Tomatidine, a natural steroidal alkaloid shows antiviral activity towards chikungunya virus in vitro

In recent decades, chikungunya virus (CHIKV) has re-emerged, leading to outbreaks of chikungunya fever in Africa, Asia and Central and South America. The disease is characterized by a rapid onset febrile illness with (poly)arthralgia, myalgia, rashes, headaches and nausea. In 30 to 40% of the cases, CHIKV infection causes persistent (poly)arthralgia, lasting for months or even years after initial infection. Despite the drastic re-emergence and clinical impact there is no vaccine nor antiviral compound available to prevent or control CHIKV infection. Here, we evaluated the antiviral potential of tomatidine towards CHIKV infection. We demonstrate that tomatidine potently inhibits virus particle production of multiple CHIKV strains. Time-of -addition experiments in Huh7 cells revealed that tomatidine acts at a post-entry step of the virus replication cycle. Furthermore, a marked decrease in the number of CHIKV-infected cells was seen, suggesting that tomatidine predominantly acts early in infection yet after virus attachment and cell entry. Antiviral activity was still detected at 24 hours post-infection, indicating that tomatidine controls multiple rounds of CHIKV replication. Solasodine and sarsasapogenin, two structural derivatives of tomatidine, also showed strong albeit less potent antiviral activity towards CHIKV. In conclusion, this study identifies tomatidine as a novel compound to combat CHIKV infection in vitro

MicroRNA profiling of human primary macrophages exposed to dengue virus identifies miRNA-3614-5p as antiviral and regulator of ADAR1 expression

ABSTARCT: Due to the high burden of dengue disease worldwide, a better understanding of the interactions between dengue virus (DENV) and its human host cells is of the utmost importance. Although microRNAs modulate the outcome of several viral infections, their contribution to DENV replication is poorly understood. METHODS AND PRINCIPAL FINDINGS: We investigated the microRNA expression profile of primary human macrophages challenged with DENV and deciphered the contribution of microRNAs to infection. To this end, human primary macrophages were challenged with GFP-expressing DENV and sorted to differentiate between truly infected cells (DENV-positive) and DENV-exposed but non-infected cells (DENV-negative cells). The miRNAome was determined by small RNA-Seq analysis and the effect of differentially expressed microRNAs on DENV yield was examined. Five microRNAs were differentially expressed in human macrophages challenged with DENV. Of these, miR-3614-5p was found upregulated in DENV-negative cells and its overexpression reduced DENV infectivity. The cellular targets of miR-3614-5p were identified by liquid chromatography/mass spectrometry and western blot. Adenosine deaminase acting on RNA 1 (ADAR1) was identified as one of the targets of miR-3614-5p and was shown to promote DENV infectivity at early time points post-infection. CONCLUSION/SIGNIFICANCE: Overall, miRNAs appear to play a limited role in DENV replication in primary human macrophages. The miRNAs that were found upregulated in DENV-infected cells did not control the production of infectious virus particles. On the other hand, miR-3614-5p, which was upregulated in DENV-negative macrophages, reduced DENV infectivity and regulated ADAR1 expression, a protein that facilitates viral replication

Complex interaction between dengue virus replication and expression of miRNA-133a

Background: Dengue virus (DENV) is the most common vector-borne viral infection worldwide with approximately 390 million cases and 25,000 reported deaths each year. MicroRNAs (miRNAs) are small non-coding RNA molecules responsible for the regulation of gene expression by repressing mRNA translation or inducing mRNA degradation. Although miRNAs possess antiviral activity against many mammalian-infecting viruses, their involvement in DENV replication is poorly understood. Methods: Here, we explored the relationship between DENV and cellular microRNAs using bioinformatics tools. We overexpressed miRNA-133a in Vero cells to test its role in DENV replication and analyzed its expression using RT-qPCR. Furthermore, the expression of polypyrimidine tract binding protein (PTB), a protein involved in DENV replication, was analyzed by western blot. In addition, we profiled miRNA-133a expression in Vero cells challenged with DENV-2, using Taqman miRNA. Results: Bioinformatic analysis revealed that the 3' untranslated region (3'UTR) of the DENV genome of all four DENV serotypes is targeted by several cellular miRNAs, including miRNA-133a. We found that overexpression of synthetic miRNA-133a suppressed DENV replication. Additionally, we observed that PTB transcription, a miRNA-133a target, is down-regulated during DENV infection. Based in our results we propose that 3' UTR of DENV downregulates endogenous expression of miRNA-133a in Vero cells during the first hours of infection. Conclusions: miRNA-133a regulates DENV replication possibly through the modulation of a host factor such as PTB. Further investigations are needed to verify whether miRNA-133a has an anti-DENV effect in vivo

