The S1 glycoprotein but not the N or M proteins of avian infectious bronchitis virus induces protection in vaccinated chickens

Abstract

The S1, N and M proteins, obtained from the nephropathogenic N1/62 strain of infectious bronchitis virus (IBV) by immunoaffinity purification with monoclonal antibodies, were used for immunization of chickens. For all three antigens multiple immunizations were necessary for induction of an antibody response. Protection of chickens vaccinated with the S1 glycoprotein against virulent challenge was demonstrated by the complete absence of virus in tracheas and kidneys of vaccinated chickens. Following four immunizations with the S1 glycoprotein 71% and 86% of chickens were protected at the level of tracheas and kidneys, respectively. Three immunizations with the S1 glycoprotein protected 70% and 10% of chickens at the level of kidney and trachea, respectively. Neither the N nor the M antigen induced protection to a virulent challenge with the nephropathogenic N1/62 strain of IBV after four immunizations. Virus neutralizing, haemagglutination inhibiting and ELISA antibodies were detected in chickens immunized with the S1 glycoprotein and inactivated N1/62 virus, however there was no correlation between the presence of any of these antibodies and protection.

Detection of infectious bronchitis virus

“…The major virus neutralizing antibody sites of IBV, which define serotype, reside in the S1 protein Mockett et al, 1984;Kant et al, 1992;Karaca et al, 1992;Parr & Collisson, 1993;Ignjatovic & Galli, 1994). As already discussed regarding antigen detection, the VNT for detection of antibodies can be performed in embryonated eggs, cell culture, or TOCs.…”

“…Haemagglutination inhibiting antibodies are induced primarily by the S1 spike protein Mockett et al, 1984;Ignjatovic & Galli, 1994). Usually, HI tests first detect antibodies between 1 and 2 weeks p.i.…”

Coronavirus avian infectious bronchitis virus

“…This leaves us far short of understanding the molecular basis of cross-protection -or lack of itas cellular immune responses play a role in protection, and these are poorly understood. We do know that the S protein alone is sufficient to induce good protective immunity [12,20,46,51,53,93,96]. There is increasing evidence that only a few amino acid differences amongst S proteins are sufficient to have a detrimental impact on cross-protection.…”

S1 gene characteristics and efficacy of vaccination against infectious bronchitis virus field isolates from the United States and Israel (1996 to 2000)

“…Mutations occur frequently in hypervariable regions of the S1 subunit of the envelope spike (S) glycoprotein gene. The S1 protein is responsible for infection of the host cell (Cavanagh & Davis, 1986;Koch et al ., 1990;Ignjatovic & Galli, 1994), inducing virusneutralizing antibody (Cavanagh et al ., 1988) and immunity (Cavanagh et al ., 1997). New variant strains may differ as much as 55% in their S1 amino acid sequence compared with vaccine strains (Kusters et al ., 1989;Gelb et al ., 1997).…”