Autoantibodies against complement proteins in patients with antiphospholipid syndrome: Prevalence and clinical associations

Seventy-seven patients with antiphospholipid syndrome were tested for autoantibodies against C1q, C3, FB, FH, and C4bp. Fifty-seven patients had at least one anti-complement antibody. IgM anti-FH positivity was associated with thrombosis when anti-C3 and anti-FB were, negatively or positively, associated with various noncriteria manifestations of antiphospholipid syndrome.

Usefulness and analytical performances of complement multiplex assay for measuring complement biomarkers in plasma

INTRODUCTION

The complement system is involved in numerous diseases, through diverse mechanisms and degree of activation. With the emergence of complement targeting therapeutic, simple and accessible tools to evaluate the extent of complement activation are strongly needed.

METHODS

We evaluated two multiplex panels, measuring complement activation fragments (C4a, C3a, C5a, Bb, Ba, sC5b9) and intact components or regulators (C1q, C2, C3, C4, C5, FD, FP, FH, FI). The specificity of each measurement was assessed by using complement proteins depleted sera and plasma collected from patients with complement deficiencies. Normal values distribution was estimated using 124 plasma samples from healthy donors and complement activation profile was assessed in plasma collected from 31 patients with various complement-mediated disorders.

RESULTS

We observed good inter-assay variation. All tested protein deficiencies were accurately detected. We established assay-specific reference values for each analyte. Except for C3, C4 and C4a, the majority of the measurements were in good agreement with references methods or published data.

CONCLUSION

Our study substantiates the utility of the Complement Multiplex assay as a tool for measuring complement activation and deficiencies. Quantifying complement cleavage fragments in patients exhibiting classical or alternative pathway activation allowed evaluating the activation state of the whole cascade.

[Pernicious anemia with false normal vitamin B12 levels caused by intrinsic factor antibodies interference: a case report]

We present a case of a 48-year-old woman with a fortuitous discovery of macrocytic anemia and thrombocytopenia. Serum folate and vitamin B12 levels were normal. However, due to the presence of indirect signs of cobalamin deficiency, such as elevated homocysteine and methylmalonic acid, and signs of dyserythropoiesis on the bone marrow aspirate, pernicious anemia was suspected. Vitamin B12 dosage was repeated finding fluctuating but always normal results. Anti-intrinsic factor antibodies were present at a very high level, explaining the fluctuations and the interference found on the assay using competitive binding chemiluminescence (CBLA). Serum vitamin B12 dosage by electrochemiluminescence, a method described as not interfering with intrinsic factor antibodies, showed a collapsed vitamin B12 level. Measurement of vitamin B12 with CBLA after adsorption of immunoglobulins in the sample using protein G SepharoseTM, confirmed the interference of the cobalamin assay with autoantibodies. This case illustrates the difficulties regarding the analysis and standardization of the vitamin B12 assay for the diagnosis of pernicious anemia.

C3 Glomerulopathy With Concurrent Thrombotic Microangiopathy: Clinical and Immunological Features

RATIONALE & OBJECTIVE

C3 glomerulopathy (C3GN) and atypical hemolytic uremic syndrome (aHUS) are 2 distinct rare kidney diseases caused by dysregulation of the alternative complement pathway. Patients with C3GN and concurrent kidney lesions of thrombotic microangiopathy (TMA) have been rarely reported. We characterized the clinical features and underlying immunological abnormalities in these patients.

STUDY DESIGN

Case series.

SETTING & PARTICIPANTS

Patients with C3GN and concomitant TMA lesions on biopsy registered from 2009 to 2019 in the French National Registry of C3GN.

FINDINGS

Among 278 registered patients with C3GN, 16 (6%) had biopsy-proven glomerular and/or vascular TMA lesions. Their median age at diagnosis was 39 years (range, 7-76), and 59% were female. Fourteen of the 16 patients (88%) had an estimated glomerular filtration rate of<30mL/min/1.73m2 and 3 of 16 (19%) required dialysis. Twelve of the 14 evaluated patients (86%) showed evidence of mechanical hemolysis. Fifty percent of the patients had low C3 levels. Six of the 14 evaluated patients had a rare variant in complement genes, and 4 of the 16 patients (25%) had monoclonal gammopathy. Among the 16 patients, 10 (63%) received eculizumab, 5 (31%) received immunosuppressive therapy, and 4 (25%) received clone-targeted chemotherapy. Median kidney survival was 49 months.

LIMITATIONS

Small retrospective case series with a limited number of biopsies including electron microscopy.

CONCLUSIONS

Concomitant C3GN and TMA is extremely rare and is associated with poor kidney outcomes. Genetic or acquired abnormalities of the alternative complement pathway are common as is the presence of monoclonal gammopathy, which may inform the selection of treatment approaches.

[Advice in autoimmunity biological diagnosis: guidelines for drafting comments on biological results]

The ISO 15189 accreditation of biological analysis requires the presence of interpretation in the analysis report. The interpretation in the field of autoimmunity which includes many analyses and methods can be complex for biologists who may not have clinical data and for clinicians who may not be aware of technical difficulties. The French group of the european group EASI (European autoimmunity standardisation initiative) proposes a list of comments and advice in order to help biologists when interpreting auto-immune analyses results in several situations. These comments should be adapted to the clinical and biological situation (other biological results, clinical data…) and should alert the clinician. A dialogue between the biologist and the clinician is essential to adjust the interpretation on clinical data in order to provide a better health care for the patient.

Preexisting autoantibodies as predictor of immune related adverse events (irAEs) for advanced solid tumors treated with immune checkpoint inhibitors (ICIs)

INTRODUCTION

Immune checkpoint inhibitors (ICIs) are now standard of care in many cancers. They can generate immune-related adverse events (irAEs), but no biomarkers are available to identify patients who are more likely to develop irAEs. We assess the association between pre-existing autoantibodies and occurrence of irAEs.

PATIENTS AND METHODS

We prospectively collected data from consecutive patients receiving ICIs for advanced cancers, in a single center between May 2015 and July 2021. Autoantibodies testing was performed before ICIs initiation including AntiNeutrophil Cytoplasmic Antibodies, Antinuclear Antibodies, Rheumatoid Factor anti-Thyroid Peroxidase and anti-Thyroglobulin. We analyzed the associations of pre-existing autoantibodies with onset, severity, time to irAEs and with survival outcomes.

RESULTS

Of the 221 patients included, most had renal cell carcinoma (n = 99; 45%) or lung carcinoma (n = 90; 41%). Grade ≥2 irAEs were more frequent among patients with pre-existing autoantibodies: 64 (50%) vs. 20 (22%) patients (Odds-Ratio= 3.5 [95% CI=1.8-6.8]; p < 0.001) in the positive vs negative group, respectively. irAEs occurred earlier in the positive group with a median time interval between ICI initiation and irAE of 13 weeks (IQR = 8.8-21.6) vs. 28.5 weeks (IQR=10.6-55.1) in the negative group (p = 0.01). Twelve patients (9.4%) experienced multiple (≥2) irAEs in the positive group vs. 2 (2%) in the negative group (OR = 4.5 [95% CI: 0.98-36], p = 0.04). After a median follow-up of 25 months, median PFS and OS were significantly longer among patients experiencing irAE (p = 0.00034 and p = 0.016, respectively).

