Measurement of antinuclear antibodies and their fine specificities: time for a change in strategy?

OBJECTIVES

The current strategy for antinuclear antibody (ANA) analysis involves screening for presence with a subsequent detailed analysis of their specificity. The aim of this study is to compare the clinical and financial efficacy of this strategy between different commercial tests in a large cohort of unselected patients.

METHODS

In all consecutive 1030 patients associations were defined between results from different ANA test systems and the pre-test probability for connective tissue disease (CTDs). Test systems were used for screening (ANA-IIF vs. CTD screen) and definition of their fine specificity (profile 3 line blot vs. CTD single analytes).

RESULTS

Positive ANA-IIF and/or CTD screen results were found in 304 sera. Further analysis for ANA-specificity by profile 3 line blot and CTD single analytes showed 86 discrepant results of which more than a third are clinically relevant, with the CTD single analyte assay performing better than the line blot in supporting or confirming the presence of a CTD. Autoantigens present in one test but absent in the other were of minor practical use. The ANA screening and identification strategies currently employed are not cost-effective as 83% of tests were performed in order to find specific autoantibodies in patients without the fitting clinical signs or symptoms. This causes many unexpected positive results and subsequent confusion with regard to interpretation.

CONCLUSIONS

We advocate that some autoantigens should be excluded from the line blot and CTD assays and propose the use of a cost-effective and selective ANA specificity testing purely based on clinical guidance.

Primary human keratinocytes as targets in predicting acute graft-versus-host disease following HLA-identical bone marrow transplantation

Graft-versus-host-disease (GVHD) remains a major problem following allogeneic bone marrow transplantation (BMT) and manifests itself mainly by damage to epithelial cells of the skin, gut and bile ducts. Reliable tests to predict GVHD are lacking. We developed an assay in which donor T cells are stimulated by patient keratinocytes (KCs), compared that with stimulation by patient peripheral blood mononuclear cells (PBMCs) and studied the relationship to GVHD. In 27 patients undergoing HLA-identical BMT for haematological malignancies, donor T-cell reactivity was determined as the helper T-lymphocyte precursor (HTLp) frequency against host PBMCs (25 patient-donor pairs) and host KCs (20 patient-donor pairs). KCs were obtained by shave biopsies and cultured with interferon (IFN)-gamma to induce HLA class II expression. In assays using patient KCs and donor T cells, anti-CD28 antibody was added to compensate for the lack of co-stimulatory molecules on KCs. Results were related to the occurrence of GVHD. As BMTs were performed with partially T cell-depleted grafts, GVHD was limited to grade 0 (five patients), grade I (seven patients) and grade II (12 patients). No differences were found in donor T-cell reactivity to patient PBMCs, as expressed as HTLp frequency in patients with or without GVHD. However, significant differences (P < 0.01) were found in donor T-cell reactivity to patient KCs when comparing patients with and without GVHD. Donor HTLp frequencies against patient KCs give a better prediction of GVHD than those against patient haemopoietic cells following HLA-identical BMT, which may indicate that at least some minor non-HLA histocompatibility antigens present on KCs are different from those on haemopoietic cells.

Comparison of Two Strategies to Generate Antigen-Specific Human Monoclonal Antibodies: Which Method to Choose for Which Purpose?

Human monoclonal antibodies (mAbs) are valuable tools to link genetic information with functional features and to provide a platform for conformational epitope mapping. Additionally, combined data on genetic and functional features provide a valuable mosaic for systems immunology approaches. Strategies to generate human mAbs from peripheral blood have been described and used in several studies including single cell sequencing of antigen-binding B cells and the establishment of antigen-specific monoclonal Epstein-Barr Virus (EBV) immortalized lymphoblastoid cell lines (LCLs). However, direct comparisons of these two strategies are scarce. Hence, we sought to set up these two strategies in our laboratory using peanut 2S albumins (allergens) and the autoantigen anti-Rho guanosine diphosphate dissociation inhibitor 2 (RhoGDI2, alternatively 'ARHGDIB') as antigen targets to directly compare these strategies regarding costs, time expenditure, recovery, throughput and complexity. Regarding single cell sequencing, up to 50% of corresponding V(D)J gene transcripts were successfully amplified of which 54% were successfully cloned into expression vectors used for heterologous expression. Seventy-five percent of heterologously expressed mAbs showed specific binding to peanut 2S albumins resulting in an overall recovery of 20.3%, which may be increased to around 29% by ordering gene sequences commercially for antibody cloning. In comparison, the establishment of monoclonal EBV-LCLs showed a lower overall recovery of around 17.6%. Heterologous expression of a mAb carrying the same variable region as its native counterpart showed comparable concentration-dependent binding abilities. By directly comparing those two strategies, single cell sequencing allows a broad examination of antigen-binding mAbs in a moderate-throughput manner, while the establishment of monoclonal EBV-LCLs is a powerful tool to select a small number of highly reactive mAbs restricted to certain B cell subpopulations. Overall, both strategies, initially set-up for peanut 2S albumins, are suitable to obtain human mAbs and they are easily transferrable to other target antigens as shown for ARHGDIB.

