Intranasal immunization with aluminum salt-adjuvanted dry powder vaccine

Abstract

Intranasal vaccination using dry powder vaccine formulation represents an attractive, non-invasive vaccination modality with better storage stability and added protection at the mucosal surfaces. Herein we report that it is feasible to induce specific mucosal and systemic antibody responses by intranasal immunization with a dry powder vaccine adjuvanted with an insoluble aluminum salt. The dry powder vaccine was prepared by thin-film freeze-drying of a model antigen, ovalbumin, adsorbed on aluminum (oxy)hydroxide as an adjuvant. Special emphasis was placed on the characterization of the dry powder vaccine formulation that can be realistically used in humans by a nasal dry powder delivery device. The vaccine powder was found to have "passable" to "good" flow properties, and the vaccine was uniformly distributed in the dry powder. An in vitro nasal deposition study using nasal casts of adult humans showed that around 90% of the powder was deposited in the nasal cavity. Intranasal immunization of rats with the dry powder vaccine elicited a specific serum antibody response as well as specific IgA responses in the nose and lung secretions of the rats. This study demonstrates the generation of systemic and mucosal immune responses by intranasal immunization using a dry powder vaccine adjuvanted with an aluminum salt.

Keywords: Aluminum salts; Dry powder; Intranasal; Mucosal immunity; Powder characterization; Vaccine.

Figure 1.

SEM/EDS of OVA-Alhydrogel® dry powder vaccine. Shown in (A) are representative SEM images of the dry powder vaccine at different magnifications. (B) A randomly selected area in a SEM graph (left panel), and representative elemental mapping (right panel, bars = 6 μm). (C) EDS spectra of the elements tested (Al, O, Na, Cl; n = 3 random areas).

Figure 2.

(A) OVA-Alhydrogel® powder cloud evolving from the nasal dry powder delivery device prepared in house. (B) A representative particle size distribution curve of the OVA-Alhydrogel® dry powder vaccine.

Figure 3.

(A) A diagram of the different sections of the nasal cast used. The vestibule (V) and nasal valve area make up the anterior region; The upper (U), middle (M), and lower (L) turbinate regions are collectively called posterior nasal cavity (P); and N indicates the nasopharynx. (B) Deposition of the OVA-Alhydrogel® dry powder vaccine in nasal casts operated at 15 L/min. F indicates the post-nasal fraction. Data are mean ± S.D. from 5 adult casts.

Fig. 4.

Serum anti-OVA IgG titers and mucosal IgA titers in rats immunized with OVA-Alhydrogel® dry powder vaccine intranasally. Rats (n = 4–5) were dosed on days 0, 14 and 28 with the dry powder vaccine intranasally (IN Powder), the liquid vaccine intranasally (IN Liquid), or subcutaneously with the liquid vaccine (SC Liquid). The dose of OVA was 20 μg per rat, and 400 μg for Alhydrogel®, in the IN Liquid and SC Liquid groups. For the IN Powder group, the dose of OVA in the first immunization was 21.6 ± 3.0 μg per rat. However, in the second and third immunizations, some rats were dosed twice, leading to an increase in the dose of OVA to more than 20 μg per rat. The anti-OVA IgG titers in serum samples (A), OVA-specific IgA titers in the nasal washes (B) and BAL samples (C) were measured 28 days after the third immunization. The titers in B and C are means from two different measurements. In (A), p = 0 .001, IN Liquid vs SC Liquid. In (B), n.s., not significant, IN Liquid vs. SC Liquid. In (C), p = 0 .01, IN Liquid vs. SC Liquid.

Fig. 4.

Serum anti-OVA IgG titers and mucosal IgA titers in rats immunized with OVA-Alhydrogel® dry powder vaccine intranasally. Rats (n = 4–5) were dosed on days 0, 14 and 28 with the dry powder vaccine intranasally (IN Powder), the liquid vaccine intranasally (IN Liquid), or subcutaneously with the liquid vaccine (SC Liquid). The dose of OVA was 20 μg per rat, and 400 μg for Alhydrogel®, in the IN Liquid and SC Liquid groups. For the IN Powder group, the dose of OVA in the first immunization was 21.6 ± 3.0 μg per rat. However, in the second and third immunizations, some rats were dosed twice, leading to an increase in the dose of OVA to more than 20 μg per rat. The anti-OVA IgG titers in serum samples (A), OVA-specific IgA titers in the nasal washes (B) and BAL samples (C) were measured 28 days after the third immunization. The titers in B and C are means from two different measurements. In (A), p = 0 .001, IN Liquid vs SC Liquid. In (B), n.s., not significant, IN Liquid vs. SC Liquid. In (C), p = 0 .01, IN Liquid vs. SC Liquid.

Fig. 4.

Serum anti-OVA IgG titers and mucosal IgA titers in rats immunized with OVA-Alhydrogel® dry powder vaccine intranasally. Rats (n = 4–5) were dosed on days 0, 14 and 28 with the dry powder vaccine intranasally (IN Powder), the liquid vaccine intranasally (IN Liquid), or subcutaneously with the liquid vaccine (SC Liquid). The dose of OVA was 20 μg per rat, and 400 μg for Alhydrogel®, in the IN Liquid and SC Liquid groups. For the IN Powder group, the dose of OVA in the first immunization was 21.6 ± 3.0 μg per rat. However, in the second and third immunizations, some rats were dosed twice, leading to an increase in the dose of OVA to more than 20 μg per rat. The anti-OVA IgG titers in serum samples (A), OVA-specific IgA titers in the nasal washes (B) and BAL samples (C) were measured 28 days after the third immunization. The titers in B and C are means from two different measurements. In (A), p = 0 .001, IN Liquid vs SC Liquid. In (B), n.s., not significant, IN Liquid vs. SC Liquid. In (C), p = 0 .01, IN Liquid vs. SC Liquid.

Figure 5.

Aluminum levels in rat brain tissues. Brain was collected 28 days after the third immunization, desiccated, and then incinerated before determining aluminum content in the samples using ICP-MS. Data are mean ± S.D. (n = 4). ANOVA did not reveal any difference among all four groups.