Viral antibodies in multiple sclerosis. A nationwide co-twin study

EBNA-1 titer gradient in families with multiple sclerosis indicates a genetic contribution

OBJECTIVE

In multiplex MS families, we determined the humoral immune response to Epstein-Barr virus nuclear antigen 1 (EBNA-1)-specific immunoglobulin γ (IgG) titers in patients with MS, their healthy siblings, and biologically unrelated healthy spouses and investigated the role of specific genetic loci on the antiviral IgG titers.

METHODS

IgG levels against EBNA-1 and varicella zoster virus (VZV) as control were measured. HLA-DRB1*1501 and HLA-A*02 tagging single-nucleotide polymorphisms (SNPs) were genotyped. We assessed the associations between these SNPs and antiviral IgG titers.

RESULTS

OR for abundant EBNA-1 IgG was the highest in patients with MS and intermediate in their siblings compared with spouses. We confirmed that HLA-DRB1*1501 is associated with abundant EBNA-1 IgG. After stratification for HLA-DRB1*1501, the EBNA-1 IgG gradient was still significant in patients with MS and young siblings compared with spouses. HLA-A*02 was not explanatory for EBNA-1 IgG titer gradient. No associations for VZV IgG were found.

CONCLUSIONS

In families with MS, the EBNA-1 IgG gradient being the highest in patients with MS, intermediate in their siblings, and lowest in biologically unrelated spouses indicates a genetic contribution to EBNA-1 IgG levels that is only partially explained by HLA-DRB1*1501 carriership.

Infections and multiple sclerosis

Multiple sclerosis is a chronic inflammatory condition of unknown cause. Increasing evidence suggests that the disease develops as a result of interactions between the environment and the immune system in genetically susceptible individuals. It has long been recognized that infections may serve as environmental triggers for the disease, and a large number of pathogens have been proposed to be associated with multiple sclerosis. Here, we detail the historical basis linking infections to multiple sclerosis and review the epidemiology of the disease, which suggests a possible relationship with infectious agents. We also describe pathophysiologic studies in animals and other human demyelinating diseases that have demonstrated a variety of mechanisms by which infectious agents may induce chronic, relapsing central nervous system disease with myelin damage and relative preservation of axons, similar to multiple sclerosis. In addition, we discuss recent studies in individuals with multiple sclerosis indicating enhanced immune responses to infectious antigens, though not consistently demonstrating evidence for ongoing infection. Taken together, these studies suggest a role for infectious agents in the development of multiple sclerosis. Conclusive evidence, however, remains lacking.

Multiple sclerosis and Epstein-Barr virus

OBJECTIVE

To evaluate the epidemiological evidence for an etiological role of Epstein-Barr virus in multiple sclerosis (MS).

DATA SOURCES

MEDLINE and Cochrane Library searches of the medical literature identified 24 studies.

DATA EXTRACTION

Studies were categorized as seroepidemiological, case-control or historical cohort, and were then classified within each group according to methodological rigour using criteria derived from published guidelines for the epidemiological study of MS.

DATA SYNTHESIS

There was significant variability in the quality of evidence, and while two well-designed cohort studies found increased relative risks of MS in subjects with infectious mononucleosis, results from other studies were unconvincing.

CONCLUSIONS

The evidence was insufficient to accept or reject the hypothesis that Epstein-Barr virus has an etiological role in MS. Further study, ideally using large samples of incident cases with blinded, trained interviewers using confirmatory sources for recalled data, is needed.

Human herpes virus 6 and multiple sclerosis: a Finnish twin study

OBJECTIVE

To investigate the possible association of human herpes virus 6- (HHV6) infection and multiple sclerosis (MS).

BACKGROUND

Despite intensive investigations of genetic and environmental factors, the etiopathogenesis of MS remains unknown. HHV6 is a possible candidate in that it is neurotropic, able to induce demyelination and become latent and be reactivated. We had access to The Finnish National Twin Cohort, which provided a unique opportunity to study the association between HHV6 and MS in genetically homogenous patients.

METHODS

Thirty-four serum samples from 17 MS twin pairs and 12 cerebrospinal fluid (CSF) samples from six MS twin pairs were tested by PCR specific for HHV6. Immunoglobulin (Ig) G and M response against HHV6 in serum and CSF were analysed using ELISA method. The samples were collected during a remission of the disease.

RESULTS

No HHV6 DNA was found in any serum (n=34) or CSF (n=12) samples. Eighty-eight percent of the twins with MS and 86% of the healthy twin siblings were positive for IgG in serum. One twin with MS was also positive for IgM in serum, whereas none of the healthy twins was IgM positive. All CSF samples were negative for IgG and IgM in both groups.

