Efficacy and safety of the developed CpG-ODN in boosting antibody production in rabbits.

(A) A three-week-interval schedule, as shown, was adopted for each cycle of immunization and serum collection. (B) 10µg of OVA was formulated with 50µg of CpG-ODN in PBS or CFA/IFA. (C) 3µg of OVA was formulated with 50µg of CpG-ODN, 1% of aluminum hydroxide gel (alum), in PBS or CFA/IFA, to determine the efficacy and safety of CpG-C4609 as an adjuvant to boost antibody production. Anti-OVA antibody titers were measured by ELISA. Data shown represent mean ± SD (n = 3 independent experiments). *P<0.05 vs. the induction by CpG-C4609 or the induction by alum plus CpG-C4609. (D) Upper panels: subcutaneous tissues at the injection sites were examined on the second day after injection of different combinations of antigens and adjuvants, as indicated. Lower panels: HE staining of sections taken from these tissues. Photos show a set of representative results of three independent experiments.(E) Upper panels: representative photos of granuloma appeared at CFA/IFA injection sites (right), and skin at the alum plus CpG-C4609 injection sites (left). Lower panels: HE staining of sections taken from the granuloma (right), and tissue from the alum plus CpG-C4609 injection sites (left). The right panels show a representative granuloma developed in 30% of CFA/IFA injected rabbits (n = 20). The left panels show injection sites of an alum plus CpG-C4609 injected rabbit which is representative for rabbits (n = 20) injected without adjuvant or with adjuvant other than CFA/IFA.