The interaction of the antimicrobial peptide cLEAP-2 and the bacterial membrane

Early intestinal development of chickens divergently selected for high or low 8-wk body weight and a commercial broiler

The early posthatch period is crucial to intestinal development, shaping long-term growth, metabolism, and health of the chick. The objective of this study was to determine the effect of genetic selection on morphological characteristics and gene expression during early intestinal development. Populations of White Plymouth Rocks have been selected for high weight (HWS) and low weight (LWS) for over 63 generations, and some LWS display symptoms of anorexia. Intestinal structure and function of these populations were compared to a commercial broiler Cobb 500 (Cobb) during the perihatch period. Egg weights, yolk-free embryo BW, yolk weights, and jejunal samples from HWS, LWS, and Cobb were collected on embryonic day (e) 17, e19, day of hatch, day (d) 3, d5, and d7 posthatch for histology and gene expression analysis. The RNAscope in-situ hybridization method was used to localize expression of the stem cell marker, olfactomedin 4 (Olfm4). Villus height (VH), crypt depth (CD), and VH/CD were measured from Olfm4 stained images using ImageJ. mRNA abundance for Olfm4, stem cell marker Lgr5, peptide transporter PepT1, goblet cell marker Muc2, marker of proliferation Ki67, and antimicrobial peptide LEAP2 were examined. Two-factor ANOVA was performed for measurements and Turkey's HSD was used for mean separation when appropriate. Cobb were heaviest and LWS the lightest (P < 0.01). at each timepoint. VH increased in Cobb and CD increased in HWS compared to LWS (P < 0.01). PepT1 mRNA was upregulated in LWS (P < 0.01), and Muc2 mRNA was decreased in both HWS and LWS compared to Cobb (P < 0.01). Selection for high or low 8-wk body weight has caused differences in intestinal gene expression and morphology when compared to a commercial broiler.

Chicken -defensin-1 peptide as a candidate anticoccidial agent in broiler chickens

The current study aimed to investigate the potentiality of using avian β-defensin-1 peptide as a candidate agent against coccidiosis infection in broiler chicken.We employed an in-silico analysis to study the primary structure of β-defensin-1 peptide as well as its 3-D and molecular dynamic structures. This will also enable obtaining adequate information about the mode of action of these peptides and the intra-cellular transduction pathways. The results revealed no significant difference among groups of broiler chicken in terms of body weight before the Eimeria challenge.The results of our study indicated a significant reduction in oocyst count in birds administered β-defensin-1 peptide treatment, vis-a-vis healthy birds. The treated group showed a 2-3 times reduction in oocyst count, compared to the positive control group. The Eimeria oocysts count evaluated for birds administered with β-defensin-1 after the Eimeria challenge showed a significant difference. The study indicated significant reduction and down-regulation in the level of expression of β-defensin 1 and 4 in the control and treatment groups.This electrostatic profile and hydrophobicity regulate the functioning of this peptide. The results may help in the development of novel approaches that could be used as alternatives or adjunct to the existing means of coccidiosis control in broilers.

Host defence peptide LEAP2 contributes to antimicrobial activity in a mustache toad (Leptobrachium liui)

BACKGROUND

The liver-expressed antimicrobial peptide 2 (LEAP2) is essential in host immunity against harmful pathogens and is only known to act as an extracellular modulator to regulate embryonic development in amphibians. However, there is a dearth of information on the antimicrobial function of amphibian LEAP2. Hence, a LEAP2 homologue from Leptobrachium liui was identified, characterized, and chemically synthesized, and its antibacterial activities and mechanisms were determined.

