Chapter three--Syrian hamster as an animal model to study oncolytic adenoviruses and to evaluate the efficacy of antiviral compounds

Oral USC-093, a novel homoserinamide analogue of the tyrosinamide (S)-HPMPA prodrug USC-087 has decreased nephrotoxicity while maintaining antiviral efficacy against human adenovirus infection of Syrian hamsters

Adenovirus infections of immunocompromised humans are a significant source of morbidity and mortality. Presently, there is no drug specifically approved for the treatment of adenovirus infections by the FDA. The state-of-the-art treatment of such infections is the off-label use of cidofovir, an acyclic nucleotide phosphonate. While cidofovir inhibits adenovirus replication, it has dose-limiting kidney toxicity. There is an apparent need for a better compound to treat adenovirus infections. To this end, we have been developing acyclic nucleotide phosphonate prodrugs that utilize an amino acid scaffold equipped with a lipophilic modifier. Here, we compare the antiviral potential of two prodrugs of HPMPA that differ only in the amino acid-based promoiety: USC-087, based on an N-hexadecyl tyrosinamide, and USC-093, based on an N-hexadecyl serinamide. Oral administration of both compounds was very efficacious against disseminated HAdV-C6 infection in immunosuppressed Syrian hamsters, suppressing virus replication and mitigating pathology even when treatment was withheld until 4 days after challenge. We saw only marginal efficacy after respiratory infection of hamsters, which may reflect suboptimal distribution to the lung. Importantly, neither compound induced intestinal toxicity, which was observed as the major adverse effect in clinical trials of brincidofovir, a prodrug of cidofovir which also contains a C-16 modifier. Notably, we found that there was a significant difference in the nephrotoxicity of the two compounds: USC-087 caused significant kidney toxicity while USC-093 did not, at effective doses. These findings will be valuable guidepoints in the future evolution of this new class of potential prodrugs to treat adenovirus infections.

[Oncolytic viruses: Actors and deliverers of therapeutic proteins against tumors]

The discovery of the unique ability of certain viruses to specifically target cancer cells has led to significant advancements in cancer immunotherapy research. In addition to inducing specific lysis of cancer cells, oncolytic viruses (OV) have been genetically modified to express molecules of interest within the tumor bed. The use of OV as vectors for therapeutic molecules has allowed to enhance antitumor responses while limiting the adverse effects associated with systemic administration of the molecule. Other studies are currently focused on delaying the neutralization and clearance of the virus by the host's immune system and improving its delivery insight tumors.

Viral Shedding in Mice following Intravenous Adenovirus Injection: Impact on Biosafety Classification

There have been numerous advances in gene therapy and oncolytic virotherapy in recent years, especially with respect to cutting-edge animal models to test these novel therapeutics. With all of these advances, it is important to understand the biosafety risks of testing these vectors in animals. We performed adenovirus-based viral shedding studies in murine models to ascertain when it is appropriate to downgrade the animals from Biosafety Level (BSL) 2 to BSL 1 for experimental handling and transport. We utilized intravenous injections of a replication-competent adenovirus and analyzed viral shedding via the collection of buccal and dermal swabs from each animal, in addition to obtaining urine and stool samples. The adenovirus hexon copy number was determined by qPCR, and plaque formation was analyzed to assess the biologic activity of viral particles. Our results demonstrate that after 72 h following viral inoculation, there is no significant quantity of biologically active virus shedding from the animals. This observation suggests that on day 4 following adenovirus injection, mice can be safely downgraded to BSL 1 for the remainder of the experiment with no concern for hazardous exposure to laboratory personnel.

Syrian hamster as an ideal animal model for evaluation of cancer immunotherapy

Cancer immunotherapy (CIT) has emerged as an exciting new pillar of cancer treatment. Although benefits have been achieved in individual patients, the overall response rate is still not satisfactory. To address this, an ideal preclinical animal model for evaluating CIT is urgently needed. Syrian hamsters present similar features to humans with regard to their anatomy, physiology, and pathology. Notably, the histological features and pathological progression of tumors and the complexity of the tumor microenvironment are equivalent to the human scenario. This article reviews the current tumor models in Syrian hamster and the latest progress in their application to development of tumor treatments including immune checkpoint inhibitors, cytokines, adoptive cell therapy, cancer vaccines, and oncolytic viruses. This progress strongly advocates Syrian hamster as an ideal animal model for development and assessment of CIT for human cancer treatments. Additionally, the challenges of the Syrian hamster as an animal model for CIT are also discussed.

Mucociliary transport deficiency and disease progression in Syrian hamsters with SARS-CoV-2 infection

Substantial clinical evidence supports the notion that ciliary function in the airways is important in COVID-19 pathogenesis. Although ciliary damage has been observed in both in vitro and in vivo models, the extent or nature of impairment of mucociliary transport (MCT) in in vivo models remains unknown. We hypothesize that SARS-CoV-2 infection results in MCT deficiency in the airways of golden Syrian hamsters that precedes pathological injury in lung parenchyma. Micro-optical coherence tomography was used to quantitate functional changes in the MCT apparatus. Both genomic and subgenomic viral RNA pathological and physiological changes were monitored in parallel. We show that SARS-CoV-2 infection caused a 67% decrease in MCT rate as early as 2 days postinfection (dpi) in hamsters, principally due to 79% diminished airway coverage of motile cilia. Correlating quantitation of physiological, virological, and pathological changes reveals steadily descending infection from the upper airways to lower airways to lung parenchyma within 7 dpi. Our results indicate that functional deficits of the MCT apparatus are a key aspect of COVID-19 pathogenesis, may extend viral retention, and could pose a risk factor for secondary infection. Clinically, monitoring abnormal ciliated cell function may indicate disease progression. Therapies directed toward the MCT apparatus deserve further investigation.

Golden Syrian Hamster Models for Cancer Research

The golden Syrian hamster (Mesocricetus auratus) has long been a valuable rodent model of human diseases, especially infectious and metabolic diseases. Hamsters have also been valuable models of several chemically induced cancers such as the DMBA-induced oral cheek pouch cancer model. Recently, with the application of CRISPR/Cas9 genetic engineering technology, hamsters can now be gene targeted as readily as mouse models. This review describes the phenotypes of three gene-targeted knockout (KO) hamster cancer models, TP53, KCNQ1, and IL2RG. Notably, these hamster models demonstrate cancer phenotypes not observed in mouse KOs. In some cases, the cancers that arise in the KO hamster are similar to cancers that arise in humans, in contrast with KO mice that do not develop the cancers. An example is the development of aggressive acute myelogenous leukemia (AML) in TP53 KO hamsters. The review also presents a discussion of the relative strengths and weaknesses of mouse cancer models and hamster cancer models and argues that there are no perfect rodent models of cancer and that the genetically engineered hamster cancer models can complement mouse models and expand the suite of animal cancer models available for the development of new cancer therapies.

