The titration of vaccinial neutralizing antibody on chorio-allantoic membranes

Abstract

A study has been made of various factors involved in performing neutralization tests with vaccinia virus on chorio-allantoic membranes.The common practice of using a single serum concentration has been shown to result in a test which is qualitative only. The linear relationship between the logarithm of the pock count of the surviving virus and the logarithm of the serum dilution can be used to determine the dilution of serum which will neutralize 50% of a virus suspension. By this method it is possible to distinguish between sera whose potencies vary by about fourfold.I gratefully acknowledge the advice and criticism given by Dr J. C. N. Westwood and Dr I. A. Macpherson, as well as the help given by Mr S. Peto with the statistical treatment of results. My thanks are also due to Mr H. B. Maber and Corporal M. Fitzpatrick, R.A.M.C., for their technical assistance.