Therapeutic effects of NogoA vaccine and olfactory ensheathing glial cell implantation on acute spinal cord injury

Zhicheng Zhang, Fang Li, Tiansheng Sun, Dajiang Ren, Xiumei Liu

PLA Institute of Orthopedics, Beijing Army General Hospital, Beijing, People's Republic of China

Background: Many previous studies have focused on the effects of IN-1, a monoclonal antibody that neutralizes Nogo (a neurite growth inhibitory protein), on neurologic regeneration in spinal cord injury (SCI). However, safety problems and the short half-life of the exogenous antibody are still problematic. In the present study, the NogoA polypeptide was used as an antigen to make a therapeutic NogoA vaccine. Rats were immunized with this vaccine and were able to secrete the polyclonal antibody before SCI. The antibody can block NogoA within the injured spinal cord when the antibody gains access to the spinal cord due to a compromised blood–spinal cord barrier. Olfactory ensheathing glial cell transplantation has been used in a spinal cord contusion model to promote the recovery of SCI. The present study was designed to verify the efficacy and safety of NogoA polypeptide vaccine, the effects of immunotherapy with this vaccine, and the synergistic effects of the vaccine and olfactory ensheathing glial cells in repair of SCI.
Methods: A 13-polypeptide fragment of NogoA was synthesized. This fragment was then coupled with keyhole limpet hemocyanin to improve the immunogenicity of the polypeptide vaccine. Immunization via injection into the abdominal cavity was performed in rats before SCI. The serum antibody level and ability of the vaccine to bind with Nogo were detected by enzyme-linked immunosorbent assay. The safety of the vaccine was evaluated according to the incidence and severity of experimental autoimmune encephalomyelitis. Olfactory ensheathing glia cells were obtained, purified, and subsequently implanted into a Wistar rat model of thoracic spinal cord contusion injury. The rats were divided into four groups, ie, an SCI model group, an olfactory ensheathing glia group, a vaccine group, and a combined treatment group. Animal behavior, histopathology, and axonal regeneration were compared between the four treatment groups.
Results: The antibody against the polypeptide was detected in rat serum by enzyme-linked immunosorbent assay. Experimental autoimmune encephalomyelitis was not found in the immunized rats. Three months after injury, Basso, Beattie, Bresnahan scores and nerve fiber counts in biotinylated dextran amine nerve tracing studies were significantly better in the combined treatment group than in the other groups.
Conclusion: The polypeptide NogoA vaccine can stimulate the humoral immune system to produce antibodies against the NogoA polypeptide. The binding reaction between the antibody and antigen was shown in ex vivo experiments. No evidence was found to suggest a relationship between NogoA vaccination and increased risk of experimental autoimmune encephalomyelitis. The combined strategy of olfactory ensheathing glial cell implantation and NogoA vaccination may promote regeneration of axons and functional recovery in the spinal cord contusion injury model. This study may provide a new strategy for combining modalities to enhance axonal regeneration and a better balance of the CNS microenvironment after SCI.

Keywords: spinal cord injury, immunotherapy, cell transplantation, olfactory ensheathing glial cells, NogoA, vaccine