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1.  Restrictive IgG antibody response against mutated citrullinated vimentin predicts response to rituximab in patients with rheumatoid arthritis 
Antibodies against mutated citrullinated vimentin (AMCV) represent a useful diagnostic marker with correlation to disease activity in patients with rheumatoid arthritis (RA). Since seropositivity for citrullinated autoantibodies was predictive for response to B-cell depleting therapy (BCDT) with rituximab (RTX), we investigated whether differences in antibody fine reactivity and immunoglobulin (Ig) isotype kinetics among AMCV-positive patients could provide additional information about outcome.
A total of 50 AMCV IgG-positive RA patients (RTX responders (RRs) n = 37 and non-responders (NRRs) n = 13) were analyzed for reactivity against MCV epitopes and co-existent AMCV isotypes IgM and IgA. Antibody titers were determined by enzyme-linked immunosorbent assay at baseline and 24 weeks after the first cycle of RTX, and compared to kinetics of rheumatoid factor (RF) and antibodies against cyclic citrullinated peptide (ACCP).
Recognized MCV epitopes by AMCV IgG of RRs and NRRs showed similar baseline patterns, with reducing reactivity in RRs and unchanged or even expanding reactivity in NRRs upon RTX treatment. At baseline, RRs were more frequently negative for AMCV subtypes, especially for IgA (68 %), compared to NRRs (31 %). Being AMCV IgA-negative at baseline indicated a good treatment response to RTX (negative predictive value = 0.86). Co-existence of AMCV IgA and IgG with stable titers upon treatment were associated with poorer responses to RTX. Furthermore, reductions of AMCV IgA levels upon RTX correlated with the improvement of 28-joint Disease Activity Score (DAS28). In comparison, subtypes of RF and ACCP were not of additional value for prediction of RTX response.
Restrictive IgG seropositivity against MCV with treatment-associated decline in fine reactivity and titers was predictive for response to RTX. Double-positivity for AMCV IgG and IgA was associated with failure to respond to BCDT, suggesting a pathogenetic and less sensitive IgA-producing B-cell subset in NRRs.
Electronic supplementary material
The online version of this article (doi:10.1186/s13075-015-0717-z) contains supplementary material, which is available to authorized users.
PMCID: PMC4535682  PMID: 26268352
2.  Glycosylation of immunoglobulin G determines osteoclast differentiation and bone loss 
Nature Communications  2015;6:6651.
Immunglobulin G (IgG) sialylation represents a key checkpoint that determines the engagement of pro- or anti-inflammatory Fcγ receptors (FcγR) and the direction of the immune response. Whether IgG sialylation influences osteoclast differentiation and subsequently bone architecture has not been determined yet, but may represent an important link between immune activation and bone loss. Here we demonstrate that desialylated, but not sialylated, immune complexes enhance osteoclastogenesis in vitro and in vivo. Furthermore, we find that the Fc sialylation state of random IgG and specific IgG autoantibodies determines bone architecture in patients with rheumatoid arthritis. In accordance with these findings, mice treated with the sialic acid precursor N-acetylmannosamine (ManNAc), which results in increased IgG sialylation, are less susceptible to inflammatory bone loss. Taken together, our findings provide a novel mechanism by which immune responses influence the human skeleton and an innovative treatment approach to inhibit immune-mediated bone loss.
The IgG sugar moiety modulates the binding of immune complexes to their Fcγ receptors resulting in pro- or anti-inflammatory response. This study shows that IgG sialylation also affects osteoclastogenesis and bone mass in mice and humans, identifying a new link between bone and the immune system.
PMCID: PMC4389255  PMID: 25825024
3.  Induction of osteoclastogenesis and bone loss by human autoantibodies against citrullinated vimentin 
The Journal of Clinical Investigation  2012;122(5):1791-1802.
Autoimmunity is complicated by bone loss. In human rheumatoid arthritis (RA), the most severe inflammatory joint disease, autoantibodies against citrullinated proteins are among the strongest risk factors for bone destruction. We therefore hypothesized that these autoantibodies directly influence bone metabolism. Here, we found a strong and specific association between autoantibodies against citrullinated proteins and serum markers for osteoclast-mediated bone resorption in RA patients. Moreover, human osteoclasts expressed enzymes eliciting protein citrullination, and specific N-terminal citrullination of vimentin was induced during osteoclast differentiation. Affinity-purified human autoantibodies against mutated citrullinated vimentin (MCV) not only bound to osteoclast surfaces, but also led to robust induction of osteoclastogenesis and bone-resorptive activity. Adoptive transfer of purified human MCV autoantibodies into mice induced osteopenia and increased osteoclastogenesis. This effect was based on the inducible release of TNF-α from osteoclast precursors and the subsequent increase of osteoclast precursor cell numbers with enhanced expression of activation and growth factor receptors. Our data thus suggest that autoantibody formation in response to citrullinated vimentin directly induces bone loss, providing a link between the adaptive immune system and bone.
