Molecular analysis of the 793/B serotype of infectious bronchitis virus in Great Britain

Abstract

SUMMARYSince the winter of 1990/91 respiratory disease of poultry in Great Britain has commonly been associated with the 793/B (or 4/91) serotype of infectious bronchitis virus (IBV). We have sequenced a variable part of the S1 region of the spike protein (5) gene. Comparison of up to 270 nucleotides of 12 British 793/B isolates, obtained in 1991 and 1993, revealed 94 to 100% nucleotide identity with each other. Eleven of them fell into one of two subgroups, A and B, one isolate forming subgroup C. Identity within subgroups A and B was > 98%. The whole S1 gene sequence (1617 nucleotides) was determined for five 793/B isolates, two from each of subgroups A and B and one from subgroup C; nucleotide identity between any two isolates was > 97%. A large proportion of the nucleotide differences corresponded to amino acid changes. The whole S1 amino acid sequence differed by 21 to 25% or more from that of all other published IBV sequences. This extensive difference has probably contributed to the persistence of the 793/B serotype in Britain even though heterologous vaccines have been used.The finding that the 793/B isolates could be placed into three subgroups suggests that either (a) they had diverged from a common progenitor present, but undetected, in Britain prior to 1990/91 or (b) at least three different strains of the 793/B serotype had entered Britain in or prior to 1990/91.

Infectious bronchitis virus: S1 gene characteristics of vaccines used in China and efficacy of vaccination against heterologous strains from China

“…Therefore, two genome-sense oligonucleotides *S1Uni2 (Adzhar et al, 1997) and IBV-87 (Liu et al, 2006), as summarized in Table 2 *were used with IBV-212 as the antisense primer for PCR amplification of the entire S1 protein genes of vaccine virus strains. The PCR profiles involved an initial denaturation for 5 min at 958C followed by 30 cycles of denaturation at 948C for 1 min, annealing at 508C for 1 min, and polymerization at 728C for 2 min.…”

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“…In most cases, these new isolates have a restricted distribution and remain associated with particular geographical areas (Gelb et al ., 2001;Smati et al ., 2002;Zanella et al ., 2003). Notwithstanding, in some cases these new strains become widely distributed and become dominant genotypes, as occurred with the 4/91 serotype (Adzhar et al ., 1997;Cavanagh et al ., 1998a). This serotype was described for the first time in the United Kingdom in the early 1990s, associated with outbreaks of respiratory disease, and rapidly spread, displacing the D274 serotype that had been dominant in the 1980s (Adzhar et al ., 1997;Cavanagh et al ., 1998a).…”

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“…A number of general oligonucleotides have been used to amplify most or all of the S1 gene, followed by sequencing or restriction fragment analysis. Recent examples include the characterization of the 793/B (4/91; CR88) type of IBV in Europe and elsewhere (Adzhar et al, 1997;Cavanagh et al, 1998, the discovery of the Delaware variant in the US (Gelb et al, 1997), and the demonstration that the 624/I serotype in Italy had a unique genotype (Capua et al, 1999).…”