Epitope-specific CD8+ T cells play a differential pathogenic role in the development of a viral disease model for multiple sclerosis.

Theiler's virus-induced demyelinating disease has been extensively investigated as a model for persistent viral infection and multiple sclerosis (MS). However, the role of CD8(+) T cells in the development of disease remains unclear. To assess the role of virus-specific CD8(+) T cells in the pathogenesis of demyelinating disease, a single amino acid substitution was introduced into the predominant viral epitope (VP3 from residues 159 to 166 [VP3(159-166)]) and/or a subdominant viral epitope (VP3(173-181)) of susceptible SJL/J mice by site-directed mutagenesis. The resulting variant viruses (N160V, P179A, and N160V/P179A) failed to induce CD8(+) T cell responses to the respective epitopes. Surprisingly, mice infected with N160V or N160V/P179A virus, which lacks CD8(+) T cells against VP3(159-166), did not develop demyelinating disease, in contrast to wild-type virus or P179A virus lacking VP3(173-181)-specific CD8(+) T cells. Our findings clearly show that the presence of VP3(159-166)-specific CD8(+) T cells, rather than viral persistence itself, is strongly correlated with disease development. VP3(173-181)-specific CD8(+) T cells in the central nervous system (CNS) of these virus-infected mice expressed higher levels of transforming growth factor ß, forkhead box P3, interleukin-22 (IL-22), and IL-17 mRNA but caused minimal cytotoxicity compared to that caused by VP3(159-166)-specific CD8(+) T cells. VP3(159-166)-specific CD8(+) T cells exhibited high functional avidity for gamma interferon production, whereas VP3(173-181)-specific CD8(+) T cells showed low avidity. To our knowledge, this is the first report indicating that the induction of the IL-17-producing CD8(+) T cell type is largely epitope specific and that this specificity apparently plays a differential role in the pathogenicity of virus-induced demyelinating disease. These results strongly advocate for the careful consideration of CD8(+) T cell-mediated intervention of virus-induced inflammatory diseases.

Molecular dissection of ALS-associated toxicity of SOD1 in transgenic mice using an exon-fusion approach.

Mutations in Cu,Zn superoxide dismutase (SOD1) are associated with amyotrophic lateral sclerosis (ALS). Among more than 100 ALS-associated SOD1 mutations, premature termination codon (PTC) mutations exclusively occur in exon 5, the last exon of SOD1. The molecular basis of ALS-associated toxicity of the mutant SOD1 is not fully understood. Here, we show that nonsense-mediated mRNA decay (NMD) underlies clearance of mutant mRNA with a PTC in the non-terminal exons. To further define the crucial ALS-associated SOD1 fragments, we designed and tested an exon-fusion approach using an artificial transgene SOD1(T116X) that harbors a PTC in exon 4. We found that the SOD1(T116X) transgene with a fused exon could escape NMD in cellular models. We generated a transgenic mouse model that overexpresses SOD1(T116X). This mouse model developed ALS-like phenotype and pathology. Thus, our data have demonstrated that a 'mini-SOD1' of only 115 amino acids is sufficient to cause ALS. This is the smallest ALS-causing SOD1 molecule currently defined. This proof of principle result suggests that the exon-fusion approach may have potential not only to further define a shorter ALS-associated SOD1 fragment, thus providing a molecular target for designing rational therapy, but also to dissect toxicities of other proteins encoded by genes of multiple exons through a 'gain of function' mechanism.

Anticapsid immunity level, not viral persistence level, correlates with the progression of Theiler's virus-induced demyelinating disease in viral P1-transgenic mice.

