Harnessing the Electrochemical Effects of Electroporation-Based Therapies to Enhance Anti-tumor Immune Responses

This study introduces a new method of targeting acidosis (low pH) within the tumor microenvironment (TME) through the use of cathodic electrochemical reactions (CER). Low pH is oncogenic by supporting immunosuppression. Electrochemical reactions create local pH effects when a current passes through an electrolytic substrate such as biological tissue. Electrolysis has been used with electroporation (destabilization of the lipid bilayer via an applied electric potential) to increase cell death areas. However, the regulated increase of pH through only the cathode electrode has been ignored as a possible method to alleviate TME acidosis, which could provide substantial immunotherapeutic benefits. Here, we show through ex vivo modeling that CERs can intentionally elevate pH to an anti-tumor level and that increased alkalinity promotes activation of naïve macrophages. This study shows the potential of CERs to improve acidity within the TME and that it has the potential to be paired with existing electric field-based cancer therapies or as a stand-alone therapy.

Investigating cell death responses associated with histotripsy ablation of canine osteosarcoma

BACKGROUND

Osteosarcoma (OS) is the most frequently occurring primary bone tumor in dogs and people and innovative treatment options are profoundly needed. Histotripsy is an emerging tumor ablation modality, and it is essential for the clinical translation of histotripsy to gain knowledge about the outcome of nonablated tumor cells that could remain postablation. The objective of this study was to characterize the cell death genetic signature and proliferation response of canine OS cells post a near complete histotripsy ablation (96% ± 1.5) and to evaluate genetic cell death signatures associated with histotripsy ablation and OS in vivo.

METHODS

In the current study, we ablated three canine OS cell lines with a histotripsy dose that resulted in near complete ablation to allow for a viable tumor cell population for downstream analyses. To assess the in vivo cell death genetic signature, we characterized cell death genetic signature in histotripsy-ablated canine OS tumors collected 24-h postablation.

RESULTS

Differential gene expression changes observed in the 4% viable D17 and D418 cells, and histotripsy-ablated OS tumor samples, but not in Abrams cells, were associated with immunogenic cell death (ICD). The 4% viable OS cells demonstrated significantly reduced proliferation, compared to control OS cells, in vitro.

CONCLUSION

Histotripsy ablation of OS cell lines leads to direct and potentially indirect cell death as evident by, reduced proliferation in remaining viable OS cells and cell death genetic signatures suggestive of ICD both in vitro and in vivo.

Cellular Context Dictates the Suppression or Augmentation of Triple-Negative Mammary Tumor Metastasis by NLRX1

Prior studies have defined multiple, but inconsistent, roles for the enigmatic pattern recognition receptor NLRX1 in regulating several cancer-associated biological functions. In this study, we explore the role of NLRX1 in the highly metastatic murine 4T1 mammary tumor model. We describe a functional dichotomy of NLRX1 between two different cellular contexts: expression in healthy host cells versus expression in the 4T1 tumor cells. Using Nlrx1-/- mice engrafted with 4T1 tumors, we demonstrate that NLRX1 functions as a tumor suppressor when expressed in the host cells. Specifically, NLRX1 in healthy host cells attenuates tumor growth and lung metastasis through suppressing characteristics of epithelial-mesenchymal transition and the lung metastatic niche. Conversely, we demonstrate that NLRX1 functions as a tumor promoter when expressed in 4T1 tumor cells using gain- and loss-of-function studies both in vitro and in vivo. Mechanistically, NLRX1 in the tumor cells augments 4T1 aggressiveness and metastasis through regulating epithelial-mesenchymal transition hallmarks, cell death, proliferation, migration, reactive oxygen species levels, and mitochondrial respiration. Collectively, we provide critical insight into NLRX1 function and establish a dichotomous role of NLRX1 in the 4T1 murine mammary carcinoma model that is dictated by cellular context.

Successful In Situ Targeting of Pancreatic Tumors in a Novel Orthotopic Porcine Model Using Histotripsy

OBJECTIVE

New therapeutic strategies and paradigms are direly needed to treat pancreatic cancer. The absence of a suitable pre-clinical animal model of pancreatic cancer is a major limitation to biomedical device and therapeutic development. Traditionally, pigs have proven to be ideal models, especially in the context of designing human-sized instruments, perfecting surgical techniques and optimizing clinical procedures for use in humans. However, pig studies have typically focused on healthy tissue assessments and are limited to general safety evaluations because of the inability to effectively model human tumors.

METHODS

Here, we establish an orthotopic porcine model of human pancreatic cancer using RAG2/IL2RG double-knockout immunocompromised pigs and treat the tumors ex vivo and in vivo with histotripsy.

RESULTS

Using these animals, we describe the successful engraftment of Panc-1 human pancreatic cancer cell line tumors and characterize their development. To illustrate the utility of these animals for therapeutic development, we determine for the first time, the successful targeting of in situ pancreatic tumors using histotripsy. Treatment with histotripsy resulted in partial ablation in vivo and reduction in collagen content in both in vivo tumor in pig pancreas and ex vivo patient tumor.

CONCLUSION

This study presents a first step toward establishing histotripsy as a non-invasive treatment method for pancreatic cancer and exposes some of the challenges of ultrasound guidance for histotripsy ablation in the pancreas. Simultaneously, we introduce a highly robust model of pancreatic cancer in a large mammal model that could be used to evaluate a variety biomedical devices and therapeutic strategies.

Ablative and Immunostimulatory Effects of Histotripsy Ablation in a Murine Osteosarcoma Model

Background: Osteosarcoma (OS) is the most frequently occurring malignant bone tumor in humans, primarily affecting children and adolescents. Significant advancements in treatment options for OS have not occurred in the last several decades, and the prognosis remains grim with only a 70% rate of 5-year survival. The objective of this study was to investigate the focused ultrasound technique of histotripsy as a novel, noninvasive treatment option for OS. Methods: We utilized a heterotopic OS murine model to establish the feasibility of ablating OS tumors with histotripsy in a preclinical setting. We investigated the local immune response within the tumor microenvironment (TME) via immune cell phenotyping and gene expression analysis. Findings: We established the feasibility of ablating heterotopic OS tumors with ablation characterized microscopically by loss of cellular architecture in targeted regions of tumors. We observed greater populations of macrophages and dendritic cells within treated tumors and the upregulation of immune activating genes 72 h after histotripsy ablation. Interpretation: This study was the first to investigate histotripsy ablation for OS in a preclinical murine model, with results suggesting local immunomodulation within the TME. Our results support the continued investigation of histotripsy as a novel noninvasive treatment option for OS patients to improve clinical outcomes and patient prognosis.

Negative regulatory NLRs mitigate inflammation via NF-κB pathway signaling in inflammatory bowel disease

A subset of Nucleotide-binding and leucine-rich repeat-containing receptors (NLRs) function to mitigate overzealous pro-inflammatory signaling produced by NF-κB activation. Under normal pathophysiologic conditions, proper signaling by these NLRs protect against potential autoimmune responses. These NLRs associate with several different proteins within both the canonical and noncanonical NF-κB signaling pathways to either prevent activation of the pathway or inhibit signal transduction. Inhibition of the NF-κB pathways ultimately dampens the production of pro-inflammatory cytokines and activation of other downstream pro-inflammatory signaling mechanisms. Dysregulation of these NLRs, including NLRC3, NLRX1, and NLRP12, have been reported in human inflammatory bowel disease (IBD) and colorectal cancer patients, suggesting the potential of these NLRs as biomarkers for disease detection. Mouse models deficient in these NLRs also have increased susceptibility to colitis and colitis-associated colorectal cancer. While current standard of care for IBD patients and FDA-approved therapeutics function to remedy symptoms associated with IBD and chronic inflammation, these negative regulatory NLRs have yet to be explored as potential drug targets. In this review, we describe a comprehensive overview of recent studies that have evaluated the role of NLRC3, NLRX1, and NLRP12 in IBD and colitis-associated colorectal cancer.

Expression profiling identifies key genes and biological functions associated with eosinophilic esophagitis in human patients

Introduction

Eosinophilic Esophagitis (EoE) is a chronic allergic disease characterized by progressive inflammation of the esophageal mucosa. This chronic inflammatory disorder affects up to 50 per 100,000 individuals in the United States and Europe yet is limited in treatment options. While the transcriptome of EoE has been reported, few studies have examined the genetics among a cohort including both adult and pediatric EoE populations. To identify potentially overlooked biomarkers in EoE esophageal biopsies that may be promising targets for diagnostic and therapeutic development.

