Medicinal leech antimicrobial peptides lacking toxicity represent a promising alternative strategy to combat antibiotic-resistant pathogens

Identification and Characterization of RK22, a Novel Antimicrobial Peptide from Hirudinaria manillensis against Methicillin Resistant Staphylococcus aureus

Staphylococcus aureus (S. aureus) infections are a leading cause of morbidity and mortality, which are compounded by drug resistance. By manipulating the coagulation system, S. aureus gains a significant advantage over host defense mechanisms, with hypercoagulation induced by S. aureus potentially aggravating infectious diseases. Recently, we and other researchers identified that a higher level of LL-37, one endogenous antimicrobial peptide with a significant killing effect on S. aureus infection, resulted in thrombosis formation through the induction of platelet activation and potentiation of the coagulation factor enzymatic activity. In the current study, we identified a novel antimicrobial peptide (RK22) from the salivary gland transcriptome of Hirudinaria manillensis (H. manillensis) through bioinformatic analysis, and then synthesized it, which exhibited good antimicrobial activity against S. aureus, including a clinically resistant strain with a minimal inhibitory concentration (MIC) of 6.25 μg/mL. The RK22 peptide rapidly killed S. aureus by inhibiting biofilm formation and promoting biofilm eradication, with good plasma stability, negligible cytotoxicity, minimal hemolytic activity, and no significant promotion of the coagulation system. Notably, administration of RK22 significantly inhibited S. aureus infection and the clinically resistant strain in vivo. Thus, these findings highlight the potential of RK22 as an ideal treatment candidate against S. aureus infection.

Peptidomics Analysis Reveals the Buccal Gland of Jawless Vertebrate Lamprey as a Source of Multiple Bioactive Peptides

Various proteins with antibacterial, anticoagulant, and anti-inflammatory properties have been identified in the buccal glands of jawless blood-sucking vertebrate lampreys. However, studies on endogenous peptides in the buccal gland of lampreys are limited. In this study, 4528 endogenous peptides were identified from 1224 precursor proteins using peptidomics and screened for bioactivity in the buccal glands of the lamprey, Lethenteron camtschaticum. We synthesized four candidate bioactive peptides (VSLNLPYSVVRGEQFVVQA, DIPVPEVPILE, VVQLPPVVLGTFG, and VPPPPLVLPPASVK), calculated their secondary structures, and validated their bioactivity. The results showed that the peptide VSLNLPYSVVRGEQFVVQA possessed anti-inflammatory activity, which significantly increased the expression of anti-inflammatory factors and decreased the expression of inflammatory factors in THP-1 cells. The peptide VVQLPPVVLGTFG showed antibacterial activity against some gram-positive bacteria. The peptide VSLNLPYSVVRGEQFVQA possessed good ACE inhibitory activity at low concentrations, but no dose-related correlation was observed. Our study revealed that the buccal glands of the jawless vertebrate lamprey are a source of multiple bioactive peptides, which will provide new insights into the blood-sucking mechanism of lamprey.

Membrane-Targeting Neolignan-Antimicrobial Peptide Mimic Conjugates to Combat Methicillin-Resistant Staphylococcus aureus (MRSA) Infections

Infections caused by methicillin-resistant Staphylococcus aureus (MRSA) continue to endanger public health. Here, we report the synthesis of neolignan isomagnolone (I) and its isomer II, and the preparation of a series of novel neolignan-antimicrobial peptide (AMP) mimic conjugates. Notably, conjugates III5 and III15 exhibit potent anti-MRSA activity in vitro and in vivo, comparable to that of vancomycin, a current effective treatment for MRSA. Moreover, III5 and III15 display not only fast-killing kinetics and low resistance frequency but also low toxicity as well as effects on bacterial biofilms. Mechanism studies reveal that III5 and III15 exhibit rapid bactericidal effects through binding to the phosphatidylglycerol (PG) and cardiolipin (CL) of the bacterial membrane, thereby disrupting the cell membranes and allowing increased reactive oxygen species (ROS) as well as protein and DNA leakage. The results indicate that these neolignan-AMP mimic conjugates could be promising antimicrobial candidates for combating MRSA infections.

