RNA secondary structures in the proximal 3′UTR of Indonesian Dengue 1 virus strains

Vector-Transmitted Flaviviruses: An Antiviral Molecules Overview

Flaviviruses cause numerous pathologies in humans across a broad clinical spectrum with potentially severe clinical manifestations, including hemorrhagic and neurological disorders. Among human flaviviruses, some viral proteins show high conservation and are good candidates as targets for drug design. From an epidemiological point of view, flaviviruses cause more than 400 million cases of infection worldwide each year. In particular, the Yellow Fever, dengue, West Nile, and Zika viruses have high morbidity and mortality-about an estimated 20,000 deaths per year. As they depend on human vectors, they have expanded their geographical range in recent years due to altered climatic and social conditions. Despite these epidemiological and clinical premises, there are limited antiviral treatments for these infections. In this review, we describe the major compounds that are currently under evaluation for the treatment of flavivirus infections and the challenges faced during clinical trials, outlining their mechanisms of action in order to present an overview of ongoing studies. According to our review, the absence of approved antivirals for flaviviruses led to in vitro and in vivo experiments aimed at identifying compounds that can interfere with one or more viral cycle steps. Still, the currently unavailability of approved antivirals poses a significant public health issue.

Interactions of host miRNAs in the flavivirus 3´UTR genome: From bioinformatics predictions to practical approaches

The genus Flavivirus of the Flaviviridae family includes important viruses, such as Dengue, Zika, West Nile, Japanese encephalitis, Murray Valley encephalitis, tick-borne encephalitis, Yellow fever, Saint Louis encephalitis, and Usutu viruses. They are transmitted by mosquitoes or ticks, and they can infect humans, causing fever, encephalitis, or haemorrhagic fever. The treatment resources for these diseases and the number of vaccines available are limited. It has been discovered that eukaryotic cells synthesize small RNA molecules that can bind specifically to sequences present in messenger RNAs to inhibit the translation process, thus regulating gene expression. These small RNAs have been named microRNAs, and they have an important impact on viral infections. In this review, we compiled the available information on miRNAs that can interact with the 3’ untranslated region (3’UTR) of the flavivirus genome, a conserved region that is important for viral replication and translation.

Evolutionary relationship of 5'-untranslated regions among Thai dengue-3 viruses, Bangkok isolates, during 24 year-evolution

OBJECTIVE

To study evolutionary relationship of the 5'untranslated regions (5'UTRs) in low passage dengue3 viruses (DEN3) isolated from hospitalized children with different clinical manifestations in Bangkok during 24 year-evolution (1977-2000) comparing to the DEN3 prototype (H87).

METHODS

The 5'UTRs of these Thai DEN3 and the H87 prototype were amplified by RT-PCR and sequenced. Their multiple sequence alignments were done by Codon Code Aligner v 4.0.4 software and their RNA secondary structures were predicted by MFOLD software. Replication of five Thai DEN3 candidates comparing to the H87 prototype were done in human (HepG2) and the mosquito (C6/36) cell lines.

RESULTS

Among these Thai DEN3, the completely identical sequences of their first 89 nucleotides, their high-order secondary structure of 5'UTRs and three SNPs including the predominant C90T, and two minor SNPs including A109G and A112G were found. The C90T of Thai DEN3, Bangkok isolates was shown predominantly before 1977. Five Thai DEN3 candidates with the predominant C90T were shown to replicate in human (HepG2) and the mosquito (C6/36) cell lines better than the H87 prototype. However, their highly conserved sequences as well as SNPs of the 5'UTR did not appear to correlate with their disease severity in human.

CONCLUSIONS

Our findings highlighted evolutionary relationship of the completely identical 89 nucleotide sequence, the high-order secondary structure and the predominant C90T of the 5'UTR of these Thai DEN3 during 24 year-evolution further suggesting to be their genetic markers and magic targets for future research on antiviral therapy as well as vaccine approaches of Thai DEN3.

Dengue virus markers of virulence and pathogenicity

The increased spread of dengue fever and its more severe form, dengue hemorrhagic fever, have made the study of the mosquito-borne dengue viruses that cause these diseases a public health priority. Little is known about how or why the four different (serotypes 1-4) dengue viruses cause pathology in humans only, and there have been no animal models of disease to date. Therefore, there are no vaccines or antivirals to prevent or treat infection and mortality rates of dengue hemorrhagic fever patients can reach up to 20%. Cases occur mainly in tropical zones within developing countries worldwide, and control measures have been limited to the elimination of the mosquito vectors. Thus, it is imperative that we develop new methods of studying dengue virus pathogenicity. This article presents new approaches that may help us to understand dengue virus virulence and the specific mechanisms that lead to dengue fever and severe disease.