Trends in Faecal Zonulin Concentrations in Paediatric Patients with Celiac Disease at Baseline and on a Gluten-Free Diet: Exploring Correlations with Other Faecal Biomarkers

Celiac disease (CeD) is an autoimmune condition triggered by gluten in genetically predisposed individuals, affecting all ages. Intestinal permeability (IP) is crucial in the pathogenesis of CeD and it is primarily governed by tight junctions (TJs) that uphold the intestinal barrier's integrity. The protein zonulin plays a critical role in modulating the permeability of TJs having emerged as a potential non-invasive biomarker to study IP. The importance of this study lies in providing evidence for the usefulness of a non-invasive tool in the study of IP both at baseline and in the follow-up of paediatric patients with CeD. In this single-centre prospective observational study, we explored the correlation between faecal zonulin levels and others faecal and serum biomarkers for monitoring IP in CeD within the paediatric population. We also aimed to establish reference values for faecal zonulin in the paediatric population. We found that faecal zonulin and calprotectin values are higher at the onset of CeD compared with the control population. Specifically, the zonulin levels were 347.5 ng/mL as opposed to 177.7 ng/mL in the control population (p = 0.001), while calprotectin levels were 29.8 μg/g stool compared to 13.9 μg/g stool (p = 0.029). As the duration without gluten consumption increased, a significant reduction in faecal zonulin levels was observed in patients with CeD (348.5 ng/mL vs. 157.1 ng/mL; p = 0.002), along with a decrease in the prevalence of patients with vitamin D insufficiency (88.9% vs. 77.8%). We conclude that faecal zonulin concentrations were higher in the patients with active CeD compared with healthy individuals or those following a gluten-free diet (GFD). The significant decrease in their values over the duration of the GFD suggests the potential use of zonulin as an additional tool in monitoring adherence to a GFD.

Clinical Characteristics of Patients With Acquired Partial Lipodystrophy: A Multicenter Retrospective Study

BACKGROUND

Barraquer-Simons syndrome (BSS) is a rare, acquired form of lipodystrophy characterized by progressive loss of upper body subcutaneous fat, which affects face, upper limbs, and trunk. The pathogenesis of the disease is not entirely known and may involve autoimmune mechanisms.

AIM

This study aimed to provide a comprehensive picture of the clinical, immunological, and metabolic features of a large cohort of patients with BSS. Our primary objectives included the validation of existing diagnostic tools, the evaluation of novel diagnostic approaches, and the exploration of potential disease triggers or genetic predispositions.

SUBJECTS AND METHODS

Twenty-six patients were diagnosed with BSS based on accepted criteria defined by international guidelines. Anthropometric parameters, biochemical tests, organ- and non-organ-specific autoantibodies, HLA status, and screening of the LMNB2 gene were performed.

RESULTS

Patients were predominantly females (73%); fat loss occurred mostly during childhood (77%) at a median age of 8 years. Among various anthropometric measures, the ratio between the proportion of fat mass in upper limbs and lower limbs showed the best predictive value for diagnosis. A total of 11.5% of patients had diabetes, 34.6% dyslipidemia, and 26.9% hepatic steatosis. Seventy-five percent of children and 50% of adults had C3 hypocomplementemia; 76% of patients were positive for 1 or more autoantibodies. HLA-DRB1 11:03 had higher allelic frequencies compared with the general population. A single variant in the LMNB2 gene was found in 1 patient.

CONCLUSION

BSS has a childhood onset and is often associated with autoimmune diseases. Skinfold thickness measurements and fat assessment by dual energy X-ray absorptiometry are useful tools to identify the disease. C3 hypocomplementemia and the presence of autoantibodies may be used as additional diagnostic supportive criteria but the prevalence of C3 hypocomplementemia may be lower than previously reported.

Influence of rheumatoid factor on serum drug levels of tumour necrosis factor inhibitors with different structures in rheumatoid arthritis

OBJECTIVES

Certolizumab pegol (CZP), an Fc-free antibody fragment, has shown stable serum levels and steady efficacy in the treatment of RA patients, irrespective of RF levels at baseline. Here, we examine, in clinical practice, the effect of baseline RF and ACPA levels on serum drug levels of IFX, ADL and CZP an Fc-free antibody fragment.

METHODS

This is a retrospective study performed in real-world patients. We assessed 170 patients with RA: 90 (53%) received IFX, 48 (28%) ADL and 32 (19%) CZP. Demographic and clinical variables, RF and ACPA levels were obtained at the baseline visit (T0), and patients were stratified based on negative, low, medium, or high levels. After 6 months (T6) serum drug levels and anti-drug antibodies (ADAb), were computed.

RESULTS

While CZP serum levels did not differ across RF groups at T6, high baseline RF was linked to lower serum drug levels compared to RF negative status in treatment with complete monoclonal antibodies IFX and ADL. No differences in disease activity measured by DAS28 at baseline were observed across RF quartiles in patients treated with IFX or ADL. ADAb was observed in 26 patients with IFX, 3 with ADL and 1 with CZP, following 6 months of treatment. Patients with high baseline RF levels dropped out more frequently by secondary non-response in IFX or ADL than CZP (80% vs. 75% vs. 33%, p=0.002).

CONCLUSIONS

In this real word data evaluation, CZP serum levels were independent of RF levels in patients however patients with high baseline RF levels who obtained IFX or ADL had lower serum drug levels at 6 months than baseline RF-negative patients. In addition, secondary non-response was more frequent in patients with high RF levels treated with IFX and ADL.

Early monitoring of anti-infliximab antibodies by drug-tolerant assay predicts later immunogenicity and drug survival in rheumatic diseases

OBJECTIVES

To investigate the appearance of anti-drug antibodies (ADA) against infliximab (IFX) determined by drug-sensitive and drug-tolerant assays and their relationship with drug levels and drug survival.

METHODS

This longitudinal observational study included 45 patients with rheumatoid arthritis (RA) and 61 with spondyloarthritis (SpA). Serum samples were obtained at weeks 2, 6, 12, 24, and 52. Serum IFX levels were measured by a capture enzyme-linked immunosorbent assay (ELISA) and ADA by an in-house drug-sensitive two-site (bridging) enzyme-linked immunosorbent assay (bELISA) and a commercially available drug-tolerant ELISA (IDK, Immundiagnostik, Germany).

RESULTS

Anti-drug antibodies were detected earlier by IDK than by bELISA. Once ADA appeared, positivity persisted throughout the study period. Patients who were bELISA ADA+ had higher IDK ADA levels (than bELISA ADA- patients). Circulating IFX levels were detected in all patients except those found to be bELISA ADA+. Serum IFX levels were lower in IDK ADA+ than in IDK ADA-patients.Most patients (64%) discontinued due to inefficacy. The early onset of immunogenicity was related to IFX survival. Both in RA and SpA, the median survival (years) was shorter in patients with earlier development of ADA (IDK+ before or at week 24) than those who became IDK+ later (after week 24) or never developed ADA.

CONCLUSION

A drug-tolerant assay detects ADA during IFX therapy earlier and more frequently than a drug-sensitive assay. The onset of immunogenicity detected by drug-tolerant assays is related to the subsequent detection of ADA by drug-sensitive assays and drug survival.

Immune response after SARS-CoV-2 vaccination in patients with inflammatory immune-mediated diseases receiving immunosuppressive treatment

BACKGROUND

Real world data on the response to the SARS-CoV-2 vaccine in patients with immunomediated diseases (IMIDs) treated with immunesuppressants is of great interest because vaccine response may be impaired. The main aim was to study the humoral and cellular immune response after SARS-CoV-2 vaccination in patients with IMIDs treated with immunosuppressants. The secondary aim was to describe the frequency of SARS-CoV-2 infections after vaccination in these patients.

