Efficacy Of Antiviral Compounds Research Articles

Alternatives to animal models and their application in the discovery of species susceptibility to SARS-CoV-2 and other respiratory infectious pathogens: A review.

The emergence of the coronavirus disease 2019 (COVID-19) caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) inspired rapid research efforts targeting the host range, pathogenesis and transmission mechanisms, and the development of antiviral strategies. Genetically modified mice, rhesus macaques, ferrets, and Syrian golden hamsters have been frequently used in studies of pathogenesis and efficacy of antiviral compounds and vaccines. However, alternatives to in vivo experiments, such as immortalized cell lines, primary respiratory epithelial cells cultured at an air-liquid interface, stem/progenitor cell-derived organoids, or tissue explants, have also been used for isolation of SARS-CoV-2, investigation of cytopathic effects, and pathogen-host interactions. Moreover, initial proof-of-concept studies for testing therapeutic agents can be performed with these tools, showing that animal-sparing cell culture methods could significantly reduce the need for animal models in the future, following the 3R principles of replace, reduce, and refine. So far, only few studies using animal-derived primary cells or tissues have been conducted in SARS-CoV-2 research, although natural infection has been shown to occur in several animal species. Therefore, the need for in-depth investigations on possible interspecies transmission routes and differences in susceptibility to SARS-CoV-2 is urgent. This review gives an overview of studies employing alternative culture systems like primary cell cultures, tissue explants, or organoids for investigations of the pathophysiology and reverse zoonotic potential of SARS-CoV-2 in animals. In addition, future possibilities of SARS-CoV-2 research in animals, including previously neglected methods like the use of precision-cut lung slices, will be outlined.

The role of pseudotype neutralization assays in understanding SARS CoV-2.

Abstract Neutralisation assays are crucial tools to quantify the presence of functional neutralising antibodies in serum samples. Since the SARS-CoV-2 virus (the causative agent of COVID-19) is designated as a category 3 biosafety level pathogen, pseudotyped viruses bearing the SARS-CoV-2 spike protein permit extensive and widespread serum/plasma screening in a BSL 2 laboratory. These assays can be used to assess viral tropism, vaccine immunogenicity, efficacy of antiviral compounds (incl. therapeutic mAbs) and serosurveillance studies. In this article, we highlight approaches to SARS-CoV-2 viral pseudotyping, its practicality, and utility in increasing our understanding of neutralising antibodies against SARS-CoV-2.

Quantification system for the viral dynamics of a highly pathogenic simian/human immunodeficiency virus based on an in vitroexperiment and a mathematical model

BackgroundDeveloping a quantitative understanding of viral kinetics is useful for determining the pathogenesis and transmissibility of the virus, predicting the course of disease, and evaluating the effects of antiviral therapy. The availability of data in clinical, animal, and cell culture studies, however, has been quite limited. Many studies of virus infection kinetics have been based solely on measures of total or infectious virus count. Here, we introduce a new mathematical model which tracks both infectious and total viral load, as well as the fraction of infected and uninfected cells within a cell culture, and apply it to analyze time-course data of an SHIV infection in vitro.ResultsWe infected HSC-F cells with SHIV-KS661 and measured the concentration of Nef-negative (target) and Nef-positive (infected) HSC-F cells, the total viral load, and the infectious viral load daily for nine days. The experiments were repeated at four different MOIs, and the model was fitted to the full dataset simultaneously. Our analysis allowed us to extract an infected cell half-life of 14.1 h, a half-life of SHIV-KS661 infectiousness of 17.9 h, a virus burst size of 22.1 thousand RNA copies or 0.19 TCID50, and a basic reproductive number of 62.8. Furthermore, we calculated that SHIV-KS661 virus-infected cells produce at least 1 infectious virion for every 350 virions produced.ConclusionsOur method, combining in vitro experiments and a mathematical model, provides detailed quantitative insights into the kinetics of the SHIV infection which could be used to significantly improve the understanding of SHIV and HIV-1 pathogenesis. The method could also be applied to other viral infections and used to improve the in vitro determination of the effect and efficacy of antiviral compounds.

