Serum antibodies to HTLV-I in human demyelinating disease

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.

Do endogenous retroviruses have etiological implications in inflammatory and degenerative nervous system diseases?

Vertebrates carry large numbers of endogenous retroviruses (ERVs) and related sequences in their genomes. These retroviral elements are inherited as Mendelian traits. Generally, ERVs are defective without the ability of being expressed as viral particles. However, ERV sequences often have a potential for expression of at least some proteins. So far, the possible biological significance of ERVs is not clear. Nonetheless, there are observations suggesting a connection between ERVs and various diseases. This is the case with murine lupus and a spinal cord disease of certain mouse strains. In the present review, we discuss possible mechanisms by which ERVs could contribute to the development of human degenerative and inflammatory nervous system diseases, including direct effects on nervous system cells and immune cells. Interactions between ERVs and infectious viruses are also discussed. Finally, we review a possible retroviral etiology of multiple sclerosis.

Pathogenesis of virus-induced demyelination

Demyelination is a component of several viral diseases of humans. The best known of these are subacute sclerosing panencephalitis (SSPE) and progressive multifocal leukoencephalopathy (PML). There are a number of naturally occurring virus infections of animals that involve demyelination and many of these serve as instructive models for human demyelinating diseases. In addition to the naturally occurring diseases, many viruses have been shown to be capable of producing demyelination in experimental situations. In discussing virus-associated demyelinating disease, the chapter reviews the architecture and functional organization of the CNS and considers what is known of the interaction of viruses with CNS cells. It also discusses the immunology of the CNS that differs in several important aspects from that of the rest of the body. Experimental models of viral-induced demyelination have also been considered. Viruses capable of producing demyelinating disease have no common taxonomic features; they include both DNA and RNA viruses, enveloped and nonenveloped viruses. The chapter attempts to summarize the important factors influencing viral demyelination, their common features, and possible mechanisms.

Lack of detectable human T-cell lymphotropic virus type I sequences in samples from multiple sclerosis patients

Recently, inconclusive results have followed the early data on the possible association between multiple sclerosis (MS) and human T-cell lymphotropic virus type I (HTLV-I) infection. For this reason, we examined this hypothesis using the polymerase chain reaction (PCR) to study samples of differing origin from Italian MS patients. In particular, we developed a systematic analysis of paraffin-embedded brain white matter from histologically defined lesions of 14 MS patients using PCR and primer sets specific for HTLV-I sequences; additionally, cerebrospinal fluids (CSFs) from 12 patients and peripheral blood mononuclear cells (PBMCs) from subjects at the early and late phase of the disease were investigated for free HTLV-I virions and specific proviral sequences, respectively. In agreement with some groups who reported lack of HTLV-I sequences in PBMCs of MS patients but in clear contrast with others, we failed to detect specific viral sequences using this broad approach.

Use of immunoreactive synthetic HTLV-1 peptides in the search for antibody reactivity in multiple sclerosis

The possible association between multiple sclerosis (MS) and antibodies to human T-cell lymphotropic virus type 1 (HTLV-1) was studied. Five synthetic and highly immunoreactive HTLV-1 peptides, four from the envelope (env) region and one from the core (gag) region, were used in an indirect enzyme-linked immunosorbent assay (ELISA). Presence of HTLV-1-specific antibodies in paired serum and cerebrospinal fluid (CSF) samples from 41 MS patients were investigated. No antibody reactivity was demonstrable in samples from 40 of them, whereas one reacted in one serum sample against the gag-peptide. Serum and CSF specimens from 15 with other neurologic diseases (OND), and negative control specimens, i.e. serum and CSF from 9 non-neurologic controls and CSF from 9 healthy controls, did not demonstrate any reactivity in the peptide-ELISAs. Our results do not support involvement of HTLV-1 infection in the etiology of MS.