Mucociliary Transport Deficiency and Disease Progression in Syrian Hamsters with SARS-CoV-2 Infection

Substantial clinical evidence supports the notion that ciliary function in the airways plays an important role in COVID-19 pathogenesis. Although ciliary damage has been observed in both in vitro and in vivo models, consequent impaired mucociliary transport (MCT) remains unknown for the intact MCT apparatus from an in vivo model of disease. Using golden Syrian hamsters, a common animal model that recapitulates human COVID-19, we quantitatively followed the time course of physiological, virological, and pathological changes upon SARS-CoV-2 infection, as well as the deficiency of the MCT apparatus using micro-optical coherence tomography, a novel method to visualize and simultaneously quantitate multiple aspects of the functional microanatomy of intact airways. Corresponding to progressive weight loss up to 7 days post-infection (dpi), viral detection and histopathological analysis in both the trachea and lung revealed steadily descending infection from the upper airways, as the main target of viral invasion, to lower airways and parenchymal lung, which are likely injured through indirect mechanisms. SARS-CoV-2 infection caused a 67% decrease in MCT rate as early as 2 dpi, largely due to diminished motile ciliation coverage, but not airway surface liquid depth, periciliary liquid depth, or cilia beat frequency of residual motile cilia. Further analysis indicated that the fewer motile cilia combined with abnormal ciliary motion of residual cilia contributed to the delayed MCT. The time course of physiological, virological, and pathological progression suggest that functional deficits of the MCT apparatus predispose to COVID-19 pathogenesis by extending viral retention and may be a risk factor for secondary infection. As a consequence, therapies directed towards the MCT apparatus deserve further investigation as a treatment modality.

Animal Models in Human Adenovirus Research

Simple Summary

Animal models are widely used to study various aspects of human diseases and disorders. Likewise, they are indispensable for preclinical testing of medicals and vaccines. Human adenovirus infections are usually self-limiting, and can cause mild respiratory symptoms with fever, eye infection or gastrointestinal symptoms, but occasional local outbreaks with severe disease courses have been reported. In addition, adenovirus infections pose a serious risk for children and patients with a weakened immune system. Human adenovirus research in animal models to study adenovirus-induced disease and tumor development started in the 1950s. Various animal species have been tested for their susceptibility to human adenovirus infection since then, and some have been shown to mimic key characteristics of the infection in humans, including persistent infection. Furthermore, some rodent species have been found to develop tumors upon human adenovirus infection. Our review summarizes the current knowledge on animal models in human adenovirus research, describing the pros and cons along with important findings and future perspectives.

Abstract

Human adenovirus (HAdV) infections cause a wide variety of clinical symptoms, ranging from mild upper respiratory tract disease to lethal outcomes, particularly in immunocompromised individuals. To date, neither widely available vaccines nor approved antiadenoviral compounds are available to efficiently deal with HAdV infections. Thus, there is a need to thoroughly understand HAdV-induced disease, and for the development and preclinical evaluation of HAdV therapeutics and/or vaccines, and consequently for suitable standardizable in vitro systems and animal models. Current animal models to study HAdV pathogenesis, persistence, and tumorigenesis include rodents such as Syrian hamsters, mice, and cotton rats, as well as rabbits. In addition, a few recent studies on other species, such as pigs and tree shrews, reported promising data. These models mimic (aspects of) HAdV-induced pathological changes in humans and, although they are relevant, an ideal HAdV animal model has yet to be developed. This review summarizes the available animal models of HAdV infection with comprehensive descriptions of virus-induced pathogenesis in different animal species. We also elaborate on rodent HAdV animal models and how they contributed to insights into adenovirus-induced cell transformation and cancer.

Interferon Alpha-Expressing Oncolytic Adenovirus for Treatment of Esophageal Adenocarcinoma

INTRODUCTION

Esophageal adenocarcinoma (EAC) has increased in incidence in Western countries, and its poor prognosis necessitates the development of novel therapeutics. We previously reported the potential of conditionally replicative adenoviruses (CRAd) as a novel therapeutic treatment for this disease. To further augment the therapeutic effectiveness of our cyclooxygenase-2 (Cox2) controlled CRAd in EAC, we inserted an interferon alpha (IFN) transgene into the viral genome that is expressed upon viral replication. In this manuscript, we analyze the cytotoxic and oncolytic effects of an IFN-expressing oncolytic adenovirus in EAC and the role of the Cox2 promoter in providing for selective replication in human tissues.

METHODS

An infectivity-enhanced IFN-expressing CRAd (5/3 Cox2 CRAd ΔE3 ADP IFN) and other control viruses were first tested in vitro with cell lines. For the in vivo study, EAC xenografts in nude mice were treated with a single intratumoral dose of virus. An ex vivo analysis with live tissue slices was conducted using surgically resected EAC patient specimens.

RESULTS

Expression of IFN significantly enhanced the cytotoxic and oncolytic effect of a Cox2-promoter controlled CRAd. This virus showed significant tumor growth suppression in a xenograft model. Furthermore, in human EAC samples, the promoter-controlled virus demonstrated selective replication in cancerous tissues, leaving normal esophageal tissue unaffected.

CONCLUSION

An IFN-expressing CRAd driven by the Cox2 promoter has strong oncolytic effects as well as cancer-specific replication. Our novel vector possesses critical characteristics that make it a potential candidate for clinical translation to treat EAC.

An immune-competent, replication-permissive Syrian Hamster glioma model for evaluating Delta-24-RGD oncolytic adenovirus

BACKGROUND

Oncolytic adenoviruses are promising new treatments against solid tumors, particularly for glioblastoma (GBM), and preclinical models are required to evaluate the mechanisms of efficacy. However, due to the species selectivity of adenovirus, there is currently no single animal model that supports viral replication, tumor oncolysis, and a virus-mediated immune response. To address this gap, we took advantage of the Syrian hamster to develop the first intracranial glioma model that is both adenovirus replication-permissive and immunocompetent.

METHODS

We generated hamster glioma stem-like cells (hamGSCs) by transforming hamster neural stem cells with hTERT, simian virus 40 large T antigen, and h-RasV12. Using a guide-screw system, we generated an intracranial tumor model in the hamster. The efficacy of the oncolytic adenovirus Delta-24-RGD was assessed by survival studies, and tumor-infiltrating lymphocytes were evaluated by flow cytometry.

RESULTS

In vitro, hamster GSCs supported viral replication and were susceptible to Delta-24-RGD mediated cell death. In vivo, hamster GSCs consistently developed into highly proliferative tumors resembling high-grade glioma. Flow cytometric analysis of hamster gliomas revealed significantly increased T cell infiltration in Delta-24-RGD infected tumors, indicative of immune activation. Treating tumor-bearing hamsters with Delta-24-RGD led to significantly increased survival compared to hamsters treated with PBS.

CONCLUSIONS

This adenovirus-permissive, immunocompetent hamster glioma model overcomes the limitations of previous model systems and provides a novel platform in which to study the interactions between tumor cells, the host immune system, and oncolytic adenoviral therapy; understanding of which will be critical to implementing oncolytic adenovirus in the clinic.

Chinese tree shrew: a permissive model for in vitro and in vivo replication of human adenovirus species B

Human adenovirus (HAdV) species B can cause severe acute respiratory diseases. However, the researches to combat this infection have been hampered by the lack of an animal model permissive to the virus. Here, we report in vitro and in vivo HAdV species B infections of tree shrews, the closest relative of primates. HAdV-3, -7, -14, and -55 efficiently replicated in primary cell cultures. After intranasal inoculation of tree shrews with HAdV-55, the viral replication in the oropharyngeal region remained high until day 5 post-infection and was still detected until day 12. HAdV-55 in the lung or turbinate bone tissues reached the highest levels between days 3 and 5 post-infection, which indicated viral replication in the upper and lower respiratory tracts. HAdV-55 infection caused severe interstitial pneumonia in the animal. IL-8, IL-10, IL-17A, and IFN-γ expression in the peripheral blood mononuclear cells from infected animals was up-regulated. The pre-vaccination with HAdV-55 cleared the virus faster in the respiratory tract, mitigated lung pathological changes. Finally, HAdV-55 infection was propagated among tree shrews. Our study demonstrated that the tree shrew is a permissive animal model for HAdV species B infection and may serve as a valuable platform for testing multiple anti-viral treatments.

