Infectious Mononucleosis Triggers Generation of IgG Auto-Antibodies against Native Myelin Oligodendrocyte Glycoprotein.

A history of infectious mononucleosis (IM), symptomatic primary infection with the Epstein Barr virus, is associated with the development of autoimmune diseases and increases the risk to develop multiple sclerosis. Here, we hypothesized that immune activation during IM triggers autoreactive immune responses. Antibody responses towards cellular antigens using a HEp-2 based indirect immunofluorescence assay and native myelin oligodendrocyte glycoprotein (MOG) using a flow cytometry-based assay were determined in 35 patients with IM and in 23 control subjects. We detected frequent immunoglobulin M (IgM) reactivity to vimentin, a major constituent of the intermediate filament family of proteins, in IM patients (27/35; 77%) but rarely in control subjects (2/23; 9%). IgG autoantibodies binding to HEp-2 cells were absent in both groups. In contrast, IgG responses to native MOG, present in up to 40% of children with inflammatory demyelinating diseases of the central nervous system (CNS), were detectable in 7/35 (20%) patients with IM but not in control subjects. Normalization of anti-vimentin IgM levels to increased total IgM concentrations during IM resulted in loss of significant differences for anti-vimentin IgM titers. Anti-MOG specific IgG responses were still detectable in a subset of three out of 35 patients with IM (9%), even after normalization to increased total IgG levels. Vimentin-specific IgM and MOG-specific IgG responses decreased following clinical resolution of acute IM symptoms. We conclude from our data that MOG-specific memory B cells are activated in subset of patients with IM.

Serum indoleamine 2,3-dioxygenase activity is associated with reduced immunogenicity following vaccination with MVA85A.

BACKGROUND: There is an urgent need for improved vaccines to protect against tuberculosis. The currently available vaccine Bacille Calmette-Guerin (BCG) has varying immunogenicity and efficacy across different populations for reasons not clearly understood. MVA85A is a modified vaccinia virus expressing antigen 85A from Mycobacterium tuberculosis which has been in clinical development since 2002 as a candidate vaccine to boost BCG-induced protection. A recent efficacy trial in South African infants failed to demonstrate enhancement of protection over BCG alone. The immunogenicity was lower than that seen in UK trials. The enzyme Indoleamine 2,3-dioxygenase (IDO) catalyses the first and rate-limiting step in the breakdown of the essential amino acid tryptophan. T cells are dependent on tryptophan and IDO activity suppresses T-cell proliferation and function. METHODS: Using samples collected during phase I trials with MVA85A across the UK and South Africa we have investigated the relationship between vaccine immunogenicity and IDO using IFN-γ ELISPOT, qPCR and liquid chromatography mass spectrometry. RESULTS: We demonstrate an IFN-γ dependent increase in IDO mRNA expression in peripheral blood mononuclear cells (PBMC) following MVA85A vaccination in UK subjects. IDO mRNA correlates positively with the IFN-γ ELISPOT response indicating that vaccine specific induction of IDO in PBMC is unlikely to limit the development of vaccine specific immunity. IDO activity in the serum of volunteers from the UK and South Africa was also assessed. There was no change in serum IDO activity following MVA85A vaccination. However, we observed higher baseline IDO activity in South African volunteers when compared to UK volunteers. In both UK and South African serum samples, baseline IDO activity negatively correlated with vaccine-specific IFN-γ responses, suggesting that IDO activity may impair the generation of a CD4+ T cell memory response. CONCLUSIONS: Baseline IDO activity was higher in South African volunteers when compared to UK volunteers, which may represent a potential mechanism for the observed variation in vaccine immunogenicity in South African and UK populations and may have important implications for future vaccination strategies. TRIAL REGISTRATION: Trials are registered at ClinicalTrials.gov; UK cohort NCT00427830, UK LTBI cohort NCT00456183, South African cohort NCT00460590, South African LTBI cohort NCT00480558.

Persistence of Epstein-Barr virus in self-reactive memory B cells.

