Intranasal delivery of Norwalk virus-like particles formulated in an in situ gelling, dry powder vaccine.

The development of a vaccine to prevent norovirus infections has been focused on immunization at a mucosal surface, but has been limited by the low immunogenicity of self-assembling Norwalk virus-like particles (NV VLPs) delivered enterically or at nasal surfaces. Nasal immunization, which offers the advantage of ease of immunization, faces obstacles imposed by the normal process of mucociliary clearance, which limits residence time of applied antigens. Herein, we describe the use of a dry powder formulation (GelVac) of an inert in situ gelling polysaccharide (GelSite) extracted from Aloe vera for nasal delivery of NV VLP antigen. Powder formulations, with or without NV VLP antigen, were similar in structure in dry form or when rehydrated in simulated nasal fluids. Immunogenicity of the dry powder VLP formulation was compared to equivalent antigen/adjuvant liquid formulations in animals. For the GelVac powder, we observed superior NV-specific serum and mucosal (aerodigestive and reproductive tracts) antibody responses relative to liquid formulations. Incorporation of the TLR7 agonist gardiquimod in dry powder formulations did not enhance antibody responses, although its inclusion in liquid formulations did enhance VLP immunogenicity irrespective of the presence or absence of GelSite. We interpret these data as showing that GelSite-based dry powder formulations (1) stabilize the immunogenic structural properties of VLPs and (2) induce systemic and mucosal antibody titers which are equal or greater than those achieved by VLPs plus adjuvant in a liquid formulation. We conclude that in situ gelation of the GelVac dry powder formulation at nasal mucosal surfaces delays mucociliary clearance and thereby prolongs VLP antigen exposure to immune effector sites.

Development and characterization of a three-dimensional organotypic human vaginal epithelial cell model.

We have developed an in vitro human vaginal epithelial cell (EC) model using the innovative rotating wall vessel (RWV) bioreactor technology that recapitulates in vivo structural and functional properties, including a stratified squamous epithelium with microvilli, tight junctions, microfolds, and mucus. This three-dimensional (3-D) vaginal model provides a platform for high-throughput toxicity testing of candidate microbicides targeted to combat sexually transmitted infections, effectively complementing and extending existing testing systems such as surgical explants or animal models. Vaginal ECs were grown on porous, collagen-coated microcarrier beads in a rotating, low fluid-shear environment; use of RWV bioreactor technology generated 3-D vaginal EC aggregates. Immunofluorescence and scanning and transmission electron microscopy confirmed differentiation and polarization of the 3-D EC aggregates among multiple cell layers and identified ultrastructural features important for nutrient absorption, cell-cell interactions, and pathogen defense. After treatment with a variety of toll-like receptor (TLR) agonists, cytokine production was quantified by cytometric bead array, confirming that TLRs 2, 3, 5, and 6 were expressed and functional. The 3-D vaginal aggregates were more resistant to nonoxynol-9 (N-9), a contraceptive and previous microbicide candidate, when compared to two-dimensional monolayers of the same cell line. A dose-dependent production of tumor necrosis factor-related apoptosis-inducing ligand and interleukin-1 receptor antagonist, biomarkers of cervicovaginal inflammation, correlated to microbicide toxicity in the 3-D model following N-9 treatment. These results indicate that this 3-D vaginal model could be used as a complementary tool for screening microbicide compounds for safety and efficacy, thus improving success in clinical trials.