Phage-displayed peptides selected for binding to Campylobacter jejuni are antimicrobial

Strategies and opportunities for engineering antifungal peptides for therapeutic applications

Antifungal peptides (AFPs) are widely described as promising prospects to treat and prevent fungal infections, though they are far less studied than their antibacterial counterparts. Although promising, AFPs have practical limitations that have hindered their use as therapeutics. Rational design and combinatorial engineering are powerful protein engineering strategies with much potential to address the limitations of AFPs by designing peptides with improved physiochemical and biological characteristics. We examine how rational design and combinatorial engineering approaches have already been used to improve the properties of AFPs and propose key opportunities for applying these strategies to push the design and application of AFPs forward.

Recent Advances on Peptide-Based Biosensors and Electronic Noses for Foodborne Pathogen Detection

Foodborne pathogens present a serious issue around the world due to the remarkably high number of illnesses they cause every year. In an effort to narrow the gap between monitoring needs and currently implemented classical detection methodologies, the last decades have seen an increased development of highly accurate and reliable biosensors. Peptides as recognition biomolecules have been explored to develop biosensors that combine simple sample preparation and enhanced detection of bacterial pathogens in food. This review first focuses on the selection strategies for the design and screening of sensitive peptide bioreceptors, such as the isolation of natural antimicrobial peptides (AMPs) from living organisms, the screening of peptides by phage display and the use of in silico tools. Subsequently, an overview on the state-of-the-art techniques in the development of peptide-based biosensors for foodborne pathogen detection based on various transduction systems was given. Additionally, limitations in classical detection strategies have led to the development of innovative approaches for food monitoring, such as electronic noses, as promising alternatives. The use of peptide receptors in electronic noses is a growing field and the recent advances of such systems for foodborne pathogen detection are presented. All these biosensors and electronic noses are promising alternatives for the pathogen detection with high sensitivity, low cost and rapid response, and some of them are potential portable devices for on-site analyses.

Chemical-Biology and Metabolomics Studies in Phage-Host Interactions

For many years, several studies have explored the molecular mechanisms involved in the infection of bacteria by their specific phages to understand the main infection strategies and the host defense strategies. The modulation of the mechanisms involved in the infection, as well as the expression of key substances in the development of the different life cycles of phages, function as a natural source of strategies capable of promoting the control of different pathogens that are harmful to human and animal health. Therefore, this chapter aims to provide an overview of the mechanisms involved in virus-bacteria interaction to explore the main compounds produced or altered as a chemical survival strategy and the metabolism modulation when occurring a host-phage interaction. In this context, emphasis will be given to the chemistry of peptides/proteins and enzymes encoded by bacteriophages in the control of pathogenic bacteria and the use of secondary metabolites recently reported as active participants in the mechanisms of phage-bacteria interaction. Finally, metabolomics strategies developed to gain new insights into the metabolism involved in the phage-host interaction and the metabolomics workflow in host-phage interaction will be presented.

Application of Campylobacter jejuni Phages: Challenges and Perspectives

Bacteriophages (phages) are the most abundant and diverse biological entities in the biosphere. Due to the rise of multi-drug resistant bacterial strains during the past decade, phages are currently experiencing a renewed interest. Bacteriophages and their derivatives are being actively researched for their potential in the medical and biotechnology fields. Phage applications targeting pathogenic food-borne bacteria are currently being utilized for decontamination and therapy of live farm animals and as a biocontrol measure at the post-harvest level. For this indication, the United States Food and Drug Administration (FDA) has approved several phage products targeting Listeria sp., Salmonella sp. and Escherichia coli. Phage-based applications against Campylobacter jejuni could potentially be used in ways similar to those against Salmonella sp. and Listeria sp.; however, only very few Campylobacter phage products have been approved anywhere to date. The research on Campylobacter phages conducted thus far indicates that highly diverse subpopulations of C. jejuni as well as phage isolation and enrichment procedures influence the specificity and efficacy of Campylobacter phages. This review paper emphasizes conclusions from previous findings instrumental in facilitating isolation of Campylobacter phages and improving specificity and efficacy of the isolates.

