Novel Alligator Cathelicidin As-CATH8 Demonstrates Anti-Infective Activity against Clinically Relevant and Crocodylian Bacterial Pathogens.

Host defense peptides (HDPs) represent an alternative way to address the emergence of antibiotic resistance. Crocodylians are interesting species for the study of these molecules because of their potent immune system, which confers high resistance to infection. Profile hidden Markov models were used to screen the genomes of four crocodylian species for encoded cathelicidins and eighteen novel sequences were identified. Synthetic cathelicidins showed broad spectrum antimicrobial and antibiofilm activity against several clinically important antibiotic-resistant bacteria. In particular, the As-CATH8 cathelicidin showed potent in vitro activity profiles similar to the last-resort antibiotics vancomycin and polymyxin B. In addition, As-CATH8 demonstrated rapid killing of planktonic and biofilm cells, which correlated with its ability to cause cytoplasmic membrane depolarization and permeabilization as well as binding to DNA. As-CATH8 displayed greater antibiofilm activity than the human cathelicidin LL-37 against methicillin-resistant Staphylococcus aureus in a human organoid model of biofilm skin infection. Furthermore, As-CATH8 demonstrated strong antibacterial effects in a murine abscess model of high-density bacterial infections against clinical isolates of S. aureus and Acinetobacter baumannii, two of the most common bacterial species causing skin infections globally. Overall, this work expands the repertoire of cathelicidin peptides known in crocodylians, including one with considerable therapeutic promise for treating common skin infections.

Antibiofilm and immunomodulatory resorbable nanofibrous filing for dental pulp regenerative procedures.

Multifunctional scaffolds with host defense peptides designed for regenerative endodontics are desirable nanobiotechnological tools for dentistry. Here, different scaffolds were tested for use during the pulp revascularization process, including poly(vinyl alcohol)-PVA hydrogels or resins, collagen hydrogels and poly(vinyl alcohol) PVA/Chitosan (PVA/CS) nanofibers. Based on time to degradation (21 days), nanofibers were chosen to be incorporated with ciprofloxacin and IDR-1002 (each at 50 mg/g). Nanofibers containing ciprofloxacin and IDR-1002 had anti-biofilm activity against Enterococcus faecalis, Staphylococcus aureus and a multispecies oral biofilm, besides anti-inflammatory activities. The in vivo subcutaneous tissue response to tooth fragments filled with nanofibers demonstrated a pulp-like tissue formation, when compared to empty teeth fragments. Thus, we designed a strong antimicrobial, immunomodulatory and regenerative candidate for pulp revascularization and regeneration procedures.

Genomic insights into the diversity, virulence and resistance of Klebsiella pneumoniae extensively drug resistant clinical isolates.

Klebsiella pneumoniae has been implicated in wide-ranging nosocomial outbreaks, causing severe infections without effective treatments due to antibiotic resistance. Here, we performed genome sequencing of 70 extensively drug resistant clinical isolates, collected from Brasília's hospitals (Brazil) between 2010 and 2014. The majority of strains (60 out of 70) belonged to a single clonal complex (CC), CC258, which has become distributed worldwide in the last two decades. Of these CC258 strains, 44 strains were classified as sequence type 11 (ST11) and fell into two distinct clades, but no ST258 strains were found. These 70 strains had a pan-genome size of 10 366 genes, with a core-genome size of ~4476 genes found in 95 % of isolates. Analysis of sequences revealed diverse mechanisms of resistance, including production of multidrug efflux pumps, enzymes with the same target function but with reduced or no affinity to the drug, and proteins that protected the drug target or inactivated the drug. ß-Lactamase production provided the most notable mechanism associated with K. pneumoniae. Each strain presented two or three different ß-lactamase enzymes, including class A (SHV, CTX-M and KPC), class B and class C AmpC enzymes, although no class D ß-lactamase was identified. Strains carrying the NDM enzyme involved three different ST types, suggesting that there was no common genetic origin.

The use of host defense peptides in root canal therapy in rats.