MATERIAL AND METHODS

This is an observational study including 86 patients with IMIDs. All patients were treated with biologic or targeted synthetic disease-modifying antirheumatic drugs [b/tsDMARDs: TNF inhibitors (TNFi), rituximab, anti-interleukin 6 receptor (anti-IL6R) or JAK inhibitors (JAKi)]. Demographic and clinical information were collected. After 4-6 weeks of 2nd and 3rd vaccine doses, humoral response was assessed using the Thermo Scientific ELiA SARS-CoV-2-Sp1 IgG Test. Also, in patients with serum SARS-CoV-2 antibody levels under 100UI/ml, cellular response was analyzed using the QuantiFERON SARS-CoV-2 Starter Pack.

RESULTS

A total of 86 patients under b/tsDMARDs and 38 healthy controls were included. Most patients received TNFi (45 with TNFi, 31 with rituximab, 5 with anti-IL6R and 5 with JAKi). SARS-CoV-2 antibodies (Ab) were present in an 86% of patients with IMIDs and in 100% healthy controls (p = 0.017). However, 12 (14%) patients had undetectable SARS-CoV-2 Ab levels, all treated with rituximab. In addition, SARS-CoV-2 Ab (IU/ml) were statistically lower in patients (Mdn (IQR): 59.5 (17-163) in patients vs 625 (405-932) in controls, p < 0.001). Patients treated with rituximab had lower Ab levels than those treated with TNFi and controls (p < 0.001). The cellular response to SARS-CoV-2 vaccine was evaluated in 30 patients. Eleven patients had a positive cellular response, being more frequent in patients treated with rituximab (p = 0.03). SARS-CoV-2 infection was reported in 43% of patients and 34% of controls after vaccination. Only 6 (7%) patients required hospitalization, most of whom treated with rituximab (67%).

CONCLUSION

SARS-CoV-2 antibody levels were lower in patients than in controls, especially in patients treated with rituximab. A cellular response can be detected despite having a poor humoral response. Severe infections in vaccinated patients with IMIDs are rare, and are observed mainly in patients treated with rituximab.

Dual role of peripheral B cells in multiple sclerosis: emerging remote players in demyelination and novel diagnostic biomarkers

Introduction

Multiple sclerosis is an inflammatory and demyelinating disease caused by a pathogenic immune response against the myelin sheath surfaces of oligodendrocytes. The demyelination has been classically associated with pathogenic B cells residing in the central nervous system that release autoreactive antibodies against myelin. The aim of the present study was to investigate whether extracellular vesicles (EVs) mediate delivery of myelin autoreactive antibodies from peripheral B cells against oligodendrocytes in multiple sclerosis (MS) and to analyze whether these EVs could mediate demyelination in vitro. We also studied the role of these EV-derived myelin antibodies as a diagnostic biomarker in MS.

Methods

This is a prospective, observational, and single-center study that includes patients with MS and two control groups: patients with non-immune white matter lesions and healthy controls. We isolated B-cell-derived EVs from the blood and cerebrospinal fluid (CSF) and analyzed their myelin antibody content. We also studied whether antibody-loaded EVs reach oligodendrocytes in patients with MS and the effect on demyelination of B-cell-derived EVs containing antibodies in vitro.

Results

This study enrolled 136 MS patients, 23 white matter lesions controls, and 39 healthy controls. We found autoreactive myelin antibodies in EVs that were released by peripheral B cells, but not by populations of B cells resident in CSF. We also identified a cut-off of 3.95 ng/mL of myelin basic protein autoantibodies in EVs from peripheral B cells, with 95.2% sensitivity and 88.2% specificity, which allows us to differentiate MS patients from healthy controls. EV-derived myelin antibodies were also detected in the oligodendrocytes of MS patients. Myelin antibody-loaded EVs from B cells induced myelin markers decrease of oligodendrocytes in vitro.

Discussion

Peripheral reactive immune cells could contribute remotely to MS pathogenesis by delivering myelin antibodies to oligodendrocytes. EV-derived myelin antibodies could play a role as diagnostic biomarker in MS.

Detection of specific RBD+ IgG+ memory B cells by flow cytometry in healthcare workers and patients with inborn errors of immunity after BNT162b2 m RNA COVID-19 vaccination

Introduction

Inborn errors of immunity (IEI) are a heterogeneous group of diseases caused by intrinsic defects of the immune system. Estimating the immune competence of immunocompromised patients for an infection risk assessment or after SARS-CoV-2 vaccination constituted a challenge.

Methods

The aim of this study was to determine the humoral responses of patients with IEI through a comprehensive analysis of specific receptor-binding domain-positive (RBD+) IgG+ memory B cells (MBCs) by flow cytometry, together with routine S-specific IgG antibodies and QuantiFERON SARS-CoV-2 (T-cell response), before the vaccine and 3 weeks after a second dose.

Results and discussion

We first analyzed the percentage of specific RBD+ IgG+ MBCs in healthy healthcare workers. Within the control group, there was an increase in the percentage of specific IgG+ RBD+ MBCs 21 days after the second dose, which was consistent with S-specific IgG antibodies.Thirty-one patients with IEI were included for the pre- and post-vaccination study; IgG+ RBD+ MBCs were not evaluated in 6 patients due to an absence of B cells in peripheral blood. We detected various patterns among the patients with IEI with circulating B cells (25, 81%): an adequate humoral response was observed in 12/25, consider by the detection of positive S-specific IgG antibodies and the presence of specific IgG+ RBD+ MBCs, presenting a positive T-cell response; in 4/25, very low S-specific IgG antibody counts correlated with undetectable events in the IgG+ RBD+ MBC compartment but with positive cellular response. Despite the presence of S-specific IgG antibodies, we were unable to detect a relevant percentage of IgG+ RBD+ MBCs in 5/25; however, all presented positive T-cell response. Lastly, we observed a profound failure of B and T-cell response in 3 (10%) patients with IEI, with no assessment of S-specific IgG antibodies, IgG+ RBD+ MBCs, and negative cellular response. The identification of specific IgG+ RBD+ MBCs by flow cytometry provides information on different humoral immune response outcomes in patients with IEI and aids the assessment of immune competence status after SARS-CoV-2 mRNA vaccine (BNT162b2), together with S-specific IgG antibodies and T-cell responses.

Characterization and Clinical Association of Autoantibodies Against Perilipin 1 in Patients With Acquired Generalized Lipodystrophy

Acquired generalized lipodystrophy (AGL) is a rare condition characterized by massive loss of adipose tissue through the body, causing severe metabolic complications. Autoimmune destruction of adipocytes is strongly suspected based on the frequent association of AGL with autoimmune disorders. In 2018, autoantibodies against perilipin 1 (PLIN1) were identified in three patients with autoimmune-associated AGL. However, the pathogenic mechanism and clinical impact of anti-PLIN1 remain unsolved. The prevalence of anti-PLIN1 autoantibodies in an AGL cohort of 40 patients was 50% (20 of 40). Among positive patients, 10 had the autoimmune variety and 10 had panniculitis-associated AGL. The IgG isotype was predominant, although some IgM antibodies were detected. Epitope-mapping studies did not identify a single, major epitope. Instead, autoantibodies typically bound to several different peptides, among which the central (233-405) domain was detected in all antibody-positive patients, for both IgG and IgM autoantibodies. In-depth epitope mapping indicated that anti-PLIN1 autoantibodies predominantly recognize the αβ-hydrolase domain containing 5 (ABHD5) binding site (383-405). Autoantibodies dose-dependently blocked the binding of PLIN1 to ABHD5 and caused a dislocation of ABHD5 toward the cytosol, leading to an increase in lipolysis and lipase activities. Finally, anti-PLIN1 titers significantly correlated with the amount of fat loss, metabolic control impairment, and severity of liver injury. Our data strongly support that anti-PLIN1 autoantibodies are a diagnostic biomarker and a cause of lipodystrophy in patients with AGL.

The study of neural antibodies in neurology: A practical summary

The field of Autoimmune Neurology is expanding rapidly, with new neural antibodies being identified each year. However, these disorders remain rare. Deciding when to test for these antibodies, when and what samples are to be obtained, how to handle and study them correctly, and how to interpret test results, is complex. In this article we review current diagnostic techniques and provide a comprehensive explanation on the study of these patients, in an effort to help with correct diagnosis minimizing false positive and false negative results. We also propose routine storage of samples and referral of certain cases to specialized research laboratories.

