WO2019077123A1 - Methods and kits for determining whether a subject has or is at risk of having of an autoimmune myopathy - Google Patents

Abstract

Autoimmune myopathy (AIM) represents a group of severe inflammatory diseases. Around 60% of patients with AIM have myositis-specific auto-antibodies (aAbs). Thus, the search for aAbs has substantially improved their diagnosis and may also inform on their prognosis, notably when there is an associated risk of cancer. Accordingly, the discovery of 10 new aAbs will help to improve the diagnosis of AIM. The present invention fulfils the need. In a cohort of 671 patients suffering from patients suffering from AIM, the inventors show that a minor percentage of them were positive for the present of MDH2 aAbs. No patient was found positive for this Ab in other autoimmune diseases. Accordingly, detection of anti-MDH2 aAbs would be suitable for the diagnosis of AIM.15

Description

METHODS AND KITS FOR DETERMINING WHETHER A SUBJECT HAS OR IS AT RISK OF HAVING OF AN AUTOIMMUNE MYOPATHY

FIELD OF THE INVENTION:

The present invention relates to methods and kits for determining whether a subject has or is at risk of having of an autoimmune myopathy.

BACKGROUND OF THE INVENTION:

Autoimmune myopathy (AIM) represents a group of severe inflammatory diseases. Originally AIM was classified into two major groups based on clinical, electromyographical, and immunohisto logical features: polymyositis (PM) and dermatomyositis (DM), the latter associating skin manifestations to muscle weakness {Bohan A, Peter JB. Polymyositis and dermatomyositis (first of two parts). N Engl J Med (1975) 292:344-7.10.1056). Sporadic inclusion-body myositis (sIBM), resistant to steroids and associating both autoimmune and degenerative components, was individualized recently (Griggs RC, Askanas V, DiMauro S, Engel A, Karpati G, Mendell JR, et al. Inclusion body myositis and myopathies. Ann Neurol (1995) 38:705-13.10.1002). When defined according to the Bohan and Peter classification, PM was initially considered as the archetype of AIM, although it seems to be an uncommon pathological entity, some experts even arguing that it barely exists. Indeed, according to newer, more stringent criteria, most AIM initially diagnosed as PM were reclassified as overlap myositis (OM), a condition with not only musculoskeletal but also extramuscular involvement and/or association to autoantibodies (aAbs) (Troyanov Y, TargoffIN, Tremblay JL, GouletJR, Raymond Y, Senecal JL. Novel classification of idiopathic inflammatory myopathies based on overlap syndrome features and autoantibodies: analysis of 100 French Canadian patients. Medicine (Baltimore) (2005) 84:231-49.10.1097). Now OM and DM are the more frequent AIM. Around 60% of patients with AIM have myositis-specific auto-antibodies (aAbs) (Mammen AL. Autoimmune myopathies: autoantibodies, phenotypes and pathogenesis. Nat Rev Neurol(2011) 7:343-54.10.1038), and it is presumable that this frequency will reach higher levels when appropriate diagnostic immunoassays are more widely used and new specificities are discovered. Thus, the search for aAbs has substantially improved their diagnosis and may also inform on their prognosis, notably when there is an associated risk of cancer. Accordingly, the discovery of new aAbs will help to improve the diagnosis of AIM.

SUMMARY OF THE INVENTION: The present invention relates to methods and kits for determining whether a subject has or is at risk of having of an autoimmune myopathy. In particular, the present invention is defined by the claims.

DETAILED DESCRIPTION OF THE INVENTION:

The first object of the present invention relates to a method of determining whether a subject has or is at risk of having of an autoimmune myopathy (AIM) comprising detecting the presence or absence of anti-MDH2 immunoglobulins (Igs) in a blood sample obtained from the subject wherein the presence of anti-MDH2 immunoglobulins (Igs) indicates that the subject has or is at risk of having an autoimmune myopathy.

In some embodiments, the method of the present invention comprises i) determining the level of anti-MDH2 immunoglobulins (Igs) in a blood sample obtained from the subject ii) comparing the level determined at step i) with a predetermined reference value and iii) concluding that the subject has or is at risk of having an autoimmune myopathy when the level determined at step i) is higher than the predetermined reference value.

As used herein the term "autoimmune myopathy", "myositis" or "AIM" has its general meaning in the art and represents a group of severe diseases that involve chronic muscle inflammation, accompanied by muscle weakness. Types of AIM include, but are not limited to idiopathic inflammatory myopathies, dermatomyositis, juvenile dermatomyositis, polymyositis, overlap myositis, immune-mediated necrotising myopathies, and inclusion body myositis.

As used herein, the term "risk" in the context of the present invention, relates to the probability that an event will occur over a specific time period and can mean a subject's "absolute" risk or "relative" risk. Absolute risk can be measured with reference to either actual observation post-measurement for the relevant time cohort, or with reference to index values developed from statistically valid historical cohorts that have been followed for the relevant time period. Relative risk refers to the ratio of absolute risks of a subject compared either to the absolute risks of low risk cohorts or an average population risk, which can vary by how clinical risk factors are assessed. Odds ratios, the proportion of positive events to negative events for a given test result, are also commonly used (odds are according to the formula p/(l-p) where p is the probability of event and (1- p) is the probability of no event) to no- conversion. "Risk evaluation," or "evaluation of risk" in the context of the present invention encompasses making a prediction of the probability, odds, or likelihood that an event or disease state may occur, the rate of occurrence of the event or conversion from one disease state to another. Risk evaluation can also comprise prediction of future clinical parameters, traditional laboratory risk factor values, or other indices of relapse, either in absolute or relative terms in reference to a previously measured population. The methods of the present invention may be used to make continuous or categorical measurements of the risk of conversion, thus diagnosing and defining the risk spectrum of a category of subjects defined as being at risk of conversion. In the categorical scenario, the invention can be used to discriminate between normal and other subject cohorts at higher risk. In some embodiments, the present invention may be used so as to discriminate those at risk from normal.

In some embodiments, the method of diagnosing described herein is applied to a subject who presents symptoms of AIM without having undergone the routine screening to rule out all possible causes for AIM. The methods described herein can be part of the routine set of tests performed on a subject who presents symptoms of AIM such as muscle weakness typically in the proximal muscles, fatigue after walking or standing, tripping or falling, and difficulty swallowing or breathing. Some individuals may have slight muscle pain or muscles that are tender to touch. The subject may also have elevated levels of various muscle enzymes. The method of the present invention can be carried out in addition of other diagnostic tools that include electromyography to record the electrical activity that controls muscles during contraction and at rest, ultrasound to look for muscle inflammation, and magnetic resonance imaging to reveal abnormal muscle and evaluate muscle disease. A muscle biopsy can be examined by microscopy for signs of chronic inflammation, mononuclear cell infiltrates, muscle fiber death, muscle regeneration, vascular changes, deposition of complement, or the changes specific to the diagnosis of IBM.

As used herein the term "blood sample" means any blood sample derived from the subject. Collections of blood samples can be performed by methods well known to those skilled in the art. In some embodiments, the blood sample is a serum sample or a plasma sample.