CONCLUSION

The presence of pre-existing autoantibodies is significantly associated with the occurrence of grade ≥2 irAEs, with earlier and multiple irAEs in patients treated with ICIs.

Hyperoxidized Species of Heme Have a Potent Capacity to Induce Autoreactivity of Human IgG Antibodies

The interaction of some human antibodies with heme results in posttranslational acquisition of binding to various self- and pathogen-derived antigens. The previous studies on this phenomenon were performed with oxidized heme (Fe³⁺). In the present study, we elucidated the effect of other pathologically relevant species of heme, i.e., species that were formed after contact of heme with oxidizing agents such as hydrogen peroxide, situations in which heme's iron could acquire higher oxidation states. Our data reveal that hyperoxidized species of heme have a superior capacity to heme (Fe³⁺) in triggering the autoreactivity of human IgG. Mechanistic studies demonstrated that oxidation status of iron was of critical importance for the heme's effect on antibodies. We also demonstrated that hyperoxidized heme species interacted at higher affinities with IgG and that this binding occurred through a different mechanism as compared to heme (Fe³⁺). Regardless of their profound functional impact on the antigen-binding properties of antibodies, hyperoxidized species of heme did not affect Fc-mediated functions of IgG, such as binding to the neonatal Fc receptor. The obtained data contribute to a better understanding of the pathophysiological mechanism of hemolytic diseases and of the origin of elevated antibody autoreactivity in patients with some hemolytic disorders.

Systematic review of atypical hemolytic uremic syndrome biomarkers

BACKGROUND AND OBJECTIVES

Observing biomarkers that affect alternative pathway dysregulation components may be effective in obtaining a new and more rapid diagnostic portrayal of atypical hemolytic uremic syndrome. We have conducted a systematic review on the aHUS biomarkers: C3, C5a, C5b-9, factor B, complement factor B, H, and I, CH50, AH50, D-dimer, as well as anti-CFH antibodies.

METHODS

An exhaustive literature search was conducted for aHUS patient population plasma/serum, collected/reported at the onset of diagnosis. A total of 60 studies were included with the data on 837 aHUS subjects, with at least one biomarker reported.

RESULTS

The biomarkers C3 [mean (SD): 72.1 (35.0), median: 70.5 vs. reference range: 75-175 mg/dl, n = 752]; CH50 [28.3 (32.1), 24.3 vs. 30-75 U/ml, n = 63]; AH50 [27.6% (30.2%), 10% vs. ≥ 46%, n = 23]; and CFB [13.1 (6.6), 12.4, vs. 15.2-42.3 mg/dl, n = 19] were lower among aHUS subjects as compared with the reference range. The biomarkers including C4 [mean (SD): 20.4 (9.5), median: 20.5 vs. reference range: 14-40 mg/dl, n = 343]; C4d [7.2 (6.5), 4.8 vs. ≤ 9.8 μg/ml, n = 108]; CFH [40.2 (132.3), 24.5 vs. 23.6-43.1 mg/dl, n = 123 subjects]; and CFI [8.05 (5.01), 6.55 mg/dl vs. 4.4-18.1 mg/dl, n = 38] were all observed to be within the reference range among aHUS subjects. The biomarkers C5a [mean (SD): 54.9 (32.9), median: 48.8 vs. reference range: 10.6-26.3 mg/dl, n = 117]; C5b-9 [466.0 (401.4), 317 (186-569.7) vs. ≤ 250 ng/ml, n = 174]; Bb [2.6 (2.1), 1.9 vs. ≤ 1.6 μg/ml, n = 77] and D-dimer [246 (65.05), 246 vs. < 2.2 ng/ml, 2, n = 2 subjects] were higher among patients with aHUS compared with the reference range.

CONCLUSION

If a comprehensive complement profile were built using our data, aHUS would be identified by low levels of C3, CH50, AH50, and CFB along with increased levels of C5a, C5b-9, Bb, anti-CFH autoantibodies, and D-dimer. A higher resolution version of the Graphical abstract is available as Supplementary information.

Repository of intra- and inter-run variations of quantitative autoantibody assays: a European multicenter study

OBJECTIVES

No reference data are available on repositories to measure precision of autoantibody assays. The scope of this study was to document inter- and intra-run variations of quantitative autoantibody assays based on a real-world large international data set.

METHODS

Members of the European Autoimmunity Standardisation Initiative (EASI) group collected the data of intra- and inter-run variability obtained with assays quantifying 15 different autoantibodies in voluntary participating laboratories from their country. We analyzed the impact on the assay performances of the type of immunoassay, the number of measurements used to calculate the coefficient of variation (CVs), the nature and the autoantibody level of the internal quality control (IQC).

RESULTS

Data were obtained from 64 laboratories from 15 European countries between February and October 2021. We analyzed 686 and 1,331 values of intra- and inter-run CVs, respectively. Both CVs were significantly dependent on: the method of immunoassay, the level of IQC with higher imprecision observed when the antibody levels were lower than 2-fold the threshold for positivity, and the nature of the IQC with commercial IQCs having lower CVs than patients-derived IQCs. Our analyses also show that the type of autoantibody has low impact on the assay' performances and that 15 measurements are sufficient to establish reliable intra- and inter-run variations.

CONCLUSIONS

This study provides for the first time an international repository yielding values of intra- and inter-run variation for quantitative autoantibody assays. These data could be useful for ISO 15189 accreditation requirements and will allow clinical diagnostic laboratories to assure quality of patient results.

Immune Signature Linked to COVID-19 Severity: A SARS-Score for Personalized Medicine

SARS-CoV-2 infection leads to a highly variable clinical evolution, ranging from asymptomatic to severe disease with acute respiratory distress syndrome, requiring intensive care units (ICU) admission. The optimal management of hospitalized patients has become a worldwide concern and identification of immune biomarkers predictive of the clinical outcome for hospitalized patients remains a major challenge. Immunophenotyping and transcriptomic analysis of hospitalized COVID-19 patients at admission allow identifying the two categories of patients. Inflammation, high neutrophil activation, dysfunctional monocytic response and a strongly impaired adaptive immune response was observed in patients who will experience the more severe form of the disease. This observation was validated in an independent cohort of patients. Using in silico analysis on drug signature database, we identify differential therapeutics that specifically correspond to each group of patients. From this signature, we propose a score-the SARS-Score-composed of easily quantifiable biomarkers, to classify hospitalized patients upon arrival to adapt treatment according to their immune profile.