Using established biorepositories for emerging research questions: a feasibility study

BACKGROUND

Proteomics and metabolomics offer substantial potential for advancing kidney transplant research by providing versatile opportunities for gaining insights into the biomolecular processes occurring in donors, recipients, and grafts. To achieve this, adequate quality and numbers of biological samples are required. Whilst access to donor samples is facilitated by initiatives such as the QUOD biobank, an adequately powered biobank allowing exploration of recipient-related aspects in long-term transplant outcomes is missing. Rich, yet unverified resources of recipient material are the serum repositories present in the immunological laboratories of kidney transplant centers that prospectively collect recipient sera for immunological monitoring. However, it is yet unsure whether these samples are also suitable for -omics applications, since such clinical samples are collected and stored by individual centers using non-uniform protocols and undergo an undocumented number of freeze-thaw cycles. Whilst these handling and storage aspects may affect individual proteins and metabolites, it was reasoned that incidental handling/storage artifacts will have a limited effect on a theoretical network (pathway) analysis. To test the potential of such long-term stored clinical serum samples for pathway profiling, we submitted these samples to discovery proteomics and metabolomics.

METHODS

A mass spectrometry-based shotgun discovery approach was used to obtain an overview of proteins and metabolites in clinical serum samples from the immunological laboratories of the Dutch PROCARE consortium. Parallel analyses were performed with material from the strictly protocolized QUOD biobank.

RESULTS

Following metabolomics, more than 800 compounds could be identified in both sample groups, of which 163 endogenous metabolites were found in samples from both biorepositories. Proteomics yielded more than 600 proteins in both groups. Despite the higher prevalence of fragments in the clinical, non-uniformly collected samples compared to the biobanked ones (42.5% vs 26.5% of their proteomes, respectively), these fragments could still be connected to their parent proteins. Next, the proteomic and metabolomic profiles were successfully mapped onto theoretical pathways through integrated pathway analysis, which showed significant enrichment of 79 pathways.

CONCLUSIONS

This feasibility study demonstrated that long-term stored serum samples from clinical biorepositories can be used for qualitative proteomic and metabolomic pathway analysis, a notion with far-reaching implications for all biomedical, long-term outcome-dependent research questions and studies focusing on rare events.

Ellipro scores of donor epitope specific HLA antibodies are not associated with kidney graft survival

In kidney transplantation, donor HLA antibodies are a risk factor for graft loss. Accessibility of donor eplets for HLA antibodies is predicted by the ElliPro score. The clinical usefulness of those scores in relation to transplant outcome is unknown. In a large Dutch kidney transplant cohort, Ellipro scores of pretransplant donor antibodies that can be assigned to known eplets (donor epitope specific HLA antibodies [DESAs]) were compared between early graft failure and long surviving deceased donor transplants. We did not observe a significant Ellipro score difference between the two cohorts, nor significant differences in graft survival between transplants with DESAs having high versus low total Ellipro scores. We conclude that Ellipro scores cannot be used to identify DESAs associated with early versus late kidney graft loss in deceased donor transplants.

