Familial multiple sclerosis: clinical, histocompatibility, and viral serological studies

The Increased Susceptibility of Women to Multiple Sclerosis

Many diseases with an auto-immune etiology have a skewed sex distribution. In the majority of instances, women are affected more frequently than men. A review of population studies demonstrates that the preponderance of women in multiple sclerosis (MS) is almost constant. We show that this preponderance is further increased in early as well as in late-onset cases, in familial cases as well as in MS twin pairs and that the HLA-DR2 allele, which has been associated with MS in Caucasian populations, is significantly more frequent in women than in men with MS. “Rules” have been established for multifactorial diseases; MS contravenes most of those rules. The skewed sex distribution in MS could be attributed to the known hormonal and gender influences on the immune response, as well as to genetic influences.

Gene-environment interactions in multiple sclerosis: innate and adaptive immune responses to human endogenous retrovirus and herpesvirus antigens and the lectin complement activation pathway

Aspects of gene-environment interactions in multiple sclerosis (MS) were analysed in serum samples from 46 MS families (25 sporadic MS cases and 42 familial MS cases): antibodies to the MS-associated human endogenous retrovirus HERV-H, and levels of three components in the innate pathogen-associated molecular pattern recognition: mannan-binding lectin (MBL), and MASP-2 and MASP-3. For representative MS families, we also determined herpesvirus serology for HSV-1, VZV, and EBV; and tissue typed for HLA-B, and HLA DR and DQ. In MS, a significant correlation between elevated immune reactivity to HERV-H Env and disease activity was demonstrated, as were indications of a protective effect of high MBL and MASP-3 levels. The HLA alleles B*07, DRB*02, and DQB1*06 were commonly present together in the MS families, both in MS patients, and in unaffected family members. Our results support that HERV-H and the antiviral immune response may play a role in MS development, and also underline the tenuous nature of specific genetic contributions to this complex disease.

Multiple sclerosis: multiple etiologies, multiple genes?

Multiple sclerosis is a chronic inflammatory disease characterized by multifocal damage of the central nervous system myelin. Both humoral and cell-mediated immune abnormalities have been observed in patients with multiple sclerosis, but their relation to the demyelination process is not understood. The etiology of the disease is still unknown; however, evidence exists for an interplay between environmental and genetic factors. Several genes are involved in determining the disease susceptibility, at least one of them encoded within human leukocyte antigen gene complex. Other genomic regions coding for components of the immune system or myelin have also been suggested. Clinical, immunological and genetic data suggest that multiple sclerosis may turn out to be a heterogeneous disease. Therefore, molecular genetic dissection of this complex disease should provide important clues to its pathogenesis as well as unravel metabolic pathways for potential therapeutic or preventive strategies. This review will give an overview of recent progress and future challenges in identifying susceptibility genes for multiple sclerosis.

Epidemiologic evidence for multiple sclerosis as an infection

The worldwide distribution of multiple sclerosis (MS) can be described within three zones of frequency: high, medium, and low. The disease has a predilection for white races and for women. Migration studies show that changing residence changes MS risk. Studies of persons moving from high- to low-risk areas indicate that in the high-risk areas, MS is acquired by about age 15. Moves from low- to high-risk areas suggest that susceptibility is limited to persons between about ages 11 and 45. MS on the Faroe Islands has occurred as four successive epidemics beginning in 1943. The disease appears to have been introduced by British troops who occupied the islands for 5 years from 1940, and it has remained geographically localized within the Faroes for half a century. What was introduced must have been an infection, called the primary MS affection (PMSA), that was spread to and from successive cohorts of Faroese. In this concept, PMSA is a single widespread systemic infectious disease (perhaps asymptomatic) that only seldom leads to clinical neurologic MS. PMSA is also characterized by a need for prolonged exposure, limited age of susceptibility, and prolonged incubation. I believe that clinical MS is the rare late outcome of a specific, but unknown, infectious disease of adolescence and young adulthood and that this infection could well be caused by a thus-far-unidentified (retro)virus.

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.

