Pegylated LyeTx I-b peptide is effective against carbapenem-resistant Acinetobacter baumannii in an in vivo model of pneumonia and shows reduced toxicity.

The World Health Organization (WHO) has been warning about the importance of developing new drugs against superbugs. Antimicrobial peptides are an alternative in this context, most of them being involved in innate immunity, acting in various ways, and some even showing synergism with commercial antimicrobial agents. LyeTx I-b is a synthetic peptide derived from native LyeTx I, originally isolated from Lycosa erythrognatha spider venom. Although LyeTx I-b is active against several multidrug-resistant bacteria, it shows some hemolytic and cytotoxic effects. To overcome this hindrance, in the present study we PEGylated LyeTx I-b and evaluated its toxicity and in vitro and in vivo activities on pneumonia caused by multi-resistant Acinetobacter baumannii. PEGylated LyeTx I-b (LyeTx I-bPEG) maintained the same MIC value as the non- PEGylated peptide, showed anti-biofilm activity, synergistic effect with commercial antimicrobial agents, and did not induce resistance. Moreover, in vivo experiments showed its activity against pneumonia. Additionally, LyeTx I-bPEG reduced hemolysis up to 10 times, was approximately 2 times less cytotoxic to HEK-293 cells and 4 times less toxic to mice in acute toxicity models, compared to LyeTx I-b. Our results show LyeTx I-bPEG as a promising antimicrobial candidate, significantly active against pneumonia caused by multidrug-resistant A. baumannii.