Cytoplasmic and endosomal RNA sensors recognize RNA virus infection and signals to protect host cells by inducing type I IFN. The cytoplasmic RNA sensors, retinoic acid inducible gene I/melanoma differentiation-associated gene 5, actually play pivotal roles in sensing virus replication. IFN-β promoter stimulator-1 (IPS-1) is their common adaptor for IFN-inducing signaling. Toll/IL-1R homology domain-containing adaptor molecule 1 (TICAM-1), also known as TRIF, is the adaptor for TLR3 that recognizes viral dsRNA in the early endosome in dendritic cells and macrophages. Poliovirus (PV) belongs to the Picornaviridae, and melanoma differentiation-associated gene 5 reportedly detects replication of picornaviruses, leading to the induction of type I IFN. In this study, we present evidence that the TLR3/TICAM-1 pathway governs IFN induction and host protection against PV infection. Using human PVR transgenic (PVRtg) mice, as well as IPS-1−/− and TICAM-1−/− mice, we found that TICAM-1 is essential for antiviral responses that suppress PV infection. TICAM-1−/− mice in the PVRtg background became markedly susceptible to PV, and their survival rates were decreased compared with wild-type or IPS-1−/− mice. Similarly, serum and organ IFN levels were markedly reduced in TICAM-1−/−/PVRtg mice, particularly in the spleen and spinal cord. The sources of type I IFN were CD8α+/CD11c+ splenic dendritic cells and macrophages, where the TICAM-1 pathway was more crucial for PV-derived IFN induction than was the IPS-1 pathway in ex vivo and in vitro analyses. These data indicate that the TLR3/TICAM-1 pathway functions are dominant in host protection and innate immune responses against PV infection.

Abstract. We previously reported that oral ingestion of Lentinula edodes mycelia (L.E.M.) extract can inhibit the growth of a subcutaneously established melanoma in a T cell-dependent manner via mitigation of regulatory T cell (Treg)-mediated immunosuppression. In this study, we tested the antitumor effect and mechanism of oral ingestion of L.E.M. extract following inoculation of murine colon carcinoma colon-26 (C26) cells into the subserosal space of the cecum (i.c.) of syngeneic mice. In this model, the primary site of the immune response was gut-associated lymphoid tissue (GALT), which is known to be an immunological toleranceinducing site for numerous dietary antigens. Oral ingestion of the L.E.M. extract suppressed the growth of i.c.-inoculated C26 cells in a T cell-dependent manner and restored the T cell response of the mesenteric lymph nodes and the spleen, not only to a tumor antigen-derived peptide, presented on H-2L d molecules, but also to C26 cells. I.c. inoculation of C26 cells increased the potential of CD4 + T cells of the mesenteric lymph nodes to produce transforming growth factor (TGF)-β, but ingestion of the L.E.M. extract decreased the ability of both CD4 + and CD8 + T cells in the mesenteric lymph nodes to produce this immunosuppressive cytokine. Although ingestion of L.E.M. showed only a marginal effect on Tregs in this model, this treatment significantly reduced the plasma levels of TGF-β and IL-6, both of which were increased in the i.c. C26-inoculated mice. In summary, our results indicate that oral ingestion of L.E.M. extract can restore antitumor T cell responses of mice even when the primary antitumor immune response is elicited in GALT, and provide important implications for anticancer immunotherapy of human colon cancer. IntroductionStudies on tumor-reactive cytotoxic T lymphocytes (CTLs) and tumor-related antigens have enabled the design of specific anticancer immunotherapies (1,2). Anticancer vaccines and adoptive immunotherapy have been applied clinically, although their efficacy has been unsatisfactory (3). Although several explanations of their unsatisfactory performance could be proposed, the major reason that these therapies fail is believed to be due to the emergence of immunosuppressive cells, including regulatory T cells (Tregs) and myeloid-derived suppressor cells (MDSCs) (4,5). In addition, the tumor-bearing state is accompanied by chronic inflammation, and it is thought that the inflammatory state of cancer patients inhibits the efficacy of anticancer immunotherapy (6,7).Lentinula edodes mycelia extract (L.E.M.) is a dried powder of a hot water extract of the mycelia of L. edodes before germination, which were cultured in a medium composed of bagasse and rice bran (8). This L.E.M. extract has been reported to exhibit antitumor activity and immunomodulatory effects both in vitro and in vivo (9,10). L.E.M. can mitigate inflammation in the liver of mice (11), suggesting that it also has an anti-inflammatory effect. In addition, we recently reported that oral ingestion of ...

Lentinula edodes mycelia (L.E.M.) is a dried powder extracted from shiitake mushrooms (Lentinula edodes). We previously demonstrated that it has immunomodulatory effects. In this paper, the direct cytotoxic effects of the polysaccharide-rich fraction of L.E.M. (L.E.M. ethanol precipitate; LEP) on HepG2 human hepatocellular carcinoma (HCC) cells were investigated. LEP directly killed the HepG2 cells efficaciously, but had only minor effects on normal rat hepatocytes and normal mouse dermal cells under the same conditions. Characteristic morphological changes associated with apoptosis such as shrinkage, rounding, and floating as well as chromatin condensation were confirmed; terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick-end labeling (TUNEL) staining was positive as determined by fluorescence microscopy analyses. The caspase-3 and -8 death receptor pathway was found largely responsible for the apoptotic death of HepG2 cells treated with LEP. In conclusion, LEP can directly induce apoptosis of HepG2 cells, and thus may have potential chemotherapeutic applications for the treatment of HCC.

New anticancer vaccines must overcome regulatory T cell (Treg)-mediated immunosuppression. We previously reported that oral ingestion of Lentinula edodes mycelia (L.E.M.) extract restores melanoma-reactive T cells in melanoma-bearing mice via a mitigation of Treg-mediated immunosuppression. In this study, we investigated the effect of oral ingestion of the extract on peptide vaccine-induced anti-tumor activity. The day after subcutaneous inoculation in the footpad with B16 melanoma, mice were freely fed the extract and were vaccinated with a tyrosinase-related protein 2(180-188) peptide. The peptide vaccine was repeated thrice weekly. Melanoma growth was significantly suppressed in mice treated with both the peptide vaccine and L.E.M. extract compared with mice treated with vaccine or extract alone, and the effect was CD8(+) T cell-dependent. The combination therapy increased H-2K(b)-restricted and B16 melanoma-reactive T cells in the draining lymph nodes and spleen. Flow cytometric and immunohistological analyses revealed that the combination therapy significantly decreased the percentage of Tregs in the draining lymph nodes and spleen of melanoma-bearing mice compared to treatment with vaccine or extract alone. Kinetic analyses of peptide-specific T cells and Tregs revealed that induction of peptide-specific T cells by the peptide vaccine alone was transient, but when combined with L.E.M. extract, it efficiently prolonged the duration of peptide-specific T cell induction without increasing the percentage of Tregs. These results indicate that combination therapy enhances peptide vaccine-induced anti-tumor activity due to attenuation of the increase in the percentage of Tregs in tumor-bearing hosts.

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