From Virulence to Therapy: T6SS-Derived Antimicrobial Peptides A7 Combats APEC and MRSA Infections

Area of Science:

• Microbiology
• Drug Discovery
• Biotechnology

Background:

• Multidrug-resistant (MDR) pathogens, including avian pathogenic Escherichia coli (APEC) and methicillin-resistant Staphylococcus aureus (MRSA), present significant threats to animal agriculture and public health.
• The rise of antibiotic resistance necessitates the development of novel therapeutic strategies and alternative treatments.

Purpose of the Study:

• To develop a novel therapeutic agent by repurposing bacterial virulence factors.
• To design and evaluate amphipathic α-helical polypeptides as potential antibiotics against MDR pathogens.

Main Methods:

• Leveraged the type VI secretion system (T6SS) of APEC strain ACN17-20 for therapeutic development.
• Designed and synthesized amphipathic α-helical polypeptides based on structural analysis.
• Assessed antibacterial activity, cytotoxicity, mechanism of action (membrane disruption, ROS induction), biofilm eradication, and in vivo efficacy in a mouse sepsis model.

Main Results:

• Polypeptide A7 demonstrated potent broad-spectrum antibacterial activity against APEC and MRSA with low mammalian cell cytotoxicity.
• A7 exhibited a dual mechanism of action, causing rapid bacterial membrane disruption and inducing lethal oxidative stress.
• Effective eradication of bacterial biofilms and significant improvement in survival rates (60-80%) in a mouse sepsis model were observed.
• Reduced bacterial loads and attenuated systemic cytokine storm (TNF-α, IL-1β) were noted in treated mice.

Conclusions:

• Polypeptide A7 is a promising therapeutic candidate against MDR bacterial infections.
• The dual mechanism of action provides a potent strategy to overcome resistance and reduce reliance on conventional antibiotics.
• This approach offers a novel therapeutic avenue for combating challenging bacterial pathogens in both veterinary and human medicine.