CMV infection attenuates the disease course in a murine model of multiple sclerosis

Cytomegalovirus, Epstein-Barr Virus, Herpes Simplex Virus, and Varicella Zoster Virus Infection Dynamics in People with Multiple Sclerosis from Northern Italy

Previous exposure to Epstein-Barr virus (EBV) is strongly associated with the development of multiple sclerosis (MS). By contrast, past cytomegalovirus (CMV) infection may have no association, or be negatively associated with MS. This study aimed to investigate the associations of herpesvirus infections with MS in an Italian population. Serum samples (n = 200) from Italian people with multiple sclerosis (PwMS) classified as the relapsing-and-remitting clinical phenotype and (n = 137) healthy controls (HCs) were obtained from the CRESM Biobank, Orbassano, Italy. Both PwMS and HCs samples were selected according to age group (20-39 years, and 40 or more years) and sex. EBV virus capsid antigen (VCA) IgG, EBV nucleic acid-1 antigen (EBNA-1) IgG, CMV IgG, herpes simplex virus (HSV) IgG, and varicella zoster virus (VZV) IgG testing was undertaken using commercial ELISAs. EBV VCA IgG and EBNA-1 IgG seroprevalences were 100% in PwMS and 93.4% and 92.4%, respectively, in HCs. EBV VCA IgG and EBNA-1 IgG levels were higher (p < 0.001) in PwMS compared with HCs. For PwMS, the EBNA-1 IgG levels decreased with age, particularly in females. The CMV IgG seroprevalence was 58.7% in PwMS and 62.9% in HCs. CMV IgG seroprevalence increased with age. The HSV IgG seroprevalence was 71.2% in PwMS and 70.8% in HCs. HSV IgG levels were lower (p = 0.0005) in PwMS compared with HCs. VZV IgG seroprevalence was 97.5% in PwMS and 98.5% in HCs. In the population studied, several herpesvirus infections markers may have been influenced by the age and sex of the groups studied. The lack of a negative association of MS with CMV infection, and the observation of lower levels of HSV IgG in PwMS compared with HCs are findings worthy of further investigation.

Is there a role for herpes simplex virus type 1 in multiple sclerosis?

Numerous studies relate the onset and severity of multiple sclerosis (MS) with viral infections. Herpes simplex virus type 1 (HSV-1), which is neurotropic and highly prevalent in the brain of healthy individuals, has been proposed to relate to MS. Here, we review and discuss the reported connections between HSV-1 and MS.

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.

Viruses and endogenous retroviruses in multiple sclerosis: From correlation to causation

Multiple sclerosis is an immune-mediated disease with an environmental component. According to a long-standing but unproven hypothesis dating to initial descriptions of multiple sclerosis (MS) at the end of the 19th century, viruses are either directly or indirectly implicated in MS pathogenesis. Whether viruses in MS are principally causal or simply contributory remains to be proven, but many viruses or viral elements-predominantly Epstein-Barr virus, human endogenous retroviruses (HERVs) and human herpesvirus 6 (HHV-6) but also less common viruses such as Saffold and measles viruses-are associated with MS. Here, we present an up-to-date and comprehensive review of the main candidate viruses implicated in MS pathogenesis and summarize how these viruses might cause or lead to the hallmark demyelinating and inflammatory lesions of MS. We review data from epidemiological, animal and in vitro studies and in doing so offer a transdisciplinary approach to the topic. We argue that it is crucially important not to interpret "absence of evidence" as "evidence of absence" and that future studies need to focus on distinguishing correlative from causative associations. Progress in the MS-virus field is expected to arise from an increasing body of knowledge on the interplay between viruses and HERVs in MS. Such interactions suggest common HERV-mediated pathways downstream of viral infection that cause both neuroinflammation and neurodegeneration. We also comment on the limitations of existing studies and provide future research directions for the field.

