Anti-neurofascin-155 antibody-positive neuromyelitis optica spectrum disorders

The prevalence of anti-neurofascin-155 antibodies in patients with neuromyelitis optica spectrum disorders

Anti-neurofascin-155 (NF155) antibodies have been observed in two cases with neuromyelitis optica spectrum disorders (NMOSD). This study investigated the prevalence of anti-NF155 antibodies in patients with NMOSD and the clinical features of anti-NF155 antibody-positive patients. Sera from 129 patients with NMOSD were screened with anti-NF155 antibodies by cell-based assay (CBA) and re-examined using immunostaining of teased mouse sciatic nerve fibres. Fifty-six patients with multiple sclerosis (MS) and 50 healthy controls (HC) were also enrolled for detecting anti-NF155 antibodies. A total of 12.40% (16 of 129) of patients with NMOSD were positive for anti-NF155 antibodies confirmed by both CBA and immunostaining. Immunoglobulin (Ig) G1 was the predominant subclass. However, none of 56 MS patients or 50 HC were positive for anti-NF155 antibodies. Anti-NF155 antibody-positive NMOSD patients had a higher proportion of co-existing with autoimmune diseases (p < 0.001) and higher positive rates of serum non-organ-specific autoantibodies, including anti-SSA antibodies (p < 0.001), anti-SSB antibodies (p = 0.008), anti-Ro-52 antibodies (p < 0.001) and rheumatoid factor (p < 0.001). Five anti-NF155 antibody-positive NMOSD patients who took part in the nerve conduction study showed mildly abnormal results. Differences in some nerve conduction study parameters were observed between anti-NF155 antibody-positive and negative patients. Anti-NF155 antibodies occurred in a small proportion of NMOSD patients. Anti-NF155 antibody-positive NMOSD patients tended to co-exist with autoimmune diseases.

Antibodies against nodo-paranodal proteins are not present in genetic neuropathies

OBJECTIVE

To study the presence of nodal and paranodal immunoglobulin M (IgM) and immunoglobulin G (IgG) antibodies in patients with genetic neuropathies.

METHODS

A total of 108 patients with genetic neuropathies from 3 different centers were included. The presence of IgG and IgM antibodies against neurofascin-155 (NF155), nodal neurofascin (NF186 and NF140), and contactin-1 (CNTN1) were investigated with a cell-based assay (CBA) using immunocytochemistry in transfected HEK293 cells. Sera with positive or uncertain results were further tested by ELISA and immunohistochemistry in pig teased-nerve fibers.

RESULTS

Six patients with Charcot-Marie-Tooth disease (CMT) had an uncertain staining pattern for IgM against nodal neurofascin that was not confirmed by ELISA. Two patients with CMT had an uncertain staining pattern for IgG against nodal neurofascin that was not confirmed by ELISA or immunohistochemistry. One patient with CMT with a confirmed GJB1 mutation tested positive for IgG against NF155 by CBA and ELISA (1/900), but was not confirmed by immunohistochemistry and was ultimately classified as negative.

CONCLUSIONS

Antibodies against nodal or paranodal antigens were not detected in our cohort of patients with CMT, as previously reported. Some patients may falsely test positive for any of the techniques; confirmatory techniques should be incorporated into the routine testing.