As used herein the term "MDH2" has its general meaning in the art and refers to the malate dehydrogenase 2 encoded by the MDH2 gene (gene ID: 4191). The term is also known as MDH; MORI ; M-MDH; EIEE51 ; and MGC :3559. A human exemplary amino acid sequence is represented by the NCBI reference sequence NP 005909.2 (SEQ ID NO: 1).

SEQ ID NO: l

1 mlsalarpas aalrrsfsts aqnnakvavl gasggigqpl slllknsplv srltlydiah

61 tpgvaadlsh ietkaavkgy lgpeqlpdcl kgcdv vipa gvprkpgmtr ddlfntnati 121 vatltaacaq hcpeamicvi anpvnstipi taevfkkhgv ynpnkifgvt tldivrantf 181 vaelkgldpa rvnvpviggh agktiiplis qctpkvdfpq dqltaltgri qeagte vka 241 kagagsatls mayagarfvf slvdamngke g vecsfvks qetectyfst plllgkkgie 301 knlgigkvss feekmisdai pelkasikkg edfvktlk As used herein, the term "immunoglobulins" or "Igs" has its general meaning in the art and relates to proteins of the immunoglobulin superfamily. The immunoglobulins are characterized by a structural domain, i.e., the immunoglobulin domain, having a characteristic immunoglobulin (Ig) fold. The term encompasses secretory immunoglobulins. Immunoglobulins generally comprise several chains, typically two identical heavy chains and two identical light chains which are linked via disulfide bonds. These chains are primarily composed of immunoglobulin domains, including the VL domain (light chain variable domain), the CL domain (light chain constant domain), the VH domain (heavy chain variable domain) and the CH domains (heavy chain constant domains) CHI, optionally a hinge region, CH2, CH3, and optionally CH4. There are five main heavy chain classes (or iso types) which determine the functional activity of an antibody molecule: mu (μ) for IgM, delta (δ) for IgD, gamma (γ) for IgG, alpha (a) for IgA and epsilon (ε) for IgE. In the context of the invention, the immunoglobulin may be an IgM, IgD, IgG, IgA or IgE. Preferably, the immunoglobulin is an IgG. As well-known from the skilled person, the IgG isotype encompasses four subclasses: the subclasses IgGl, lgG2, lgG3 and lgG4. In the context of the invention, the immunoglobulin may be of any IgG subclass. Preferably, the immunoglobulin is an IgGl

As use herein the term "anti-MDH2 Ig" refers to the immunoglobulin (i.e. antibodies) which are produced by the immune system of the subject and that are directed against subject's MDH2 own protein. The term thus include "autoantibodies" or "aAbs".

A further object of the present invention relates to a method of predicting the risk of relapse in a subject suffering from AIM i) comprising determining the level of blood anti- MDH2 Igs in a blood sample obtained from the subject ii) comparing the level determined at step i) with a predetermined reference value and iii) concluding that the subject is at risk of relapse when the level determined at step i) is higher than the predetermined reference value.

As used herein, the term "relapse" refers to the return of signs and symptoms of a disease after a subject has enjoyed a remission after a treatment. Thus, if initially the target disease is alleviated or healed, or progression of the disease was halted or slowed down, and subsequently the disease or one or more characteristics of the disease resume (e.g. muscle weakness), the subject is referred to as being "relapsed." Typically, the treatment is an immunosuppressive treatment.

Typically, the predetermined reference value is a threshold value or a cut-off value. Typically, a "threshold value" or "cut-off value" can be determined experimentally, empirically, or theoretically. A threshold value can also be arbitrarily selected based upon the existing experimental and/or clinical conditions, as would be recognized by a person of ordinary skilled in the art. For example, retrospective measurement in properly banked historical subject samples may be used in establishing the predetermined reference value. The threshold value has to be determined in order to obtain the optimal sensitivity and specificity according to the function of the test and the benefit/risk balance (clinical consequences of false positive and false negative). Typically, the optimal sensitivity and specificity (and so the threshold value) can be determined using a Receiver Operating Characteristic (ROC) curve based on experimental data. For example, after determining the expression level of the selected peptide in a group of reference, one can use algorithmic analysis for the statistic treatment of the expression levels determined in samples to be tested, and thus obtain a classification standard having significance for sample classification. The full name of ROC curve is receiver operator characteristic curve, which is also known as receiver operation characteristic curve. It is mainly used for clinical biochemical diagnostic tests. ROC curve is a comprehensive indicator that reflects the continuous variables of true positive rate (sensitivity) and false positive rate (1- specificity). It reveals the relationship between sensitivity and specificity with the image composition method. A series of different cut-off values (thresholds or critical values, boundary values between normal and abnormal results of diagnostic test) are set as continuous variables to calculate a series of sensitivity and specificity values. Then sensitivity is used as the vertical coordinate and specificity is used as the horizontal coordinate to draw a curve. The higher the area under the curve (AUC), the higher the accuracy of diagnosis. On the ROC curve, the point closest to the far upper left of the coordinate diagram is a critical point having both high sensitivity and high specificity values. The AUC value of the ROC curve is between 1.0 and 0.5. When AUC>0.5, the diagnostic result gets better and better as AUC approaches 1. When AUC is between 0.5 and 0.7, the accuracy is low. When AUC is between 0.7 and 0.9, the accuracy is moderate. When AUC is higher than 0.9, the accuracy is high. This algorithmic method is preferably done with a computer. Existing software or systems in the art may be used for the drawing of the ROC curve, such as: MedCalc 9.2.0.1 medical statistical software, SPSS 9.0, ROCPO WER. S AS , DESIGNROC.FOR, MULTIREADER POWER.SAS, CREATE- ROC.SAS, GB STAT VIO.O (Dynamic Microsystems, Inc. Silver Spring, Md., USA), etc.

In some embodiments, the predetermined reference value is the level of blood anti- MDH2 Ig determined in a population of healthy individuals. Typically, it is concluded that the patient suffers from AIM or is at risk of relapse when the level of blood anti-MDH2 Ig is at least 0.5, 1, 1.5, 2, 2.5, 3, 3.5, 4, 5, 6, 7, 8, 9, 10, 15, 20, 30, 40, 50, 100 fold higher than the level determined in a population of healthy individuals. A further object of the present invention relates to a method of determining whether the subject achieves a response with a treatment comprising i) determining the level of blood anti- MDH2 Ig in a blood sample obtained from the subject before the treatment ii) determining the level of blood anti-MDH2 Ig in a blood sample obtained from the subject before the treatment, iii) comparing the level determined at step i) with the level determined at step ii) and iv) concluding that the subject achieves a response when the level determined at step ii) lower higher than the level determined at step i).

The method is thus particularly suitable for discriminating responder from non- responder. As used herein the term "responder" in the context of the present disclosure refers to a subject that will achieve a response, i.e. a subject who is under remission and more particularly a subject who does not suffer from muscle weakness. A non-responder subject includes subjects for whom the disease does not show reduction or improvement after the treatment (e.g. the muscle weakness remains stable or increases). According to the present invention, the treatment consists in any method or drug that could be suitable for the treatment of AIM. For instance, the treatment consists in an antibody depleting strategy, which typically include plasma exchange, plasmapheresis or immunoadsorption. In some embodiments, the treatment consists in administering immunoglobulins (e.g. by intravenous route). In some embodiments, the treatment consists in cell therapy or gene therapy. In some embodiments, the treatment consists in administering a drug selected from the group of Jak inhibitors (e.g. ruxolitnib), anti-oxidant drugs, and inhibitors of complement.

