Tracheal antimicrobial peptide, a cysteine-rich peptide from mammalian tracheal mucosa: peptide isolation and cloning of a cDNA

Defensins: A novel weapon against Mycobacterium tuberculosis?

Tuberculosis (TB) is a serious airborne communicable disease caused by organisms of the Mycobacterium tuberculosis (Mtb) complex. Although the standard treatment antimicrobials, including isoniazid, rifampicin, pyrazinamide, and ethambutol, have made great progress in the treatment of TB, problems including the rising incidence of multidrug-resistant tuberculosis (MDR-TB) and extensively drug-resistant tuberculosis (XDR-TB), the severe toxicity and side effects of antimicrobials, and the low immunity of TB patients have become the bottlenecks of the current TB treatments. Therefore, both safe and effective new strategies to prevent and treat TB have become a top priority. As a subfamily of cationic antimicrobial peptides, defensins are rich in cysteine and play a vital role in resisting the invasion of microorganisms and regulating the immune response. Inspired by studies on the roles of defensins in host defence, we describe their research history and then review their structural features and antimicrobial mechanisms, specifically for fighting Mtb in detail. Finally, we discuss the clinical relevance, therapeutic potential, and potential challenges of defensins in anti-TB therapy. We further debate the possible solutions of the current application of defensins to provide new insights for eliminating Mtb.

Bovine Airway Models: Approaches for Investigating Bovine Respiratory Disease

Bovine respiratory disease (BRD) is a multifactorial condition where different genera of bacteria, such as Mannheimia haemolytica, Histophilus somni, Pasteurella multocida, and Mycoplasma bovis, and viruses, like bovine respiratory syncytial virus, bovine viral diarrhea virus, and bovine herpes virus-1, infect the lower respiratory tract of cattle. These pathogens can co-infect cells in the respiratory system, thereby making specific treatment very difficult. Currently, the most common models for studying BRD include a submerged tissue culture (STC), where monolayers of epithelial cells are typically covered either in cellular or spent biofilm culture medium. Another model is an air-liquid interface (ALI), where epithelial cells are exposed on their apical side and allowed to differentiate. However, limited work has been reported on the study of three-dimensional (3D) bovine models that incorporate multiple cell types to represent the architecture of the respiratory tract. The roles of different defense mechanisms in an infected bovine respiratory system, such as mucin production, tight junction barriers, and the production of antimicrobial peptides in in vitro cultures require further investigation in order to provide a comprehensive understanding of the disease pathogenesis. In this report, we describe the different aspects of BRD, including the most implicated pathogens and the respiratory tract, which are important to incorporate in disease models assembled in vitro. Although current advancements of bovine respiratory cultures have led to knowledge of the disease, 3D multicellular organoids that better recapitulate the in vivo environment exhibit potential for future investigations.

Modulation of innate immunity in airway epithelium for host-directed therapy

Innate immunity of the mucosal surfaces provides the first-line defense from invading pathogens and pollutants conferring protection from the external environment. Innate immune system of the airway epithelium consists of several components including the mucus layer, mucociliary clearance of beating cilia, production of host defense peptides, epithelial barrier integrity provided by tight and adherens junctions, pathogen recognition receptors, receptors for chemokines and cytokines, production of reactive oxygen species, and autophagy. Therefore, multiple components interplay with each other for efficient protection from pathogens that still can subvert host innate immune defenses. Hence, the modulation of innate immune responses with different inducers to boost host endogenous front-line defenses in the lung epithelium to fend off pathogens and to enhance epithelial innate immune responses in the immunocompromised individuals is of interest for host-directed therapy. Herein, we reviewed possibilities of modulation innate immune responses in the airway epithelium for host-directed therapy presenting an alternative approach to standard antibiotics.

Roles of Different β-Defensins in the Human Reproductive System: A Review Study

Human β-defensins (hBDs) are cationic peptides with an amphipathic spatial shape and a high cysteine content. The members of this peptide family have been found in the human body with various functions, including the human reproductive system. Of among β-defensins in the human body, β-defensin 1, β-defensin 2, and β-defensin 126 are known in the human reproductive system. Human β-defensin 1 interacts with chemokine receptor 6 (CCR6) in the male reproductive system to prevent bacterial infections. This peptide has a positive function in antitumor immunity by recruiting dendritic cells and memory T cells in prostate cancer. It is necessary for fertilization via facilitating capacitation and acrosome reaction in the female reproductive system. Human β-defensin 2 is another peptide with antibacterial action which can minimize infection in different parts of the female reproductive system such as the vagina by interacting with CCR6. Human β-defensin 2 could play a role in preventing cervical cancer via interactions with dendritic cells. Human β-defensin 126 is required for sperm motility and protecting the sperm against immune system factors. This study attempted to review the updated knowledge about the roles of β-defensin 1, β-defensin 2, and β-defensin 126 in both the male and female reproductive systems.

Role of Defensins in Tumor Biology

Defensins have long been considered as merely antimicrobial peptides. Throughout the years, more immune-related functions have been discovered for both the α-defensin and β-defensin subfamily. This review provides insights into the role of defensins in tumor immunity. Since defensins are present and differentially expressed in certain cancer types, researchers started to unravel their role in the tumor microenvironment. The human neutrophil peptides have been demonstrated to be directly oncolytic by permealizing the cell membrane. Further, defensins can inflict DNA damage and induce apoptosis of tumor cells. In the tumor microenvironment, defensins can act as chemoattractants for subsets of immune cells, such as T cells, immature dendritic cells, monocytes and mast cells. Additionally, by activating the targeted leukocytes, defensins generate pro-inflammatory signals. Moreover, immuno-adjuvant effects have been reported in a variety of models. Therefore, the action of defensins reaches beyond their direct antimicrobial effect, i.e., the lysis of microbes invading the mucosal surfaces. By causing an increase in pro-inflammatory signaling events, cell lysis (generating antigens) and attraction and activation of antigen presenting cells, defensins could have a relevant role in activating the adaptive immune system and generating anti-tumor immunity, and could thus contribute to the success of immune therapy.

