Development of ELISA for Ophiostoma ulmi using antigen-coated wells

A simple sensitive ELISA test has been developed that detects either antibodies to, or antigens of, the Dutch elm pathogen, Opiostoma ( Ceratocystis ) ulmi. The dilution end point for antisera raised in mice againt mycelial antigens was 10^-4. The minimum amount of antigen detected in wells passively coated with antigens solubilized in phosphate-buffered saline was 500 pg/ml. The assay proved an effective method for rapidly screening large numbers of hybridoma supernatants for monoclonal antibodies that recognize O. ulmi antigens and it has also been used to detect fungal antigens in saline extracts of diseased tissue. Non-specific binding of preimmune antiserum to plant extracts was markedly higher in extracts from diseased than non-diseased tissue. Production by the diseased host or by the pathogen in vivo of a protein A or lectin-like molecule that binds non-specifically to immunoglobulins is postulated.