Roles of antimicrobial peptides such as defensins in innate and adaptive immunity

The immune enhancing effect of antimicrobial peptide LLv on broilers chickens

To evaluate the effect and its mechanism of heat-resistant antimicrobial peptide LLv on broilers, three hundred 1-day-old healthy AA+ female broilers were allocated into 5 groups with 6 replicates in each group and 10 birds in each replicate. Birds were given a basal diet, an antibiotic diet (10.2 mg/kg chlortetracycline hydrochloride), and the basal diet supplemented with 10, 50, and 100 mg/kg LLv for 42 d, respectively. Compared with the group which birds were fed an antibiotic-free basal diet (control group), supplementing 100 mg/kg LLv increased 21-day IgA, IgM, IL-4, AIV-Ab, IFN-γ levels and 42-day IgA, IgM, IL-4, AIV-Ab levels and reduced 42-day IL-1 levels in serum (P < 0.05). Compared with antibiotic group, the 10 and 50 mg/kg LLv decreased 42-day IgM levels in serum (P < 0.05). The 100 mg/kg LLv increased 21-day AIV-Ab levels and 42-day IL-4, AIV-Ab levels and reduced 42-day IL-1 levels in serum (P < 0.05). Compared with control group, the 100 mg/kg LLv increased the expression rate of sIgA secretory cells and sIgA content in jejunal mucosa at 21 d and 42 d (P < 0.05), which did not differ from antibiotic group (P > 0.05). Compared with antibiotic group, the 10 mg/kg LLv reduced 21-day sIgA content and the 50 mg/kg LLv reduced 42-d the expression rate of sIgA secretory cells in jejunal mucosa (P < 0.05). Compared with control group, the 100 mg/kg LLv increased the expression of TCR, IL-15, CD28, BAFF, CD86, CD83, MHC-II, and CD40 genes in jejunal mucosa at 21 d and 42 d (P < 0.05). Compared with antibiotic group, the 100 mg/kg LLv increased the expression of 21-day BAFF, CD40, MHC-II, CD83 genes and the expression of 42-day BAFF, TCR, IL-15, CD40, CD83 genes in jejunal mucosa (P < 0.05). The results showed that the addition of LLv to the ration had a promotional effect on the immune function of broiler chickens.

Mechanistic Insight into the role of Vitamin D and Zinc in Modulating Immunity Against COVID-19: A View from an Immunological Standpoint

The pathophysiology of coronavirus disease-19 (COVID-19) is characterized by worsened inflammation because of weakened immunity, causing the infiltration of immune cells, followed by necrosis. Consequently, these pathophysiological changes may lead to a life-threatening decline in perfusion due to hyperplasia of the lungs, instigating severe pneumonia, and causing fatalities. Additionally, severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection can cause mortality due to viral septic shock, resulting from unrestrained and backfiring immune reactions to the pathogen. Sepsis can cause premature organ failure in COVID-19 patients, as well. Notably, vitamin D and its derivatives and minerals, such as zinc and magnesium, have been reported to improve the immune system against respiratory illnesses. This comprehensive review aims to provide updated mechanistic details of vitamin D and zinc as immunomodulators. Additionally, this review also focuses on their role in respiratory illnesses, while specifically delineating the plausibility of employing them as a preventive and therapeutic agent against current and future pandemics from an immunological perspective. Furthermore, this comprehensive review will attract the attention of health professionals, nutritionists, pharmaceuticals, and scientific communities, as it encourages the use of such micronutrients for therapeutic purposes, as well as promoting their health benefits for a healthy lifestyle and wellbeing.

Antimicrobial Peptides: The Production of Novel Peptide-Based Therapeutics in Plant Systems

The increased prevalence of antibiotic resistance is alarming and has a significant impact on the economies of emerging and underdeveloped nations. The redundancy of antibiotic discovery platforms (ADPs) and injudicious use of conventional antibiotics has severely impacted millions, across the globe. Potent antimicrobials from biological sources have been extensively explored as a ray of hope to counter the growing menace of antibiotic resistance in the population. Antimicrobial peptides (AMPs) are gaining momentum as powerful antimicrobial therapies to combat drug-resistant bacterial strains. The tremendous therapeutic potential of natural and synthesized AMPs as novel and potent antimicrobials is highlighted by their unique mode of action, as exemplified by multiple research initiatives. Recent advances and developments in antimicrobial discovery and research have increased our understanding of the structure, characteristics, and function of AMPs; nevertheless, knowledge gaps still need to be addressed before these therapeutic options can be fully exploited. This thematic article provides a comprehensive insight into the potential of AMPs as potent arsenals to counter drug-resistant pathogens, a historical overview and recent advances, and their efficient production in plants, defining novel upcoming trends in drug discovery and research. The advances in synthetic biology and plant-based expression systems for AMP production have defined new paradigms in the efficient production of potent antimicrobials in plant systems, a prospective approach to countering drug-resistant pathogens.

Antimicrobial Peptides in Infectious Diseases and Beyond-A Narrative Review

Despite recent medical research and clinical practice developments, the development of antimicrobial resistance (AMR) significantly limits therapeutics for infectious diseases. Thus, novel treatments for infectious diseases, especially in this era of increasing AMR, are urgently needed. There is ongoing research on non-classical therapies for infectious diseases utilizing alternative antimicrobial mechanisms to fight pathogens, such as bacteriophages or antimicrobial peptides (AMPs). AMPs are evolutionarily conserved molecules naturally produced by several organisms, such as plants, insects, marine organisms, and mammals, aiming to protect the host by fighting pathogenic microorganisms. There is ongoing research regarding developing AMPs for clinical use in infectious diseases. Moreover, AMPs have several other non-medical applications in the food industry, such as preservatives, animal husbandry, plant protection, and aquaculture. This review focuses on AMPs, their origins, biology, structure, mechanisms of action, non-medical applications, and clinical applications in infectious diseases.

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.

Myopia Control Efficacy and Long-Term Safety of a Novel Orthokeratology Lens (MESOK Study)-A Randomized Controlled Clinical Trial Combining Clinical and Tear Proteomics Data

Myopia control efficacy and long-term safety of the Breath-O-Correct orthokeratology (OK) lens was evaluated in a 2-year randomized, single vision (SV) spectacle lens-controlled, single-blind clinical trial combining clinical and tear proteomics data. A total of 71 children (43 OK, 9.8 ± 1.3 years; 28 SV, 9.5 ± 1.4 years) completed the 2-year study. Axial length (AL), cycloplegic refraction, clinical safety parameters (best-corrected visual acuity, central cornea thickness, corneal endothelial health, ocular surface disease index), and quantitative tear proteomics were evaluated by masked examiners. Mean 2-year-normalized AL elongations in the OK and SV groups differed significantly (p = 0.03) and were 0.37 ± 0.37 mm and 0.60 ± 0.41 mm, respectively. OK-mediated myopia control efficacy was 37.1%. No significant difference was found in clinical safety parameters of both groups (p > 0.10), except for a thinner central corneal thickness in the OK group (p = 0.01). Proteomics revealed modest OK lens-mediated effects on immune response proteins, including an increased abundance of haptoglobin at 6 and 12 months and a decreased abundance of two proteins (neutrophil defensin 3 and histone 4) at 6 months. The changes were further validated using a high-resolution multiple-reaction monitoring (MRM^HR) mass spectrometry. In summary, the Breath-O-Correct OK lens significantly reduced AL elongation in schoolchildren without adverse clinical effects or subclinical inflammatory responses.

