Manipulation of innate immunity by a bacterial secreted peptide: lantibiotic nisin Z is selectively immunomodulatory

Intestinal delivery of encapsulated bacteriocin peptides in cross-linked alginate microcapsules

Oral delivery of larger bioactive peptides (>20 amino acids) to the small intestine remains a challenge due to their sensitivity to proteolytic degradation and chemical denaturation during gastrointestinal transit. In this study, we investigated the capacity of crosslinked alginate microcapsules (CLAMs) formed by spray drying to protect Plantaricin EF (PlnEF) (C-EF) in gastric conditions and to dissolve and release PlnEF in the small intestine. PlnEF is an unmodified, two-peptide (PlnE: 33 amino acids; PlnF: 34 amino acids) bacteriocin produced by Lactiplantibacillus plantarum with antimicrobial and gut barrier protective properties. After 2 h incubation in simulated gastric fluid (SGF) (pH 1.5), 43.39 % ± 8.27 % intact PlnEF was liberated from the CLAMs encapsulates, as determined by an antimicrobial activity assay. Transfer of the undissolved fraction to simulated intestinal fluid (SIF) (pH 7) for another 2 h incubation resulted in an additional release of 16.13 % ± 4.33 %. No active PlnEF was found during SGF or sequential SIF incubations when pepsin (2,000 U/ml) was added to the SGF. To test PlnEF release in C-EF contained in a food matrix, C-EF was mixed in peanut butter (PB) (0.15 g C-EF in 1.5 g PB). A total of 12.52 % ± 9.09 % active PlnEF was detected after incubation of PB + C-EF in SGF without pepsin, whereas no activity was found when pepsin was included. Transfer of the remaining PB + C-EF fractions to SIF yielded the recovery of 46.67 % ± 13.09 % and 39.42 % ± 11.53 % active PlnEF in the SIF following exposure to SGF and to SGF with pepsin, respectively. Upon accounting for the undissolved fraction after SIF incubation, PlnEF was fully protected in the CLAMs-PB mixture and there was not a significant reduction in active PlnEF when pepsin was present. These results show that CLAMs alone do not guard PlnEF bacteriocin peptides from gastric conditions, however, mixing them in PB protected against proteolysis and improved intestinal release.

Immunomodulatory properties of Bacillus subtilis extracellular vesicles on rainbow trout intestinal cells and splenic leukocytes

Extracellular vesicles (EVs) are cell-derived membrane-surrounded vesicles that carry bioactive molecules. Among EVs, outer membrane vesicles (OMVs), specifically produced by Gram-negative bacteria, have been extensively characterized and their potential as vaccines, adjuvants or immunotherapeutic agents, broadly explored in mammals. Nonetheless, Gram-positive bacteria can also produce bilayered spherical structures from 20 to 400 nm involved in pathogenesis, antibiotic resistance, nutrient uptake and nucleic acid transfer. However, information regarding their immunomodulatory potential is very scarce, both in mammals and fish. In the current study, we have produced EVs from the Gram-positive probiotic Bacillus subtilis and evaluated their immunomodulatory capacities using a rainbow trout intestinal epithelial cell line (RTgutGC) and splenic leukocytes. B. subtilis EVs significantly up-regulated the transcription of several pro-inflammatory and antimicrobial genes in both RTgutGC cells and splenocytes, while also up-regulating many genes associated with B cell differentiation in the later. In concordance, B. subtilis EVs increased the number of IgM-secreting cells in splenocyte cultures, while at the same time increased the MHC II surface levels and antigen-processing capacities of splenic IgM+ B cells. Interestingly, some of these experiments were repeated comparing the effects of B. subtilis EVs to EVs obtained from another Bacillus species, Bacillus megaterium, identifying important differences. The data presented provides evidence of the immunomodulatory capacities of Gram-positive EVs, pointing to the potential of B. subtilis EVs as adjuvants or immunostimulants for aquaculture.

Effects of dietary Nisin on growth performance, immune function, and gut health of broilers challenged by Clostridium perfringens

Nisin (Ni) is a polypeptide bacteriocin produced by lactic streptococci (probiotics) that can inhibit the majority of gram-positive bacteria, and improve the growth performance of broilers, and exert antioxidative and anti-inflammatory properties. The present study investigated the potential preventive effect of Nisin on necrotic enteritis induced by Clostridium perfringens (Cp) challenge. A total of 288 Arbor Acres broiler chickens of 1-d-olds were allocated using 2 × 2 factorial arrangement into four groups with six replicates (12 chickens per replicate), including: (1) control group (Con, basal diet), (2) Cp challenge group (Cp, basal diet + 1.0 × 108 CFU/mL Cp), (3) Ni group (Ni, basal diet + 100 mg/kg Ni), and (4) Ni + Cp group (Ni + Cp, basal diet + 100 mg/kg Ni + 1.0 × 108 CFU/mL Cp). The results showed that Cp challenge decreased the average daily gain (ADG) of days 15 to 21 (P<0.05) and increased interleukin-6 (IL-6) content in the serum (P < 0.05), as well as a significant reduction in villus height (VH) and the ratio of VH to crypt depth (VCR) (P<0.05) and a significant increase in crypt depth (CD) of jejunum (P<0.05). Furthermore, the mRNA expressions of Occludin and Claudin-1 were downregulated (P<0.05), while the mRNA expressions of Caspase3, Caspase9, Bax, and Bax/Bcl-2 were upregulated (P<0.05) in the jejunum. However, the inclusion of dietary Ni supplementation significantly improved body weight (BW) on days 21 and 28, ADG of days 15 to 21 (P<0.05), decreased CD in the jejunum, and reduced tumor necrosis factor-α (TNF-α) content in the serum (P<0.05). Ni addition upregulated the mRNA levels of Claudin-1 expression and downregulated the mRNA expression levels of Caspase9 in the jejunum (P<0.05). Moreover, Cp challenge and Ni altered the cecal microbiota composition, which manifested that Cp challenge decreased the relative abundance of phylum Fusobacteriota and increased Shannon index (P<0.05) and the trend of phylum Proteobacteria (0.05 Collapse

Key Words

• Clostridium perfringens
• broiler
• gut health
• necrotic enteritis
• nisin

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MESH Headings

• Animals
• Clostridium perfringens
• Chickens
• Intestines
• Clostridium Infections/prevention & control
• Clostridium Infections/veterinary
• Clostridium Infections/microbiology
• Nisin/pharmacology
• Claudin-1
• bcl-2-Associated X Protein/pharmacology
• Diet/veterinary
• RNA, Messenger/genetics
• Immunity
• Poultry Diseases/microbiology
• Dietary Supplements
• Animal Feed/analysis

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Affiliation(s)

Hua Yuan College of Animal Science and Technology, Northeast Agricultural University, Harbin 150030, China
Guangdong Bai College of Animal Science and Technology, Northeast Agricultural University, Harbin 150030, China College of Animal Science and Technology, Southwest University, Chongqing 400715, China
Yu Lin College of Animal Science and Technology, Northeast Agricultural University, Harbin 150030, China
Xilong Yu College of Animal Science and Technology, Northeast Agricultural University, Harbin 150030, China
Qinghui Yang College of Animal Science and Technology, Northeast Agricultural University, Harbin 150030, China
Renkai Dou College of Animal Science and Technology, Northeast Agricultural University, Harbin 150030, China
Hao Sun College of Animal Science and Technology, Northeast Agricultural University, Harbin 150030, China
Zeyu Zhao College of Animal Science and Technology, Northeast Agricultural University, Harbin 150030, China
Zhongyu Li College of Animal Science and Technology, Northeast Agricultural University, Harbin 150030, China
Zhihui Chen College of Animal Science and Technology, Northeast Agricultural University, Harbin 150030, China
Liangmei Xu College of Animal Science and Technology, Northeast Agricultural University, Harbin 150030, China

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Bioactive Ingredients from Dairy-Based Lactic Acid Bacterial Fermentations for Functional Food Production and Their Health Effects

Lactic acid bacteria are traditionally applied in a variety of fermented food products, and they have the ability to produce a wide range of bioactive ingredients during fermentation, including vitamins, bacteriocins, bioactive peptides, and bioactive compounds. The bioactivity and health benefits associated with these ingredients have garnered interest in applications in the functional dairy market and have relevance both as components produced in situ and as functional additives. This review provides a brief description of the regulations regarding the functional food market in the European Union, as well as an overview of some of the functional dairy products currently available in the Irish and European markets. A better understanding of the production of these ingredients excreted by lactic acid bacteria can further drive the development and innovation of the continuously growing functional food market.