Intracranial infection of Theiler's murine encephalomyelitis virus (TMEV) induces demyelination and a neurological disease in susceptible SJL/J (SJL) mice that resembles multiple sclerosis. While the virus is cleared from the central nervous system (CNS) of resistant C57BL/6 (B6) mice, it persists in SJL mice. To investigate the role of viral persistence and its accompanying immune responses in the development of demyelinating disease, transgenic mice expressing the P1 region of the TMEV genome (P1-Tg) were employed. Interestingly, P1-Tg mice with the B6 background showed severe reductions in both CD4(+) and CD8(+) T-cell responses to capsid epitopes, while P1-Tg mice with the SJL background displayed transient reductions following viral infection. Reduced antiviral immune responses in P1-Tg mice led to >100- to 1,000-fold increases in viral persistence at 120 days postinfection in the CNS of mice with both backgrounds. Despite the increased CNS TMEV levels in these P1-Tg mice, B6 P1-Tg mice developed neither neuropathological symptoms nor demyelinating lesions, and SJL P1-Tg mice developed significantly less severe TMEV-induced demyelinating disease. These results strongly suggest that viral persistence alone is not sufficient to induce disease and that the level of T-cell immunity to viral capsid epitopes is critical for the development of demyelinating disease in SJL mice.

Normal Th1 development following long-term therapeutic blockade of CD154-CD40 in experimental autoimmune encephalomyelitis.

Experimental autoimmune encephalomyelitis (EAE) is a Th1-mediated demyelinating disease of the CNS with similarities to multiple sclerosis. We and others have shown that a short-term course of anti-CD154 mAb treatment to block CD154-CD40 interactions can be used to prevent or even treat ongoing PLP139-151-induced relapsing EAE. However, little is known of the long-term effects of CD154 blockade on the development of antigen-specific T cell function. Here, we show that short-term treatment with anti-CD154 at the time of PLP139-151/CFA immunization inhibits clinical disease for up to 100 days after immunization. At this point, comparable numbers of Th1 cells are observed in anti-CD154 and control Ig-treated mice, as assessed by antigen-specific ELISPOT assays. Thus, the long-term Th1/Th2 balance is largely unaffected. Inflammatory responses are diminished in anti-CD154-treated mice, as indicated by reduced in vivo delayed-type hypersensitivity and reduced levels of splenic IFN-gamma secretion in vitro. However, upon adoptive transfer of T cells isolated from the spleens of anti-CD154-treated mice, these cells contributed as effectively to clinical disease as those obtained from control-treated mice. Thus, anti-CD154 therapy leads to long-term therapeutic efficacy without exerting a long-term influence on Th1 development.

CCR2 regulates development of Theiler's murine encephalomyelitis virus-induced demyelinating disease.

Theiler's murine encephalomyelitis virus (TMEV)-induced demyelinating disease, a murine model for multiple sclerosis, involves recruitment of T cells and macrophages to the CNS after infection. We hypothesized that CCR2, the only known receptor for CCL2, would be required for TMEV-induced demyelinating disease development because of its role in macrophage recruitment. TMEV-infected SJL CCR2 knockout (KO) mice showed decreased long-term clinical disease severity and less demyelination compared with controls. Flow cytometric data indicated that macrophages (CD45(high) CD11b(+) ) in the CNS of TMEV-infected CCR2 KO mice were decreased compared with control mice throughout disease. CD4(+) and CD8(+) T cell percentages in the CNS of TMEV-infected control and CCR2 KO mice were similar over the course of disease. There were no apparent differences between CCR2 KO and control peripheral immune responses. The frequency of interferon-gamma-producing T cells in response to proteolipid protein 139-151 in the CNS was also similar during the autoimmunity stage of TMEV-induced demyelinating disease. These data suggest that CCR2 is important for development of clinical disease by regulating macrophage accumulation after TMEV infection.

Transient anti-CD154-mediated immunotherapy of ongoing relapsing experimental autoimmune encephalomyelitis induces long-term inhibition of disease relapses.

