Preparation and Evaluation of Immune Complexes as Vaccine Candidate for Fowl Adenovirus Infection associated with Hydropericardium Syndrome in Domestic Fowl

Immune complex (Icx) vaccine is an antigen-antibody complex which will engage all immunocytes with Fc binding capabilities, enhance early maturation and B memory cell formation. In vitro preformed Icx have been shown to be 100 times more efficient in inducing humoral immune response in vivo than the native protein antigen. In present study, immune complexes were prepared by mixing varying quantities of HPS virus with different concentrations of egg derived immunoglobulins (IgY). The efficacy of immune complex formulations as vaccine was checked in broiler birds. The Icx vaccinated birds exhibited protection in the range of 53.4% to 66.7% following challenge with virulent HPS virus. Birds vaccinated with 40 and 80 units of IgY with 100 TCID₅₀ HPS virus did not shed virus in feces following challenge and induced better antibody response. No significant change in body weight gain was observed between survived birds from vaccinated and control groups. The study showed that immune complex vaccines significantly reduced the mortality and stopped the excretion of the virus in feces thus afforded protection and prevented the horizontal transmission of virus by oral-fecal route.