Antibodies against citrullinated proteins of IgA isotype are associated with progression to rheumatoid arthritis in individuals at-risk.

OBJECTIVE: Events triggering disease outbreak in individuals at-risk for rheumatoid arthritis (RA at-risk) remain unclear, and the role of the various anticitrullinated protein antibody (ACPA) isotypes in this process is still to be established. We aimed to investigate the prevalence of IgA ACPA in RA at-risk individuals, their role in the transition from the RA at-risk status to RA and their dynamics during this transition. METHODS: Cross-sectional measurement of serum IgA1 and IgA2 ACPA levels was conducted in healthy controls, RA at-risk individuals and patients with RA and compared with the frequency of RA development in at risk individuals during a follow-up of 14 months. In addition, longitudinal measurements of serum IgA1 and IgA2 ACPA levels prior to, at and after the onset of RA were performed. RESULTS: Approximately two-thirds of RA at-risk individuals were positive for serum IgA1 and IgA2 ACPA in levels comparable to IgG ACPA positive patients with RA. IgA1, but not IgA2 ACPA positivity was associated with the transition from the RA at-risk state to RA within the following 14 months. Interestingly, during this transition process, IgA1 ACPA levels declined at RA onset and also thereafter during the early phase of RA. This decline was confirmed in a second, independent cohort. CONCLUSION: Both IgA1 and IgA2 ACPA are present in RA at-risk individuals, but only IgA1 ACPA are associated with the progression to RA. The observed decline in serum IgA1 ACPA levels before the onset of RA might indicate starting barrier leakiness prior to disease outbreak.

A mechanism of self-lipid endocytosis mediated by the receptor Mincle.

Cellular lipid uptake (through endocytosis) is a basic physiological process. Dysregulation of this process underlies the pathogenesis of diseases such as atherosclerosis, obesity, diabetes, and cancer. However, to date, only some mechanisms of lipid endocytosis have been discovered. Here, we show a previously unknown mechanism of lipid cargo uptake into cells mediated by the receptor Mincle. We found that the receptor Mincle, previously shown to be a pattern recognition receptor of the innate immune system, tightly binds a range of self-lipids. Moreover, we revealed the minimal molecular motif in lipids that is sufficient for Mincle recognition. Superresolution microscopy showed that Mincle forms vesicles in cytoplasm and colocalizes with added fluorescent lipids in endothelial cells but does not colocalize with either clathrin or caveolin-1, and the added lipids were predominantly incorporated in vesicles that expressed Mincle. Using a model of ganglioside GM3 uptake in brain vessel endothelial cells, we show that the knockout of Mincle led to a dramatic decrease in lipid endocytosis. Taken together, our results have revealed a fundamental lipid endocytosis pathway, which we call Mincle-mediated endocytosis (MiME), and indicate a prospective target for the treatment of disorders of lipid metabolism, which are rapidly increasing in prevalence.

Recombinant HBsAg of the Wild-Type and the G145R Escape Mutant, included in the New Multivalent Vaccine against Hepatitis B Virus, Dramatically Differ in their Effects on Leukocytes from Healthy Donors In Vitro.

Immune-escape hepatitis B virus (HBV) mutants play an important role in HBV spread. Recently, the multivalent vaccine Bubo®-Unigep has been developed to protect against both wild-type HBV and the most significant G145R mutant. Here, we compared the effects of recombinant HBsAg antigens, wild-type and mutated at G145R, both included in the new vaccine, on activation of a human high-density culture of peripheral blood mononuclear cells (PBMC) in vitro. The antigens were used either alone or in combination with phytohemagglutinin (PHA). None of the antigens alone affected the expression of CD40, HLA-DR or CD279. Wild-type HBsAg enhanced CD86 and CD69 expression, and induced TNF-α, IL-10, and IFN-γ, regardless of the anti-HBsAg status of donor. In the presence of PHA, wild-type HBsAg had no effect on either of the tested surface markers, but increased IFN-γ and IL-10 and inhibited IL-2. In contrast, the G145R mutant alone did not affect CD86 expression, it induced less CD69, and stimulated IL-2 along with lowering levels of TNF-α, IL-10, and IFN-γ. The G145R mutant also suppressed PHA-induced activation of CD69. The dramatic differences in the immune responses elicited by wild-type HBsAg and the G145R mutant HBsAg suggest distinct adaptive capabilities of the G145R mutant HBV.

