Antiviral Chemotherapy Research Articles

Analyzing and Critically Evaluating the Problems of Antiviral Chemotherapy

Antiviral chemotherapy, an indispensable tool in combating viral infections, faces numerous challenges that often undermine its overall effectiveness and application. This review critically examines the multifaceted issues associated with antiviral chemotherapy, drawing on comprehensive data from NCBI, PubMed, and other reputable academic sources. The primary purpose of this research is to analyze and evaluate key problems such as the development of drug resistance, narrow therapeutic windows, limited spectrum of activity, toxicity, high costs, viral latency, and the complexities inherent in combination therapy. These challenges necessitate a delicate and strategic balance in the development, regulation, and application of antiviral drugs. The research methodology included an exhaustive review of peer-reviewed articles and clinical studies sourced from PubMed and NCBI databases, focusing on ten critical challenges in antiviral chemotherapy. The findings underscore the persistent issue of drug resistance, particularly in RNA viruses like HIV and hepatitis C, which demand ongoing innovation in antiviral drug design and implementation. Additionally, the analysis reveals the significant risks posed by the narrow therapeutic index of many antiviral drugs, which often increases the likelihood of adverse effects, thus limiting their safe and effective use. The study also highlights the formidable challenges posed by viral latency and the limited efficacy of current therapies against emerging and re-emerging viral threats. This research significantly contributes to the understanding of the inherent limitations in existing antiviral therapies and underscores the pressing need for more effective, accessible, and safe treatments. The practical significance lies in offering insights that could guide future research, clinical practice, and policy decisions, ultimately improving global health outcomes in the fight against viral diseases.

Lymphocyte counts predict optimal timing of chemotherapy reinitiation after antivirus treatment for herpes zoster in children with leukemia.

Herpes zoster (HZ) is rare in healthy children, but more prevalent in those with leukemia. Optimal timing of chemotherapy reinitiation after HZ treatment is challenging because chemotherapy suppresses immunity and increases risk of HZ relapse. We aimed to optimize the timing of chemotherapy reinitiation after HZ therapy in children with leukemia. The study included 31 children with acute leukemia and HZ infection. General information, clinical symptoms, laboratory test results, duration of HZ treatment, and prognosis were compared with those of children with leukemia alone. Correlation analysis was performed for 20 children who restarted chemotherapy after HZ treatment. Of 31 children with leukemia and HZ, 67.74% had lesions at multiple sites. The median time from chemotherapy initiation to HZ onset was 14.1 (1.5-29.5) months. Among 27 children included in the follow-up, there was one case of HZ relapse. After excluding children who did not continue chemotherapy after HZ treatment, the median interval between completion of HZ therapy and chemotherapy reinitiation in the remaining 20 children was 8.00 (-3 to 27) days. Lymphocyte counts (LY#) on restarting chemotherapy correlated inversely with HZ lesion healing time (p < 0.05). LY# at the time of HZ onset were lower than those pre- and post-onset, and lower than those in the control group (p < 0.05). In conclusion, children with leukemia have a good HZ prognosis, but an increased risk of HZ recurrence. LY# at the time of chemotherapy reinitiation may be a useful indicator for selecting the optimal interval between antiviral therapy completion and chemotherapy reinitiation.

Antiviral Chemotherapy in Avian Medicine-A Review.

This review article describes the current knowledge about the use of antiviral chemotherapeutics in avian species, such as farm poultry and companion birds. Specific therapeutics are described in alphabetical order including classic antiviral drugs, such as acyclovir, abacavir, adefovir, amantadine, didanosine, entecavir, ganciclovir, interferon, lamivudine, penciclovir, famciclovir, oseltamivir, ribavirin, and zidovudine, repurposed drugs, such as ivermectin and nitazoxanide, which were originally used as antiparasitic drugs, and some others substances showing antiviral activity, such as ampligen, azo derivates, docosanol, fluoroarabinosylpyrimidine nucleosides, and novel peptides. Most of them have only been used for research purposes and are not widely used in clinical practice because of a lack of essential pharmacokinetic and safety data. Suggested future research directions are also highlighted.

Antiviral options and therapeutics against influenza: history, latest developments and future prospects.

