A sensitive radioimmunosorbent assay for the detection of plant viruses

A simple and highly sensitive radioimmunosorbent assay (RISA) for the detec-tion of plant viruses is described. The RISA procedure is a microplate method based on the principle of'double-antibody sandwich ' and follows essentially the protocol of the enzyme-linked immunosorbent assay (ELISA) (Clark & Adams, 1977), with the exception that t2~I-tabelled y-globulin is substituted for the y-globulin enzyme conjugate; the bound 125I-y-globulin is dissociated by acidifi-cation from the double-antibody sandwich. The radioactivity is proportional to virus concentration, and cauliflower mosaic virus (CaMV) and lettuce mosaic virus (LMV) could be detected at concentrations a low as 5 and 2 ng/ml, respectively. Direct evidence of the adverse ffects of conjugation with enzyme on the binding abilities of antibodies is presented. The RISA procedure should prove valuable with viruses for which the ELISA values are too low to be dependable