Chikungunya virus (CHIKV)
Several patients suffer from a chronic polyarthritis that can severely incapacitate the patient for weeks up to several years after the acute stage.
Death from chikungunya is rare.
Millions of CHIKV cases have been reported in the Caribbean region and several countries of Central and South America. Local transmission cases have been also reported in Europe (e.g. Italy and France). Despite being rarely fatal, CHIKV infections have high socioeconomic impact due to the chronic painful incapacitating phase of the disease. There are no approved vaccines or antivirals available for the prevention or treatment of CHIKV infection.
Cell-based assays
CPE reduction assay
This antiviral assay measures the ability of a tested compound to protect infected cells from virus-induced cytopathic effects (mostly virus-induced cell death). The cell viability can be determined in a colorimetric assay using MTS/PMS method.Virus yield assay
This antiviral assay measures the ability of a tested compound to inhibit the viral replication in an infected cell culture through quantifying the viral RNA and the infectious virus loads released in the supernatant. This assay can be used for validation of compounds that show efficacy in CPE-reduction assays and to confirm that the compounds have direct effect on viral replication (not only cytoprotective).Delay of treatment assay (Time-of-addition)
This a test to determine the stage(s) of the viral replication cycle at which the compound exerts its antiviral effect. Briefly, cells are treated with the compound at different time points prior or after the infection with the virus then cells are incubated for example until the end of one or 2 replication cycles. At the end of incubation, the intracellular and extracellular viral RNA loads at each time point are quantified by qRT-PCR to determine at which stage(s) the compound is still effective and when it loses its antiviral efficacy.Plaque assay
This assay is a standard method to quantify infectious virus titers in a sample. Briefly, the test sample is serially diluted then aliquot of each dilution is added to a well in a cell culture plate with incubation to allow virus attachment followed by removal of the viral input and adding overlay of agarose or similar viscous material that limit the spread of viral infection. Under this condition, the attached virion will start to replicate producing more virions that will kill surrounding cells to generate a hole or plaque in the cell monolayer. By removal of the overlay and staining the live cells for e.g. by Crystal violet or methylene blue, this will provide a dark background for clear visualization of plaques. By counting the plaques at certain dilution(s), the plaque forming units (PFU)/mL can be calculated.High-throughput screening
High throughput screening (HTS)
HTS is an approach in antiviral drug discovery involving the use of automated equipment to rapidly test huge libraries of chemical or biological materials with the aim of identifying hit molecules against specific viruses. HTS is usually done in culture plates with 384 or 1536 wells format using high performance liquid/plate handling devices.Recombinant viruses
Reverse genetic system
A reverse genetic system is mostly a plasmid-based system that can be used to insert the desired mutations in the viral genome to study the effect of these mutations on viral replication, virulence, sensitivity to antiviral compounds in vitro and in vivo.Reporter viruses
Reporter viruses are recombinant viruses engineered to carry reporter genes such as the one coding for fluorescent or luminescent proteins for development of high throughput antiviral assays or easily detection method for in vivo replication.Animal infection models
