A rapid streptavidin-capture ELISA specific for the detection of antibodies to feline foamy virus.

We report a simple procedure for the rapid development of an ELISA with the potential for wide application to any defined protein antigen. The procedure involves the expression of protein encoded by a PCR product, using a commercially available T-vector that adds a biotin tag, and a single step purification by affinity for streptavidin for direct use in ELISA. In our experiments, a recombinant protein from the nucleocapsid domain of the feline foamy virus gag gene was expressed as a fusion protein with a biotin tag and then applied directly to streptavidin-coated ELISA wells. An extract from a clone with the insert in antisense orientation was used as a control. Non-specific reactions with antigen extracts from both sense and antisense clones were observed in 6 of the 376 (1.6%) sera tested. Antibody to feline foamy virus, which forms a stable persistent infection in cats, was detected in 107 of 201 (53%) Australian cats, but none of 175 sera from veterinarians. There was a 100% correlation between FeFV antibody detected by ELISA, immunoblot, serum neutralisation and virus isolation, confirming that this test is sensitive and specific.