Background: We have already reported that antigen-specific IgG1 antibody production in WBB6F1-W/Wv (W/Wv) mice after oral administration of ovalbumin (OVA) was extremely high. Active systemic anaphylaxis (ASA) was induced in these mice after intraperitoneal (i.p.) administration of OVA, and Th2-dominant helper T-cell activation occurred. In this study, we examined the effect of CpG oligodeoxynucleotide (ODN) conjugation of OVA on oral immunization of W/Wv mice.
Methods: W/Wv mice were sensitized by administration of 0.1 mg OVA or CpG ODN-OVA by gavage every day for 4 weeks, and the serum titers of OVA-specific IgG1, IgE, and IgG2a antibody were determined. ASA was induced by i.p. injection of OVA, and the changes in body temperature were monitored. In vitro production of Th1- and Th2- type cytokines by splenocytes re-stimulated with antigen was also measured.
Results: The antigen-specific IgG1 antibody titer in the CpG ODN-OVA-sensitized W/Wv mice was lower than in the OVA-sensitized group, but the IgG2a titer was higher. ASA was not induced by i.p. OVA challenge. There were significant increases in the production of Th1-type cytokine (IFN-gamma) by splenocytes in the CpG ODN-OVA-sensitized mice, but the Th2-type cytokine (IL-4) level in the splenocyte culture medium was lower.
Conclusions: These results indicated that oral administration of CpG ODN-OVA conjugate significantly induced antigen-specific Th1 responses and reduced Th2 responses (allergic reactions) on re-stimulation. These findings suggest that CpG ODN-antigen conjugate may be useful as an oral vaccine.