Ying C. Q. Zang

Cross-reactivity with myelin basic protein and human herpesvirus-6 in multiple sclerosis.

Viral infections are though to play an important role in the pathogenesis of multiple sclerosis (MS) potentially through molecular mimicry. An identical sequence was found in both myelin basic protein (MBP, residues 96–102), a candidate autoantigen for MS, and human herpesvirus‐6 (HHV‐6 U24, residues 4–10) that is a suspected viral agent associated with MS. In this study, we showed that greater than 50% of T cells recognizing MBP93‐105 cross‐reacted with and could be activated by a synthetic peptide corresponding to residues 1 to 13 of HHV‐6 U24 in MS patients. The estimated precursor frequency of these cross‐reactive T cells recognizing both peptides, MBP93‐105 and HHV‐6 (U24)1‐13, was significantly elevated in MS patients compared with that in healthy controls. These cross‐reactive CD4+ T cells represented the same Th1 phenotype as that of monospecific T cells recognizing MBP93‐105. There were increased antibody titers for both peptide HHV‐6 (U24)1‐13 and peptide MBP93‐105 in the same patients with MS compared with those in healthy controls, suggesting B‐cell sensitization to the antigens in MS patients. The study provides important evidence in the understanding of the potential role of HHV‐6 infection/reactivation in the activation of autoimmune reactivity to MBP and its implication in the pathogenesis of MS. Ann Neurol 2003

Increased CD8+ Cytotoxic T Cell Responses to Myelin Basic Protein in Multiple Sclerosis

Autoreactive T cells of CD4 and CD8 subsets recognizing myelin basic protein (MBP), a candidate myelin autoantigen, are thought to contribute to and play distinct roles in the pathogenesis of multiple sclerosis (MS). In this study we identified four MBP-derived peptides that had high binding affinity to HLA-A2 and HLA-A24 and characterized the CD8+ T cell responses and their functional properties in patients with MS. There were significantly increased CD8+ T cell responses to 9-mer MBP peptides, in particular MBP111–119 and MBP87–95 peptides that had high binding affinity to HLA-A2, in patients with MS compared with healthy individuals. The resulting CD8+ T cell lines were of the Th1 phenotype, producing TNF-α and IFN-γ and belonged to a CD45RA−/CD45RO+ memory T cell subset. Further characterization indicated that the CD8+ T cell lines obtained were stained with MHC class I tetramer (HLA-A2/MBP111–119) and exhibited specific cytotoxicity toward autologous target cells pulsed with MBP-derived peptides in the context of MHC class I molecules. These cytotoxic CD8+ T cell lines derived from MS patients recognized endogenously processed MBP and lysed COS cells transfected with genes encoding MBP and HLA-A2. These findings support the potential role of CD8+ CTLs recognizing MBP in the injury of oligodendrocytes expressing both MHC class I molecules and MBP.

IMPAIRED APOPTOTIC DELETION OF MYELIN BASIC PROTEIN-REACTIVE T CELLS IN PATIENTS WITH MULTIPLE SCLEROSIS

T cell responses to myelin basic protein (MBP) may play an important role in the pathogenesis of multiple sclerosis (MS). If MBP‐reactive T cells are involved in the disease processes and undergo clonal activation and expansion, their precursor frequency would be increased in patients with MS. The frequency of MBP‐reactive T cells is also influenced by regulatory mechanisms in vivo, including apoptotic deletion. In this study, we examined changes in the frequency of MBP‐reactive T cells in patients with MS as a function of the apoptotic deletional mechanism in vivo, using a cell culture‐based assay. A significantly increased frequency of MBP‐reactive T cells was found in patients with MS relative to healthy individuals only when Fas‐ligand antibody was used to block apoptosis. This result indicates that a significant proportion of MBP‐reactive T cells are sensitive to apoptosis and are not deleted in vivo in patients with MS, as opposed to healthy individuals, thus suggesting a functional deficit in apoptotic deletional mechanism. Surviving Fas‐sensitive MBP‐reactive T cell lines represent distinct subpopulations preferentially recognizing the 111–139 region of MBP and exhibiting a Th2 cytokine profile. The findings are relevant to our understanding of regulation of MBP‐reactive T cells in vivo in MS.

