Characterization of Guangzhou Porcine Reproductive and Respiratory Syndrome Virus (PRRSV) Field Isolates

Abstract

A direct method was used to detect the presence of Porcine Reproductive and Respiratory Syndrome Virus (PRRSV) in tissue samples of infected pigs collected from different farms in Guangzhou, based on reverse transcription of the viral RNA coupled to DNA amplification by polymerase chain reaction (RT-PCR). Several sets of primers were designed based on both the North American (VR-2332) and the European (LV) genome sequences within ORF1b encoding the polymerase protein in order to perform a rapid multiplex PCR assay. DNA products with unique size characteristics of each genotype were obtained. From three (named D2, D3 & AV) Guangzhou field isolates, amplified fragment of 108 bp was cloned and sequenced. Alignment with North American strain (VR-2332) sequences revealed a 95.5% homology. Among all, AV Guangzhou strain tissue homogenates were inoculated into MARC-145 cells and after the sixth passage, cytopathic effects (CPE) of infected cell were observed. Analysis of purified virions of AV Guangzhou strain by SDS-PAGE and western immunoblotting using porcine hyperimmune sera revealed that four major viral proteins: 15, 19, 26 and 45 kDa proteins.