Cytomegalovirus infection exacerbates autoimmune mediated neuroinflammation

Case report: Autoimmune encephalomyelitis following cytomegalovirus infection after allogeneic hematopoietic stem cell transplantation

Introduction

Cytomegalovirus (CMV) can cause various end-organ diseases in immunocompromised hosts, including allogeneic hematopoietic cell transplant (allo-HSCT) recipients. Interestingly, CMV viremia has been associated with various complications and poor prognosis in allo-HSCT recipients. Complications involving the central nervous system (CNS) occur in 9-14% of patients following allo-HSCT. However, autoimmune encephalitis (AE) secondary to CMV infection after allo-HSCT has rarely been reported. Here we report a case of possible AE following CMV viremia after allo-HSCT, which was successfully treated with high-dose pulsed methylprednisolone and intravenous immunoglobulins (IVIg).

Case description

A 53-year-old female underwent allo-HSCT for T-lymphoblastic lymphoma/leukemia. The patient developed CMV viremia on day 36 after transplantation, and serum CMV-DNA remained positive after initiating ganciclovir antiviral therapy, turning negative one month later. Four months later, she started experiencing memory impairment, weakness in the left limbs, cognitive dysfunction, and hallucinations. A magnetic resonance imaging brain scan showed scattered ischemic lesions under the bilateral frontal cortex. Viral detection in cerebral spinal fluid (CSF) by next-generation gene sequencing technology showed no obvious abnormality. Antibodies specific to AE and paraneoplastic diseases in serum and CSF were absent. The oligoclonal bands in the CSF were detected using isoelectric focusing and immunofixation, and the results were negative. However, after extensive investigation regarding infections, autoimmune disorders, and recurrence of the malignancy, possible AE could not be excluded. The patient was treated with high-dose steroids combined with IVIg therapy; the patient's symptoms were significantly improved.

Conclusion

The mechanisms of AE after allo-HSCT and the relationship with CMV infection should be further studied. Therefore, reporting this and similar cases will improve our awareness and understanding of the underlying disease mechanisms.

Involvement of expanded cytotoxic and proinflammatory CD28null T cells in primary Sjögren's syndrome

OBJECTIVE

The absence of CD28 is a feature of antigen-experienced, highly differentiated and aged T cells. The pathogenicity of CD28null T cells remains elusive in primary Sjögren's syndrome (pSS). Therefore, this study was performed to explore the characteristics of CD28null T cells in both peripheral blood and minor salivary glands (MSGs) of pSS patients.

METHODS

pSS patients and paired healthy controls (HCs) were enrolled. The phenotype of peripheral CD28null T cells was analyzed using flow cytometry. In vitro functional assays were performed to evaluate the cytotoxic and proinflammatory effects of peripheral CD28null T cells. In addition, polychromatic immunofluorescence staining was performed to investigate infiltrating CD28null T cells in MSGs.

RESULTS

A significant expansion of peripheral CD28null T cells was observed in pSS patients compared with HCs (p < 0.001), which were primarily CD8+CD28null T cells. The proportion of peripheral CD8+CD28null T cells moderately correlated with the erythrocyte sedimentation rate (r = 0.57, p < 0.01) and IgG levels (r = 0.44, p < 0.01). Peripheral CD28null T cells had stronger capacities to secrete granzyme B and perforin, but comparable capacities to secrete IFN-γ and TNF-α than their CD28+ counterparts. An abundant amount of cytotoxic and pro-inflammatory CD28null T cells was also found in MSGs. Moreover, a high expression of the chemokine receptor CXCR3 was found on peripheral and tissue-resident CD28null T cells, with its ligands CXCL9/10 abundantly present in MSGs.

CONCLUSION

Increasing CD28null T cells with strong cytotoxicity and proinflammatory effects were observed in both peripheral blood and MSGs from pSS patients. The precise mechanism of action and migration still needs further investigation.

The Impact of Cytomegalovirus Infection on Natural Killer and CD8+ T Cell Phenotype in Multiple Sclerosis

Multiple sclerosis (MS) is a debilitating neurological disease that has been classified as an immune-mediated attack on myelin, the protective sheath of nerves. Some aspects of its pathogenesis are still unclear; nevertheless, it is generally established that viral infections influence the course of the disease. Cytomegalovirus (CMV) is a major pathogen involved in alterations of the immune system, including the expansion of highly differentiated cytotoxic CD8+ T cells and the accumulation of adaptive natural killer (NK) cells expressing high levels of the NKG2C receptor. In this study, we evaluated the impact of latent CMV infection on MS patients through the characterization of peripheral NK cells, CD8+ T cells, and NKT-like cells using flow cytometry. We evaluated the associations between immune cell profiles and clinical features such as MS duration and MS progression, evaluated using the Expanded Disability Status Scale (EDSS). We showed that NK cells, CD8+ T cells, and NKT-like cells had an altered phenotype in CMV-infected MS patients and displayed high levels of the NKG2C receptor. Moreover, in MS patients, increased NKG2C expression levels were found to be associated with higher EDSS scores. Overall, these results support the hypothesis that CMV infection imprints the immune system by modifying the phenotype and receptor repertoire of NK and CD8+ T cells, suggesting a detrimental role of CMV on MS progression.

Understanding the link between neurotropic viruses, BBB permeability, and MS pathogenesis

Neurotropic viruses can infiltrate the CNS by crossing the blood-brain barrier (BBB) through various mechanisms including paracellular, transcellular, and "Trojan horse" mechanisms during leukocyte diapedesis. These viruses belong to several families, including retroviruses; human immunodeficiency virus type 1 (HIV-1), flaviviruses; Japanese encephalitis (JEV); and herpesviruses; herpes simplex virus type 1 (HSV-1), Epstein-Barr virus (EBV), and mouse adenovirus 1 (MAV-1). For entering the brain, viral proteins act upon the tight junctions (TJs) between the brain microvascular endothelial cells (BMECs). For instance, HIV-1 proteins, such as glycoprotein 120, Nef, Vpr, and Tat, disrupt the BBB and generate a neurotoxic effect. Recombinant-Tat triggers amendments in the BBB by decreasing expression of the TJ proteins such as claudin-1, claudin-5, and zona occludens-1 (ZO-1). Thus, the breaching of BBB has been reported in myriad of neurological diseases including multiple sclerosis (MS). Neurotropic viruses also exhibit molecular mimicry with several myelin sheath proteins, i.e., antibodies against EBV nuclear antigen 1 (EBNA1) aa411-426 cross-react with MBP and EBNA1 aa385-420 was found to be associated with MS risk haplotype HLA-DRB1*150. Notably, myelin protein epitopes (PLP139-151, MOG35-55, and MBP87-99) are being used to generate model systems for MS such as experimental autoimmune encephalomyelitis (EAE) to understand the disease mechanism and therapeutics. Viruses like Theiler's murine encephalomyelitis virus (TMEV) are also commonly used to generate EAE. Altogether, this review provide insights into the viruses' association with BBB leakiness and MS along with possible mechanistic details which could potentially use for therapeutics.