Nisin a probiotic bacteriocin mitigates brain microbiome dysbiosis and Alzheimer's disease-like neuroinflammation triggered by periodontal disease

INTRODUCTION

Periodontitis-related oral microbial dysbiosis is thought to contribute to Alzheimer's disease (AD) neuroinflammation and brain amyloid production. Since probiotics can modulate periodontitis/oral dysbiosis, this study examined the effects of a probiotic/lantibiotic, nisin, in modulating brain pathology triggered by periodontitis.

METHODS

A polymicrobial mouse model of periodontal disease was used to evaluate the effects of this disease on brain microbiome dysbiosis, neuroinflammation, Alzheimer's-related changes, and nisin's therapeutic potential in this context.

RESULTS

16S sequencing and real-time PCR data revealed that Nisin treatment mitigated the changes in the brain microbiome composition, diversity, and community structure, and reduced the levels of periodontal pathogen DNA in the brain induced by periodontal disease. Nisin treatment significantly decreased the mRNA expression of pro-inflammatory cytokines (Interleukin-1β/IL-1 β, Interleukin 6/IL-6, and Tumor Necrosis Factor α/TNF-α) in the brain that were elevated by periodontal infection. In addition, the concentrations of amyloid-β 42 (Aβ42), total Tau, and Tau (pS199) (445.69 ± 120.03, 1420.85 ± 331.40, 137.20 ± 36.01) were significantly higher in the infection group compared to the control group (193.01 ± 31.82, 384.27 ± 363.93, 6.09 ± 10.85), respectively. Nisin treatment markedly reduced the Aβ42 (261.80 ± 52.50), total Tau (865.37 ± 304.93), and phosphorylated Tau (82.53 ± 15.77) deposition in the brain of the infection group.

DISCUSSION

Nisin abrogation of brain microbiome dysbiosis induces beneficial effects on AD-like pathogenic changes and neuroinflammation, and thereby may serve as a potential therapeutic for periodontal-dysbiosis-related AD.

Multiple potential strategies for the application of nisin and derivatives

Nisin is a naturally occurring bioactive small peptide produced by Lactococcus lactis subsp. lactis and belongs to the Type A (I) lantibiotics. Due to its potent antimicrobial activity, it has been broadly employed to preserve various food materials as well as to combat a variety of microbial pathogens. The present review discusses the antimicrobial properties of nisin and different types of their derivatives employed to treat microbial pathogens with a detailed underlying mechanism of action. Several alternative strategies such as combination, conjugation, and nanoformulations have been discussed in order to address several issues such as rapid degradation, instability, and reduced activity due to the various environmental factors that arise in the applications of nisin. Furthermore, the evolutionary relationship of many nisin genes from different nisin-producing bacterial species has been investigated. A detailed description of the natural and bioengineered nisin variants, as well as the underlying action mechanisms, has also been provided. The chemistry used to apply nisin in conjugation with natural or synthetic compounds as a synergetic mode of antimicrobial action has also been thoroughly discussed. The current review will be useful in learning about recent and past research that has been performed on nisin and its derivatives as antimicrobial agents.

Discovery and Characterization of a Myxobacterial Lanthipeptide with Unique Biosynthetic Features and Anti-inflammatory Activity

The genomes of myxobacteria harbor a variety of biosynthetic gene clusters encoding numerous secondary metabolites, including ribosomally synthesized and post-translationally modified peptides (RiPPs) with diverse chemical structures and biological activities. However, the biosynthetic potential of RiPPs from myxobacteria remains barely explored. Herein, we report a novel myxobacteria lanthipeptide myxococin identified from Myxococcus fulvus. Myxococins represent the first example of lanthipeptides, of which the characteristic multiple thioether rings are installed by employing a Class II lanthipeptide synthetase MfuM and a Class I lanthipeptide cyclase MfuC in a cascaded way. Unprecedentedly, we biochemically characterized the first M61 family aminopeptidase MfuP involved in RiPP biosynthesis, demonstrating that MfuP showed the activity of an endopeptidase activity. MfuP is leader-independent but strictly selective for the multibridge structure of myxococin A and responsible for unwrapping two rings via amide bond hydrolysis, yielding myxococin B. Furthermore, the X-ray crystal structure of MfuP and structural analysis, including active-site mutations, are reported. Finally, myxococins are evaluated to exhibit anti-inflammatory activity in lipopolysaccharide-induced macrophages without detectable cytotoxicity.

Discovery of phosphorylated lantibiotics with proimmune activity that regulate the oral microbiome

Lantibiotics are ribosomally synthesized and posttranslationally modified peptides (RiPPs) that are produced by bacteria. Interest in this group of natural products is increasing rapidly as alternatives to conventional antibiotics. Some human microbiome-derived commensals produce lantibiotics to impair pathogens' colonization and promote healthy microbiomes. Streptococcus salivarius is one of the first commensal microbes to colonize the human oral cavity and gastrointestinal tract, and its biosynthesis of RiPPs, called salivaricins, has been shown to inhibit the growth of oral pathogens. Herein, we report on a phosphorylated class of three related RiPPs, collectively referred to as salivaricin 10, that exhibit proimmune activity and targeted antimicrobial properties against known oral pathogens and multispecies biofilms. Strikingly, the immunomodulatory activities observed include upregulation of neutrophil-mediated phagocytosis, promotion of antiinflammatory M2 macrophage polarization, and stimulation of neutrophil chemotaxis-these activities have been attributed to the phosphorylation site identified on the N-terminal region of the peptides. Salivaricin 10 peptides were determined to be produced by S. salivarius strains found in healthy human subjects, and their dual bactericidal/antibiofilm and immunoregulatory activity may provide new means to effectively target infectious pathogens while maintaining important oral microbiota.

BacSp222 bacteriocin as a novel ligand for TLR2/TLR6 heterodimer

OBJECTIVE AND DESIGN

BacSp222 bacteriocin is a bactericidal and proinflammatory peptide stimulating immune cells to produce selected cytokines and NO in NF-ĸB dependent manner. This study aims to identify the receptor which mediates this activity.

METHODS

We applied fluorescently labeled BacSp222 and a confocal microscopy imaging to analyze the direct interaction of the bacteriocin with the cells. Reporter HEK-Blue cells overexpressing human toll-like receptors (TLR2, TLR4, TLR5 or TLR2/TLR1 and TLR2/TLR6 heterodimers) were stimulated with BacSp222, and then the activity of NF-ĸB-dependent secreted embryonic alkaline phosphatase (SEAP) was measured. In turn, formylated peptide receptor (FPR) or TLR2 antagonists were used to verify bacteriocin-stimulated TNF production by murine monocyte-macrophage cell lines.

RESULTS

BacSp222 undergoes internalization into cells without disturbing the cell membrane. FPR antagonists do not affect TNF produced by BacSp222-stimulated murine macrophage-like cells. In contrast, BacSp222 stimulates NF-ĸB activation in HEK-Blue overexpressing TLR2 or TLR2/TLR6 heterodimer, but not TLR2/TLR1, TLR4 or TLR5 receptors. Moreover, TLR2-specific antagonists inhibit NF-ĸB signaling in BacSp222-stimulated HEK-Blue TLR2/TLR6 cells and reduce TNF release by BacSp222-treated RAW 264.7 and P388.D1.

CONCLUSIONS

BacSp222 is a novel ligand for TLR2/TLR6 heterodimer. By binding TLR complex the bacteriocin undergoes internalization, inducing proinflammatory signaling that employs MyD88 and NF-ĸB pathways.

Anti-inflammatory and wound healing properties of lactic acid bacteria and its peptides

Recent studies manifest an increase of inflammatory diseases at an alarming rate due to gut microbiota dysbiosis, genetic and other environmental factors. Lactic acid bacteria (LAB) are known for their antimicrobial properties and their extensive applications in food and pharmaceutical industries. Cyclic peptides are receiving increased attention due to their remarkable stability to withstand variations in temperature and pH. LAB produces anti-inflammatory that can inhibit lipopolysaccharide-induced production of proinflammatory cytokines in macrophages. The structural backbones of cyclic peptides offer a promising approach for the treatment of chronic inflammatory conditions. The current review aims to present the overview of anti-inflammatory and wound healing properties of LAB-derived cyclic peptides.

