Characterisation of ORF3, M, N and E Gene Sequences of Porcine Epidemic Diarrhoea Virus from Domestic Pigs in Poland

INTRODUCTION: Porcine epidemic diarrhoea virus (PEDV) is an enteric pathogen causing porcine epidemic diarrhoea and acute gastroenteritis in pigs of all ages. Previous analysis of the viral genome of PEDV in Poland was only based on the spike protein (S) gene sequences and no analysis of other genes has been performed. The aim of this study was to analyse the envelope (E), membrane (M) and nucleocapsid (N) protein and open reading frame 3 (ORF3) gene sequences. MATERIAL AND METHODS: Viral RNA from 18 Polish pig faecal samples that were quantitative reverse transcription PCR-positive for PEDV was analysed in four genomic regions (E, M, N and ORF3). RESULTS: Phylogenetic analysis based on these regions’ sequences revealed that Polish PEDV isolates were highly related and were clustered into group G2a across the four genes compared. Moreover, the Polish strains were located in distinct subclusters on the phylogenetic trees, which suggests the presence of at least three independently evolving PEDV genetic lines circulating in Poland. The occurrence of unique mutations in the sequences of Polish PEDV strains suggests that PEDV continues to undergo evolutionary processes, accumulating the mutations necessary for viral fitness in its natural hosts. The Polish PEDV strains differed genetically from the CV777 vaccine strain, suggesting the risk of relatively low vaccine efficacy if this strain is used. CONCLUSION: Our results promote a better understanding of the genetic diversity of PEDV field isolates in Poland and highlight the importance of molecular characterisation of PEDV field strains for the development of an effective vaccine against PEDV.