Infectious bronchitis is a highly contagious respiratory disease of chickens that can be fatal in young birds due to secondary bacterial infections, and sometimes kidney disease. Infection of egg-layers results in a drop in egg production. The disease, which has economic consequences to the poultry industry throughout the world, is caused by infectious bronchitis virus (IBV), a coronavirus. IBV has been reported to be the number one cause of infectious disease-related economic loss in the UK poultry industry and is a continual threat, in part due to the existence of a large number of IBV serotypes. There are numerous vaccines available for the control of IBV, although protection is short-lived and poorly cross-protective between serotypes.
The Avian Endemic Viruses Group are investigating the potential for genetic manipulation of the IBV genome to rationally attenuate field strains predictably and specifically for vaccine production, including for in ovo vaccination. In order to do this they are identifying the IBV genes involved in virulence, as well as host factors involved in virus replication and viral replication machinery. They are presently modifying the IBV genome using a reverse genetics approach developed by them in order to achieve an optimum balance between attenuation of virulence and capacity to induce immunity. Establishing the virulence factors of IBV may allow the development of vaccines that could be administered in ovo without causing harm to the imminently hatching chicks.
The group are focussed on the design of sustainable methods of controlling infectious diseases in chickens. To this end, they are evaluating the potential of the use of recombinant viruses as vaccines that can be grown in a cell line. Current IBV vaccines must be grown in embryonated eggs, a cumbersome and expensive process; the ability to grow vaccines on a cell line would be highly advantageous. They are investigating the possibility of utilizing IBV as a vector for the expression and delivery of foreign genes. The length of the IBV genome (27,600 nucleotides) suggests that it could accommodate large inserts from other pathogens, making possible the use of IBV as a vaccine vector against infectious bronchitis and other avian diseases.
Current research projects are divided into the following areas:
- Development of rationally attenuated live vaccines for effective control of infectious bronchitis
- Molecular characterisation of the avian coronavirus infectious bronchitis virus to identify regions of the genome involved in virulence
- Modification of the infectious bronchitis virus spike protein for growth in Vero cells; potential for vaccine growth and production in cell culture
- Analysis of the Function of Infectious Bronchitis Virus Accessory Proteins
- Investigation on how passage in eggs results in attenuation, is this due to selection or random mutation with the aim to reduce the risk of vaccine reversion
- Determination of cross protection and genetic plasticity of IBV with the aim to control the virus.
IBV is a major problem with affects to the global poultry industry in spite of available vaccines. We have developed an approach to study the function of individual genes which gave us a better understanding of the disease and how to design better vaccines. We have been collaborating with pharmaceutical companies using our novel approaches to design vaccines for new strains. The poultry industry and farmers have benefitted from improved understanding of the disease and the continued investment into new vaccines that will reduce financial losses due to this disease.