Kari K. Nissen

The Etiology of Multiple Sclerosis: Genetic Evidence for the Involvement of the Human Endogenous Retrovirus HERV-Fc1

We have investigated the role of human endogenous retroviruses in multiple sclerosis by analyzing the DNA of patients and controls in 4 cohorts for associations between multiple sclerosis and polymorphisms near viral restriction genes or near endogenous retroviral loci with one or more intact or almost-intact genes. We found that SNPs in the gene TRIM5 were inversely correlated with disease. Conversely, SNPs around one retroviral locus, HERV-Fc1, showed a highly significant association with disease. The latter association was limited to a narrow region that contains no other known genes. We conclude that HERV-Fc1 and TRIM5 play a role in the etiology of multiple sclerosis. If these results are confirmed, they point to new modes of treatment for multiple sclerosis.

Expression of HERV-Fc1, a human endogenous retrovirus, is increased in patients with active Multiple Sclerosis

ABSTRACT Multiple sclerosis (MS) is considered to be an autoimmune disease with an unknown cause and with immune system dysregulation. Among environmental factors, viruses are most often connected with the etiology of MS. Human endogenous retroviruses (HERVs) constitute 5 to 8% of human genomic DNA and have been detected as transcripts and proteins in the central nervous system (CNS) and peripheral blood, frequently in the context of neuroinflammation. HERV-Fc1, which belongs to the HERV-H/F family, has received our attention largely because of the genetic association with MS. We studied the expression of a capsid (Gag) protein of HERV-H/F origin by flow cytometry in peripheral blood mononuclear cells (PBMCs) from healthy controls and from MS patients with nonactive or active disease. There was a significant increase in HERV-H/F Gag expression in CD4+ (P < 0.001) and CD8+ (P < 0.001) T lymphocytes and in monocytes (P = 0.0356) in PBMCs from MS patients with active disease. Furthermore, we have undertaken the first rigorous SYBR green-based absolute quantitative PCR (Q-PCR) evaluation approach to quantify extracellular HERV-Fc1 RNA viral loads in plasma from MS patients and healthy controls. We found a 4-fold increase in extracellular HERV-Fc1 RNA titers in patients with active MS compared with healthy controls (P < 0.001). These findings strengthen the link between HERV-Fc1 and the pathology of MS. The cause and biological consequences of these differential expression levels will be the subject of further investigation. HERV-Fc1 biology could be a compelling area for understanding the pathology of MS and possibly other autoimmune disorders.

Genetic association of multiple sclerosis with the marker rs391745 near the endogenous retroviral locus HERV-Fc1: analysis of disease subtypes

We have previously described the occurrence of multiple sclerosis (MS) to be associated with human endogenous retroviruses, specifically the X-linked viral locus HERV-Fc1. The aim of this study was to investigate a possible association of the HERV-Fc1 locus with subtypes of MS. MS patients are generally subdivided into three categories: Remitting/Relapsing and Secondary Progressive, which together constitute Bout Onset MS, and Primary Progressive. In this study of 1181 MS patients and 1886 controls we found that Bout Onset MS was associated with the C-allele of the marker rs391745 near the HERV-Fc1 locus (p = 0.003), while primary progressive disease was not. The ability to see genetic differences between subtypes of MS near this gene speaks for the involvement of the virus HERV-Fc1 locus in modifying the disease course of MS.

Endogenous retroviruses and multiple sclerosis–new pieces to the puzzle

The possibility that retroviruses play a role in multiple sclerosis (MS) has long been considered; accumulating findings suggest this to be most likely in the form of human endogenous retroviruses (HERVs). A genetic test series of fifty endogenous retroviral loci for association with MS in Danes showed SNP markers near a specific endogenous retroviral locus, HERV-Fc1 located on the X-chromosome, to be positive. Bout Onset MS was associated with the HERV-Fc1 locus, while a rarer form, Primary Progressive MS, was not. Moreover, HERV-Fc1 Gag RNA in plasma was increased 4-fold in patients with recent history of attacks, relative to patients in a stable state and to healthy controls.Finally, genetic variations in restriction genes for retroviruses influence the risk of MS, providing further support for a role of retroviral elements in disease.We speculate that endogenous retroviruses may activate the innate immune system in a variety of ways, involving the host proteins, TRIMs, TLRs, TREXs and STING. Observations in HIV-positive patients suggest that antiretroviral drugs can curb MS. Thus, these new findings regarding the etiology and pathogenesis of MS, suggest alternative ways to challenge autoimmune diseases.

(Some) Cellular Mechanisms Influencing the Transcription of Human Endogenous Retrovirus, HERV-Fc1

DNA methylation and histone acetylation are epigenetic modifications that act as regulators of gene expression. DNA methylation is considered an important mechanism for silencing of retroelements in the mammalian genome. However, the methylation of human endogenous retroviruses (HERVs) is not well investigated. The aim of this study was to investigate the transcriptional potential of HERV-Fc1 proviral 5′LTR in more detail, and examined the specific influence of CpG methylation on this LTR in number of cell lines. Specifically, the role of demethylating chemicals e.g. 5-aza-2′ deoxycytidine and Trichostatin-A, in inducing or reactivating expression of HERV-Fc1 specific sequences and the mechanisms were investigated. In our present study, 5-aza-dC is shown to be a powerful inducer of HERV-Fc1, and at the same time it strongly inhibits methylation of DNA. Treatment with this demethylating agent 5-aza-dC, results in significantly increased levels of HERV-Fc1 expression in cells previously not expressing HERV-Fc1, or with a very low expression level. The extent of expression of HERV-Fc1 RNAs precisely correlates with the apparent extent of demethylation of the related DNA sequences. In conclusion, the results suggest that inhibition of DNA methylation/histone deacetylase can interfere with gene silencing mechanisms affecting HERV-Fc1 expression in human cells.

