Differential induction of experimental autoimmune encephalomyelitis by myelin basic protein molecular mimics in mice...

Area of Science:

• Neuroimmunology
• Autoimmune Diseases
• Molecular Mimicry

Background:

• Multiple sclerosis (MS) is a chronic autoimmune neurological disease affecting the central nervous system (CNS).
• Epidemiological data suggest infectious agents may trigger MS through molecular mimicry, where foreign epitopes resemble self-antigens like myelin basic protein (MBP).
• Previous studies identified cross-reactivity between an MS patient's MBP(85-99)-specific T cells and bacterial mimic peptides in vitro.

Purpose of the Study:

• To investigate if bacterial mimic peptides, previously shown to cross-react with MBP-specific T cells, can induce clinical disease in a mouse model of MS.
• To determine if molecular mimicry can serve as a mechanism for triggering autoimmune responses in the CNS.

Main Methods:

• Utilized transgenic mice expressing a human MBP(85-99)-specific T cell receptor (TCR) and HLA-DR2 (MHC Class II).
• Administered bacterial-derived mimic peptides to induce experimental autoimmune encephalomyelitis (EAE).
• Assessed clinical disease patterns, CNS inflammatory cell infiltration (CD4+ T cells, F4/80+ macrophages), and ex vivo splenocyte responses.

Main Results:

• The mimic peptides induced clinical disease in two different transgenic mouse strains, exhibiting distinct patterns (relapsing-remitting vs. monophasic).
• Clinical disease onset correlated with increased infiltration of CD4+ T cells and F4/80+ macrophages in the CNS.
• No correlation was observed between clinical disease and in vitro splenocyte proliferation or cytokine production in response to MBP(85-99) or mimic peptides.

Conclusions:

• Bacterial mimic peptides can induce experimental autoimmune encephalomyelitis (EAE) in mice expressing relevant human TCR and MHC molecules, supporting the molecular mimicry hypothesis for MS pathogenesis.
• Clinical manifestations of MS-like disease in this model are associated with CNS immune cell infiltration rather than solely in vitro immune cell reactivity.
• These findings provide in vivo evidence for how infections might initiate or exacerbate autoimmune responses targeting myelin in the CNS.