Abstract CT021: INVAC-1, an optimized telomerase DNA vaccine in patients with advanced solid tumors: Final results of first-in-human phase I study

Background INVAC-1 is an optimized DNA plasmid encoding an inactive form of human Telomerase Reverse Transcriptase (hTERT), a universal tumor antigen expressed in most of human tumors with little or no expression in normal somatic cells. Primary pharmacodynamics, safety and toxicology studies showed that INVAC-1 was enzymatically inactive, immunogenically safe and well tolerated. In murine models, we demonstrated that INVAC-1 was able to induce hTERT specific cellular immune responses with CD4+ Th1 effector and memory CD8+ T-cells as well as slow tumor growth and increase survival rate by 50% in tumor-bearing mice. Methods We conducted a First-In-Human (FIH) study, 2-centre, Phase I, open label, 3+3 escalation design and multiple dose study examining the safety and tolerability of INVAC-1 administered at three dose levels (100, 400 and 800 µg) in 26 patients with relapsed or solid refractory tumors. INVAC-1 was administered either by intradermal (ID) injection followed by electroporation (EP) (n=20) or by Tropis® Needle Free Injection System (n=6). Results INVAC-1 vaccination was safe and well tolerated when administered ID (either with EP or by Tropis®) at the three tested doses. Only one treatment-related grade 3 SAE was reported. 58% of patients experienced disease stabilization up to 9.9 months. One-year survival was reached for 65% of patients. INVAC-1 elicited both hTERT specific Th1-dominant CD4 and cytotoxic CD8 T cell responses with no vaccine-induced peripheral immunosuppression. Anti-hTERT immune responses were enhanced by adding anti-PD-1 immune checkpoint inhibitor ex vivo. In addition, INVAC-1 vaccination was able to promote epitope spreading. Finally, correlation analysis between clinical and immunological data showed that patients with OS &gt;1 year presented a significantly higher hTERT immune response after INVAC-1 vaccination compared to patients with OS &lt;1 year. Moreover, estimated median OS in INVAC-1 immune responders was 17.4 months vs. 7 months for non-responders. Conclusion INVAC-1 vaccination was safe, well tolerated and immunogenic when administered ID at the three tested doses. Disease stabilization was observed for the majority of patients during the treatment period and beyond. Clinical trial identification #NCT02301754

Citation Format: Julie Garibal, Jacques Medioni, Luis Teixeira, Olivier Adotevi, Marie-Agnès Dragon-Durey, Caroline Laheurte, Claire Germain, Marie Escande, Maria Wehbe, Valérie Doppler, Thierry Huet, Pierre Langlade Demoyen. INVAC-1, an optimized telomerase DNA vaccine in patients with advanced solid tumors: Final results of first-in-human phase I study [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr CT021.

Intracellular Factor H Drives Tumor Progression Independently of the Complement Cascade

The complement system is a powerful and druggable innate immune component of the tumor microenvironment. Nevertheless, it is challenging to elucidate the exact mechanisms by which complement affects tumor growth. In this study, we examined the processes by which the master complement regulator factor H (FH) affects clear cell renal cell carcinoma (ccRCC) and lung cancer, two cancers in which complement overactivation predicts poor prognosis. FH was present in two distinct cellular compartments: the membranous (mb-FH) and intracellular (int-FH) compartments. Int-FH resided in lysosomes and colocalized with C3. In ccRCC and lung adenocarcinoma, FH exerted protumoral action through an intracellular, noncanonical mechanism. FH silencing in ccRCC cell lines resulted in decreased proliferation, due to cell-cycle arrest and increased mortality, and this was associated with increased p53 phosphorylation and NFκB translocation to the nucleus. Moreover, the migration of the FH-silenced cells was reduced, likely due to altered morphology. These effects were cell type-specific because no modifications occurred upon CFH silencing in other FH-expressing cells tested: tubular cells (from which ccRCC originates), endothelial cells (human umbilical vein endothelial cells), and squamous cell lung cancer cells. Consistent with this, in ccRCC and lung adenocarcinoma, but not in lung squamous cell carcinoma, int-FH conferred poor prognosis in patient cohorts. Mb-FH performed its canonical function of complement regulation but had no impact on tumor cell phenotype or patient survival. The discovery of intracellular functions for FH redefines the role of the protein in tumor progression and its use as a prognostic biomarker or potential therapeutic target.See article by Daugan et al., p. 891 (36).

Differential association between inflammatory cytokines and multiorgan dysfunction in COVID-19 patients with obesity

To investigate the mechanisms underlying the SARS-CoV-2 infection severity observed in patients with obesity, we performed a prospective study of 51 patients evaluating the impact of multiple immune parameters during 2 weeks after admission, on vital organs' functions according to body mass index (BMI) categories. High-dimensional flow cytometric characterization of immune cell subsets was performed at admission, 30 systemic cytokines/chemokines levels were sequentially measured, thirteen endothelial markers were determined at admission and at the zenith of the cytokines. Computed tomography scans on admission were quantified for lung damage and hepatic steatosis (n = 23). Abnormal BMI (> 25) observed in 72.6% of patients, was associated with a higher rate of intensive care unit hospitalization (p = 0.044). SARS-CoV-2 RNAaemia, peripheral immune cell subsets and cytokines/chemokines were similar among BMI groups. A significant association between inflammatory cytokines and liver, renal, and endothelial dysfunctions was observed only in patients with obesity (BMI > 30). In contrast, early signs of lung damage (ground-glass opacity) correlated with Th1/M1/inflammatory cytokines only in normal weight patients. Later lesions of pulmonary consolidation correlated with BMI but were independent of cytokine levels. Our study reveals distinct physiopathological mechanisms associated with SARS-CoV-2 infection in patients with obesity that may have important clinical implications.

Complement C1s and C4d as Prognostic Biomarkers in Renal Cancer: Emergence of Noncanonical Functions of C1s

The complement system plays a complex role in cancer. In clear cell renal cell carcinoma (ccRCC), local production of complement proteins drives tumor progression, but the mechanisms by which they do this are poorly understood. We found that complement activation, as reflected by high plasma C4d or as C4d deposits at the tumor site, was associated with poor prognosis in two cohorts of patients with ccRCC. High expression of the C4-activating enzyme C1s by tumor cells was associated with poor prognosis in three cohorts. Multivariate Cox analysis revealed that the prognostic value of C1s was independent from complement deposits, suggesting the possibility of complement cascade-unrelated, protumoral functions for C1s. Silencing of C1s in cancer cell lines resulted in decreased proliferation and viability of the cells and in increased activation of T cells in in vitro cocultures. Tumors expressing high levels of C1s showed high infiltration of macrophages and T cells. Modification of the tumor cell phenotype and T-cell activation were independent of extracellular C1s levels, suggesting that C1s was acting in an intracellular, noncanonical manner. In conclusion, our data point to C1s playing a dual role in promoting ccRCC progression by triggering complement activation and by modulating the tumor cell phenotype and tumor microenvironment in a complement cascade-independent, noncanonical manner. Overexpression of C1s by tumor cells could be a new escape mechanism to promote tumor progression.See related Spotlight by Magrini and Garlanda, p. 855. See article by Daugan et al., p. 909 (40).

Lupus anticoagulant single positivity at acute phase is not associated with venous thromboembolism or in-hospital mortality in COVID-19

Objective

The clinical relevance of antiphospholipid antibodies (aPLs) in COVID‐19 is controversial. This study was undertaken to investigate the prevalence and prognostic value of conventional and nonconventional aPLs in patients with COVID‐19.

Methods

This was a multicenter, prospective observational study in a French cohort of patients hospitalized with suspected COVID‐19.

