Antiviral Testing Research Articles

Generation of SARS-CoV-2 reporter replicon for high-throughput antiviral screening and testing

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) research and antiviral discovery are hampered by the lack of a cell-based virus replication system that can be readily adopted without biosafety level 3 (BSL-3) restrictions. Here, the construction of a noninfectious SARS-CoV-2 reporter replicon and its application in deciphering viral replication mechanisms and evaluating SARS-CoV-2 inhibitors are presented. The replicon genome is replication competent but does not produce progeny virions. Its replication can be inhibited by RdRp mutations or by known SARS-CoV-2 antiviral compounds. Using this system, a high-throughput antiviral assay has also been developed. Significant differences in potencies of several SARS-CoV-2 inhibitors in different cell lines were observed, which highlight the challenges of discovering antivirals capable of inhibiting viral replication in vivo and the importance of testing compounds in multiple cell culture models. The generation of a SARS-CoV-2 replicon provides a powerful platform to expand the global research effort to combat COVID-19.

A trans-complementation system for SARS-CoV-2 recapitulates authentic viral replication without virulence

The biosafety level 3 (BSL-3) requirement to culture severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is a bottleneck for research. Here, we report a trans-complementation system that produces single-round infectious SARS-CoV-2 that recapitulates authentic viral replication. We demonstrate that the single-round infectious SARS-CoV-2 can be used at BSL-2 laboratories for high-throughput neutralization and antiviral testing. The trans-complementation system consists of two components: a genomic viral RNA containing ORF3 and envelope gene deletions, as well as mutated transcriptional regulator sequences, and a producer cell line expressing the two deleted genes. Trans-complementation of the two components generates virions that can infect naive cells for only one round but does not produce wild-type SARS-CoV-2. Hamsters and K18-hACE2 transgenic mice inoculated with the complementation-derived virions exhibited no detectable disease, even after intracranial inoculation with the highest possible dose. Thus, the trans-complementation platform can be safely used at BSL-2 laboratories for research and countermeasure development.

National influenza mid-season report, 2020-2021.

Canada's national influenza season typically starts in the latter half of November (week 47) and is defined as the week when at least 5% of influenza tests are positive and a minimum of 15 positive tests are observed. As of December 12, 2020 (week 50), the 2020-2021 influenza season had not begun. Only 47 laboratory-confirmed influenza detections were reported from August 23 to December 12, 2020; an unprecedentedly low number, despite higher than usual levels of influenza testing. Of this small number of detections, 64% were influenza A and 36% were influenza B. Influenza activity in Canada was at historically low levels compared with the previous five seasons. Provinces and territories reported no influenza-associated adult hospitalizations. Fewer than five hospitalizations were reported by the paediatric sentinel hospitalization network. With little influenza circulating, the National Microbiology Laboratory had not yet received samples of influenza viruses collected during the 2020-2021 season for strain characterization or antiviral resistance testing. The assessment of influenza vaccine effectiveness, typically available in mid-March, is expected to be similarly limited if low seasonal influenza circulation persists. Nevertheless, Canada's influenza surveillance system remains robust and has pivoted its syndromic, virologic and severe outcomes system components to support coronavirus disease 2019 (COVID-19) surveillance. Despite the COVID-19 pandemic, the threat of influenza epidemics and pandemics persists. It is imperative 1) to maintain surveillance of influenza, 2) to remain alert to unusual or unexpected events and 3) to be prepared to mitigate influenza epidemics when they resurge.

Efficacy of limited antiviral treatment, testing, hospitalization, and social distancing for COVID-19 pandemic

The control measures of a pandemic must be cautiously evaluated, especially when resources are “limited”. A model of COVID-19 transmission dynamics is applied to assess the impact of antiviral treatment, testing, hospitalization, and social distancing. Under the assumption of “unlimited” resources, five control strategies involving social distancing, testing, hospitalization, and antiviral treatment are tested. Then these “optimal” policies are sought in the case of limited resources on behalf of a COVID-19 pandemic scenario. The amplitude of peak epidemics will often be minimized by executing strategies from the beginning of a pandemic, spreading the epidemics’ greatest impact over a longer time frame. Therefore, the timing and potency of control measures can reduce the pressure on the system during the top of the epidemic through the pandemic, decreasing the pressure on the healthcare infrastructure. In case of limited access to antiviral supplies, the role of testing, hospitalization, and social distancing strategies is emphasized in this study.

