Type 1 diabetes (T1D) is a multifactorial autoimmune disease with a strong genetic basis. However, evidence suggests a role for environmental factors such as viral infections in triggering disease onset. One viral infection that is highly correlated with T1D is the Coxsackievirus B (CVB) serotype. Sensing of CVB is mediated by the melanoma differentiation-associated protein 5 (MDA5), a cytosolic sensor of dsRNA, which is encoded by the IFIH1 gene. Stimulation of the MDA5 signaling pathway activates the transcription factors IRF3 and NFκB p65, which induce type I IFNs synthesis. Type I IFNs can signal in an autocrine manner through the JAK/STAT pathway to initiate an antiviral transcriptional program. Single nucleotide polymorphisms (SNP) in the IFIH1 gene such as rs1990760, which results in a non-synonymous mutation that changes alanine at position 946 to a threonine, is highly associated with increased risk for T1D. Studies in human PBMCs and mice have demonstrated that the A946T SNP results in an increased sensitivity to viral ligands and subsequently a stronger downstream IFN response. We hypothesize that cells overexpressing the type I diabetes-associated variant 946T will have enhanced downstream signaling and subsequent type I IFN secretion in response to viral ligands and CVB infection. To test this, we stably overexpressed MDA5 with the 946A or 946T variants in HeLa cells. We anticipate that signaling events downstream of CVB infection and synthetic ligand poly (I:C) treatment, such as levels of phosphorylated IRF3 and NFκB p65 will be increased in cells expressing the T1D-associated allele 946T in contrast to cells overexpressing the non-risk allele 946A. Corroborating the increase in IRF3 and NFκB p65 pathway activation, we expect to observe enhanced production and secretion of type I IFNs were measured using HEK Blue IFN reporter cells that may partly explain how CVB infections can trigger autoimmune diabetes.
J.P. Taylor: None. H.M. Tse: None.
National Institutes of Health