Association of Structural Entheseal Lesions With an Increased Risk of Progression From Psoriasis to Psoriatic Arthritis.

OBJECTIVE: To test whether the presence of structural entheseal lesions in psoriasis patients influences the risk of progression to psoriatic arthritis (PsA). METHODS: We conducted a prospective cohort study of psoriasis patients without clinical evidence of musculoskeletal involvement who underwent baseline assessment of structural entheseal lesions and volumetric bone mineral density (vBMD) at entheseal and intraarticular sites by high-resolution peripheral quantitative computed tomography. Adjusted relative risks of developing PsA associated with baseline vBMD and the presence of structural entheseal lesions were calculated using multivariable Cox regression models. RESULTS: The cohort included 114 psoriasis patients (72 men and 42 women) with a mean ± SD follow-up duration of 28.2 ± 17.7 months, during which 24 patients developed PsA (9.7 per 100 patient-years [95% confidence interval (95% CI) 6.2-14.5]). Patients with structural entheseal lesions were at higher risk of developing PsA compared to patients without such lesions (21.4 per 100 patient-years [95% CI 12.5-34.3]; hazard ratio [HR] 5.10 [95% CI 1.53-16.99], P = 0.008). With respect to vBMD, a 1-SD increase in entheseal, but not intraarticular, vBMD was associated with an ~30% reduced risk of progression to PsA. Especially, higher cortical vBMD at entheseal segments was associated with a lower risk of developing PsA (HR 0.32 per 1 SD [95% CI 0.14-0.71]), and the association remained robust after multiple imputation of missing data (HR 0.64 [95% CI 0.42-0.98]). CONCLUSION: The presence of structural entheseal lesions as well as low cortical vBMD at entheseal segments are associated with an increased risk of developing PsA in patients with psoriasis.

IgA anti-citrullinated protein antibodies are associated with flares during DMARD tapering in rheumatoid arthritis.

OBJECTIVES: A substantial proportion of RA patients flare upon withdrawal of DMARDs, and thus the definition of prognostic markers is crucial. ACPA positivity has been identified as a risk factor for flare. However, only the role of IgG ACPA is established in this context, while the role of IgA ACPA is poorly defined. We thus aimed to investigate the role of IgA ACPA in flaring of RA. METHODS: Serum levels of IgA1 and IgA2 ACPA at baseline and after 12 months were measured in 108 patients from the randomized controlled RETRO study. RA patients in stable remission for at least 6 months at study recruitment were assigned to either one of the DMARD tapering arms or to continuation of DMARDs. RESULTS: In patients remaining in remission but not in the ones who flared, IgA2 ACPA levels and proportion of IgA2 in ACPA (IgA2% ACPA) significantly declined (median of 17.5%; P < 0.0001). This seemed to be independent of the treatment choice, as there was no difference in IgA2 ACPA dynamics between the study arms. IgA2% ACPA was associated with disease activity (DAS28) at flare (r = 0.36; P = 0.046). IgA and IgG ACPA showed a tendency towards independent contribution to the risk of flare with the highest risk if a patient had both antibody classes. CONCLUSION: In this study, IgA ACPA was identified as a risk factor for flare in combination with IgG ACPA. IgA2 ACPA levels were associated with flare severity and declined in patients in stable remission.

Autoantibodies in Rheumatoid Arthritis: Historical Background and Novel Findings.