OBJECTIVES: In order to evaluate host defense peptides (HDPs) HHC-10 and synoeca-MP activity in in vitro osteoclastogenesis process and in vivo induced apical periodontitis, testing the effect of molecules in the inflammatory response and in apical periodontitis size/volume after root canal treatment. MATERIALS AND METHODS: In vitro osteoclastogenesis was assessed on bone marrow cell cultures extracted from mice, while in vivo endodontic treatment involved rats treated with Ca(OH)2 or HDPs. In vitro osteoclasts were subjected to TRAP staining, and in vivo samples were evaluated by radiographic and tomographic exams, as well as histologic analysis. RESULTS: None of the substances downregulated the in vitro osteoclastogenesis. Nevertheless, all treatments affected the average of apical periodontitis size in rats, although only teeth treated with HDPs demonstrated lower levels of the inflammatory process. These results demonstrated the in vivo potential of HDPs. Radiographic analysis suggested that HHC-10 and synoeca-MP-treated animals presented a similar lesion size than Ca(OH)2-treated animals after 7-day of endodontic treatment. However, tomography analysis demonstrated smaller lesion volume in synoeca-MP-treated animals than HHC-10 and Ca(OH)2-treated animals, after 7 days. CONCLUSIONS: These molecules demonstrated an auxiliary effect in endodontic treatment that might be related to its immunomodulatory ability, broad-spectrum antimicrobial activity, and possible induction of tissue repair at low concentrations. These results can encourage further investigations on the specific mechanisms of action in animal models to clarify the commercial applicability of these biomolecules for endodontic treatment. CLINICAL SIGNIFICANCE: HDPs have the potential to be adjuvant substances in endodontic therapy due to its potential to reduce inflammation in apical periodontitis.

EcDBS1R6: A novel cationic antimicrobial peptide derived from a signal peptide sequence.

BACKGROUND: Bacterial infections represent a major worldwide health problem the antimicrobial peptides (AMPs) have been considered as potential alternative agents for treating these infections. Here we demonstrated the antimicrobial activity of EcDBS1R6, a peptide derived from a signal peptide sequence of Escherichia coli that we previously turned into an AMP by making changes through the Joker algorithm. METHODS: Antimicrobial activity was measured by broth microdilution method. Membrane integrity was measured using fluorescent probes and through scanning electron microscopy imaging. A sliding window of truncated peptides was used to determine the EcDBS1R6 active core. Molecular dynamics in TFE/water environment was used to assess the EcDBS1R6 structure. RESULTS: Signal peptides are known to naturally interact with membranes; however, the modifications introduced by Joker transformed this peptide into a membrane-active agent capable of killing bacteria. The C-terminus was unable to fold into an α-helix whereas its fragments showed poor or no antimicrobial activity, suggesting that the EcDBS1R6 antibacterial core was located at the helical N-terminus, corresponding to the signal peptide portion of the parent peptide. CONCLUSION: The strategy of transforming signal peptides into AMPs appears to be promising and could be used to produce novel antimicrobial agents. GENERAL SIGNIFICANCE: The process of transforming an inactive signal peptide into an antimicrobial peptide could open a new venue for creating new AMPs derived from signal peptides.

In Vitro and In Vivo Antibiotic Capacity of Two Host Defense Peptides.

Two nonamidated host defense peptides named Pin2[G] and FA1 were evaluated against three types of pathogenic bacteria: two (Staphylococcus aureus UPD13 and Pseudomonas aeruginosa UPD3) isolated from diabetic foot ulcer patients, and another (Salmonella enterica serovar Typhimurium [ATCC 14028]) from a commercial collection. In vitro experiments showed that the antimicrobial performance of the synthetic peptides Pin2[G] and FA1 was modest, although FA1 was more effective than Pin2[G]. In contrast, Pin2[G] had superior in vivo anti-infective activity to FA1 in rabbit wound infections by the diabetic foot ulcer pathogens S. aureus UPD13 and P. aeruginosa UPD3. Indeed, Pin2[G] reduced bacterial colony counts of both S. aureus UPD13 and P. aeruginosa UPD3 by >100,000-fold after 48 to 72 h on skin wounds of infected rabbits, while in similar infected wounds, FA1 had no major effects at 72 to 96 h of treatment. Ceftriaxone was equally effective versus Pseudomonas but less effective versus S. aureus infections. Additionally, the two peptides were evaluated in mice against intragastrically inoculated S. enterica serovar Typhimurium (ATCC 14028). Only Pin2[G] at 0.56 mg/kg was effective in reducing systemic (liver) infection by >67-fold, equivalent to the effect of treatment with levofloxacin. Pin2[G] showed superior immunomodulatory activity in increasing chemokine production by a human bronchial cell line and suppressing polyinosinic-polycytidylic acid (poly[I:C])-induced proinflammatory IL-6 production. These data showed that the in vitro antimicrobial activity of these peptides was not correlated with their in vivo anti-infective activity and suggest that other factors such as immunomodulatory activity were more important.

