TLR7 Variants Enhance Responsiveness and Broaden RNA Specificity To Drive Human Lupus

Abstract Dysregulated nucleic acid sensing underlies lethal viral infections and autoimmunity. Endosomal Toll-like receptor 7 (TLR7) recognizes guanosine and oligoribonucleotides (ORNs) from single-stranded RNA via two ligand-binding sites in its leucine-rich repeat (LRR) ectodomain. Recent genetic studies have demonstrated that TLR7 gain-of-function (GOF) variants cause childhood lupus or immune thrombocytopenic purpura by enhancing TLR7 responses to canonical TLR7 ligands. However, no study has demonstrated that altered ligand specificity of TLR7 contributes to autoimmunity. Here, we provide direct evidence that relaxation of ligand specificity by TLR7 genetic variants causes lupus in both humans and mice. We describe a pediatric systemic lupus erythematosus (SLE) patient carrying a private GOF TLR7 missense variant, V825M (VarM), located within the C-terminal region of the LRR (LRR-CT). Knock-in mice harboring VarM allele spontaneously develop lupus-like systemic inflammation, including duodenitis, recapitulating the patient’s clinical features. Mechanistically, the VarM variant markedly amplifies NF-κB activation by synthetic small-molecule agonists and guanosine analogs. Notably, the VarM variant broadens the spectrum of ORN sequences that can engage the receptor. Moreover, certain pathogenic TLR7 variants located at the dimerization interface display functional properties closely resembling those of VarM. Collectively, our findings establish a new paradigm in which alterations in ligand recognition specificity by TLR7 genetic variations can trigger human autoimmune disease. Competing Interest Statement The authors have declared no competing interest. Funding Statement This work was supported by Grant-in-Aid for Transformative Research Areas (KaM, grant number 23H04765), Grant-in Aid for Scientific Research/KAKENHI (KaM, grant number 23K07875; TaS, grant number 16K08827/19H03451/25K02480) from Japan Society for Promotion of Science (JSPS), Medical Research Grant from Takeda Science Foundation (to KaM), Chiba University Futuristic Medical Fund (KaM), The Japan Agency for Medical Research and Development (AMED) (JP20ek0109385 to TaS), The Mochida Memorial Foundation for Medical and Pharmaceutical Research (to TaS), The Young Researcher Encouragement Grant by the Chemo-Sero Therapeutic Research Institute (to TaS), and the MUFJ-FG Vaccine Development Grant (to TaS). This work was also supported by the Japan Science and Technology Agency (Moonshot R&D) grant (HN, grant number JPMJMS2025), and the Agency for Medical Research and Development (AMED)-SCARDA (HN, grant number 223fa627003h0002). This research was partially supported by Initiative on Rare and Undiagnosed Diseases (grant number JP24ek0109760) from the Japan Agency for Medical Research and Development (ToO, ToI). Author Declarations I confirm all relevant ethical guidelines have been followed, and any necessary IRB and/or ethics committee approvals have been obtained. Yes The details of the IRB/oversight body that provided approval or exemption for the research described are given below: Chiba University Hospital IRB gave ethical approval for this work (HS202207-05). I confirm that all necessary patient/participant consent has been obtained and the appropriate institutional forms have been archived, and that any patient/participant/sample identifiers included were not known to anyone (e.g., hospital staff, patients or participants themselves) outside the research group so cannot be used to identify individuals. Yes I understand that all clinical trials and any other prospective interventional studies must be registered with an ICMJE-approved registry, such as ClinicalTrials.gov. I confirm that any such study reported in the manuscript has been registered and the trial registration ID is provided (note: if posting a prospective study registered retrospectively, please provide a statement in the trial ID field explaining why the study was not registered in advance). Yes I have followed all appropriate research reporting guidelines, such as any relevant EQUATOR Network research reporting checklist(s) and other pertinent material, if applicable. Yes Data Availability Supplementary Text is available from the corresponding author upon reasonable request.