CXCL12 Retargeting of an Oncolytic Adenovirus Vector to the Chemokine CXCR4 and CXCR7 Receptors in Breast Cancer

Breast cancer is the most frequently diagnosed cancer in women under 60, and the second most diagnosed cancer in women over 60. While significant progress has been made in developing targeted therapies for breast cancer, advanced breast cancer continues to have high mortality, with poor 5-year survival rates. Thus, current therapies are insufficient in treating advanced stages of breast cancer; new treatments are sorely needed to address the complexity of advanced-stage breast cancer. Oncolytic virotherapy has been explored as a therapeutic approach capable of systemic administration, targeting cancer cells, and sparing normal tissue. In particular, oncolytic adenoviruses have been exploited as viral vectors due to their ease of manipulation, production, and demonstrated clinical safety profile. In this study, we engineered an oncolytic adenovirus to target the chemokine receptors CXCR4 and CXCR7. The overexpression of CXCR4 and CXCR7 is implicated in the initiation, survival, progress, and metastasis of breast cancer. Both receptors bind to the ligand, CXCL12 (SDF-1), which has been identified to play a crucial role in the metastasis of breast cancer cells. This study incorporated a T4 fibritin protein fused to CXCL12 into the tail domain of an adenovirus fiber to retarget the vector to the CXCR4 and CXCR7 chemokine receptors. We showed that the modified virus targets and infects CXCR4- and CXCR7-overexpressing breast cancer cells more efficiently than a wild-type control vector. In addition, the substitution of the wild-type fiber and knob with the modified chimeric fiber did not interfere with oncolytic capability. Overall, the results of this study demonstrate the feasibility of retargeting adenovirus vectors to chemokine receptor-positive tumors.

A Tumor-Targeted Replicating Oncolytic Adenovirus Ad-TD-nsIL12 as a Promising Therapeutic Agent for Human Esophageal Squamous Cell Carcinoma

Esophageal squamous cell carcinoma (ESCC) is one of the most lethal cancers in China and existing therapies have been unable to significantly improve prognosis. Oncolytic adenoviruses (OAds) are novel promising anti-tumor drugs and have been evaluated in several cancers including ESCC. However, the antitumour efficacy of the first generation OAds (H101) as single agent is limited. Therefore, more effective OAds are needed. Our previous studies demonstrated that the novel oncolytic adenovirus Ad-TD-nsIL12 (human adenovirus type 5 with E1ACR2, E1B19K, E3gp19K-triple deletions)harboring human non-secretory IL-12 had significant anti-tumor effect, with no toxicity, in a Syrian hamster pancreatic cancer model. In this study, we evaluated the anti-tumor effect of Ad-TD-nsIL12 in human ESCC. The cytotoxicity of Ad-TD-nsIL12, H101 and cisplatin were investigated in two newly established patient-derived tumor cells (PDCs) and a panel of ESCC cell lines in vitro. A novel adenovirus-permissive, immune-deficient Syrian hamster model of PDCs subcutaneous xenograft was established for in vivo analysis of efficacy. The results showed that Ad-TD-nsIL12 was more cytotixic to and replicated more effectively in human ESCC cell lines than H101. Compared with cisplatin and H101, Ad-TD-nsIL12 could significantly inhibit tumor growth and tumor angiogenesis as well as enhance survival rate of animals with no side effects. These findings suggest that Ad-TD-nsIL12 has superior anti-tumor potency against human ESCC with a good safety profile.

Animal models for COVID-19

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is the aetiological agent of coronavirus disease 2019 (COVID-19), an emerging respiratory infection caused by the introduction of a novel coronavirus into humans late in 2019 (first detected in Hubei province, China). As of 18 September 2020, SARS-CoV-2 has spread to 215 countries, has infected more than 30 million people and has caused more than 950,000 deaths. As humans do not have pre-existing immunity to SARS-CoV-2, there is an urgent need to develop therapeutic agents and vaccines to mitigate the current pandemic and to prevent the re-emergence of COVID-19. In February 2020, the World Health Organization (WHO) assembled an international panel to develop animal models for COVID-19 to accelerate the testing of vaccines and therapeutic agents. Here we summarize the findings to date and provides relevant information for preclinical testing of vaccine candidates and therapeutic agents for COVID-19.

Generation and characterization of an Il2rg knockout Syrian hamster model for XSCID and HAdV-C6 infection in immunocompromised patients

Model animals are indispensable for the study of human diseases, and in general, of complex biological processes. The Syrian hamster is an important model animal for infectious diseases, behavioral science and metabolic science, for which more experimental tools are becoming available. Here, we describe the generation and characterization of an interleukin-2 receptor subunit gamma (Il2rg) knockout (KO) Syrian hamster strain. In humans, mutations in IL2RG can result in a total failure of T and natural killer (NK) lymphocyte development and nonfunctional B lymphocytes (X-linked severe combined immunodeficiency; XSCID). Therefore, we sought to develop a non-murine model to study XSCID and the infectious diseases associated with IL2RG deficiency. We demonstrated that the Il2rg KO hamsters have a lymphoid compartment that is greatly reduced in size and diversity, and is impaired in function. As a result of the defective adaptive immune response, Il2rg KO hamsters developed a more severe human adenovirus infection and cleared virus less efficiently than immune competent wild-type hamsters. Because of this enhanced virus replication, Il2rg KO hamsters developed more severe adenovirus-induced liver pathology than wild-type hamsters. This novel hamster strain will provide researchers with a new tool to investigate human XSCID and its related infections.

Immunology of Adenoviral Vectors in Cancer Therapy

Adenoviruses are a commonly utilized virus for gene therapy platforms worldwide. Since adenovirus components are characterized as highly immunogenic, their immunogenicity inhibits the widespread use of adenoviral vectors to treat genetic disorders. However, stimulation of the immune response can be exploited for cancer immunotherapy platforms, and thus adenoviral vectors are used for therapeutic gene transfer, vaccines, and oncolytic agents in the cancer gene therapy field. It is now accepted that the generation of anti-tumor immune responses induced by oncolytic adenovirus treatments is critical for their anti-tumor efficacy. As such, in cancer immunotherapy with adenoviral vectors, a balance must be struck between induction of anti-adenoviral and anti-tumor immune responses. The recent trend in adenoviral-based cancer gene therapy is the development of adenoviral vectors to enhance immune responses and redirect them toward tumors. This review focuses on anti-adenoviral immunity and how adenovirotherapies skew the immune response toward an anti-tumor response.

Macrophage migration inhibitory factor of Syrian golden hamster shares structural and functional similarity with human counterpart and promotes pancreatic cancer

Macrophage migration inhibitory factor (MIF) is a pleiotropic cytokine that increasingly is being studied in cancers and inflammatory diseases. Though murine models have been instrumental in understanding the functional role of MIF in different pathological conditions, the information obtained from these models is biased towards a specific species. In experimental science, results obtained from multiple clinically relevant animal models always provide convincing data that might recapitulate in humans. Syrian golden hamster (Mesocricetus auratus), is a clinically relevant animal model for multiple human diseases. Hence, the major objectives of this study were to characterize the structure and function of Mesocricetus auratus MIF (MaMIF) and finally evaluate its effect on pancreatic tumor growth in vivo. Initially, the recombinant MaMIF was cloned, expressed and purified in a bacterial expression system. The MaMIF primary sequence, biochemical properties, and crystal structure analysis showed greater similarity with human MIF. The crystal structure of MaMIF illustrates that it forms a homotrimer as known in human and mouse. However, MaMIF exhibits some minor structural variations when compared to human and mouse MIF. The in vitro functional studies show that MaMIF has tautomerase activity and enhances activation and migration of hamster peripheral blood mononuclear cells (PBMCs). Interestingly, injection of MaMIF into HapT1 pancreatic tumor-bearing hamsters significantly enhanced the tumor growth and tumor-associated angiogenesis. Together, the current study shows a structural and functional similarity between the hamster and human MIF. Moreover, it has demonstrated that a high level of circulating MIF originating from non-tumor cells might also promote pancreatic tumor growth in vivo.

