COVID-19 Alpha Variant (B.1.1.7): Humoral, memory B and T cells in COVID-19 pediatric convalescents.

BACKGROUND: Studies of anti-SARS-CoV-2 humoral and adaptive response in COVID-19 non-vaccinated pediatric convalescents are controversial and further evidence from the pediatric population are needed. OBJECTIVES: To elucidate SARS-CoV-2 humoral and memory B- and T-cells responses in pediatric convalescents as compared with the adult. METHODS: Blood samples were obtained from 80 non-vaccinated, IgG-positive, COVID-19 convalescents (age 8.0-61.0 years), 4.0 months from onset. Frequency of responders and magnitudes of SARS-COV-2 IgG, memory B-cells (MBC) and IFNg- and IL2-secreting memory T-cells (MTC) in response to immuno-dominant peptide pools in pediatric, young adults and middle-aged adults with onset age 8-18 years (N = 20), 19-39 years (N = 30) and 40-61 years (N = 30), respectively, were analyzed. SARS-CoV-2 IgG were detected by ELISA (Euroimmun, Germany). MBC, IFNg-, IL2- and IFNg+IL2-secreting MTC (IFNg-MTC, IL2-MTC and IFNg+IL2-MTC) were detected using FluoroSpot (Mabtech, Sweden). RESULTS: MBC level was lower in pediatric as compared with the middle-aged adults (median 12.75 interquartile range [IQR] 4.27-33.7 and 32.0 IQR 6.0-124.2, respectively, p = .003). MBC level in young adults was lower than in middle-aged adults (median 18.5 IQR 1.7-43.8 and 32.0 IQR 6.0-124.2, respectively, p = .006). The level of IL2-MTC was lower in the pediatric group as compared with middle aged-adults (median 2.1 IQR 0-16.9 and 28.6 IQR 11-49.6, respectively, p < .03) and in young adults lower than in middle-aged adults (median 1.45 IQR 0-18.6 and 28.6 IQR 11-49.6, respectively, p = .02). In addition, the level of IFNg-MTC was lower in pediatric as compared with young adults (median 4.25 IQR 0.0-15.0 and 20.9 IQR 0-75.2, respectively, p = .05). The level of IgG was comparable between pediatric and both young and middle-aged adult groups (4.82 ± 2.95, 3.70 ± 2.65 and 4.9 ± 2.94, respectively, p > .34). CONCLUSION: Non-vaccinated COVID-19 pediatric convalescents have lower adaptive immune responses than adults sustaining the recommendation for vaccination of the pediatric population.

RAM-589.555 favors neuroprotective and anti-inflammatory profile of CNS-resident glial cells in acute relapse EAE affected mice.

BACKGROUND: Targeting RNA polymerase-1 (POL1) machinery is a new strategy for suppression of multiple sclerosis (MS) relapse activity. Oral administration of POL1 inhibitor RAM-589.555, which is characterized by high permeability and bioavailability in naïve mice, ameliorates proteolipid protein (PLP)-induced experimental autoimmune encephalomyelitis (EAE) by suppressing activated autoreactive lymphocytes. We assessed the accessibility of RAM-589.555 to the central nervous system (CNS) of EAE-mice and further investigated its immunomodulatory effects on CNS-resident astro- and micro-glial cells in-vitro and in-vivo. METHODS: Effects of RAM-589.555 on activated microglia and astrocyte viability, proliferation, and secretion of neurotrophic factors were assessed in-vitro. The pharmacokinetic of RAM-589.555 was evaluated in the blood and central nervous system (CNS) of EAE-affected mice. High-dimensional single-cell mass cytometry was applied to characterize the effect of RAM-589.555 on EAE-affected mice's CNS-resident micro- and astroglial cells and CNS-infiltrating immune cells, which were obtained seven days after RAM-589.555 administration at EAE onset. Simultaneously, the expression level of pre-rRNA, the POL1 end product, was assessed in blood cells, microglia, and astrocytes to monitor RAM-589.555 effects. RESULTS: RAM-589.555 demonstrated blood and CNS permeability in EAE mice. In-vitro, incubation with 400 nM of RAM-589.555 significantly reduced viability and proliferation of lipopolysaccharide (LPS)-activated microglia by 70% and 45% (p < 0.05), respectively, while tumor necrosis factor α (TNFα)-activated astrocytes were not affected. The secretion of neurotrophic factors was preserved. Furthermore, 7 days after administration of RAM-589.555 at EAE onset, the level of pre-rRNA transcript in peripheral blood mononuclear cells (PBMC) was decreased by 38.6% (p = 0.02), while levels of pre-rRNA transcript in microglia and astrocytes remained unchanged. The high-dimensional single-cell mass cytometry analysis showed decreased percentages of CNS-resident microglia and astrocytes, diminished pro-inflammatory cytokines (IL-1ß, IL-6, IL-12, IL-17, TNFα, and IFNγ), and an increase of their anti-inflammatory cytokines (IL-4, IL-10, and TGFß) in RAM-589.555-treated compared to vehicle-treated mice (p < 0.05). CONCLUSIONS: These data correlate RAM-589.555-induced clinical amelioration and its CNS-permeability to decreased CNS-inflammation, and decreased micro- and astrogliosis, while restoring micro- and astroglial anti-inflammatory and neuroprotective capacity.

