Improving laboratory diagnostics in myasthenia gravis

ABSTRACT

Introduction: Myasthenia gravis (MG) is a prototypical autoimmune disease, characterized by pathogenic autoantibodies targeting structures of the neuromuscular junction. Radioimmunoprecipitation assays (RIPAs) represent the gold standard for their detection. However, new methods are emerging to complement, or overcome RIPAs, also with the perspective of eliminating the use of radioactive reagents.

Areas covered: We discuss advances in laboratory methods, prompted especially by cell-based assays (CBAs), for the detection of the autoantibodies of MG diagnostics, above all those to the nicotinic acetylcholine receptor (AChR), muscle-specific kinase (MuSK), and low molecular-weight receptor-related low-density lipoprotein-4 (LRP4).

Expert opinion: CBA technology makes AChRs aggregate on cell membranes, thus allowing to detect autoantibodies to clustered AChRs, with reduction of seronegative MG cases. The diagnostic relevance of RIPA/CBA-measurable LRP4 antibodies is still unclear, in Caucasian patients at least. Live CBAs for the detection of AChR, MuSK, and LRP4 antibodies might represent an alternative to RIPAs, but first require full validation. CBAs could be used as screening tests, limiting RIPAs for antibody quantification. To this end, ELISAs might be an alternative.

Fixation procedures preserving enough degree of antigen conformationality could yield AChR and MuSK CBAs suitable for a wide use in clinical-chemistry laboratories

KEYWORDS:

• Autoantibody
• cell-based assay
• enzyme-linked immunosorbent assay
• laboratory diagnostics
• low molecular weight receptor related low-density lipoprotein 4
• muscle specific tyrosine kinase
• myasthenia gravis
• neuroimmunology
• nicotinic acetylcholine receptor
• radioimmunoprecipitation assay

Article highlights

• Laboratory diagnostics is fundamental for the recognition of different phenotypes of myasthenia gravis

• Live cell-based assays (CBAs), expressing AChR and MuSK in their native conformation, have advanced laboratory diagnostics of myasthenia gravis

• Antibodies to clustered AChRs can be detected with CBAs only

• CBAs are promising candidates for eliminating, or limiting the use of radioactive reagents required by the highly performing radioimmunoprecipitation assays

• ELISAs may be not so accurate as CBAs and radioimmunoprecipitation assays for conformational sensitive antibodies

Acknowledgments

The authors thank the anonymous peer reviewers for their insightful comments. The authors also thank Prof A. Vincent and D. Beeson for kindly providing the AChR plasmids used for the CBA showed in the pictures.

Declaration of interest

The author(s) have no relevant affiliations or financial involvement with any organization or entity with a financial interest in or financial conflict with the subject matter or materials discussed in the manuscript. This includes employment, consultancies, honoraria, stock ownership or options, expert testimony, grants or patents received or pending, or royalties.

Reviewer disclosures

Peer reviewers on this manuscript have no relevant financial or other relationships to disclose.

Additional information

Funding

The paper was supported by the Italian Ministry of Health under the grant ‘Progetto Z844A 5x1000ʹ to the IRCCS Ospedale Policlinico San Martino, and ‘Progetto RC20011C ricerca corrente’, Grant to the IRCCS Mondino Foundation.