A Mouse-Adapted SARS-CoV-2 Induces Acute Lung Injury and Mortality in Standard Laboratory Mice

The SARS-CoV-2 pandemic has caused extreme human suffering and economic harm. We generated and characterized a new mouse-adapted SARS-CoV-2 virus that captures multiple aspects of severe COVID-19 disease in standard laboratory mice. This SARS-CoV-2 model exhibits the spectrum of morbidity and mortality of COVID-19 disease as well as aspects of host genetics, age, cellular tropisms, elevated Th1 cytokines, and loss of surfactant expression and pulmonary function linked to pathological features of acute lung injury (ALI) and acute respiratory distress syndrome (ARDS). This model can rapidly access existing mouse resources to elucidate the role of host genetics, underlying molecular mechanisms governing SARS-CoV-2 pathogenesis, and the protective or pathogenic immune responses related to disease severity. The model promises to provide a robust platform for studies of ALI and ARDS to evaluate vaccine and antiviral drug performance, including in the most vulnerable populations (i.e., the aged) using standard laboratory mice.

Chikungunya virus replication in skeletal muscle cells is required for disease development

Chikungunya virus (CHIKV) is an arbovirus capable of causing a severe and often debilitating rheumatic syndrome in humans. CHIKV replicates in a wide variety of cell types in mammals, which has made attributing pathologic outcomes to replication at specific sites difficult. To assess the contribution of CHIKV replication in skeletal muscle cells to pathogenesis, we engineered a CHIKV strain exhibiting restricted replication in these cells via incorporation of target sequences for skeletal muscle cell-specific miR-206. This virus, which we term SKE, displayed diminished replication in skeletal muscle cells in a mouse model of CHIKV disease. Mice infected with SKE developed less severe disease signs, including diminished swelling in the inoculated foot and less necrosis and inflammation in the interosseous muscles. SKE infection was associated with diminished infiltration of T cells into the interosseous muscle as well as decreased production of Il1b, Il6, Ip10, and Tnfa transcripts. Importantly, blockade of the IL-6 receptor led to diminished swelling of a control CHIKV strain capable of replication in skeletal muscle, reducing swelling to levels observed in mice infected with SKE. These data implicate replication in skeletal muscle cells and release of IL-6 as important mediators of CHIKV disease.

IL-1α Is Essential for Oviduct Pathology during Genital Chlamydial Infection in Mice

Chlamydia trachomatis infection of the female genital tract can lead to irreversible fallopian tube scarring. In the mouse model of genital infection using Chlamydia muridarum, IL-1R signaling plays a critical role in oviduct tissue damage. In this study, we investigated the pathologic role of IL-1α, one of the two proinflammatory cytokines that bind to IL-1R. Il1a^-/- mice infected with C. muridarum cleared infection at their cervix at the same rate as wild-type (WT) mice, but were significantly protected from end point oviduct damage and fibrosis. The contribution of IL-1α to oviduct pathology was more dramatic than observed in mice deficient for IL-1β. Although chlamydial burden was similar in WT and Il1a^-/- oviduct during peak days of infection, levels of IL-1β, IL-6, CSF3, and CXCL2 were reduced in Il1a^-/- oviduct lysates. During infection, Il1a^-/- oviducts and uterine horns exhibited reduced neutrophil infiltration, and this reduction persisted after the infection resolved. The absence of IL-1α did not compromise CD4 T cell recruitment or function during primary or secondary chlamydial infection. IL-1α is expressed predominantly by luminal cells of the genital tract in response to infection, and low levels of expression persisted after the infection cleared. Ab-mediated depletion of IL-1α in WT mice prevented infection-induced oviduct damage, further supporting a key role for IL-1α in oviduct pathology.

A mouse-adapted model of SARS-CoV-2 to test COVID-19 countermeasures

Coronaviruses are prone to transmission to new host species, as recently demonstrated by the spread to humans of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the causative agent of the coronavirus disease 2019 (COVID-19) pandemic1. Small animal models that recapitulate SARS-CoV-2 disease are needed urgently for rapid evaluation of medical countermeasures2,3. SARS-CoV-2 cannot infect wild-type laboratory mice owing to inefficient interactions between the viral spike protein and the mouse orthologue of the human receptor, angiotensin-converting enzyme 2 (ACE2)4. Here we used reverse genetics5 to remodel the interaction between SARS-CoV-2 spike protein and mouse ACE2 and designed mouse-adapted SARS-CoV-2 (SARS-CoV-2 MA), a recombinant virus that can use mouse ACE2 for entry into cells. SARS-CoV-2 MA was able to replicate in the upper and lower airways of both young adult and aged BALB/c mice. SARS-CoV-2 MA caused more severe disease in aged mice, and exhibited more clinically relevant phenotypes than those seen in Hfh4-ACE2 transgenic mice, which express human ACE2 under the control of the Hfh4 (also known as Foxj1) promoter. We demonstrate the utility of this model using vaccine-challenge studies in immune-competent mice with native expression of mouse ACE2. Finally, we show that the clinical candidate interferon-λ1a (IFN-λ1a) potently inhibits SARS-CoV-2 replication in primary human airway epithelial cells in vitro-both prophylactic and therapeutic administration of IFN-λ1a diminished SARS-CoV-2 replication in mice. In summary, the mouse-adapted SARS-CoV-2 MA model demonstrates age-related disease pathogenesis and supports the clinical use of pegylated IFN-λ1a as a treatment for human COVID-196.

