Rous sarcoma growth in lines congenic for major histocompatibility (B) complex recombinants

Rous sarcoma virus (RSV)-induced tumor growth was examined in congenic lines of chickens with different major histocompatibility (B) complex recombinant haplotypes on the highly inbred line UCD 003 (B17B17) genetic background. Males bearing an individual B complex recombinant were mated to UCD 003 females followed by 10 backcross generations. Matings among heterozygotes for each recombinant produced homozygous chickens estimated to contain 99.9% of the line UCD 003 background genome. The 5 lines having distinct serologically identified MHC recombinant haplotypes, which arose from separate recombinational events, were as follows: 003.R1, 003.R2, 003.R4, 003. R5, and 003.R6. Chicks from each of the recombinant lines were challenged with 10 pfu subgroup A RSV at 6 wk of age. Tumors were scored for size 6 times over 10 wk postinoculation. Each bird was assigned a tumor profile index (TPI) based on the 6 tumor size scores. Hatch and B genotype were main effects in the statistical analysis. Least squares ANOVA was used to evaluate rank-transformed TPI values and mean tumor sizes through a repeated measures design. Tumor growth and TPI values were greater for 003.R1 and 003.R4 chickens than for the other 3 congenic lines. Among serologically similar recombinants 003.R2 and 003.R4, higher tumor growth and TPI in 003.R4 indicate unique genetic variation affecting RSV tumors compared with 003.R2. The similar tumor growth of 003.R5 and 003.R6 chickens, which have BF/BL21 but different BG regions, demonstrated no BG effect on RSV tumors.