China Animal Husbandry and Veterinary Medicine ›› 2021, Vol. 48 ›› Issue (10): 3795-3802.doi: 10.16431/j.cnki.1671-7236.2021.10.032

• Preventive Veterinary Medicine • Previous Articles     Next Articles

Genetic Evolution Analysis of ORF5 Gene of Porcine Reproductive and Respiratory Syndrome Virus Isolated from Hunan Province

DENG Jiping1, CHEN Zhilong1, GUO Songyangnian1, ZHANG Kun1,2, XU Daojun1, YANG Qing1, YUAN Anwen1   

  1. 1. College of Veterinary Medicine, Hunan Agricultural University, Changsha 410128, China;
    2. Animal Disease Control and Prevention Center of Hunan Province, Changsha 410014, China
  • Revised:2021-03-12 Online:2021-10-20 Published:2021-09-30

Abstract: In order to explore infection of Porcine reproductive and respiratory syndrome virus (PRRSV) in native pig breeding farms of Hunan province, 287 blood samples were collected from two native pig breeding farms during 2019 to 2020. PRRSV were detected by RT-PCR in 41 mixed seral samples. Open reading frame 5 (ORF5) gene of PRRSV were amplified from PRRSV positive samples by high fidelity PCR. DNAStar software was performed to analyze the genetic evolution of ORF5 gene and GP5 amino acid between these PRRSV strains and different PRRSV strains from China and abroad after sequencing. Finally, PRRSV positive seral were inoculated in Marc-145 cells followed by blind passaging. The titer of the isolated PRRSV was determined by Reed-Muench method. The results showed that 3 samples from the 41 mixed samples were positive for PRRSV. Six ORF5 sequences were amplified from PRRSV positive mixed samples, all of which belonged to branch lineage 8 of PRRSV-2 strain, and the nucleotide homology was 99.2% to 99.8%. The corresponding GP5 protein acid sequences encoded by six ORF5 gene sequences were different in the signal peptide region (position 23), potential N-glycosylation site (position 33) and epitope C (position 59). Obvious cytopathic effect (CPE) was observed in the Marc-145 cells inoculated the PRRSV positive sera after five blind passages. A stain of PRRSV designated as NX-1 was obtained with a TCID50 of 4×105/mL. The data indicated that there existed infection of PRRSV in Hunan native pig breeding farms. The prevalent PRRSV isolate belonged to lineage 8 of PRRSV-2 with several variations in the amino acid sequence of GP5, which might be associated with immune failure. The present study could supply a foundation for immune prevention and control in Hunan native pig breeding farms.

Key words: porcine reproductive and respiratory syndrome (PRRSV); ORF5 gene; genetic evolution analysis

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