Rheumatoid factors revisited in the age of biologic therapy

The discovery of RF has been instrumental in diagnosing and classifying RA. Various RF isotypes, including IgM-RF and IgA-RF, have been linked to disease severity and treatment responses. The role of RF in RA pathogenesis, primarily through the formation of immune complexes, also carries the potential to influence the response to different medications. Recent progress in biologic therapies has further elucidated the role of RF in RA management. Treatments such as rituximab, abatacept and tocilizumab have shown differential efficacy based on RF status, with RF-positive patients often exhibiting better responses. Recent research also suggests that TNF inhibitors (TNFi) lacking the IgG1-Fc fragment like certolizumab pegol (CZP) may offer advantages over TNFi with an IgG1-Fc fragment, in RF-positive patients by preventing immune complex formation. Since this early observation is predominantly derived from previous multicentre studies with heterogeneous populations and potentially varying RF measurement methods, prospective randomized studies directly addressing this issue are essential for a more thorough and reliable evaluation. This paper is a narrative review outlining the evolving understanding of RF in the context of biologic therapies, emphasizing the need for personalized treatment approaches based on serological profiles and underlying immune mechanisms.

Autoantibodies as Diagnostic Markers and Mediator of Joint Inflammation in Arthritis

Rheumatoid arthritis is a systemic, polygenic, and multifactorial syndrome characterized by erosive polyarthritis, damage to joint architecture, and presence of autoantibodies against several self-structures in the serum and synovial fluid. These autoantibodies (anticitrullinated protein/peptide antibodies (ACPAs), rheumatoid factors (RF), anticollagen type II antibodies, antiglucose-6 phosphate isomerase antibodies, anticarbamylated protein antibodies, and antiacetylated protein antibodies) have different characteristics, diagnostic/prognostic value, and pathological significance in RA patients. Some of these antibodies are present in the patients' serum several years before the onset of clinical disease. Various genetic and environmental factors are associated with autoantibody production against different autoantigenic targets. Both the activating and inhibitory FcγRs and the activation of different complement cascades contribute to the downstream effector functions in the antibody-mediated disease pathology. Interplay between several molecules (cytokines, chemokines, proteases, and inflammatory mediators) culminates in causing damage to the articular cartilage and bones. In addition, autoantibodies are proven to be useful disease markers for RA, and different diagnostic tools are being developed for early diagnosis of the clinical disease. Recently, a direct link was proposed between the presence of autoantibodies and bone erosion as well as in the induction of pain. In this review, the diagnostic value of autoantibodies, their synthesis and function as a mediator of joint inflammation, and the significance of IgG-Fc glycosylation are discussed.

Using the Immunophenotype to Predict Response to Biologic Drugs in Rheumatoid Arthritis

Tumour necrosis factor (TNF)-α is a key mediator of inflammation in rheumatoid arthritis, and its discovery led to the development of highly successful anti-TNF therapy. Subsequently, other biologic drugs targeting immune pathways, namely interleukin-6 blockade, B cell depletion, and T cell co-stimulation blockade, have been developed. Not all patients respond to a biologic drug, leading to a knowledge gap between biologic therapies available and the confident prediction of response. So far, genetic studies have failed to uncover clinically informative biomarkers to predict response. Given that the targets of biologics are immune pathways, immunological study has become all the more pertinent. Furthermore, advances in single-cell technology have enabled the characterization of many leucocyte subsets. Studying the blood immunophenotype may therefore, define biomarker profiles relevant to each individual patient's disease and treatment outcome. This review summarises our current understanding of how immune biomarkers might be able to predict treatment response to biologic drugs.

Predictors of European League Against Rheumatism (EULAR) good response, DAS-28 remission and sustained responses to TNF-inhibitors in rheumatoid arthritis: a prospective study in refractory disease

