DETERMINATION OF OPTIMUM FORMULATION OF A NOVEL INFECTIOUS BURSAL DISEASE VIRUS (IBDV) VACCINE CONSTRUCTED BY MIXING BURSAL DISEASE ANTIBODY WITH IBDV

A novel vaccine against infectious bursal disease virus (IBDV) has bee n developed. The new vaccine was constructed by mixing bursal disease antibody (BDA) contained in whole antiserum with live IBDV before lyop hilization. To establish various formulations of BDA and IBDV, several BDA doses between 5 units and 80 units of BDA/50 pi were mixed with 1 00 EID(50)/50 mu l of IBDV suspension in Expt. 1; in Expt. 2, several IBDV doses between 10 EID(50)/50 mu l and 977 EID(50)/50 mu l of IBDV suspension were mixed with 24 units of BDA/50 mu l. Vaccine preparatio ns were administered subcutaneously to the nape of I-day-old specific- pathogen-free (SPF) chicks. Safety, potency, and immunogenicity of the different vaccine formulations were evaluated using bursal weight, bu rsal gross examination, and IBDV antibody titer. Some bursae were exam ined histologically to confirm gross examinations. Several vaccine for mulations were safe and efficacious and met the safety, potency, and i mmunogenicity criteria. A vaccine construct of 100 EID(50) mixed with 24 units of BDA was selected as the release dose. When administered at 1 day of age, the novel vaccine allows for delayed infection of the b ursa until after days 6-8 of age in SPF chicks, while initiating poten cy and immunogenicity to an IBDV challenge. The addition of BDA to the IBDV results in a complex vaccine that allows for safer immunization in SPF birds than under administration of the vaccine virus without BD A.