Drugs and chemotherapeutics have helped to manage devastating impacts of infectious diseases since the concept of 'magic bullet'. The World Health Organization estimates about 650,000 deaths due to respiratory diseases linked to seasonal influenza each year. Pandemic influenza, on the other hand, is the most feared health disaster and probably would have greater and immediate impact on humanity than climate change. While countermeasures, biosecurity and vaccination remain the most effective preventive strategies against this highly infectious and communicable disease, antivirals are nonetheless essential to mitigate clinical manifestations following infection and to reduce devastating complications and mortality. Continuous emergence of the novel strains of rapidly evolving influenza viruses, some of which are intractable, require new approaches towards influenza chemotherapeutics including optimization of existing anti-infectives and search for novel therapies. Effective management of influenza infections depend on the safety and efficacy of selected anti-infective in-vitro studies and their clinical applications. The outcomes of therapies are also dependent on understanding diversity in patient groups, co-morbidities, co-infections and combination therapies. In this extensive review, we have discussed the challenges of influenza epidemics and pandemics and discoursed the options for anti-viral chemotherapies for effective management of influenza virus infections.

A retrospective study of Kaposi's sarcoma in Hotan region of Xinjiang, China.

Kaposi sarcoma (KS) is the most common cancer in patients with human immunodeficiency virus/acquired immunodeficiency syndrome (AIDS). In 1994, Chang and Moore discovered Kaposi sarcoma associated herpesvirus for the first time in KS lesions in AIDS patients. KS is a low-grade mesenchymal neoplasm of blood and lymphatic vessels that primarily affects the skin, although the disease may become disseminated to the lymphatic system, lungs, airways, or abdominal viscera. In this research, clinical characteristics and treatment of patients of Kaposi sarcoma were retrospectively analyzed in Hotan District, Xinjiang China. We look into the clinical traits, prognosis, and therapy of Kaposi sarcoma. From May 2017 to August 2022, 32 patients were treated in the People's Hospital of Hotan District, Xinjiang Uygur Autonomous Region, China. Twenty-two of these were classic Kaposi sarcomas (cKS), and 10 of these were Kaposi sarcomas linked to AIDS (AIDS-KS). The majority of KS patients were Uyghur. In terms of age at onset, AIDS-KS patients were younger than cKS patients. cKS and AIDS-KS are most frequently manifested in the feet and lower limbs. Ten patients with AIDS-KS have treated with combination antiretroviral therapy (combination antiretroviral therapy) combination chemotherapy, 5 of 10 patients had a complete response, 2 patients achieved partial response, the overall effective rate was 70%, and CD4 + T cells were greater than before. For cKS and AIDS-KS, the median overall survival was 56 and 50.8 months, respectively (P > .05). As a result, antiviral combination chemotherapy can also improve the prognosis of AIDS-KS patients.

A history of virology

Virology was born at the end of the 19th century from the recognition of so-called filterable infectious agents that passed through filters designed to retain bacteria. The study of these agents, in particular the tobacco mosaic virus and bacteriophages, has shown the originality of their structural and physico-chemical properties while stimulating the development of molecular biology. Animal viruses, in addition to their own characterization, have served as probes to explore the molecular functioning of eukaryotic cells, including genome organization, transcriptional regulation and mechanisms of oncogenesis. In the early 1960s, a precise definition of virions and mode of virus replication as well as an internationally recognized classification based on the molecular properties of these agents were published. Understanding the pathophysiology of viral infections over the past decades has led to the identification of many new viruses and the development of standardized procedures for virological diagnosis, specific antiviral chemotherapy and effective vaccinations. Combined with the success of more basic studies, these advances have contributed to the exceptionally positive record of virology over the past hundred year.

5-Arylidenerhodanines as P-gp Modulators: An Interesting Effect of the Carboxyl Group on ABCB1 Function in Multidrug-Resistant Cancer Cells.

