A cluster of type I interferon-regulated genes associates with disease activity and prognosis in patients with IgA nephropathy

The exact pathogenesis of IgA nephropathy (IgAN) is complex and so far, not well defined. Since it has been shown that microbial infections could induce high levels of type I interferon (IFN-I) and there is an evident link between mucosal infection and gross hematuria in IgAN, we hypothesized that IFN-I may play a role in the pathogenic process. In this study, we investigated the type I interferon status in IgAN based on the expression of 17 IFN-regulated genes (IRGs) in whole blood from 59 IgAN patients in a cross-sectional study, of which 34 patients followed longitudinally. Analysis of the IFN-score showed that there was a significant elevated IFN-score in the IgAN patients compared with healthy controls (n = 28, p = 9.80 × 10-3), and we observed an elevated IFN-score in the group with less tubular atrophy/interstitial fibrosis (p = 1.07 × 10-2) and with a lower proportion of mesangial hypercellularity (p = 1.23 × 10-2). In the longitudinal analysis, Cox regression analysis revealed that a higher IFN level was associated with a better renal outcome in IgAN after adjustments for gender and age (hazard ratio, 0.90; 95 % confidence interval, 0.81 to 0.97; p = 4.20 × 10-2). In conclusion, our finding suggested that IFN score may represent a novel type of biomarker in IgAN, which requires further exploration on its mechanism and therapeutic targeting.

A cluster of type II interferon-regulated genes associates with disease activity in patients with systemic lupus erythematosus

Upregulation of interferon-regulated genes (IRGs), denoted IFN signature, in peripheral blood has been used as an indirect measure of IFN pathway activation in patients with systemic lupus erythematosus (SLE). However, it has not been determined, which IFN signatures that optimally reflect clinical disease activity. In this study, we determined an IFN signature based on the expression of 128 IRGs in whole blood from 34 SLE patients in a cross-sectional (CS) study, 11 with active lupus nephritis followed longitudinally (LS) and 15 healthy controls. Blood samples were collected in PAXgene tubes and RNA was extracted and purified using a PAXgene blood RNA kit (Qiagen). Gene expression was measured using the NanoString nCounter Gene Expression platform. The CS SLE patients with higher disease activity displayed thrice as many upregulated IRGs (n = 46) as the rest. These IRGs clustered in three groups, consisting of IRGs known to be predominantly stimulated by type I (gene cluster K1) and type II (gene clusters K2 and 3) IFNs. SLEDAI-2K scores associated with the K2 and K3 gene scores (β = 0.372 and β = 0.419, both p < 0.015) but not with K1. In the longitudinal study, the mean SLEDAI-2K score decreased after an average follow-up of 360 days (β = -2.08, P = 5.09 × 10^-12). The mean K1, K2 and K3 gene scores did not change over time, however longitudinal changes in SLEDAI-2K and K3 scores were associated (β = 0.814, p = 0.007). This study validates the presence of type I IRG subsets that do not associate with disease activity in SLE patients. The novel finding in this study is the association between a type II IRG subset and disease activity. Both findings may have significant implications for choosing IRGs defining clinically relevant IFN signatures.