Humoral and cellular immune responses to Pfizer-BioNTech BNT162b2 SARS-CoV-2 vaccine in adolescents with liver transplantation: Single center experience

Background

Immune responses to vaccines against severe acute respiratory syndrome (SARS)-coronavirus (CoV)-2 are variable. In the absence of disease, youngsters are expected to better react to vaccines than adults. Nevertheless, chronic immunosuppression in transplant recipients may impair their capability to generate protection. We aim to explore immune responses after BNT162b2 SARS-CoV-2 vaccination in our cohort of young liver-transplanted patients.

Methods

A prospective study of adolescent liver-transplanted patients (n=33) in the long-term follow-up was performed. Immune responses after receiving Pfizer-BioNTech BNT162b2 vaccine were analyzed at two time-points: baseline and 30 days after the second dose. Humoral responses were measured by fluoroenzyme-immunoassay and T-cell responses by interferon-γ-release assay. Post-vaccine coronavirus disease (COVID-19) events were recorded by a survey.

Results

Pre-vaccine SARS-CoV-2-specific antibodies were undetectable in 27/32 (84.4%), negative/indeterminate in 3/32 (9.4%) and positive in 2/32 (6.3%) patients. Cellular responses at baseline were negative in 12/18 (66.6%), positive in 3/18 (16.6%) and indeterminate in 3/18 (16.6%) recipients. None of the baseline positives recalled any symptoms. Post-vaccine antibodies were detected in all patients and 92.6% showed levels >816 BAU/mL. Twenty (71.4%) recipients had positive T-cell responses. Regarding post-vaccine SARS-Cov-2 infection, 10 (30.3%) patients reported COVID-19 without hospitalization and 21 (63.6%) did not notify any infection. Negative and positive cell-response groups after vaccination showed statistically significant differences regarding COVID-19 cases (62.5% vs 22.2%, respectively; p=0.046).

Conclusions

Adolescents and young adults with liver transplantation responded to SARS-Cov-2 vaccine, generating both humoral and cellular responses. Recipients developing cellular responses after vaccination had a lower incidence of COVID-19.

POS0647 DOES TNF INHIBITOR MOLECULAR STRUCTURE MATTER? ANALYSIS OF IMPACT OF BASELINE RHEUMATOID FACTOR TITERS ON DRUG LEVELS IN PATIENTS WITH RHEUMATOID ARTHRITIS

Background

Elevated rheumatoid factor (RF) in patients with rheumatoid arthritis (RA) is associated with higher disease activity and increased risk for disease progression1.

Recent publications indicate significantly lower efficacy of TNF inhibitors (TNFi) in RA patients with high RF levels compared with low/negative RF subgroup2,3. Fab therapy with Certolizumab pegol (CZP), a PEGylated, Fc-free monoclonal antibody (mAb), has shown comparable efficacy and consistent serum levels irrespective of baseline RF4.

RF binds the Fc region of IgG1, the subtype used to engineer the majority of mAbs5. Formation of large immune complexes may likely explain the inceased clearance of mAbs in patients with high RF titers and reported reduced TNFi efficacy.

Objectives

We aimed to evaluate in clinical practice whether RF levels in RA patients influence serum drug levels of 3 TNFi with different molecular structures.

Methods

We evaluated retrospectively a cohort of RA patients from La Paz University Hospital (RA-Paz Registry, 1999-2019) treated with Infliximab (IFX), Adalimumab (ADA) or CZP. Clinical and demographic data were collected at baseline (T0) and after 6 months (T6) of treatment. RF titers and serum drug levels were measured at T0 and T6 using nephelometry and ELISA respectively. Association between baseline RF titers and drug levels was assessed using non-parametric test (Mann-Whitney).

Results

168 patients were evaluated: 90 received IFX, 48 ADA and 32 CZP. Characteristics at T0 are shown in Table 1. All patients had active disease at baseline and 76% were RF positive: ADA subgroup had lower percentage of positive RF than IFX and CZP subgroups. Patients were stratified into quartiles based on baseline RF titers: low (20-57 IU/ml), medium (57-380 IU/ml), high (>380 IU/ml) and seronegative (<20 IU/ml).

Table 1.

Baseline characteristics.

CharacteristicsTotal (n=168)IFX (n=90)ADL (n=48)CZP (n=32)p valueAge, years*55.5(45.3-66)57(46-65)50(42-64)61(47-70)0.08Body mass index, Kg/m2*24.5(21.7-29)24.2(21.8-27.7)24.7(21.5-30.3)24.6(22.2-30.3)0.3Male, n(%)28(17%)14(15%)9(19%)5(17%)0.2Disease duration, years*8.7(4.5-14.3)8.4 (4.4-14.3)8.8 (3.9-16)9.7(5-12)0.06Smoking status, n(%)0.03Currently/ex-smoker66(39%)29(32%)22(48%)16(57%)Non-smoker96(57%)61(68%)24(52%)12(43%)RF, n(%)128(76%)75(83%)28(58%)25(81%)0.002ACPA, n(%)134(80%)73(81%)35(73%)27(84%)0.3DAS28**5.1(1.3)5.4(1.3)4.5(1.3)4.9(1.3)0.002CRP levels*7.8(3-21.8)10.3(3.2-25.2)5.1(1.4-10.1)7.8(2.3-18.2)0.1Prior bDMARDs, n(%)26(15%)10 (11%)10 (21%)6(20%)0.2Monotherapy, n(%)16(10%)8(9%)8(17%)00.2csDMARDS, n(%)152(90%)82(91%)82(91%)32(100%)Methotrexate, n(%)112(67%)64(78%)33(83%)17(53%)0.2Other csDMARDs, n(%)24(24%)18(22%)7(18%)15(50%)0.0008Prednisone, n(%)85(51%)49(54%)21(44%)16(50%)0.6

*Median and interquartile range;**mean and standard deviation

Drug levels of IFX and ADA at T6 were significantly lower in those patients who had higher RF titers at T0 compared to seronegative. In contrast, CZP levels remained stable irrespectively of baseline RF titers, without significant differences among quartiles (Figure 1).

Conclusion

Higher baseline RF titers are associated with lower IFX and ADA levels at T6 in a cohort of RA patients. A concentration-response association has been clearly established for TNFi, and baseline RF levels appear to influence drug levels.

Reduced immune complexes formation with CZP may result in a limited impact of baseline RF titers on drug levels.

References

[1]Aletaha D. Arthritis Res Ther2015;17(1):229.

[2]Bobbio-Pallavicini F. Ann Rheum Dis 2007;66(3):302–7.

[3]Potter C. Ann Rheum Dis 2009;68(1):69–74.

[4]Tanaka Y. APLAR 2020. Oral Communication.

[5]Levy RA. Immunotherapy 2016;8(12):1427-1436.

Acknowledgements

This study was funded by an anrestricted reserch grant from UCB pharma.

Disclosure of Interests

ANA MARTÍNEZ-FEITO: None declared, Borja Hernández-Breijo: None declared, Marta Novella-Navarro Grant/research support from: UCB, Alejandro Villalba: None declared, Diana Peiteado: None declared, Pilar Nozal: None declared, DORA PASCUAL-SALCEDO Speakers bureau: Abbvie, Pfizer, Novartis, Takeda, Menarini and MSD., Grant/research support from: Abbvie, Pfizer, Novartis, Takeda, Menarini and MSD., Alejandro Balsa Speakers bureau: Pfizer, AbbVie, Galapagos, Lilly, Gilead, UCB, Nordic, Sandoz, Consultant of: Galapagos, Pfizer, AbbVie, Lilly, UCB, Nordic, Grant/research support from: Pfizer, Abbvie, UCB, Chamaida Plasencia Speakers bureau: Abbvie, Pfizer, UCB, Sandoz, Sanofi, Biogen, Lilly, Roche and Novartis, Grant/research support from: Abbvie, Pfizer, UCB, Sandoz, Sanofi, Biogen, Lilly, Roche and Novartis

POS0264 CHARACTERIZATION OF THE IMMUNE RESPONSE IN PATIENTS WITH INFLAMMATORY IMMUNE-MEDIATED DISEASES ON IMMUNOSUPPRESSIVE TREATMENT AFTER ONE MONTH OF SARS-CoV-2 VACCINATION

Background

The relevance of studying immune response after SARS-CoV-2 vaccination in patients with inflammatory immune-mediated diseases (IMIDs) represents a deep concern regarding the risk estimation and management of patients with these diseases on immunomodulatory drugs. It is well known that certain treatments as anti CD20 therapies results in a diminished immunogenicity against common vaccines but it is a scarce data regarding the cellular protection obtained upon vaccination between patients with different IMID and between different treatments.

