FIG 4.

Effect of preimmunization of mice with T4 head proteins on phage activity against bacterial infection. Mice (n = 6) were preimmunized with purified T4 head proteins up to equal levels (according to the developed schedule of immunization; see Materials and Methods), as confirmed by ELISA. Then mice were infected with E. coli at 10⁹ CFU/mouse and 1 h later treated with T4 phage at 10⁹ PFU/mouse. Numbers of living animals in particular groups on days 0 to 5 are presented. Animal condition was monitored during the whole experiment. The model of infection was developed experimentally as follows: 50% of phage-treated mice survived 5 days of the infection, and untreated mice were all dead within 4 days. The experiment was terminated on day 5 due to ethical reasons.