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Bacterial infections are the primary cause of pathogenic sepsis. An uropathogenic E. coli (UPEC) model of monomicrobial sepsis represents a useful tool for interrogating the host immune response to this pathogen. Here, we present a protocol for inducing monomicrobial sepsis in mice using UPEC. We describe steps for preparing the bacteria, delivering UPEC into mice, and monitoring the mice post-infection. We then detail procedures for measuring cytokine response and detecting immune cell subsets using flow cytometry. For complete details on the use and execution of this protocol, please refer to Martin et al.1.

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Human sepsis is a complex disease that manifests with a diverse range of phenotypes and inherent variability among individuals, making it hard to develop a comprehensive animal model. Despite this difficulty, numerous models have been developed that capture many key aspects of human sepsis. The robustness of these models is vital for conducting pre-clinical studies to test and develop potential therapeutics. In this article, we describe four different models of murine sepsis that can be used to address different scientific questions relevant to the pathology and immune response during and after a septic event. Basic Protocol 1 details a non-synchronous cecal ligation and puncture (CLP) model of sepsis, where mice are subjected to polymicrobial exposure through surgery at different time points within 2 weeks. This variation in sepsis onset establishes each mouse at a different state of inflammation and cytokine levels that mimics the variability observed in humans when they present in the clinic. This model is ideal for studying the long-term impact of sepsis on the host. Basic Protocol 2 is also a type of polymicrobial sepsis, where injection of a specific amount of cecal slurry from a donor mouse into the peritoneum of recipient mice establishes immediate inflammation and sepsis without any need for surgery. Basic Protocol 3 describes infecting mice with a defined gram-positive or -negative bacterial strain to model a subset of sepsis observed in humans infected with a single pathogen. Basic Protocol 4 describes administering LPS to induce sterile endotoxemia. This form of sepsis is observed in humans exposed to bacterial toxins from the environment. © 2024 The Authors. Current Protocols published by Wiley Periodicals LLC. Basic Protocol 1: Non-synchronous cecal ligation and puncture Basic Protocol 2: Cecal slurry model of murine sepsis Basic Protocol 3: Monomicrobial model of murine sepsis Basic Protocol 4: LPS model of murine sepsis.

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The increasing use of nuclear energy sources inevitably raises the risk of accidental or deliberate radiation exposure and associated immune dysfunction. However, the extent to which radiation exposure impacts memory CD8 T cells, potent mediators of immunity to recurring intracellular infections and malignancies, remains understudied. Using P14 CD8 T cell chimeric mice (P14 chimeras) with an lymphocytic choriomeningitis virus (LCMV) infection model, we observed that sublethal (5Gy) whole-body irradiation (WBI) induced a rapid decline in the number of naive (TN) and P14 circulating memory CD8 T cells (TCIRCM), with the former being more susceptible to radiation-induced numeric loss. While TN cell numbers rapidly recovered, as previously described, the number of P14 TCIRCM cells remained low at least 9 mo after radiation exposure. Additionally, the remaining P14 TCIRCM in irradiated hosts exhibited an inefficient transition to a central memory (CD62L+) phenotype compared to nonirradiated P14 chimeras. WBI also resulted in long-lasting T cell intrinsic deficits in memory CD8 T cells, including diminished cytokine and chemokine production along with impaired secondary expansion upon cognate Ag reencounter. Irradiated P14 chimeras displayed significantly higher bacterial burden after challenge with Listeria monocytogenes expressing the LCMV GP33-41 epitope relative to nonirradiated controls, likely due to radiation-induced numerical and functional impairments. Taken together, our findings suggest that sublethal radiation exposure caused a long-term numerical, impaired differentiation, and functional dysregulation in preexisting TCIRCM, rendering previously protected hosts susceptible to reinfection.

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Currently approved inhibitors of the PD-1/PD-L1 pathway represent a major advance for the treatment of lung cancers, yet they are ineffective in a majority of patients due to lack of preexisting T-cell reactivity. Here, we show that a TLR9 agonist delivered by inhalation is able to prime T-cell responses against poorly immunogenic lung tumors and to complement the effects of PD-1 blockade. Inhaled TLR9 agonist causes profound remodeling in tumor-bearing lungs, leading to the formation of tertiary lymphoid structures adjacent to the tumors, CD8+ T-cell infiltration into the tumors, dendritic cell expansion, and antibody production. Inhalation of TLR9 agonist also increased the pool of functional PD-1lowT-bethigh effector CD8+ T cells in tumor-bearing lungs. Effector CD8+ T cells generated by inhaled TLR9 agonist treatment were licensed by PD-1 blockade to become highly functional CTLs, leading to a durable rejection of both lung tumors and tumor lesions outside the lungs. CD4+ T cells activated in response to inhaled TLR9 play a critical role in this process by controlling the proliferation, preventing exhaustion, and guiding the differentiation of optimally functional CTLs. This study characterizes a strategy to apply localized TLR9 stimulation to a tumor type not accessible for direct injection, a strategy that may expand the therapeutic potential of PD-1 blockade in non-small cell lung cancer.Significance: These findings demonstrate that local delivery of a toll-like receptor 9 agonist can change the immune content of an entire organ and enhance the efficacy of immune checkpoint inhibition.Graphical Abstract: http://cancerres.aacrjournals.org/content/canres/78/17/4943/F1.large.jpg Cancer Res; 78(17); 4943-56. ©2018 AACR.

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Microproteomic studies have improved our knowledge of cell biology. Yet, with mass spectrometry (MS) analysis, accuracy can be lost for protein identification and quantification when using heterogeneous samples. Laser capture microdissection (LCM) allows for the enrichment of specific subsets of cells to study their proteome; however, sample fixation is necessary. Unfortunately, fixation hampers MS results due to protein cross-linking. The aim of this study was to identify both a fixation protocol and an extraction method that returns the best yield of proteins for downstream MS analysis, while preserving cellular structures. We compared glutaraldehyde (GLU), a common fixative to preserve cells, to dithiobispropionimidate (DTBP), a cleavable cross-linker. Our DTBP fixation/extraction protocol greatly increased the protein recovery. In fact, while 1000 GLU fixed cells returned only 159 unique protein hits, from 1464 unique peptides of 1994 unique collected spectra, 1000 DTBP fixed cells resulted in 567 unique collected protein hits, from 7542 unique peptides, of 10,401 unique collected spectra. That is, a 3.57-fold increase in protein hits, 5.15-fold increase in unique peptides, and a 5.22-fold increase in unique collected spectra. Overall, the novel protocol introduced here allows for a very efficient protein recovery and good sample quality for MS after sample collection using LCM.

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