Syrian Hamster as an Animal Model for the Study on Infectious Diseases

Infectious diseases still remain one of the biggest challenges for human health. In order to gain a better understanding of the pathogenesis of infectious diseases and develop effective diagnostic tools, therapeutic agents, and preventive vaccines, a suitable animal model which can represent the characteristics of infectious is required. The Syrian hamster immune responses to infectious pathogens are similar to humans and as such, this model is advantageous for studying pathogenesis of infection including post-bacterial, viral and parasitic pathogens, along with assessing the efficacy and interactions of medications and vaccines for those pathogens. This review summarizes the current status of Syrian hamster models and their use for understanding the underlying mechanisms of pathogen infection, in addition to their use as a drug discovery platform and provides a strong rationale for the selection of Syrian hamster as animal models in biomedical research. The challenges of using Syrian hamster as an alternative animal model for the research of infectious diseases are also addressed.

Drug development against human adenoviruses and its advancement by Syrian hamster models

The symptoms of human adenovirus infections are generally mild and self-limiting. However, these infections have been gaining importance in recent years because of a growing number of immunocompromised patients. Solid organ and hematopoietic stem cell transplant patients are subjected to severe immunosuppressive regimes and cannot efficaciously eliminate virus infections. In these patients, adenovirus infections can develop into deadly multi-organ disseminated disease. Presently, in the absence of approved therapies, physicians rely on drugs developed for other purposes to treat adenovirus infections. As there is a need for anti-adenoviral therapies, researchers have been developing new agents and repurposing existing ones to treat adenovirus infections. There are several small molecule drugs that are being tested for their efficacy against human adenoviruses; some of these have reached clinical trials, while others are still in the preclinical phase. Besides these compounds, research on immunotherapy against adenoviral infection has made significant progress, promising another modality for treatment. The availability of an animal model confirmed the activity of some drugs already in clinical use while proving that others are inactive. This led to the identification of several lead compounds that await further development. In the present article, we review the current status of anti-adenoviral therapies and their advancement by in vivo studies in the Syrian hamster model.

Overcoming the limitations of locally administered oncolytic virotherapy

Adenovirus (Ad) has been most extensively evaluated gene transfer vector in clinical trials due to facile production in high viral titer, highly efficient transduction, and proven safety record. Similarly, an oncolytic Ad, which replicates selectively in cancer cells through genetic modifications, is actively being evaluated in various phases of clinical trials as a promising next generation therapeutic against cancer. Most of these trials with oncolytic Ads to date have employed intratumoral injection as the standard administration route. Although these locally administered oncolytic Ads have shown promising outcomes, the therapeutic efficacy is not yet optimal due to poor intratumoral virion retention, nonspecific shedding of virion to normal organs, variable infection efficacy due to heterogeneity of tumor cells, adverse antiviral immune response, and short biological activity of oncolytic viruses in situ. These inherent problems associated with locally administered Ad also holds true for other oncolytic viral vectors. Thus, this review will aim to discuss various nanomaterial-based delivery strategies to improve the intratumoral administration efficacy of oncolytic Ad as well as other types of oncolytic viruses.

Oncolytic viro-chemotherapy exhibits antitumor effect in laryngeal squamous cell carcinoma cells and mouse xenografts

Background: Oncolytic virus can specifically replicate in and then lyse tumor cells, but seldom in normal cells. Further studies have shown the significant therapeutic effect of oncolytic virotherapy combining with other strategies, such as chemo-, radio-, and immunotherapy et al. In this study, we investigated the combinational effect of oncolytic virus ZD55-TRAIL and chemotherapy drug doxorubicin (DOX) on human laryngeal squamous cell carcinoma (LSCC).

Methods: The effect of ZD55-TRAIL combined with DOX on cell growth was assessed in LSCC Hep2 cells and normal cells by MTT assay. Hochest 33342 staining was performed to observe cell morphological changes. Western blot was used to detect the expression of apoptotic activation proteins. The in vivo antitumor efficacy of combination treatment was estimated in laryngeal cancer xenograft models.

Results: The combination of ZD55-TRAIL and DOX exhibited enhanced inhibitory effects on laryngocarcinoma cell growth, and had few side effects to normal cells in vitro. Chemotherapy drug increased the inducement of tumor cell apoptosis mediated by oncolytic virus. In vivo experiment confirmed that the combination treatment significantly inhibited Hep2 laryngocarcinoma xenografts growth in mice.

Conclusion: The oncolytic viro-chemotherapy is a potent therapeutic approach for in vitro cytotoxicity evaluation of Hep2 cells and xenograft growth in vivo.

The Development of Oncolytic Adenovirus Therapy in the Past and Future - For the Case of Pancreatic Cancer

Pancreatic cancer is an aggressive malignant disease and the efficacy of current treatments for unresectable diseases is quite limited despite recent advances. Gene therapy /virotherapy strategies may provide new options for the treatment of various cancers including pancreatic cancer. Oncolytic adenovirus shows an antitumoral effect via its intratumoral amplification and strong cytocidal effect in a variety of cancers and it has been employed for the development of potent oncolytic virotherapy agents for pancreatic cancer. Our ultimate goal is to develop an oncolytic adenovirus enabling the treatment of patients with advanced or spread diseases by systemic injection. Systemic application of oncolytic therapy mandates more efficient and selective gene delivery and needs to embody sufficient antitumor effect even with limited initial delivery to the tumor location. In this review, the current status of oncolytic adenoviruses from the viewpoints of vector design and potential strategies to overcome current obstacles for its clinical application will be described. We will also discuss the efforts to improve the antitumor activity of oncolytic adenovirus, in in vivo animal models, and the combination therapy of oncolytic adenovirus with radiation and chemotherapy.

Rodents Versus Pig Model for Assessing the Performance of Serotype Chimeric Ad5/3 Oncolytic Adenoviruses

Oncolytic adenoviruses (Ad) are promising tools for cancer therapeutics. Most Ad-based therapies utilize species C serotypes, with Adenovirus type 5 (Ad5) most commonly employed. Prior clinical trials demonstrated low efficiency of oncolytic Ad5 vectors, mainly due to the absence of Ad5 primary receptor (Coxsackie and Adenovirus Receptor, CAR) on cancer cells. Engineering serotype chimeric vectors (Ad5/3) to utilize Adenovirus type 3 (Ad3) receptors has greatly improved their oncolytic potential. Clinical translation of these infectivity-enhanced vectors has been challenging due to a lack of replication permissive animal models. In this study, we explored pigs as a model to study the performance of fiber-modified Ad5/3 chimeric vectors. As a control, the Ad5 fiber-unmodified virus was used. We analyzed binding, gene transfer, replication, and cytolytic ability of Ad5 and Ad5/3 in various non-human cell lines (murine, hamster, canine, porcine). Among all tested cell lines only porcine cells supported active binding and replication of Ad5/3. Syrian hamster cells supported Ad5 replication but showed no evidence of productive viral replication after infection with Ad5/3 vectors. Transduction and replication ability of Ad5/3 in porcine cells outperformed Ad5, a phenomenon often observed in human cancer cell lines. Replication of Ad5 and Ad5/3 was subsequently evaluated in vivo in immunocompetent pigs. Quantitative PCR analyses 7 days post infection revealed Ad5 and Ad5/3 DNA and replication-dependent luciferase activity in the swine lungs and spleen indicating active replication in these tissues. These studies demonstrated the flaws in using Syrian hamsters for testing serotype chimeric Ad5/3 vectors. This is the first report to validate the pig as a valuable model for preclinical testing of oncolytic adenoviruses utilizing Adenovirus type 3 receptors. We hope that these data will help to foster the clinical translation of oncolytic adenoviruses including those with Ad3 retargeted tropism.

