Contactin 1 IgG4 associates to chronic inflammatory demyelinating polyneuropathy with sensory ataxia

Abstract

A Spanish group recently reported that four patients with chronic inflammatory demyelinating polyneuropathy carrying IgG4 autoantibodies against contactin 1 showed aggressive symptom onset and poor response to intravenous immunoglobulin. We aimed to describe the clinical and serological features of Japanese chronic inflammatory demyelinating polyneuropathy patients displaying the anti-contactin 1 antibodies. Thirteen of 533 (2.4%) patients with chronic inflammatory demyelinating polyneuropathy had anti-contactin 1 IgG4 whereas neither patients from disease or normal control subjects did (P = 0.02). Three of 13 (23%) patients showed subacute symptom onset, but all of the patients presented with sensory ataxia. Six of 10 (60%) anti-contactin 1 antibody-positive patients had poor response to intravenous immunoglobulin, whereas 8 of 11 (73%) antibody-positive patients had good response to corticosteroids. Anti-contactin 1 IgG4 antibodies are a possible biomarker to guide treatment option.

Keywords: autoantibody; chronic inflammatory demyelinating polyneuropathy; contactin 1; myelin; nodes of Ranvier.

Chronic inflammatory demyelinating polyneuropathy (CIDP) is clinically heterogeneous and shows varying responses to immunotherapy. In a cohort of 533 Japanese patients with CIDP, Miura et al. identify 13 patients with IgG4 antibodies against the axonal adhesion molecule, contactin-1. Antibodies are associated with subacute onset, sensory ataxia and good response to corticosteroids.

Figure 1

Identification of CNTN1 as a target for autoantibodies in CIDP. (A) The sera from a CIDP patient (Patient 1) was tested on mouse sciatic nerve fibres. Human IgG antibodies (green) bound specifically to the paranodal regions, which flank voltage-gated sodium (Nav) channels (red) at nodes. (B) The IgG (green) from the same CIDP patient labelled the surface of cultured neocortical neurons, here stained with microtubule-associated protein 2 (MAP2) (red). Scale bar = 10 μm. (C) Neocortical neurons were incubated with normal control (NC) (left) and CIDP (right) IgG antibodies, and the target antigens were immunoprecipitated, separated on SDS-PAGE gels, and stained with Imperial blue. Protein bands around 140 kDa (arrowheads) were excized and identified by mass spectrometry as CNTN1. Molecular weight markers are shown on the left in kDa. (D) The CNTN1 reactive sera were then tested by immunostaining on mouse teased nerve fibres. All the anti-CNTN1 IgG4 antibody-positive patients showed a clear IgG binding (green) at paranodal regions, which co-localized with CNTN1 (red). Here we show immunolabelling obtained with a CIDP patient (Patient 2). Scale bar = 10 μm. (E and F) Dorsal root ganglion sections were immunostained for CNTN1 (red) and Na_v channels (green; E) or a representative CIDP serum (green; Patient 9; F). CNTN1 was found in large DRG neurons, whereas Na_v channel staining was more prominent in small neurons. CIDP IgG antibodies bound preferentially to large CNTN1-positive neurons (asterisks) and co-localized with CNTN1 at paranodes of sensory axons (arrowheads). Scale bars = 20 μm.

Figure 2

CIDP autoantibodies recognize the protein core of CNTN1 and are directed against the Ig domains. (A–D) Human embryonic kidney cells were transfected with constructs encoding full-length CNTN1 (A), Ig domains 1-6 (B), Ig domains 5-6 + fibronectin type III (Fn) domains (C), or Fn domains (D). Living cells were then incubated with a representative CIDP patient’s serum (red), fixed, and stained for CNTN1 (green). CIDP IgG antibodies recognized the Ig domains of CNTN1, but did not bind the Fn domains. (E and F) Human embryonic kidney cells were transfected with full-length CNTN1, then treated with tunicamycin (F) or normal medium (E). Cells were then fixed, permeabilized and stained for CNTN1 (green) and CIDP IgG (red). Serum IgG antibodies recognized CNTN1 from tunicamycin-treated cells, indicating that the antibodies target the unglycosylated protein core. Scale bar = 10 μm. (G) Protein samples from human CNTN1 (hCNTN1) transfected human embryonic kidney cells were untreated (−) or treated (+) with peptide N-glycosidase F (PNGaseF), and immunoblotted against CNTN1 (left) or two representative CIDP sera (Patients 3 and 1). The goat anti-CNTN1 antibodies recognized the two glycosylated forms of CNTN1 around 140 kDa (arrowheads on the left) and the deglycosylated protein core (arrowheads on the right). Similarly, CIDP IgG antibodies recognized both glycosylated and deglycosylated CNTN1. Molecular weight markers are shown on the left in kDa.