Efficient affinity-tagging of M13 phage capsid protein IX for immobilization of protein III-displayed oligopeptide probes on abiotic platforms

We developed a genetic approach to efficiently add an affinity tag to every copy of protein IX (pIX) of M13 filamentous bacteriophage in a population. Affinity-tagged phages can be immobilized on a surface in a uniform monolayer in order to position the pIII-displayed peptides or proteins for optimal interaction with ligands. The tagging consists of two major steps. First, gene IX (gIX) of M13 phage is mutated in Escherichia coli via genetic recombineering with the gIX::aacCI insertion allele. Second, a plasmid that co-produces the affinity-tagged pIX and native pVIII is transformed into the strain carrying the defective M13 gIX. This genetic complementation allows the formation of infective phage particles that carry a full complement (five copies per virion) of the affinity-tagged pIX. To demonstrate the efficacy of our method, we tagged a M13 derivative phage, M13KE, with Strep-tag II. In order to tag pIX with Strep-tag II, the phage genes for pIX and pVIII were cloned and expressed from pASG-IBA4 which contains the E. coli OmpA signal sequence and Strep-Tag II under control of the tetracycline promoter/operator system. We achieved the maximum phage production of 3 × 10¹¹ pfu/ml when Strep-Tag II-pIX-pVIII fusion was induced with 10 ng/ml of anhydrotetracycline. The complete process of affinity tagging a phage probe takes less than 5 days and can be utilized to tag any M13 or fd pIII-displayed oligopeptide probes to improve their performance.

Inhibition of multidrug resistant Listeria monocytogenes by peptides isolated from combinatorial phage display libraries

The aim of the study was to isolate and characterize novel antimicrobial peptides from peptide phage library with antimicrobial activity against multidrug resistant Listeria monocytogenes. Combinatorial phage-display library was used to affinity select peptides binding to the cell surface of multidrug resistant L. monocytogenes. After several rounds of affinity selection followed by sequencing, three peptides were revealed as the most promising candidates. Peptide L2 exhibited features common to antimicrobial peptides (AMPs), and was rich in Asp, His and Lys residues. Peptide L3 (NSWIQAPDTKSI), like peptide L2, inhibited bacterial growth in vitro, without any hemolytic or cytotoxic effects on eukaryotic cells. L1 peptide showed no inhibitory effect on Listeria. Structurally, peptides L2 and L3 formed random coils composed of α-helix and β-sheet units. Peptides L2 and L3 exhibited antimicrobial activity against multidrug resistant isolates of L. monocytogenes with no haemolytic or toxic effects. Both peptides identified in this study have the potential to be beneficial in human and veterinary medicine.

A phage-displayed peptide recognizing porcine aminopeptidase N is a potent small molecule inhibitor of PEDV entry

Three phage-displayed peptides designated H, S and F that recognize porcine aminopeptidase N (pAPN), the cellular receptor of porcine transmissible gastroenteritis virus (TGEV) were able to inhibit cell infection by TGEV. These same peptides had no inhibitory effects on infection of Vero cells by porcine epidemic diarrhea virus (PEDV). However, when PEDV, TGEV and porcine pseudorabies virus were incubated with peptide H (HVTTTFAPPPPR), only infection of Vero cells by PEDV was inhibited. Immunofluoresence assays indicated that inhibition of PEDV infection by peptide H was independent of pAPN. Western blots demonstrated that peptide H interacted with PEDV spike protein and that pre-treatment of PEDV with peptide H led to a higher inhibition than synchronous incubation with cells. These results indicate direct interaction with the virus is necessary to inhibit infectivity. Temperature shift assays demonstrated that peptide H inhibited pre-attachment of the virus to the cells.

Bacteriophage therapy for safeguarding animal and human health: a review

Since the discovery of bacteriophages at the beginning of the 19th century their contribution to bacterial evolution and ecology and use in a variety of applications in biotechnology and medicine has been recognized and understood. Bacteriophages are natural bacterial killers, proven as best biocontrol agents due to their ability to lyse host bacterial cells specifically thereby helping in disease prevention and control. The requirement of such therapeutic approach is straight away required in view of the global emergence of Multidrug Resistant (MDR) strains of bacteria and rapidly developing resistance to antibiotics in both animals and humans along with increasing food safety concerns including of residual antibiotic toxicities. Phage typing is a popular tool to differentiate bacterial isolates and to identify and characterize outbreak-associated strains of Salmonella, Campylobacter, Escherichia and Listeria. Numerous methods viz. plaque morphology, ultracentrifugation in the density gradient of CsCl2, and random amplified polymorphic DNA (RAPD) have been found to be effective in detection of various phages. Bacteriophages have been isolated and recovered from samples of animal waste products of different livestock farms. High titer cocktails of broad spectrum lytic bacteriophages are usually used for clinical trial for assessing their therapeutic efficacy against antibiotic unresponsive infections in different animals. Bacteriophage therapy also helps to fight various bacterial infections of poultry viz. colibacillosis, salmonellosis and listeriosis. Moreover, the utility of phages concerning biosafety has raised the importance to explore and popularize the therapeutic dimension of this promising novel therapy which forms the topic of discussion of the present review.

