Immunopeptides: immunomodulatory strategies and prospects for ocular immunity applications

Immunopeptides have low toxicity, low immunogenicity and targeting, and broad application prospects in drug delivery and assembly, which are diverse in application strategies and drug combinations. Immunopeptides are particularly important for regulating ocular immune homeostasis, as the eye is an immune-privileged organ. Immunopeptides have advantages in adaptive immunity and innate immunity, treating eye immune-related diseases by regulating T cells, B cells, immune checkpoints, and cytokines. This article summarizes the application strategies of immunopeptides in innate immunity and adaptive immunity, including autoimmunity, infection, vaccine strategies, and tumors. Furthermore, it focuses on the mechanisms of immunopeptides in mediating ocular immunity (autoimmune diseases, inflammatory storms, and tumors). Moreover, it reviews immunopeptides' application strategies and the therapeutic potential of immunopeptides in the eye. We expect the immune peptide to get attention in treating eye diseases and to provide a direction for eye disease immune peptide research.

In Vitro, In Vivo and In Silico Assessment of the Antimicrobial and Immunomodulatory Effects of a Water Buffalo Cathelicidin (WBCATH) in Experimental Pulmonary Tuberculosis

Tuberculosis (TB) is considered the oldest pandemic in human history. The emergence of multidrug-resistant (MDR) strains is currently considered a serious global health problem. As components of the innate immune response, antimicrobial peptides (AMPs) such as cathelicidins have been proposed to have efficacious antimicrobial activity against Mycobacterium tuberculosis (Mtb). In this work, we assessed a cathelicidin from water buffalo, Bubalus bubalis, (WBCATH), determining in vitro its antitubercular activity (MIC), cytotoxicity and the peptide effect on bacillary loads and cytokines production in infected alveolar macrophages. Our results showed that WBCATH has microbicidal activity against drug-sensitive and MDR Mtb, induces structural mycobacterial damage demonstrated by electron microscopy, improves Mtb killing and induces the production of protective cytokines by murine macrophages. Furthermore, in vivo WBCATH showed decreased bacterial loads in a model of progressive pulmonary TB in BALB/c mice infected with drug-sensitive or MDR mycobacteria. In addition, a synergistic therapeutic effect was observed when first-line antibiotics were administered with WBCATH. These results were supported by computational modeling of the potential effects of WBCATH on the cellular membrane of Mtb. Thus, this water buffalo-derived cathelicidin could be a promising adjuvant therapy for current anti-TB drugs by enhancing a protective immune response and potentially reducing antibiotic treatment duration.

Evaluation of circulating serum cathelicidin levels as a potential biomarker to discriminate between active and latent tuberculosis in Uganda

Background

Tuberculosis remains a major public health problem worldwide accounting for 1.4 million deaths annually. LL-37 is an effector molecule involved in immunity with both antimicrobial and immunomodulatory properties. The purpose of this study was to compare LL-37 circulatory levels among participants with active and latent tuberculosis and to determine its ability to discriminate between the two infectious states.

Methods

A cross-sectional study was performed among 56 active tuberculosis patients, 49 latent tuberculosis individuals, and 43 individuals without tuberculosis infection. The enzyme-linked immunosorbent assay was used to assess LL-37 levels. Data analysis was performed using STATA software and Graph pad Prism version 8. Mann-Whitney U test was used for correlation between variables with two categories and the Kruskal-Wallis test for three or more categories.

Results

The study had more female participants than males, with similar median ages across the three groups, 29.5, 25.0, and 23.0 years respectively. Active tuberculosis patients had significantly higher LL-37 levels compared to those with latent tuberculosis and without tuberculosis. The median/interquartile ranges were 318.8 ng/ml (157.9–547.1), 242.2 ng/ml (136.2–579.3), 170.9 ng/ml (129.3–228.3); p = 0.002 respectively. Higher LL-37 was found in the male participant with median/interquartile range, 424.8 ng/ml (226.2–666.8) compared to the females 237.7 ng/ml (129.6–466.6); p = 0.045. LL-37 had better discriminatory potential between active tuberculosis and no tuberculosis (AUC = 0.71, sensitivity 71.4% specificity = 69.8%) than with latent tuberculosis (AUC = 0.55, sensitivity = 71.4%, specificity = 44.9%). There was moderate differentiation between latent tuberculosis and no tuberculosis (AUC = 0.63, sensitivity = 44.9% specificity = 90.7%).

Conclusion

Significantly higher LL-37 levels were observed among active tuberculosis patients than those without tuberculosis infection and were, therefore able to discriminate between active tuberculosis and other tuberculosis infectious states, especially with no tuberculosis. Further assessment of this biomarker as a screening tool to exclude tuberculosis is required.

The antimicrobial peptide cathelicidin drives development of experimental autoimmune encephalomyelitis in mice by affecting Th17 differentiation

Multiple sclerosis (MS) is a highly prevalent demyelinating autoimmune condition; the mechanisms regulating its severity and progression are unclear. The IL-17-producing Th17 subset of T cells has been widely implicated in MS and in the mouse model, experimental autoimmune encephalomyelitis (EAE). However, the differentiation and regulation of Th17 cells during EAE remain incompletely understood. Although evidence is mounting that the antimicrobial peptide cathelicidin profoundly affects early T cell differentiation, no studies have looked at its role in longer-term T cell responses. Now, we report that cathelicidin drives severe EAE disease. It is released from neutrophils, microglia, and endothelial cells throughout disease; its interaction with T cells potentiates Th17 differentiation in lymph nodes and Th17 to exTh17 plasticity and IFN-γ production in the spinal cord. As a consequence, mice lacking cathelicidin are protected from severe EAE. In addition, we show that cathelicidin is produced by the same cell types in the active brain lesions in human MS disease. We propose that cathelicidin exposure results in highly activated, cytokine-producing T cells, which drive autoimmunity; this is a mechanism through which neutrophils amplify inflammation in the central nervous system.

Upregulating Human Cathelicidin Antimicrobial Peptide LL-37 Expression May Prevent Severe COVID-19 Inflammatory Responses and Reduce Microthrombosis

COVID-19 is characterized by hyperactivation by inflammatory cytokines and recruitment of macrophages, neutrophils, and other immune cells, all hallmarks of a strong inflammatory response that can lead to severe complications and multi-organ damage. Mortality in COVID-19 patients is associated with a high prevalence of neutrophil extracellular trap (NET) formation and microthrombosis that are exacerbated by hyperglycemia, diabetes, and old age. SARS-CoV-2 infection in humans and non-human primates have revealed long-term neurological consequences of COVID-19, possibly concomitant with the formation of Lewy bodies in the brain and invasion of the nervous system via the olfactory bulb. In this paper, we review the relevance of the human cathelicidin LL-37 in SARS-CoV-2 infections. LL-37 is an immunomodulatory, host defense peptide with direct anti-SARS-CoV-2 activity, and pleiotropic effects on the inflammatory response, neovascularization, Lewy body formation, and pancreatic islet cell function. The bioactive form of vitamin D and a number of other compounds induce LL-37 expression and one might predict its upregulation, could reduce the prevalence of severe COVID-19. We hypothesize upregulation of LL-37 will act therapeutically, facilitating efficient NET clearance by macrophages, speeding endothelial repair after inflammatory tissue damage, preventing α-synuclein aggregation, and supporting blood-glucose level stabilization by facilitating insulin release and islet β-cell neogenesis. In addition, it has been postulated that LL-37 can directly bind the S1 domain of SARS-CoV-2, mask angiotensin converting enzyme 2 (ACE2) receptors, and limit SARS-CoV-2 infection. Purposeful upregulation of LL-37 could also serve as a preventative and therapeutic strategy for SARS-CoV-2 infections.