Human T-cell lymphotropic virus type I sequences detected by nested polymerase chain reactions are not associated with multiple sclerosis

The hypothesis that human T-cell lymphotropic virus type I (HTLV-I) infection is associated with multiple sclerosis (MS) was tested by using primers specific to gag and pol regions of HTLV-I in an analysis that used polymerase chain reactions. No amplification of DNA from patients with MS was detected with primers for either region. After application of a more sensitive scheme with use of nested primers, however, half the samples, including patients with MS and normal control subjects, were found to contain pol DNA sequences. No sequences related to the HTLV-I gag region were detected among patients with MS by using nested primers. Sequences of the amplified HTLV-I pol genomes were determined. Regardless of their origin (MS or normal control), the pol region sequences were similar to HTLV-I sequences reported by other investigators. We conclude that HTLV-I does not have a distinct association with MS, but HTLV-I-related sequences, although in extremely low copy number, may be present in human genomes.

Amplifications of multiple regions of the HTLV-I genome from DNA of an Italian spastic paraparesis patient but not from DNA of multiple sclerosis patients

We searched for evidence of infection by the human T-cell lymphoma/leukemia virus type I (HTLV-I) in patients with multiple sclerosis (40 cases); brainstem encephalitis (1 case); Friedreich's ataxia (1 case); spastic paraparesis of unknown etiology (1 case). All patients were from the region of Abruzzo, Italy. Sera were all negative for anti-HTLV-I reactivity by the Western blotting (WB) analysis. DNAs from peripheral blood mononuclear cells were amplified using the polymerase chain reaction (PCR) technique with primers specific for the HTLV-I gag, pol, and env proviral regions. HTLV-I sequences were amplified only in the patient with spastic paraparesis of unknown etiology. In this case, HTLV-I infection might have been related to blood transfusions received 2 years prior to the onset of the neurologic symptoms. Members of the patient's family were negative for HTLV-I by PCR and WB. These data indicate that HTLV-I associated myelopathy is present also in Italy, but fail to substantiate an association of HTLV-I with multiple sclerosis.

Retrovirus in multiple sclerosis

Presence of cytopathic effect and enzyme reverse transcriptase in cultures of peripheral blood mononuclear cells is described in 2 of 15 patients with multiple sclerosis and none of healthy controls. These findings might indicate: the presence of a new human retrovirus in these individuals, despite the low detection rate, and the shortcomings inherent in methodology used for detection of known human retroviruses in the study of new groups of diseases, such as those with possible autoimmune background.

Low-titer antibodies reactive with HTLV-I gag p19 in patients with chronic myeloneuropathy

To elucidate the possible association of human T-lymphotropic virus type I (HTLV-I) and chronic neurological diseases, 156 serum samples from patients with various neurological diseases, including multiple sclerosis, chronic progressive myelopathy, chronic inflammatory polyradiculoneuropathy, myasthenia gravis, polymyositis, motor neuron disease, and tension headache, and healthy control subjects were examined for IgG antibodies to HTLV-I by three independent techniques--gelatin particle agglutination test, enzyme-linked immunosorbent assay, and Western blot assay. Specificity of antibodies was assessed by homologous competitive inhibition on Western blot assay. Six patients (3 with chronic progressive myelopathy, 1 with chronic inflammatory polyradiculoneuropathy, 1 with motor neuron disease, and 1 with tension headache) had high-titer HTLV-I antibodies. Twelve patients (5 with multiple sclerosis, 1 with chronic progressive myelopathy, 2 with chronic inflammatory polyradiculoneuropathy, 2 with myasthenia gravis, and 2 with motor neuron disease) had low-titer HTLV-I antibodies that reacted with a single gag protein, p19 or p24, on Western blot assay. In 4 (2 with multiple sclerosis, 1 with chronic progressive myelopathy, and 1 with chronic inflammatory polyradiculoneuropathy) of these 12, the antibodies that were all directed to p19 were determined to be specific by homologous competitive inhibition. In the remaining 8 patients (3 with multiple sclerosis, 1 with chronic inflammatory polyradiculoneuropathy, 2 with myasthenia gravis, and 2 with motor neuron disease), restricted reactions against p19 or p24 were considered to be nonspecific because they were not inhibited by homologous competitive inhibition. The results suggest that in some patients chronic myeloneuropathy diagnosed as chronic progressive multiple sclerosis, chronic progressive myelopathy, and chronic inflammatory polyradiculoneuropathy may be associated with HTLV-I or related retroviruses.

