Sequence Analysis and Expression of ORF5 in Korean Isolate of Porcine Reproductive and Respiratory Syndrome Virus

ABSTRACT

Porcine reproductive and respiratory syndrome virus (PRRSV) is the causative agent of reproductive failure and respiratory disorders in pigs. The viral genome consists of eight overlapping open reading frames (ORFs). ORF5 encodes one of the major glycoproteins and is known as an immunologically important structural protein associated with virus neutralization. The ORF5 gene of the Korean PRRSV isolate, CNV-1, was amplified by reverse transcription-polymerase chain reaction (RT-PCR), cloned and sequenced. The nucleotide and amino acid sequences of CNV-1 ORF5 shared 91% and 83% identity, respectively, with the American isolate (VR2332 strain) and 57% and 49% identity with the European isolate. For the expression and easy purification of ORF5, the cDNA containing the complete ORF5 sequence fused in-frame with sequence encoding glutathione S-transferase (GST) was cloned into a baculovirus transfer vector and transfected into Sf9 cells. The GST-ORF5 fusion protein produced in Sf9 cells was detected by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and Western blotting. Sequencing results confirmed that the recombinant baculovirus from Sf9 cells contains the complete ORF5 gene. Further studies in this direction will address whether ORF5 can be a good candidate for a subunit vaccine against PRRSV in Korea.