Immunomodulatory effects of bacteriocinogenic and non-bacteriocinogenic Lactococcus cremoris of aquatic origin on rainbow trout (Oncorhynchus mykiss, Walbaum)

Lactic Acid Bacteria (LAB) are a group of bacteria frequently proposed as probiotics in aquaculture, as their administration has shown to confer positive effects on the growth, survival rate to pathogens and immunological status of the fish. In this respect, the production of antimicrobial peptides (referred to as bacteriocins) by LAB is a common trait thoroughly documented, being regarded as a key probiotic antimicrobial strategy. Although some studies have pointed to the direct immunomodulatory effects of these bacteriocins in mammals, this has been largely unexplored in fish. To this aim, in the current study, we have investigated the immunomodulatory effects of bacteriocins, by comparing the effects of a wild type nisin Z-expressing Lactococcus cremoris strain of aquatic origin to those exerted by a non-bacteriocinogenic isogenic mutant and a recombinant nisin Z, garvicin A and Q-producer multi-bacteriocinogenic strain. The transcriptional response elicited by the different strains in the rainbow trout intestinal epithelial cell line (RTgutGC) and in splenic leukocytes showed significant differences. Yet the adherence capacity to RTgutGC was similar for all strains. In splenocyte cultures, we also determined the effects of the different strains on the proliferation and survival of IgM⁺ B cells. Finally, while the different LAB elicited respiratory burst activity similarly, the bacteriocinogenic strains showed an increased ability to induce the production of nitric oxide (NO). The results obtained reveal a superior capacity of the bacteriocinogenic strains to modulate different immune functions, pointing to a direct immunomodulatory role of the bacteriocins, mainly nisin Z.

Antimicrobial Activity and Immunomodulatory Properties of Acidocin A, the Pediocin-like Bacteriocin with the Non-Canonical Structure

Pediocin-like bacteriocins are among the natural antimicrobial agents attracting attention as scaffolds for the development of a new generation of antibiotics. Acidocin A has significant structural differences from most other members of this subclass. We studied its antibacterial and cytotoxic activity, as well as effects on the permeability of E. coli membranes in comparison with avicin A, the typical pediocin-like bacteriocin. Acidocin A had a more marked tendency to form an alpha-helical structure upon contact with detergent micelles, as was shown by CD spectroscopy, and demonstrated considerably less specific mode of action: it inhibited growth of Gram-positive and Gram-negative strains, which were unsusceptible to avicin A, and disrupted the integrity of outer and inner membranes of E. coli. However, the peptide retained a low toxicity towards normal and tumor human cells. The effect of mutations in the pediocin box of acidocin A (on average, a 2-4-fold decrease in activity) was less pronounced than is usually observed for such peptides. Using multiplex analysis, we showed that acidocin A and avicin A modulated the expression level of a number of cytokines and growth factors in primary human monocytes. Acidocin A induced the production of a number of inflammatory mediators (IL-6, TNFα, MIG/CXCL9, MCP-1/CCL2, MCP-3/CCL7, and MIP-1β) and inhibited the production of some anti-inflammatory factors (IL-1RA, MDC/CCL22). We assumed that the activity of acidocin A and similar peptides produced by lactic acid bacteria might affect the functional state of the human intestinal tract, not only through direct inhibition of various groups of symbiotic and pathogenic bacteria, but also via immunomodulatory effects.

Surface Functionalization of Ti6Al4V-ELI Alloy with Antimicrobial Peptide Nisin

Implant-associated infections are a severe global concern, especially in the case of orthopedic implants intended for long-term or permanent use. The traditional treatment through systemic antibiotic administration is often inefficient due to biofilm formation, and concerns regarding the development of highly resistant bacteria. Therefore, there is an unfulfilled need for antibiotic-free alternatives that could simultaneously support bone regeneration and prevent bacterial infection. This study aimed to perform, optimize, and characterize the surface functionalization of Ti6Al4V-ELI discs by an FDA-approved antimicrobial peptide, nisin, known to hold a broad antibacterial spectrum. Accordingly, nisin bioactivity was also evaluated by in vitro release tests both in physiological and inflammatory pH conditions. Several methods, such as X-ray photoelectron spectroscopy (XPS), and Kelvin Probe atomic force microscopy confirmed the presence of a physisorbed nisin layer on the alloy surface. The functionalization performed at pH 6-7 was found to be especially effective due to the nisin configuration exposing its hydrophobic tail outwards, which is also responsible for its antimicrobial action. In addition, the first evidence of gradual nisin release both in physiological and inflammatory conditions was obtained: the static contact angle becomes half of the starting one after 7 days of soaking on the functionalized sample, while it becomes 0° on the control samples. Finally, the evaluation of the antibacterial performance toward the pathogen Staphylococcus aureus after 24 h of inoculation showed the ability of nisin adsorbed at pH 6 to prevent bacterial microfouling into biofilm-like aggregates in comparison with the uncoated specimens: viable bacterial colonies showed a reduction of about 40% with respect to the un-functionalized surface and the formation of (microcolonies (biofilm-like aggregates) is strongly affected.

Tonsillar Microbiome-Derived Lantibiotics Induce Structural Changes of IL-6 and IL-21 Receptors and Modulate Host Immunity

Emerging evidence emphasizes the functional impacts of host microbiome on the etiopathogenesis of autoimmune diseases, including rheumatoid arthritis (RA). However, there are limited mechanistic insights into the contribution of microbial biomolecules especially microbial peptides toward modulating immune homeostasis. Here, by mining the metagenomics data of tonsillar microbiome, a deficiency of the encoding genes of lantibiotic peptides salivaricins in RA patients is identified, which shows strong correlation with circulating immune cells. Evidence is provided that the salivaricins exert immunomodulatory effects in inhibiting T follicular helper (Tfh) cell differentiation and interleukin-21 (IL-21) production. Mechanically, salivaricins directly bind to and induce conformational changes of IL-6 and IL-21 receptors, thereby inhibiting the bindings of IL-6 and IL-21 to their receptors and suppressing the downstream signaling pathway. Finally, salivaricin administration exerts both prophylactic and therapeutic effects against experimental arthritis in a murine model of RA. Together, these results provide a mechanism link of microbial peptides-mediated immunomodulation.

Bacteriocin BacSp222 and Its Succinylated Forms Exhibit Proinflammatory Activities Toward Innate Immune Cells

Purpose

The zoonotic opportunistic pathogen Staphylococcus pseudintermedius 222 produces BacSp222 - an atypical peptide exhibiting the features of a bacteriocin, a virulence factor, and a molecule modulating the host inflammatory reaction. The peptide is secreted in an unmodified form and, additionally, two forms modified posttranslationally by succinylation. This study is a comprehensive report focusing on the proinflammatory properties of such molecules.

Methods

The study was performed on mouse monocyte/macrophage-like and endothelial cell lines as well as human neutrophils. The following peptides were studied: BacSp222, its succinylated forms, the form deprived of formylated methionine, and a reference bacteriocin - nisin. The measurements of the nitric oxide (NO) level, induced NO synthase (iNOS) expression, the profile of secreted cytokines, NF-kappa-B activation, reactive oxygen species (ROS) biosynthesis, and the formation of extracellular traps were conducted to evaluate the proinflammatory activity of the studied peptides.

Results

BacSp222 and its succinylated forms effectively induced NO production and iNOS expression when combined with IFN-gamma in macrophage-like cells. All natural BacSp222 forms used alone or with IFN-gamma stimulated the production of TNF-alpha, MCP-1, and IL-1-alpha, while the co-stimulation with IFN-gamma increased IL-10 and IL-27. Upregulated TNF-alpha secretion observed after BacSp222 exposition resulted from increased expression but not from membrane TNF-alpha proteolysis. In neutrophils, all forms of bacteriocin upregulated IL-8, but did not induce ROS production or NETs formation. In all experiments, the activities of deformylated bacteriocin were lower or unequivocal in comparison to other forms of the peptide.

Conclusion

All naturally secreted forms of BacSp222 exhibit proinflammatory activity against monocyte-macrophage cells and neutrophils, confirming that the biological role of BacSp222 goes beyond bactericidal and cytotoxic effects. The atypical posttranslational modification (succinylation) does not diminish its immunomodulatory activity in contrast to the lower antibacterial potential or cytotoxicity of such modified form established in previous studies.

