Neutralization Tests with Eastern Equine Encephalomyelitis Virus in the Chick Embryo: A Statistical Treatment of the Results by the Probit Method

Abstract

Summary The chick embryo has been successfully employed for the quantitative assay of residual equine encephalomyelitis virus in tests with immune serum. Under the conditions of these experiments maximum neutralization of equine encephalomyelitis virus by antiserum was attained within a few seconds of mixing the virus and the serum. Less neutralization was apparent if the virus-serum mixtures were kept at 4 C prior to inoculation. The amount of neutralization which was apparent was related directly to the susceptibility of the embryo or inversely to the number of virus particles necessary to initiate a lethal infection. The greatest neutralization was shown when 15 day eggs were inoculated by the yolk sac route and the least neutralization when 15 day eggs were inoculated by the chorio-allantoic route. Eleven day eggs inoculated by either route showed intermediate degrees of neutralization.