Nasal aluminum (oxy)hydroxide enables adsorbed antigens to induce specific systemic and mucosal immune responses.

Some insoluble aluminum salts are commonly used in injectable vaccines as adjuvants to accelerate, prolong, or enhance the antigen-specific immune responses. Data from previous studies testing the nasal mucosal vaccine adjuvant activity of aluminum salts are conflicting. The present study is designed to further assess the feasibility of using aluminum salts in injectable vaccines as nasal mucosal vaccine adjuvants. Using Alhydrogel®, the international scientific standard of aluminum (oxy)hydroxide gels, and ovalbumin or 3 × M2e-HA2, a synthetic influenza virus fusion protein, as antigens, we showed in a mouse model that when dosed intranasally Alhydrogel® enables antigens adsorbed on it to induce stronger antigen-specific immune responses in both serum samples (e.g., specific IgG) and nasal and lung mucosal secretions (i.e., specific IgA) in all immunized mice, as compared with nasal immunization with the antigens alone. Rerouting insoluble aluminum salts in injectable vaccines may represent a viable approach for (nasal) mucosal vaccine adjuvant discovery.