Assay sensitivity and differentiation of monoclonal antibody specificity in ELISA with different coating buffers

Buffers of different pH and ionic strength were employed as coating buffers for antigen adsorption to microtitre plates. Their efficiency for coating plates with rinderpest virus (RPV) and foot-and-mouth disease virus (FMDV) antigens was studied by ELISA with polyclonal and monoclonal antibody preparations. While the adsorption and detection of RPV antigen with polyclonal antiserum was highly dependent on the ionic strength and pH of coating buffer, adsorption of antigenically active FMDV antigen was relatively unaffected by the buffering conditions. Both antigens were adsorbed optimally in 0.01 M phosphate buffer, pH 8.0. When monoclonal antibodies were used to detect antigen, there was a greater degree of dependence on the coating buffer than that found with polyclonal antisera. Moreover, when they were used to detect antigen adsorbed under several buffering conditions, monoclonal antibodies showed a variety of preferred buffers. The usefulness of this differential reactivity in distinguishing epitope specificity is demonstrated.