New Concepts in Chronic Inflammatory Neuropathies: from biomarkers to individualize therapy – NeCCIN

1. Identify new antigen targets by proteomic approaches: We have selected CIN patients (n > 50) presenting strong reactivities against specific nerve compartments. We will use the patients IgG to directly immunoprecipitate the target antigens from neuronal and glial cell culture and from human nerve samples. These novel antigens will be identified by mass spectrometry.
2. Characterization of blood markers for CIN: We have constituted a large bank of CIN sera with clinical data (n >650). We are purifying the recombinant antigens to perform ELISA and have set up the detection technique. We will determine the prevalence and specificity of all the newly identified autoantibodies to better define their clinical correlate.
3. Define novel clinical biomarkers in CIN: Electrophysiology and clinical imagery strongly help CIN diagnosis. We propose to perform refined electrophysiological examinations as well as quantitative muscle and nerve MRI to improve CIN stratification by combining these to serological and biological data.
4. Measure morphological alterations in biopsies: Skin and sural nerve biopsies are used to evaluate gross nerve alterations. We will perform immunostaining on patients' biopsies to scrutinize fine structural alterations of nodes, paranodes, and myelin compartments to establish novel selective markers of pathology.
5. Correlate specific biomarkers with different subgroups of CIN patients: We will perform a combinatorial analysis of the gathered data to identify groups of markers that will be specific of CIN entities. This work will help revise the actual diagnostic criteria for CIN and better delineate novel entities such as nodopathy or chronic painful inflammatory neuropathies.

1. Identify new antigen targets by proteomic approaches: We have successfully used our immunoprecipitation strategies using cell cultures and have identified novel targets (Neuropilin-1, MCAM, and the alpha subunit of the Na+/K+ ATPase). We have developed a novel approach of immunoprecipitation using human nerve from autopsy.
2. Characterization of blood markers for CIN: Our ANR consortium have refined the clinical criteria associated with paranodopathy (CNTN1, NF155 or Caspr1) and ameliorated the therapeutic treatments of the patients. We have also constituted a large cohort of Caspr1-reactive patients which has helped better define the clinical presentation of these patients. In parallel, we have identified Caspr2 as the target of autoantibodies in a subset of patients presenting with purely painful neuropathy that lacks conduction velocity alterations. These works have been published in three papers.
3. Define novel clinical biomarkers in CIN: We first focused on the electrophysiological presentation of patients with known autoantibodies (Caspr1, CNTN1, NF155, MAG, or gangliosides). Our work demonstrate that patients with autoantibodies targeting the paranodal regions or the compact myelin present with electrophysiological alterations that are undistinguishable from typical CIN.
4. Measure morphological alterations in biopsies: We have examined biopsies from patients with autoantibodies reacting against paranodal proteins or the compact myelin compartment. The immune reactivity against paranodal proteins is associated with the destruction of the paranodal regions, whereas antibodies to compact myelin are associated with segmental macrophage-mediated demyelination. These data demonstrate that autoantibodies have different pathogenic mechanisms but ultimately result in similar conduction abnormalities.

We have described three mechanisms responsible for the conduction defects in peripheral neuropathy or responsible for neuropathic pain. The first mechanism is linked to paranodopathy, our data indicate that anti-Caspr1 or CNTN1 IgG4 are pathogenic and associated with a subgroup of patients. Skin and nerve biopsies revealed that these antibodies lead to a destruction of paranodal specialization and to severe conduction slowing.
The second mechanism demonstrate the implication of humoral and cellular responses in the pathophysiology of CIN. We have demonstrated that some CIN patients present with autoantibodies that target compact myelin and induce myelin degradation by macrophages. This leads to segmental demyelination, and electrophysiological alterations with excessive temporal dispersion.
Finally, we have demonstrated that Caspr2 is a novel target in peripheral neuropathies, notably in patients with neuropathic pain. These data indicate that small fiber neuropathy can have a dysimmune origin and be mediated by autoantibodies. The difficulty to monitor pain limits painful neuropathy diagnostic. Our data should help diminish the patient wandering.
In the next years, we will continue all the objectives as described in the proposal. We expect to identify novel antigenic targets, and examine their prevalence in CIN patients, as well as their morphological and electrophysiological correlates. We will continue to deposit all patient information in the database including the electrophysiological, clinical, and morphometric data and the serologic reactivity. This will enable us to stratify CIN and orientate therapeutic choice.

