Evaluation of NR2B peptide as subunit vaccines against experimental neuropathic pain.
BACKGROUND
NR2B containing N-methyl-D-aspartate (NMDA) receptor plays an important role in the facilitation and maintenance of neuropathic pain. The discrete distribution of NR2B subunit in the central nervous system (CNS) may support reduced side effects of agents that act selectively at this site. Therefore, we investigated the hypothesis that a humoral autoimmune response targeting the NR2B subunit of NMDA receptor relieves pain like behaviours produced by peripheral injury.


METHODS
Rats were immunized subcutaneously with NR2B-Keyhole Limpet Hemocyanin (NR2B-KLH) three times at two-week intervals. NR2B specific IgG titres in sera and cerebrospinal fluid were determined by indirect ELISA. Seven days after the third immunization, 2 of the 3 terminal branches of the sciatic nerve (tibial and common peroneal nerves) were tightly ligated. Behavioural testing was carried out on every other day after surgery, until 7 days after surgery. The lumbar spinal cord (L4-6) was removed on day 7 after ligation. The expression of NR2B protein in the lumbar spinal cord was determined using Western blotting.


RESULTS
After the second vaccination, NR2B specific IgG in sera was detected to be > 0.5 microg/ml in six of nine rats. After the third vaccination, all the immunized rats had > 2.2 microg/ml. Titres of NR2B specific IgG in sera peaked 42 days post initial immunization and persisted for over 70 days. No NR2B specific IgG was detected in sera from PBS or KLH group. The behavioural thresholds in NR2B group were significantly higher than those in PBS and KLH groups on day 7 after ligation. NR2B specific IgG in CSF in NR2B group could not be detected on day 1 before spinal dissection; but could be detected on day 7 after surgery. The expression of NR2B protein in group NR2B was significantly lower than in PBS and KLH groups on day 7 after surgery.


CONCLUSIONS
The NR2B peptide could be used as a vaccine against neuropathic pain, which could be associated with reduction of NR2B protein in the lumbar spinal cord.
Wang
Gong-Ming
GM
Department of Anaesthesiology, Tongji Hospital of Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China.
Tian
Yu-Ke
YK
Chen
Jian-Ping
JP
Tian
Xu-Bi
XB
Gao
Feng
F
Yang
Hui
H
An
Ke
K
Ma
Guo-Ping
GP
D000276:Adjuvants, Immunologic; D000818:Animals; D015153:Blotting, Western; D004195:Disease Models, Animal; D004797:Enzyme-Linked Immunosorbent Assay; D005260:Female; D006433:Hemocyanins / Q000276:immunology; D007074:Immunoglobulin G / Q000276:immunology; D009437:Neuralgia / Q000276:immunology* / Q000503:physiopathology / Q000517:prevention & control; D010147:Pain Measurement; D051381:Rats; D017207:Rats, Sprague-Dawley; D016194:Receptors, N-Methyl-D-Aspartate / Q000276:immunology* / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000008:administration & dosage / Q000276:immunology; D013116:Spinal Cord / Q000187:drug effects / Q000378:metabolism / Q000503:physiopathology; D013997:Time Factors; D014612:Vaccines / Q000008:administration & dosage / Q000276:immunology*
D000276:Adjuvants, Immunologic; D007074:Immunoglobulin G; D016194:Receptors, N-Methyl-D-Aspartate; D011993:Recombinant Fusion Proteins; D014612:Vaccines; D006433:Hemocyanins; C032808:keyhole-limpet hemocyanin