Powder and particle-mediated approaches for delivery of DNA and protein vaccines into the epidermis

The epidermis of the skin is both a sensitive immune organ and a practical target site for vaccine administration. However, administration of vaccines into the epidermis is difficult to achieve using conventional vaccine delivery methods employing a needle and syringe. A needle-free vaccine delivery system has been developed that efficiently delivers powdered or particulate DNA and protein vaccines into the epidermal tissue. The delivery system can be used to directly transfect antigen presenting cells (APCs) by formulating DNA or protein vaccines onto gold particles (particle-mediated immunization). Antigen can be directly presented to the immune system by the transfected APCs. Antigen can also be expressed and secreted by transfected keratinocytes and picked up by resident APCs through the exogenous antigen presentation pathway. Alternatively, protein antigens can be formulated into a powder and delivered into the extracellular environment where they are picked up by APCs (epidermal powder immunization). Using any of these formulations, epidermal immunization offers the advantage of efficiently delivering vaccines into the APC-rich epidermis. Recent studies demonstrate that epidermal vaccine delivery induces humoral, cellular, and protective immune responses against infectious diseases in both laboratory animals and man. (C) 2003 Elsevier Science Ltd. All rights reserved.