Biodegradable Polymers and Polymer Composites with Antibacterial Properties

Antibiotic resistance is one of the greatest threats to global health and food security today. It becomes increasingly difficult to treat infectious disorders because antibiotics, even the newest ones, are becoming less and less effective. One of the ways taken in the Global Plan of Action announced at the World Health Assembly in May 2015 is to ensure the prevention and treatment of infectious diseases. In order to do so, attempts are made to develop new antimicrobial therapeutics, including biomaterials with antibacterial activity, such as polycationic polymers, polypeptides, and polymeric systems, to provide non-antibiotic therapeutic agents, such as selected biologically active nanoparticles and chemical compounds. Another key issue is preventing food from contamination by developing antibacterial packaging materials, particularly based on degradable polymers and biocomposites. This review, in a cross-sectional way, describes the most significant research activities conducted in recent years in the field of the development of polymeric materials and polymer composites with antibacterial properties. We particularly focus on natural polymers, i.e., polysaccharides and polypeptides, which present a mechanism for combating many highly pathogenic microorganisms. We also attempt to use this knowledge to obtain synthetic polymers with similar antibacterial activity.

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.

Towards the development of subunit vaccines against tuberculosis: The key role of adjuvant

According to the World Health Organization (WHO), tuberculosis (TB) is the leading cause of death triggered by a single infectious agent, worldwide. Bacillus Calmette-Guerin (BCG) is the only currently licensed anti-TB vaccine. However, other strategies, including modification of recombinant BCG vaccine, attenuated Mycobacterium tuberculosis (Mtb) mutant constructs, DNA and protein subunit vaccines, are under extensive investigation. As whole pathogen vaccines can trigger serious adverse reactions, most current strategies are focused on the development of safe anti-TB subunit vaccines; this is especially important given the rising TB infection rate in immunocompromised HIV patients. The whole Mtb genome has been mapped and major antigens have been identified; however, optimal vaccine delivery mode is still to be established. Isolated protein antigens are typically poorly immunogenic so adjuvants are required to induce strong and long-lasting immune responses. This article aims to review the developmental status of anti-TB subunit vaccine adjuvants.

Microbial derived antimicrobial peptides as potential therapeutics in atopic dermatitis

Atopic dermatitis (AD) is a common chronic inflammatory skin disease that significantly affects the patient's quality of life. A disrupted skin barrier, type 2 cytokine-dominated inflammation, and microbial dysbiosis with increased Staphylococcus aureus colonization are critical components of AD pathogenesis. Patients with AD exhibit decreased expression of antimicrobial peptides (AMPs) which is linked to increased colonization by Staphylococcus aureus. The skin microbiome itself is a source of several AMPs. These host- and microbiome-derived AMPs define the microbial landscape of the skin based on their differential antimicrobial activity against a range of skin microbes or their quorum sensing inhibitory properties. These are particularly important in preventing and limiting dysbiotic colonization with Staphylococcus aureus. In addition, AMPs are critical for immune homeostasis. In this article, we share our perspectives about the implications of microbial derived AMPs in AD patients and their potential effects on overlapping factors involved in AD. We argue and discuss the potential of bacterial AMPs as therapeutics in AD.

The role of pyroptosis in endothelial dysfunction induced by diseases

Most organs in the body rely on blood flow, and vesicular damage is the leading cause of injury in multiple organs. The endothelium, as the barriers of vessels, play a critical role in ensuring vascular homeostasis and angiogenesis. The rapid development of risk factors in endothelial injuries has been seen in the past decade, such as smoking, infectious, and diabetes mellites. Pyroptotic endothelium is an inflammatory mode of governed endothelial cell death that depend on the metabolic disorder and severe infectious such as atherosclerosis, and sepsis-related acute lung injury, respectively. Pyroptotic endothelial cells need GSDMD cleaved into N- and C-terminal by caspase1, and the cytokines are released by a pore constructed by the N-terminal of GSDMD in the membrane of ECs, finally resulting in severe inflammation and pyroptotic cell death. This review will focus on the patho-physiological and pharmacological pathways of pyroptotic endothelial metabolism in diseases. Overall, this review indicates that pyroptosis is a significant risk factor in diseases and a potential drug target in related diseases.

The role of pyroptosis in endothelial dysfunction induced by diseases

Most organs in the body rely on blood flow, and vesicular damage is the leading cause of injury in multiple organs. The endothelium, as the barriers of vessels, play a critical role in ensuring vascular homeostasis and angiogenesis. The rapid development of risk factors in endothelial injuries has been seen in the past decade, such as smoking, infectious, and diabetes mellites. Pyroptotic endothelium is an inflammatory mode of governed endothelial cell death that depend on the metabolic disorder and severe infectious such as atherosclerosis, and sepsis-related acute lung injury, respectively. Pyroptotic endothelial cells need GSDMD cleaved into N- and C-terminal by caspase1, and the cytokines are released by a pore constructed by the N-terminal of GSDMD in the membrane of ECs, finally resulting in severe inflammation and pyroptotic cell death. This review will focus on the patho-physiological and pharmacological pathways of pyroptotic endothelial metabolism in diseases. Overall, this review indicates that pyroptosis is a significant risk factor in diseases and a potential drug target in related diseases.

Lactococcus lactis engineered to deliver hCAP18 cDNA alleviates DNBS-induced colitis in C57BL/6 mice by promoting IL17A and IL10 cytokine expression

With its antimicrobial and immunomodulating properties, the cathelicidin (LL37) plays an important role in innate immune system. Here, we attempted to alleviate chemically induced colitis using a lactococci strain that either directly expressed the precursor to LL37, hCAP18 (LL-pSEC:hCAP18), or delivered hCAP18 cDNA to host cells under the control of the cytomegalovirus promoter (LL-Probi-H1:hCAP18). We also investigated whether the alleviation of symptoms could be explained through modification of the gut microbiota by hCAP18. Mice were administered daily doses of LL-pSEC:hCAP18 or LL-Probi-H1:hCAP18. On day 7, colitis was induced by DNBS. During autopsy, we assessed macroscopic tissue damage in the colon and collected tissue samples for the characterization of inflammation markers and histological analysis. Feces were collected at day 7 for 16S DNA sequencing. We also performed a fecal transplant experiment in which mice underwent colon washing and received feces from Lactococcus lactis-treated mice before DNBS-colitis induction. Treatment with LL-Probi-H1:hCAP18 reduced the severity of colitis symptoms. The protective effects were accompanied by increased levels of IL17A and IL10 in mesenteric lymph node cells. L. lactis administration altered the abundance of Lachnospiraceae and Muribaculaceae. However, fecal transplant from L. lactis-treated mice did not improve DNBS-induced symptoms in recipient mice.

Design of Multi-Epitope Vaccine for Staphylococcus saprophyticus: Pan-Genome and Reverse Vaccinology Approach

Staphylococcus saprophyticus is a Gram-positive coccus responsible for the occurrence of cystitis in sexually active, young females. While effective antibiotics against this organism exist, resistant strains are on the rise. Therefore, prevention via vaccines appears to be a viable solution to address this problem. In comparison to traditional techniques of vaccine design, computationally aided vaccine development demonstrates marked specificity, efficiency, stability, and safety. In the present study, a novel, multi-epitope vaccine construct was developed against S. saprophyticus by targeting fully sequenced proteomes of its five different strains, which were examined using a pangenome and subtractive proteomic strategy to characterize prospective vaccination targets. The three immunogenic vaccine targets which were utilized to map the probable immune epitopes were verified by annotating the entire proteome. The predicted epitopes were further screened on the basis of antigenicity, allergenicity, water solubility, toxicity, virulence, and binding affinity towards the DRB*0101 allele, resulting in 11 potential epitopes, i.e., DLKKQKEKL, NKDLKKQKE, QDKLKDKSD, NVMDNKDLE, TSGTPDSQA, NANSDGSSS, GSDSSSSNN, DSSSSNNDS, DSSSSDRNN, SSSDRNNGD, and SSDDKSKDS. All these epitopes have the efficacy to cover 99.74% of populations globally. Finally, shortlisted epitopes were joined together with linkers and three different adjuvants to find the most stable and immunogenic vaccine construct. The top-ranked vaccine construct was further scrutinized on the basis of its physicochemical characterization and immunological profile. The non-allergenic and antigenic features of modeled vaccine constructs were initially validated and then subjected to docking with immune receptor major histocompatibility complex I and II (MHC-I and II), resulting in strong contact. In silico cloning validations yielded a codon adaptation index (CAI) value of 1 and an ideal percentage of GC contents (46.717%), indicating a putative expression of the vaccine in E. coli. Furthermore, immune simulation demonstrated that, after injecting the proposed MEVC, powerful antibodies were produced, resulting in the sharpest peaks of IgM + IgG formation (>11,500) within 5 to 15 days. Experimental testing against S. saprophyticus can evaluate the safety and efficacy of these prophylactic vaccination designs.