A novel cancer syndrome caused by KCNQ1-deficiency in the golden Syrian hamster

BACKGROUND

The golden Syrian hamster is an emerging model organism. To optimize its use, our group has made the first genetically engineered hamsters. One of the first genes that we investigated is KCNQ1 which encodes for the KCNQ1 potassium channel and also has been implicated as a tumor suppressor gene.

MATERIALS AND METHODS

We generated KCNQ1 knockout (KO) hamsters by CRISPR/Cas9-mediated gene targeting and investigated the effects of KCNQ1-deficiency on tumorigenesis.

RESULTS

By 70 days of age seven of the eight homozygous KCNQ1 KOs used in this study began showing signs of distress, and on necropsy six of the seven ill hamsters had visible cancers, including T-cell lymphomas, plasma cell tumors, hemangiosarcomas, and suspect myeloid leukemias.

CONCLUSIONS

None of the hamsters in our colony that were wild-type or heterozygous for KCNQ1 mutations developed cancers indicating that the cancer phenotype is linked to KCNQ1-deficiency. This study is also the first evidence linking KCNQ1-deficiency to blood cancers.

Vaccine development for human mastadenovirus

Human mastadenovirus (HAdVs) can cause a broad spectrum of diseases in both children and adults, including acute respiratory infection, gastroenteritis, epidemic keratoconjunctivitis. Populations susceptible to adenovirus infection include children, immunocompromised patients and military recruits. To date, seven species (A-G) including more than 79 genotypes have been characterized, of which HAdV-B3, B4, B7 and the recently reemerged types 14 and 55 often lead to severe pneumonia. The live oral enteric-coated adenovirus type 4 and 7 vaccine, which was approved for use in US military personnel of 17 through 50 years of age, had been shown to be safe and highly effective in numerous clinical trials and by ongoing surveillance of febrile respiratory illness. However, there is currently no vaccine approved for general use in children and adults in any part of the world. This review article will summarize the epidemiological data available for adenovirus and the effectiveness of the adenovirus vaccine in the US military. It will also provide a brief overview of innovative vaccine strategies, animal models for vaccine evaluation, and issues regarding vaccine production.

USC-087 protects Syrian hamsters against lethal challenge with human species C adenoviruses

Human adenoviruses (AdV) cause generally mild infections of the respiratory and GI tracts as well as some other tissues. However, AdV can cause serious infection in severely immunosuppressed individuals, especially pediatric patients undergoing allogeneic hematopoietic stem cell transplantation, where mortality rates are up to 80% with disseminated disease. Despite the seriousness of AdV disease, there are no drugs approved specifically to treat AdV infections. We report here that USC-087, an N-alkyl tyrosinamide phosphonate ester prodrug of HPMPA, the adenine analog of cidofovir, is highly effective against multiple AdV types in cell culture. USC-087 is also effective against AdV-C6 in our immunosuppressed permissive Syrian hamster model. In this model, hamsters are immunosuppressed by treatment with high dose cyclophosphamide. Injection of AdV-C6 (or AdV-C5) intravenously leads to a disseminated infection that resembles the disease seen in humans, including death. We have tested the efficacy of orally-administered USC-087 against the median lethal dose of intravenously administered AdV-C6. USC-087 completely prevented or significantly decreased mortality when administered up to 4 days post challenge. USC-087 also prevented or significantly decreased liver damage caused by AdV-C6 infection, and suppressed virus replication even when administered 4 days post challenge. These results imply that USC-087 is a promising candidate for drug development against HAdV infections.

Production of Genetically Engineered Golden Syrian Hamsters by Pronuclear Injection of the CRISPR/Cas9 Complex

The pronuclear (PN) injection technique was first established in mice to introduce foreign genetic materials into the pronuclei of one-cell stage embryos. The introduced genetic material may integrate into the embryonic genome and generate transgenic animals with foreign genetic information following transfer of the injected embryos to foster mothers. Following the success in mice, PN injection has been applied successfully in many other animal species. Recently, PN injection has been successfully employed to introduce reagents with gene-modifying activities, such as the CRISPR/Cas9 system, to achieve site-specific genetic modifications in several laboratory and farm animal species. In addition to mastering the special set of microinjection skills to produce genetically modified animals by PN injection, researchers must understand the reproduction physiology and behavior of the target species, because each species presents unique challenges. For example, golden Syrian hamster embryos have unique handling requirements in vitro such that PN injection techniques were not possible in this species until recent breakthroughs by our group. With our species-modified PN injection protocol, we have succeeded in producing several gene knockout (KO) and knockin (KI) hamsters, which have been used successfully to model human diseases. Here we describe the PN injection procedure for delivering the CRISPR/Cas9 complex to the zygotes of the hamster, the embryo handling conditions, embryo transfer procedures, and husbandry required to produce genetically modified hamsters.

Male Syrian hamsters are more susceptible to intravenous infection with species C human adenoviruses than are females

Recently, increasing attention has been focused on the influence of sex on the course of infectious diseases. Thus far, the best-documented examples point toward an immune-mediated mechanism: the generally stronger immune response in females can result in a faster clearance of the pathogen or, conversely, a more severe immune-mediated pathology. Here, we report that human species C adenoviruses replicate more and cause more pathology in male Syrian hamsters than in females. We also show that this sex disparity is not caused by a stronger immune response to the infection by the female hamsters. Rather, the liver of male hamsters is more susceptible to adenovirus infection: after intravenous injection, more hepatocytes become infected in male animals than in females. We hypothesize that Kupffer cells (hepatic tissue macrophages) of female animals are more active in sequestering circulating virions, and thus protect hepatocytes more efficiently than those of males.

HAdV-C6 Is a More Relevant Challenge Virus than HAdV-C5 for Testing Antiviral Drugs with the Immunosuppressed Syrian Hamster Model

Adenovirus infections of immunocompromised patients can cause a severe multi-organ disease that often results in the patients' death. Presently, there are no drugs specifically approved to treat adenovirus infections, and clinicians resort to the off-label use of antivirals that are approved to treat other DNA virus infections, most frequently cidofovir (CDV). CDV, however, has considerable nephrotoxicity, thus it is recommended only for the most severe cases of adenovirus infections. To facilitate the development of effective, non-toxic antivirals against adenovirus, we have developed a permissive animal model based on the Syrian hamster that can be used to test the efficacy of antiviral compounds. Here, we show that in the hamster model, HAdV-C6 is a more useful challenge virus than the previously described HAdV-C5, because it is filtered out by tissue macrophages to a lesser extent. HAdV-C6 has a 10-fold lower LD50 in hamsters than HAdV-C5 and the pathology is caused by virus replication to a larger extent. We show that valganciclovir (VGCV), a drug that was shown to be active against intravenous HAdV-C5 infection previously, is efficacious against HAdV-C6 when administered either prophylactically or therapeutically. Further, we show for the first time that VGCV, and to a lesser extent CDV, can be used to treat respiratory adenovirus infections in the hamster model. These results extend the utility of the hamster model, and demonstrate the efficacy of two drugs available for clinicians to treat adenovirus infections.

