Antibacterial Properties and Efficacy of a Novel SPLUNC1-Derived Antimicrobial Peptide, α4-Short, in a Murine Model of Respiratory Infection

Abstract

Multidrug resistance (MDR) by bacterial pathogens constitutes a global health crisis, and resistance to treatment displayed by biofilm-associated infections (e.g., cystic fibrosis, surgical sites, and medical implants) only exacerbates a problem that is already difficult to overcome. Antimicrobial peptides (AMPs) are a promising class of therapeutics that may be useful in the battle against antibiotic resistance, although certain limitations have hindered their clinical development. The goal of this study was to examine the therapeutic potential of novel AMPs derived from the multifunctional respiratory host defense protein SPLUNC1. Using standard growth inhibition and antibiofilm assays, we demonstrated that a novel structurally optimized AMP, α4-short, was highly effective against the most common group of MDR bacteria while showing broad-spectrum bactericidal and antibiofilm activities. With negligible hemolysis and toxicity to white blood cells, the new peptide also demonstrated in vivo efficacy when delivered directly into the airway in a murine model of Pseudomonas aeruginosa-induced respiratory infection. The data warrant further exploration of SPLUNC1-derived AMPs with optimized structures to assess the potential application to difficult-to-cure biofilm-associated infections. IMPORTANCE The rise of superbugs underscores the urgent need for novel antimicrobial agents. Antimicrobial peptides (AMPs) have the ability to kill superbugs regardless of resistance to traditional antibiotics. However, AMPs often display a lack of efficacy in vivo. Sequence optimization and engineering are promising but may result in increased host toxicity. We report here the optimization of a novel AMP (α4-short) derived from the multifunctional respiratory protein SPLUNC1. The AMP α4-short demonstrated broad-spectrum activity against superbugs as well as in vivo efficacy in the P. aeruginosa pneumonia model. Further exploration for clinical development is warranted.

Acidic Microenvironment Determines Antibiotic Susceptibility and Biofilm Formation of Pseudomonas aeruginosa

“…Evolution studies were carried out using the m63 medium (same as biofilm assay). The bead transfer-based biofilm evolution model was described previously (Poltak and Cooper, 2011;Cooper, 2018;Jiang et al, 2019). Briefly, the PA14 ancestor was added to 5 mL of pH 6.5/7.5 m63 (media pH adjusted by HCl) with 1/2 MIC of antibiotic treatment at day 1.…”

Cystic Fibrosis Acidic Microenvironment Determines Antibiotic Susceptibility and Biofilm Formation ofPseudomonas aeruginosa

“…Evolution studies were carried out using m63 medium (same as biofilm assay). The bead transfer-based biofilm evolution model was described previously (55)(56)(57). Briefly, the PA14 ancestor was added to 5mL of pH 6.5/7.5 m63 (media pH adjusted by HCl) with ½ MIC of antibiotic treatment at day 1.…”

Antibiofilm peptides: overcoming biofilm-related treatment failure

“…This peptide also exhibited efficacy against clinical P. aeruginosa isolates as well as biolms formed on a CF ALI model. 113 In another study, a lung ALI model was inoculated with P. aeruginosa at the apical site, unattached cells were removed aer 1 h and 16 mM SPLUNC1-derived HDPs, a4 or a4-short, were added for 5 h. 114 Following the treatment, enumeration of biolm bacteria showed that a4-short could inhibit and eradicate biolms. However, it must be stated that neither timing nor experimental conditions allowed a clear conclusion as to whether this model can truly be considered a biolm model.…”

“…However, it must be stated that neither timing nor experimental conditions allowed a clear conclusion as to whether this model can truly be considered a biofilm model. 114 …”