[#2008-12] Maitake Obi, Nobuko et al. Inhibitory Effect of TNF-α Produced by Macrophages Stimulated with Grifola frondosa Extract (ME) on the Growth of Influenza A/Aichi/2/68 Virus in MDCK Cells al.

Inhibitory Effect of TNF-α Produced by Macrophages Stimulated with Grifola frondosa Extract (ME) on the Growth of Influenza A/Aichi/2/68 Virus in MDCK Cells

Nobuko Obi,^∗,‡ Katsumi Hayashi,§ Tatsurou Miyahara,† Yutaka Shimada,^∗,‡Katsutoshi Terasawa,‡^,§ Masataka Watanabe,/ Masahide Takeyama, Ryosuke Obi^∗ and Hiroshi Ochiai†^,‡

^∗Departments of Oriental Medicine and
†Human Science, Faculty ofMedicine
‡21st Century COE Program, University of Toyama
§Department of Frontier Japanese Oriental (Kampo) Medicine
Graduate School of Medicine, Chiba University

Abstract: We investigated the inhibitory effect of the conditioned medium (CM) from P338D1 (D1) cells, amurine macrophage cell line, stimulated for 10hours with a fixed dose (100µg/ml) of the extracts from the fruit bodies of Grifola frondosa (ME) or its ultra filtration-based fractions (MFs), on the growth of influenza A/Aichi/2/68 virus in Madin-Darby canine kidney cells. Direct addition of ME and 3 kinds of MFs (MF1, MF2 and MF3) to the infected cells had no obvious inhibitory effect. However, virus yields were reduced in the presence of CMs. Notably, the inhibitory effect of the CM prepared by using MF2 (molecular weight of 30Kd to 100Kd) was the strongest (28% reduction compared to the control). RT-PCR and ELISA assays showed that the CMs could induce the expression of TNF-α mRNA in D1 cells leading to production of TNF-α, known as an antiviral cytokine. These findings suggest that ME and MFs (especially MF-2) might induce the production of certain factors, including TNF-α, which are responsible for the inhibition of viral growth in vitro.