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The LL-37 Antimicrobial Peptide as a Treatment for Systematic Infection of Acinetobacter baumannii in a Mouse Model
Ehsan Zarei-Mehrvarz1, Shohreh Fahimirad1, Ehsanollah Ghaznavi-Rad1,2
1Molecular and Medicine Research Center, Arak University of Medical Sciences, Arak, Iran.
Background:
The antimicrobial peptides (AMPs) played a critical role in the innate immunity of the host and are considered natural sources illustrating a broad-spectrum antimicrobial activity with high specificity and low cytotoxicity. AMPs generally possess a net positive charge and have amphipathic structures. Thus, AMPs can bind and interact with negatively charged bacterial cell membranes, leading to destructive defects in biomembranes and ending in cell death. LL37 is the only human cathelicidin-derived antimicrobial peptide that shows a broad spectrum of antimicrobial activity.
Materials And Methods:
To determine the antibacterial efficiency of LL37 in a mouse model of systemic A. baumannii infection, LL37 corresponding gene was expressed in E. coli, purification and refolding situations were optimized. The antimicrobial performance of produced LL-37 against A. baumannii was evaluated in vitro via MIC and Time Kill assays, and its destructive effects on the bacterial cell were confirmed by SEM image.
Results:
The recombinant LL37 showed strong antibacterial function against A. baumannii at 1.5 μg/mL concentration. Time kill assay showed a sharp reduction of cell viability during the first period of exposure, and complete cell death was recorded after 40 min exposure.
Conclusion:
Furthermore, in vivo results represented a significant ability of LL37 in the treatment of systematic infected mouse models, and all infected mice receiving LL37 protein survived without no trace of bacteria in their blood samples.
Insights
Human antimicrobial peptide LL37 effectively combats Acinetobacter baumannii infections. This study demonstrates LL37’s potent antibacterial activity in vitro and its life-saving efficacy in a mouse model of systemic infection.
Area of Science:
- Microbiology
- Immunology
- Biochemistry
Background:
- Antimicrobial peptides (AMPs) are crucial for innate immunity, offering broad-spectrum activity with low cytotoxicity.
- AMPs, like LL37, possess positive charges and amphipathic structures, enabling them to disrupt negatively charged bacterial membranes.
- LL37 is the sole human cathelicidin-derived AMP known for its wide-ranging antimicrobial properties.
Purpose of the Study:
- To evaluate the antibacterial efficacy of LL37 against Acinetobacter baumannii.
- To assess LL37's therapeutic potential in a mouse model of systemic A. baumannii infection.
Main Methods:
- Recombinant LL37 was expressed in E. coli, with optimized purification and refolding.
- In vitro antibacterial activity was determined using MIC and Time Kill assays.
- Scanning Electron Microscopy (SEM) confirmed LL37's disruptive effects on bacterial cells.
Main Results:
- Recombinant LL37 demonstrated potent antibacterial activity against A. baumannii at a concentration of 1.5 μg/mL.
- Time kill assays revealed rapid bacterial viability reduction, with complete cell death occurring within 40 minutes.
- SEM images confirmed LL37's destructive impact on bacterial cell membranes.
Conclusions:
- LL37 exhibits significant antibacterial function against A. baumannii in vitro.
- LL37 proved effective in treating systemic A. baumannii infections in a mouse model.
- All mice treated with LL37 survived the infection, with no detectable bacteria in their blood samples.