Pathology in Permissive Syrian Hamsters after Infection with Species C Human Adenovirus (HAdV-C) Is the Result of Virus Replication: HAdV-C6 Replicates More and Causes More Pathology than HAdV-C5

Syrian hamsters are permissive for the replication of species C human adenoviruses (HAdV-C). The virus replicates to high titers in the liver of these animals after intravenous infection, while respiratory infection results in virus replication in the lung. Here we show that two types belonging to species C, HAdV-C5 and HAdV-C6, replicate to significantly different extents and cause pathology with significantly different severities, with HAdV-C6 replicating better and inducing more severe and more widespread lesions. The virus burdens in the livers of HAdV-C6-infected hamsters are higher than the virus burdens in HAdV-C5-infected ones because more of the permissive hepatocytes get infected. Furthermore, when hamsters are infected intravenously with HAdV-C6, live, infectious virus can be isolated from the lung and the kidney, which is not seen with HAdV-C5. Similarly to mouse models, in hamsters, HAdV-C6 is sequestered by macrophages to a lesser degree than HAdV-C5. Depletion of Kupffer cells from the liver greatly increases the replication of HAdV-C5 in the liver, while it has only a modest effect on the replication of HAdV-C6. Elimination of Kupffer cells also dramatically increases the pathology induced by HAdV-C5. These findings indicate that in hamsters, pathology resulting from intravenous infection with adenoviruses is caused mostly by replication in hepatocytes and not by the abortive infection of Kupffer cells and the following cytokine storm.IMPORTANCE Immunocompromised human patients can develop severe, often lethal adenovirus infections. Respiratory adenovirus infection among military recruits is a serious problem, in some cases requiring hospitalization of the patient. Furthermore, adenovirus-based vectors are frequently used as experimental viral therapeutic agents. Thus, it is imperative that we investigate the pathogenesis of adenoviruses in a permissive animal model. Syrian hamsters are susceptible to infection with certain human adenoviruses, and the pathology accompanying these infections is similar to what is observed with adenovirus-infected human patients. We demonstrate that replication in permissive cells in a susceptible host animal is a major part of the mechanism by which systemic adenovirus infection induces pathology, as opposed to the chiefly immune-mediated pathology observed in nonsusceptible hosts. These findings support the use of compounds inhibiting adenovirus replication as a means to block adenovirus-induced pathology.

The Efficacy of Oncolytic Adenovirus Is Mediated by T-cell Responses against Virus and Tumor in Syrian Hamster Model

PURPOSE

Oncolytic adenoviruses (Ad) represent an innovative approach to cancer therapy. Its efficacy depends on multiple actions, including direct tumor lysis and stimulation of antiviral and antitumor immune responses. In this study, we investigated the roles of T-cell responses in oncolytic adenoviral therapy.

EXPERIMENTAL DESIGN

An immunocompetent and viral replication-permissive Syrian hamster tumor model was used. The therapeutic mechanisms of oncolytic Ad were investigated by T-cell deletion, immunohistochemical staining, and CTL assay.

RESULTS

Deletion of T cells with an anti-CD3 antibody completely demolished the antitumor efficacy of oncolytic Ad. Intratumoral injection of Ad induced strong virus- and tumor-specific T-cell responses, as well as antiviral antibody response. Both antiviral and antitumor T-cell responses contributed to the efficacy of oncolytic Ad. Deletion of T cells increased viral replication and extended the persistence of infectious virus within tumors but almost abrogated the antitumor efficacy. Preexisting antiviral immunity promoted the clearance of injected oncolytic Ad from tumors but had no effect on antitumor efficacy. Strikingly, the repeated treatment with oncolytic Ad has strong therapeutic effect on relapsed tumors or tumors insensitive to the primary viral therapy.

CONCLUSIONS

These results demonstrate that T cell-mediated immune responses outweigh the direct oncolysis in mediating antitumor efficacy of oncolytic Ad. Our data have a high impact on redesigning the regimen of oncolytic Ad for cancer treatment. Clin Cancer Res; 23(1); 239-49. ©2016 AACR.

Syngeneic syrian hamster tumors feature tumor-infiltrating lymphocytes allowing adoptive cell therapy enhanced by oncolytic adenovirus in a replication permissive setting

Adoptive transfer of tumor-infiltrating lymphocytes (TIL) has shown promising yet sometimes suboptimal results in clinical trials for advanced cancer, underscoring the need for approaches improving efficacy and safety. Six implantable syngeneic tumor cell lines of the Syrian hamster were used to initiate TIL cultures. TIL generated from tumor fragments cultured in human interleukin-2 (IL-2) for 10 d were adoptively transferred into tumor-bearing hamsters with concomitant intratumoral injections of oncolytic adenovirus (Ad5-D24) for the assessment of antitumor efficacy. Pancreatic cancer (HapT1) and melanoma (RPMI 1846) TIL exhibited potent and tumor-specific cytotoxicity in effector-to-target (E/T) assays. MHC Class I blocking abrogated the cell killing of RPMI 1846 TIL, indicating cytotoxic CD8(+) T-cell activity. When TIL were combined with Ad5-D24 in vitro, HapT1 tumor cell killing was significantly enhanced over single agents. In vivo, the intratumoral administration of HapT1 TIL and Ad5-D24 resulted in improved tumor growth control compared with either treatment alone. Additionally, splenocytes derived from animals treated with the combination of Ad5-D24 and TIL killed autologous tumor cells more efficiently than monotherapy-derived splenocytes, suggesting that systemic antitumor immunity was induced. For the first time, TIL of the Syrian hamster have been cultured, characterized and used therapeutically together with oncolytic adenovirus for enhancing the efficacy of TIL therapy. Our results support human translation of oncolytic adenovirus as an enabling technology for adoptive T-cell therapy of solid tumors.

Transcriptome sequencing and development of an expression microarray platform for liver infection in adenovirus type 5-infected Syrian golden hamsters

The Syrian golden hamster is an attractive animal for research on infectious diseases and other diseases. We report here the sequencing, assembly, and annotation of the Syrian hamster transcriptome. We include transcripts from ten pooled tissues from a naïve hamster and one stimulated with lipopolysaccharide. Our data set identified 42,707 non-redundant transcripts, representing 34,191 unique genes. Based on the transcriptome data, we generated a custom microarray and used this new platform to investigate the transcriptional response in the Syrian hamster liver following intravenous adenovirus type 5 (Ad5) infection. We found that Ad5 infection caused a massive change in regulation of liver transcripts, with robust up-regulation of genes involved in the antiviral response, indicating that the innate immune response functions in the host defense against Ad5 infection of the liver. The data and novel platforms developed in this study will facilitate further development of this important animal model.

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Syrian hamster transcriptome; 42,707 transcripts representing 34,191 unique genes

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Syrian hamster custom expression microarray platform

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Ad5 intravenous infection of the Syrian hamster liver

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Ad5 upregulation of hamster liver genes involved in innate antiviral response.

Antiadenovirus drug discovery: potential targets and evaluation methodologies

Human adenoviruses (HAdV) are the cause of many acute infections, mostly in the respiratory and gastrointestinal (GI) tracts, as well as conjunctivitis. HAdV diseases in immunocompetent individuals are mostly self-limiting; however, in immunocompromised individuals, especially in pediatric units, HAdV infections are the cause of high morbidity and mortality. Despite the significant clinical impact, there are currently no approved antiviral therapies for HAdV infections. Here, we provide an overview of the different targets that could be considered for the design of specific drugs against HAdV, as well as the available in vitro and in vivo tools for the screening and evaluation of candidate molecules.

