Sáez Álvarez, Yanira

Microsporidia are opportunistic intracellular parasites, generating serious pathology in individuals with a compromised immune system. Infection by microsporidia inhibits p53 and Caspase 3, proteins involved in apoptosis and the cell cycle, which are vital in the malignant process of epithelial cells. The presence of microsporidia in the intestinal tissues of 87 colon cancer (CC) patients and 25 healthy controls was analyzed by real-time PCR and an immunofluorescence antibody test. Anti-Encephalitozoon antibodies were analyzed in serum samples by ELISA (enzyme linked immunosorbent assay). In 36 (41.3%) CC cases, microsporidia infections were identified in their tissues vs. no cases among control subjects (p < 0.0001). An increase in IgG and IgE anti-Encephalitozoon antibodies was found in patients with CC, which would demonstrate continuous and previous contact with the parasite. The high prevalence of microsporidia in tissues and the seroprevalence in patients with CC suggest a relationship between microsporidia and the etiopathogenesis of CC.

West Nile virus (WNV) is a re-emergent mosquito-borne RNA virus that causes major outbreaks of encephalitis around the world. However, there is no therapeutic treatment to struggle against WNV, and the current treatment relies on alleviating symptoms. Therefore, due to the threat virus poses to animal and human health, there is an urgent need to come up with fast strategies to identify and assess effective antiviral compounds. A relevant target when developing drugs against RNA viruses is the viral RNA-dependent RNA polymerase (RdRp), responsible for the replication of the viral genome within a host cell. RdRps are key therapeutic targets based on their specificity for RNA and their essential role in the propagation of the infection. We have developed a fluorescence-based method to measure WNV RdRp activity in a fast and reliable real-time way. Interestingly, rilpivirine has shown in our assay inhibition of the WNV RdRp activity with an IC50 value of 3.3 μM and its antiviral activity was confirmed in cell cultures. Furthermore, this method has been extended to build up a high-throughput screening platform to identify WNV polymerase inhibitors. By screening a small chemical library, novel RdRp inhibitors 1-4 have been identified. When their antiviral activity was tested against WNV in cell culture, 4 exhibited an EC50 value of 2.5 μM and a selective index of 12.3. Thus, rilpivirine shows up as an interesting candidate for repurposing against flavivirus. Moreover, the here reported method allows the rapid identification of new WNV RdRp inhibitors.

Zika virus (ZIKV) is a mosquito-borne pathogen responsible for neurological disorders (Guillain-Barré syndrome) and congenital malformations (microcephaly). Its ability to cause explosive epidemics, such as that of 2015 to 2016, urges the identification of effective antiviral drugs. Viral polymerase inhibitors constitute one of the most successful fields in antiviral research. Accordingly, the RNA-dependent RNA polymerase activity of flavivirus nonstructural protein 5 (NS5) provides a unique target for the development of direct antivirals with high specificity and low toxicity. Here, we describe the discovery and characterization of two novel nonnucleoside inhibitors of ZIKV polymerase. These inhibitors, TCMDC-143406 (compound 6) and TCMDC-143215 (compound 15) were identified through the screening of an open-resource library of antikinetoplastid compounds using a fluorescence-based polymerization assay based on ZIKV NS5. The two compounds inhibited ZIKV NS5 polymerase activity in vitro and ZIKV multiplication in cell culture (half-maximal effective concentrations [EC50] values of 0.5 and 2.6mM for compounds 6 and 15, respectively). Both compounds also inhibited the replication of other pathogenic flaviviruses, namely, West Nile virus (WNV; EC50 values of 4.3 and 4.6mM for compounds 6 and 15, respectively) and dengue virus 2 (DENV-2; EC50 values of 3.4 and 9.6mM for compounds 6 and 15, respectively). Enzymatic assays confirmed that the polymerase inhibition was produced by a noncompetitive mechanism. Combinatorial assays revealed an antagonistic effect between both compounds, suggesting that they would bind to the same region of ZIKV polymerase. The nonnucleoside inhibitors of ZIKV polymerase here described could constitute promising lead compounds for the development of anti-ZIKV therapies and, eventually, broad-spectrum antiflavivirus drugs.

Zika virus (ZIKV) is an emerging pathogen that has been associated with large numbers of cases of severe neurologic disease, including Guillain-Barré syndrome and microcephaly. Despite its recent establishment as a serious global public health concern there are no licensed therapeutics to control this virus. Accordingly, there is an urgent need to develop methods for the high-throughput screening of antiviral agents. We describe here a fuorescence-based method to monitor the real-time polymerization activity of Zika virus RNA-dependent RNA polymerase (RdRp). By using homopolymeric RNA template molecules, de novo RNA synthesis can be detected with a fuorescent dye, which permits the specifc quantifcation and kinetics of double-strand RNA formation. ZIKV RdRp activity detected using this fuorescence-based assay positively correlated with traditional assays measuring the incorporation of radiolabeled nucleotides. We also validated this method as a suitable assay for the identifcation of ZIKV inhibitors targeting the viral polymerase using known broad-spectrum inhibitors. The assay was also successfully adapted to detect RNA polymerization activity by diferent RdRps, illustrated here using purifed RdRps from hepatitis C virus and foot-and-mouth disease virus. The potential of fuorescence-based approaches for the enzymatic characterization of viral polymerases, as well as for high-throughput screening of antiviral drugs, are discussed.

Los virus de ARN son patógenos de alta impacto clínico y veterinario, muchos de ellos de reciente aparición como el SARS-CoV-2 o bien los reemergentes como el Zika se han convertido en un foco de interés. Todos los virus de ARN replican sus genomas a través de una ARN polimerasa dependiente de ARN (RdRp). Esta proteína es única, lo que la convierte en una diana para el desarrollo de antivirales con alta especificidad. Aquí se describe un método basado en fluorescencia para monitorizar la actividad de polimerización a tiempo real de las RdRp. El uso de moldes de ARNmc homopolimérico, permite detectar la síntesis de novo de ARNbc con un tinte intercalante. Gracias a este método, se han podido descubrir y caracterizar dos nuevos INAN de la polimerasa del virus del Zika: TCMDC-143406 y TCMDC-143215. Además, mediante ligeras adaptaciones, se ha podido medir en tiempo real la actividad de las RdRp de FMDV y HCV junto con la polimerasa de SARS-CoV-2. Los resultados demuestran que la plataforma basada en fluorescencia para medir la actividad polimerasa a tiempo real, representa una alternativa rápida, económica, fiable y eficaz para la medida de la actividad de distintas RdRp y el cribado de compuestos con potencial efecto inhibitorio frente a estas proteínas.