Selective anticancer activity of synthetic peptides derived from the host defence peptide tritrpticin.

Antimicrobial peptides (AMPs) constitute a diverse family of peptides with the ability to protect their host against microbial infections. In addition to their ability to kill microorganisms, several AMPs also exhibit selective cytotoxicity towards cancer cells and are collectively referred to as anticancer peptides (ACPs). Here a large library of AMPs, mainly derived from the porcine cathelicidin peptide, tritrpticin (VRRFPWWWPFLRR), were assessed for their anticancer activity against the Jurkat T cell leukemia line. These anticancer potencies were compared to the cytotoxicity of the peptides towards normal cells isolated from healthy donors, namely peripheral blood mononuclear cells (PBMCs) and red blood cells (RBCs; where hemolytic activity was assessed). Among the active tritrpticin derivatives, substitution of Arg by Lys enhanced the selectivity of the peptides towards Jurkat cells when compared to PBMCs. Additionally, the side chain length of the Lys residues was also optimized to further enhance the tritrpticin ACP selectivity at low concentrations. The mechanism of action of the peptides with high selectivity involved the permeabilization of the cytoplasmic membrane of Jurkat cells, without formation of apoptotic bodies. The incorporation of non-natural Lys-based cationic amino acids could provide a new strategy to improve the selectivity of other synthetic ACPs to enhance their potential for therapeutic use against leukemia cells.

Short Cationic Peptide Derived from Archaea with Dual Antibacterial Properties and Anti-Infective Potential.

Bacterial biofilms and associated infections represent one of the biggest challenges in the clinic, and as an alternative to counter bacterial infections, antimicrobial peptides have attracted great attention in the past decade. Here, ten short cationic antimicrobial peptides were generated through a sliding-window strategy on the basis of the 19-amino acid residue peptide, derived from a Pyrobaculum aerophilum ribosomal protein. PaDBS1R6F10 exhibited anti-infective potential as it decreased the bacterial burden in murine Pseudomonas aeruginosa cutaneous infections by more than 1000-fold. Adverse cytotoxic and hemolytic effects were not detected against mammalian cells. The peptide demonstrated structural plasticity in terms of its secondary structure in the different environments tested. PaDBS1R6F10 represents a promising antimicrobial agent against bacteria infections, without harming human cells.

In silico optimization of a guava antimicrobial peptide enables combinatorial exploration for peptide design.

Plants are extensively used in traditional medicine, and several plant antimicrobial peptides have been described as potential alternatives to conventional antibiotics. However, after more than four decades of research no plant antimicrobial peptide is currently used for treating bacterial infections, due to their length, post-translational modifications or  high dose requirement for a therapeutic effect . Here we report the design of antimicrobial peptides derived from a guava glycine-rich peptide using a genetic algorithm. This approach yields guavanin peptides, arginine-rich α-helical peptides that possess an unusual hydrophobic counterpart mainly composed of tyrosine residues. Guavanin 2 is characterized as a prototype peptide in terms of structure and activity. Nuclear magnetic resonance analysis indicates that the peptide adopts an α-helical structure in hydrophobic environments. Guavanin 2 is bactericidal at low concentrations, causing membrane disruption and triggering hyperpolarization. This computational approach for the exploration of natural products could be used to design effective peptide antibiotics.

Induction by innate defence regulator peptide 1018 of pro-angiogenic molecules and endothelial cell migration in a high glucose environment.

Synthetic innate defence regulator (IDR) peptides such as IDR-1018 modulate immunity to promote key protective functions including chemotaxis, wound healing, and anti-infective activity, while suppressing pro-inflammatory responses to non-pathological levels. Here we demonstrated that IDR-1018 induced, by up to 75-fold, pro-angiogenic VEGF-165 in keratinocytes but suppressed this isoform in endothelial cells. It also induced early angiogenin and prolonged anti-inflammatory TGFß expression on endothelial cells, while suppressing early pro-inflammatory IL-1ß expression levels. IDR-1018 also down-regulated the hypoxia induced transcription factor HIF-1α in both keratinocytes and endothelial cells. Consistent with these data, in an in vitro wound healing scratch assay, IDR-1018 induced migration of endothelial cells under conditions of hypoxia while in epithelial cells migration increased only under conditions of normoxia.

An Immunomodulatory Peptide Confers Protection in an Experimental Candidemia Murine Model.

