Relationship between serum trough infliximab levels, pretreatment C reactive protein levels, and clinical response to infliximab treatment in patients with rheumatoid arthritis

Objective: To investigate the relationship between serum trough infliximab levels and clinical response to infliximab treatment in patients with rheumatoid arthritis (RA). Methods: Disease activity and serum trough infliximab levels before and 2, 6, and 14 weeks after initiation of infliximab treatment at a dose of 3 mg/kg in a cohort of 105 patients with RA were assessed. Serum trough infliximab levels in responders and non-responders were compared. Additionally, the clinical responses of patients with high, intermediate, and low serum trough infliximab levels at 14 weeks were compared. Results: After 14 weeks of treatment non-responders had lower serum trough levels of infliximab than responders ( median (interquartile range) 0.5 (0.2 - 2.2) v 3.6 (1.4 - 8.2) mg/l; p <0.01)). Patients with low serum trough infliximab levels at 14 weeks had significantly less improvement in the 28 joint count Disease Activity Score (DAS28) score than patients with intermediate or high serum trough infliximab levels at 14 weeks. Pretreatment C reactive protein (CRP) levels correlated negatively with serum trough infliximab levels at 14 weeks after the start of treatment ( Spearman rank correlation r(s) = -.43, p <0.001). Conclusion: Serum trough levels of infliximab correlate with the clinical response to treatment with infliximab and pretreatment CRP levels. This study indicates that patients with high pretreatment CRP levels might benefit from higher dosages of infliximab or shorter dosing interval

Immunogenicity negatively influences the outcome of adalimumab treatment in Crohn's disease

Background: Adalimumab is an effective treatment in patients with Crohn's disease; as it is a humanized anti-tumour necrosis factor monoclonal antibody, immunogenicity is thought not to be of any significance. Aim: To assess whether antibodies to adalimumab (ATAs) affect adalimumab treatment outcome in patients with Crohn's disease previously treated with infliximab. Methods: A retrospective study was p

A common theme in interaction of bacterial immunoglobulin-binding proteins with immunoglobulins illustrated in the equine system

The M protein of Streptococcus equi subsp. equi known as fibrinogen-binding protein (FgBP) is a cell wall-associated protein with antiphagocytic activity that binds IgG. Recombinant versions of the seven equine IgG subclasses were used to investigate the subclass specificity of FgBP. FgBP bound predominantly to equine IgG4 and IgG7, with little or no binding to the other subclasses. Competitive binding experiments revealed that FgBP could inhibit the binding of staphylococcal protein A and streptococcal protein G to both IgG4 and IgG7, implicating the Fc interdomain region in binding to FgBP. To identify which of the two IgG Fc domains contributed to the interaction with FgBP, we tested two human IgG1/IgA1 domain swap mutants and found that both domains are required for full binding, with the CH3 domain playing a critical role. The binding site for FgBP was further localized using recombinant equine IgG7 antibodies with single or double point mutations to residues lying at the CH2-CH3 interface. We found that interaction of FgBP with equine IgG4 and IgG7 was able to disrupt C1q binding and antibody-mediated activation of the classical complement pathway, demonstrating an effective means by which S. equi may evade the immune response. The mode of interaction of FgBP with IgG fits a common theme for bacterial Ig-binding proteins. Remarkably, for those interactions studied in detail, it emerges that all the Ig-binding proteins target the CH2-CH3 domain interface, regardless of specificity for IgG or IgA, streptococcal or staphylococcal origin, or host species (equine or human)

Immunogenicity does not influence treatment with etanercept in patients with ankylosing spondylitis

Background: Immunogenicity, specifically the onset of antibodies against tumour necrosis factor (TNF) blocking agents, seems to play an important role in non-response to treatment with these drugs. Objectives: To assess the relation of clinical response of ankylosing spondylitis (AS) to etanercept with etanercept levels, and the presence of antibodies to etanercept. Methods: Patients with AS were treated with etanercept 25 mg twice weekly, according to the international Assessment in Ankylosing Spondylitis (ASAS) working group consensus statement. Sera were collected at baseline and after 3 and 6 months of treatment. Clinical response was defined as a 50% improvement or as an absolute improvement of 2 points on a (0-10 scale) Bath Ankylosing Spondylitis Disease Activity Index (BASDAI) score. Functional etanercept levels were measured by a newly developed ELISA, measuring the binding of etanercept to TNF. Antibodies against etanercept were measured with a two-site assay and antigen binding test. Clinical data were used to correlate disease activity with serum etanercept levels. Results: In all, 53 consecutive patients were included. After 3 months of treatment 40 patients (76%) fulfilled the response criteria. Mean etanercept levels were 2.7 mg/litre and 3.0 mg/litre after 3 and 6 months respectively. Characteristics and etanercept levels of responders and non-responders were similar. No antibodies to etanercept were detected with any of the assays. Conclusion: Etanercept levels of responders and non-responders were similar and no antibodies to etanercept were detected with any of the assays. This study indicates that etanercept is much less immunogenic compared with the other TNF-blocking agent