Differential Runx3, Eomes, and T-bet expression subdivides MS-associated CD4+ T cells with brain-homing capacity

Multiple sclerosis (MS) is a common and devastating chronic inflammatory disease of the CNS. CD4+ T cells are assumed to be the first to cross the blood-central nervous system (CNS) barrier and trigger local inflammation. Here, we explored how pathogenicity-associated effector programs define CD4+ T cell subsets with brain-homing ability in MS. Runx3- and Eomes-, but not T-bet-expressing CD4+ memory cells were diminished in the blood of MS patients. This decline reversed following natalizumab treatment and was supported by a Runx3+ Eomes+ T-bet- enrichment in cerebrospinal fluid samples of treatment-naïve MS patients. This transcription factor profile was associated with high granzyme K (GZMK) and CCR5 levels and was most prominent in Th17.1 cells (CCR6+ CXCR3+ CCR4-/dim ). Previously published CD28- CD4 T cells were characterized by a Runx3+ Eomes- T-bet+ phenotype that coincided with intermediate CCR5 and a higher granzyme B (GZMB) and perforin expression, indicating the presence of two separate subsets. Under steady-state conditions, granzyme Khigh Th17.1 cells spontaneously passed the blood-brain barrier in vitro. This was only found for other subsets including CD28- cells when using inflamed barriers. Altogether, CD4+ T cells contain small fractions with separate pathogenic features, of which Th17.1 seems to breach the blood-brain barrier as a possible early event in MS.

Delimiting MOGAD as a disease entity using translational imaging

The first formal consensus diagnostic criteria for myelin oligodendrocyte glycoprotein antibody-associated disease (MOGAD) were recently proposed. Yet, the distinction of MOGAD-defining characteristics from characteristics of its important differential diagnoses such as multiple sclerosis (MS) and aquaporin-4 antibody seropositive neuromyelitis optica spectrum disorder (NMOSD) is still obstructed. In preclinical research, MOG antibody-based animal models were used for decades to derive knowledge about MS. In clinical research, people with MOGAD have been combined into cohorts with other diagnoses. Thus, it remains unclear to which extent the generated knowledge is specifically applicable to MOGAD. Translational research can contribute to identifying MOGAD characteristic features by establishing imaging methods and outcome parameters on proven pathophysiological grounds. This article reviews suitable animal models for translational MOGAD research and the current state and prospect of translational imaging in MOGAD.

The effects of cytomegalovirus on brain structure following sport-related concussion

The neurotrophic herpes virus cytomegalovirus is a known cause of neuropathology in utero and in immunocompromised populations. Cytomegalovirus is reactivated by stress and inflammation, possibly explaining the emerging evidence linking it to subtle brain changes in the context of more minor disturbances of immune function. Even mild forms of traumatic brain injury, including sport-related concussion, are major physiological stressors that produce neuroinflammation. In theory, concussion could predispose to the reactivation of cytomegalovirus and amplify the effects of physical injury on brain structure. However, to our knowledge this hypothesis remains untested. This study evaluated the effect of cytomegalovirus serostatus on white and grey matter structure in a prospective study of athletes with concussion and matched contact-sport controls. Athletes who sustained concussion (n = 88) completed MRI at 1, 8, 15 and 45 days post-injury; matched uninjured athletes (n = 73) completed similar visits. Cytomegalovirus serostatus was determined by measuring serum IgG antibodies (n = 30 concussed athletes and n = 21 controls were seropositive). Inverse probability of treatment weighting was used to adjust for confounding factors between athletes with and without cytomegalovirus. White matter microstructure was assessed using diffusion kurtosis imaging metrics in regions previously shown to be sensitive to concussion. T1-weighted images were used to quantify mean cortical thickness and total surface area. Concussion-related symptoms, psychological distress, and serum concentration of C-reactive protein at 1 day post-injury were included as exploratory outcomes. Planned contrasts compared the effects of cytomegalovirus seropositivity in athletes with concussion and controls, separately. There was a significant effect of cytomegalovirus on axial and radial kurtosis in athletes with concussion but not controls. Cytomegalovirus positive athletes with concussion showed greater axial (P = 0.007, d = 0.44) and radial (P = 0.010, d = 0.41) kurtosis than cytomegalovirus negative athletes with concussion. Similarly, there was a significant association of cytomegalovirus with cortical thickness in athletes with concussion but not controls. Cytomegalovirus positive athletes with concussion had reduced mean cortical thickness of the right hemisphere (P = 0.009, d = 0.42) compared with cytomegalovirus negative athletes with concussion and showed a similar trend for the left hemisphere (P = 0.036, d = 0.33). There was no significant effect of cytomegalovirus on kurtosis fractional anisotropy, surface area, symptoms and C-reactive protein. The results raise the possibility that cytomegalovirus infection contributes to structural brain abnormalities in the aftermath of concussion perhaps via an amplification of concussion-associated neuroinflammation. More work is needed to identify the biological pathways underlying this process and to clarify the clinical relevance of this putative viral effect.

Immunopathogenesis of viral infections in neurological autoimmune disease

Autoimmune diseases develop due to self-tolerance failure in recognizing self and non-self-antigens. Several factors play a role in inducing autoimmunity, including genetic and environmental elements. Several studies demonstrated the causative role of viruses; however, some studies showed the preventive effect of viruses in the development of autoimmunity. Neurological autoimmune diseases are classified based on the targets of autoantibodies, which target intracellular or extracellular antigens rather than neurons. Several theories have been hypothesized to explain the role of viruses in the pathogenesis of neuroinflammation and autoimmune diseases. This study reviewed the current data on the immunopathogenesis of viruses in autoimmunity of the nervous system.

PARP in the neuropathogenesis of cytomegalovirus infection - Possible role and therapeutic perspective

Cytomegalovirus infects the majority of the population globally. Congenital CMV infection acquired through primary maternal infection in pregnancy is the most common intrauterine infection with a high mortality rate due to severe long-term neurodevelopmental sequelae. The demyelination and neuroinflammation during CMV infection have been attributed to altered immune response and ROS-mediated apoptosis. PARP-1 protein is linked to apoptotic neuronal loss with subsequent neurotoxicity and CNS injury as a result of PARP hyperactivation. PARP-1 play a critical role in the establishment of latency including EBV, HHV-8 and HIV. Research on PARP inhibitors recently shows significant progress against neurodegenerative diseases such as Alzheimer's disease and cancer therapy including malignant lymphoma and hepatitis B virus-induced hepatocellular carcinoma. The role of PARP1 in the neuropathogenesis of CMV and the potential of PARP inhibitors in the prevention of neurological sequelae is still elusive. Further studies on the role of PARP on the neuropathogenesis of CMV infection can help thwart neurodegeneration through the potential development of PARP inhibitors such as small molecule inhibitors.

Comprehensive Investigations Relationship Between Viral Infections and Multiple Sclerosis Pathogenesis

Multiple sclerosis (MS) is a chronic autoimmune disease that affects the central nervous system (CNS). Compared to other types of self-limiting myelin disorders, MS compartmentalizes and maintains chronic inflammation in the CNS. Even though the exact cause of MS is unclear, it is assumed that genetic and environmental factors play an important role in susceptibility to this disease. The progression of MS is triggered by certain environmental factors, such as viral infections. The most important viruses that affect MS are Epstein-Barr virus (EBV), human herpes virus 6 (HHV-6), human endogenous retrovirus (HERV), cytomegalovirus (CMV), and varicella zoster virus (VZV). These viruses all have latent stages that allow them to escape immune detection and reactivate after exposure to various stimuli. Furthermore, their tropism for CNS and immune system cells explains their possible deleterious function in neuroinflammation. In this study, the effect of viral infections on MS disease focuses on the details of viruses that can change the risk of the disease. Paying attention to the most recent articles on the role of SARS-CoV-2 in MS disease, laboratory indicators show the interaction of the immune system with the virus. Also, strategies to prevent viruses that play a role in triggering MS are discussed, such as EBV, which is one of the most important.