In some embodiments, the treatment is an immunosuppressive treatment. As used herein, the term "immunosuppressive treatment" refers to any substance capable of producing an immunosuppressive effect, e.g., the prevention or diminution of the immune response and in particular the prevention or diminution of the production of Ig. Immunosuppressive drugs include, without limitation thiopurine drugs such as azathioprine (AZA) and metabolites thereof; nucleoside triphosphate inhibitors such as mycophenolic acid (Cellcept) and its derivative (Myfortic); derivatives thereof; prodrugs thereof; and combinations thereof. Other examples include but are not limited to 6-mercaptopurine ("6-MP"), cyclophosphamide, mycophenolate, prednisolone, sirolimus, dexamethasone, rapamycin, FK506, mizoribine, azothioprine and tacrolimus.

In some embodiments the immunosuppressive drug is a calcineurin inhibitor. As used herein, the term "calcineurin inhibitor" has its general meaning in the art and refers to substances which block calcineurin (i.e. calcium/calmodulin-regulated protein phosphatase involved in intracellular signalling) dephosphorylation of appropriate substrates, by targeting calcineurin phosphatase (PP2B, PP3), a cellular enzyme that is involved in gene regulation. A calcineurin inhibitor of the present invention is typically an immunophilin-binding compound having calcineurin inhibitory activity. Immunophilin-binding calcineurin inhibitors are compounds forming calcineurin inhibiting complexes with immunophilins, e.g. cyclophilin and macrophilin. Examples of cyclophilin-binding calcineurin inhibitors are cyclosporines or cyclosporine derivatives (hereinafter cyclosporines) and examples of macrophilin-binding calcineurin inhibitors are ascomycin (FR 520) and ascomycin derivatives (hereinafter ascomycins). A wide range of ascomycin derivatives are known, which either are naturally occurring among fungal species or are obtainable by manipulation of fermentation procedures or by chemical derivatization. Ascomycin-type macro lides include ascomycin, tacrolimus (FK506), sirolimus and pimecrolimus. Cyclosporine, originally extracted from the soil fungus Potypaciadium infilatum, has a cyclic 11 -amino acid structure and includes e.g. Cyclosporines A through I, such as Cyclosporine A, B, C, D and G. Voclosporin is a next-generation calcineurin inhibitor that is a more potent and less toxic semi-synthetic derivative of cyclosporine A. In some embodiments, the calcineurin inhibitor of the present invention is the trans-version of voclosporin, trans-ISA247 (Cas number 368455-04-3) which is described in, for example, US Patent Publication No.: 2006/0217309, which is hereby incorporated herein by reference. Further compositions of voclosporin are described, for example, in U.S. Pat. No. 7,060,672, which is hereby incorporated herein by reference. Tacrolimus (FK506) is another calcineurin inhibitor which is also a fungal product, but has a macrolide lactone structure. Sirolimus (rapamycin) is a microbial product isolated from the actinomycete Streptomyces hygroscopicus. Sirolimus binds to an immunophilin (FK-binding protein 12, FKBP12) forming a complex, which inhibits the mammalian target of rapamycin (mTOR) pathway through directly binding the mTOR Complex 1 (mTORCl). Pimecrolimus is also a calcineurin inhibitor. Calcineurin inhibitors such as cyclosporine A, voclosporin, ascomycin, tacrolimus, pimecrolimus, an analog thereof, or a pharmaceutically acceptable salt thereof, can be utilized in a mixed micellar composition of the present disclosure.

In some embodiments, the immunosuppressive drug is a corticosteroid. As used, the term "corticosteroids" has its general meaning in the art and refers to class of active ingredients having a hydrogenated cyclopentoperhydrophenanthrene ring system endowed with an antiinflammatory activity. Corticosteroid drugs typically include cortisone, Cortisol, hydrocortisone (l ip,17-dihydroxy, 21-(phosphonooxy)-pregn-4-ene, 3,20-dione disodium), dihydroxycortisone, dexamethasone (21 -(acetyloxy)-9-fluoro- 1 β, 17-dihydroxy- 16a-m- ethylpregna-l,4-diene-3,20-dione), and highly derivatized steroid drugs such as beconase (beclomethasone dipropionate, which is 9-chloro-l 1-β, 17,21, trihydroxy-16P-methylpregna- 1,4 diene-3,20-dione 17,21 -dipropionate). Other examples of corticosteroids include flunisolide, prednisone, prednisolone, methylprednisolone, triamcinolone, deflazacort and betamethasone, corticosteroids, for example, cortisone, hydrocortisone, methylprednisolone, prednisone, prednisolone, betamethesone, beclomethasone dipropionate, budesonide, dexamethasone sodium phosphate, flunisolide, fluticasone propionate, triamcinolone acetonide, betamethasone, fluocinolone, fluocinonide, betamethasone dipropionate, betamethasone valerate, desonide, desoximetasone, fluocinolone, triamcinolone, triamcinolone acetonide, clobetasol propionate, and dexamethasone.

