Assessment of recombinant beak and feather disease virus capsid protein as a vaccine for psittacine beak and feather disease.

Beak and feather disease virus (BFDV) is a significant pathogen of wild Australasian and African psittacine birds. We assessed the immunogenicity of recombinant BFDV capsid (recBFDVcap) to protect against the development of psittacine beak and feather disease (PBFD). Long-billed corellas (Cacatua tenuirostris) (n=13) received (by injection) 1 ml vaccine containing 10 microg recBFDVcap on day 0 and 0.4 ml vaccine containing 66.8 microg recBFDVcap on day 11. All vaccinated corellas and five non-vaccinated control corellas were given 0.4 ml BFDV suspension [titre=log(2) 12 haemagglutination units (HAU) 50 microl(-1)] intramuscularly and 0.1 ml orally 16 days after booster vaccination. Blood was collected during the vaccination period and blood and feathers were collected after BFDV administration. Testing of blood samples included BFDV DNA detection by PCR and quantitative PCR (qPCR) as well as antibody detection by haemagglutination inhibition (HI) and on feather samples, BFDV DNA and antigen was detected by haemagglutination (HA) and qPCR. Four of 97 blood samples collected from vaccinated birds after virus challenge tested positive by PCR, whereas 17 of 35 samples taken from non-vaccinated control corellas tested positive. Vaccinated birds did not develop feather lesions, had only transient PCR-detectable viraemia and had no evidence of persistent infection 270 days post-challenge using PCR, histopathology and immunohistochemistry. Non-vaccinated control corellas developed transient feather lesions and had PCR, HI and HA test results consistent with PBFD. They were BFDV PCR-positive for up to 41 days post-challenge and qPCR demonstrated reduced virus replication in vaccinated birds compared with non-vaccinated control birds.