Autoimmune Encephalitis and Paraneoplastic Neurologic Syndromes: A Nationwide Study on Epidemiology and Antibody Testing Performance

BACKGROUND AND OBJECTIVES

Autoimmune encephalitis (AIE) and paraneoplastic neurologic syndromes (PNSs) encompass a heterogeneous group of antibody-associated disorders. Both the number of syndromes and commercially available antibody tests have increased considerably over the past decade. High-quality population-based data on epidemiology of these disorders and real-world performance of antibody tests are needed.

METHODS

In this nationwide retrospective cohort study, we identified all serum and CSF samples tested for antibodies against intracellular antigens (IAs: Hu [ANNA1], Yo [PCA1], CV2 [CRMP5], Ri [ANNA2], Ma1, Ma2 [Ta], amphiphysin, GAD65, GFAP, KLHL11, CARP VIII) or extracellular antigens (EAs: NMDAR, LGI1, Caspr2, GABA-B-R, GABA-A-R, AMPAR, DPPX, GlyR, mGluR1, VGCC, IgLON5, Tr [DNER]) between January 2016 and December 2021 in the Netherlands. Nationwide coverage was guaranteed for all antibodies except anti-GAD65 and anti-VGCC. We calculated sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV); obtained clinical information about patients who tested positive; assigned diagnosis of AIE/PNS according to diagnostic criteria; and calculated incidence rates for IA, EA, and individual antibody-associated syndromes.

RESULTS

In the study period, 2,877 (9.5%) of 30,246 samples, belonging to 1,228 patients, tested positive. Sensitivity and specificity were high (>95%) to very high (>99%) for most tests in both serum and CSF. PPVs for several tests were moderate to poor, especially for serum testing of IA antibodies (25%-80%). Clinical data were available for 940 (76.5%) of 1,228 patients. A total of 578 AIE/PNS diagnoses were made. The incidence rate for AIE/PNS (per million person-years) increased from 4.70 (95% CI 3.72-5.85) in 2016 to 5.76 (4.69-7.00) in 2021. Overall, the incidence rate was 5.57 (5.13-6.05), 2.96 (2.64-3.31) for the EA and 2.61 (2.31-2.94) for the IA subgroup. The 4 most common AIE/PNS types were anti-NMDAR, anti-LGI1, anti-Hu, and anti-GAD65, together comprising almost two-thirds of all diagnoses (364/578, 63.0%).

DISCUSSION

Most commercial antibody tests perform well overall, but important pitfalls remain. Although almost all tests had high specificity, PPV was only modest in the setting of these rare diseases and mass testing. We observe trends toward increasing incidence of antibody-associated AIE/PNS.

Association of autoantibodies with the IFN signature and NETosis in patients with systemic lupus erythematosus

Objective

Systemic lupus erythematosus (SLE) is an autoimmune disease characterized by a variety of disease symptoms and an unpredictable clinical course. To improve treatment outcome, stratification based on immunological manifestations commonly seen in patients with SLE such as autoantibodies, type I interferon (IFN) signature and neutrophil extracellular trap (NET) release may help. It is assumed that there is an association between these immunological phenomena, since NET release induces IFN production and IFN induces autoantibody formation via B-cell activation. Here we studied the association between autoantibodies, the IFN signature, NET release, and clinical manifestations in patients with SLE.

Methods

We performed principal component analysis (PCA) and hierarchical clustering of 57 SLE-related autoantibodies in 25 patients with SLE. We correlated each autoantibody to the IFN signature and NET inducing capacity.

Results

We observed two distinct clusters: one cluster contained mostly patients with a high IFN signature. Patients in this cluster often present with cutaneous lupus, and have higher anti-dsDNA concentrations. Another cluster contained a mix of patients with a high and low IFN signature. Patients with high and low NET inducing capacity were equally distributed between the clusters. Variance between the clusters is mainly driven by antibodies against histones, RibP2, RibP0, EphB2, RibP1, PCNA, dsDNA, and nucleosome. In addition, we found a trend towards increased concentrations of autoantibodies against EphB2, RibP1, and RNP70 in patients with an IFN signature. We found a negative correlation of NET inducing capacity with anti-FcER (r = -0.530; p = 0.007) and anti-PmScl100 (r = -0.445; p = 0.03).

Conclusion

We identified a subgroup of patients with an IFN signature that express increased concentrations of antibodies against DNA and RNA-binding proteins, which can be useful for further patient stratification and a more targeted therapy. We did not find positive associations between autoantibodies and NET inducing capacity. Our study further strengthens the evidence of a correlation between RNA-binding autoantibodies and the IFN signature.