Epstein-Barr virus infection has been epidemiologically associated with the development of multiple autoimmune diseases, particularly systemic lupus erythematosus and multiple sclerosis. Currently, there is no known mechanism that can account for these associations. The germinal-center (GC) model of EBV infection and persistence proposes that EBV gains access to the memory B cell compartment via GC reactions by driving infected cells to differentiate using the virus-encoded LMP1 and LMP2a proteins, which act as functional homologues of CD40 and the B cell receptor, respectively. The ability of LMP2a, when expressed in mice, to allow escape of autoreactive B cells suggests that it could perform a similar role in infected GC B cells, permitting the survival of potentially pathogenic autoreactive B cells. To test this hypothesis, we cloned and expressed antibodies from EBV(+) and EBV(-) memory B cells present during acute infection and profiled their self- and polyreactivity. We find that EBV does persist within self- and polyreactive B cells but find no evidence that it favors the survival of pathogenic autoreactive B cells. On the contrary, EBV(+) memory B cells express lower levels of self-reactive and especially polyreactive antibodies than their uninfected counterparts do. Our work suggests that EBV has only a modest effect on the GC process, which allows it to access and persist within a subtly unique niche of the memory compartment characterized by relatively low levels of self- and polyreactivity. We suggest that this might reflect an active process where EBV and its human host have coevolved so as to minimize the virus's potential to contribute to autoimmune disease.

Killer immunoglobulin-like receptor locus polymorphisms in multiple sclerosis.

OBJECTIVE: The objective of this study was to analyze whether inhibitory and activating killer cell immunoglobulin-like receptors (KIRs) and human leukocyte antigen (HLA) class I alleles defined by their KIR binding motifs are associated with multiple sclerosis (MS) susceptibility or severity. METHOD: We performed a population-based case-control study in 321 patients with clinically isolated syndrome (CIS) and clinically definite MS (CDMS) and 156 healthy blood donors (HD). Inhibitory and activating KIRs and HLA class I alleles were genotyped using polymerase chain reaction (PCR) sequence-specific primers. Allelic frequencies were correlated with prevalence, age of onset, disability and disease duration of CIS and CDMS. RESULTS: The frequency of the inhibitory KIR2DL3 gene was significantly reduced in patients with CIS and CDMS (p = 3.1 × 10(-5)). KIR2DL3-dependent risk reduction remained significant after elimination of patients carrying MS-associated DRB1*15, DRB1*03, DRB1*01 alleles. In addition, individuals carrying two copies for KIR2DL2/KIR2DS2 but lacking KIR2DL3 were overrepresented in the CIS/CDMS cohort. However, both genes did not affect disease risk in presence of KIR2DL3. We did not detect any association between the presence or absence of KIR genes with clinical disease parameters. CONCLUSION: Absence of the inhibitory KIR2DL3 gene is associated with the development of CIS/CDMS. These findings, if confirmed in larger cohorts, suggest that KIR-mediated recognition of HLA class I molecules should be further explored as potential disease mechanism in MS.

EBV-specific immune responses in patients with multiple sclerosis responding to IFNß therapy.

BACKGROUND: Symptomatic primary infection with the human γ-herpesvirus Epstein-Barr virus (EBV) and elevated immune responses to EBV are associated with the development and progression of multiple sclerosis (MS). Interferon-beta (IFNß), first-line treatment for relapse-onset MS, exhibits complex immunoregulatory and antiviral activities. OBJECTIVE: To determine EBV-specific immune responses in patients with MS during IFNß therapy. METHODS: We evaluated cellular and humoral immune responses to EBV- and human cytomegalovirus (HCMV)-encoded antigens in patients with MS before and 1 year after IFNß treatment by ELISA and flow cytometry. Twenty-eight patients with MS who showed a clinical response to IFNß as defined by the absence of relapses and lack of progression on the Expanded Disability Status Scale score during the first 2 years of treatment were included. RESULTS: Clinically effective IFNß-therapy was associated with a downregulation of proliferative T cell responses to the latent EBV nuclear antigen-1 (EBNA1). EBNA1-specific IgG responses as well as cellular and humoral immune responses to MHC class I restricted EBV antigens expressed during lytic replication and viral B cell transformation were similar before and after IFNß therapy. Although HCMV-specific IgG levels slightly decreased, proliferative T-cell responses towards HCMV antigens remained unchanged during IFNß therapy. CONCLUSION: Clinically effective IFNß therapy is associated with a reduction of proliferative T-cell responses to EBNA1.

Intrathymic Epstein-Barr virus infection is not a prominent feature of myasthenia gravis.