Multidrug resistance (MDR) is considered one of the major mechanisms responsible for the failure of numerous anticancer and antiviral chemotherapies. Various strategies to overcome the MDR phenomenon have been developed, and one of the most attractive research directions is focused on the inhibition of MDR transporters, membrane proteins that extrude cytotoxic drugs from living cells. Here, we report the results of our studies on a series newly synthesized of 5-arylidenerhodanines and their ability to inhibit the ABCB1 efflux pump in mouse T-lymphoma cancer cells. In the series, compounds possessing a triphenylamine moiety and the carboxyl group in their structure were of particular interest. These amphiphilic compounds showed over 17-fold stronger efflux pump inhibitory effects than verapamil. The cytotoxic and antiproliferative effects of target rhodanines on T-lymphoma cells were also investigated. A putative binding mode for 11, one of the most potent P-gp inhibitors tested here, was predicted by molecular docking studies and discussed with regard to the binding mode of verapamil.

Pathogenetic Therapy in Patients with Recurrent Herpetic Infection

When treating patients with recurrent herpesvirus infection, it is necessary to use combination therapy, which involves the use of both chemotherapy and immunotropic drugs. Simultaneous use of drugs with different mechanisms of action allows to achieve greater efficiency than the use of monotherapy. The effectiveness of Cycloferon, an interferon inducer, which has an anti-inflammatory and immunomodulatory effect in combination therapy in patients with labial herpes, has been established. An accelerated elevation of rashes was observed against the background of the use of Cycloferon in combination therapy with acyclic nucleosides (Acyclovir); the severity of general intoxication syndrome, subjective symptoms (pain, itching, burning), and signs of inflammation (edema, hyperemia) decreased by half compared with the control group. Also, an increase in the duration of remission by 2–2.5 times was observed in patients taking Cycloferon. High efficiency, good tolerance by patients, as well as the possibility of using it with the main antiviral chemotherapy drugs indicate the advisability of including Cycloferon in the combination therapy in patients with recurrent herpes infection.

The gateway to guanine nucleotides: Allosteric regulation of IMP dehydrogenases.

Inosine 5′‐monophosphate dehydrogenase (IMPDH) is an evolutionarily conserved enzyme that mediates the first committed step in de novo guanine nucleotide biosynthetic pathway. It is an essential enzyme in purine nucleotide biosynthesis that modulates the metabolic flux at the branch point between adenine and guanine nucleotides. IMPDH plays key roles in cell homeostasis, proliferation, and the immune response, and is the cellular target of several drugs that are widely used for antiviral and immunosuppressive chemotherapy. IMPDH enzyme is tightly regulated at multiple levels, from transcriptional control to allosteric modulation, enzyme filamentation, and posttranslational modifications. Herein, we review recent developments in our understanding of the mechanisms of IMPDH regulation, including all layers of allosteric control that fine‐tune the enzyme activity.

Inhibitors of Nucleotide Biosynthesis as Candidates for a Wide Spectrum of Antiviral Chemotherapy.

Emerging and re-emerging viruses have been a challenge in public health in recent decades. Host-targeted antivirals (HTA) directed at cellular molecules or pathways involved in virus multiplication represent an interesting strategy to combat viruses presently lacking effective chemotherapy. HTA could provide a wide range of agents with inhibitory activity against current and future viruses that share similar host requirements and reduce the possible selection of antiviral-resistant variants. Nucleotide metabolism is one of the more exploited host metabolic pathways as a potential antiviral target for several human viruses. This review focuses on the antiviral properties of the inhibitors of pyrimidine and purine nucleotide biosynthesis, with an emphasis on the rate-limiting enzymes dihydroorotate dehydrogenase (DHODH) and inosine monophosphate dehydrogenase (IMPDH) for which there are old and new drugs active against a broad spectrum of pathogenic viruses.

Exploring Natural Product Activity and Species Source Candidates for Hunting ABCB1 Transporter Inhibitors: An In Silico Drug Discovery Study.