Nanocarriers for effective delivery: modulation of innate immunity for the management of infections and the associated complications

Innate immunity is the first line of defense against invading pathogens. Innate immune cells can recognize invading pathogens through recognizing pathogen-associated molecular patterns (PAMPs) via pattern recognition receptors (PRRs). The recognition of PAMPs by PRRs triggers immune defense mechanisms and the secretion of pro-inflammatory cytokines such as TNF-α, IL-1β, and IL-6. However, sustained and overwhelming activation of immune system may disrupt immune homeostasis and contribute to inflammatory disorders. Immunomodulators targeting PRRs may be beneficial to treat infectious diseases and their associated complications. However, therapeutic performances of immunomodulators can be negatively affected by (1) high immune-mediated toxicity, (2) poor solubility and (3) bioactivity loss after long circulation. Recently, nanocarriers have emerged as a very promising tool to overcome these obstacles owning to their unique properties such as sustained circulation, desired bio-distribution, and preferred pharmacokinetic and pharmacodynamic profiles. In this review, we aim to provide an up-to-date overview on the strategies and applications of nanocarrier-assisted innate immune modulation for the management of infections and their associated complications. We first summarize examples of important innate immune modulators. The types of nanomaterials available for drug delivery, as well as their applications for the delivery of immunomodulatory drugs and vaccine adjuvants are also discussed.

Probiotic-Based Bacteriocin: Immunity Supplementation Against Viruses. An Updated Review

Viral infections are a major cause of severe, fatal diseases worldwide. Recently, these infections have increased due to demanding contextual circumstances, such as environmental changes, increased migration of people and product distribution, rapid demographic changes, and outbreaks of novel viruses, including the COVID-19 outbreak. Internal variables that influence viral immunity have received attention along with these external causes to avert such novel viral outbreaks. The gastrointestinal microbiome (GIM), particularly the present probiotics, plays a vital role in the host immune system by mediating host protective immunity and acting as an immune regulator. Bacteriocins possess numerous health benefits and exhibit antagonistic activity against enteric pathogens and immunobiotics, thereby inhibiting viral infections. Moreover, disrupting the homeostasis of the GIM/host immune system negatively affects viral immunity. The interactions between bacteriocins and infectious viruses, particularly in COVID-19, through improved host immunity and physiology are complex and have not yet been studied, although several studies have proven that bacteriocins influence the outcomes of viral infections. However, the complex transmission to the affected sites and siRNA defense against nuclease digestion lead to challenging clinical trials. Additionally, bacteriocins are well known for their biofunctional properties and underlying mechanisms in the treatment of bacterial and fungal infections. However, few studies have shown the role of probiotics-derived bacteriocin against viral infections. Thus, based on the results of the previous studies, this review lays out a road map for future studies on bacteriocins for treating viral infections.

Identification and Functional Characterization of Peptides With Antimicrobial Activity From the Syphilis Spirochete, Treponema pallidum

The etiological agent of syphilis, Treponema pallidum ssp. pallidum, is a highly invasive “stealth” pathogen that can evade the host immune response and persist within the host for decades. This obligate human pathogen is adept at establishing infection and surviving at sites within the host that have a multitude of competing microbes, sometimes including pathogens. One survival strategy employed by bacteria found at polymicrobial sites is elimination of competing microorganisms by production of antimicrobial peptides (AMPs). Antimicrobial peptides are low molecular weight proteins (miniproteins) that function directly via inhibition and killing of microbes and/or indirectly via modulation of the host immune response, which can facilitate immune evasion. In the current study, we used bioinformatics to show that approximately 7% of the T. pallidum proteome is comprised of miniproteins of 150 amino acids or less with unknown functions. To investigate the possibility that AMP production is an unrecognized defense strategy used by T. pallidum during infection, we developed a bioinformatics pipeline to analyze the complement of T. pallidum miniproteins of unknown function for the identification of potential AMPs. This analysis identified 45 T. pallidum AMP candidates; of these, Tp0451a and Tp0749 were subjected to further bioinformatic analyses to identify AMP critical core regions (AMPCCRs). Four potential AMPCCRs from the two predicted AMPs were identified and peptides corresponding to these AMPCCRs were experimentally confirmed to exhibit bacteriostatic and bactericidal activity against a panel of biologically relevant Gram-positive and Gram-negative bacteria. Immunomodulation assays performed under inflammatory conditions demonstrated that one of the AMPCCRs was also capable of differentially regulating expression of two pro-inflammatory chemokines [monocyte chemoattractant protein-1 (MCP-1) and interleukin-8 (IL-8)]. These findings demonstrate proof-of-concept for our developed AMP identification pipeline and are consistent with the novel concept that T. pallidum expresses AMPs to defend against competing microbes and modulate the host immune response.

Nisin Z attenuates lipopolysaccharide-induced mastitis by inhibiting the ERK1/2 and p38 mitogen-activated protein kinase signaling pathways

Nisin Z is a possible alternative for treating bovine mastitis by inhibiting mastitis-causing pathogens and having anti-inflammatory activity. However, the anti-inflammatory mechanism of nisin Z on mastitis is unknown. Our study aimed to investigate the mechanisms of nisin Z on mastitis. Our results showed that nisin Z inhibited the activation of the ERK1/2 and p38 mitogen-activated protein kinase (MAPK) signaling pathway, decreased the release of pro-inflammatory cytokines (i.e., tumor necrosis factor-α, IL-1β, and IL-6), and increased the anti-inflammatory cytokine (IL-10) in lipopolysaccharide (LPS)-induced MCF10A cells. After intraperitoneal injection, nisin Z significantly decreased inflammatory cell infiltration in the mammary gland, as well as decreased myeloperoxidase and pro-inflammatory cytokines in serum and mammary gland. Western blot analysis revealed that nisin Z also dramatically suppressed the activation of the ERK1/2 and p38 MAPK signaling pathways in LPS-induced mastitis mice. We also found that nisin Z treatment could enhance the blood-milk barrier. In summary, our study demonstrated that nisin Z exerted an anti-inflammatory effect by inhibiting the ERK1/2 and p38 MAPK signaling pathway and promoting the blood-milk barrier on LPS-induced mastitis.

Molecular and Cellular Mechanisms Influenced by Postbiotics

In recent years, commensal bacteria colonizing the human body have been recognized as important determinants of health and multiple pathologic conditions. Among the most extensively studied commensal bacteria are the gut microbiota, which perform a plethora of functions, including the synthesis of bioactive products, metabolism of dietary compounds, and immunomodulation, both through attenuation and immunostimulation. An imbalance in the microbiota population, i.e., dysbiosis, has been linked to many human pathologies, including various cancer types and neurodegenerative diseases. Targeting gut microbiota and microbiome-host interactions resulting from probiotics, prebiotics, and postbiotics is a growing opportunity for the effective treatment of various diseases. As more research is being conducted, the microbiome field is shifting from simple descriptive analysis of commensal compositions to more molecular, cellular, and functional studies. Insight into these mechanisms is of paramount importance for understanding and modulating the effects that microbiota, probiotics, and their derivatives exert on host health.

The antimicrobial and immunomodulatory effects of Ionophores for the treatment of human infection

Ionophores are a diverse class of synthetic and naturally occurring ion transporter compounds which demonstrate both direct and in-direct antimicrobial properties against a broad panel of bacterial, fungal, viral and parasitic pathogens. In addition, ionophores can regulate the host-immune response during communicable and non-communicable disease states. Although the clinical use of ionophores such as Amphotericin B, Bedaquiline and Ivermectin highlight the utility of ionophores in modern medicine, for many other ionophore compounds issues surrounding toxicity, bioavailability or lack of in vivo efficacy studies have hindered clinical development. The antimicrobial and immunomodulating properties of a range of compounds with characteristics of ionophores remain largely unexplored. As such, ionophores remain a latent therapeutic avenue to address both the global burden of antimicrobial resistance, and the unmet clinical need for new antimicrobial therapies. This review will provide an overview of the broad-spectrum antimicrobial and immunomodulatory properties of ionophores, and their potential uses in clinical medicine for combatting infection.