Efficacy of natural antimicrobial peptides versus peptidomimetic analogues: a systematic review

Aims: This systematic review was carried out to determine whether synthetic peptidomimetics exhibit significant advantages over antimicrobial peptides in terms of in vitro potency. Structural features - molecular weight, charge and length - were examined for correlations with activity. Methods: Original research articles reporting minimum inhibitory concentration  values against Escherichia coli, indexed until 31 December 2020, were searched in PubMed/ScienceDirect/Google Scholar and evaluated using mixed-effects models. Results: In vitro antimicrobial activity of peptidomimetics resembled that of antimicrobial peptides. Net charge significantly affected minimum inhibitory concentration values (p < 0.001) with a trend of 4.6% decrease for increments in charge by +1. Conclusion: AMPs and antibacterial peptidomimetics exhibit similar potencies, providing an opportunity to exploit the advantageous stability and bioavailability typically associated with peptidomimetics.

Effects of Medicinal Leech-Related Cationic Antimicrobial Peptides on Human Blood Cells and Plasma

Cationic antimicrobial peptides (CAMPs) are considered as next-generation antibiotics with a lower probability of developing bacterial resistance. In view of potential clinical use, studies on CAMP biocompatibility are important. This work aimed to evaluate the behavior of synthetic short CAMPs (designed using bioinformatic analysis of the medicinal leech genome and microbiome) in direct contact with blood cells and plasma. Eight CAMPs were included in the study. Hemolysis and lactate dehydrogenase assays showed that the potency to disrupt erythrocyte, neutrophil and mononuclear cell membranes descended in the order pept_1 > pept_3 ~ pept_5 > pept_2 ~ pept_4. Pept_3 caused both cell lysis and aggregation. Blood plasma and albumin inhibited the CAMP-induced hemolysis. The chemiluminescence method allowed the detection of pept_3-mediated neutrophil activation. In plasma coagulation assays, pept_3 prolonged the activated partial thromboplastin time (APTT) and prothrombin time (at 50 μM by 75% and 320%, respectively). Pept_3 was also capable of causing fibrinogen aggregation. Pept_6 prolonged APTT (at 50 μM by 115%). Pept_2 was found to combine higher bactericidal activity with lower effects on cells and coagulation. Our data emphasize the necessity of investigating CAMP interaction with plasma.

Characterising four Sarconesiopsis magellanica (Diptera: Calliphoridae) larval fat body-derived antimicrobial peptides

BACKGROUND

The inappropriate use of antibiotics has led to the accelerated growth of resistance to antibiotics. The search for new therapeutic strategies (i.e., antimicrobial peptides-AMPs) has thus become a pressing need.

OBJECTIVE

Characterising and evaluating Sarconesiopsis magellanica larval fat body-derived AMPs.

METHODS

Fat body extracts were analysed by reversed-phase high-performance liquid chromatography (RP-HPLC); mass spectrometry was used for characterising the primary structure of the AMPs so found. ProtParam (Expasy) was used for analysing the AMPs' physico-chemical properties. Synthetic AMPs' antibacterial activity was evaluated.

FINDINGS

Four new AMPs were obtained and called sarconesin III, IV, V and VI. Sarconesin III had an α-helix structure and sarconesins IV, V and VI had linear formations. Oligomer prediction highlighted peptide-peptide interactions, suggesting that sarconesins III, V and VI could form self-aggregations when in contact with the microbial membrane. AMPs synthesised from their native molecules' sequences had potent activity against Gram-positive bacteria and, to a lesser extent, against Gram-negative and drug-resistant bacteria. Sarconesin VI was the most efficient AMP. None of the four synthetic AMPs had a cytotoxic effect.

MAIN CONCLUSIONS

S. magellanica larval fat body-derived antimicrobial peptides are an important source of AMPs and could be used in different antimicrobial therapies and overcoming bacterial resistance.