Cytomegalovirus infection exacerbates autoimmune mediated neuroinflammation

Cytomegalovirus (CMV) is a latent virus which causes chronic activation of the immune system. Here, we demonstrate that cytotoxic and pro-inflammatory CD4⁺CD28^null T cells are only present in CMV seropositive donors and that CMV-specific Immunoglobulin (Ig) G titers correlate with the percentage of these cells. In vitro stimulation of peripheral blood mononuclear cells with CMVpp65 peptide resulted in the expansion of pre-existing CD4⁺CD28^null T cells. In vivo, we observed de novo formation, as well as expansion of CD4⁺CD28^null T cells in two different chronic inflammation models, namely the murine CMV (MCMV) model and the experimental autoimmune encephalomyelitis (EAE) model for multiple sclerosis (MS). In EAE, the percentage of peripheral CD4⁺CD28^null T cells correlated with disease severity. Pre-exposure to MCMV further aggravated EAE symptoms, which was paralleled by peripheral expansion of CD4⁺CD28^null T cells, increased splenocyte MOG reactivity and higher levels of spinal cord demyelination. Cytotoxic CD4⁺ T cells were identified in demyelinated spinal cord regions, suggesting that peripherally expanded CD4⁺CD28^null T cells migrate towards the central nervous system to inflict damage. Taken together, we demonstrate that CMV drives the expansion of CD4⁺CD28^null T cells, thereby boosting the activation of disease-specific CD4⁺ T cells and aggravating autoimmune mediated inflammation and demyelination.

Making Mouse Models That Reflect Human Immune Responses

Humans are infected with a variety of acute and chronic pathogens over the course of their lives, and pathogen-driven selection has shaped the immune system of humans. The same is likely true for mice. However, laboratory mice we use for most biomedical studies are bred in ultra-hygienic environments, and are kept free of specific pathogens. We review recent studies that indicate that pathogen infections are important for the basal level of activation and the function of the immune system. Consideration of these environmental exposures of both humans and mice can potentially improve mouse models of human disease.

Papel de las enfermedades infecciosas en el desarrollo de la esclerosis múltiple: evidencia científica

Introducción

La esclerosis múltiple (EM) es el trastorno inflamatorio más común del sistema nervioso central (SNC) y la causa principal de discapacidad neurológica en adultos jóvenes. Los factores ambientales e infecciosos han sido fuertemente asociados al incremento de la ocurrencia de la enfermedad, hasta más del doble, en los últimos 10 años. En este artículo de revisión se describen los principales hallazgos reportados sobre la relación entre ciertas infecciones virales y bacterianas con la aparición y progresión de la EM.

Métodos

Se realizó un plan metodológico de búsqueda de artículos científicos relacionados con infección y EM, mediante la búsqueda de artículos científicos, principalmente publicados en inglés, en las plataformas virtuales de Pubmed, Medline y Cochrane. Para la búsqueda se utilizaron como palabras claves (términos MeSH): «virus, bacteria, autoimmune disease of the nervous system, multiple sclerosis». Se eligieron artículos publicados en revistas indexadas durante los últimos 15 años.

Resultados

Estudios epidemiológicos sugieren que la EM tiene un componente etiológico infeccioso que origina un proceso inflamatorio que puede contribuir a la iniciación o exacerbación de la enfermedad. Particularmente, la infección viral y los eventos de desmielinización en el SNC puede deberse a la penetración de un virus como el virus Epstein-Barr (EBV), a través del torrente sanguíneo, específicamente hacia el SNC. Por otro lado, las infecciones bacterianas crónicas pueden causar procesos de desmielinización en el SNC que agravan la enfermedad de EM.

Conclusiones

Este estudio contribuye a aportar evidencia científica donde se demuestra la multicausalidad implicada en la ocurrencia de la EM. Aún falta desarrollar más estudios epidemiológicos que demuestren y comprueben la relación y la implicación de agentes virales y bacterianos en el origen, el desarrollo y la severidad de la enfermedad.