A conditional mouse expressing an activating mutation in NRF2 displays hyperplasia of the upper gastrointestinal tract and decreased white adipose tissue

Activation of the nuclear factor (erythroid-derived 2)-like 2 (NFE2L2 or NRF2) transcription factor is a critical and evolutionarily conserved cellular response to oxidative stress, metabolic stress, and xenobiotic insult. Deficiency of NRF2 results in hypersensitivity to a variety of stressors, whereas its aberrant activation contributes to several cancer types, most commonly squamous cell carcinomas of the esophagus, oral cavity, bladder, and lung. Between 10% and 35% of patients with squamous cell carcinomas display hyperactive NRF2 signaling, harboring activating mutations and copy number amplifications of the NFE2L2 oncogene or inactivating mutations or deletions of KEAP1 or CUL3, the proteins of which co-complex to ubiquitylate and degrade NRF2 protein. To better understand the role of NRF2 in tumorigenesis and more broadly in development, we engineered the endogenous Nfe2l2 genomic locus to create a conditional mutant LSL-Nrf2^E79Q mouse model. The E79Q mutation, one of the most commonly observed NRF2-activating mutations in human squamous cancers, codes for a mutant protein that does not undergo KEAP1/CUL3-dependent degradation, resulting in its constitutive activity. Expression of NRF2 E79Q protein in keratin 14 (KRT14)-positive murine tissues resulted in hyperplasia of squamous cell tissues of the tongue, forestomach, and esophagus, a stunted body axis, decreased weight, and decreased visceral adipose depots. RNA-seq profiling and follow-up validation studies of cultured NRF2^E79Q murine esophageal epithelial cells revealed known and novel NRF2-regulated transcriptional programs, including genes associated with squamous cell carcinoma (e.g. Myc), lipid and cellular metabolism (Hk2, Ppard), and growth factors (Areg, Bmp6, Vegfa). These data suggest that in addition to decreasing adipogenesis, KRT14-restricted NRF2 activation drives hyperplasia of the esophagus, forestomach, and tongue, but not formation of squamous cell carcinoma. © 2020 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

Abstract 3966: The procancer effects of obesity can be reversed by moderate weight loss or an anti-inflammatory drug in a mouse model of colon cancer

Purpose: Obesity is associated with an increased risk of colon cancer. Our current study examines whether moderate weight loss or treatment with the non-steroidal anti-inflammatory drug sulindac suppresses the tumor-promoting effects of obesity in a mouse model of colon cancer.

Methods: Male FVB mice were treated with azoxymethane (10 mg/kg i.p.) for 5 weeks, then randomized to a control (10% kcal from fat) or diet-induced obesity (DIO, 60% kcal from fat) diet. After 15 weeks, there was an interim sacrifice of 5 mice/group. The DIO mice were then further randomized to remain on DIO or switch to control diet to induce weight loss and become formerly obese mice (FOB), and within each diet group (control, DIO, and FOB), half the mice were randomized to start sulindac treatment (140 ppm in the diet). Eight weeks later, all mice were euthanized.

Results: The DIO mice, compared to controls, had significantly greater body weight and body fat (P<0.05), while FOB mice had intermediate levels of adiposity. Sulindac did not affect adiposity in any diet group. At the interim timepoint, DIO mice had 10-fold greater tumor multiplicity relative to control mice (P=0.07). At study endpoint, DIO mice had greater tumor multiplicity compared to both control (P<0.05) and FOB (P<0.01) mice, which did not significantly differ from each other. Sulindac reduced tumor multiplicity in both control (P<0.05) and DIO (P<0.0001) mice, but not FOB mice. Serum levels of several inflammation-related proteins, including interleukin 6, chemokine (C-X-C motif) ligand 1, monocyte chemoattractant protein 1, and vascular endothelial growth factor, were elevated in DIO mice versus control (P<0.05) and DIO+sulindac (P<0.01) mice, but not in comparison to FOB mice. Gene expression in paired colon tumor and mesenteric adipose tissue samples was assessed by microarray. Ingenuity pathway analysis (IPA) of the significant (P<0.05) differentially expressed tumor genes indicated that both weight loss and sulindac reduced signaling related to matrix metalloproteinases (MMPs) and inflammation. In the visceral adipose tissue, IPA demonstrated that weight loss reduced signaling related to B cell receptors and glucose/fatty acid metabolism while sulindac decreased MMP, prostaglandin, and PPAR signaling. Additional analyses to explore the potential role of cross-talk between these two tissues are being performed, and key findings will be validated in the tissues at the protein level and via mechanistic cell culture experiments.

Conclusions: Both moderate weight loss and sulindac treatment completely reverse the effects of chronic obesity on colon tumorigenesis, the latter independent of any change in adiposity. Our findings suggest that an investigation regarding the effects of NSAID treatment on colon cancer risk and/or progression in obese patients is warranted, particularly for those unable to achieve moderate weight loss.

Citation Format: Laura W. Bowers, Arunima Punjala, Alison Q. Jeffries, Stephanie A. Montgomery, Andrew J. Dannenberg, Stephen D. Hursting. The procancer effects of obesity can be reversed by moderate weight loss or an anti-inflammatory drug in a mouse model of colon cancer [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 3966.