RESULTS

In this study, LEAP2 gene (Ll-LEAP2) cDNA was cloned and sequenced from the Chong'an Moustache Toad (Leptobrachium liui). The predicted amino acid sequence of Ll-LEAP2 comprises a signal peptide, a mature peptide, and a prodomain. From sequence analysis, it was revealed that Ll-LEAP2 belongs to the cluster of amphibian LEAP2 and displays high similarity to the Tropical Clawed Frog (Xenopus tropicalis)'s LEAP2. Our study revealed that LEAP2 protein was found in different tissues, with the highest concentration in the kidney and liver of L. liui; and Ll-LEAP2 mRNA transcripts were expressed in various tissues with the kidney having the highest mRNA expression level. As a result of Aeromonas hydrophila infection, Ll-LEAP2 underwent a noticeable up-regulation in the skin while it was down-regulated in the intestines. The chemically synthesized Ll-LEAP2 mature peptide was selective in its antimicrobial activity against several in vitro bacteria including both gram-positive and negative bacteria. Additionally, Ll-LEAP2 can kill specific bacteria by disrupting bacterial membrane and hydrolyzing bacterial gDNA.

CONCLUSIONS

This study is the first report on the antibacterial activity and mechanism of amphibian LEAP2. With more to uncover, the immunomodulatory functions and wound-healing activities of Ll-LEAP2 holds great potential for future research.

Chicken LEAP2 Level Substantially Changes with Feed Intake and May Be Regulated by CDX4 in Small Intestine

Ghrelin O-acyltransferase (GOAT), ghrelin, and GHSR have been reported to play important roles that influence feed intake in mammals. LEAP2, an endogenous antagonist of GHSR, plays an important role in the regulation of feed intake. However, chicken ghrelin has also been reported to have an inhibitory effect on feed intake. The role of the GOAT-Ghrelin-GHSR-LEAP2 axis in chicken-feed intake remains unclear. Therefore, it is necessary to systematically evaluate the changes in the tissue expression levels of these genes under different energy states. In this study, broiler chicks in different energy states were subjected to starvation and feeding, and relevant gene expression levels were measured using quantitative real-time PCR. Different energy states significantly modulated the expression levels of LEAP2 and GHSR but did not significantly affect the expression levels of GOAT and ghrelin. A high expression level of LEAP2 was detected in the liver and the whole small intestine. Compared to the fed group, the fasted chicks showed significantly reduced LEAP2 expression levels in the liver and the small intestine; 2 h after being refed, the LEAP2 expression of the fasted chicks returned to the level of the fed group. Transcription factor prediction and results of a dual luciferase assay indicated that the transcription factor CDX4 binds to the LEAP2 promoter region and positively regulates its expression. High expression levels of GHSR were detected in the hypothalamus and pituitary. Moreover, we detected GHSR highly expressed in the jejunum-this finding has not been previously reported. Thus, GHSR may regulate intestinal motility, and this aspect needs further investigation. In conclusion, this study revealed the function of chicken LEAP2 as a potential feed-intake regulator and identified the potential mechanism governing its intestine-specific expression. Our study lays the foundations for future studies on avian feed-intake regulation.

Role of the ghrelin system in alcohol use disorder and alcohol-associated liver disease: A narrative review

Unhealthy alcohol consumption is a global health problem. Adverse individual, public health, and socioeconomic consequences are attributable to harmful alcohol use. Epidemiological studies have shown that alcohol use disorder (AUD) and alcohol-associated liver disease (ALD) are the top two pathologies among alcohol-related diseases. Consistent with the major role that the liver plays in alcohol metabolism, uncontrolled drinking may cause significant damage to the liver. This damage is initiated by excessive fat accumulation in the liver, which can further progress to advanced liver disease. The only effective therapeutic strategies currently available for ALD are alcohol abstinence or liver transplantation. Any molecule with dual-pronged effects at the central and peripheral organs controlling addictive behaviors and associated metabolic pathways are a potentially important therapeutic target for treating AUD and ALD. Ghrelin, a hormone primarily derived from the stomach, has such properties, and regulates both behavioral and metabolic functions. In this review, we highlight recent advances in understanding the peripheral and central functions of the ghrelin system and its role in AUD and ALD pathogenesis. We first discuss the correlation between blood ghrelin concentrations and alcohol use or abstinence. Next, we discuss the role of ghrelin in alcohol-seeking behaviors and finally its role in the development of fatty liver by metabolic regulations and organ crosstalk. We propose that a better understanding of the ghrelin system could open an innovative avenue for improved treatments for AUD and associated medical consequences, including ALD.

