Spike gene analysis of the DE072 strain of infectious bronchitis virus: Origin and evolution

The entire S2 gene of the DE072 strain of infectious bronchitis virus (IBV) was sequenced. The nucleotide and amino acid sequence was most similar to the D1466 strain and was 84.8% and 89.9% identity, respectively. The nucleo tide and amino acid sequence similarity among the DE072 strain and other IB V strains was less than 71.9% and 76.6%, respectively. Phylogenetic analysi s, based on both nucleotide and amino acid sequence, showed that IBV isolat es were divided into two distinct groups. The DE072 strain clustered only w ith the D1466 strain, and all of the other strains were distinct from those two viruses. Further the nucleotide sequence analysis of the entire spike glycoprotein gene of the DE072 strain demonstrated that most of the gene co ntained a D1466-like sequence, and five putative cross-over sites were iden tified. Based on cross-over site, phylogenetic trees were constructed for d ifferent regions of the spike gene, and a difference in topology between th ese trees was observed. Considering the difference in S2 gene sequence iden tity and tree topology, we assume that DE072 and D1466 viruses share a diff erent origin from other isolates of IBV. Furthermore, entire spike gene ana lysis indicates that the DE072 strain has undergone recombination event as well as extensive antigenic variation.