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A7803 - Upper Airway TLR2 Immune Modulators Prime Broad Respiratory Immunity Against Rhinovirus and Influenza Infection and Inhibit Subsequent Lung Inflammation
Author Block: N. W. Bartlett1, J. Girkin1, C. Wong2, G. Deliyannis2, W. Zeng2, C. Demaison3, D. C. Jackson2; 1University of Newcastle, Newcastle, Australia, 2University of Melbourne, Melbourne, Australia, 3Ena Therapeutics Pty Ltd, Melbourne, Australia.
Introduction Respiratory viruses are widely recognised as the most important cause of exacerbation of chronic respiratory inflammatory diseases, such as asthma and COPD. However, the diversity of viral serotypes and their rapid adaptation has frustrated attempts to make vaccines and treatments for common causes such as rhinovirus and influenza. Given that most infections occur via fomites (transfer of virus to the upper airway mucosa by touching infected surfaces), we reasoned that targeting the upper airway with immune-modulating TLR-2 agonists might provide broad protection. Here we report that these agonists not only inhibit viral dissemination from the upper respiratory tract to the lower respiratory tract, but also reduced rhinovirus-induced airway inflammation. Methods Mouse rhinovirus lung infection model. Female Balb/c mice (6-8 weeks old, 6 animals per group) were infected intranasally (i.n.) with 5 x 106 TCID50 of rhinovirus 1B (RV1B) using a volume that reaches the lungs. Mice were treated with candidate TLR2 agonists either 7 days (day -7) and/or 1 day (day -1) prior to RV1B infection. At two days post-infection, lung viral RNA was measured by qPCR and immune cell populations in BAL were enumerated by differential staining. Furthermore, inflammatory mediators (CXCL1 and TNFα) were measured by ELISA. Mouse influenza challenge via the upper respiratory tract. On day 0, groups of C57BL/6 mice (5 animals per group) were treated with different doses of candidate TLR2 agonist. After 1- or 7-days, mice were infected i.n. with a microvolume of 500 pfu of A/Udorn/307/72 (H3N2) influenza virus that was retained entirely in the nasal turbinates. Viral titers in the lungs were determined by plaque formation in MDCK cell monolayers 5 days post-infection. Results For all treatment regimens, the candidate TLR2 agonists significantly reduced the level of rhinovirus RNA in lung tissue. Day -7/day -1 treatment was most effective with >90% reduced viral load. The enhanced anti-rhinoviral response was associated with reduced airway CXCL1 and TNFα expression as well as reduced neutrophilic inflammation. When delivered to the upper respiratory tract only, the agonist also significantly inhibited the progression of influenza virus from the nasal mucosa to the lungs of mice when administered 1 or 7 days prior to infection. Conclusion Prophylactic TLR2 immune modulation protected against respiratory viral infection, including influenza dissemination to the lower respiratory tract and reduced rhinovirus-induced airway inflammation. These results provide the rationale to pursue this agonist as a treatment of viral-induced asthma and/or COPD exacerbations.