Oncolytic adenovirus research evolution: from cell-cycle checkpoints to immune checkpoints

Oncolytic adenoviruses are modified to exploit the aberrant expression of proteins in cancer cells to obtain cancer-selective replication. Moreover, the natural tropism of oncolytic adenoviruses can be redirected to tumor cells. Clinical trials revealed that oncolytic viruses showed poor replication in the tumor that is due in part to the immune response against the virus. More recent data demonstrated that tumor infection might subvert the tumor immune system and lead to an anti-tumor immune response. In the next few years, combination of adenoviruses with immune checkpoint antibodies and other immune modulators will be tested in clinical trials.

Valganciclovir inhibits human adenovirus replication and pathology in permissive immunosuppressed female and male Syrian hamsters

Adenovirus infections of immunocompromised pediatric hematopoietic stem cell transplant patients can develop into serious and often deadly multi-organ disease. There are no drugs approved for adenovirus infections. Cidofovir (an analog of 2-deoxycytidine monophosphate) is used at times but it can be nephrotoxic and its efficacy has not been proven in clinical trials. Brincidofovir, a promising lipid-linked derivative of cidofovir, is in clinical trials. Ganciclovir, an analog of 2-deoxyguanosine, has been employed occasionally but with unknown efficacy in the clinic. In this study, we evaluated valganciclovir against disseminated adenovirus type 5 (Ad5) infection in our permissive immunosuppressed Syrian hamster model. We administered valganciclovir prophylactically, beginning 12 h pre-infection or therapeutically starting at Day 1, 2, 3, or 4 post-infection. Valganciclovir significantly increased survival, reduced viral replication in the liver, and mitigated the pathology associated with Ad5 infection. In cultured cells, valganciclovir inhibited Ad5 DNA replication and blocked the transition from early to late stage of infection. Valganciclovir directly inhibited Ad5 DNA polymerase in vitro, which may explain, at least in part, its mechanism of action. Ganciclovir and valganciclovir are approved to treat infections by certain herpesviruses. Our results support the use of valganciclovir to treat disseminated adenovirus infections in immunosuppressed patients.

Oncolytic adenovirus expressing interferon alpha in a syngeneic Syrian hamster model for the treatment of pancreatic cancer

BACKGROUND

The addition of interferon (IFN) alpha to adjuvant chemoradiotherapy regimens resulted in remarkable improvements in survival for pancreatic cancer patients. However, systemic toxicities and insufficient levels of IFN at the tumor sites have limited its widespread adoption in treatment schemes. We have previously developed an IFN-expressing conditionally replicative oncolytic adenovirus and demonstrated its therapeutic effects both in vitro and in vivo. Here, the same vectors were tested in a syngeneic and immunocompetent Syrian hamster model to better understand the roles of adenoviral replication and of the pleiotropic effects of IFN on pancreatic tumor growth suppression.

METHODS

Oncolytic adenoviruses expressing human or hamster IFN were designed and generated. Viral vectors were tested in vitro to determine qualitative and quantitative cell viability, cyclooxygenase 2 (Cox2) promoter activity, and IFN production. For the in vivo studies, subcutaneous hamster pancreatic cancer tumors were treated with 1 intratumoral dose of virus. Similarly, 1 intraperitoneal dose of virus was used to prolong survival in a carcinomatosis model.

RESULTS

All cell lines tested demonstrated Cox2 promoter activity. The oncolytic potential of a replication competent adenovirus expressing the IFN cytokine was clearly demonstrated. These viruses resulted in significant tumor growth suppression and survival increases compared with controls in a hamster model.

CONCLUSION

The profound therapeutic potential of an IFN-expressing oncolytic adenovirus for the treatment of pancreatic cancer was demonstrated in a syngeneic Syrian hamster model. These results strongly suggest the potential application of our viruses as part of combination regimens with other therapeutics.

Virotherapy targeting cyclin E overexpression in tumors with adenovirus-enhanced cancer-selective promoter

Oncolytic virotherapy can selectively destroy cancer cells and is a potential approach in cancer treatment. A strategy to increase tumor-specific selectivity is to control the expression of a key regulatory viral gene with a tumor-specific promoter. We have previously found that cyclin E expression is augmented in cancer cells after adenovirus (Ad) infection. Thus, the cyclin E promoter that is further activated by Ad in cancer cells may have unique properties for enhancing oncolytic viral replication. We have shown that high levels of viral E1a gene expression are achieved in cancer cells infected with Ad-cycE, in which the endogenous Ad E1a promoter was replaced with the cyclin E promoter. Ad-cycE shows markedly selective oncolytic efficacy in vitro and destroys various types of cancer cells, including those resistant to ONYX-015/dl1520. Furthermore, Ad-cycE shows a strong capacity to repress A549 xenograft tumor growth in nude mice and significantly prolongs survival. This study suggests the potential of Ad-cycE in cancer therapy and indicates the advantages of using promoters that can be upregulated by virus infection in cancer cells in development of oncolytic viruses. Key messages: Cyclin E promoter activity is high in cancer cells and enhanced by adenovirus infection. Cyclin E promoter is used to control the E1a gene of a tumor-specific oncolytic adenovirus. Ad-cycE efficiently targets cancer cells and induces oncolysis. Ad-cycE significantly repressed xenograft tumor and prolonged survival.

Cidofovir and brincidofovir reduce the pathology caused by systemic infection with human type 5 adenovirus in immunosuppressed Syrian hamsters, while ribavirin is largely ineffective in this model

There are no drugs approved specifically to treat disseminated adenovirus (Ad) infections in humans. Cidofovir is active against Ad in cell culture, and it is used frequently in the clinic with disseminated infection in pediatric transplant patients; however, controlled clinical studies have not been conducted to prove the anti-Ad efficacy of cidofovir. Brincidofovir, a lipid-linked derivative of cidofovir, which has strong activity against Ad in cell culture and in animal models, is a promising new drug currently in clinical trials. Ribavirin, which has modest activity against some Ad types in cell culture, has been used in the clinic against disseminated Ad, but the efficacy of ribavirin is unknown. In the current study, we have examined the activity of cidofovir, brincidofovir, and ribavirin against disseminated Ad5 infection in the immunosuppressed Syrian hamster model. Hamsters are immunosuppressed by treatment with cyclophosphamide, then infected intravenously with Ad5, leading to disseminated Ad5 infection, especially in the liver. We found that cidofovir and brincidofovir have excellent activity against Ad5 pathology and replication in the liver, even when administered therapeutically starting at 3 days post-challenge with Ad5. Ribavirin did not have anti-Ad5 activity in our model. Our data support the use of cidofovir and brincidofovir in humans for the treatment of disseminated Ad infections in humans.

Efficient gene targeting in golden Syrian hamsters by the CRISPR/Cas9 system

The golden Syrian hamster is the model of choice or the only rodent model for studying many human diseases. However, the lack of gene targeting tools in hamsters severely limits their use in biomedical research. Here, we report the first successful application of the CRISPR/Cas9 system to efficiently conduct gene targeting in hamsters. We designed five synthetic single-guide RNAs (sgRNAs)--three for targeting the coding sequences for different functional domains of the hamster STAT2 protein, one for KCNQ1, and one for PPP1R12C--and demonstrated that the CRISPR/Cas9 system is highly efficient in introducing site-specific mutations in hamster somatic cells. We then developed unique pronuclear (PN) and cytoplasmic injection protocols in hamsters and produced STAT2 knockout (KO) hamsters by injecting the sgRNA/Cas9, either in the form of plasmid or mRNA, targeting exon 4 of hamster STAT2. Among the produced hamsters, 14.3% and 88.9% harbored germline-transmitted STAT2 mutations from plasmid and mRNA injection, respectively. Notably, 10.4% of the animals produced from mRNA injection were biallelically targeted. This is the first success in conducting site-specific gene targeting in hamsters and can serve as the foundation for developing other genetically engineered hamster models for human disease.

