Indirect ELISA Methods for the Broad Specificity Detection of Plant Viruses

Abstract

Summary Indirect ELISA on plates not precoated with antibodies enabled the detection of cross-reactions among a wider range of serologically related viruses in the tymo-, tombus-, como-, tobamo-, potex-, carla- and potyvirus groups than was possible with the direct double-antibody-sandwich method. Used with purified virus preparations and unfractionated antisera which have to be preabsorbed with crude plant sap the method seems promising for the detection of serological relationships among plant viruses, especially when the latter can be purified only with a low yield or when antisera are in short supply and immuno-electron microscopy is not possible. The quantitative outcome of the test was influenced by the concentration of the reactants, the purity and specific adsorption characteristics of the virus and the length of the immunization period. Strains of Andean potato latent virus (APLV) were detected reliably in crude plant sap when indirect ELISA was done on plates precoated with antiviral antibodies from rabbit or guinea-pig (‘first antibodies’). The trapped virus particles were reacted with antiviral antibodies from chicken (‘second antibodies’) which were then detected by enzyme-labelled rabbit anti-chicken antibodies. Other combinations of ‘first’ and ‘second’ antibodies resulted in non-specific reactions in the presence of crude plant sap. The specificity of direct ELISA was not sufficiently broadened to enable the routine detection of APLV strains when antisera were used which, due to altered immunization schemes, were expected to have an especially broad cross-reactivity.