Identification of Chikungunya virus nucleocapsid core assembly modulators

AbstractThe alphavirus Chikungunya virus is transmitted to humans via infected mosquitos. Most infected humans experience symptoms which can range from short-term fatigue and fever to debilitating arthritis that can last for months or years. Some patients relapse and experience symptoms months or years after the initial bout of disease. The capsid protein of Chikungunya virus forms a shell around the viral RNA genome; this structure is called the nucleocapsid core. The core protects the genome during virus transmission and with the correct environmental trigger, this proteinaceous shell dissociates and releases the viral genome to initiate infection. We hypothesized that targeting compounds to interfere with the nucleocapsid cores function would constrain virus spread either by inhibiting the release of viral genomes during entry or by reducing the number of infectious virus particles assembled. We implemented a high throughput, in vitro, FRET-based assay to monitor nucleic acid packaging by purified Chikungunya capsid protein as a proxy for nucleocapsid core assembly and disassembly. We screened 10,000 compounds and found 45 that substantially modulated the assembly of core-like particles. A subset of compounds was selected to study their effects in virus-infected vertebrate cells. Our results show that four compounds inhibit infectious virus production by at least 90% in a dose-dependent manner. The most promising inhibitor was tested and found to reduce the amount of nucleocapsid cores inside the cell during Chikungunya virus infection. These compounds could be the foundation for anti-viral therapeutics.\n\nHighlightsO_LIA FRET-based assay to detect nucleic acid packaging by Chikungunya virus capsid protein\nC_LIO_LIIdentification of small molecules that modulate core-like particle assembly\nC_LIO_LIA subset of compounds that interfere with in vitro assembly also inhibit Chikungunya virus production in cell culture\nC_LIO_LIIdentification of antiviral molecules that may not be identified by assays using reporter viruses\nC_LIO_LIPotential starting compounds for developing direct-acting antivirals\nC_LI