- A polymeric bacterial protein activates dendritic cells via Toll-like Receptor 4.

BERGUER P, MUNDIÑANO J, PIAZZON I, GOLDBAUM F

Kiel, Germany

Congreso; 36th Annual Meeting of the DGfI German Society of Immunology and 36th Annual Meeting of the SSI Scandinavian Society for Immunology; 2005

<!-- /* Style Definitions */ p.MsoNormal, li.MsoNormal, div.MsoNormal {mso-style-parent:""; margin:0cm; margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:10.0pt; font-family:"Times New Roman"; mso-fareast-font-family:"Times New Roman"; mso-fareast-language:EN-US;} @page Section1 {size:612.0pt 792.0pt; margin:70.85pt 3.0cm 70.85pt 3.0cm; mso-header-margin:36.0pt; mso-footer-margin:36.0pt; mso-paper-source:0;} div.Section1 {page:Section1;} --> The enzyme lumazine synthase from Brucella spp. (BLS) is a highly immunogenic protein that folds as a stable dimer of pentamers. It is possible to insert foreign proteins at its ten N- terminus, and these chimeras elicit systemic and oral immunity without adjuvants. The ability of BLS to activate dendritic cells (DCs) was tested. As BLS is produced by genetically engineered Escherichia coli cells, it was always detoxified with polymyxin B-agarose to remove LPS. BALB/c mice bone marrow DCs (BMDCs) were incubated with 5mM of BLS for 18h. BLS stimulated BMDCs to upregulate the levels of costimulatory molecules CD40, CD80, CD86 and MHCII antigen, as assessed by FACS. BLS did not increase the expression of costimulatory molecules on BMDCs from TLR4-defective C.C3H-Tlr4lps-d mice. Culture supernatants were analyzed for cytokine production by ELISA. BLS induced IL-6, IL-12p70 and TNF-a production in BALB/c but not in C.C3H-Tlr4lps-d mice BMDCs. We analyzed chemokine mRNA levels in BLS-stimulated BMDCs by RNAse Protection Assays. After BLS exposure, BALB/c BMDCs significantly increased the levels of MIP-1a, MIP-1b, MIP-2, MCP-1 and RANTES. None of these were induced in C.C3H-Tlr4lps-d mice BMDCs. We then injected 10mg of BLS into mice footpads and 2 days later the popliteal lymph nodes were subjected to FACS. In BALB/c mice, BLS significantly increased the absolute number of CD11c+ cells and the percentage and absolute number of DCs expressing high levels of CD62L in the draining lymph node. BLS did not lead to those increases in C.C3H-Tlr4lps-d mice. This results show that BLS activates BMDCs in vitro via TLR4 and suggest that in vivo is able to induce a TLR4 dependent recruitment of DCs to the draining lymph node, explaining at least in part its immunogenic properties.