( the abdominal skin and a single ...)Delivery of pCMV-S DNA Using the Helios Gene Gun System Is Superior to Intramuscular Injection in Balb/c Mice

For intramuscular delivery, 100 g of pCMV-S DNA in endotoxin-free water with 0.2 M CpG oligonucleotide was administered into the quadriceps muscle using a 1 ml insulin syringe. Mice were not anesthetized and the muscle was not pretreated prior to vaccination.

Vaccination Protocols
Two separate experiments were undertaken to assess DNA delivery by the Helios gene gun.

In the first experiment, one or two vaccinations by gene gun delivery were compared to the intramuscular route. Two groups of six mice received one pCMV-S DNA vaccination by either gene gun or intramuscular delivery. Another two groups of six mice received one pCMV-S DNA vaccination each at weeks 0 and 2 by either gene gun or intramuscular delivery. Antisera were then obtained at week 4 by postmortem cardiac puncture.

In the second experiment, the duration and degree of antibody response generated following two gene gun vaccinations was investigated. Six mice received one pCMV-S vaccination each by gene gun at weeks 0 and 2, and then antisera were obtained by tail bleeds at weeks 4, 6, 9, and 12 after vaccination.

ELISA to Show Antibody Response to pCMV-S DNA Vaccination
ELISA was performed as described by Davis et al. (1996). Microplates (96-well) were coated with 100 l of 1 g/ml HBsAg subtype ayw (Rhein Biotech, Dusseldorf, Germany) and stored at 4C overnight. Plates were then washed twice in phosphate buffered saline (PBS) containing 0.1% Tween 20, and blocked with 200 l of 10% fetal calf serum (FCS) in carbonate/bicarbonate buffer pH 9.6 (0.159 g Na₂CO₃ and 0.293 g NaHCO<
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