AniAMPpred: artificial intelligence guided discovery of novel antimicrobial peptides in animal kingdom

With advancements in genomics, there has been substantial reduction in the cost and time of genome sequencing and has resulted in lot of data in genome databases. Antimicrobial host defense proteins provide protection against invading microbes. But confirming the antimicrobial function of host proteins by wet-lab experiments is expensive and time consuming. Therefore, there is a need to develop an in silico tool to identify the antimicrobial function of proteins. In the current study, we developed a model AniAMPpred by considering all the available antimicrobial peptides (AMPs) of length $\in $[10 200] from the animal kingdom. The model utilizes a support vector machine algorithm with deep learning-based features and identifies probable antimicrobial proteins (PAPs) in the genome of animals. The results show that our proposed model outperforms other state-of-the-art classifiers, has very high confidence in its predictions, is not biased and can classify both AMPs and non-AMPs for a diverse peptide length with high accuracy. By utilizing AniAMPpred, we identified 436 PAPs in the genome of Helobdella robusta. To further confirm the functional activity of PAPs, we performed BLAST analysis against known AMPs. On detailed analysis of five selected PAPs, we could observe their similarity with antimicrobial proteins of several animal species. Thus, our proposed model can help the researchers identify PAPs in the genome of animals and provide insight into the functional identity of different proteins. An online prediction server is also developed based on the proposed approach, which is freely accessible at https://aniamppred.anvil.app/.

3D Reconstruction of HvRNASET2 Molecule to Understand Its Antibacterial Role

Recent studies performed on the invertebrate model Hirudo verbana (medicinal leech) suggest that the T2 ribonucleic enzyme HvRNASET2 modulates the leech's innate immune response, promoting microbial agglutination and supporting phagocytic cells recruitment in challenged tissues. Indeed, following injection of both lipoteichoic acid (LTA) and Staphylococcus aureus in the leech body wall, HvRNASET2 is expressed by leech type I granulocytes and induces bacterial aggregation to aid macrophage phagocytosis. Here, we investigate the HvRNASET2 antimicrobial role, in particular assessing the effects on the Gram-negative bacteria Escherichia coli. For this purpose, starting from the three-dimensional molecule reconstruction and in silico analyses, the antibacterial activity was evaluated both in vitro and in vivo. The changes induced in treated bacteria, such as agglutination and alteration in wall integrity, were observed by means of light, transmission and scanning electron microscopy. Moreover, immunogold, AMPs (antimicrobial peptides) and lipopolysaccharide (LPS) binding assays were carried out to evaluate HvRNASET2 interaction with the microbial envelopes and the ensuing ability to affect microbial viability. Finally, in vivo experiments confirmed that HvRNASET2 promotes a more rapid phagocytosis of bacterial aggregates by macrophages, representing a novel molecule for counteracting pathogen infections and developing alternative solutions to improve human health.

The Hirudo Medicinalis Microbiome Is a Source of New Antimicrobial Peptides

Antimicrobial peptides (AMPs) are considered a promising new class of anti-infectious agents. This study reports new antimicrobial peptides derived from the Hirudo medicinalis microbiome identified by a computational analysis method applied to the H. medicinalis metagenome. The identified AMPs possess a strong antimicrobial activity against Gram-positive and Gram-negative bacteria (MIC range: 5.3 to 22.4 μM), including Staphylococcus haemolyticus, an opportunistic coagulase-negative pathogen. The secondary structure analysis of peptides via CD spectroscopy showed that all the AMPs except pept_352 have mostly disordered structures that do not change under different conditions. For peptide pept_352, the α-helical content increases in the membrane environment. The examination of the mechanism of action of peptides suggests that peptide pept_352 exhibits a direct membranolytic activity. Furthermore, the cytotoxicity assay demonstrated that the nontoxic peptide pept_1545 is a promising candidate for drug development. Overall, the analysis method implemented in the study may serve as an effective tool for the identification of new AMPs.

Synergies with and Resistance to Membrane-Active Peptides

Membrane-active peptides (MAPs) have long been thought of as the key to defeating antimicrobial-resistant microorganisms. Such peptides, however, may not be sufficient alone. In this review, we seek to highlight some of the common pathways for resistance, as well as some avenues for potential synergy. This discussion takes place considering resistance, and/or synergy in the extracellular space, at the membrane, and during interaction, and/or removal. Overall, this review shows that researchers require improved definitions of resistance and a more thorough understanding of MAP-resistance mechanisms. The solution to combating resistance may ultimately come from an understanding of how to harness the power of synergistic drug combinations.

