence of EV-G in swine herds. Together, our findings demonstrate that the isolated EV-G is pathogenic in piglets and may be advantageous in providing more trustworthy data on the evolution and pathological properties of EV-G.