Genetic differentiation of the nucleocapsid protein of Korean isolates of porcine epidemic diarrhoea virus by RT-PCR based restriction fragment length polymorphism analysis

A reverse transcriptase polymerase chain reaction (RT-PCR) based restriction fragment length polymorphism (RFLP) analysis based on the nucleocapsid (N) gene was developed to differentiate between field isolates of porcine epidemic diarrhoea virus (PEDV) and a vaccine strain, J-vac. Thirteen field isolates of PEDV from Korea were distinguishable from the vaccine strain and the prototype PEDV strain CV777 by RFLP using Tru9I. RFLP patterns in 11 of 13 field PEDV isolates were different from the vaccine strain using AspLEI, HgaI and MspR9I. Sequence analysis of the PEDV N gene revealed that Korean field PEDV isolates had 93.6% and 89.6% identity with the vaccine virus at nucleotide and amino acid sequence levels, respectively, suggesting progressive point mutations of the PEDV genome in the field. RFLP analysis of the PEDV N gene is a promising tool for distinguishing field strains from the vaccine-derived virus.