ABSTRACT
Development of nasal immunization for human use is hindered by the lack of acceptable adjuvants. Although CT is an effective adjuvant, its toxicity will likely prevent its use in nasal vaccines. This study compared non-toxin adjuvants to CT for their ability to induce protective antibody responses with nasal immunization. C3H/HeN and C57BL/6 mice were immunized with rPA formulated with the following adjuvants: CT, IL-1α, LPS, CpG, Pam3CSK4, 3M-019, resiquimod/R848 or c48/80. Serum and nasal wash cytokine concentrations were monitored 6h post-vaccination as biomarkers for acute activation of the innate immune system. Not all of the adjuvants induced significant changes in innate serum or nasal wash cytokines, but when changes were observed, the cytokine signatures were unique for each adjuvant. All adjuvants except Pam3CSK4 induced significantly increased anti-rPA serum IgG titers in both strains of mice, while only IL-1α, c48/80 and CpG enhanced mucosal anti-rPA IgA. Pam3CSK4 was the only adjuvant unable to enhance the induction of serum LeTx-neutralizing antibodies in C3H/HeN mice while c48/80 was the only adjuvant to induce increased serum LeTx-neutralizing antibodies in C57BL/6 mice. Only CT enhanced total serum IgE in C3H/HeN mice while IL-1α enhanced total serum IgE in C57BL/6 mice. The adjuvant influenced antigen-specific serum IgG subclass and T cell cytokine profiles, but these responses did not correlate with the induction of LeTx-neutralizing activity. Our results demonstrate the induction of diverse innate and adaptive immune responses by non-toxin nasal vaccine adjuvants that lead to protective humoral immunity comparable to CT and that these responses may be influenced by the host strain.
Subject(s)
Adjuvants, Immunologic/administration & dosage , Anthrax Vaccines/administration & dosage , Anthrax Vaccines/immunology , Antigens, Bacterial/immunology , Bacterial Toxins/immunology , Administration, Intranasal , Animals , Antibodies, Bacterial/blood , Antibodies, Neutralizing/blood , Antitoxins/blood , Cytokines/analysis , Female , Immunity, Mucosal , Immunoglobulin G/blood , Mice , Mice, Inbred C3H , Mice, Inbred C57BL , Serum/immunology , Vaccines, Synthetic/administration & dosage , Vaccines, Synthetic/immunologyABSTRACT
BACKGROUND: We previously reported that the immunogenicity of Hcßtre, a botulinum neurotoxin A (BoNT/A) immunogen, was enhanced by fusion to an epithelial cell binding domain, Ad2F, when nasally delivered to mice with cholera toxin (CT). This study was performed to determine if Ad2F would enhance the nasal immunogenicity of Hcßtre in rabbits, an animal model with a nasal cavity anatomy similar to humans. Since CT is not safe for human use, we also tested the adjuvant activity of compound 48/80 (C48/80), a mast cell activating compound previously determined to safely exhibit nasal adjuvant activity in mice. METHODS: New Zealand White or Dutch Belted rabbits were nasally immunized with Hcßtre or Hcßtre-Ad2F alone or combined with CT or C48/80, and serum samples were tested for the presence of Hcßtre-specific binding (ELISA) or BoNT/A neutralizing antibodies. RESULTS: Hcßtre-Ad2F nasally administered with CT induced serum anti-Hcßtre IgG ELISA and BoNT/A neutralizing antibody titers greater than those induced by Hcßtre + CT. C48/80 provided significant nasal adjuvant activity and induced BoNT/A-neutralizing antibodies similar to those induced by CT. CONCLUSIONS: Ad2F enhanced the nasal immunogenicity of Hcßtre, and the mast cell activator C48/80 was an effective adjuvant for nasal immunization in rabbits, an animal model with a nasal cavity anatomy similar to that in humans.