Objectives

To compare a potential detriment on cellular and antibody-mediated protection upon SARS-CoV-2 vaccination in patients with IMIDs treated with immunosuppressive drugs.

Methods

We recruited 73 patients with rheumatoid arthritis-RA-(n=49), spondylarthritis-SpA-(n=19), inflammatory bowel disease-IBD-(n=5), idiopathic juvenile arthritis-IJA- (n=2) and heterogenous group composed of sclerodermia, lupus, uveitis…(n=6). They were treated mainly with rituximab (n=27), TNFi (n=37) or JAKi (n=3). We collected data of age,sex, csDMARDs, previous SARS-CoV-2 infection, last RTX infusion and prednisone use.

After one month of vaccination, we assessed the humoral response performing the Thermo Scientific EliA SARS-CoV-2-Sp1 IgG Test (positivity cut-off >0.70 IU/ml) which was also compared with the data with of 35 healthy controls. In addition, in 40 patients who had serum antibody levels under 100UI/ml, we analysed the cellular response by the use of the QuantiFERON SARS-CoV-2 Starter Pack (Quiagen). A cut-off value of 0.15 IU/ml discriminate between positive or negative cell-mediated immune responses. We compared differences among the different IMIDs and between the different immunosuppressive treatments through non-parametric test (p<0.05)

Results

Regarding demographic characteristics of patients, older patients (>56 years) and female sex were factors which were associated with low titles of serum antibodies.

Anti-spike IgG antibodies were present in an 86% of the IMIDs patients and in 100% healthy controls with significant different IgG titre (median [IQR]): 51[11-184] vs 700[440-940]; p<0.0001.

The differences between (median [IQR]) serum antibody levels were statistically different between IMID type: 33[1-138] in RA vs 94[34-191] in SpA vs 204[187-204] in IBD vs 133[61-204] in IJA vs 13[1.5-31.8] in the rest; p=0.04. Remarkably, patients with IBD who had the highest antibodies titles were the youngest compared with the other patients.

Target of the therapy played also an important role in serum antibody levels being these: 3.6 [0.7-51] in RTX patients vs 156 [45-204] in TNFi vs 40 [18-58] in JAKi patients; p<0.0001. In those patients who the last infusion of rituximab was, at least, one year before vaccination presented CD19+ B cells detected by flow cytometry and anti-spike IgG antibodies as well.

Cell-mediated responses to SARS-CoV-2 were positive in 33% of IMIDs patients, indeterminated in 3% and negative in 65% of the patients. Strikingly, out of the 33% positive patients, 85% were treated with RTX. A 61% of the RTX patients had inducible cell-mediated responses vs 14% of the patients treated with TNFi; p<0.01. On the other hand, there were not differences in cell-mediated responses between positive and negative antibody patients.

Conclusion

Titres of serum antibodies against spike protein of SARS-CoV-2 were lower in IMIDs patients than in controls. Patients with RTX had lower rates of positivity humoral response as well as lower serum titles than patients treated with other therapies regardless the patients ‘age. Neverthless, in those patients in whom RTX infusion was delayed because of vaccination they conserved a humoral response.

On the other hand, more patients treated with RTX had inducible cell-mediated responses compared with patients with TNFi.

Disclosure of Interests

ANA MARTÍNEZ-FEITO: None declared, Pilar Nozal: None declared, Marta Novella-Navarro: None declared, Elisa Fernández-Fernández: None declared, Lucia del pino molina: None declared, Milagros Casas Temprano: None declared, Ibtissam Akatbach Bousaid: None declared, Maria Dolores Martin Arranz: None declared, Alejandro Balsa Speakers bureau: Pfizer,Abbvie,Lilly, Galapos,BMS, Sandoz,Nordic,Gebro,Roche, UCB, Consultant of: Pfizer,Abbvie,Lilly, Galapos,BMS, Sandoz,Nordic, Sanofi,UCB, Grant/research support from: Pfizer,Abbvie,BMS,Nordic,Gebro,Roche, UCB, Chamaida Plasencia Grant/research support from: Abbvie, Pfizer, UCB, Sandoz, Sanofi, Biogen, Lilly, Roche and Novartis

Characterization of hypersensitivity reactions to polysulfone hemodialysis membranes

BACKGROUND

In recent years, cases have been reported in which unexpected systemic hypersensitivity reactions occurred in patients dialyzed with polysulfone- or polyethersulfone-biocompatible membranes in the absence of other risk factors. The pathomechanisms involved in these reactions are largely unknown.

OBJECTIVE

To characterize hypersensitivity reactions to polysulfone hemodialysis using clinical and laboratory data and to identify biomarkers suitable for endotype identification and diagnosis.

METHODS

We prospectively collected data from 29 patients with suspected hypersensitivity reactions to polysulfone hemodialysis membranes. Clinical laboratory parameters such as tryptase, blood cell counts, and complement levels were recorded. Acute samples were obtained from 18 cases for the ex vivo assessment of basophil activation by flow cytometry analysis of CD63, CD203, and FcεRI cell membrane expression. Serum cytokines and anaphylatoxin concentrations were evaluated in 16 cases by Luminex and cytometric bead array analysis.

RESULTS

Tryptase was elevated during the acute reaction in 4 cases. Evidence of basophil activation was obtained in 10 patients. Complement activation was found in only 2 cases. However, C5a serum levels tended to increase during the acute reaction in those patients with hypoxemia. Significantly higher serum levels of interleukin-6 were observed during the acute reactions to polysulfone hemodialysis (P = .0103).

CONCLUSION

Based on biomarker analysis, various endotypes were identified, including type I-like (with the involvement of mast cells or basophils), complement, and cytokine (interleukin-6) release-related reactions, with some patients showing mixed reactions. Further research is needed to unravel the exact mechanisms involved in the activation of these cellular and molecular pathways.

Differential effects of the second SARS-CoV-2 mRNA vaccine dose on T cell immunity in naive and COVID-19 recovered individuals

The rapid development of mRNA-based vaccines against the severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) led to the design of accelerated vaccination schedules that have been extremely effective in naive individuals. While a two-dose immunization regimen with the BNT162b2 vaccine has been demonstrated to provide a 95% efficacy in naive individuals, the effects of the second vaccine dose in individuals who have previously recovered from natural SARS-CoV-2 infection has not been investigated in detail. In this study, we characterize SARS-CoV-2 spike-specific humoral and cellular immunity in naive and previously infected individuals during and after two doses of BNT162b2 vaccination. Our results demonstrate that, while the second dose increases both the humoral and cellular immunity in naive individuals, COVID-19 recovered individuals reach their peak of immunity after the first dose. These results suggests that a second dose, according to the current standard regimen of vaccination, may be not necessary in individuals previously infected with SARS-CoV-2.

