title: Activation of Toll-like receptor 2 by a novel preparation of cell wall skeleton from Mycobacterium bovis BCG Tokyo (SMP-105) sufficiently enhances immune responses against tumors.
abstract: The cell wall skeleton of Mycobacterium bovis BCG has been investigated as an immunopotentiating adjuvant for immuno-therapy of malignant tumors via Toll-like receptor (TLR) 2 and TLR4. However, due to its high molecular weight, highly complicated lipoglycan structure, and complicated purification and isolation procedure, its exact structure-activity relationship has not been well established. We have newly isolated the cell wall skeleton from M. bovis BCG Tokyo (SMP-105) and examined the binding of SMP-105 with TLR. It was revealed that highly purified SMP-105 activates the nuclear factor-kB promoter in a TLR2-dependent manner, not a TLR4-dependent manner, using a reporter gene assay system. Peritoneal exudated cells of TLR2 and MyD88 knockout mice severely reduced the induction of tumor necrosis factor-alpha and interleukin-6 in the presence of SMP-105, whereas cells from TLR4 knockout mice produced similar levels of cytokines to wild-type mice. Dendritic cells and macrophages accumulated in the draining lymph nodes of treated mice. When mice were administered both SMP-105 and mitomycin C-inactivated Lewis lung carcinoma cells simultaneously, interferon-gamma-producing cells reacting to the tumor were increased distinctly in draining lymph nodes. When C57BL/6 mice, into which splenocytes from OT-I transgenic mice had been transferred, were administered with both SMP-105 and E.G7-OVA, OVA-specific cytotoxic T lymphocytes (CTL) increased markedly. Mice treated with SMP-105 and inactivated Lewis lung carcinoma cells suppressed the growth of implanted tumors. These results suggest that the activation of TLR2 by SMP-105 sufficiently enhanced immune responses, such as the number of interferon-gamma-producing cells and CTL, and prevented the growth of tumors without the contribution of TLR4.
authors.affiliation: Pharmacology Research Laboratories, Drug Research Division, Dainippon Sumitomo Pharma, 3-1-98, Kasugade Naka, Konohana-ku, Osaka 554-0022, Japan. masashi-murata@ds-pharma.co.jp
authors.forename: Masashi
authors.initials: M
authors.lastname: Murata
mesh_terms: D000276:Adjuvants, Immunologic / Q000494:pharmacology*; D000818:Animals; D045744:Cell Line, Tumor; D017358:Cell Wall Skeleton / Q000737:chemistry*; D003713:Dendritic Cells / Q000276:immunology; D005260:Female; D007371:Interferon-gamma / Q000096:biosynthesis; D008213:Lymphocyte Activation; D017737:Macrophages, Peritoneal / Q000276:immunology; D051379:Mice; D008810:Mice, Inbred C57BL; D009163:Mycobacterium bovis / Q000737:chemistry*; D053594:Myeloid Differentiation Factor 88 / Q000502:physiology; D009369:Neoplasms / Q000276:immunology*; D018417:Th1 Cells / Q000276:immunology; D051195:Toll-Like Receptor 2 / Q000502:physiology*; D051197:Toll-Like Receptor 4 / Q000502:physiology
chemical_list: D000276:Adjuvants, Immunologic; D017358:Cell Wall Skeleton; C507780:Myd88 protein, mouse; D053594:Myeloid Differentiation Factor 88; C493486:Tlr2 protein, mouse; C493487:Tlr4 protein, mouse; D051195:Toll-Like Receptor 2; D051197:Toll-Like Receptor 4; D007371:Interferon-gamma