B-Cell Reconstitution After Autologous Hematopoietic Stem Cell Transplantation in Multiple Sclerosis

BACKGROUND AND OBJECTIVES

Autologous hematopoietic stem cell transplantation (aHSCT) is increasingly used to treat aggressive forms of multiple sclerosis (MS). This procedure is believed to result in an immune reset and restoration of a self-tolerant immune system. Immune reconstitution has been extensively studied for T cells, but only to a limited extent for B cells. As increasing evidence suggests an important role of B cells in MS pathogenesis, we sought here to better understand reconstitution and the extent of renewal of the B-cell system after aHSCT in MS.

METHODS

Using longitudinal multidimensional flow cytometry and immunoglobulin heavy chain (IgH) repertoire sequencing following aHSCT with BCNU + Etoposide + Ara-C + Melphalan anti-thymocyte globulin, we analyzed the B-cell compartment in a cohort of 20 patients with MS in defined intervals before and up to 1 year after aHSCT and compared these findings with data from healthy controls.

RESULTS

Total B-cell numbers recovered within 3 months and increased above normal levels 1 year after transplantation, successively shifting from a predominantly transitional to a naive immune phenotype. Memory subpopulations recovered slowly and remained below normal levels with reduced repertoire diversity 1 year after transplantation. Isotype subclass analysis revealed a proportional shift toward IgG1-expressing cells and a reduction in IgG2 cells. Mutation analysis of IgH sequences showed that highly mutated memory B cells and plasma cells may transiently survive conditioning while the analysis of sequence cluster overlap, variable (IGHV) and joining (IGHJ) gene usage and repertoire diversity suggested a renewal of the late posttransplant repertoire. In patients with early cytomegalovirus reactivation, reconstitution of naive and memory B cells was delayed.

DISCUSSION

Our detailed characterization of B-cell reconstitution after aHSCT in MS indicates a reduced reactivation potential of memory B cells up to 1 year after transplantation, which may leave patients susceptible to infection, but may also be an important aspect of its mechanism of action.

Neuroinflammation in neurodegeneration via microbial infections

Recent epidemiological studies show a noticeable correlation between chronic microbial infections and neurological disorders. However, the underlying mechanisms are still not clear due to the biological complexity of multicellular and multiorgan interactions upon microbial infections. In this review, we show the infection leading to neurodegeneration mediated by multiorgan interconnections and neuroinflammation. Firstly, we highlight three inter-organ communications as possible routes from infection sites to the brain: nose-brain axis, lung-brain axis, and gut-brain axis. Next, we described the biological crosstalk between microglia and astrocytes upon pathogenic infection. Finally, our study indicates how neuroinflammation is a critical player in pathogen-mediated neurodegeneration. Taken together, we envision that antibiotics targeting neuro-pathogens could be a potential therapeutic strategy for neurodegeneration.

When Helpers Go Above and Beyond: Development and Characterization of Cytotoxic CD4+ T Cells

Once regarded as an experimental artefact, cytotoxic CD4⁺ T cells (CD4 CTL) are presently recognized as a biologically relevant T cell subset with important functions in anti-viral, anti-tumor, and autoimmune responses. Despite the potentially large impact on their micro-environment, the absolute cell counts of CD4 CTL within the peripheral circulation are relatively low. With the rise of single cell analysis techniques, detection of these cells is greatly facilitated. This led to a renewed appraisal of CD4 CTL and an increased insight into their heterogeneous nature and ontogeny. In this review, we summarize the developmental path from naïve CD4⁺ T cells to terminally differentiated CD4 CTL, and present markers that can be used to detect or isolate CD4 CTL and their precursors. Subsets of CD4 CTL and their divergent functionalities are discussed. Finally, the importance of local cues as triggers for CD4 CTL differentiation is debated, posing the question whether CD4 CTL develop in the periphery and migrate to site of inflammation when called for, or that circulating CD4 CTL reflect cells that returned to the circulation following differentiation at the local inflammatory site they previously migrated to. Even though much remains to be learned about this intriguing T cell subset, it is clear that CD4 CTL represent interesting therapeutic targets for several pathologies.

Effect of Cytomegalovirus Infection on the Central Nervous System: Implications for Psychiatric Disorders

Cytomegalovirus (CMV) is a common herpesvirus that establishes lifelong latent infections and interacts extensively with the host immune system, potentially contributing to immune activation and inflammation. Given its proclivity for infecting the brain and its reactivation by inflammatory stimuli, CMV is well known for causing central nervous system complications in the immune-naïve (e.g., in utero) and in the immunocompromised (e.g., in neonates, individuals receiving transplants or cancer chemotherapy, or people living with HIV). However, its potentially pathogenic role in diseases that are characterized by more subtle immune dysregulation and inflammation such as psychiatric disorders is still a matter of debate. In this chapter, we briefly summarize the pathogenic role of CMV in immune-naïve and immunocompromised populations and then review the evidence (i.e., epidemiological studies, serological studies, postmortem studies, and recent neuroimaging studies) for a link between CMV infection and psychiatric disorders with a focus on mood disorders and schizophrenia. Finally, we discuss the potential mechanisms through which CMV may cause CNS dysfunction in the context of mental disorders and conclude with a summary of the current state of play as well as potential future research directions in this area.

CD8+ T Cell Senescence: Lights and Shadows in Viral Infections, Autoimmune Disorders and Cancer

CD8⁺ T lymphocytes are a heterogeneous class of cells that play a crucial role in the adaptive immune response against pathogens and cancer. During their lifetime, they acquire cytotoxic functions to ensure the clearance of infected or transformed cells and, in addition, they turn into memory lymphocytes, thus providing a long-term protection. During ageing, the thymic involution causes a reduction of circulating T cells and an enrichment of memory cells, partially explaining the lowering of the response towards novel antigens with implications in vaccine efficacy. Moreover, the persistent stimulation by several antigens throughout life favors the switching of CD8⁺ T cells towards a senescent phenotype contributing to a low-grade inflammation that is a major component of several ageing-related diseases. In genetically predisposed young people, an immunological stress caused by viral infections (e.g., HIV, CMV, SARS-CoV-2), autoimmune disorders or tumor microenvironment (TME) could mimic the ageing status with the consequent acceleration of T cell senescence. This, in turn, exacerbates the inflamed conditions with dramatic effects on the clinical progression of the disease. A better characterization of the phenotype as well as the functions of senescent CD8⁺ T cells can be pivotal to prevent age-related diseases, to improve vaccine strategies and, possibly, immunotherapies in autoimmune diseases and cancer.

Molecular Mechanisms of Immunosenescene and Inflammaging: Relevance to the Immunopathogenesis and Treatment of Multiple Sclerosis

Aging is characterized, amongst other features, by a complex process of cellular senescence involving both innate and adaptive immunity, called immunosenescence and associated to inflammaging, a low-grade chronic inflammation. Both processes fuel each other and partially explain increasing incidence of cancers, infections, age-related autoimmunity, and vascular disease as well as a reduced response to vaccination. Multiple sclerosis (MS) is a lifelong disease, for which considerable progress in disease-modifying therapies (DMTs) and management has improved long-term survival. However, disability progression, increasing with age and disease duration, remains. Neurologists are now involved in caring for elderly MS patients, with increasing comorbidities. Aging of the immune system therefore has relevant implications for MS pathogenesis, response to DMTs and the risks mediated by these treatments. We propose to review current evidence regarding markers and molecular mechanisms of immunosenescence and their relevance to understanding MS pathogenesis. We will focus on age-related changes in the innate and adaptive immune system in MS and other auto-immune diseases, such as systemic lupus erythematosus and rheumatoid arthritis. The consequences of these immune changes on MS pathology, in interaction with the intrinsic aging process of central nervous system resident cells will be discussed. Finally, the impact of immunosenescence on disease evolution and on the safety and efficacy of current DMTs will be presented.

