Browsing by Author "Fox-Robichaud, Alison E."

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    Development and characterization of a fecal-induced peritonitis model of murine sepsis: results from a multi-laboratory study and iterative modification of experimental conditions
    (2023-07-17) Sharma, Neha; Chwastek, Damian; Dwivedi, Dhruva J.; Schlechte, Jared; Yu, Ian-Ling; McDonald, Braedon; Arora, Jaskirat; Cani, Erblin; Eng, Mikaela; Engelberts, Doreen; Kuhar, Eva; Medeiros, Sarah K.; Bourque, Stephane L.; Cepinskas, Gediminas; Gill, Sean E.; Jahandideh, Forough; Macala, Kimberly F.; Panahi, Sareh; Pape, Cynthia; Sontag, David; Sunohara-Neilson, Janet; Fergusson, Dean A.; Fox-Robichaud, Alison E.; Liaw, Patricia C.; Lalu, Manoj M.; Mendelson, Asher A.
    Abstract Background Preclinical sepsis models have been criticized for their inability to recapitulate human sepsis and suffer from methodological shortcomings that limit external validity and reproducibility. The National Preclinical Sepsis Platform (NPSP) is a consortium of basic science researchers, veterinarians, and stakeholders in Canada undertaking standardized multi-laboratory sepsis research to increase the efficacy and efficiency of bench-to-bedside translation. In this study, we aimed to develop and characterize a 72-h fecal-induced peritonitis (FIP) model of murine sepsis conducted in two independent laboratories. The experimental protocol was optimized by sequentially modifying dose of fecal slurry and timing of antibiotics in an iterative fashion, and then repeating the experimental series at site 1 and site 2. Results Escalating doses of fecal slurry (0.5–2.5 mg/g) resulted in increased disease severity, as assessed by the modified Murine Sepsis Score (MSS). However, the MSS was poorly associated with progression to death during the experiments, and mice were found dead without elevated MSS scores. Administration of early antibiotics within 4 h of inoculation rescued the animals from sepsis compared with late administration of antibiotics after 12 h, as evidenced by 100% survival and reduced bacterial load in peritoneum and blood in the early antibiotic group. Site 1 and site 2 had statistically significant differences in mortality (60% vs 88%; p < 0.05) for the same dose of fecal slurry (0.75 mg/g) and marked differences in body temperature between groups. Conclusions We demonstrate a systematic approach to optimizing a 72-h FIP model of murine sepsis for use in multi-laboratory studies. Alterations to experimental conditions, such as dose of fecal slurry and timing of antibiotics, have clear impact on outcomes. Differences in mortality between sites despite rigorous standardization warrants further investigations to better understand inter-laboratory variation and methodological design in preclinical studies.
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    Impact of age on the host response to sepsis in a murine model of fecal-induced peritonitis
    (2024-03-08) Sharma, Neha; Chen, Alex; Heinen, Leah; Liu, Ruth; Dwivedi, Dhruva J.; Zhou, Ji; Lalu, Manoj M.; Mendelson, Asher A.; McDonald, Braedon; Kretz, Colin A.; Fox-Robichaud, Alison E.; Liaw, Patricia C.
    Abstract Introduction Despite older adults being more vulnerable to sepsis, most preclinical research on sepsis has been conducted using young animals. This results in decreased scientific validity since age is an independent predictor of poor outcome. In this study, we explored the impact of aging on the host response to sepsis using the fecal-induced peritonitis (FIP) model developed by the National Preclinical Sepsis Platform (NPSP). Methods C57BL/6 mice (3 or 12 months old) were injected intraperitoneally with rat fecal slurry (0.75 mg/g) or a control vehicle. To investigate the early stage of sepsis, mice were culled at 4 h, 8 h, or 12 h to investigate disease severity, immunothrombosis biomarkers, and organ injury. Mice received buprenorphine at 4 h post-FIP. A separate cohort of FIP mice were studied for 72 h (with buprenorphine given at 4 h, 12 h, and then every 12 h post-FIP and antibiotics/fluids starting at 12 h post-FIP). Organs were harvested, plasma levels of Interleukin (IL)-6, IL-10, monocyte chemoattract protein (MCP-1)/CCL2, thrombin-antithrombin (TAT) complexes, cell-free DNA (CFDNA), and ADAMTS13 activity were quantified, and bacterial loads were measured. Results In the 12 h time course study, aged FIP mice demonstrated increased inflammation and injury to the lungs compared to young FIP mice. In the 72 h study, aged FIP mice exhibited a higher mortality rate (89%) compared to young FIP mice (42%) (p < 0.001). Aged FIP non-survivors also exhibited a trend towards elevated IL-6, TAT, CFDNA, CCL2, and decreased IL-10, and impaired bacterial clearance compared to young FIP non-survivors. Conclusion To our knowledge, this is the first study to investigate the impact of age on survival using the FIP model of sepsis. Our model includes clinically-relevant supportive therapies and inclusion of both sexes. The higher mortality rate in aged mice may reflect increased inflammation and worsened organ injury in the early stage of sepsis. We also observed trends in impaired bacterial clearance, increase in IL-6, TAT, CFDNA, CCL2, and decreased IL-10 and ADAMTS13 activity in aged septic non-survivors compared to young septic non-survivors. Our aging model may help to increase the scientific validity of preclinical research and may be useful for identifying mechanisms of age-related susceptibility to sepsis as well as age-specific treatment strategies.
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    Understanding Brain Injury-Induced Immunosuppression and the Relationship to the Development of Infection
    (2018-06-05) Scott, Brittney Noelle Vivian; Kubes, Paul; Zygun, David A.; Kramer, Andreas H.; Ousman, Shalina S.; Schryvers, Anthony B.; Fox-Robichaud, Alison E.
    Infection is a leading cause of morbidity and mortality among hospitalized patients. It has become increasingly apparent that patients with neurological injury have an increased risk for infection due to secondary immunodeficiency. Previous work from our research group found a novel role for invariant natural killer (iNKT) cells in stroke-induced immune suppression, characterized by a shift from a Th1- to Th2-dominant systemic cytokine profile and an increased risk for infection. This work better defined the crosstalk that occurs between the brain and systemic immune system after ischemic stroke, however, many questions remained and whether similar mechanisms were involved in other types of brain injury was unclear. Thus, we evaluated the relationship between iNKT cells, Th1 and Th2 systemic cytokine profiles, and the development of infection among critically ill patients with traumatic brain injury and haemorrhagic stroke. We found that these patients had significantly subnormal levels of many immune mediators, including IFN-γ and TNF-α, indicative of systemic immune suppression. Moreover, iNKT cells were activated among these patients and positively associated with plasma Th2/Th1 cytokine ratios. Infection was common and occurred among forty-six percent of the patients. Additionally, we used animal models to investigate traumatic brain injury-induced immune modulation and its relationship to infection. We observed rapid activation of iNKT cells in the circulation and a >2-fold increase in plasma Th2/Th1 cytokine ratios, which peaked at 8 hours after injury. Remarkably, we also observed rapid changes in the lung microenvironment induced by traumatic brain injury, which influenced the outcome after infection. Moreover, in an attempt to better understand the epidemiology of infection among patients with traumatic brain injury, we conducted a systematic review of the world’s literature on this topic. We summarize and discuss the reported occurrence rates of infection, and the microbiology and risk factors associated with different types of infection, among patients hospitalized after traumatic brain injury. This thesis provides new insights into the relationship between brain injury and the development of infection. Understanding the unique risk for infection after acute brain injury will ultimately translate to better prevention and treatment regimens for these patients.