Identification of Z-Tyr-Ala-CHN 2, a Cathepsin L Inhibitor with Broad-Spectrum Cell-Specific Activity against Coronaviruses, including SARS-CoV-2.

The ongoing COVID-19 pandemic, caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), is partly under control by vaccination. However, highly potent and safe antiviral drugs for SARS-CoV-2 are still needed to avoid development of severe COVID-19. We report the discovery of a small molecule, Z-Tyr-Ala-CHN 2, which was identified in a cell-based antiviral screen. The molecule exerts sub-micromolar antiviral activity against SARS-CoV-2, SARS-CoV-1, and human coronavirus 229E. Time-of-addition studies reveal that Z-Tyr-Ala-CHN 2 acts at the early phase of the infection cycle, which is in line with the observation that the molecule inhibits cathepsin L. This results in antiviral activity against SARS-CoV-2 in VeroE6, A549-hACE2, and HeLa-hACE2 cells, but not in Caco-2 cells or primary human nasal epithelial cells since the latter two cell types also permit entry via transmembrane protease serine subtype 2 (TMPRSS2). Given their cell-specific activity, cathepsin L inhibitors still need to prove their value in the clinic; nevertheless, the activity profile of Z-Tyr-Ala-CHN 2 makes it an interesting tool compound for studying the biology of coronavirus entry and replication

Host cell responses to dengue virus infection

Dengue (ook wel knokkelkoorts) is de meest voorkomende virale infectieziekte dat wordt overgedragen door muggen in de wereld met naar schatting 390 miljoen infecties per jaar. Ondanks de grote klinische impact en economische schade van het dengue virus is er nog steeds geen behandeling beschikbaar. Het onderzoek beschreven in het proefschrift getiteld: “Host cell responses to dengue virus infection” bestudeert de moleculaire interacties tussen het virus en de gastheercel. We hebben onder andere vastgesteld welke cellen in ons lichaam met name worden besmet met het dengue virus. Macrofagen, belangrijke fagocyterende cellen, spelen een belangrijke rol in de productie van nieuwe dengue virusdeeltjes. Ook hebben we ontrafeld hoe antistoffen tegen het dengue virus het infectieproces in macrofagen versterken in plaats van neutraliseren. Daarnaast is onderzocht welke rol microRNAs (kleine humane RNA moleculen) hebben op het replicatieproces van het dengue virus in macrofagen. Een van deze moleculen bleek het replicatieproces van dengue af te remmen en we beschrijven het mogelijke werkingsmechanisme hiervan. Verder is onderzocht hoe dengue virus het cellulaire stress mechanisme reguleert om zodoende virus productie te waarborgen. In het laatste hoofdstuk beschrijf ik de ontdekking van een potentieel nieuw antiviraal middel tegen dengue. Toevoeging van tomatidine aan cellen remt virusproductie met 99.9% en werkt zowel profylactisch als therapeutisch. Samenvattend, door de studies beschreven in dit proefschrift hebben we een beter inzicht gekregen in de moleculaire interacties tussen het virus en de gastheercel. Daarbij hebben we een nieuw antiviraal middel ontdekt en vervolgstudies zullen moeten uitwijzen of dit molecuul inderdaad de potentie heeft het ziektebeeld van dengue te matigen

Tomatidine and analogs thereof for use as antiviral agent

The invention relates to the fields of medicine and virology, more in particular to means and methods for treating a viral disease caused by flaviviruses or alphaviruses. Provided is tomatidine or an analog thereof for use in a method of treating a viral infection caused by a flavivirus or an alphavirus, such as dengue virus or Chikungunya virus. Also provided is a pharmaceutical composition comprising tomatidine or an analog thereof, and at least one further antiviral agent