Relapsing experimental autoimmune encephalomyelitis (R-EAE) is a Th1-mediated central nervous system (CNS) autoimmune disease with pathology similar to that of relapsing-remitting multiple sclerosis. Among recent therapeutic approaches to prevent or treat relapsing disease is the strategic blockade of the CD154-CD40 ligand pair interactions. We have previously shown that CD154 blockade at the peak of acute disease can, in the short term, inhibit spontaneous disease relapse and this is at least partly associated with the inhibition of T cell effector function and blockade of inflammatory cell recruitment to and/or retention in the CNS. However, little is understood about the long-term effects of CD154 blockade in the inhibition of immune responses to encephalitogenic antigens. Here we demonstrate that transient anti-CD154 blockade of CD154-CD40 interactions at the peak of acute phase of R-EAE resulted in significant long-term inhibition (by >80%) of clinical relapses and that clinical disease in those mice that did relapse was reduced in duration and severity compared to control antibody-treated mice. Additionally, we show that this strategy permanently inhibits DTH responses of T cells specific for relapse-associated encephalitogenic epitopes. Thus, transient CD154 blockade during ongoing disease has a long-term therapeutic efficacy in preventing disease relapses.

Distal axonopathy in an alsin-deficient mouse model.

Mutations in Alsin are associated with chronic juvenile amyotrophic lateral sclerosis (ALS2), juvenile primary lateral sclerosis and infantile-onset ascending spastic paralysis. The primary pathology and pathogenic mechanism of the disease remain largely unknown. Here we show that alsin-deficient mice have motor impairment and degenerative pathology in the distal corticospinal tracts without apparent motor neuron pathology. Our data suggest that ALS2 is predominantly a distal axonopathy, rather than a neuronopathy in the central nervous system of the mouse model, implying that alsin plays an important role in maintaining the integrity of the corticospinal axons.

Anti-CCL2 treatment inhibits Theiler's murine encephalomyelitis virus-induced demyelinating disease.

Theiler's murine encephalomyelitis virus induces a demyelinating disease (TMEV-IDD) of the central nervous system (CNS) in susceptible mouse strains with accompanying histopathology characterized by mononuclear cell infiltrates. In susceptible strains of mice such as SJL, virus establishes a persistent infection in macrophages, induces a CNS infiltration by macrophages, T cells, and B cells, which results in chronic-progressive paralysis. In the present report the authors have investigated the functional role of CCL2 (monocyte chemotactic protein-1) in the induction and progression of demyelinating disease. Treatment of infected mice at day 0, 14, or 28 with anti-CCL2 resulted in a significant decrease in the clinical disease progression. Further analysis of anti-CCL2-treated mice revealed decreased CNS inflammation and mononuclear cell infiltration with an accompanying change in inflammatory cytokine responses. There was an overall decrease in the absolute numbers of CNS-infiltrating CD4+ T cells, macrophages, and B cells. Finally, anti-CCL2 treatment resulted in decreased viral load in the CNS. These data directly demonstrate a role for CCL2 in the pathogenesis of TMEV-IDD.

Conversion to the amyotrophic lateral sclerosis phenotype is associated with intermolecular linked insoluble aggregates of SOD1 in mitochondria.

Twenty percent of the familial form of amyotrophic lateral sclerosis (ALS) is caused by mutations in the Cu, Zn-superoxide dismutase gene (SOD1) through the gain of a toxic function. The nature of this toxic function of mutant SOD1 has remained largely unknown. Here we show that WT SOD1 not only hastens onset of the ALS phenotype but can also convert an unaffected phenotype to an ALS phenotype in mutant SOD1 transgenic mouse models. Further analyses of the single- and double-transgenic mice revealed that conversion of mutant SOD1 from a soluble form to an aggregated and detergent-insoluble form was associated with development of the ALS phenotype in transgenic mice. Conversion of WT SOD1 from a soluble form to an aggregated and insoluble form also correlates with exacerbation of the disease or conversion to a disease phenotype in double-transgenic mice. This conversion, observed in the mitochondrial fraction of the spinal cord, involved formation of insoluble SOD1 dimers and multimers that are crosslinked through intermolecular disulfide bonds via oxidation of cysteine residues in SOD1. Our data thus show a molecular mechanism by which SOD1, an important protein in cellular defense against free radicals, is converted to aggregated and apparently ALS-associated toxic dimers and multimers by redox processes. These findings provide evidence of direct links among oxidation, protein aggregation, mitochondrial damage, and SOD1-mediated ALS, with possible applications to the aging process and other late-onset neurodegenerative disorders. Importantly, rational therapy based on these observations can now be developed and tested.

