Detection of G Protein-Coupled Receptor Autoantibodies in Postural Orthostatic Tachycardia Syndrome Using Standard Methodology (2022) Hall et al

M

Milo

Senior Member (Voting Rights)
Detection of G Protein-Coupled Receptor Autoantibodies in Postural Orthostatic Tachycardia Syndrome Using Standard Methodology

(the title is a bit misleading, read the whole abstract)
Main author is Dr Satish Raj from Calgary.

Abstract
Background: Postural orthostatic tachycardia syndrome (POTS) is a disorder of orthostatic intolerance that primarily affects women of childbearing age. The underlying pathophysiology of POTS is not fully understood, but it has been suggested that autoimmunity may play a role. The aim of this study was to compare concentrations of autoantibodies to cardiovascular G protein-coupled receptors between patients with POTS and healthy controls.

Methods: Sera were collected from 116 patients with POTS (91% female; mean age, 29 years) and 81 healthy controls (84% female; mean age, 27 years) from Calgary, Canada, and Malmö, Sweden. Samples were evaluated for autoantibodies to 11 receptors (adrenergic, muscarinic, angiotensin II, and endothelin) using a commercially available enzyme-linked immunosorbent assay.

Results: Autoantibody concentrations against all of the receptors tested were not significantly different between controls and patients with POTS. The majority of patients with POTS (98.3%) and all controls (100%) had α1 adrenergic receptor autoantibody concentrations above the seropositive threshold provided by the manufacturer (7 units/mL). The proportion of patients with POTS versus healthy controls who fell above the diagnostic thresholds was not different for any tested autoantibodies. Receiver operating characteristic curves showed a poor ability to discriminate between patients with POTS and controls.

Conclusion: Patients with POTS and healthy controls do not differ in their enzyme-linked immunosorbent assay-derived autoantibody concentrations to cardiovascular G protein-coupled receptors. These findings suggest that these tests are not useful for establishing the role of autoimmunity in POTS.

Abstract only here
 
Full open access text here
https://www.ahajournals.org/doi/epdf/10.1161/CIRCULATIONAHA.122.059971

This study has been planned for a number of years and was part funded by Dysautonomia International. In simple terms they wanted to find out if the CellTrend test was any good or not. Artur Fedorowski from Sweden and one of the authors of this paper gave a presentation about the work at the 2021 Dysautonomia International Conference and I noted the summary then.



I believe Dr Satish Raj, the other main author on this paper is very highly respected in the POTS research and patient community.

This supports the previous ME/CFS finding by Jonas Berquist et al that the CellTrend test for ME/CFS is no good for individual diagnostics, only perhaps interesting for group to group comparisons in a research setting.

Back in 2018, Berlin Cures published a paper showing ELISA with human antibodies (such as CellTrend) was not a good test in comparison to animal antibodies.
Paper : Difference between beta1-adrenoceptor autoantibodies of human and animal origin-Limitations detecting beta1-adrenoceptor autoantibodies using peptide based ELISA technology
https://pubmed.ncbi.nlm.nih.gov/29425252/

Abstract

Cell-based analytics for the detection of the beta1-adrenoceptor autoantibody (beta1-AAB) are functional, yet difficult to handle, and should be replaced by easily applicable, routine lab methods. Endeavors to develop solid-phase-based assays such as ELISA to exploit epitope moieties for trapping autoantibodies are ongoing. These solid-phase-based assays, however, are often unreliable when used with human patient material, in contrast to animal derived autoantibodies.

We therefore tested an immunogen peptide-based ELISA for the detection of beta1-AAB, and compared commercially available goat antibodies against the 2nd extracellular loop of human beta1-adrenoceptor (ADRB1-AB) to autoantibodies enriched from patient material. The functionality of these autoantibodies was tested in a cell based assay for comparison and their structural appearance was investigated using 2D gel electrophoresis.

The ELISA showed a limit of detection for ADRB1-AB of about 1.5 nmol antibody/L when spiked in human control serum and only about 25 nmol/L when spiked in species identical (goat) matrix material. When applied to samples of human origin, the ELISA failed to identify the specific beta1-AABs. A low concentration of beta1-AAB, together with structural inconsistency of the patient originated samples as seen from the 2D Gel appearance, might contribute to the failure of the peptide based ELISA technology to detect human beta1-AABs.
Click to expand...
 
Fedorowski (one of the authors) flogged this for a while, when it became clearer that it wasn't a useful test someone (CellTrend?) put forward a grouping of CellTrend AAB results that still promised to be diagnostic and I recall him discussing plans to test that. This paper refers to analysis against AAB groupings that still do not show a diagnostic yield high enough to be clinically significant.

The paper references the importance of functional cell-based assays (to detect AAB activity - prior Raj work) but I thought there were also some promising alternative tests for more reliable detection too - I expect we'll get some updates on these at the Dysautonomia conference in July.
 
Is it logical to say then that autoantibodies for cell receptors in ME patients at Cell Trend is likely to be problematic as well? Does it invalidate the work published from Germany?
 
Milo said:
I will have to replay that, I could not watch any of the morning presentations because it was too darn early for my time zone.
Click to expand...
Please do add any comments on this and other talks on the forum threads about the conference. There was too much for those of us 'officially' reporting for S4ME to cover and anyway more perspectives will be welcome.
 
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