Viral antibody titers, immunogenetic markers, and their interrelations in multiple sclerosis patients and controls

Our purpose was to investigate possible interrelations between antibody titers against seven viruses (measles, rubella, herpes simplex, mumps, varicella-zoster, coronavirus, cytomegalovirus), HLA-class II antigens, and immunoglobulin Gm allotypes in multiple sclerosis (MS). We studied 57 MS patients and 59 controls with similar age and sex distributions. In MS patients, we found the classical increased frequency of HLA-DR2, HLA-DQw1 and also an excess of Gm (3; +/- 23; 5*). Mumps antibody levels were higher in MS patients than in controls; elevation was not significant for measles antibodies. Analysis suggests that an association between HLA-DQw1 and antibody titers against various viruses exists in controls but is absent in MS patients. In particular, we found that mumps antibody titers were higher in DQw1-positive than in DQw1-negative controls, while there was no significant difference among MS cases. Accordingly, we found that the overall difference between patients and controls was due to the fact that DQw1-positive patients had higher titers than controls, while DQw1-negative cases had similar titers as controls. These findings suggest that biological and molecular characteristics of DQw1 might differ in MS patients.

DNA length polymorphism 5' to the myelin basic protein gene is associated with multiple sclerosis

A site of DNA polymorphism linked to the myelin basic protein gene, identified as restriction fragment length polymorphism, was analyzed in a population-based study comparing patients with clinically definite multiple sclerosis (MS) and population-matched control subjects. A 0.9-kilobase (kb) genomic DNA fragment (EcoG) encompassing the first exon of the human myelin basic protein gene, located on the long arm of chromosome 18, identified ten alleles arising from a region of DNA, 1.5 kb 5' to the myelin basic protein gene first exon coding region. Produced by RsaI digests and ranging in length from 2.05 to 2.15 kb, these alleles vary in size by up to 100 base pairs due to insertion or deletion, or both, from a 1-kb length of repetitive DNA. Allele frequencies among 65 patients with MS were compared with those of 63 control subjects. Chi square for these data was significant (p less than 0.001), largely due to a preponderance in the patients with MS of alleles in the 2.14- to 2.15-kb range. Comparison of the numbers of patients with MS and control subjects bearing specific alleles showed that 45% of the patients carried at least one allele of 2.14 to 2.15 kb as opposed to 19% of control subjects (p less than 0.005). These data, while preliminary, suggest that patients with MS differ from population-matched control subjects with respect to DNA polymorphism linked to the myelin basic protein gene. Although no pathogenic relationship between this polymorphism and MS can be presupposed, this finding raises the possibility that the myelin basic protein gene or some other myelin basic protein-linked locus may be a factor in susceptibility to MS.

Identification of a locus on mouse chromosome 3 involved in differential susceptibility to Theiler's murine encephalomyelitis virus-induced demyelinating disease

Theiler's virus-induced demyelinating disease results from a chronic infection in the white matter of the central nervous system and provides an excellent model for human multiple sclerosis. Like multiple sclerosis, there are genetic risk factors in disease development, including genes associated with the major histocompatibility complex and with those encoding the beta chain of the T-cell receptor. Comparisons of the susceptible DBA/2 and resistant C57BL/6 strains have indicated an important role for the H-2D locus and for a non-H-2 gene (not involving the beta chain of the T-cell receptor) in differential susceptibility. In the present report, analysis of recombinant-inbred strains (BXD) between the DBA/2 and C57BL/6 strains indicated that this non-H-2 locus is located at the centromeric end of chromosome 3 near (4 +/- 4 centimorgans) the carbonic anhydrase-2 (Car-2) enzyme locus.

Familial multiple sclerosis

Siblings of patients with multiple sclerosis have an increased risk of developing the disease. In this report we describe 3 families with multiple affected members, representing the largest published aggregation of cases in first degree relatives. In the 2 families in which HLA tissue-typing was performed the affected individuals shared part of the haplotype HLA-DR2 (+ HLA-DQW1), BfS (+ C2C), C4A3, C4B1. The implications of these findings for the aetiology of multiple sclerosis are discussed.

HLA and susceptibility to multiple sclerosis

The study of the joint segregation of multiple sclerosis and HLA, using affected sib pairs as well as whole pedigrees, shows that these two traits are not independently transmitted. The hypothesis of a single susceptibility locus inside HLA region could explain all the observed data, only if a high gene frequency, a very low penetrance, and some environmental correlation between relatives are assumed. Linkage analysis performed on the basis of this hypothesis for 58 multiple sclerosis families concludes to a strict linkage. We obtained a maximum score of 3.11 at theta = 0.00 for a dominant gene of frequency 0.18 and penetrance of 0.02. This result contrasts with the large recombination fraction obtained by other authors and the discrepancy is explained by the very low gene frequency used in their analysis. Some environmental correlation, in addition to the genetic determinant in HLA region, may explain the overall familial aggregation, but an alternative is the existence of additional genetic determinants.