Fungal Candida species are commensals present in the mammalian skin and mucous membranes. Candida spp. are capable of breaching the epithelial barrier of immunocompromised patients with neutrophil and cell-mediated immune dysfunctions and can also disseminate to multiple organs through the bloodstream. Here we examined the action of innate defense regulator 1018 (IDR-1018), a 12-amino-acid-residue peptide derived from bovine bactenecin (Bac2A): IDR-1018 showed weak antifungal and antibiofilm activity against a Candida albicans laboratory strain (ATCC 10231) and a clinical isolate (CI) (MICs of 32 and 64 µg · ml-1, respectively), while 8-fold lower concentrations led to dissolution of the fungal cells from preformed biofilms. IDR-1018 at 128 µg · ml-1 was not hemolytic when tested against murine red blood cells and also has not shown a cytotoxic effect on murine monocyte RAW 264.7 and primary murine macrophage cells at the tested concentrations. IDR-1018 modulated the cytokine profile during challenge of murine bone marrow-derived macrophages with heat-killed C. albicans (HKCA) antigens by increasing monocyte chemoattractant protein 1 (MCP-1) and interleukin-10 (IL-10) levels, while suppressing tumor necrosis factor alpha (TNF-α), IL-1ß, IL-6, and IL-12 levels. Mice treated with IDR-1018 at 10 mg · kg-1 of body weight had an increased survival rate in the candidemia model compared with phosphate-buffered saline (PBS)-treated mice, together with a diminished kidney fungal burden. Thus, IDR-1018 was able to protect against murine experimental candidemia and has the potential as an adjunctive therapy.

Structural Studies of a Lipid-Binding Peptide from Tunicate Hemocytes with Anti-Biofilm Activity.

Clavanins is a class of peptides (23aa) histidine-rich, free of post-translational modifications. Clavanins have been studied largely for their ability to disrupt bacterial membranes. In the present study, the interaction of clavanin A with membranes was assessed by dynamic light scattering, zeta potential and permeabilization assays. We observed through those assays that clavanin A lysis bacterial cells at concentrations corresponding to its MIC. Further, the structure and function of clavanin A was investigated. To better understand how clavanin interacted with bacteria, its NMR structure was elucidated. The solution state NMR structure of clavanin A in the presence of TFE-d3 indicated an α-helical conformation. Secondary structures, based on circular dichroism measurements in anionic sodium dodecyl sulfate (SDS) and TFE (2,2,2-trifluorethanol), in silico lipid-peptide docking and molecular simulations with lipids DPPC and DOPC revealed that clavanin A can adopt a variety of folds, possibly influencing its different functions. Microcalorimetry assays revealed that clavanin A was capable of discriminating between different lipids. Finally, clavanin A was found to eradicate bacterial biofilms representing a previously unrecognized function.

A polyalanine peptide derived from polar fish with anti-infectious activities.

Due to the growing concern about antibiotic-resistant microbial infections, increasing support has been given to new drug discovery programs. A promising alternative to counter bacterial infections includes the antimicrobial peptides (AMPs), which have emerged as model molecules for rational design strategies. Here we focused on the study of Pa-MAP 1.9, a rationally designed AMP derived from the polar fish Pleuronectes americanus. Pa-MAP 1.9 was active against Gram-negative planktonic bacteria and biofilms, without being cytotoxic to mammalian cells. By using AFM, leakage assays, CD spectroscopy and in silico tools, we found that Pa-MAP 1.9 may be acting both on intracellular targets and on the bacterial surface, also being more efficient at interacting with anionic LUVs mimicking Gram-negative bacterial surface, where this peptide adopts α-helical conformations, than cholesterol-enriched LUVs mimicking mammalian cells. Thus, as bacteria present varied physiological features that favor antibiotic-resistance, Pa-MAP 1.9 could be a promising candidate in the development of tools against infections caused by pathogenic bacteria.

LL-37 immunomodulatory activity during Mycobacterium tuberculosis infection in macrophages.

