Glycyrrhizin Improves the Resistance of MAIDS Mice to Opportunistic Infection of Candida albicans through the Modulation of MAIDS-Associated Type 2 T Cell Responses

Compared with normal mice, MAIDS mice (mice infected with LP-BM5 murine leukemia virus) exhibited an increase up to 100 times greater in susceptibility to infection with Candida albicans. The impaired resistance of MAIDS mice to the infection was recovered to levels observed in normal mice by the administration of glycyrrhizin (GR), an active component of licorice roots. MAIDS mice inoculated with CD4+ T cells from GR-treated mice were also resistant to C. albicans infection. Normal mice inoculated with CD4+ T helper type 2 cells (Th2 cells) from MAIDS mice were susceptible to C. albicans infection at the same levels shown in MAIDS mice. The susceptibility of normal mice inoculated with type 2 T cells was reversible by (i) administration of GR and (ii) inoculation of CD4+ T cells from GR-treated mice and injection of a mixture of mAbs targeted against type 2 cytokines (IL-4 and IL-10). Type 2 cytokines were not detected in sera of MAIDS mice inoculated with CD4+ T cells from GR-treated mice, while they were present in sera of MAIDS mice treated with saline. These results suggest that, by inducing CD4+ T cells which suppress type 2 cytokine production by MAIDS-associated Th2 cells, GR improves the resistance of MAIDS mice to C. albicans infection.