Effect of 6-azacytidine on the course of experimental adenoviral infection in newborn Syrian hamsters

Current antiviral agents against human adenoviruses associated with respiratory infections

Human adenoviruses (HAdVs) are important pathogens responsible for respiratory infections. In children and immunocompromised patients, respiratory infections can cause considerable morbidity and mortality. Currently, there are no approved effective and safe antiviral therapeutics for the clinical treatment of HAdV infections, even those that have undergone preclinical/clinical trials. However, many compounds and molecules with anti-HAdV activity have been explored, and some candidates are undergoing clinical development. Here, we reviewed the reported in vitro and in vivo efficacies, as well as the therapeutic potential of these antiviral compounds, providing an overview and a summary of the current status of anti-HAdV drug development.

Antiviral Drugs in Adenovirus-Induced Keratoconjunctivitis

Human adenovirus (HAdV) is one of the most common causes of conjunctivitis worldwide. Depending on specific serotypes and other factors, it can lead to several ocular manifestations, ranging from isolated, self-limited disease to epidemic and potentially sight-threatening keratoconjunctivitis. To date, no antiviral agent against ocular adenovirus has been licensed, and its management is still based on hygienic and supportive measures alone. In this review, a literature search up to August 2021 was performed to find peer-reviewed articles, with the primary aim to investigate drugs or other compounds with any antiviral activity against adenovirus. Finally, we included 70 articles, consisting of both in vitro, and in vivo studies on animal models and clinical trials of any phase, as well as a case-report, and analyzed each compound separately. Many antiviral agents proved to be effective on in vivo and in vitro studies on animal models, and in pre-clinical trials, but lacked reliability in large, controlled clinical investigations. The design of such studies, though, presented several hurdles, due to the nature and the specific characteristics of adenovirus-induced ocular diseases. Nevertheless, some promising compounds are currently under study, and further investigations are needed to prove their efficacy in the management of adenovirus conjunctivitis.

2-Hydroxyimino-6-aza-pyrimidine nucleosides: synthesis, DFT calculations, and antiviral evaluations

Synthesis, DFT calculations, and antiviral evaluation of a series of novel 2-hydroxyimino-6-aza-pyrimidine ribonucleosides is reported. The hydrogen bonding between the C²N–OH moiety and N³–H and/or N³ moieties shapes the pyrimidine nucleoside as purine.

[The effect of combination of glycyrrhizic acid with alpha-glutamyl-tryptophan on the experimental adenoviral infection]

In this work, the activity of glycyrrhizic acid (GL) and dipeptide alpha-glutamyl-tryptophane (EW) as single preparations or in combination (GL+EW) against experimental adenoviral infection in the syrian hamsters was studied. Application of gl and GL+EW was shown to decrease the level of the adenovirus replication in liver tissue by 0.6 - 1.2 lgTCID50 depending on the composition and time point of the post infection. It was also demonstrated that normalization of the structure of the liver tissue was required, which was shown on the level of both optical and electron microscopy. The results obtained in this work suggest that gl and GL+EW may be considered as potential component of the complex therapy of adenoviral infection.

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

The Syrian (golden) hamster (Mesocricetus auratus) has served as a useful model for different aspects of biology for at least 50 years, and its use has been expanding recently. In earlier years, among other things, it was a model for cancer development. More recently, it has become a model for many different infectious diseases. It has also become an alternative model for the study of oncolytic adenovirus vectors for cancer gene therapy. Among several other human pathogens, the hamster is permissive for the replication of human species C adenoviruses, which are the parental virus for the majority of adenovirus vectors in use today. These vectors replicate in some of the established hamster tumor cell lines that can be used to generate tumors in vivo, that is, one can study oncolytic (replication competent) adenoviruses in a permissive, immunocompetent model. This has afforded the opportunity to study the effect of the host immune system on the vector-infected tumor and has allowed the use of a more relevant animal model to determine the safety and biodistribution of replication-competent adenoviruses. The hamster has also been used to evaluate antiviral compounds and vaccines against many viruses, including adenoviruses, flaviviruses, alphaviruses, arenaviruses, bunyaviruses, and paramyxoviruses.

