1Division of Animal Biotechnology, Indian Veterinary Research Institute, Bareilly-243122, India.
2National Institute of Animal Health, Baghpat, Uttar Pradesh, India.
3Center for Biosystems Research, University of Maryland Biotechnology Institute, Maryland, USA.
Abstracts of the papers presented at the International Conference of Indian Virological Society on “Emerging and Re-emerging viral Diseases of the Tropics and Subtropics” at Indian Agricultural Research Institute, New Delhi, India, December 11–14, 2007.
Infectious bursal disease virus (IBDV), belonging to the family Birnaviridae, exhibits an immunosuppressive disease of young chicken characterized by severe depletion of B-lymphocytes in the bursa of Fabricius. To provide antigens for diagnostic tests and vaccines, its major structural protein VP2 was expressed in the yeast Saccharomyces cerevisae. The electron microscopy demonstrated IBDV-VP2 expressed in yeast cells formed virus like sub particles (SVPs). Recombinant VP2 antigen based single serum dilution enzyme linked immunosorbent assay (ELISA) using the virus sub-particles detected the IBDV specific antibodies. The recombinant VP2 antigen based kit when tested against a panel of chicken serum samples successfully identified all samples previously determined to be AGID test positive. Moreover, the recombinant VP2 antigen specifically reacted with IBDV positive sera and not with IBDV negative and NDV positive sera. An effort was made in this study to simplify and optimize as many steps in the ELISA procedure as possible. A linear relationship was found to exist between the predicted antibody titres at a single working dilution of 1: 1 000 and the corresponding observed serum titres as determined by the standard serial-dilution method. Regression analysis was used to determine a standard curve from which an equation was derived that allowed demonstration of the mentioned correlation. The equation was then used to convert the corrected absorbance readings of the single working dilution directly into the predicted ELISA antibody titres. The single serum dilution ELISA developed in this study had a sensitivity of 94.70% and a specificity of 96.96% relative to AGID test. The ELISA appears to be more sensitive than AGID test and is able to detect antibody activity against IBDV in field samples that is not detectable by the AGID test.
