In early rheumatoid arthritis, anticitrullinated peptide antibodies associate with low number of affected joints and rheumatoid factor associates with systemic inflammation

Bone-protective effects of neutralizing angiopoietin-like protein 4 monoclonal antibody in rheumatoid arthritis

Despite recent advances, rheumatoid arthritis (RA) patients remain refractory to therapy. Dysregulated overproduction of angiopoietin-like protein 4 (ANGPTL4) is thought to contribute to the disease development. ANGPTL4 was initially identified as a regulator of lipid metabolism, which is hydrolyzed to N-terminal and C-terminal (cANGPTL4) fragments in vivo. cANGPTL4 is involved in several non-lipid-related processes, including angiogenesis and inflammation. This study revealed that the level of ANGPTL4 was markedly elevated in the sera and synovial tissues from patients with RA versus controls. The administration of a neutralizing antibody against cANGPTL4 (anti-cANGPTL4 Ab) resulted in the inhibition of inflammatory processes and bone loss in animal models of collagen-induced arthritis and adjuvant-induced arthritis (AIA). Transcriptomic and proteomic profiling of synovial tissues from an AIA model indicated that the anti-cANGPTL4 Ab inhibited fibroblast-like synoviocyte (FLS) immigration and inflammatory-induced osteoclastogenesis. Mechanistically, the anti-cANGPTL4 Ab has been shown to inhibit TNF-α-induced inflammatory cascades in RA-FLS through the sirtuin 1/nuclear factor-κB signaling pathway. Moreover, the anti-cANGPTL4 Ab was found to block FLS invasion- and immigration-induced osteoclast activation. Collectively, these findings identify ANGPTL4 as a prospective biomarker for the diagnosis of RA, and targeting cANGPTL4 should represent a potential therapeutic strategy.

Predictors of functional improvement and pain reduction in rheumatoid arthritis patients who achieved low disease activity with disease-modifying antirheumatic drugs: a retrospective study of the FIRST Registry

BACKGROUND

Rheumatoid arthritis (RA) patients sometimes exhibit different levels of improvement in health assessment questionnaire-disability index (HAQ-DI) and subjective pain visual analogue score (VAS) even after achieving low disease activities (LDA). This study aimed to identify factors associated with improvement in HAQ-DI and pain VAS among those who achieved LDA.

METHODS

Data of the FIRST registry, a multi-institutional cohort of RA patients treated with biological and targeted-synthetic DMARDs (b/tsDMARDs) were analyzed. Patients who were enrolled from August 2013 to February 2023 and who achieved clinical LDA [clinical disease activity index (CDAI) ≤ 10.0] at 6 months after starting treatment were included. Multiple logistic regression analyses were conducted to identify the factors that associated with achieving HAQ-DI normalization (< 0.5), HAQ-DI improvement (by > 0.22), or pain VAS reduction (≤ 40 mm).

RESULTS

Among 1424 patients who achieved LDA at 6 months, 732 patients achieved HAQ-DI normalization and 454 achieved pain VAS reduction. The seropositivity and the use of JAK inhibitor compared with TNF inhibitor were associated with both HAQ-DI < 0.5 and pain VAS reduction at 6 months. On the other hand, older age, past failure in ≥ 2 classes of b/tsDMARDs, higher HAQ-DI at baseline, and use of glucocorticoid were associated with the lower likelihood of HAQ-DI normalization and pain VAS reduction. Longer disease duration, being female, and higher disease activity at baseline was negatively associated HAQ-DI normalization alone. Comorbidities were not associated with the outcomes.

CONCLUSIONS

These results suggest some preferable treatment may exist for improvement of HAQ-DI and pain VAS reduction in the early stage of the treatment, which is a clue to prevention of a criteria of difficult-to-treat RA.

The peculiar features, diversity and impact of citrulline-reactive autoantibodies

Since entering the stage 25 years ago as a highly specific serological biomarker for rheumatoid arthritis, anti-citrullinated protein antibodies (ACPAs) have been a topic of extensive research. This hallmark B cell response arises years before disease onset, displays interpatient autoantigen variability, and is associated with poor clinical outcomes. Technological and scientific advances have revealed broad clonal diversity and intriguing features including high levels of somatic hypermutation, variable-domain N-linked glycosylation, hapten-like peptide interactions, and clone-specific multireactivity to citrullinated, carbamylated and acetylated epitopes. ACPAs have been found in different isotypes and subclasses, in both circulation and tissue, and are secreted by both plasmablasts and long-lived plasma cells. Notably, although some disease-promoting features have been reported, results now demonstrate that certain monoclonal ACPAs therapeutically block arthritis and inflammation in mouse models. A wealth of functional studies using patient-derived polyclonal and monoclonal antibodies have provided evidence for pathogenic and protective effects of ACPAs in the context of arthritis. To understand the roles of ACPAs, one needs to consider their immunological properties by incorporating different facets such as rheumatoid arthritis B cell biology, environmental triggers and chronic antigen exposure. The emerging picture points to a complex role of citrulline-reactive autoantibodies, in which the diversity and dynamics of antibody clones could determine clinical progression and manifestations.