CONCLUSIONS

During a clinical remission of MS the detection of antibodies against HHV6 in CSF and HHV6 DNA in serum, CSF supernatant or CSF leukocytes is unlikely. However, the results do not exclude a possibility of HHV6 reactivation during MS exacerbation or acute HHV6 infection being one of the triggering agents in development of MS long before its clinical manifestation.

The multiple sclerosis trait and the development of multiple sclerosis: Genetic vulnerability and environmental effect

The remarkably low rate of concordance of multiple sclerosis (MS) in monozygotic twins has never been fully explained but it implies the possibility of a systemic condition called the multiple sclerosis trait (MST), which is quite different from asymptomatic MS. It results from the action of an antigenic challenge on the immune system of a genetically vulnerable person that does not cause damage to the nervous parenchyma; it may never evolve into the disease MS. A subsequent environmental viral-antigenic event in some MST-carriers can change the trait into the disease. This event could be an infection, which need not be symptomatic, or a vaccination. The MS may become symptomatic, remain asymptomatic, or manifested only by lesions visible by MRI. It is likely that the development of the MST, called activation, occurs early in life, while the transition from MST to MS, called acquisition, takes place at puberty in most patients. Differences in prevalence between pre-puberal migrants, and the locally born children of migrants, and their population of origin may also be explained by the MST.

Environmental risk factors in multiple sclerosis aetiology

The epidemiology of multiple sclerosis (MS) has been intensively studied. It is conceptualised as a complex disease in which genetic and environmental factors act together to cause disease. There are temporal and geographic variations in disease risk, and risk of disease may be affected by migration between regions of differing risk. Numerous potential causal factors including infection, immunisations, physical and emotional stressors, climate, diet, and occupational exposures have been studied using various observational study designs. Thus far, no single environmental exposure has been consistently identified as a causal factor in MS, but sufficient data have accumulated that causal pathways should be postulated and tested. This review will focus on the environmental epidemiology of MS.

Multiple sclerosis trait: the premorbid stage of multiple sclerosis. A hypothesis

The unexpectedly low rate of concordance in monozygotic (MZ) twins with multiple sclerosis (MS) suggests that they share a systemic condition called the multiple sclerosis trait. This trait constitutes the premorbid stage of the disease and is quite distinct from asymptomatic MS. It results from the action of an antigenic challenge to the immune system of a genetically susceptible person but is short of producing lesions of the central nervous system parenchyma; in fact, the disease may never develop in people with the trait. An environmental triggering event is required to transform the trait into the disease. The discordance of clinical involvement and magnetic resonance images in MZ twins reflects differences in the effect of environmental influences.

Markers of viral infection in monozygotic twins discordant for chronic fatigue syndrome

To estimate the prevalence of viruses associated with chronic fatigue syndrome (CFS) and to control for genetic and environmental factors, we conducted a co-twin control study of 22 monozygotic twin pairs, of which one twin met criteria for CFS and the other twin was healthy. Levels of antibodies to human herpesvirus (HHV)-8, cytomegalovirus, herpes simplex virus 1 and 2, and hepatitis C virus were measured. Polymerase chain reaction (PCR) assays for viral DNA were performed on peripheral blood mononuclear cell specimens to detect infection with HHV-6, HHV-7, HHV-8, cytomegalovirus, Epstein-Barr virus, herpes simplex virus, varicella zoster virus, JC virus, BK virus, and parvovirus B19. To detect lytic infection, plasma was tested by PCR for HHV-6, HHV-8, cytomegalovirus, and Epstein-Barr virus DNA, and saliva was examined for HHV-8 DNA. For all assays, results did not differ between the group of twins with CFS and the healthy twins.

Serological differences in monozygotic twin pairs discordant for multiple sclerosis

OBJECTIVES

The etiology of MS is unknown but genetic factors are supported by a high concordance in twins. Geographic distribution and migration studies indicate, however, the importance of environmental factors.

MATERIAL AND METHODS

We studied 3 pairs of genetically identical twins who had shared the same environment but were discordant for MS. Serum samples were assayed for antibodies against 21 viruses, 4 bacteria and Toxoplasma gondii.

RESULTS AND CONCLUSION

No common factor present only in the affected twins was identified but differences were found in serum titers against some neurotropic microorganisms. In general the serum titers were strikingly similar in the twins, indicating no major disturbances of the humoral immune system in MS.

