There are likely to be significant economic advantages to the broiler industry in having a greater proportion of male chickens than female chickens in each hatch. It has been estimated that CAV infection results in lower body weights and higher mortality. Infection appears to be controlled in the chicken by the presence of serum antibody. It is therefore possible to achieve improvements in performance by ensuring that breeder flocks have an adequate level of immunity as a result of vaccination or natural exposure. Monitoring antibody levels in breeder flocks is important to ensure the virus is not passed onto the flock's progeny.
Current assays use native virus grown in tissue culture.
The hypothesis behind this work was that the use of alternative antigens would improve the reliability of the assay. The strategy adopted in this project therefore was to attempt to produce a more reliable source of antigen by expression of viral genes which had been cloned into E.coli or baculovirus. The genes coding for the major viral proteins of CAV were cloned and expressed in various expression systems. Initial analysis of some of the expressed proteins demonstrated strong reactions with CAV positive sera. An intense effort was initiated to reduce or remove these high backgrounds but with only limited success.