Host defense peptides as immunomodulators: The other side of the coin

Host defense peptides (HDPs) exhibit a broad range of antimicrobial and immunomodulatory activities. In this sense, both functions are like different sides of the same coin. The direct antimicrobial side was discovered first, and widely studied for the development of anti-infective therapies. In contrast, the immunomodulatory side was recognized later and in the last 20 years the interest in this field has been continuously growing. Different to their antimicrobial activities, the immunomodulatory activities of host defense peptides are more effective in vivo. They offer a great opportunity for new therapeutic applications in the fields of anti-infective therapy, chronic inflammatory diseases treatment, novel vaccine adjuvants development and anticancer immunotherapy. These immune related functions of HDPs includes chemoattraction of leukocytes, modulation of inflammation, enhancement of antigen presentation and polarization of adaptive immune responses. Our attempt with this review is to make a careful evaluation of different aspects of the less explored, but attractive immunomodulatory side of the HDP functional coin.

Recombinant CRAMP-producing Lactococcus lactis attenuates dextran sulfate sodium-induced colitis by colonic colonization and inhibiting p38/NF-κB signaling

Background

Inflammatory bowel diseases (IBDs) are generally characterized by persistent abdominal pain and diarrhea caused by chronic inflammation in the intestine. Cathelicidins are antimicrobial peptides with pleiotropic roles in anti-infection, wound healing, and immune modulation. However, the sensitivity to the acidic environment and short half-life of cathelicidins limit their application in IBD treatment. Recombinant cathelicidin-related antimicrobial peptide (CRAMP)-producing Lactococcus lactis may represent a potential approach for IBD therapy.

Objective

The aim of this study was to develop recombinant CRAMP-producing L. lactis NZ9000 and explore the role and mechanism of recombinant L. lactis NZ9000 expressing CRAMP in colitis.

Design

We constructed two strains of CRAMP-producing L. lactis NZ9000 with different plasmids pMG36e (L.L-pMU45CR) or pNZ8148 (L.L-pNU45CR), which use a Usp45 secretion signal to drive the secretion of CRAMP. Bacterial suspensions were orally supplemented to mice with a syringe for 4 days after dextran sodium sulfate (DSS) treatment. Body weight change, disease active score, colon length, and colonic histology were determined. The expression of tight junction (ZO-1, ZO-2, and Occludin) and cytokines (IL-6, IL-1β, TNF-α, and IL-10) in colon was performed by qPCR. The expression of p-ERK, p-p38, and p-p65 was determined by Western blot analysis.

Results

Both CRAMP-producing L. lactis NZ9000 strains protected against colitis, as shown by reduced weight loss and disease activity score, improved colon shortening, and histopathological injury. In addition, CRAMP-producing L. lactis NZ9000 restored gut barrier by upregulating ZO-1, ZO-2, and occludin. Moreover, CRAMP-producing L. lactis NZ9000 regulated the colonic cytokines profile with reduced IL-6, IL-1β, and TNF-α production, and increased IL-10 production. By further analysis, we found that CRAMP-producing L. lactis NZ9000 reduced the expression of p-p38 and p-p65.

Conclusions

Together, our data suggested that CRAMP-secreting L. lactis NZ9000 attenuated dextran sulfate sodium-induced colitis by colonic colonization and inhibiting p38/NF-κB signaling. Orally administered recombinant CRAMP-secreting L. lactis NZ9000 represents a potential strategy for colitis therapy.

Dissecting the relationship between antimicrobial peptides and mesenchymal stem cells

Among the various biological properties presented by Mesenchymal Stem Cells (MSCs), their ability to control the immune response and fight pathogen infection through the production of antimicrobial peptides (AMPs) have been the subject of intense research in recent years. AMPs secreted by MSCs exhibit activity against a wide range of microorganisms, including bacteria, fungi, yeasts, and viruses. The main AMPs produced by these cells are hepcidin, cathelicidin LL-37, and β-defensin-2. In addition to acting against pathogens, those AMPs have also been shown to interact with MSCs to modulate MSC proliferation, migration, and regeneration, indicating that such peptides exert a more diverse biological effect than initially thought. In the present review, we discuss the production of AMPs by MSCs, revise the multiple functions of these peptides, including their influence over MSCs, and present an overview of clinical situations in which the antimicrobial properties of MSCs may be explored for therapy. Finally, we discuss possibilities of combining MSCs and AMPs to generate improved therapeutic strategies.

B-cells are abnormal in psychosocial stress and regulate meningeal myeloid cell activation

There is increasing interest in how immune cells, including those within the meninges at the blood-brain interface, influence brain function and mood disorders, but little data on humoral immunity in this context. Here, we show that in mice exposed to psychosocial stress, there is increased splenic B cell activation and secretion of the immunoregulatory cytokine interleukin (IL)-10. Meningeal B cells were prevalent in homeostasis but substantially decreased following stress, whereas Ly6Chi monocytes increased, and meningeal myeloid cells showed augmented expression of activation markers. Single-cell RNA sequencing of meningeal B cells demonstrated the induction of innate immune transcriptional programmes following stress, including genes encoding antimicrobial peptides that are known to alter myeloid cell activation. Cd19-/- mice, that have reduced B cells, showed baseline meningeal myeloid cell activation and decreased exploratory behaviour. Together, these data suggest that B cells may influence behaviour by regulating meningeal myeloid cell activation.

Are Host Defense Peptides and Their Derivatives Ready to be Part of the Treatment of the Next Coronavirus Pandemic?

The term host defense peptides arose at the beginning to refer to those peptides that are part of the host's immunity. Because of their broad antimicrobial capacity and immunomodulatory activity, nowadays, they emerge as a hope to combat resistant multi-drug microorganisms and emerging viruses, such as the case of coronaviruses. Since the beginning of this century, coronaviruses have been part of different outbreaks and a pandemic, and they will be surely part of the next pandemics, this review analyses whether these peptides and their derivatives are ready to be part of the treatment of the next coronavirus pandemic.