Post-CNS-inflammation expression of CXCL12 promotes the endogenous myelin/neuronal repair capacity following spontaneous recovery from multiple sclerosis-like disease.

BACKGROUND: Demyelination and axonal degeneration, hallmarks of multiple sclerosis (MS), are associated with the central nervous system (CNS) inflammation facilitated by C-X-C motif chemokine 12 (CXCL12) chemokine. Both in MS and in experimental autoimmune encephalomyelitis (EAE), the deleterious CNS inflammation has been associated with upregulation of CXCL12 expression in the CNS. We investigated the expression dynamics of CXCL12 in the CNS with progression of clinical EAE and following spontaneous recovery, with a focus on CXCL12 expression in the hippocampal neurogenic dentate gyrus (DG) and in the corpus callosum (CC) of spontaneously recovered mice, and its potential role in promoting the endogenous myelin/neuronal repair capacity. METHODS: CNS tissue sections from mice with different clinical EAE phases or following spontaneous recovery and in vitro differentiated adult neural stem cell cultures were analyzed by immunofluorescent staining and confocal imaging for detecting and enumerating neuronal progenitor cells (NPCs) and oligodendrocyte precursor cells (OPCs) and for expression of CXCL12. RESULTS: Our expression dynamics analysis of CXCL12 in the CNS with EAE progression revealed elevated CXCL12 expression in the DG and CC, which persistently increases following spontaneous recovery even though CNS inflammation has subsided. Correspondingly, the numbers of NPCs and OPCs in the DG and CC, respectively, of EAE-recovered mice increased compared to that of naïve mice (NPCs, p < 0.0001; OPCs, p < 0.00001) or mice with active disease (OPCs, p < 0.0005). Notably, about 30 % of the NPCs and unexpectedly also OPCs (~50 %) express CXCL12, and their numbers in DG and CC, respectively, are higher in EAE-recovered mice compared with naïve mice and also compared with mice with ongoing clinical EAE (CXCL12(+) NPCs, p < 0.005; CXCL12(+) OPCs, p < 0.0005). Moreover, a significant proportion (>20 %) of the CXCL12(+) NPCs and OPCs co-express the CXCL12 receptor, CXCR4, and their numbers significantly increase with recovery from EAE not only relative to naïve mice (p < 0.0002) but also to mice with ongoing EAE (p < 0.004). CONCLUSIONS: These data link CXCL12 expression in the DG and CC of EAE-recovering mice to the promotion of neuro/oligodendrogenesis generating CXCR4(+) CXCL12(+) neuronal and oligodendrocyte progenitor cells endowed with intrinsic neuro/oligondendroglial differentiation potential. These findings highlight the post-CNS-inflammation role of CXCL12 in augmenting the endogenous myelin/neuronal repair capacity in MS-like disease, likely via CXCL12/CXCR4 autocrine signaling.