A mouse-adapted SARS-CoV-2 model for the evaluation of COVID-19 medical countermeasures

Coronaviruses are prone to emergence into new host species most recently evidenced by SARS-CoV-2, the causative agent of the COVID-19 pandemic. Small animal models that recapitulate SARS-CoV-2 disease are desperately needed to rapidly evaluate medical countermeasures (MCMs). SARS-CoV-2 cannot infect wildtype laboratory mice due to inefficient interactions between the viral spike (S) protein and the murine ortholog of the human receptor, ACE2. We used reverse genetics to remodel the S and mACE2 binding interface resulting in a recombinant virus (SARS-CoV-2 MA) that could utilize mACE2 for entry. SARS-CoV-2 MA replicated in both the upper and lower airways of both young adult and aged BALB/c mice. Importantly, disease was more severe in aged mice, and showed more clinically relevant phenotypes than those seen in hACE2 transgenic mice. We then demonstrated the utility of this model through vaccine challenge studies in immune competent mice with native expression of mACE2. Lastly, we show that clinical candidate interferon (IFN) lambda-1a can potently inhibit SARS-CoV-2 replication in primary human airway epithelial cells in vitro , and both prophylactic and therapeutic administration diminished replication in mice. Our mouse-adapted SARS-CoV-2 model demonstrates age-related disease pathogenesis and supports the clinical use of IFN lambda-1a treatment in human COVID-19 infections.

An orally bioavailable broad-spectrum antiviral inhibits SARS-CoV-2 in human airway epithelial cell cultures and multiple coronaviruses in mice

Coronaviruses (CoVs) traffic frequently between species resulting in novel disease outbreaks, most recently exemplified by the newly emerged SARS-CoV-2, the causative agent of COVID-19. Here, we show that the ribonucleoside analog β-d-N⁴-hydroxycytidine (NHC; EIDD-1931) has broad-spectrum antiviral activity against SARS-CoV-2, MERS-CoV, SARS-CoV, and related zoonotic group 2b or 2c bat-CoVs, as well as increased potency against a CoV bearing resistance mutations to the nucleoside analog inhibitor remdesivir. In mice infected with SARS-CoV or MERS-CoV, both prophylactic and therapeutic administration of EIDD-2801, an orally bioavailable NHC prodrug (β-d-N⁴-hydroxycytidine-5'-isopropyl ester), improved pulmonary function and reduced virus titer and body weight loss. Decreased MERS-CoV yields in vitro and in vivo were associated with increased transition mutation frequency in viral, but not host cell RNA, supporting a mechanism of lethal mutagenesis in CoV. The potency of NHC/EIDD-2801 against multiple CoVs and oral bioavailability highlights its potential utility as an effective antiviral against SARS-CoV-2 and other future zoonotic CoVs.

Targeted inhibition of gut bacterial β-glucuronidase activity enhances anticancer drug efficacy

Irinotecan treats a range of solid tumors, but its effectiveness is severely limited by gastrointestinal (GI) tract toxicity caused by gut bacterial β-glucuronidase (GUS) enzymes. Targeted bacterial GUS inhibitors have been shown to partially alleviate irinotecan-induced GI tract damage and resultant diarrhea in mice. Here, we unravel the mechanistic basis for GI protection by gut microbial GUS inhibitors using in vivo models. We use in vitro, in fimo, and in vivo models to determine whether GUS inhibition alters the anticancer efficacy of irinotecan. We demonstrate that a single dose of irinotecan increases GI bacterial GUS activity in 1 d and reduces intestinal epithelial cell proliferation in 5 d, both blocked by a single dose of a GUS inhibitor. In a tumor xenograft model, GUS inhibition prevents intestinal toxicity and maintains the antitumor efficacy of irinotecan. Remarkably, GUS inhibitor also effectively blocks the striking irinotecan-induced bloom of Enterobacteriaceae in immune-deficient mice. In a genetically engineered mouse model of cancer, GUS inhibition alleviates gut damage, improves survival, and does not alter gut microbial composition; however, by allowing dose intensification, it dramatically improves irinotecan's effectiveness, reducing tumors to a fraction of that achieved by irinotecan alone, while simultaneously promoting epithelial regeneration. These results indicate that targeted gut microbial enzyme inhibitors can improve cancer chemotherapeutic outcomes by protecting the gut epithelium from microbial dysbiosis and proliferative crypt damage.

In Vivo Targeting of Clostridioides difficile Using Phage-Delivered CRISPR-Cas3 Antimicrobials

