Adjuvant Activity of Mycobacterium paratuberculosis in Enhancing the Immunogenicity of Autoantigens During
Davide Cossu1, Yuji Tomizawa2, Eiichi Momotani2
1Department of Neurology, Juntendo University; Biomedical Research Core Facilities, Juntendo University; davide@juntendo.ac.jp.
Abstract:
Experimental autoimmune encephalomyelitis (EAE) induced by myelin oligodendrocyte glycoprotein (MOG) requires immunization by a MOG peptide emulsified in complete Freund's adjuvant (CFA) containing inactivated Mycobacterium tuberculosis. The antigenic components of the mycobacterium activate dendritic cells to stimulate T-cells to produce cytokines that promote the Th1 response via toll-like receptors. Therefore, the amount and species of mycobacteria present during the antigenic challenge are directly related to the development of EAE. This methods paper presents an alternative protocol to induce EAE in C57BL/6 mice using a modified incomplete Freund's adjuvant containing the heat-killed Mycobacterium avium subspecies paratuberculosis strain K-10. M. paratuberculosis, a member of the Mycobacterium avium complex, is the causative agent of Johne's disease in ruminants and has been identified as a risk factor for several human T-cell-mediated disorders, including multiple sclerosis. Overall, mice immunized with Mycobacterium paratuberculosis showed earlier onset and greater disease severity than mice immunized with CFA containing the strain of M. tuberculosis H37Ra at the same doses of 4 mg/mL. The antigenic determinants of Mycobacterium avium subspecies paratuberculosis (MAP) strain K-10 were able to induce a strong Th1 cellular response during the effector phase, characterized by significantly higher numbers of T-lymphocytes (CD4+ CD27+), dendritic cells (CD11c+ I-A/I-E+), and monocytes (CD11b+ CD115+) in the spleen compared to mice immunized with CFA. Furthermore, the proliferative T-cell response to the MOG peptide appeared to be highest in M. paratuberculosis-immunized mice. The use of an encephalitogen (e.g., MOG35-55) emulsified in an adjuvant containing M. paratuberculosis in the formulation may be an alternative and validated method to activate dendritic cells for priming myelin epitope-specific CD4+ T-cells during the induction phase of EAE.
Insights
This study introduces a new method for inducing experimental autoimmune encephalomyelitis (EAE) in mice using Mycobacterium avium subspecies paratuberculosis (MAP) instead of Mycobacterium tuberculosis. MAP induced EAE faster and more severely, offering a potential alternative for EAE research.
Area of Science:
- Immunology
- Neuroscience
- Microbiology
Background:
- Experimental autoimmune encephalomyelitis (EAE) is a common model for multiple sclerosis, typically induced using myelin oligodendrocyte glycoprotein (MOG) and complete Freund's adjuvant (CFA) containing Mycobacterium tuberculosis.
- The efficacy of EAE induction is linked to the type and amount of mycobacteria used in the adjuvant, which influences dendritic cell activation and T-cell responses.
- Mycobacterium avium subspecies paratuberculosis (MAP), a known pathogen in ruminants and a risk factor for human T-cell disorders, has not been widely explored as an adjuvant for EAE induction.
Purpose of the Study:
- To present an alternative protocol for inducing EAE in C57BL/6 mice.
- To evaluate the efficacy of using heat-killed Mycobacterium avium subspecies paratuberculosis (MAP) strain K-10 as an adjuvant in incomplete Freund's adjuvant (IFA) for EAE induction.
- To compare the EAE induction and immune response generated by MAP with the conventional CFA/M. tuberculosis method.
Main Methods:
- C57BL/6 mice were immunized with MOG peptide emulsified in modified IFA containing heat-killed MAP strain K-10.
- Disease onset and severity were monitored and compared to mice immunized with MOG peptide in CFA containing M. tuberculosis H37Ra.
- Immune cell populations, including T-lymphocytes, dendritic cells, and monocytes, were analyzed in the spleen via flow cytometry.
- Proliferative T-cell responses to the MOG peptide were assessed.
Main Results:
- Mice immunized with MAP showed an earlier onset and greater severity of EAE compared to those immunized with CFA/M. tuberculosis.
- MAP immunization induced a robust Th1 cellular response, evidenced by significantly higher numbers of CD4+ CD27+ T-lymphocytes, CD11c+ I-A/I-E+ dendritic cells, and CD11b+ CD115+ monocytes in the spleen.
- The proliferative T-cell response to the MOG peptide was highest in mice immunized with MAP.
Conclusions:
- Heat-killed Mycobacterium avium subspecies paratuberculosis (MAP) strain K-10 is an effective adjuvant for inducing experimental autoimmune encephalomyelitis (EAE) in mice.
- MAP immunization leads to earlier EAE onset, increased disease severity, and a stronger Th1 cellular immune response compared to conventional M. tuberculosis-based adjuvants.
- Using MAP in an adjuvant formulation offers a validated alternative method for activating dendritic cells and priming myelin epitope-specific CD4+ T-cells for EAE induction.
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