( Andrew Conn Lindy Durra...)Delivery of pCMV-S DNA Using the Helios Gene Gun System Is Superior to Intramuscular Injection in Balb/c Mice

Andrew Conn, Lindy Durrant, and Ian Spendlove, Cancer Research Campaign Academic Unit, Nottingham City Hospital, Hucknall Road, Nottingham NG5 1PB, UK

Introduction
Gene gun immunization through the skin is a reliable and reproducible method of DNA vaccine delivery, and has been shown to be capable of inducing protective immunity in animal models to both infectious diseases and cancer (Chen et al. 2000, Chen et al. 1999). Delivery of DNA using the gene gun is a highly efficient method of achieving antigen presentation, and, as a result, immunizations require 2502,500 times less DNA than standard intramuscular delivery (Fynan et al. 1993). This is due to the dense network of Langerhans cells that are found in the epidermis, acting as a source of antigen-presenting cells.

Bio-Rads Helios gene gun system delivers DNA to the epidermis using helium-driven bombardment of DNA-coated gold microparticles. The nature of immune responses generated following vaccination with DNA depends on a number of key factors, such as the route, method, and vaccination schedule employed. We have therefore performed a series of pilot experiments with a DNA plasmid that encodes the hepatitis B surface antigen (HBsAg) to investigate the use of the Helios gene gun system in a Balb/c mouse model. A comparison has been made between delivery of this plasmid by gene gun and by intramuscular injection.

Methods
Plasmids
The pCMV-S plasmid encoding the HBsAg subtype ayw was kindly provided by Dr Robert Whalen, Maxygen, USA. DNA was prepared using the QIAGEN EndoFree Plasmid Mega kit. The presence of the HBsAg insert was verified by restriction enzym
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