The aim of this study was to survey factors related to EULAR good response, the DAS-28 definition of remission, ACR 50 response, sustained response to tumor necrosis factor inhibitors (TNF-I) therapy in biologic naïve patients with refractory rheumatoid arthritis. This was a single center observational clinical prospective 2 years' study, EULAR response criteria, DAS 28, HAQ and radiographic changes were recorded. Eighty patients included (64 females and 16 males, mean age was 48.4 + -17.9 years, mean disease duration 7.3 + -5.9 years). At 6 months 70% achieved EULAR good response, 51.8% achieved DAS-28 remission. Good response/sustained responses inversely correlated with baseline DAS-28 and radiographic erosions P <0.05. EULAR good response/remission by 6 months, sustained response at 2 years positively correlated with the decline in RF titers (r = 0.33, P < 0.05 & r = 0.30, P < 0.03 respectively), negatively correlated with the baseline HAQ. Regression analysis identified higher serum hemoglobin concentration, lower baseline HAQ scores, and the absence of radiographic erosions as significant predictors of good as well as sustained responses after adjustment for potential covariates. Methotrexate was associated with favorable responses and remission at 6 months (ORs = 1.13, 1.30 respectively). The study concluded that a lower baseline DAS-28 and HAQ scores, the lack of radiographic erosions favored EULAR good response and were significant predictors of sustained response to TNF-I.

Response to Tumor Necrosis Factor Inhibitors in Rheumatoid Arthritis for Function and Pain is Affected by Rheumatoid Factor

Objectives :

To investigate differences in response to tumor necrosis factor inhibitor treatment (TNFi) in seropositive (rheumatoid factor positive; RF+) versus seronegative (RF-) patients with established RA as measured by the Health Assessment Questionnaire Disability Index (HAQ-DI) and pain.

Methods :

RA patients from an established RA cohort were studied according to rheumatoid factor (RF) status for change in HAQ-DI and pain (0-3 VAS) one year after starting treatment with a TNFi.

Results :

There were 238 patients treated with TNFi who had follow-up data (178 RF+ and 60 RF-). Disease duration was longer in RF+ vs RF- (12+8 vs 8+8 years) but the proportion of females (82% vs 72%, P=0.7), baseline HAQ-DI (1.44+0.63 vs 1.41+0.63, P=0.8) and pain (1.92+0.67 vs 1.93+0.67, P=0.9) were not different. The mean duration of treatment of first TNFi was 2.8 vs 2.3 years, P=0.1 and 68% of RF+ vs 62% of RF- were still receiving first TNFi at last visit (P=0.5). For patients with data at baseline and one year, the one-year HAQ-DI change was significantly greater in 90 RF+ patients (-0.356) versus 38 RF- patients (-0.126; P=0.04). The mean pain improvement was also greater in 77 RF+ vs 32 RF- patients (-0.725 vs -0.332 respectively; P=0.03). Numbers are small, data are missing and comorbidities, DAS28 and anti-CCP were not collected.

Conclusion :

Despite limitations in the data, in established RA after failure of DMARDs, RF+ patients may be more responsive to TNFi therapy as measured by changes in HAQ-DI and pain.

Innovation :

There may be a better response to TNFi in RA if RF positive for function and pain.

Rheumatoid factor and response to TNF antagonists in rheumatoid arthritis: systematic review and meta-analysis of observational studies

OBJECTIVE

To systematically analyze literature with the aim of examining whether rheumatoid factor (RF) is a predictor of response to tumor necrosis factor (TNF) antagonists in rheumatoid arthritis (RA).

METHODS

A systematic review and meta-analysis of observational studies were conducted. All studies on the association of baseline RF (titer and/or status) and response to any TNF antagonists, or with enough information to estimate this association were included. Qualitative analysis and meta-analysis using random-effects approach by type of outcome response and RF test was performed. Risk of publication bias was also evaluated.

RESULTS

The systematic review included 18 studies of 4163 identified articles, involving 5703 patients with homogeneous baseline characteristics. The most common outcome to assess response was European League Against Rheumatism (EULAR) response criteria, normally merging good and moderate categories as response. The weighted mean difference (WMD) of baseline IgM RF titer in meta-analysis was higher in the non-responders group [-101.58 (95% CI -156.58,-46.59) I2=0.0]. Combined odds ratios (ORs) of positive IgM RF, positive IgA RF, and positive IgG RF to achieve good/moderate response were 1.08 (0.80, 1.47), I2=40.9%; 0.83 (0.39, 1.73), I2=39.8%, and 1.30 (0.48, 3.51), I2=62.9%, respectively. We did not find an association between a positive IgM RF and EULAR good response or remission.

CONCLUSIONS

This meta-analysis does not support baseline IgM RF titer as a predictor of response to TNF antagonists in RA. However, this conclusion is hampered by high heterogeneity in the studies included in this meta-analysis.