Epstein–Barr virus infection and type I interferon signature in patients with systemic lupus erythematosus

Epstein–Barr (EB) virus infection has long been speculated to evoke systemic lupus erythematosus (SLE). Since a virus infection can induce interferon (IFN) system activation, we aimed to discover the relationship between the two in the progression of SLE in a Chinese inpatient cohort. Methods Peripheral blood mononuclear cells and sera were isolated from 116 SLE patients and 76 healthy controls. Antibodies against EBV-VCA (IgM and IgG) and EBNA (IgG) along with IFNα in patient sera were detected with enzyme-linked immunosorbent assays. The EB virus DNA load was detected by real-time quantitative polymerase chain reaction. Peripheral blood mononuclear cells both from patients and controls were isolated immediately. The mRNA from these samples was subjected to real-time PCR for the latent genes EBNA1, EBNA2 and LMP1 of EB virus, as well as four IFN-stimulated genes (ISGs) ( OASL, MX1, ISG15 and LY6E). The antibody results were used to determine the stage of EBV infection (lytic, latent, or previous). Results SLE patients had a higher rate of lytic infection defined as positive EBV-VCA IgM antibody (39.66% vs 10.53%, p = 0.027), but not the EB virus DNA load. Patients with lytic EB virus infection had higher SLEDAI scores than patients with non-lytic infection (15.24 ± 2.63 vs 13.79 ± 3.24, p = 0.012). LMP1 was the only EBV gene that had a higher expression level in SLE patients than in healthy controls (3.26 ± 2.95 vs 1.00 ± 2.89, p = 0.000). It was also positively correlated with SLEDAI scores ( r = 0.462, p = 0.000). Levels of IFNα and the four ISGs were all significantly higher in SLE patients than in healthy controls ( p < 0.05). LMP1 was positively correlated with the four ISGs ( r = 0.403 ∼ 0.494, p < 0.05) in SLE patients but not in healthy controls ( r = −0.153 ∼ 0.129, p > 0.05). Neither EBNA1 nor EBNA2 was correlated with the ISGs in SLE patients or in healthy controls. Conclusions The SLE patients had higher rates of lytic EB virus infection and higher latent gene LMP1 expression, which might be associated with the development and/or the progression of SLE via the type I IFN pathway. The underlying mechanism needs more study.