Genome-Wide Association Study and Gene Expression Analysis Identifies CD84 as a Predictor of Response to Etanercept Therapy in Rheumatoid Arthritis

Anti-tumor necrosis factor alpha (anti-TNF) biologic therapy is a widely used treatment for rheumatoid arthritis (RA). It is unknown why some RA patients fail to respond adequately to anti-TNF therapy, which limits the development of clinical biomarkers to predict response or new drugs to target refractory cases. To understand the biological basis of response to anti-TNF therapy, we conducted a genome-wide association study (GWAS) meta-analysis of more than 2 million common variants in 2,706 RA patients from 13 different collections. Patients were treated with one of three anti-TNF medications: etanercept (n = 733), infliximab (n = 894), or adalimumab (n = 1,071). We identified a SNP (rs6427528) at the 1q23 locus that was associated with change in disease activity score (ΔDAS) in the etanercept subset of patients (P = 8×10-8), but not in the infliximab or adalimumab subsets (P>0.05). The SNP is predicted to disrupt transcription factor binding site motifs in the 3′ UTR of an immune-related gene, CD84, and the allele associated with better response to etanercept was associated with higher CD84 gene expression in peripheral blood mononuclear cells (P = 1×10-11 in 228 non-RA patients and P = 0.004 in 132 RA patients). Consistent with the genetic findings, higher CD84 gene expression correlated with lower cross-sectional DAS (P = 0.02, n = 210) and showed a non-significant trend for better ΔDAS in a subset of RA patients with gene expression data (n = 31, etanercept-treated). A small, multi-ethnic replication showed a non-significant trend towards an association among etanercept-treated RA patients of Portuguese ancestry (n = 139, P = 0.4), but no association among patients of Japanese ancestry (n = 151, P = 0.8). Our study demonstrates that an allele associated with response to etanercept therapy is also associated with CD84 gene expression, and further that CD84 expression correlates with disease activity. These findings support a model in which CD84 genotypes and/or expression may serve as a useful biomarker for response to etanercept treatment in RA patients of European ancestry. © 2013 Cui et al

A genome-wide association study of rheumatoid arthritis without antibodies against citrullinated peptides

Introduction. Rheumatoid arthritis (RA) patients can be classified based on presence or absence of anticitrullinated peptide antibodies (ACPA) in their serum. This heterogeneity among patients may reflect important biological differences underlying the disease process. To date, the majority of genetic studies have focused on the ACPA-positive group. Therefore, our goal was to analyse the genetic risk factors that contribute to ACPA-negative RA. Methods. We performed a large-scale genome-wide association study (GWAS) in three Caucasian European cohorts comprising 1148 ACPA-negative RA patients and 6008 controls. All patients were screened using the Illumina Human Cyto-12 chip, and controls were genotyped using different genome-wide platforms. Population-independent analyses were carried out by means of logistic regression. Meta-analysis with previously published data was performed as follow-up for selected signals (reaching a total of 1922 ACPA-negative RA patients and 7087 controls). Imputation of classical HLA alleles, aminoacid residues and single nucleotide polymorphisms was undertaken. Results. The combined analysis of the studied cohorts resulted in identification of a peak of association in the HLA-region and several suggestive non-HLA associations. Meta-analysis with previous reports confirmed the association of the HLA region with this subset and an observed association in the CLYBL locus remained suggestive. The imputation and deep interrogation of the HLA region led to identification of a two aminoacid model (HLA-B at position 9 and HLA-DRB1 at position 11) that accounted for the observed genome-wide associations in this region. Conclusions. Our study shed light on the influence of the HLA region in ACPA-negative RA and identified a suggestive risk locus for this condition