Newly Developed Antimicrobial Peptide May Protect from Lethal Bacterial Infections

In a new study researchers from Japan suggest that a synthetic antimicrobial peptide identified as L5 may prevent death in mice suffering from life-threatening bacterial infections, such as MRSA, by activating the host immune response. They report their findings in the June 2009 issue of the journal Antimicrobial Agents and Chemotherapy.

Innate immunity, the universal defense system shared by all animals, activates when the body responds to foreign pathogens at an early stage of infection. Cationic antimicrobial peptides (known for their antibacterial, antifungal, antiviral, antiprotozoal and antiseptic properties) are part of the innate immune response which kills microorganisms.

In a previous study researchers developed the cationic antimicrobial peptide L5 out of antibacterial proteins from Sarcophaga peregrina and found it to be an effective prophylactic treatment of MRSA in infected mice. In this study mice were administered intra-abdominal implantation as well as normal injections of L5 and observed for its ability to prevent death when challenged with lethal bacterial infections. Results showed that treatments with L5 were highly effective in preventing death when inoculated with Staphylococcus aureus Smith, Enterococcus faecalis SR1004, and Escherichia coli EC14. More specifically, normal injections of L5 prior to infection greatly reduced rates of death and intra-abdominal administration of L5 increased antibacterial activity in the abdominal cavity.

"In conclusion, we found that L5 induced the activation of the host immune responses and protected the mice from death due to infection," say the researchers. "We propose a novel therapeutic intervention that activates the host immunity in infectious diseases and has an advantage in treatment of antibiotic-resistant bacterial infection."