Histocompatibility antigens in familial multiple sclerosis in a high-risk area of the disease

Fourteen Finnish families, each with two or more cases of multiple sclerosis (MS), were analysed for HLA antigens. Seventy family members were studied. They were all born in a high-risk area of MS and came from families with an unusually high frequency of MS. The frequencies of B7, B12 and DR2 were increased both in patients and their healthy relatives, whereas A1, B8 and DR1 were decreased in patients. MS patients shared the HLA haplotypes more often than expected.

Family studies in multiple sclerosis: HLA haplotypes of affected sib-pairs

The occurrence of multiple sclerosis (MS) in several members of families has been observed in 4.8% of 105 MS patients from a limited epidemiological area of Rostock. Typing of the HLA antigens in 4 affected sib-pairs showed two identical HLA haplotypes in 3 of the pairs: 1 pair shared one haplotype. These findings point to a dominant mode of inheritance of the disease susceptibility gene together with the HLA haplotype. The assessment of family studies in MS is discussed.

The affected sib method. II. The intermediate model

An iteration procedure is outlined which uses HLA haplotype sharing data from sib pairs in which both sibs have the disease of interest. The procedure allows estimation of the degree of dominance of the HLA linked 'disease' allele, and its frequency in the population, for intermediate models where it is assumed that individuals who do not have at least one copy of the 'disease' allele do not contract the disease. Parameter estimates from sib-pair data on multiple sclerosis, insulin dependent diabetes mellitus, haemochromatosis, coeliac disease juvenile rheumatoid arthritis, and Graves' and Hashimoto's diseases are given.

Power of the affected-sib-pair method to defect disease susceptibility loci of small effect: an application to multiple sclerosis

The distribution of marker locus identity-by-descent scores in affected sib pairs provides a powerful tool for detecting the presence of a linked non-Mendelian disease susceptibility locus. This basic approach is here extended to include a trio of sibs. A special type of sib trio consisting of two affected and one unaffected sib is investigated. It is shown that compared to affected-sib-pairs, trios with the above configuration are less efficient in detecting the presence of a linked disease susceptibility locus. When the generalized two-allele single locus model is fitted to sib pairs affected with multiple sclerosis, an estimate of the recombination fraction of 0.21 between the putative disease susceptibility locus and the HLA complex is obtained. However, this transmission model is deemed inadequate since a recombination fraction this large is inconsistent with the variety of HLA associations observed at the population level.

HLA profiles in multiple sclerosis suggest two forms of disease and the existence of protective haplotypes

261 multiple sclerosis (MS) patients were HLA-A and -B typed and 94 were HLA-D typed. The results were compared to those of controls typed for HLA-A; HLA-B (356) and HLA-D (113). We confirm and extend earlier findings (Oger et al. 1980b) that some phenotypes could modulate the expression of the MS susceptibility gene linked to B7-DR2: DR3 was found together with DR2 in 12/94 MS and only 3/113 controls and could be marker for an "augmentor" gene. In contrast, B35 and DR1 as well as B12 and DR7 could be markers of protector genes. We compared typing results of patients subgrouped on clinical features. 61 patients with progressive evolution showed increased A1, A1-B8, B8-DR3 and A1-B8-DR3 when compared to 200 patients with remitting evolution. When compared to controls both groups showed increased B7 but only the remitting group showed increased DR2. 71 patients with "benign MS" showed increased B7-DR2 and A3-B7-DR2. 54 patients with "severe disease" showed increased DR3 and A1-B8-DR3 when compared to controls. Both groups showed increased B7 (49.2% and 44.4% versus 25.5% for controls). 120 patients treated greater than 5 years with azathioprine were divided into "no progression" and "progression" while treated. Both groups showed increased B7 when compared to controls. DR2 was increased only in the "no progression" group. B8-DR3 and A1-B8-DR3 were found increased in the "progression" group only. We conclude that two forms of MS exist with different HLA profiles.