Host cell virus entry mechanisms enhance anti-JCV-antibody switch in natalizumab-treated multiple sclerosis patients.

Estimating the individual risk for the development of progressive multifocal leukoencephalopathy (PML) in anti-John Cunningham virus (JCV) antibody-negative patients with multiple sclerosis (MS) treated with natalizumab is a major challenge. A serological conversion occurring under treatment from anti-JCV antibody-negative to positive status may significantly increase this risk. We investigated changes in peripheral blood cells' gene expression induced by natalizumab treatment in anti-JCV antibody-negative MS patients and tested blood transcriptional profile that characterizes patients predisposed to antibody switch under natalizumab treatment. After 3 years of natalizumab treatment, 24.6 % of anti-JCV antibody-negative MS patients switched to become anti-JCV antibody-positive (JCV switchers). Natalizumab induced 946 and 1186 significantly differentiating genes in JCV switchers and non-switchers, respectively. In JCV switchers, the signature was enriched by over-expression of genes associated with the first stages of viral entry to host cells including macropinocytosis (p = 1.82E-06), virus entry via endocytosis (p = 1.60E-06), clathrin-mediated endocytosis (p = 1.13E-04), and caveolar-mediated endocytosis (p = 4.50E-04) pathways. Further analysis to identify pre-existing transcriptional differences that characterize future JCV switchers prior to treatment initiation also demonstrated a transcriptional signature enriched by similar viral entry mechanisms. These findings, verified in an additional independent cohort of natalizumab-treated patients, could lead to future identification of patients that remain anti-JCV antibody-negative thus allowing safe continuation of treatment, as well as the development of future targeted therapeutic interventions to reduce the risk of PML.

Faster progression to multiple sclerosis disability is linked to neuronal pathways associated with neurodegeneration: An ethnicity study.

Although the causes of multiple sclerosis are largely unknown, genetic and environmental components play an important role. Geographic distribution, varying with latitude, reflects both genetic and environmental influences. We conducted a retrospective exploratory observational study to characterize the disability progression of 2396 Jewish patients with relapsing-remitting multiple sclerosis, followed at the Sheba Multiple Sclerosis Center, Tel-Aviv, Israel; 188 patients who originated in Iraq and 2207 patients who originated in northern Europe. Peripheral blood microarray gene expression analysis was performed in a subgroup of patients to identify molecular pathways associated with faster disability progression. During a follow-up period of 18.8 and 19.8 years, respectively, 51.6% of patients with an Iraqi origin progressed to moderate disability defined as expanded disability status scale (EDSS) score of 3.0 to 5.5, compared to 44.2% of patients with a northern European origin (odds ratio 1.347, 95% CI 1.0-1.815, p = 0.049). An Iraqi origin was associated with increased risk of progression to moderate disability adjusted for sex, disease duration, age at onset, and treatment with immunomodulatory drugs (hazard ratio 1.323; 95% CI, 1.049-1.668, p = 0.02), but not to severe disability defined as EDSS score > = 6.0 (i.e., walking aids are required for a distance of 100 meters, (hazard ratio 1.311; 95% CI, 0.918-1.874, p = 0.136). Gene expression analysis disclosed 98 differentially expressed genes (79 over-expressed and 19 under-expressed) between relapsing-remitting multiple sclerosis patients of Iraqi origin (N = 17) and northern European (N = 34) origin. Interestingly, this gene expression was enriched with genes related to neuronal pathways associated with morphology of axons, branching of neurites, proliferation of neocortical neurons, and formation of myelin sheath, suggesting an augmented process of neurodegeneration in relapsing-remitting multiple sclerosis patients with an Iraqi origin. The study results suggest that relapsing-remitting multiple sclerosis patients with an Iraqi origin progress faster to disability possibly due to an enhanced process of neurodegeneration.

SARS-CoV-2 memory B and T cell profiles in mild COVID-19 convalescent patients.