Results

Two hundred forty‐nine patients were hospitalized with suspected COVID‐19, in whom COVID‐19 was confirmed in 154 and not confirmed in 95. We found a significant increase in lupus anticoagulant (LAC) positivity among patients with COVID‐19 compared to patients without COVID‐19 (60.9% versus 23.7%; P < 0.001), while prevalence of conventional aPLs (IgG and IgM anti–β₂‐glycoprotein I and IgG and IgM anticardiolipin isotypes) and nonconventional aPLs (IgA isotype of anticardiolipin, IgA isotype of anti‐β₂‐glycoprotein I, IgG and IgM isotypes of anti–phosphatidylserine/prothrombin, and IgG and IgM isotypes of antiprothrombin) was low in both groups. Patients with COVID‐19 who were positive for LAC, as compared to patients with COVID‐19 who were negative for LAC, had higher levels of fibrinogen (median 6.0 gm/liter [interquartile range 5.0–7.0] versus 5.3 gm/liter [interquartile range 4.3–6.4]; P = 0.028) and C‐reactive protein (CRP) (median 115.5 mg/liter [interquartile range 66.0–204.8] versus 91.8 mg/liter [interquartile range 27.0–155.1]; P = 0.019). Univariate analysis did not show any association between LAC positivity and higher risks of venous thromboembolism (VTE) (odds ratio 1.02 [95% confidence interval 0.44–2.43], P = 0.95) or in‐hospital mortality (odds ratio 1.80 [95% confidence interval 0.70–5.05], P = 0.24). With and without adjustment for CRP level, age, and sex, Kaplan‐Meier survival curves according to LAC positivity confirmed the absence of an association with VTE or in‐hospital mortality (unadjusted P = 0.64 and P = 0.26, respectively; adjusted hazard ratio 1.13 [95% confidence interval 0.48–2.60] and 1.80 [95% confidence interval 0.67–5.01], respectively).

Conclusion

Patients with COVID‐19 have an increased prevalence of LAC positivity associated with biologic markers of inflammation. However, LAC positivity at the time of hospital admission is not associated with VTE risk and/or in‐hospital mortality.

Sheep Erythrocyte Preparation for Hemolytic Tests Exploring Complement Functional Activities

Sheep erythrocytes (SE) are commonly used in complement functional tests. Non sensitized SE are useful to study the FH activity of cell protection. Indeed, as the cell surface of sheep erythrocytes is rich in sialic acids, Factor H (FH) is able to bind on it and therefore they represent a model of nonactivating surface. Because of their high capacity of complement regulation SE need to be modified to explore other functionality of the complement pathways, like the Complement hemolytic 50 (CH50) or the AP C3 convertase decay assays. For these tests, SE are sensitized with an anti-sheep red blood cell stroma antibody. In presence of serum or plasma complement components, sensitized SE may initiate complement cascade activation via the classic pathway explored in the CH50 assay. Sensitized SE may also be used to prepare C3b-coated SE that, with the use of buffers favoring AP, are suitable for the C3 Nef hemolytic assay and for the hemolytic assay studying the AP decay activity of FH. In this chapter we describe how to prepare SE for these different hemolytic tests.

Hemolytic Tests Exploring Factor H Functional Activities

Impairment of the complement regulatory protein Factor H (FH) is implicated in the physiopathological mechanisms of different diseases like atypical hemolytic and uremic syndrome and C3 glomerulopathies. It may be due to genetic abnormalities or acquired with the development of autoantibodies. FH has several ligands; therefore, the exploration of its functions requires to perform different tests. Among them, two hemolytic tests are very useful because they give specific and complementary information about FH functions. The first one is dedicated to explore the FH capacity to dissociate the alternative pathway C3 convertase, whereas the second one is designed to explore the capacity of FH to bind cell surfaces and to protect them from complement attack. This chapter describes the procedures to perform these two hemolytic tests, exploring in a complementary way the FH functionality.

Precision of autoantibody assays in clinical diagnostic laboratories: What is the reality?

BACKGROUND

ISO 15189 accreditation remains a challenge for specialized laboratories. In the field of autoimmunity, beside the crucial problem of absence of standardization, laboratories have to manage the analytical performances of the large panel of assays in terms of sensitivity and specificity, but also on their measurement precision for which no reference values are available on biorepositories.

METHODS

As an initiative of the French EASI (European Autoimmunity Standardization Initiative) group, French clinical diagnostic laboratories were requested to participate in a survey aiming to analyze the coefficients of variation (CVs) of intra-run and inter-run variability obtained with assays quantifying 14 different autoantibodies. Two performance goals corresponding to the 90th percentile and the 50th percentile (lowest CV values reached by 90% and 50% of laboratories respectively) defined for three levels of concentration were calculated. The impact on the assay performances of the number of measurements, of the nature of the internal quality control (IQC) and the type of immunoassay, was also analyzed.

RESULTS

414 and 616 values of intra-run and inter-run CVs were collected, respectively. The 50th percentile performance goals were comprised between 1.0% and 8.9% for the intra-run CVs, and between 1.8% and 14.6% for the inter-run CVs. At 90th percentile, the performance goals were comprised between 3.2% and 13.5% for the intra-run CVs, and between 7.3% and 30.8% for the inter-run CVs. CVs calculated from 10 values were similar to those obtained from more values. Higher imprecision was observed when the antibody levels of the IQC was lower than 2 fold the positive threshold. Commercial IQCs gave lower CVs than IQCs derived from patient samples.

CONCLUSION

Our results allow proposing some acceptability limits for the precision performances of the autoantibody assays, compatible with the reality of life in diagnostic laboratories and clinical care.

Analytical validation of an alternative method to quantify specific antibodies in 3 applications

The detection and the quantification of specific antibodies represent essential tools for the diagnosis and for the biological monitoring of immune humoral response in many clinical situations in particular in autoimmune diseases or in the context of immunotherapy using monoclonal antibodies. This article focuses on the development of a specific antibody measuring method (Patent n°PCT/IB2014/064437). The principle of this method is based on the combined use of a monoclonal antibody as standard and the protein G as immunoglobulins detecting agent. We performed a complete analytical validation of this method for the quantification of antibodies in three different applications: autoantibodies, alloantibodies and therapeutic monoclonal antibody. The results showed good performances compatible with the use of these assays as diagnostic tools. This method allows avoiding the use of products from human origin as reagent that causes ethical and infectious concerns but also storage and long term stock management problems. Moreover, this approach is particularly useful when no commercial reagent is available, especially in the case of rare diseases.