In some embodiments, the immunosuppressive drug is a B cell depleting agent. As used herein, the term "B cell depleting agent" refers to any agent that is capable of triggering lymphodepletion of B cells. In some embodiments, the B cell depleting agent is an antibody having specificity for CD20. Examples of antibodies having specificity for CD20 include: "C2B8" which is now called "Rituximab" ("RITUXAN®") (U.S. Pat. No. 5,736,137, expressly incorporated herein by reference), a chimaeric pan-B antibody targeting CD20; the yttrium- [90]-labeled 2B8 murine antibody designated "Y2B8" or "Ibritumomab Tiuxetan" ZEVALIN® (U.S. Pat. No. 5,736,137, expressly incorporated herein by reference), a murine IgGl kappa mAb covalently linked to MX-DTPA for chelating to yttrium- [90]; murine IgG2a "BI," also called "Tositumomab," optionally labeled with radioactive 1311 to generate the "1311-B1" antibody (iodine 131 tositumomab, BEXXAR™) (U.S. Pat. No. 5,595,721, expressly incorporated herein by reference); murine monoclonal antibody "1F5" (Press et al. Blood 69 (2):584-591 (1987) and variants thereof including "framework patched" or humanized 1F5 (WO03/002607, Leung, S.; ATCC deposit HB-96450); murine 2H7 and chimeric 2H7 antibody (U.S. Pat. No. 5,677,180, expressly incorporated herein by reference); humanized 2H7, also known as ocrelizumab (PRO-70769); Ofatumumab (Arzerra), a fully human IgGl against a novel epitope on CD20 huMax-CD20 (Genmab, Denmark; WO2004/035607 (U.S. Ser. No. 10/687,799, expressly incorporated herein by reference)); AME-133 (ocaratuzumab; Applied Molecular Evolution), a a fully- humanized and optimized IgGl mAb against CD20; A20 antibody or variants thereof such as chimeric or humanized A20 antibody (cA20, bA20, respectively) (U.S. Ser. No. 10/366,709, expressly incorporated herein by reference, Immunomedics); and monoclonal antibodies L27, G28-2, 93-1B3, B-CI or NU-B2 available from the International Leukocyte Typing Workshop (Valentine et al, In: Leukocyte Typing III (McMichael, Ed., p. 440, Oxford University Press (1987)). Further, suitable antibodies include e.g. antibody GAlOl (obinutuzumab), a third generation humanized anti-CD20-antibody of Biogen Idec/Genentech/Roche. Moreover, BLX-301 of Bio lex Therapeutics, a humanized anti CD20 with optimized glycosylation or Veltuzumab (hA20), a 2nd-generation humanized antibody specific for CD20 of Immunomedics or DXL625, derivatives of veltuzumab, such as the bispecific hexavalent antibodies of IBC Pharmaceuticals (Immunomedics) which are comprised of a divalent anti-CD20 IgG of veltuzumab and a pair of stabilized dimers of Fab derived from milatuzumab, an anti-CD20 mAb enhanced with InNexus' Dynamic Cross Linking technology, of Inexus Biotechnology both are humanized anti-CD20 antibodies are suitable. Further suitable antibodies are BM-ca (a humanized antibody specific for CD20 (Int J. Oncol. 2011 February; 38(2):335-44)), C2H7 (a chimeric antibody specific for CD20 (Mol Immunol. 2008 May; 45(10):2861-8)), PROD 1921 (a third generation antibody specific for CD20 developed by Genentech), Reditux (a biosimilar version of rituximab developed by Dr Reddy's), PBO-326 (a biosimilar version of rituximab developed by Probiomed), a biosimilar version of rituximab developed by Zenotech, TL-011 (a biosimilar version of rituximab developed by Teva), CMAB304 (a biosimilar version of rituximab developed by Shanghai CP Guojian), GP-2013 (a biosimilar version of rituximab developed by Sandoz (Novartis)), SAIT- 101 (a biosimilar version of rituximab developed by Samsung BioLogics), a biosimilar version of rituximab developed by Intas Biopharmaceuticals, CT-P10), a biosimilar version of rituximab developed by Celltrion), a biosimilar version of rituximab developed by Biocad, Ublituximab (LFB-R603, a transgenically produced mAb targeting CD20 developed by GTC Biotherapeutics (LFB Biotechnologies)), PF-05280586 (presumed to be a biosimilar version of rituximab developed by Pfizer), Lymphomun (Bi-20, a trifunctional anti-CD20 and anti-CD3 antibody, developed by Trion Pharma), a biosimilar version of rituximab developed by Natco Pharma, a biosimilar version of rituximab developed by iBio, a biosimilar version of rituximab developed by Gedeon Richter/Stada, a biosimilar version of rituximab developed by Curaxys, a biosimilar version of rituximab developed by Coherus Biosciences/Daiichi Sankyo, a biosimilar version of rituximab developed by BioXpress, BT-D004 (a biosimilar version of rituximab developed by Protheon), AP-052 (a biosimilar version of rituximab developed by Aprogen), a biosimilar version of ofatumumab developed by BioXpress, MG-1106 (a biosimilar version of rituximab developed by Green Cross), IBI-301 (a humanized monoclonal antibody against CD20 developed by Innovent Biologies), BVX-20 (a humanized mAb against the CD20 developed by Vaccinex), 20-C2-2b (a bispecific mAb-IFNalpha that targets CD20 and human leukocyte antigen-DR (HLA-DR) developed by Immunomedics), MEDI-552 (developed by Medlmmune/AstraZeneca), the anti-CD20/streptavidin conjugates developed by NeoRx (now Poniard Pharmaceuticals), the 2nd generation anti-CD20 human antibodies developed by Favrille (now MMRGlobal), TRU-015, an antibody specific for CD20 fragment developed by Trubion/Emergent BioSolutions, as well as other precloinical approaches by various companies and entities. All aforementioned publications, references, patents and patent applications are incorporated by reference in their entireties. All antibodies disclosed in therein may be used within the present invention.

A decrease in the level after the treatment compared to the level before the treatment of at least 5%, at least 10%, at least 20%, at least 30%, at least 40%, at least 50%, at least 60%, at least 70%), at least 80%>, at least 90%>, 100% typically indicated that the subject achieves a response. More preferably a level which returns to the basal level (i.e. the level determined in a population of healthy individuals) indicates that the subject has achieved a response.

The detection and quantification of anti-MDH2 Igs in the blood sample can be detected by any method known in the art.

Typically the detection and quantification is performed by Enzyme-linked immunosorbent assay, also called ELISA, enzyme immunoassay or EIA, is a biochemical technique used mainly in immunology to detect the presence of an antibody or an antigen in a sample. A known amount of antigen (MDH2) is immobilized on a solid support (e.g. a polystyrene micro titer plate) either non-specifically (via adsorption to the surface) or specifically (via capture by another antibody specific to the same antigen, in a "sandwich" ELISA). Then the sample, suspected of containing anti-MDH2 Ig, is washed over the surface so that the auto-antibodies can bind to the immobilized antigen. The surface is washed to remove any unbound protein and a detection antibody is applied to the surface. The detection antibody should be an anti-human Ig antibody. The detection antibody can be covalently linked to an enzyme, or can itself be detected by a secondary antibody which is linked to an enzyme through bio-conjugation. Enzymes which can be used to detectably label the antibodies of the present invention include, but are not limited to, malate dehydrogenase, staphylococcal nuclease, delta- V- steroid isomerase, yeast alcohol dehydrogenase, alpha-glycerophosphate dehydrogenase, triose phosphate isomerase, horseradish peroxidase, alkaline phosphatase, asparaginase, glucose oxidase, beta-galactosidase, ribonuclease, urease, catalase, glucose- VI- phosphate dehydrogenase, glucoamylase and acetylcholinesterase. Between each step the plate is typically washed with a mild detergent solution to remove any proteins or antibodies that are not specifically bound. After the final wash step the plate is developed by adding an enzymatic substrate to produce a visible signal, which indicates the quantity of antigen in the sample. In some embodiments, a competitive ELISA is used. Purified anti-MDH2 antibodies that are not derived from the subject are coated on the solid phase of multi- wells. Serum sample recombined MDH2, (the antigen) or fragments thereof and horseradish peroxidase labeled with anti- MDH2 antibodies (conjugated) are added to coated wells, and form competitive combination. After incubation, if the auto-antibody level against MDH2 content is high in the sample, a complex of MDH2-auto-antibodies-anti-MDH2 labelled with HRP will form. Wash wells will remove the complex, and incubate with TMB (3, 3', 5, 5'- tetramethylbenzidene) color development substrate for localization of horseradish peroxidase- conjugated antibodies in the wells. Subsequently there will be no color change or little color change. If there are no auto-anti-MDH2 Ig in the serum sample, there will be much color change. Such a competitive ELSA test is specific, sensitive, reproducible and easy to operate. In some embodiments, the detection antibody is labelled with a fluorescent compound. When the fluorescently labelled antibody is exposed to light of the proper wavelength, its presence can then be detected due to fluorescence. Among the most commonly used fluorescent labelling compounds are CY dyes, fluorescein isothiocyanate, rhodamine, phycoerytherin, phycocyanin, allophycocyanin, o- phthaldehyde and fluorescamine. Other fluorophores known to those skilled in the art can also be used, for example those available from Life Technologies (Invitrogen; Molecular Probes (Eugene, Oreg.)) and including the ALEXA FLUOR® series of dyes (for example, as described in U.S. Pat. Nos. 5,696,157, 6, 130, 101 and 6,716,979), the BODIPY series of dyes (dipyrrometheneboron difluoride dyes, for example as described in U.S. Pat. Nos. 4,774,339, 5,187,288, 5,248,782, 5,274,113, 5,338,854, 5,451,663 and 5,433,896), Cascade Blue (an amine reactive derivative of the sulfonated pyrene described in U.S. Pat. No. 5,132,432) and Marina Blue (U.S. Pat. No. 5,830,912). In some embodiments, the detection antibody can also be detectably labelled using fluorescence emitting metals such as ¹⁵²Eu, or others of the lanthanide series. These metals can be attached to the antibody using such metal chelating groups as diethylenetriaminepentaacetic acid (DTP A) or ethylenediaminetetraacetic acid (EDTA).