Long-term exposure to particulate matter from air pollution alters airway β-defensin-3 and -4 and cathelicidin host defense peptides production in a murine model

Epidemiological studies have associated long-term exposure to environmental air pollution particulate matter (PM) with the development of diverse health problems. They include infectious respiratory diseases related to the deregulation of some innate immune response mechanisms, such as the host defense peptides' expression. Herein, we evaluated in BALB/c mice the effect of long-standing exposure (60 days) to urban-PM from the south of Mexico City, with aerodynamic diameters below 2.5 μm (PM_2.5) and 10 μm (PM₁₀) on the lung's gene expression and production of three host defense peptides (HDPs); murine beta-defensin-3, -4 (mBD-3, mBD-4) and cathelin-related antimicrobial peptide (CRAMP). We also evaluated mRNA levels of Il1b and Il10, two cytokines related to the expression of host defense peptides. Exposure to PM_2.5 and PM₁₀ differentially induced lung inflammation, being PM_2.5, which caused higher inflammation levels, probably associated with a differential deposition on the airways, that facilitate the interaction with alveolar macrophages. Inflammation levels were associated with an early upregulation of the three HDPs assessed and an increment in Il1b mRNA levels. Interestingly, after 28 days of exposure, Il10 mRNA upregulation was observed and was associated with the downregulation of HDPs and Il1b mRNA levels. The upregulation of Il10 mRNA and suppression of HDPs might facilitate microbial colonization and the development of diseases associated with long-term exposure to PM.

The neutrophil antimicrobial peptide cathelicidin promotes Th17 differentiation

The host defence peptide cathelicidin (LL-37 in humans, mCRAMP in mice) is released from neutrophils by de-granulation, NETosis and necrotic death; it has potent anti-pathogen activity as well as being a broad immunomodulator. Here we report that cathelicidin is a powerful Th17 potentiator which enhances aryl hydrocarbon receptor (AHR) and RORγt expression, in a TGF-β1-dependent manner. In the presence of TGF-β1, cathelicidin enhanced SMAD2/3 and STAT3 phosphorylation, and profoundly suppressed IL-2 and T-bet, directing T cells away from Th1 and into a Th17 phenotype. Strikingly, Th17, but not Th1, cells were protected from apoptosis by cathelicidin. We show that cathelicidin is released by neutrophils in mouse lymph nodes and that cathelicidin-deficient mice display suppressed Th17 responses during inflammation, but not at steady state. We propose that the neutrophil cathelicidin is required for maximal Th17 differentiation, and that this is one method by which early neutrophilia directs subsequent adaptive immune responses.

Combating Implant Infections: Shifting Focus from Bacteria to Host

The widespread use of biomaterials to support or replace body parts is increasingly threatened by the risk of implant-associated infections. In the quest for finding novel anti-infective biomaterials, there generally has been a one-sided focus on biomaterials with direct antibacterial properties, which leads to excessive use of antibacterial agents, compromised host responses, and unpredictable effectiveness in vivo. This review sheds light on how host immunomodulation, rather than only targeting bacteria, can endow biomaterials with improved anti-infective properties. How antibacterial surface treatments are at risk to be undermined by biomaterial features that dysregulate the protection normally provided by critical immune cell subsets, namely, neutrophils and macrophages, is discussed. Accordingly, how the precise modification of biomaterial surface biophysical cues, or the incorporation of immunomodulatory drug delivery systems, can render biomaterials with the necessary immune-compatible and immune-protective properties to potentiate the host defense mechanisms is reviewed. Within this context, the protective role of host defense peptides, metallic particles, quorum sensing inhibitors, and therapeutic adjuvants is discussed. The highlighted immunomodulatory strategies may lay a foundation to develop anti-infective biomaterials, while mitigating the increasing threat of antibacterial drug resistance.

Cathelicidins Modulate TLR-Activation and Inflammation

Cathelicidins are short cationic peptides that are part of the innate immune system. At first, these peptides were studied mostly for their direct antimicrobial killing capacity, but nowadays they are more and more appreciated for their immunomodulatory functions. In this review, we will provide a comprehensive overview of the various effects cathelicidins have on the detection of damage- and microbe-associated molecular patterns, with a special focus on their effects on Toll-like receptor (TLR) activation. We review the available literature based on TLR ligand types, which can roughly be divided into lipidic ligands, such as LPS and lipoproteins, and nucleic-acid ligands, such as RNA and DNA. For both ligand types, we describe how direct cathelicidin-ligand interactions influence TLR activation, by for instance altering ligand stability, cellular uptake and receptor interaction. In addition, we will review the more indirect mechanisms by which cathelicidins affect downstream TLR-signaling. To place all this information in a broader context, we discuss how these cathelicidin-mediated effects can have an impact on how the host responds to infectious organisms as well as how these effects play a role in the exacerbation of inflammation in auto-immune diseases. Finally, we discuss how these immunomodulatory activities can be exploited in vaccine development and cancer therapies.

Significance of LL-37 on Immunomodulation and Disease Outcome

LL-37, also called cathelicidin, is an important part of the human immune system, which can resist various pathogens. A plethora of experiments have demonstrated that it has the multifunctional effects of immune regulation, in addition to antimicrobial activity. Recently, there have been increasing interest in its immune function. It was found that LL-37 can have two distinct functions in different tissues and different microenvironments. Thus, it is necessary to investigate LL-37 immune functions from the two sides of the same coin. On the one side, LL-37 promotes inflammation and immune response and exerts its anti-infective and antitumor effects; on the other side, it has the ability to inhibit inflammation and promote carcinogenesis. This review presents a brief summary of its expression, structure, and immunomodulatory effects as well as brief discussions on the role of this small peptide as a key factor in the development and treatment of various inflammation-related diseases and cancers.

Immunomodulatory significance of natural peptides in mammalians: Promising agents for medical application

Modulation of immune responses by immunoregulatory agents, such as the natural or synthetic immunomodulatory peptides, has been suggested as a potential strategy to modulate immune system against infection and other immune-related diseases. These compositionally simple peptides have attracted much attention for many drug developers, due to their high activity, low toxicity and clear target specificity. Host defence peptides and milk-derived peptides are two kinds of natural immunomodulatory peptides which have been widely studied in mammalians. They could participate at the interface of innate and adaptive immunity by regulating immune effector cells. This review summarizes the recent advances in host defence peptides and milk-derived peptides as well as their general characteristics, immunomodulatory functions and possible applications.

Chicken CATH-2 Increases Antigen Presentation Markers on Chicken Monocytes and Macrophages

Abstract: Background

Cathelicidins are a family of Host Defense Peptides (HDPs), that play an important role in the innate immune response. They exert both broad-spectrum antimicrobial activity against pathogens, and strong immunomodulatory functions that affect the response of innate and adaptive immune cells.

Objective

The aim of this study was to investigate immunomodulation by the chicken cathelicidin CATH-2 and compare its activities to those of the human cathelicidin LL-37.

Methods

Chicken macrophages and chicken monocytes were incubated with cathelicidins. Activation of immune cells was determined by measuring surface markers Mannose Receptor C-type 1 (MRC1) and MHC-II. Cytokine production was measured by qPCR and nitric oxide production was determined using the Griess assay. Finally, the effect of cathelicidins on phagocytosis was measured using carboxylate-modified polystyrene latex beads.