Mesenchymal Stem Cell-Derived Antimicrobial Peptides as Potential Anti-Neoplastic Agents: New Insight into Anticancer Mechanisms of Stem Cells and Exosomes

Mesenchymal stem cells (MSCs), as adult multipotent cells, possess considerable regenerative and anti-neoplastic effects, from inducing apoptosis in the cancer cells to reducing multidrug resistance that bring them up as an appropriate alternative for cancer treatment. These cells can alter the behavior of cancer cells, the condition of the tumor microenvironment, and the activity of immune cells that result in tumor regression. It has been observed that during inflammatory conditions, a well-known feature of the tumor microenvironment, the MSCs produce and release some molecules called “antimicrobial peptides (AMPs)” with demonstrated anti-neoplastic effects. These peptides have remarkable targeted anticancer effects by attaching to the negatively charged membrane of neoplastic cells, disrupting the membrane, and interfering with intracellular pathways. Therefore, AMPs could be considered as a part of the wide-ranging anti-neoplastic effects of MSCs. This review focuses on the possible anti-neoplastic effects of MSCs-derived AMPs and their mechanisms. It also discusses preconditioning approaches and using exosomes to enhance AMP production and delivery from MSCs to cancer cells. Besides, the clinical administration of MSCs-derived AMPs, along with their challenges in clinical practice, were debated.

Mucosal and systemic immune effects of Bacillus subtilis in rainbow trout (Oncorhynchus mykiss)

Bacillus spp. are well known for their probiotic properties. Hence, the long-term feeding of Bacillus spp. strains to different fish species has been proved to confer beneficial effects regarding growth or pathogen resistance, among others. However, whether these strains could function as mucosal adjuvants, up-regulating immune responses after a single administration, has not yet been investigated in fish. Thus, in the current work, we have performed a series of experiments in rainbow trout (Oncorhynchus mykiss) aimed at establishing the potential of two Bacillus subtilis spore-forming strains, designated as ABP1 and ABP2, as oral adjuvants/immunostimulants. As an initial step, we evaluated their transcriptional effects on the rainbow trout intestinal epithelial cell line RTgutGC, and in gut tissue explants incubated ex vivo with the two strains. Their capacity to adhere to RTgutGC cells was also evaluated by flow cytometry. Although both strains had the capacity to modulate the transcription of several genes related to innate and adaptive immune responses, it was the ABP1 strain that led to stronger transcriptional effects, also exerting a higher binding capacity to intestinal epithelial cells. Consequently, we selected this strain to establish its effects on splenic B cells upon in vitro exposure as well as to determine the transcriptional effects exerted in the spleen, kidney, and gut after a single oral administration of the bacteria. Our results showed that B. subtilis ABP1 had the capacity to modulate the proliferation, IgM secreting capacity and MHC II surface expression of splenic B cells. Finally, we confirmed that this strain also induced the transcription of genes involved in inflammation, antimicrobial genes, and genes involved in T cell responses upon a single oral administration. Our results provide valuable information regarding how B. subtilis modulates the immune response of rainbow trout, pointing to the usefulness of the ABP1 strain to design novel oral vaccination strategies for aquaculture.

Compartmentalized Innate Immune Response of Human Fetal Membranes against Escherichia coli Choriodecidual Infection

An infectious process into the uterine cavity represents a major endangered condition that compromises the immune privilege of the maternal-fetal unit and increases the risk for preterm birth (PTB) and premature rupture of membranes (PROM). Fetal membranes are active secretors of antimicrobial peptides (AMP), which limit bacterial growth, such as Escherichia coli. Nevertheless, the antibacterial responses displayed by chorioamniotic membranes against a choriodecidual E. coli infection have been briefly studied. The objective of this research was to characterize the profile of synthesis, activity, and spatial distribution of a broad panel of AMPs produced by fetal membranes in response to E. coli choriodecidual infection. Term human chorioamniotic membranes were mounted in a two independent compartment model in which the choriodecidual region was infected with live E. coli (1 × 10⁵ CFU/mL). Amnion and choriodecidual AMP tissue levels and TNF-α and IL-1β secretion were measured by the enzyme-linked immunosorbent assay. The passage of bacterium through fetal membranes and their effect on structural continuity was followed for 24 h. Our results showed that E. coli infection caused a progressive mechanical disruption of the chorioamniotic membranes and an activated inflammatory environment. After the challenge, the amnion quickly (2-4 h) induced production of human beta defensins (HBD)-1, HBD-2, and LL-37. Afterwards (8-24 h), the amnion significantly produced HBD-1, HBD-2, HNP-1-3, S100A7, sPLA2, and elafin, whereas the choriodecidua induced LL-37 synthesis. Therefore, we noticed a temporal- and tissue-specific pattern regulation of the synthesis of AMPs by infected fetal membranes. However, fetal membranes were not able to contain the collagen degradation or the bacterial growth and migration despite the battery of produced AMPs, which deeply increases the risk for PTB and PROM. The mixture of recombinant HBDs at low concentrations resulted in increased bactericidal activity compared to each HBD alone in vitro, encouraging further research to study AMP combinations that may offer synergy to control drug-resistant infections in the perinatal period.

Immunomodulatory and Allergenic Properties of Antimicrobial Peptides

With the growing problem of the emergence of antibiotic-resistant bacteria, the search for alternative ways to combat bacterial infections is extremely urgent. While analyzing the effect of antimicrobial peptides (AMPs) on immunocompetent cells, their effect on all parts of the immune system, and on humoral and cellular immunity, is revealed. AMPs have direct effects on neutrophils, monocytes, dendritic cells, T-lymphocytes, and mast cells, participating in innate immunity. They act on B-lymphocytes indirectly, enhancing the induction of antigen-specific immunity, which ultimately leads to the activation of adaptive immunity. The adjuvant activity of AMPs in relation to bacterial and viral antigens was the reason for their inclusion in vaccines and made it possible to formulate the concept of a “defensin vaccine” as an innovative basis for constructing vaccines. The immunomodulatory function of AMPs involves their influence on cells in the nearest microenvironment, recruitment and activation of other cells, supporting the response to pathogenic microorganisms and completing the inflammatory process, thus exhibiting a systemic effect. For the successful use of AMPs in medical practice, it is necessary to study their immunomodulatory activity in detail, taking into account their pleiotropy. The degree of maturity of the immune system and microenvironment can contribute to the prevention of complications and increase the effectiveness of therapy, since AMPs can suppress inflammation in some circumstances, but aggravate the response and damage of organism in others. It should also be taken into account that the real functions of one or another AMP depend on the types of total regulatory effects on the target cell, and not only on properties of an individual peptide. A wide spectrum of biological activity, including direct effects on pathogens, inactivation of bacterial toxins and influence on immunocompetent cells, has attracted the attention of researchers, however, the cytostatic activity of AMPs against normal cells, as well as their allergenic properties and low stability to host proteases, are serious limitations for the medical use of AMPs. In this connection, the tasks of searching for compounds that selectively affect the target and development of an appropriate method of application become critically important. The scope of this review is to summarize the current concepts and newest advances in research of the immunomodulatory activity of natural and synthetic AMPs, and to examine the prospects and limitations of their medical use.

