Ssl. Chan et al., A sensitive assay for the measurement of serum chondroitin sulfate 3B3(-) epitope levels in human rheumatic diseases, CLIN EXP RH, 19(5), 2001, pp. 533-540
Objective To develop a sensitive assay to quantitate serum 3B3(-) levels in
patients with rheumatoid arthritis (RA) and osteoarthritis (OA) as well as
levels in control sera.
Methods An enzyme-linked immunosorbent assay (ELISA) was developed using th
e monoclonal antibody (MAb) 3B3 to detect a chondroitin sulfate (CS) epitop
e in the sera and synovial fluid (SF) of RA and OA patients. Keratan sulfat
e levels were measured in the same biological fluids using the 5D4 monoclon
al antibody.
Results The detection limit for our 3B3(-) assay was 2 mug/L. Most OA sera
sample curves run on the 3B3 assay were parallel (87.5%) to the standard cu
rve and detectable (90.0%). RA sera sample curves were 87.1% detectable and
85.2% parallel. The 3B3(-) epitope was detectable in 60% of control sera a
nd of these 66.7% of sample curves were parallel to the standard curve. All
RA and OA SF had detectable quantities of 3B3(-). For the 3B3 assay, the O
A and RA sera levels were significantly higher than for control sera (P = 0
.03, P = 0.04 respectively). We found a significant correlation in a subset
of paired OA sera and SF 3B3(-) concentrations. No correlation was found b
etween age, joint activity scores, HAQ and CRP in RA patients and sera 3B3(
-) and 5D4 levels.
Conclusion We have validated this assay for the quantification of 3B3(-) ep
itope in RA and OA serum. Levels of this epitope are significantly higher i
n sera from RA and OA patients than controls. 3B3(-) levels in RA sera were
found to correlate with disease duration.