In some embodiments, the detection antibody is detectably labelled by coupling it to a chemiluminescent compound. The presence of the chemiluminescent-antibody is then determined by detecting the presence of luminescence that arises during the course of a chemical reaction. Examples of particularly useful chemiluminescent labeling compounds are luminol, luciferin, isoluminol, theromatic acridinium ester, imidazole, acridinium salt and oxalate ester. In some embodiments, an automated assay systems is used and include, e.g., the BIO-FLASH™, the BEST 2000™, the DS2™, the ELx50 WASHER, the ELx800 WASHER, the ELx800 READER, and the Autoblot S20™ (INOVA Diagnostics, Inc., San Diego, CA). In some embodiments, the immunoassays comprise beads coated with native or recombinant MDH2 protein as described. Commonly used are beads that are dyed to establish a unique identity. Detection is performed by flow cytometry. Autoantibody detection using multiplex technologies. Other types of bead- based immunoassays are well known in the art, e. g. laser bead immunoassays and related magnetic bead assays (Fritzler, Marvin J; Fritzler, Mark L, Expert Opinion on Medical Diagnostics, 2009, pp. 3: 81-89). In some embodiments, the method of the present invention involves the use of a multiplex technology. Multiplex technology is the collective term for a variety of techniques which can assess multiple antibody specificities simultaneously on small volumes of blood sample. The advantage of multiplex technology is that it is able to provide very rapid test times and very high throughput of samples. One such technique, is the addressable laser bead immunoassay (ALBIA), which is commercially available on Luminex™.based platforms. For instance, ALBIA is a semiquantitative homogenous fluorescence-based microparticle immunoassay that can be used for the simultaneous detection of several autoantibodies (e.g. up to 10 autoantibodies). Each antigen (e.g. MDH2, SRP (signal recognition particle), and HMGCR (3-hydroxy-3- methylglutaryl-coenzyme A reductase)) is covalently coupled to a set of distinct uniform size colour-coded microspheres. The blood sample is then incubated microspheres in a filter membrane bottomed microplate. The beads were washed and then incubated for 3an anti-human Ig conjugated to a fluorescent label (e.g. phycoerythrin). After washing again the beads were analysed on a system in which separate lasers identified antigen by bead colour and quantified the antibody by measuring the fluorescence of the fluorescent label. Said quantification thus indicated the level of the auto-antibodies.

In some embodiments, a dot blot, or a line blot is used to carry out the method of the present invention. In some embodiments, a test strip that has been coated with one or more band of the MDH2 antigen purified, preferably to at least 80, 90, 95 or 99 % purity, prior to the coating procedure. If two or more antigens are used, they are preferably spatially separated. Preferably, the width of the bands is at least 30, more preferably 40, 50, 60, 70 or 80 % the width of the test strip. The test strip may comprise one or more control bands for confirming that it has been contacted with sample sufficiently long and under sufficient conditions, in particular human serum, antibody conjugate, or both. In some embodiments, a flow path in a lateral flow immunoassay device is used. For example, the MDH2 antigen can be attached or immobilized on a porous membrane, such as a PVDF membrane (e.g., an Immobilon™ membrane), a nitrocellulose membrane, polyethylene membrane, nylon membrane, or a similar type of membrane. A further object of the present invention relates to a kit or device for identifying the presence or the level of anti-MDH2 Ig in a blood sample from a subject comprising: at least a MDH2 protein or fragments thereof; and at least one solid support wherein the MDH2 protein or fragments thereof is deposited on the support. In some embodiments, the MDH2 protein or fragments thereof that is deposited on the solid support is immobilized on the support. In some embodiments, the solid support is selected from the group comprising a bead, preferably a paramagnetic particle, a test strip, a microtiter plate, a blot (e.g. line blot and dot blot), a glass surface, a slide, a biochip and a membrane. In some embodiments, the devices or kits described herein can further comprise a second labelled MDH2 protein or a fragment thereof which produces a detectable signal; a detection antibody, wherein the detection antibody is specific for the anti-MDH2 Ig in the sample of the subject and the detection antibody produces a detectable signal; or a nephelo meter cuvette. In some embodiments, the device performs an immunoassay wherein an antibody-protein complex is formed, such as a serological immunoassay or a nephelometric immunoassay. In some embodiments, provided herein are kits that comprise devices described herein and a detection antibody, wherein the detection antibody is specific for the anti-MDH2 Ig in the sample of the subject and produces a detectable signal. In some embodiments, the kit can include a second labelled MDH2 protein or a fragment thereof which produces a detectable signal. In some embodiments, the kits described herein further comprise standards of known amounts of the MDH2 or fragments thereof. In some embodiments, the kits described herein further comprise reference values of the levels of anti- MDH2 antibodies. The reference values are average levels of anti-MDH2 antibodies in samples from a population of healthy individuals. Reference values can be provided as numerical values, or as standards of known amounts or titres of anti-MDH2 antibodies presented in pg/ml^g/ml. In some embodiments, the kits described herein further comprise at least one sample collection container for sample collection. Collection devices and container include but are not limited to syringes, lancets, BD VACUTAINER® blood collection tubes. In some embodiments, the kits described herein further comprise instructions for using the kit and interpretation of results.

In some aspects, the removal of the anti-MDH2 Ig is expected to be of therapeutic value. Accordingly a further object of the present invention relates to a method of treating a subject suffering from an autoimmune myopathy (AIM) by removing anti-MDH2 Ig from body fluid from the subject comprising the steps of a) providing the extracellular body fluid (e.g. blood) which has been obtained from a subject, b) contacting the extracellular body fluid with a biocompatible solid support capable of capturing the anti-MDH2 Ig, and c) reinfusing the extracellular body fluid from step into the subject. The removing of the anti-MDH2 Ig is performed by any well-known method in the art and can typically involve plasma exchange or plasmapheresis. Two methods are typically used in plasmapheresis to membrane filtration and extracorporeal centrifugation. In extracorporeal immunoadsorption, circulating antibodies are extracorporeally removed using an immunoadsorbent column specific for the endogenous antibody. Blood from the patient is withdrawn either continuously or discontinuously, separated into its cellular components and plasma, and the plasma is perfused through the immunoadsorbent material in order to remove the antibody. The treated plasma and cellular components of the blood are then reinfused into the patient, either separately or simultaneously.