Prevalence of Cytomegalovirus in Patients With Multiple Sclerosis: A Case-Control Study in Northern Iran

BACKGROUND

Multiple sclerosis (MS) is a chronic debilitating disease known as one of the most common neurological dysfunctions in young adults. Recent studies suggest that infections with herpesviruses play a critical role in the pathogenesis of MS.

OBJECTIVES

The present investigation aimed to detect the presence of cytomegalovirus (CMV) in patients with MS using polymerase chain reaction (PCR) and enzyme-linked immunosorbent assay (ELISA) methods.

PATIENTS AND METHODS

Plasma and peripheral blood mononuclear cells (PBMCs) were collected from MS patients (n = 82) and from blood donors as control group (n = 89). They were tested for the presence of CMV antibodies and DNA by ELISA and PCR, respectively.

RESULTS

Anti-CMV was positive in 65 (79.3%) and 69 (77.5%) of the MS patients and healthy subjects, respectively (P= 0.853). Similarly, 23 (28%) and 2 (2.2%) patients were positive for CMV DNA among the MS and control groups, respectively. Statistical analysis showed that the frequency of CMV DNA in the MS patients was significantly higher than in the healthy controls (P < 0.001).

CONCLUSIONS

The results of this study showed a possible association between CMV infection and MS. Further experimental and epidemiological studies using case-control approaches are needed to confirm this association.

Adaptive natural killer cell response to cytomegalovirus and disability progression in multiple sclerosis

BACKGROUND

Human cytomegalovirus (HCMV) causes a highly prevalent infection which may have a multifaceted impact on chronic inflammatory disorders. However, its potential influence in multiple sclerosis (MS) remains controversial. The HCMV-host interaction may induce an adaptive reconfiguration of the natural killer (NK) cell compartment, whose hallmark is a persistent expansion of peripheral NKG2C+ NK-cells.

OBJECTIVE

The purpose of this study was to evaluate whether the HCMV-driven NKG2C+ NK-cell expansion is related to the MS clinical course.

METHODS

Multicentre analysis of NKG2C expression and genotype according to HCMV serostatus and time of assignment of irreversible disability scores in 246 MS patients prospectively followed up in our institutions.

RESULTS

NKG2C expression was unrelated to disease-modifying drugs, remained stable under steady-state conditions, and was higher in HCMV(+) NKG2C(+/+) homozygous individuals. NKG2C+ NK-cell expansion in HCMV(+) patients, as compared to HCMV(+) or HCMV(-) patients with lower NKG2C+ NK-cells proportions, conferred a lower risk of progression in Cox regression analysis (Expanded Disability Status Scale (EDSS)>3.0, hazard ratio (HR)=0.33, 95% confidence interval (CI) 0.15-0.71, p=0.005; EDSS>5.5, HR=0.23, 95% CI 0.07-0.74, p=0.014). Neither HCMV serostatus nor NKG2C genotype appeared to be related to disability progression.

CONCLUSIONS

HCMV may exert a beneficial influence on MS, decreasing the risk of disability progression in those patients displaying a virus-driven NKG2C+ NK-cell expansion.

Human cytomegalovirus and autoimmune disease

Human cytomegalovirus (HCMV) represents a prototypic pathogenic member of the β-subgroup of the herpesvirus family. A range of HCMV features like its lytic replication in multiple tissues, the lifelong persistence through periods of latency and intermitting reactivation, the extraordinary large proteome, and extensive manipulation of adaptive and innate immunity make HCMV a high profile candidate for involvement in autoimmune disorders. We surveyed the available literature for reports on HCMV association with onset or exacerbation of autoimmune disease. A causative linkage between HCMV and systemic lupus erythematosus (SLE), systemic sclerosis (SSc), diabetes mellitus type 1, and rheumatoid arthritis (RA) is suggested by the literature. However, a clear association of HCMV seroprevalence and disease could not be established, leaving the question open whether HCMV could play a coresponsible role for onset of disease. For convincing conclusions population-based prospective studies must be performed in the future. Specific immunopathogenic mechanisms by which HCMV could contribute to the course of autoimmune disease have been suggested, for example, molecular mimicry by UL94 in SSc and UL83/pp65 in SLE patients, as well as aggravation of joint inflammation by induction and expansion of CD4+/CD28− T-cells in RA patients. Further studies are needed to validate these findings and to lay the grounds for targeted therapeutic intervention.

