title: Active immunization with myelin-derived altered peptide ligand reduces mechanical pain hypersensitivity following peripheral nerve injury.
abstract: BACKGROUND
  T cells have been implicated in neuropathic pain that is caused by peripheral nerve injury. Immunogenic myelin basic protein (MBP) peptides have been shown to initiate mechanical allodynia in a T cell-dependent manner. Antagonistic altered peptide ligands (APLs) are peptides with substitutions in amino acid residues at T cell receptor contact sites and can inhibit T cell function and modulate inflammatory responses. In the present study, we studied the effects of immunization with MBP-derived APL on pain behavior and neuroinflammation in an animal model of peripheral nerve injury.
  
  
  METHODS
  Lewis rats were immunized subcutaneously at the base of the tail with either a weakly encephalitogenic peptide of MBP (cyclo-MBP87-99) or APL (cyclo-(87-99)[A(91),A(96)]MBP87-99) in complete Freund's adjuvant (CFA) or CFA only (control), following chronic constriction injury (CCI) of the left sciatic nerve. Pain hypersensitivity was tested by measurements of paw withdrawal threshold to mechanical stimuli, regulatory T cells in spleen and lymph nodes were analyzed by flow cytometry, and immune cell infiltration into the nervous system was assessed by immunohistochemistry (days 10 and 30 post-CCI). Cytokines were measured in serum and nervous tissue of nerve-injured rats (day 10 post-CCI).
  
  
  RESULTS
  Rats immunized with the APL cyclo-(87-99)[A(91),A(96)]MBP87-99 had significantly reduced mechanical pain hypersensitivity in the ipsilateral hindpaw compared to cyclo-MBP87-99-treated and control rats. This was associated with significantly decreased infiltration of T cells and ED1+ macrophages in the injured nerve of APL-treated animals. The percentage of anti-inflammatory (M2) macrophages was significantly upregulated in the APL-treated rats on day 30 post-CCI. Compared to the control rats, microglial activation in the ipsilateral lumbar spinal cord was significantly increased in the MBP-treated rats, but was not altered in the rats immunized with the MBP-derived APL. In addition, immunization with the APL significantly increased splenic regulatory T cells. Several cytokines were significantly altered after CCI, but no significant difference was observed between the APL-treated and control rats.
  
  
  CONCLUSIONS
  These results suggest that immune deviation by active immunization with a non-encephalitogenic MBP-derived APL mediates an analgesic effect in animals with peripheral nerve injury. Thus, T cell immunomodulation warrants further investigation as a possible therapeutic strategy for the treatment of peripheral neuropathic pain.
authors.affiliation: School of Medical Sciences, University of New South Wales, UNSW Medicine, Sydney, NSW, 2052, Australia. h.c.perera@student.unsw.edu.au.
authors.forename: Chamini J
authors.initials: CJ
authors.lastname: Perera
authors.affiliation: School of Medical Sciences, University of New South Wales, UNSW Medicine, Sydney, NSW, 2052, Australia. s.duffy@student.unsw.edu.au.
authors.forename: Samuel S
authors.initials: SS
authors.lastname: Duffy
authors.affiliation: School of Medical Sciences, University of New South Wales, UNSW Medicine, Sydney, NSW, 2052, Australia. justin.lees@unsw.edu.au.
authors.forename: Justin G
authors.initials: JG
authors.lastname: Lees
authors.affiliation: School of Medical Sciences, University of New South Wales, UNSW Medicine, Sydney, NSW, 2052, Australia. cristinafkim@gmail.com.
authors.forename: Cristina F
authors.initials: CF
authors.lastname: Kim
authors.affiliation: Centre for Infection and Inflammation Research, School of Medical Sciences, University of New South Wales, Sydney, NSW, 2052, Australia. B.Cameron@unsw.edu.au.
authors.forename: Barbara
authors.initials: B
authors.lastname: Cameron
authors.affiliation: College of Health and Biomedicine, Centre for Chronic Disease Prevention and Management, Victoria University, Melbourne, VIC, Australia. vasso@scientist.com.
authors.forename: Vasso
authors.initials: V
authors.lastname: Apostolopoulos
authors.affiliation: School of Medical Sciences, University of New South Wales, UNSW Medicine, Sydney, NSW, 2052, Australia. gila@unsw.edu.au.
authors.forename: Gila
authors.initials: G
authors.lastname: Moalem-Taylor
mesh_terms: D000818:Animals; D018834:Chaperonin 60 / Q000276:immunology; D016207:Cytokines / Q000097:blood; D004195:Disease Models, Animal; D005620:Freund's Adjuvant / Q000009:adverse effects; D007839:Functional Laterality; D005727:Ganglia, Spinal / Q000166:cytology; D006930:Hyperalgesia / Q000188:drug therapy* / Q000209:etiology*; D008264:Macrophages / Q000378:metabolism; D008297:Male; D004676:Myelin Basic Protein / Q000009:adverse effects / Q000276:immunology; D017288:Pain Threshold / Q000187:drug effects; D010446:Peptide Fragments / Q000009:adverse effects / Q000276:immunology; D051381:Rats; D011917:Rats, Inbred Lew; D020426:Sciatic Neuropathy / Q000150:complications*; D011984:Sensory Receptor Cells / Q000187:drug effects / Q000378:metabolism; D013997:Time Factors; D014611:Vaccination / Q000379:methods*
chemical_list: C000591158:APL-1 peptide; D018834:Chaperonin 60; D016207:Cytokines; D004676:Myelin Basic Protein; D010446:Peptide Fragments; D005620:Freund's Adjuvant