In some embodiments, an amount of Protein A or Protein G is immobilized in the solid support. Protein A or Protein G (for example, obtained from Miltenyi Biotec, Germany) are components of the cell wall of the bacterium Staphylococcus and have the capacity to bind nonselective immunoglobulins of the IgG class because of their high affinity to the Fc portion of the IgG antibodies.

Specific removal of circulating antibodies by extracorporeal immunoadsorption employing an immobilized antigen has been described by various investigators. See generally Kohler et al, (201 1) J Clin Apher. (6):347-55; Muller et al, (2012) Dermatology. ;224(3):224- 7; Koziolek et al, (2012) J Neuroinflammation. 9(1):80; Bontadi et al, (2012) J Clin Apher. doi: 10.1002/jca.21229; Westermann et al, (2012) J Dermatol. 39(2): 168-71. Moreover this approach has been successfully commercialized as a viable system to specifically remove circulating antibodies, as exemplified by immunoadsorption columns sold under the trademarks Prosorba®, Immunosorba®, sold by Fresenius, St. Wendel, Germany, and Selesorb® sold by Kaneka, Wiesbaden, Germany.

In some embodiments, an amount of a recombinant MDH2 polypeptide is immobilized in the solid support. In said embodiments, the immunoadsorption is more specific so that only Ig specific to MDH2 are captured on the solid support; the other Ig are eluted in the extracellular body fluid.

In general, in any of these immunoadsorbent methods and compositions, the body fluids are obtained, handled and re-infused under aseptic conditions using methods and systems that are well known to a person skilled in the art. For example, blood is withdrawn via a needle that is introduced into, for example, a peripheral vein connected via a suitable tube to the container containing the biocompatible solid support and re-infused into the patient via an inlet tube connected to a needle inserted into another vein. In situations where large volumes are to be withdrawn from the subject, blood may be withdrawn, for instance, from the vena subclavia. Optionally, an anticoagulation substance such as sodium citrate, heparin, or dextran can be added to the blood when withdrawn from the body to prevent coagulation of the blood. Dextran reduces the viscosity of the blood and, in combination with addition of saline, ensures an increased distance between the blood cells and the blood platelets. Such anticoagulants may be added in quantities sufficient for non-coagulation of the blood. Before reinfusion of the treated blood into the subject the anticoagulation effect of e.g. heparin, may be reduced with the appropriate amount of heparinase, protamine and/or vitamin K etc.

Suitable columns and perfusion systems for extracorporeal adsorption are commercially available, for example from Fresenius, St. Wendel, Germany. Contact temperatures in the range of 35°C to about 40°C are typically used. The contact time will typically be in the range of about 1 to about 6 hours. The unbound portion of the blood or plasma is then collected for reintroduction into the patient or it can be reintroduced directly on a continuous basis. The subject's anti-MDH2 Ig titer may be monitored by immunoassay before and /or after the procedure to monitor the efficiency of the procedure.

To reduce the risk of embolism, precautions can be taken to avoid adsorption medium particles entering the patient upon reinfusion. Accordingly a particle capture device is typically employed downstream of the adsorption medium container to remove any residual particles from the remainder of the body fluid before it is returned to the patient. The particle capture device may be a filter or mesh having openings of a size that retain any particulate material of the adsorption medium while letting the non-adsorbed entities of the body fluid pass through. The extracorporeal blood perfusion may be performed continuously, or alternatively, discrete volumes of blood may be removed from the patient, treated as described above, and the treated plasma and cellular components of the blood returned to the patient after the treatment is complete.

A wide variety of materials will be suitable as biocompatible solid supports, for use in any of these immunoadsorbent methods and compositions, and ideally, the support matrix will be mechanically strong, sufficiently hydrophilic to avoid non-specific binding of proteins, stable and compatible with to blood and other aqueous solutions. Suitable biocompatible matrix materials include, for example, synthetic and natural polymers, polysaccharides, polyamides, glass beads, particulate silica, porous glass, silica, resins, synthetic matrixes including acrylamide derivatives, methacrylamide derivatives or polystyrene derivatives, etc, in various forms including beads, fibrous form, sheets or hollow fibers. Exemplary polymers include natural and synthetic polysaccharides and other carbohydrate based polymers, including agar, alginate, carrageenan, guar gum, gum arabic, gum ghatti, gum tragacanth, karaya gum, locust bean gum, xanthan gum, agaroses, celluloses, pectins, mucins, dextrans, starches, heparins, chitosans, hydroxy starches, hydroxypropyl starches, carboxymethyl starches, hydroxyethyl celluloses, hydroxypropyl celluloses, and carboxymethyl celluloses. Synthetic organic polymers and monomers resulting in polymers, including acrylic polymers, polyamides, polyimides, polyesters, polyethers, polymeric vinyl compounds, polyalkenes, and substituted derivatives thereof, as well as copolymers comprising more than one such polymer functionality, and substituted derivatives thereof; and mixtures thereof.

In any of these extracorporeal methods and compositions, the MDH2 polypeptides are typically, covalently coupled to the biocompatible solid support, and standard methods for coupling proteins such as the MDH2 polypeptides are well known to those of skill in the art (see. e.g. Affinity Chromatography, Principles and Methods (Pharmacia-LKB), Dean,P.G., et al, eds., 1985, Affinity Chromatography: A practical approach, IRL Press, Oxford, and Scouten, W.H., 1981, Affinity Chromatography, Wiley Intersclence, New York), "Immobilized Affinity Ligand Techniques" by Hermanson et al., Academic Press, Inc., San Diego, 1992). The biocompatible solid support may be derivatized (activated) to form a reactive substance that can react with one or more functional chemical groups within the MDH2 polypeptide, thereby forming a chemical covalent bond to couple the MDH2 polypeptide to the biocompatible solid support. Thus, materials comprising hydroxyl, amino, amide, carboxyl or thiol groups may be activated or derivatized using various activating chemicals, e.g., chemicals such as cyanogen bromide, divinyl sulfone, epichlorohydrin, bisepoxyranes, dibromopropanol, glutaric dialdehyde, carbodiimides, anhydrides, hydrazines, periodates, benzoquinones, triazines, tosylates, tresylates, and/or diazonium ions, etc. Specific exemplary activated biocompatible solid supports for use in any of these methods and compositions include for example CNBr- Sepharose, celluloses, such as CNBr- activated Sepharose 4B (Amersham), or Epoxy-activated agarose (Sigma). Biocompatible spacers (like for example NHS-activated Sepharose 4 Fast Flow) or without (like for example CNBr- activated Sepharose 4B) may be employed and are commercially available, and methods for coupling such materials to MDH2 polypeptides are well known in the art, and can be optimized by routine experimentation based on the manufacturer's directions.

The invention will be further illustrated by the following figures and examples.

However, these examples and figures should not be interpreted in any way as limiting the scope of the present invention.

FIGURES: Figure 1. Detection of anti-MDH2 antibodies. (A) Development the quantitative assay for the detection of anti-MDH2 aAb in human sera using the human orthologous protein. Validation of the test using corresponding commercial Ab. (B) Quantification of anti-MDH2 aAb in different patient cohorts using ALBIA technology. HD: healthy donors; sAIM: suspicion of autoimmune myopathy; HIgG: Hyper-IgG syndrome; IBM: inclusion body myositis; ASS: anti-synthetase syndrome; RA: rheumatoid arthritis; SLE: systemic lupus erythematosus; SS : Sjogren's syndrome. (C) Inhibition by human recombinant MDH2 on high titer anti-MDH2 patient serum.