Clinical application of the polymerase chain reaction in the detection of HLA-B27 alleles

Most patients with ankylosing spondylitis (AS) express HLA-B27 antigens, which in routine clinical practice are conventionally detected by serological assays. Recent reports have been published demonstrating that HLA-B27 can also be detected by the polymerase chain reaction (PCR), with the purported advantages that the latter is faster, cheaper and more reliable than serological detection. In this study the technical reliability of HLA-B27 detection by PCR was demonstrated by the successful amplification of all the defined types of HLA-B27 alleles, while relevant non-HLA-B27 alleles could not be amplified. We have compared the sensitivity, specificity and practical applicability of HLA-B27 typing by serology versus PCR. HLA-B27 typing of 100 random individuals yielded identical results between serology and PCR, indicating that the sensitivity and specificity of serology and PCR are equal. Therefore, PCR with its practical advantages, may be considered the technique of choice for detecting HLA-B27 antigens.

A 21-bp deletion in the complement regulator CD55 promotor region is associated with multifocal motor neuropathy and its disease course

BACKGROUND AND AIMS

To further substantiate the role of antibody-mediated complement activation in multifocal motor neuropathy (MMN) immunopathology, we investigated the distribution of promotor polymorphisms of genes encoding the membrane-bound complement regulators CD46, CD55, and CD59 in patients with MMN and controls, and evaluated their association with disease course.

METHODS

We used Sanger sequencing to genotype five common polymorphisms in the promotor regions of CD46, CD55, and CD59 in 133 patients with MMN and 380 controls. We correlated each polymorphism to clinical parameters.

RESULTS

The genotype frequencies of rs28371582, a 21-bp deletion in the CD55 promotor region, were altered in patients with MMN as compared to controls (p .009; Del/Del genotype 16.8% vs. 7.7%, p .005, odds ratio: 2.43 [1.27-4.58]), and patients carrying this deletion had a more favorable disease course (mean difference 0.26 Medical Research Council [MRC] points/year; 95% confidence interval [CI]: 0.040-0.490, p .019). The presence of CD59 rs141385724 was associated with less severe pre-diagnostic disease course (mean difference 0.940 MRC point/year; 95% CI: 0.083-1.80, p .032).

INTERPRETATION

MMN susceptibility is associated with a 21-bp deletion in the CD55 promotor region (rs2871582), which is associated with lower CD55 expression. Patients carrying this deletion may have a more favorable long-term disease outcome. Taken together, these results point out the relevance of the pre-C5 level of the complement cascade in the inflammatory processes underlying MMN.

Complement component C3 and C5b-9 deposition on hypoxia reperfused endothelial cells by non-HLA antibodies against RhoGDI2: A player involved in graft failure?

Antibodies against Rho GDP-dissociation inhibitor 2 (RhoGDI2) are associated with inferior graft survival in transplant patients receiving a kidney from deceased donors. Although this suggests that these antibodies contribute to graft injury because of ischemia, it remains unknown whether they are also pathogenically involved in the process of graft loss. To study this, we firstly analyzed the IgG subclass profile of anti-RhoGDI2 antibodies in kidney transplant recipients, and whether antibody titers change over time or because of acute rejection. Next, we investigated the expression of RhoGDI2 on primary kidney and lung endothelial cells (ECs) upon hypoxia reperfusion. In addition, the complement-fixing properties of anti-RhoGDI2 antibodies were studied using imaging flow cytometry. Anti-RhoGDI2 antibodies in patients are mainly IgG1, and titers remained stable and seemed not be changed because of rejection. Antibodies against RhoGDI2, which surface expression seemed to increase upon hypoxia reperfusion, co-localized with C3 on ECs. Binding of human IgG1 monoclonal anti-RhoGDI2 antibodies as well as patient derived antibodies, resulted in complement activation, suggesting that these antibodies are complement fixing. This study suggested a potential pathogenic role of anti-RhoGDI2 antibodies in kidney graft loss. During ischemia reperfusion, the ability of these antibodies to fix complement could be one of the mechanisms resulting in tissue injury.