Evolutionary trend of bovine β-defensin proteins toward functionality prediction: A domain-based bioinformatics study

Defensins are small cationic cysteine-rich and amphipathic peptides that form of three-dimensional β-strand structure connected by disulfide bonds. Defensins form key elements of the innate immune system of multicellular organisms. They not only possess broad-spectrum antimicrobial activity but also have diverse roles, including cell signaling, ion channel agitation, toxic functions, and enzyme inhibitor activities in various animals. Although the role of β-defensins in immune responses against infectious agents and reproduction could be significant, inadequate genomic information is available to explain the whole β-defensin repertoire in cattle. No domain or motif-based functional analyses have been previously reported. In addition, how do defensins possess this magnitude of functions in the immune system is still not clear. Our present study, therefore, investigated the sequence divergence and evolutionary relations of bovine defensin proteins with those of humans. Our domain-based evolutionary analysis revealed four major clusters with significant domain variation while reserving a main antimicrobial activity. Our study revealed the β-defensin domain as the ancestor domain, and it is preserved in the first group of defensin protein with no α-helix in its structure. Due to natural selection, some domains have evolved independently within clusters II and III, while some proteins have lost their domain characteristics. Cluster IV contains the most recently evolved domains. Some proteins of all but cluster I might have adopted the functional characteristics of α-defensins which is largely absent in cattle. The proteins show different patterns of disulfide bridges and multiple signature patterns which might render them specialized functions in different tissue to combat against various pathogens.

Yak DEFB124 alleviates intestinal injury caused by Staphylococcus aureus infection

To investigate the characteristics and functions of yak β-defensin 124 (DEFB124), prokaryotic expression, analysis of gut microbiological and other methods were used in this study. The results showed that the sequence of yak DEFB124 gene was 306 bp in length and 207 bp in open reading frame, which encoded 68 amino acids. Yak DEFB124 protein was highly conserved and had the closest relationship with cattle. Yak DEFB124 protein was a secreted cationic β-defensin. The recombinant expression plasmid pET32a-DEFB124 was constructed, and an about 24 kDa protein was successfully expressed. Yak DEFB124 protein had inhibitory activity against Staphylococcus aureus (S. aureus), and its MIC value was 64 μg/mL. After treating with yak DEFB124 protein, the activities of alkaline phosphatase (AKP) and total superoxide dismutase (T-SOD) were higher (P < 0.01) in the jejunum tissue, but the activity of lysozyme (LZM) was lower (P < 0.01). The number of goblet cells in the duodenum, jejunum, and ileum of the mice in the DEFB124 group was increased (P < 0.01). Besides, the expressions of MUC2 mRNA and protein were increased (P < 0.05) after the treatment with yak DEFB124 protein. Furthermore, the relative abundance of Lactobacillus in jejunum of mice in DEFB124 group was also increased. In summary, yak DEFB124 protein could increase the number of goblet cells in mice intestine and the abundance of intestinal probiotics Lactobacillus, thereby protecting the intestinal tract and alleviating intestinal damage.

β-defensin-4 as an endogenous biomarker in cows with mastitis

Introduction

Defensins are peptides with antimicrobial and immunomodulatory effects. Their concentration could be altered during infections and thus provide information on the prognosis and course of the disease. The aim of the present study was to investigate the defensin concentration in cows with mastitis in order to find correlations between clinical expression and course of the disease and the defensin concentration in milk and blood.

Methods

A total of 85 dairy cows were examined. Of these, 30 animals suffered from acute clinical mastitis, 25 animals were diagnosed with subclinical mastitis and 30 animals were considered a healthy comparison group. Beta-Defensin-4 (DEFB-4) was determined by a species-specific enzyme-linked immunosorbent assay (ELISA) (Bovine Defensin Beta 4 ELISA Kit, MyBioSource).

Results

The highest concentrations of DEFB-4 were detected in the animals with acute clinical mastitis. Values of 0 to 895 pg/mL (median: 115 pg/mL) were measured in milk and 40-1,016 pg/mL (median: 245 pg/mL) in serum. The concentrations of this group differed significantly from those of the animals with subclinical mastitis (p < 0.0001 serum; p = 0.015 milk). In this group, concentrations of 15-211 pg/mL (median: 46 pg/mL) were recorded in milk and 20-271 pg/mL (median: 85 pg/mL) in serum.

Discussion

Our results also show that in cases of acute mastitis after 12 days of treatment there is still an active inflammatory process in the tissue, because no significant reduction of somatic cells and defensin could be found after re-examination. Since the DEFB-4 concentrations of animals with clinical mastitis that had to be treated with antibiotics differed significantly from those of animals with subclinical mastitis that did not require antibiotic treatment, it can be assumed that bovine DEFB-4 is an important endogenous parameter for the defense against bacterial infections of the udder.

β-defensinas como posibles indicadores de la actividad inflamatoria en la enfermedad periodontal

Periodontal disease (gingivitis and periodontitis) is an inflam-matory process caused by the activity of pathogenic bacteria and their products on the gingival sulcus, with the consequent activation of the immune response. Saliva and crevicular fluid contain a wide variety of enzymes and antimicrobial factors that are in contact with the supragingival and subgingival region, in-cluding β-defensins (hBDs). hHBDs are non-glycosylated, cysteine-rich cationic peptides produced by epithelial cells with antimicrobial and immunoregulatory effects, thus contributing to maintaining homeostasis in periodontal tissues. The changes in the microbiota and the immune response from a healthy peri-odontium to gingivitis and, finally, to periodontitis are complex. Their sever-ity depends on a dynamic balance between bacteria associated with plaque, genetic and environmental factors. Recent advances have made it possible to understand the implication of hBDs in the detection, diagnosis, and therapy of periodontal disease and the relationship between periodontitis and other inflammatory conditions. This review aims to describe the effect of hBDs on the immune response and its use as a possible marker of the inflammatory activity of the periodontal disease.

The characteristics and roles of antimicrobial peptides as potential treatment for antibiotic-resistant pathogens: a review

The emergence of antibiotic-resistant bacteria has become a significant and ever-increasing threat to global public health, increasing both morbidity and mortality rates, and the financial burden on health services. Infection by drug-resistant bacteria is anticipated to contribute to the demise of almost 10 million people by the year 2050 unless a competent and effective response is devised to engage with this issue. The emergence and spread of resistance are commonly caused by the excessive or inappropriate use of antibiotics and substandard pharmaceuticals. It arises when pathogens adapt to different conditions and develop self-defence mechanisms. Currently, novel antimicrobial peptides (AMPs) have been reported to be the sole cure for some clinical cases of infectious diseases such as sepsis and skin infections, although these agents may, on occasion, require administration together with an adjunctive low-dose antibiotic. Although AMPs are a promising alternative form of anti-microbial therapy and easily applied in the medical sector, they still have limitations that should not be taken lightly. Hence, this review explores the characteristics, advantages and disadvantages of AMPs for their potential in treating antibiotic-resistant pathogens.

