Effects of c-myc tag on binding activity of single chain antibody fragments to antigens

Objective To investigate the affects of affinity tag on binding activity of single chain variable fragment (ScFv) to antigen using different immunological assays. Methods A c-myc tag was conjugated to C-terminus of V L in the V H-linker-V L of ScFv against acetylcholine receptor (AChR). Solid phase radioimmunoassay (SPRIA), in which the ScFv was first caught by fixed anti-c-myc antibody, and radioimmunoassay (RIA), in which the ScFv was directly bound to AChR, were used to determine the binding activity of the ScFv to AChR. Results The ScFv could not bind to AChR in SPRIA, whereas it was able to bind to AChR in RIA. Conclusion Affinity tag conjugated to ScFv may interfere with the binding activity of ScFv to antigen in different immunological assays.