From "Hunger Hormone" to "It's Complicated": Ghrelin Beyond Feeding Control

Discovered as a peptide involved in releasing growth hormone, ghrelin was initially characterized as the "hunger hormone." However, emerging research indicates that ghrelin appears to play an important part in relaying information regarding nutrient availability and value and adjusting physiological and motivational processes accordingly. These functions make ghrelin an interesting therapeutic candidate for metabolic and neuropsychiatric diseases involving disrupted nutrition that can further potentiate the rewarding effect of maladaptive behaviors.

Self-assembled nanoparticles containing photosensitizer and polycationic brush for synergistic photothermal and photodynamic therapy against periodontitis

Background

Periodontitis is a chronic inflammatory disease in oral cavity owing to bacterial infection. Photothermal therapy (PTT) and photodynamic therapy (PDT) have many advantages for antibacterial treatment. As an excellent photosensitizer, indocyanine green (ICG) shows prominent photothermal and photodynamic performances. However, it is difficult to pass through the negatively charged bacterial cell membrane, thus limiting its antibacterial application for periodontitis treatment.

Results

In this work, self-assembled nanoparticles containing ICG and polycationic brush were prepared for synergistic PTT and PDT against periodontitis. First, a star-shaped polycationic brush poly(2-(dimethylamino)ethyl methacrylate) (sPDMA) was synthesized via atom transfer radical polymerization (ATRP) of DMA monomer from bromo-substituted β-cyclodextrin initiator (CD-Br). Next, ICG was assembled with sPDMA to prepare ICG-loaded sPDMA (sPDMA@ICG) nanoparticles (NPs) and the physicochemical properties of these NPs were characterized systematically. In vitro antibacterial effects of sPDMA@ICG NPs were investigated in porphyromonas gingivalis (Pg), one of the recognized periodontitis pathogens. A ligature-induced periodontitis model was established in Sprague–Dawley rats for in vivo evaluation of anti-periodontitis effects of sPDMA@ICG NPs. Benefiting from the unique brush-shaped architecture of sPDMA polycation, sPDMA@ICG NPs significantly promoted the adsorption and penetration of ICG into the bacterial cells and showed excellent PTT and PDT performances. Both in vitro and in vivo, sPDMA@ICG NPs exerted antibacterial and anti-periodontitis actions via synergistic PTT and PDT.

Conclusions

A self-assembled nanosystem containing ICG and polycationic brush has shown promising clinical application for synergistic PTT and PDT against periodontitis.

Graphical Abstract

Supplementary Information

The online version contains supplementary material available at 10.1186/s12951-021-01114-w.

LEAP-2/ghrelin interplay in adult growth hormone deficiency: Cause or consequence? A pilot study

Ghrelin and its endogenous antagonist liver-expressed antimicrobial peptide-2 (LEAP-2) are involved in GH secretion and glucose/lipids metabolism. LEAP-2 expression in conditions of metabolic impairment may be upregulated, usually pairing with a concomitant reduction in ghrelin secretion. Adult growth hormone deficiency (aGHD) is characterized by insulin resistance, weight gain, and increased fat mass. Therefore, the primary endpoint of this cross-sectional observational pilot study was to compare circulating LEAP-2 and ghrelin levels in aGHD and healthy controls. Thirty patients were included in the study. Group A included adult GHD: 15 patients, 8 females, and 7 males. Median and interquartile range age of the group was 53 (41-57) years, while BMI was 27.1 (25-35) kg/m² . Group B was formed by 15 healthy controls (10 females and 5 males). Median and interquartile range age was 47 (36-57) years, while BMI 22.9 (20.8-33.1) kg/m² . They were evaluated for serum glucose and insulin, HOMA-index, QUICKI-index, total/LDL/HDL cholesterol, triglycerides, IGF-1, ghrelin, and LEAP-2. Ghrelin levels in the aGHD group were significantly lower than in healthy controls. In contrast, LEAP-2 showed a trend toward higher levels, although the differences were not significant. However, the LEAP-2/Ghrelin ratio was significantly higher in aGHD. No significant correlations between ghrelin and LEAP-2 with BMI and HOMA index were found in aGHD population. However, a significant inverse correlation (r²  = 0.15, p = .047) between BMI and ghrelin was evidenced when considering the whole population. Taken together, these results may suggest a body adaptation to a metabolic scenario typical of aGHD. The decrease in ghrelin production could prevent further weight gain and fat mass increase, although losing its secretagogue effect.

