TABLE 1.

Comparison of pathogenicities of rMd5, rMd5/ΔvIL-8, rMd5/vIL-8-ELR, and rMd5/ΔvIL-8-RV in 15 × 7 MDV maternal antibody-negative chickens^a

Virusb	No. of chickens that died/no. tested (%)	No. of chickens with tumor/no. tested (%)
Mock	0/17 (0)	0/17 (0)
rMd5	15/17 (88.2)	13/17 (76.7)
rMd5/ΔvIL-8	1/17 (4.3)*	3/17 (17.6)*
rMd5/vIL-8-ELR	16/17 (94.1)	15/17 (88.2)
rMd5/ΔvIL-8-RV	17/17 (100)	13/17 (76.7)

^aThis experiment was repeated two times separately. *, Student's t test (P ≤ 0.001) analysis indicated value was significantly different from those for the other groups.

^bAll chickens were inoculated with 2,000 PFU of the indicated viruses.