Establishment of a mouse melanoma model system for the efficient infection and replication of human adenovirus type 5-based oncolytic virus

Due to poor adenoviral infectivity and replication in mouse tumor cell types compared with human tumor cell types, use of human-type adenoviral vectors in mouse animal model systems was limited. Here, we demonstrate enhanced infectivity and productive replication of adenovirus in mouse melanoma cells following introduction of both the Coxsackievirus and adenovirus receptor (CAR) and E1B-55K genes. Introduction of CAR into B16BL6 or B16F10 cells increased the infectivity of GFP-expressing adenovirus; however, viral replication was unaffected. We demonstrated a dramatic increase of adenoviral replication (up to 100-fold) in mouse cells via E1B-55K expression and subsequent viral spreading in mouse tissue. These results reveal for the first time that human adenovirus type 5 (Ad5)-based oncolytic virus can be applied to immunocompetent mouse with the introduction of CAR and E1B-55K to syngenic mouse cell line.

Ganciclovir inhibits human adenovirus replication and pathogenicity in permissive immunosuppressed Syrian hamsters

Adenovirus infections of immunocompromised patients can develop into deadly multiorgan or systemic disease. The virus is especially threatening for pediatric allogeneic hematopoietic stem cell transplant recipients; according to some studies, 10% or more of these patients succumb to disease resulting from adenovirus infection. At present, there is no drug approved for the treatment or prevention of adenovirus infections. Compounds that are approved to treat other virus infections are used off-label to combat adenovirus, but only anecdotal evidence of the efficacy of these drugs exists. Ganciclovir, a drug approved for the treatment of herpesvirus infection, was previously reported to be effective against human adenoviruses in vitro. To model adenovirus infections in immunocompromised humans, we examined ganciclovir's efficacy in immunosuppressed Syrian hamsters intravenously infected with type 5 human adenovirus (Ad5). This animal model is permissive for Ad5 replication, and the animals develop symptoms similar to those seen in humans. We demonstrate that ganciclovir suppresses Ad5 replication in the liver of infected hamsters and that it mitigates the consequences of Ad5 infections in these animals when administered prophylactically or therapeutically. We show that ganciclovir inhibits Ad5 DNA synthesis and late gene expression. The mechanism of action for the drug is not clear; preliminary data suggest that it exerts its antiadenoviral effect by directly inhibiting the adenoviral DNA polymerase. While more extensive studies are required, we believe that ganciclovir is a promising drug candidate to treat adenovirus infections. Brincidofovir, a drug with proven activity against Ad5, was used as a positive control in the prophylactic experiment.

Evaluation of apoptogenic adenovirus type 5 oncolytic vectors in a Syrian hamster head and neck cancer model

Human adenovirus (HAdV) vectors are intensely investigated for virotherapy of a wide variety of human cancers. Here, we have evaluated the effect of two apoptogenic HAdV5 vectors in an immunocompetent Syrian hamster animal model of head and neck cancer. We established two cell lines of hamster cheek pouch squamous cell carcinomas, induced by treatment with 9, 10-dimethyl-1, 2-benzanthracene (DMBA). These cell lines, when infected with HAdV5 mutants lp11w and lp11w/Δ55K (which are defective in the expression of either E1B-19K alone or both E1B-19K and E1B-55K proteins) exhibited enhanced apoptotic and cytotoxic responses. The cheek pouch tumor cells transplanted either subcutaneously at the flanks or in the cheek pouches of hamsters readily formed tumors. Intra-tumoral administration of HAdV5 E1B mutants efficiently suppressed the growth of tumors at both sites. Histological examination of orthotopic tumors revealed reduced vascularity and the expression of the viral fiber antigen in virus-administered cheek pouch tumors. These tumors also exhibited increased caspase-3 levels, suggesting virus-induced apoptosis may contribute to tumor growth suppression. Our results suggest that the apoptogenic HAdV5 vectors may have utility for the treatment of human head and neck cancers.

Delta-24-RGD oncolytic adenovirus elicits anti-glioma immunity in an immunocompetent mouse model

Background

Emerging evidence suggests anti-cancer immunity is involved in the therapeutic effect induced by oncolytic viruses. Here we investigate the effect of Delta-24-RGD oncolytic adenovirus on innate and adaptive anti-glioma immunity.

Design

Mouse GL261-glioma model was set up in immunocompetent C57BL/6 mouse for Delta-24-RGD treatment. The changes of the immune cell populations were analyzed by immunohistochemistry and flow cytometry. The anti-glioma immunity was evaluated with functional study of the splenocytes isolated from the mice. The efficacy of the virotherapy was assessed with animal survival analysis. The direct effect of the virus on the tumor-associated antigen presentation to CD8+ T cells was analyzed with an in vitro ovalbumin (OVA) modeling system.

Results

Delta-24-RGD induced cytotoxic effect in mouse glioma cells. Viral treatment in GL261-glioma bearing mice caused infiltration of innate and adaptive immune cells, instigating a Th1 immunity at the tumor site which resulted in specific anti-glioma immunity, shrunken tumor and prolonged animal survival. Importantly, viral infection and IFNγ increased the presentation of OVA antigen in OVA-expressing cells to CD8+ T-cell hybridoma B3Z cells, which is blocked by brefeldin A and proteasome inhibitors, indicating the activity is through the biosynthesis and proteasome pathway.

Conclusions

Our results demonstrate that Delta-24-RGD induces anti-glioma immunity and offers the first evidence that viral infection directly enhances presentation of tumor-associated antigens to immune cells.

Evaluation of the HC-04 cell line as an in vitro model for mechanistic assessment of changes in hepatic cytochrome P450 3A during adenovirus infection

HC-04 cells were evaluated as an in vitro model for mechanistic study of changes in the function of hepatic CYP3A during virus infection. Similar to in vivo observations, infection with a first generation recombinant adenovirus significantly inhibited CYP3A4 catalytic activity in an isoform-specific manner. Virus (MOI 100) significantly reduced expression of the retinoid X receptor (RXR) by 30% 96 hours after infection. Cytoplasmic concentrations of the pregnane X receptor (PXR) were reduced by 50%, whereas the amount of the constitutive androstane receptor (CAR) in the nuclear fraction doubled with respect to uninfected controls. Hepatocyte nuclear factor 4α (HNF-4α) and peroxisome proliferator-activated receptor γ coactivator 1α (PGC-1α) were also reduced by ∼70% during infection. Virus suppressed CYP3A4 activity in the presence of the PXR agonist rifampicin and did not affect CYP3A4 activity in the presence of the CAR agonist CITCO [6-(4-chlorophenyl) imidazo[2,1-b][1,3]thiazole-5-carbaldehyde-O-(3,4-dichlorobenzyl)oxime], suggesting that virus-induced modification of PXR may be responsible for observed changes in hepatic CYP3A4. The HC-04 cell line is easy to maintain, and CYP3A4 in these cells was responsive to known inducers and suppressors. Dexamethasone (200 μM) and phenobarbital (500 μM) increased activity by 230 and 124%, whereas ketoconazole (10 μM) and lipopolysaccharide (LPS) (10 μg/ml) reduced activity by 90 and 92%, respectively. This suggests that HC-04 cells can be a valuable tool for mechanistic study of drug metabolism during infection and for routine toxicological screening of novel compounds prior to use in the clinic.