Time to Change Theory; Medical Leech from a Molecular Medicine Perspective Leech Salivary Proteins Playing a Potential Role in Medicine

Followed by developing modern medicine, leeches did not have extensive use as before; however, in the late 19th century, they were still used in most countries all over the world. Thus far, leeches were utilized in treating various diseases like skin disorders, arthritis, and cancer. In Egypt, using leeches for treatment dates back to early 1500 BC. A medical leech’s salivary glands involve over 100 bioactive proteins and the salivary gland secretion contains bacteriostatic, analgesic, and anticoagulation influences; with resolving activity, it causes microcirculation disorders elimination, restoring the hurt vascular permeability of organs and tissues, removing hypoxia, decreasing blood pressure and detoxifying the organism by antioxidant paths. The current work reviews the innovative treatment with medical leech, especially proteins in leech saliva extraction (LSE) with high potential in medicine. The virtue of salivary gland secretions which are proteinaceous enzymes, leech acts on various diseases such as venous congestion in reconstructive and plastic surgery, osteoarthritis, cardiovascular diseases caused by blood coagulation disorders, pain management, priapism, macroglossia, cancer complications, wounds and many other. To confirm the potential therapeutic impacts of leech treatment, more studies are required in more extensive areas with more exact methodologies.

Antimicrobial peptide selection from Lippia spp leaf transcriptomes

Antimicrobial resistance is considered a health issue worldwide. This public health problem underscores the importance of searching for new antimicrobial molecules with different mechanisms of action. Leaf transcriptomes were used to search and develop synthetic antimicrobial peptides derived from mRNA sequences. The in silico search for new AMPs from the L. rotundifolia and L. alba transcriptomes allowed the identification of 120 putative peptide mRNA sequences. Eight of them fitted into optimal parameters and were translated and chemically synthesized antimicrobial peptides. Their biological activity was tested in both Gram-positive and Gram-negative bacteria against which they exhibited antibacterial activity. However, they showed an important hemolytic effect. Afterwards, two active peptides showing bactericidal activity isolated from each plant transcriptome tested were modified and modeled in 11 new variants to increase their antimicrobial activity and stability and to reduce or eliminate their hemolytic effect from their original peptides. The La-AMP1 (MSLLERKLLMHFLRV) the original peptide from L. alba showed a 52% hemolytic effect while the derived peptide La-AMP1a (GLMKLLRELLHMFSRVG) had its hemolytic effect reduced to 0.5% at 128 μg.mL^-1. Similarly, we observed that the original peptide from L. rotundifolia, Lr-AMP1 (MRIGLRFVLM), displayed a 71.5% hemolytic effect, while its derived peptide Lr-AMP1f (GSVLRAIMRMFAKLMG) showed 0% hemolysis at 128 μg.mL^-1, tested with fresh human erythrocytes. Our results indicate a promising method for the search for novel antimicrobial agents with reduced or zero hemolytic effect, as well as prediction and optimization of their activity from plant mRNA libraries.

Recent Developments in Infectious Disease Chemotherapy: Review for Emergency Department Practitioners 2020

Purpose of Review

We discuss and review new antimicrobials for treatment of bacterial, viral, fungal, and parasitic infections with indications, contraindications, and side effects for each. We will also review new information and indications on older agents that are relevant to clinical practice. Many of them may be unfamiliar to Emergency Physicians given their newness and at times hospital restrictions on their use. We also review some new promising agents that are not yet in the clinical pipeline.

Recent Findings

As new antibiotics become available for clinicians to use, new information becomes available with respect to the drugs' indications, efficacy, pathogen resistance, drug-drug interactions, and side effects.

Summary

This article provides Emergency Department clinicians with a useful summary with new information on antibiotic use and recent research into agents which may become available.

Curved or linear? Predicting the 3-dimensional structure of α-helical antimicrobial peptides in an amphipathic environment

α-Helical membrane-active antimicrobial peptides (AMPs) are known to act via a range of mechanisms, including the formation of barrel-stave and toroidal pores and the micellisation of the membrane (carpet mechanism). Different mechanisms imply that the peptides adopt different 3D structures when bound at the water-membrane interface, a highly amphipathic environment. Here, an evolutionary algorithm is used to predict the 3D structure of a range of α-helical membrane-active AMPs at the water-membrane interface by optimising amphipathicity. This amphipathic structure prediction (ASP) is capable of distinguishing between curved and linear peptides solved experimentally, potentially allowing the activity and mechanism of action of different membrane-active AMPs to be predicted. The ASP algorithm is accessible via a web interface at http://atb.uq.edu.au/asp/.