Autoimmune complications of COVID-19

Coronavirus disease 2019 (COVID-19) is still propagating a year after the start of the pandemic. Besides the complications patients face during the COVID-19 disease period, there is an accumulating body of evidence concerning the late-onset complications of COVID-19, of which autoimmune manifestations have attracted remarkable attention from the first months of the pandemic. Autoimmune hemolytic anemia, immune thrombocytopenic purpura, autoimmune thyroid diseases, Kawasaki disease, Guillain-Barre syndrome, and the detection of autoantibodies are the cues to the discovery of the potential of COVID-19 in inducing autoimmunity. Clarification of the pathophysiology of COVID-19 injuries to the host, whether it is direct viral injury or autoimmunity, could help to develop appropriate treatment.

Immunosenescence: an unexplored role in glomerulonephritis

Immunosenescence is a natural ageing phenomenon with alterations in innate and especially adaptive immunity and contributes to reduced antimicrobial defence and chronic low‐grade inflammation. This is mostly reflected by an increase in organ‐directed and/or circulating reactive and cytolytic terminally differentiated T cells that have lost their expression of the costimulatory receptor CD28. Apart from being induced by a genetic predisposition, ageing or viral infections (particularly cytomegalovirus infection), immunosenescence is accelerated in many inflammatory diseases and uraemia. This translates into an enhancement of vascular inflammation and cardiovascular disease varying from endothelial dysfunction to plaque rupture. Emerging data point to a mechanistic role of CD28^null T cells in glomerulonephritis, where they initiate and propagate local inflammation in concordance with dendritic cells and macrophages. They are suitably equipped to escape immunological dampening by the absence of homing to lymph nodes, anti‐apoptotic properties and resistance to suppression by regulatory T cells. Early accumulation of senescent CD28^null T cells precedes glomerular or vascular injury, and targeting these cells could open avenues for early treatment interventions that aim at abrogating a detrimental vicious cycle.

Clinical risk factors and prognostic model for idiopathic inflammatory demyelinating diseases after haploidentical hematopoietic stem cell transplantation in patients with hematological malignancies

Idiopathic inflammatory demyelinating diseases (IIDDs) of the central nervous system (CNS) are rare but serious neurological complications of haploidentical hematopoietic stem cell transplantation (haplo-HSCT). However, the risk factors and a method to predict the prognosis of post-transplantation CNS IIDDs are not available. This retrospective study first reviewed data from 4532 patients who received haplo-HSCT during 2008-2019 in our center, and 184 patients (4.1%) with IIDDs after haplo-HSCT were identified. Grades II to IV acute graft-versus-host disease (aGVHD) (p < 0.001) and chronic GVHD (cGVHD) (p = 0.009) were identified as risk factors for developing IIDDs after haplo-HSCT. We then divided the 184 IIDD patients into a derivation cohort and validation cohort due to transplantation time to develop and validate a model for predicting the prognosis of IIDDs. In the multivariate analysis of the derivation cohort, four candidate predictors were entered into the final prognostic model: cytomegalovirus (CMV) infection, Epstein-Barr virus (EBV) infection, IgG synthesis (IgG-syn) and spinal cord lesions. The prognostic model had an area under the receiver operating characteristic curve of 0.864 (95% CI: 0.803-0.925) in the internal validation cohort and 0.871 (95% CI: 0.806-0.931) in the external validation cohort. The calibration plots showed a high agreement between the predicted and observed outcomes. Decision curve analysis indicated that IIDD patients could benefit from the clinical application of the prognostic model. The identification of IIDD patients after allo-HSCT who have a poor prognosis might allow timely treatment and improve patient survival and outcomes.

Sex-specific remodeling of T-cell compartment with aging: Implications for rat susceptibility to central nervous system autoimmune diseases

The incidence of multiple sclerosis (MS) and susceptibility of animals to experimental autoimmune encephalomyelitis (EAE), the most commonly used experimental model of MS, decrease with aging. Generally, autoimmune diseases develop as the ultimate outcome of an imbalance between damaging immune responses against self and regulatory immune responses (keeping the former under control). Thus, in this review the age-related changes possibly underlying this balance were discussed. Specifically, considering the central role of T cells in MS/EAE, the impact of aging on overall functional capacity (reflecting both overall count and individual functional cell properties) of self-reactive conventional T cells (Tcons) and FoxP3+ regulatory T cells (Tregs), as the most potent immunoregulatory/suppressive cells, was analyzed, as well. The analysis encompasses three distinct compartments: thymus (the primary lymphoid organ responsible for the elimination of self-reactive T cells - negative selection and the generation of Tregs, compensating for imperfections of the negative selection), peripheral blood/lymphoid tissues ("afferent" compartment), and brain/spinal cord tissues ("target" compartment). Given that the incidence of MS and susceptibility of animals to EAE are greater in women/females than in age-matched men/males, sex as independent variable was also considered. In conclusion, with aging, sex-specific alterations in the balance of self-reactive Tcons/Tregs are likely to occur not only in the thymus/"afferent" compartment, but also in the "target" compartment, reflecting multifaceted changes in both T-cell types. Their in depth understanding is important not only for envisaging effects of aging, but also for designing interventions to slow-down aging without any adverse effect on incidence of autoimmune diseases.

Cytomegalovirus infection in malignant pleural mesothelioma

Human cytomegalovirus (HCMV) is a highly prevalent herpes virus which persists as a latent infection and has been detected in several different tumor types. HCMV disease is rare but may occur in high-risk settings, often manifesting as a pulmonary infection. To date HCMV has not been investigated in malignant pleural mesothelioma (MPM). In a consecutive case series of 144 MPM patients we evaluated two biomarkers of HCMV: IgG serostatus (defined as positive and negative) and DNAemia (>100 copies/mL of cell free HCMV DNA in serum). Approximately half of the MPM patient population was HCMV IgG seropositive (51%). HCMV DNAemia was highly prevalent (79%) in MPM and independent of IgG serostatus. DNAemia levels consistent with high level current infection (>1000 copies/mL serum) were present in 41% of patients. Neither IgG serostatus nor DNAemia were associated with patient survival. In tissues, we observed that HCMV DNA was present in 48% of tumors (n = 40) and only 29% of normal pleural tissue obtained from individuals without malignancy (n = 21). Our results suggest nearly half of MPM patients have a high level current HCMV infection at the time of treatment and that pleural tissue may be a reservoir for latent HCMV infection. These findings warrant further investigation to determine the full spectrum of pulmonary infections in MPM patients, and whether treatment for high level current HCMV infection may improve patient outcomes.

Autoimmune phenomena following SARS-CoV-2 vaccination

Vaccines represent an attractive possible solution to the severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) pandemic. Widespread vaccine distribution has yet to occur in most countries, partially due to public concerns regarding possible side effects. While studies indicate the vaccine is exceptionally safe, rare systemic side effects remain possible. In Israel, where a large percentage of the population has been rapidly vaccinated, such adverse events may be more apparent. We report a series of patients presenting with de-novo or flares of existing autoimmune conditions associated with the Pfizer BNT162b2 mRNA SARS-CoV-2 vaccine. All patients were assessed in our tertiary care center in Israel and had no history of previous SARS-COV-2 infection. We observed that while immune phenomena may occur following vaccination, they usually follow a mild course and require modest therapy. We briefly expound on the theoretical background of vaccine related autoimmunity and explore future research prospects.

