Clinical and functional characterization of a novel TNFRSF9 variant causing immune dysregulation with predisposition to EBV-driven lymphomagenesis
Peiwei Zhao, Kailan Chen, Li Yang, Chunhui Wan, Lei Zhang, Sukun Luo, Xuelian He
Abstract
Introduction The TNFRSF9 gene encodes the costimulatory receptor CD137, also known as 4-1BB, which plays a critical role in sustaining effective cytotoxic T-cell responses. Variants in the TNFRSF9 gene are associated with an extremely rare autosomal recessive primary immunodeficiency disorder characterized by recurrent sinopulmonary infections and EBV-induced lymphoproliferation. Methods We report a case siblings exhibiting EBV viremia, recurrent respiratory infections, and Burkitt lymphoma. Whole-exome sequencing (WES) was performed. Sanger sequencing was used to validate the variants. In vitro functional study was performed by western blot, flow cytometry assays and luciferase assays. Results Genetic analysis identified a novel missense variant in the TNFRSF9 gene (NM_001561.5: c.359G>C, p.C120S). Functional analysis in vitro demonstrated that this variant decreased the expression of TNFRSF9 both mRNA and protein levels. Western blot analysis revealed a significant decrease in phosphorylated-AKT. Luciferase assays showed that the p.C120S variant diminished the activity of the NF-κB pathway. Immunophenotyping of the patient’s peripheral blood revealed a significant reduction in CD27+ memory B cells, which are critical for long-term humoral immunity. Additionally, there was a notable decrease in IFN-γ secretion in CD8+ T cells, suggesting impaired cytotoxic T-cell function. These findings align with the clinical presentation of immunodeficiency and lymphoproliferation observed in the patients. We also reviewed 9 previously reported patients with homozygous or compound heterozygous TNFRSF9 variants. The clinical manifestations among these patients were highly heterogeneous, ranging from asymptomatic to malignancies. Discussion In summary, we identified a novel TNFRSF9 variant associated with immunodeficiency and lymphoproliferation, supported by functional evidence demonstrating its impact on gene expression, AKT and NF-κB signaling pathways, and immune cell function. Our findings expand the mutation spectrum of the TNFRSF9 gene and provide new insights into the molecular mechanisms underlying this rare immunodeficiency disorder.