engleski

Actual chicken protection against infectious bursal disease by oil-adjuvanted vaccines and planed protection by immune complexes.

AIM: The main goal of our studies is the production of vaccines which should elicit uniform levels of antibodies against infectious bursal disease virus (IBDV) in parent flocks, resulting in improved progeny performance. Also, we plain to prepared the vaccines, which administered to the offspring at an appropriate level of maternal antibodies (MAbs), are sufficient for protection against field viruses. METHODS: Light layers and heavy breeders were vaccinated under laboratory and field conditions. IBDV was administered alone as a single vaccine or incorporated in multiple vaccines. The amount of viral material incorporated in a vaccine dose corresponded to 1 x 106.5 EID50 of non-inactivated Winterfiled 2512 strain of IBDV. Each of pullets was vaccinated before laying period by intramuscular administration of 0.5 ml vaccine prepared in the form of multiple water-in-oil-in-water emulsion (WOWE). WOWE was prepared by mixing oil- and water-phase in a proportion of 1:2. The actual concentration of both water- and mineral oil-soluble surfactants in WOWE was 3.3% w/v. The WOWE characterizes a low viscosity (n = 3.45), high hydrophile-lipophile balance value (HLB = 9.53), and high stability. RESULTS: WOWE enhanced immunogenicity and extended the duration of the protection of mono- and polyvalent IBDV vaccines. Vaccines were easy for injection due to their low content of mineral oil and low viscosity. None of the side effects that accompany of oil-adjuvanted vaccines, were detected at the site of injection. A single revaccination of replacement flocks before the lay was sufficient to generate high antibody titers during the whole laying period and egg production was not affected by the vaccination. The levels of specific antibodies in the egg yolk were at least twice higher than those in the sera of dams. The level of maternal antibodies transferred to the progeny could ensure passive protection during the first days of life. STUDIES PLANED: Our researches concerning chicken protection against Newcastle disease proved that viral antigenic subunits bound to specific antibodies in immune complexes (ICs) generated strong humoral and cell-mediated immune responses. Accordingly, we plan to prepare an ecologically safe IC vaccine composed of IBDV antigenic proteins, e.g. VP2, bound at equivalence to specific antibodies. ICs alone or prepared in the form of WOWE will be applied for protection of young chickens with or without maternally derived Abs.

chickens; infectious bursal disease; immunoprophylaxis

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