Bacteriophage lambda is a highly stable DNA vaccine delivery vehicle

The stability of whole bacteriophage X particles, used as a DNA vaccine delivery system has been examined. Phage were found to be highly stable undernormal storage conditions. In liquid suspension, no decrease in titre was observed over a 6-month period at 4 and -70degreesC, and phage stability was unaffected by freeze/thawing. The measured half life of phage in suspension was 36 days at 20degreesC, 3.4 days at 37degreesC and 2.3 days at 42degreesC. 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 20degreesC, 2.6 to 38 days at 37degreesC, 2.1 to 26 days at 42degreesC, 7 to 33 h at 70degreesC, and 1.3 to 6 m at 100degreesC. In all cases the addition of trehalose significantly increased the stability of the desiccated phage. When stored at -70degreesC, desiccated phage appeared to be stable in the absence of stabilizers. When phage X was diluted into water, a marginal loss in titre was observed over a 2-week period. Over a 24 It period, liquid phage suspensions were stable within the pH range F-H 3-11, therefore oral administration of bacteriophage DNA vaccines via drinking water may be possible. (C) 2004 Elsevier Ltd. All rights reserved.