Artificial intelligence and machine learning could support drug development for hepatitis A virus internal ribosomal entry sites

Hepatitis A virus(HAV)infection is still an important health issue worldwide.Although several effective HAV vaccines are available,it is difficult to perform universal vaccination in certain countries.Therefore,it may be better to develop antivirals against HAV for the prevention of severe hepatitis A.We found that several drugs potentially inhibit HAV internal ribosomal entry site-dependent translation and HAV replication.Artificial intelligence and machine learning could also support screening of anti-HAV drugs,using drug repositioning and drug rescue approaches.

IRESfinder:Identifying RNA internal ribosome entry site in eukaryotic cell using framed k-mer features

In eukaryotic cells, initiation of protein translation is to recruit the ribosome to a specific mRNA, which is generally dependent on the 5＇ cap structure. However, protein translation can also be initiated in a cap-independent manner by using a cis-regulatory element termed the internal ribosome entry site （IRES）. The first experimentally validated IRES was reported in the poliovirus （Pelletier and Sonenberg, 1988）. Then eukaryotic cellular mRNAs were also validated to contain IRES elements.

CONSTRUCTION OF THE DICISTRONIC ADENOVIRUS VECTOR EXPRESSING BIOACTIVE HUMAN INTERLEUKIN-12

The full-length cDNA encoding the subunits p40 and p35 of human interleukin12(hIL12) were cloned separately by RTPCR, linked together by internal ribosomal entry site (IRES) of encephalomyocarditis virus which initiates capindependent translation to form a dicistronic gene fragment. The dicistronic fragment was placed between the cytomegalovirus (CMV) promoter and SV40 polyA signal to form a dicistronic expression cassette. Subsequently, the dicistronic expression cassette was inserted into E1 region of Ad5 genome in cosmid vector pAx1cw of E1substitution type. By homologous recombination with EcoT22Idigested Ad5 DNATPC in 293 cells, the replicationdeficient recombinant adenoviruses of hIL12 were generated efficiently. After infected with hIL12 recombinant adenoviruses in vitro, 293 cells, human hepatocellular carcinoma cells HepG2, and primary human skin fibroblasts expressed and secreted hIL12 at comparable levels (30～60ng/ 106cells/24hr), which could stimulate the proliferation and IFNγ production of human lymphoblasts. These suggest that the dicistronic adenovirus vector of hIL12 could effectively mediate the expression of bioactive hIL12 and might be used in cancer gene therapy.

Immune Responses to a Dicistronic Plasmid Expressing HBsAg of Hepatitis B Virus and Interferon-γ

DNA vaccines encoding a viral protein have been shown to induce antiviral immune responses and provide pro-tection against subsequent viral challenge. The present article deals with the efficacy of a DNA vaccine greatly im-proved by the simultaneous expression of HBsAg and interferon-T gene. We constructed a dual expression vector pHIN encoding the HBsAg of Hepatitis B virus and murine IFN-T which are connected with Internal Ribosome Entry Site（IRES）. Mice immunized with this dual expression DNA vaccine exhibited the enhancement of cellular immune response and increased the production of anti-HBV surface antibody, compared with the mice of single gene expres-sion control. Taken together, these results demonstrate that the application of a cytokine gene in a DNA vaccine for-mulation as an adjuvant can improve its immunigenicity.

Structure-function relationship in viral RNA genomes: The case of hepatitis C virus

The acquisition of a storage information system beyond the nucleotide sequence has been a crucial issue for the propagation and dispersion of RNA viruses. This system is composed by highly conserved, complex structural units in the genomic RNA, termed functional RNA domains. These elements interact with other regions of the viral genome and/or proteins to direct viral translation, replication and encapsidation. The genomic RNA of the hepatitis C virus(HCV) is a good model for investigating about conserved structural units. It contains functional domains, defined by highly conserved structural RNA motifs, mostly located in the 5'-untranslatable regions(5'UTRs) and 3'UTR, but also occupying long stretches of the coding sequence. Viral translation initiation is mediated by an internal ribosome entry site located at the 5' terminus of the viral genome and regulated by distal functional RNA domains placed at the 3' end. Subsequent RNA replication strongly depends on the 3'UTR folding and is also influenced by the 5' end of the HCV RNA. Further increase in the genome copy number unleashes the formation of homodimers by direct interaction of two genomic RNA molecules, which are finally packed and released to the extracellular medium. All these processes, as well as transitions between them, are controlled by structural RNA elements that establish a complex, direct and long-distance RNARNA interaction network. This review summarizes current knowledge about functional RNA domains within the HCV RNA genome and provides an overview of the control exerted by direct, long-range RNA-RNA contacts for the execution of the viral cycle.