Autoantibodies Against Collapsin Response Mediator Proteins Associated With Encephalopathy/Myelopathy: A Single-Center Retrospective Study

Abstract

Background: Collapsin response mediator protein (CRMP) consists of five subtypes (CRMP1-5), which share high homology and are expressed in the nervous system. Anti-CRMP2 and anti-CRMP5 antibodies (Abs) have been reported in autoimmune encephalitis (AE). This study retrospectively evaluated the diagnostic value of CRMP auto-Abs in patients with suspected immune-mediated encephalopathy/myelopathy.

Methods: Patients with encephalopathy/myelopathy attributed to autoimmune or infectious causes, as well as those with encephalopathy of unclear etiology, were recruited from our department between January 2017 and November 2019. Clinical data, as well as serum and/or cerebrospinal fluid (CSF) samples, were collected. Measurement of Abs against CRMPs in patient samples was performed using a cell-based assay (CBA) with HEK293 cells expressing CRMP proteins and confirmed by a tissue-based assay (TBA) with mouse brain sections.

Results: A total of 400 patients and 77 healthy controls were recruited. The male-to-female ratio of the patients was 0.88, and the average age was 39.22 ± 16.59 years. CBA testing was performed with 200 paired CSF and serum samples, along with 99 CSF samples and 101 serum samples. Of the patients, 22 (5.5%) presented with anti-CRMPs Abs. Anti-CRMP1 was the most commonly detected Ab (17/22, 77.3%), either alone or in combination with CRMP2 and CRMP3. Titers of anti-CRMPs Abs ranged from 1: 3.2 to 1:10 in CSF samples and 1:32 to 1:320 in serum samples. Patients with anti-CRMPs Abs experienced more headaches and had higher levels of chloride in CSF compared to those without anti-CRMPs Abs. Fourteen of the 22 patients with anti-CRMPs Abs were diagnosed with encephalitis, exhibiting a higher frequency of fever and headache, CSF pleocytosis, and more frequent treatment with immunotherapy, steroids, antibiotics, and antiviral therapy compared to non-inflammatory encephalopathy patients.

Conclusion: Anti-CRMPs Abs may indicate immune-mediated neuronal damage in encephalopathy, including encephalitis, and may serve as potential biomarkers for neuronal injury.

Keywords: Collapsin response mediator proteins; autoantibodies; biomarker; encephalitis; encephalopathy.

FIGURE 1

The inclusion flowchart of the patients. CBA, cell‐based assay; CRMPs, Collapsin response mediator proteins; CSF, cerebrospinal fluid; SE, Serum.

FIGURE 2

CRMPs antibody distribution of the patients. Of the 22 patients, anti‐CRMP1 antibodies were the most detected, followed by anti‐CRMP2 and anti‐CRMP3 antibodies. The distribution of anti‐CRMPs antibodies across the two diagnostic groups showed no significant difference. CRMPs, Collapsin response mediator proteins; CSF, cerebrospinal fluid.

FIGURE 3

The CBA test of selected patients. (A) The CBA tests of serum or CSF from selected patients revealed anti‐CRMPs antibodies detected in the cytoplasm of HEK293 cells expressing different CRMPs, shown as red fluorescence staining (indicated by white arrows), upper panel. The same sample showed no red fluorescence staining in cells expressing the vector control, lower panel. (B and C) Serum samples from a selected patient without CRMPs Abs (B) or healthy controls (C) did not show red fluorescence staining in the cells expressing different CRMPs. CBA, cell based assay; CSF, cerebrospinal fluid; CRMPs, Collapsin response mediator proteins.

FIGURE 4

TBA/Immunohistochemistry test of selected patients. (A) Immunostaining from serum samples of selected patients was evident in the cytosolic compartments of neurons from the cortex, hippocampus, and cerebellum in TBA sections, as indicated by green fluorescence staining. This was not observed in the sample from patient 22, who had anti‐CRMP4 Abs, which showed neurofilament‐like staining. (B) TBA staining of commercial antibodies against five subtypes of CRMPs in the hippocampus and cerebellum of mice showed a similar pattern to the samples from patients with corresponding anti‐CRMPs Abs. CRMPs, Collapsin response mediator proteins; TBA, tissue‐based assay.

FIGURE 5

The image findings of the included patients. Cranial MRI of P5 revealed mild white matter degeneration (indicated by arrow). Cranial MRI of P8 suggested thickening of the bilateral cerebellar tentorium. In P15, multiple abnormal signals were observed in T1, T2, and FLAIR, suggesting demyelinating changes (indicated by arrows). Diffuse white matter changes were observed in the periventricular white matter (indicated by arrows) without enhancement in P22's cranial MRI. Cranial MRI of P10 was normal. FLAIR, fluid‐attenuated inversion recovery; MRI, magnetic resonance imaging.