The P-glycoprotein (P-gp/ABCB1) is responsible for a xenobiotic efflux pump that shackles intracellular drug accumulation. Additionally, it is included in the dud of considerable antiviral and anticancer chemotherapies because of the multidrug resistance (MDR) phenomenon. In the search for prospective anticancer drugs that inhibit the ABCB1 transporter, the Natural Product Activity and Species Source (NPASS) database, containing >35,000 molecules, was explored for identifying ABCB1 inhibitors. The performance of AutoDock4.2.6 software to anticipate ABCB1 docking score and pose was first assessed according to available experimental data. The docking scores of the NPASS molecules were predicted against the ABCB1 transporter. Molecular dynamics (MD) simulations were conducted for molecules with docking scores lower than taxol, a reference inhibitor, pursued by molecular mechanics-generalized Born surface area (MM-GBSA) binding energy estimations. On the basis of MM-GBSA calculations, five compounds revealed promising binding affinities as ABCB1 inhibitors with ΔGbinding < −105.0 kcal/mol. The binding affinity and stability of the identified inhibitors were compared to the chemotherapeutic agent. Structural and energetical analyses unveiled great steadiness of the investigated inhibitors within the ABCB1 active site throughout 100 ns MD simulations. Conclusively, these findings point out that NPC104372, NPC475164, NPC2313, NPC197736, and NPC477344 hold guarantees as potential ABCB1 drug candidates and warrant further in vitro/in vivo tests.

The Non-Pharmaceutical Interventions to Control the Spread of Covid-19

The COVID-19 pandemic is considered the most crucial global health problem of the 21st century and the greatest challenge that affects humans globally. In late December 2019, a new infectious respiratory disease emerged from Wuhan city of Hubei province in China. Since then, it has since spread around the world, thus declared a pandemic on 11th March 2020 by the World Health Organisation. The outbreak of the novel coronavirus has become a clinical threat to the common population and healthcare workers worldwide. The intensity and speed with which it struck were almost unimaginable as it turns out to have infected over 327,793,472 people and caused more than 5,539,108 deaths globally as of the 17th of January 2022. Likewise, in Nigeria, as of 17th of January 2022; 250,929 confirmed cases, 3,103 deaths, and 224,052 recovered had been reported by NCDC, 2022. At the time of writing this review, no approved antiviral chemotherapy is available instead, use of some recommended vaccines by WHO. Therefore, nonpharmaceutical interventions are adopted by the national government as possible preventive measures to mitigate the spread of the virus globally. These measures include total lockdown, wearing of face mask in public, regular handwashing with soap and water, use of alcohol-based hand sanitizers, maintaining social and physical distance and coughing or sneezing into the elbow, and general enlightenment.

Structure-Function Relationships in the Human P-Glycoprotein (ABCB1): Insights from Molecular Dynamics Simulations.

P-Glycoprotein (P-gp) is a transmembrane protein belonging to the ATP binding cassette superfamily of transporters, and it is a xenobiotic efflux pump that limits intracellular drug accumulation by pumping compounds out of cells. P-gp contributes to a reduction in toxicity, and has broad substrate specificity. It is involved in the failure of many cancer and antiviral chemotherapies due to the phenomenon of multidrug resistance (MDR), in which the membrane transporter removes chemotherapeutic drugs from target cells. Understanding the details of the ligand–P-gp interaction is therefore critical for the development of drugs that can overcome the MDR phenomenon, for the early identification of P-gp substrates that will help us to obtain a more effective prediction of toxicity, and for the subsequent outdesign of substrate properties if needed. In this work, a series of molecular dynamics (MD) simulations of human P-gp (hP-gp) in an explicit membrane-and-water environment were performed to investigate the effects of binding different compounds on the conformational dynamics of P-gp. The results revealed significant differences in the behaviour of P-gp in the presence of active and non-active compounds within the binding pocket, as different patterns of movement were identified that could be correlated with conformational changes leading to the activation of the translocation mechanism. The predicted ligand–P-gp interactions are in good agreement with the available experimental data, as well as the estimation of the binding-free energies of the studied complexes, demonstrating the validity of the results derived from the MD simulations.