Antimicrobial Peptides and Their Applications in Biomedical Sector

In a report by WHO (2014), it was stated that antimicrobial resistance is an arising challenge that needs to be resolved. This resistance is a critical issue in terms of disease or infection treatment and is usually caused due to mutation, gene transfer, long-term usage or inadequate use of antimicrobials, survival of microbes after consumption of antimicrobials, and the presence of antimicrobials in agricultural feeds. One of the solutions to this problem is antimicrobial peptides (AMPs), which are ubiquitously present in the environment. These peptides are of concern due to their special mode of action against a wide spectrum of infections and health-related problems. The biomedical field has the highest need of AMPs as it possesses prominent desirable activity against HIV-1, skin cancer, breast cancer, in Behcet's disease treatment, as well as in reducing the release of inflammatory cells such as TNFα, IL-8, and IL-1β, enhancing the production of anti-inflammatory cytokines such as IL-10 and GM-CSF, and in wound healing properties. This review has highlighted all the major functions and applications of AMPs in the biomedical field and concludes the future potential of AMPs.

Therapeutic Application of Lantibiotics and Other Lanthipeptides: Old and New Findings

Lanthipeptides are ribosomally synthesized and posttranslationally modified peptides, with modifications that are incorporated during biosynthesis by dedicated enzymes. Various modifications of the peptides are possible, resulting in a highly diverse group of bioactive peptides that offer a potential reservoir for use in the fight against a plethora of diseases. Their activities range from the antimicrobial properties of lantibiotics, especially against antibiotic-resistant strains, to antiviral activity, immunomodulatory properties, antiallodynic effects, and the potential to alleviate cystic fibrosis symptoms. Lanthipeptide biosynthetic genes are widespread within bacterial genomes, providing a substantial repository for novel bioactive peptides. Using genome mining tools, novel bioactive lanthipeptides can be identified, and coupled with rapid screening and heterologous expression technologies, the lanthipeptide drug discovery pipeline can be significantly sped up. Lanthipeptides represent a group of bioactive peptides that hold great potential as biotherapeutics, especially at a time when novel and more effective therapies are required. With this review, we provide insight into the latest developments made toward the therapeutic applications and production of lanthipeptides, specifically looking at heterologous expression systems.

Bacteriocins from Lactic Acid Bacteria. A Powerful Alternative as Antimicrobials, Probiotics, and Immunomodulators in Veterinary Medicine

In the search for an alternative treatment to reduce antimicrobial resistance, bacteriocins shine a light on reducing this problem in public and animal health. Bacteriocins are peptides synthesized by bacteria that can inhibit the growth of other bacteria and fungi, parasites, and viruses. Lactic acid bacteria (LAB) are a group of bacteria that produce bacteriocins; their mechanism of action can replace antibiotics and prevent bacterial resistance. In veterinary medicine, LAB and bacteriocins have been used as antimicrobials and probiotics. However, another critical role of bacteriocins is their immunomodulatory effect. This review shows the advances in applying bacteriocins in animal production and veterinary medicine, highlighting their biological roles.

Nisin-A lantibiotic with immunomodulatory properties: A review

Nisin, a member of class I bacteriocins known as lantibiotics, is produced by the lactic acid bacterium Lactococcus lactis and is characterized by a wide spectrum of antibacterial activity against gram-positive bacteria. This characteristic in conjunction with its low toxicity and safety of use in food has contributed to the worldwide success of nisin as a natural food preservative. This lantibiotic has attracted interest as a potential natural therapeutic agent for the control of bacterial infections. However, similar to other antimicrobial peptides of natural origin, the spectrum of biological activity of nisin surpasses its antibacterial properties, encompassing interesting and incompletely understood immunotropic characteristics. This paper is a systematic review of the current information about the potential immunomodulatory properties of nisin based on in vitro and in vivo studies in various experimental models. We also discuss the effect of potentially probiotic, nisin-producing L. lactis strains on the immune system of animals.

Proteomic Adaptation of Clostridioides difficile to Treatment with the Antimicrobial Peptide Nisin

Clostridioides difficile is the leading cause of antibiotic-associated diarrhea but can also result in more serious, life-threatening conditions. The incidence of C. difficile infections in hospitals is increasing, both in frequency and severity, and antibiotic-resistant C. difficile strains are advancing. Against this background antimicrobial peptides (AMPs) are an interesting alternative to classic antibiotics. Information on the effects of AMPs on C. difficile will not only enhance the knowledge for possible biomedical application but may also provide insights into mechanisms of C. difficile to adapt or counteract AMPs. This study applies state-of-the-art mass spectrometry methods to quantitatively investigate the proteomic response of C. difficile 630∆erm to sublethal concentrations of the AMP nisin allowing to follow the cellular stress adaptation in a time-resolved manner. The results do not only point at a heavy reorganization of the cellular envelope but also resulted in pronounced changes in central cellular processes such as carbohydrate metabolism. Further, the number of flagella per cell was increased during the adaptation process. The potential involvement of flagella in nisin adaptation was supported by a more resistant phenotype exhibited by a non-motile but hyper-flagellated mutant.

Cyclic peptide production from lactic acid bacteria (LAB) and their diverse applications

In recent years, cyclic peptides gave gained increasing attention owing to their pH tolerance, heat stability and resistance to enzymatic actions. The increasing outbreaks of antibiotic resistant pathogens and food spoilage have prompted researchers to search for new approaches to combat them. The increasing number of reports on novel cyclic peptides from lactic acid bacteria (LAB) is considered as a breakthrough due to their potential applications. Although an extensive investigation is required to understand the mechanism of action and range of applications, LAB cyclic peptides can be considered as potential substitutes for commercially available antibiotics and bio preservatives. This review summarizes the current updates of LAB cyclic peptides with emphasis on their structure, mode of action and applications. Recent trends in cyclic peptide applications are also discussed.

Activity of five antimicrobial peptides against periodontal as well as non-periodontal pathogenic strains

Background: Due to the increasing emergence of multi-resistant bacteria the search for alternative antimicrobial substances is of high interest. Promising agents are antimicrobial peptides which are host defense molecules of the innate immune system in a wide range of different species. Objectives: The aim of this study was to assess the activity of nisin, melittin, lactoferrin, parasin-1 and LL-37 against 35 oral bacteria and Candida albicans employing the gold standard method for anaerobic susceptibility testing. Methods: The activity of the peptides was determined by an agar dilution method under anaerobic and aerobic conditions. The test media contained final peptide concentrations between 0.125 µg/ml and 8 µg/ml (melittin, lactoferrin, parasin-1, LL-37) and between 0.125 µg/ml and 128 µg/ml (nisin). Results: Nisin completely inhibited the growth of Megasphaera sp., Bifidobacterium longum, Parvimonas micra, Actinomyces israelii, Actinomyces naeslundii, Actinomyces odontolyticus, Prevotella intermedia, Streptococcus anginosus, Streptococcus constellatus and Staphylococcus aureus. Melittin and lactoferrin reduced the growth of Megasphaera sp., P. micra, B. longum (melittin) and Selenomonas flueggei (lactoferrin). Parasin-1 and LL-37 showed no activity. Conclusion: AMPs, especially nisin and to a smaller degree lactoferrin, might be promising alternatives to antibiotics because of their antimicrobial activity, high resistance to environmental conditions and partially low costs.

Probiotics at War Against Viruses: What Is Missing From the Picture?

Our world is now facing a multitude of novel infectious diseases. Bacterial infections are treated with antibiotics, albeit with increasing difficulty as many of the more common causes of infection have now developed broad spectrum antimicrobial resistance. However, there is now an even greater challenge from both old and new viruses capable of causing respiratory, enteric, and urogenital infections. Reports of viruses resistant to frontline therapeutic drugs are steadily increasing and there is an urgent need to develop novel antiviral agents. Although this all makes sense, it seems rather strange that relatively little attention has been given to the antiviral capabilities of probiotics. Over the years, beneficial strains of lactic acid bacteria (LAB) have been successfully used to treat gastrointestinal, oral, and vaginal infections, and some can also effect a reduction in serum cholesterol levels. Some probiotics prevent gastrointestinal dysbiosis and, by doing so, reduce the risk of developing secondary infections. Other probiotics exhibit anti-tumor and immunomodulating properties, and in some studies, antiviral activities have been reported for probiotic bacteria and/or their metabolites. Unfortunately, the mechanistic basis of the observed beneficial effects of probiotics in countering viral infections is sometimes unclear. Interestingly, in COVID-19 patients, a clear decrease has been observed in cell numbers of Lactobacillus and Bifidobacterium spp., both of which are common sources of intestinal probiotics. The present review, specifically motivated by the need to implement effective new counters to SARS-CoV-2, focusses attention on viruses capable of co-infecting humans and other animals and specifically explores the potential of probiotic bacteria and their metabolites to intervene with the process of virus infection. The goal is to help to provide a more informed background for the planning of future probiotic-based antiviral research.