Early monitoring of infliximab serum trough levels predicts long-term therapy failure in patients with axial spondyloarthritis

Objective: To evaluate whether serum infliximab trough levels (ITL) during the early stages of treatment are predictive of long-term clinical failure in patients with axial spondyloarthritis (axSpA).Method: Longitudinal observational study involving 81 patients with axSpA monitored during infliximab therapy. Serum ITL were measured before starting infliximab treatment and at weeks 2 (W2), W6 and W12 of treatment. Disease activity was assessed by Ankylosing Spondylitis Disease Activity Score (ASDAS) at baseline, W24 and W52, and every 6 months thereafter until treatment discontinuation, regardless of the reason. Non-clinically important improvement was defined by ΔASDAS<1.1. The association between serum levels during the early stages and clinical outcomes (non-clinically important improvement at W52, drug survival and drop-out due to secondary inefficacy) was investigated through logistic regression models and Kaplan Meier curves. Receiver operating characteristic (ROC) curves were employed to determine the best cut-off for serum ITL.Results: Out of the 81 patients, 45 (56%) did not achieve clinical improvement at W52. These patients had lower serum ITL at W12 compared to those who improved: ITL [median (IQR)]: 4.1(0.9-8.3) µg/mL vs 7.1 (4.3-11.3) µg/mL, respectively;p = 0.007). ITL<6.7 µg/mL at W12 was significantly associated with: i) not achieving clinical improvement at W52 (OR: 2.3; 95%CI: 1.3-3.9); ii) shorter drug survival (5.0 years (95% CI 3.8-6.2) vs 7.0 years (95% CI 4.8-6.9; p = 0.04), and iii) higher drop-out rates due to secondary inefficacy (OR: 3.5; 95% CI: 1.2-10.2).Conclusion: Low serum ITL at W12 were associated with long-term clinical failure in patients with axSpA, due to secondary inefficacy.

Complement Factor D (adipsin) Levels Are Elevated in Acquired Partial Lipodystrophy (Barraquer-Simons syndrome)

Complement overactivation has been reported in most patients with Barraquer-Simons syndrome (BSS), a rare form of acquired partial lipodystrophy. Complement Factor D (FD) is a serine protease with a crucial role in the activation of the alternative pathway of the complement system, which is mainly synthesized by adipose tissue. However, its role in the pathogenesis of BSS has not been addressed. In this study, plasma FD concentration was measured in 13 patients with BSS, 20 patients with acquired generalized lipodystrophy, 22 patients with C3 glomerulopathy (C3G), and 50 healthy controls. Gene expression and immunohistochemistry studies were assayed using atrophied adipose tissue from a patient with BSS. We found significantly elevated FD levels in BSS cases compared with the remaining cohorts (p < 0.001). There were no significant differences in FD levels between sexes but FD was strongly and directly associated with age in BSS (r = 0.7593, p = 0.0036). A positive correlation between FD and C3 was seen in patients with C3G, characterized by decreased FD levels due to chronic C3 consumption, but no correlation was detected for BSS. Following mRNA quantification in the patient's adipose tissue, we observed decreased CFD and C3 but elevated C5 transcript levels. In contrast, the increased FD staining detected in the atrophied areas reflects the effects of persistent tissue damage on the adipose tissue, thus providing information on the ongoing pathogenic process. Our results suggest that FD could be a reliable diagnostic biomarker involved in the pathophysiology of BSS by promoting unrestrained local complement system activation in the adipose tissue environment.

POS0617 ANTI INFLIXIMAB ANTIBODIES DETECTED BY A DRUG TOLERANT ASSAY ARE FREQUENT BUT, IN MANY CASES, WITHOUT RELEVANT CLINICAL SIGNIFICANCE

Background:

Infliximab (Ifx) has proven effective in treating rheumatoid arthritis (RA) and spondyloarthropathies (SpA), although around 40% of cases fails, mainly due to immunogenicity. Formation of immunocomplexes between antibodies to Ifx (ATI) and Ifx can increase drug clearance, leading to treatment failure. Standard ELISA assays which are drug -sensitive are frequently used, being able to detect only free ATI. Interest in drug-tolerant assays to measure total ATI (free and complexed) is increasing.

Objectives:

To compare the development of ATI using both drug-tolerant and drug-sensitive assays at early stages of Ifx therapy. To analyse the relationship of ATI detected by both assays with the drop-out of treatment.

Methods:

This is a prospective observational study including 45 patients with RA and 61 with axial-SpA treated with standard doses of Ifx (3mg/kg and 5mg/kg, respectively) enrolled at Biological Therapy Unit of Hospital La Paz. Serum samples were obtained at 2, 6, 12 and 22 weeks (W) after Ifx initiation. The data about discontinuation for inefficacy was obtained from the database. ATI presence was evaluated by a drug-sensitive in-house two-site (bridging) ELISA (bELISA) and a drug-tolerant commercial ELISA assay (Immundiagnostik®,IDK). All comparisons were performed throughout non-parametrical test. In SpA group, due to the low number of ATI+ patients at W12 by bELISA the statistical analysis to compare both assays were not performed.

Results:

ATI detection by both assays at early stages (≤22 W) of treatment is shown in Table 1a. ATI were always detected earlier by IDK than bELISA and also in RA than in SpA patients probably reflecting the effect of lower Ifx doses. Three out of 106 (3%) vs 0 (0%) patients had ATI at W 2 and 62 (58%) vs 20 (18%) patients at W22, by IDK and bELISA, respectively.

Table 1.

Patient characteristics of all included patients

W2W6W12W22ARSpAARSpAARSpAARSpAa) ATI+ patients (n, %) at early stagesbELISA003(7%)010(22%)1(2%)13(29%)7(12%)IDK1(2%)2(3%)7(16%)2(3%)16(36%)16(26%)28(62%)34(56%)b) Patients who discontinued (n, %) Ifx therapy considering ATI status at early stagesbELISA+9(90%)*1(100%)*12(92%)4(57%)bELISA-23(66%) 22(37%)20(63%)19(35%)IDK+15(94%)*7(44%)24(86%)13(38%)IDK-17(59%)11(24%)13(77%)10(27%)

*p<0.05 comparing between ATI+ vs ATI- in each assay.

Once ATIs appeared, regardless both methods, they persisted throughout the follow-up, indicating that immunogenicity was not transient.

At W22, only 13/28 (46%) and 7/34 (21%) patients with ATI detected by IDK were also positive by bELISA in RA and SpA, respectively.

ATI levels by IDK were higher in ATI+ by bELISA than in ATI- patients at early stages: ATI levels by IDK at W12: 91[74-348] ng/ml ATI+ vs 21.7[15-59.5] ng/ml ATI- (p<0.01) and at W22: 132 [89-372] ng/ml ATI+ vs 23[13-66] ng/ml ATI- (p<0.001). However, only in 4% (2/45) patients with RA and in 13% (8/61) patients with SpA the detection by IDK was earlier than by bELISA at W12.

Free IFX in serum was not detected in bELISA ATI+ patients. In IDK ATI+ patients low circulating Ifx levels were present as compare to ATI- since W6 to the end of follow-up (p<0.01).

More ATI+ patients dropped out Ifx at W12 and W22 regardless de assay (Table 1.b), being statistically significant for both assays in patients with RA and only for bELISA in patients with SpA.

Conclusion:

ATI measured by a drug-tolerant assay are always detected earlier than ATI detected by bELISA, indicating that immunogenicity, at least with Ifx, is usually an early event. High levels of ATI by IDK are associated with an earlier detection by bELISA in case of RA patients. ATI detected only by drug tolerant assays are associated with low levels of circulating Ifx but not with a complete drug neutralization and may do not have clinical relevance compared to ATI detected by bELISA. Many patients have low levels of ATI which can only be detected by drug tolerant assays after long-term of follow-up.

The reasons why ATI levels rise rapidly in some patients while in others remain low are currently unknown but may be relevant if the clinical effect of immunogenicity is to be minimized.

Acknowledgements:

We are grateful to all the rheumatologists and nurses of the Daycare Department for Biologics and to the laboratory technicians of the Immunological Unit

Disclosure of Interests:

ANA MARTÍNEZ-FEITO: None declared, Borja Hernández-Breijo: None declared, Marta Novella-Navarro: None declared, Victoria Navarro-Compán Grant/research support from: AbbVie, Janssen, Lilly, Novartis, Pfizer, and UCB, Cristina Diego: None declared, Irene Monjo: None declared, Laura Nuño: None declared, Alejandro Villalva: None declared, Diana Peiteado: None declared, DORA PASCUAL-SALCEDO: None declared, Pilar Nozal: None declared, Alejandro Balsa Grant/research support from: Abbvie, Pfizer, Novartis, Roche.Amgen, Sandoz, Lilly, UCB. Personal fees and non- financial support from BMS. Grants, personal fees and non- financial support from Nordic., Chamaida Plasencia Grant/research support from: AbbVie, Lilly, Novartis, Pfizer,Sanofi, Biogen and UCB.

