Production of virus specific egg yolk antibodies for the diagnosis of Newcastle disease, infectious bronchitis and Gumboro disease by the direct fluorescent antibody technique

Abstract

The suitability of egg yolk antibodies (IgY) for the detection of the Newcastle disease virus (NDV), infectious bronchitis virus (IBV) and Gumboro disease virus (IBDV) by the direct immunofluorescent antibody test was examined. Laying hens were immunized with commercially available vaccines containing inactivated NDV, IBV and IBDV. High titers of specific antiviral egg yolk antibodies were detectable from 4 to 8 weeks after initial immunization for a period of about 20 weeks. IgY was precipitated from the yolk with ammonium sulfate and consecutively purified by affinity chromatography, attaining 1.46 mg specific IgY per yolk on average. After labeling with fluorescein-isothiocyanate (FITC) the sensitivity and specificity of the conjugates were evaluated on coverslip cell cultures. In the direct fluorescent antibody test the 1:4 or 1:8 in PBS diluted conjugates reacted specifically with their homologous antigen in impression smears prepared from organs of experimentally infected chicks and in coverslip cell cultures. Reactions with heterologous antigens did not occur and non-specific fluorescence was successfully suppressed by absorption of conjugates with liver powder. It is concluded that FITC-labeled egg yolk antibodies can be produced in a simple and economical way on a large scale and therefore present an interesting alternative to the common practice of producing fluorescent antibodies for the diagnosis of NDV, IBV and IBDV from the serum of chickens or rabbits, particularly for laboratories with limited financial resources.