Mechanistic underpinning of an inside-out concept for autoimmunity in multiple sclerosis

The neuroinflammatory disease multiple sclerosis is driven by autoimmune pathology in the central nervous system. However, the trigger of the autoimmune pathogenic process is unknown. MS models in immunologically naïve, specific‐pathogen‐free bred rodents support an exogenous trigger, such as an infection. The validity of this outside–in pathogenic concept for MS has been frequently challenged by the difficulty to translate pathogenic concepts developed in these models into effective therapies for the MS patient. Studies in well‐validated non‐human primate multiple sclerosis models where, just like in humans, the autoimmune pathogenic process develops from an experienced immune system trained by prior infections, rather support an endogenous trigger. Data reviewed here corroborate the validity of this inside–out pathogenic concept for multiple sclerosis. They also provide a plausible sequence of events reminiscent of Wilkin’s primary lesion theory: (i) that autoimmunity is a physiological response of the immune system against excess antigen turnover in diseased tissue (the primary lesion) and (ii) that individuals developing autoimmune disease are (genetically predisposed) high responders against critical antigens. Data obtained in multiple sclerosis brains reveal the presence in normally appearing white matter of myelinated axons where myelin sheaths have locally dissociated from their enwrapped axon (i.e., blistering). The ensuing disintegration of axon–myelin units potentially causes the excess systemic release of post‐translationally modified myelin. Data obtained in a unique primate multiple sclerosis model revealed a core pathogenic role of T cells present in the normal repertoire, which hyper‐react to post‐translationally modified (citrullinated) myelin–oligodendrocyte glycoprotein and evoke clinical and pathological aspects of multiple sclerosis.

Treg-Resistant Cytotoxic CD4+ T Cells Dictate T Helper Cells in Their Vicinity: TH17 Skewing and Modulation of Proliferation

Cytotoxic CD4⁺ T cells (CD4 CTL) are terminally differentiated T helper cells that contribute to autoimmune diseases, such as multiple sclerosis. We developed a novel triple co-culture transwell assay to study mutual interactions between CD4 CTL, conventional TH cells, and regulatory T cells (Tregs) simultaneously. We show that, while CD4 CTL are resistant to suppression by Tregs in vitro, the conditioned medium of CD4 CTL accentuates the suppressive phenotype of Tregs by upregulating IL-10, Granzyme B, CTLA-4, and PD-1. We demonstrate that CD4 CTL conditioned medium skews memory TH cells to a TH17 phenotype, suggesting that the CD4 CTL induce bystander polarization. In our triple co-culture assay, the CD4 CTL secretome promotes the proliferation of TH cells, even in the presence of Tregs. However, when cell−cell contact is established between CD4 CTL and TH cells, the proliferation of TH cells is no longer increased and Treg-mediated suppression is restored. Taken together, our results suggest that when TH cells acquire cytotoxic properties, these Treg-resistant CD4 CTL affect the proliferation and phenotype of conventional TH cells in their vicinity. By creating such a pro-inflammatory microenvironment, CD4 CTL may favor their own persistence and expansion, and that of other potentially pathogenic TH cells, thereby contributing to pathogenic responses in autoimmune disorders.

A new clustering method identifies multiple sclerosis-specific T-cell receptors

OBJECTIVE

To characterize T-cell receptors (TCRs) and identify target epitopes in multiple sclerosis (MS).

METHODS

Peripheral blood mononuclear cells were obtained from 39 MS patients and 19 healthy controls (HCs). TCR repertoires for α/β/δ/γ chains, TCR diversity, and V/J usage were determined by next-generation sequencing. TCR β chain repertoires were compared with affectation status using a novel clustering method, Grouping of Lymphocyte Interactions by Paratope Hotspots (GLIPH). Cytomegalovirus (CMV)-IgG was measured in an additional 113 MS patients and 93 HCs. Regulatory T cells (Tregs) were measured by flow cytometry.

RESULTS

TCR diversity for all four chains decreased with age. TCRα and TCRβ diversity was higher in MS patients (P = 0.0015 and 0.024, respectively), even after age correction. TRAJ56 and TRBV4-3 were more prevalent in MS patients than in HCs (p^corr  = 0.027 and 0.040, respectively). GLIPH consolidated 208,674 TCR clones from MS patients into 1,294 clusters, among which two candidate clusters were identified. The TRBV4-3 cluster was shared by HLA-DRB1*04:05-positive patients (87.5%) and predicted to recognize CMV peptides (CMV-TCR). MS Severity Score (MSSS) was lower in patients with CMV-TCR than in those without (P = 0.037). CMV-IgG-positivity was associated with lower MSSS in HLA-DRB1*04:05 carriers (P = 0.0053). HLA-DRB1*04:05-positive individuals demonstrated higher CMV-IgG titers than HLA-DRB1*04:05-negative individuals (P = 0.017). CMV-IgG-positive patients had more Tregs than CMV-IgG-negative patients (P = 0.054).

INTERPRETATION

High TCRα/TCRβ diversity, regardless of age, is characteristic of MS. Association of a CMV-recognizing TCR with mild disability indicates CMV's protective role in HLA-DRB1*04:05-positive MS.

A Review of Murine Cytomegalovirus as a Model for Human Cytomegalovirus Disease-Do Mice Lie?

Since murine cytomegalovirus (MCMV) was first described in 1954, it has been used to model human cytomegalovirus (HCMV) diseases. MCMV is a natural pathogen of mice that is present in wild mice populations and has been associated with diseases such as myocarditis. The species-specific nature of HCMV restricts most research to cell culture-based studies or to the investigation of non-invasive clinical samples, which may not be ideal for the study of disseminated disease. Initial MCMV research used a salivary gland-propagated virus administered via different routes of inoculation into a variety of mouse strains. This revealed that the genetic background of the laboratory mice affected the severity of disease and altered the extent of subsequent pathology. The advent of genetically modified mice and viruses has allowed new aspects of disease to be modeled and the opportunistic nature of HCMV infection to be confirmed. This review describes the different ways that MCMV has been used to model HCMV diseases and explores the continuing difficulty faced by researchers attempting to model HCMV congenital cytomegalovirus disease using the mouse model.

The Relationship of the Mechanisms of the Pathogenesis of Multiple Sclerosis and the Expression of Endogenous Retroviruses

Simple Summary

Multiple sclerosis is a neurodegenerative disease of the central nervous system, develops at an early age and often leads to a disability. The etiological cause of the disease has not been fully elucidated, and as a result, no effective treatment is available. This review summarizes the current knowledge about the relationship between the expression of human endogenous retroviruses and the pathogenesis of multiple sclerosis. The epigenetic mechanisms of transcriptional regulation, the role of transcription factors, cytokines, and exogenous viruses are also addressed in this review. The elucidation of the mechanisms of an increase in endogenous retrovirus expression in multiple sclerosis could help to develop therapeutic strategies and novel methods for early diagnosis and treatment of the disease.