Methods

We used microarray analysis to interrogate gene expression using esophageal biopsies from EoE and Control subjects with a wide age distribution. Analysis of differential gene expression (DEGs) and prediction of impaired pathways was compared using conventional transcriptome analysis (TAC) and artificial intelligence-based (ADVAITA) programs. Principal Components Analysis revealed samples cluster by disease status (EoE and Control) irrespective of clinical features like sex, age, and disease severity.

Results

Global transcriptomic analysis revealed differential expression of several genes previously reported in EoE (CCL26, CPA3, POSTN, CTSC, ANO1, CRISP3, SPINK7). In addition, we identified differential expression of several genes from the MUC and SPRR families, which have been limited in previous reports.

Discussion

Our findings suggest that there is epithelial dysregulation demonstrated by DEGs that may contribute to impaired barrier integrity and loss of epidermal cell differentiation in EoE patients. These findings present two new gene families, SPRR and MUC, that are differentially expressed in both adult and pediatric EoE patients, which presents an opportunity for a future therapeutic target that would be useful in a large demographic of patients.

NLRX1 functions as a tumor suppressor in Pan02 pancreatic cancer cells

Pancreatic cancer is a deadly malignancy with limited treatment options. NLRX1 is a unique, understudied member of the Nod-like Receptor (NLR) family of pattern recognition receptors that regulates a variety of biological processes that are highly relevant to pancreatic cancer. The role of NLRX1 in cancer remains highly enigmatic, with some studies defining its roles as a tumor promoter, while others characterize its contributions to tumor suppression. These seemingly contradicting roles appear to be due, at least in part, to cell type and temporal mechanisms. Here, we define roles for NLRX1 in regulating critical hallmarks of pancreatic cancer using both gain-of-function and loss-of-function studies in murine Pan02 cells. Our data reveals that NLRX1 increases susceptibility to cell death, while also suppressing proliferation, migration, and reactive oxygen species production. We also show that NLRX1 protects against upregulated mitochondrial activity and limits energy production in the Pan02 cells. Transcriptomics analysis revealed that the protective phenotypes associated with NLRX1 are correlated with attenuation of NF-κB, MAPK, AKT, and inflammasome signaling. Together, these data demonstrate that NLRX1 diminishes cancer-associated biological functions in pancreatic cancer cells and establishes a role for this unique NLR in tumor suppression.

Improved Therapeutic Delivery Targeting Clinically Relevant Orthotopic Human Pancreatic Tumors Engrafted in Immunocompromised Pigs Using Ultrasound-Induced Cavitation: A Pilot Study

Pancreatic tumors can be resistant to drug penetration due to high interstitial fluid pressure, dense stroma, and disarrayed vasculature. Ultrasound-induced cavitation is an emerging technology that may overcome many of these limitations. Low-intensity ultrasound, coupled with co-administered cavitation nuclei consisting of gas-stabilizing sub-micron scale SonoTran Particles, is effective at increasing therapeutic antibody delivery to xenograft flank tumors in mouse models. Here, we sought to evaluate the effectiveness of this approach in situ using a large animal model that mimics human pancreatic cancer patients. Immunocompromised pigs were surgically engrafted with human Panc-1 pancreatic ductal adenocarcinoma (PDAC) tumors in targeted regions of the pancreas. These tumors were found to recapitulate many features of human PDAC tumors. Animals were intravenously injected with the common cancer therapeutics Cetuximab, gemcitabine, and paclitaxel, followed by infusion with SonoTran Particles. Select tumors in each animal were targeted with focused ultrasound to induce cavitation. Cavitation increased the intra-tumor concentrations of Cetuximab, gemcitabine, and paclitaxel by 477%, 148%, and 193%, respectively, compared to tumors that were not targeted with ultrasound in the same animals. Together, these data show that ultrasound-mediated cavitation, when delivered in combination with gas-entrapping particles, improves therapeutic delivery in pancreatic tumors under clinically relevant conditions.

Humoral and T-cell-mediated responses to a pre-clinical Zika vaccine candidate that utilizes a unique insect-specific flavivirus platform

Vaccination is critical for the control and prevention of viral outbreaks, yet conventional vaccine platforms may involve trade-offs between immunogenicity and safety. Insect-specific viruses have emerged as a novel vaccine platform to overcome this challenge. Detailed studies of humoral and T-cell responses induced by new insect-specific flavivirus (ISFV)-based vaccine platforms are needed to better understand correlates of protection and improve vaccine efficacy. Previously, we used a novel ISFV called Aripo virus (ARPV) to create a Zika virus (ZIKV) vaccine candidate (designated ARPV/ZIKV). ARPV/ZIKV demonstrated exceptional safety and single-dose efficacy, completely protecting mice from a lethal ZIKV challenge. Here, we explore the development of immune responses induced by ARPV/ZIKV immunization and evaluate its correlates of protection. Passive transfer of ARPV/ZIKV-induced immune sera to naïve mice prior to challenge emphasized the importance of neutralizing antibodies as a correlate of protection. Depletion of T-cells in vaccinated mice and adoptive transfer of ARPV/ZIKV-primed T-cells to naïve mice prior to challenge indicated that ARPV/ZIKV-induced CD4 + and CD8 + T-cell responses contribute to the observed protection but may not be essential for protection during ZIKV challenge. However, vaccination of Rag1 KO, Tcra KO, and muMt - mice demonstrated the critical role for ARPV/ZIKV-induced T-cells in developing protective immune responses following vaccination. Overall, both humoral and T-cell-mediated responses induced by ISFV-based vaccines are important for comprehensive immunity, and ISFV platforms continue to be a promising method for future vaccine development.

Mechanical High-Intensity Focused Ultrasound (Histotripsy) in Dogs With Spontaneously Occurring Soft Tissue Sarcomas

INTRODUCTION

Histotripsy is a non-invasive focused ultrasound therapy that uses controlled acoustic cavitation to mechanically disintegrate tissue. To date, there are no reports investigating histotripsy for the treatment of soft tissue sarcoma (STS).

OBJECTIVE

This study aimed to investigate the in vivo feasibility of ablating STS with histotripsy and to characterize the impact of partial histotripsy ablation on the acute immunologic response in canine patients with spontaneous STS.

METHODS

A custom 500 kHz histotripsy system was used to treat ten dogs with naturally occurring STS. Four to six days after histotripsy, tumors were surgically resected. Safety was determined by monitoring vital signs during treatment and post-treatment physical examinations, routine lab work, and owners' reports. Ablation was characterized using radiologic and histopathologic analyses. Systemic immunological impact was evaluated by measuring changes in cytokine concentrations, and tumor microenvironment changes were evaluated by characterizing changes in infiltration with tumor-associated macrophages (TAMs) and tumor-infiltrating lymphocytes (TILs) using multiplex immunohistochemistry and differential gene expression.

RESULTS

Results showed histotripsy ablation was achievable and well-tolerated in all ten dogs. Immunological results showed histotripsy induced pro-inflammatory changes in the tumor microenvironment. Conclusion & Significance: Overall, this study demonstrates histotripsy's potential as a precise, non-invasive treatment for STS.

A hepatitis B virus core antigen-based virus-like particle vaccine expressing SARS-CoV-2 B and T cell epitopes induces epitope-specific humoral and cell-mediated immune responses but confers limited protection against SARS-CoV-2 infection

The hepatitis B virus core antigen (HBcAg) tolerates insertion of foreign epitopes and maintains its ability to self-assemble into virus-like particles (VLPs). We constructed a ∆HBcAg-based VLP vaccine expressing three predicted severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) B and T cell epitopes and determined its immunogenicity and protective efficacy. The recombinant ∆HBcAg-SARS-CoV-2 protein was expressed in Escherichia coli, purified, and shown to form VLPs. K18-hACE2 transgenic C57BL/6 mice were immunized intramuscularly with ∆HBcAg VLP control (n = 15) or ∆HBcAg-SARS-CoV-2 VLP vaccine (n = 15). One week after the 2nd booster and before virus challenge, five ∆HBcAg-SARS-CoV-2 vaccinated mice were euthanized to evaluate epitope-specific immune responses. There is a statistically significant increase in epitope-specific Immunoglobulin G (IgG) response, and statistically higher interleukin 6 (IL-6) and monocyte chemoattractant protein-1 (MCP-1) expression levels in ∆HBcAg-SARS-CoV-2 VLP-vaccinated mice compared to ∆HBcAg VLP controls. While not statistically significant, the ∆HBcAg-SARS-CoV-2 VLP mice had numerically more memory CD8+ T-cells, and 3/5 mice also had numerically higher levels of interferon gamma (IFN-γ) and tumor necrosis factor (TNF). After challenge with SARS-CoV-2, ∆HBcAg-SARS-CoV-2 immunized mice had numerically lower viral RNA loads in the lung, and slightly higher survival, but the differences are not statistically significant. These results indicate that the ∆HBcAg-SARS-CoV-2 VLP vaccine elicits epitope-specific humoral and cell-mediated immune responses but they were insufficient against SARS-CoV-2 infection.

