Microassay for Sindbis virus and interferon activity.

A simple and rapid microplaque assay for Sindbis virus was developed which uses microtiter plates and overlay medium consisting of methylcellulose and specific antibody to Sindbis virus. Discrete plaque formation was consistently observed on baby hamster kidney (BHK-15) cells within 24 h. The assay was reproducible, quantitative, and had about the same sensitivity as the agar overlay technique on chicken embryo cells in 35-mm petri dishes. The microplaque assay could be accurately applied to measuring interferon activity, particularly at low interferon levels. Overall, the microassay methods described here for assay of Sindbis virus yields and interferon activity retain the accuracy of chicken cell macroplaque assays while offering greater simplicity, rapidity, and economy of materials. This assay is also potentially applicable for use with other togaviruses.