A <i>Trans</i>-Complementation System for SARS-CoV-2

The biosafety level-3 (BSL-3) requirement to culture severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is a bottleneck for research and countermeasure development. Here we report a trans-complementation system that produces single-round infectious SARS-CoV-2 that recapitulates authentic viral replication. We demonstrate that the single-round infectious SARS-CoV-2 can be used at BSL-2 laboratories for high-throughput neutralization and antiviral testing. The trans-complementation system consists of two components: a genomic viral RNA containing a deletion of ORF3 and envelope gene, and a producer cell line expressing the two deleted genes. Trans-complementation of the two components generates virions that can infect naive cells for only one round, but does not produce wild-type SARS-CoV-2. Hamsters and K18-hACE2 transgenic mice inoculated with the complementation-derived virions exhibited no detectable disease, even after intracranial inoculation with the highest possible dose. The results suggest that the trans-complementation platform can be safely used at BSL-2 laboratories for research and countermeasure development.Funding: P.-Y.S. was supported by NIH grants AI142759, AI134907, AI145617, and UL1TR001439; awards from the Sealy & Smith Foundation, Kleberg Foundation, John S. Dunn Foundation, Amon G. Carter Foundation, Gilson Longenbaugh Foundation, and Summerfield Robert Foundation; and fund in sponsored research agreement from Q2 Solutions. M.S.D. was supported by R01 AI157155. V.D.M. was supported by NIH grants U19AI100625, R00AG049092, R24AI120942, and a STARs Award from the University of Texas System. S.C.W. was supported by NIH grant R24 AI120942. J.L. is supported by the postdoctoral fellowship from the McLaughlin Fellowship Endowment at UTMB. P.R. and X.X. were partially supported by the Sealy & Smith Foundation.Conflict of Interest: X.Z., X.X., and P.-Y.S. have filed a patent on the trans-complementation system of SARS CoV-2. M.S.D. is a consultant for Inbios, Vir Biotechnology, NGM Biopharmaceuticals, and Carnival Corporation, and on the Scientific Advisory Boards of Moderna and Immunome. The Diamond laboratory has received unrelated funding support in sponsored research agreements from Moderna, Vir Biotechnology, and Emergent BioSolutions.Ethical Approval: Animal studies were carried out in accordance with the recommendations in the Guide for the Care and Use of Laboratory Animals of the National Institutes of Health. The protocols were approved by the Institutional Animal Care and Use Committee at the Washington University School of Medicine (assurance number A3381–01). The research protocol for use of human serum specimens was approved by the University of Texas Medical Branch (UTMB) Institutional Review Board (IRB protocol number 20-0070). All human serum specimens were obtained at the UTMB with patient information de-identified. All aspects of this study were approved by the Institutional Biosafety Committee of the University of Texas Medical Branch at Galveston before the initiation of this study.

Clinical severe acute respiratory syndrome coronavirus 2 isolation and antiviral testing.

Severe acute respiratory syndrome coronavirus 2 is an RNA virus currently causing a pandemic. Due to errors during replication, mutations can occur and result in cell adaptation by the virus or in the rise of new variants. This can change the attachment receptors' usage, result in different morphology of plaques, and can affect as well antiviral development. Indeed, a molecule can be active on laboratory strains but not necessarily on circulating strains or be effective only against some viral variants. Experiments with clinical samples with limited cell adaptation should be performed to confirm the efficiency of drugs of interest. In this protocol, we present a method to culture severe acute respiratory syndrome coronavirus 2 from nasopharyngeal swabs, obtain a high viral titer while limiting cell adaptation, and assess antiviral efficiency.

Human Challenge Studies with Coronaviruses Old and New.