Quantification system for the viral dynamics of a highly pathogenic simian/human immunodeficiency virus based on an in vitro experiment and a mathematical model

Developing a quantitative understanding of viral kinetics is useful for determining the pathogenesis and transmissibility of the virus, predicting the course of disease, and evaluating the effects of antiviral therapy. The availability of data in clinical, animal, and cell culture studies, however, has been quite limited. Many studies of virus infection kinetics have been based solely on measures of total or infectious virus count. Here, we introduce a new mathematical model which tracks both infectious and total viral load, as well as the fraction of infected and uninfected cells within a cell culture, and apply it to analyze time-course data of an SHIV infection in vitro. We infected HSC-F cells with SHIV-KS661 and measured the concentration of Nef-negative (target) and Nef-positive (infected) HSC-F cells, the total viral load, and the infectious viral load daily for nine days. The experiments were repeated at four different MOIs, and the model was fitted to the full dataset simultaneously. Our analysis allowed us to extract an infected cell half-life of 14.1 h, a half-life of SHIV-KS661 infectiousness of 17.9 h, a virus burst size of 22.1 thousand RNA copies or 0.19 TCID50, and a basic reproductive number of 62.8. Furthermore, we calculated that SHIV-KS661 virus-infected cells produce at least 1 infectious virion for every 350 virions produced. Our method, combining in vitro experiments and a mathematical model, provides detailed quantitative insights into the kinetics of the SHIV infection which could be used to significantly improve the understanding of SHIV and HIV-1 pathogenesis. The method could also be applied to other viral infections and used to improve the in vitro determination of the effect and efficacy of antiviral compounds.

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.

58: Efficacy of anti-viral compounds in HHV-6 infected glial cells

Epstein–Barr virus (EBV), human herpesvirus type 6 (HHV-6), and human herpesvirus type 8 (HHV-8) comprise a group of lymphotropic herpesviruses which are responsible for a wide range of diseases, including lymphoproliferative disorders and tumors. We have developed several flow cytometric assay (FACS) systems to evaluate antiviral efficacy against EBV, HHV-6 and HHV-8. Assays using either EBV or HHV-8, members of the gammaherpesvirus subfamily, have shown that while EBV responds well to acyclovir (ACV), HHV-8 was most sensitive to cidofovir (CDV). Since HHV-6 strains are divided into two sub-groups, A and B, we evaluated antiviral efficacy for strains from each group. The group A strain, HHV-6GS, was inhibited by foscarnet (PFA), CDV and ganciclovir (GCV) in both Sup-T1 and HSB-2 cell lines. HHV-6Z-29, a representative group B virus, was inhibited by GCV and CDV but not by PFA. Our findings indicate that flow cytometry can be utilized to efficiently evaluate new antiviral agents against lymphotropic herpesviruses and that the results are comparable to those obtained by other methods such as immunofluorescence.

Efficacy of antiviral compounds in human herpesvirus-6–infected glial cells

The beta-herpesvirus human herpesvirus-6 (HHV-6) is becoming increasingly recognized as an important pathogen in immunocompromised patients, particularly in post bone marrow transplant (BMT). Reactivation of latent HHV-6 resulting in encephalitis has been reported in BMT and stem cell transplant (SCT) patients. The development of HHV-6 encephalitis can be a fatal complication, the frequency of which is increasing likely due to improved diagnosis with quantitative polymerase chain reaction (PCR) of cerebrospinal fluid. There are currently no antiviral compounds approved for HHV-6, nor have any controlled clinical trials been conducted. The frequency and severity of HHV-6 encephalitis in both immunocompetent and immunocompromised patients necessitates studies on the usefulness of currently available anti-viral compounds. The authors compared the antiviral efficacy of four drugs currently used for cytomegalovirus (CMV) infection, a beta-herpesvirus sharing homology with HHV-6. In HHV-6A- and HHV-6B-infected T cells, acyclovir, ganciclovir, foscarnet, and cidofovir exhibited antiviral activity consistent with that published in other studies. In HHV-6-infected human astrocytes (U251), however, only foscarnet and cidofovir exhibited antiviral activity and this effect was restricted to infection with HHV-6 variant A. In pathological brain sections from patients with neurological disorders such as multiple sclerosis and epilepsy, HHV-6 has been localized to glial cells. Determination of antiviral activity in human glial fibrillary acidic protein (GFAP)-positive astrocytes of currently used antiviral compounds is essential for potential treatment of HHV-6 and neurological disorders. Our data highlight the necessity for further study of antiviral compound in HHV-6-infected glial cells as well as the development of more selective compounds for HHV-6.

Use of Cell Cultures with Persistent Virus Infections to Test the Efficacy of Antiviral Compounds

BHK-21 cells persistently infected with either vaccinia or foot and mouth disease virus were used to study the efficacy of antiviral compounds. The results of the persistent infection cell culture (PICC) test were compared with those obtained by the plaque reduction (PR) test. The comparison showed that: (1) the PICC test is more informative than the PR test; (2) stimulative as well as inhibitory activities of compounds are detectable, and (3) since the PICC test can be carried on for several weeks or even months this test is especially well suited to study the problem of drug resistance in cell cultures.