Lentinan has a stimulatory effect on innate and adaptive immunity against murine Listeria monocytogenes infection

Lentinan, a (1-3)-beta glucan from Lentinus edodes, is licensed as an immunostimulatory drug. We tested the effect of lentinan in the well-established model system of the murine Listeria monocytogenes infection. Pre-treatment of bone marrow macrophages and dendritic cells with lentinan resulted in increased production of TNF-alpha and IL-12 after L. monocytogenes infection in vitro. After lentinan treatment bone marrow macrophages showed increased NO-production and enhanced cytotoxic activity against L. monocytogenes. Pre-treatment of mice with lentinan resulted in increased concentrations of TNF-alpha, IL-12 and IFN-gamma and also an increased number of L. monocytogenes specific CD8 T cells in the spleen. The bacterial burden in spleen and liver of mice was significantly reduced during primary and secondary Listeria infection after lentinan pre-treatment of mice. In summary these results show that lentinan enhances the protective CD8 T-cell response against L. monocytogenes probably by a mechanism that involves the IL-12-mediated augmentation of the specific antilisterial CD8 T-cell response.