Quantitative and rapid assays of togaviruses by immunofluorescence

For the quantitative assay of selected togaviruses, suspensions of BHK cells were inoculated with virus and grown in spinner cultures. At intervals, dependent on the growth characteristics of the viruses, about 10(3) cells were centrifuged on to microscope slides and then stained with fluorescent antibody. For rapid demonstration (2--3 hr) of specific viral antigens, virus was bound in successive dilutions onto microscope slides and stained. Binding of specific anti-virus antibodies in both methods, was determined either by a second labelled antibody against complement or by labelled protein A. By these methods the determination of viral antigens (Sindbis, Semliki Forest, West Nile and hog cholera viruses) was independent from the source of immune sera.