Modern aspects of complex therapy for recurrent genital herpes

Incidence of reported cases of genital herpes in different countries has increased dramatically during the last years, which is essentially caused by spread of asymptomatic or atypical types of herpes. Frequent relapses of herpes infection are characterized by changes in the immunological status. The authors of presented article analysed the findings of foreign and domestic studies on the treatment of the disease, systematized information about the features of antiviral chemotherapy drugs used in the treat-ment of genital herpes, identified criteria for the efficacy and duration of suppressive therapy, and the feasibility of its combination with courses of immunomodulatory drugs. The article summarizes the authors’ own experience in the treatment of genital herpes in 50 patients, who were randomly divided into 2 groups: (active treatment) group 1 consisted of 25 women who received antiviral (acyclovir and its analogues) and immunomodulatory therapy (aminodihydrophthalasindione sodium, suppositories), (comparison) group 2 consisted of 25 patients who received antiviral therapy only. The following were criteria for the inclusion of patients: genital herpes history, clinical presentation of genital herpes during the prodromal period or exacerbation, and no more than 48 hours after the rash occurred.The results of evaluation of the treatment effectiveness showed that the vesicles disappeared and the crusts formed during aminodihydrophthalasindione sodium therapy in the active treatment group of patients as early as Day 2-5 after starting treatment, while the acute phase of local inflammation in the comparison group was reversed only by Day 4-5. Complete reepitheli-alization occurred in the active treatment and comparison groups by Day 6-7 of the treatment. At the same time, the PCR test did not detect HSV-2 in smears in 24 (96.0%) women in the active treatment group and in 25 (88.0%) women in the comparison group. No one had any fresh rashes in the course of treatment with the drug. In addition, the authors reported prolongation of clinical remission in the active treatment group up to 5 months (up to 55 days on average).As can be seen from the above, the inclusion of immunomodulatory drugs in the combination specific antiviral therapy leads to faster achievement of the clinical effect, allows to reduce frequency of relapses and improves the patients’ quality of life.

Enhancement of Antibody-Dependent Cellular Cytotoxicity and Phagocytosis in Anti-HIV-1 Human-Bovine Chimeric Broadly Neutralizing Antibodies.

No prophylactic vaccine has provided robust protection against human immunodeficiency virus type 1 (HIV-1). Vaccine-induced broadly neutralizing antibodies (bNAbs) have not been achieved in humans and most animals; however, cows vaccinated with HIV-1 envelope trimers produce bNAbs with unusually long third heavy complementarity-determining regions (CDRH3s). Alongside neutralization, Fc-mediated effector functions, including antibody-dependent cellular cytotoxicity (ADCC) and phagocytosis (ADP), may be critical for in vivo bNAb antiviral activity. Here, we aimed to augment the Fc-dependent effector functions of a chimeric human-bovine bNAb, NC-Cow1, which binds the CD4 binding site (CD4bs) and exhibits broader and more potent neutralization than most human CD4bs bNAbs by using an exceptionally long 60-amino acid (aa) CDRH3. The bovine variable region of NC-Cow1 was paired with a human IgG1 Fc region mutated to create the following three variants: G236R/L328R (GRLR) that abrogates Fc-gamma receptor (FcγR) binding, and two variants that enhance binding, namely, G236A/S239D/I332E (GASDIE) and G236A/S239D/A330L/I332E (GASDALIE). Both GASDIE and GASDALIE improved binding to human FcγRIIA and FcγRIIIA, enhanced human natural killer (NK) cell activation, and mediated higher levels of ADCC and ADP activity than the wild-type human IgG1 Fc. GASDALIE mediated higher phagocytic activity than GASDIE. As expected, GRLR eliminated binding to FcγRs and did not mediate ADCC or ADP. We demonstrated that mutations in the human Fc region of bovine chimeric antibodies with ultralong CDRH3s could enhance antibody effector functions while maintaining envelope binding and neutralization. This study will have significant implications in the development of multifunctional anti-HIV antibodies, which may be important to prevent HIV-1 transmission in an antibody-based topical microbicide. IMPORTANCE Despite successful antiviral chemotherapy, human immunodeficiency virus (HIV) is still a lifelong persistent virus, and no vaccine yet prevents HIV transmission. Topical microbicides offer an important alternative method to prevent sexual transmission of HIV-1. With the production of highly potent anti-HIV-1 broadly neutralizing antibodies (bNAbs) and multifunctional antibodies, monoclonal antibodies are now important prophylactic agents. Recently discovered anti-HIV-1 bovine bNAbs (with higher potency and breadth than most human bNAbs) could be novel candidates as potent topical microbicides. Our study is significant as it demonstrates the compatibility of combining bovine-derived neutralization with human-derived antibody-effector functions. This study is a new approach to antibody engineering that strengthens the feasibility of using high-potency bovine variable region bNAbs with augmented Fc function and promotes them as a strong candidate for antibody-mediated therapies.