Human Cryptic Host Defence Peptide GVF27 Exhibits Anti-Infective Properties against Biofilm Forming Members of the Burkholderia cepacia Complex

Therapeutic solutions to counter Burkholderia cepacia complex (Bcc) bacteria are challenging due to their intrinsically high level of antibiotic resistance. Bcc organisms display a variety of potential virulence factors, have a distinct lipopolysaccharide naturally implicated in antimicrobial resistance. and are able to form biofilms, which may further protect them from both host defence peptides (HDPs) and antibiotics. Here, we report the promising anti-biofilm and immunomodulatory activities of human HDP GVF27 on two of the most clinically relevant Bcc members, Burkholderia multivorans and Burkholderia cenocepacia. The effects of synthetic and labelled GVF27 were tested on B. cenocepacia and B. multivorans biofilms, at three different stages of formation, by confocal laser scanning microscopy (CLSM). Assays on bacterial cultures and on human monocytes challenged with B. cenocepacia LPS were also performed. GVF27 exerts, at different stages of formation, anti-biofilm effects towards both Bcc strains, a significant propensity to function in combination with ciprofloxacin, a relevant affinity for LPSs isolated from B. cenocepacia as well as a good propensity to mitigate the release of pro-inflammatory cytokines in human cells pre-treated with the same endotoxin. Overall, all these findings contribute to the elucidation of the main features that a good therapeutic agent directed against these extremely leathery biofilm-forming bacteria should possess.

Bioactive Peptides: Synthesis, Sources, Applications, and Proposed Mechanisms of Action

Bioactive peptides are a group of biological molecules that are normally buried in the structure of parent proteins and become active after the cleavage of the proteins. Another group of peptides is actively produced and found in many microorganisms and the body of organisms. Today, many groups of bioactive peptides have been marketed chemically or recombinantly. This article reviews the various production methods and sources of these important/ubiquitous and useful biomolecules. Their applications, such as antimicrobial, antihypertensive, antioxidant activities, blood-lipid-lowering effect, opioid role, antiobesity, ability to bind minerals, antidiabetic, and antiaging effects, will be explored. The types of pathways proposed for bioactive applications will be in the next part of the article, and at the end, the future perspectives of bioactive peptides will be reviewed. Reading this article is recommended for researchers interested in various fields of physiology, microbiology, biochemistry, and nanotechnology and food industry professionals.

Multiple Precursor Proteins of Thanatin Isoforms, an Antimicrobial Peptide Associated With the Gut Symbiont of Riptortus pedestris

Thanatin is an antimicrobial peptide (AMP) generated by insects for defense against bacterial infections. In the present study, we performed cDNA cloning of thanatin and found the presence of multiple precursor proteins from the bean bug, Riptortus pedestris. The cDNA sequences encoded 38 precursor proteins, generating 13 thanatin isoforms. In the phylogenetic analysis, thanatin isoforms were categorized into two groups based on the presence of the membrane attack complex/perforin (MACPF) domain. In insect-bacterial symbiosis, specific substances are produced by the immune system of the host insect and are known to modulate the symbiont’s population. Therefore, to determine the biological function of thanatin isoforms in symbiosis, the expression levels of three AMP genes were compared between aposymbiotic insects and symbiotic R. pedestris. The expression levels of the thanatin genes were significantly increased in the M4 crypt, a symbiotic organ, of symbiotic insects upon systemic bacterial injection. Further, synthetic thanatin isoforms exhibited antibacterial activity against gut-colonized Burkholderia symbionts rather than in vitro-cultured Burkholderia cells. Interestingly, the suppression of thanatin genes significantly increased the population of Burkholderia gut symbionts in the M4 crypt under systemic Escherichia coli K12 injection. Overgrown Burkholderia gut symbionts were observed in the hemolymph of host insects and exhibited insecticidal activity. Taken together, these results suggest that thanatin of R. pedestris is a host-derived symbiotic factor and an AMP that controls the population of gut-colonized Burkholderia symbionts.

Mesenchymal Stromal/Stem Cells-Derived Exosomes as an Antimicrobial Weapon for Orodental Infections

The oral cavity as the second most various microbial community in the body contains a broad spectrum of microorganisms which are known as the oral microbiome. The oral microbiome includes different types of microbes such as bacteria, fungi, viruses, and protozoa. Numerous factors can affect the equilibrium of the oral microbiome community which can eventually lead to orodental infectious diseases. Periodontitis, dental caries, oral leukoplakia, oral squamous cell carcinoma are some multifactorial infectious diseases in the oral cavity. In defending against infection, the immune system has an essential role. Depending on the speed and specificity of the reaction, immunity is divided into two different types which are named the innate and the adaptive responses but also there is much interaction between them. In these responses, different types of immune cells are present and recent evidence demonstrates that these cell types both within the innate and adaptive immune systems are capable of secreting some extracellular vesicles named exosomes which are involved in the response to infection. Exosomes are 30-150 nm lipid bilayer vesicles that consist of variant molecules, including proteins, lipids, and genetic materials and they have been associated with cell-to-cell communications. However, some kinds of exosomes can be effective on the pathogenicity of various microorganisms and promoting infections, and some other ones have antimicrobial and anti-infective functions in microbial diseases. These discrepancies in performance are due to the origin of the exosome. Exosomes can modulate the innate and specific immune responses of host cells by participating in antigen presentation for activation of immune cells and stimulating the release of inflammatory factors and the expression of immune molecules. Also, mesenchymal stromal/stem cells (MSCs)-derived exosomes participate in immunomodulation by different mechanisms. Ease of expansion and immunotherapeutic capabilities of MSCs, develop their applications in hundreds of clinical trials. Recently, it has been shown that cell-free therapies, like exosome therapies, by having more advantages than previous treatment methods are emerging as a promising strategy for the treatment of several diseases, in particular inflammatory conditions. In orodental infectious disease, exosomes can also play an important role by modulating immunoinflammatory responses. Therefore, MSCs-derived exosomes may have potential therapeutic effects to be a choice for controlling and treatment of orodental infectious diseases.

Immunoinformatics Approach to Design Multi-Epitope- Subunit Vaccine against Bovine Ephemeral Fever Disease

Bovine ephemeral fever virus (BEFV) is an overlooked pathogen, recently gaining widespread attention owing to its associated enormous economic impacts affecting the global livestock industries. High endemicity with rapid spread and morbidity greatly impacts bovine species, demanding adequate attention towards BEFV prophylaxis. Currently, a few suboptimum vaccines are prevailing, but were confined to local strains with limited protection. Therefore, we designed a highly efficacious multi-epitope vaccine candidate targeted against the geographically distributed BEFV population. By utilizing immunoinformatics technology, all structural proteins were targeted for B- and T-cell epitope prediction against the entire allele population of BoLA molecules. Prioritized epitopes were adjoined by linkers and adjuvants to effectively induce both cellular and humoral immune responses in bovine. Subsequently, the in silico construct was characterized for its physicochemical parameters, high immunogenicity, least allergenicity, and non-toxicity. The 3D modeling, refinement, and validation of ligand (vaccine construct) and receptor (bovine TLR7) then followed molecular docking and molecular dynamic simulation to validate their stable interactions. Moreover, in silico cloning of codon-optimized vaccine construct in the prokaryotic expression vector (pET28a) was explored. This is the first time HTL epitopes have been predicted using bovine datasets. We anticipate that the designed construct could be an effective prophylactic remedy for the BEF disease that may pave the way for future laboratory experiments.

