Isolation and characterization of mammalian orthoreoviruses using a cell line resistant to sapelovirus infection

Genetic diversity, reassortment, and recombination of mammalian orthoreoviruses from Japanese porcine fecal samples

Mammalian orthoreoviruses (MRVs) are non-enveloped double-stranded RNA viruses with a broad host range. MRVs are prevalent worldwide, and in Japan, they have been isolated from various hosts, including humans, dogs, cats, wild boars, and pigs, and they have also been found in sewage. However, Japanese porcine MRVs have not been genetically characterized. While investigating porcine enteric viruses including MRV, five MRVs were isolated from the feces of Japanese pigs using MA104 cell culture. Genetic analysis of the S1 gene revealed that the Japanese porcine MRV isolates could be classified as MRV-2 and MRV-3. Whole genome analysis showed that Japanese porcine MRVs exhibited genetic diversity, although they shared sequence similarity with porcine MRV sequences in the DDBJ/EMBL/GenBank database. Several potential intragenetic reassortment events were detected among MRV strains from pigs, sewage, and humans in Japan, suggesting zoonotic transmission. Furthermore, homologous recombination events were identified in the M1 and S1 genes of Japanese porcine MRV. These findings imply that different strains of Japanese porcine MRV share a porcine MRV genomic backbone and have evolved through intragenetic reassortment and homologous recombination events.

Characterization of parainfluenza virus 5 from diarrheic piglet highlights its zoonotic potential

Parainfluenza virus 5 (PIV5), a member of paramyxoviruses, causes respiratory and neurological infection in several animal species. Whereas information on PIV5 infection in digestive system is very scarce. Here, we successfully isolated one PIV5 strain from diarrhetic piglets. After four times plaque purification and ultracentrifugation, the paramyxovirus-like particles were observed by electron microscopy. The genome-wide phylogenetic analysis showed that the isolated strain was closely related to the PIV5 strain from a lesser panda and pigs in China. Therefore, we characterized this isolated PIV5 and found that this virus could hemagglutinate red blood cells from both guinea pigs and chickens. Further, we observed that this PIV5 could infect cell lines from various host species including pig, human, monkey, bovine, dog, cat, rabbit, hamster, and mouse, which was confirmed with the immunofluorescent assay. To evaluate the distribution of PIV5 in the field, we developed an indirect ELISA (iELISA) for the first time to detect the specific antibodies based on recombinant nucleocapsid protein. A total of 530 porcine serum samples were tested and the PIV5-positive rate was 75.7%. To our knowledge, this is the first report describing the full characterization of PIV5 strain isolated from a diarrheic piglet. The ability of this PIV5 strain to infect a wide range of mammalian cell types indicates that PIV5 can transmit across different species, providing a remarkable insight into potential zoonosis. The virus strain and iELISA developed in this study can be used to investigate the pathogenesis, epidemiology, and zoonotic potential of PIV5. This article is protected by copyright. All rights reserved.

Isolation and Characterization of a Subtype 4b of Hepatitis E Virus Using a PLC/PRF/5 cell-derived Cell Line Resistant to Porcine Sapelovirus Infection

A human hepatocarcinoma cell line, PLC/PRF/5, is susceptible to hepatitis E virus (HEV) infection and is used for isolating this virus. It is difficult to use this cell line for the isolation of HEV directly from fecal specimens of swine or wild boar contaminated with porcine sapelovirus (PSV), because PSV infection results in rapid and extensive cytopathic effects in PLC/PRF/5 cells, interrupting the growth of HEV. Herein, we used a PSV infection-resistant cell line, N1380 derived from PLC/PRF/5 cells, and we successfully isolated an HEV-4b strain from a PSV-positive swine fecal specimen. Our results indicate that N1380 cells are a useful tool for the isolation of HEV from swine or wild boar fecal specimens, even when they are co-infected with PSV.

Isolation and characterization of mammalian orthoreovirus type 3 from a fecal sample from a wild boar in Japan

Mammalian orthoreoviruses (MRVs) have been identified in various mammalian species, including humans, bats, and pigs. However, isolation and complete genome sequences of MRVs from wild boars have not yet been reported. In this study, we isolated, sequenced, and analyzed an MRV from a free-living wild boar in Japan using the porcine-sapelovirus-resistant cell line N1380. Complete and empty virus particles were obtained from the N1380 cell culture supernatants, and complete genome sequences were obtained from complete virus particles. Sequence analysis revealed that the isolated MRV, named TY-14, could be classified as MRV3 and had a close genetic relationship to an MRV2 isolate from a lion in a Japanese zoo (L2, L3, and M3 genes) and a human MRV2 isolate from Japan (S2 gene). Phylogenetic analysis showed that TY-14 clustered only with bat MRVs in the M1 phylogenetic tree but formed a cluster with several animal MRVs in the M2 and S3 phylogenetic trees and branched independently in the L1, S1, and S4 phylogenetic trees, suggesting a genetic relationship to viruses of unknown origin. Recombination events were identified in the M2 gene. These results suggest that TY-14 was generated by reassortment and recombination events involving MRVs circulating in Japan, viruses from bats, and other viruses of unknown origin.