LAUSR

IFN Scores are increasingly important as biomarkers to stratify RMDs and select patients for interferon targeted therapies. Several studies have previously demonstrated that different sets of interferon stimulated genes (ISGs) have different clinical associations. We validated a 2-score system of ISGs expression consisting of Score A (a set of ISGs included in most interferon signature assays) and Score B (a set of less commonly measured ISGs). Score B consistently demonstrated stronger clinical associations in studies of diagnosis, prediction of progression to SLE in At-Risk individuals, response to rituximab and imaging-proven synovitis. Previous literature suggested that subsets of ISGs were explained by different interferon subtypes.To understand the determinants of IFN Score A and IFN Score B.PBMCs and whole blood Tempus from 4 different healthy doners were stimulated with various cytokines and IFNs at 6- and 24-hour time points. RNA from both sample types were extracted and the expression of 26 interferon stimulated genes were measured using TaqMan and normalised to house-keeping gene PPIA. IFN Scores A and B were calculated as previously described [1]. To compare relative increase in expression with each condition, we calculated delta Ct fold change relative to non-stimulated. To represent greater expression as numerically higher positive values, relative expression was calculated as (fold change*-100) +100. Independent T-test calculated the significant differences between each condition compared to IFN α stimulation.Table 1 shows differences between each condition compared with IFN α at the 6-hour time point. In both sample types, all conditions excluding IFN β stimulation were shown to induce significantly lower expression of both scores compared to IFN α (p <0.01). At 6 and 24 hours, IFN α and IFN β showed a strong induction of IFN score A and B. At 6 hours, IFN γ, κ, and λ induced IFN score A and B but weaker than IFN α and β which was shown in both sample types. We did not observe a difference between the expression of these two scores according to interferon subtype. Other cytokines (TNF, IL-1 and IL-6) weakly induced expression of Score A and B. For IL-10 there was a possible discordant effect with increase in expression of Score B, but decreased expression of Score A, however these changes were small in magnitude.Table 1.ConditionIFN Score AIFN Score BMean relative expression vs. non-stimulatedP value(vs IFN α)Mean relative expression vs. non-stimulatedP value(vs IFN α)PBMCIFN α103.4-71.8-IFN β97.10.37364.70.352IFN γ37.5<0.00129.50.002IFN κ16.6<0.0013.1<0.001IFN λ24.8<0.00111.1<0.001IL-19.7<0.0014.4<0.001IL-64.5<0.0014.1<0.001IL-10-15.2<0.0018.0<0.001TNF α9.6<0.0011.2<0.001Whole BloodIFN α116.7-74.1-IFN β116.60.99773.20.894IFN κ23.00.0017.90.003IFN λ23.00.0017.6<0.001We found a difference in the induction of ISG expression between subtypes of Type I interferon, as well as other interferons and cytokines. However, the relative expression of IFN Score A and IFN Score B is not easily explained by the subtypes of interferon. We have also previously shown that these scores are both similarly expressed comparing different cell subsets. The explanation for the coordinated expression of these ISGs is therefore unclear and future work will explore the scores with a combination of conditions.[1]El-Sherbiny, Y.M., et al. Scientific Reports, 2018. 8(1): p. 5793.Zoe Wigston: None declared, Agata Burska: None declared, Miriam Wittmann Consultant of: Abbvie, Celgene, Janssen, L’Oreal, Novartis and Pfizer, Edward Vital Speakers bureau: Becton Dickinson and GSK, Consultant of: AstraZeneca, GSK, Roche/Genentech, and Sandoz, Grant/research support from: AstraZeneca, Roche/Genentech