Avian Coronavirus Diseases and Infectious Bronchitis Vaccine Development
Paul Britton and Dave Cavanagh
from: Coronaviruses: Molecular and Cellular Biology (Edited by: Volker Thiel). Caister Academic Press, U.K. (2007)
Infectious bronchitis virus (IBV), a Group 3 coronavirus, is responsible for economic losses and welfare problems with chickens (the domestic fowl) globally. In addition to all respiratory epithelial surfaces it replicates throughout the alimentary tract, kidneys and gonads. Despite live and inactivated vaccines, it continues to be a major problem due to extensive antigenic variation; there is poor cross-protection. Susceptibility to the outcome of IBV infection is genetically determined. Coronaviruses that are genetically and antigenically similar to IBV cause enteric disease in turkeys, and respiratory and kidney disease in pheasants. IBV-like viruses have recently been reported in several other gallinaceous (fowl-like, order Galliformes) birds, - peafowl, partridge, guinea fowl - and in a duck (teal); some of these isolates may be IBVs that have crossed into other species. Group 3 coronaviruses with additional open reading frames have been detected in greylag goose, pigeon and mallard duck. A group 2 coronavirus has been reportedly isolated from a Manx shearwater (Puffinus puffinus), and a coronavirus of an undetermined Group has been isolated from a parrot. Inactivated vaccines are ineffective unless preceded by live attenuated vaccines to prime the protective immune response. The S1 spike protein subunit is necessary and sufficient to induce protective immunity. Differences in as few as 5% of the amino acids in S1 can decrease cross-protection. Genetic manipulation of the IBV genome is underway for the rational attenuation of IBV, and for the development of IB vaccines that can be applied in ovo read more ...