Studies of Avian Sarcoma and Erythroblastosis (Strain 13). I. Titration of Infectivity by the Use of Wing-Web Inoculation2

Abstract

Avian sarcoma and erythroblastosis (strain 13) were studied in 7 titrations. Three virus preparations and 1,070 chicks were used. The level of virus could be determined by the graphic probit estimate of the median log latent period by use of the accumulative frequencies, in probits, of log time to tumor appearance. The median log latent period was a linear function of the logarithm of virus dose. Quantal response analysis was also used to estimate the amount of virus. A linear function was obtained by the probit of the total percentage of chicks with sarcomas plotted for the various log dilutions of the virus preparation. The mean Gaddum's precision index, λ, determined from the latent-period response data for 7 experiments, was 1.52. The average value of λ derived from quantal response data for the same experiments was 1.56. These findings establish that latent-period procedures, equally accurate and more practical than quantal response analysis, may be effectively used in the bioassay of this avian tumor virus.