Figure 4.

Comparison of A3R and 676Z phage immunogenicity in different administration routes: intraperitoneal (IP) and per os. Intensity of anti-phage IgG induction by A3R and 676Z phages applied per os or intraperitoneally (A), and efficiency of plating of A3R and 676Z phages with plasma samples from mice treated with A3R or 676Z phage per os and intraperitoneally (B). Mice (N = 5, 6, or 7) were administered purified preparations of phages A3R or 676Z in drinking water as a sole water source continuously for 100 days or they were injected with the phages intraperitoneally (IP). For oral treatment a dose of 4 × 10⁹ pfu/ml was used, thus making ~2 × 10¹⁰ pfu/mouse daily, 2 × 10¹² in total. Intraperitoneal immunization was done with three successive injections of 1 × 10¹⁰ pfu/mouse on days 0, 20, and 50. Antibody levels were tested in samples collected on day 100. Results were normalized and ELISA units were calculated with regard to a standard curve obtained for reference phage-specific sera (41, 48, 49). EOP was tested for plasma samples collected on day 100 and diluted 2,000-fold. Exemplary results are presented. Statistically significant differences between groups are marked with asterisks: *p < 0.04, **p < 0.006, ***p ≤ 0.0003, ****p < 0.0001 (one-way ANOVA Brown-Forsythe and Welch test; outliers were excluded).