Results

CATH-2 and its all-D enantiomer D-CATH-2 increased MRC1 and MHC-II expression, markers for antigen presentation, on primary chicken monocytes, whereas LL-37 did not. D-CATH-2 also increased the MRC1 and MHC-II expression if a chicken macrophage cell line (HD11 cells) was used. In addition, LPS-induced NO production by HD11 cells was inhibited by CATH-2 and D-CATH-2.

Conclusion

These results are a clear indication that CATH-2 (and D-CATH-2) affect the activation state of monocytes and macrophages, which leads to optimization of the innate immune response and enhancement of the adaptive immune response.

Amyloids in Site-Specific Autoimmune Reactions and Inflammatory Responses

Amyloid deposition is a histological hallmark of common human disorders including Alzheimer's disease (AD) and type 2 diabetes. Although some reports highlight that amyloid fibrils might activate the innate immunity system via pattern recognition receptors, here, we provide multiple lines of evidence for the protection by site-specific amyloid protein analogs and fibrils against autoimmune attacks: (1) strategies targeting clearance of the AD-related brain amyloid plaque induce high risk of deadly autoimmune destructions in subjects with cognitive dysfunction; (2) administration of amyloidogenic peptides with either full length or core hexapeptide structure consistently ameliorates signs of experimental autoimmune encephalomyelitis; (3) experimental autoimmune encephalomyelitis is exacerbated following genetic deletion of amyloid precursor proteins; (4) absence of islet amyloid coexists with T-cell-mediated insulitis in autoimmune diabetes and autoimmune polyendocrine syndrome; (5) use of islet amyloid polypeptide agonists rather than antagonists improves diabetes care; and (6) common suppressive signaling pathways by regulatory T cells are activated in both local and systemic amyloidosis. These findings indicate dual modulation activity mediated by amyloid protein monomers, oligomers, and fibrils to maintain immune homeostasis. The protection from autoimmune destruction by amyloid proteins offers a novel therapeutic approach to regenerative medicine for common degenerative diseases.

Human antimicrobial peptides in autoimmunity

Antimicrobial peptides (AMPs) were firstly discovered as cytotoxic substances that killed bacteria. Later they were described as biologically active peptides that are able not only to kill invaders but also to modulate host immunity. In particular, it is shown that human antimicrobial peptides are able to influence the activity of different innate and adaptive immunity components, thus, obviously, they also participate in autoimmune processes. In this review we discuss the nature of human AMPs and analyze their role in such autoimmune disorders like type 1 diabetes mellitus, rheumatoid arthritis, systemic lupus erythematosus, psoriasis, Crohn's disease and sarcoidosis. These peptides were shown to have a "double-sided" influence on the autoimmune disease pathogenesis. Thus, described facts should be taken into account for the development of new pharmaceutical agents to cure patients with autoimmune disorders. These agents could derive from natural antimicrobial peptides that in some cases modulate immune response. For example, it was shown that human AMPs are able to modulate complement system dysregulation of which is known to be one of the most dangerous pathogenic factors during autoimmune processes.

Antimicrobial Peptides and Vaccine Development to Control Multi-drug Resistant Bacteria

Antimicrobial resistance (AMR) reported to increase globally at alarming levels in the recent past. A number of potential alternative solutions discussed and implemented to control AMR in bacterial pathogens. Stringent control over the clinical application of antibiotics for a reduction in uses is a special consideration along with alternative solutions to fight against AMR. Although alternatives to conventional antibiotics like antimicrobial peptides (AMP) might warrant serious consideration to fight against AMR, there is a thriving recognition for vaccines in encountering the problem of AMR. Vaccines can reduce the prevalence of AMR by reducing the number of specific pathogens, which result in cutting down the antimicrobial need and uses. However, conventional vaccines produced using live or attenuated microorganisms while the presence of immunologically redundant biological components or impurities might cause major side effects and health related problems. Here we discussed AMPs based vaccination strategies as an emerging concept to overcome the disadvantages of traditional vaccines while boosting the AMPs to control multidrug resistant bacteria or AMR. Nevertheless, the poor immune response is a major challenge in the case of peptide vaccines as minimal antigenic epitopes used for immunization in peptide vaccines.

Enhancement of Macrophage Function by the Antimicrobial Peptide Sublancin Protects Mice from Methicillin-Resistant Staphylococcus aureus

Methicillin-resistant Staphylococcus aureus (MRSA) is the major pathogen responsible for community and hospital bacterial infections. Sublancin, a glucosylated antimicrobial peptide isolated from Bacillus subtilis 168, possesses antibacterial infective effects. In this study, we investigated the role and anti-infection mechanism of sublancin in a mouse model of MRSA-induced sublethal infection. Sublancin could modulate innate immunity by inducing the production of IL-1β, IL-6, TNF-α, and nitric oxide, enhancing phagocytosis and MRSA-killing activity in both RAW264.7 cells and mouse peritoneal macrophages. The enhanced macrophage function by the peptide in vitro correlated with stronger protective activity in vivo in the MRSA-invasive sublethal infection model. Macrophage activation by sublancin was found to be partly dependent on TLR4 and the NF-κB and MAPK signaling pathways. Moreover, oral administration of sublancin increased the frequencies of CD⁴⁺ and CD⁸⁺ T cells in mesenteric lymph nodes. The protective activity of sublancin was associated with in vivo augmenting phagocytic activity of peritoneal macrophages and partly improving T cell-mediated immunity. Macrophages thus represent a potentially pivotal and novel target for future development of innate defense regulator therapeutics against S. aureus infection.

Antimicrobial peptide KR-32 alleviates Escherichia coli K88-induced fatty acid malabsorption by improving expression of fatty acid transporter protein 4 (FATP4)1

Bacterial infection causes nutrient malabsorption in small intestine. KR-32, a kind of synthetic antimicrobial peptide, has the bacteriostatic effect. In the present study, 2 experiments were designed to analyze the effects of KR-32 on fat absorption of piglets with or without Escherichia coli infection. In Exp. 1, 12 weaning piglets (21 d old) were allocated to 2 groups: piglets with an intraperitoneal (i.p.) injection of antimicrobial peptide KR-32 (APK) and piglets with an i.p. injection of an equivalent volume (1 mL) of phosphate-buffered saline (PBS) (CON-1). Results showed that after 7 d of growth, KR-32 did not significantly change growth performance and apparent total tract digestibility (ATTD) of feed nutrients of normal pigs. To confirm whether KR-32 affects those of enterotoxigenic Escherichia coli (ETEC) K88-challenged pigs, we performed Exp. 2, in which 18 piglets (28 d old) were divided into the following 3 groups: 1) piglets orally challenged with 1 × 1010 cfu ETEC K88 on day 1 followed by an i.p. injection of 0.6 mg/kg KR-32 (K88 + APK); 2) piglets orally challenged with 1 × 1010 cfu ETEC K88 on day 1 followed by an i.p. injection of an equivalent volume (1 mL) of PBS (K88); and 3) piglets with an oral administration of fresh Luria-Bertani broth (50 mL) followed by an i.p. injection of an equivalent volume of PBS (CON-2). Results showed that ETEC K88 challenge led to poor ADFI, ADG, and G:F in piglets; decreased ATTD of feed nutrients, especially CP and ether extract (EE); and intestinal morphology disorder. After i.p. injection of KR-32, ADG and ATTD of CP and EE were greatly increased, G:F was significantly reduced (P < 0.05), and, especially, ATTD of EE returned to a normal level compared with group CON-2. Fatty acid absorption also highly increased after KR-32 injection. Then we focused on fat digestion and fatty acid uptake. The pH in the intestine and pancreas lipase showed no difference among the 3 treatment groups, whereas fatty acid transporter protein 4 (FATP4) expression was remarkably improved (P < 0.05) and the epithelial barrier was recovered after i.p. injection of KR-32. In conclusion, KR-32, given to ETEC K88-challenged piglets, improved growth performance, ATTD of EE, fatty acid absorption, and intestinal morphology, which indicated that KR-32 was likely to improve the expression of FATP4 and by repairing the epithelial barrier, thereby alleviating fatty acid malabsorption.

