Introduction: Sepsis is a leading cause of death in critically ill patients. Conventional methods of diagnostics in patients with suspected sepsis have limited sensitivity and long turnaround times. These factors contribute to indiscriminate use of broad-spectrum antibiotics and antimicrobial resistance. Our goal was to investigate where direct molecular analysis of circulating cell-free DNA in plasma could identify the microbial etiology of sepsis and improve assessment of prognosis. Methods: We conducted a prospective study of 30 consecutive patients suspected of sepsis in the Surgical Trauma ICU and compared with 22 healthy volunteer controls. Longitudinal plasma samples were collected at the time of workup for sepsis (day 0) and on days 7 and 14. Blood samples were collected in Streck Cell-Free DNA tubes and processed within 24 hours. DNA was extracted using QIAamp Circulating Nucleic Acid Kit. We measured mtDNA levels in plasma using real-time quantitative PCR targeting the mitochondrial NADH1 gene. Absolute mtDNA copies were calculated by comparing with known standards, pre-quantified using droplet digital PCR. Whole genome sequencing of cell-free DNA from plasma samples of three patients with positive blood cultures and 1 healthy volunteer control were performed to detect pathogen DNA. Results: We analyzed 72 serial plasma samples from 30 patients with suspected sepsis. Median mtDNA levels in controls were 602 ± 636 copies/µL of plasma (median ± IQR). In comparison, median mtDNA levels at day 0 in patients with SIRS were 3318 ± 1960 copies/µL (p<10⁻⁸, area under the ROC curve: 0.939). mtDNA levels were correlated with peripheral WBC count and respiratory rate (p=0.026 and 0.013 respectively) but not with temperature, heart rate or systolic BP. 3/30 patients died within the same hospital stay and last recorded mtDNA levels were higher as compared to survivors (p=0.028). Three out of thirty patients with a diagnosis of sepsis had positive blood cultures. Concordant results were found between conventional microbiology and next-generation sequencing of cell-free plasma DNA in 1 patient. Conclusions: Circulating mtDNA levels in patients with suspected sepsis are five-fold higher than healthy controls. Longitudinal changes in mtDNA are correlated with conventional markers of systemic inflammatory response and can be a biomarker for outcomes. Sequencing of cell-free DNA in plasma of sepsis patients can enable identification of bacteria and viral pathogens, although additional optimization of laboratory and informatics protocols is needed.

Introduction: Annually, an estimated 2.5 million traumatic brain injuries (TBI) occur in the United States, of which, over 50,000 result in deaths. Currently, 5.3 million Americans are living with neurological dysfunction secondary to TBIs leading to a $60 billion dollar cost in medical expenses and productivity losses. To date, there are limited treatments available to cure or ease the morbidity of TBI. Despite preventative efforts, traumatic brain injuries (TBI) occur at a staggering rate and it is estimated that 15-20% of survivors develop persistent post-traumatic neurological impairment. The purposed source of neurological dysfunction is a result of circuit reorganization when the brain rebuilds itself. After diffuse TBI, rodents have been shown to develop a late-onset, gain-of-function sensory sensitivity to whisker stimulation; similar to phonophobia and photophobia experienced by human TBI survivors. This morbidity coincides with evidence of post-TBI circuit reorganization, however the etiology of post-traumatic neurological impairment remains largely unknown. Thrombospondin-1 (TSP-1) and thrombospondin-2 (TSP-2) are heavily expressed during pediatric neuronal synapse development. Expression of TSPs, however declines with age. Mechanistically during development, TSP mediates synaptogenesis via bindingα2δ-1 subunit of the voltage-gated calcium channel receptor (α2δ-1). After neurological insult, re-expression of TSPs has been demonstrated and experimental modulation of the TSP/α2δ-1 interaction has led to changes in morbidity. We therefore hypothesize that experimental diffuse TBI will result in re-expression of TSPs, which will be synchronous with increases in synaptic markers in the thalamocortical whisker circuit. Methods: Adult male Sprague-Dawley rats underwent sham or moderate midline fluid percussion brain injury. At multiple time points over 2-months post-injury, expression of TSPs and synaptic markers were quantified from thalamocortical circuit (ventroposterior medial thalamus (VPM), primary somatosensory barrel fields (S1BF)) biopsies using qPCR and automated capillary westerns, respectively. Results: TSP-1 gene expression and protein levels increase in the VPM during the first week after injury. Gene expression of TSP-1 did not significantly change over time in the S1BF, however, there was a significant increase in protein levels in the first and second weeks after injury. No significant changes were demonstrated in synaptic markers in the VPM over the time course. TSP-1 protein levels demonstrated a similar multimodal response to synaptic markers in the S1BF.Conclusion: Re-expression of TSP-1 and synchronous changes in synaptic marker supports a role for TSP-1 mediated synaptogenesis after experimental diffuse TBI in the S1BF. These data positions us for future investigation of pharmacological inhibition of TSP-mediated synaptogenesis after TBI; which may represent a prophylactic strategy against circuit reorganization and neurological dysfunction after TBI.