Induction of experimental ataxic sensory neuronopathy in cats by immunization with purified SGPG

Abstract

IgM paraproteins in about 50% of the patients with neuropathy associated with IgM gammopathy react with carbohydrate moieties in myelin-associated glycoprotein (MAG) and in sulfated glucuronic glycolipids (SGGLs) in human peripheral nerves. However, the role of anti-MAG/SGGL antibodies in the pathogenesis of neuropathy remains unclear. In order to induce an animal model of neuropathy associated with anti-MAG/SGGL antibodies, cats were immunized with sulfoglucuronyl paragloboside (SGPG). All four cats immunized with SGPG developed clinical signs of sensory neuronopathy within 11 months after initial immunization, characterized by unsteadiness, falling, hind limb weakness and ataxia. In two cats the ataxia and hind limb paralysis were so severe that the animals had to be euthanized. Pathological examination revealed sensory ganglionitis with inflammatory infiltrates in the dorsal root ganglia. No overt signs of pathology were noted in the examined roots or nerves. High titer anti-SGPG/MAG antibodies were detected in all 4 cats immunized with SGPG but not in 3 control cats. Our data demonstrate that immunization of cats with SGPG induced anti-SGPG antibodies and sensory neuronopathy clinically resembling the sensory ataxia of patients with monoclonal IgM anti-MAG/SGPG antibodies. This study suggests that these anti-MAG/SGPG antibodies play a role in the pathogenesis of this neuropathy.

Figure 1

Antibody titers in sera of cats immunized with SGPG

Figure 2

Binding of cat antibodies to sulfoglucuronyl glycolipids. Lane 1 in each panel contained bovine brain gangliosides for reference. Lane 2 in each panel contained purified SGPG and SGLPG. Panel A depicts orcinol stained glycolipids. Panels B and C depict TLC after overlay with serum from a cat immunized with SGPG (C-1) followed by peroxidase-labeled goat anti-cat IgM (μ chain specific) and peroxidase-labeled goat anti-cat IgG -chain specific), (γ chain specific), respectively.

Figure 3

Immunoblots showing binding of cat antibodies to bovine MAG. Western blot following 12 % SDS-PAGE of bovine CNS myelin proteins (80 μg / lane). (Lane 1) stained with a 1:500 dilution of serum from cat C-1, followed by HRP-conjugated goat anti-cat IgM. (Lane 2) stained with a 1:500 dilution of a mouse monoclonal antibody (B11F7) followed by HRP-conjugated goat anti-mouse IgG.

Figure 4

SGPG immunized cats with neuropathy. (A) Cat C-1 had severe ataxia and hind limb weakness. (B,C,D) Cat C-3 had hind limb weakness, severe ataxia and difficulty walking. She was slipping and falling. (E, F) Hematoxylin & eosin stained cross section of root/dorsal root ganglion of cat C-2 demonstrates lymphocytic infiltrates around the ganglionic neurons. (G, H) Bielschowsky stain: Dorsal root/ganglia, corresponding to (E,F) shows inflammation around myelinated fibers.