Ultrasound-guided noninvasive pancreas ablation using histotripsy: feasibility study in an in vivo porcine model

Pancreatic cancer is a malignant disease associated with poor survival and nearly 80% present with unresectable tumors. Treatments such as chemotherapy and radiation therapy have shown overall improved survival benefits, albeit limited. Histotripsy is a noninvasive, non-ionizing, and non-thermal focused ultrasound ablation modality that has shown efficacy in treating hepatic tumors and other malignancies. In this novel study, we investigate histotripsy for noninvasive pancreas ablation in a pig model. In two studies, histotripsy was applied to the healthy pancreas in 11 pigs using a custom 32-element, 500 kHz histotripsy transducer attached to a clinical histotripsy system, with treatments guided by real-time ultrasound imaging. A pilot study was conducted in 3 fasted pigs with histotripsy applied at a pulse repetition frequency (PRF) of 500 Hz. Results showed no pancreas visualization on coaxial ultrasound imaging due to overlying intestinal gas, resulting in off-target injury and no pancreas damage. To minimize gas, a second group of pigs (n = 8) were fed a custard diet containing simethicone and bisacodyl. Pigs were euthanized immediately (n = 4) or survived for 1 week (n = 4) post-treatment. Damage to the pancreas and surrounding tissue was characterized using gross morphology, histological analysis, and CT imaging. Results showed histotripsy bubble clouds were generated inside pancreases that were visually maintained on coaxial ultrasound (n = 4), with 2 pigs exhibiting off-target damage. For chronic animals, results showed the treatments were well-tolerated with no complication signs or changes in blood markers. This study provides initial evidence suggesting histotripsy's potential for noninvasive pancreas ablation and warrants further evaluation in more comprehensive studies.

Magic bubbles: utilizing histotripsy to modulate the tumor microenvironment and improve systemic anti-tumor immune responses

Focused Ultrasound (FUS) is emerging as a promising primary and adjunct therapy for the treatment of cancer. This includes histotripsy, which is a noninvasive, non-ionizing, non-thermal ultrasound guided ablation modality. As histotripsy has progressed from bench-to-bedside, it has become evident that this therapy has benefits beyond local tumor ablation. Specifically, histotripsy has the potential to shift the local tumor microenvironment from immunologically 'cold' to 'hot'. This is associated with the production of damage associated molecular patterns, the release of a selection of proinflammatory mediators, and the induction of inflammatory forms of cell death in cells just outside of the treatment zone. In addition to the induction of this innate immune response, histotripsy can also improve engagement of the adaptive immune system and promote systemic anti-tumor immunity targeting distal tumors and metastatic lesions. These tantalizing observations suggest that, in settings of widely metastatic disease burden, selective histotripsy of a limited number of accessible tumors could be a means of maximizing responsiveness to systemic immunotherapy. More work is certainly needed to optimize treatment strategies that best synergize histotripsy parameters with innate and adaptive immune responses. Likewise, rigorous clinical studies are still necessary to verify the presence and repeatability of these phenomena in human patients. As this technology nears regulatory approval for clinical use, it is our expectation that the insights and immunomodulatory mechanisms summarized in this review will serve as directional guides for rational clinical studies to validate and optimize the potential immunotherapeutic role of histotripsy tumor ablation.

High intensity focused ultrasound for the treatment of solid tumors: a pilot study in canine cancer patients

PURPOSE

To investigate the safety, feasibility, and outcomes of High-Intensity Focused Ultrasound (HIFU) for the treatment of solid tumors in a spontaneous canine cancer model.

METHODS

Dogs diagnosed with subcutaneous solid tumors were recruited, staged and pretreatment biopsies were obtained. A single HIFU treatment was delivered to result in partial tumor ablation using a commercially available HIFU unit. Tumors were resected 3-6 days post HIFU and samples obtained for histopathology and immunohistochemistry. Total RNA was isolated from paired pre and post treated FFPE tumor samples, and quantitative gene expression analysis was performed using the nCounter Canine IO Panel.

RESULTS

A total of 20 dogs diagnosed with solid tumors were recruited and treated in the study. Tumors treated included Soft Tissue Sarcoma (n = 15), Mast Cell Tumor (n = 3), Osteosarcoma (n = 1), and Thyroid Carcinoma (n = 1). HIFU was well tolerated with only 1 dog experiencing a clinically significant adverse event. Pathology confirmed the presence of complete tissue ablation at the HIFU targeted site and immunohistochemistry indicated immune cell infiltration at the treated/untreated tumor border. Quantitative gene expression analysis indicated that 28 genes associated with T-cell activation were differentially expressed post-HIFU.

CONCLUSIONS

HIFU appears to be safe and feasible for the treatment of subcutaneous canine solid tumors, resulting in ablation of the targeted tissue. HIFU induced immunostimulatory changes, highlighting the canine cancer patient as an attractive model for studying the effects of focal ablation therapies on the tumor microenvironment.

High-Frequency Irreversible Electroporation (H-FIRE) Induced Blood-Brain Barrier Disruption Is Mediated by Cytoskeletal Remodeling and Changes in Tight Junction Protein Regulation

Glioblastoma is the deadliest malignant brain tumor. Its location behind the blood-brain barrier (BBB) presents a therapeutic challenge by preventing effective delivery of most chemotherapeutics. H-FIRE is a novel tumor ablation method that transiently disrupts the BBB through currently unknown mechanisms. We hypothesized that H-FIRE mediated BBB disruption (BBBD) occurs via cytoskeletal remodeling and alterations in tight junction (TJ) protein regulation. Intracranial H-FIRE was delivered to Fischer rats prior to sacrifice at 1-, 24-, 48-, 72-, and 96 h post-treatment. Cytoskeletal proteins and native and ubiquitinated TJ proteins (TJP) were evaluated using immunoprecipitation, Western blotting, and gene-expression arrays on treated and sham control brain lysates. Cytoskeletal and TJ protein expression were further evaluated with immunofluorescent microscopy. A decrease in the F/G-actin ratio, decreased TJP concentrations, and increased ubiquitination of TJP were observed 1-48 h post-H-FIRE compared to sham controls. By 72-96 h, cytoskeletal and TJP expression recovered to pretreatment levels, temporally corresponding with increased claudin-5 and zonula occludens-1 gene expression. Ingenuity pathway analysis revealed significant dysregulation of claudin genes, centered around claudin-6 in H-FIRE treated rats. In conclusion, H-FIRE is capable of permeating the BBB in a spatiotemporal manner via cytoskeletal-mediated TJP modulation. This minimally invasive technology presents with applications for localized and long-lived enhanced intracranial drug delivery.

Detecting DNA: An Overview of DNA Recognition by Inflammasomes and Protection against Bacterial Respiratory Infections

The innate immune system plays a key role in modulating host immune defense during bacterial disease. Upon sensing pathogen-associated molecular patterns (PAMPs), the multi-protein complex known as the inflammasome serves a protective role against bacteria burden through facilitating pathogen clearance and bacteria lysis. This can occur through two mechanisms: (1) the cleavage of pro-inflammatory cytokines IL-1β/IL-18 and (2) the initiation of inflammatory cell death termed pyroptosis. In recent literature, AIM2-like Receptor (ALR) and Nod-like Receptor (NLR) inflammasome activation has been implicated in host protection following recognition of bacterial DNA. Here, we review current literature synthesizing mechanisms of DNA recognition by inflammasomes during bacterial respiratory disease. This process can occur through direct sensing of DNA or indirectly by sensing pathogen-associated intracellular changes. Additionally, DNA recognition may be assisted through inflammasome–inflammasome interactions, specifically non-canonical inflammasome activation of NLRP3, and crosstalk with the interferon-inducible DNA sensors Stimulator of Interferon Genes (STING) and Z-DNA Binding Protein-1 (ZBP1). Ultimately, bacterial DNA sensing by inflammasomes is highly protective during respiratory disease, emphasizing the importance of inflammasome involvement in the respiratory tract.