Coronavirus infections have been known to cause disease in animals since as early as the 1920s. However, only seven coronaviruses capable of causing human disease have been identified thus far. These Human Coronaviruses (HCoVs) include the causes of the common cold, but more recent coronaviruses that have emerged (i.e. SARS-CoV, MERS-CoV and SARS-CoV-2) are associated with much greater morbidity and mortality. HCoVs have been relatively under-studied compared to other common respiratory infections, as historically they have presented with mild symptoms. This has led to a relatively limited understanding of their animal reservoirs, transmission and determinants of immune protection. To address this, human infection challenge studies with HCoVs have been performed that enable a detailed clinical and immunological analysis of the host response at specific time points under controlled conditions with standardised viral inocula. Until recently, all such human challenge studies were conducted with common cold HCoVs, with the study of SARS-CoV and MERS-CoV unacceptable due to their greater pathogenicity. However, with the emergence of SARS-CoV-2 and the COVID-19 pandemic during which severe outcomes in young healthy adults have been rare, human challenge studies with SARS-CoV-2 are now being developed. Two SARS-CoV-2 human challenge studies in the UK studying individuals with and without pre-existing immunity are underway. As well as providing a platform for testing of antivirals and vaccines, such studies will be critical for understanding the factors associated with susceptibility to SARS-CoV-2 infection and thus developing improved strategies to tackle the current as well as future HCoV pandemics. Here, we summarise the major questions about protection and pathogenesis in HCoV infection that human infection challenge studies have attempted to answer historically, as well as the knowledge gaps that aim to be addressed with contemporary models.

582. Safety and Efficacy of High-Dose Ganciclovir versus Standard Dosing for Cytomegalovirus Viremia in Solid Organ Transplant (SOT) Recipients

BackgroundStandard dose ganciclovir (SD-GCV) for treatment of CMV infection/disease is 5 mg/kg every 12 hours, although higher doses (7.5–10 mg/kg every 12 hours) may be considered for resistant CMV. Literature on safety/efficacy of high dose GCV (HD-GCV) is limited. We sought to evaluate safety and clinical outcomes of SD-GCV vs HD-GCV strategies.MethodsRetrospective single center study of adult SOT recipients with CMV viremia from 1/1/2017-1/31/2019 who received IV GCV therapy. Primary objective was to compare incidence of cytopenias between SD-GCV and HD-GCV. Secondary outcomes compared CMV viremia clearance, incidence of CMV disease and recurrent viremia within 30 days, granulocyte colony stimulating factor (G-CSF) use, and antiviral resistance testing rates.ResultsWe evaluated 121 patients: 74 received SD-GCV, 47 received HD-GCV. Baseline characteristics were similar between groups. Most patients received a liver transplant (46% SD vs 36% HD) and had D+/R- CMV serostatus (55.4% SD vs 68% HD). Induction immunosuppression occurred in 75%, mostly with anti-thymocyte globulin. Median baseline CMV viral loads were similar (4620 IU/mL SD vs 7770 IU/mL HD, p=0.25).Incidence of cytopenias was similar between groups: leukopenia (43% SD vs 43% HD, p=0.96), neutropenia (15% SD vs 13% HD, p= 0.75), thrombocytopenia (24% SD vs 31% HD, p=0.62). HD-GCV did not significantly impact CMV clearance (HR: 0.79 [95% CI 0.52–1.21], p=0.27). There was no difference in incidence of CMV disease (35% SD vs 38% HD, p=0.72) or incidence of recurrent CMV viremia (15% SD vs 28% HD, p=0.098).G-CSF requirement was not different (23.7% SD vs 14.3% HD, p=0.295), however, patients on HD-GCV received more doses of G-CSF (median 2 SD vs 5 HD, p=0.001). More patients in HD-GCV group were tested for antiviral resistance: 15 (21%) SD vs 20 (43%) HD, p=0.01. Of these, there was no difference in rate of resistance detection (7/15 (47%) SD vs 11/20 (55%) HD, p=0.95).ConclusionTherapy with HD-GCV did not demonstrate increased incidence of cytopenias compared to SD-GCV, nor did we observe improved time to CMV clearance or incidence of CMV disease between groups. Opportunities exist for improving stewardship of antiviral resistance testing and use of G-CSF when considering HD-GCV therapy.Disclosures All Authors: No reported disclosures

Stable Expression of a Hepatitis E Virus (HEV) RNA Replicon in Two Mammalian Cell Lines to Assess Mechanism of Innate Immunity and Antiviral Response.

