We have previously discovered a synergistically therapeutic combination of two Toll-like receptor ligands, an oligodeoxynucleotide (ODN) and Pam2CSK4. Aerosolization of these ligands stimulates innate immunity within the lungs to prevent pneumonia from bacterial and viral pathogens. Here we examined the safety and tolerability of this treatment in mice, and characterized the expression of biomarkers of innate immune activation. We found that neutrophils appeared in lung lavage fluid 4 h after treatment, reached a peak at 48 h, and resolved by 7 days. The peak of neutrophil influx was accompanied by a small increase in lung permeability. Despite the abundance of neutrophils in lung lavage fluid, only rare neutrophils were visible histopathologically in the interstitium surrounding bronchi and veins and none were visible in alveolar airspaces. The cytokines interleukin 6 (IL-6), tumour necrosis factor, and Chemokine (C-X-C motif) ligand 2 rose several hundred-fold in lung lavage fluid 4 h after treatment in a dose-dependent and synergistic manner, providing useful biomarkers of lung activation. IL-6 rose fivefold in serum with delayed kinetics compared to its rise in lavage fluid, and might serve as a systemic biomarker of immune activation of the lungs. The dose–response relationship of lavage fluid cytokines was preserved in mice that underwent myeloablative treatment with cytosine arabinoside to model the treatment of hematologic malignancy. There were no overt signs of distress in mice treated with ODN/Pam2CSK4 in doses up to eightfold the therapeutic dose, and no changes in temperature, respiratory rate, or behavioral signs of sickness including sugar water preference, food disappearance, cage exploration or social interaction, though there was a small degree of transient weight loss. We conclude that treatment with aerosolized ODN/Pam2CSK4 is well tolerated in mice, and that innate immune activation of the lungs can be monitored by the measurement of inflammatory cytokines in lung lavage fluid and serum.
Keywords: pneumonia, innate immunity, Toll-like receptor, oligodeoxynucleotide, lipopeptide, aerosol, myeloablation
Citation: Alfaro VY, Goldblatt DL, Valverde GR, Munsell MF, Quinton LJ, Walker AK, Dantzer R, Varadhachary A, Scott BL, Evans SE, Tuvim MJ and Dickey BF (2014) Safety, tolerability, and biomarkers of the treatment of mice with aerosolized Toll-like receptor ligands. Front. Pharmacol. 5:8. doi: 10.3389/fphar.2014.00008
Received: 25 October 2013; Accepted: 15 January 2014;
Published online: 06 February 2014.
Edited by:Paolo Montuschi, Università Cattolica del Sacro Cuore, Italy
Reviewed by:Paolo Montuschi, Università Cattolica del Sacro Cuore, Italy
Copyright © 2014 Alfaro, Goldblatt, Valverde, Munsell, Quinton, Walker, Dantzer, Varadhachary, Scott, Evans, Tuvim and Dickey. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) or licensor are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.
*Correspondence: Burton F. Dickey, Department of Pulmonary Medicine, Unit 1462, The University of Texas MD Anderson Cancer Center, 1515 Holcombe Boulevard, Houston, TX 77030, USA e-mail: email@example.com