Antibody response to EV knockout viruses.

Groups of mice (5 mice per group) were inoculated by tail scarification with 10⁵ pfu of recombinant viruses A33Rko, B5Rko, A33R/B5Rko, or the parent, DV-3. Immune sera obtained 3 weeks after vaccination were tested in vitro for vaccinia-specific IgG by ELISA (A) and the neutralization of ~ 300 pfu of purified vaccinia virus strain WR MV (B). Data represent mean IgG titer (A) or mean neutralizing titer (B), and error bars represent standard deviation.