Hepatitis E virus (HEV) is one of the major etiological agents responsible for acute hepatitis. Hepatitis E virus does not replicate efficiently in mammalian cell cultures, thus a useful model that mimics persistent HEV replication is needed to dissect the molecular mechanism of pathogenesis. Here we report a genotype-3 HEV RNA replicon expressing an EGFP-Zeocin (EZ) resistant gene (p6-EZ) that persistently self-replicated in cell lines of human (Huh-7-S10-3) or hamster (BHK-21) origin after transfection with in vitro RNA transcripts and subsequent drug screening. Two cell lines, S10-3-EZ and BHK-21-EZ, stably expressed EGFP in the presence of Zeocin during continuous passages. Both genomic and subgenomic HEV RNAs and viral replicase proteins were stably expressed in persistent HEV replicon cells. The values of the cell models in antiviral testing, innate immune RNA sensing and type I IFN in host defense were further demonstrated. We revealed a role of RIG-I like receptor-interferon regulatory factor 3 in host antiviral innate immune sensing during HEV replication. We further demonstrated that treatment with interferon (IFN-α) or ribavirin significantly reduced expression of replicon RNA in a dose-dependent manner. The availability of the models will greatly facilitate HEV-specific antiviral development, and delineate mechanisms of HEV replication.

Effect of Zinc(II)-2,4,5-triphenyl-1H-imidazole Complex Against Replication DENV-2 in Vero Cell

Dengue virus (DENV) is a significant pathogen emerging worldwide as a cause of infectious disease. DENVs are transmitted to humans through female mosquitoes from Aedes aegypti and Aedes albopictus species. Indonesia is one of the largest countries in the world in dengue endemic regions worldwide. Dengue fever was occurred for the first time as an outbreak in Surabaya and Jakarta in 1968. Many efforts have been made to prevent and treat DENV infections, and clinical trials of a number of vaccines are currently underway. Antiviral testing of DENV is an important alternative for drug characterization and development. Complex compounds are formed as a result of metal and organic complex reactions. Complex compounds can be used as an anti-inflammatory, antimicrobial antifungal, antibacterial, antivirus. The Zn2+ ion can be used as an antiviral candidate. The purpose of this project was investigated Zinc(II)-2,4,5-triphenyl-1H-imidazole antiviral compound to be further tested for inhibitory effect on the replication of DENV-2 in cell culture. DENV replication was measured by antiviral activity assay and cytotoxicity assay. The inhibitory activity of Zinc(II)-2,4,5-triphenyl-1H-imidazole complex compound was determined by Viral ToxGloTM Assay. The cytotoxicity of Zinc(II)-2,4,5-triphenyl-1H-imidazole complex compound was determined by CellTiter96® AQuoeus assay. The inhibitory concentration (IC50) of Zinc(II)-2,4,5-triphenyl- 1H-imidazole against dengue virus type-2 was 34.42 μg/ml. The cytotoxic concentration (CC50) of compound against Vero cell was <100 μg/ml. The results of this study demonstrate the antidengue serotype 2 inhibitory activity of investigated Zinc(II)-2,4,5-triphenyl-1H-imidazole complex and its high toxicity in Vero cells. Further studies are not required before investigated Zinc(II)-2,4,5-triphenylimidazole can be applied in the treatment of DENV-2 infections

A Perspective on Organoids for Virology Research.

Animal models and cell lines are invaluable for virology research and host–pathogen interaction studies. However, it is increasingly evident that these models are not sufficient to fully understand human viral diseases. With the advent of three-dimensional organotypic cultures, it is now possible to study viral infections in the human context. This perspective explores the potential of these organotypic cultures, also known as organoids, for virology research, antiviral testing, and shaping the virology landscape.

Immortalized stem cell-derived hepatocyte-like cells: An alternative model for studying dengue pathogenesis and therapy.