Ganglioside Alters Phospholipase Trafficking, Inhibits NF-κB Assembly, and Protects Tight Junction Integrity

Background and Aims: Dietary gangliosides are present in human milk and consumed in low amounts from organ meats. Clinical and animal studies indicate that dietary gangliosides attenuate signaling processes that are a hallmark of inflammatory bowel disease (IBD). Gangliosides decrease pro-inflammatory markers, improve intestinal permeability, and reduce symptoms characteristic in patients with IBD. The objective of this study was to examine mechanisms by which dietary gangliosides exert beneficial effects on intestinal health. Methods: Studies were conducted in vitro using CaCo-2 intestinal epithelial cells. Gangliosides were extracted from milk powder and incubated with differentiated CaCo-2 cells after exposure to pro-inflammatory stimuli. Gut barrier integrity was assessed by electron microscopy, epithelial barrier function was examined by measuring transepithelial electric resistance, and content of HBD-2, IL-23, NF-κB, and sPLA₂ was assessed by ELISA. Results: Ganglioside attenuated the decrease in integrity of tight junctions induced by pro-inflammatory stimuli and improved epithelial barrier function (P < 0.05). Ganglioside decreased the basolateral secretion of sPLA₂ (P ≤ 0.05), lowered HBD-2 and IL-23 levels (P ≤ 0.05), and inhibited NF-κB activation (P ≤ 0.05). Conclusions: In summary, the present study indicates that ganglioside GD3 improves intestinal integrity by altering sPLA₂ trafficking, and the production of pro-inflammatory mediators is mitigated by decreasing assembly of the NF-κB complex. Dietary gangliosides may have promising potential beneficial effects in IBD as decreased inflammatory signaling, improved intestinal integrity, and maintenance of epithelial barrier function have been demonstrated in vitro.

Activity of Anti-Microbial Peptides (AMPs) against Leishmania and Other Parasites: An Overview

Anti-microbial peptides (AMPs), small biologically active molecules, produced by different organisms through their innate immune system, have become a considerable subject of interest in the request of novel therapeutics. Most of these peptides are cationic-amphipathic, exhibiting two main mechanisms of action, direct lysis and by modulating the immunity. The most commonly reported activity of AMPs is their anti-bacterial effects, although other effects, such as anti-fungal, anti-viral, and anti-parasitic, as well as anti-tumor mechanisms of action have also been described. Their anti-parasitic effect against leishmaniasis has been studied. Leishmaniasis is a neglected tropical disease. Currently among parasitic diseases, it is the second most threating illness after malaria. Clinical treatments, mainly antimonial derivatives, are related to drug resistance and some undesirable effects. Therefore, the development of new therapeutic agents has become a priority, and AMPs constitute a promising alternative. In this work, we describe the principal families of AMPs (melittin, cecropin, cathelicidin, defensin, magainin, temporin, dermaseptin, eumenitin, and histatin) exhibiting a potential anti-leishmanial activity, as well as their effectiveness against other microorganisms.

Antimicrobial and immunomodulatory in vitro profile of double antibiotic paste

AIM

To evaluate the antimicrobial and immunomodulatory activity of double antibiotic paste (DAP) in an in vitro infection model.

METHODOLOGY

The minimum inhibitory and bactericidal concentrations (MIC and MBC) and the antibiofilm activities (TTC assay) of DAP and its components (ciprofloxacin and metronidazole) were evaluated against Staphylococcus aureus and Enterococcus faecalis compared with triple antibiotic paste (TAP). The cellular viability of RAW 264.7 macrophages (24 and 72 h) and L929 fibroblasts (48 and 72 h) was evaluated by MTT. Furthermore, the production of TNF-α, IL-12, IL-6, IL-1α, IL-10 and NO (on RAW 264.7), besides IL-6, TGF-β and NO (on L929), stimulated with DAP in baseline and associated with heat-killed microbial-antigen conditions was measured by ELISA and Griess reaction. Data were analysed using the one-way ANOVA test with Bonferroni's corrections.

RESULTS

The MBC of pharmacopoeia DAP was similar to TAP for E. faecalis (0.25 μg.  mL^-1 ) and lower for S. aureus (DAP 1 μg. mL^-1 and TAP 2 μg. mL^-1 ; p < .001). Ciprofloxacin was the most effective antibiofilm drug from the pastes (35% of reduction for E. faecalis and S. aureus; p < .0001), and both pastes had a similar antibiofilm eradication against both biofilm species (29% and 35% for S. aureus and 76% and 85% for E. faecalis; p < .0001). DAP was cytotoxic against the tested cells. DAP significantly upregulated IL-1α (p < .001), IL-6 (p < .0001), TNF-α (p < .01) and IL-12 (p < .05; in the absence of antigens) and significantly reduced IL-6 (p < .0001; in the presence of HK-S. aureus) and IL-10 (p < .05; in the presence of both antigens) on macrophages. Furthermore, DAP upregulated IL-6 (p < .001) and NO (p < .05; in the absence of antigens), IL-6 (p < .001; in the presence of HK-S. aureus) and reduced NO (p < .001; in the presence of HK-S. aureus).

CONCLUSIONS

Double antibiotic paste and TAP had similar antimicrobial activity against S. aureus and E. faecalis. DAP upregulated pro-inflammatory cytokines mainly in the absence of antigens and had pro- and anti-inflammatory activity in RAW 264.7 macrophages and L929 fibroblasts in the presence of antigens involved in pulp infections.

Recent advances in design of antimicrobial peptides and polypeptides toward clinical translation

The recent outbreaks of infectious diseases caused by multidrug-resistant pathogens have sounded a piercing alarm for the need of new effective antimicrobial agents to guard public health. Among different types of candidates, antimicrobial peptides (AMPs) and the synthetic mimics of AMPs (SMAMPs) have attracted significant enthusiasm in the past thirty years, due to their unique membrane-active antimicrobial mechanism and broad-spectrum antimicrobial activity. The extensive research has brought many drug candidates into clinical and pre-clinical development. Despite tremendous progresses have been made, several major challenges inherent to current design strategies have slowed down the clinical translational development of AMPs and SMAMPs. However, these challenges also triggered many efforts to redesign and repurpose AMPs. In this review, we will first give an overview on AMPs and their synthetic mimics, and then discuss the current status of their clinical translation. Finally, the recent advances in redesign and repurposing AMPs and SMAMPs are highlighted.

Delving Into the Origin of Destructive Inflammation in COVID-19: A Betrayal of Natural Host Defense Peptides?

In contrast to other pathogenic agents that directly destroy host cells and tissues, the lethal power of SARS-CoV-2 resides in the over-reactive immune response triggered by this virus. Based on numerous evidences indicating that the lipid composition of host membranes is dramatically affected by COVID-19, and in the fact that our endogenous antimicrobial peptides (AMPs) are sensitive to the membrane composition of pathogenic agents, we propose that such destructive immune response is due to the direct action of AMPs. In a scenario where most host cell membranes are dressed by a pathogenic lipid composition, AMPs can indiscriminately attack them. This is why we use the "AMP betrayal" term to describe this mechanism. Previously proposed cytokine/bradykinin storm mechanisms are not incompatible with this new proposal. Interestingly, the harmful action of AMPs could be prevented by new therapies aimed to reestablish the lipid composition or to inhibit the action of specific peptides.

