Resumen de Circular rnas: from host rna molecules to novel broad-spectrum antivirals
The clinical importance of the mosquito-borne viruses, such as dengue virus (DENV), zika virus (ZIKV) chikungunya virus (CHIKV) and West Nile virus (WNV), has dramatically increased over the last years, resulting in a global health problem. Currently, there are no available treatments or effective vaccines to treat these infections. All these viruses produce acute infections that require to be treated early after the onset of the symptoms for drugs to be effective. However, an early diagnosis remains still as an unsolved challenge. This brings to the spotlight the need to uncover novel fundamental virus-cell interactions that could be targeted and to develop efficient broad-spectrum antiviral therapies that could be administered before an accurate diagnosis is achieved. In this thesis we addressed these two major concerns with a focus in circular RNAs (circRNAs).
CircRNAs are a class of RNAs generated from linear RNA progenitors by an alternative splicing mechanism termed back splicing. They are highly stable relative to their linear spliced counterparts due to exonuclease resistance. Currently, cellular circRNAs are described to be involved in viral infections. However, their precise role is mainly unknown. The first chapter of the thesis addresses this intriguing issue using HCV as a model system and analyzing the effect of the identified circRNAs in mosquito-borne viruses that belong to the same viral group. By RNA-Seq analyses we identified 73 HCV-differentially expressed circRNAs whose changes could not be explained by parallel changes in linear mRNAs. Silencing of five selected HCV-induced up-regulated circRNAs altered viral infectivity, acting either as anti-viral or pro-viral molecules. Further characterization of one of the selected circRNAs, cPSD3, show, that it also impaired DENV infections.
The second chapter focuses on the generation of a novel and versatile circRNA-based platform to develop broad-spectrum antivirals. In contrast to other RNA-based therapies, circRNAs are highly stable molecules, a trait that will simplify their therapeutic use. The designed synthetic circRNAs contain long sequences that hybridize to multiple target sequences in the viral RNA genome involved in forming RNA structures essential for virus survival. These features greatly hamper the emergence of resistant mutants, a major problem of traditional drugs treating RNA viruses. As a proof of concept, we have successfully validated circRNAs that inhibit HCV, DENV, CHIKV or WNV. Furthermore, we have generated circRNAs with broad-spectrum antiviral capacity and optimized the production in vitro of these molecules to obtain high amounts at low price.
In conclusion, our results (i) emphasize the complexity of the interaction between cellular circRNAs and viruses and (ii) uncover the great potential of artificial circRNAs as novel platforms for drug development
