Enzyme immunoassay for feline oncornavirus-associated cell membrane antigen (FOCMA) and detection of FOCMA in cell extract by enzyme immunoassay inhibition test.

An enzyme immunoassay (EIA) for FOCMA has been developed. The assay uses alkaline phosphatase-conjugated rabbit anti-cat IgG as the second antibody and p-nitrophenyl phosphate as the substrate for the enzyme to detect cat FOCMA antibody bound to the target cells. In comparison with the indirect immunofluorescence (IIF) test, which was originally used for FOCMA assay, our results showed a good correlation between the two methods. The EIA gives a more objective measure of FOCMA reactivity than does IIF. FOCMA was successfully extracted from FOCMA-positive cell membranes by 0.5% Triton X-100 and further fractionated by ammonium sulfate. The FOCMA activity was assayed by IIF and EIA inhibition test. Most of the FOCMA activity was found in the fractions precipitated by 30% and 50% ammonium sulfate saturation.