Activity of Ingavirin (6-[2-(1H-Imidazol-4-yl)ethylamino]-5-oxo-hexanoic Acid) Against Human Respiratory Viruses in in Vivo Experiments

Respiratory viral infections constitute the most frequent reason for medical consultations in the World. They can be associated with a wide range of clinical manifestations ranging from self-limited upper respiratory tract infections to more devastating conditions such as pneumonia. In particular, in serious cases influenza A leads to pneumonia, which is particularly fatal in patients with cardiopulmonary diseases, obesity, young children and the elderly. In the present study, we show a protective effect of the low-molecular weight compound Ingavirin (6-[2-(1H-imidazol-4-yl)ethylamino]-5-oxohexanoic acid) against influenza A (H1N1) virus, human parainfluenza virus and human adenovirus infections in animals. Mortality, weight loss, infectious titer of the virus in tissues and tissue morphology were monitored in the experimental groups of animals. The protective action of Ingavirin was observed as a reduction of infectious titer of the virus in the lung tissue, prolongation of the life of the infected animals, normalization of weight dynamics throughout the course of the disease, lowering of mortality of treated animals compared to a placebo control and normalization of tissue structure. In case of influenza virus infection, the protective activity of Ingavirin was similar to that of the reference compound Tamiflu. Based on the results obtained, Ingavirin should be considered as an important part of anti-viral prophylaxis and therapy.

New pancreatic carcinoma model for studying oncolytic adenoviruses in the permissive Syrian hamster

Syrian hamster is a practical animal model for studying the systemic effects of oncolytic vectors derived from adenovirus serotype 5 (Ad5). Ad5 replicates well in Syrian hamster tissues, and Syrian hamster cell lines are available that are known to support Ad5 replication. In this study, we established four new Syrian hamster cell lines from transplantable pancreatic, renal, hepatic and lung tumors. The pancreatic cell line (SHPC6) and the renal cell line were highly permissive for Ad5 replication. The SHPC6 cell line formed disseminated intraperitoneal tumors when cells were injected into the peritoneal cavity. INGN 007, an oncolytic Ad5-based vector, completely reversed the growth of disseminated intraperitoneal SHPC6 tumor nodules following intraperitoneal injection of the vector, leading to 100% survival of the treated animals. SHPC6 cells also formed subcutaneous tumors, whose growth was suppressed by INGN 007 following intratumoral injection. INGN 007 replicated in both the intraperitoneal and subcutaneous SHPC6 tumors. Following intraperitoneal injection, INGN 007 did not replicate in the livers of hamsters with intraperitoneal SHPC6 tumors, and was not hepatotoxic. These studies suggest that the SHPC6 cell line may be useful as a model for disseminated pancreatic cancer, and that INGN 007 may be a safe and effective vector to treat these tumors.

Clinical features and treatment of adenovirus infections

Adenoviruses (Ads) are common opportunistic pathogens that are rarely associated with severe clinical symptoms in healthy individuals. In contrast, in patients with compromised immunity, Ad infections often result in disseminated and potentially life-threatening disease. Among these are AIDS patients, individuals with hereditary immunodeficiencies and recipients of solid organ or haematopoietic stem cell transplants (HSCT) who receive immunosuppressive therapy. The latter account for the largest number of severe Ad infections. There is currently no formally approved antiviral therapy for the treatment of severe Ad keratoconjunctivitis and life-threatening Ad infections in immunocompromised patients. Here we update current knowledge on Ad biology, the clinical features observed in different patient groups and specific immune responses towards Ad infections. In addition, we review current and future treatment options, including: (i) the antiviral drugs cidofovir, ribavirin and new investigational compounds, as evaluated in the clinic or in relevant animal models, as well as (ii) novel immunotherapeutic strategies.

Hexadecyloxypropyl-cidofovir, CMX001, prevents adenovirus-induced mortality in a permissive, immunosuppressed animal model

Adenoviruses (Ads) cause a wide array of end-organ and disseminated diseases in severely immunosuppressed patients. For example, approximately 20% of pediatric allogeneic hematopoietic stem cell transplant recipients develop disseminated Ad infection, and the disease proves fatal in as many as 50-80% of these patients. Ad infections are a serious problem for solid-organ transplant recipients and AIDS patients as well. Unfortunately, there are no antiviral drugs approved specifically to treat these infections. A suitable animal model that is permissive for Ad replication would help in the discovery process. Here we identify an animal model to study Ad pathogenesis and the efficacy of antiviral compounds. We show that human serotype 5 Ad (Ad5) causes severe systemic disease in immunosuppressed Syrian hamsters that is similar to that seen in immunocompromised patients. We also demonstrate that hexadecyloxypropyl-cidofovir (CMX001) rescues the hamsters from a lethal challenge with Ad5. The antiviral drug provided protection both prophylactically and when given up to 2 days after i.v. exposure to Ad5. CMX001 acts by reducing Ad replication in key target organs. Thus, the immunosuppressed Syrian hamster is a powerful model to evaluate anti-Ad drugs, and its use can facilitate the entry of drugs such as CMX001 into clinical trials.