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Antimicrobial Agents and Chemotherapy, August 2007, p. 2969-2978, Vol. 51, No. 8
0066-4804/07/$08.00+0     doi:10.1128/AAC.00268-07
Copyright © 2007, American Society for Microbiology. All Rights Reserved.

Investigating Toll-Like Receptor Agonists for Potential To Treat Hepatitis C Virus Infection

Amy Thomas, Carl Laxton, Joanne Rodman, Nisha Myangar, Nigel Horscroft, and Tanya Parkinson^*

Discovery Biology, Pfizer Global Research and Development, Sandwich, Kent CT13 9NJ, United Kingdom

Received 22 February 2007/ Returned for modification 16 March 2007/ Accepted 24 May 2007

Toll-like receptors (TLRs) are key mediators of innate immunity, and their activation by microbial components leads to the production of cytokines and interferons. Recombinant alpha interferon has been used to treat several viral diseases and is the current standard of care for hepatitis C virus (HCV) infection. Recently, agonists of TLR7 and TLR9 have been shown to have clinical efficacy in HCV patients, and this is correlated with their ability to induce endogenous type I interferon production. We have carried out a comprehensive study of agonists of TLRs 1 to 9 to determine if any additional TLRs can induce antiviral molecules from human peripheral blood mononuclear cells (PBMCs). The agonists were incubated with PBMCs, and the supernatant was then removed and added to HCV replicon cells to assess antiviral activity. Agonists of TLRs 3, 4, 7, 8, and 9 were found to be potent inducers of antiviral activity in PBMC supernatants, and the activity correlated with the induction of alpha interferon and the interferon-induced antiviral biomarker 2',5'-oligoadenylate synthase. Antiviral activity of TLR7 and TLR8 agonists was blocked by an antibody that binds to the type I interferon receptor, confirming that the antiviral activity results from type I interferon induction. TLR4 and TLR8 agonists were found to strongly induce the proinflammatory cytokines interleukin 1ß and tumor necrosis factor alpha at concentrations similar to those inducing antiviral activity. This raises concerns about adverse side effects if these were to be used as antiviral agents. We therefore conclude that TLRs 3, 7, and 9 represent the most attractive targets for the development of new HCV therapies.

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* Corresponding author. Mailing address: Discovery Biology IPC424, Pfizer Global Research and Development, Ramsgate Road, Sandwich, Kent CT13 9NJ, United Kingdom. Phone: 44 (0) 1304 648153. Fax: 44 (0) 1304 651819. E-mail: tanya.parkinson{at}pfizer.com

Published ahead of print on 4 June 2007.

Present address: Department of Medicine, University College London, London, United Kingdom.

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Antimicrobial Agents and Chemotherapy, August 2007, p. 2969-2978, Vol. 51, No. 8
0066-4804/07/$08.00+0     doi:10.1128/AAC.00268-07
Copyright © 2007, American Society for Microbiology. All Rights Reserved.

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