Endocannabinoid Anandamide Attenuates Acute Respiratory Distress Syndrome through Modulation of Microbiome in the Gut-Lung Axis

Acute respiratory distress syndrome (ARDS) is a serious lung condition characterized by severe hypoxemia leading to limitations of oxygen needed for lung function. In this study, we investigated the effect of anandamide (AEA), an endogenous cannabinoid, on Staphylococcal enterotoxin B (SEB)-mediated ARDS in female mice. Single-cell RNA sequencing data showed that the lung epithelial cells from AEA-treated mice showed increased levels of antimicrobial peptides (AMPs) and tight junction proteins. MiSeq sequencing data on 16S RNA and LEfSe analysis demonstrated that SEB caused significant alterations in the microbiota, with increases in pathogenic bacteria in both the lungs and the gut, while treatment with AEA reversed this effect and induced beneficial bacteria. AEA treatment suppressed inflammation both in the lungs as well as gut-associated mesenteric lymph nodes (MLNs). AEA triggered several bacterial species that produced increased levels of short-chain fatty acids (SCFAs), including butyrate. Furthermore, administration of butyrate alone could attenuate SEB-mediated ARDS. Taken together, our data indicate that AEA treatment attenuates SEB-mediated ARDS by suppressing inflammation and preventing dysbiosis, both in the lungs and the gut, through the induction of AMPs, tight junction proteins, and SCFAs that stabilize the gut-lung microbial axis driving immune homeostasis.

Antimicrobial Peptides: An Update on Classifications and Databases

Antimicrobial peptides (AMPs) are distributed across all kingdoms of life and are an indispensable component of host defenses. They consist of predominantly short cationic peptides with a wide variety of structures and targets. Given the ever-emerging resistance of various pathogens to existing antimicrobial therapies, AMPs have recently attracted extensive interest as potential therapeutic agents. As the discovery of new AMPs has increased, many databases specializing in AMPs have been developed to collect both fundamental and pharmacological information. In this review, we summarize the sources, structures, modes of action, and classifications of AMPs. Additionally, we examine current AMP databases, compare valuable computational tools used to predict antimicrobial activity and mechanisms of action, and highlight new machine learning approaches that can be employed to improve AMP activity to combat global antimicrobial resistance.

Directed Expression of Tracheal Antimicrobial Peptide as a Treatment for Bovine-Associated Staphylococcus Aureus-Induced Mastitis in Mice

Bovine mastitis is perplexing the dairy industry since the initiation of intensive dairy farming, which has caused a reduction in the productivity of cows and an escalation in costs. The use of antibiotics causes a series of problems, especially the formation of bacterial antimicrobial resistance. However, there are limited antibiotic-free therapeutic strategies that can effectively relieve bacterial infection of bovine mammary glands. Hence, in this study, we constructed a mammary gland tissue-specific expression vector carrying the antimicrobial peptide of bovine-derived tracheal antimicrobial peptide (TAP) and evaluated it in both primary bovine mammary epithelial cells (pBMECs) and mice. The results showed that the vector driven by the β-lactoglobulin gene (BLG) promoter could efficiently direct the expression of TAP in pBMECs and the mammary gland tissue of mice. In addition, significant antibacterial effects were observed in both in vitro and in vivo experiments when introducing this vector to bovine-associated Staphylococcus aureus-treated pBMECs and mice, respectively. This study demonstrated that the mammary gland tissue-specific expression vector could be used to introduce antimicrobial peptide both in in vitro and in vivo and will provide a new therapeutic strategy in the treatment of bovine mastitis.

Discovery, Optimization, and Clinical Application of Natural Antimicrobial Peptides

Antimicrobial peptides (AMPs) are widespread in multicellular organisms. These structurally diverse molecules are produced as the first line of defense against pathogens such as bacteria, viruses, fungi, and parasites. Also known as host defense peptides in higher eukaryotic organisms, AMPs display immunomodulatory and anticancer activities. During the last 30 years, technological advances have boosted the research on antimicrobial peptides, which have also attracted great interest as an alternative to tackling the antimicrobial resistance scenario mainly provoked by some bacterial and fungal pathogens. However, the introduction of natural AMPs in clinical trials faces challenges such as proteolytic digestion, short half-lives, and cytotoxicity upon systemic and oral application. Therefore, some strategies have been implemented to improve the properties of AMPs aiming to be used as effective therapeutic agents. In the present review, we summarize the discovery path of AMPs, focusing on preclinical development, recent advances in chemical optimization and peptide delivery systems, and their introduction into the market.

Local Defence System in Healthy Lungs

Background: The respiratory system is one of the main entrance gates for infection. The aim of this work was to compare the appearance of specific mucosal pro-inflammatory and common anti-microbial defence factors in healthy lung tissue, from an ontogenetic point of view. Materials and methods: Healthy lung tissues were collected from 15 patients (three females and 12 males) in the age range from 18 to 86. Immunohistochemistry to human β defensin 2 (HBD-2), human β defensin 3 (HBD-3), human β defensin 4 (HBD-4), cathelicidine (LL-37) and interleukine 17A (IL-17A) were performed. Results: The lung tissue material contained bronchial and lung parenchyma material in which no histological changes, connected with the inflammatory process, were detected. During the study, various statistically significant differences were detected in immunoreactive expression between different factors in all lung tissue structures. Conclusion: All healthy lung structures, but especially the cartilage, alveolar epithelium and the alveolar macrophages, are the main locations for the baseline synthesis of antimicrobial proteins and IL-17A. Cartilage shows high functional plasticity of this structure, including significant antimicrobial activity and participation in local lung protection response. Interrelated changes between antimicrobial proteins in different tissue confirm baseline synergistical cooperation of all these factors in healthy lung host defence.

Antimicrobial peptides in domestic animals and their applications in veterinary medicine

Antimicrobial peptides (AMPs) are molecules with a broad-spectrum activity against bacteria, fungi, protozoa, and viruses. These peptides are widely distributed in insects, amphibians and mammals. Indeed, they are key molecules of the innate immune system with remarkable antimicrobial and immunomodulatory activity. Besides, these peptides have also shown regulatory activity for gut microbiota and have been considered inductors of growth performance. The current review describes the updated findings of antimicrobial peptides in domestic animals, such as bovines, goats, sheep, pigs, horses, canines and felines, analyzing the most relevant aspects of their use as potential therapeutics and their applications in Veterinary medicine.

MicroRNA: Could It Play a Role in Bovine Endometritis?

Endometritis in dairy cows is a major economic problem worldwide; without advances in lifestyle management and drug treatment, it causes high morbidity and death. Micro ribonucleic acid (miRNAs) these days is seen as an important part of gene control networks. It is a class of small nucleotides 20-25, single-stranded RNA molecules. In endometritis, the inflammatory response caused by the gram-negative bacteria Escherichia coli (E. coli) alters the expression of miRNA which can regulate the innate immune system. This manuscript reviews (1) the interaction of miRNAs with the signaling of NF-κB and dysregulation of miRNAs and NF-κB activity in endometritis and (2) the activity of miR-let-7c, miR-148a, and miR-488 in NF-κB activation and their effect on endometritis. Cows with reduced immunity are more vulnerable to transition diseases, such as endometritis. During post-partum, cows undergo stress, metabolic disorders, hormonal imbalance, negative energy balance, and changes in diet. One of the many categories of regulatory molecules, which explain its natural function and pathological impact on NF-κB dysregulation, is important to inform the complexity of the immune system and to develop treatments for endometritis. It shows that miRNAs could have multiple applications in veterinary medicine. Nevertheless, a comprehensive study of is essential which should be aimed at exploring the role of microRNA at physiological level and its effect due to dysfunction and dysregulation.