Both Monoclonal and Polyclonal Immunoglobulin Contingents Mediate Complement Activation in Monoclonal Gammopathy Associated-C3 Glomerulopathy

C3 glomerulopathy (C3G) results from acquired or genetic abnormalities in the complement alternative pathway (AP). C3G with monoclonal immunoglobulin (MIg-C3G) was recently included in the spectrum of “monoclonal gammopathy of renal significance.” However, mechanisms of complement dysregulation in MIg-C3G are not described and the pathogenic effect of the monoclonal immunoglobulin is not understood. The purpose of this study was to investigate the mechanisms of complement dysregulation in a cohort of 41 patients with MIg-C3G. Low C3 level and elevated sC5b-9, both biomarkers of C3 and C5 convertase activation, were present in 44 and 78% of patients, respectively. Rare pathogenic variants were identified in 2/28 (7%) tested patients suggesting that the disease is acquired in a large majority of patients. Anti-complement auto-antibodies were found in 20/41 (49%) patients, including anti-FH (17%), anti-CR1 (27%), anti-FI (5%) auto-antibodies, and C3 Nephritic Factor (7%) and were polyclonal in 77% of patients. Using cofactor assay, the regulation of the AP was altered in presence of purified IgG from 3/9 and 4/7 patients with anti-FH or anti-CR1 antibodies respectively. By using fluid and solid phase AP activation, we showed that total purified IgG of 22/34 (65%) MIg-C3G patients were able to enhance C3 convertase activity. In five documented cases, we showed that the C3 convertase enhancement was mostly due to the monoclonal immunoglobulin, thus paving the way for a new mechanism of complement dysregulation in C3G. All together the results highlight the contribution of both polyclonal and monoclonal Ig in MIg-C3G. They provide direct insights to treatment approaches and opened up a potential way to a personalized therapeutic strategy based on chemotherapy adapted to the B cell clone or immunosuppressive therapy.

Routinely used immunoassays do not detect circulating anti-GBM antibodies against native NC1 hexamer and EA epitope of the α3 chain of type IV collagen

Detection of circulating anti-GBM antibodies has a key role for the diagnosis of Goodpasture syndrome but immunoassays using purified or recombinant alpha3(IV)NC1 as antigen do not recognize all anti-GBM antibodies. We show that anti-GBM antibodies directed against epitopes in their native conformation or cryptic epitopes are detected by indirect immunofluorescence.

Eculizumab reversed severe distal ischemic syndrome and glomerulonephritis with isolated C3 deposits associated with anti-factor H autoantibodies: a case report

B-cell clones can produce a monoclonal immunoglobulin, which may be responsible for visceral involvements. Kidney involvement is frequent, affecting 20 to 50% of patients with multiple myeloma. One mechanism underlying this involvement is a dysregulation of the complement alternative pathway, leading to C3 glomerulopathies. We report a patient who had a multiple myeloma, C3 glomerulopathy related to factor H autoantibody, and digital ischemia, who was treated successfully with eculizumab, an anti-complement therapy, without any relapse in 2 years of follow-up.

Auto-immunité et gestion des toxicités des traitements par anti-check point inhibiteurs

AUTOIMMUNITY AND MANAGEMENT OF THE IMMUNE-RELATED ADVERSE EFFECTS OF THE IMMUNE CHECKPOINT INHIBITORS: The immune checkpoint molecules such as CTLA-4 and PD-1 are involved in the tolerance mechanisms preventing the immune system to react against the self-antigens. When these receptors expressed on the lymphocyte membrane, bind to their ligands, they induce a negative signal to the cell which becomes unable to be completely activated in the presence of its antigen. In a context of tumor, the infiltrating T cells are frequently exhausted due to the expression of CTLA-4 and PD-1 ligands by the microenvironment impairing the antitumoral immunity. The use of antagonistic antibodies targeting these receptors or their ligands (called checkpoint inhibitors) aims to block their interaction unbalancing the negative regulation of the antitumoral lymphocytes. However, this effect affects all lymphocytes and may also disrupt the negative regulation of the peripheral autoreactive lymphocytes. Thus, a significant proportion of patients treated by these molecules develop immune-related symptoms affecting different tissues and organs due to lymphocyte activation. These symptoms are called immune-related adverse events (irAEs). This article aims to summarize the scientific data demonstrating the implication of these molecules in the tolerance mechanisms and in the autoimmune diseases. It also reports on the IrAEs observed in treated patients and gives an outline of guidelines to monitor and manage these patients.

Targeting renin-angiotensin system in malignant hypertension in atypical hemolytic uremic syndrome

Hypertension is common in hemolytic uremic syndrome (HUS) and often difficult to control. Local renin-angiotensin activation is believed to be an important part of thrombotic microangiopathy, leading to a vicious cycle of progressive renal injury and intractable hypertension. This has been demonstrated in vitro via enhanced tissue factor expression on glomerular endothelial cells which is enhanced by angiotensin II. We report two pediatric cases of atypical HUS with severe refractory malignant hypertension, in which we targeted the renin-angiotensin system by using intravenous (IV) enalaprilat, oral aliskiren, and oral enalapril with quick and dramatic response of blood pressure. Both drugs, aliskiren and IV enalaprilat, were effective in controlling hypertension refractory to multiple antihypertensive medications. These appear to be promising alternatives in the treatment of severe atypical HUS-induced hypertension and hypertensive emergency.

Eculizumab for atypical hemolytic-uremic syndrome in India: First report from India and the challenges faced

Much progress has been made in understanding the pathophysiology and treatment of atypical hemolytic uremic syndrome (aHUS). Plasma therapy is the mainstay of treatment for aHUS. The availability of the first effective anti-complement therapeutic agent, eculizumab, has dramatically changed the outlook of this disease. However, its use in clinical practice raises important questions, such as who should receive the drug, when to start such therapy, and is it safe to stop treatment once the disease is controlled. We describe here for the 1^st time in India, use of eculizumab in a 12-year-old boy with aHUS. We also describe in this report challenges faced in procuring the drug, and an ideal, evidence-based method of treating aHUS in children.

Application of Deamidated Gliadin Antibodies in the Follow-Up of Treated Celiac Disease

Introduction

The role of serological tests such as IgA anti-transglutaminase autoantibodies has become increasingly important in celiac disease (CD) diagnosis. However, the efficiency of these tests for patient follow-up is controversial. We investigated the correlation of 12 different serological tests, including recent deamidated gliadin and actin IgA tests, with villous atrophy (VA) in a retrospective cohort of treated celiac patients.

Materials and Methods

Serum samples were collected from 100 treated CD patients who had intestinal biopsy in the course of their follow-up. Antibodies against transglutaminase, deamidated gliadin peptides, and native gliadin were measured, along with IgA anti-actin. The biopsy slides were all blind-reviewed and scored according to Marsh classification.

Results

For all deamidated gliadin and transglutaminase tests, we found that a positive result was significantly associated with persistence of intestinal VA, with a diagnostic efficacy up to 80%. Furthermore, antibodies titers directly correlated with the degree of VA, indicating a strong link between disease activity and presence of antibodies in the serum. Interestingly, the tests with the highest association with persistent VA were those for deamidated gliadin IgG. Using a test positivity pattern analysis, we were also able to identify several groups of patients with distinct antibody profiles that showed significant differences in intestinal damage and diet compliance.

Conclusions

Altogether, these results show that deamidated gliadin antibodies are strongly correlated with VA and should be considered valuable tools in CD follow-up and that multiplex serologic analysis for treated CD represents a promising tool for personalized patient management.

A case of C3 glomerulonephritis successfully treated with eculizumab

BACKGROUND

C3 glomerulonephritis (C3GN) is a rare form of glomerulopathy that is characterized by predominant C3 deposits. Eculizumab, a humanized monoclonal C5 antibody, has recently emerged as a treatment option for C3GN. We report a C3GN patient successfully treated with eculizumab.