EXAMPLE:

Material & Methods

Mice

lcos ¹- and WT NOD mice were bred and housed in our facilities under specific pathogen free conditions. lcos '^~ NOD mice were generated as previously described (Prevot et al. 2010). Animal experiments were approved by the ethic committee under number 2015080516503136.

2D-migration and western-blotting

Proteins were extracted from 40 weeks-old lcos^'*1', IcosL^~/~ and WT NOD mice muscles by denaturing buffer and then loaded on isoelectric focusing strips (pH 3-10). After migration, a second-dimension separation was performed in SDS-PAGE to separate proteins by molecular weight. For each sample analyzed, 2 identical gels were run in parallel: one for hybridization with sera from Icos^~/~, IcosL^~/~ or WT NOD mice and a second for Coomassie blue staining. Spots identified on 2-D gels using Icos '^~, lcosL^~'^~ and WT NOD sera were excised from corresponding gels, trypsin digested and separated by reverse-phase HPLC. Generated peptides were analyzed by mass spectrometry and their parent protein identified by reference to proteomic databases.

Label-free proteomic analysis

Proteins from lcos^'*1' and WT NOD mice muscles were extracted and concentrated in order to obtain 25 μg of proteins on a SDS-PAGE. After Coomassie blue staining, spots were excised, digested and washed. Each sample was dissolved in 0.1% formic acid and analyzed on a mass spectrometer (LTQ Orbitrap Velos, Thermo Scientific, Waltham, Ma, USA) equipped with a nano-ESI source and paired to a liquid nano- chromatography apparatus (Easy-nLC II, Thermo Scientific, Waltham, Ma, USA). Samples were loaded onto an enrichment column (C8, 0.5x2mm, Michrom bioressources, Auburn, Ca, USA). Separation was performed on a reverse- phase column (Cis, L 153 mm, ID 5μιη, ΙΟθΑ, Nikkyo Technos, Tokyo, Japan). Peptides were eluted from the reverse phase column into the mass spectrometer, using a 2-40% linear gradient. The mass spectrometer was operated in the data-dependent mode with survey full scan mass spectra acquired from 400 to 2000 m/z. The system selected the 20 most intense ions for CID fragmentation within the trap.

Raw data were imported in Progenesis LC-MS software (V4.0.4441.29989, Nonlinear

Dynamics, Quayside, UK). After alignment and feature exclusion, raw abundances of all features were normalized. Statistical analysis was performed using normalized abundances for one-way analysis of variance (ANOVA) calculations. Features presenting adequate p-value and q-value were selected. Corresponding peak lists were searched for using the MASCOT search engine (version 2.2, Matrix Science, Boston, Ma, USA) against the SwissProt database.

Addressable laser beads immune-assay (ALBIA) methods

he murine targets of aAbs were identified in mass spectrometry and the corresponding human recombinant proteins were fused with his-tag from Origene technologies (Rockville, Md, USA) (or Antibodies-online (Aachen, Germany). 10 μg/mL of recombinant proteins were coupled to Bio-Plex pro magnetic carboxylated beads n°55 using Bio-Plex amine coupling kit from Bio-Rad (Hercules, Ca, USA).

Validations of the tests were performed using commercial antibody targeting corresponding protein (e.g. rabbit polyclonal anti-MDH2 from Abeam, Paris, France).

Beads were incubated with sera, controls or alternatively control antibodies (as previously for validation) for 2 hours at room temperature. After washing, appropriate secondary antibody was added for 1 hour (biotinylated mouse anti-human IgG (H+L) antibodies from Southern Biotech, Birmingham, Al, USA or rat anti-mouse from Thermo Fischer Scientific, Waltham, Ma, USA). Revelation was then performed by incubation with 50 μΐ of streptavidin-R-PE (Qiagen, Venlo, Netherlands) for 15 minutes.

Mean fluorescence intensity (MFI) of each sample was determined on a Bio-Plex apparatus (Bio-Rad, Hercules, Ca, USA). Two controls were added in each experiment: a calibrator reaching the plateau (maximum value of MFI) and an internal quality control yielding a fluorescence value close to 40% of the plateau. Autoantibody titers were determined as previously described (Benveniste et al. 2011) and expressed in arbitrary unit (AU)/mL. For human sera, 2 cut-offs were determined: the first, calculated as the mean of healthy control titers + 3 standard deviations, the second as the maximum titer recovered in healthy controls. When a sample seems to be positive, further dilutions were performed and higher titer before decrease was retained.

Patients and clinical data For aAbs detection by ALBIA, different cohorts were constituted of sera from healthy donors (HD), patients referred to hospital for suspicion of auto-immune myositis (sAIM), patients with inclusion body myositis (IBM), anti-synthetase syndrome (ASS), or from patient with irrelevant autoimmune disease as rheumatoid arthritis (RA), systemic lupus erythematosus (SLE), Sjogren's syndrome (SS) or hypergammaglobulinemia (HIgG).

For patients who score positive for MDH2 assay, we retrieved and analyzed the following parameters: descriptive characteristics including sex, diagnosis (when available), clinical and pathological muscle features, CK levels and autoantibody status.

Statistical analyzes

Appropriate statistical tests were performed as indicated in figure legends using

GraphPad Prism 5.00 software.

Results

Identification of candidate auto-antigens from myopathic murine muscles.

Because myositis-associated and myositis-specific Ab become of importance in myositis classification and diagnosis, but a large proportion of patients with myositis are seronegative for these Ab, we wondered if NOD mice invalidated for ICOS/ICOSL could be a good experimental model to discover new myositis biomarkers.

In the attempt to identify new biomarkers in the ICOS/ICOSL deficient NOD model, we searched for antigenic reactivities after migration of muscle proteins on 2D gel and hybridization with corresponding serum from Icos^~'^~ (n=10), lcosL^~'^~ (n=7) or WT (n=3) NOD mice. After adequate revelation, each spot revealed on lcos ^1' or IcosL^~/~ but not on WT materials was identified using mass spectrometry. Therefore, we identified 4 candidate auto-antigens (aAg). Among these aAg is malate dehydrogenase 2 (MDH2), an enzyme of Krebs cycle.

Identification of patients with anti-MDH2 antibodies and myositis.

To search for new biomarkers in patients, we developed ALBIA for candidate aAg identified in mice using corresponding ortholog recombinant human proteins. As previously, we evaluated coupling of each recombinant protein on different batch of beads using serial dilutions of corresponding commercial Ab (Figure 1A).

