Rapid serological profiling by enzyme-linked immunosorbent assay. III. Simultaneous measurements of antibody titers to infectious bronchitis, infectious bursal disease, and Newcastle disease viruses in a single serum dilution.

The present paper describes a method for measuring enzyme-linked immunosorbent assay (ELISA) antibody titers to infectious bronchitis (IB), infectious bursal disease (IBD), and Newcastle disease (ND) viruses from a single serum dilution using the same assay procedures and analyses. A regression line equation generated for predicting NDV ELISA antibody titers at a single serum dilution was successfully used to predict ELISA antibody titers to IB and IBD antigen preparations at the same test sera dilutions. Duplicate samples of 46 field and control sera were transferred simultaneously, with the aid of a replica plating device, from a reservoir plate to three different test plates, which were coated separately with IB, IBD, and ND antigens. After similar indirect ELISA parameters were conducted for each antigen, raw absorbance values from duplicate tests and controls were transmitted directly from an ELISA reader to a microcomputer, which subsequently processed average corrected absorbance values directly into individual ELISA antibody titer for each test antigen. The computer output listed individual field and control sample titers to each antigen, as well as graphing the relative ELISA titer distribution of the entire test group to each antigen. In a comparative study, test sera were evaluated for ELISA antibody titer to NDV, IBV, and IBDV by this method in three separate assays. Consistent titer values were obtained in all assays, as 96% of the 414 replicate titers evaluated varied less than twofold.