Orchestration of Adaptive T Cell Responses by Neutrophil Granule Contents

Neutrophils are the most abundant leukocytes in peripheral blood and respond rapidly to danger, infiltrating tissues within minutes of infectious or sterile injury. Neutrophils were long thought of as simple killers, but now we recognise them as responsive cells able to adapt to inflammation and orchestrate subsequent events with some sophistication. Here, we discuss how these rapid responders release mediators which influence later adaptive T cell immunity through influences on DC priming and directly on the T cells themselves. We consider how the release of granule contents by neutrophils—through NETosis or degranulation—is one way in which the innate immune system directs the phenotype of the adaptive immune response.

Human cathelicidin peptide LL-37 as a therapeutic antiviral targeting Venezuelan equine encephalitis virus infections

Venezuelan equine encephalitis virus (VEEV), a new world alphavirus belonging to the Togaviridae family, causes periodic disease outbreaks in humans and equines with high associated mortality and morbidity. VEEV is highly infectious via the aerosol route and so has been developed as a biological weapon (Hawley and Eitzen, 2001). Despite its current classification as a category B select agent, there are no FDA approved vaccines or therapeutics to counter VEEV infections. Here we utilize a naturally occurring host defense peptide, LL-37, as a therapeutic strategy to inhibit VEEV multiplication in infected cells. LL-37 has previously demonstrated activity against several viruses by directly interacting with viral particles and indirectly by establishing an antiviral state in the host cell. We show that LL-37 exhibited potent antiviral activity against VEEV by inhibiting viral replication. Genomic RNA copies of the TC-83 strain of VEEV and viral titers were significantly reduced compared to non-treated controls. LL-37 also inhibited the virulent Trinidad Donkey (TrD) strain of VEEV. Entry assays revealed a robust reduction of viral RNA copies at the early stages of TC-83 infection. Pre-incubation of cells with LL-37 and TC-83 resulted in a strong inhibitory response, indicating that LL-37 impacts early stages of the infectious process. Confocal and electron microscopy images confirmed the aggregation of viral particles, which potentially accounts for entry prevention and hence reduced viral infection. LL-37 treatment also modulated type I interferon (IFN) expression in infected cells. LL-37 treatment dramatically increased IFNβ1 expression in treated cells in a time-dependent manner. Our results establish LL-37 as a relevant and novel potential therapeutic strategy for the treatment of VEEV infections.

Cathelicidins: Immunomodulatory Antimicrobials

Cathelicidins are host defense peptides with antimicrobial and immunomodulatory functions. These effector molecules of the innate immune system of many vertebrates are diverse in their amino acid sequence but share physicochemical characteristics like positive charge and amphipathicity. Besides being antimicrobial, cathelicidins have a wide variety in immunomodulatory functions, both boosting and inhibiting inflammation, directing chemotaxis, and effecting cell differentiation, primarily towards type 1 immune responses. In this review, we will examine the biology and various functions of cathelicidins, focusing on putting in vitro results in the context of in vivo situations. The pro-inflammatory and anti-inflammatory functions are highlighted, as well both direct and indirect effects on chemotaxis and cell differentiation. Additionally, we will discuss the potential and limitations of using cathelicidins as immunomodulatory or antimicrobial drugs.

P17, an Original Host Defense Peptide from Ant Venom, Promotes Antifungal Activities of Macrophages through the Induction of C-Type Lectin Receptors Dependent on LTB4-Mediated PPARγ Activation

Despite the growing knowledge with regard to the immunomodulatory properties of host defense peptides, their impact on macrophage differentiation and on its associated microbicidal functions is still poorly understood. Here, we demonstrated that the P17, a new cationic antimicrobial peptide from ant venom, induces an alternative phenotype of human monocyte-derived macrophages (h-MDMs). This phenotype is characterized by a C-type lectin receptors (CLRs) signature composed of mannose receptor (MR) and Dectin-1 expression. Concomitantly, this activation is associated to an inflammatory profile characterized by reactive oxygen species (ROS), interleukin (IL)-1β, and TNF-α release. P17-activated h-MDMs exhibit an improved capacity to recognize and to engulf Candida albicans through the overexpression both of MR and Dectin-1. This upregulation requires arachidonic acid (AA) mobilization and the activation of peroxisome proliferator-activated receptor gamma (PPARγ) nuclear receptor through the leukotriene B4 (LTB4) production. AA/LTB4/PPARγ/Dectin-1-MR signaling pathway is crucial for P17-mediated anti-fungal activity of h-MDMs, as indicated by the fact that the activation of this axis by P17 triggered ROS production and inflammasome-dependent IL-1β release. Moreover, we showed that the increased anti-fungal immune response of h-MDMs by P17 was dependent on intracellular calcium mobilization triggered by the interaction of P17 with pertussis toxin-sensitive G-protein-coupled receptors on h-MDMs. Finally, we also demonstrated that P17-treated mice infected with C. albicans develop less severe gastrointestinal infection related to a higher efficiency of their macrophages to engulf Candida, to produce ROS and IL-1β and to kill the yeasts. Altogether, these results identify P17 as an original activator of the fungicidal response of macrophages that acts upstream PPARγ/CLRs axis and offer new immunomodulatory therapeutic perspectives in the field of infectious diseases.

CRAMP deficiency leads to a pro-inflammatory phenotype and impaired phagocytosis after exposure to bacterial meningitis pathogens

BACKGROUND

Antimicrobial peptides are important components of the host defence with a broad range of functions including direct antimicrobial activity and modulation of inflammation. Lack of cathelin-related antimicrobial peptide (CRAMP) was associated with higher mortality and bacterial burden and impaired neutrophil granulocyte infiltration in a model of pneumococcal meningitis. The present study was designed to characterize the effects of CRAMP deficiency on glial response and phagocytosis after exposure to bacterial stimuli.

METHODS

CRAMP-knock out and wildtype glial cells were exposed to bacterial supernatants from Streptococcus pneumoniae and Neisseria meningitides or the bacterial cell wall components lipopolysaccharide and peptidoglycan. Cell viability, expression of pro- and anti-inflammatory mediators and activation of signal transduction pathways, phagocytosis rate and glial cell phenotype were investigated by means of cell viability assays, immunohistochemistry, real-time RT-PCR and Western blot.

