Enhancement and regulation effect of myrcene on antibody response in immunization with ovalbumin and Ag85B in mice.

BACKGROUND MF59, which is an adjuvant belonging to C₃₀ member of the terpene family, is a T helper type-2 (Th2)-biased immune enhancer. Our previous studies showed that pyriproxyfen, a member of the terpene family with fewer carbon atoms (C₂₀) than MF59, enhanced active T helper type-1 (Th1)-biased immune responses. OBJECTIVE This study was performed to investigate the enhancement of antigen-specific immune responses by myrcene, a member of the terpene family with fewer carbon atoms (C₁₀) than pyriproxyfen. METHOD Ovalbumin (OVA) was used as an antigen to determine the effects of myrcene on the immune response. The IgG subtypes and cytokines induced by immunization of OVA with or without myrcene were monitored. Thereafter, we determined the effects of myrcene in the immune response against Ag85B, which is a dominant protective antigen for tuberculosis. RESULTS The results showed that 0.8 mg/dose of myrcene enhanced antigen-specific total IgG immune response to OVA. Direct mixing of the antigen with myrcene was required for the enhancement of antibody production. Myrcene increased OVA-specific IgG2a titer, suggesting induction of Th1-immune response. The level of Th1 cytokines, IFN-γ was increased at 8 weeks after immunization, although IL-13 was also increased at the same time point. However, finally myrcene was found to increase Ag85B-specific total IgG titers at 5 weeks and specific IgG2a titer was increased at both 5 and 8 weeks. The results suggested that myrcene could enhance Th1 immune response. CONCLUSIONS Myrcene enhanced specific immune responses against OVA and Ag85B. This study suggested the tendency of the enhancement of Th1 immune response by myrcene.