Screening of human sera was first performed on healthy donors (HD), patients with suspicion of autoimmune myopathy (sAIM) and patients with hypergammaglobulinemia (HIgG). For each ALBIA, 2 cut-offs were determined: the first, calculated as the mean of HD titers + 3 standard deviations, the second as the maximum titer recovered in HD. Patients with HIgG served as control as they frequently display IgG directed against numerous and nonspecific targets. We then extended the number of patients by adding supplementary cohorts: patients with precise diagnosis of myositis (inclusion body myositis, IBM; anti-synthetase syndrome, ASS) and patients with irrelevant autoimmune diseases as controls (rheumatoid arthritis, RA; systemic lupus erythematosus, SLE; Sjogren's syndrome, SS) (Figure IB). Thanks to this test, 10 patients among 671 were scored positive for anti-MDH2 Ab in sAIM cohort (i.e. upper than the more drastic cut-off) and only 1 other in patients with HIgG displaying low titer as compared with patients with sAIM. No patient was found positive for this Ab neither in specific myositis cohorts nor in autoimmune diseases ones (Figure IB). To test if Ab are directed specifically against MDH2 protein or can recognize a non-specific target composing fluorescent beads, serum with higher titer was incubated with growing level of free MDH2 recombinant protein before performing ALBIA. Higher was the level of free MDH2, higher was signal inhibition in ALBIA, proving that anti-MDH2 Ab in this serum are directed against the commercial MDH2 and not against a non-specific epitope on ALBIA beads (Figure 1C). Taken together these results suggest that a percentage of patients with sAIM can display anti-MDH2 antibodies. Here, it is evaluated around 1.5% of sAIM patients.

Characteristics of patients with anti-MDH2 antibodies.

Epidemiological data retrieved from the 10 patients with anti-MDH2 Ab and exposed in table 1 revealed that median age was 63 years (range 52-82) and that sex ratio was 1.5 (6 men and 4 women). CK levels in these patients were variable with a median of 1 050 and a range from normal to 2 600 and no correlation with anti-MDH2 level. Interestingly patients with anti-MDH2 Ab did not have known myositis-associated or myositis-specific Ab, except for 1 patient (#427922) who had very low level of anti-Ku and anti-PL12. Among medical histories of patient, 3 cases of cancer were noted: 2 lymphomas (#63247038, #420975) and 1 lung cancer (#432126). Concerning autoimmunity analyzes, 1 patient (#412492) presented with anti-cardiolipin IgM (antiphospho lipid syndrome biomarker) and anti-CCP IgG (RA biomarker) and another patient (#432126) with anti-Ro52 and anti-SSB antibodies associated to Raynaud's syndrome.

To determine either anti-MDH2 Ab can be detected using routine techniques before confirmation, each of the 10 serums were screened on Hep-2 cells. No mutual characteristic was determined among the 10 patients (data not shown) whereas 3 patients displayed aAb: 1 patient with granular cytoplasmic fluorescence, another with slightly peri-nuclear fluorescence (#427922) and the last with homogeneous and speckled plus cytoplasmic fluorescence (#432126) . Because MDH2 is a mitochondrial protein and anti-mitochondrion Ab are routinely screened on slides with stomach, liver and kidney tissues; we screened some anti-MDH2 positive serums using this technique. We did not observe any mutual pattern characteristic of our aAb (data not shown).

Among the 10 patients with anti-MDH2 Ab, 6 underwent muscle biopsy (Table 2). Patient #415512 with the higher level of anti-MDH2 (34.7 AU/mL) displayed minor abnormalities and non-specific lesions on a previous biopsy (regrettably, latest results of muscular biopsy were not retrieved in medical file). For patient #412492 (15 AU/mL), pathological analyze of muscular biopsy concluded to mitochondrial myopathy after observation of a predominance of type 1 fibers, few regenerating features, presence of ragged- red fibers and numerous cytochrome C oxidase (COX)-negative fibers. Non-specific lesions, including changes in fibrillar structure in type 1 fibers and atrophy of type 2 fibers were observed in patient #444184 (7.9 AU/mL). Concerning patient #427922, medical record reported a necrotizing myopathy. A case of IBM was constituted by patient #420975 whose presented an inflammatory infiltrate associated to MHC-I expression, necrosis features, mitochondrial abnormalities and presence of vacuoles. Finally, muscular biopsy of patient #430633 displayed disorders in intermyo fibrillar structure, endomysial fibrosis, necrosis/regenerating features, variability in fiber size, a predominance of type 1 fibers and a major inflammatory infiltrate composed of CD4⁺ and CD8⁺ T cells, B cells and plasma cells, some images with CD4⁺ T cells invading fibers (data not shown).

TABLES:

Table 1. Characteristics of seropositive patients.

Table 2. Muscle features in seropositive patients.

REFERENCES:

Throughout this application, various references describe the state of the art to which this invention pertains. The disclosures of these references are hereby incorporated by reference into the present disclosure.

Claims

CLAIMS:

1. A method of determining whether a subject has or is at risk of having of an autoimmune myopathy (AIM) comprising detecting the presence or absence of anti-MDH2 immunoglobulins in a blood sample obtained from the subject wherein the presence indicates that the subject has or is at risk of having an autoimmune myopathy.

2. The method of claim 1 which comprises i) determining the level of anti-MDH2 immunoglobulins (Igs) in a blood sample obtained from the subject ii) comparing the level determined at step i) with a predetermined reference value and iii) concluding that the subject has or is at risk of having an autoimmune myopathy when the level determined at step i) is higher than the predetermined reference value.

3. The method of claim 1 wherein the blood sample is a serum sample.

4. The method of claim 2 wherein the predetermined reference value is the level of plasma anti-MDH2 Ig determined in a population of healthy individuals.

5. The method of claim 1 when the immunoglobulins are IgG immunoglobulins, such as IgGl, IgG2, IgG3 or IgG4 immunoglobulins.

6. A method of predicting the risk of relapse in a subject suffering from AIM i) comprising determining the level of blood anti-MDH2 Igs in a blood sample obtained from the subject ii) comparing the level determined at step i) with a predetermined reference value and iii) concluding that the subject is at risk of relapse when the level determined at step i) is higher than the predetermined reference value.

7. A method of determining whether the subject achieves a response with a treatment comprising i) determining the level of blood anti-MDH2 Ig in a blood sample obtained from the subject before the treatment ii) determining the level of blood anti-MDH2 Ig in a blood sample obtained from the subject before the treatment, iii) comparing the level determined at step i) with the level determined at step ii) and iv) concluding that the subject achieves a response when the level determined at step ii) lower higher than the level determined at step i).

8. The method of claim 7 wherein the treatment is plasma exchange or plasmapheresis.

9. The method of claim 7 wherein the treatment is an immunosuppressive treatment.

10. The method of claim 9 wherein the immunosuppressive agent is selected from the group consisting of 6-mercaptopurine ("6-MP"), cyclophosphamide, mycophenolate, prednisolone, sirolimus, dexamethasone, rapamycin, FK506, mizoribine, azothioprine and tacrolimus.

11. The method of claim 9 wherein the immunosuppressive agent is selected from the group consisting of calcineurin inhibitors, corticosteroids, and B cell depleting agents.

12. The method of claim 11 wherein the B cell depleting agent is rituximab.

13. The method of claim 7 wherein a level which decreases or returns to the basal level indicates that the subject has achieved a response.

14. A method of treating a subject suffering from an autoimmune myopathy (AIM) by removing anti-MDH2 Ig from body fluid from the subject comprising the steps of a) providing the extracellular body fluid (e.g. blood) which has been obtained from a subject, b) contacting the extracellular body fluid with a biocompatible solid support capable of capturing the anti-MDH2 Ig, and c) reinfusing the extracellular body fluid from step into the subject.

15. The method of claim 14 wherein an amount of a recombinant MDH2 polypeptide is immobilized in the solid support.