PROJECT SUMMARY How external signals and stressors such as nutrition and diet act to regulate genetic diseases remains largely unknown. With millions globally at risk of under and over nutrition, understanding how nutritional stress impacts disease is of key importance. As early life diet is one of the first external inputs experienced both during gestation and after birth, it is poised to play a critical role in shaping lifelong disease phenotypes. Sickle cell disease (SCD), a genetic disease largely driven by one mutation shows significant variability in presentation and we hypothesize that diet and nutritional stress may contribute to this. The largest global burden of mortality in children under five, highlighting the importance of research on how early life exposures impact SCD severity. The immune system is a fundamental player in the pathogenesis of SCD where neutrophils promote inflammation and vaso-occlusion. Diet can regulate neutrophils, but it is unclear how early life exposures compare to those later in life. Using blood samples from patients with SCD, we propose to evaluate the correlation between diet, disease severity, and neutrophil activity. Using a mouse model of SCD, we will evaluate when and how dietary inputs modulate disease severity and the contribution of neutrophils to this process. As such, we seek to investigate the intersection of early life nutritional stress, neutrophils, and SCD with the intent to identify regulators of neutrophil function and production that may serve as novel targets for SCD therapy. In Aim 1, we investigate how early life nutritional stress impacts neutrophil development in the bone marrow and neutrophil function. Our preliminary data suggest that exposure to high fat diet (HFD) early in life expands neutrophils compared to later in life treatment. As such, we will assess neutrophil progenitors in the bone marrow in response to different nutritional stressors. By comparing early life exposure compared to later in life exposure, we will determine if there is a key window for setting lifelong neutrophil levels. We will also measure neutrophil function in response to early life nutritional stress. In Aim 2, we study how nutritional stress modulates neutrophil function in SCD by using a mouse model of SCD and blood samples from patients with SCD. We assess neutrophil function in SCD mice experiencing early life nutritional stress and determine effects on SCD severity. Subsequently, we will correlate neutrophil function in adults and children with SCD with patient characteristics such as BMI and diet along with SCD disease severity. Together, this proposal investigates the intersection of nutritional stress, neutrophils and SCD with the goal of uncovering novel targets for therapeutics in neutrophil-mediated diseases, such as SCD.