Lymph node-type T- and B-cell infiltrates with germinal centers are characteristic features of the hyperplastic thymus in early onset myasthenia gravis (EOMG).Epstein-Barr virus (EBV) infection confers survival advantages on B cells, and has recently been implicated in tertiary lymphoid tissue formation in EOMG. We evaluated the frequency of intrathymic EBV-infected B-lineage cells and antiviral immune responses in treatment-naive patients with EOMG. Real-time polymerase chain reaction was performed to quantify the content of genomic EBV DNA (BamHI-W repeat region) in thymic cell suspensions. Serial paraffin sections of EOMG thymi were analyzed for the presence of EBV-encoded RNA by in situ hybridization and for viral gene expression by immunohistochemistry. Humoral and cellular immune responses to viral antigens were quantified by enzyme-linked immunosorbent assay and flow cytometry-based intracellular cytokine staining. We detected minimal levels of viral DNA-corresponding to single viral genomes-in only 6 of 16 hyperplastic EOMG thymi, indicating extreme rarity of viral copy numbers in the investigated thymic samples. That was confirmed by similar rarity of EBV-encoded RNA and viral proteins identified in thymic sections. Furthermore, EBV-specific T- and B-cell responses were unchanged in patients with EOMG. These findings do not support an etiologic role for EBV in the initiation of EOMG.

Environmental triggers of multiple sclerosis.

Multiple sclerosis is a chronic immune-mediated disease of the central nervous system that develops in young adults with a complex genetic predisposition. Similar to other autoimmune disease, HLA-DR and -DQ alleles within the HLA class II region on chromosome 6p21 are by far the strongest risk-conferring genes. Less robust susceptibility effects have been reported for non-MHC related genetic variants. Improvements in the design of epidemiological studies helped to identify consistent environmental risk-associations such as the increased susceptibility for MS in individuals with a history of infectious mononucleosis, a symptomatic primary infection with the human γ-herpesvirus Epstein-Barr virus (EBV). Sun exposure and serum vitamin D levels are emerging non-infectious environmental risk factors that may have independent roles. The analysis of environmental effects will likely expand in the next few years and will allow for the generation of testable hypotheses as to how environmental insults interact with genetic factors to jointly determine the susceptibility to MS. Insights gained from these studies might facilitate the development of prevention strategies and more effective treatments for MS.

Viral triggers of multiple sclerosis.

Genetic and environmental factors jointly determine the susceptibility to develop Multiple Sclerosis (MS). Collaborative efforts during the past years achieved substantial progress in defining the genetic architecture, underlying susceptibility to MS. Similar to other autoimmune diseases, HLA-DR and HLA-DQ alleles within the HLA class II region on chromosome 6p21 are the highest-risk-conferring genes. Less-robust susceptibility effects have been identified for MHC class I alleles and for non-MHC regions. The role of environmental risk factors and their interaction with genetic susceptibility alleles are much less well defined, despite the fact that infections have long been associated with MS development. Current data suggest that infectious triggers are most likely ubiquitous, i.e., highly prevalent in the general population, and that they require a permissive genetic trait which predisposes for MS development. In this review article, we illustrate mechanisms of infection-induced immunopathologies in experimental animal models of autoimmune CNS inflammation, discuss challenges for the translation of these experimental data into human immunology research, and provide future perspectives on how novel model systems could be utilized to better define the role of viral pathogens in MS.

B cell expression of the inhibitory Fc gamma receptor is unchanged in early MS.

Expression of the inhibitory Fcgamma receptor IIB (FcgammaRIIB) has emerged as a late checkpoint during peripheral B cell development which prevents autoreactive memory B lymphocytes from becoming long-lived plasma cells. Decreased expression of FcgammaRIIB or non-functional FcgammaRIIB variants are associated with the development of autoimmune tissue inflammation. We determined the expression profile of FcgammaRIIB in peripheral blood cells in treatment-naïve patients with early MS. Twenty-five patients with clinically isolated syndrome (CIS) who converted to clinically definite MS (CDMS) and 25 demographically matched healthy donors were included in the study. Frequencies of peripheral blood monocytes and B cell subsets as well as FcgammaRIIB expression profile was determined by flow cytometry. FcgammaRIIB expression levels were higher in B cells compared to monocytes (p<0.0001) and higher in memory B cells compared to their naïve counterparts (p<0.0001). However, FcgammaRIIB expression in naïve and memory B cells as well as monocytes was unchanged in patients with early MS at onset of symptoms as well as after conversion to CDMS compared to controls. No significant correlations were found between FcgammaRIIB expression levels and brain MRI-derived metrics or EDSS progression during follow-up. These data indicate that FcgammaRIIB expression, a critical late B cell differentiation checkpoint preventing the occurrence of autoreactive long-lived plasma cells, is not impaired in treatment-naïve patients with MS, at least in the early phases of the disease.