POS0875 MYOSITIS-SPECIFIC ANTIBODIES IN A RETROSPECTIVE SINGLE-CENTER OBSERVATIONAL STUDY

Background:

Myositis-specific antibodies (MSA) are highly specific and useful to classify patients as having syndromes with distinct clinical features and prognosis. MSA are almost always mutually exclusive and quite specific, adding value as a useful biomarker for diagnosis. Although individual autoantibodies aren’t sensitive enough to detect the full spectrum of idiopathic inflammatory myopathies (IIM), the sensitivity of a myositis panel is increasing as more autoantibodies are discovered, and as better assays become available.

Objectives:

We aimed to analyze the usefulness of a myositis-specific immunoblot for the diagnosis of IIM in a hospital cohort from January 2019 to December 2020. We also seek to correlate immunological findings with the risk of associated interstitial lung disease (ILD), cancer, or death.

Methods:

Retrospective single-center observational study conducted in a Spanish tertiary hospital. In patients with high clinical suspicion of IIM, a myositis immunoblot was performed including Jo1, PL-7, PL-12, EJ, SRP, Mi2, Ku, MDA-5, TIF1-γ, HMGCR, PM-Scl and Ro52 antibodies. The demographic characteristics, the risk of ILD, cancer and death were analyzed.

Results:

In a cohort of 313 patients with high suspicion of IIM, 87 patients (27.8%) presented a positive MSA (MSA+ve). The mean age at diagnosis was 56.7±16.9 years, with no significant differences between MSA+ve and MSA-ve (p=0.597). Most of the patients were women with significant differences between both groups (80.5% MSA+ve vs 68.1% MSA-ve, p=0.030).

IIM were classified as antisynthetase syndrome (ARS) (38%), dermatomyositis (DM) (31%), overlap myopathy (OM) (16.9%) and necrotizing myopathy (NM) (14.1%) according to the manifestations and MSA found (Jo1, PL-12, PL-7, EJ in ARS; Mi-2, MDA-5 and TIF1-γ in DM; Ku and PM-Scl in OM; HMGCR and SRP in NM). The most frequent MSA were anti-Jo1 (16.9%), TIF1-γ (15.5%), Ku (12.7%), Mi-2 (9.9%), PL-7 (9.9%), HMCGR (8.5%), PL-12 (7%), MDA-5 (5.6%), SRP (5.6%) and EJ (4.2%). The presence of Ro52 associated with other MSA was found in 20 patients (22.9%).

ILD was the most frequent manifestation (45.2% of the MSA+ve). Non-specific interstitial pneumonia (NSIP) was the most frequent ILD (39.5%), followed by usual interstitial pneumonia (34.2%). The main risk factors associated with IIM-ILD were some subtypes of the MSAs (p<0.001), the association of Ro52 (p<0.001), and older age (p=0.027). Among the IIM, ARS and OM (p<0.001) were more frequently associated with IIM-ILD. The MSAs most associated with IIM-ILD were Jo1, PL-7, PM-Scl, Ku and SRP (p<0.001).

Cancer was found in 9.6% of MSA+ve patients. The most frequent tumors were gynecological (37.5%), followed by gastrointestinal (25%) and breast cancer (12.5%). Factors associated with cancer were age (p=0.010), TIF1-γ (p<0.001), SRP (p=0.004), PL-12 (p=0.013), PL-7 (p=0.047) and HMGCR (p=0.027).

The mortality of these patients was 3.5%. There were no differences regarding MSA+ve/-ve (p = 0.911). However, MDA-5 (p=0.033) and older age (p=0.001) were associated with higher mortality. There were no significant differences between the IIM classifications, the associated SAD, the presence of cancer or ILD. However, longer follow-up periods and future studies are necessary to confirm these results.

Conclusion:

The use of a myositis blot allowed classifying, stratifying the risk of ILD, the risk of cancer and the risk of mortality in IIM. IIM-ILD was the most frequent complication, usually manifested as NSIP. The associated risk factors were ARS, OM, some MSAs, Ro52+ and older age. Cancer was a serious and frequent manifestation in these patients, especially in patients with TIF1-γ and other MSAs, so it is essential to know the risk factors and perform an early screening, especially in older patients.

A better knowledge of the serological profiles of IIM will provide more individualized approaches and better risk stratification, helping in the management and treatment of these patients.

References:

[1]Satoh et al. Clin Rev Allergy Immunol. 2017 Feb;52(1):1-19.

[2]Betteridge et al. J Intern Med. 2016 Jul;280(1):8-23.

Disclosure of Interests:

None declared

Complement Genetic Variants and FH Desialylation in S. pneumoniae-Haemolytic Uraemic Syndrome

Haemolytic Uraemic Syndrome associated with Streptococcus pneumoniae infections (SP-HUS) is a clinically well-known entity that generally affects infants, and could have a worse prognosis than HUS associated to E. coli infections. It has been assumed that complement genetic variants associated with primary atypical HUS cases (aHUS) do not contribute to SP-HUS, which is solely attributed to the action of the pneumococcal neuraminidase on the host cellular surfaces. We previously identified complement pathogenic variants and risk polymorphisms in a few Hungarian SP-HUS patients, and have now extended these studies to a cohort of 13 Spanish SP-HUS patients. Five patients presented rare complement variants of unknown significance, but the frequency of the risk haplotypes in the CFH-CFHR3-CFHR1 region was similar to the observed in aHUS. Moreover, we observed desialylation of Factor H (FH) and the FH-Related proteins in plasma samples from 2 Spanish and 4 Hungarian SP-HUS patients. To analyze the functional relevance of this finding, we compared the ability of native and "in vitro" desialylated FH in: (a) binding to C3b-coated microtiter plates; (b) proteolysis of fluid-phase and surface-bound C3b by Factor I; (c) dissociation of surface bound-C3bBb convertase; (d) haemolytic assays on sheep erythrocytes. We found that desialylated FH had reduced capacity to control complement activation on sheep erythrocytes, suggesting a role for FH sialic acids on binding to cellular surfaces. We conclude that aHUS-risk variants in the CFH-CFHR3-CFHR1 region could also contribute to disease-predisposition to SP-HUS, and that transient desialylation of complement FH by the pneumococcal neuraminidase may have a role in disease pathogenesis.

Infliximab concentrations in two non-switching cohorts of patients with inflammatory bowel disease: originator vs. biosimilar

Biosimilars are replacing originator compounds due to their similar effectiveness, safety and pharmacokinetics. Our objective was to compare the differences in pharmacokinetics and clinical outcomes between the originator infliximab (Ifx) and the biosimilar CT-P13 in a patient cohort with inflammatory bowel disease (IBD). Our cohort study included 86 patients from a historical and a prospective cohort from the start of infliximab treatment to 22 weeks later. Serum infliximab, antidrug antibody levels and other serum biomarkers were measured at weeks 0, 2, 6, 14 and 22. Remission outcomes were evaluated at weeks 14 and 22. Drug levels were measured prospectively and analysed using MANOVA. Of the 86 patients, 44 (51%) and 42 (49%) were administered the originator and CT-P13, respectively. Originator trough levels were higher than the biosimilar trough levels (35 vs. 21, 20.1 vs. 11, 6.6 vs. 2.9 and 4.3 vs. 1.7 μg/mL at weeks 2, 6, 14 and 22, respectively). A post-hoc analysis demonstrated changes in mean serum drug levels over time (p < 0.001) and according to the drug employed (p = 0.001). At week 22, 13 (81%) patients administered the originator achieved clinical remission compared with 5 (19%) patients with the biosimilar (p = 0.02). None of the patients administered the originator withdrew from the treatment compared with 7 for the biosimilar. During the study, there were significant differences in serum infliximab levels between the originator and the CT-P13 in the patients with IBD. The clinical outcomes were influenced by the type of compound administered.

