Virus dilution affects the anti-Rous sarcoma response of progressor but not regressor major histocompatibility (B) complex genotypes.

Responses to tumors induced by three dilutions of Rous sarcoma virus (RSV) were studied in UNH 105, a noninbred line of New Hampshire chickens. Single-male matings produced progeny of three B genotypes: B23/B23 (tumor regressor) and B23/B24 and B24/B24 (tumor progressors). A total of 223 6-wk-old chicks were wingweb inoculated with one of three dilutions (10(-3), 4 X 10(-3), and 10(-4)) of a pseudotype of Bryan high titer RSV designated as BH RSV (RAV-1). A tumor profile index (TPI), an indicator of antitumor response, was assigned to each chick based on six postinoculation tumor size scores. Incidence of mortality was itemized for B genotypes at each virus dilution and the number of days to death (DTD) was recorded for 44 chicks with terminal tumors. Analysis of mean TPI revealed a virus dilution X B genotype interaction, with significant differences among B24/B24 chickens at a 10(-3) virus dilution (TPI 3.1), a 4 X 10(-3) virus dilution (TPI 2.6), and all other subclasses (TPI 1.8 or less). Both virus dilution and B genotype affected the incidence of mortality as shown by chi-square analysis. These data demonstrate that virus dilution influenced the antitumor response in progressor but not in regressor B complex genotypes.