Development of pH responsive cationic amphipathic LAH4-L1 peptide as a novel DNA vaccine delivery system

Abstract

DNA vaccines use plasmid DNA to encode antigenic proteins to induce both local and systemic immune responses to protect human from infectious diseases. However, the immunogenicity of most DNA vaccines was not satisfactory, mainly due to the poor DNA stability and inefficient DNA delivery, resulting in insufficient antigen presentation and immunity activation. The aim of this project is to develop an efficient non-viral DNA vaccine delivery system, using synthetic amphipathic peptide LAH4-L1 as DNA delivery vector. In our previous study, LAH4-L1 has been shown as an efficient non-viral gene delivery system due to its ability of protecting nucleic acid from nuclease degradation, enhancing cellular uptake and plasmid expression through promoting endosomal escape in target cells [Ref 1]. However, its potential in DNA vaccine formulation remains to be investigated. In this study, the plasmid DNA transfection efficiency of LAH4-L1 on A549 (human alveolar epithelial cancer cells), Calu-3 (human airway epithelial cancer cells), RAW264.7 (mouse macrophages) and JAWSII (mouse immature dendritic cells) were found comparable to the commercial transfection reagent Lipofectamine™ 2000. Furthermore, LAH4-L1 peptide can enhance the hepatitis B antigen plasmid induced immune responses in vitro: Firstly, the enzyme-linked immunosorbent assay (ELISA) showed that significant increase of IL-6 and TNF-α secretion was observed after delivering hepatitis B surface antigen encoding plasmid by LAH4-L1 to RAW264.7 macrophages and JAWSII dendritic cells. Secondly, the macrophage phenotype analysis indicated LAH4-L1 could efficiently facilitate the differentiation and maturation of professional antigen presenting cells (APCs) by increasing the expression of CD40, CD80 and CD86 co-stimulatory molecules as maturation markers. These properties make LAH4-L1 a promising DNA vaccine delivery system candidate. Reference 1. Lam K.W., Liang W.L., Lan Y. et al. (2012) Journal of Controlled Release 158:293-303.