Preparation and Characterization of DNA Liposomes Vaccine

Abstract

Genetic immunization is a process that uses plasmid DNA encoding antigens from bacteria, viruses, protozoa, and cancers to establish protective humoral and cell-mediated immunity system. The introducing antigen-encoding naked plasmid DNA in vivo by intramuscular injection can trigger humoral and cell-mediated protective immunity against infection. However, the major limitation of naked DNA vaccines is the degradation of naked DNA by deoxyribonuclease so that the DNA is unable to act on antigen presenting cells (APCs) effectively. This is because the muscle cells can absorb and degrade DNA when the naked DNA is administered by intramuscular injection. To avoid DNA degradation and enable DNA vaccine to reach APCs, the liposomes can be used as DNA vaccine carriers, referring to as DNA liposome vaccines. For this purpose, the plasmid DNA is encapsulated into liposomes by the dehydration-rehydration procedure. The entrapped DNA by liposomes can protect the DNA content from local nucleases at injection site and deliver the DNA liposome vaccine to APCs in the lymph nodes. Usually, the neutral, anionic, and cationic liposomes can quantitatively encapsulate a DNA vaccine and are capable of transfecting APC cells in vitro with varying efficiency, but the vesicle surface charge, size, and lipid composition of the liposomes influence the transfection efficiency of the DNA vaccine into APC cells, thereby affecting the expressions of cytokines or immune-stimulating effects (Gregoriadis et al., J Drug Target 3(6):469–475, 1996). This chapter mainly deals with a simple and high-yield approach for producing DNA liposome vaccines using a dehydration-rehydration procedure, followed by describing their characterization.