Encephalitogenic and tolerogenic potential of altered peptide ligands of MOG and PLP in Biozzi ABH mice.

Altered peptide ligands (APL) are highly effective in inhibiting experimental autoimmune encephalomyelitis (EAE) in rodents although clinical trials in multiple sclerosis reveal severe limitations probably due to the diverse and differential effects of APL in vivo compared to in vitro. Myelin oligodendrocyte glycoprotein (MOG 8-21) induces relapsing EAE in ABH (A(g7)) mice associated with broadening of the autoimmune repertoire thus providing a dynamic system to examine the efficacy of peptide analogues. Subtle changes in MOG 8-21 dramatically influenced disease susceptibility and T cell responses in vitro. Non-encephalitogenic APL that induce production of the 'regulatory' cytokines IL-10 and/or TGFbeta and concomitant low levels of the 'proinflammatory' cytokines IFNgamma and TNFalpha modulated relapsing EAE but were far less effective than the 'proinflammatory' wild-type MOG 8-21 peptide. These data reveal that APL differ greatly in their ability to activate encephalitogenic T cells. The extensive heterogeneity of responses of APL in vitro suggests that selection of APL on this criteria is highly unpredictable and probably less effective for therapy than selecting the dominant wild-type epitope and delivering it using a tolerogenic route.

Effect of intranasal administration of Semliki Forest virus recombinant particles expressing reporter and cytokine genes on the progression of experimental autoimmune encephalomyelitis.

We have initiated studies to determine the feasibility of employing the Semliki Forest virus (SFV) expression system as a central nervous system (CNS) vector. We investigated the effects of infecting Balb/c mice intranasally (i.n.) with recombinant SFV particles expressing the enhanced green fluorescent protein (EGFP) reporter gene. EGFP expression was detected by fluorescence microscopy in the olfactory bulb as early as 1 day postinfection. No pathological changes were associated with infection. Viral RNA could be detected in the olfactory mucosa only, whereas fluorescence was detected in axons in the olfactory bulb, indicating that only the expressed protein was present. A vector expressing interleukin 10 (IL-10) was constructed and shown to induce good cytokine expression in cultured cells. IL-10 expression in the nasal passage and olfactory bulb of infected mice was enhanced following i.n. administration of such particles. Mice induced for experimental autoimmune encephalomyelitis (EAE) were treated i.n. with vectors expressing EGFP and IL-10 and with empty vector. The EGFP-expressing and empty vectors were found to exacerbate EAE, whereas that expressing IL-10 ameliorated EAE. It is concluded that the mice showed a significant biological response when treated i.n. with recombinant SFV particles and that such particles administered by the i.n. route have potential as a noninvasive vector for protein delivery to the CNS.

Pathological and regulatory effects of anti-myelin antibodies in experimental allergic encephalomyelitis in mice.

Neurological deficit in experimental allergic encephalomyelitis (EAE) and multiple sclerosis (MS) is probably a consequence of synergy between T and B cell responses to CNS antigens. During the demyelinating phase of chronic relapsing EAE in ABH mice, anti-myelin oligodendrocyte glycoprotein (MOG) responses were increased compared to the inflammatory acute phase, but such levels did not correlate with the severity of clinical disease. The pathogenicity of antibodies (Ab) to MOG, myelin basic protein (MBP), proteolipid protein (PLP) and galactocerebroside (GalC) was investigated in vivo following injection at the onset of EAE. An IgG2a monoclonal Ab (mAb), clone Z12, directed to MOG augmented clinical disease and demyelination in ABH and C57BL/6 mice, but not MOG knock-out mice. No effect was observed with F(ab(2))' fragments of Z12 or with the anti-MOG IgG1 mAbs, clones Y10 or 8-18C5. Cobra venom factor partially reduced the augmenting effect of mAb Z12 suggesting a role for complement. The pathogenic effect of anti-myelin Abs was not restricted to MOG since an anti-GalC mAb exacerbated inflammation in the CNS while an MBP mAb (clone 22) reduced clinical disease. Taken together, these data provide further evidence that myelin-reactive Abs generated during autoimmune neurological disease may play an important role not only in the pathogenesis of disease but also the regulation of myelin-targeted autoimmune disease.

Encephalitogenic and immunogenic potential of myelin-associated glycoprotein (MAG), oligodendrocyte-specific glycoprotein (OSP) and 2',3'-cyclic nucleotide 3'-phosphodiesterase (CNPase) in ABH and SJL mice.

Synthetic peptides of myelin-associated glycoprotein (MAG), oligodendrocyte-specific glycoprotein (OSP) and 2',3'-cyclic nucleotide 3'-phosphodiesterase (CNPase) were screened for their ability to induce experimental allergic encephalomyelitis (EAE) in ABH (H-2A(g7)) and SJL (H-2(s)) mice. The use of overlapping 16mer MAG peptides identified residues 97-112 as a T-cell and encephalitogenic epitope in ABH mice which induced clinical and histological signs of acute EAE. Immunization of SJL mice with MAG peptides failed to induce disease whereas immunization of SJL mice with synthetic peptides of OSP induced major T-cell responses to OSP 73-88 and 81-96. Another epitope, OSP 57-72, that induced EAE, failed to induce T-cell responses in mice immunised with peptides based on the whole sequence supporting a role for cryptic epitopes. In comparison, whilst immunization of ABH mice with OSP revealed two immunodominant T-cell epitopes (49-64 and 137-152), an encephalitogenic epitope was not identified. Similarly, immunization of both SJL and ABH mice with CNPase peptides induced T-cell responses to several epitopes. However, these were not encephalitogenic. This study is the first to identify an encephalitogenic epitope of MAG and immunodominant epitopes of MAG, OSP and CNPase in SJL and ABH mice. The ability of both cryptic and noncryptic peptide epitopes of these myelin antigens to initiate EAE suggests that mice at least are not tolerant to some regions of MAG and OSP and that such specific autoimmune responses may play an important role in the pathogenesis of immune-mediated neurological diseases such as multiple sclerosis.