DefinePK

Abstract

Gumboro disease or infectious bursal disease (IBD), caused by IBDV agents, leads to significant economic losses due to its acute and contagious nature, affecting chickens aged three to six weeks, resulting in immunosuppression with high morbidity and mortality rates. Despite preventive measures, including vaccination, outbreaks of IBD still occur. Variations in antigenic relatedness between vaccine strains and field viruses can affect vaccination efficacy. This study aimed to assess the antigenic relatedness between the Lukert strain and vvIBD through homologous and heterologous cross-neutralization tests using chicken embryo fibroblast (CEF) cultures. Twenty-five serum samples from five chicken groups were tested. The control group remained unvaccinated, while the first and second groups received a single dose of the Lukert strain or vvIBD vaccine at two weeks of age. The third and fourth groups were revaccinated twice with the Lukert strain or vvIBD vaccine. Neutralization test results and antigenic relatedness was determined using the Archeti and Horsfall formula. Virus re-identification was performed using PCR and sequencing. The neutralization test revealed an antigenic relatedness of 11.14% between the Lukert and vvIBD, indicating they belong to the same serotype with major differences in subtypes. Consequently, there is a low indication of cross-protection between the two strains. There was a significant (P<0.05) difference between the test group of viruses and serum sample antibodies. Given the low antigenic relationship, reference is needed for the development of vaccines homologous to field virus strains.