Gender bias in Theiler's virus-induced demyelinating disease correlates with the level of antiviral immune responses.

Multiple sclerosis is an immune-mediated disease of the CNS and shows a sex-biased distribution in which 60-75% of all cases are female. A mouse model of multiple sclerosis, Theiler's murine encephalomyelitis virus (TMEV)-induced demyelinating disease, also displays a gender bias. However, in the C57L/J strain of mice, males are susceptible to disease whereas females are completely resistant. In this study we determined the gender differences in the TMEV-specific immune response, which may be responsible for the gender bias in clinical disease. Our data clearly demonstrate that female C57L/J mice induce significantly higher levels of TMEV-specific neutralizing Ab as well as a stronger peripheral T cell response throughout the course of viral infection. In contrast, male mice have a higher level of TMEV-specific CD4(+) and CD8(+) T cell infiltration into the CNS as well as viral persistence. These results suggest that a higher level of the initial antiviral immune response in female mice may be able to effectively clear virus from the periphery and CNS and therefore prevent further disease manifestations. Male mice in contrast do not mount as effective an immune response, thereby allowing for eventual viral persistence in the CNS and continuous T cell expansion leading to clinical symptoms.

CD40/CD40L interaction is essential for the induction of EAE in the absence of CD28-mediated co-stimulation.

CD28 provides a co-stimulatory signal critical for optimal T cell activation. We and others have shown that the B7/CD28 co-stimulatory pathway is a major regulatory pathway for the control of immune responses. Experimentally induced models of autoimmunity have been shown to be prevented or reduced in intensity in mice deficient for CD28. Here, we show that EAE and accompanying neuroantigen-specific immune responses are drastically reduced in the absence of CD28. However, we go on to show that EAE can be induced in CD28-deficient mice following two immunizations. After re-immunization, CD28-deficient mice develop severe EAE with myelin-specific responses equal to those of wildtype controls, and extensive demyelination in the spinal cord. Treatment of CD28-deficient mice with anti-CD40L at the time of immunization significantly reduced DTH responses and prevented the development of EAE following two immunizations, indicating a critical role for CD40/CD40L signaling in the absence of CD28. Taken together, our results indicate that CD28-mediated co-stimulation does not regulate immunological anergy. Instead, CD28 appears to adjust the threshold for activation and expansion of autoreactive cells.

CD154 blockade results in transient reduction in Theiler's murine encephalomyelitis virus-induced demyelinating disease.

Transient CD154 blockade at the onset of Theiler's murine encephalomyelitis virus-induced demyelinating disease ameliorated disease progression for 80 days, reduced immune cell infiltration, and transiently increased viral loads in the central nervous system. Peripheral antiviral and autoimmune T-cell responses were normal, and disease severity returned to control levels by day 120.

De novo central nervous system processing of myelin antigen is required for the initiation of experimental autoimmune encephalomyelitis.