OBJECTIVES: Antiviral adaptive immunity involves memory B cells (MBC) and memory T cells (MTC). The dynamics of MBC and MTC in severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) convalescents warrant further investigation. METHODS: In this cross-sectional and longitudinal study, blood-derived MBC and MTC responses were evaluated in 68 anti-spike IgG-positive mild coronavirus disease 2019 (COVID-19) convalescents at visit 1, between 1 and 7 months (median 4.1 months) after disease onset. SARS-CoV-2 anti-spike IgG was determined by ELISA, MBC by SARS-CoV-2-specific receptor binding domain (RBD) ELISpot, and interferon gamma (IFN-γ)-, interleukin 2 (IL2)-, and IFN-γ+IL2-secreting MTC by IFN-γ and IL2 SARS-CoV-2 FluoroSpot. For 24 patients sampled at the first visit, the IgG, MBC, and MTC analyses were also performed 3 months later at the second visit. RESULTS: Seventy-two percent of convalescents were both MBC- and MTC-positive, 18% were MBC-positive and MTC-negative, and 10% were MTC-positive and MBC-negative. The peak MBC response level was detected at 3 months after COVID-19 onset and persisted up to 7 months post infection. Significant MTC levels were detected 1 month after onset in response to S1, S2_N, and SNMO peptide pools. The frequency and magnitude of the MTC response to SNMO was higher than those to S1 and S2_N. Longitudinal analysis demonstrated that even when specific humoral immunity declined, the cellular immunity persisted. CONCLUSIONS: The study findings demonstrate the durability of adaptive cellular immunity at least for 7 months after SARS-CoV-2 infection, suggesting long-lasting protection.

Clinical and transcriptional recovery profiles in pediatric and adult multiple sclerosis patients.

OBJECTIVE: To determine whether pediatric-onset multiple sclerosis (POMS) and adults-onset multiple sclerosis (AOMS) patients are different in initial disease severity and recovery and to investigate the associations with peripheral blood mononuclear cells (PBMCs) transcriptional profiles. METHODS: Clinical and radiological severity of first and second relapses and 6-month recovery were analyzed in 2153 multiple sclerosis (MS) patients and compared between POMS (onset at 8-18years old) and AOMS (onset at 19-40 years old) patients. PBMCs transcriptomes of 15 POMS and 15 gender-matched AOMS patients were analyzed 6 months after the first relapse and compared to 55 age-matched healthy controls. Differentially Expressed Genes (DEGs) with a false discovery rate ≤ 10% were evaluated using the Partek software. RESULTS: POMS had increased Expanded Disability Status Scale (EDSS) score at first and second relapses, higher brain gadolinium-enhancing T1-lesions volume at first relapse, and more complete recovery after both relapses compared to AOMS. POMS patients, who recovered completely from the first relapse, were characterized by 19 DEGs that were mainly related to suppression of antigen presentation. Six upstream regulators of these genes were differentially expressed between pediatric and adult healthy controls. POMS patients, who showed no recovery from the first relapse, were characterized by 28 DEGs that were mainly associated with B-cell activation. Five upstream regulators of these genes were differentially expressed between pediatric and adult healthy controls. INTERPRETATION: POMS patients may have more severe first and second relapses than AOMS. However, most often, POMS have better recovery that may be attributed to PBMCs age-related transcriptional profiles associated with antigen presentation and B-cell activation.

Humoral immune response in multiple sclerosis patients following PfizerBNT162b2 COVID19 vaccination: Up to 6 months cross-sectional study.

Appropriate immune response following COVID-19 vaccination is important in the context of disease-modifying treatments (DMTs). In a prospective cross-sectional study, we determined SARS-COV-2 IgG response up to 6 months following PfizerBNT162b2 vaccination in 414 multiple sclerosis (MS) patients and 89 healthy subjects. Protective response was demonstrated in untreated MS patients (N = 76, 100%), treated with Cladribine (N = 48, 100%), Dimethyl fumarate (N = 35, 100%), Natalizumab (N = 32, 100%), and Teriflunomide (N = 39, 100%), similarly to healthy subjects (N = 89, 97.8%). Response was decreased in Fingolimod (N = 42, 9.5%), Ocrelizumab (N = 114, 22.8%) and Alemtuzumab (N = 22, 86.4%) treated patients. IgG response can help tailor adequate vaccine guidelines for MS patients under various DMTs.