Clostridioides difficile is an important nosocomial pathogen that causes approximately 500,000 cases of C. difficile infection (CDI) and 29,000 deaths annually in the United States. Antibiotic use is a major risk factor for CDI because broad-spectrum antimicrobials disrupt the indigenous gut microbiota, decreasing colonization resistance against C. difficile Vancomycin is the standard of care for the treatment of CDI, likely contributing to the high recurrence rates due to the continued disruption of the gut microbiota. Thus, there is an urgent need for the development of novel therapeutics that can prevent and treat CDI and precisely target the pathogen without disrupting the gut microbiota. Here, we show that the endogenous type I-B CRISPR-Cas system in C. difficile can be repurposed as an antimicrobial agent by the expression of a self-targeting CRISPR that redirects endogenous CRISPR-Cas3 activity against the bacterial chromosome. We demonstrate that a recombinant bacteriophage expressing bacterial genome-targeting CRISPR RNAs is significantly more effective than its wild-type parent bacteriophage at killing C. difficile both in vitro and in a mouse model of CDI. We also report that conversion of the phage from temperate to obligately lytic is feasible and contributes to the therapeutic suitability of intrinsic C. difficile phages, despite the specific challenges encountered in the disease phenotypes of phage-treated animals. Our findings suggest that phage-delivered programmable CRISPR therapeutics have the potential to leverage the specificity and apparent safety of phage therapies and improve their potency and reliability for eradicating specific bacterial species within complex communities, offering a novel mechanism to treat pathogenic and/or multidrug-resistant organisms.IMPORTANCEClostridioides difficile is a bacterial pathogen responsible for significant morbidity and mortality across the globe. Current therapies based on broad-spectrum antibiotics have some clinical success, but approximately 30% of patients have relapses, presumably due to the continued perturbation to the gut microbiota. Here, we show that phages can be engineered with type I CRISPR-Cas systems and modified to reduce lysogeny and to enable the specific and efficient targeting and killing of C. difficilein vitro and in vivo. Additional genetic engineering to disrupt phage modulation of toxin expression by lysogeny or other mechanisms would be required to advance a CRISPR-enhanced phage antimicrobial for C. difficile toward clinical application. These findings provide evidence into how phage can be combined with CRISPR-based targeting to develop novel therapies and modulate microbiomes associated with health and disease.

CD8+ T cells regulate liver injury in obesity-related nonalcoholic fatty liver disease

Nonalcoholic steatohepatitis (NASH) has increased in Western countries due to the prevalence of obesity. Current interests are aimed at identifying the type and function of immune cells that infiltrate the liver and key factors responsible for mediating their recruitment and activation in NASH. We investigated the function and phenotype of CD8⁺ T cells under obese and nonobese NASH conditions. We found an elevation in CD8 staining in livers from obese human subjects with NASH and cirrhosis that positively correlated with α-smooth muscle actin, a marker of hepatic stellate cell (HSC) activation. CD8⁺ T cells were elevated 3.5-fold in the livers of obese and hyperlipidemic NASH mice compared with obese hepatic steatosis mice. Isolated hepatic CD8⁺ T cells from these mice expressed a cytotoxic IL-10-expressing phenotype, and depletion of CD8⁺ T cells led to significant reductions in hepatic inflammation, HSC activation, and macrophage accumulation. Furthermore, hepatic CD8⁺ T cells from obese and hyperlipidemic NASH mice activated HSCs in vitro and in vivo. Interestingly, in the lean NASH mouse model, depletion and knockdown of CD8⁺ T cells did not impact liver inflammation or HSC activation. We demonstrated that under obese/hyperlipidemia conditions, CD8⁺ T cell are key regulators of the progression of NASH, while under nonobese conditions they play a minimal role in driving the disease. Thus, therapies targeting CD8⁺ T cells may be a novel approach for treatment of obesity-associated NASH.NEW & NOTEWORTHY Our study demonstrates that CD8⁺ T cells are the primary hepatic T cell population, are elevated in obese models of NASH, and directly activate hepatic stellate cells. In contrast, we find CD8⁺ T cells from lean NASH models do not regulate NASH-associated inflammation or stellate cell activation. Thus, for the first time to our knowledge, we demonstrate that hepatic CD8⁺ T cells are key players in obesity-associated NASH.

Comparative therapeutic efficacy of remdesivir and combination lopinavir, ritonavir, and interferon beta against MERS-CoV

Middle East respiratory syndrome coronavirus (MERS-CoV) is the causative agent of a severe respiratory disease associated with more than 2468 human infections and over 851 deaths in 27 countries since 2012. There are no approved treatments for MERS-CoV infection although a combination of lopinavir, ritonavir and interferon beta (LPV/RTV-IFNb) is currently being evaluated in humans in the Kingdom of Saudi Arabia. Here, we show that remdesivir (RDV) and IFNb have superior antiviral activity to LPV and RTV in vitro. In mice, both prophylactic and therapeutic RDV improve pulmonary function and reduce lung viral loads and severe lung pathology. In contrast, prophylactic LPV/RTV-IFNb slightly reduces viral loads without impacting other disease parameters. Therapeutic LPV/RTV-IFNb improves pulmonary function but does not reduce virus replication or severe lung pathology. Thus, we provide in vivo evidence of the potential for RDV to treat MERS-CoV infections.

Comparative therapeutic efficacy of remdesivir and combination lopinavir, ritonavir, and interferon beta against MERS-CoV

Middle East respiratory syndrome coronavirus (MERS-CoV) is the causative agent of a severe respiratory disease associated with more than 2468 human infections and over 851 deaths in 27 countries since 2012. There are no approved treatments for MERS-CoV infection although a combination of lopinavir, ritonavir and interferon beta (LPV/RTV-IFNb) is currently being evaluated in humans in the Kingdom of Saudi Arabia. Here, we show that remdesivir (RDV) and IFNb have superior antiviral activity to LPV and RTV in vitro. In mice, both prophylactic and therapeutic RDV improve pulmonary function and reduce lung viral loads and severe lung pathology. In contrast, prophylactic LPV/RTV-IFNb slightly reduces viral loads without impacting other disease parameters. Therapeutic LPV/RTV-IFNb improves pulmonary function but does not reduce virus replication or severe lung pathology. Thus, we provide in vivo evidence of the potential for RDV to treat MERS-CoV infections.

