Chitosan nanoparticle encapsulated hemagglutinin-split influenza virus mucosal vaccine.

Subunit/split influenza vaccines are less reactogenic compared with the whole virus vaccines. However, their immunogenicity is relatively low and thus required proper adjuvant and/or delivery vehicle for immunogenicity enhancement. Influenza vaccines administered intramuscularly induce minimum, if any, mucosal immunity at the respiratory mucosa which is the prime site of the infection. In this study, chitosan (CS) nanoparticles were prepared by ionic cross-linking of the CS with sodium tripolyphosphate (TPP) at the CS/TPP ratio of 1:0.6 using 2 h mixing time. The CS/TPP nanoparticles were used as delivery vehicle of an intranasal influenza vaccine made of hemagglutinin (HA)-split influenza virus product. Innocuousness, immunogenicity, and protective efficacy of the CS/TPP-HA vaccine were tested in influenza mouse model in comparison with the antigen alone vaccine. The CS/TPP-HA nanoparticles had required characteristics including nano-sizes, positive charges, and high antigen encapsulation efficiency. Mice that received two doses of the CS/TPP-HA vaccine intranasally showed no adverse symptoms indicating the vaccine innocuousness. The animals developed higher systemic and mucosal antibody responses than vaccine made of the HA-split influenza virus alone. The CS/TPP-HA vaccine could induce also a cell-mediated immune response shown as high numbers of IFN-γ-secreting cells in spleens while the HA vaccine alone could not. Besides, the CS nanoparticle encapsulated HA-split vaccine reduced markedly the influenza morbidity and also conferred 100% protective rate to the vaccinated mice against lethal influenza virus challenge. Overall results indicated that the CS nanoparticles invented in this study is an effective and safe delivery vehicle/adjuvant for the influenza vaccine.

Intranasal chitosan-DNA vaccines that protect across influenza virus subtypes.

An egg-free and broadly effective influenza vaccine that can be produced rapidly, adequately and cost-effectively is needed. In this study, chitosan-associated DNAs prepared at various nitrogen/phosphate charge (N/P) ratios were studied for their physicochemical properties, stability, cytotoxicity, and protein expression ability. The chitosan-DNA complexes (chitoplexes) of the N/P ratio 2 had the required characteristics including optimal size range, positive surface charge, high DNA association efficiency, tolerability to DNase digestion and mammalian cell viability compatibility. The N/P ratio 2-chitoplexes revealed the highest green fluorescent protein and luciferase expressions in the transfected mammalian cell cultures and in the mouse lungs. Mice immunized intranasally with the N/P ratio 2-chitoplex vaccines carrying DNAs coding for conserved proteins of influenza virus, i.e., ion channel protein (M2) and/or nucleoprotein (NP), had both mucosal and systemic humoral as well as cell mediated immune responses to the in vivo expressed antigens which conferred protection in mice against the lethal challenges not only with the homologous influenza virus subtype (H1N1), but also the heterologous subtype (H3N2). The chitoplexes should be considered as influenza vaccine candidates especially during the period of high vaccine demand. They are suitable for developing areas of the world where conventional vaccine production capacity is lacking.