To determine if the ability of A49 to bind β-TrCP and thus inhibit NF-κB signaling is the only reason for attenuation, recombinant VACVs bearing A49 S7/12A or S7/12E or lacking the first 12 aa (Δ12) were constructed, and the virulence of these viruses was tested by measuring weight change after infection (Fig. 7A). This evidence concerns the gene BTRC and infection.