The aqueous extracts of <i>Inonotus obliquus</i> (Chaga) augment host defense against <i>Listeria monocytogenes</i> infection

Listeria monocytogenes, which grows in host cells intracellularly, is important as an opportunistic pathogen. Extracts of Chaga mushroom, Inonotus obliquus, have been shown to possess various biological activities. This study explores the impact of Chaga extracts on host defense against infection with L. monocytogenes, which induces T-helper (Th)1-type immune response. Chaga extracts enhanced cytokine production including tumor necrosis factor-α, interleukin (IL-6), and IL-12 but suppressed IL-10 production in murine macrophages and dendritic cells. Oral administration of Chaga extracts inhibited the proliferation of L. monocytogenes in the livers of infected mice. Interferon-γ (IFN-γ) and IL-12 production was enhanced in the spleen cell cultures of the extract-treated mice. Chaga extract treatment augmented the clearance of L. monocytogenes from the livers and spleens during re-infection. IFN-γ production was also enhanced in the spleen cell cultures of primarily infected mice. Together, the results indicate that Chaga extracts possess protective potentials for infectious diseases such as listeriosis.