Alginic Acid-Coated Chitosan Nanoparticles Loaded with Legumain DNA Vaccine: Effect against Breast Cancer in Mice

Ze Liu,Shu Liu,Xiaoyue Tan,Da Wang,Min Xiong,Junbo Gong,Dan Lv,Xiaoniao Chen,Rong Xiang,Xiaoming He

doi:10.1371/journal.pone.0060190

Ze Liu, Shu Liu + Show 8 more

Open Access

https://doi.org/10.1371/journal.pone.0060190

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Abstract

Legumain-based DNA vaccines have potential to protect against breast cancer. However, the lack of a safe and efficient oral delivery system restricts its clinical application. Here, we constructed alginic acid-coated chitosan nanoparticles (A.C.NPs) as an oral delivery carrier for a legumain DNA vaccine. First, we tested its characteristic in acidic environments in vitro. DNA agarose electrophoresis data show that A.C.NPs protected DNA better from degradation in acidic solution (pH 1.5) than did chitosan nanoparticles (C.NPs). Furthermore, size distribution analysis showed that A.C.NPs tended to aggregate and form micrometer scale complexes in pH<2.7, while dispersing into nanoparticles with an increase in pH. Mice were intragastrically administrated A.C.NPs carrying EGFP plasmids and EGFP expression was detected in the intestinal Peyer’s patches. Full-length legumain plasmids were loaded into different delivery carriers, including C.NPs, attenuated Salmonella typhimurium and A.C.NPs. A.C.NPs loaded with empty plasmids served as a control. Oral vaccination was performed in the murine orthotopic 4T1 breast cancer model. Our data indicate that tumor volume was significantly smaller in groups using A.C.NPs or attenuated Salmonella typhimurium as carriers. Furthermore, splenocytes co-cultured them with 4T1 cells pre-stimulated with CoCl2, which influenced the translocation of legumain from cytoplasm to plasma membrane, showed a 4.7 and 2.3 folds increase in active cytotoxic T lymphocytes (CD3+/CD8+/CD25+) when treated with A.C.NPs carriers compared with PBS C.NPs. Our study suggests that C.NPs coated with alginic acid may be a safe and efficient tool for oral delivery of a DNA vaccine. Moreover, a legumain DNA vaccine delivered orally with A.C.NPs can effectively improve autoimmune response and protect against breast cancer in mice.

Highlights

DNA-based vaccines provide protection against cancers in a variety of animal models [1,2,3,4]
Development of non-toxic and efficient delivery systems has always been a challenge with the application of DNA vaccines [32,33]
Many efforts have been put into the design and modification of chitosan nanoparticles, a viable oral delivery system for DNA vaccines is still lacking [33]

Summary

Introduction

DNA-based vaccines provide protection against cancers in a variety of animal models [1,2,3,4]. Host autoimmunity is activated, resulting in significant suppression of tumor growth and metastasis [5,6,7,8,9]. An asparaginyl endopeptidase, is significantly overexpressed on tumor-associated macrophages [6,12]. DNA vaccines targeting legumain and delivered by attenuated Salmonella typhimurium exhibited efficiency in improving both the survival time of tumor-bearing mice and reducing tumor growth [1,13]. Given the promising results from previous animal experiments, it may be that a legumain DNA vaccine could be used to treat cancer in the humans. One significant obstacle is the lack of a suitable carrier [14]

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