Designing Inhibitors for the SARS CoV Main Protease as Anti-SARS Drugs

Severe Acute Respiratory Syndrome (SARS) is a serious respiratory illness reported in parts of Asia and Canada. A novel coronavirus (CoV) has been isolated and identified as the cause of the SARS for which there is currently no effective treatment. Given the epidemic, the rapid development of efficacious antiviral drugs is needed. The key replicative enzyme SARS CoV main protease (Mpro) represents an attractive target for antiviral chemotherapy. Detailed structural study of the substrate binding cavity led to the generation of a 3-D pharmacophore. Subsets of chemical structures were extracted from the commercial databases by using the defined pharmacophore. Compound mapping to the pharmacophore were docked into the substrate-binding cavity and scored. The selected chemicals were assayed against the SARS CoV Mpro for their inhibitory activity. Three of the compounds showed significant inhibition of the SARS CoV Mpro at low micromolar concentration. This study provides potential lead compounds for specific SARS CoV protease inhibitors. It also signifies the utility of computational techniques for rapid discovery of inhibitors for novel targets.

Complicating Infections Associated with Common Endemic Human Respiratory Coronaviruses.

Coronaviruses OC43, 229E, NL63, and HKU1 are endemic human respiratory coronaviruses that typically cause mild to moderate upper respiratory infections, similar to the common cold. They also may cause simple and complicated lower respiratory infections, otitis media, asthma exacerbations, gastroenteritis, and a few systemic complications. These viruses are usually seasonal (with winter dominance) and affect nearly all age groups. The seasonal and annual variation in virus prevalence has implications for understanding the concept of acquired immunity and its persistence or diminution. Coronaviruses generally have outbreak potential in susceptible populations of any age, particularly in patients with comorbidities, who tend to have increased clinical disease. These 4 coronaviruses are often found in the context of what appears to be coinfection with other pathogens, but especially other viruses. If coronaviruses are not specifically tested for, the sole detection of a viral copathogen would suggest the pathogen is the causative agent, when a coronavirus may be culpable, or both. The detection of these viruses in circumstances where respiratory viruses are generally sought in clinical samples is, therefore, justified. These pathogens can be chronically shed from the respiratory tract, which is more likely to occur among immunocompromised and complicated patients. These viruses share the potential for genetic drift. The genome is among the largest of RNA viruses, and the capability of these viruses to further change is likely underestimated. Given the potential disease among humans, it is justified to search for effective antiviral chemotherapy for these viruses and to consider uses in niche situations should effective therapy be defined. Whereas SARS-CoV-2 may follow the epidemiological pattern of SARS-CoV and extinguish slowly over time, there is yet concern that SARS-CoV-2 may establish itself as an endemic human respiratory coronavirus similar to OC43, 2299E, NL63, and HKU1. Until sufficient data are acquired to better understand the potential of SARS-CoV-2, continued work on antiviral therapy and vaccination is imperative.

Infection à cytomégalovirus au cours du lupus érythémateux systémique. Série de 12 cas cliniques et revue de la littérature

IntroductionPatients with systemic lupus erythematosus (SLE) are at risk of cytomegalovirus (CMV) infection, due to the disease itself or to drug-induced immunosuppression. Also, active CMV infection may trigger or worsen SLE flare-up. MethodsIn this retrospective single-centre cohort study, we reported all adult inpatients with a diagnosis of SLE, presenting with active and confirmed CMV infection. The goal was to describe their characteristics and outcomes (evolution of CMV infection, secondary infections and SLE flare-up), and to review the existing literature. ResultsWe identified 400 patients with confirmed SLE, including 12 who presented with active CMV infection. Severe CMV manifestations were present in 7 patients treated with immunosuppressive regimen out of 10, and in one patient out of two without immunosuppressive therapy. Six patients developed other infections, and 3 showed characterised SLE flare-up over the 3-month follow-up. All patients were alive at end of follow-up. DiscussionAmong patients with SLE, CMV infection affected more frequently those treated with immunosuppressive drugs, but treatment-free patients were sometimes severely affected. CMV infection was associated with an increased incidence of SLE flare-up and infectious complications. Our results suggest that early anti-viral chemotherapy may be beneficial in these patients.

