Research Article: Immunogenic Properties of a BCG Adjuvanted Chitosan Nanoparticle-Based Dengue Vaccine in Human Dendritic Cells

Date Published: September 22, 2015

Publisher: Public Library of Science

Author(s): Taweewun Hunsawong, Panya Sunintaboon, Saradee Warit, Butsaya Thaisomboonsuk, Richard G. Jarman, In-Kyu Yoon, Sukathida Ubol, Stefan Fernandez, Scott F. Michael.

Abstract: Dengue viruses (DENVs) are among the most rapidly and efficiently spreading arboviruses. WHO recently estimated that about half of the world’s population is now at risk for DENV infection. There is no specific treatment or vaccine available to treat or prevent DENV infections. Here, we report the development of a novel dengue nanovaccine (DNV) composed of UV-inactivated DENV-2 (UVI-DENV) and Mycobacterium bovis Bacillus Calmette-Guerin cell wall components (BCG-CWCs) loaded into chitosan nanoparticles (CS-NPs). CS-NPs were prepared by an emulsion polymerization method prior to loading of the BCG-CWCs and UVI-DENV components. Using a scanning electron microscope and a zetasizer, DNV was determined to be of spherical shape with a diameter of 372.0 ± 11.2 nm in average and cationic surface properties. The loading efficacies of BCG-CWCs and UVI-DENV into the CS-NPs and BCG-CS-NPs were up to 97.2 and 98.4%, respectively. THP-1 cellular uptake of UVI-DENV present in the DNV was higher than soluble UVI-DENV alone. DNV stimulation of immature dendritic cells (iDCs) resulted in a significantly higher expression of DCs maturation markers (CD80, CD86 and HLA-DR) and induction of various cytokine and chemokine productions than in UVI-DENV-treated iDCs, suggesting a potential use of BCG- CS-NPs as adjuvant and delivery system for dengue vaccines.

Partial Text: Dengue viruses (DENVs) are among the most rapidly and efficiently spreading arboviruses with more than 3 million reported dengue cases in the Americas [1], Southeast Asia and the Western Pacific in 2011 [2], compared with nearly1.2 million in 2008. While WHO estimates that 50–100 million DENV infections occur per year, a more recent estimate using a cartographic approach placed the number at 390 million infections annually, of which 96 million are symptomatic [3]. DENVs are not only a major public health problem but also the cause of significant economic losses for the families of those infected and public health systems.

We developed a novel DENV-2 nanovaccine composed of UVI-DENV antigen and BCG-CWC absorbed into CS-NPs and tested its immunological properties in an in vitro system. The capability of DNV or BCG-adjuvanted chitosan NPs based dengue vaccine to stimulate host immune response has already been demonstrated in an in vivo study in a mouse experiment. Mice were i.p. vaccinated with various concentrations of DNV, which strongly induced anti-dengue IgM/IgG antibodies including neutralizing antibody against DENV-2. Inflammatory cytokine and chemokine production was also demonstrated. Furthermore, DNV increased the frequencies of IFNγ producing CD4+ and CD8+ T cells in a dose-dependent manner [24]. NPs-based vaccines are widely used [25]. The size of the DNV (372 nm in diameter) is thought to stabilize the antigen and facilitate its diffusion through cellular compartments. Its cationic surface charge (28.8 mV) is believed to increase the vaccine adhesive properties to the cell surface [26]. Several studies point to the NPs size as an important immunomodulatory element. For example, HBsAg, when present in polylactide-NPs (PLA-NPs) of 2–8 μm in diameter, induced stronger anti-HBsAg antibody responses than smaller PLA-NPs (200–600 nm) [27]. Other studies reported that smaller NPs, poly(lactic-co-glycolic acid) (PLGA-NPs, 100–500 nm in diameter) induced higher antibody titers than larger ones (>1 μm) [28]. These findings are not limited to antibody generation. HIV TAT protein absorbed on cationic polymeric NPs (220–630 nm) induced stronger TAT specific cellular immune response while inducing anti-TAT antibodies at lower titers than larger NPs (>2 μm) [29].



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