Biologically Targeted Photo-Crosslinkable Nanopatch to Prevent Postsurgical Peritoneal Adhesion

Peritoneal adhesion occurs in a majority of patients following abdominal surgery and can result in significant side effects and complications. Current strategies to minimize adhesions involve the use of nontargeted anatomical barriers that are either inefficient in protecting injured areas or lacking the adequate residence time to prevent adhesions. Herein, the development of a biologically targeted photo-crosslinkable nanopatch (pCNP) is reported that can prevent postsurgical adhesion. It is demonstrated that pCNP can form a compact protective barrier over surfaces with exposed collagen IV. Using a rat parietal peritoneal excision adhesion model, it is showed that pCNP is highly effective and safe in preventing postsurgical adhesions. This work presents a novel approach to preventing peritoneal adhesion with nanomaterials.

Abstract 2843: Advanced age and obesity separately and interactively potentiate triple negative breast cancer progression

Advanced age and obesity are major risk factors for breast cancer (BC) mortality that are independently associated with aggressive disease and therapeutic resistance. Despite this, preclinical models of BC mainly utilize young lean mice. The mechanisms underlying age- and obesity-related BC progression are currently unknown, highlighting a critical gap in our understanding of BC biology. To address this gap, we generated aged (16 mos) and young (6 mos) cohorts of lean and obese mice by placement on either low-fat control (10% kcal from fat) or diet-induced obesity (DIO; 60% kcal from fat) diet, respectively, beginning at 8-weeks of age. This resulted in four experimental groups: aged lean, aged DIO, young lean, young DIO. Mice were orthotopically injected with one of two triple negative BC cell lines (E0771 or Met-MWNTLung), which represent aggressive BC subtypes associated with poor prognosis in humans. Outcomes included primary tumor weight and lung metastasis quantification. Biochemical and molecular analyses included serum cytokines and gene expression within tumor and adjacent normal mammary tissue. Our TNBC models indicate tumor growth is similarly increased in young DIO and aged lean mice, with both significantly higher than young lean mice. Moreover, the combination of advanced age and obesity in aged DIO mice significantly increased tumor growth relative to all other experimental groups. Preliminary pathology analyses in Met-MWNTLung-bearing mice reveal that advanced age enhances lung metastasis beyond that of young mice regardless of diet. Increased tumor burden in both the aged lean and young DIO mice is accompanied by increased serum proinflammatory cytokines (IL-1b, CXCL13, CCL11, among others). Consistent with these findings, Gene Set Enrichment Analysis (GSEA) of Met-MWNTLungtumor and adjacent normal mammary microarray data demonstrated enrichment of inflammatory pathways, including IFNγ response, IFNα response, IL-2/STAT5 signaling, and IL-6/JAK/STAT3 signaling in aged lean and young DIO mice relative to young lean mice. Interestingly, tumor-adjacent mammary from aged lean and young DIO mice was also enriched for markers of EMT, consistent with age- and DIO-associated phenotypic switching of cells within the tumor-adjacent microenvironment. Taken together, our findings reveal that obesity and advanced age augment BC progression and promote inflammation within the local (mammary & tumor) and systemic (serum) microenvironments. Ongoing analyses are investigating the role of cellular senescence, a stress-induced cell cycle arrest in which cells acquire a proinflammatory secretome. Knowledge gained from this study will help to elucidate the mechanisms underlying advanced age- and obesity-related BC progression, which is urgently needed to develop new strategies for reducing adverse TNBC outcomes associated with advanced age and obesity in human populations.

Citation Format: Laura A. Smith, Magdalena A. Rainey, Nishita T. Sheth, Stephanie A. Montgomery, Stephen D. Hursting. Advanced age and obesity separately and interactively potentiate triple negative breast cancer progression [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 2843.

A nanoparticle-incorporated STING activator enhances antitumor immunity in PD-L1-insensitive models of triple-negative breast cancer

Triple-negative breast cancer (TNBC) has few therapeutic options, and alternative approaches are urgently needed. Stimulator of IFN genes (STING) is becoming an exciting target for therapeutic adjuvants. However, STING resides inside the cell, and the intracellular delivery of CDNs, such as cGAMP, is required for the optimal activation of STING. We show that liposomal nanoparticle-delivered cGAMP (cGAMP-NP) activates STING more effectively than soluble cGAMP. These particles induce innate and adaptive host immune responses to preexisting tumors in both orthotopic and genetically engineered models of basal-like TNBC. cGAMP-NPs also reduce melanoma tumor load, with limited responsivity to anti-PD-L1. Within the tumor microenvironment, cGAMP-NPs direct both mouse and human macrophages (M), reprograming from protumorigenic M2-like phenotype toward M1-like phenotype; enhance MHC and costimulatory molecule expression; reduce M2 biomarkers; increase IFN-γ-producing T cells; augment tumor apoptosis; and increase CD4+ and CD8+ T cell infiltration. Activated T cells are required for tumor suppression, as their depletion reduces antitumor activity. Importantly, cGAMP-NPs prevent the formation of secondary tumors, and a single dose is sufficient to inhibit TNBC. These data suggest that a minimal system comprised of cGAMP-NP alone is sufficient to modulate the tumor microenvironment to effectively control PD-L1-insensitive TNBC.

