LR-IL-22 for Mitigation and Management of Radiation Injuries

Abstract: Mitigation of damage caused by total body irradiation (TBI) or partial body irradiation (PBI) requires targeting the acute gastrointestinal syndrome. Parenteral administration of radiation mitigators for the hematopoietic syndrome may also ameliorate the gastrointestinal syndrome; however, drug delivery to the intestinal crypts is ineffective due to irradiation damage to the intestinal microvasculature. We have demonstrated that oral administration of engineered Lactobacillus reuteri, which produces and releases IL-22 (LR-IL-22), ameliorates the TBI induced acute gastrointestinal syndrome. Effective mitigation is associated with preservation of Lgr5+ intestinal crypt stem cells and their regeneration capacity. We will now establish the underlying mechanism of radiation mitigation by LR-IL-22, and will develop a microbial therapeutic with enhanced safety and efficacy. Preliminary data demonstrate that LR-IL-22 restores irradiation-induced suppression of gene transcription in Lgr5+ stem cells. TBI reduces expression of the aryl hydrocarbon receptor (AhR) in the intestine and its generation of downstream products, including IL-22. We hypothesize that TBI-induced intestinal damage will be further mitigated by combining LR-IL-22 with a probiotic (R2Ic) that naturally induces AhR to stimulate recovery of intrinsic IL-22 levels. Furthermore, we will establish that priming the release of IL-22 by our engineered probiotic increases therapeutic efficacy and the biological and environmental safety profiles. The First Specific Aim tests the hypothesis that LR-IL-22 restores radiation suppressed transcription at the molecular level in Lgr5+GFP+ intestinal stem cells. The Second Specific Aim tests the hypothesis that the activation of AhR in irradiation weakened cells by LR-IL-22 is further boosted by oral gavage of R2Ic to induce intrinsic IL-22 production. The Third Specific Aim addresses the need to provide biological and environmental containment of LR-IL-22, while improving the therapeutic efficacy. Successful completion of the proposed studies will lead to translation of LR-IL-22 to the National stockpile, as an effective mitigator of the acute radiation induced gastrointestinal syndrome.