CASE DIAGNOSIS/TREATMENT

A 5-year-old boy who presented with proteinuria, hematuria, high ASO titers, and low C3 levels was initially diagnosed with post-streptococcal GN. His first kidney biopsy confirmed this diagnosis, but complement investigations identified three alternative pathway dysregulation factors: C3 nephritic factor, complement factor I heterozygous mutation (I398L), and anti-factor H autoantibodies (4,500 AU/ml). A second biopsy performed 11 months after initial presentation (nephrotic range proteinuria) showed a C3GN suggestive of isolated C3 deposits. Despite the use of intensive immunosuppressive therapy (rituximab, corticosteroids, mycophenolate), nephrotic-range proteinuria persisted and a third kidney biopsy showed the same C3GN pattern with more endocapillary proliferation. The serum C5b-9 level was elevated. Eculizumab was initiated and resulted in a significant decline of proteinuria (5.3 to 1.3 g/day) and an improvement in pathologic features. A transient interruption of eculizumab resulted in a rapid rise in proteinuria to 9.3 g/day, which decreased to 0.8 g/day after resumption of treatment.

CONCLUSIONS

The administration of anti-C5 antibodies may represent a valuable therapeutic option in patients with C3GN.

Anti-factor H autoantibodies in C3 glomerulopathies and in atypical hemolytic uremic syndrome: one target, two diseases

Autoantibodies targeting factor H (FH), which is a main alternative complement pathway regulatory protein, have been well characterized in atypical hemolytic uremic syndrome (aHUS) but have been less well described in association with alternative pathway-mediated glomerulopathies (GP). In this study, we studied 17 patients presenting with GP who were positive for anti-FH IgG. Clinical data were collected and biological characteristics were compared with those of patients presenting with anti-FH Ab-associated aHUS. In contrast to the aHUS patients, the GP patients had no circulating FH-containing immune complexes, and their anti-FH IgG had a weaker affinity for FH. Functional studies demonstrated that these Abs induced no perturbations in FH cell surface protection or the binding of FH to its ligand. However, anti-FH IgG samples isolated from three patients were able to affect the factor I cofactor activity of FH. Epitope mapping identified the N-terminal domain of FH as the major binding site for GP patient IgG. No homozygous deletions of the CFHR1 and CFHR3 genes, which are frequently associated with the anti-FH Ab in aHUS patients, were found in the GP patients. Finally, anti-FH Abs were frequently associated with the presence of C3 nephritic factor in child GP patients and with monoclonal gammopathy in adult GP patients, who frequently showed Ig Lchain restriction during reactivity against factor H. These data provide deeper insights into the pathophysiological differences between aHUS and GP, demonstrating heterogeneity of anti-FH IgG.

Inhibition of the mTORC pathway in the antiphospholipid syndrome

BACKGROUND

Although thrombosis is considered the cardinal feature of the antiphospholipid syndrome, chronic vascular lesions are common, particularly in patients with life-threatening complications. In patients who require transplantation, vascular lesions often recur. The molecular pathways involved in the vasculopathy of the antiphospholipid syndrome are unknown, and adequate therapies are lacking.

METHODS

We used double immunostaining to evaluate pathway activation in the mammalian target of rapamycin complex (mTORC) and the nature of cell proliferation in the vessels of patients with primary or secondary antiphospholipid syndrome nephropathy. We also evaluated autopsy specimens from persons who had catastrophic antiphospholipid syndrome. The molecular pathways through which antiphospholipid antibodies modulate the mTORC pathway were evaluated in vitro, and potential pharmacologic inhibitors were also tested in vitro. Finally, we studied the effect of sirolimus in kidney-transplant recipients with the antiphospholipid syndrome.

RESULTS

The vascular endothelium of proliferating intrarenal vessels from patients with antiphospholipid syndrome nephropathy showed indications of activation of the mTORC pathway. In cultured vascular endothelial cells, IgG antibodies from patients with the antiphospholipid syndrome stimulated mTORC through the phosphatidylinositol 3-kinase (PI3K)-AKT pathway. Patients with antiphospholipid syndrome nephropathy who required transplantation and were receiving sirolimus had no recurrence of vascular lesions and had decreased vascular proliferation on biopsy as compared with patients with antiphospholipid antibodies who were not receiving sirolimus. Among 10 patients treated with sirolimus, 7 (70%) had a functioning renal allograft 144 months after transplantation versus 3 of 27 untreated patients (11%). Activation of mTORC was also found in the vessels of autopsy specimens from patients with catastrophic antiphospholipid syndrome.

CONCLUSIONS

Our results suggest that the mTORC pathway is involved in the vascular lesions associated with the antiphospholipid syndrome. (Funded by INSERM and others.).

Functional evaluation of factor H genetic and acquired abnormalities: application for atypical hemolytic uremic syndrome (aHUS)

The atypical hemolytic uremic syndrome (aHUS) is a paradigm of a disease, caused by overactivation of the alternative complement pathway secondary to a not well-understood trigger event. About 60 % of the patients present genetic or acquired abnormalities in the proteins of the alternative complement pathway. In 40 % of the cases the affected protein is the complement regulator Factor H (FH)-30 % due to mutations and 10 % because of anti-FH autoantibodies. Here we describe the detailed protocol for a rapid test to analyse the functional defect associated with genetic or acquired FH-related abnormalities. It can be applied for the characterization of the underlying complement defect in aHUS, based on spontaneous lysis of non-sensitized sheep erythrocytes in contact with patients' plasma or serum.

Anti-factor H autoantibodies assay

Non-Shiga-toxin-associated hemolytic uremic syndrome (atypical HUS) is a rare form of thrombotic microangiopathy which associates hemolytic anemia, thrombocytopenia, and acute renal failure. In 10 % of cases the disease is linked to presence of autoantibodies directed against Factor H (FH), the main plasmatic alternative complement pathway regulatory protein. Their presence induces an acquired functional FH deficiency. The anti-FH autoantibodies screening must be performed at the very onset of the disease in all cases of HUS, in order, first, to make the proper diagnosis as early as possible, and second to support an appropriate therapy including early plasma exchanges and immunosuppressive treatments. Thus, anti-CFH IgG represents a diagnostic marker and the titer determination is useful for assessing disease evolution, because changes precede clinical symptoms, and for monitoring of treatment. Presence of anti-FH IgG has been recently reported to be associated with other clinical context such as C3 glomerulopathies, but their pathogenicity in these conditions remains to be assessed. Here we describe the ELISA assay allowing the detection of these autoantibodies and report the analysis which can be performed concomitantly to improve the diagnosis.

Autoantibodies against complement components and functional consequences

The complement system represents a major component of our innate immune defense. Although the physiological contribution of the complement system is beneficial, it can cause tissue damage when inappropriately activated or when it is a target of an autoantibody response. Autoantibodies directed against a variety of individual complement components, convertases, regulators and receptors have been described. For several autoantibodies the functional consequences are well documented and clear associations exist with clinical presentation, whereas for other autoantibodies targeting complement components this relation is currently insufficiently clear. Several anti-complement autoantibodies can also be detected in healthy controls, indicating that a second hit is required for such autoantibodies to induce or participate in pathology or alternatively that these antibodies are part of the natural antibody repertoire. In the present review, we describe autoantibodies against complement components and their functional consequences and discuss about their clinical relevance.

