Abstract: Leptospirosis, caused by pathogenic Leptospira, is the most widespread zoonosis in the world. Effective vaccine for leptospirosis is not currently available. We aimed to utilize chitosan, a non-toxic biodegradable and biocompatible polymer, as a DNA vaccine delivery system for leptospirosis. It has the potential to condense anionic DNA to a compact structure through electrostatic interaction. LipL32 encoding the major outer membrane protein that is conserved in pathogenic Leptospira was used as a vaccine candidate in our study. The 819-bp PCR product of lipL32 was amplified from Leptospira interrogans serovar Pomona and was cloned into pVITRO plasmid. The transfection efficiency was evaluated in human embryonic kidney cell-line 293T (HEK293T) cells by Western blot analysis. The chitosan was then used to encapsulate pVITRO-lipL32 in vitro. The copolymer was complexed with plasmid DNA in various copolymer/DNA (N/P) charge ratios, and the complexes were characterized. Chitosan/ pVITRO-lipL32 (N/P) showed good DNA binding ability, and low cytotoxicity to Raw 264.7 macrophage cell line in comparison with untransfected control.
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