Background/Purpose:

Systemic Lupus Erythematosus (SLE) is a systemic autoimmune disease characterized by periods of elevated and suppressed disease activity. Epstein Barr Virus (EBV) has been associated with SLE. EBV maintains latency in infected B cells and shows intermittent reactivation. Elevated concentrations of EBV Early Antigen (EA) IgG, a measure of viral reactivation, increase the probability of transitioning to SLE in unaffected family members, which underscores the importance of EBV reactivation in SLE autoimmune responses. Viral IL10 (vIL10), an EBV lytic protein, is a homolog of interleukin 10. Monocytes are one of the first cells to respond following infection and dysregulation of monocytes plays a dynamic role in the systemic autoimmune response in SLE. However, the effects of vIL-10 on monocyte function in the context of increased human or cellular IL10 (hIL10) have not been examined. In this study we examine whether vIL10 has similar inhibitory effects on monocytes as hIL10.

Methods: Plasma from 20 SLE patients (10 European American and 10 African American) with varying disease activity and 19 age, race and sex matched healthy unrelated controls were concentrated and vIL10 detected by western blotting. The band intensities were normalized to pooled sera from infectious mononucleosis patients. Plasma IL10 levels were measured by xMAP assays. Monocytes were enriched from peripheral blood mononuclear cells from healthy donors. STAT phosphorylation, cytokine secretion and expression of cell surface markers were determined by flow cytometry. Gene expression was by quantitative PCR.

Results: SLE patients had significantly higher levels of plasma vIL10 (8516±3291; 6509±1953, p=0.03), and significantly higher levels of hIL10. No correlation was observed between vIL10 and hIL10. To determine the functional consequences of increased vIL10 in the presence of high levels of endogenous cellular IL10, we performed in vitro stimulation of monocytes with hIL10 in the presence or absence of vIL10. As expected, hIL10 induced phosphorylated STAT3 (pSTAT3), which is required for anti-inflammatory gene expression induced by IL10, while vIL-10 induced significantly lower pSTAT3. The presence of vIL10 reduced hIL10 induced pSTAT3 in a dose dependent manner, suggesting that vIL10 can act as a competitive inhibitor of hIL10 activity. vIL10 increased pro-inflammatory gene expression, but was unable to downregulate IL10R1 gene expression. However, neutralizing antibody to IL10R1 reduced pSTAT3 and inhibited upregulation CD163 induced by both hIL10 and vIL10, suggesting that vIL10 signals through IL10R1. We did not see any significant differences between the frequency of cells positive for intracellular hIL10 in monocytes stimulated with hIL10 or vIL10.

Conclusion: Lupus patients have increased levels of plasma vIL-10, possibly due to increased EBV reactivation. vIL10 signals through IL10R1 and can suppress hIL10 induced STAT3 phosphorylation. Suppression of hIL10 induced anti-inflammatory genes by vIL10, together with an increase in inflammatory gene expression may overcome the anti-inflammatory effect of IL10 and exacerbate autoimmune responses in SLE.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/regulation-of-monocyte-function-by-epstein-barr-virus-interleukin-10-vil10-in-systemic-lupus-erythematosus/