RESULTS

CRAMP-deficiency was associated with stronger expression of pro-inflammatory and weakened expression of anti-inflammatory cytokines indicating a higher degree of glial cell activation even under resting-state conditions. Furthermore, increased translocation of nuclear factor 'kappa-light-chain-enhancer' of activated B-cells was observed and phagocytosis of S. pneumoniae was reduced in CRAMP-deficient microglia indicating impaired antimicrobial activity.

CONCLUSIONS

In conclusion, the present study detected severe alterations of the glial immune response due to lack of CRAMP. The results indicate the importance of CRAMP to maintain and regulate the delicate balance between beneficial and harmful immune response in the brain.

Antimicrobial and immunomodulatory activity of host defense peptides, clavanins and LL-37, in vitro: An endodontic perspective

Endodontic treatment is mainly based on root canal disinfection and its failure may be motivated by microbial resistance. Endodontic therapy can be benefitted by host defense peptides (HDPs), which are multifunctional molecules that act against persistent infection and inflammation. This study aimed to evaluate the antimicrobial, cytotoxic and immunomodulatory activity of several HDPs, namely clavanin A, clavanin A modified (MO) and LL-37, compared to intracanal medication Ca(OH)₂. HDPs and Ca(OH)₂ were evaluated by: (1) antimicrobial assays against Candida albicans and Enterococcus faecalis, (2) cytotoxicity assays and (3) cytokine tumor necrosis factor (TNF)-α, monocyte chemoattractant protein (MCP)-1, interleukin (IL)-1α, IL-6, IL-10 and IL-12 and nitric oxide (NO) production by RAW 264.7 cells incubated with or without heat-killed (HK) C. albicans or E. faecalis combined or not with interferon-γ. The minimum inhibitory concentration (MIC) was established only for E. faecalis (LL-37, 57μM). Considering cytotoxicity, clavanin MO was able to reduce cell viability in many groups and demonstrated lowest LC₅₀. The Ca(OH)₂ up-regulated the production of MCP-1, TNF-α, IL-12 and IL-6 and down-regulated IL-1α, IL-10 and NO. Clavanins up-regulated the TNF-α and NO and down-regulated IL-10 production. LL-37 demonstrated up-regulation of IL-6 and TNF-α production and down-regulation in IL-10 and NO production. In conclusion, LL-37 demonstrated better antibacterial potential. In addition, Ca(OH)₂ demonstrated a proinflammatory response, while the HDPs modulated the inflammatory response from non-interference with the active cytokines in the osteoclastogenesis process, probably promoting the health of periradicular tissues.

Cathelicidins Inhibit Escherichia coli-Induced TLR2 and TLR4 Activation in a Viability-Dependent Manner

Activation of the immune system needs to be tightly regulated to provide protection against infections and, at the same time, to prevent excessive inflammation to limit collateral damage to the host. This tight regulation includes regulating the activation of TLRs, which are key players in the recognition of invading microbes. A group of short cationic antimicrobial peptides, called cathelicidins, have previously been shown to modulate TLR activation by synthetic or purified TLR ligands and may play an important role in the regulation of inflammation during infections. However, little is known about how these cathelicidins affect TLR activation in the context of complete and viable bacteria. In this article, we show that chicken cathelicidin-2 kills Escherichia coli in an immunogenically silent fashion. Our results show that chicken cathelicidin-2 kills E. coli by permeabilizing the bacterial inner membrane and subsequently binds the outer membrane-derived lipoproteins and LPS to inhibit TLR2 and TLR4 activation, respectively. In addition, other cathelicidins, including human, mouse, pig, and dog cathelicidins, which lack antimicrobial activity under cell culture conditions, only inhibit macrophage activation by nonviable E. coli In total, this study shows that cathelicidins do not affect immune activation by viable bacteria and only inhibit inflammation when bacterial viability is lost. Therefore, cathelicidins provide a novel mechanism by which the immune system can discriminate between viable and nonviable Gram-negative bacteria to tune the immune response, thereby limiting collateral damage to the host and the risk for sepsis.

Immuno-Stimulatory Peptides as a Potential Adjunct Therapy against Intra-Macrophagic Pathogens

The treatment of infectious diseases is increasingly prone to failure due to the rapid spread of antibiotic-resistant pathogens. Antimicrobial peptides (AMPs) are natural components of the innate immune system of most living organisms. Their capacity to kill microbes through multiple mechanisms makes the development of bacterial resistance less likely. Additionally, AMPs have important immunomodulatory effects, which critically contribute to their role in host defense. In this paper, we review the most recent evidence for the importance of AMPs in host defense against intracellular pathogens, particularly intra-macrophagic pathogens, such as mycobacteria. Cathelicidins and defensins are reviewed in more detail, due to the abundance of studies on these molecules. The cell-intrinsic as well as the systemic immune-related effects of the different AMPs are discussed. In the face of the strong potential emerging from the reviewed studies, the prospects for future use of AMPs as part of the therapeutic armamentarium against infectious diseases are presented.

Synergistic antibiotic effect of looped antimicrobial peptide CLP-19 with bactericidal and bacteriostatic agents

The treatment of drug-resistant infections is complicated and the alarming rise in infectious diseases poses a unique challenge for development of effective therapeutic strategies. Antibiotic-induced liberation of the bacterial endotoxin lipopolysaccharide (LPS) may have immediate adverse effects promoting septic shock in patients. In the present study, we first confirmed our previous finding that looped antimicrobial peptide CLP-19 exerts non-specific direct antibacterial activity with no toxic to mammalian cells and second revealed that CLP-19 has synergistic effect to enhance the antibacterial activities of other conventional bactericidal (ampicillin and ceftazidime) and bacteriostatic (erythromycin and levofloxacin) agents. Third, the underlying mechanism of antibiotic effect was likely associated with stimulation of hydroxyl radical generation. Lastly, CLP-19 was shown to effectively reduce the antibiotic-induced liberation of LPS, through direct neutralization of the LPS. Thus, CLP-19 is a potential therapeutic agent for combinatorial antibiotic therapy.

Interspecies cathelicidin comparison reveals divergence in antimicrobial activity, TLR modulation, chemokine induction and regulation of phagocytosis

Cathelicidins are short cationic peptides initially described as antimicrobial peptides, which can also modulate the immune system. Because most findings have been described in the context of human LL-37 or murine CRAMP, or have been investigated under varying conditions, it is unclear which functions are cathelicidin specific and which functions are general cathelicidin properties. This study compares 12 cathelicidins from 6 species under standardized conditions to better understand the conservation of cathelicidin functions. Most tested cathelicidins had strong antimicrobial activity against E. coli and/or MRSA. Interestingly, while more physiological culture conditions limit the antimicrobial activity of almost all cathelicidins against E. coli, activity against MRSA is enhanced. Seven out of 12 cathelicidins were able to neutralize LPS and another 7 cathelicidins were able to neutralize LTA; however, there was no correlation found with LPS neutralization. In contrast, only 4 cathelicidins enhanced DNA-induced TLR9 activation. In conclusion, these results provide new insight in the functional differences of cathelicidins both within and between species. In addition, these results underline the importance not to generalize cathelicidin functions and indicates that caution should be taken in extrapolating results from LL-37- or CRAMP-related studies to other animal settings.