Antimicrobial peptides as an alternative to relieve antimicrobial growth promoters in poultry

1. This review describes different classes of antimicrobial peptides (AMP) found in the gastrointestinal (GI) tract of avian species, and their antimicrobial and immunomodulatory activities. The potential benefits of synthetic AMP in poultry production are examined, in the context of the use of AMP as alternatives to antimicrobial growth promoters (AGP).2. Since the mid-1950s, antibiotic growth promoters (AGP) have been used in feed at low prophylactic doses to modulate the homoeostasis of intestinal microbiota, decreasing the risk of intestinal dysbacteriosis and the growth of pathogens within the avian gut. Over the last three decades, AGP have faced major regulatory restrictions due to concerns of generating antimicrobial resistance (AMR). It is now well documented that the rate of infectious disease outbreaks is higher in flocks that are not fed prophylactic antibiotics, resulting in a compensatory increase in antimicrobial use for therapeutic purposes.3. Endogenous natural AMP production is associated with the presence of microbiota and their interaction with the intestinal epithelial and lamina propria lymphoid cells. Their antimicrobial activity shapes the beneficial microbiota population and controls intestinal pathogens such Clostridium and Salmonella spp., and stimulates the development and maturation of the local immune system.4. Similar to AGP, AMP can establish a well-balanced gut beneficial microbiota for adequate immune-competence, animal health and high growth performance parameters such as feed intake, daily weight, feed conversion and accumulated mortality.5. Antimicrobial proteins and peptides constitute an essential part of the innate immune system of all organisms and protect the host from invading pathogenic bacteria, viruses, fungi, and parasites by interacting with the negatively charged pathogen membranes.

Human liver-expressed antimicrobial peptide 2 elevation in the cerebrospinal fluid in bacterial meningitis

OBJECTIVE

To study the presence of liver-expressed antimicrobial peptide 2 (LEAP2) in human cerebrospinal fluid (CSF) and to measure its concentrations in neurological disorders.

MATERIALS & METHODS

We identified the presence of LEAP2 in human CSF by chromatographic analysis and a LEAP2-specific enzyme immunoassay. We measured LEAP2 concentrations in the CSF of 35 patients with neurological disorders.

RESULTS

CSF LEAP2 concentrations in the bacterial meningitis group (mean ± SD, 9.32 ± 3.76 ng/ml) were significantly higher (p < .05) than those in the other four groups (psychosomatic disorder, 0.56 ± 0.15 ng/ml; peripheral autoimmune disease, 1.00 ± 0.60 ng/ml; multiple sclerosis, 0.62 ± 0.30 ng/ml; aseptic meningitis, 1.59 ± 0.69 ng/ml).

CONCLUSIONS

This is the first study to identify the presence of human LEAP2 in the CSF. Levels of LEAP2 were increased in the CSF of patients with bacterial meningitis. LEAP2 may have potential as a biomarker for bacterial meningitis.

The effects of tributyrin supplementation on weight gain and intestinal gene expression in broiler chickens during Eimeria maxima-induced coccidiosis