The Median Eminence, A New Oligodendrogenic Niche in the Adult Mouse Brain.

The subventricular zone (SVZ) of the lateral ventricles and the subgranular zone (SGZ) of the dentate gyrus in the hippocampus are known as neurogenic niches. We show that the median eminence (ME) of the hypothalamus comprises BrdU+ newly proliferating cells co-expressing NG2 (oligodendrocyte progenitors) and RIP (pre-myelinating oligodendrocytes), suggesting their differentiation toward mature oligodendrocytes (OLs). ME cells can generate neurospheres (NS) in vitro, which differentiate mostly to OLs compared with SVZ-NS that typically generate neurons. Interestingly, this population of oligodendrocyte progenitors is increased in the ME from experimental autoimmune encephalomyelitis (EAE)-affected mice. Notably, the thrombospondin 1 (TSP1) expressed by astrocytes, acts as negative regulator of oligodendrogenesis in vitro and is downregulated in the ME of EAE mice. Importantly, transplanted ME-NS preferentially differentiate to MBP+ OLs compared with SVZ-NS in Shiverer mice. Hence, discovering the ME as a new site for myelin-producing cells has a great importance for advising future therapy for demyelinating diseases and spinal cord injury.

Polymerase-1 pathway activation in acute multiple sclerosis relapse.

BACKGROUND: Increased expression of RNA polymerase 1 (POL1) molecular pathway was reported to be associated with increased disease activity in patients with multiple sclerosis (MS). However, the operating molecular mechanisms that characterize the pattern of acute MS relapse activity has not been thoroughly studied. OBJECTIVE: To assess POL1 pathway expression during acute MS relapse. METHODS: We studied POL1 pathway associated biomarkers during the first acute optic neuritis attack of MS, and in relapsing-remitting MS patients treated with disease-modifying drugs (DMDs) experiencing an acute MS relapse or a radiological relapse using gene expression microarrays and quantitative RT-PCR. RESULTS: In MS patients (N = 6) during the first acute optic neuritis attack POL1 pathway activation was evident by over-expression of POL1 related network including transcription factor UBTF and downstream components of Assembly of RNA POL1 complex (p=1.92E-03). POL1 related biomarkers RRN3, POLR1D and LRPPRC were over-expressed x1.6 (p = .002), ×1.7 (p = .01) and x2.0 (p = .001) times higher respectively, in MS patients (N = 30) during acute clinical relapse as compared with remission. Similarly, in MS patients (N = 21) that presented with a radiological relapse, we observed significant activation of POL1 related biomarkers including RRN3 (p = .01), POLR1D (p = .002), POLR1E (p = .0001) and LRPPRC (p = .006), as compared with remission, as well as overexpression of a large group of genes encoding ribosomal proteins like RPS6KA3 (p = 7.2E-6), RRP8 (p = .0002) and RPCS9 (p = .0008). CONCLUSIONS: Our findings demonstrated increased POL1 pathway activity in acute MS relapse and suggest that targeted inactivation of POL1 pathway represent a novel strategy for a better treatment of acute MS relapse.

Prickle1 as positive regulator of oligodendrocyte differentiation.

Spontaneous neural repair from endogenous neural stem cells' (NSCs) niches occurs in response to central nervous system (CNS) injuries to only a limited extent. Uncovering the mechanisms that control neural repair and can be further manipulated to promote NSCs toward oligodendrocyte progenitors cells (OPCs) and myelinating oligodendrocytes is a major objective. In the current study, we describe high-throughput transcriptional changes in adult mouse subventricular zone (SVZ)-NSCs during differentiation in vitro. In order to identify myelin-specific transcriptional regulators among large transcriptional changes associated with differentiation, we have focused on transcripts encoding transcription factors and regulators showing expression profile that is highly correlated with expression of myelin-encoding genes. We have revealed previously undescribed effect of Prickle1 and Nfe2l3 transcriptional regulators that are positively correlated with expression of myelin basic protein (MBP). Using Prickle1 and Nfe2l3 silencing and immunocytochemistry approaches, we demonstrated that silencing of Prickle1 dramatically decreases differentiation to NG2+OPCs while Nfe2l3 moderately decreases as compared with control siRNA. Moreover, silencing of Prickle1 also decreases maturation of OPCs to MBP+ oligodendrocytes (OLs). Accordingly, overexpression of Prickle1 increases the differentiation of NSCs to CNPase+ pre-myelinating and myelinating MBP+ OLs. In particular, the necessity of Prickle1 for oligodendrocyte differentiation is demonstrated in purified OPCs cultures. Our findings demonstrate the role of Prickle1 in positive regulation of differentiation and maturation of oligodendrocytes suggesting that targeting Prickle1 in CNS injuries and particularly in demyelinating disease could promote generation of myelinating oligodendrocytes from endogenous niches to replenish damaged oligodendrocytes.