Leveraging orthogonal mass spectrometry based strategies for comprehensive sequencing and characterization of ribosomal antimicrobial peptide natural products

Covering: Up to July 2020Ribosomal antimicrobial peptide (AMP) natural products, also known as ribosomally synthesized and post-translationally modified peptides (RiPPs) or host defense peptides, demonstrate potent bioactivities and impressive complexity that complicate molecular and biological characterization. Tandem mass spectrometry (MS) has rapidly accelerated bioactive peptide sequencing efforts, yet standard workflows insufficiently address intrinsic AMP diversity. Herein, orthogonal approaches to accelerate comprehensive and accurate molecular characterization without the need for prior isolation are reviewed. Chemical derivatization, proteolysis (enzymatic and chemical cleavage), multistage MS fragmentation, and separation (liquid chromatography and ion mobility) strategies can provide complementary amino acid composition and post-translational modification data to constrain sequence solutions. Examination of two complex case studies, gomesin and styelin D, highlights the practical implementation of the proposed approaches. Finally, we emphasize the importance of heterogeneous AMP peptidoforms that confer varying biological function, an area that warrants significant further development.

Antimicrobial Peptides in Farm Animals: An Updated Review on Its Diversity, Function, Modes of Action and Therapeutic Prospects

Antimicrobial peptides (AMPs) are the arsenals of the innate host defense system, exhibiting evolutionarily conserved characteristics that are present in practically all forms of life. Recent years have witnessed the emergence of antibiotic-resistant bacteria compounded with a slow discovery rate for new antibiotics that have necessitated scientific efforts to search for alternatives to antibiotics. Research on the identification of AMPs has generated very encouraging evidence that they curb infectious pathologies and are also useful as novel biologics to function as immunotherapeutic agents. Being innate, they exhibit the least cytotoxicity to the host and exerts a wide spectrum of biological activity including low resistance among microbes and increased wound healing actions. Notably, in veterinary science, the constant practice of massive doses of antibiotics with inappropriate withdrawal programs led to a high risk of livestock-associated antimicrobial resistance. Therefore, the world faces tremendous pressure for designing and devising strategies to mitigate the use of antibiotics in animals and keep it safe for posterity. In this review, we illustrate the diversity of farm animal-specific AMPs, and their biochemical foundations, mode of action, and prospective application in clinics. Subsequently, we present the data for their systematic classification under the major and minor groups, antipathogenic action, and allied bioactivities in the host. Finally, we address the limitations of their clinical implementation and envision areas for further advancement.

Early immune innate hallmarks and microbiome changes across the gut during Escherichia coli O157: H7 infection in cattle

The zoonotic enterohemorrhagic Escherichia coli (EHEC) O157: H7 bacterium causes diarrhea, hemorrhagic colitis, and hemolytic uremic syndrome (HUS) in humans. Cattle are primary reservoirs and EHEC O157: H7; the bacteria predominately inhabit the colon and recto-anal junctions (RAJ). The early innate immune reactions in the infected gut are critical in the pathogenesis of EHEC O157: H7. In this study, calves orally inoculated with EHEC O157: H7 showed infiltration of neutrophils in the lamina propria of ileum and RAJ at 7 and 14 days post-infection. Infected calves had altered mucin layer and mast cell populations across small and large intestines. There were differential transcription expressions of key bovine β defensins, tracheal antimicrobial peptide (TAP) in the ileum, and lingual antimicrobial peptide (LAP) in RAJ. The main Gram-negative bacterial/LPS signaling Toll-Like receptor 4 (TLR4) was downregulated in RAJ. Intestinal infection with EHEC O157: H7 impacted the gut bacterial communities and influenced the relative abundance of Negativibacillus and Erysipelotrichaceae in mucosa-associated bacteria in the rectum. Thus, innate immunity in the gut of calves showed unique characteristics during infection with EHEC O157: H7, which occurred in the absence of major clinical manifestations but denoted an active immunological niche.

Host Defense Peptides as Templates for Antifungal Drug Development

Current treatment for invasive fungal diseases is limited to three classes of antifungal drugs: azoles, polyenes, and echinocandins. The most recently introduced antifungal class, the echinocandins, was first approved nearly 30 years ago. The limited antifungal drug portfolio is rapidly losing its clinical utility due to the inexorable rise in the incidence of invasive fungal infections and the emergence of multidrug resistant (MDR) fungal pathogens. New antifungal therapeutic agents and novel approaches are desperately needed. Here, we detail attempts to exploit the antifungal and immunoregulatory properties of host defense peptides (HDPs) in the design and evaluation of new antifungal therapeutics and discuss historical limitations and recent advances in this quest.

Calcium homeostasis plays important roles in the internalization and activities of the small synthetic antifungal peptide PAF26

Fungal diseases are responsible for the deaths of over 1.5 million people worldwide annually. Antifungal peptides represent a useful source of antifungals with novel mechanisms-of-action, and potentially provide new methods of overcoming resistance. Here we investigate the mode-of-action of the small, rationally designed synthetic antifungal peptide PAF26 using the model fungus Neurospora crassa. Here we show that the cell killing activity of PAF26 is dependent on extracellular Ca²⁺ and the presence of fully functioning fungal Ca²⁺ homeostatic/signaling machinery. In a screen of mutants with deletions in Ca²⁺ -signaling machinery, we identified three mutants more tolerant to PAF26. The Ca²⁺ ATPase NCA-2 was found to be involved in the initial interaction of PAF26 with the cell envelope. The vacuolar Ca²⁺ channel YVC-1 was shown to be essential for its accumulation and concentration within the vacuolar system. The Ca²⁺ channel CCH-1 was found to be required to prevent the translocation of PAF26 across the plasma membrane. In the wild type, Ca²⁺ removal from the medium resulted in the peptide remaining trapped in small vesicles as in the Δyvc-1 mutant. It is, therefore, apparent that cell killing by PAF26 is complex and unusually dependent on extracellular Ca²⁺ and components of the Ca²⁺ -regulatory machinery.

