Isolation And Identification Of Porcine Teschovirus And Preliminary Serological Survey

Porcine teschoviruse(PTV), belonging to Teschovirus genus of Picornaviridae, comprises of eleven distinct serotypes, is a highly contagious disease infecting pigs. PTV infection shows a wild variety of clinical symptoms: polioencephalomyelitis, diarrhea, pneumonia, myocarditis, pericarditis, dermal lesions and fertility disorders.PTV has been widely disseminated to the North America, Australia, Africa and Asia. The main diagnostic methods included virus isolation, genomic sequence analysis, immunohistochemical detection etc. Presently, the disease is rarely reported in China, and the extent of its damage is still unclear.In this study, a strain of porcine teschovirus named as JF613 strain was isolated from a pigfarm near Harbin. The strain can propagate in IBRS-2 cell line and produce distinct cytopathic effects. The VP1 gene which encodes the structure protein was amplified by reverse transcript polymerase chain reaction (RT-PCR). The whole sequence is 789bp long, encoding 263aa.Compared with other published PTV VP1 genes, PTV-H1 VP1showed homologies varying from 73% to 91%.Nine forty-day-old pigs which antibody free were divided into two groups. One group was inoculated intravenously with 3×105TCID50 of JF613; the other was inoculated intravenously with nothing as control. Both groups were killed at 16 days post-infection. The infected group appeared slight clinical symptoms compared with the control group. The pathological changes observed included thrombus and neuronal necroses in brain issue with other issues normal, indicating that the PTV we isolated had lower virulence to forty-day-old piglets..To develop a serological detection system for PTV, a pair of primers targeting JF613 VP1 gene was designed. VP1 gene was amplified by RT-PCR and inserted into the eukaryotic expression vector pCAGGS, constructing recombinant plasmid pCAGGS-VP1.Indirect immunofluorescence assay (IFA) was developed to detect the expression of VP1. This VP1 expression system can be used to detect antibodies against PTV in serum of pigs using IFA.A total of 575 serum samples from different regions around Harbin were tested. The results showed that the positive rate of PTV antibody was 60.17%, suggesting a high infection rate in pigs.