Antibodies in sera from Norwegian multiple sclerosis patients and the general population reacting with HTLV-1. A pilot study

By using enzyme-linked immunosorbent assay, Western blot and passive agglutination we have performed a pilot study involving the testing of 349 sera from the general population of 3 coastal regions in southern Norway, 230 sera from multiple sclerosis patients from western Norway, 109 age- and sex-matched controls and 34 sera from patients with other neurological diseases, for antibodies to HTLV-I. About 2% and 4% of sera from the general population had antibodies reacting with HTLV-I in ELISA and Adult T-cell Leukemia Antigen by agglutination, respectively, whereas about 8% and 5% of the multiple sclerosis sera had such antibodies. In the general population antibodies were more frequent among young individuals and there appeared to be some prevalent regional differences. Western blot confirmatory tests showed that in some instances antibodies reacted with the gag proteins, in particular p19. The results obtained in this study do not indicate an association between HTLV-I and multiple sclerosis, although at this stage we cannot rule out that another retrovirus is involved.

Absence of antibodies to HTLV-1 in sera from Hungarian MS patients

The aim of this study is to examine the association between multiple sclerosis (MS) and anti-human T-lymphotropic virus type I (HTLV-I) antibody. Serum samples from 16 Hungarian caucasians with MS, 2 gipsy patients with MS, 13 Hungarian caucasians with other neurological diseases (OND) and 2 gipsy patients with OND were tested by Western blot combined with autoradiography using disrupted virus from MT-2 cell line and recombinant p24 as antigens. Negative results were obtained in all samples except for 3 Hungarian OND which were reactive to disrupted virus, but not to recombinant p24.

Detection of DNA transcripts of measles genes in multiple sclerosis brain tissue by transfection

Transfection studies on DNA obtained from 16 multiple sclerosis (MS) and 13 non-MS brain tissues suggested that 3/16 (19%) MS and 3/13 (23%) non-MS samples contained contaminating measles virus double-stranded RNA, and that 6/16 (38%) MS and 0/13 non-MS samples contained DNA transcripts of measles genes. It is argued that the DNA transcripts most probably originated from dual retrovirus and measles infections in the subjects.

Seroprevalence of antibodies to HTLV-I in patients with chronic neurological disorders other than tropical spastic paraparesis

Human T-lymphotropic virus type I (HTLV-I), the etiological agent of adult T-cell leukemia/lymphoma, also appears to be the cause of tropical spastic paraparesis, a chronic myelopathy reported in several different regions of the world. The prevalence of antibodies to HTLV-I in patients with chronic neurodegenerative disorders other than tropical spastic paraparesis and in patients with some muscle inflammatory disorders has been investigated. IgG antibodies to HTLV-I were measured in the sera and/or cerebrospinal fluid from 82 Guamanian patients with amyotrophic lateral sclerosis and parkinsonism-dementia, 164 Guamanian normal controls, 10 patients with kuru from the Eastern Highlands of Papua New Guinea, 4 patients with Viliuisk encephalomyelitis from the Iakut region of eastern Siberia, 45 Italian patients with multiple sclerosis, and 56 patients with polymyositis (49 from the United States and 7 from Jamaica). As determined by enzyme-linked immunosorbent assay, Western immunoblot, and gelatin particle agglutination techniques, serological evidence of HTLV-I infection was found in 1 patient with amyotrophic lateral sclerosis and 1 control subject from Guam, and in 1 patient from the United States and all 7 Jamaican patients with polymyositis. Except for the high seropositivity rate among the group of Jamaican patients with polymyositis, our data indicate that HTLV-I is an unlikely causative agent in the spectrum of the neurological diseases examined. The seropositivity of the 7 Jamaican patients with polymyositis requires further study.