Are human endogenous retroviruses triggers of autoimmune diseases? Unveiling associations of three diseases and viral loci

Autoimmune diseases encompass a plethora of conditions in which the immune system attacks its own tissue, identifying them as foreign. Multiple factors are thought to contribute to the development of immune response to self, including differences in genotypes, hormonal milieu, and environmental factors. Viruses including human endogenous retroviruses have long been linked to the occurrence of autoimmunity, but never proven to be causative factors. Endogenous viruses are retroviral sequences embedded in the host germline DNA and transmitted vertically through successive generations in a Mendelian manner. In this study by means of genetic epidemiology, we have searched for the involvement of endogenous retroviruses in three selected autoimmune diseases: multiple sclerosis, type 1 diabetes mellitus, and rheumatoid arthritis. We found that at least one human endogenous retroviral locus was associated with each of the three diseases. Although there was a significant overlap, most loci only occurred in one of the studied disease. Remarkably, within each disease, there was a statistical interaction (synergy) between two loci. Additional synergy between retroviral loci and human lymphocyte antigens is reported for multiple sclerosis. We speculate the possibility that recombinants or mixed viral particles are formed and that the resulting viruses stimulate the innate immune system, thereby initiating the autoimmune response.

Restriction Genes for Retroviruses Influence the Risk of Multiple Sclerosis

We recently described that the autoimmune, central nervous system disease, multiple sclerosis (MS), is genetically associated with the human endogenous retroviral locus, HERV-Fc1, in Scandinavians. A number of dominant human genes encoding factors that restrict retrovirus replication have been known for a long time. Today human restriction genes for retroviruses include amongst others TRIMs, APOBEC3s, BST2 and TREXs. We have therefore looked for a role of these retroviral restriction genes in MS using genetic epidemiology. We here report that markers in two TRIMs, TRIM5 and TRIM22 and a marker in BST2, associated statistically with the risk of getting MS, while markers in or near APOBEC3s and TREXs showed little or no effect. This indicates that the two TRIMs and BST2 influence the risk of disease and thus supports the hypothesis of a viral involvement.

No additional copies of HERV-Fc1 in the germ line of multiple sclerosis patients

BackgroundHuman endogenous retroviruses (HERVs) are suspected to play a role in the development of multiple sclerosis (MS). This suspicion has in part been based on increased expression of viral RNA or proteins or antibodies targeting retroviral products in MS patients. Recently, our group provided genetic evidence for association between the endogenous retrovirus HERV-Fc1 and MS, suggesting that HERV-Fc1 plays a role in this multifactorial disease. We have found increased expression of HERV-Fc1 in MS patients suffering from recent attack, but the underlying mechanism for association is still unknown.FindingsEvidence from animal models indicates that ERV implication in the pathogenesis of diseases can be a result of extra copies of the virus in the germ line. Therefore, we investigated the genome of 81 individuals, 74 patients with MS and 7 healthy controls, by means of Southern blotting, for presence of extra HERV-Fc1 copies. The known insertion at the Xq21.33 position was readily detectable, but no additional insertions in other genomic contexts could be identified in any studied individuals. This substantiates our previous copy-number PCR findings of a 2:1 ratio of HERV-Fc1 DNA between women and men, as expected from the X-chromosome location; there was no difference between patient and control individuals.ConclusionsNo additional germ line copies of HERV-Fc1 could be identified, precluding such copies to underlie the association between this provirus and multiples sclerosis.

Association of a single nucleotide polymorphic variation in the human chromosome 19q13.3 with drug responses in the NCI60 cell lines.

We studied the importance of certain polymorphisms on human chromosome 19q13.3 for drug sensitivity in human tumor cell cultures. NCI60 is a panel of 60 established tumor-derived cell lines, which have been tested for their sensitivity to tens of thousands of different drugs. Here we investigate the correlations between the responses of the NCI60 cells to different anticancer drugs and their respective alleles of five DNA polymorphisms located in a cancer-related chromosomal area. One polymorphism, located in the 5′ noncoding region of the gene ASE-1, alias CD3EAP, proved to be associated with drug sensitivity (P = 0.025). The same polymorphism has previously been associated with treatment response of multiple myeloma after bone marrow ablation. The polymorphism ASE-1-e1 was of importance for the drug response in the human cancer cell lines investigated and could eventually become important for individualized drug treatment in humans.

Two endogenous retroviral loci appear to contribute to Multiple Sclerosis

BackgroundTwo endogenous retroviral loci seem to be involved in the human disease Multiple sclerosis (MS).ResultsThe two retroviral loci synergize in and contribute to MS (shown by ANOVA). Synergy probably means recombination or complementation of the activated viruses. Similar observations may be true for Type 1 Diabetes and Rheumatoid arthritis. In MS the genes also synergize with the immune system; this could well be a common phenomenon.ConclusionWe formulate various theories about the role of the viruses. Also, the concept is developing that some forms of autoimmunity should be treatable with antiretrovirals. In the case of MS, this idea is gradually gaining weight.