Polymerase I pathway inhibitor ameliorates experimental autoimmune encephalomyelitis.

Applying high throughput gene expression microarrays we identified that the suppression of polymerase 1 (POL1) pathway is associated with benign course of multiple sclerosis (MS). This finding supports the rationale for direct targeting of the POL1 transcription machinery as an innovative strategy to suppress MS. To evaluate the effects of a specific polymerase I inhibitor (POL1-I) on experimental autoimmune encephalomyelitis (EAE), we immunized female C57BL/6J mice (8 weeks) with MOG35-55/CFA. A new POL1-I was administered at a daily dose of 12.5mg/kg body weight by oral gavage either from the day of immunization until disease onset (EAE score 1.0, immunization model), at disease onset (EAE score=1.0) for the following 14 days (treatment model), or by alternate daily dose of 25.0mg/kg body weight, by oral gavage from the day of immunization for the following 25 days (combined model). POL1-I remarkably suppressed EAE in the immunization model; while in the Vehicle group the onset of EAE occurred on day 10.0±0.4 with maximal clinical score of 3.2±0.2, in the POL1-I treated mice onset was significantly delayed and occurred on day 16.9±1.1 (p=0.001), and maximal disease score 2.0±0.1 was reduced (p=0.004). In the treatment model POL1-I treatment significantly reduced disease activity; maximal score was 2.0±0.5 while in the Vehicle group it reached a mean maximal score of 3.9±0.1, (p=0.0008). In the combined model, POL1-I treatment completely inhibited disease activity. The effect of POL1-I treatment was modulated through decreased expression of POL1 pathway key-related genes LRPPRC, pre-RNA, POLR1D and RRN3 together with activation of P53 dependent apoptosis of CD4+ splenocytes. Our findings demonstrate that POL1 pathway inhibition delayed and suppressed the development of EAE and ameliorated the disease in mice with persistent clinical signs.

'Multi-epitope-targeted' immune-specific therapy for a multiple sclerosis-like disease via engineered multi-epitope protein is superior to peptides.

Antigen-induced peripheral tolerance is potentially one of the most efficient and specific therapeutic approaches for autoimmune diseases. Although highly effective in animal models, antigen-based strategies have not yet been translated into practicable human therapy, and several clinical trials using a single antigen or peptidic-epitope in multiple sclerosis (MS) yielded disappointing results. In these clinical trials, however, the apparent complexity and dynamics of the pathogenic autoimmunity associated with MS, which result from the multiplicity of potential target antigens and "epitope spread", have not been sufficiently considered. Thus, targeting pathogenic T-cells reactive against a single antigen/epitope is unlikely to be sufficient; to be effective, immunospecific therapy to MS should logically neutralize concomitantly T-cells reactive against as many major target antigens/epitopes as possible. We investigated such "multi-epitope-targeting" approach in murine experimental autoimmune encephalomyelitis (EAE) associated with a single ("classical") or multiple ("complex") anti-myelin autoreactivities, using cocktail of different encephalitogenic peptides vis-a-vis artificial multi-epitope-protein (designated Y-MSPc) encompassing rationally selected MS-relevant epitopes of five major myelin antigens, as "multi-epitope-targeting" agents. Y-MSPc was superior to peptide(s) in concomitantly downregulating pathogenic T-cells reactive against multiple myelin antigens/epitopes, via inducing more effective, longer lasting peripheral regulatory mechanisms (cytokine shift, anergy, and Foxp3+ CTLA4+ regulatory T-cells). Y-MSPc was also consistently more effective than the disease-inducing single peptide or peptide cocktail, not only in suppressing the development of "classical" or "complex EAE" or ameliorating ongoing disease, but most importantly, in reversing chronic EAE. Overall, our data emphasize that a "multi-epitope-targeting" strategy is required for effective immune-specific therapy of organ-specific autoimmune diseases associated with complex and dynamic pathogenic autoimmunity, such as MS; our data further demonstrate that the "multi-epitope-targeting" approach to therapy is optimized through specifically designed multi-epitope-proteins, rather than myelin peptide cocktails, as "multi-epitope-targeting" agents. Such artificial multi-epitope proteins can be tailored to other organ-specific autoimmune diseases.