Tuberculosis is one of the most important infectious diseases worldwide. The susceptibility to this disease depends to a great extent on the innate immune response against mycobacteria. Host defense peptides (HDP) are one of the first barriers to counteract infection. Cathelicidin (LL-37) is an HDP that has many immunomodulatory effects besides its weak antimicrobial activity. Despite advances in the study of the innate immune response in tuberculosis, the immunological role of LL-37 during M. tuberculosis infection has not been clarified. Monocyte-derived macrophages were infected with M. tuberculosis strain H37Rv and then treated with 1, 5, or 15 µg/ml of exogenous LL-37 for 4, 8, and 24 h. Exogenous LL-37 decreased tumor necrosis factor alpha (TNF-α) and interleukin-17 (IL-17) while inducing anti-inflammatory IL-10 and transforming growth factor ß (TGF-ß) production. Interestingly, the decreased production of anti-inflammatory cytokines did not reduce antimycobacterial activity. These results are consistent with the concept that LL-37 can modulate the expression of cytokines during mycobacterial infection and this activity was independent of the P2X7 receptor. Thus, LL-37 modulates the response of macrophages during infection, controlling the expression of proinflammatory and anti-inflammatory cytokines.

Antibiofilm peptides increase the susceptibility of carbapenemase-producing Klebsiella pneumoniae clinical isolates to ß-lactam antibiotics.

Multidrug-resistant carbapenemase-producing Klebsiella pneumoniae (KpC) strains are becoming a common cause of infections in health care centers. Furthermore, Klebsiella can develop multicellular biofilms, which lead to elevated adaptive antibiotic resistance. Here, we describe the antimicrobial and antibiofilm activities of synthetic peptides DJK-5, DJK-6, and 1018 against five KpC isolates. Using static microplate assays, it was observed that the concentration required to prevent biofilm formation by these clinical isolates was below the MIC for planktonic cells. More-sophisticated flow cell experiments confirmed the antibiofilm activity of the peptides against 2-day-old biofilms of different KpC isolates, and in some cases, the peptides induced significant biofilm cell death. Clinically relevant combinations of DJK-6 and ß-lactam antibiotics, including the carbapenem meropenem, also prevented planktonic growth and biofilm formation of KpC strain1825971. Interestingly, peptide DJK-6 was able to enhance, at least 16-fold, the ability of meropenem to eradicate preformed biofilms formed by this strain. Using peptide DJK-6 to potentiate the activity of ß-lactams, including meropenem, represents a promising strategy to treat infections caused by KpC isolates.

Ability of innate defence regulator peptides IDR-1002, IDR-HH2 and IDR-1018 to protect against Mycobacterium tuberculosis infections in animal models.

Tuberculosis is an ongoing threat to global health, especially with the emergence of multi drug-resistant (MDR) and extremely drug-resistant strains that are motivating the search for new treatment strategies. One potential strategy is immunotherapy using Innate Defence Regulator (IDR) peptides that selectively modulate innate immunity, enhancing chemokine induction and cell recruitment while suppressing potentially harmful inflammatory responses. IDR peptides possess only modest antimicrobial activity but have profound immunomodulatory functions that appear to be influential in resolving animal model infections. The IDR peptides HH2, 1018 and 1002 were tested for their activity against two M. tuberculosis strains, one drug-sensitive and the other MDR in both in vitro and in vivo models. All peptides showed no cytotoxic activity and only modest direct antimicrobial activity versus M. tuberculosis (MIC of 15-30 µg/ml). Nevertheless peptides HH2 and 1018 reduced bacillary loads in animal models with both the virulent drug susceptible H37Rv strain and an MDR isolate and, especially 1018 led to a considerable reduction in lung inflammation as revealed by decreased pneumonia. These results indicate that IDR peptides have potential as a novel immunotherapy against TB.

Activity of LL-37, CRAMP and antimicrobial peptide-derived compounds E2, E6 and CP26 against Mycobacterium tuberculosis.

Tuberculosis (TB) is a major worldwide health problem in part due to the lack of development of new treatments and the emergence of new strains such as multidrug-resistant (MDR) and extensively drug-resistant strains that are threatening and impairing the control of this disease. In this study, the efficacy of natural and synthetic cationic antimicrobial (host defence) peptides that have been shown often to possess broad-spectrum antimicrobial activity was tested. The natural antimicrobial peptides human LL-37 and mouse CRAMP as well as synthetic peptides E2, E6 and CP26 were tested for their activity against Mycobacterium tuberculosis both in in vitro and in vivo models. The peptides had moderate antimicrobial activities, with minimum inhibitory concentrations ranging from 2 µg/mL to 10 µg/mL. In a virulent model of M. tuberculosis lung infection, intratracheal therapeutic application of these peptides three times a week at doses of ca. 1mg/kg led to significant 3-10-fold reductions in lung bacilli after 28-30 days of treatment. The treatments worked both against the drug-sensitive H37Rv strain and a MDR strain. These results indicate that antimicrobial peptides might constitute a novel therapy against TB.