Efficacy of pyrazinoic acid dry powder aerosols in resolving necrotic and non-necrotic granulomas in a guinea pig model of tuberculosis

New therapeutic strategies are needed to treat drug resistant tuberculosis (TB) and to improve treatment for drug sensitive TB. Pyrazinamide (PZA) is a critical component of current first-line TB therapy. However, the rise in PZA-resistant TB cases jeopardizes the future utility of PZA. To address this problem, we used the guinea pig model of TB and tested the efficacy of an inhaled dry powder combination, referred to as Pyrazinoic acid/ester Dry Powder (PDP), which is comprised of pyrazinoic acid (POA), the active moiety of PZA, and pyrazinoic acid ester (PAE), which is a PZA analog. Both POA and PAE have the advantage of being able to act on PZA-resistant Mycobacterium tuberculosis. When used in combination with oral rifampicin (R), inhaled PDP had striking effects on tissue pathology. Effects were observed in lungs, the site of delivery, but also in the spleen and liver indicating both local and systemic effects of inhaled PDP. Tissue granulomas that harbor M. tuberculosis in a persistent state are a hallmark of TB and they pose a challenge for therapy. Compared to other treatments, which preferentially cleared non-necrotic granulomas, R+PDP reduced necrotic granulomas more effectively. The increased ability of R+PDP to act on more recalcitrant necrotic granulomas suggests a novel mechanism of action. The results presented in this report reveal the potential for developing therapies involving POA that are optimized to target necrotic as well as non-necrotic granulomas as a means of achieving more complete sterilization of M. tuberculosis bacilli and preventing disease relapse when therapy ends.

The Inhibitory Innate Immune Sensor NLRP12 Maintains a Threshold against Obesity by Regulating Gut Microbiota Homeostasis

In addition to high-fat diet (HFD) and inactivity, inflammation and microbiota composition contribute to obesity. Inhibitory immune receptors, such as NLRP12, dampen inflammation and are important for resolving inflammation, but their role in obesity is unknown. We show that obesity in humans correlates with reduced expression of adipose tissue NLRP12. Similarly, Nlrp12-/- mice show increased weight gain, adipose deposition, blood glucose, NF-κB/MAPK activation, and M1-macrophage polarization. Additionally, NLRP12 is required to mitigate HFD-induced inflammasome activation. Co-housing with wild-type animals, antibiotic treatment, or germ-free condition was sufficient to restrain inflammation, obesity, and insulin tolerance in Nlrp12-/- mice, implicating the microbiota. HFD-fed Nlrp12-/- mice display dysbiosis marked by increased obesity-associated Erysipelotrichaceae, but reduced Lachnospiraceae family and the associated enzymes required for short-chain fatty acid (SCFA) synthesis. Lachnospiraceae or SCFA administration attenuates obesity, inflammation, and dysbiosis. These findings reveal that Nlrp12 reduces HFD-induced obesity by maintaining beneficial microbiota.

CD30-Redirected Chimeric Antigen Receptor T Cells Target CD30+ and CD30- Embryonal Carcinoma via Antigen-Dependent and Fas/FasL Interactions

Tumor antigen heterogeneity limits success of chimeric antigen receptor (CAR) T-cell therapies. Embryonal carcinomas (EC) and mixed testicular germ cell tumors (TGCT) containing EC, which are the most aggressive TGCT subtypes, are useful for dissecting this issue as ECs express the CD30 antigen but also contain CD30^-/dim cells. We found that CD30-redirected CAR T cells (CD30.CAR T cells) exhibit antitumor activity in vitro against the human EC cell lines Tera-1, Tera-2, and NCCIT and putative EC stem cells identified by Hoechst dye staining. Cytolytic activity of CD30.CAR T cells was complemented by their sustained proliferation and proinflammatory cytokine production. CD30.CAR T cells also demonstrated antitumor activity in an in vivo xenograft NOD/SCID/γcnull (NSG) mouse model of metastatic EC. We observed that CD30.CAR T cells, while targeting CD30⁺ EC tumor cells through the CAR (i.e., antigen-dependent targeting), also eliminated surrounding CD30^- EC cells in an antigen-independent manner, via a cell-cell contact-dependent Fas/FasL interaction. In addition, ectopic Fas (CD95) expression in CD30⁺ Fas^- EC was sufficient to improve CD30.CAR T-cell antitumor activity. Overall, these data suggest that CD30.CAR T cells might be useful as an immunotherapy for ECs. Additionally, Fas/FasL interaction between tumor cells and CAR T cells can be exploited to reduce tumor escape due to heterogeneous antigen expression or to improve CAR T-cell antitumor activity. Cancer Immunol Res; 6(10); 1274-87. ©2018 AACR.