Cell Fusion Induced by a Fusion-Active Form of Human Cytomegalovirus Glycoprotein B (gB) Is Inhibited by Antibodies Directed at Antigenic Domain 5 in the Ectodomain of gB.

Human cytomegalovirus (HCMV) is a ubiquitous pathogen that can cause severe clinical disease in allograft recipients and infants infected in utero Virus-neutralizing antibodies defined in vitro have been proposed to confer protection against HCMV infection, and the virion envelope glycoprotein B (gB) serves as a major target of neutralizing antibodies. The viral fusion protein gB is nonfusogenic on its own and requires glycoproteins H (gH) and L (gL) for membrane fusion, which is in contrast to requirements of related class III fusion proteins, including vesicular stomatitis virus glycoprotein G (VSV-G) or baculovirus gp64. To explore requirements for gB's fusion activity, we generated a set of chimeras composed of gB and VSV-G or gp64, respectively. These gB chimeras were intrinsically fusion active and led to the formation of multinucleated cell syncytia when expressed in the absence of other viral proteins. Utilizing a panel of virus-neutralizing gB-specific monoclonal antibodies (MAbs), we could demonstrate that syncytium formation of the fusogenic gB/VSV-G chimera can be significantly inhibited by only a subset of neutralizing MAbs which target antigenic domain 5 (AD-5) of gB. This observation argues for differential modes of action of neutralizing anti-gB MAbs and suggests that blocking the membrane fusion function of gB could be one mechanism of antibody-mediated virus neutralization. In addition, our data have important implications for the further understanding of the conformation of gB that promotes membrane fusion as well as the identification of structures in AD-5 that could be targeted by antibodies to block this early step in HCMV infection.IMPORTANCE HCMV is a major global health concern, and antiviral chemotherapy remains problematic due to toxicity of available compounds and the emergence of drug-resistant viruses. Thus, an HCMV vaccine represents a priority for both governmental and pharmaceutical research programs. A major obstacle for the development of a vaccine is a lack of knowledge of the nature and specificities of protective immune responses that should be induced by such a vaccine. Glycoprotein B of HCMV is an important target for neutralizing antibodies and, hence, is often included as a component of intervention strategies. By generation of fusion-active gB chimeras, we were able to identify target structures of neutralizing antibodies that potently block gB-induced membrane fusion. This experimental system provides an approach to screen for antibodies that interfere with gB's fusogenic activity. In summary, our data will likely contribute to both rational vaccine design and the development of antibody-based therapies against HCMV.

Pandemic COVID-19: Current status and challenges of antiviral therapies

The pandemic COVID-19, caused by a new coronavirus SARS-CoV-2 infection, has infected over 12 million individuals and caused more than 55,200 death worldwide. Currently, there is no specific drug to treating this disease. Here we summarized the mechanisms of antiviral therapies and the clinic findings from different countries. Antiviral chemotherapies have been conducted by in multiple cohorts in different counties. Although FDA has fast approved remdesivir for treating COVID-19, it only speeds up recovery from COVID-19 with mildly reduced mortality. The chloroquine was suggested a potential drug against SARS-CoV-2 infection due to its in vitro antiviral effects, it is imperative high-quality data from worldwide clinical trials are necessitated for an approved therapy. In terms of hydroxychloroquine (HCQ) therapy, although WHO has stopped all the clinic trials due to its strong side-effects in COVID patients, large scale clinical trials with a long-term outcome follow-up may warrant HCQ and azithromycin combination in combating the virus. Convalescent plasma (CP) therapy suggested its safety use in SARS-CoV-2 infection; but both CP immunotherapy and NK cellular therapy must be manufactured and utilized according to scrupulous ethical and controlled conditions to guarantee a possible role of these products of human origin. Further research should be conducted to define the exact mechanism of SARS-CoV-2 pathogenesis, suitable animal models or ex vivo human lung tissues aid in studying replication, transmission and spread of the novel viruses, thereby facilitating highly effective therapies.