NLRX1 Deficiency Alters the Gut Microbiome and Is Further Exacerbated by Adherence to a Gluten-Free Diet

Patients with gluten sensitivities present with dysbiosis of the gut microbiome that is further exacerbated by a strict adherence to a gluten-free diet (GFD). A subtype of patients genetically susceptible to gluten sensitivities are Celiac Disease (CeD) patients, who are carriers of the HLA DR3/DQ2 or HLA DR4/DQ8 haplotypes. Although 85-95% of all CeD patients carry HLA DQ2, up to 25-50% of the world population carry this haplotype with only a minority developing CeD. This suggests that CeD and other gluten sensitivities are mediated by factors beyond genetics. The contribution of innate immune system signaling has been generally understudied in the context of gluten sensitivities. Thus, here we examined the role of NOD-like receptors (NLRs), a subtype of pattern recognition receptors, in maintaining the composition of the gut microbiome in animals maintained on a GFD. Human transcriptomics data revealed significant increases in the gene expression of multiple NLR family members, across functional groups, in patients with active CeD compared to control specimens. However, NLRX1 was uniquely down-regulated during active disease. NLRX1 is a negative regulatory NLR that functions to suppress inflammatory signaling and has been postulate to prevent inflammation-induced dysbiosis. Using Nlrx1^-/- mice maintained on either a normal or gluten-free diet, we show that loss of NLRX1 alters the microbiome composition, and a distinctive shift further ensues following adherence to a GFD, including a reciprocal loss of beneficial microbes and increase in opportunistic bacterial populations. Finally, we evaluated the functional impact of an altered gut microbiome by assessing short- and medium-chain fatty acid production. These studies revealed significant differences in a selection of metabolic markers that when paired with 16S rRNA sequencing data could reflect an overall imbalance and loss of immune system homeostasis in the gastrointestinal system.

Cold sensor, hot topic: TRPM8 plays a role in monocyte function and differentiation

Understanding the innate immune system and how aberrant activation or impaired inhibition leads to the development of hyperinflammatory conditions, including inflammatory bowel disease, is crucial for patient management and treatment. An emerging area of interest surrounding dysregulated inflammation focuses on membrane bound transient receptor potential (TRP) ion channels. These channels are permeable to calcium and other cations involved in the balance of leukocyte membrane potential and function, as well as afferent neuron signaling within the myenteric plexus of the GI tract, bladder, and skin. A particular channel, TRPM8, is an important cell surface marker for prostate cancer and participates in the function of cold sensing neurons. Specifically, this ion‐gated receptor is shown to be activated by agonists such as menthol and eucalyptus, which aid in the soothing, cooling effects of these agents. Furthermore, the TRPM8 channel is also identified on the surface of resident tissue Mϕs and is also linked to the protective role and release of calcitonin gene‐related peptide (CGRP) by sensory neurons.

The Goldilocks Conundrum: The protective and adverse roles of immunoregulation by NOD-like receptors (NLRs) during brucellosis

Brucellosis (Brucella spp.) is a bacterial zoonotic disease characterized by immune evasion. By hiding inside of macrophage vacuoles, Brucella often persist in hosts and instigate lifelong chronic inflammatory conditions. Despite mechanisms to combat host immune defense, NOD-like (NLR) pattern recognition receptors play an important role in immunoregulation during brucellosis. We have previously demonstrated that formation of pro-inflammatory NLRs into the multi-protein complex termed the inflammasome plays a protective role against brucellosis, resulting from the initiation of inflammatory cell death following recognition of Brucella genomic (g)DNA. Despite this investigation, the role of anti-inflammatory NLRs such as NLRX1 during brucellosis has not been determined. Here, we infected wildtype (WT) and Nlrx1−/− mice with Brucella abortus to evaluate the effect of an anti-inflammatory NLR during brucellosis. We found that WT mice displayed a stronger phenotypic presentation of infection, exhibiting increased splenomegaly, as well as elevated bacterial load and WBC infiltration in the liver when compared with knockout mice. This indicates that NLRX1 may exacerbate brucellosis presentation in vivo. Through further in vitro studies infecting murine WT and Nlrx1−/− macrophages, we found that NLRX1 attenuated inflammation, particularly in response to Brucella gDNA, and led to increased bacterial load in WT macrophages. Ultimately, these results indicate that NLRX1 may play an adverse role during brucellosis through reducing inflammation. This study further emphasizes the multifaceted role of NLRs during brucellosis and “Goldilocks Conundrum” in establishing immune system homeostasis in NLR-mediated diseases.

Supported by the Virginia-Maryland College of Veterinary Medicine (VT/UMD Joint Seed Grant; DVM/PhD Student Support) and the NIH/NIAID (R03AI151494)

Supported by the Virginia-Maryland College of Veterinary Medicine (VT/UMD Joint Seed Grant; DVM/PhD Student Support) and the NIH/NIAID (R03AI151494)

Chemokine CXCL10’s role in the immune response to SARS-CoV-2

Since the beginning of the SARS-CoV-2 pandemic in early 2020, it was apparent that one of the most striking clinical features of the disease caused by the virus, COVID-19, was the lung damage that occurs. This lung damage is often the result of an immune response gone awry as the host attempts to clear the virus. This overactive immune response, the ‘cytokine storm,’ is responsible for much of the most severe cases of COVID-19 as well as the Multisystem Inflammatory Syndrome in pediatric patients. Since the start of the pandemic, a few key players have been identified in the progression of COVID-19 disease as well as the immune response to it. These include pro-inflammatory cytokines IL-6, TNF-alpha, and CXCL10. Many clinical reports have especially shown the importance of the chemokine CXCL10 as a prognostic biomarker with patients having higher levels of CXCL10 often having more severe outcomes. Recent studies have also shown an increase in CXCL10 and its associated pathways in animal models of COVID-19. Here we continue to provide evidence for the importance of the protein CXCL10 in SARS-CoV-2 immunity through whole genome transcriptomics studies in human and k18-hACE2 mice. Following these, further studies with a mouse-adapted SARS-CoV-2 virus and Cxcl10−/− mice also showed a decreased level of effectiveness in viral clearance in the absence of effective CXCL10. These data continue to show the importance of the chemokine CXCL10 in both disease severity and viral clearance of SARS-CoV-2 infection adding to the growing body of evidence related to SARS-CoV-2 pathobiology.

“X”ploring the multifaceted functions of NLRX1 in triple-negative breast cancer

Breast cancer is a devastatingly common and deadly malignancy, and despite improved survival resulting from improved detection and treatment, triple-negative breast cancer (TNBC) remains difficult to treat. While historically studied in the context of infectious diseases, a multifaceted anti-inflammatory pattern recognition receptor called NLRX1 has recently been investigated in several types of cancers due to its involvement in several pathways significant to tumorigenesis and disease progression. This project seeks to define the role of NLRX1 in TNBC. To achieve this, we generated novel Nlrx1−/−(KO) mice compatible with the widely-used 4T1 murine model of TNBC. We also generated 4T1 cells that either overexpress or knockdown NLRX1, as well as their respective controls (4T1OE, 4T1OE-CTL, 4T1KD, 4T1KD-CTL). KO and wild-type (WT) mice were then injected with unaltered 4T1 cells or one of the four altered 4T1 cell lines. We then quantified tumor growth, final tumor volume, and lung metastasis as a measure of disease burden. This in vivo work demonstrated that NLRX1 is protective against disease burden when expressed in healthy host tissues but is problematic when overexpressed by 4T1 cells. Ex vivo and in vitro experiments then revealed a pro-migratory phenotype in 4T1OE cells, likely as the result of altered TGF-β signaling and/or the PI3K-Akt-mTOR pathway as a means to impact epithelial-mesenchymal transition. Combined, we believe the function of NLRX1 in TNBC depends on the cell in which it is expressed (i.e. healthy vs cancerous), and that this function may ultimately be a result of altered epithelial-mesenchymal transition pathways.

Alginate microencapsulation of an attenuated O-antigen mutant of Francisella tularensis LVS as a model for a vaccine delivery vehicle

Francisella tularensis is the etiologic agent of tularemia and a Tier I Select Agent. Subspecies tularensis (Type A) is the most virulent of the four subspecies and inhalation of as few as 10 cells can cause severe disease in humans. Due to its niche as a facultative intracellular pathogen, a successful tularemia vaccine must induce a robust cellular immune response, which is best achieved by a live, attenuated strain. F. tularensis strains lacking lipopolysaccharide (LPS) O-antigen are highly attenuated, but do not persist in the host long enough to induce protective immunity. Increasing the persistence of an O-antigen mutant may help stimulate protective immunity. Alginate encapsulation is frequently used with probiotics to increase persistence of bacteria within the gastrointestinal system, and was used to encapsulate the highly attenuated LVS O-antigen mutant WbtI_G191V. Encapsulation with alginate followed by a poly-L-lysine/alginate coating increased survival of WbtI_G191V in complement-active serum. In addition, BALB/c mice immunized intraperitoneally with encapsulated WbtI_G191V combined with purified LPS survived longer than mock-immunized mice following intranasal challenge. Alginate encapsulation of the bacteria also increased antibody titers compared to non-encapsulated bacteria. These data suggest that alginate encapsulation provides a slow-release vehicle for bacterial deposits, as evidenced by the increased antibody titer and increased persistence in serum compared to freely suspended cells. Survival of mice against high-dose intranasal challenge with the LVS wildtype was similar between mice immunized within alginate capsules or with LVS, possibly due to the low number of animals used, but bacterial loads in the liver and spleen were the lowest in mice immunized with WbtI_G191V and LPS in beads. However, an analysis of the immune response of surviving mice indicated that those vaccinated with the alginate vehicle upregulated cell-mediated immune pathways to a lesser extent than LVS-vaccinated mice. In summary, this vehicle, as formulated, may be more effective for pathogens that require predominately antibody-mediated immunity.

