Purpose The aim is to investigate the association among TLR7 and TLR9 serum levels with previous viral infections, disease activity and proinflammatory cytokine levels in SLE patients.
Methods Cross-sectional observational study in SLE patients (SLICC/ACR 2012 criteria) and healthy controls (HC). Previous infection data with RNA (HCV) and DNA virus (CMV, Epstein-Barr, Herpes simplex, Parvovirus B19 or HBV), disease activity and clinical data were collected. Biological samples of SLE patients and HC from the medical visit were supplied to the TLR7, TLR9, IL10 and INF1A determination by enzyme-linked immunoassay.
Results 94 SLE patients (91.5% female) with a mean age of 51 (13) years old and 35 HC (80% female) and 42 (12) years old were recruited. Mean age at diagnosis was 33 (14) years old and mean disease evolution was 19 (10) years. Mean SLEDAI index was 5.35 (4.58).
The 48.94% of patients reported almost one DNA virus infections, the 2.13% reported HCV infection, the 4.25% with HCV and DNA virus, and the 31.92% not reported any infection. HC had no history of acute (3 months) or lasting chronic infections with viruses of bacteria.
TLR7 and TLR9 did not correlate between them. TLR9 levels were significantly higher in SLE patients than HC (P<0,001). Even though TLR7 levels did not show any difference between both groups, an association with the age of individuals was observed (P<0,001).
No association among TLR7 or TLR9 levels with CRP, ESR, anti-dsDNA, ENAs or antiphospholipid antibodies was observed, and nor with disease activity, age at diagnosis and disease evolution time. In contrast, however, we reported low TLR7 levels in SLE patients and antiphospholipid syndrome in comparison to those without antiphospholipid syndrome (P=0,001).
High TLR9 levels were significantly associated to increased levels of IL10 and INF1A in SLE patients (P<0,001). TLR7 levels were not associated with INF1A levels but it is noticeable that there is a tendency to increase TLR7 levels in cases with increase of IL10 levels.
Conclusions TLR9 is increased in SLE patients in comparison to HC. TLR7 increases with age. No evidence of association between previous infections and TLR levels was found. Nor do we observe any difference in TLR level according to autoantibodies presence or disease activity, probably due to the long-term SLE evolution and a good control of the disease. There was, however, an association between high TLR9 levels and increase of IL10 and INF1A.
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