Novel point-of-care liquid biopsy for early detection of sepsis-associated organ damage - Sepsis, defined as a dysregulated immune response to infection leading to end-organ damage, is a critical problem that imposes considerable burdens on health care systems globally. However, despite its importance, sepsis is notoriously challenging to diagnose with precision, since neither infection nor organ dysfunction may be evident upon initial clinical assessment. Our overall objective in this application is to develop a novel circulating cellular biomarker for the early detection and assessment of sepsis-induced organ damage. Our team pioneered the “liquid biopsy” approach to cancer detection and monitoring, and we have recently extended this approach to systemic infection, detecting circulating lung epithelial cells in severe COVID-19, and cardiomyocytes in children with cardiac manifestations of multisystem inflammatory syndrome (MIS-C), providing proof of concept for extending our approach to infectious diseases. Our central hypothesis is that the detection of tissue-derived circulating rare cells (tCRCs, e.g. cells originating from the lungs, kidney, etc.) in the peripheral blood of sepsis patients will serve as a measurement of early organ/tissue damage to enable early diagnosis and monitoring of patients. The ability to noninvasively sample tissues affected by sepsis, COVID-19 and hyperinflammatory sequelae such as MIS-C, and ultimately other systemic infectious or inflammatory syndromes may both (1) clarify diagnosis of these syndromes that often lack specific diagnostic criteria or tests and (2) provide important insights into disease mechanisms, tropisms, and treatment response. To minimize one source of heterogeneity (anatomical source of infection) in this pilot study of a notoriously heterogeneous clinical syndrome, we will limit enrollment to sepsis of suspected pulmonary source. We propose two specific aims: In Aim 1, we propose to optimize a microfluidic enrichment and droplet- based digital PCR (ddPCR) assay to detect tCRCs first in spike-in samples, then in a series of 60 patients with pneumonia at risk for sepsis (n = 30 adjudicated to have sepsis, and 30 without). In Aim 2, we will identify tCRC transcriptional signatures for early detection of sepsis-induced organ damage via bulk (n = 60) and single-cell (n = 15) RNA-Seq. We will use patient enrollment criteria that we have successfully used in prior studies of sepsis. The proposed research is innovative because our approach has the potential to fill the significant gaps in (1) diagnosis and monitoring of disease progression and treatment response via non-invasive methods (i.e., liquid biopsy) with high sensitivity and specificity, and (2) early, non-invasive pathophysiological characterization of sepsis and potentially other inflammatory conditions. The project is significant because it has the potential to provide a blood-based cellular biomarker for a common and critical illness, via an approach that can potentially extend to other systemic diseases. Ultimately, building upon this pilot proposal, we anticipate in the longer term that this novel approach can offer a novel diagnostic tool to non-invasively sample end-organs affected by systemic infection, just as circulating tumor cell detection has revolutionized the detection of cancer metastasis.