Autoantibodies represent a hallmark of rheumatoid arthritis (RA), with the rheumatoid factor (RF) and antibodies against citrullinated proteins (ACPA) being the most acknowledged ones. RA patients who are positive for RF and/or ACPA ("seropositive") in general display a different etiology and disease course compared to so-called "seronegative" patients. Still, the seronegative patient population is very heterogeneous and not well characterized. Due to the identification of new autoantibodies and advancements in the diagnosis of rheumatic diseases in the last years, the group of seronegative patients is constantly shrinking. Aside from antibodies towards various post-translational modifications, recent studies describe autoantibodies targeting some native proteins, further broadening the spectrum of recognized antigens. Next to the detection of new autoantibody groups, much research has been done to answer the question if and how autoantibodies contribute to the pathogenesis of RA. Since autoantibodies can be detected years prior to RA onset, it is a matter of debate whether their presence alone is sufficient to trigger the disease. Nevertheless, there is gathering evidence of direct autoantibody effector functions, such as stimulation of osteoclastogenesis and synovial fibroblast migration in in vitro experiments. In addition, autoantibody positive patients display a worse clinical course and stronger radiographic progression. In this review, we discuss current findings regarding different autoantibody types, the underlying disease-driving mechanisms, the role of Fab and Fc glycosylation and clinical implications.

Detection of S-HBsAg Mutations in Patients with Hematologic Malignancies.

Multiple studies of hepatitis B virus (HBV) genetic variability and its relationship with the disease pathogenesis are currently ongoing, stemming from growing evidence of the clinical significance of HBV mutations. It is becoming increasingly evident that patients with hematologic malignancies may be particularly prone to a higher frequency of such mutations. The present report is the first extensive study of the prevalence of escape mutations in S-HBsAg, performed using isolates from 59 patients from hospital hematology departments with diagnoses of leukemia (n = 32), lymphoma (n = 20), multiple myeloma (n = 3), and non-tumor blood diseases (n = 4). The isolates were serologically examined for the presence of HBV markers and sequenced using either next-generation sequencing (NGS) or Sanger sequencing. Occult hepatitis B was found in 5.1% of cases. Genetic analysis of the region corresponding to S-HBsAg demonstrated an exceptionally high mutation frequency in patients with leukemias (93.4%) and lymphomas (85.0%), along with the prominent mutation heterogeneity. Additionally, more than 15 mutations in one sample were found in patients with leukemias (6.3% of cases) and lymphomas (5.0% of cases). Most of the mutations were clinically significant. The study analyzes the mutation profile of HBV in different oncohematological diseases and the frequency of individual mutations. The data strongly suggest that the NGS method, capable of detecting minor populations of HBV mutations, provides a diagnostic advantage, lays the foundation for the development of screening methods, and allows for the study of the virological and pathogenetic aspects of hepatitis B.

Apremilast inhibits inflammatory osteoclastogenesis.

OBJECTIVES: Psoriatic arthritis (PsA) is associated with bone erosion and inflammation-induced bone loss, which are mediated by osteoclasts (OC) and modulated by inflammatory cytokines. Apremilast (APR) (a selective phosphodiesterase 4 inhibitor) is efficacious in PsA and acts by inhibiting cytokine production. However, there are no direct data informing whether and how APR affects osteoclast formation in humans. METHODS: Osteoclastogenic cytokine production by activated human peripheral blood mononuclear cells (PBMCs) was measured in the presence and absence of APR. Effects of APR on osteoclast differentiation were tested (i) in co-cultures of activated PBMCs and human CD14+ blood monocytes as well as (ii) in CD14+ blood monocytes stimulated with activated-PBMCs supernatant, TNF or IL-17A. Bone resorption was measured on OsteoAssay plates. Effects of APR on ex vivo osteoclast differentiation were compared in PsA, pre-PsA and psoriasis patients, as well as in healthy controls. RESULTS: APR significantly impaired the expression of key osteoclastogenic cytokines in activated PBMCs. Furthermore, APR dose-dependently and significantly inhibited activated PBMC-driven osteoclast differentiation and ex vivo osteoclast differentiation of PBMCs derived from PsA and pre-PsA patients, but not from psoriasis patients or healthy controls. TNF and IL-17A-enhanced osteoclastogenesis and osteolytic activity of CD14+ blood monocytes from PsA patients was also significantly inhibited by APR. Finally, APR inhibited expression of the key osteoclast fusion protein dendritic cell-specific transmembrane protein. CONCLUSION: Phosphodiesterase 4 targeting by APR not only inhibits osteoclastogenic cytokine production, but also directly suppresses inflammation-driven osteoclastogenesis. These data provide initial evidence that APR has the potential to provide a direct bone protective effect in PsA.

