Intraperitoneal treatment with antimicrobial peptide rescues mice from a pulmonaryFrancisellainfection

Abstract

7Our long-term goal is to identify new antimicrobial peptides that might be effective 8 against pneumonic Francisella infection in mice. Previously, our group searched the peptidome 9 of the American alligator for novel cationic antimicrobial peptides and identified a naturally-10 occurring C-terminal fragment of apolipoprotein C-1, which we called Apo6. This peptide was 11 found to have antibacterial activity against the ESKAPE pathogens, including those exhibiting 12 multi-drug resistance. In this work, we tested Apo6 and synthetic derivatives for antibacterial 13 activity against Francisella tularensis including the virulent strain F. tularensis SchuS4.14 Francisella is inherently highly resistant to the cyclic peptide polymyxin antibiotics and beta-15 lactam antibiotics. We found that our synthetic peptide derivatives (called GATR peptides), 16 designed with increased hydrophobicity and charge, had generally stronger in vitro antimicrobial 17 activity against Francisella than the parent peptide Apo6. The GATR peptides had a greater 18 effect on the bacterial membrane than the Apo6 peptide and were able to bind Francisella LPS, 19 suggesting their mechanism of action against Francisella. Cytotoxicity experiments showed low 20 cytotoxicity for most of the GATR peptides, and whole organism toxicity studies in the 21 waxworm allowed us to down-select to two our lead peptides, GATR-3 and GATR-6. These 22 peptides were tested in a murine pulmonary tularemia model. We found that the GATR-3 peptide 23 rescued 50-60% of mice from lethal tularemia infection when administered systemically through 24 2 the intraperitoneal route. This peptide is a candidate for further pre-clinical studies for a potential 25 peptide-based approach to tularemia. 26

GATR-3, a Peptide That Eradicates Preformed Biofilms of Multidrug-Resistant Acinetobacter baumannii

“…We found that these two peptides had antibacterial activity against S. aureus, B. ceres, E. coli, P. aeruginosa, and A. baumannii [23,24]. We further developed these peptides into GATR-3 peptides by modifying the peptide sequence to optimize its amphipathicity and net charge [25]. The sequence and properties of GATR-3 are summarized in Table 1 and were designed to improve the overall amphipathicity, improve the hydrophobic face, and increase the net positive charge.…”