Evaluation of the Effects of Chitosan on Immune Responses due to Infectious Bursal Disease Virus (IBDV) Vaccine in Chicken

Introduction: Inactivated Infectious Bursal Disease Virus (IBDV) is administrated against Infectious Bursal Disease (IBD). Chitosan biopolymer is capable of inducing proper immune responses to an antigen while being non-toxic and degradable. In this study, the effect of chitosan on improving the humoral immune responses against IBD virus (IBDV) was investigated. Methods: The antigen was prepared by inoculating IBDV in embryonated chicken eggs and inactivation by ethylenimine. Chitosan solutions at final concentrations of 0.5% and 1% were made and used as an adjuvant. One-day-old chickens were randomly divided in 8 groups and received intramuscularly different profiles of the inactivated antigen and chitosan solution. Serum samples were collected before the prime and booster injection as well as at the defined intervals and assayed by ELISA and serum neutralization tests. Results: After 2-dose intramuscular immunization with inactivated IBDV in combination with chitosan, significant increases (P < 0.05) in antibody titers were observed compared with other administration groups. The addition of 1% chitosan to inactivated IBDV resulted in higher level of neutralizing antibody titer than 0.5% chitosan. However, the difference in the enhancing of antibody titers and the neutralization index between these concentrations was not significant. Conclusion: These data revealed that chitosan as an antigen carrier has the potential to enhance specific immune responses induced by inactived IBDV.