Epstein-Barr virus and multiple sclerosis

It has been suggested that the Epstein-Barr virus (EBV) plays a role in the etiology of multiple sclerosis (MS), but individual epidemiologic studies have been inconclusive, in part because of the high prevalence of previous infection among individuals without MS. We conducted a systematic review of case-control studies comparing EBV serology in MS patients and controls. Eight published investigations were identified, including a total of 1,005 cases and 1,060 controls. The summary odds ratio of MS comparing EBV seropositive individuals with EBV seronegative individuals was 13.5 (95% CI = 6.3-31.4). The strength and consistency of this association and the high sensitivity and specificity of EBV serology suggest that these results are not readily explained by an aspecific immune activation among MS patients. These findings support a role of EBV in the etiology of MS.

The pathogenesis of multiple sclerosis: reconsideration of the role of viral agents and defence mechanisms

Numerous ubiquitous ribonucleic acid and deoxyribonucleic acid viruses, inducing acute, monophasic infections (mostly childhood diseases) have been considered as potential causes of multiple sclerosis. The present hypothesis reconsiders the role of the viral agent: not the virus, but the reaction of the defense system to the viral persistence, appearing after the acute phase, is postulated as a key factor. A prerequisite of multiple sclerosis is polygenetically determined or acquired immunodeficiency; the defense system is not able to stop repeated viral reactivations induced by a set of exogenous and/or endogenous factors. Thus, an aberrant virus production can appear repeatedly. If the virus spreads from primary target--the lymphoreticular system--into the central nervous system, the multiple sclerosis process can be initiated. Activated T cells and endothelial cells serve as first-host cells. Their infection triggers a set of reactive events: multiple microthrombosis and inflammation play a key role, both of which can result in nonspecific degradation of the myelin. An increased release of myelin antigens induces a homeostatic autoimmunity. Long-term repetition of the shifts and the infection of inflammatory cells can lead to disturbances in self-tolerance. A dysregulated pathological autoimmunity can develop, which acts as a main effector of the specific demyelination.

The value of CSF analysis for the differential diagnosis of HTLV-I associated myelopathy and multiple sclerosis

Cerebrospinal fluid (CSF) and serum of 17 patients with HAM/TSP (HTLV-I associated myelopathy/tropical spastic paraparesis), six with multiple sclerosis and six with idiopathic epilepsy (non inflammatory control) from Brazil were analysed for the presence of intrathecal synthesis of virus-specific antibodies against measles, rubella, varicella zoster virus and herpes simplex virus by enzyme-linked immunosorbent assay (ELISA). All HAM/TSP and multiple sclerosis cases had an intrathecal immune response (oligoclonal IgG). In HAM/TSP, only 1/17 case showed a polyspecific intrathecal immune response against measles and rubella virus. In multiple sclerosis, specific antibodies against measles and rubella (MRZ response) were observed in all patients but not in the control with idiopathic epilepsy. The diagnostic and theoretical relevance of mono- and polyspecific immune responses is discussed for these chronic neurological diseases.

The epidemiology of multiple sclerosis: a general overview

Epidemiological studies of multiple sclerosis (MS) have shown the importance of genetic susceptibility factors that are modified by as yet unknown environmental influences. The often-cited interrelation between prevalence and latitude is no longer viable, with the important but unexplained exception of Australia and New Zealand. The standardization and increasing use of uniform diagnostic criteria lend new credibility to the results of MS surveys. More precise criteria are offered for symptoms of disease onset, Devic's syndrome, and progressive disease. The role of magnetic resonance imaging in the diagnosis of MS, and the pitfalls of its abuse, are reviewed. Reports of epidemics of MS are examined and discarded because they are based on the biologically meaningless date of diagnosis or that of onset, rather than when MS was probably acquired, that is, before puberty. The concept of onset-adjusted prevalence suggests that patients who are symptomatic should be included retrospectively in epidemiological surveys, even before they have been formally diagnosed as having MS, but individuals who were symptomatic before moving to a study area should not. The importance of ethnic homogeneity of patients and control subjects cannot be overemphasized in prevalence and risk factor studies. In the latter, close attention must be paid to biological plausibility and to prudent statistical interpretation. The hypothesis of the MS trait describes a systemic, asymptomatic condition that does not affect the nervous system, and may explain the low concordance of the disease in monozygotic twins.

