Chelisa Cardinez, Australia
Australian National University Department of Immunology and Infectious DiseasePresenter of 1 Presentation
GAIN-OF-FUNCTION IKBKB MUTATION CAUSES HUMAN COMBINED IMMUNE DEFICIENCY
Abstract
Background and Aims
Elucidating the genetic basis of immune diseases allows for important diagnostic accuracy for affected individuals and often produces greater insights into human immunity. Here, we describe a new immune syndrome arising from a gain-of-function (GoF) mutation in IKBKB, which encodes IKK2 of the NF-kB signalling pathway. Through whole-exome sequencing, we identified identical IKBKB variants in two probands from geographically distinct kindreds.
Methods
To confirm causal effect of mutation, we generated a CRISPR/cas9-engineered mouse model bearing the orthologous mutation. Cellular and biochemical analysis, including flow cytometry and western blot, was conducted using peripheral blood mononuclear cells (PBMCs) from probands, cultured fibroblasts, cell lines, and the CRISPR/cas9 mice.
Results
We confirmed that the mutation conferred GoF in both patients and mutant mice by analysing NF-kB signalling, which showed enhanced and constitutive proliferation of IkB. Cellular analysis of mutant mice and probands revealed an abnormal immunophenotype, specifically reduced naïve T cells, heightened propensity to T cell activation, and increased regulatory T cells. It is noteworthy that despite evidence for increased T cell activation, there is no evidence so far for increased inflammation or autoimmunity. This may be due to the concurrent increase in Tregs. Therefore, further analysis will be conducted to characterise in detail immune regulation in GoF IKBKB.
Conclusions
Overall, the mouse model revealed combined cellular features of immunodeficiency and dysregulation, consistent with the proband’s immunophenotype. Our study has led to the discovery of a novel human immunodeficiency and supports the use of mouse models to confirm function of novel mutations in rare immunological diseases.