Abstract 1032: Novel mouse models of high-risk HPV-related oral cancers

The rate of HPV-induced head and neck squamous cell carcinoma (HNSCC) is steadily increasing and implicated in approximately 60% of all oropharyngeal carcinomas. The advent of whole genome, transcriptome, and proteome analyses have aided in identifying altered signaling pathways in HPV-induced HNSCCs, however, additional tools such as mouse models are needed to study the role of HPV oncogenes in oral tumor initiation and progression. Current inducible models of HPV-driven oral cancer do not accurately recapitulate the levels, stoichiometric ratios, or anatomic location of oncoprotein expression. To address these limitations, we developed a tractable genetically engineered mouse model (GEMM) that enables directed expression of high-risk HPV16 E6 and E7 oncogenes (Rosa26-loxP-STOP-loxP-E7iresE6; “H”) in the oral epithelium. Analysis of mouse embryonic fibroblasts treated with Cre recombinase confirmed E6 and E7 expression and changes in mRNA expression of known E6 and E7 targets. We crossed our H mice to several tissue-specific transgenic Cre-driver mouse strains including the EBV lytic promoter (ED-L2-Cre recombinase; “L”) to drive robust expression in the oropharyngeal squamous epithelia. Analysis of epithelial tissues isolated from LH mice displayed increased oral volumes and cutaneous epithelial thickening associated with hyperplasia, dysplasia, accumulation of neutrophils and recruitment of cytotoxic and regulatory T cells. A second cross to the keratin 14 promoter (KRT14-Cre; “K”) line enabled targeted expression to the basal epithelial layer (KH) and confirmed increased oral volumes and cutaneous epithelial thickening associated with increased suprabasal proliferation and expression of canonical E7 targets. Lastly, a third cross to a tamoxifen-inducible Cre (CreERT2) line driven by the keratin 14 promoter (KRT14-CreERT2; “iK”) enabled conditional and inducible post-natal E6 and E7 expression in basal epithelia (iKH). To prevent systemic oncogene expression in K14+ cells, we validated a method for submucosal delivery of tamoxifen to the tongue. We confirmed that this approach prevents tamoxifen spread and anatomically restricts activation oncogene expression to intra-lingual regions using an optical reporter mouse recently generated by the Amelio lab (Rosa26-loxP-STOP-loxP-LumiFluor; “F”) crossed to the iK line (“iKF”). Notably, direct intra-lingual injection yields higher recombination and reporter activation using 40% less overall tamoxifen than traditional i.p. administration routes. Moreover, immunofluorescent staining revealed mosaic transgene activation in the oropharynx, an important feature for modeling HPV-induced OSCC. In fact, intra-lingual injection of tamoxifen in iKH mice coupled with 4-nitroquniloline 1-oxide (4NQO) administration led to E6 and E7 expression and dysplasia in the tongue epithelia. Ongoing studies are evaluating cooperating mutations in driving HNSCC development.

Citation Format: Miranda B. Carper, Scott Troutman, Kevin M. Byrd, Bethany Wagner, Erin C. Henry, Stephanie A. Montgomery, Scott E. Williams, Joseph L. Kissil, Antonio L. Amelio. Novel mouse models of high-risk HPV-related oral cancers [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 1032.

Abstract LB-126: Nanoparticle-incorporated STING activator as an immunotherapeutic for PD-L1 resistant triple-negative breast cancer

Current immune checkpoint inhibitors (eg. PD-L1) shows limited efficacy for varies cancer types, especially the difficult-to-treat triple-negative breast cancer. This study uses liposomal nanoparticles (NPs) to deliver the STING agonist, cGAMP, as an alternative approach to amplify innate immune activation and anti-tumor treatment. We studied the impact of cGAMP-NPs on macrophage reprograming and activation by determining M1/M2 biomarkers on polarized M2(+) cells and cytokines from secreted supernatants. The critical role of STING/IFNAR signaling in cGAMP-NP-mediated response was also examined. The efficacy was further evaluated in an orthotopically-transplanted model (C3(1)Tag model) for basal-like triple-negative breast cancer (TNBC) and a spontaneous genetic engineered mouse (GEM) model of basal-like TNBC (C3(1)Tag GEM). Both of these preclinical models that are resistant to PD-L1 checkpoint blockade and most other therapies, which parallels TNBC in humans. cGAMP-NPs were shown to activate STING and induce both innate and adaptive host immune responses. Also, cGAMP-NPs accumulated within macrophages at the tumor site and reversed a pro-tumorigenic microenvironment. Effective tumor suppression was achieved by intravenous delivery in orthotopic and GEM of TNBC with no responsivity to anti-PD-L1 and in B16F10 melanoma with limited responsivity to anti-PD-L1. The anti-tumor immunity was achieved in a STING-dependent fashion that relies on T cells and macrophages but does not require prior knowledge of the tumor antigen. cGAMP-NPs were shown to induce M2-like macrophages to skew towards a M1-like phenotype, cytokine production, MHC and co-stimulatory molecule expression, enhanced CD4+ and CD8+ T cells infiltration, and tumor apoptosis. Moreover, cGAMP-NPs alone induced durable anti-tumor T cell responses and prevented the formation of secondary tumors. We demonstrated the amplified efficacy of liposome formulation relative to soluble cGAMP as an anti-tumor therapeutic that obviates the need of intratumoral injection. Our data suggested that cGAMP-NPs are a potent treatment regimen to modulate the microenvironment of tumors with limited or no responsivity to anti-PD-L1.

