Virucide usage is extremely common, particularly within farming, veterinary, and hospital environments. Virucides prevent infection from ever occurring by inactivating viruses that are present on solid surfaces (such as countertops, door handles, or hands) or in liquid suspension. Traditionally, inactivation of viruses was evaluated by observing the development of CPE in permissible cells, typically in the form of a plaque assay. However, CPE evaluation based on visual interpretation of cell culture deterioration is extremely subjective, and there is no universally accepted standard on how CPEs are scored. The xCELLigence system offers an alternative method for evaluating viral CPE in virucidal efficacy testing with precise measurement and extraordinary reproducibility.
In an effort to identify novel virucides, and citing that “A major problem with the testing of virucidal efficacy using current protocols is that scoring of virus-induced cytopathic effect is dependent on subjective visual interpretation using light microscopy,” E.H. Venter and colleagues at the University of Pretoria evaluated the xCELLigence CPE assay as a novel means for testing virucide efficacy.
- A commercially available virucide was incubated at the manufacturer’s recommended concentration with infectious bursal disease virus (IBDV) for 20 minutes.
- The virus was diluted serially and added to confluent Vero cells in E-Plates.
As seen in Figure A, the untreated virus causes a cytopathic effect, with the time of CPE onset being dependent on the virus titer. However, pre-treatment of IBDV with virucide significantly diminished infectivity: whereas the 10x dilution of virus was still able to induce a CPE, 100x and higher dilutions of the virus had no effect on the Vero cells (Figure B).
In light of the above data, the authors concluded, “Although the modified [virucide] assay using the xCELLigence system yielded identical results as the traditional [virucide] assay, the system allows virucidal efficacy and cytotoxicity to be measured in a more precise and reproducible fashion.”
Protecting Vero cells from IBDV using virucide. Vero cells infected with serial dilutions of IBDV that had not been pre-treated with virucide (A), or which had not been pre-treated with virucide (B). After exposure to virucide, only the most concentrated solution of virus is still able to induce a cytopathic effect. Virus concentrations are denoted as fold dilutions (i.e. 101=10x dilution, 102=100x dilution, etc.). Data adapted from reference 1.
xCELLigence instruments that are compatible with virology/vaccine applications:
|Dual Purpose||Single Plate||Multi Plate||High Throughput|
|3×16 wells||1×96 wells||6×96 wells||Up to 4×384 wells|
- An improved method for determining virucidal efficacy of a chemical disinfectant using an electrical impedance assay. J Virol Methods. 2014 Apr;199:25-8.