A peptide derived from phage display library exhibits antibacterial activity against E. coli and Pseudomonas aeruginosa

Emergence of drug resistant strains to currently available antibiotics has resulted in the quest for novel antimicrobial agents. Antimicrobial peptides (AMPs) are receiving attention as alternatives to antibiotics. In this study, we used phage-display random peptide library to identify peptides binding to the cell surface of E. coli. The peptide with sequence RLLFRKIRRLKR (EC5) bound to the cell surface of E. coli and exhibited certain features common to AMPs and was rich in Arginine and Lysine residues. Antimicrobial activity of the peptide was tested in vitro by growth inhibition assays and the bacterial membrane permeabilization assay. The peptide was highly active against gram-negative organisms and showed significant bactericidal activity against E. coli and P. aeruginosa resulting in a reduction of 5 log(10) CFU/ml. In homologous plasma and platelets, incubation of EC5 with the bacteria resulted in significant reduction of E. coli and P. aeruginosa, compared to the peptide-free controls. The peptide was non-hemolytic and non-cytotoxic when tested on eukaryotic cells in culture. EC5 was able to permeabilize the outer membrane of E. coli and P. aeruginosa causing rapid depolarization of cytoplasmic membrane resulting in killing of the cells at 5 minutes of exposure. The secondary structure of the peptide showed a α-helical conformation in the presence of aqueous environment. The bacterial lipid interaction with the peptide was also investigated using Molecular Dynamic Simulations. Thus this study demonstrates that peptides identified to bind to bacterial cell surface through phage-display screening may additionally aid in identifying and developing novel antimicrobial peptides.

Identification and evaluation of a novel peptide binding to the cell surface of Staphylococcus aureus

Identification of short peptides that serve as specific ligands to biological materials such as microbial cell surfaces has major implications in better understanding the molecular recognition of cell surfaces. In this study we screened a commercially available random phage-display library against Staphylococcus aureus cells and identified peptides specifically binding to the bacteria. A synthetic peptide (SA5-1) representing the consensus sequence (VPHNPGLISLQG) of the bacteria-binding peptide was evaluated for its binding potential against S. aureus. Dot-blot, immunoblot assay and ELISA results revealed the SA5-1 peptide to be highly specific to S. aureus. The SA5-1 peptide binding was optimal between pH 6.0 and 8.0. Nanogold Transmission Electron Microscopy demonstrated that the SA5-1 binds to the outer membrane surface of S. aureus. Diagnostic potential of the SA5-1 peptide was evaluated in human platelet samples spiked with S. aureus and specific detection of the bacteria by biotinylated-SA5-1 and streptavidin-conjugated fluorescent quantum dots. Fluorometry results indicated that the peptide was able to detect ∼100 organisms per ml in a spiked biological sample providing a proof-of-concept towards potential of this peptide as a S. aureus diagnostic tool that can be of use in different detection platforms.

Development of anti-infectives using phage display: biological agents against bacteria, viruses, and parasites

The vast majority of anti-infective therapeutics on the market or in development are small molecules; however, there is now a nascent pipeline of biological agents in development. Until recently, phage display technologies were used mainly to produce monoclonal antibodies (MAbs) targeted against cancer or inflammatory disease targets. Patent disputes impeded broad use of these methods and contributed to the dearth of candidates in the clinic during the 1990s. Today, however, phage display is recognized as a powerful tool for selecting novel peptides and antibodies that can bind to a wide range of antigens, ranging from whole cells to proteins and lipid targets. In this review, we highlight research that exploits phage display technology as a means of discovering novel therapeutics against infectious diseases, with a focus on antimicrobial peptides and antibodies in clinical or preclinical development. We discuss the different strategies and methods used to derive, select, and develop anti-infectives from phage display libraries and then highlight case studies of drug candidates in the process of development and commercialization. Advances in screening, manufacturing, and humanization technologies now mean that phage display can make a significant contribution in the fight against clinically important pathogens.