Butyrate is a feed additive that has been shown to have antibacterial properties and improve gut health in broilers. Here, we examined the performance and gene expression changes in the ileum of tributyrin–supplemented broilers infected with coccidia. Ninety-six, Ross 708 broilers were fed either a control corn–soybean–based diet (−BE) or a diet supplemented with 0.25% (w/w) tributyrin (+BE). Birds were further divided into groups that were inoculated with Eimeria maxima oocysts (EM) or sham-inoculated (C) on day 21 posthatch. At 7 d postinfection (7 d PI), the peak of pathology in E. maxima infection, tributyrin-supplemented birds had significantly improved feed conversion ratios (FCR, P < 0.05) and body weight gain (BWG, P < 0.05) compared with -BE-infected birds, despite both groups having similar feed intake (FI, P > 0.05). However, at 10 d post-infection (10 d PI) no significant effects of feed type or infection were observed. Gene expression in the ileum was examined for insights into possible effects of infection and tributyrin supplementation on genes encoding proteins related to immunity, digestion, and gut barrier integrity. Among immune-related genes examined, IL-1B and LEAP2 were only significantly affected at 7 d PI. Transcription of genes related to digestion (APN, MCT1, FABP2, and MUC2) were primarily influenced by infection at 7 d PI and tributyrin supplementation (FABP2 and MUC2) at 10 d PI. With exception of ZO1, tight junction genes were affected by either infection or feed type at 7 d PI. At 10 d PI, only CLDN1 was not affected by either infection or feed type. Overall tributyrin shows promise as a supplement to improve performance during coccidiosis in broiler chickens; however, its effect on gene expression and mode of action requires further research.

A Multifunctional Nanosystem Based on Bacterial Cell-Penetrating Photosensitizer for Fighting Periodontitis Via Combining Photodynamic and Antibiotic Therapies

Photodynamic therapy (PDT), an emerging approach that involves photosensitizers, light, and molecular oxygen, has shown promise for fighting periodontitis. However, PDT does not always acquire the desired therapeutic outcomes since some photosensitizers have strong hydrophobic properties and are difficult to absorb efficiently by periodontal pathogenic bacteria. Here, a hydrophobic photosensitizer chlorin e6 (Ce6) was hydrophilically modified via conjugation with TAT peptide, a cationic cell-penetrating peptide, to improve its solubility and enhance its bacterial adsorption by promoting its interaction with the negatively charged cell walls and penetration through the cell membranes. The obtained TAT-Ce6 conjugate (TAT-Ce6) was used to prepare self-assembled nanoparticles (NPs) for loading tinidazole (TDZ), a clinically used antibiotic agent, thus hoping to achieve synergistic antiperiodontitis effects through combining PDT and antibiotic therapy. Compared to free Ce6, TAT-Ce6 nanoparticles (TAT-Ce6 NPs) had greatly enhanced adsorption and penetration abilities for periodontal pathogen bacteria and also exhibited significantly increased PDT efficiencies in both periodontal pathogen bacteria and monocyte macrophages. Upon 635 nm laser irradiation, TDZ-loaded TAT-Ce6 (TAT-Ce6/TDZ) NPs exerted remarkable synergistic antiperiodontitis effects of PDT and antibiotic therapy, reflecting in the effective killing of periodontal pathogenic bacteria in vitro and the reduced adsorption of alveolar bone in the Sprague-Dawley rat model of periodontitis. Altogether, this study develops a novel photosensitizer that can be efficiently absorbed by the periodontal pathogenic bacteria and also provides a potent combination strategy of PDT with antibiotic therapy for clinical periodontitis treatment.

The effects of quercetin on immunity, antioxidant indices, and disease resistance in zebrafish (Danio rerio)

The main purpose of this study was to evaluate the immunity, antioxidant indices, and disease resistance of quercetin in zebrafish (Danio rerio). A total of 630 fish were assigned to 21 tanks with 30 fish/tank, and they were exposed to 0, 0.01, 0.1, 1, 10, 100, and 1000 μg/L quercetin, respectively, for 56 days. Results indicated that the immune indices including acid phosphatase (ACP), myeloperoxidase (MPO), lysozyme activities, and Complement 3 (C3), C4, IgM contents were significantly higher in 1 μg/L quercetin group than these parameters in the control group (P < 0.05). TNF-α and IL-8 mRNA expressions significantly decreased as the levels of quercetin increased up to 1 μg/L and increased thereafter (P < 0.05). 1 and 10 μg/L quercetin groups showed significantly lower TNF-α and IL-8 mRNA levels than the quercetin-free group. Transforming growth factor-β and IL-10 mRNA levels showed an obviously opposite trend with TNF-α expression. The SOD, GPX, CAT, T-AOC activities, and SOD and GPX gene expression in the liver were enhanced with increasing quercetin up to 1 μg/L, and decreased thereafter. MDA contents were affected by quercetin, in which 1 and 10 μg/L quercetin had a significantly lower level than that of the control group (P < 0.05). Defensin and Leap-II mRNA expression in the liver were the highest for fish exposed to 1 μg/L quercetin. The fish that exposed to 1 μg/L quercetin also showed a significantly higher survival rate than these of fish exposed to 0, 0.01, and 1000 μg/L quercetin (P < 0.05). In conclusion, the optimal level of quercetin promotes immunostimulant properties, antioxidant indices, and disease resistance of zebrafish.

