Immunization with a peptide of Semliki Forest virus promotes remyelination in experimental autoimmune encephalomyelitis.

Remyelination is one of the elusive topics in treatment of multiple sclerosis (MS). Our previous studies have shown that Semliki Forest virus (SFV)-infected δ-knock-out (KO) mice did not exhibit the extensive remyelination, seen in wild type (WT) B6 mice, after viral clearance and demyelination. The Remyelination in SFV-infected WT mice started on day 15 and was completed by day 35 post-infection (pi), whereas the KO mice remained partially demyelinated through day 42 pi. Treatment with E2 peptide2 in incomplete Freund's adjuvant (IFA), resulted in higher antibody production and earlier remyelination in SFV-infected KO (day 28 pi), than WT mice. This finding suggested that anti-E2 peptide2 antibody could play a part in remyelination. In the current study, the effect of E2 peptide2 treatment was evaluated in the experimental autoimmune encephalomyelitis (EAE) model. Mice with established EAE were treated with E2 peptide2 in IFA to develop antibody. Treated EAE mice made significantly higher anti-E2 peptide2 antibody than untreated EAE group. Average clinical disease scores were significantly lower in peptide treated compared to untreated EAE mice. Furthermore, histopathological and immunohistochemical studies demonstrated increased remyelinating areas and higher number of activated oligodendrocytes and astrocytes, in treated compared to untreated EAE groups. Moreover, the anti-E2 peptide2 antibody showed higher binding to the myelinated areas of treated than untreated EAE mice. We conclude that treatment with, or antibody to, SFV E2 peptide2 triggers some mechanism that promotes remyelination.

Role of γδ T cells in antibody production and recovery from SFV demyelinating disease.

Semliki Forest Virus (SFV) encephalomyelitis has been used to study the pathogenesis of virus-induced demyelination and serves as a model for multiple sclerosis. SFV-infection of mice invariably leads to clinical weakness accompanied by CNS inflammation, viral clearance and primary demyelination by day 21 postinfection (pi), followed by recovery and remyelination by day 35 pi. We have applied this model to the examination of the effects of γδ T cells in antibody production and the pathogenesis of demyelinating lesions. SFV-infection of γδ T cell KO mice resulted in more severe clinical signs than in wild type (WT) B6 mice. SFV-infected WT and γδ KO mice both cleared virus by day 10 pi and inflammation was comparable. Demyelination also appeared to be similar in both groups except that KO mice did not exhibit extensive remyelination which was seen in WT mice by day 21. SFV-infected WT mice showed widespread remyelination by day 35 pi, whereas KO mice still displayed some demyelination through day 42 pi. Both WT and KO mice developed serum antibodies to SFV. However, the reactivity of WT sera with the SFV epitope, E2 T(h) peptide2, was significantly higher than in KO sera. Immunization with E2 T(h) peptide2 resulted in elevated antibody production to this peptide (p<0.05) and earlier remyelination (day 28 pi) in KO mice. Thus, our study has shown for the first time that immunization of SFV-infected γδ T cell KO mice with a viral peptide, E2 T(h) peptide2 led to enhanced recovery and repair of the CNS.

Prevention of axonal injury using calpain inhibitor in chronic progressive experimental autoimmune encephalomyelitis.

Axonal injury is the major correlate of permanent disability in neurodegenerative diseases such as multiple sclerosis (MS), especially in secondary-progressive MS which follows relapsing-remitting disease course. Proteolytic enzyme, calpain, is a potential candidate for causing axonal injury. Most current treatment options only target the inflammatory component of MS. Previous work using calpain inhibitor CYLA in our laboratory showed significant reduction in clinical sign, demyelination and tissue calpain content in acute experimental autoimmune encephalomyelitis (EAE). Here we evaluated markers of axonal injury (amyloid precursor protein, Na(v)1.6 channels), neuronal calpain content and the effect of CYLA on axonal protection using histological methods in chronic EAE [myelin oligodendrocyte glycoprotein (MOG)-induced disease model of MS]. Intraperitoneal application of CYLA (2 mg/mouse/day) significantly reduced the clinical signs, tissue calpain content, demyelination and inflammatory infiltration of EAE. Similarly, markers for axonal injury were barely detectable in the treated mice. Thus, this novel drug, which markedly suppresses the disease course, axonal injury and its progression, is a candidate for the treatment of a neurodegenerative disease such as multiple sclerosis.

Microinfusion into the rat brain of antibodies against Semliki Forest Virus produces changes in behavioral response to apomorphine.

Anti-SFV antibodies generated during SFV infection may affect CNS function due to cross-reactivity with a peptide of oligodendrocyte myelin glycoprotein. To explore this possibility, total IgG from SFV immunized or normal control rabbits was unilaterally microinfused into the subthalamic region of normal rat brain. Behavior of the IgG-infused rats was determined using a bioassay, measuring rotational locomotion following systemic injection of apomorphine. Anti-SFV IgG-infused rats demonstrated a significantly increased (p<0.005) ipsilateral turning response compared to control rats, persisting for at least a month. Results suggest that brain cross-reactive antibodies in anti-SFV IgG may affect brain function.

A novel calpain inhibitor for the treatment of acute experimental autoimmune encephalomyelitis.

Aberrant activation of calpain plays a key role in the pathophysiology of several neurodegenerative disorders. Calpain is increasingly expressed in inflammatory cells in EAE and is significantly elevated in the white matter of patients with multiple sclerosis, thus calpain inhibition could be a target for therapeutic intervention. The experiments reported here employed a myelin oligodendrocyte glycoprotein-induced disease model in C57Bl/6 mice (EAE) and a novel calpain inhibitor, targeted to nervous tissue. CYLA was found to reduce clinical signs of EAE and prevent demyelination and inflammatory infiltration in a dose- and time-dependent manner. Oral administration of the diacetal prodrug was equally effective.

Semliki Forest virus-induced demyelination and remyelination--involvement of B cells and anti-myelin antibodies.

Semliki Forest virus (SFV) infection induces a demyelinating encephalomyelitis in the central nervous system (CNS) of mice and serves as a model for multiple sclerosis (MS). This study investigated CNS immune responses at different stages of infection and during SFV-induced demyelination and remyelination. Following the initial CNS inflammation, pathology and viral clearance on days 6-10 post-infection (pi), primary demyelination was observed in cerebellar, brainstem and corpus collosal white matter by days 15-21 pi, with plasma cells and microglia as main participants, and this was followed by remyelination. By day 35 pi, the tissue appeared almost normal. Fluorescent antibody cell sorter (FACS) analysis showed that brain CD8(+) T cells increased during the initial inflammatory response and gradually decreased thereafter. Brain B cell (B220(+)CD19(+)) numbers did not change significantly during the course of infection; however, from days 14 to 35 pi, they matured and produced antibodies to viral and myelin proteins (and peptides) during the period of demyelination and remyelination. The proportion of CD3(-)B220(-)CD11b(+) cells also progressively increased throughout the periods of de- and remyelination. Our results suggest that CD8(+) T cells are involved in the initial destruction of CNS tissue during the first weeks of SFV infection, while B cells, antibodies and microglia may contribute to the myelin pathology seen after recovery.