Regulation of chemokine receptor CCR5 and production of RANTES and MIP-1α by interferon-β

Abstract Trafficking of inflammatory T cells into the brain is associated with interactions of certain chemokines with their receptors, which plays an important role in the pathogenesis of multiple sclerosis (MS). We examined whether interferon-β (IFN-β) had the ability to regulate the production of chemokines and the expression of their receptors in T cells derived from patients with MS. It was demonstrated for the first time that in vitro exposure of T cells to IFN-β-1a selectively inhibited mRNA expression for RANTES and MIP-1α and their receptor CCR5. T cell surface expression of CCR5 was significantly reduced in MS patients treated with IFN-β, correlating with decreased T cell transmigration toward RANTES and MIP-1α. The study provides new evidence suggesting that IFN-β treatment impairs chemokine-induced T cell trafficking by reducing the production of RANTES and MIP-1α and the expression of their receptors CCR5.

Gene expression profiling of relevant biomarkers for treatment evaluation in multiple sclerosis

Multiple sclerosis (MS) is thought to correlate with an array of clinically relevant biomarkers produced during inflammatory process. In this study, a novel gene expression profiling technology was developed and characterized to quantitatively measure the expression profiles of 34 genes selected based on their role in inflammation and their susceptibility to regulation by current MS treatment agents, beta-interferon (IFN) and glatiramer acetate (GA). Potential clinical applications of the technology were evaluated by in vitro and ex vivo analyses in peripheral blood mononuclear cells (PBMC) obtained from MS patients and controls. Interferon-inducible genes were universally up-regulated after in vitro treatment with beta-IFN while the expression of other selected genes encoding cytokines and molecules related to T cell trafficking, activation and apoptosis was variably affected. Beta-IFN and GA exhibited distinctive and characteristic regulatory effects on the expression of the selected genes. Similar regulatory properties of beta-IFN and GA were seen by ex vivo analysis of PBMC specimens in a self-paired study by comparing specific changes induced by beta-IFN or GA treatment in the same patients as well as in a group study by measuring specific profiles in treatment groups compared with an untreated group. Furthermore, the technology served as a simple and sensitive assay for detection of beta-IFN neutralizing antibody based on the blocking effect of serum antibodies on the known regulatory properties of beta-IFN on PBMC. The findings provide important information on the immunoregulatory properties of beta-IFN and GA and support potential clinical applications of this technology in detection of neutralizing antibody (NAB) and evaluation of treatment responses in MS patients.

Regulatory effects of estriol on T cell migration and cytokine profile: inhibition of transcription factor NF-κB

The protective role of pregnancy in autoimmune conditions, such as multiple sclerosis (MS), is potentially associated with immune regulation by sex hormones produced during pregnancy. This study was undertaken to examine the regulatory effects of estriol on the T cell functions, including transmigration and the cytokine production. The results revealed for the first time that estriol significantly inhibited T cell transmigration at a concentration range typical of pregnancy, which correlated with decreased T cell expression of matrix metalloproteinase-9. Estriol was also found to alter the cytokine profile of T cells toward Th2 phenotype by up-regulating the production of IL-10 and inhibiting TNFalpha secretion of T cells. However, the inhibitory effects of estriol on T cells were not antigen-dependent. Further characterization indicated that estriol inhibited nuclear transcription factor kappa B (NF-kappa B), which controls a variety of immune-related genes. This study provides new evidence that estriol is a potent regulator for the T cell functions potentially through its interaction with the NF-kappa B signaling pathway.

Regulatory effects of IFN-β on production of osteopontin and IL-17 by CD4+ T Cells in MS

IFN‐β currently serves as one of the major treatments for MS. Its anti‐inflammatory mechanism has been reported as involving a shift in cytokine balance from Th1 to Th2 in the T‐cell response against elements of the myelin sheath. In addition to the Th1 and Th2 groups, two other important pro‐inflammatory cytokines, IL‐17 and osteopontin (OPN), are believed to play important roles in CNS inflammation in the pathogenesis of MS. In this study, we examined the potential effects of IFN‐β on the regulation of OPN and IL‐17 in MS patients. We found that IFN‐β used in vitro at 0.5–3 ng/mL significantly inhibited the production of OPN in primary T cells derived from PBMC. The inhibition of OPN was determined to occur at the CD4+ T‐cell level. In addition, IFN‐β inhibited the production of IL‐17 and IL‐21 in CD4+ T cells. It has been described that IFN‐β suppresses IL‐17 production through the inhibition of a monocytic cytokine, the intracellular translational isoform of OPN. Our further investigation demonstrated that IFN‐β also acted directly on the CD4+ T cells to regulate OPN and IL‐17 expression through the type I IFN receptor‐mediated activation of STAT1 and suppression of STAT3 activity. Administration of IFN‐β to EAE mice ameliorated the disease severity. Furthermore, spinal cord infiltration of OPN+ and IL‐17+ cells decreased in IFN‐β‐treated EAE mice along with decreases in serum levels of OPN and IL‐21. Importantly, decreased OPN production by IFN‐β treatment contributes to the reduced migratory activity of T cells. Taken together, the results from both in vitro and in vivo experiments indicate that IFN‐β treatment can down‐regulate the OPN and IL‐17 production in MS. This study provides new insights into the mechanism of action of IFN‐β in the treatment of MS.