Citation Format: Ning Cheng, Rebecca Watkins-Schulz, Robert Junkins, Clément David, Brandon M. Johnson, Stephanie A. Montgomery, Kevin J. Peine, David B. Darr, Hong Yuan, Karen P. McKinnon, Qi Liu, Lei Miao, Leaf Huang, Eric M. Bachelder, Kristy M. Ainslie, Jenny P-y Ting. Nanoparticle-incorporated STING activator as an immunotherapeutic for PD-L1 resistant triple-negative breast cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr LB-126.

Human herpesvirus-encoded kinase induces B cell lymphomas in vivo

Kaposi's sarcoma-associated herpesvirus (KSHV) is a gammaherpesvirus that is the etiological agent of the endothelial cell cancer Kaposi's sarcoma (KS) and 2 B cell lymphoproliferative disorders, primary effusion lymphoma (PEL) and multicentric Castleman's disease (MCD). KSHV ORF36, also known as viral protein kinase (vPK), is a viral serine/threonine kinase. We previously reported that KSHV vPK enhances cell proliferation and mimics cellular S6 kinase to phosphorylate ribosomal protein S6, a protein involved in protein synthesis. We created a mouse model to analyze the function of vPK in vivo. We believe this is the first mouse tumor model of a viral kinase encoded by a pathogenic human virus. We observed increased B cell activation in the vPK transgenic mice compared with normal mice. We also found that, over time, vPK transgenic mice developed a B cell hyperproliferative disorder and/or a high-grade B cell non-Hodgkin lymphoma at a greatly increased incidence compared with littermate controls. This mouse model shows that a viral protein kinase is capable of promoting B cell activation and proliferation as well as augmenting lymphomagenesis in vivo and may therefore contribute to the development of viral cancers.

IL-10 Paradoxically Promotes Autoimmune Neuropathy through S1PR1-Dependent CD4+ T Cell Migration

Chronic inflammatory demyelinating polyneuropathy (CIDP) is a debilitating condition caused by autoimmune demyelination of peripheral nerves. CIDP is associated with increased IL-10, a cytokine with well-described anti-inflammatory effects. However, the role of IL-10 in CIDP is unclear. In this study, we demonstrate that IL-10 paradoxically exacerbates autoimmunity against peripheral nerves. In IL-10-deficient mice, protection from neuropathy was associated with an accrual of highly activated CD4+ T cells in draining lymph nodes and absence of infiltrating immune cells in peripheral nerves. Accumulated CD4+ T cells in draining lymph nodes of IL-10-deficient mice expressed lower sphingosine-1-phosphate receptor 1 (S1pr1), a protein important in lymphocyte egress. Additionally, IL-10 stimulation in vitro induced S1pr1 expression in lymph node cells in a STAT3-dependent manner. Together, these results delineate a novel mechanism in which IL-10-induced STAT3 increases S1pr1 expression and CD4+ T cell migration to accelerate T cell-mediated destruction of peripheral nerves.

Toward Personalized Gene Therapy: Characterizing the Host Genetic Control of Lentiviral-Vector-Mediated Hepatic Gene Delivery

The success of lentiviral vectors in curing fatal genetic and acquired diseases has opened a new era in human gene therapy. However, variability in the efficacy and safety of this therapeutic approach has been reported in human patients. Consequently, lentiviral-vector-based gene therapy is limited to incurable human diseases, with little understanding of the underlying causes of adverse effects and poor efficacy. To assess the role that host genetic variation has on efficacy of gene therapy, we characterized lentiviral-vector gene therapy within a set of 12 collaborative cross mouse strains. Lentiviral vectors carrying the firefly luciferase cDNA under the control of a liver-specific promoter were administered to female mice, with total-body and hepatic luciferase expression periodically monitored through 41 weeks post-vector administration. Vector copy number per diploid genome in mouse liver and spleen was determined at the end of this study. We identified major strain-specific contributions to overall success of transduction, vector biodistribution, maximum luciferase expression, and the kinetics of luciferase expression throughout the study. Our results highlight the importance of genetic variation on gene-therapeutic efficacy; provide new models with which to more rigorously assess gene therapy approaches; and suggest that redesigning preclinical studies of gene-therapy methodologies might be appropriate.

The innate immune receptor, NLRX1, functions as a tumor suppressor by reducing colon tumorigenesis and key tumor-promoting signals

NLR (NOD-like receptor) proteins are intracellular innate immune sensors/receptors that regulate immunity. This work shows that NLRX1 serves as a tumor suppressor in colitis-associated cancer (CAC) and sporadic colon cancer by keeping key tumor promoting pathways in check. Nlrx1−/− mice were highly susceptible to CAC, showing increases in key cancer-promoting pathways including NF-kB, MAPK, STAT3 and IL-6. The tumor-suppressive function of NLRX1 originated primarily from the non-hematopoietic compartment. This prompted an analysis of NLRX1 function in the Apcmin/+genetic model of sporadic gastrointestinal cancer. NLRX1 attenuated Apcmin/+colon tumorigenesis, cellular proliferation, NF-kB, MAPK, STAT3 activation and IL-6 levels. Application of anti-IL6R antibody therapy reduced tumor burden, increased survival and reduced STAT3 activation in Nlrx1−/−Apcmin/+mice. As an important clinical correlate, human colon cancer samples expressed lower levels of NLRX1 than healthy controls in multiple patient cohorts. These data implicate anti-IL6R as a personalized therapeutics for colon cancers with reduced NLRX1.