Bacteriophage lambda is a highly stable DNA vaccine delivery vehicle

Abstract

The stability of whole bacteriophage λ particles, used as a DNA vaccine delivery system has been examined. Phage were found to be highly stable under normal storage conditions. In liquid suspension, no decrease in titre was observed over a 6-month period at 4 and −70 °C, and phage stability was unaffected by freeze/thawing. The measured half life of phage in suspension was 36 days at 20 °C, 3.4 days at 37 °C and 2.3 days at 42 °C. Freeze drying of a phage suspension (with or without the stabilizers dry skim milk or trehalose) resulted in 5–20% residual viability. Following desiccation (with or without stabilizers), measured half lives ranged from 20 to 100 days at 20 °C, 2.6 to 38 days at 37 °C, 2.1 to 26 days at 42 °C, 7 to 33 h at 70 °C, and 1.3 to 6 m at 100 °C. In all cases the addition of trehalose significantly increased the stability of the desiccated phage. When stored at −70 °C, desiccated phage appeared to be stable in the absence of stabilizers. When phage λ was diluted into water, a marginal loss in titre was observed over a 2-week period. Over a 24 h period, liquid phage suspensions were stable within the pH range pH 3–11, therefore oral administration of bacteriophage DNA vaccines via drinking water may be possible.