Different natural and synthetic biodegradable polymers have been used in vaccine formulations as adjuvant and delivery system but have faced various limitations. Chitosan is a new delivery system with the potential to improve development of nano vaccines and drugs. However, chitosan is only soluble in acidic solutions of low concentration inorganic acids such as dilute acetic acid and dilute hydrochloric acid and in pure organic solvents, which greatly limits its application. Chemical modification of chitosan is an important way to improve its weak solubility. Quaternized chitosan not only retains the excellent properties of chitosan, but also improves its water solubility for a wider application. Recently, quaternized chitosan nanoparticles have been widely used in biomedical field. This review focuses on some quaternized chitosan nanoparticles, and points out the advantages and research direction of quaternized chitosan nanoparticles. As shown by the applications of quaternized chitosan nanoparticles as adjuvant and delivery carrier in vaccines, quaternized chitosan nanoparticles have promising potential in application for the development of nano vaccines in the future.

BACKGROUND: Rift Valley fever virus (RVFV) is an emerging arbovirus in Africa and the Arabian Peninsula, in which infection with RVFV poses a serious threat to humans and livestock globally. Approved treatments for RVFV infection, especially for use in humans, have not yet been developed. There is an urgent need for effective drugs to prevent RVFV disease.
METHODS: In previous study, we developed RVFV virus like particles (VLPs) expressing the surface glycoproteins Gn and Gc. The morphology was shown to be similar to live RVFV under electron microscopy. In this study, we immunized horses with RVFV VLPs, prepared the immunoglobulin F(ab\')2 fragments, and characterized its in vitro neutralization and in vivo efficacy in mice.
RESULTS: F(ab\')2 was found to potently neutralize RVFV in VeroE6 cells, and passive transfer of immunoglobulin F(ab\')2 fragments resulting in reduced mortality in RVFV infected mice.
CONCLUSIONS: Our results show that passive immunotherapy with equine immunoglobulin F(ab\')2 fragments is a promising strategy to treat RVFV infections.