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Altered peptide ligand modulation of experimental allergic encephalomyelitis: immune responses within the CNS
L Santambrogio1, M B Lees, R A Sobel
1Biomedical Sciences Division, E. K. Shriver Center, Waltham, MA 02254, USA.
Abstract:
An altered peptide ligand (analog) of the encephalitogenic epitope of proteolipid protein residues 139-151 (p139-151) in which residues 144 and 147 are substituted with leucine and arginine, respectively (LR), protects from clinical but not histological experimental allergic encephalomyelitis (EAE). To understand in situ events associated with this protection, T cells from brains of mice immunized with either native p139-151, the analog LR or a combination of the two were isolated and characterized. High proportions of cells from co-immunized mice (38%) and LR-immunized mice (58%) reacted to both p139-151 and LR, whereas fewer cells from p139-151 immunized mice (7%) were cross-reactive. T cell clones derived from brains of LR- and co-immunized mice were also cross-reactive in vitro. By reverse transcriptase-based polymerase chain reaction, higher levels of TGF-beta mRNA, and lower levels of TNF-alpha and IFN-gamma mRNA were found in the central nervous system (CNS) tissue of LR and co-immunized mice. Immunohistochemistry demonstrated greater TGF-beta immunoreactivity in CNS inflammatory foci in co-immunized and LR-immunized mice. There were no significant differences in CD4+ or CD8+ cell infiltrates among the groups and differences in other cytokines were not identified by immunocytochemistry. Protection from clinical EAE in LR and co-immunized mice was partially abolished by anti-TGF-beta antibody treatment. Thus, protection from clinical disease following immunization with the analog LR is associated with infiltration into the CNS of a T cell population that could potentially recognize the native PLP peptide and with enhanced TGF-beta production by cells within CNS inflammatory foci.
Insights
An altered peptide ligand analog protects from clinical experimental allergic encephalomyelitis (EAE) by inducing cross-reactive T cells and increasing TGF-beta in the central nervous system (CNS). This suggests a novel therapeutic strategy for autoimmune diseases.
Area of Science:
- Neuroimmunology
- Autoimmune Diseases
- T cell immunology
Background:
- Experimental allergic encephalomyelitis (EAE) is a model for multiple sclerosis.
- Altered peptide ligands (APLs) are used to modulate autoimmune responses.
- Proteolipid protein (PLP) is a key autoantigen in EAE.
Purpose of the Study:
- To investigate the in situ immune mechanisms underlying protection from clinical EAE induced by an APL of PLP 139-151.
- To characterize T cell responses and cytokine profiles in the central nervous system (CNS) following immunization with native PLP peptide or its analog.
Main Methods:
- Induction of EAE in mice using native PLP 139-151 or an APL (LR).
- Isolation and characterization of T cells from the CNS.
- Analysis of T cell cross-reactivity in vitro.
- Quantification of cytokine mRNA (TGF-beta, TNF-alpha, IFN-gamma) and protein in CNS tissue.
- Immunohistochemistry and flow cytometry for immune cell infiltrates.
- Treatment with anti-TGF-beta antibodies.
Main Results:
- Immunization with the LR analog conferred protection from clinical EAE but not histological EAE.
- A significant proportion of CNS T cells from LR- and co-immunized mice showed cross-reactivity to both native and analog peptides.
- Elevated TGF-beta mRNA and protein levels were observed in the CNS of LR-immunized mice.
- Anti-TGF-beta antibody treatment partially reversed the protection.
Conclusions:
- Protection from clinical EAE by the LR analog is associated with CNS infiltration of cross-reactive T cells.
- Enhanced TGF-beta production within CNS inflammatory foci contributes to this protection.
- APL therapy may induce regulatory T cell responses, offering a potential therapeutic avenue for autoimmune encephalomyelitis.