Abstract

Two human endogenous retroviruses of the HERV-W family can act as cofactors triggering multiple sclerosis (MS): MS-associated retrovirus (MSRV) and ERVWE1. Endogenous retroviral elements are believed to have integrated in our ancestors’ DNA millions of years ago. Their involvement in the pathogenesis of various diseases, including neurodegenerative pathologies, has been demonstrated. Numerous studies have shown a correlation between the deterioration of patients’ health and increased expression of endogenous retroviruses. The exact causes and mechanisms of endogenous retroviruses activation remains unknown, which hampers development of therapeutics. In this review, we will summarize the main characteristics of human endogenous W retroviruses and describe the putative mechanisms of activation, including epigenetic mechanisms, humoral factors as well as the role of the exogenous viral infections.

B Cells in Multiple Sclerosis and Virus-Induced Neuroinflammation

Neuroinflammation can be defined as an inflammatory response within the central nervous system (CNS) mediated by a complex crosstalk between CNS-resident and infiltrating immune cells from the periphery. Triggers for neuroinflammation not only include pathogens, trauma and toxic metabolites, but also autoimmune diseases such as neuromyelitis optica spectrum disorders and multiple sclerosis (MS) where the inflammatory response is recognized as a disease-escalating factor. B cells are not considered as the first responders of neuroinflammation, yet they have recently gained focus as a key component involved in the disease pathogenesis of several neuroinflammatory disorders like MS. Traditionally, the prime focus of the role of B cells in any disease, including neuroinflammatory diseases, was their ability to produce antibodies. While that may indeed be an important contribution of B cells in mediating disease pathogenesis, several lines of recent evidence indicate that B cells are multifunctional players during an inflammatory response, including their ability to present antigens and produce an array of cytokines. Moreover, interaction between B cells and other cellular components of the immune system or nervous system can either promote or dampen neuroinflammation depending on the disease. Given that the interest in B cells in neuroinflammation is relatively new, the precise roles that they play in the pathophysiology and progression of different neuroinflammatory disorders have not yet been well-elucidated. Furthermore, the possibility that they might change their function during the course of neuroinflammation adds another level of complexity and the puzzle remains incomplete. Indeed, advancing our knowledge on the role of B cells in neuroinflammation would also allow us to tackle these disorders better. Here, we review the available literature to explore the relationship between autoimmune and infectious neuroinflammation with a focus on the involvement of B cells in MS and viral infections of the CNS.

Genetic Determinants of Antibody-Mediated Immune Responses to Infectious Diseases Agents: A Genome-Wide and HLA Association Study

BACKGROUND

Infectious diseases are causally related to a large array of noncommunicable diseases (NCDs). Identifying genetic determinants of infections and antibody-mediated immune responses may shed light on this relationship and provide therapeutic targets for drug and vaccine development.

METHODS

We used the UK biobank cohort of up to 10 000 serological measurements of infectious diseases and genome-wide genotyping. We used data on 13 pathogens to define 46 phenotypes: 15 seropositivity case-control phenotypes and 31 quantitative antibody measurement phenotypes. For each of these, we performed genome-wide association studies (GWAS) using the fastGWA linear mixed model package and human leukocyte antigen (HLA) classical allele and amino acid residue associations analyses using Lasso regression for variable selection.

RESULTS

We included a total of 8735 individuals for case-control phenotypes, and an average (range) of 4286 (276-8555) samples per quantitative analysis. Fourteen of the GWAS yielded a genome-wide significant (P < 5 ×10-8) locus at the major histocompatibility complex (MHC) on chromosome 6. Outside the MHC, we found a total of 60 loci, multiple associated with Epstein-Barr virus (EBV)-related NCDs (eg, RASA3, MED12L, and IRF4). FUT2 was also identified as an important gene for polyomaviridae. HLA analysis highlighted the importance of DRB1*09:01, DQB1*02:01, DQA1*01:02, and DQA1*03:01 in EBV serologies and of DRB1*15:01 in polyomaviridae.

CONCLUSIONS

We have identified multiple genetic variants associated with antibody immune response to 13 infections, many of which are biologically plausible therapeutic or vaccine targets. This may help prioritize future research and drug development.

Role of Viruses in the Pathogenesis of Multiple Sclerosis

Multiple sclerosis (MS) is an immune inflammatory disease, where the underlying etiological cause remains elusive. Multiple triggering factors have been suggested, including environmental, genetic and gender components. However, underlying infectious triggers to the disease are also suspected. There is an increasing abundance of evidence supporting a viral etiology to MS, including the efficacy of interferon therapy and over-detection of viral antibodies and nucleic acids when compared with healthy patients. Several viruses have been proposed as potential triggering agents, including Epstein-Barr virus, human herpesvirus 6, varicella-zoster virus, cytomegalovirus, John Cunningham virus and human endogenous retroviruses. These viruses are all near ubiquitous and have a high prevalence in adult populations (or in the case of the retroviruses are actually part of the genome). They can establish lifelong infections with periods of reactivation, which may be linked to the relapsing nature of MS. In this review, the evidence for a role for viral infection in MS will be discussed with an emphasis on immune system activation related to MS disease pathogenesis.

Integrated single cell analysis of blood and cerebrospinal fluid leukocytes in multiple sclerosis

Cerebrospinal fluid (CSF) protects the central nervous system (CNS) and analyzing CSF aids the diagnosis of CNS diseases, but our understanding of CSF leukocytes remains superficial. Here, using single cell transcriptomics, we identify a specific location-associated composition and transcriptome of CSF leukocytes. Multiple sclerosis (MS) – an autoimmune disease of the CNS – increases transcriptional diversity in blood, but increases cell type diversity in CSF including a higher abundance of cytotoxic phenotype T helper cells. An analytical approach, named cell set enrichment analysis (CSEA) identifies a cluster-independent increase of follicular (TFH) cells potentially driving the known expansion of B lineage cells in the CSF in MS. In mice, TFH cells accordingly promote B cell infiltration into the CNS and the severity of MS animal models. Immune mechanisms in MS are thus highly compartmentalized and indicate ongoing local T/B cell interaction.

Here the authors provide a single-cell characterization of cerebrospinal fluid and blood of newly diagnosed multiple sclerosis (MS) patients, revealing altered composition of lymphocyte and monocyte subsets, validated by other methods including the interrogation of the TFH subset in mouse models of MS.

Cytomegalovirus antigenemia in patients with autoimmune and non-autoimmune diseases in Beijing: A 10-year single hospital experience

Background

Primary cytomegalovirus (CMV) infection is prevalent worldwide and usually results in latency in immunocompetent populations. Reactivation of latent CMV can cause life-threatening complications in immunocompromised hosts.

Methods

We used the CMV Brite assay to test CMV antigenemia (pp65) in whole blood samples from 22,192 patients with or without autoimmune diseases in Beijing during 2008–2018.

Results

The overall prevalence of CMV antigenemia was 19.5% (9.7%, males; 26.0%, females). The prevalence of CMV antigenemia was 35.1%, 58.6% and 11.4% in whole patients with autoimmune diseases, in patients with systemic lupus erythematosus (SLE) and in patients with non-SLE autoimmune diseases, respectively. All patients with non-autoimmune diseases, patients with HIV/AIDS or transplantation were found to have 5.0%, 27% or 14.8%, respectively. Patients≤20 years with SLE had a significantly higher prevalence of CMV antigenemia than did all SLE patients, on average. Patients>51 years with non-SLE autoimmune diseases had a significantly higher prevalence than did all patients with non-SLE autoimmune diseases, on average. The prevalence of CMV antigenemia in patients admitted to intensive-care units (ICUs) were 9.2%, which was significantly higher than that among all patients with non-autoimmune diseases. Patients with SLE had 23.8% of negative conversion of CMV antigenemia, significantly lower than the percentage of patients with non-SLE autoimmune (64.3%) and non-autoimmune (61.0%) diseases. The mean number of days to negative conversion of CMV antigenemia in patients with SLE was 35.3±35.8 days, which was significantly longer than that in patients with non-SLE autoimmune diseases (15.4±11.9 days) and non-autoimmune diseases (13.6±7.7 days).

