Fig 4.
vIL-8 expression is dispensable for lytic replication but impairs disease development and tumor formation in vivo. (A and B) qPCR analysis of the viral ICP4 gene and host iNOS gene. Blood samples of animals infected with ΔIRL, vΔMetvIL-8, or vΔMetvIL-8rev were taken at 4, 7, 10, 14, 21, and 28 days p.i. Mean MDV genome copy numbers per 1 × 106 cells of eight infected chickens per group are shown. Viral titers in the blood in Exp 1 (A) (Kruskal-Wallis test, P > 0.05; n = 24 for all time points) and Exp 2 (B) (Mann-Whitney U test, P = 0.01 for 14 days p.i. and P = 0.002 for 21 and 28 days p.i.; n = 24 for all time points) decreased in vΔMetvIL-8-infected animals compared to vΔMetvIL-8rev-infected animals. (C and D) Survival analysis of chickens infected with indicated viruses during Exp 1 (C) and Exp 2 (D). (E and F) Tumor incidence in chickens infected with the indicated viruses. Necropsies were performed on chickens upon onset of clinical symptoms or after termination of the experiment. Tumor incidence is shown as a percentage of animals per group. (E) Exp 1 (Fisher-Freeman-Hamilton test, P = 0.32); (F) Exp 2 (*, Fisher's exact test, P = 0.001).