HBsAg-specific immunoglobulin G (IgG) isotype responses after intranasal (IN) immunization using large volume. BALB/c mice (n = 5–10) were immunized by a single IN inhalation of 1 µg HBsAg with 1 or 10 µg of CT, CTB, LT, LTK63, and/or CpG ODN as adjuvants in a volume of 150 µl. Each bar represents the group geometric mean of the ELISA end-point dilution titer for HBsAg-specific antibodies (anti-HBs geometric mean titers; GMT) of IgG1 (white portion of bars) or IgG2a (black portion of bars) isotypes in plasma taken 4 weeks after immunization. Titers were defined as the highest plasma dilution resulting in an absorbance value two times that of nonimmune plasma, with a cut-off value of 0.05. HBsAg, purified hepatitis B surface antigen; CT, cholera toxin; CTB, subunit of cholera toxin; LTK63, nontoxic derivative of Escherichia coli heat labile enterotoxin; CpG ODN, oligodeoxynucleotides containing cytosine-guanine phosphate-linked dinucleotides.