Using the virus challenge dose in the analysis of virus neutralization assays.

We propose a new basis for adjusting the results of virus neutralization assays. These assays consist of two separate experiments performed in parallel: a virus titration experiment and a serum dilution assay. In the virus titration experiment, one estimates the amount of virus used in the assay (the virus challenge dose). In a typical virus neutralization assay, the virus challenge dose may range over an order of magnitude. In the serial dilution assay, one measures the serum neutralizing activity against a particular virus. Most standard methods use the virus titration results only to ensure that the overall experiment is acceptable; the specific results of the virus titration experiment are not used to adjust the estimate of serum neutralizing activity. Although adjustment based on calibration with reference sera could be done, this seldom occurs in practice. We use results from recent studies of the kinetics and stoichiometry of polio virus neutralization with monoclonal antibodies to develop a method to use results from the virus titration experiment to adjust the serum neutralizing activity directly. Our results also indicate that a simple ad hoc procedure can improve the accuracy of the estimated serum neutralizing activity.