We have used a
surface plasmon resonance biosensor (SPR, BIACORE 2000) to detect
antibodies against glucose 6-phosphate isomerase (GPI) in
synovial fluids of
rheumatoid arthritis (RA) and
osteoarthritis (OA). Recombinant
human GPI
proteins fused with or without NusA were expressed in E. coli, purified to homogeneity and immobilized in flow
cells of CM5 sensor chips. The flow
cells immobilized with NusA
protein or
bovine serum albumin were used to monitor non-specific binding.
Synovial fluid samples from RA
patients showed a significantly higher level of binding to recombinant GPI
proteins than samples from OA
patients.
Proteins which bound to the recombinant GPI
proteins were confirmed to be
immunoglobulin through the
administration of anti-
human immunoglobulin. NusA fusion
protein was excellent for this assay because of a low background binding activity in the SPR
analysis and its advantage of increased
solubility in
recombinant protein production. These results suggested a useful utilization of recombinant NusA-GPI fusion
protein for the
detection of
autoantibodies against GPI in RA
patients.