Profiling and Role of Bioactive Molecules from Puntius sophore (Freshwater/Brackish Fish) Skin Mucus with Its Potent Antibacterial, Antiadhesion, and Antibiofilm Activities

Epidermal fish mucus comprises of diverse bioactive metabolites which plays an immense role in defense mechanisms and other important cellular activities. Primarily, this study aims to screen the unexplored mucus extract of Puntius sophore(P. sophore) for its antagonistic potential against common pathogens, which are commonly implicated in foodborne and healthcare associated infections, with effects on their adhesion and biofilm formation. Profiling of the skin mucus was carried out by High Resolution-Liquid Chromatography Mass Spectrometry (HR-LCMS), followed by antibacterial activity and assessment of antibiofilm potency and efficacy on the development, formation, and texture of biofilms. Furthermore, bacterial cell damage, viability within the biofilm, checkerboard test, and cytotoxicity were also evaluated. As a result, P. sophore mucus extract was found to be effective against all tested strains. It also impedes the architecture of biofilm matrix by affecting the viability and integrity of bacterial cells within biofilms and reducing the total exopolysaccharide content. A synergy was observed between P. sophore mucus extract and gentamicin for Escherichia coli(E. coli), Pseudomonas aeruginosa(P. aeruginosa), and Bacillus subtilis(B. subtilis), whereas, an additive effect for Staphylococcus aureus(S. aureus). Thus, our findings represent the potent bioactivities of P. sophore mucus extract for the first time, which could be explored further as an alternative to antibiotics or chemically synthesized antibiofilm agents.

Engineered Cationic Antimicrobial Peptides (eCAPs) to Combat Multidrug-Resistant Bacteria

The increasing rate of antibiotic resistance constitutes a global health crisis. Antimicrobial peptides (AMPs) have the property to selectively kill bacteria regardless of resistance to traditional antibiotics. However, several challenges (e.g., reduced activity in the presence of serum and lack of efficacy in vivo) to clinical development need to be overcome. In the last two decades, we have addressed many of those challenges by engineering cationic AMPs de novo for optimization under test conditions that typically inhibit the activities of natural AMPs, including systemic efficacy. We reviewed some of the most promising data of the last two decades in the context of the advancement of the field of helical AMPs toward clinical development.

Diminished systemic levels of antimicrobial peptides in tuberculous lymphadenitis and their reversal after anti-tuberculosis treatment

Pulmonary tuberculosis is associated with higher plasma levels of antimicrobial peptides (AMPs) and lower granulysin levels. However, the association of AMPs with tuberculous lymphadenitis (TBL) is not well studied. Hence, we measured the plasma levels of human beta defensin-2 (HBD2), granulysin, human neutrophil peptides 1-3 (HNP1-3) and cathelicidin (LL37) in TBL compared to latent tuberculosis (LTB) and healthy controls (HC) and in TBL individuals upon completion of anti-tuberculosis treatment (ATT). We examined the association of AMPs with TBL lymph node culture grade or lymph node involvement. Finally, the discriminatory potential of these proteins was assessed using receiver operating characteristic (ROC) analysis. TBL individuals display significantly diminished circulating levels of AMPs (granulysin and HNP1-3) but not HBD-2 and LL-37 in comparison to LTB and HCs. Similarly, after ATT, both HBD-2 and HNP1-3 were significantly elevated and LL-37 was significantly reduced in TBL individuals. Granulysin and HNP1-3 discriminates TBL from LTB and HC individuals upon ROC analysis. AMPs did not exhibit significant correlation either with lymph node culture grades or lymph node involvement. Overall, TBL individuals show decreased AMPs and their reversal after ATT suggesting their association with underlying immune alteration in this poorly studied form of TB disease.

Defensins: Transcriptional regulation and function beyond antimicrobial activity

Defensins are one the largest group of antimicrobial peptides and are part of the innate defence. Defensins are produced by animals, plants and fungi. In animals and plants, defensins can be constitutively or differentially expressed both locally or systemically which confer defence before and a stronger response after infection. Immune signalling pathways regulate the gene expression of defensins. These pathways include cellular receptors, which recognise pathogen-associated molecular patterns and are found both in plants and animals. After recognition, signalling pathways and, subsequently, transcriptional factors are activated. There is an increasing number of novel functions in defensins, such as immunomodulators and immune cell attractors. Identification of defensin triggers could help us to elucidate other new functions. The present article reviews the different elicitors of defensins with a main focus on human, fish and marine invertebrate defensins.

Short communication: Inhibition of DNA methyltransferase and histone deacetylase increases β-defensin expression but not the effects of lipopolysaccharide or 1,25-dihydroxyvitamin D3 in bovine mammary epithelial cells

Antimicrobial peptides are a common defense against bacterial infections in many species and a significant part of the innate immune response of the bovine mammary gland. The objective of this study was to investigate the influence of epigenetic factors on vitamin D and toll-like receptor-mediated induction of β-defensins in mammary epithelial cells. Primary bovine mammary epithelial cells were treated with lipopolysaccharide (LPS, 0 or 100 ng/mL), 1,25-dihydroxyvitamin D₃ [1,25(OH)₂D₃, 0 or 10 nM], and 5-aza-2'-deoxycytidine (5-Aza, inhibitor of DNA methyltransferase, 0 or 5 μM) or trichostatin A (TSA, inhibitor of histone deacetylase, 0 or 80 nM) in a factorial arrangement. Effects of treatments on β-defensin gene expression along with genes for cytokines and enzymes known to be induced by LPS or 1,25(OH)₂D₃ were evaluated by quantitative PCR. The LPS treatment induced expression of β-defensin (DEFB)3, DEFB5, DEFB7, DEFB10, enteric β-defensin (EBD), lingual antimicrobial peptide (LAP), and tracheal antimicrobial peptide (TAP); whereas, the 1,25(OH)₂D₃ treatment increased DEFB5 and DEFB7 expression and decreased LAP. The 5-Aza treatment increased expression of DEFB3, DEFB5, DEFB10, EBD, LAP, and TAP in the presence and absence of LPS. The TSA treatment increased expression of DEFB3, DEFB4, DEFB5, DEFB7, and DEFB10 in the absence of LPS but decreased LPS-induced expression of and LAP and TAP. Together these results indicate that β-defensin expression in bovine mammary epithelial cells is likely influenced by DNA methylation and histone acetylation. Investigation of environmental and nutritional factors that influence epigenetic control of β-defensins in the mammary gland may be beneficial for improving resistance to intramammary infections.

