Tissue-Culture Systems with Newcastle Disease Virus and Relationship of Antigenicity to Immunogenicity among Strains

Abstract

The serum neutralization (SN) test is used most commonly as an aid for diagnosis of a disease, for measuring concentrations of antibodies in the blood serum, and less frequently to determine antigenic relationship between strains of a virus. At times, the neutralizing capacity of an antiserum is used as a gauge for evaluating resistance to a disease (3). Embryonating chicken eggs have been used for a number of years for conducting titrations, and the SN test for Newcastle disease as well as for other viruses. With the introduction of tissue culture techniques, a number of procedures, including the SN test, have been employed with the new host system, but few reports have been made on the accuracy of the methods used. Bang (2) has shown that duplicate titrations of two strains of ND virus (Strain B Beaudette, and California 11914) in chicken embryonating eggs did not differ by more than 0.4 log. On the other hand, use of the embryo in the SN test may not be as sensitive because of the manner in which embryos are generally employed for conducting the test. Burnet (7) and Walker and Horsfall (12) showed that antiserums, as they are diluted, rapidly lose efficiency in their ability to neutralize virus. When neutralization tests were carried out with dilutions of virus and constant quantities of