Enzymes as a Reservoir of Host Defence Peptides

Host defence peptides (HDPs) are powerful modulators of cellular responses to various types of insults caused by pathogen agents. To date, a wide range of HDPs, from species of different kingdoms including bacteria, plant and animal with extreme diversity in structure and biological activity, have been described. Apart from a limited number of peptides ribosomally synthesized, a large number of promising and multifunctional HDPs have been identified within protein precursors, with properties not necessarily related to innate immunity, consolidating the fascinating hypothesis that proteins have a second or even multiple biological mission in the form of one or more bio-active peptides. Among these precursors, enzymes constitute certainly an interesting group, because most of them are mainly globular and characterized by a fine specific internal structure closely related to their catalytic properties and also because they are yet little considered as potential HDP releasing proteins. In this regard, the main aim of the present review is to describe a panel of HDPs, identified in all canonical classes of enzymes, and to provide a detailed description on hydrolases and their corresponding HDPs, as there seems to exist a striking link between these structurally sophisticated catalysts and their high content in cationic and amphipathic cryptic peptides.

Addressing Antimicrobial Resistance Through Nanoantibiotics

In recent years, the irrational use of antibiotics has escalated the evolution of multidrug-resistant (MDR) bacterial strains. The infectious diseases caused by these MDR bacterial strains remain a major threat to human health and have emerged as the leading cause of morbidity and mortality. The WHO and CDC have expressed serious concern regarding the continued increase in the development of multidrug resistance among bacteria. The antimicrobial resistance (AMR) poses a severe global threat of growing concern to human health and economic burden. Bacteria have developed the ability to resist antimicrobials by altering target site/enzyme, inactivation of the enzyme, decreasing cell permeability, increasing efflux due to over-expression of efflux pumps, target protection, target overproduction, and many other ways. The shortage of new antimicrobials and rapid rise in antibiotic resistance demands pressing need to develop alternate antibacterial agents.

Serum defensin levels in patients with systemic sclerosis

BACKGROUND

Systemic sclerosis (SSc) is an autoimmune disease characterized by fibrosis of skin and lung as well as involvement of kidney, gastrointestinal system and heart. Aetiology and exact mechanism of disease is poorly understood. The association between antimicrobial peptides (AMPs) and other diseases such as idiopathic pulmonary fibrosis, diffuse panbronchiolitis, pulmoner alveolar proteinosis and psoriasis have been reported. A small number of studies have examined the role of AMPs on autoimmune diseases which has not been studied in scleroderma yet. We aimed to investigate AMP serum levels and their association with disease characteristics of SSc.

METHODS

Forty-two patients (40 female, mean age 42 years) and 38 healthy subjects (32 female, mean age 38 years) were enrolled. For SSc patients, the following data were recorded: disease subset (limited/diffuse), autoantibodies (antinuclear, anti-centromere (ACA), and anti-SCL-70), blood tests, erythrocyte sedimentation rate (ESR), and C-reactive protein (CRP), modified Rodnan skin score, presence and history of digital ulcers, kidney, gastrointestinal disease and lung involvement assessed by computed tomography and pulmonary function tests. Association between serum AMPs and disease characteristics were analysed.

RESULTS

Twenty-nine of the patients had diffuse (69%) and 13 of the patients had limited (31%) systemic sclerosis. Average disease duration was 5.5 years. Pulmonary involvement was detected in 20 patients (47.6%). Serum concentration of alpha defensin was higher than healthy subjects (563 ± 415 vs 377 ± 269 ng/mL, p = 0.02). However, no difference was observed for beta-1 and beta-2 defensins in SSc patients and healthy controls. In sub-group analysis patients with interstitial lung disease had higher levels of alpha defensin than those without lung involvement (684 ± 473 vs 430 ± 299 ng/ml, p = 0.04). There was also correlation between alfa defensin serum concentrations and CRP (r = 0.34).

CONCLUSIONS

Alpha defensin levels are increased in scleroderma patients and correlated with lung involvement indicating a role in the pathogenesis of disease.

TRIAL REGISTRATION

This study is not a clinical trial study.

Beta-defensin 1 gene polymorphisms in the pathologies of the oral cavity-Data from meta-analysis: Association only with rs1047031 not with rs1800972, rs1799946, and rs11362

OBJECTIVES

The purpose of this meta-analysis was to reveal a potential association of the four functional polymorphisms in human Beta-defensin 1 (DEFB1) gene: rs1047031(c*5G > A) at 3'UTR and rs11362 (-20 G > A), rs1800972(-44 C > G), and rs1799946 (-52 G > A) at 5'UTR with the risk of common oral cavity pathologies that included periodontitis, caries, lichen planus, and recurrent aphthous stomatitis.

METHODS

The relevant studies were obtained by the two researchers from PubMed, Scopus, and Web of Science up to April 29, 2020. The manual search of the reference lists was also performed. Studies on DEFB1 gene polymorphisms and oral cavity disorders, using the case-control genetic association analysis approach, and published as full texts in English were included. To assess the association strength, odds ratios (ORs) with their 95% confidence intervals (CIs) were extracted.

RESULTS

Thirteen publications met the inclusion criteria and were incorporated in this meta-analysis. Statistically significant values of the association tests were found only for the rs1047031 polymorphism. Allele distribution in the rs1047031 polymorphism was significantly associated with susceptibility to oral cavity pathologies (adjusted P value = 0.003). The rare variant allele carriers had a significantly higher risk for oral disasters under recessive (CC vs CT + TT), and CC vs CT models. No significant correlations between rs11362, rs1800972, and rs1799946 and the risk of oral pathologies were revealed.

CONCLUSIONS

Significant association between rs1047031 polymorphism and risk of oral pathologies has been found, and therefore, we suggest to include this polymorphism in future research concerning the genetic background of the oral cavity diseases.

Potential of the Escherichia coli LT(R192G/L211A) toxoid as a mucosal adjuvant for rainbow trout (Oncorhynchus mykiss)

Oral vaccines are highly demanded by aquaculture sector that requires alternatives to injectable vaccines, involving fish handling, stress-related immunosuppression and mortalities. However, most previous attempts to obtain effective oral vaccines have failed due to a restricted tolerance mechanisms in intestine, whose mucosa is at the frontline of antigen encounter and has to balance the equilibrium between tolerance and immunity in a microbe-rich environment. Thus, the search for oral adjuvants that could augment immune responses triggered by antigens allowing them to circumvent intestinal tolerance is of great relevance. The present work focuses on the adjuvant potential of the Escherichia coli LT(R192G/L211A) toxoid (dmLT). To undertake an initial screening of the potential that dmLT has as an oral adjuvant in rainbow trout (Oncorhynchus mykiss), we have analyzed its transcriptional effects alone or in combination with Aeromonas salmonicida subsp. salmonicida or viral hemorrhagic septicemia virus (VHSV) on rainbow trout intestinal epithelial cell line RTgutGC and gut explants. Our results show that although dmLT provoked no significant effects by itself, it increased the transcription of pro-inflammatory cytokines and antimicrobial genes induced by the bacteria. In contrast, when combined with VHSV, dmLT only increased the transcription of Mx and the intracellular adhesion molecule 1 (ICAM1). Therefore, the protocol designed is an effective method to initially evaluate the effects of potential oral adjuvants, and points to dmLT as an effective adjuvant for oral antibacterial vaccines.

Designing an efficient multi-epitope vaccine displaying interactions with diverse HLA molecules for an efficient humoral and cellular immune response to prevent COVID-19 infection

Background

The novel SARS-CoV-2 coronavirus, the causative agent of the ongoing pandemic COVID-19 disease continues to infect people globally and has infected millions of humans worldwide. However, no effective vaccine against this virus exists.

Method

Using Immunoinformatics, epitopic sequences from multiple glycoproteins that play crucial role in pathogenesis were identified. Particularly, epitopes were mapped from conserved receptor-binding domain of spike protein which have been experimentally validated in SARS-CoV-1 as a promising target for vaccine development.