Molecular mechanisms of LL-37-induced receptor activation: An overview

The human cathelicidin peptide LL-37 plays a crucial role in the immune system on many levels, from the first line of defense in epithelial cells to restoring the tissue after infection. On host cells, the majority of the LL-37-induced effects are mediated via the direct or indirect activation of several structurally unrelated cell surface receptors or intracellular targets. How LL-37 is able to affect multiple receptors is currently not well understood. So far, the mechanistic details underlying receptor activation are poorly investigated and evidence for a conventional ligand/receptor interaction is scarce. Over the past few decades, a large number of studies have reported on the activation of a receptor and/or components of the downstream signal transduction pathway induced by LL-37. This review summarizes the current knowledge on molecular mechanisms underlying LL-37-induced receptor activation.

Glucose levels affect LL-37 expression in monocyte-derived macrophages altering the Mycobacterium tuberculosis intracellular growth control

Diabetes mellitus (DM)-2 patients have an increased susceptibility to develop pulmonary tuberculosis; this is partly due to the impairment of the innate immunity because of their higher glucose concentrations. In the present study, we determined the effect of the glucose concentrations in the LL-37 expression in infected and non-infected macrophages. Our results showed that the increasing glucose concentrations correlates with the low cathelicidin expression in non-infected cells, however in Mycobacterium tuberculosis infected cells, LL-37 expression was substantially increased in higher glucose concentrations, nevertheless the mycobacterial burden also increased, this phenomena can be associated with the cathelicidin immunomodulatory activity. Further evaluation for LL-37 needs to be done to determine whether this peptide can be used as a biomarker of tuberculosis progression in DM2 patients.

Vitamin D Activation and Function in Human Corneal Epithelial Cells During TLR-Induced Inflammation

PURPOSE

Vitamin D is recognized to be an important modulator of the immune system. In the eye, studies have shown that deficiencies and genetic differences in vitamin D-related genes have a significant impact on the development of various ocular diseases. Our current study examines the ability of human corneal epithelial cells (HCEC) to activate vitamin D and the effect of vitamin D treatment on antimicrobial peptide production and cytokine modulation during inflammation, with the ultimate goal of using vitamin D therapeutically for corneal inflammation.

METHODS

Human corneal epithelial cells were treated with 10-7M vitamin D3 (D3) or 25-hydroxyvitamin D3 (25D3) for 24 hours and 1,25-dihydroxyvitamin D3 (1,25D3) detected by immunoassay. Human cathelicidin (LL-37) expression was examined by RT-PCR, immunoblot, and immunostaining following 1,25D3 treatment and antimicrobial activity of 1,25D3-treated cells was determined. Cells were stimulated with TLR3 agonist polyinosinic-polycytidylic acid (Poly[I:C]) for 24 hours and cytokine levels measured by RT-PCR, ELISA, and Luminex. Immunostaining determined expression of vitamin D receptor (VDR) and retinoic acid inducible gene-1 receptor (RIG-1) as well as NF-κB nuclear translocation.

RESULTS

When treated with inactive vitamin D metabolites, HCEC produced active 1,25D3, leading to enhanced expression of the antimicrobial peptide, LL-37, dependent on VDR. 1,25-D3 decreased the expression of proinflammatory cytokines (IL-1β, IL-6, TNFα, and CCL20) and MMP-9 induced by Poly(I:C) as well as pattern recognition receptor expression (TLR3, RIG-1, MDA5). However, early activation of NF-κB was not affected.

CONCLUSIONS

These studies demonstrate the protective ability of vitamin D to attenuate proinflammatory mediators while increasing antimicrobial peptides and antipseudomonas activity in corneal cells, and further our knowledge on the immunomodulatory functions of the hormone.

Antibiotic adjuvants: diverse strategies for controlling drug-resistant pathogens

The growing number of bacterial pathogens that are resistant to numerous antibiotics is a cause for concern around the globe. There have been no new broad-spectrum antibiotics developed in the last 40 years, and the drugs we have currently are quickly becoming ineffective. In this article, we explore a range of therapeutic strategies that could be employed in conjunction with antibiotics and may help to prolong the life span of these life-saving drugs. Discussed topics include antiresistance drugs, which are administered to potentiate the effects of current antimicrobials in bacteria where they are no longer (or never were) effective; antivirulence drugs, which are directed against bacterial virulence factors; host-directed therapies, which modulate the host's immune system to facilitate infection clearance; and alternative treatments, which include such therapies as oral rehydration for diarrhea, phage therapy, and probiotics. All of these avenues show promise for the treatment of bacterial infections and should be further investigated to explore their full potential in the face of a postantibiotic era.

LL-37 immunomodulatory activity during Mycobacterium tuberculosis infection in macrophages

Tuberculosis is one of the most important infectious diseases worldwide. The susceptibility to this disease depends to a great extent on the innate immune response against mycobacteria. Host defense peptides (HDP) are one of the first barriers to counteract infection. Cathelicidin (LL-37) is an HDP that has many immunomodulatory effects besides its weak antimicrobial activity. Despite advances in the study of the innate immune response in tuberculosis, the immunological role of LL-37 during M. tuberculosis infection has not been clarified. Monocyte-derived macrophages were infected with M. tuberculosis strain H37Rv and then treated with 1, 5, or 15 μg/ml of exogenous LL-37 for 4, 8, and 24 h. Exogenous LL-37 decreased tumor necrosis factor alpha (TNF-α) and interleukin-17 (IL-17) while inducing anti-inflammatory IL-10 and transforming growth factor β (TGF-β) production. Interestingly, the decreased production of anti-inflammatory cytokines did not reduce antimycobacterial activity. These results are consistent with the concept that LL-37 can modulate the expression of cytokines during mycobacterial infection and this activity was independent of the P2X7 receptor. Thus, LL-37 modulates the response of macrophages during infection, controlling the expression of proinflammatory and anti-inflammatory cytokines.

Antimicrobial Peptides in Human Sepsis

Nearly 100 years ago, antimicrobial peptides (AMPs) were identified as an important part of innate immunity. They exist in species from bacteria to mammals and can be isolated in body fluids and on surfaces constitutively or induced by inflammation. Defensins have anti-bacterial effects against Gram-positive and Gram-negative bacteria as well as anti-viral and anti-yeast effects. Human neutrophil peptides (HNP) 1-3 and human beta-defensins (HBDs) 1-3 are some of the most important defensins in humans. Recent studies have demonstrated higher levels of HNP 1-3 and HBD-2 in sepsis. The bactericidal/permeability-increasing protein (BPI) attenuates local inflammatory response and decreases systemic toxicity of endotoxins. Moreover, BPI might reflect the severity of organ dysfunction in sepsis. Elevated plasma lactoferrin is detected in patients with organ failure. HNP 1-3, lactoferrin, BPI, and heparin-binding protein are increased in sepsis. Human lactoferrin peptide 1-11 (hLF 1-11) possesses antimicrobial activity and modulates inflammation. The recombinant form of lactoferrin [talactoferrin alpha (TLF)] has been shown to decrease mortality in critically ill patients. A phase II/III study with TLF in sepsis did not confirm this result. The growing number of multiresistant bacteria is an ongoing problem in sepsis therapy. Furthermore, antibiotics are known to promote the liberation of pro-inflammatory cell components and thus augment the severity of sepsis. Compared to antibiotics, AMPs kill bacteria but also neutralize pathogenic factors such as lipopolysaccharide. The obstacle to applying naturally occurring AMPs is their high nephro- and neurotoxicity. Therefore, the challenge is to develop peptides to treat septic patients effectively without causing harm. This overview focuses on natural and synthetic AMPs in human and experimental sepsis and their potential to provide significant improvements in the treatment of critically ill with severe infections.

