Herpes virus plaque assays

Plaque assays, at present, apply to only a very limited number of viruses, e.g. poliovirus, herpes virus, human rotavirus. The principle ofthese assays is as follows test virus is dried on to coverslips which are immersed in various concentrations oftest disinfectant... 

For assaying herpes virus, monolayers of baby hamster kidney (BHK) cells are used. Virus titre is expressed as the number of plaque-forming units (pfu) per millilitre before and after exposure to a disinfectant, so that the virucidal efficacy of the test agent can be determined. A diagrammatic representation is given in Fig. 11.7. 

A lyophylisate of the expressed sap of . purpurea in cultures of mice L-cells (clone 929) at a concentration of 10 ig/ml to 100 Llg/ml exhibited no direct antiviral activity against encephalomyocarditis virus (EMC virus) or vesicular-stomatitis-virus (VSV). An antiviral effect was only observed when the sap was added together with DEAR dextran. DEAE dextran itself showed no effect. The authors concluded an interferon-like activity [145]. By the colorimetric assay according to Finter and by the Plaque-Reduction-Assay it could be shown, that mice L-929 cells or HeLa cells became resistant for 24 h against influenza-, herpes- and vesicular-stomatitis-virus by 50-80%, when the cells were pretreated 4-6 h with 20 ig/ml of an . purpurea expressed sap preparation. Together with hyaluronidase, no effect was observed. The active component could not be inactivated by heat (60-80 C) [146]. 

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