Open Peer Review Any reports and responses or comments on the article can be found at the end of the article. RESEARCH ARTICLE Modulation of proinflammatory activity by the engineered cationic antimicrobial peptide WLBU-2 [version 1; peer review: 2 approved] Shruti M Paranjape , Thomas W Lauer , Ronald C Montelaro , Timothy A Mietzner , Neeraj Vij 1 Eudowood Division of Pediatric Respiratory Sciences, Department of Pediatrics, John Hopkins University, Baltimore, MD, 21287, USA Department of Microbiology and Molecular Genetics, University of Pittsburgh, Pittsburgh, PA, 15261, USA Center for Vaccine Research, University of Pittsburgh, Pittsburgh, PA, 15261, USA Lake Erie College of Osteopathic Medicine, Seton Hill University, Greensburg, PA, 15601, USA Abstract Host-derived (LL-37) and synthetic (WLBU-2) cationic Background: antimicrobial peptides (CAPs) are known for their membrane-active bactericidal properties. LL-37 is an important mediator for immunomodulation, while the mechanism of action of WLBU-2 remains unclear. To determine if WLBU-2 induces an early proinflammatory Objective: response that facilitates bacterial clearance in cystic fibrosis (CF). C57BL6 mice were given intranasal or intraperitoneal 1×10 Methods: cfu/mL (PA) and observed for 2h, followed by Pseudomonas aeruginosa instillation of LL-37 or WLBU-2 (2-4mg/kg) with subsequent tissue collection at 24h for determination of bacterial colony counts and quantitative RT-PCR measurement of cytokine transcripts. CF airway epithelial cells (IB3-1, ΔF508/W1282X) were cultured in appropriate media with supplements. WLBU-2 (25μM) was added to the media with RT-PCR measurement of TNF-α and IL-1β transcripts after 20, 30, and 60min. Flow cytometry was used to determine if WLBU-2 assists in cellular uptake of Alexa 488-labeled LPS. In murine lung exposed to intranasal or intraperitoneal WLBU-2, Results: there was a reduction in the number of surviving PA colonies compared to controls. Murine lung exposed to intraperitoneal WLBU-2 showed fewer PA colonies compared to LL-37. After 24h WLBU-2 exposure, PA-induced IL-1β transcripts from lungs showed a twofold decrease (p<0.05), while TNF-α levels were unchanged. LL-37 did not significantly change transcript levels. In IB3-1 cells, WLBU-2 exposure resulted in increased TNF-α and IL-1β transcripts that decreased by 60min. WLBU-2 treatment of IB3-1 cells displayed increased LPS uptake, suggesting a potential role for CAPs in inducing protective proinflammatory responses. Taken together, the cytokine response, LPS uptake, and established antimicrobial activity of WLBU-2 demonstrate its ability to modulate proinflammatory signaling as a protective mechanism to clear infection. The immunomodulatory properties of WLBU-2 reveal a Conclusions: 1 1 2,3 4 1 1 2 3 4 Reviewer Status Invited Reviewers version 1 published 08 Feb 2013 1 2 report report , McGill University, Montréal, Anastasia Nijnik Canada 1 , Brigham Young University, Provo, Paul Savage UT, USA 2 08 Feb 2013, :36 ( First published: 2 ) https://doi.org/10.12688/f1000research.2-36.v1 08 Feb 2013, :36 ( Latest published: 2 ) https://doi.org/10.12688/f1000research.2-36.v1 v1 6 Page 1 of 9 F1000Research 2013, 2:36 Last updated: 16 MAY 2019