Synergism between Host Defence Peptides and Antibiotics Against Bacterial Infections

Background:

Antimicrobial resistance (AMR) to conventional antibiotics is becoming one of the main global health threats and novel alternative strategies are urging. Antimicrobial peptides (AMPs), once forgotten, are coming back into the scene as promising tools to overcome bacterial resistance. Recent findings have attracted attention to the potentiality of AMPs to work as antibiotic adjuvants.

Methods:

In this review, we have tried to collect the currently available information on the mechanism of action of AMPs in synergy with other antimicrobial agents. In particular, we have focused on the mechanisms of action that mediate the inhibition of the emergence of bacterial resistance by AMPs.

Results and Conclusion:

We find in the literature many examples where AMPs can significantly reduce the antibiotic effective concentration. Mainly, the peptides work at the bacterial cell wall and thereby facilitate the drug access to its intracellular target. Complementarily, AMPs can also contribute to permeate the exopolysaccharide layer of biofilm communities, or even prevent bacterial adhesion and biofilm growth. Secondly, we find other peptides that can directly block the emergence of bacterial resistance mechanisms or interfere with the community quorum-sensing systems. Interestingly, the effective peptide concentrations for adjuvant activity and inhibition of bacterial resistance are much lower than the required for direct antimicrobial action. Finally, many AMPs expressed by innate immune cells are endowed with immunomodulatory properties and can participate in the host response against infection. Recent studies in animal models confirm that AMPs work as adjuvants at non-toxic concentrations and can be safely administrated for novel combined chemotherapies.

Antimicrobial activity of protein-containing fractions isolated from Lactobacillus plantarum NRRL B-4496 culture

The interest in lactic acid bacteria, including Lactobacillus plantarum NRRL B-4496, has increased in recent years as bio-preservatives, due to the production of secondary metabolites capable of inhibiting pathogenic bacteria. The objectives of this study were to evaluate the antimicrobial activity, cytotoxicity and the anti-inflammatory response of L. plantarum NRRL B-4496 cell-free supernatant (CFS). Furthermore, the CFS was fractionated by size exclusion chromatography using Sephadex G-25, and a minimal inhibitory volume test was determined against a panel of pathogenic bacteria. The cytotoxicity and the inflammatory activities of the fractions were evaluated using the human-derived THP-1 cell line. Results of this study indicates that CFS of L. plantarum NRRL B-4496 possesses antimicrobial protein compounds against the pathogen Listeria monocytogenes and showed no toxicity nor a pro-inflammatory response to human macrophages. The obtained results contribute to the development of novel bio-preservatives, L. plantarum cell-free supernatant or its fractions, with a potential use in the food industry.

Anastomotic leak in colorectal cancer patients: New insights and perspectives

Anastomotic leak (AL) remains a potentially life-threatening sequela of colorectal surgery impacting on mortality, short- and long-term morbidity, quality of life, local recurrence (LR) and disease-free survival. Despite technical improvements and the identification of several surgery- and patient-related factors associated to the risk of AL, its incidence has not significantly changed over time. In this context, the clarification of the mechanisms underlying anastomotic healing remains an important unmet need, crucial for improving patients' outcomes. This review concentrates on novel key findings in the etiopathogenesis of AL, how they can contribute in determining LR, and measures which may contribute to reducing its incidence. AL results from a complex, dynamic interplay of several factors and biological processes, including host genetics, gut microbiome, inflammation and the immune system. Many of these factors seem to act in concert to drive both AL and LR, even if the exact mechanisms remain to be elucidated. The next generation sequencing technology, including the microbial metagenomics, could lead to tailored bowel preparations targeting only those pathogens that can cause AL. Significant progress is being made in each of the reviewed areas, moving toward translational and targeted therapeutic strategies to prevent the difficult complication of AL.

Nisin J, a Novel Natural Nisin Variant, Is Produced by Staphylococcus capitis Sourced from the Human Skin Microbiota

The skin microbiota is thought to play a key role in host protection from infection. Nisin J is a novel nisin variant produced by Staphylococcus capitis APC 2923, a strain isolated from the toe web space area in a screening study performed on the human skin microbiota. Whole-genome sequencing and mass spectrometry of the purified peptide confirmed that S. capitis APC 2923 produces a 3,458-Da bacteriocin, designated nisin J, which exhibited antimicrobial activity against a range of Gram-positive pathogens, including methicillin-resistant Staphylococcus aureus (MRSA) and Cutibacterium acnes The gene order in the nisin J gene cluster (nsjFEGBTCJP) differs from that of other nisin variants in that it is lacking the nisin regulatory genes, nisRK, as well as the nisin immunity gene nisI Nisin J has 9 amino acid changes compared to prototypical nisin A, with 8 amino acid substitutions, 6 of which are not present in other nisin variants (Ile4Lys, Met17Gln, Gly18Thr, Asn20Phe, Met21Ala, Ile30Gly, Val33His, and Lys34Thr), and an extra amino acid close to the C terminus, rendering nisin J the only nisin variant to contain 35 amino acids. This is the first report of a nisin variant produced by a Staphylococcus species and the first nisin producer isolated from human skin.IMPORTANCE This study describes the characterization of nisin J, the first example of a natural nisin variant, produced by a human skin isolate of staphylococcal origin. Nisin J displays inhibitory activity against a wide range of bacterial targets, including MRSA. This work demonstrates the potential of human commensals as a source for novel antimicrobials that could form part of the solution to antibiotic resistance across a broad range of bacterial pathogens.

A potential probiotic Chromobacterium aquaticum with bacteriocin-like activity enhances the expression of indicator genes associated with nutrient metabolism, growth performance and innate immunity against pathogen infections in zebrafish (Danio rerio)

The use of probiotics as alternatives to antibiotics for disease control is a relatively eco-friendly approach in aquaculture; hence, studies isolating and assessing the benefit of potential probiotics to fish farming are common. The zebrafish is an excellent model system for validating beneficial functions of potential probiotics before their practical application in aquaculture. Here, a potentially probiotic Chromobacterium aquaticum was isolated from lake water samples and characterized by biochemical analysis and 16S rDNA sequencing. The probiotic produced extracellular enzymes (protease and xylanase) and a bacteriocin-like substance, which exhibited tolerance to extreme pH and high-temperature conditions and broad-spectrum bactericidal activity against diverse pathogens, including aquatic, foodborne, clinical and plant pathogens. The effects of C. aquaticum on zebrafish nutrient metabolism, growth performance and innate immunity were evaluated by measuring the expression of indicator genes after C. aquaticum feeding for 8 weeks. Fish administered the probiotic exhibited significantly increased hepatic mRNA expression of carbohydrate metabolism-related genes, including glucokinase (GK), hexokinase (HK), glucose-6-phosphatase (G6Pase), and pyruvate kinase (PK-L), and growth-related genes, including the growth hormone receptor (GHR) and insulin-like growth factor-1 (IGF-1). Innate immune-related genes (IL-1β, IL-6, TNF-α, IL-10, IL-21, NF-κb, lysozyme and complement C3b) were induced in fish with probiotic supplementation. Probiotic-treated fish exhibited a higher survival rate than control fish after challenge with Aeromonas hydrophila and Streptococcus iniae. Together, these data suggest that C. aquaticum, as a probiotic feed supplement, could enhance nutrient metabolism and growth performance and could modulate innate immunity against A. hydrophila and S. iniae in zebrafish.

In vitro synergistic activity of erythromycin and nisin against clinical Group B Streptococcus isolates

AIMS

This study investigated the potential synergy between erythromycin and nisin against clinical Group B Streptococcus (GBS) strains.

METHODS AND RESULTS

The combination of erythromycin and nisin was examined for synergistic activity using checkerboard and time-kill assays against invasive and colonizing GBS strains. Additionally, the immunological effect of the antibiotic combination was investigated in vitro using human U937 cells and ELISA analysis. Checkerboard assays confirmed an additive effect when the antimicrobials were combined, while time-kill assays demonstrated a synergistic effect when antimicrobials were combined for invasive GBS isolates. Furthermore, a significantly lower TNF-alpha response (P < 0·05) was observed in U937 cells challenged with GBS when erythromycin and nisin were used in combination.

CONCLUSIONS

The results suggest that erythromycin and nisin can act synergistically to inhibit the growth of GBS.