1. Kouton et al (2020) Electrophysiological Features of Chronic Inflammatory Demyelinating Polyradiculoneuropathy Associated With IgG4 Antibodies Targeting Neurofascin 155 or Contactin 1 Glycoproteins. Clin Neurophysiol, 131 (4): 921-927.
2. Eshed-Eisenbach et al (2020) Precise Spatiotemporal Control of Nodal Na+ Channel Clustering by Bone Morphogenetic Protein-1/Tolloid-like Proteinases. Neuron, 106 (5): 806-815.
3. Vallat et al (2020) Antibody- And Macrophage-Mediated Segmental Demyelination in Chronic Inflammatory Demyelinating Polyneuropathy: Clinical, Electrophysiological, Immunological and Pathological Correlates. Eur J Neurol. 27(4):692-701.
4. Cortese et al (2020) Antibodies to neurofascin, contactin-1, and Caspr1 in CIDP: clinical relevance of IgG isotype. Neurol Neuroimmunol Neuroinflamm. 7(1)

Chronic inflammatory neuropathies (CIN) are rare auto-immune disorders affecting peripheral myelinated axons that lead to significant disabilities. Distinct CIN groups have been distinguished according to disease course, sensory-motor presentation, symmetric/asymmetric distribution, and the presence of biological markers. Nonetheless, these groups are still heterogeneous entities with unwell defined borders, and a heterogeneous therapeutic response to conventional therapies. Identifying specific biomarkers of these pathologies is a major challenge and could improve diagnosis and therapeutic choice. During the past years, our group have shown that accurate examination of medical imaging and electrophysiology can help better individualize subgroups of patients and define specific therapeutic approaches. In addition, we recently identified autoantibody targets in patients with chronic inflammatory demyelinating polyneuropathy (CIDP). These autoantibodies have clinical benefits and help orientate patients’ treatment. One group of CIDP patients show IgG4 antibodies against contactin-1, Caspr-1, or neurofascin-155, and specific alterations of paranodes. Another subgroup present IgG4 targeting neurofascin-186, a cell adhesion molecule of the node of Ranvier. Interestingly, this latter group appears to form a distinct entity, Nodopathy, showing a severe presentation and conduction defects suggesting alterations at the nodes of Ranvier. These findings demonstrated that autoantibodies can help better delineate CIN subgroups together with specific clinical and biological markers. In keeping with this view, we observed that some patients with painful chronic neuropathies presented an immunoreactivity against small fibers and a good response to immunomodulatory treatments. Also, we identified a group of CIN patients with clear demyelinating features on EMG and nerve biopsies presenting a strong IgG or IgM reactivity against Schwann cell.
Our concept is that CIN are triggered by diverse immune mechanisms that are targeting distinct nerve antigens. Here, we propose to characterize the physiopathogenic mechanisms in order to extract explicit clinical, biological, morphological and electrophysiological features that will serve to better delineate CIN entities. Our goals are as follows:
1. Identify new antigen targets by proteomic approaches: We have selected CIN patients (n > 50) presenting strong reactivities against specific nerve compartments. Our recent methodological progresses will enable us to isolate the target antigens directly from nerve samples. These novel antigens will be identified by mass spectrometry, and thoroughly characterized.
2. Characterization of blood markers for CIN: We have constituted a large bank of CIN sera with clinical data (n >650). We will determine the prevalence and specificity of all the newly identified autoantibodies to better define their clinical correlate.
3. Define novel clinical biomarkers in CIN: Electrophysiology and clinical imagery strongly help CIN diagnosis. We propose to perform refined electrophysiological examinations as well as quantitative muscle and nerve MRI to improve CIN stratification by combining these to serological and biological data.
4. Measure morphological alterations in biopsies: Skin and sural nerve biopsies are used to evaluate gross nerve alterations. Here, we will scrutinize fine structural alterations of nodes, paranodes, and myelin compartments to establish novel selective markers of pathology.
5. Correlate specific biomarkers with different subgroups of CIN patients: We will perform a combinatorial analysis of the gathered data to identify groups of markers that will be specific of CIN entities. This work will help revise the actual diagnostic criteria for CIN and better delineate novel entities such as nodopathy or chronic painful inflammatory neuropathies.
This study will help elucidate the immune processes responsible for CIN and improve diagnosis and treatment.