IgA Complexes Induce Neutrophil Extracellular Trap Formation More Potently Than IgG Complexes.

Neutrophil extracellular trap (NET) formation is a powerful instrument to fight pathogens, but may induce collateral damage in the affected tissues. Besides pathogen-derived factors, immune complexes are potent inducers of NET formation. Neutrophils express IgA and IgG specific Fc receptors (FcRs) and therefore respond to complexed IgA and IgG. Especially in the context of autoimmune diseases, IgA and IgG immune complexes have been shown to trigger NET formation, a process that putatively contributes to disease severity. However, it is of question if both antibody classes stimulate neutrophils to the same extent. In this study, we compared the capability of IgA and IgG complexes formed by heat aggregation to induce NET formation. While stimulation of neutrophils with IgA complexes robustly induced NET formation, complexed IgG only marginally increased the amount of NETs compared to the unstimulated control. Mixing IgA with IgG before heat aggregation did not increase the effect of complexed IgA on neutrophils. By contrast, the presence of IgG complexes seemed to disturb neutrophil stimulation by IgA complexes. The capacity of complexed IgG to induce NET formation could not be increased by the addition of autologous serum or the removal of terminal sialic acid in the Fc glycan. Together, our data show that IgA is a much more potent inducer of NET formation than IgG. IgA may thus be the main driving force in (auto)immune complex-mediated NET formation.

Ethanol consumption inhibits TFH cell responses and the development of autoimmune arthritis.

Alcohol consumption is a consistent protective factor for the development of autoimmune diseases such as rheumatoid arthritis (RA). The underlying mechanism for this tolerance-inducing effect of alcohol, however, is unknown. Here we show that alcohol and its metabolite acetate alter the functional state of T follicular helper (TFH) cells in vitro and in vivo, thereby exerting immune regulatory and tolerance-inducing properties. Alcohol-exposed mice have reduced Bcl6 and PD-1 expression as well as IL-21 production by TFH cells, preventing proper spatial organization of TFH cells to form TFH:B cell conjugates in germinal centers. This effect is associated with impaired autoantibody formation, and mitigates experimental autoimmune arthritis. By contrast, T cell independent immune responses and passive models of arthritis are not affected by alcohol exposure. These data clarify the immune regulatory and tolerance-inducing effect of alcohol consumption.

A set of serum markers detecting systemic inflammation in psoriatic skin, entheseal, and joint disease in the absence of C-reactive protein and its link to clinical disease manifestations.

BACKGROUND: C-reactive protein (CRP) is often normal in patients with psoriatic disease. Herein, we aimed to define markers of systemic inflammation in patients with monomorphic and polymorphic psoriatic skin, entheseal, and joint disease. METHODS: Three-step approach: (i) selection of serum markers elevated in psoriatic arthritis compared healthy controls from a panel of 10 different markers reflecting the pathophysiology of psoriatic disease; (ii) testing of these selected markers as well as C-reactive protein (CRP) in a larger cohort of 210 individuals- 105 healthy controls and 105 patients with psoriatic disease with either monomorphic skin (S), entheseal (E) or joint (A) involvement or polymorphic disease with various combinations of skin, entheseal and joint disease (SE, SA, EA, SEA); (iii) testing whether tumor necrosis factor (TNF) and interleukin (IL)-17 inhibitor therapy normalizes these markers. RESULTS: CRP was not elevated or was rarely elevated in the subgroups (S 0%, E 0%, A 20%, SE 7%, SA 33%, EA 27%, SEA 33%) despite active psoriatic disease. In sharp contrast, beta-defensin 2 and lipocalin-2 levels were elevated in the majority of patients with monomorphic skin (93% and 73%) and entheseal (both 53%), but not joint disease (27% and 20%). Conversely, elevations of calprotectin and IL-8 were found in the majority of patients with monomorphic joint disease (both 73%). IL-22 was elevated in all three monomorphic disease manifestations (S 60%, E 46%; A 60%). Furthermore, the vast majority of patients with polymorphic psoriatic disease (SE, SA, EA, SEA) showed widespread marker elevation. IL-17- and TNF inhibitor treatment significantly lowered all 5 markers of inflammation in PsA patients. CONCLUSIONS: Systemic inflammation is detectable in the majority of patients with psoriatic disease, even if CRP is normal. The respective marker pattern depends on the manifestation of psoriatic disease with respect to skin, entheseal, and joint involvement.

