Figure 6. Prevention of toxin contamination in phage lysates.

Human PBMCs were treated with phage lysates generated from RF122Δnuc or RF122-19Δnuc, an isogenic strain lacking 10 superantigen and 11 cytotoxin genes. (A) After 3 day incubation, proliferation of T cells caused by superantigens in phage lysages was measured by incorporation of radioactive ³H-thymidine into the cellular DNA using liquid scintillation counter. Bars indicate the count per minute (cpm) of radioactivity combined from triple measurements of three independent experiments (n = 9). Asterisk indicates statistical significance in student t-test, compared to the results from the RF122Δnuc (p < 0.001). (B) After 3 h incubation, cytotoxicity caused by cytotoxins in phage lysates was measured by incorporation of propidium iodide into dead cells (propidium iodide positive, PI+) using flow cytometry. Data shown are representative results repeated in three independent experiments.