A novel chemosynthetic peptide with β-sheet motif efficiently kills Klebsiella pneumoniae in a mouse model

Abstract

Klebsiella pneumoniae (Kp) is one of the most common pathogens in nosocomial infections and is increasingly becoming multiple drug resistant. However, the molecular pathogenesis of Kp in causing tissue injury and dysregulated host defense remains elusive, further dampening the development of novel therapeutic measures. We have previously screened a series of synthetic antimicrobial beta-sheet forming peptides and identified a peptide (IRIKIRIK; ie, IK8L) with a broad range of bactericidal activity and low cytotoxicity in vitro. Here, employing an animal model, we investigated the antibacterial effects of IK8L in acute infection and demonstrated that peritoneal injection of IK8L to mice down-regulated inflammatory cytokines, alleviated lung injury, and importantly, decreased mortality compared to sham-injected controls. In addition, a math model was used to evaluate in vivo imaging data and predict infection progression in infected live animals. Mechanistically, IK8L can kill Kp by inhibiting biofilm formation and modulating production of inflammatory cytokines through the STAT3/JAK signaling both in vitro and in vivo. Collectively, these findings reveal that IK8L may have potential for preventing or treating Kp infection.

Keywords:

• bacterial pathogenesis
• inflammatory cytokines
• infectious diseases
• bactericidal activity
• antimicrobial peptides
• STAT3/JAK signaling transduction

Supplementary materials

Figure S1 IK8L decreased the dissemination of infection.

Notes: (A–C) The liver, spleen, and kidneys showed significantly decreased bacterial burdens after infection with Kp in IK8L-treated mice compared with sham-treated mice. IK8L-treated mice and sham-treated mice were infected with 1×10⁵ CFU/mouse Kp at 8 and 24 hours. Fresh tissues were homogenized in PBS. The same amounts of tissue were evaluated for testing bacterial colonies and the unit is CFU/g. The data are representative of four mice per group. ***P<0.001; Mann–Whitney U-test.

Abbreviations: CFU, colony-forming unit; Ctrl, control; h, hours; Kp, Klebsiella pneumoniae; PBS, phosphate-buffered saline.

Figure S2 Prediction of infection with time using the mathematical model.

Notes: (A) Data obtained from in vivo imaging were quantified using relative LUC units of the two groups in sham-treated and IK8L-treated mice at 1 hour, 2 hours, 4 hours, 8 hours, and 12 hours. Sham- and IK8L-treated mice were infected with 1×10⁵ CFU/mouse of Kp Xen-39 by nasal cavity. Semiquantitatively, bioluminescence intensity was obtained using IVIS XRII software. Regression equation was calculated using SPSS software calculations. (B) The data showing predicted relative LUC units of two groups according to two regression equations in (A) at 24 hours, 36 hours, 48 hours, and 50 hours according to our regression equation. (C) The data showing actual LUC units of the two groups in sham-treated and IK8L-treated mice at 24 hours, 36 hours, 48 hours, and 50 hours. Sham- and IK8L-treated mice were infected with 1×10⁵ CFU of Kp Xen-39 by nasal cavity.

Abbreviations: CFU, colony-forming units; LUC, luminescence unit counts.

Acknowledgments

This work was funded by the Flight Attendant Medical Research Institute (FAMRI, Grant #103007), National Institute of Health AI109317-01A1, AI101973-01, AI097532-01A1, National Natural Science Foundation of China (31260276, 30760057, and 30960091), Yunnan Province Science and Technology Innovation Team (2011CI123, 2012Z053, and 2012S208), and Institute of Bioengineering and Nanotechnology (Biomedical Research Council, Agency for Science, Technology and Research, Singapore).

Disclosure

The authors declare no conflicts of interest in this work.