FIG. 1.

Construction and characterization of a recombinant VAC with an inducible A11R ORF (vA11Ri). (A) Genome structure of vA11Ri. The three loci at which vA11Ri differs from the WR strain are shown as boxes: J2R (thymidine kinase; TK), A11R and A56R (hemagglutinin; HA). Below the boxes are schematics of the modifications. Additional abbreviations: T7pol, bacteriophage T7 RNA polymerase gene; lacO, lac operator; P11, a VAC late promoter; P7.5, a VAC early/late promoter; lacI, E. coli lac repressor gene; gpt, E. coli guanine phosphoribosyltransferase gene; PT7, bacteriophage T7 promoter;EMC, encephalomyocarditis virus cap-independent translation enhancer element. (B) Plaque phenotype of vA11Ri. BS-C-1 cells were infected with vA11Ri, vA11Ri/A11R and vT7lacOI in the absence or presence of 25 μM IPTG. After 48 h, the cells were fixed and stained with crystal violet. (C) Dependency of vA11Ri replication on IPTG. BS-C-1 cells were infected with 10 PFU per cell of vT7lacOI (•) or with vA11Ri (○) in the presence of 0 to 100 μM IPTG, and the viral yield was determined after 24 h. (D) One-step growth curve of vA11Ri. BS-C-1 cells were infected with 10 PFU per cell of vT7lacOI (•) or vA11Ri in the absence (□) or presence (○) of 25 μM IPTG, and the virus yield was determined from 2 to 48 h postinfection (h p.i.).