Formulation and Characterization of Nanoemulsion Intranasal Adjuvants: Effects of Surfactant Composition on Mucoadhesion and Immunogenicity

Abstract

Development of effective intranasal vaccines is of great interest due to their potential to induce both mucosal and systemic immunity. Here we produced oil-in-water nanoemulsion (NE) formulations containing various cationic and nonionic surfactants for use as adjuvants for the intranasal delivery of vaccine antigens. NE induced immunogenicity and antigen delivery are believed to be facilitated through initial contact interactions between the NE droplet and mucosal surfaces which promote prolonged residence of the vaccine at the site of application, and thus cellular uptake. However, the details of this mechanism have yet to be fully characterized experimentally. We have studied the physicochemical properties of the NE droplet surfactant components and demonstrate that properties such as charge and polar head group geometry influence the association of the adjuvant with the mucus protein, mucin. Association of NE droplets with mucin in vitro was characterized by various biophysical and imaging methods including dynamic light scattering (DLS), zeta potential (ZP), and surface plasmon resonance (SPR) measurements as well as transmission electron microscopy (TEM). Emulsion surfactant compositions were varied in a systematic manner to evaluate the effects of hydrophobicity and polar group charge/size on the NE-mucin interaction. Several cationic NE formulations were found to facilitate cellular uptake of the model antigen, ovalbumin (OVA), in a nasal epithelial cell line. Furthermore, fluorescent images of tissue sections from mice intranasally immunized with the same NEs containing green fluorescent protein (GFP) antigen demonstrated that these NEs also enhanced mucosal layer penetration and cellular uptake of antigen in vivo. NE-mucin interactions observed through biophysical measurements corresponded with the ability of the NE to enhance cellular uptake. Formulations that enhanced antigen uptake in vitro and in vivo also led to the induction of a more consistent antigen specific immune response in mice immunized with NEs containing OVA, linking NE-facilitated mucosal layer penetration and cellular uptake to enhancement of the immune response. These findings suggest that biophysical measurement of the mucoadhesive properties of emulsion based vaccines constitutes an effective in vitro strategy for selecting NE candidates for further evaluation in vivo as mucosal adjuvants.

Mucosal delivery switches the response to an adjuvanted tuberculosis vaccine from systemic TH1 to tissue-resident TH17 responses without impacting the protective efficacy

“…In this regard it is interesting to note that the oil-free formulation of ID93+GLA was as immunogenic and protective in the present study as the emulsion-based formulation. While no safety concerns have been reported with oil-in-water emulsion based intranasal formulations [31], the aqueous suspension formulation of GLA contains much less excipient content, thereby reducing manufacturing cost as well as the potential for any reactogenicity due to the oil and emulsifier excipients present in the emulsion. Moreover, previous reports of intranasally administered aqueous suspension of the TLR4 ligand MPL have shown promising safety and immunogenicity results in preclinical and clinical testing [32-34].…”

Micellisation and thermodynamic properties of sodium dodecyl sulphate in water-1,2-alkanediol co-solvents: chain length effect

“…[4][5][6][7] The studies in various solvent mixtures are relevant for the improvement of surfactant micellisation properties to enhance their performances since properties of the solutions can be optimised for various industrial formulations and commercial applications. [8][9][10][11] It is well established that the self-association of surfactants is governed by the intricate balance between the hydrophobic interaction and other types of non-covalent solute-solute and solute-solvent interactions. [12] The presence of polar organic solvent as an additive can significantly influence the micellisation thermodynamic properties of an ionic surfactant in water.…”

Current and New Approaches for Mucosal Vaccine Delivery

“…Despite the promising results of in vitro and animal studies, the application of nanoemulsions for nasal delivery in humans appears to be hindered mainly by the lack of detailed toxicology studies and the lack of extensive clinical trials [198]. A cationic nanoemulsion formulation could have facilitated cellular uptake of model antigen ovalbumin in the nasal epithelial cell line [199]. The intranasal vaccination of HIV gp120 immunogen formulated in oil-inwater nanoemulsions induced robust serum anti-gp120 IgG and Th1-polarized systemic cellular immune responses [200].…”