Molecular characterization of the NK-lysin in a teleost fish, Boleophthalmus pectinirostris: Antimicrobial activity and immunomodulatory activity on monocytes/macrophages

NK-lysin (NKL) is a cationic host defense peptide that plays an important role in host immune responses against various pathogens. However, the immunomodulatory activity of NKL in fishes is rarely investigated. In this study, we characterized a cDNA sequence encoding an NK-lysin homolog (BpNKL) from the fish, mudskipper (Boleophthalmus pectinirostris). Sequence analysis revealed that BpNKL is most closely related to tiger puffer (Takifugu rubripes) NKL. BpNKL transcript was detected in all the tested tissues, with the highest level in the gill, followed by the spleen and kidney. Upon Edwardsiella tarda infection, the mRNA expression of BpNKL in the mudskipper was significantly upregulated in the spleen, kidney, and gill. A shortened peptide derived from BpNKL, BpNKLP40, was then chemically synthesized and its biological functions were investigated. BpNKLP40 exhibited a direct antibacterial activity against some Gram-negative bacteria, including E. tarda, Vibrio parahaemolyticus, Vibrio alginolyticus, and Vibrio harveyi, and induced hydrolysis of E. tarda genomic DNA. Intraperitoneal injection of 1.0 μg/g BpNKLP40 significantly improved the survival of mudskipper following E. tarda infection and reduced the bacterial burden in tissues and blood. Moreover, 1.0 μg/ml BpNKLP40 treatment had an enhanced effect on the intracellular killing of E. tarda by monocytes/macrophages (MO/MФ) as well as on the mRNA expression of pro-inflammatory cytokines in MO/MФ. In conclusion, our study reveals that BpNKL plays a role against E. tarda infection in the mudskipper by not only directly killing bacteria but also through an immunomodulatory activity on MO/MФ.

Host defense peptide LEAP-2 contributes to monocyte/macrophage polarization in barbel steed (Hemibarbus labeo)

The liver-expressed antimicrobial peptide 2 (LEAP-2) plays a vital role in host immunity against pathogenic organisms. In the present study, cDNA of the LEAP-2 gene was cloned and sequenced from the barbel steed (Hemibarbus labeo). The predicted amino acid sequence of the barbel steed LEAP-2 comprises a signal peptide and a prodomain, which is followed by the mature peptide. Sequence analysis revealed that barbel steed LEAP-2 belongs to the fish LEAP-2A cluster and that it is closely related to zebrafish LEAP-2A. We found that barbel steed LEAP-2 transcripts were expressed in a wide range of tissues, with the highest mRNA levels detected in the liver. In response to lipopolysaccharide (LPS) treatment, LEAP-2 was significantly upregulated in the liver, head kidney, spleen, gill, and mid intestine. A chemically synthesized LEAP-2 mature peptide exhibited selective antimicrobial activity against several bacteria in vitro. Moreover, LEAP-2, alone or in combination with LPS or phorbol 12-myristate 13-acetate, strongly induced a pro-inflammatory reaction in barbel steed monocytes/macrophages (MO/MФ), involving the induction of iNOS activity, respiratory burst, and the pro-inflammatory cytokines IFN-γ, TNF-α, and IL-1β. Collectively, the results of this study indicate the importance of fish LEAP-2 in the M1-type polarization of MO/MΦ.