Transcriptomics analysis of host liver and meta-transcriptome analysis of rumen epimural microbial community in young calves treated with artificial dosing of rumen content from adult donor cow

In mammals, microbial colonization of the digestive tract (GIT) occurs right after birth by several bacterial phyla. Numerous human and mouse studies have reported the importance of early gut microbial inhabitants on host health. However, few attempts have been undertaken to directly interrogate the role of early gut/rumen microbial colonization on GIT development or host health in neonatal ruminants through artificial manipulation of the rumen microbiome. Thus, the molecular changes associated with bacterial colonization are largely unknown in cattle. In this study, we dosed young calves with exogenous rumen fluid obtained from an adult donor cow, starting at birth, and repeated every other week until six weeks of age. Eight Holstein bull calves were included in this study and were separated into two groups of four: the first group was treated with rumen content freshly extracted from an adult cow, and the second group was treated with sterilized rumen content. Using whole-transcriptome RNA-sequencing, we investigated the transcriptional changes in the host liver, which is a major metabolic organ and vital to the calf’s growth performance. Additionally, the comparison of rumen epimural microbial communities between the treatment groups was performed using the rRNA reads generated by sequencing. Liver transcriptome changes were enriched with genes involved in cell signaling and protein phosphorylation. Specifically, up-regulation of SGPL1 suggests a potential increase in the metabolism of sphingolipids, an essential molecular signal for bacterial survival in digestive tracts. Notably, eight genera, belonging to four phyla, had significant increases in abundance in treated calves. Our study provides insight into host liver transcriptome changes associated with early colonization of the microbial communities in neonatal calves. Such knowledge provides a foundation for future probiotics-based research in microbial organism mediated rumen development and nutrition in ruminants.

Diversifying selection signatures among divergently selected subpopulations of Polish Red cattle

Polish Red cattle is one of the few indigenous breeds of European red cattle which is characterized by several desired features, such as high disease resistance, good health, longevity, good fertility, and high nutritional value of milk. Currently, Polish Red cattle population is a subject of two independent breeding programs: (i) improvement program and (ii) genetic resources conservation program. The aim of the improvement program is the genetic progress in terms of milk production and body conformation traits, while the conservation program mainly focuses on protection of the genetic resources of Polish Red cattle and preservation of the existing, original gene pool. By the analysis of F_ST genetic distances across genome-wide SNP panel, we detected diversifying selection signatures among these two subpopulations and indicated (among others) the significance of DGAT1 and FGF2 genes for milk production traits in these cattle. We also found that among genes being presumably under selection in terms of milk production, there are genes responsible, for example, for mammary gland development (e.g., SOSTDC1, PYGO2, MED1, and CCND1) and immune system response (e.g., IL10RA, IL12B, and IL21). The most important finding of this study is that the most pronounced genetic differences between the analyzed populations were associated with β-defensin genes (e.g., DEFB1, DEFB4A, DEFB5, DEFB7, DEFB10, DEFB13, EBD, BNBD-6, and LAP) located within so-called bovine cluster D on BTA27. The β-defensins are expressed mainly in the mammary gland and are antimicrobial peptides against the Gram-negative and Gram-positive bacteria, viruses, and other unicellular parasites. This suggests that antimicrobial resistance of mammary gland is of high importance during selection towards increased milk production and that genes responsible for this process are selected together with increasing levels of productivity.

β-Defensins: Farming the Microbiome for Homeostasis and Health

Diverse commensal populations are now regarded as key to physiological homeostasis and protection against disease. Although bacteria are the most abundant component of microbiomes, and the most intensively studied, the microbiome also consists of viral, fungal, archael, and protozoan communities, about which comparatively little is known. Host-defense peptides (HDPs), originally described as antimicrobial, now have renewed significance as curators of the pervasive microbial loads required to maintain homeostasis and manage microbiome diversity. Harnessing HDP biology to transition away from non-selective, antibiotic-mediated treatments for clearance of microbes is a new paradigm, particularly in veterinary medicine. One family of evolutionarily conserved HDPs, β-defensins which are produced in diverse combinations by epithelial and immune cell populations, are multifunctional cationic peptides which manage the cross-talk between host and microbes and maintain a healthy yet dynamic equilibrium across mucosal systems. They are therefore key gatekeepers to the oral, respiratory, reproductive and enteric tissues, preventing pathogen-associated inflammation and disease and maintaining physiological normality. Expansions in the number of genes encoding these natural antibiotics have been described in the genomes of some species, the functional significance of which has only recently being appreciated. β-defensin expression has been documented pre-birth and disruptions in their regulation may play a role in maladaptive neonatal immune programming, thereby contributing to subsequent disease susceptibility. Here we review recent evidence supporting a critical role for β-defensins as farmers of the pervasive and complex prokaryotic ecosystems that occupy all body surfaces and cavities. We also share some new perspectives on the role of β-defensins as sensors of homeostasis and the immune vanguard particularly at sites of immunological privilege where inflammation is attenuated.

PU.1 and epigenetic signals modulate 1,25-dihydroxyvitamin D3 and C/EBPα regulation of the human cathelicidin antimicrobial peptide gene in lung epithelial cells

LL-37, the only known human cathelicidin which is encoded by the human antimicrobial peptide (CAMP) gene, plays a critical role in protection against bacterial infection. We previously demonstrated that cathelicidin is induced by 1,25-dihydroxyvitamin D₃ (1,25(OH) ₂ D ₃ ) in human airway epithelial cells with a resultant increase in bactericidal activity. In this study we identify key factors that co-operate with 1,25(OH) ₂ D ₃ in the regulation of CAMP. Our results show for the first time that PU.1, the myeloid transcription factor (which has also been identified in lung epithelial cells), co-operates with the vitamin D receptor and CCAAT/enhancer binding protein α (CEBPα) to enhance the induction of CAMP in lung epithelial cells. Our findings also indicate that enhancement of 1,25(OH) ₂ D ₃ regulation of CAMP by histone deacetylase inhibitors involves co-operation between acetylation and chromatin remodeling through Brahma-related gene 1 (BRG1; a component of the SWItch/sucrose nonfermentable [SWI/SNF] complex). BRG1 can be an activator or repressor depending on BRG1-associated factors. Protein arginine methyltransferase 5 (PRMT5), a methlytransferase which interacts with BRG1, represses 1,25(OH) ₂ D ₃ induced CAMP in part through dimethylation of H4R3. Our findings identify key mediators involved in the regulation of the CAMP gene in lung epithelial cells and suggest new approaches for therapeutic manipulation of gene expression to increase the antibacterial capability of the airway.

Antibacterial activities of plasma from the common (Chelydra serpentina) and alligator snapping turtle (Macrochelys temminckii)

Innate immunity provides a fast-acting and nonspecific defense against microbial infection, and appears to have particular importance in the immune response of ectothermic vertebrates. Chelonians are a globally distributed and diverse group, yet little is known about their basic immune function. The chelonian family Chelydridae is made up of two genera (Chelydra and Macrochelys), represented in our study by the widespread common snapping turtle ( Chelydra serpentina; CST) and the southeast USA endemic alligator snapping turtle ( Macrochelys temminckii; AST). Our goal was to quantify the innate immune response of the family Chelydridae, using the antibacterial activity of plasma as a measure of immune function. Our results show that the plasma of both species has strong antibacterial properties, but CST plasma kills a higher percentage of bacteria than AST plasma. In addition, while both species showed the highest antibacterial activity at 25 to 30°C, CST plasma retained its antibacterial properties at lower and higher temperatures than AST plasma. Our results indicate that, like many ectotherms, Chelydridae have a relatively strong innate immune response. The stronger, more robust immune response of CSTs compared with ASTs is likely correlated to the differences in geographic ranges but may also have implications for each species' tolerance to anthropogenic habitat degradation and global climate change.