IgA subclasses have different effector functions associated with distinct glycosylation profiles.

Monomeric serum immunoglobulin A (IgA) can contribute to the development of various autoimmune diseases, but the regulation of serum IgA effector functions is not well defined. Here, we show that the two IgA subclasses (IgA1 and IgA2) differ in their effect on immune cells due to distinct binding and signaling properties. Whereas IgA2 acts pro-inflammatory on neutrophils and macrophages, IgA1 does not have pronounced effects. Moreover, IgA1 and IgA2 have different glycosylation profiles, with IgA1 possessing more sialic acid than IgA2. Removal of sialic acid increases the pro-inflammatory capacity of IgA1, making it comparable to IgA2. Of note, disease-specific autoantibodies in patients with rheumatoid arthritis display a shift toward the pro-inflammatory IgA2 subclass, which is associated with higher disease activity. Taken together, these data demonstrate that IgA effector functions depend on subclass and glycosylation, and that disturbances in subclass balance are associated with autoimmune disease.

The Role of Dietary Fiber in Rheumatoid Arthritis Patients: A Feasibility Study.

Short-chain fatty acids are microbial metabolites that have been shown to be key regulators of the gut-joint axis in animal models. In humans, microbial dysbiosis was observed in rheumatoid arthritis (RA) patients as well as in those at-risk to develop RA, and is thought to be an environmental trigger for the development of clinical disease. At the same time, diet has a proven impact on maintaining intestinal microbial homeostasis. Given this association, we performed a feasibility study in RA patients using high-fiber dietary supplementation with the objective to restore microbial homeostasis and promote the secretion of beneficial immunomodulatory microbial metabolites. RA patients (n = 36) under routine care received daily high-fiber bars or cereals for 28 days. Clinical assessments and laboratory analysis of immune parameters in blood and stool samples from RA patients were done before and after the high-fiber dietary supplementation. We observed an increase in circulating regulatory T cell numbers, favorable Th1/Th17 ratios, as well as decreased markers of bone erosion in RA patients after 28 days of dietary intervention. Furthermore, patient-related outcomes of RA improved. Based on these results, we conclude that controlled clinical studies of high-fiber dietary interventions could be a viable approach to supplement or complement current pharmacological treatment strategies.

Certolizumab pegol in the treatment of Takayasu arteritis.

Objectives: Certolizumab pegol (CZP) is a PEGylated antigen-binding fragment-fragment of a humanized mAb neutralizing TNF. It lacks Fc-fragment and has a very low potential to cross the placenta. We aimed to report the efficacy and safety of CZP in a case series of patients with refractory Takayasu arteritis (TA). Methods: Ten females of reproductive age (18-35 years) with TA were treated with CZP (at a dose of 400 mg at weeks 0, 2 and 4 and at 200 mg every 2 weeks thereafter) for a median of 10 months (range 3-28). Prior to CZP administration all patients received glucocorticoids and ± MTX, CYC, AZA, HCQ, LEF or MMF. Six patients were previously treated with other biological anti-cytokine drugs. The National Institutes of Health criteria and the Indian Takayasu Clinical Activity Score 2010 were used to define disease activity. Results: All patients rapidly responded to treatment with CZP and were able to taper prednisone and MTX doses. Treatment with CZP resulted in a significant decrease in median serum CRP levels and normalization of Indian Takayasu Clinical Activity Score 2010 score in 9 of 10 patients. Remission of systemic vasculitis was achieved in all patients. Seven patients maintained remission for at least 4 months, while one patient developed relapse after 2 years of CZP treatment. Side effects included mild infections (n = 5). Conclusion: Our case series suggests that CZP may be an effective and steroid-sparing treatment option in patients with active TA even if they did not previously respond to other TNF inhibitors or tocilizumab.