Evidence of ongoing complement activation on adipose tissue from an 11-year-old girl with Barraquer-Simons syndrome

Barraquer-Simons syndrome (BSS), a form of acquired partial lipodystrophy, is a rare condition characterized by gradual loss of adipose tissue from the upper body, keeping intact the white adipose tissue of the lower extremities. The etiology of BSS is not well understood, and clinical follow-up studies have not been assessed in these patients. Moreover, no histological studies have been conducted during the active phase of the disease, and complement system activation products have not been sought in the affected areas. The objective of this work was to analyze the clinical, immunological and histological events in an 11-year-old girl with BSS over a 5-year follow-up period. Clinical data were collected during six regular visits for a time period of 5 years. The circulating levels of C3, C3adesArg (a product released upon C3 activation), C4 and immunoglobulins (Ig) were quantified in serum while fat tissue from lipoatrophic areas was examined by immunohistochemical and immunofluorescence approaches. In her regular visits, no clinical or laboratory abnormalities had been observed in the patient, except for the progression of lipoatrophy linked to the C3 hypocomplementemia and the occurrence of C3 nephritic factor. Adipose tissue from the patient showed atrophied and dead adipocytes, an abnormal production of extracellular matrix, and a remarkable accumulation of infiltrating CD68 macrophages and adipocyte precursors (marked by c-Kit positiveness). Simultaneous detection of IgG, C3, C5a and C5b-9 proved the ongoing complement activity and complement-directed injury within the adipose tissue. Our results showed the first evidence that the complement system hyperactivation occurs within the adipose tissue and is linked with fat loss in patients with BSS.

Blood Lymphocyte Subsets for Early Identification of Non-Remission to TNF Inhibitors in Rheumatoid Arthritis

Background: TNF inhibitors (TNFis) are widely used for the treatment of rheumatoid arthritis (RA), although the response rates to this therapy in patients with RA remains heterogeneous and < 50% achieve remission (REM). Objective: To analyze baseline peripheral blood leukocytes profiles in order to search for biomarkers identifying patients who will most likely not achieve REM under TNFi treatment. Methods: A prospective bi-center pilot study including 98 RA patients treated with TNFis and followed-up during 6 months. Patients were classified according to DAS28 as follows: those who achieved REM (DAS28 ≤ 2.6) and those who did not (DAS28 > 2.6) at 6 months after starting TNFis. These rates were also assessed by simplified disease activity index (SDAI ≤ 3.3 and SDAI > 3.3, respectively). Peripheral blood immune cells were studied by flow cytometry before treatment initiation. Results: At 6 months, 61 or 80% of patients did not achieve REM by DAS28 or SDAI, respectively. Basal leukocyte profiles differed between REM vs. non-REM patients. Non-REM patients showed lower percentages of total and naïve B cells at baseline than REM subjects. A B lymphocyte/CD4+ lymphocyte ratio (BL/CD4 ratio) <0.2 clearly associated with a higher probability of non-REM status based on DAS28 at 6 months (OR = 9.2, p = 0.006). These data were confirmed when patient response was evaluated by SDAI index. Conclusion: Our results strongly suggest that BL/CD4 ratio could be considered as a useful biomarker for the early identification of non-remitters to TNFi in clinical practice.

Immunological features of patients affected by Barraquer-Simons syndrome

Background

C3 hypocomplementemia and the presence of C3 nephritic factor (C3NeF), an autoantibody causing complement system over-activation, are common features among most patients affected by Barraquer-Simons syndrome (BSS), an acquired form of partial lipodystrophy. Moreover, BSS is frequently associated with autoimmune diseases. However, the relationship between complement system dysregulation and BSS remains to be fully elucidated. The aim of this study was to provide a comprehensive immunological analysis of the complement system status, autoantibody signatures and HLA profile in BSS. Thirteen subjects with BSS were recruited for the study. The circulating levels of complement components, C3, C4, Factor B (FB) and Properdin (P), as well as an extended autoantibody profile including autoantibodies targeting complement components and regulators were assessed in serum. Additionally, HLA genotyping was carried out using DNA extracted from peripheral blood mononuclear cells.

Results

C3, C4 and FB levels were significantly reduced in patients with BSS as compared with healthy subjects. C3NeF was the most frequently found autoantibody (69.2% of cases), followed by anti-C3 (38.5%), and anti-P and anti-FB (30.8% each). Clinical data showed high prevalence of autoimmune diseases (38.5%), the majority of patients (61.5%) being positive for at least one of the autoantibodies tested. The HLA allele DRB1*11 was present in 54% of BSS patients, and the majority of them (31%) were positive for *11:03 (vs 1.3% allelic frequency in the general population).

Conclusions

Our results confirmed the association between BSS, autoimmunity and C3 hypocomplementemia. Moreover, the finding of autoantibodies targeting complement system proteins points to complement dysregulation as a central pathological event in the development of BSS.

Serum complexes between C1INH and C1INH autoantibodies for the diagnosis of acquired angioedema

Acquired angioedema due to C1-inhibitor (C1INH) deficiency (AAE) is caused by secondary C1INH deficiency leading to bradykinin-mediated angioedema episodes. AAE typically presents in adulthood and is associated with B cell lymphoproliferation. Anti-C1INH autoantibodies (antiC1INHAbs) are detectable in a subset of AAE cases and considered a hallmark of the disease. When free antiC1INHAbs and malignant tumors are not detectable, diagnosis relies on the finding of low C1INH levels and/or function, lack of family history and SERPING1 mutations, age at onset and low or undetectable C1q levels, none of which is specific for AAE. We tested the diagnostic value of a novel enzyme-linked immunosorbent assay (ELISA) for the detection of circulating complexes between C1INH and antiC1INHAbs (C1INH-antiC1INHAb) in the serum of 20 European AAE patients characterized on the basis of their complement levels and function. Free antiC1INHAbs were detected in nine of 20 patients [six of immunoglobulin (Ig)G class, two of IgM class and one simultaneously presenting IgG and IgM classes], whereas C1INH-antiC1INHAb complexes were found in 18 of 20 of the AAE cases, regardless of the presence or absence of detectable free anti-C1INHAbs. Of note, nine of 20 patients showed negative free antiC1INHabs, but positive C1INH-antiC1INHAb complexes in their first measurement. In the cohort presented, IgM-class C1INH-antiC1INHAb are specifically and strongly associated with low C1q serum levels. Detection of C1INH-antiC1-INHAbs provides an added value for AAE diagnosis, especially in those cases in whom no free anti-C1INH antibodies are detected. The link between IgM-class C1INH-antiC1INHAb complexes and C1q consumption could have further implications for the development of autoimmune manifestations in AAE.

Nephritic Factors: An Overview of Classification, Diagnostic Tools and Clinical Associations

Nephritic factors comprise a heterogeneous group of autoantibodies against neoepitopes generated in the C3 and C5 convertases of the complement system, causing its dysregulation. Classification of these autoantibodies can be clustered according to their stabilization of different convertases either from the classical or alternative pathway. The first nephritic factor described with the capacity to stabilize C3 convertase of the alternative pathway was C3 nephritic factor (C3NeF). Another nephritic factor has been characterized by the ability to stabilize C5 convertase of the alternative pathway (C5NeF). In addition, there are autoantibodies against assembled C3/C5 convertase of the classical and lectin pathways (C4NeF). These autoantibodies have been mainly associated with kidney diseases, like C3 glomerulopathy and immune complex-associated-membranoproliferative glomerulonephritis. Other clinical situations where these autoantibodies have been observed include infections and autoimmune disorders such as systemic lupus erythematosus and acquired partial lipodystrophy. C3 hypocomplementemia is a common finding in all patients with nephritic factors. The methods to measure nephritic factors are not standardized, technically complex, and lack of an appropriate quality control. This review will be focused in the description of the mechanism of action of the three known nephritic factors (C3NeF, C4NeF, and C5NeF), and their association with human diseases. Moreover, we present an overview regarding the diagnostic tools for its detection, and the main therapeutic approach for the patients with nephritic factors.

