Isolation And Identification Of Infectious Bovine Rhinotracheitis Virus (ibrv) LN01/08 Strain And Sequences Analysis Of Major Functional Genes

In order to understand the epidemic situation of infectious bovine rhinotracheitis (IBR) of the bovine herds in China, a serological survey of IBRV infection was conducted in some cattle or dairy herds of different areas in China. In addition, one IBRV field strain was isolated and identified. Serological investigation was taken place in five provinces or special districts, and they were Beijing, Liaoning, Jilin, Shanxi Province and Inner Mongolia, In the survey, a total of 776 bovine serum samples were collected and detected by microtiter virus neutralization assay. The result demostrated that 226 serum samples were SN serological positive and the serological prevalences of the five provinces were 10%, 35.1%, 35.5%, 66.7% and 35%, respectively, with an average rate of 35.6%. In the study, a virus field strain was isolated from the nasal swab samples collected from a sick cow, which demonstrated IBR-like syndrome, from a farm in Liaoning Province. The isolate replicated well on MDBK cell culture, produced cytopathic effect (CPE) typical to IBRV. Finally, the virus isolate was identified as an IBRV strain by specific indirect immunofluorescent assay, microtiter virus neutralization assay, PCR method, and electronic microscope examination. Based on the date and place of isolation, the virus isolate was named as IBRV LN01/08 strain. Using the third passage harvests of the isolate, an experimental infection study was conducted in IBRV antibody-free calves with age of 6-9 months. After inoculation, calves developed fever for consecutive days, nasal discharges, formation of white plaques on nasal mucosa, and other typical clinical syndromes of IBRV infection, suggesting that the newly isolated IBRV LN01/08 is virulent to cattle.To collect the genetic information of the isolated IBRV LN01/08, a PCR assay was conducted using 10 pairs of primers designed based on IBRV's gB, gC, gD and gE regions's sequences (AJ004801 reported in GenBank), and the IBRV LN01/08 genes were amplified and sequences were synthesized and analyzed. Results demonstrated a nucleotide homology over 90% in the IBRV LN01/08, comparing to other IBRV strains reported in GenBank. These results are very important for the future studies on the IBRV LN01/08 strain. The results of epidemiology investigation (serological investigation and virus isolation) provided theoretical evidences for monitoring and controling of IBRV. The newly isolated IBRV LN01/08 strain is a good candidate for future research and virus candicate for vaccine development in IBR control.