Cloning and nucleotide analysis of segment A gene of infectious bursal disease virus detected in Korea.

ABSTRACT

A strain of infectious bursal disease virus (IBDV) was detected from bursal tissues of chicks which suffered from infectious bursal disease (IBD) in Chinju, Korea and provisionally named as Chinju strain. A full-length cDNA clone for segment A gene of the virus was constructed, and complete nucleotide sequence of the gene including noncoding region was determined and analyzed by comparison with that of other IBDV strains. The segment A gene of Chinju strain consisted of 3,269 nucleotides including 862 adenine (26.4%), 917 cytosine (28.0%), 854 guanine (26.1%) and 636 thymine (19.5%). There were regions for two open reading frames (ORFs), ORF1 encoding the VP5 with ATG codon at nucleotides 98-100 and ORF2 encoding the polyprotein of VP2, VP4 and VP3 in the nucleotides 132-3,170. In deduced translation the ORF2 encoded 1,012 amino acids. The full nucleotide sequence of segment A gene and amino acid sequence of ORF2 of the Chinju strain showed 98-99% homology with those of the very virulent IBDVs (vvIBDVs) such as HK46, OKYM, UK661, UPM97/ 61, D6948 and BD3/99. In phylogenetic analysis of nucleotide and amino acid sequences, the Chinju strain was also related closely to the vvIBDVs. Hence, it was suggested that the Chinju strain is a vvIBDV. The nucleotide and amino acid sequences of the Chinju strain with pertinent information can be useful for the development of genetically engineered vaccines and diagnostic reagents against vvIBDV.