Changes in the ORF3 gene sequence of the ES strain of porcine epizootic diarrhea virus
The ORF3 gene sequence in the vaccine ES strain of the porcine epidemic diarrhea virus (PEDV) at the passage levels of 70 and 110 was compared with that of the reference CV777 strain and of a wild type PEDV isolate. The ORF sequence of the ES strain contains a 5'-terminal deletion of 29 bases at the passage level of 70 and 38 bases at the passage level of 110. The ORF3 sequence of the field isolate does not contain a deletion but instead contains 17 substitutions. The role of mutations in ORF3 in PEDV adaptation to growth in cell cultures is discussed. The role of mutations in other PEDV genes in variability of field virus populations is discussed in regard of variability of the diease manifestation in various geographic regions.