Conclusions

CMV antigenemia is found more likely in women than in men, more prevalently in patients with SLE than those with HIV/AIDS or transplant recipients, more frequently in patients admitted to ICUs. Patients with SLE had prolonged CMV antigenemia. The role of CMV appears important in SLE.

Viruses and Autoimmunity: A Review on the Potential Interaction and Molecular Mechanisms

For a long time, viruses have been shown to modify the clinical picture of several autoimmune diseases, including type 1 diabetes (T1D), systemic lupus erythematosus (SLE), rheumatoid arthritis (RA), Sjögren’s syndrome (SS), herpetic stromal keratitis (HSK), celiac disease (CD), and multiple sclerosis (MS). Best examples of viral infections that have been proposed to modulate the induction and development of autoimmune diseases are the infections with enteric viruses such as Coxsackie B virus (CVB) and rotavirus, as well as influenza A viruses (IAV), and herpesviruses. Other viruses that have been studied in this context include, measles, mumps, and rubella. Epidemiological studies in humans and experimental studies in animal have shown that viral infections can induce or protect from autoimmunopathologies depending on several factors including genetic background, host-elicited immune responses, type of virus strain, viral load, and the onset time of infection. Still, data delineating the clear mechanistic interaction between the virus and the immune system to induce autoreactivity are scarce. Available data indicate that viral-induced autoimmunity can be activated through multiple mechanisms including molecular mimicry, epitope spreading, bystander activation, and immortalization of infected B cells. Contrarily, the protective effects can be achieved via regulatory immune responses which lead to the suppression of autoimmune phenomena. Therefore, a better understanding of the immune-related molecular processes in virus-induced autoimmunity is warranted. Here we provide an overview of the current understanding of viral-induced autoimmunity and the mechanisms that are associated with this phenomenon.

A robust pipeline with high replication rate for detection of somatic variants in the adaptive immune system as a source of common genetic variation in autoimmune disease

The role of somatic variants in diseases beyond cancer is increasingly being recognized, with potential roles in autoinflammatory and autoimmune diseases. However, as mutation rates and allele fractions are lower, studies in these diseases are substantially less tolerant of false positives, and bio-informatics algorithms require high replication rates. We developed a pipeline combining two variant callers, MuTect2 and VarScan2, with technical filtering and prioritization. Our pipeline detects somatic variants with allele fractions as low as 0.5% and achieves a replication rate of >55%. Validation in an independent data set demonstrates excellent performance (sensitivity > 57%, specificity > 98%, replication rate > 80%). We applied this pipeline to the autoimmune disease multiple sclerosis (MS) as a proof-of-principle. We demonstrate that 60% of MS patients carry 2–10 exonic somatic variants in their peripheral blood T and B cells, with the vast majority (80%) occurring in T cells and variants persisting over time. Synonymous variants significantly co-occur with non-synonymous variants. Systematic characterization indicates somatic variants are enriched for being novel or very rare in public databases of germline variants and trend towards being more damaging and conserved, as reflected by higher phred-scaled combined annotation-dependent depletion (CADD) and genomic evolutionary rate profiling (GERP) scores. Our pipeline and proof-of-principle now warrant further investigation of common somatic genetic variation on top of inherited genetic variation in the context of autoimmune disease, where it may offer subtle survival advantages to immune cells and contribute to the capacity of these cells to participate in the autoimmune reaction.

CD28 null CD4 T-cell expansions in autoimmune disease suggest a link with cytomegalovirus infection

Immunosenescence is thought to contribute to the increase of autoimmune diseases in older people. Immunosenescence is often associated with the presence of an expanded population of CD4 T cells lacking expression of CD28 (CD28 ^null). These highly cytotoxic CD4 T cells were isolated from disease-affected tissues in patients with rheumatoid arthritis, systemic lupus erythematosus, multiple sclerosis, or other chronic inflammatory diseases and their numbers appeared to be linked to disease severity. However, we recently demonstrated that the common herpes virus, cytomegalovirus (CMV), not ageing, is the major driver of this subset of cytotoxic T cells. In this review, we discuss how CMV might potentiate and exacerbate autoimmune disease through the expansion of CD28 ^null CD4 T cells.

Cytokine-Mediated Induction and Regulation of Tissue Damage During Cytomegalovirus Infection

Human cytomegalovirus (HCMV) is a β-herpesvirus with high sero-prevalence within the human population. Primary HCMV infection and life-long carriage are typically asymptomatic. However, HCMV is implicated in exacerbation of chronic conditions and associated damage in individuals with intact immune systems. Furthermore, HCMV is a significant cause of morbidity and mortality in the immunologically immature and immune-compromised where disease is associated with tissue damage. Infection-induced inflammation, including robust cytokine responses, is a key component of pathologies associated with many viruses. Despite encoding a large number of immune-evasion genes, HCMV also triggers the induction of inflammatory cytokine responses during infection. Thus, understanding how cytokines contribute to CMV-induced pathologies and the mechanisms through which they are regulated may inform clinical management of disease. Herein, we discuss our current understanding based on clinical observation and in vivo modeling of disease of the role that cytokines play in CMV pathogenesis. Specifically, in the context of the different tissues and organs in which CMV replicates, we give a broad overview of the beneficial and adverse effects that cytokines have during infection and describe how cytokine-mediated tissue damage is regulated. We discuss the implications of findings derived from mice and humans for therapeutic intervention strategies and our understanding of how host genetics may influence the outcome of CMV infections.

Strain differences in thymic atrophy in rats immunized for EAE correlate with the clinical outcome of immunization

An accumulating body of evidence suggests that development of autoimmune pathologies leads to thymic dysfunction and changes in peripheral T-cell compartment, which, in turn, perpetuate their pathogenesis. To test this hypothesis, thymocyte differentiation/maturation in rats susceptible (Dark Agouti, DA) and relatively resistant (Albino Oxford, AO) to experimental autoimmune encephalomyelitis (EAE) induction was examined. Irrespective of strain, immunization for EAE (i) increased the circulating levels of IL-6, a cytokine causally linked with thymic atrophy, and (ii) led to thymic atrophy reflecting partly enhanced thymocyte apoptosis associated with downregulated thymic IL-7 expression. Additionally, immunization diminished the expression of Thy-1, a negative regulator of TCRαβ-mediated signaling and activation thresholds, on CD4+CD8+ TCRαβ^lo/hi thymocytes undergoing selection and thereby impaired thymocyte selection/survival. This diminished the generation of mature CD4+ and CD8+ single positive TCRαβ^hi thymocytes and, consequently, CD4+ and CD8+ recent thymic emigrants. In immunized rats, thymic differentiation of natural regulatory CD4+Foxp3+CD25+ T cells (nTregs) was particularly affected reflecting a diminished expression of IL-7, IL-2 and IL-15. The decline in the overall thymic T-cell output and nTreg generation was more pronounced in DA than AO rats. Additionally, differently from immunized AO rats, in DA ones the frequency of CD28- cells secreting cytolytic enzymes within peripheral blood CD4+ T lymphocytes increased, as a consequence of thymic atrophy-related replicative stress (mirrored in CD4+ cell memory pool expansion and p16^INK4a accumulation). The higher circulating level of TNF-α in DA compared with AO rats could also contribute to this difference. Consistently, higher frequency of cytolytic CD4+ granzyme B+ cells (associated with greater tissue damage) was found in spinal cord of immunized DA rats compared with their AO counterparts. In conclusion, the study indicated that strain differences in immunization-induced changes in thymopoiesis and peripheral CD4+CD28- T-cell generation could contribute to rat strain-specific clinical outcomes of immunization for EAE.

