Using DNA Shuffling to Create Novel Infectious Bronchitis Virus S1 Genes: Implications for S1 Gene Recombination

Abstract

We employed the staggered extension process (StEP) to shuffle the S1 genes from four infectious bronchitis virus (IBV) strains representing four unique serotypes. Upon creating a shuffled S1 gene library, we randomly selected 25 clones and analyzed them by DNA sequencing. In total, eleven clones contained novel S1 gene recombinants. Based on sequence data, each recombinant was unique and contained a full-length open reading frame. The average number of crossovers per recombinant was 5 and the average number of point mutations was 1.3, leading mostly to non-synonymous amino acid changes. No recombinant contained sequences from all four parental genes and no recombinant contained any sequence from the distantly related Delaware 072 strain. Our data suggests that recombination between distantly related IBV strains within the S1 gene probably does not readily occur. This finding is extremely important in light of the common industry vaccination practice of mixing different live-attenuated IBV strains.

Complete genomic sequence analysis of infectious bronchitis virus Ark DPI strain and its evolution by recombination

“…Recombination hot spots have been demonstrated for IBV isolates by many researchers. These hot spots have been detected in the IG region [ 23 ], S1 gene [ 27 ], 3' terminus of S2, N and between N gene and 3'UTR [ 8 , 28 ]. Some earlier sequencing studies had provided circumstantial evidence of recombination events in field isolates of IBV [ 7 , 29 , 30 ].…”

Assessment of the potential relationship between egg quality and infectious bronchitis virus infection in Australian layer flocks

“…Sequencing of the S1 gene was also inhibited by the need to amplify the entire S1 gene (≈ 1600 bp) for comparison. Partial S1 gene sequencing is unreliable for strain characterisation because of the extensively reported ability of IBVs to recombine in the S1 gene region …”