Strategies for Antiviral Screening Targeting Early Steps of Virus Infection

Viral infection begins with the entry of the virus into the host target cell and initiates replication. For this reason, the virus entry machinery is an excellent target for antiviral therapeutics. In general, a virus life cycle includes several major steps: cell-surface attachment, entry, replication, assembly, and egress, while some viruses involve another stage called latency. The early steps of the virus life cycle include virus attachment, receptor binding, and entry. These steps involve the initial interactions between a virus and the host cell and thus are major determinants of the tropism of the virus infection, the nature of the virus replication, and the diseases resulting from the infection. Owing to the pathological importance of these early steps in the progress of viral infectious diseases, the development of inhibitors against these steps has been the focus of the pharmaceutical industry. In this review, Herpes Simplex Virus (HSV), Hepatitis C Virus (HCV), and Human Enterovirus 71 (EV71) were used as representatives of enveloped DNA, enveloped RNA, and non-enveloped viruses, respectively. The current mechanistic understanding of their attachment and entry, and the strategies for antagonist screenings are summarized herein.

Transcriptome profiling highlights regulated biological processes and type III interferon antiviral responses upon Crimean-Congo hemorrhagic fever virus infection

Crimean-Congo hemorrhagic fever virus(CCHFV)is a biosafety level-4(BSL-4)pathogen that causes Crimean-Congo hemorrhagic fever(CCHF)characterized by hemorrhagic manifestation,multiple organ failure and high mortality rate,posing great threat to public health.Despite the recently increasing research efforts on CCHFV,host cell responses associated with CCHFV infection remain to be further characterized.Here,to better understand the cellular response to CCHFV infection,we performed a transcriptomic analysis in human kidney HEK293 cells by high-throughput RNA sequencing(RNA-seq)technology.In total,496 differentially expressed genes(DEGs),including 361 up-regulated and 135 down-regulated genes,were identified in CCHFV-infected cells.These regulated genes were mainly involved in host processes including defense response to virus,response to stress,regulation of viral process,immune response,metabolism,stimulus,apoptosis and protein catabolic process.Therein,a significant up-regulation of type III interferon(IFN)signaling pathway as well as endoplasmic reticulum(ER)stress response was especially remarkable.Subsequently,representative DEGs from these processes were well validated by RT-qPCR,confirming the RNA-seq results and the typical regulation of IFN responses and ER stress by CCHFV.Furthermore,we demonstrate that not only type I but also type III IFNs(even at low dosages)have substantial anti-CCHFV activities.Collectively,the data may provide new and comprehensive insights into the virus-host interactions and particularly highlights the potential role of type III IFNs in restricting CCHFV,which may help inform further mechanistic delineation of the viral infection and development of anti-CCHFV strategies.

ANTIVIRAL EFFECTS OF BACTERIOCIN AGAINST ANIMAL-TO-HUMAN TRANSMITTABLE MUTATED SARS-COV-2:A SYSTEMATIC REVIEW

The COVID-19 caused by SARS-CoV-2 has resulted in millions of people being infected and thousands of deaths globally since November 2019.To date,no unique therapeutic agent has been developed to slow the progression of this pandemic.Despite possessing antiviral traits the potential of bacteriocins to combat SARS-CoV-2 infection has not been fully investigated.This review summarizes the mechanisms by which bacteriocins can be manipulated and implemented as effective virus entry blockers with infection suppression potential properties to highly transmissible viruses through comprehensive immune modulations that are potentially effective against COVID-19.These antimicrobial peptides have been suggested as effective antiviral therapeutics and therapeutic supplements to prevent rapid virus transmission.This review also provides a new insight into the cellular and molecular alterations which have made SARS-CoV-2 self-modified with diversified infection patterns.In addition,the possible applications of antimicrobial peptides through both natural and induced mechanisms in infection prevention perspectives on changeable virulence cases are comprehensively analyzed.Specific attention is given to the antiviral mechanisms of the molecules along with their integrative use with synthetic biology and nanosensor technology for rapid detection.Novel bacteriocin based therapeutics with cutting-edge technologies might be potential substitutes for existing time-consuming and expensive approaches to fight this newly emerged global threat.

Development of cell-based pseudovirus entry assay to identify potential viral entry inhibitors and neutralizing antibodies against SARS-CoV-2

Severe acute respiratory syndrome coronavirus 2(SARS-CoV-2)is the causative virus of the coronavirus disease 2019(COVID-19)pandemic.To establish a safe and convenient assay system for studying entry inhibitors and neutralizing antibodies against SARS-CoV-2,we constructed a codon-optimized,full-length C-terminal mutant spike(S)gene of SARS-CoV-2.We generated a luciferase(Luc)-expressing pseudovirus containing the wild-type or mutant S protein of SARS-CoV-2 in the envelope-defective HIV-1 backbone.The key parameters for this pseudovirus-based assay,including the S mutants and virus incubation time,were optimized.This pseudovirus contains a Luc reporter gene that enabled us to easily quantify virus entry into angiotensin-converting enzyme 2(ACE2)-expressing 293T cells.Cathepsin(Cat)B/L inhibitor E64d could significantly block SARS-CoV-2 pseudovirus infection in 293T-ACE2 cells.Furthermore,the SARS-CoV-2 spike pseudotyped virus could be neutralized by sera from convalescent COVID-19 patients or recombinant ACE2 with the fused Fc region of human IgG1.Thus,we developed a pseudovirus-based assay for SARS-CoV-2,which will be valuable for evaluating viral entry inhibitors and neutralizing antibodies against this highly pathogenic virus.

A review on the Ebola virus,outbreak history and the current research tools to control the disease

The Ebola virus is a zoonotic pathogen causing hemorrhagic fever disease with a high mortality rate.The distribution of this pathogen has been limited to woodlands from Central and West Africa and the forest-savannah ecotone in East Africa.The likely reservoir species are frugivorous bats living in these areas.This pathogen is becoming an increasing threat to human populations since its distribution range is expanding faster than expected.The current Ebola outbreaks in Western Africa and in the Democratic Republic of Congo have rapidly spread infecting high numbers of individuals in five African countries.The disease has reached the United States and Spain.This expansion is due partly to increasing global connectivity.This situation represents a new challenge to control the spread of the disease.Experimental drugs have been used to treat a few infected people with promising results.This gives hope for an effective treatment against Ebola hemorrhagic fever in the near future,though thousands of people remain at risk of infection.The present review aims to give an update of the knowledge on the disease,including features of the Ebola virus,the history of disease outbreaks in Africa and the tools that are being developed in order to control this re-emergent disease.