We demonstrate the absolute requirement for a functioning class II-restricted Ag processing pathway in the CNS for the initiation of experimental autoimmune encephalomyelitis (EAE). C57BL/6 (B6) mice deficient for the class II transactivator, which have defects in MHC class II, invariant chain (Ii), and H-2M (DM) expression, are resistant to initiation of myelin oligodendrocyte protein (MOG) peptide, MOG(35-55)-specific EAE by both priming and adoptive transfer of encephalitogenic T cells. However, class II transactivator-deficient mice can prime a suboptimal myelin-specific CD4(+) Th1 response. Further, B6 mice individually deficient for Ii and DM are also resistant to initiation of both active and adoptive EAE. Although both Ii-deficient and DM-deficient APCs can present MOG peptide to CD4(+) T cells, neither is capable of processing and presenting the encephalitogenic peptide of intact MOG protein. This phenotype is not Ag-specific, as DM- and Ii-deficient mice are also resistant to initiation of EAE by proteolipid protein peptide PLP(178-191). Remarkably, DM-deficient mice can prime a potent peripheral Th1 response to MOG(35-55), comparable to the response seen in wild-type mice, yet maintain resistance to EAE initiation. Most striking is the demonstration that T cells from MOG(35-55)-primed DM knockout mice can adoptively transfer EAE to wild-type, but not DM-deficient, mice. Together, these data demonstrate that the inability to process antigenic peptide from intact myelin protein results in resistance to EAE and that de novo processing and presentation of myelin Ags in the CNS is absolutely required for the initiation of autoimmune demyelinating disease.

Selective formation of certain advanced glycation end products in spinal cord astrocytes of humans and mice with superoxide dismutase-1 mutation.

Recent studies have documented carbonyl stress involvement in the pathogenesis of sporadic amyotrophic lateral sclerosis (ALS). The aim of the present study was to assess a role for carbonyl stress in motor neuron degeneration associated with superoxide dismutase-1 (SOD1) mutant familial ALS and its transgenic mouse model, using an immunohistochemical investigation of advanced glycation end products (AGEs) and advanced lipoxidation end products (ALEs). In the spinal cords from six familial ALS patients with SOD1 A4V mutation and six transgenic mice expressing G93A mutant human SOD1, immunoreactivities for N(epsilon)-(carboxyethyl)lysine, argpyrimidine, pyrraline and N(epsilon)-(carboxymethyl)lysine as AGEs were distinct in almost all of the reactive astrocytes and obscure in the residual neurons, whereas no immunoreactivity for pentosidine as an AGE, or 4-hydroxy-2-nonenal-histidine, malondialdehyde-lysine or acrolein-lysine as ALEs was detectable. Spinal cords from age-matched control humans and mice exhibited no significant immunoreactivities for the examined products. Our results indicate that protein glycation, but not lipid peroxidation, is enhanced in ALS patients with an SOD1 mutation and mutant SOD1 transgenic mice, in which certain AGEs are selectively formed in the spinal cord astrocytes.

Molecular biological approaches to neurological disorders including knockout and transgenic mouse models.

Advances of molecular biology have provided a great variety of new approaches to research on human disorders. This article gives an outline of molecular biological approaches to analysis of neurological disorders such as giant cell glioblastoma (GGBM) and amyotrophic lateral sclerosis (ALS), and their respective animal models: p53 knockout mice for GGBM and mutant superoxide dismutase-1 transgenic mice for ALS. Genomic DNA extracted from fresh-frozen tissue is examined by Southern blotting for screening mutations in a certain gene. Polymerase chain reaction (PCR) products of a gene in genomic DNA are examined by single-stranded conformation polymorphism, sequencing and agarose gel electrophoresis for identifying mutations, and for preparing and evaluating DNA probes used in Southern blotting and DNA in situ hybridization (ISH). Total RNA from tissue is examined by northern blotting for quantifying and verifying a certain mRNA. Reverse transcription-PCR products of a certain mRNA in total RNA are examined by sequencing and agarose gel electrophoresis for preparing and evaluating cDNA probes used in northern blotting and mRNA ISH. Tissue total protein is immunoblotted for quantifying and verifying a certain protein, and for evaluating the specificity of antibodies used in western blotting and immunohistochemistry. Immunoprecipitates are immunoblotted for evaluating a profile of protein or other substances. Enzyme-linked immunosorbent assay is used for measuring tissue concentration of protein or other substances, and for determining titers of specific antibodies. By these procedures, chronological analysis of animal models for human diseases contribute to elucidating pathogenic mechanisms and exploiting new therapies. Noticing both the similarity and difference between human and animal disorders will help understand the nature of disease.