Histotripsy for the Treatment of Cholangiocarcinoma in a Patient-Derived Xenograft Mouse Model

Histotripsy is a focused ultrasound ablation therapy being developed for the treatment of liver tumors. A recent study investigating the feasibility of using histotripsy for the ablation of cholangiocarcinoma (CC), bile duct cancer that is difficult to treat with current therapies because of its location near critical structures and fibrous tissue, reported the feasibility of treating CC in an acute mouse model. Here, we investigate histotripsy for the in vivo ablation of CC in a chronic study using a 1-MHz transducer at an applied dose of 500 pulses/point. A pilot study determined that treating the CC tumors plus a 1- to 2-mm margin induced significant injuries to intestinal tissues, thus precluding the use of this strategy. Next, histotripsy was applied to CCs (n = 6) with the treatment contained to the tumor. Post-treatment, the ablation was visualized using ultrasound, and subjects were monitored over time. Histotripsy achieved an average of 73% reduction of tumor diameter 26 d after treatment, with no significant adverse events. Notably, three of six treated tumors were undetectable after 2.5 wk. The treated animals were found to have significantly increased tumor progression-free and overall survival. Overall, results indicate that histotripsy can be used as a safe and effective method for treating CC.

Experimental and Numerical Investigation of Parameters Affecting High-frequency Irreversible Electroporation for Prostate Cancer Ablation

While the primary goal of focal therapy for prostate cancer (PCa) is conserving patient quality of life by reducing oncological burden, available modalities use thermal energy or whole-gland radiation which can damage critical neurovascular structures within the prostate and increase risk of genitourinary dysfunction. High-frequency irreversible electroporation (H-FIRE) is a promising alternative ablation modality that utilizes bursts of pulsed electric fields (PEFs) to destroy aberrant cells via targeted membrane damage. Due to its non-thermal mechanism, H-FIRE offers several advantages over state-of-the-art treatments, but waveforms have not been optimized for treatment of PCa. In this study, we characterize lethal electric field thresholds (EFTs) for H-FIRE waveforms with three different pulse widths as well as three interpulse delays in vitro and compare them to conventional IRE. Experiments were performed in non-neoplastic and malignant prostate cells to determine the effect of waveforms on both targeted (malignant) and adjacent (non-neoplastic) tissue. A numerical modeling approach was developed to estimate the clinical effects of each waveform including extent of non-thermal ablation, undesired thermal damage, and nerve excitation. Our findings indicate that H-FIRE waveforms with pulse durations of 5 and 10 µs provide large ablations comparable to IRE with tolerable levels of thermal damage and minimized muscle contractions. Lower duration (2 µs) H-FIRE waveforms exhibit the least amount of muscle contractions but require increased voltages which may be accompanied by unwanted thermal damage.

Employing Novel Porcine Models of Subcutaneous Pancreatic Cancer to Evaluate Oncological Therapies

Immunocompromised mice are commonly utilized to study pancreatic cancer and other malignancies. The ability to xenograft tumors in either subcutaneous or orthotopic locations provides a robust model to study diverse biological features of human malignancies. However, there is a dire need for large animal models that better recapitulate human anatomy in terms of size and physiology. These models will be critical for biomedical device development, surgical optimization, and drug discovery. Here, we describe the generation and application of immunocompromised pigs lacking RAG2 and IL2RG as a novel model for human xenograft studies. These SCID-like pigs closely resemble NOD scid gamma mice and are receptive to human tumor tissue, cell lines, and organoid xenografts. However, due to their immunocompromised nature, these immunocompromised animals require housing and maintenance under germfree conditions. In this protocol, we describe the use of these pigs in a subcutaneous tumor injection study with human PANC1 cells. The tumors demonstrate a steady, linear growth curve, reaching 1.0 cm within 30 days post injection. The model described here is focused on subcutaneous injections behind the ear. However, it is readily adaptable for other locations and additional human cell types.

Histotripsy Ablation of Bone Tumors: Feasibility Study in Excised Canine Osteosarcoma Tumors

Osteosarcoma (OS) is a primary bone tumor affecting both dogs and humans. Histotripsy is a non-thermal, non-invasive focused ultrasound method using controlled acoustic cavitation to mechanically disintegrate tissue. In this study, we investigated the feasibility of treating primary OS tumors with histotripsy using a 500-kHz transducer on excised canine OS samples harvested after surgery at the Veterinary Teaching Hospital at Virginia Tech. Samples were embedded in gelatin tissue phantoms and treated with the 500-kHz histotripsy system using one- or two-cycle pulses at a pulse repetition frequency of 250 Hz and a dosage of 4000 pulses/point. Separate experiments also assessed histotripsy effects on normal canine bone and nerve using the same pulsing parameters. After treatment, histopathological evaluation of the samples was completed. To determine the feasibility of treating OS through intact skin/soft tissue, additional histotripsy experiments assessed OS with overlying tissues. Generation of bubble clouds was achieved at the focus in all tumor samples at peak negative pressures of 26.2 ± 4.5 MPa. Histopathology revealed effective cell ablation in treated areas for OS tumors, with no evidence of cell death or tissue damage in normal tissues. Treatment through tissue/skin resulted in generation of well-confined bubble clouds and ablation zones inside OS tumors. Results illustrate the feasibility of treating OS tumors with histotripsy.

Properties of tissue within prostate tumors and treatment planning implications for ablation therapies

Irreversible electroporation (IRE) is a promising alternative therapy for the local treatment of prostate tumors. The procedure involves the direct insertion of needle electrodes into the target zone, and subsequent delivery of short but high-voltage pulses. Successful outcomes rely on adequate exposure of the tumor to a threshold electrical field. To aid in predicting this exposure, computational models have been developed, yet often do not incorporate the appropriate tissue-specific properties. This work aims to quantify electrical conductivity behavior during IRE for three types of tissue present in the target area of a prostate cancer ablation: the tumor tissue itself, the surrounding healthy tissue, and potential areas of necrosis within the tumor. Animal tissues were used as a stand-in for primary samples. The patient-derived prostate tumor tissue showed very similar responses to healthy porcine prostate tissue. An examination of necrotic tissue inside the tumors revealed a large difference, however, and a computational model showed that a necrotic core with differing electrical properties can cause unexpected inhomogeneities within the treatment region.

Enemy of My Enemy: A Novel Insect-Specific Flavivirus Offers a Promising Platform for a Zika Virus Vaccine

Vaccination remains critical for viral disease outbreak prevention and control, but conventional vaccine development typically involves trade-offs between safety and immunogenicity. We used a recently discovered insect-specific flavivirus as a vector in order to develop an exceptionally safe, flavivirus vaccine candidate with single-dose efficacy. To evaluate the safety and efficacy of this platform, we created a chimeric Zika virus (ZIKV) vaccine candidate, designated Aripo/Zika virus (ARPV/ZIKV). ZIKV has caused immense economic and public health impacts throughout the Americas and remains a significant public health threat. ARPV/ZIKV vaccination showed exceptional safety due to ARPV/ZIKV’s inherent vertebrate host-restriction. ARPV/ZIKV showed no evidence of replication or translation in vitro and showed no hematological, histological or pathogenic effects in vivo. A single-dose immunization with ARPV/ZIKV induced rapid and robust neutralizing antibody and cellular responses, which offered complete protection against ZIKV-induced morbidity, mortality and in utero transmission in immune-competent and -compromised murine models. Splenocytes derived from vaccinated mice demonstrated significant CD4⁺ and CD8⁺ responses and significant cytokine production post-antigen exposure. Altogether, our results further support that chimeric insect-specific flaviviruses are a promising strategy to restrict flavivirus emergence via vaccine development.

