Source: Annual Congress 2008 - Mechanisms of respiratory infections: interaction between the pathogen and the host
Disease area: Airway diseases, Respiratory infections

Abstract

There is a growing body of evidence that COPD patients suffer from mixed infections of bacteria and virus. The interactions of nontypeable H. influenzae (NTHi) and Toll-like receptor (TLR) 3 and 7 agonists are largely unknown. We wanted to assess if TLR agonists have an additive effect with bacterium on the inflammatory response in alveolar epithelial cells type II (AEC-II) and mononuclear cells (MNC). Infection of A549 cells and MNC was performed with various concentrations of NTHi representing bacterium-to-cell ratios of 100:1 to 1:1 . NTHi increased IL-8 production in A549 cells in a dose- and time-dependent manner. Coincubation was performed with or without the TLR3 agonist PI:C, 25ug/ml and TLR7 agonist CL097,1ug/ml. After 3, 8 and 24h supernatants were harvested for ELISA. IL-8 concentrations increased significantly after combined stimulation with NTHi/PI:C when compared to NTHi/CL097 or NTHi monoinfection (NTHi/PI:C 16.92±2.77ng/ml vs. NTHi/CL097 7.11±1.6ng/ml, NTHi 6.55±1.34ng/ml, p< 0.05, n=3). In MNC increased inflammatory response was associated with TLR7 coincubation. MNC were also assessed for apoptosis using life-death staining. Infection with NTHi at multiplicity of infection (MOI) of 1,10,100 showed increased death rates in a dose-dependent manner. When treated with CL097, 50% of infected monocyte cells demonstrated apoptotic profiles. In contrast, NTHi monoinfection resulted only in 10% death rates.
Costimulation of NTHi and TLR agonists shows an additive effect on the inflammatory response in AEC and mononuclear cells which is associated with increased apoptosis rates of host cells.

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E. G. Chen, D. Droemann, J. Rupp, G. Rohde, D. Dalhoff (Luebeck, Bochum, Germany). Additive effect of haemophilus influenzae and toll-like receptor 3 agonist on IL-8 production by A549 cells. Eur Respir J 2008; 32: Suppl. 52, 2285

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