Background/Purpose: We previously identify a p.Arg90His (p.R90H) substitution encoded in phagocyte neutrophil cytosolic factor (NCF1) as a novel risk variant for SLE, with decreased and increasedNCF1copy numbers predisposing to and protecting against SLE, respectively. Our data highlights the pathogenic role of reduced reactive oxygen species (ROS) production in SLE. To study how reduced ROS promotes lupus, we established a C57BL/6 (B6) mouse model with a knock-in (KI) 90H mutation in Ncf1locus by CRISPR/Cas9 genome editing.

Methods: We compared 90H KI and wild-type (WT) R90 littermates for R90H genotypic effects on ROS production, type I interferon (IFN-I) signature and immune cell subsets in splenocytes, autoantibody production by ELISA and slide-based antigen array, renal IgG and C3 deposition and pathology. Pristane was injected intraperitoneally twice as an environmental trigger (0.1ml at 8wks and 0.5ml at 10wks), and lupus-like features were assessed at 30-36 wks.

Results: Compared with R90 WT littermates,untreated 5-week-old 90H KI mice exhibited reduced phorbol myristate acetate-induced extracellular ROS in splenocytes (n=5, p=0.03), splenomegaly (n=5, p=0.02),elevated IFN-I scores (p=0.047), as well as increased numbers of CD4⁺CXCR5⁺⁺PD-1⁺⁺follicular helper T cells (Tfh, p=0.045) and CD19⁺CD23^highCD21^intfollicular B cells (p=0.005). Because KI mice had no spontaneous kidney disease at one-year old, we used pristane injection to induce lupus. Compared with pristane-treated female WT mice (n=10), 30-36-week-old female KI littermates (n=8) developed lupus-like manifestations including splenomegaly (p=0.02), increased IgG anti-RNP (p=0.02) and total IgG (p=0.004) levels, glomerulonephritis with increased glomerular score (p=0.046), elevated renal deposition of IgG (p=0.005) and C3 (p=0.04). IgG autoantibody profiles confirmed elevated IgG anti-Sm, dsDNA and RNP in those female KI mice. Increased numbers of B220⁺IgD^lowCD95^highGL7^highgerminal center B cells (p=0.03) and CD4⁺CXCR5⁺⁺PD-1⁺⁺(p=0.04) or CD4⁺Bcl-6⁺(p=0.02) Tfh were found in 30-36-week-old pristane-treated KI mice.

Conclusion: A single nucleotide polymorphism p.Arg90His (p.R90H) in the Ncf1gene resulted in reduced oxidative burst, elevated IFN-I scores, splenomegaly, and increased cell numbers of Tfh and follicular B cells in 5-week-old 90H KI C57BL/6 mice. Pristane treatment caused increased IgG autoantibodies and kidney disease development in 30-36-week-old female 90H KI C57BL/6 mice. The disease development might be attributed to increased cell numbers of Tfh, facilitating germinal center formation and autoantibody production.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/a-human-sle-variant-ncf1-r90h-drives-lupus-like-kidney-disease-in-a-pristane-induced-murine-lupus-model/