Testing the role of microbial infections in the development of auto-antibodies to type I interferons - PROJECT SUMMARY/ABSTRACT Type I interferons (IFN) are crucial to anti-viral immunity. Neutralizing autoantibodies (AAb) to IFN are found in the general population, increase in prevalence with age, and are linked to worse, often fatal, outcomes in some of the most lethal acute respiratory viral diseases known to date, including fulminant influenza and COVID-19 pneumonia. Despite this, the mechanisms behind the formation of IFN AAb remain unknown. Human data suggest that impairments in thymic tolerance—due to dysfunction of autoimmune regulator (AIRE) and medullary thymic epithelial cells (mTEC)—may be required for the development of IFN AAb. AIRE is a transcription factor expressed by mTEC that is essential for establishing T cell tolerance in the thymus. In mTEC, AIRE promotes the expression and presentation of antigens from extrathymic tissues to developing T cells (thymocytes). This allows for the elimination of auto-reactive thymocyte clones, thereby preventing autoimmunity. Interestingly, AIRE+ mTEC have been shown to express IFN at steady-state conditions in the thymus suggesting that, in this context, AIRE+ mTEC act as antigen-presenting cells to thymocytes to mediate T cell tolerance to IFN. Supporting this idea, individuals with Autoimmune Polyglandular Syndrome 1 (APS1), who lack AIRE and experience T cell tolerance loss, consistently develop IFN AAb. These AAb are isotype- switched and somatically hypermutated, supporting the notion that a failure of T cell tolerance, rather than solely B cell tolerance, is necessary for their generation. However, additional findings suggest that loss of thymic T cell tolerance alone is insufficient for IFN AAb to develop. First, APS1 patients do not typically present IFN AAb at birth or infancy; instead, they develop these AAb later in life after exposure to pathogens is likely to have occurred. Second, IFN AAb have not been observed in specific pathogen-free, Aire-deficient mice. Combined, these observations suggest that pathogen exposure, in addition to AIRE and mTEC dysfunction, may be required for IFN AAb to develop. This proposal aims to understand how infections, combined with AIRE deficiency, contribute to the loss of thymic tolerance to IFN. My central hypothesis is that in individuals with predisposing AIRE deficiency, infections that induce IFN expression act as a double hit, promoting the development of neutralizing IFN AAb. Until now, methods to detect neutralizing IFN AAb in mice have been lacking, which has hindered the field's ability to test this hypothesis. I have developed a novel, sensitive, reproducible, and high-throughput assay for detecting murine neutralizing IFN AAb. This new tool will serve as the basis for this proposal and will facilitate exploration of how microbial infections and thymic defects contribute to the development of IFN AAb in an animal model. The findings from this work will deepen our understanding of how tolerance to IFN is mediated and may inform strategies to prevent IFN AAb development in affected individuals.