Suitable cell models are essential to advance our understanding of the pathogenesis of liver diseases and the development of therapeutic strategies. Primary human hepatocytes (PHHs), the most ideal hepatic model, are commercially available, but they are expensive and vary from lot-to-lot which confounds their utility. We have recently developed an immortalized hepatocyte-like cell line (imHC) from human mesenchymal stem cells, and tested it for use as a substitute model for hepatotropic infectious diseases. With a special interest in liver pathogenesis of viral infection, herein we determined the suitability of imHC as a host cell target for dengue virus (DENV) and as a model for anti-viral drug testing. We characterized the kinetics of DENV production, cellular responses to DENV infection (apoptosis, cytokine production and lipid droplet metabolism), and examined anti-viral drug effects in imHC cells with comparisons to the commonly used hepatoma cell lines (HepG2 and Huh-7) and PHHs. Our results showed that imHC cells had higher efficiencies in DENV replication and NS1 secretion as compared to HepG2 and Huh-7 cells. The kinetics of DENV infection in imHC cells showed a slower rate of apoptosis than the hepatoma cell lines and a certain similarity of cytokine profiles to PHHs. In imHC, DENV-induced alterations in levels of lipid droplets and triacylglycerols, a major component of lipid droplets, were more apparent than in hepatoma cell lines, suggesting active lipid metabolism in imHC. Significantly, responses to drugs with DENV inhibitory effects were greater in imHC cells than in HepG2 and Huh-7 cells. In conclusion, our findings suggest superior suitability of imHC as a new hepatocyte model for studying mechanisms underlying viral pathogenesis, liver diseases and drug effects.

Вірусінфікований калюс квасолі та його оздоровлення in vitro за дії ліпосомальних препаратів

The aim of the study was to develop a recovery means for beans infected by Bean yellow mosaic virus (BYMV) as well as Bean common mosaic virus (BCMV) using callus culture and liposomal glycan preparations. Methods. Cultivation of explants and callus cultures was carried out in vitro using conventional methods of plant biotechnology. The tissue culture propagation was performed during the spring or summer seasons. The presence of viral infection was tested by reverse transcription polymerase chain reaction. The virus-specific primers that allowed amplifying the conserved regions of the capsid protein gene of BCMV or BYMV were used for virus identification. Results. The culture of bean callus infected with BCMV was obtained and adapted for antiviral agents testing. It has been shown that during long-term cultivation (10–12 weeks) in the presence of liposomal preparation containing Ganoderma adspersum glucan (10–100 mg/l), plant tissue culture become free from viruses following virus eradication. This is evidenced by the absence in the callus tissue of 391 bp sequences typical for the virus coat protein gene. Conclusions. The full suppression of virus reproduction and gradual elimination of virus occurred in callus tissue obtained from BCMV-infected beans and cultured on B-5 medium supplemented with liposomal glycanglycolipid complex (10–100 mg/l). The data obtained can be useful for the development of practical control method to cure plant virus diseases using callus culture and antiviral-active glycan-glycolipid complexes.

Broad Anti-coronavirus Activity of Food and Drug Administration-Approved Drugs against SARS-CoV-2 In Vitro and SARS-CoV In Vivo.

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) emerged in China at the end of 2019 and has rapidly caused a pandemic, with over 20 million recorded COVID-19 cases in August 2020 (https://covid19.who.int/). There are no FDA-approved antivirals or vaccines for any coronavirus, including SARS-CoV-2. Current treatments for COVID-19 are limited to supportive therapies and off-label use of FDA-approved drugs. Rapid development and human testing of potential antivirals is urgently needed. Numerous drugs are already approved for human use, and subsequently, there is a good understanding of their safety profiles and potential side effects, making them easier to fast-track to clinical studies in COVID-19 patients. Here, we present data on the antiviral activity of 20 FDA-approved drugs against SARS-CoV-2 that also inhibit SARS-CoV and Middle East respiratory syndrome coronavirus (MERS-CoV). We found that 17 of these inhibit SARS-CoV-2 at non-cytotoxic concentrations. We directly followed up seven of these to demonstrate that all are capable of inhibiting infectious SARS-CoV-2 production. Moreover, we evaluated two of these, chloroquine and chlorpromazine, in vivo using a mouse-adapted SARS-CoV model and found that both drugs protect mice from clinical disease.IMPORTANCE There are no FDA-approved antivirals for any coronavirus, including SARS-CoV-2. Numerous drugs are already approved for human use that may have antiviral activity and therefore could potentially be rapidly repurposed as antivirals. Here, we present data assessing the antiviral activity of 20 FDA-approved drugs against SARS-CoV-2 that also inhibit SARS-CoV and MERS-CoV in vitro We found that 17 of these inhibit SARS-CoV-2, suggesting that they may have pan-anti-coronaviral activity. We directly followed up seven of these and found that they all inhibit infectious-SARS-CoV-2 production. Moreover, we evaluated chloroquine and chlorpromazine in vivo using mouse-adapted SARS-CoV. We found that neither drug inhibited viral replication in the lungs, but both protected against clinical disease.