PMCID: PMC3336988  PMID: 22505457
4.  Immediate determination of ACPA and rheumatoid factor - a novel point of care test for detection of anti-MCV antibodies and rheumatoid factor using a lateral-flow immunoassay 
Arthritis Research & Therapy  2010;12(3):R120.
Autoantibodies against mutated and citrullinated vimentin (MCV) represent a novel diagnostic marker for rheumatoid arthritis (RA). Recently, an increased sensitivity for anti-MCV compared to autoantibodies against cyclic citrullinated peptides (anti-CCP2) was shown in cohorts of patients with early RA and established disease.
The aim of this study was to develop and evaluate a point of care test (POCT) for detection of anti-MCV antibodies immediately at the first visit or at the bed side.
A lateral-flow immunoassay was developed for simultaneous detection of anti-MCV antibodies and rheumatoid factor (RF-IgG) and evaluated in a prospective setting. Analyses were performed from whole blood samples of patients with seropositive RA (n = 108), seronegative RA as well as other rheumatic disorders (n = 122), and healthy blood donors (n = 200) and compared to detection via ELISA.
Using the POCT, anti-MCV antibodies were detected in 54.6% and RF-IgG in 56.5% of patients with RA. Specificity was 99.1% for anti-MCV antibodies and 91.2% for RF-IgG. Compared to ELISA's results, POCT sensitivity was 69.3% for anti-MCV and 55.6% for RF-IgG, specificity was 99.7% and 97.2%, respectively.
This POCT for detection of anti-MCV antibodies and RF-IgG provides high specificity for the diagnosis of RA and is useful in clinical practice due to its simplicity and its reliable performance. This test can greatly improve a timely management of RA and may help in screening patients with suspected RA in non-specialized settings prompting early referrals.
PMCID: PMC2911914  PMID: 20569500
5.  Modulation of transcription factor NF-κB by enantiomers of the nonsteroidal drug ibuprofen 
British Journal of Pharmacology  1998;123(4):645-652.
The nonsteroidal drug ibuprofen exists as an R(−)- and S(+)-enantiomer. Only the S(+)-enantiomer is an effective cyclo-oxygenase inhibitor, while the R(−)-enantiomer is inactive in this respect. Thus the molecular mechanism by which R(−)-ibuprofen exerts its anti-inflammatory and antinociceptive effects remains unknown.In this study the effects of the enantiomers of ibuprofen on modulation of transcription factors have been examined with electrophoretic mobility-shift assay (EMSA), transient transfection experiments, confocal immunofluorescence and nuclear import experiments, to determine their selectivity and potency as inhibitors of the activation of transcription factor nuclear factor-κB (NF-κB).R(−)-ibuprofen (IC50: 121.8 μM) as well as the S(+)-enantiomer (IC50: 61.7 μM) inhibited the activation of NF-κB in response to T-cell stimulation. The effect of ibuprofen was specific because, at concentrations up to 10 mM, ibuprofen did not affect the heat shock transcription factor (HSF) and the activation of NF-κB by prostaglandin E2 (PGE2). Very high concentrations of ibuprofen (20 mM) did not prevent NF-κB binding to DNA in vitro. Immunofluorescence and nuclear import experiments indicate that the site of ibuprofen action appeared to be upstream of the dissociation of the NF-κB-IκB-complex.Our data raise the possibility that R(−)-ibuprofen exerts some of its effects by inhibition of NF-κB activation.
PMCID: PMC1565210  PMID: 9517383
R-Ibuprofen; NF-κB; heat shock transcription factor; prostaglandin E2; electrophoretic mobility-shift assay; transient transfection; immunofluorescence; nuclear import experiments
7.  A chronic model of arthritis supported by a strain-specific periarticular lymph node in BALB/c mice 
Nature Communications  2013;4:1644-.
Current animal models of arthritis only partially reflect the complexity of rheumatoid arthritis and typically lack either chronicity or autoantibody formation. Here we describe a model that combines features of antigen-induced arthritis and collagen-induced arthritis, which can be efficiently induced in BALB/c and C57BL/6 mice. However, BALB/c mice generate significantly higher titres of anticollagen and anticitrullinated peptide antibodies, show a stronger progressive joint destruction, and in the chronic phase the disease spreads between joints. Concomitant to the observation of a more severe pathology, we discovered a previously undescribed small periarticular lymph node in close proximity to the knee joint of BALB/c mice, which acts as the primary draining lymph node for the synovial cavity. Our model more closely reflects the pathology of rheumatoid arthritis than classical models of arthritis and is hence particularly suitable for further studies of disease pathogenesis.
Mouse models of arthritis generally do not result in both chronic disease and autoantibody production—two key features of the human disease. Here the authors obtain both features by combining two common protocols, and find that disease severity is associated with the presence of a previously unidentified lymph node.
PMCID: PMC3644064  PMID: 23552059

Results 1-7 (7)