Results

A multi-epitopic vaccine construct comprising of B-cell, CTL, HTL epitopes was developed along with fusion of adjuvant and linkers. The epitopes identified herein are reported for the first time and were predicted to be highly antigenic, stable, nonallergen, nontoxic and displayed conservation across several SARS-CoV-2 isolates from different countries. Additionally, the epitopes associated with maximum HLA alleles and population coverage analysis shows the proposed epitopes would be a relevant representative of large proportion of the world population. A reliable three-dimensional structure of the vaccine construct was developed. Consequently, docking and molecular-dynamics simulation ensured the stable interaction between vaccine and innate-immune receptor.

Stem cell-derived enteroid cultures as a tool for dissecting host-parasite interactions in the small intestinal epithelium

Toxoplasma gondii and Cryptosporidium spp. can cause devastating pathological effects in humans and livestock, and in particular to young or immunocompromised individuals. The current treatment plans for these enteric parasites are limited due to long drug courses, severe side effects or simply a lack of efficacy. The study of the early interactions between the parasites and the site of infection in the small intestinal epithelium has been thwarted by the lack of accessible, physiologically relevant and species-specific models. Increasingly, 3D stem cell-derived enteroid models are being refined and developed into sophisticated models of infectious disease. In this review, we shall illustrate the use of enteroids to spearhead research into enteric parasitic infections, bridging the gap between cell line cultures and in vivo experiments.

Antiviral and Immunomodulatory Properties of Antimicrobial Peptides Produced by Human Keratinocytes

Keratinocytes, the main cells of the epidermis, are the first site of replication as well as the first line of defense against many viruses such as arboviruses, enteroviruses, herpes viruses, human papillomaviruses, or vaccinia virus. During viral replication, these cells can sense virus associated molecular patterns leading to the initiation of an innate immune response composed of pro-inflammatory cytokines, chemokines, and antimicrobial peptides. Human keratinocytes produce and secrete at least nine antimicrobial peptides: human cathelicidin LL-37, types 1–4 human β-defensins, S100 peptides such as psoriasin (S100A7), calprotectin (S100A8/9) and koebnerisin (S100A15), and RNase 7. These peptides can exert direct antiviral effects on the viral particle or its replication cycle, and indirect antiviral activity, by modulating the host immune response. The purpose of this review is to summarize current knowledge of antiviral and immunomodulatory properties of human keratinocyte antimicrobial peptides.

Out-Smarting the Host: Bacteria Maneuvering the Immune Response to Favor Their Survival

Bacteria adapt themselves to various environmental conditions in nature, which can lead to bacterial adaptation and persistence in the host as commensals or pathogens. In healthy individuals, host defense mechanisms prevent the opportunistic bacteria/commensals from becoming a pathological infection. However, certain pathological conditions can impair normal defense barriers leading to bacterial survival and persistence. Under pathological conditions such as chronic lung inflammation, bacteria employ various mechanisms from structural changes to protease secretion to manipulate and evade the host immune response and create a niche permitting commensal bacteria to thrive into infections. Therefore, understanding the mechanisms by which pathogenic bacteria survive in the host tissues and organs may offer new strategies to overcome persistent bacterial infections. In this review, we will discuss and highlight the complex interactions between airway pathogenic bacteria and immune responses in several major chronic inflammatory diseases such as asthma and chronic obstructive pulmonary disease (COPD).

Mechanisms of TREG cell adaptation to inflammation

Inflammation is an important defense mechanism. In this complex and dynamic process, drastic changes in the tissue micro-environment play key roles in dictating the nature of the evolving immune response. However, uncontrolled inflammation is detrimental, leading to unwanted cellular damage, loss of physiological functions, and even death. As such, the immune system possesses tools to limit inflammation while ensuring rapid and effective clearance of the inflammatory trigger. Foxp3⁺ regulatory T (T_REG ) cells, a potently immunosuppressive CD4⁺ T cell subset, play a crucial role in immune tolerance by controlling the extent of the response to self and non-self Ags, all-the-while promoting a quick return to immune homeostasis. T_REG cells adapt to changes in the local micro-environment enabling them to migrate, proliferate, survive, differentiate, and tailor their suppressive ability at inflamed sites. Several inflammation-associated factors can impact T_REG cell functional adaptation in situ including locally released alarmins, oxygen availability, tissue acidity and osmolarity and nutrient availability. Here, we review some of these key signals and pathways that control the adaptation of T_REG cell function in inflammatory settings.

Designing of a multi-epitope vaccine candidate against Nipah virus by in silico approach: a putative prophylactic solution for the deadly virus

Nipah virus (NPV) is one of the most notorious viruses with a very high fatality rate. Because of the recurrent advent of this virus and its severe neurological implications, often leading to high mortality, the WHO R&D Blueprint, 2018 has listed the Nipah virus as one of the emerging infectious diseases requiring urgent research and development effort. Yet there is a major layback in the development of effective vaccines or drugs against NPV. In this study, we have designed a stable multivalent vaccine combining several T-cell and B-cell epitopes of the essential Nipah viral proteins with the help of different ligands and adjuvants which can effectively induce both humoral and cellular immune responses in human. Different advanced immune-informatic tools confirm the stability, high immunogenicity and least allergenicity of the vaccine candidate. The standard molecular dynamic cascade analysis validates the stable interaction of the vaccine construct with the human Toll-like receptor 3 (TLR3) complex. Later, codon optimization and in silico cloning in a known pET28a vector system shows the possibility for the expression of this vaccine in a simple organism like E.coli. It is believed that with further in vitro and in vivo validation, this vaccine construct can pose to be a better prophylactic solution to the Nipah viral disease. Communicated by Ramaswamy H. Sarma.

NK-lysin, dicentracin and hepcidin antimicrobial peptides in European sea bass. Ontogenetic development and modulation in juveniles by nodavirus

Antimicrobial peptides (AMPs) are considered to be amongst the most powerful tools for the fight against pathogens in fish, since they form part of the innate immune response, which is especially vital in eggs and early larval stages, when the immune system is developing. The fish responsible for a large part of the profits in Mediterranean aquaculture is European sea bass (Dicentrarchus labrax), a species greatly susceptible to nodavirus (NNV), especially in the larval and juvenile stages. In this work, polyclonal antibodies were developed and used to detect and quantify NK-lysin, dicentracin and hepcidin AMPs in European sea bass eggs and during larval development, as well as to evaluate their regulation in juvenile specimens upon NNV infection. Basal and detectable levels of all the AMPs studied were present in eggs, confirming the maternal transfer of peptides, which increased in one or two waves during larval development up to 69 days post-fertilization. After NNV infection, the mRNA of all the AMPs analysed was up-regulated five days after infection in most of the tissues, whilst peptide quantification of all three AMPs decreased in the brain, the target tissue for NNV, but increased in the head-kidney 5 days after infection. Further research should be carried out to ascertain the role of AMPs in fish innate immunity and to understand how NNV evades the immune response to be disseminated.

Regulation of host-microbe interactions at oral mucosal barriers by type 17 immunity

The oral mucosa is a primary barrier site and a portal for entry of microbes, food, and airborne particles into the gastrointestinal tract. Nonetheless, mucosal immunity at this barrier remains understudied compared with other anatomical barrier sites. Here, we review basic aspects of oral mucosal histology, the oral microbiome, and common and clinically significant diseases that present at oral mucosal barriers. We particularly focus on the role of interleukin-17 (IL-17)/T helper 17 (TH17) responses in protective immunity and inflammation in the oral mucosa. IL-17/TH17 responses are highly relevant to maintaining barrier integrity and preventing pathogenic infections by the oral commensal fungus Candida albicans On the other hand, aberrant IL-17/TH17 responses are implicated in driving the pathogenesis of periodontitis and consequent bone and tooth loss. We discuss distinct IL-17-secreting T cell subsets, emphasizing their regulation and function in oropharyngeal candidiasis and periodontitis.