Low cytomegalovirus seroprevalence in early multiple sclerosis: a case for the 'hygiene hypothesis'?

BACKGROUND AND PURPOSE

Cytomegalovirus (CMV) infection has recently been associated with a lower multiple sclerosis (MS) susceptibility, although it remains controversial whether it has a protective role or is merely an epiphenomenon related to westernization and early-life viral infections. We aimed to evaluate whether CMV serostatus may differ in patients with early MS as compared with patients with non-early MS, analyzing the putative association of this virus with MS clinical course and humoral immune responses against other herpesviruses.

METHODS

Multicentric analysis was undertaken of 310 patients with MS (early MS, disease duration ≤5 years, n = 127) and controls (n = 155), evaluating specific humoral responses to CMV, Epstein-Barr virus and human herpesvirus-6, as well as T-cell and natural killer (NK)-cell immunophenotypes.

RESULTS

Cytomegalovirus seroprevalence in early MS was lower than in non-early MS or controls (P < 0.01), being independently associated with disease duration (odds ratio, 1.04; 95% confidence interval, 1.01-1.08, P < 0.05). CMV+ patients with MS displayed increased proportions of differentiated T-cells (CD27-CD28-, CD57+, LILRB1+) and NKG2C+ NK-cells, which were associated with a lower disability in early MS (P < 0.05). CMV+ patients with early MS had an age-related decline in serum anti-EBNA-1 antibodies (P < 0.01), but no CMV-related differences in anti-human herpesvirus-6 humoral responses.

CONCLUSIONS

Low CMV seroprevalence was observed in patients with early MS. Modification of MS risk attributed to CMV might be related to the induction of differentiated T-cell and NK-cell subsets and/or modulation of Epstein-Barr virus-specific immune responses at early stages of the disease.

The influence and impact of ageing and immunosenescence (ISC) on adaptive immunity during multiple sclerosis (MS) and the animal counterpart experimental autoimmune encephalomyelitis (EAE)

The human ageing process encompasses mechanisms that effect a decline in homeostasis with increased susceptibility to disease and the development of chronic life-threatening illness. Increasing age affects the immune system which undergoes a progressive loss of efficiency, termed immunosenescence (ISC), to impact on quantitative and functional aspects of innate and adaptive immunity. The human demyelinating disease multiple sclerosis (MS) and the corresponding animal model experimental autoimmune encephalomyelitis (EAE) are strongly governed by immunological events that primarily involve the adaptive arm of the immune response. MS and EAE are frequently characterised by a chronic pathology and a protracted disease course which thereby creates the potential for exposure to the inherent, on-going effects and consequences of ISC. Collective evidence is presented to confirm the occurrence of established and unendorsed biological markers of ISC during the development of both diseases. Moreover, results are discussed from studies during the course of MS and EAE that reveal a premature upregulation of ISC-related biomarkers which indicates untimely alterations to the adaptive immune system. The effects of ISC and a prematurely aged immune system on autoimmune-associated neurodegenerative conditions such as MS and EAE are largely unknown but current evaluation of data justifies and encourages further investigation.

Immune responses to congenital cytomegalovirus infection

Human cytomegalovirus (HCMV) is the most common cause of viral infection acquired in utero. Even though the infection has been studied for several decades, immune determinants important for virus control and mechanisms of long-term sequelae caused by infection are still insufficiently characterized. Animal models of congenital HCMV infection provide unique opportunity to study various aspects of human disease. In this review, we summarize current knowledge on the role of immune system in congenital CMV infection, with emphasis on lessons learned from mouse model of congenital CMV infection.

Cytotoxic CD4+ T Cells Drive Multiple Sclerosis Progression

Multiple sclerosis (MS) is the leading cause of chronic neurological disability in young adults. The clinical disease course of MS varies greatly between individuals, with some patients progressing much more rapidly than others, making prognosis almost impossible. We previously discovered that cytotoxic CD4+ T cells (CD4+ CTL), identified by the loss of CD28, are able to migrate to sites of inflammation and that they contribute to tissue damage. Furthermore, in an animal model for MS, we showed that these cells are correlated with inflammation, demyelination, and disability. Therefore, we hypothesize that CD4+ CTL drive progression of MS and have prognostic value. To support this hypothesis, we investigated whether CD4+ CTL are correlated with worse clinical outcome and evaluated the prognostic value of these cells in MS. To this end, the percentage of CD4+CD28null T cells was measured in the blood of 176 patients with relapsing-remitting MS (=baseline). Multimodal evoked potentials (EP) combining information on motoric, visual, and somatosensoric EP, as well as Kurtzke expanded disability status scale (EDSS) were used as outcome measurements at baseline and after 3 and 5 years. The baseline CD4+CD28null T cell percentage is associated with EP (P = 0.003, R2 = 0.28), indicating a link between these cells and disease severity. In addition, the baseline CD4+CD28null T cell percentage has a prognostic value since it is associated with EP after 3 years (P = 0.005, R2 = 0.29) and with EP and EDSS after 5 years (P = 0.008, R2 = 0.42 and P = 0.003, R2 = 0.27). To the best of our knowledge, this study provides the first direct link between the presence of CD4+ CTL and MS disease severity, as well as its prognostic value. Therefore, we further elaborate on two important research perspectives: 1° investigating strategies to block or reverse pathways in the formation of these cells resulting in new treatments that slow down MS disease progression, 2° including immunophenotyping in prediction modeling studies to aim for personalized medicine.

A B Cell-Driven Autoimmune Pathway Leading to Pathological Hallmarks of Progressive Multiple Sclerosis in the Marmoset Experimental Autoimmune Encephalomyelitis Model

The absence of pathological hallmarks of progressive multiple sclerosis (MS) in commonly used rodent models of experimental autoimmune encephalomyelitis (EAE) hinders the development of adequate treatments for progressive disease. Work reviewed here shows that such hallmarks are present in the EAE model in marmoset monkeys (Callithrix jacchus). The minimal requirement for induction of progressive MS pathology is immunization with a synthetic peptide representing residues 34–56 from human myelin oligodendrocyte glycoprotein (MOG) formulated with a mineral oil [incomplete Freund’s adjuvant (IFA)]. Pathological aspects include demyelination of cortical gray matter with microglia activation, oxidative stress, and redistribution of iron. When the peptide is formulated in complete Freund’s adjuvant, which contains mycobacteria that relay strong activation signals to myeloid cells, oxidative damage pathways are strongly boosted leading to more intensive pathology. The proven absence of immune potentiating danger signals in the MOG34–56/IFA formulation implies that a narrow population of antigen-experienced T cells present in the monkey’s immune repertoire is activated. This novel pathway involves the interplay of lymphocryptovirus-infected B cells with MHC class Ib/Caja-E restricted CD8+ CD56+ cytotoxic T lymphocytes.