Plaque-associated expression of human herpesvirus 6 in multiple sclerosis.

Abstract

Representational difference analysis was used to search for pathogens in multiple sclerosis brains. We detected a 341-nucleotide fragment that was 99.4% identical to the major DNA binding protein gene of human herpesvirus 6 (HHV-6). Examination of 86 brain specimens by PCR demonstrated that HHV-6 was present in >70% of MS cases and controls and is thus a commensal virus of the human brain. By DNA sequencing, 36/37 viruses from MS cases and controls were typed as HHV-6 variant B group 2. Other herpesviruses, retroviruses, and measles virus were detected infrequently or not at all. HHV-6 expression was examined by immunocytochemistry with monoclonal antibodies against HHV-6 virion protein 101K and DNA binding protein p41. Nuclear staining of oligodendrocytes was observed in MS cases but not in controls, and in MS cases it was observed around plaques more frequently than in uninvolved white matter. MS cases showed prominent cytoplasmic staining of neurons in gray matter adjacent to plaques, although neurons expressing HHV-6 were also found in certain controls. Since destruction of oligodendrocytes is a hallmark of MS, these studies suggest an association of HHV-6 with the etiology or pathogenesis of MS.Multiple sclerosis (MS) is a disease of young adults that is characterized clinically by a variable relapsing and remitting course and pathologically by the progressive accumulation of plaques of demyelination within the white matter of the central nervous system. In normal white matter, the axons of neurons are surrounded by myelin sheaths, made from the cell membranes of oligodendrocytes. In MS plaques, the myelin sheaths are destroyed, leaving the naked axons intact but impaired in their conduction of action potentials. The currently held view is that an autoimmune inflammatory reaction against components of myelin results in destruction of oligodendrocytes. The demyelinating lesions in MS are found throughout the central nervous system, with a predilection for the periventricular white matter, optic nerve, brainstem, spinal cord, and cerebellum, resulting in a disease that is pleiomorphic in its clinical presentation.In spite of the substantial evidence that autoimmunemediated demyelination plays a major role in the progression of MS, epidemiologic studies suggest that an infectious agent may also be involved (1). Prior reports have suggested that viral infection of cells within the central nervous system may initiate the events leading to focal demyelination (2), and a number of viruses have been implicated in the pathogenesis of MS (3). Despite extensive investigation, however, none of these associations has been confirmed (4), and the issue of viral involvement in the pathogenesis of MS remains unresolved.To search for an MS-associated pathogen, we used representational difference analysis (RDA) (5). In RDA, successive rounds of subtractive hybridization and PCR amplification enriched for DNA sequences that were present in a DNA preparation from diseased tissue (MS brain) but absent from control DNA (n...

Expression of Human Herpesvirus-6 Antigens in Benign and Malignant Lymphoproliferative Diseases

“…Sections (4 m) mounted on positively charged slides were deparaffinized with xylene and rehydrated, immersed for 10 minutes in 3% hydrogen peroxide/methanol to quench endogenous peroxidase, and microwaved for 10 minutes in citrate buffer. 28 After slow cooling, the sections were incubated successively with primary antibody, biotin-labeled goat antimouse or anti-rabbit Ig, streptavidin-biotin peroxidase complex, and 3,3Ј-diaminobenzidine tetrahydrochloride chromogen. Tissues were counterstained with hematoxylin.…”

“…Mouse IgG1 monoclonal antibody (mAb) to HHV-6B virion protein p101K (late antigen) was obtained from P. Pellett (Centers for Disease Control and Prevention, Atlanta, GA) and from Chemicon International (Temecula, CA) and used at a dilution of 1:200. 28,31 Mouse IgG2a mAb C5 to DNA binding protein p41 (early antigen) was used at a dilution of 1:50 (Biodesign International, Kennebunkport, ME). 28,32 Mouse IgG2b mAb to gp106 (late antigen) 33 and IgG2b mAb to gp116 (late antigen) (both from Advanced Biotechnologies, Inc., Columbia, MD) were used at a dilution of 1:50.…”

“…28,31 Mouse IgG2a mAb C5 to DNA binding protein p41 (early antigen) was used at a dilution of 1:50 (Biodesign International, Kennebunkport, ME). 28,32 Mouse IgG2b mAb to gp106 (late antigen) 33 and IgG2b mAb to gp116 (late antigen) (both from Advanced Biotechnologies, Inc., Columbia, MD) were used at a dilution of 1:50. The specificity of these antibodies was confirmed by testing isotype-matched control mouse mAbs against human IgG (IgG1, X931; IgG2a, X943; and IgG2b, X944; Dakopatts, Glostrup, Denmark) in selected HHV-6-positive cases.…”

“…Recently, this technical approach has been revealed to be successful in localizing HHV-6-infected cells in brain tissues from patients with multiple sclerosis, providing the first strong evidence toward an etiological relationship. 28 Thus, we judged it appropriate to use immunohistochemistry with a panel of antibodies for different viral antigens to look for the presence and distribution of HHV-6 antigen-expressing cells in the lymphoid tissues positive for the presence of HHV-6 DNA from a well characterized series of patients with benign, atypical, and malignant lymphoproliferative diseases.…”

Allelic association of sequence variants in the herpes virus entry mediator-B gene (PVRL2) with the severity of multiple sclerosis

“…44 Consistent with this observation and the results reported here, recent experimental studies have shown that human oligodendrocytelike cells are highly susceptible to HSV-1 infection, 45 and that differences in virus-host cell interactions, and hence HSV-1 susceptibility, are probably genetically determined. 46 Interestingly, another member of the Herpesviridae family, human herpesvirus 6 , has also been associated with MS. 47 In summary, our study suggests that sequence variants in a 16.6 kb block spanning intron 1 to intron 2 of PVRL2 may influence the severity of MS in a subset of patients. It is currently unknown whether these variants, or others in LD with them, alter the functionality of the viral receptor region, or affect gene splicing.…”