Development of an Immune Complex Vaccine against Infectious Bursal Disease Virus and its Potential Response in Poultry Birds

 Infectious Bursal Disease is characterized by destroying the Bursa of Fabricius (Primary lymphoid organ), where B cells mature and differentiate. The virus is very stable and resistant to physical and chemical agents, heat, and ultraviolet radiation. Thus, it persists in poultry houses for several weeks after cleaning and disinfection. The present study was designed to develop the IBD immune complex to evaluate immunoprophylactic potential.

 The infectious bursal disease virus (IBDV) was procured from the infected Bursae collected from the disease outbreak areas of the Faisalabad District, and molecular detection was done through RT-PCR. The inactivated IBD virus was injected into the layer birds to raise egg yolk antibodies (IgY). The eggs were collected, and the yolk containing antibodies were processed to separate IgY through the ammonium sulfate precipitation method. The known quantity of antigen and antibodies were mixed to develop the immune complex (Icx) antigen. The immune response of immune complex IBD antigen was determined in rabbits. The comparative immune response of immune complex IBD antigen and IBD commercial vaccine was made in poultry birds, and the comparative mean antibody titers were determined through factorial analysis. Eighty, one day old, semi-specific pathogen-free (SPF) chickens were kept in four groups. Chickens were bled weekly to evaluate infectious bursal virus antibody titers by I-ELISA. All the groups were challenged with local IBD virus strain on day 28, and the Bursa to bodyweight ratios was compared after being challenged on day 35.

The study revealed that the antibody titers of G-III were significantly higher (P ≤ 0.05) than those of other groups on days 28, 35, and 42. On day 35, the Bursa to the bodyweight of group-III was significantly lower (P ≤ 0.05) than the challenged control group.

 The findings showed that the immune complex (Icx) antigen induced a strong and persistent immunogenic response in terms of antibody titer compared to a conventional live vaccine. Icx provoked better protective immunity and protected chickens against the IBD virus challenge and may be considered a substitute for the IBDV vaccine.