Generation of Tumor-activated T cells using electroporation

Expansion of cytotoxic T lymphocytes (CTLs) is a crucial step in almost all cancer immunotherapeutic methods. Current techniques for expansion of tumor-reactive CTLs present major limitations. This study introduces a novel method to effectively produce and expand tumor-activated CTLs using high-voltage pulsed electric fields. We hypothesize that utilizing high-voltage pulsed electric fields may be an ideal method to activate and expand CTLs due to their non-thermal celldeath mechanism. Tumor cells were subjected to high-frequency irreversible electroporation (HFIRE) with various electric field magnitudes (1250, 2500 V/cm) and pulse widths (1, 5, and 10 µs), or irreversible electroporation (IRE) at 1250 V/cm. The treated tumor cells were subsequently cocultured with CD4+ and CD8+ T cells along with antigen-presenting cells. We show that tumor-activated CTLs can be produced and expanded when exposed to treated tumor cells. Our results suggest that CTLs are more effectively expanded when pulsed with HFIRE conditions that induce significant cell death (longer pulse widths and higher voltages). Activated CD8+ T cells demonstrate cytotoxicity to untreated tumor cells suggesting effector function of the activated CTLs. The activated CTLs produced with our technique could be used for clinical applications with the goal of targeting and eliminating the tumor.

Isolation of a novel insect-specific flavivirus with immunomodulatory effects in vertebrate systems

We describe the isolation and characterization of a novel insect-specific flavivirus (ISFV), tentatively named Aripo virus (ARPV), that was isolated from Psorophora albipes mosquitoes collected in Trinidad. The ARPV genome was determined and phylogenetic analyses showed that it is a dual host associated ISFV, and clusters with the main mosquito-borne flaviviruses. ARPV antigen was significantly cross-reactive with Japanese encephalitis virus serogroup antisera, with significant cross-reactivity to Ilheus and West Nile virus (WNV). Results suggest that ARPV replication is limited to mosquitoes, as it did not replicate in the sandfly, culicoides or vertebrate cell lines tested. We also demonstrated that ARPV is endocytosed into vertebrate cells and is highly immunomodulatory, producing a robust innate immune response despite its inability to replicate in vertebrate systems. We show that prior infection or coinfection with ARPV limits WNV-induced disease in mouse models, likely the result of a robust ARPV-induced type I interferon response.

Noncanonical NF-κB Signaling Upregulation in Inflammatory Bowel Disease Patients is Associated With Loss of Response to Anti-TNF Agents

Objectives: Targeting tumor necrosis factor (TNF) with biologic agents, such as infliximab and adalimumab, is a widely used and effective therapeutic strategy in inflammatory bowel disease (IBD). Unfortunately, a significant number of patients fail to respond or lose response over time to these agents. Previous studies have defined multiple complex roles for canonical NF-κB signaling in the pathogenesis of IBD. However, preliminary evidence suggests that the lesser defined noncanonical NF-κB signaling pathway also contributes to disease pathogenesis and response to anti-TNF agents. The objective of this study was to evaluate this hypothesis in Crohn’s disease (CD) and ulcerative colitis (UC) patients.

Design: A total of 27 subjects with IBD (19 with CD and 8 with UC) and 15 control subjects were tested. Clinical criteria, patient history, and endoscopic disease activity were factors used to categorize patients and define therapeutic response. Biopsy specimens were collected during colonoscopy and expression was determined for 88 target genes known to be associated with noncanonical NF-κB signaling and IBD.

Results: Noncanonical NF-κB signaling was significantly upregulated in IBD patients and was associated with increased gastrointestinal inflammation, epithelial cell death, lymphocyte migration, and Nod-like receptor signaling. Furthermore, noncanonical NF-κB signaling was further upregulated in patients unresponsive to anti-TNF agents and was suppressed in responsive patients. MAP3K14, NFKB2, CCL19, CXCL12, and CXCL13 were significantly dysregulated, as were genes that encode pathway regulators, such as CYLD, NLRP12, and BIRC2/3.

Conclusion: Our study identifies a previously uncharacterized role for the understudied noncanonical NF-κB signaling pathway in the pathogenesis of IBD and anti-TNF therapy responsiveness. The genes and pathways identified may ultimately prove useful in IBD management and could potentially be used as biomarkers of drug response.

Focused ultrasound tumour ablation in small animal oncology

The cancer incidence rates for humans and animals remain high, and efforts to improve cancer treatment are crucial. Cancer treatment for solid tumours includes both treatment of the primary tumour and of metastasis. Surgery is commonly employed to resect primary and metastatic tumours, but is invasive, and is not always the optimal treatment modality. Prevention and treatment of metastatic disease often utilizes a multimodal approach, but metastasis remains a major cause of death for both human and veterinary cancer patients. Focused ultrasound (FUS) tumour ablation techniques represent a novel non-invasive approach to treating cancer. FUS ablation is precise, thus sparing adjacent critical structures while ablating the tumour. FUS ablation can occur in a thermal or non-thermal fashion. Thermal FUS ablation, also known as high intensity focused ultrasound (HIFU) ablation, destroys tumour cells via heat, whereas non-thermal FUS, known as histotripsy, ablates tumour cells via mechanical disintegration of tissue. Not only can HIFU and histotripsy ablate tumours, they also demonstrate potential to upregulate the host immune system towards an anti-tumour response. The aim of this report is provide a description of HIFU and histotripsy tumour ablation, with a focus on the basic principles of their ablation mechanisms and their clinical applicability in the field of veterinary oncology.

Irreversible electroporation stimulates a pro-inflammatory tumor microenvironment that facilitate antigen presentation in pancreatic cancer

Pancreatic cancer is now the third leading cause of cancer-related death and is projected to turn out to be the second by 2030. Pancreatic cancer is often late-diagnosed with few treatment options with extremely low survival rates. Surgical candidacy is only 15% of total diagnosed patients. Irreversible electroporation (IRE), a novel form of tumor non-thermal ablation applies high-voltage microsecond pulses to permeabilize the cell membrane that is irreversible and leads to apoptotic cell death. IRE has had strong success in clinical trials for pancreatic cancer patients. Nevertheless, little is known on the effect of IRE beyond the initiation of cell death in the tumor tissue. We hypothesize that IRE can induce a pro-inflammatory type of cell death in pancreatic cancer that can promote inflammation and anti-tumor immune system responses. We have used in vitro, ex vivo, and immunocompetent in vivo murine models to investigate alterations to pancreatic cancer and its microenvironment. Our findings reveal programmed necrotic cell death, promotion of pro-inflammatory cytokine production, and shifts in immune cell populations from a pro-tumor (such as MDSCs and T regulatory cells) to a proinflammatory types containing cytotoxic lymphocytes and neutrophils after IRE treatment. Progression-free survival was significantly longer for the treated mice. Intriguingly, IRE treatment increases IFNγ signaling and generates viable antigens for presentation to the adaptive immune system but also promotes PD-L1 expression which in turn causes immunological stalemate. Our results suggest possible therapeutic targets for use in combination with IRE, such as gemcitabine or PD-1/PD-L1 inhibitors, to improve patient survival.

Non-Thermal Histotripsy Ablation of Osteosarcoma Causes a Local Acute Immune Response

While surgery, chemotherapy, and radiotherapy are available as treatments for osteosarcoma, there is only a 60% 5 year overall survival rate. To address this need, novel therapies are being developed and investigated. Histotripsy is a non-invasive, non-thermal focused-ultrasound ablation therapy that uses acoustic cavitation to mechanically lyse targeted cells. Recent evidence suggests that it is immunomodulatory, and can shift the tumor microenvironment to being more pro-inflammatory. However, given histotripsy’s mechanical mechanism, it is not established to be able to treat stronger tissues such as osteosarcomas at a dose that will allow for the preservation of immune stimulating molecules. In this study, mice with subcutaneous osteosarcoma DLM8 tumors were treated with histotripsy and acute changes to the local tumor immune response were analyzed 72 hours later. Using partial ablation to avoid off-target damage, a 40% average reduction in tumor size was achieved with targeted tissues being fully ablated. Through rtPCR, the levels of various cytokines associated with wound healing were significantly increased in the treated tumors following histotripsy treatment, with the greatest fold change observed in the concentrations for IL-6 and IL-13 over a given period of time. An increase in fold change for CD274, also known as PD-L1, was also observed, implicating the potential to pair histotripsy with checkpoint inhibitors for osteosarcoma therapy. The overall results of the study suggest that histotripsy is able to shift the tumor microenvironment following partial-ablation treatment. Thus, upon activation of the immune system, wound and tissue repair mechanisms are subsequently activated and responses are regulated.