Neuromyelitis optica (Devic's syndrome) in two sisters

Neuromyelitis optica (Devic's syndrome) typically occurs in a sporadic pattern. We studied the disorder in two sisters, ages 6 and 10 years, who presented with sudden loss of vision at age 3 years, followed 5 months later by a transverse myelopathy. The older girl had only light perception in either eye, persistent paraparesis and progressive scoliosis; her sister had a visual acuity of 20/200 in both eyes and mild spinal cord dysfunction. Results of electrodiagnostic tests correlated well with the severity of clinical neurologic deficits and provided objective estimates of the extent of tissue damage in both the optic nerves and the spinal cord. The presence of Devic's syndrome in these two sisters could be coincidental; however, the possibility of a shared genetic factor(s) should be considered.

HLA family studies and multiple sclerosis: A common gene, dominantly expressed

All available Australian families with more than one member suffering multiple sclerosis (MS) were HLA typed. As with all other individual published studies, convincing evidence for linkage between the HLA system and disease was not obtained. An analysis of 100 published affected sib-pairs and 17 cousin-pairs, however, established the existence of an HLA-linked disease susceptibility gene for MS, which is likely to be dominantly expressed. Dominance was also supported by the finding of only three HLA-DR2 (Dw2) homozygous individuals out of 60 unrelated patients which enabled rejection of a recessive gene hypothesis (p less than 0.02). Analysis of the sib-pair data strongly suggested that this MS gene is not rare in the normal population and may be as common as DR2.

The significance of abnormal immune responses in patients with multiple sclerosis

Early diagnosis of multiple sclerosis (MS) may be assisted by tests for the abnormal immune responses of the central nervous system (CNS) including oligoclonal IgG bands in the cerebrospinal fluid (CSF), increased CNS IgG synthesis, increased CNS antibody synthesis against multiple viruses and increased numbers of enlarged lymphoid cells in the CSF. Alterations in immunological responses are important in the pathogenesis of MS. Further studies are needed, however, to identify the antigen(s) and/or antibodies responsible for oligoclonal IgG in the CSF of MS patients. Also, the cause(s) for the other immunological abnormalities with diagnostic importance need to be identified. The increased synthesis of antibodies against multiple unrelated viruses suggests generalized alteration in the immune regulatory system. The etiology of MS might be multifactorial involving abnormal immunological responses, possibly precipitated by infectious agents acquired during childhood by genetically susceptible individuals. The immunological responses including alterations in myelin basic protein concentration, antimyelin antibody and immune complex activities in CSF, and in vitro stimulation, suppression and migration inhibition of blood lymphocytes appear to correlate with stage of MS and severity of CNS damage. Some of the tests may become useful in estimating the prognosis of the disease. Longitudinal studies are needed to clarify the sensitivity of the diagnostic and prognostic immunological tests and etiological significance of these abnormalities in MS.

Diagnostic techniques in multiple sclerosis

Although multiple sclerosis (MS) has been an area of great interest and effort in numerous scientific disciplines, its etiology, pathogenesis and therapy remain mysterious. Perhaps the most significant advances have resulted from the ability to be more precise in establishing the diagnosis of MS. Among the most important of the new diagnostic tools are electrophysiological techniques for examination of the visual and oculomotor systems. Tests such as the visually evoked potential (VEP) can confirm the existence of clinically suspected lesions and document the presence of asymptomatic ones. Various electrophysiological techniques for detection and evaluation of MS, as well as CSF analysis, psychological and neuroradiological procedures, and immunological observations are described. The relationship between optic neuritis and MS is reviewed, as are therapeutic regimens in use and under study.

A comparison of composition and fluidity of multiple sclerosis and normal myelin

Myelin was isolated from normal-appearing white matter from the brains of 11 multiple sclerosis (MS) patients, 11 normal individuals, and 1 patient with subacute sclerosing panencephalitis (SSPE). Ratios of protein, cholesterol, and phospholipid content, total fatty acid content, and total amino acid content were determined. The lipid bilayer fluidity of the myelin was measured using electron spin resonance and fluorescence polarization spectroscopy. The protein-to-phospholipid ratio was higher than normal, the cholesterol-to-protein ratio was lower than normal while the cholesterol-to-phospholipid ratio was normal in MS myelin. This suggested a relative increase of protein to lipid content in MS myelin. Of the fatty acid content of a total lipid extract, MS myelin had relatively more 16:0, less 18:3, and less 22:3, 24:1 than normal. The total amino acid content of MS myelin was altered in a way which suggested a decreased percentage of basic protein and an increased percentage of proteolipids. SSPE myelin had similar changes in amino acid content but not in protein-to-cholesterol or -phospholipid ratios or fatty acid content as MS myelin. There was no significant difference in myelin fluidity, however, between MS and normal myelin using fatty acid spin labels or fluorescent probes. A correlation was found between the fluidity and the cholesterol-to-phospholipid ratio but the MS and normal samples varied over a similar range. Although these alterations in lipid and protein composition had no effect on fluidity, they may nevertheless have serious consequences for myelin structure.

