Amplified detection, using a monoclonal antibody, of an aphid-specific epitope exposed during digestion in the gut of a predator

Monoclonal antibodies are invaluable tools for identifying and quantifying prey remains in the fore-guts of predators. However, they must be target-sp ecific, detect an epitope that is well replicated within the prey (to enhan ce assay sensitivity) and, critically, recognise a site that can resist dig estion. A monoclonal antibody is reported that proved to be aphid-specific and capable of detecting. and accurately identifying, as little as 16.5 ng of aphid protein within a heterologous mixture of invertebrate material. Th e antibody was selected by screening hybridoma lines for antibodies that bo und with semi-digested aphid proteins. The antibody detected an epitope tha t was found, against expectation, to significantly increase in concentratio n with time (by approx. 50% over 6 h) in the gut of the carabid predator Pt erostichus melanarius. The resultant extended antigen detection period and half-life, and the high specificity of this antibody, showed it to be an en hanced tool for studying interactions between aphids and their predators in the field. It was concluded that the antibody was initially generated to a surface epitope on a high molecular weight native protein (>200 kD). This epitope, however, was then either replicated on internal sites progressivel y revealed by digestion, or new epitopes became available as the conformati on of the protein changed during digestion. (C) 1999 Elsevier Science Ltd. All rights reserved.