β-Defensins Coordinate In Vivo to Inhibit Bacterial Infections of the Trachea

β-defensins are predicted to play an important role in innate immunity against bacterial infections in the airway. We previously observed that a type III-secretion product of Bordetella bronchiseptica inhibits the NF-κB-mediated induction of a β-defensin in airway epithelial cells in vitro. To confirm this in vivo and to examine the relative roles of other β-defensins in the airway, we infected wild-type C57BL/6 mice and mice with a deletion of the mBD-1 gene with B. bronchiseptica wild-type strain, RB50 and its mutant strain lacking the type III-secretion system, WD3. The bacteria were quantified in the trachea and the nasal tissue and mRNA levels of mouse β-defensin-3 (mBD-3) were assessed after 24 h. Infection with the wild-type bacterial strain resulted in lower mBD-3 mRNA levels in the trachea than in mice infected with the type III-deficient strain. Furthermore, we observed an increase in bacterial numbers of RB50 only in the tracheas of mBD-1-deficient mice. Neutrophils were also more abundant on the trachea in RB50 infected WT mice but not in the bronchiolar lavage fluid (BAL), compared with WD3 infected WT and mBD-1^−/− mice, indicating that the coordination of β-defensin chemotactic effects may be confined to tracheal epithelial cells (TEC). RB50 decreased the ability of mice to mount an early specific antibody response, seven days after infection in both WT and mBD-1^−/− mice but there were no differences in titers between RB50-infected WT and mBD-1^−/− mice or between WD3-infected WT and mBD-1^−/− mice, indicating mBD-1 was not involved in induction of the humoral immune response to the B. bronchiseptica. Challenge of primary mouse TEC in vitro with RB50 and WD3, along with IL-1β, further corroborated the in vivo studies. The results demonstrate that at least two β-defensins can coordinate early in an infection to limit the growth of bacteria in the trachea.

A Differential Innate Immune Response in Active and Chronic Stages of Bovine Infectious Digital Dermatitis

Digital dermatitis (DD) commonly associated with Treponema spp. infection is a prevalent infectious bovine foot disease characterized by ulcerative and necrotic lesions. Lesions associated with DD are often classified using the M-stage scoring system, with M0 indicating healthy heel skin and M4 indicating chronic lesions. Current treatments utilizing antimicrobials or chemical footbaths are often ineffective and rarely cure DD lesions. Understanding the function of the innate immune response in the pathogenesis of DD will help to identify novel therapeutic approaches. In this study, the expression of the local innate host defense peptides cathelicidins and β-defensins was investigated in cows with DD and associated with the presence of treponemes and inflammatory reactions. Samples from active ulcerative DD lesions (M2) had considerable epidermal neutrophilic infiltration and increased gene expression of β-defensin tracheal antimicrobial peptides compared to control skin. Samples from acute lesions also had elevated local Cxcl-8 and TLR4 gene expression and abundant treponemes as identified by direct visualization, immunohistochemistry, and culture. Conversely, the anti-inflammatory peptide IL-10 was elevated in skin from chronic (M4) lesions, whereas bovine cathelicidin myeloid antimicrobial peptide 28 (Bmap-28) was increased in skin from oxytetracycline-treated M2 lesions. Experiments using cultured human keratinocytes challenged with Treponema spp. isolated from clinical cases of bovine DD showed that structural products from treponemes are able to initiate the innate immune response, in part through TLR2 signaling. These findings indicate that neutrophil influx, Cxcl-8, and β-defensin are key markers of active DD. Cathelicidins and IL-10 seem important in response to treatment or during the chronic proliferative stages of the disease.

Antibacterial properties of plasma from the prairie rattlesnake (Crotalus viridis)

The innate immune system functions to quickly respond to pathogens and is likely the primary line of defense for ectothermic vertebrates. Snake populations appear to be in widespread decline globally, but despite the threats from emerging pathogens, very little work has been conducted to characterize their basic immune function. We used a wide-ranging snake species, the Prairie Rattlesnake (Crotalus viridis), to measure effects of snake plasma on the growth of eight bacterial species. Additionally, we quantified bacterial killing ability and kinetics of the immune response. Our results show that Prairie Rattlesnakes have robust innate immune systems, and concentrations of 10% snake plasma inhibit growth of 6 of 8 bacteria tested. Undiluted snake plasma inhibited nearly all bacterial growth. The immune response was fairly rapid, inhibiting 73% of bacterial growth within 20 min of exposure. These results are encouraging for conservation of wild populations, as snakes appear to exhibit a strong innate immune response. However, further work needs to be directed toward the evaluation of immune system capabilities in individual populations of conservation concern, and against pathogens known to cause mortality in wild snakes.

Modulation of ovine SBD-1 expression by Saccharomyces cerevisiae in ovine ruminal epithelial cells

Background

The ovine rumen is involved in host defense responses and acts as the immune interface with the environment. The ruminal mucosal epithelium plays an important role in innate immunity and secretes antimicrobial innate immune molecules that have bactericidal activity against a variety of pathogens. Defensins are cationic peptides that are produced by the mucosal epithelia and have broad-spectrum antimicrobial activity. Sheep β-defensin-1 (SBD-1) is one of the most important antibacterial peptides in the rumen. The expression of SBD-1 is regulated by the probiotic, Saccharomyces cerevisiae (S.c); however, the regulatory mechanism has not yet been elucidated. In the current study, the effects of S.c on the expression and secretion of SBD-1 in ovine ruminal epithelial cells were investigated using quantitative real-time PCR (qPCR) and enzyme-linked immunosorbent assay (ELISA). In addition, specific inhibitors were used to block the nuclear factor kappa-light-chain enhancer of activated B cells (NF-κB), p38, JNK, and ERK1/2 signalling pathways separately or simultaneously, to determine the regulatory mechanism(s) governing S.c-induced SBD-1 upregulation.

Results

Incubation with S.c induced release of SBD-1 by ovine ruminal epithelial cells, with SBD-1 expression peaking after 12 h of incubation. The highest SBD-1 expression levels were achieved after treatment with 5.2 × 10⁷ CFU∙mL^− 1 S.c. Treatment with S.c resulted in significantly increased NF-κB, p38, JNK, ERK1/2, TLR2, and MyD88 mRNA expression. Whereas inhibition of mitogen-activated protein kinases (MAPKs) and NF-κB gene expression led to a decrease in SBD-1 expression.