SIGNIFICANCE AND IMPACT OF THE STUDY

Group B Streptococcus is the leading cause of invasive neonatal disease worldwide and is becoming increasingly more prevalent in adults. Resistance to some conventionally used antibiotics, such as erythromycin and clindamycin, continue to rise among GBS, indicating a need for alternative treatments. This study demonstrates the potential of an erythromycin-nisin combination for treatment of GBS infections and encourages further investigation of this treatment option.

Migration of Bacteriocins Across Gastrointestinal Epithelial and Vascular Endothelial Cells, as Determined Using In Vitro Simulations

Little is known about the migration of bacteriocins across human cells. In this study, we report on migration of three bacteriocins nisin, plantaricin 423 and bacST4SA across colonic adenocarcinoma (Caco-2) cells and human umbilical vein endothelial cells (HUVECs). Bacteriocins were fluorescently labelled while still maintaining antimicrobial activity. Migration of fluorescently labelled bacteriocins across monolayers was assessed in vitro using transmigration well inserts. After 3 h, 75% of nisin, 85% of plantaricin 423 and 82% of bacST4SA migrated across the Caco-2 cell monolayer. Over the same time span, 88% nisin, 93% plantaricin 423 and 91% bacST4SA migrated across the HUVEC monolayer. The viability of both cell types remained unchanged when exposed to 50 µM of nisin, plantaricin 423 or bacST4SA. The effect of human plasma on bacteriocin activity was also assessed. Activity loss was dependent on bacteriocin type and concentration, with the class-IIa bacteriocins retaining more activity compared to nisin. This is the first report of bacteriocins migrating across simulated gastrointestinal- and vascular-barriers. This study provides some of the first evidence that bacteriocins are capable of crossing the gut-blood-barrier. However, in vivo studies need to be performed to confirm these findings and expand on the role of bacteriocin migration across cell barriers.

Immunomodulatory potential of Nisin A with application in wound healing

Antimicrobial peptides can have a dual role with both antimicrobial activity against a broad range of bacteria and immunomodulatory effect, making them attractive as therapeutic treatment of difficult wounds. Nisin A is widely known for its antimicrobial activity, and a preliminary study demonstrated that it increased wound closure, but the mechanism behind its effect is unknown. The aim of this study is to elucidate the wound healing potential of Nisin A and the mechanism behind. First, an epithelial and endothelial cell line, human keratinocyte (HaCaT) and human umbilical vein endothelial cell, were used to demonstrate migration and proliferation effects in vitro. From HaCaT cells and peripheral blood mononuclear cell, changes in cytokine levels were shown by quantitative polymerase chain reaction and enzyme-linked immunosorbent assay. Second, the ex vivo porcine wound healing model was used to investigate the re-epithelization potential of Nisin A. Finally, the model Galleria mellonella was used to confirm antimicrobial activity and to investigate potential immunomodulatory effects in vivo. Here, we demonstrated that Nisin A affected migration significantly of both human umbilical vein endothelial cell and HaCaT cells (p < 0.05) but not proliferation, potentially by decreasing the levels of proinflammatory cytokines tumor necrosis factor-α, interleukin-6, and interleukin-8 (p < 0.001). Furthermore, Nisin A treatment diminished lipopolysaccharide-induced tumor necrosis factor-α levels from peripheral blood mononuclear cells and monocyte chemoattractant protein-1 from HaCaT cells (p < 0.001). Furthermore, Nisin A did not affect proliferation ex vivo either but increased re-epithelization of the porcine skin. Nisin A improved survival of G. mellonella significantly from Staphylococcus epidermidis (p < 0.001) but not from Escherichia coli, indicating that Nisin A did not help the larvae to survive the infection in a different than direct antimicrobial way. All together this makes Nisin A a potential treatment to use in wound healing, as it increases the mobility of skin cells, dampens the effect of lipopolysaccharide and proinflammatory cytokines, and decreases bacterial growth.

In vitro immunomodulatory effect of nisin on porcine leucocytes

Nisin, a lantibiotic bacteriocin, has been used for years as a natural food preservative. In addition to its antimicrobial activity, nisin also shows immunomodulatory properties, and the nisin-producing Lactococcus lactis strain has been successfully tested as a probiotic in weaned piglets. However, the impact of nisin on porcine immune cells has not yet been explored. The objective of the present study was to examine the in vitro immunomodulatory effect of nisin on porcine peripheral blood leucocytes. The whole heparinized blood samples or freshly isolated peripheral blood mononuclear cells (PBMCs) were incubated with different nisin concentrations (0, 1.56, 3.125, 6.25, 12.5, 25 or 50 µg/ml) for 1, 24, 48 or 72 hr. Escherichia coli bacteria were used to stimulate blood phagocytes, while concanavalin A and lipopolysaccharide from E. coli were used as mitogens. Control cells remained unstimulated. MTT colorimetric assay was used to evaluate PBMCs viability and mitogenic response. Phagocyte activity and T-cell proliferation were measured by flow cytometry. Flow cytometer was also used for immunophenotyping of T cells. Cytokine levels in the culture media were determined using commercial immunoassay (ELISA) kits. The highest concentration of nisin exhibited proliferative activity (p ˂ 0.05), stimulated interleukin-1 beta (IL-1β) and interleukin-6 (IL-6) production (both at p ˂ 0.001), and increased the percentage of CD4⁺ CD8⁺ T cells (p ˂ 0.001) among unstimulated leucocytes. After cell stimulation, however, the highest nisin concentration showed antiproliferative activity (p ˂ 0.05), decreased phagocytic functions (p ˂ 0.05) and inhibited the synthesis of IL-6 (time- and concentration-dependent effect). As a typical bacterial product, nisin had a stronger impact on innate immune cells, and its effect on T cells was likely a consequence of the modulation of the activity of antigen-presenting cells. Nisin may be a good candidate as an immunomodulator in pig breeding.

A Review: The Fate of Bacteriocins in the Human Gastro-Intestinal Tract: Do They Cross the Gut-Blood Barrier?

The intestinal barrier, consisting of the vascular endothelium, epithelial cell lining, and mucus layer, covers a surface of about 400 m2. The integrity of the gut wall is sustained by transcellular proteins forming tight junctions between the epithelial cells. Protected by three layers of mucin, the gut wall forms a non-permeable barrier, keeping digestive enzymes and microorganisms within the luminal space, separate from the blood stream. Microorganisms colonizing the gut may produce bacteriocins in an attempt to outcompete pathogens. Production of bacteriocins in a harsh and complex environment such as the gastro-intestinal tract (GIT) may be below minimal inhibitory concentration (MIC) levels. At such low levels, the stability of bacteriocins may be compromised. Despite this, most bacteria in the gut have the ability to produce bacteriocins, distributed throughout the GIT. With most antimicrobial studies being performed in vitro, we know little about the migration of bacteriocins across epithelial barriers. The behavior of bacteriocins in the GIT is studied ex vivo, using models, flow cells, or membranes resembling the gut wall. Furthermore, little is known about the effect bacteriocins have on the immune system. It is generally believed that the peptides will be destroyed by macrophages once they cross the gut wall. Studies done on the survival of neurotherapeutic peptides and their crossing of the brain-blood barrier, along with other studies on small peptides intravenously injected, may provide some answers. In this review, the stability of bacteriocins in the GIT, their effect on gut epithelial cells, and their ability to cross epithelial cells are discussed. These are important questions to address in the light of recent papers advocating the use of bacteriocins as possible alternatives to, or used in combination with, antibiotics.

In Vitro Cytotoxic Activity of a Lactococcus lactis Antimicrobial Peptide Against Breast Cancer Cells

BACKGROUND

Nisin, an effective natural food preservative, is an antimicrobial peptide produced by Lactococcus lactis. Although it has been mainly studied and developed as a potential alternative for antibiotics, other pharmacological effects of the nisin including cytotoxic and anti-tumor activity have been attracted many attentions.

OBJECTIVES

Here, we aimed to evaluate in vitro cytotoxic activity of the nisin against breast cancer cells.

MATERIALS AND METHODS

The effect of temperature, pH, and chemical composition of the medium on the yield of nisin production was evaluated. As well, the anti-proliferative effect of nisin against a breast cancer cell line (i. e., MCF-7) and a non-cancerous cell line (i.e, HUVEC) was determined using MTT assay. Furthermore, the potential of the synergistic effect of the nisin on the doxorubicin cytotoxicity was evaluated.

