Mechanism of Immune Dysfunction and Morbid Outcomes in Response to Shock/Sepsis

Project Summary/Abstract At last count, sepsis was reported to be the leading cause of death in U.S hospital intensive care units (ICU); accounting for ~1 in 5 deaths world-wide; its incidence is anticipated to rise as the populations in developed countries age; and it was the consensus cause of death assigned to those dying from COVID-19 infection. Most frustrating, is that while we continue to optimize the supportive care for these critically ill patients, we have yet to see a novel molecular etiology-based therapy make a sustained impact on overall septic morbidity/ mortality. Excitingly, while working for years on defining numerous defects of components of both adaptive and innate immune responsiveness induced by shock and/or sepsis, we have uncovered novel role(s) for a number of the B7-family of cell-associated co-inhibitory receptors, Programmed Cell Death Receptor-1 [PD-1], B-/T- Lymphocyte Attenuator [BTLA], recently, V-domain Immunoglobulin Suppressor of T cell Activation [VISTA, a.k.a., B7-H5, PD-1H] and their respective cell surface ligands; popularly referred to as checkpoint proteins. In this competitive renewal of our MIRA program, we propose to continue to push forward the 3 project areas we brought together previously under the over-arching concept that by understanding the mechanism(s) of injury/shock and/or sepsis that serve to predispose animals (experimentally) or critically ill/injured patients to develop morbid outcomes, we can elucidate not only novel prognostic markers of patient’s course, but uncover unique therapeutic targets for their treatment. In the 1st Project area we will determine how the select expression of PD-1, BTLA or VISTA, on myeloid as opposed to lymphoid cells alters the development of morbid events associated with sepsis; then, how the expression of ligands for these co-inhibitory molecules, on leukocytes and/or endothelial/epithelial cells, contribute to the onset of septic liver, intestine and/or kidney dysfunction. In our 2nd Project area, we will utilize a novel murine model of indirect-acute lung injury (iALI)(dual insults of hemorrhage shock followed by cecal ligation & puncture [CLP]) to ask how checkpoint protein expression not only effect the patho-mechanisms driving the development of iALI, but how are these co- inhibitors alter cell ‘priming’/’innate immune memory’/function by following pulmonary immune/non-immune cell transcriptomic/epigenomic fate/programing. Finally, (3rd Project) since the neonate possesses a unique/naïve immune system and is more susceptible to morbid response in the face of infectious challenge; we ask how the expression of members of the B-7 family of proteins and/or their ligands not only have a comparative impact on the response to septic insult, but how this alters their microbiota and epigenetic makeup/immune function as survivors mature? To do this we will interrogate these 3 cogent models of sepsis, shock/sepsis and/or neonatal sepsis, by applying a combination genetic/Cre-Lox mouse models, adoptive transfer, single cell RNA-seq/ATAC- seq, 16S microbiota RNA-seq and bisulfite/pyrosequencing to examine these questions/hypotheses along with select observational clinical studies in the critical ill patient population.