An engineered construct combining complement regulatory and surface-recognition domains represents a minimal-size functional factor H

Complement is an essential humoral component of innate immunity; however, its inappropriate activation leads to pathology. Polymorphisms, mutations, and autoantibodies affecting factor H (FH), a major regulator of the alternative complement pathway, are associated with various diseases, including age-related macular degeneration, atypical hemolytic uremic syndrome, and C3 glomerulopathies. Restoring FH function could be a treatment option for such pathologies. In this article, we report on an engineered FH construct that directly combines the two major functional regions of FH: the N-terminal complement regulatory domains and the C-terminal surface-recognition domains. This minimal-size FH (mini-FH) binds C3b and has complement regulatory functions similar to those of the full-length protein. In addition, we demonstrate that mini-FH binds to the FH ligands C-reactive protein, pentraxin 3, and malondialdehyde epitopes. Mini-FH was functionally active when bound to the extracellular matrix and endothelial cells in vitro, and it inhibited C3 deposition on the cells. Furthermore, mini-FH efficiently inhibited complement-mediated lysis of host-like cells caused by a disease-associated FH mutation or by anti-FH autoantibodies. Therefore, mini-FH could potentially be used as a complement inhibitor targeting host surfaces, as well as to replace compromised FH in diseases associated with FH dysfunction.

Genetics and outcome of atypical hemolytic uremic syndrome: a nationwide French series comparing children and adults

BACKGROUND AND OBJECTIVES

Atypical hemolytic uremic syndrome (aHUS) is a rare complement-mediated kidney disease that was first recognized in children but also affects adults. This study assessed the disease presentation and outcome in a nationwide cohort of patients with aHUS according to the age at onset and the underlying complement abnormalities.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

A total of 214 patients with aHUS were enrolled between 2000 and 2008 and screened for mutations in the six susceptibility factors for aHUS and for anti-factor H antibodies.

RESULTS

Onset of aHUS occurred as frequently during adulthood (58.4%) as during childhood (41.6%). The percentages of patients who developed the disease were 23%, 40%, 70%, and 98% by age 2, 18, 40, and 60 years, respectively. Mortality was higher in children than in adults (6.7% versus 0.8% at 1 year) (P=0.02), but progression to ESRD after the first aHUS episode was more frequent in adults (46% versus 16%; P<0.001). Sixty-one percent of patients had mutations in their complement genes. The renal outcome was not significantly different in adults regardless of genetic background. Only membrane cofactor protein (MCP) and undetermined aHUS were less severe in children than adults. The frequency of relapse after 1 year was 92% in children with MCP-associated HUS and approximately 30% in all other subgroups.

CONCLUSION

Mortality rate was higher in children than adults with aHUS, but renal prognosis was worse in adults than children. In children, the prognosis strongly depends on the genetic background.

Overall neutralization of complement factor H by autoantibodies in the acute phase of the autoimmune form of atypical hemolytic uremic syndrome

Complement is a major innate immune surveillance system. One of its most important regulators is the plasma protein factor H (FH). FH inactivation by mutations or by autoantibodies is associated with a thrombotic microangiopathy disease, atypical hemolytic uremic syndrome. In this study, we report the characterization of blood samples from 19 anti-FH Ab-positive atypical hemolytic uremic syndrome patients collected at the acute phase of the disease. Analyses of the functional consequences and epitope mapping, using both fluid phase and solid phase approaches, were performed. The anti-FH Abs perturbed FH-mediated cell protection (100%), inhibited FH interaction with C3 (46%), and caused C3 consumption (47%). The Abs were directed against multiple FH epitopes located at the N and C termini. In all tested patients, high titers of FH-containing circulating immune complexes were detected. The circulating immune complex titers correlated with the disease stage better than did the Ab titers. Our results show that anti-FH autoantibodies induce neutralization of FH at acute phase of the disease, leading to an overall impairment of several functions of FH, extending the role of autoantibodies beyond the impairment of the direct cell surface protection.

Acquired and genetic complement abnormalities play a critical role in dense deposit disease and other C3 glomerulopathies

Dense deposit disease and glomerulonephritis with isolated C3 deposits are glomerulopathies characterized by deposits of C3 within or along the glomerular basement membrane. Previous studies found a link between dysregulation of the complement alternative pathway and the pathogenesis of these diseases. We analyzed the role of acquired and genetic complement abnormalities in a cohort of 134 patients, of whom 29 have dense deposit disease, 56 have glomerulonephritis with isolated C3 deposits, and 49 have primary membranoproliferative glomerulonephritis type I, with adult and pediatric onset. A total of 53 patients presented with a low C3 level, and 65 were positive for C3 nephritic factor that was significantly more frequently detected in patients with dense deposit disease than in other histological types. Mutations in CFH and CFI genes were identified in 24 patients associated with a C3 nephritic factor in half the cases. We found evidence for complement alternative pathway dysregulation in 26 patients with membranoproliferative glomerulonephritis type I. The complement factor H Y402H variant was significantly increased in dense deposit disease. We identified one at-risk membrane cofactor protein (MCP) haplotype for glomerulonephritis with isolated C3 deposits and membranoproliferative glomerulonephritis type I. Thus, our results suggest a critical role of fluid-phase alternative pathway dysregulation in the pathogenesis of C3 glomerulopathies as well as in immune complex-mediated glomerular diseases. The localization of the C3 deposits may be under the influence of MCP expression.

Clinical features of anti-factor H autoantibody-associated hemolytic uremic syndrome

Atypical hemolytic uremic syndrome (aHUS) is a rare form of thrombotic microangiopathy that associates, in 70% of cases, with genetic or acquired disorders leading to dysregulation of the alternative pathway of complement. Autoantibody directed against Factor H causes at least 6% to 10% of aHUS cases, but only a few clinical reports are available. Here, we describe the clinical, biologic, genetic features, treatment, and outcome of 45 patients who presented with aHUS associated with anti-FH autoantibody. We found that this form of aHUS primarily affects children between 9 and 13 years old but it also affects adults. It presents with a high frequency of gastrointestinal symptoms and with extrarenal complications and has a relapsing course. Activation of the alternative pathway of complement at the onset of disease portends a poor prognosis. Early specific treatment may lead to favorable outcomes. These data should improve the recognition and diagnosis of this form of aHUS and help identify patients at high risk of a poor outcome.

Anti-factor H autoantibody-associated hemolytic uremic syndrome: review of literature of the autoimmune form of HUS

Non-Shiga toxin-associated hemolytic uremic syndrome (atypical HUS) is a rare form of thrombotic microangiopathy that associates hemolytic anemia, thrombocytopenia, and acute renal failure. The disease has been demonstrated to be linked with a complement alternative pathway dysregulation due to genetic defects but also to development of autoantibodies to factor H (FH), the main plasmatic alternative pathway regulatory protein. In this review, we summarize the more recent data of this autoimmune form of HUS at the level of epidemiology and its clinical and biological features. We propose the performance of anti-FH autoantibodies screening at the very onset of the disease in all cases of HUS to first make the proper diagnosis as early as possible, and second to support an appropriate therapy including early plasma exchanges and immunosuppressive treatments.

