Systemic lupus erythematosus and human endogenous retroviruses

Impact of sex disparities on the clinical manifestations in patients with systemic lupus erythematosus: A systematic review and meta-analysis

BACKGROUND

Systemic lupus erythematosus (SLE) is a chronic autoimmune multiorgan disorder of unknown etiology. It affects both men and women, but with different disease manifestations of differing disease severity and in varying proportion, with a female predominance of approximately 90%. There have been numerous studies addressing this issue, especially its implications in relation to optimal sex-tailored treatment and improvement of survival rate; however, further research is warranted. A meta-analysis of studies was performed to compare the impact of sex on the clinical outcomes of SLE in different populations.

METHODS

A literature search of the MEDLINE/PubMed and EMBASE databases (until January 2016) was conducted to identify relevant articles. Clinical manifestations reported in these patients were considered as endpoints for this meta-analysis. Two independent reviewers determined eligibility criteria. A fixed-effect model has been used where a small heterogeneity was observed, or else, a random-effect model has been used among the studies. Odd ratio (OR) with 95% confidence interval (CI) was used to express the pooled effect on dichotomous variables, and the pooled analyses were performed with RevMan 5.3.

RESULTS

Sixteen studies consisting of a total of 11,934 SLE patients (10,331 females and 1603 males) have been included in this meta-analysis. The average female-to-male ratio of all the included studies is around 9.3:1. Several statistically significant differences were found: alopecia, photosensitivity, and oral ulcers were significantly higher in female patients (OR 0.36, 95% CI 0.29-0.46, P < 0.00001; OR 0.72, 95% CI 0.63-0.83, P < 0.00001; and OR 0.70, 95% CI 0.60-0.82, P < 0.00001, respectively). Malar rash was significantly higher in female patients (OR 0.68, 95% CI 0.53-0.88, P = 0.003), and arthritis was significantly lower in male patients (OR 0.72, 95% CI 1.25-1.84, P < 0.00001). However, serositis and pleurisies were significantly higher in female patients (OR 1.52, 95% CI 1.25-1.84 P < 0.0001; and OR 1.26, 95% CI 1.07-1.48, P = 0.006, respectively). Renal involvement was higher in male patients (OR 1.51, 95% CI 1.31-1.75, P < 0.00001).

CONCLUSION

The results of this meta-analysis suggest that alopecia, photosensitivity, oral ulcers, arthritis, malar rash, lupus anticoagulant level, and low level of C3 were significantly higher in female lupus patients, whereas renal involvement, serositis and pleurisies, thrombocytopenia, and anti-double stranded deoxyribonucleic acid level were predominant in male patients.

Expression and regulation of human endogenous retrovirus W elements

Human endogenous retroviruses (HERV) comprise 8% of the human genome and can be classified into at least 31 families. A typical HERV provirus consists of internal gag, pol and env genes, flanked by two long terminal repeats (LTRs). No single provirus is capable of engendering infectious particles. HERV are by nature repetitive and have with few notable exceptions lost their protein-coding capacity. Therefore, HERV have consistently been excluded from array-based expression studies and hence little is known of their expression, regulation, and potential functional significance. An increasing number of studies have, however, observed expression of the W family of HERV in various human tissues and cells, predominantly in placenta. HERV-W LTRs act as promoters in directing transcription of HERV-W members, contribute to their tissue-specific and highly diversified expression pattern. Furthermore, leaky transcription originating from adjacent genes plays a role in the transcription initiation of HERV-W psudoelements. It has been reported that HERV-W elements, including ERVWE1 (the so far only known HERV-W locus harboring a gene (env) functionally adopted by the human host to critically participate in placenta biogenesis), can become transactivated in a range of human non-placental cell-lines during exogenous virus infections. Aberrant expression of HERV-W has been associated with human diseases, such as cancer, multiple sclerosis, and schizophrenia. Based on published reports, transcriptional activities of HERV-W appear to be influenced by several mechanisms; binding of transcription factors to LTR promoters and enhancers outside of LTRs, genetic variation and alteration in DNA methylation and histone modification. Emerging mechanistic studies support the notion that HERV-W represents a potential marker or mediator of environmental exposures (e.g., virus infection) in the development of chronic complex diseases.

Human Endogenous Retroviruses (HERVs) and Autoimmune Rheumatic Disease: Is There a Link?

