Original Article
Nanostructured SBA-15 silica: An effective protective vehicle to oral hepatitis B vaccine immunization

https://doi.org/10.1016/j.nano.2016.06.003Get rights and content

Abstract

Due to its physicochemical properties, nanostructured mesoporous SBA-15 silica shows great potential as a vaccine adjuvant. This study evaluated the capacity of SBA-15 to encapsulate/adsorb the recombinant purified HBsAg from the Hepatitis B virus and the immunoresponsiveness of mice orally immunized with HBsAg inside SBA-15. A simulation of small angle X-ray scattering experimental results, together with the nitrogen adsorption isotherms data, allowed to determine the appropriate mass ratio of HBsAg:SBA-15, indicating antigen encapsulation into SBA-15 macroporosity. This was also evaluated by bicinchoninic acid assay and gel electrophoresis. The recruitment of inflammatory cells, an increase in production of specific antibodies, and the non-influence of silica on TH1 or TH2 polarization were observed after oral immunization. Besides, SBA-15 enhanced the phagocytosis of ovalbumin by dendritic cells, an important key to prove how this adjuvant works. Thus, it seems clear that the nanostructured SBA-15 is an effective and safe adjuvant for oral immunizations.

Graphical abstract

After proper oral immunization schedules using SBA-15 as adjuvant, the recruitment of inflammatory cells to Peyer’s patches and mesenteric lymph nodes and the enhanced production of specific antibodies, as well as the non-influence of silica in the polarization to TH1 or TH2 immune responses, were shown.

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Section snippets

Animals

Female 8 to 12 week-old BALB/c mice, supplied by Butantan Institute animal facilities, were used to evaluate the adjuvant effect of SBA-15 silica toward oral immunizations. The experiments were conducted according to protocols approved by the Animal Use and Care Ethics Committee from the Butantan Institute (Protocol 672/09) and under ethical conditions according to the international rules of animal care by the International Animal Welfare Recommendations.38

SBA-15 silica synthesis and physical characterization

Mesoporous SBA-15 silica samples were

Incorporation analysis of HBsAg into nanostructured SBA-15 silica

Considering the dimension of HBsAg around 22 nm with more than 3000 kDa of molecular weight,41, 42 it is reasonable to suppose that the proteins are encapsulated inside the silica macroporosity (macropores larger than 50 nm, IUPAC), obstructing the entrance of the 10 nm mesopores.

Figure 1 presents the SAXS results, in particular, including the extra scattering factors (SC-Extra) related to the HBsAg presence in the silica matrix, according to the SAXS model of Reference,1 as well as the simulation

Discussion

Nature itself is definitively the major agent of vaccination, and the most important and efficacious memory promoter. Silica is the second most common element on earth, present in all environments, and as ordered nanostructures, it constitutes a variety of diatomaceous algae species, abundant in aquatic environments. The physical chemical characterization of the SBA-15 particles loaded with HBsAg was important to show the presence of the proteins in the silica macroporosity, as well to point

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    This work was supported by funds in Brazil from the INCTTOX-CNPq/FAPESP Program, CeTICS-FAPESP (2013/07467-1), and Cristália Pharmaceutics. M.C.A. Fantini, C.L.P. Oliveira, M.T.D. Orlando, D.V. Tambourgi, and O.A. Sant’Anna are researchers of CNPq. Our thanks to Dr. E. Tenório for providing the protein concentrate of HBsAg. This research is under the scope of the International Patents WO07/030901, IN 248654, ZA 2008/02277, KR 1089400, MX 297263, HK 1124791, JP 5091863, CN 101287491B, CA 2621373, US 8642258 B2, and EP 1942934 B1.

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