Disruption of Immune Responses By Type I Diabetes Exacerbates SARS-CoV-2 Mediated Lung Injury

COVID-19 commonly presents as pneumonia, with those most severely affected progressing to respiratory failure. Patient responses to SARS-CoV-2 infection are varied, with comorbidities acting as major contributors to varied outcomes. Focusing on one such major comorbidity, we assessed whether pharmacological induction of Type I Diabetes Mellitus (T1DM) would increase the severity of lung injury in a murine model of COVID-19 pneumonia utilizing wild type mice infected with mouse-adapted SARS-CoV-2. Hyperglycemic mice exhibited increased weight loss and reduced blood oxygen saturation in comparison to their euglycemic counterparts, suggesting that these animals indeed experienced more severe lung injury. Transcriptomic analysis revealed a significant impairment of the adaptive immune response in the lungs of diabetic mice compared to those of control. In order to expand the limited options available for tissue analysis due to biosafety restrictions, we also employed a novel technique to digest highly fixed tissue into a single cell suspension, which allowed for flow cytometric analysis as well as single cell RNA sequencing. Flow immunophenotyping and scRNA-Seq confirmed impaired recruitment of T cells into the lungs of T1DM animals. Additionally, scRNA-Seq revealed a distinct, highly inflammatory macrophage profile in the diabetic cohort that correlates with the more severe infection these mice experienced clinically, allowing insight into a possible mechanism for this phenomenon. Recognizing the near certainty that respiratory viruses will continue to present significant public health concerns for the foreseeable future, our study provides key insights into how T1DM results in a much more severe infection and identifies possible targets to ameliorate comorbidity-associated severe disease.