Genetic segregation of multiple sclerosis and histocompatibility (HLA) haplotypes

The possibility that a gene determining susceptibility to multiple sclerosis (MSS) may be closely linked to the major histocompatibility locus (HLA) is suggested by observation of a loose association between multiple sclerosis (MS) and certain HLA determinants. In the present study, the possible association was analyzed by studying the segregation of MS and the HLA haplotypes in families with more than one case of MS. Analysis of 48 published families revealed that the haplotype shared by those with MS within the family was also shared by those without clinical signs of MS at close to the 50% frequency expected by chance. Thus, we were unable to demonstrate that MS is associated with one HLA defined parental haplotype. We discussed reasons for this apparent failure to demonstrate existence of an MSS gene using available multiplex MS families.

Has myelin basic protein received a fair trial in the treatment of multiple sclerosis?

Autosensitization to some central nervous system antigen still remains one of the best hypotheses for the continuing pathogenesis of multiple sclerosis (MS). Enough is now known about the cause, pathogenesis, and treatment of experimental allergic encephalomyelitis (EAE) to test this hypothesis. Reports of therapeutic failure of the encephalitogen myelin basic protein (BP) in the treatment of MS have their counterparts in similar therapeutic failures in EAE. Only highly inbred strain 13 guinea pigs respond consistently to BP therapy, and this only when BP is administered in relatively high doses. Noninbred guinea pigs respond much less well to simple BP therapy, and monkeys hardly at all. In both strains of monkeys so far studied, a nonspecific adjunctive factor--an antibiotic in Macaca mulatta and a steroid in Macaca fascicularis--is also required. Accordingly, human trials of the therapeutic efficacy of BP in MS should include its administration in large concentrations together with an adjunctive agent.

Strong linkage disequilibrium between HLA-Dw2 and and BfS in multiple sclerosis and in the normal population

An increased frequency of the S allele of Properdin factor B (BfS) was found amongst 162 patients with multiple sclerosis (MS) compared with 470 normal controls. This increase was shown to be due to a strong linkage disequilibrium (LD) between BfS and HLA-Dw2 in 77 patients typed for both systems (delta = 3.84%, P = .0002). The same LD was demonstrated amongst 100 normal controls (delta = 2.24%, P = .0049) and 31 patients with idiopathic demyelination of the peripheral nervous system (IDPN). A total of 70 haplotypes with HLA-Dw2 were encountered (40 MS, seven IDPN and 23 normal controls) and all contained BfS. In the MS patient group, a much weaker association was noted between BfS and HLA-B7 suggesting either that the Bf locus is musch closer to the HLA-D than the HLA-B locus or (and) that HLA-D and Bf products selectively interact (perhaps on the surface of B lymphocytes) with evolutionary advantage or disadvantage resulting from certain allelic combinations. Strong associations between BfS1 and HLA-Bw21 (P = .0000) and BfF1 and HLA-B18 (P = .0001), both previously reported, were confirmed in the current study. No increase in the frequency of a glyoxalase (GLO) allele was found amongst the MS patients and no LD was encountered between HLA-Dw2 and a GLO allele. The possibility that the HLA-Dw2, BfS disequilibrium has resulted from a selective advantage conferred on the general community but at the expense of increasing susceptibility to MS should be considered.

Measles antibodies and kappa-lambda light chain distribution in immunoglobulins of patients affected with multiple sclerosis

The presence of measles antibodies in serum immunoglobulin G fractions from seven patients affected with multiple sclerosis was investigated with HI technic. The kappa-lambda light chain ratios of all samples under investigation were evaluated. Three multiple sclerosis patients, who displayed either fractionation or a tendency towards fractionation in their serum, had slightly elevated measles antibody titers associated to increased kappa/lambda ratios.