Variation in the spike protein of the 793/B type of infectious bronchitis virus, in the field and during alternate passage in chickens and embryonated eggs

Abstract

The degree of variation exhibited within the 793/B serotype (also known as 4/91 and CR88 serotypes) was investigated with nine French and 10 British isolates, collected between 1985 and 1994. The S1 part (1644 nucleotides) of the spike protein gene of the first known isolate of this serotype, FR/CR85131/85, had 95.9% to 97% nucleotide identity with the other isolates. Partial sequencing of isolates from Iran and Saudi Arabia, isolated in 2000, revealed approximately 95% nucleotide identity with European isolates, including the two live 793/B vaccinal strains, showing that they were not re-isolations of vaccinal virus. The data indicates that strains within the 793/B serotype have > or =96% nucleotide identity within the whole S1 gene and > or =93% nucleotide identity within the first 560 nucleotides, and > or =92% and > or =86% amino acid identities in the corresponding protein regions. This is similar to the identities exhibited within the Massachusetts serotype. Sequence analysis of a 793/B field isolate after passage in embryonated eggs, then in chickens and then again in eggs revealed selection for a serine and alanine at S1 amino acid position 95 in chicken-passaged and egg-passaged virus, respectively. There was no change in pathogenicity. This is the first demonstration at gene sequence level of host-driven selection for infectious bronchitis virus.

Genetic mutations in live infectious bronchitis vaccine viruses following single or dual in vitro infection of tracheal organ cultures

“…These results are in concurrence with previous in vivo work, which demonstrated that the majority of nucleotide variations in 793B were synonymous (Cavanagh et al, 2005). However, in the presence of Mass (Group C), there was a marked increase in 793B SNPs per 100 bp (particularly at 4 days p.i., 0.55 per 100 bp in the dual compared with 0.03 in the single vaccinations), with the majority now causing a change in the amino acid composition.…”

Molecular characterization of avian infectious bronchitis virus strains from outbreaks in Argentina (2001–2008)

“…Vaccination programmes against IB must be based on the identification of the IBV strains causing the disease in the field (Hofstad, 1981) because nucleotide differences between isolates in S1 sequences are sufficient to change the serotype, and there is poor cross-protection between them (Cavanagh & Naqi, 2003;Cavanagh et al, 2005). Therefore, identification is important for the selection of the most appropriate vaccine to control the outbreak (Farsang et al, 2002).…”

Genetic Analysis of the S1 Gene of 4/91 Type Infectious Bronchitis Virus Isolated in Japan

“…Since it was first described in the early nineties in United Kingdam, 4/91 type IBVs was identified in many other countries and became one of the most predominant genotype in Europe [4,6]. Almost all IBVs recently isolated in Japan have been classified into three major genotypes, JP-I, JP-II and JP-III, but isolates of the 4/91 genotype have been sporadically detected since 2003.…”

“…Cavanagh et al [4] examined passage of the 4/91 vaccine strain in chickens, compared the S1 sequences of vaccine strains and examined the pathogenicity of egg-passaged and chick-passaged strains. In their report, they recognized one amino acid substitution at position 95, alanine in the vaccine strain and serine (S) in the chick-passaged strain, in the strain after 10 passages in the chicken, but the pathogenicity of the chick-passaged strain did not change.…”