The contradictory functions of NLRX1 in breast cancer allow for suppression or promotion of tumor growth and metastasis in a cell-specific manner

Breast cancer is a deadly malignancy that is responsible for 15% of all cancer-related deaths in women. Examining the innate immune system in breast cancer has revealed the importance of pattern recognition receptors, such as NLRX1, in disease progression. NLRX1 has been implicated as a tumor suppressor because it suppresses inflammation by many mechanisms, including by inhibiting the NF-κB pathway. Here, we investigated the potential of NLRX1 as a tumor suppressor in breast cancer when it is expressed either by healthy host cells or cancer cells. To determine the role of NLRX1 in healthy host cells, we used the 4T1 breast cancer model in WT and Nlrx1−/− (KO) mice. KO mice exhibited increased lung metastasis and tumor size compared to WT mice. Gene expression data revealed increased expression of proliferation, survival, growth, invasion, and metastatic genes in tumors from KO mice compared to WT mice. Thus, NLRX1 in healthy host cells is protective against breast cancer tumor growth and metastasis. Next, we investigated the role of NLRX1 in breast cancer cells. 4T1 cells were transduced to overexpress NLRX1 and injected into WT (WTOE) and KO(KOOE) mice. Transduction controls were also generated and injected into WT (WTOE-CTL) and KO (KOOE-CTL) mice. KOOE mice developed larger tumors than KOOE-CTL mice. KOOE mice also developed more lung metastasis compared to WTOE, WTOE-CTL, and KOOE-CTL mice. This suggests NLRX1 in breast cancer cells contributes to tumor growth and metastasis, which directly contradicts the function of NLRX1 in healthy host cells and demonstrates a cell-specific function of NLRX1 in breast cancer. These cell-specific differences are critical foundations for the development of NLR-based breast cancer therapies.

Novel Mechanisms of Innate Immune System Regulation Following SARS-CoV-2 Exposure

The SARS-CoV-2 pandemic has wreaked havoc on our public health system and economy. The outcome of SARS-CoV-2 infection is determined by host-virus interactions and anti-viral immune responses. A delicate balance must be struck between mounting a vigorous immune response to eradicate the virus and quelling overactive inflammation to protect the host. Indeed, overzealous inflammation is associated with the “cytokine storm” reported in an alarming number of COVID-19 patients and underlies the Multisystem Inflammatory Syndrome reported in pediatric cases. Initial studies have suggested that SARS-CoV-2 is capable of inhibiting type-I interferon signaling, hijacking cell death processes, and inducing robust pro-inflammatory cytokine production in patients with poor outcomes. Here, we confirm many of these previous findings using whole genome transcriptomics approaches in human patients and complementary mechanistic studies using SARS-CoV-2 infection in K18-hACE2 mice. Using these approaches, we further identify 12 critical cytokines that appear to be associated with the overzealous immune response in COVID-19 patients. Further studies and pathway analysis identified members of the NBD-LRR (NLR) family of pattern recognition receptors that regulate distinct mechanisms underlying overzealous inflammation. Together, these data provide insight into novel mechanisms of immune system regulation that appear responsible for modulating several aspects of SARS-CoV-2 pathobiology.

Till cell death do us part: The protective role of inflammasome-mediated pyroptosis and genomic DNA recognition during brucellosis

Brucellosis, a zoonotic disease instigated by the bacteria Brucella, results in chronic inflammatory symptoms. Despite mechanisms utilized by Brucella for immune evasion, some pattern recognition receptors, specifically NOD-like receptors (NLRs), sense Brucella pathogen-associated molecular patterns (PAMPS) and form a multi-protein complex termed the inflammasome. The inflammasome attenuates Brucella pathogenesis through caspase-1 (canonical) or caspase-11 (non-canonical) mediated cleavage of pro-inflammatory cytokines IL-18 & IL-1β. It can also activate inflammatory cell death known as pyroptosis, a mechanism rarely implicated with canonical inflammasome activation in brucellosis. Here, we evaluated in vivo canonical (Asc−/−) and non-canonical (Caspase-11−/−) inflammasome mouse models infected with Brucella abortus and determined that wildtype mice displayed increased survival and recruitment of WBCs with decreased bacteria load in comparison with Asc−/− mice. This indicates that the canonical inflammasome plays a necessary, defensive role against Brucella. Conducting in vitro B. abortus infections in Asc−/− macrophages, we further determined this protective mechanism of canonical inflammasome activation results from the activation of pyroptosis. We also found that the Brucella PAMP genomic (g)DNA instigated a high inflammatory response in wildtype macrophages that was suppressed in Asc−/− and amplified in anti-inflammatory NLR knockouts. This suggests that NLR activation occurs through sensing gDNA and may involve mechanisms of interaction among NLRs. Ultimately, these results suggest a greater importance and continued exploration of pyroptosis and the recognition of gDNA during brucellosis.

Histotripsy ablation stimulates the innate immune system and modulates anti-tumor immunity in pancreatic cancer

With an overall 5-year survival rate of less than 9%, pancreatic cancer is a substantial cause of cancer related death in the United States. This high mortality has been associated with the immunosuppressive tumor microenvironment (TME) and the shortage of effective late-stage therapeutic options. Histotripsy is a non-thermal, non-ionizing, non-invasive cancer ablation modality that rapidly lyses targeted cells. To investigate how histotripsy can change the pancreatic TME, a Pan02 cell culture model of pancreatic adenocarcinoma was employed to determine the neoantigen release following histotripsy treatment and other standard ablation modalities. Histotripsy was found to release potential neoantigens at a level similar to other non-thermal ablations and superior to thermal ablation, which paralleled the increased innate immune system activation in vivo. For in vivo studies, subcutaneous Pan02 tumors in mice were treated with histotripsy. To monitor changes in the TME after treatment, rtPCR and flow cytometry were used and compared to untreated animals. Progression-free and overall survival were significantly improved with histotripsy treatment. Within 24 hours of treatment there was increased activation of the innate immune system and by 14 days there were decreased tumor-associated immune cell populations. This work illustrates the feasibility of using histotripsy to treat pancreatic cancer and shift the TME as well as providing mechanistic understanding into the activation of the innate immune system post-treatment. Future studies are needed to establish the mechanism of immunomodulation of the TME and the extent of potential systemic effects.

Targeted Delivery of Persulfides to the Gut: Effects on the Microbiome

Persulfides (R-SSH) have been hypothesized as potent redox modulators and signaling compounds. Reported herein is the synthesis, characterization, and in vivo evaluation of a persulfide donor that releases N-acetyl cysteine persulfide (NAC-SSH) in response to the prokaryote-specific enzyme nitroreductase. The donor, termed NDP-NAC, decomposed in response to E. coli nitroreductase, resulting in release of NAC-SSH. NDP-NAC elicited gastroprotective effects in mice that were not observed in animals treated with control compounds incapable of persulfide release or in animals treated with Na2 S. NDP-NAC induced these effects by the upregulation of beneficial small- and medium-chain fatty acids and through increasing growth of Turicibacter sanguinis, a beneficial gut bacterium. It also decreased the populations of Synergistales bacteria, opportunistic pathogens implicated in gastrointestinal infections. This study reveals the possibility of maintaining gut health or treating microbiome-related diseases by the targeted delivery of reactive sulfur species.

Multi-Tissue Analysis on the Impact of Electroporation on Electrical and Thermal Properties

OBJECTIVE

Tissue electroporation is achieved by applying a series of electric pulses to destabilize cell membranes within the target tissue. The treatment volume is dictated by the electric field distribution, which depends on the pulse parameters and tissue type and can be readily predicted using numerical methods. These models require the relevant tissue properties to be known beforehand. This study aims to quantify electrical and thermal properties for three different tissue types relevant to current clinical electroporation.

METHODS

Pancreatic, brain, and liver tissue were harvested from pigs, then treated with IRE pulses in a parallel-plate configuration. Resulting current and temperature readings were used to calculate the conductivity and its temperature dependence for each tissue type. Finally, a computational model was constructed to examine the impact of differences between tissue types.

RESULTS

Baseline conductivity values (mean 0.11, 0.14, and 0.12 S/m) and temperature coefficients of conductivity (mean 2.0, 2.3, and 1.2 % per degree Celsius) were calculated for pancreas, brain, and liver, respectively. The accompanying computational models suggest field distribution and thermal damage volumes are dependent on tissue type.

CONCLUSION

The three tissue types show similar electrical and thermal responses to IRE, though brain tissue exhibits the greatest differences. The results also show that tissue type plays a role in the expected ablation and thermal damage volumes.

SIGNIFICANCE

The conductivity and its changes due to heating are expected to have a marked impact on the ablation volume. Incorporating these tissue properties aids in the prediction and optimization of electroporation-based therapies.