Cathelicidin impact on inflammatory cells

Cathelicidins, like other antimicrobial peptides, exhibit direct antimicrobial activities against a broad spectrum of microbes, including both Gram-positive and Gram-negative bacteria, enveloped viruses, and fungi. These host-derived peptides kill the invaded pathogens by perturbing their cell membranes and can neutralize biological activities of endotoxin. Nowadays, more and more data indicate that these peptides, in addition to their antimicrobial properties, possess various immunomodulatory activities. Cathelicidins have the potential to influence and modulate, both directly and indirectly, the activity of various cell populations involved in inflammatory processes and in host defense against invading pathogens. They induce migration of neutrophils, monocytes/macrophages, eosinophils, and mast cells and prolong the lifespan of neutrophils. These peptides directly activate inflammatory cells to production and release of different pro-inflammatory and immunoregulatory mediators, cytokines, and chemokines, however cathelicidins might mediate the generation of anti-inflammatory cytokines as well. Cathelicidins also modulate epithelial cell/keratinocyte responses to infecting pathogens. What is more, they affect activity of monocytes, dendritic cells, keratinocytes, or epithelial cells acting in synergy with cytokines or β-defensins. In addition, these peptides indirectly balance TLR-mediated responses of monocytes, macrophages, dendritic cells, epithelial cells, and keratinocytes. This review discusses the role and significance of cathelicidins in inflammation and innate immunity against pathogens.

Peptides and Peptidomimetics for Antimicrobial Drug Design

The purpose of this paper is to introduce and highlight a few classes of traditional antimicrobial peptides with a focus on structure-activity relationship studies. After first dissecting the important physiochemical properties that influence the antimicrobial and toxic properties of antimicrobial peptides, the contributions of individual amino acids with respect to the peptides antibacterial properties are presented. A brief discussion of the mechanisms of action of different antimicrobials as well as the development of bacterial resistance towards antimicrobial peptides follows. Finally, current efforts on novel design strategies and peptidomimetics are introduced to illustrate the importance of antimicrobial peptide research in the development of future antibiotics.

Immune activation efficacy of indolicidin is enhanced upon conjugation with carbon nanotubes and gold nanoparticles

Antibiotic resistance is concern of today's world. Search for alternative molecules, for treatment and immune stimulation, remains at the forefront. One such group of biomolecules with promise, along the line of immune stimulation or therapy, is host defense peptide (HDP). These molecules, however, are required at a higher dose to be effective which leads to high cost. To alleviate such problems, an aid can be used to achieve similar efficacy but at a smaller effective dose of the immune stimulant. We hypothesised that by conjugating HDPs with carbon nanotubes and/or gold nanoparticles, it would be possible to stimulate a protective immune response in host system at a lower dosage of HDP. In this report, we characterized, using biophysical methodologies, conjugation of Indolicidin, as a representative of HDP. We further established efficacy of peptide-nanomaterial conjugates in activating innate immunity and protecting against pathogen infection in vitro at a significantly small dose.

Nutrigenetics and nutrigenomics insights into diabetes etiopathogenesis

Diabetes mellitus (DM) is considered a global pandemic, and the incidence of DM continues to grow worldwide. Nutrients and dietary patterns are central issues in the prevention, development and treatment of this disease. The pathogenesis of DM is not completely understood, but nutrient-gene interactions at different levels, genetic predisposition and dietary factors appear to be involved. Nutritional genomics studies generally focus on dietary patterns according to genetic variations, the role of gene-nutrient interactions, gene-diet-phenotype interactions and epigenetic modifications caused by nutrients; these studies will facilitate an understanding of the early molecular events that occur in DM and will contribute to the identification of better biomarkers and diagnostics tools. In particular, this approach will help to develop tailored diets that maximize the use of nutrients and other functional ingredients present in food, which will aid in the prevention and delay of DM and its complications. This review discusses the current state of nutrigenetics, nutrigenomics and epigenomics research on DM. Here, we provide an overview of the role of gene variants and nutrient interactions, the importance of nutrients and dietary patterns on gene expression, how epigenetic changes and micro RNAs (miRNAs) can alter cellular signaling in response to nutrients and the dietary interventions that may help to prevent the onset of DM.

The porcine innate immune system: an update

Over the last few years, we have seen an increasing interest and demand for pigs in biomedical research. Domestic pigs (Sus scrofa domesticus) are closely related to humans in terms of their anatomy, genetics, and physiology, and often are the model of choice for the assessment of novel vaccines and therapeutics in a preclinical stage. However, the pig as a model has much more to offer, and can serve as a model for many biomedical applications including aging research, medical imaging, and pharmaceutical studies to name a few. In this review, we will provide an overview of the innate immune system in pigs, describe its anatomical and physiological key features, and discuss the key players involved. In particular, we compare the porcine innate immune system to that of humans, and emphasize on the importance of the pig as model for human disease.

LL-37 modulates human neutrophil responses to influenza A virus

Recent studies have shown that the human cathelicidin, LL-37, has antiviral activity against IAV in vitro and in vivo. Neutrophils are important cellular components of the initial innate response to IAV infection. In addition to its direct antimicrobial activities, LL-37 has important immunomodulatory effects. In this study, we explore how LL-37 affects interactions of IAV with human neutrophils. LL-37 did not alter neutrophil uptake of IAV but significantly increased neutrophil H2O2 responses to the virus. IAV stimulated production of NETs in vitro, and this response was increased by preincubating the virus with LL-37. NADPH-oxidase blockade did not reduce IAV-induced NET formation or the increased NET response stimulated by LL-37 + IAV. The increased respiratory burst and NET responses were, however, inhibited by preincubating cells with a formyl peptide receptor blocker, indicating that LL-37 engages these receptors when complexed with IAV. Responses to IAV alone were not inhibited by formyl peptide receptor blockade. It has been reported that LL-37 reduces proinflammatory cytokine responses during IAV infection in vivo. We now show that IAV alone potentiated release of IL-8 from neutrophils, and preincubation with LL-37 reduced IAV-stimulated IL-8 release. These results confirm that LL-37 modulates human neutrophil responses to IAV in a distinctive manner and could have important bearing on the protective effects of LL-37 during IAV infection in vivo.