Background/Purpose: IFN-alpha is a pathogenic factor in SLE. High serum interferon activity (IFN-high) marks a subgroup of SLE patients strongly associated with double-stranded DNA (dsDNA) antibodies. However, the pathologic differences between IFN-high patients remain largely unknown. It is likely that IFN-high versus IFN-low patients will have differences in basic disease biology and will exhibit different responses to treatment. In this study, we sought to better characterize the IFN-high and IFN-low subgroups in human SLE by studying the stimulated cytokine responses post whole blood stimulation by Toll-like receptor (TLR) agonists.

Methods: SLE patients (n= 32) meeting ACR criteria for SLE and healthy controls (n=10) were recruited. Serum IFN-activity scores were calculated using the WISH assay and used to bin patients as IFN-high and IFN-low. Whole blood was dispensed into tubes coated with the TLR agonists LPS, CpG and R848 (Tru-Culture.) The stimulated IFN-alpha production was measured by WISH. Cytokine production in patient sera and after whole blood TLR stimulation was measured by bead-based multiplex assay.

Results: Of the 32 patients studied, 9 were IFN-high and 23 were IFN-low. Compared to IFN-low, IFN-high tended to be younger (27.3 versus 54.3 years), more associated elevated dsDNA titers (62.5% vs. 47.6%) and low C4 levels (62.5% vs. 13.0%). Usage of hydroxycholorquine and prednisone was similar between groups. Principal component analysis on cytokine levels in SLE patient sera identified distinct clusters according to serum IFN activity. IFN-high patients responded more dramatically to the TLR-4 agonist LPS than IFN-low (p<0.05), and controls (p=0.05). Post TLR-4 stimulation, IFN-high patients produced more CXCL9 (p=0.025), and less IL-12 (p=0.015) and VEGF (p=0.015) than IFN-low patients. In addition, post TLR-4 stimulation, VEGF and IL-1beta (p=0.0003) and VEGF/IL-12(p=0.002) were positively correlated in the IFN-high group, but not in the IFN-low group. In the IFN-low group, very different cytokine clusters emerged featuring IL-17, for example; IL-17/IL-4 (p<0.0001) and IL-17/IL-5 (p<0.0001).

Conclusion: We have observed clinical and novel biologic differences between IFN-high and low SLE subgroups. High-IFN SLE patients tend to be younger and more serologically active than their low-IFN counterparts. We demonstrate that IFN-high patients are significantly more responsive to TLR4 stimulation and produce a distinct inflammatory cytokine profile post TLR4 stimulation compared to IFN-low SLE. A recent study demonstrated that anti-dsDNA antibodies bind to TLR4 to activate the NLRP3 inflammasome in monocytes from SLE patients, and this interaction was associated with elevated IL1b and IL-17 secretion (Zhang et al. J Transl Med,2016, 14:156). Taken together with our preliminary findings, this suggests the novel possibility that the NLRP3 inflammasome is aberrantly or differentially activated in IFN-high compared to IFN-low SLE, and may offer novel insight into SLE pathogenesis and targeted treatment. Further studies directed at inflammasome activation in the context of IFN-high and IFN-low SLE are underway.

« Back to 2016 ACR/ARHP Annual Meeting

ACR Meeting Abstracts - https://acrabstracts.org/abstract/hyper-responsiveness-to-tlr-4-stimulation-in-sle-association-with-high-levels-of-serum-ifn-alpha-and-a-distinct-inflammatory-cytokine-profile/