T cell responses to myelin basic protein in patients with spinal cord injury and multiple sclerosis

Autoimmune inflammation secondary to myelin destruction may play an inhibitory role in restoration of nerve functions in spinal cord injury (SCI). In this study, we demonstrated that T cells recognizing myelin basic protein (MBP) occurred at a high precursor frequency in patients with SCI, which was compatible to that in patients with multiple sclerosis (MS), a disease of presumed autoimmune pathology. The findings suggest of hyperactivity of MBP-reactive T cells in patients with SCI. MBP-reactive T cell lines derived from patients with SCI exhibited a preferential recognition pattern toward the 81-99 and the 151-169 regions of MBP. There were functional differences in the epitope recognition and cytokine profile between two panels of MBP-reactive T cell lines derived from patients with SCI and patients with MS. The study provides new evidence important for further investigation of the role of the inflammatory component in SCI.

Preferential recognition of TCR hypervariable regions by human anti-idiotypic T cells induced by T cell vaccination.

T cell responses to myelin basic protein (MBP) are potentially involved in the pathogenesis of multiple sclerosis (MS). Immunization with irradiated MBP-reactive T cells (T cell vaccination) induces anti-idiotypic T cell responses that suppress circulating MBP-reactive T cells. This T cell-T cell interaction is thought to involve the recognition of TCR expressed on target T cells. The study was undertaken to define the idiotypic determinants responsible for triggering CD8+ cytotoxic anti-idiotypic T cell responses by T cell vaccination in patients with MS. A panel of 9-mer synthetic TCR peptides corresponding to complementarity-determining region 2 (CDR2) and CDR3 of the immunizing MBP-reactive T cell clones were used to isolate anti-idiotypic T cell lines from immunized MS patients. The resulting TCR-specific T cell lines expressed exclusively the CD8 phenotype and recognized preferentially the CDR3 peptides. CDR3-specific T cell lines were found to lyze specifically autologous immunizing MBP-reactive T cell clones. The findings suggest that CDR3-specific T cells represented anti-idiotypic T cell population induced by T cell vaccination. In contrast, the CDR2 peptides were less immunogenic and contained cryptic determinants as the CDR2-specific T cell lines did not recognize autologous immunizing T cell clones from which the peptide sequence was derived. The study has important implications in our understanding of in vivo idiotypic regulation of autoimmune T cells and the regulatory mechanism underlying T cell vaccination.

T cell vaccination in multiple sclerosis: results of a preliminary study.

Abstract Myelin basic protein (MBP)-reactive T cells are potentially involved in the pathogenesis of multiple sclerosis (MS), and can be depleted by subcutaneous inoculations with irradiated autologous MBP-reactive T cells (T cell vaccination). This preliminary open label study was undertaken to evaluate whether depletion of MBP-reactive T cells would be clinically beneficial to patients with MS. Fifty-four patients with relapsing-remitting (RR) MS (n=28) or secondary progressive (SP) MS (n=26) were immunized with irradiated autologous MBP-reactive T cells and monitored for changes in rate of relapse, expanded disability scale score (EDSS) and MRI lesion activity over a period of 24 months. Depletion of MBP-reactive T cells correlated with a reduction (40 %) in rate of relapse in RR-MS patients as compared with the pre-treatment rate in the same cohort. However, the reduction in EDSS was minimal in RR-MS patients while the EDSS was slightly increased in SP-MS patients over a period of 24 months. Serial semi-quantitative MRI examinations suggest stabilization in lesion activity as compared with baseline MRI. The findings suggest some potential clinical benefit of T cell vaccination in MS and encourage further investigations to evaluate the treatment efficacy of T cell vaccination in controlled trials.