The effect of methotrexate versus other disease-modifying anti-rheumatic drugs on serum drug levels and clinical response in patients with rheumatoid arthritis treated with tumor necrosis factor inhibitors

To investigate the effect of concomitant conventional synthetic disease-modifying anti-rheumatic drugs (csDMARDs) with adalimumab or infliximab on maintaining serum drug and clinical outcomes after the first year of treatment in patients with rheumatoid arthritis (RA). Second, to assess the influence of methotrexate (MTX) dose on these outcomes. Ninety-two patients with RA starting infliximab (n = 67) or adalimumab (n = 25) tumor necrosis factor inhibitor (TNFi) with available drug levels and clinical improvement assessment (European League Against Rheumatism [EULAR] response) after 12 months were included. Patients were grouped according to concomitant csDMARD use: (i) TNFi monotherapy; (ii) TNFi+MTX; (iii) TNFi with csDMARDs other than MTX (TNFi+OD). Patients receiving MTX were also classified by dose as < 15 mg/week (TNFi+MTX<15) and ≥ 15 mg/week (TNFi+MTX≥15). Logistic regression analyses were employed. More TNFi+MTX patients had circulating serum TNFi at 12 months (71% TNFi+MTX vs. 20% TNFi+OD vs. 9% TNFi monotherapy). Of these, the probability of maintaining serum TNFi levels was twice (OR 2.3; p = 0.06) than that of patients without MTX. However, statistically significant results were observed only for the highest MTX dose (OR 4.9; p = 0.02). Most patients achieving good EULAR response were treated with TNFi+MTX (81%). The probability of achieving this response was three times higher in patients within the TNFi+MTX group (OR 3.4; p = 0.03); however, no differences were found with regard to MTX dose. The persistence of serum TNFi and the probability of achieving clinical response are influenced by MTX but not by OD in patients with RA treated with infliximab or adalimumab.

Autoantibodies against alternative complement pathway proteins in renal pathologies

Complement system activation plays an important role in several renal pathologies, including antibody-mediated glomerulonephritis, ischaemia-reperfusion injury of trasplanted kidneys or renal allograft rejection. Besides these conditions, alternative pathway abnormalities are directly involved in the pathogenesis of C3 glomerulopathies and atypical haemolytic uraemic syndrome. These abnormalities may be inherited or acquired, the latter as autoantibodies directed against the various components and regulators of the alternative complement pathway. The functional consequences of some of these antibodies and their association with these conditions are well known, whereas for other antibodies only isolated cases have been reported. This article describes the autoantibodies that target the alternative complement pathway proteins, their characteristics and their clinical relevance in renal pathologies.

Testing the Activity of Complement Convertases in Serum/Plasma for Diagnosis of C4NeF-Mediated C3 Glomerulonephritis

Autoantibodies termed C3-nephritic factor (C3NeF), which stabilize convertases of the alternative complement pathway, often stimulate autoinflammatory diseases. However, knowledge about analogous autoantibodies acting on the classical pathway (C4NeF) is limited to a few reports, which indicate association with kidney dysfunction, systemic lupus erythematous, and infections. C4NeF may appear independently from C3NeF, but the lack of a routine diagnostic method predisposes C4NeF for being an underestimated player in autoinflammatory episodes. We tested the activity of classical convertases directly in serum/plasma to screen samples from 13 patients with C3 glomerulopathies and identified one patient showing significantly prolonged half-life of these enzymes. Observed effect was reproduced by immunoglobulins purified from patient's plasma and additionally confirmed on classical convertase built from purified components. Isolated immunoglobulins protected classical convertases from both spontaneous and inhibitor-driven decay but not from C4b proteolysis. The patient had a decreased serum level of C3, elevated sC5b-9, and normal concentrations of factor B and C4. Neither C3NeF nor other autoantibodies directed against alternative pathway proteins (factor H, factor B, factor I, C3, and properdin) were found. Genetic analysis showed no mutations in C3, CFB, CFH, CFI, MCP, THBD, and DGKE genes. Renal biopsy revealed a membranoproliferative pattern with intense C3 deposits. Our results underline the importance of C4NeF as an independent pathogenic factor and a need for the implementation of routine examination of classical convertase activity. Proposed method may enable robust inspection of such atypical cases.

Serum properdin consumption as a biomarker of C5 convertase dysregulation in C3 glomerulopathy

Properdin (P) stabilizes the alternative pathway (AP) convertases, being the only known positive regulator of the complement system. In addition, P is a pattern recognition molecule able to initiate directly the AP on non-self surfaces. Although P deficiencies have long been known to be associated with Neisseria infections and P is often found deposited at sites of AP activation and tissue injury, the potential role of P in the pathogenesis of complement dysregulation-associated disorders has not been studied extensively. Serum P levels were measured in 49 patients with histological and clinical evidence of C3 glomerulopathy (C3G). Patients were divided into two groups according to the presence or absence of C3 nephritic factor (C3NeF), an autoantibody that stabilizes the AP C3 convertase. The presence of this autoantibody results in a significant reduction in circulating C3 (P < 0·001) and C5 levels (P < 0·05), but does not alter factor B, P and sC5b-9 levels. Interestingly, in our cohort, serum P levels were low in 17 of the 32 C3NeF-negative patients. This group exhibited significant reduction of C3 (P < 0·001) and C5 (P < 0·001) and increase of sC5b-9 (P < 0·001) plasma levels compared to the control group. Also, P consumption was correlated significantly with C3 (r = 0·798, P = 0·0001), C5 (r = 0·806, P < 0·0001), sC5b-9 (r = -0·683, P = 0·043) and a higher degree of proteinuria (r = -0·862, P = 0·013). These results illustrate further the heterogeneity among C3G patients and suggest that P serum levels could be a reliable clinical biomarker to identify patients with underlying surface AP C5 convertase dysregulation.

Laboratory guidelines for the diagnosis and follow-up of patients with monoclonal gammopathies

We present guidelines from the Immunochemistry group of the Spanish Society for Immunology that are designed to provide a practical tool for the diagnosis and follow-up of monoclonal gammopathies. We review the clinical and analytical features of various monoclonal gammopathies, international consensus guidelines and techniques used to detect and follow-up monoclonal components.

Case report: lupus nephritis with autoantibodies to complement alternative pathway proteins and C3 gene mutation

Background

Glomerulonephritis is one of the most severe complications of lupus, a systemic disease with multi-organ involvement, with tissue damage produced mainly by complement activation. As a result of this activation, patients with active lupus present hypocomplementemia during disease flares, but C3 and C4 levels are recovered between episodes.

Case presentation

We present a patient who suffered two lupus nephritis episodes in 5 years, achieving complete remission with treatment after both of them, but with C3 levels persistently below normal range. Genetic study revealed that the patient carried a mutation in heterozygosis in the C3 gene. Serial sera samples were analyzed, and autoantibodies to complement alternative pathway proteins (Factor I, Factor B, C3 and Properdin) were found. Functional assays showed that these autoantibodies cause alternative pathway activation.

Conclusion

This case is the first reported of a heterozygous C3 mutation associated with lupus nephritis and autoantibodies against complement alternative pathway proteins (Factor I, Factor B, C3 and Properdin).These autoantibodies cause activation of this pathway and this fact could explain that the tissue damage is restricted to the kidney.

Electronic supplementary material

The online version of this article (doi:10.1186/s12882-015-0032-6) contains supplementary material, which is available to authorized users.

Anti-factor H antibody affecting factor H cofactor activity in a patient with dense deposit disease

Complement alternative pathway dysregulation seems to be the pathophysiological basis of Dense Deposit Disease (DDD). Here, we describe a monoclonal anti-factor H (FH) autoantibody in a woman diagnosed with DDD with a monoclonal gammapathy. Enzyme-linked immunosorbent assays evidenced the presence of anti-FH antibodies in the patient's serum and showed that they were associated with the monoclonal IgG-λ fraction. These autoantibodies recognize the N-terminal region of FH and interfere with its regulatory function. In summary, in the DDD patient described here, the activation of complement alternative pathway was favoured by the presence of anti-FH autoantibodies that recognize the regulatory region of this protein and impede its function and which could ultimately cause the glomerulopathy.