The myelin-associated oligodendrocytic basic protein (MOBP) as a relevant primary target autoantigen in multiple sclerosis.

Multiple sclerosis (MS) is a disease of the human CNS, characterized by perivascular inflammation, demyelination and axonal damage. Although the etiology of MS is unknown, it is believed that the disease results from destructive autoimmune mechanisms, presumably initiated by abnormal activation of potentially pathogenic autoimmune T-cells recognizing CNS components. The myelin-associated oligodendrocyte basic protein (MOBP), a relatively abundant CNS-specific myelin protein, which plays a role in stabilizing the myelin sheath in the CNS, has recently been implicated in the pathogenesis of MS. Here we review studies showing that MOBP is as an important candidate target antigen in MS as the other widely studied target antigens, myelin basic protein (MBP), proteolipid protein (PLP), and myelin oligodendrocyte glycoprotein (MOG). The studies summarized below indicate that T-cell autoimmunity against MOBP can be detected in MS patients; T-cells reactive against MOBP can be pathogenic in several mouse strains as well as in the "humanized" HLA-DR15-Tg mice; and, that the HLA-DQ6-restricted, but not HLA-DR15-restricted, MOBP-reactive T-cells cause in HLA-DR15-Tg mice MS-like clinical disease associated with perivascular and parenchymal infiltration, demyelination, axonal loss, and optic neuritis. Accordingly, the MOBP should be considered a bona fide primary target antigen in MS, in addition to MBP, PLP, and MOG.

Pathogenic T cells in MOBP-induced murine EAE are predominantly focused to recognition of MOBP21F and MOBP27P epitopic residues.

Myelin-associated oligodendrocytic basic protein (MOBP) is a central nervous system (CNS)-specific myelin constituent important in stabilizing the unique multi-layered structure of the CNS-myelin sheath. Although autoimmunity against MOBP has been associated with multiple sclerosis pathogenesis, anti-MOBP pathogenic T cells have been poorly investigated as compared to T cells against other encephalitogenic myelin proteins. We have recently determined MOBP15-36 as the major encephalitogenic epitope of MOBP for SJL/J mice. In this study, epitope-specificity was dissected to the level of residues crucial for activation/control of MOBP-specific encephalitogenic T cells. Structural bioinformatic analysis of MOBP15-36/I-A(s) interaction and experimental data have determined MOBP21F and MOBP27P of I-A(s)-binding nonameric core epitope (MOBP20-28) as TCR-contact residues critical for functional activation of encephalitogenic MOBP-specific T cells. Accordingly, the non-encephalitogenic/nonstimulatory pMOBP16-21A27A-33 inhibited encephalitogenic MOBP-reactive T cells, shifted their cytokine secretion profile, and effectively suppressed pMOBP15-36-induced EAE. Moreover, pMOBP16-21A27A-33 fully reversed ongoing clinical EAE induced by whole MOBP as well as by pMOBP15-36. Data show that encephalitogenic MOBP-reactive T cells are predominantly focused to recognition of MOBP21F and MOBP27P, and suggest that both their selection and control are governed by MOBP21F and MOBP27P epitopic residues. Such focused epitopic recognition may affect profoundly on peripheral self-tolerance to MOBP and on potential altered peptide ligand-mediated therapy of MOBP-related autoimmune pathogenesis.