Plant Extracts as Antiviral Agents

With the advent of COVID-19, an infectious disease, caused by severe acute respiratory syndrome corona virus 2 (SARS-COV-2), which has claimed the death of thousands around the globe, there is an urgent intense need to screen plant extracts, in addition to the search for synthetic medicines and a vaccine to neutralize the coronavirus. Whilst the use of plant extracts for antimicrobial, antidiabetic and other assays have reached their zenith, research in the use of plant extracts as antiviral agents lacks comparison. Such research would also come in close scrutiny in the future, considering that the virus can mutate and lead to antiviral strains. Thus, research in this area, should seek the approval of health organisations, locally and international and may become increasing difficult to pursue, considering the emergence of COVID-19 disease. Viruses can mutate in the presence of chemicals and other mutating agents to produce Novel viral strains, with devastating effect on the human race. Viruses detrimental to the human race, can emerge from any countries. Once approval is sought, for antiviral research, herbal antiviral medicinal research should intensified. Guyana diverse flora offers a promising source for natural antiviral agents and needs continual screening in this direction. However, it would need approval from world health organisations for antiviral testing.

Live Visualization of Hemagglutinin Dynamics During Infection by Using a Novel Reporter Influenza A Virus.

Live visualization of influenza A virus (IAV) structural proteins during viral infection in cells is highly sought objective to study different aspects of the viral replication cycle. To achieve this, we engineered an IAV to express a Tetra Cysteine tag (TC tag) from hemagglutinin (HA), which allows intracellular labeling of the engineered HA protein with biarsenic dyes and subsequent fluorescence detection. Using such constructs, we rescued a recombinant IAV with TC tag inserted in HA, in A/Puerto Rico/8/1934(H1N1) background (HA-TC). This recombinant HA-TC tag reporter IAV was replication-competent; however, as compared to wild type PR8 IAV, it was attenuated in multicycle replication. We confirmed expression of TC tag and biarsenical labeling of HA by immunofluorescence assay in cells infected with an HA-TC tag reporter IAV. Further, we used this reporter virus to visualize HA expression and translocation in IAV infected cells by live confocal imaging. We also tested the utility of the HA-TC IAV in testing chemical inhibitors of the HA translocation. Overall, HA-TC IAV is a versatile tool that will be useful for studying viral life cycle events, virus-host interactions, and anti-viral testing.

Novel coronavirus treatment with ribavirin: Groundwork for an evaluation concerning COVID-19.

Confronting the challenge of the outbreak of COVID‐19 should sharpen our focus on global drug access as a key issue in antiviral therapy testing. The testing and adoption of effective therapies for novel coronaviruses are hampered by the challenge of conducting controlled studies during a state of emergency. The access to direct antiviral drugs, such as ribavirin, that have an existing inventory and reliable supply chain may be a priority consideration for therapies developed for the 2019‐nCoV infection outbreaks and any strain variants that may emerge. On the basis of the direct antiviral activity of ribavirin against 2019‐nCoV in vitro and evidence for potency enhancement strategies developed during the prior SARS and MERS outbreaks, ribavirin may significantly impact our ability to end the lingering outbreaks in China and slow outbreaks in other countries. The apparent COVID‐19 pandemic provides an opportunity to follow dosage guidelines for treatment with ribavirin, test new therapeutic concepts, and conduct controlled testing to apply the scientific rigor required to address the controversy around this mainstay of antiviral therapy.

Animal Models of Lassa Fever.