Pregnancy-associated hemolytic uremic syndrome revisited in the era of complement gene mutations

In contrast to pregnancy-associated thrombotic thrombocytopenic purpura, the pathogenesis and presentation of pregnancy-associated atypical hemolytic uremic syndrome (P-aHUS) remain ill-defined. We conducted a retrospective study to assess the presentation and outcomes of patients presenting with P-aHUS and the prevalence of alternative C3 convertase dysregulation. P-aHUS occurred in 21 of the 100 adult female patients with atypical HUS, with 79% presenting postpartum. We detected complement abnormalities in 18 of the 21 patients. The outcomes were poor: 62% reached ESRD by 1 month and 76% by last follow-up. The risk for P-aHUS was highest during a second pregnancy. Thirty-five women, 26 (74%) of whom had complement abnormalities, had at least one pregnancy before the onset of a non-pregnancy-related aHUS. Outcomes did not differ between patients with pregnancy-related and non-pregnancy-related aHUS. Mutations in the SCR19-20 domains of factor H were less frequent in P-aHUS patients compared with non-pregnancy-related aHUS. Pregnancies in female patients with complement abnormalities (n = 44) were complicated by fetal loss and preeclampsia in 4.8% and 7.7%, respectively. Better understanding of complement dysregulation in pregnancy complications is essential, especially to guide development of pharmacologic agents to modulate this system.

Pulse cyclophosphamide therapy and clinical remission in atypical hemolytic uremic syndrome with anti-complement factor H autoantibodies

We report 3 children with atypical hemolytic uremic syndrome associated with anti-complement factor H (CFH) autoantibodies who presented with sustained remission with low antibody titers and normal kidney function after plasma exchanges (PEs) and cyclophosphamide pulses. The 3 children initially presented with acute vomiting, fatigue, gross hematuria, hypertension, hemolytic anemia, thrombocytopenia, nephrotic syndrome, and acute kidney injury. C3 levels were normal in patients 1 and 3 and low in patient 2 (0.376 mg/mL [0.376 g/L]). CFH antibody titers were increased (15,000 to > 32,000 arbitrary units [AU]). Patient 1, an 11-year-old boy, was treated with 12 PEs, leading to a decrease in CFH antibody titer (to 800 AU). A first relapse 1 month later was treated with 6 PEs and 4 rituximab infusions. A second relapse 3 months later required 5 PEs, and the patient received oral steroids (0.5 mg/d/kg body weight) and 5 cyclophosphamide pulses (1 g/1.73 m(2)), leading to sustained remission with normal kidney function (estimated glomerular filtration rate [eGFR], 120 mL/min/1.73 m(2) [2.0 mL/s/1.73 m(2)]) and a stable decrease in CFH antibody titer (to 2,000 AU) 3 years later. Patient 2, a 5-year-old boy, required dialysis therapy for 2 weeks. He received 3 plasma infusions without remission. Six PEs associated with 2 cyclophosphamide pulses (0.5 g/1.73 m(2)) and steroids (1 mg/d/kg body weight) led to rapid remission, with eGFR of 107 mL/min/1.73 m(2) [1.78 mL/s/1.73 m(2)] and a prolonged decrease in CFH antibody titer after 15 months (1,300 AU). Patient 3, a 16-month-old boy, was treated with oral steroids (1 mg/d/kg body weight), 2 PEs, and 2 cyclophosphamide pulses (0.5 g/1.73 m(2)), resulting in a stable decrease in CFH antibody titer to 276 AU. Kidney function quickly normalized (eGFR, 110 mL/min/1.73 m(2) [1.83 mL/s/1.73 m(2)]) and has remained normal after 14 months. All 3 patients show a homozygous deletion mutation of the CFHR1 and CFHR3 genes. Cyclophosphamide pulses with PE may lead to a prolonged decrease in CFH antibody titers and a favorable outcome of atypical hemolytic uremic syndrome and kidney function.

Atypical hemolytic uremic syndrome associated with complement factor H autoantibodies and CFHR1/CFHR3 deficiency

Although genetic defect of complement factor H (CFH) is a common cause of atypical hemolytic uremic syndrome (aHUS), development of autoantibodies to CFH (CFH-Ab) is also known to be an acquired cause of aHUS. Recently, a correlation between the development of CFH-Ab and the deficiency of the CFH-related proteins, CFHR1 and CFHR3, was identified. In this study, plasma complement profiles were measured and genetic analysis of the CFH, CFI, MCP, CFHR1, and CFHR3 genes were performed in three female patients diagnosed with aHUS with positive CFH-Ab. Acute stage plasmas of all the three patients revealed low C3, low or low-normal CFH antigenic levels, and high titers of CFH-Ab. All the patients also showed complete plasma CFHR1 deficiency and homozygous genomic deletion of CFHR1/CFHR3, but none had CFH, CFI, or MCP mutations. All the patients were treated with plasmapheresis, and two patients required additional immunosuppressive therapy. These patients had a novel subgroup of aHUS characterized by a combination of genetic (a homozygous deletion of CFHR1/CFHR3) and acquired (development of CFH-Ab) factors. Patients with this disease may need intensive immunosuppressive therapy in addition to plasmapheresis. Screening for CFH-Ab and the CFHR1/CFHR3 deficiency should be included in the diagnostic tests for patients with aHUS.

Varicella as a trigger of atypical haemolytic uraemic syndrome associated with complement dysfunction: two cases

We report two cases of children who presented with haemolytic uraemic syndrome following varicella infection. One of them had a membrane cofactor protein mutation, and the other had anti-factor H antibodies. These observations show that infectious agents such as varicella-zoster virus may be the trigger of haemolytic uraemic syndrome in patients with complement dysregulation.

Differential impact of complement mutations on clinical characteristics in atypical hemolytic uremic syndrome

Mutations in factor H (CFH), factor I (IF), and membrane cofactor protein (MCP) genes have been described as risk factors for atypical hemolytic uremic syndrome (aHUS). This study analyzed the impact of complement mutations on the outcome of 46 children with aHUS. A total of 52% of patients had mutations in one or two of known susceptibility factors (22, 13, and 15% of patients with CFH, IF, or MCP mutations, respectively; 2% with CFH+IF mutations). Age <3 mo at onset seems to be characteristic of CFH and IF mutation-associated aHUS. The most severe prognosis was in the CFH mutation group, 60% of whom reached ESRD or died within <1 yr. Only 30% of CFH mutations were localized in SCR20. MCP mutation-associated HUS has a relapsing course, but none of the children reached ESRD at 1 yr. Half of patients with IF mutation had a rapid evolution to ESRD, and half recovered. Plasmatherapy seemed to have a beneficial effect in one third of patients from all groups except for the MCP mutation group. Only eight (33%) of 24 kidney transplantations that were performed in 15 patients were successful. Graft failures were due to early graft thrombosis (50%) or HUS recurrence. In conclusion, outcome of HUS in patients with CFH mutation is catastrophic, and posttransplantation outcome is poor in all groups except for the MCP mutation group. New therapies are urgently needed, and further research should elucidate the unexplained HUS group.