Immunogenic and protective properties of chicken anaemia virus proteins expressed by baculovirus

The coding information for three putative chicken anaemia virus proteins (VP1, VP2, VP3) was inserted into a baculovirus vector and expressed in insect cells. The immunogenic properties of the chicken anaemia virus (CAV) proteins produced separately or together in insect-cell cultures were analysed by inoculating them into chickens. Only lysates of insect cells which have synthesised equivalent amounts of all three recombinant CAV proteins or cells which synthesised mainly VP1 plus VP2 induced neutralising antibodies directed against CAV in inoculated chickens. Progeny of those chickens were protected against clinical disease after CAV challenge. Inoculation of a mixture of lysates of cells that were separately infected with VP1-, VP2- and VP3-recombinant baculovirus did not induce significant levels of neutralising antibody directed against CAV and their progeny were not protected against CAV challenge. Our results indicate that expression in the same cell of at least two CAV proteins, VP1 plus VP2, is required to obtain sufficient protection in chickens. Therefore, recombinant CAV proteins produced by baculovirus vectors can be used as a sub-unit vaccine against CAV infections.