Lassa virus (LASV), the causative agent of Lassa fever, is estimated to be responsible for up to 300,000 new infections and 5000 deaths each year across Western Africa. The most recent 2018 and 2019 Nigerian outbreaks featured alarmingly high fatality rates of up to 25.4%. In addition to the severity and high fatality of the disease, a significant population of survivors suffer from long-term sequelae, such as sensorineural hearing loss, resulting in a huge socioeconomic burden in endemic regions. There are no Food and Drug Administration (FDA)-approved vaccines, and therapeutics remain extremely limited for Lassa fever. Development of countermeasures depends on relevant animal models that can develop a disease strongly mimicking the pathogenic features of Lassa fever in humans. The objective of this review is to evaluate the currently available animal models for LASV infection with an emphasis on their pathogenic and histologic characteristics as well as recent advances in the development of a suitable rodent model. This information may facilitate the development of an improved animal model for understanding disease pathogenesis of Lassa fever and for vaccine or antiviral testing.

Characterization of Influenza Viruses - China, 2019-2020.

Introduction: Influenza surveillance is necessary for detection of emerging variants of influenza viruses and determining their epidemiological and clinical significance. Vaccination and antiviral drugs remain the most useful ways to protect against seasonal influenza and its potentially severe consequences. This study describes the epidemiology, antigenic and genetic characteristics, and antiviral susceptibilities of influenza viruses isolated from the mainland of China during the April 1, 2019 through October 4, 2020. Methods: All viruses analyzed were isolated and submitted by Chinese National Influenza Surveillance Network laboratories. The Chinese National Influenza Center performed antigenic analysis, sequencing, and antiviral resistance testing after propagation of the viruses. Antigenic characterizations were determined by hemagglutinin inhibition assay;next-generation sequencing was used for genetic analyses;phenotypic assay and next-generation sequencing were used for determining antiviral resistance. Results: The influenza positivity rate declined significantly starting in late January 2020 and has remained low. There was no summer influenza peak season in south China. Influenza A(H3N2) and B/Victoria lineage viruses were the dominant subtype/lineage during April 1, 2019 through October 4, 2020. The majority of influenza viruses were antigenically and genetically similar to reference viruses representing components of vaccines for the 2020-2021 northern hemisphere influenza season. Nearly all seasonal influenza viruses were susceptible to oseltamivir and zanamivir. Conclusions and Implications for Public Health Practice: Since the outbreak of COVID-19, the influenza positivity rate declined with implementation of strong COVID-19 control measures. The majority of circulating viruses are well matched with the current 2020-2021 northern hemisphere influenza vaccine viruses. Circulating seasonal influenza viruses were sensitive to neuraminidase inhibitors and Baloxavir marboxil. This study provided evidence for World Health Organization (WHO) recommendations for vaccine viruses, for prevention and control of influenza, and for clinical use of antiviral medications.

Cytomegalovirus viremia and resistance patterns in immunocompromised children: An 11-year experience

We noted a recent increase in number of immunocompromised children with CMV viremia at our institution. The purpose of this study was to determine the frequency of CMV viremia in this population and evaluate factors associated with drug-resistant mutations. A retrospective review of immunocompromised hosts, 0–21 years of age, who had CMV viremia during 2007–2017. CMV viremia was detected using PCR assays. Genetic mutation assays were performed using PCR sequencing of the phosophotransferase UL 97 gene and the polymerase UL54 gene of CMV using Quest Diagnostics (San Juan Capistrano, CA, USA) or ARUP Labs (Salt Lake City, UT, USA). Thirty-one patients were identified, including 10 (32%) during the last 2 years. Of the 31 patients, 18 had hematopoietic stem cell transplantation (HSCT), 5 had primary immunodeficiency, 4 had malignancies, 3 had heart transplantation and 1 had new Human Immunodeficiency virus (HIV) infection. Antiviral resistance testing was performed on isolates from seven patients: five with persistent viremia (>1 mo), and two prior to starting antiviral therapy. Resistance was identified in three patients’ isolates: two with common variable immunodeficiency (CVID) and one with recurrent Hodgkin’s lymphoma who had undergone autologous HSCT. The two patients with CVID had chronic diarrhea and malabsorption and had received prolonged oral valganciclovir courses prior to emergence of resistance. The patient with Hodgkin’s lymphoma had received a prolonged IV ganciclovir course. All three tested positive for UL97 mutation and two had both UL97 and UL54 gene mutations. Majority of our patients (21/31) with CMV viremia were transplant recipients and ganciclovir resistance developed in 10%. Two had intestinal malabsorption. Treatment with oral valganciclovir should be avoided in patients with poor gut absorption as that may increase the risk of resistance.