A new myositis-specific autoantibody directed against melanoma differentiation-associated gene 5 (anti-MDA5) has been described in patients with dermatomyositis (DM). We report the clinical characteristics of patients with anti-MDA5 in a large Mediterranean cohort of DM patients from a single center, and analyze the feasibility of detecting this autoantibody in patient sera using new assays with commercially available recombinant MDA5. The study included 117 white adult patients with DM, 15 (13%) of them classified as clinically amyopathic dermatomyositis (CADM). Clinical manifestations were analyzed, with special focus on interstitial lung disease and its severity. Determination of anti-MDA5 antibodies was performed by a new ELISA and immunoblot technique. In sera, from 14 (12%) DM patients (8 CADM), MDA5 was recognized by ELISA, and confirmed by immunoblot. Eight of the 14 anti-MDA5-positive patients (57.14%) presented rapidly-progressive interstitial lung disease (RP-ILD) versus 3 of 103 anti-MDA5-negative patients (2.91%) (P < 0.05; OR: 44.4, 95% CI 9.3–212). The cumulative survival rate was significantly lower in anti-MDA5-positive patients than in the remainder of the series (P < 0.05). Patients with anti-MDA5-associated ILD presented significantly lower 70-month cumulative survival than antisynthetase-associated ILD patients. Among the cutaneous manifestations, only panniculitis was significantly associated with the presence of anti-MDA5 antibodies (P < 0.05; OR: 3.85, 95% CI 1.11–13.27). These findings support the reliability of using commercially available recombinant MDA5 for detecting anti-MDA5 antibodies and confirm the association of these antibodies with RP-ILD in a large series of Mediterranean patients with DM.

Eight per cent of the human genome is derived from the integration of retroviral sequences that were incorporated in our DNA more than 25 million years ago. Although some of these elements show mutations and deletions, some HERVs are transcriptionally active and produce functional proteins. Different mechanisms have been described which link HERVs to some chronic diseases such as several cancers, nervous system diseases and autoimmune rheumatic and connective tissue diseases. They could cause disease because of their capacity for being moved and inserted next to certain genes whose expression would be consequentially altered. Another way in which disease could potentially arise is when HERV-encoded proteins are expressed. These proteins would be considered as [foreign] and they could trigger B-cells to produce antibodies against them, which, in turn, might cross-react with other proteins of our bodies. This mechanism could give rise to autoimmune diseases such as rheumatoid arthritis (RA), lupus erythematosus, Sjögren's syndrome (SJS), mixed connective tissue diseases and inflammatory neurological disease. Furthermore, it should be pointed out that HERV-proteins may act as superantigens. Interestingly, some environmental agents seem to induce the expression of HERVs. Thus, ultraviolet light and several chemical agents could reactivate such sequences by altering their structure without modifying their nucleotide composition when the methylation pattern is changed. Therefore, the epigenetic changes observed in pathological conditions such as systemic lupus erythematosus (SLE) or cancer could be translated into an effect on the activation of some of the retroelements present in our genome which ultimately could have a direct or indirect role on the initiation and clinical evolution of certain chronic diseases.

Global DNA hypomethylation in CD4+ T cells has been detected in systemic lupus erythematosus (SLE), and it seems to be linked to its pathogenesis. We investigated the relationship between overall DNA methylation and the expression of two methyl CpG-binding domain (MBD) proteins. DNA deoxymethylcytosine (d(m)C) content of purified CD4(+) T cells from 29 SLE patients and 30 healthy controls was measured by means of an ELISA. Transcript levels of two methyl CpG-binding proteins (MBD2 and MBD4) were quantified by real-time RT-PCR. Association studies were also carried out with several laboratory parameters, as well as with the patients' clinical manifestations. SLE patients had significantly less CD4+ T cell DNA d(m)C content than controls (0.802+/-0.134 vs. 0.901+/-0.133; P=0.007). MBD2 and MBD4 mRNA levels were considerably higher in the patients' group: 0.975 +/- 0683 versus 0.604 +/- 0.614 (P=0.004) and 0.359 +/- 0.330 versus 0.092 +/- 0.169, respectively (P<0.0005). It is interesting that SLE patients showed a negative correlation between methylation indices and MBD2 (r=-0.609, P<0.0005) and MBD4 (r=-0.395, P=0.034) transcript levels. MBD2 and MBD4 transcript overexpression and inverse correlations with DNA methylation indices indicate that both enzymes may really have a direct and active role on the genome-wide DNA hypomethylation observed in CD4+ T cells from SLE patients.

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In mammals, DNA methylation only occurs at cytosine residues found within cytosine-phosphate-guanosine (CpG) dinucleotides and it involves methylation in the fifth carbon of the pyrimidine ring, leading to the formation of 5-methylcytosine (5-m C). The majority of CpG sites (70-80%) in human DNA are methylated and many of the non-methylated sites are found in the so-called CpG islands, which are normally on functioning promoters. Several studies report a strong correlation between DNA methylation and genetic inactivity.1 On the other hand, DNA methylation inhibitors [5-azacytidine (5-aza-C)] are able to re-activate genes that have been previously methylated and silenced.2 Thus, DNA methylation is an epigenetic process linked to the regulation of several biological events, including embryonic development, 3 transcriptional regulation of gene expression, X-chromosome inactivation, genomic 'imprinting', chromatin modification and the silencing of endogenous retroviruses. 4-7Altered DNA-methylation patterns have been detected and widely studied in tumorigenic events. 8The enzymes that methylate DNA are known as DNA cytosine-5-methyltransferases (DNMTs), the most studied among them being DNMT1. DNMT1 prefers hemimethylated DNA as a substrate and therefore will methylate newly replicated DNA only when the template nucleotides are methylated. DNMT1 is constitutively expressed and is required to maintain global methylation after DNA replication has taken place. Recently, other enzymes with the ability to methylate DNA have been identified, including DNMT3A and DNMT3B, which appear to be involved in SummaryGlobal DNA hypomethylation in CD4 + T cells has been detected in systemic lupus erythematosus (SLE) and it seems to be linked to its pathogenesis. We investigated the relationship between overall DNA methylation and the expression of three DNA (cytosine-5) methyltransferases involved in the DNA methylation process. The DNA deoxymethylcytosine (dmC) content of purified CD4 + T cells from 29 SLE patients and 30 healthy controls was measured by means of an enzyme-linked immunosorbent assay (ELISA). The transcript levels of DNA cytosine-5-methyltransferase 1 (DNMT1), DNA cytosine-5-methyltransferase 3A (DNMT3A) and DNA cytosine-5-methyltransferase 3B (DNMT3B) were quantified by real-time reverse transcription-polymerase chain reaction (RT-PCR). Association studies were also carried out with several laboratory parameters, as well as with the patients' clinical manifestations. SLE patients had a significantly lower CD4 + T-cell DNA dmC content than controls (0Á802 ± 0Á134 versus 0Á901 ± 0Á133) (P = 0Á007). No differences in transcript levels were observed for DNMT1, DNMT3A and DNMT3B between patients and controls. The simultaneous association of low complement counts with lymphopenia, high titres of anti-double-stranded DNA (anti-dsDNA), or an SLE disease activity index (SLEDAI) of > 5, resulted in the increase of at least one of the three DNA methyltransferases. It is possible that patients were reacting indirectly to an u...