Autoimmune rheumatic diseases, such as RA and SLE, are caused by genetic, hormonal and environmental factors. Human Endogenous Retroviruses (HERVs) may be triggers of autoimmune rheumatic disease. HERVs are fossil viruses that began to be integrated into the human genome some 30-40 million years ago and now make up 8% of the genome. Evidence suggests HERVs may cause RA and SLE, among other rheumatic diseases. The key mechanisms by which HERVS are postulated to cause disease include molecular mimicry and immune dysregulation. Identification of HERVs in RA and SLE could lead to novel treatments for these chronic conditions. This review summarises the evidence for HERVs as contributors to autoimmune rheumatic disease and the clinical implications and mechanisms of pathogenesis are discussed.

Human endogenous retroviruses in multiple sclerosis: potential for novel neuro-pharmacological research

There is growing evidence that the env genes of two or more human endogenous retroviruses (HERVs) of the W family are contributing to the inflammatory processes, and thus to the pathogenesis, of multiple sclerosis (MS). Increasing understanding of the human endogenous retroviral locus, ERVWE1, and the putative multiple sclerosis associated retrovirus, or MSRV, and in particular of the HERV-W env sequences associated with these, offers the potential of new lines of pharmacological research that might assist diagnosis, prognosis and therapy of multiple sclerosis.

The distribution of human endogenous retrovirus K-113 in health and autoimmune diseases in Poland

OBJECTIVE

During the evolution of the human genome, a number of retroviral integrations have occurred creating a group of human endogenous retroviruses (HERVs). As of now several studies have pointed to the association of HERVs with certain autoimmune diseases such as RA, SLE, multiple sclerosis (MS) and SS as well as various neoplasms. In this study, we investigated the prevalence of HERV-K113 in patients with RA, SLE and in healthy subjects in the Polish population.

METHODS

Genomic DNA samples from 155 RA patients, 139 SLE patients and 261 newborns (as controls) were tested for the presence of the HERV-K113 allele using PCR. Each individual's DNA was genotyped for null, homozygous or heterozygous insertion of HERV-K113.

RESULTS

Our data revealed statistically significant differences in the insertion frequencies of HERV-K113 between the groups of RA and SLE patients vs healthy controls (provirus DNA was found in 14.19, 15.11 and 8.05% of individuals, respectively). No homozygous individuals for the K113 allele were found in each of the groups. There was no evidence for HERV-K113 association with clinical features in either group.

CONCLUSION

Our study-the first such performed for the Polish population-provides a consistent observation with previous reports on the genetic association of HERV-K113 integrations in autoimmune disorders. Here, we found that the prevalence of insertionally polymorphic HERV-K113 was significantly increased in Polish patients with SLE and RA.

Endogenous retroviruses in systemic response to stress signals

Infection of germline cells with retroviruses initiates permanent proviral colonization of the germline genome. The germline-integrated proviruses, called endogenous retroviruses (ERVs), are inherited to offspring in a Mendelian order and belong to the transposable element family. Endogenous retroviruses and other long terminal repeat retroelements constitute ~8% and ~10% of the human and mouse genomes, respectively. It is likely that each individual has a distinct genomic ERV profile. Recent studies have revealed that a substantial fraction of ERVs retains the coding potentials necessary for virion assembly and replication. There are several layers of potential mechanisms controlling ERV expression: intracellular transcription environment (e.g., transcription factor pool, splicing machinery, hormones), epigenetic status of the genome (e.g., proviral methylation, histone acetylation), profile of transcription regulatory elements on each ERV's promoter, and a range of stress signals (e.g., injury, infection, environment). Endogenous retroviruses may exert pathophysiologic effects by infection followed by random reintegration into the genome, by their gene products (e.g., envelope, superantigen), and by altering the expression of neighboring genes. Several studies have provided evidence that ERVs are associated with a range of pathogenic processes involving multiple sclerosis, systemic lupus erythematosus, breast cancer, and the response to burn injury. For instance, the proinflammatory properties of the human ERV-W envelope protein play a central role in demyelination of oligodendrocytes. As reviewed in this article, recent advances in ERV biology and mammalian genomics suggest that ERVs may have a profound influence on various pathogenic processes including the response to injury and infection. Understanding the roles of ERVs in the pathogenesis of injury and infection will broaden insights into the underlying mechanisms of systemic immune disorder and organ failure in these patients.

Possible mechanisms of gender bias in SLE: a new hypothesis involving a comparison of SLE with atopy

The prevalence of systemic lupus erythematosus (SLE) is far higher in females than in males, and numerous investigations of this gender bias have been performed from several perspectives. Sex hormones, particularly estrogens, may be significant in causing the gender discrepancy. This article discusses the possible importance of estrogens in regulating the expression of and responsivity to autoantigens in SLE and in atopic disorders, which are associated with hyperreactivity to exogenous antigens. Estrogens seem to play an important role in the overexpression of endogenous autoantigens, such as human endogenous retroviruses (HERV), and this may be related to the existence of a gender bias in the incidence of SLE but not atopy.