Surface Grafted MSI-78A Antimicrobial Peptide has High Potential for Gastric Infection Management

As we approach the end of the antibiotic era, newer therapeutic options, such as antimicrobial peptides (AMPs), are in urgent demand. AMP surface grafting onto biomaterials has been described as a good strategy to overcome problems associated with their in vivo stability. Helicobacter pylori is among the bacteria that pose greatest threat to human health, being MSI-78A one of the few bactericidal AMPs against this bacterium. Here, we report that MSI-78A grafted onto model surfaces (Self-Assembled Monolayers –SAMs), in a concentration of 30.3 ± 1.2 ng/cm² determined by quartz crystal microbalance with dissipation (QCM-D), was able to kill, by contact, 98% of planktonic H. pylori in only 2 h. This fact was not verified against the control bacteria (Staphylococcus epidermidis), although the minimal inhibitory concentration (MIC) of MSI-78A in solution is much lower for S. epidermidis (2 μg/mL) than for H. pylori (64 μg/mL). Our results also demonstrated that, in opposite to other bacteria, H. pylori cells were attracted to ethylene glycol terminated (antiadhesive) surfaces, which can explain the high bactericidal potential of grafted MSI-78A. This proof of concept study establishes the foundations for development of MSI-78A grafted nanoparticles for gastric infection management within a targeted nanomedicine concept.

Antimicrobial peptides: new hope in the war against multidrug resistance

The discovery of antibiotics marked a golden age in the revolution of human medicine. However, decades later, bacterial infections remain a global healthcare threat, and a return to the pre-antibiotic era seems inevitable if stringent measures are not adopted to curb the rapid emergence and spread of multidrug resistance and the indiscriminate use of antibiotics. In hospital settings, multidrug resistant (MDR) pathogens, including carbapenem-resistant Pseudomonas aeruginosa, vancomycin-resistant enterococci (VRE), methicillin-resistant Staphylococcus aureus (MRSA), and extended-spectrum β-lactamases (ESBL) bearing Acinetobacter baumannii, Escherichia coli, and Klebsiella pneumoniae are amongst the most problematic due to the paucity of treatment options, increased hospital stay, and exorbitant medical costs. Antimicrobial peptides (AMPs) provide an excellent potential strategy for combating these threats. Compared to empirical antibiotics, they show low tendency to select for resistance, rapid killing action, broad-spectrum activity, and extraordinary clinical efficacy against several MDR strains. Therefore, this review highlights multidrug resistance among nosocomial bacterial pathogens and its implications and reiterates the importance of AMPs as next-generation antibiotics for combating MDR superbugs.

Natural Occurrence in Venomous Arthropods of Antimicrobial Peptides Active against Protozoan Parasites

Arthropoda is a phylum of invertebrates that has undergone remarkable evolutionary radiation, with a wide range of venomous animals. Arthropod venom is a complex mixture of molecules and a source of new compounds, including antimicrobial peptides (AMPs). Most AMPs affect membrane integrity and produce lethal pores in microorganisms, including protozoan pathogens, whereas others act on internal targets or by modulation of the host immune system. Protozoan parasites cause some serious life-threatening diseases among millions of people worldwide, mostly affecting the poorest in developing tropical regions. Humans can be infected with protozoan parasites belonging to the genera Trypanosoma, Leishmania, Plasmodium, and Toxoplasma, responsible for Chagas disease, human African trypanosomiasis, leishmaniasis, malaria, and toxoplasmosis. There is not yet any cure or vaccine for these illnesses, and the current antiprotozoal chemotherapeutic compounds are inefficient and toxic and have been in clinical use for decades, which increases drug resistance. In this review, we will present an overview of AMPs, the diverse modes of action of AMPs on protozoan targets, and the prospection of novel AMPs isolated from venomous arthropods with the potential to become novel clinical agents to treat protozoan-borne diseases.

Association of vitamin D3, VDR gene polymorphisms, and LL-37 with a clinical form of Chagas Disease

INTRODUCTION

Chagas disease (CD) is an important public health problem in Brazil and worldwide. Aging and obesity are important matters in patients with CD, as is hypovitaminosis D3, which can decrease the quality of life of these patients. Immunomodulation mediated by vitamin D3, especially the production of antimicrobial peptides such as cathelicidin LL-37, might be related to the severity and symptoms of CD. This study aimed to determine the serum levels of vitamin D and LL-37 and VDR gene polymorphisms in patients with chronic CD.

METHODS

This study included male patients with cardiac and indeterminate clinical forms of CD. Clinical, anthropometric, and blood parameters were obtained. Serum levels of 25(OH)D3 and LL-37 were determined by chemiluminescence and enzyme-linked immunosorbent assay respectively. Fok (rs731236), Bsm (rs1544410), Apa (rs7975232), and Taq (rs731236) polymorphisms of the VDR gene were investigated by PCR-RFLP.

RESULTS

Sixty-four patients were included in the study: 18 of the cardiac form and 46 of the indeterminate form. No differences in age, ethnicity, BMI, arterial hypertension, diabetes mellitus, or dyslipidemias were observed between groups. However, the serum levels of 25(OH)D3, but not of LL-37, were lower in the cardiac form group. The association among polymorphisms, vitamin D, and clinical form was not significant.

CONCLUSIONS

Decreased levels of vitamin D suggest an association with the cardiac form of CD. Studies investigating the roles of vitamin D and LL-37 in the immune response and their associations with VDR polymorphisms and disease susceptibility are necessary.

Human Antimicrobial Peptides as Therapeutics for Viral Infections

Successful in vivo infection following pathogen entry requires the evasion and subversion of multiple immunological barriers. Antimicrobial peptides (AMPs) are one of the first immune pathways upregulated during infection by multiple pathogens, in multiple organs in vivo. In humans, there are many classes of AMPs exhibiting broad antimicrobial activities, with defensins and the human cathelicidin LL-37 being the best studied examples. Whereas historically the efficacy and therapeutic potential of AMPs against bacterial infection has been the primary focus of research, recent studies have begun to elucidate the antiviral properties of AMPs as well as their role in regulation of inflammation and chemoattraction. AMPs as therapeutic tools seem especially promising against emerging infectious viral pathogens for which no approved vaccines or treatments are currently available, such as dengue virus (DENV) and Zika virus (ZIKV). In this review, we summarize recent studies elucidating the efficacy and diverse mechanisms of action of various classes of AMPs against multiple viral pathogens, as well as the potential use of human AMPs in novel antiviral therapeutic strategies.

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

The rise of antibiotic resistance has necessitated the development of alternative strategies for the treatment of infectious diseases. Antimicrobial peptides (AMPs), components of the innate immune response in various organisms, are promising next-generation drugs against bacterial infections. The ability of the medicinal leech Hirudo medicinalis to store blood for months with little change has attracted interest regarding the identification of novel AMPs in this organism. In this study, we employed computational algorithms to the medicinal leech genome assembly to identify amino acid sequences encoding potential AMPs. Then, we synthesized twelve candidate AMPs identified by the algorithms, determined their secondary structures, measured minimal inhibitory concentrations against three bacterial species (Escherichia coli, Bacillus subtilis, and Chlamydia thrachomatis), and assayed cytotoxic and haemolytic activities. Eight of twelve candidate AMPs possessed antimicrobial activity, and only two of them, 3967 (FRIMRILRVLKL) and 536-1 (RWRLVCFLCRRKKV), exhibited inhibition of growth of all tested bacterial species at a minimal inhibitory concentration of 10 μmol. Thus, we evidence the utility of the developed computational algorithms for the identification of AMPs with low toxicity and haemolytic activity in the medicinal leech genome assembly.