Vaccination onto bare skin

Abstract

We report here that applying genetic vectors onto the skin in a relatively non-invasive manner can elicit an immune response against the protein encoded by the vector. This procedure requires no special skill or equipment and so may reduce medical costs and offer a unique method for vaccination.

Main

To elicit a specific immune response, we anaesthetized mice and removed hair and cornified epithelium over a restricted area of abdominal skin using a depilatory (for example Nair)¹. We pipetted roughly 10⁸ plaque-forming units (PFU) of adenovirus vector in a volume of 10-50 μl onto the pre-shaved and Nair-treated skin. We allowed the adenovirus vector to incubate with the naked skin until the animal recovered from anaesthesia, which took between 30 min and 1 h.

After application of AdCMV-hcea, an adenovirus vector encoding the human carcinoembryonic antigen (CEA) gene, onto the skin of mice (strain C57BL/6), we monitored the production of antibodies against the human CEA protein by assaying sera from tail-bleeds. The test sera reacted in western blots with purified human CEA protein, but not with bovine serum albumin (Fig. 1a). Of 24 vaccinated mice, 23 (96%) produced antibodies against the human CEA protein after a month, indicating that specific antibodies were produced against exogenous proteins encoded by adenovirus vectors as a result of the treatment. Antibodies against adenoviral proteins were also found in some of the treated animals.

Figure 1: a, Detection of antibodies to the human CEA protein by western blot analysis.

Serum from a vaccinated mouse taken one month after applying AdCMV-hcea to the skin was diluted 1:500 and reacted with purified human CEA protein (provided by T. Strong) and adenoviral proteins separated on a 5% SDS-polyacrylamide gel. The products were transferred to membranes as in ref. 3. Lane 1, human CEA (0.5 μg); lane 2, BSA (0.5 μg); lane 3, adenovirus (10⁷ PFU). b, Detection of antibodies against the human GM-CSF protein. Purified human GM-CSF protein (CalBiochem), separated on a 15% SDS-polyacrylamide gel, was transferred to membranes and allowed to react with diluted serum. Lane 1, human GM-CSF (0.25 μg); lane 2, BSA (0.25 μg); lane 3, adenovirus (10⁷ PFU).

To test whether this technique might be generally applicable, we applied AdCMV-hgmcsf, an adenovirus vector encoding the human granulocyte macrophage colony stimulating factor (hGM-CSF), in the same way. The test sera reacted with purified human GM-CSF protein (Fig. 1b) in 6 of 14 mice showing that 43% produced antibodies against the human GM-CSF protein after application of AdCMV-hgmcsf. Pre-immune sera collected before treatment, sera from untreated animals, and sera from animals treated with AdCMV-luc² all failed to react with the human CEA and GM-CSF proteins.

To our knowledge, this is the first demonstration that animals can be vaccinated in a simple, painless, and economical manner by topical application of genetic vectors onto the skin. This strategy may allow the development of vaccines that could be administered by individuals without specialized medical training or equipment.

Figure 2: b, Detection of antibodies to the human CEA protein by western blot analysis.

Serum from a vaccinated mouse taken one month after applying AdCMV-hcea to the skin was diluted 1:500 and reacted with purified human CEA protein (provided by T. Strong) and adenoviral proteins separated on a 5% SDS-polyacrylamide gel. The products were transferred to membranes as in ref. 3. Lane 1, human CEA (0.5 μg); lane 2, BSA (0.5 μg); lane 3, adenovirus (10⁷ PFU). b, Detection of antibodies against the human GM-CSF protein. Purified human GM-CSF protein (CalBiochem), separated on a 15% SDS-polyacrylamide gel, was transferred to membranes and allowed to react with diluted serum. Lane 1, human GM-CSF (0.25 μg); lane 2, BSA (0.25 μg); lane 3, adenovirus (10⁷ PFU).