Selection of an scFv phage antibody that recognizes bluetongue virus from a large synthetic library and its use in ELISAs to detect viral antigen and antibodies.

A filamentous phage library displaying a vast repertoire of synthetic single chain fragment variable (scFv) antibody fragments was subjected to affinity selection on purified bluetongue virus (BTV) particles. After four rounds of selection and amplification, 73 out of a total of 90 fusion phage clones tested were found to bind to purified BTV in ELISA. One of these, the clone producing the highest ELISA signal, was selected for an investigation of its potential as an immunodiagnostic reagent. The binding of this phage antibody (designated A12) could be inhibited by free virus and by antibodies in immune serum. Inhibition with antibodies in guinea-pig sera suggested that it recognized an antigenic region on BTV that was similar on at least 10 different BTV serotypes. A sandwich ELISA utilizing antibody A12 was capable of detecting approximately 60 ng of purified BTV.