Exhaled Nitric Oxide Reflects the Immune Reactions of the Airways in Early Rheumatoid Arthritis

Patients with rheumatoid arthritis (RA) have altered levels of exhaled nitric oxide (NO) compared with healthy controls. Here, we investigated whether the clinical features of and immunological factors in RA pathogenesis could be linked to the NO lung dynamics in early disease. A total of 44 patients with early RA and anti-citrullinated peptide antibodies (ACPAs), specified as cyclic citrullinated peptide 2 (CCP2), were included. Their exhaled NO levels were measured, and the alveolar concentration, the airway compartment diffusing capacity and the airway wall concentration of NO were estimated using the Högman-Meriläinen algorithm. The disease activity was measured using the Disease Activity Score for 28 joints. Serum samples were analysed for anti-CCP2, rheumatoid factor, free secretory component, secretory component containing ACPAs, antibodies against Porphyromonas gingivalis (Rgp) and total levels of IgA, IgA1 and IgA2. Significant negative correlations were found between the airway wall concentration of NO and the number of swollen joints (Rho -0.48, p = 0.004), between the airway wall concentration of NO and IgA rheumatoid factor (Rho -0.41, p = 0.017), between the alveolar concentration and free secretory component (Rho -0.35, p = 0.023) and between the alveolar concentration and C-reactive protein (Rho -0.36, p = 0.016), but none were found for anti-CCP2, IgM rheumatoid factor or the anti-Rgp levels. In conclusion, altered NO levels, particularly its production in the airway walls, may have a role in the pathogenesis of ACPA-positive RA.

Shift in perspective: autoimmunity protecting against rheumatoid arthritis

A hallmark of rheumatoid arthritis (RA) is the increased levels of autoantibodies preceding the onset and contributing to the classification of the disease. These autoantibodies, mainly anti-citrullinated protein antibody (ACPA) and rheumatoid factor, have been assumed to be pathogenic and many attempts have been made to link them to the development of bone erosion, pain and arthritis. We and others have recently discovered that most cloned ACPA protect against experimental arthritis in the mouse. In addition, we have identified suppressor B cells in healthy individuals, selected in response to collagen type II, and these cells decrease in numbers in RA. These findings provide a new angle on how to explain the development of RA and maybe also other complex autoimmune diseases preceded by an increased autoimmune response.

Anti-Toxoplasma gondii antibodies as a risk factor for the prevalence and severity of systemic lupus erythematosus

BACKGROUND

Systemic lupus erythematosus (SLE) is a complex systemic autoimmune disease characterized by the presence of numerous autoantibodies. The interaction of infectious agents (viruses, bacteria and parasites) and a genetically susceptible host may be a key mechanism for SLE. Toxoplasma gondii is a widespread intracellular parasite that has been implicated in the pathogenesis of autoimmune diseases. However, the relationship between T. gondii infection and the increased risk of SLE in Chinese populations remains unclear.

METHODS

The seroprevalence of T. gondii infection was assessed in 1771 serum samples collected from Chinese individuals (908 healthy controls and 863 SLE patients) from different regions of China using an enzyme-linked immunosorbent assay. Serum autoantibodies and clinical information were obtained and analysed.

RESULTS

Our observations revealed a higher prevalence of anti-T. gondii antibodies (ATxA) immunoglobulin G (IgG) in serum samples from SLE patients (144/863, 16.7%) than in those from the healthy controls (53/917, 5.8%; P < 0.0001), indicating a 2.48-fold increased risk of SLE in the ATxA-IgG+ population, after adjustment for age and sex (95% confidence interval [CI] 1.70-3.62, P < 0.0001). ATxA-IgG+ SLE patients also showed a 1.75-fold higher risk of developing moderate and severe lupus symptoms (95% CI 1.14-2.70, P = 0.011) compared to ATxA-IgG- patients. Relative to ATxA-IgG- patients, ATxA-IgG+ patients were more likely to develop specific clinical symptoms, including discoid rash, oral ulcer, myalgia and alopecia. Seven antibodies, namely anti-ribosomal RNA protein (rRNP), anti-double stranded DNA (dsDNA), anti-cell membrane DNA (cmDNA), anti-scleroderma-70 (Scl-70), anti-cardiolipin (CL), anti-beta2-glycoprotein-I (B2GPI) and rheumatoid factor (RF), occurred more frequently in ATxA-IgG+ patients. When combined with anti-dsDNA and RF/anti-rRNP/anti-cmDNA/ESR, ATxA-IgG significantly increased the risk for severe lupus.

CONCLUSIONS

Our results suggest that ATxA-IgG may be a significant risk factor for SLE prevalence and severity in Chinese populations.