RESULTS

The optimum culture condition for the nisin production by L. lactis was found to be MRS medium (pH 6.3) supplemented with the tryptone and incubation at 30 °C. MTT assay results indicate that nisin exhibits a high and selective cytotoxicity against MCF-7 cell line with IC50 value of 5 μM. Furthermore, a combination of nisin and doxorubicin at sub-inhibitory concentrations were more cytotoxic compared to either of drugs alone.

CONCLUSION

It could be suggested that nisin, either alone or in combination with other chemotherapeutic agents, could be a potential therapeutic for the breast cancer cells.

The lantibiotic gallidermin acts bactericidal against Staphylococcus epidermidis and Staphylococcus aureus and antagonizes the bacteria-induced proinflammatory responses in dermal fibroblasts

Antimicrobial resistance needs to be tackled from new angles, and antimicrobial peptides could be future candidates for combating bacterial infections. This study aims to investigate in vitro the bactericidal effects of the lantibiotic gallidermin on Staphylococcus epidermidis and Staphylococcus aureus, possible cytotoxic effects and its impact on host-microbe interactions. Minimal inhibitory concentration (MIC) and minimal bactericidal concentration (MBC) of gallidermin were determined, and cytotoxicity and proinflammatory effects of gallidermin on fibroblasts, red blood cells (RBCs) and in whole blood were investigated. Both MIC and MBC for all four tested strains of S. epidermidis was 6.25 μg/ml. Both MIC and MBC for methicillin-sensitive S. aureus was 12.5 μg/ml and for methicillin-resistant S. aureus (MRSA) 1.56 μg/ml. Gallidermin displayed no cytotoxic effects on fibroblasts, only a high dose of gallidermin induced low levels of CXCL8 and interleukin-6. Gallidermin hemolyzed less than 1% of human RBCs, and did not induce reactive oxygen species production or cell aggregation in whole blood. In cell culture, gallidermin inhibited the cytotoxic effects of the bacteria and totally suppressed the bacteria-induced release of CXCL8 and interleukin-6 from fibroblasts. We demonstrate that gallidermin, expressing low cell cytotoxicity, is a promising candidate for treating bacterial infections caused by S. epidermidis and S. aureus, especially MRSA.

Impacts of environmental and biological stressors on immune system of Macrobrachium rosenbergii

Macrobrachium rosenbergii commonly called giant freshwater prawn is a widely farmed crustacean in freshwater. Similar to other aquatic organisms, their growth and well‐being is influenced by various physical, chemical and biological factors. We discuss about the critical growth limiting factors as well as disease causing agents and the potential immune molecules of M. rosenbergii that are proved to involve in preventing and/or responding to those limiting factors.

Employing the promiscuity of lantibiotic biosynthetic machineries to produce novel antimicrobials

As the number of new antibiotics that reach the market is decreasing and the demand for them is rising, alternative sources of novel antimicrobials are needed. Lantibiotics are potent peptide antimicrobials that are ribosomally synthesized and stabilized by post-translationally introduced lanthionine rings. Their ribosomal synthesis and enzymatic modifications provide excellent opportunities to design and engineer a large variety of novel antimicrobial compounds. The research conducted in this area demonstrates that the modularity present in both the peptidic rings as well as in the combination of promiscuous modification enzymes can be exploited to further increase the diversity of lantibiotics. Various approaches, where the modifying enzymes and corresponding leader peptides are decoupled from their natural core peptide and integrated in designed plug-and-play production systems, enable the production of modified peptides that are either derived from vast genomic data or designed using functional parts from a wide diversity of core peptides. These approaches constitute a powerful discovery platform to develop novel antimicrobials with high therapeutic potential.

The Lantibiotic NAI-107 Efficiently Rescues Drosophila melanogaster from Infection with Methicillin-Resistant Staphylococcus aureus USA300

We used the fruit fly Drosophila melanogaster as a cost-effective in vivo model to evaluate the efficacy of novel antibacterial peptides and peptoids for treatment of methicillin-resistant Staphylococcus aureus (MRSA) infections. A panel of peptides with known antibacterial activity in vitro and/or in vivo was tested in Drosophila Although most peptides and peptoids that were effective in vitro failed to rescue lethal effects of S. aureus infections in vivo, we found that two lantibiotics, nisin and NAI-107, rescued adult flies from fatal infections. Furthermore, NAI-107 rescued mortality of infection with the MRSA strain USA300 with an efficacy equivalent to that of vancomycin, a widely applied antibiotic for the treatment of serious MRSA infections. These results establish Drosophila as a useful model for in vivo drug evaluation of antibacterial peptides.

Efficacy of Lantibiotic Treatment of Staphylococcus aureus-Induced Skin Infections, Monitored by In Vivo Bioluminescent Imaging

Staphylococcus aureus is a bacterial pathogen responsible for the majority of skin and soft tissue infections. Antibiotics are losing their efficacy as treatment for skin and soft tissue infections as a result of increased resistance in a variety of pathogens, including S. aureus It is thus imperative to explore alternative antimicrobial treatments to ensure future treatment options for skin and soft tissue infections. A select few lantibiotics, a group of natural defense peptides produced by bacteria, inhibit the growth of numerous clinical S. aureus isolates, including methicillin-resistant strains. In this study, the antimicrobial activities of nisin, clausin, and amyloliquecidin, separately administered, were compared to that of a mupirocin-based ointment, which is commonly used as treatment for S. aureus-induced skin infections. Full-thickness excisional wounds, generated on the dorsal surfaces of mice, were infected with a bioluminescent strain of S. aureus (strain Xen 36). The infections were monitored in real time using in vivo bioluminescent imaging. Lantibiotic treatments significantly reduced the bioluminescence of S. aureus Xen 36 to a level similar to that recorded with mupirocin treatment. Wound closure, however, was more pronounced during lantibiotic treatment. Lantibiotics thus have the potential to be used as an alternative treatment option for S. aureus-induced skin infections.

Biomedical applications of nisin

Nisin is a bacteriocin produced by a group of Gram-positive bacteria that belongs to Lactococcus and Streptococcus species. Nisin is classified as a Type A (I) lantibiotic that is synthesized from mRNA and the translated peptide contains several unusual amino acids due to post-translational modifications. Over the past few decades, nisin has been used widely as a food biopreservative. Since then, many natural and genetically modified variants of nisin have been identified and studied for their unique antimicrobial properties. Nisin is FDA approved and generally regarded as a safe peptide with recognized potential for clinical use. Over the past two decades the application of nisin has been extended to biomedical fields. Studies have reported that nisin can prevent the growth of drug-resistant bacterial strains, such as methicillin-resistant Staphylococcus aureus, Streptococcus pneumoniae, Enterococci and Clostridium difficile. Nisin has now been shown to have antimicrobial activity against both Gram-positive and Gram-negative disease-associated pathogens. Nisin has been reported to have anti-biofilm properties and can work synergistically in combination with conventional therapeutic drugs. In addition, like host-defence peptides, nisin may activate the adaptive immune response and have an immunomodulatory role. Increasing evidence indicates that nisin can influence the growth of tumours and exhibit selective cytotoxicity towards cancer cells. Collectively, the application of nisin has advanced beyond its role as a food biopreservative. Thus, this review will describe and compare studies on nisin and provide insight into its future biomedical applications.

Changes in protein abundance are observed in bacterial isolates from a natural host

Bacterial proteomic studies frequently use strains cultured in synthetic liquid media over many generations. It is uncertain whether bacterial proteins expressed under these conditions will be the same as the repertoire found in natural environments, or when bacteria are infecting a host organism. Thus, genomic and proteomic characterization of bacteria derived from the host environment in comparison to reference strains grown in the lab, should aid understanding of pathogenesis. Isolates of Corynebacterium pseudotuberculosis were obtained from the lymph nodes of three naturally infected sheep and compared to a laboratory reference strain using bottom-up proteomics, after whole genome sequencing of each of the field isolates. These comparisons were performed following growth in liquid media that allowed us to reach the required protein amount for proteomic analysis. Over 1350 proteins were identified in the isolated strains, from which unique proteome features were revealed. Several of the identified proteins demonstrated a significant abundance difference in the field isolates compared to the reference strain even though there were no obvious differences in the DNA sequence of the corresponding gene or in nearby non-coding DNA. Higher abundance in the field isolates was observed for proteins related to hypoxia and nutrient deficiency responses as well as to thiopeptide biosynthesis.