Cardiovascular function, pulmonary gas exchange and tissue oxygenation in isoflurane-anesthetized, mechanically ventilated Beagle dogs with four levels of positive end-expiratory pressure

OBJECTIVES

To compare pulmonary gas exchange, tissue oxygenation and cardiovascular effects of four levels of end-expiratory pressure: no positive end-expiratory pressure (ZEEP), positive end-expiratory pressure (PEEP) of maximal respiratory system compliance (PEEPmaxC_rs), PEEPmaxC_rs + 2 cmH₂O (PEEPmaxC_rs+2), PEEPmaxC_rs + 4 cmH₂O (PEEPmaxC_rs+4), in isoflurane-anesthetized dogs.

STUDY DESIGN

Prospective randomized crossover study.

ANIMALS

A total of seven healthy male Beagle dogs, aged 1 year and weighing 10.2 ± 0.7 kg (mean ± standard deviation).

METHODS

The dogs were administered acepromazine and anesthesia was induced with propofol and maintained with isoflurane. Ventilation was controlled for 4 hours with ZEEP, PEEPmaxC_rs, PEEPmaxC_rs+2 or PEEPmaxC_rs+4. Cardiovascular, pulmonary gas exchange and tissue oxygenation data were evaluated at 5, 60, 120, 180 and 240 minutes of ventilation and compared using a mixed-model anova followed by Bonferroni test. p < 0.05 was considered significant.

RESULTS

Cardiac index (CI) and mean arterial pressure (MAP) were lower in all PEEP treatments at 5 minutes when compared with ZEEP. CI persisted lower throughout the 4 hours only in PEEPmaxC_rs+4 with the lowest CI at 5 minutes (2.15 ± 0.70 versus 3.45 ± 0.94 L minute^-1 m^-2). At 180 and 240 minutes, MAP was lower in PEEPmaxC_rs+4 than in PEEPmaxC_rs, with the lowest value at 180 minutes (58 ± 7 versus 67 ± 7 mmHg). Oxygen delivery index (DO₂I) was lower in PEEPmaxC_rs+4 than in ZEEP at 5, 60, 120 and 180 minutes. Venous admixture was not different among treatments.

CONCLUSION AND CLINICAL RELEVANCE

The use of PEEP caused a transient decrease in MAP and CI in lung-healthy dogs anesthetized with isoflurane, which improved after 60 minutes of ventilation in all levels of PEEP except PEEPmaxC_rs+4. A clinically significant improvement in arterial oxygenation and DO₂I was not observed with PEEPmaxC_rs and PEEPmaxC_rs+2 in comparison with ZEEP, whereas PEEPmaxC_rs+4 decreased DO₂I.

ASC-Mediated Inflammation and Pyroptosis Attenuates Brucella abortus Pathogenesis Following the Recognition of gDNA

Brucella abortus is a zoonotic pathogen that causes brucellosis. Because of Brucella's unique LPS layer and intracellular localization predominately within macrophages, it can often evade immune detection. However, pattern recognition receptors are capable of sensing Brucella pathogen-associated molecular patterns (PAMPS). For example, NOD-like receptors (NLRs) can form a multi-protein inflammasome complex to attenuate Brucella pathogenesis. The inflammasome activates IL-1β and IL-18 to drive immune cell recruitment. Alternatively, inflammasome activation also initiates inflammatory cell death, termed pyroptosis, which augments bacteria clearance. In this report, we assess canonical and non-canonical inflammasome activation following B. abortus infection. We conducted in vivo studies using Asc-/- mice and observed decreased mouse survival, immune cell recruitment, and increased bacteria load. We also conducted studies with Caspase-11-/- mice and did not observe any significant impact on B. abortus pathogenesis. Through mechanistic studies using Asc-/- macrophages, our data suggests that the protective role of ASC may result from the induction of pyroptosis through a gasdermin D-dependent mechanism in macrophages. Additionally, we show that the recognition of Brucella is facilitated by sensing the PAMP gDNA rather than the less immunogenic LPS. Together, these results refine our understanding of the role that inflammasome activation and pyroptosis plays during brucellosis.

Using Computer-based Image Analysis to Improve Quantification of Lung Metastasis in the 4T1 Breast Cancer Model

Breast cancer is a devastating malignancy, accounting for 40,000 female deaths and 30% of new female cancer diagnoses in the United States in 2019 alone. The leading cause of breast cancer related deaths is the metastatic burden. Therefore, preclinical models for breast cancer need to analyze metastatic burden to be clinically relevant. The 4T1 breast cancer model provides a spontaneously-metastasizing, quantifiable mouse model for stage IV human breast cancer. However, most 4T1 protocols quantify the metastatic burden by manually counting stained colonies on tissue culture plates. While this is sufficient for tissues with lower metastatic burden, human error in manual counting causes inconsistent and variable results when plates are confluent and difficult to count. This method offers a computer-based solution to human counting error. Here, we evaluate the protocol using the lung, a highly metastatic tissue in the 4T1 model. Images of methylene blue-stained plates are acquired and uploaded for analysis in Fiji-ImageJ. Fiji-ImageJ then determines the percentage of the selected area of the image that is blue, representing the percentage of the plate with metastatic burden. This computer-based approach offers more consistent and expeditious results than manual counting or histopathological evaluation for highly metastatic tissues. The consistency of Fiji-ImageJ results depends on the quality of the image. Slight variations in results between images can occur, thus it is recommended that multiple images are taken and results averaged. Despite its minimal limitations, this method is an improvement to quantifying metastatic burden in the lung by offering consistent and rapid results.

Starting a Fire Without Flame: The Induction of Cell Death and Inflammation in Electroporation-Based Tumor Ablation Strategies

New therapeutic strategies and paradigms are direly needed for the treatment of cancer. While the surgical removal of tumors is favored in most cancer treatment plans, resection options are often limited based on tumor localization. Over the last two decades, multiple tumor ablation strategies have emerged as promising stand-alone or combination therapeutic options for patients. These strategies are often employed to treat tumors in areas where surgical resection is not possible or where chemotherapeutics have proven ineffective. The type of cell death induced by the ablation modality is a critical aspect of therapeutic success that can impact the efficacy of the treatment and systemic anti-tumor immune system responses. Electroporation-based ablation technologies include electrochemotherapy, irreversible electroporation, and other modalities that rely on pulsed electric fields to create pores in cell membranes. These pores can either be reversible or irreversible depending on the electric field parameters and can induce cell death either alone or in combination with a therapeutic agent. However, there have been many controversial findings among these technologies as to the cell death type initiated, from apoptosis to pyroptosis. As cell death mechanisms can impact treatment side effects and efficacy, we review the main types of cell death induced by electroporation-based treatments and summarize the impact of these mechanisms on treatment response. We also discuss potential reasons behind the variability of findings such as the similarities between cell death pathways, differences between cell-types, and the variation in electric field strength across the treatment area.

Patient Derived Xenografts Expand Human Primary Pancreatic Tumor Tissue Availability for ex vivo Irreversible Electroporation Testing

New methods of tumor ablation have shown exciting efficacy in pre-clinical models but often demonstrate limited success in the clinic. Due to a lack of quality or quantity in primary malignant tissue specimens, therapeutic development and optimization studies are typically conducted on healthy tissue or cell-line derived rodent tumors that don't allow for high resolution modeling of mechanical, chemical, and biological properties. These surrogates do not accurately recapitulate many critical components of the tumor microenvironment that can impact in situ treatment success. Here, we propose utilizing patient-derived xenograft (PDX) models to propagate clinically relevant tumor specimens for the optimization and development of novel tumor ablation modalities. Specimens from three individual pancreatic ductal adenocarcinoma (PDAC) patients were utilized to generate PDX models. This process generated 15-18 tumors that were allowed to expand to 1.5 cm in diameter over the course of 50-70 days. The PDX tumors were morphologically and pathologically identical to primary tumor tissue. Likewise, the PDX tumors were also found to be physiologically superior to other in vitro and ex vivo models based on immortalized cell lines. We utilized the PDX tumors to refine and optimize irreversible electroporation (IRE) treatment parameters. IRE, a novel, non-thermal tumor ablation modality, is being evaluated in a diverse range of cancer clinical trials including pancreatic cancer. The PDX tumors were compared against either Pan02 mouse derived tumors or resected tissue from human PDAC patients. The PDX tumors demonstrated similar changes in electrical conductivity and Joule heating following IRE treatment. Computational modeling revealed a high similarity in the predicted ablation size of the PDX tumors that closely correlate with the data generated with the primary human pancreatic tumor tissue. Gene expression analysis revealed that IRE treatment resulted in an increase in biological pathway signaling associated with interferon gamma signaling, necrosis and mitochondria dysfunction, suggesting potential co-therapy targets. Together, these findings highlight the utility of the PDX system in tumor ablation modeling for IRE and increasing clinical application efficacy. It is also feasible that the use of PDX models will significantly benefit other ablation modality testing beyond IRE.