The pathogenesis of multiple sclerosis. Additional considerations

Multiple sclerosis (MS) is acquired as a systemic "trait" by individuals who are genetically susceptible. This condition does not involve the central nervous system (CNS) and is characterized by a state of hyperactive immunocompetent responsiveness. It develops as the result of an antigenic challenge by a viral protein, either from a viral infection or a vaccination. In order for MS to become a disease affecting the CNS, it is necessary for the blood-brain barrier's (BBB) impermeability to be altered. This is now a fully recognized fact. As a result of this change, the MS lesion, which consists of edema and inflammation occurs. It may but need not lead to demyelination. Several mechanisms can cause this increased permeability of the BBB. The role of the immune system, and in particular of T lymphocytes in initiating and continuing the process of lesion formation remains extremely controversial. In fact, there are unanswered questions regarding the actual target of MS: is it the myelin sheath itself or its forming cell, the oligodendrocyte, or is it the BBB itself leading to bystander demyelination? The role of mild, concussional trauma to the CNS in producing the alteration of the BBB and therefore acting as a trigger or facilitator in the development or enlargement of MS lesions in the CNS, is based on considerable clinical, neuropathological and experimental evidence. Along with another viral infection, it must be one of the commonest causes of progression of MS, and quite often leads to the onset of the clinical manifestations of an hitherto asymptomatic condition.

IgG paraproteins in neurological diseases: lack of association with neurotropic viral/bacterial antigens

In this study we tested the hypothesis that IgG paraproteins in neurological diseases might be regarded as an anti-idiotypic response raised by a nervous system antigen associated with certain neurotropic agents. After initial ELISA screen, positive samples from 34 neurological patients who had paraproteins in their CSF and serum on routine IEF investigation, were tested by immunoblot technique for the presence of specific monoclonal immunoglobulin G (IgG) against eight different neurotropic antigens. Only one patient had specific monoclonal IgG against herpes simplex virus. The results of this study did not confirm our hypothesis. Further study of IgM/IgA paraproteins is indicated.

Multiple sclerosis. Observations and reflections--a personal memoir

The pathogenesis of MS has become better understood as a result of recent advances in several areas, particularly in epidemiology and neuro-imaging. A number of epidemiologically based conclusions need to be revised, most importantly the putative direct relationship between prevalence and latitude, and the concept that epidemics of MS have occurred in some parts of the world. It is now clear that genetic factors play a much more important role in the genesis of the disease than environmental factors, although the latter cannot be ignored. The existence of a genetic susceptibility, coupled with either protective or enhancing factors, which may be genetic or environmental, is recognized as being most important in individuals of northern European origin. Much evidence suggests that the disease is initiated by a viral illness (or possibly a vaccination) at some time before puberty. This first antigenic challenge results in the development of what is called the "MS trait", a systemic condition that may never develop into the actual disease and may be observed as well in the unaffected siblings of MS patients. The trait is almost certainly a manifestation of an alteration of the immune system; its most important effect is to render the blood-brain barrier more vulnerable to a variety of agents that will increase its permeability. In order for MS to involve the central nervous system, loss of integrity of the blood-brain barrier is an obligatory step, an observation which has now been amply confirmed by neuroimaging studies. This effect upon the blood-brain barrier appears to be non-specific, since it may result from such diverse causes as a viral infection, a vaccination, or mild trauma. Edema and inflammation follow, but myelinoclasia is not always a consequence; thus plaque formation may not occur and the initial lesion of MS may disappear without leaving a trace. The actual mechanism of myelinoclasia, and the role played in it by lymphocytes, remain unknown. Although the disease does affect the central nervous system, it may remain asymptomatic for a long time after the actual plaque is formed, even for the person's entire life.

The effects of exposure to dietary nickel and zinc upon humoral and cellular immunity in SJL mice

We are interested in potential interactions between environmental trace metal exposures and immune function. In particular, we have wondered whether dietary exposure to nickel and zinc cations can influence T and B cell proliferation and function. To study this question, we fed SJL female mice supplemental nickel and zinc sulfate from 4-8 weeks of age, and immunized the animals intraperitoneally (i.p.) with keyhole limpet hemocyanin (KLH) at 8 weeks. Eight days later, we measured antibody responses to KLH. Both IgG and IgM antibody responses to KLH were significantly depressed in vivo in the nickel fed animals (p less than 0.005). In vitro antigenic responsiveness to KLH of splenocytes from nickel fed animals was also depressed compared with control and zinc supplemented animals (p less than 0.002). This altered antigenic responsiveness persisted even after cells had been cultured for 5 days in standard media. The zinc supplemented diets did not seem to affect antibody responsiveness and proliferation. The proliferative responses of B cells to the mitogen lipopolysaccharide (LPS) were significantly depressed in Ni fed mice, but were not affected in the zinc fed animals. T cell mitogenic responses to concanavalin A were not affected in the nickel fed animals, and were enhanced in zinc fed animals. We conclude that dietary exposure to certain trace metals may induce persisting alterations in immunity in this animal model.