Discovery and characterization of a novel porcine paramyxovirus

Abstract

Most emerging infectious diseases in humans are zoonotic agents. Since the emergence of severe acute respiratory syndrome (SARS), swine-origin influenza and avian influenza epidemics, the study of novel and emerging viruses with zoonotic potential has been considered more and more important. Paramyxoviruses have been known for their potential to cross species barrier and infect new hosts. In the last decade, a number of novel and emerging paramyxoviruses have been reported in various animals. Our research group recently identified three novel bat paramyxoviruses, Tuhoko viruses 1, 2 and 3 (ThkPV-1, 2, and 3) from fruit bats in mainland China, an unclassified paramyxovirus, named Tailam virus (TlmPV) from Sikkim rats and a novel feline paramyxovirus, called Feline morbillivirus(FmoPV) from domestic cats in Hong Kong, suggesting that there is still a diversity of undescribed paramyxoviruses in animals.

In this study, a novel porcine paramyxovirus, Swine parainfluenza virus 1 (SpiPV-1), was discovered and characterized from deceased pigs in Hong Kong. A total of 951 samples from 386 deceased pigs were collected, including 386 nasopharyngeal swab, 303 rectal swab, 153 blood, 56 lung and 53 liver samples. And SpiPV-1 was detected in 12 (3.1%) of 386 nasopharyngeal swab and 2 (0.7%) of 303 rectal swab samples by RT-PCR. All the blood, lung and liver samples showed negative results. The complete genome sequences of three strains (SpiPV-1 S033N, SpiPV-1 S119N and SpiPV-1 S206N) from three pigs were amplified and determined. The genome organization of SpiPV-1 is similar to that of viruses under genus Respirovirus, subfamily Paramyxovirinae. The genome contains six genes (3’-N-P/V/C-M-F-HN-L-5’) and putatively codes for the nucleocapsid (N), phosphoprotein (P/V/C), matrix (M), fusion (F), attachment (HN) and large (L) proteins.Like other respiroviruses, the P gene of SpiPV-1 can produce more than one protein, including P, V and W proteins by mRNA editing and C protein by alternative translation initiation. And phylogenetic analysis showed that in all six phylogenetic trees constructed byusing the N, P, M, F, HN and L genes, the three strains SpiPV-1 S033N, S119N and S206N formed a distinct cluster among the known respiroviruses and were most closely related to Sendai virus (SenPV) and Human parainfluenza virus 1 (HpiPV-1). The genome organization, P gene analysis and phylogenetic analysis all suggested that SpiPV-1 is a novel paramyxovirus under genus Respirovirus, subfamily Paramyxovirinae. Seven porcine samples positive for SpiPV-1 were cultured in five different cell lines for viral isolation. However, no cytopathic effect was observed and no viral replication was detected in any of the cell lines.

The pathogenicity and emergent potential of SpiPV-1 remain to be determined. Further studies on serology and development of cell cultures for viral isolation may provide better insight into this novel paramyxovirus.