Association between antibodies to multiple infectious and food antigens and new onset schizophrenia among US military personnel

INTRODUCTION

Multiple studies have documented immune activation in many individuals with schizophrenia suggesting that antigens capable of generating a prolonged immune response may be important environmental factors in many cases of this disorder. While existing studies have found single-agent associations of antibodies to food and neurotropic infectious agents with schizophrenia, a simultaneous examination of multiple agents may shed light on agent interactions or possible etiopathogenic pathways.

METHODS

We used traditional regression and novel statistical techniques to examine associations of single and combined infectious and food antigens with schizophrenia. We tested 6106 serum samples from 855 cases and 1165 matched controls.

RESULTS

Higher antibody levels to casein were borderline significant in the prediction of schizophrenia (HR=1.08, p=0.06). Study participants with higher cytomegalovirus (CMV) IgG antibody levels had a reduced risk of developing schizophrenia (HR=0.90; p=0.02). While IgG antibodies to gliadin, Toxoplasma gondii, vaccinia, measles, and human herpesvirus-6 (HHV-6) showed no significant independent associations with schizophrenia, the increase in antibody levels to several combinations of agents, to include casein, measles, CMV, T. gondii and vaccinia, was predictive of an 18-34% increase in the risk of developing schizophrenia.

CONCLUSION

Certain patterns of antibodies, involving some agents, were predictive of developing schizophrenia, with the magnitude of association rising when the level of antibodies increased to two or more agents. A heightened antibody response to a combination of several infectious/food antigens might be an indicator of an altered immune response to antigenic stimuli.

Cytomegalovirus seropositivity is negatively associated with multiple sclerosis

BACKGROUND

Epidemiological data suggest a role for common viruses in the pathogenesis of multiple sclerosis (MS), and recent data showed a negative association of past cytomegalovirus (CMV) infection on pediatric MS risk.

OBJECTIVE

Our aim was to analyze the association of CMV infection with MS risk in an adult case-control material. A meta-analysis was performed to validate our findings.

METHODS

Epidemiological Investigation in MS (EIMS) is a case-control study with incident cases and population-based controls. Anti-CMV antibody titers were measured with ELISA, and HLA-A and DRB1 genotyping was performed with SSP-PCR, in 658 MS cases, who all fulfilled the McDonald criteria for MS, and 786 controls.

RESULTS

CMV seropositivity was associated with a decreased MS risk, OR = 0.73 (0.58-0.92 95% CI), p = 0.005, adjusted for index age, gender, smoking, sun exposure, EBNA1 IgG titer and HLA-A*02 and DRB1*15. When we removed all cases and controls younger than 18 years at index, the protective effect was still apparent.

CONCLUSIONS

CMV is negatively associated with adult-onset MS pathology, consistent with results from a study on pediatric MS cases. It remains to be shown whether this negative association is due to a true protective effect of CMV infection on MS risk.

Multiple sclerosis and herpesvirus interaction

Multiple sclerosis is the most common autoimmune inflammatory demyelinating disease of the central nervous system, and its etiology is believed to have both genetic and environmental components. Several viruses have already been implicated as triggers and there are several studies that implicate members of the Herpesviridae family in the pathogenesis of MS. The most important characteristic of these viruses is that they have periods of latency and exacerbations within their biological sanctuary, the central nervous system. The Epstein-Barr, cytomegalovirus, human herpesvirus 6 and human herpesvirus 7 viruses are the members that are most studied as being possible triggers of multiple sclerosis. According to evidence in the literature, the herpesvirus family is strongly involved in the pathogenesis of this disease, but it is unlikely that they are the only component responsible for its development. There are probably multiple triggers and more studies are necessary to investigate and define these interactions.