Conclusions

S.c was induced SBD-1 expression and the S.c-induced up-regulation of SBD-1 expression may be related to TLR2 and MyD88 in ovine ruminal epithelial cells. This is likely simultaneously regulated by the MAPKs and NF-κB pathways with the p38 axis of the MAPKs pathway acting as the primary regulator. Thus, the pathways regulating S.c-induced SBD-1 expression may be related to TLR2-MyD88-NF-κB/MAPKs, with the TLR2-MyD88-p38 component of the TLR2-MyD88-MAPKs signalling acting as the main pathway.

Amidated Scolopin-2 inhibits proliferation and induces apoptosis of Hela cells in vitro and in vivo

This study aimed to investigate the effect of Scolopin-2, a cationic antimicrobial peptide from centipede venoms, and amidated Scolopin-2 on Hela cell viability in vitro and in vivo. The cellular proliferation was investigated with the MTT assay. Confocal laser scanning, flow cytometry, and Western blot analysis were employed to localize Scolopin-2-NH₂ in Hela cells and to study the caused cells apoptosis. We subcutaneously injected Hela cells into BALB/c nude mice and studied if Scolopin-2-NH₂ suppressed tumor growth in the mice. Scolopin-2-NH₂ inhibited Hela proliferation in vitro in a dose-dependent manner with an IC₅₀ of 35 μM. In addition, Scolopin-2-NH₂ combined with mitochondria and regulated caspase-related apoptosis pathways in Hela cells. Scolopin-2-NH₂ significantly suppressed tumor growth in the tumor-bearing mice without side effects, such as weight loss or abnormal changes in tissues, including liver, spleen, kidney, and lung. These results indicate Scolopin-2-NH₂ may be a good therapeutic candidate for the treatment of Hela cervical cancer.

Antimicrobial peptides of buffalo and their role in host defenses

Antimicrobial peptides (AMPs) are highly conserved components of the innate immune system found among all classes of life. Buffalo (Bubalus bubalis), an important livestock for milk and meat production, is known to have a better resistance to many diseases as compared to cattle. They are found to express many AMPs such as defensins, cathelicidins, and hepcidin which play an important role in neutralizing the invading pathogens. Buffalo AMPs exhibit broad-spectrum antimicrobial activity against both Gram-positive and Gram-negative bacteria. Similar to its natural form, synthetic analogs of buffalo AMPs are also antimicrobial against bacteria and even fungus making them a good target for the development of therapeutic antimicrobials. In addition to its antimicrobial effect, AMPs have been demonstrated to have a number of immunomodulatory functions, and their genes are responsive to infections. Further, induction of their gene expression by external factors may help in preventing infectious diseases. This review briefly discusses the AMPs of buffalo identified to date and their possible role in innate immunity.

The role of natural antimicrobial peptides during infection and chronic inflammation

Natural antimicrobial peptides (AMPs), a family of small polypeptides that are produced by constitutive or inducible expression in organisms, are integral components of the host innate immune system. In addition to their broad-spectrum antibacterial activity, natural AMPs also have many biological activities against fungi, viruses and parasites. Natural AMPs exert multiple immunomodulatory roles that may predominate under physiological conditions where they lose their microbicidal properties in serum and tissue environments. Increased drug resistance among microorganisms is occurring far more quickly than the discovery of new antibiotics. Natural AMPs have shown promise as 'next generation antibiotics' due to their broad-spectrum curative effects, low toxicity, the fact that they are not residual in animals, and the low rates of resistance exhibited by many pathogens. Many types of synthetic AMPs are currently being tested in clinical trials for the prevention and treatment of various diseases such as chemotherapy-associated infections, diabetic foot ulcers, catheter-related infections, and other conditions. Here, we provide an overview of the types and functions of natural AMPs and their role in combating microorganisms and different infectious and inflammatory diseases.

β-defensins: An innate defense for bovine mastitis

Immune challenges are inevitable for livestock that are exposed to a varied range of adverse conditions ranging from environmental to pathogenic stresses. The β-defensins are antimicrobial peptides, belonging to “defensin” family and therefore acts as the first line of defense against the major infections occurring in dairy cattle including intramammary infections. The better resistance to mastitis displayed by Bos indicus is implicit in the fact that they have better adapted and also has more sequence variation with rare allele conserved due to lesser artificial selection pressure than that of Bos taurus. Among the 58 in silico predicted β-defensins, only a few have been studied in the aspect of intramammary infections. The data on polymorphisms occurring in various β-defensin genes is limited in B. indicus, indicating toward higher possibilities for exploring marker for mastitis resistance. The following review shall focus on concisely summarizing the up-to-date research on β-defensins in B. taurus and discuss the possible scope for research in B. indicus.

Modulation of Human β-Defensin-1 Production by Viruses

While initially identified as a broad-spectrum antimicrobial peptide, constitutively expressed in epithelia, human β-defensin (hBD)-1 is now recognized to have a more complex pattern of expression of its gene, DEFB1, as well as activities that extend beyond direct antimicrobial. These observations suggest a complex role for hBD-1 in the host defense against viral infections, as evidenced by its expression in cells involved in viral defense, and its gene regulation in response to viral challenge. This regulation is observed both in vitro and in vivo in humans, as well as with the murine homolog, mBD-1. While numerous reviews have summarized the existing literature on β-defensin gene expression and activity, here we provide a focused review of relevant studies on the virus-mediated regulation of hBD-1 and how this regulation can provide a crucial aspect of the innate immune defense against viral infection.

Role of Streptococcus mutans two-component systems in antimicrobial peptide resistance in the oral cavity

Approximately 100 trillion microorganisms exist in the oral cavity. For the commensal bacteria of the oral cavity, it is important to adapt to environmental stimuli, including human- or bacteria-derived antimicrobial agents. Recently, bacterial-specific signal transduction regulatory systems, called two-component systems (TCSs), which appear to be focused on sensing and adapting to the environment, were discovered. Streptococcus mutans is an oral commensal bacteria and is also known as a cariogenic bacteria. Although the virulence factors of S. mutans have been well demonstrated, the mechanism underlying the adaptation of the species to the oral cavity is poorly understood. S. mutans UA159 has 15 sets of TCSs. Among them, several have been demonstrated to be involved in acid tolerance, competence and biofilm formation. Recently, together with our findings, it was demonstrated that 5 TCSs were involved in resistance to antimicrobial agents. Furthermore, another TCS was associated with the production of bacteriocin. Six of 15 TCSs are associated with antimicrobial agents, implying that S. mutans can survive in the oral cavity by resisting various antimicrobial peptides.

In this review, we highlight the role of antimicrobial peptides in the oral cavity.