Dynamics of Structural Barriers and Innate Immune Components during Incubation of the Avian Egg: Critical Interplay between Autonomous Embryonic Development and Maternal Anticipation

The integrated innate immune features of the calcareous egg and its contents are a critical underpinning of the remarkable evolutionary success of the Aves clade. Beginning at the time of laying, the initial protective structures of the egg, i.e., the biomineralized eggshell, egg-white antimicrobial peptides, and vitelline membrane, are rapidly and dramatically altered during embryonic development. The embryo-generated extra-embryonic tissues (chorioallantoic/amniotic membranes, yolk sac, and associated chambers) are all critical to counteract degradation of primary egg defenses during development. With a focus on the chick embryo (Gallus gallus domesticus), this review describes the progressive transformation of egg innate immunity by embryo-generated structures and mechanisms over the 21-day course of egg incubation, and also discusses the critical interplay between autonomous development and maternal anticipation.

Expression of nutrient transporters and host defense peptides in Campylobacter challenged broilers

Campylobacter is a bacterium that colonizes the lower gastrointestinal tract of poultry and may influence the intestinal environment to promote its survival. The objective of this study was to characterize the effects of Campylobacter challenge on the mRNA abundance of nutrient transporters and host defense peptides (HDP), such as the avian β-defensins (AvBD) and liver expressed antimicrobial peptide 2 (LEAP2). On the day of hatch, broiler chicks were challenged with one of three (106, 107, 108 colony-forming units, cfu) levels of Campylobacter jejuni. Quantitative PCR analysis revealed that there were dose-, tissue-, and age-specific changes in gene expression for both nutrient transporters and HDP. Expression of zinc transporter 1 (ZnT1) mRNA increased on d 7 in the duodenum, ileum, and cecum of birds challenged with 106 cfu of C. jejuni. At d 14, there was upregulation of the amino acid transporter bo,+AT mRNA in the duodenum, jejunum, and ileum of birds challenged with 106 cfu of C. jejuni. Other transporters such as EAAT3, GLUT2, SGLT1, and ZnT1 showed upregulation of mRNA in the ileum of the 106 cfu challenged group. There was a delayed response of the HDP to the C. jejuni challenge, with only a few HDP changed at d 7 but all HDP changed at d 14. At d 7, there was upregulation of AvBD10 mRNA in the duodenum of the 106 cfu challenged group but downregulation of AvBD10 in the ileum and AvBD12 and LEAP2 in the cecum of the 108 cfu challenged group. At d 14, there was upregulation of AvBD1, AvBD6, AvBD8, AvBD10, AvBD11, AvBD12, and AvBD13 mRNA in the ileum and cecum of the 106 cfu challenged group but not the 107 and 108 cfu challenged groups compared to control. These results indicated that at a low dose (106 cfu) of C. jejuni, intestinal cells increased nutrient transporter and AvBD mRNA abundance to try to counter the infection, but that at higher doses the cellular response was suppressed.

Identification of duck liver-expressed antimicrobial peptide 2 and characterization of its bactericidal activity

Objective

This study was conducted to identify duck liver-expressed antimicrobial peptide 2 (LEAP-2) and demonstrate its antimicrobial activity against various pathogens.

Methods

Tissue samples were collected from 6 to 8-week-old Pekin ducks (Anas platyrhynchos domesticus), total RNA was extracted, and cDNA was synthesized. To confirm the duck LEAP-2 transcript expression levels, quantitative real-time polymerase chain reaction was conducted. Two kinds of peptides (a linear peptide and a disulfide-type peptide) were synthesized to compare the antimicrobial activity. Then, antimicrobial activity assay and fluorescence microscopic analysis were conducted to demonstrate duck LEAP-2 bactericidal activity.

Results

The duck LEAP-2 peptide sequence showed high identity with those of other avian species (>85%), as well as more than 55% of identity with mammalian sequences. LEAP-2 mRNA was highly expressed in the liver with duodenum next, and then followed by lung, spleen, bursa and jejunum and was the lowest in the muscle. Both of LEAP-2 peptides efficiently killed bacteria, although the disulfide-type LEAP-2 showed more powerful bactericidal activity. Also, gram-positive bacteria was more susceptible to duck LEAP-2 than gram-negative bacteria. Using microscopy, we confirmed that LEAP-2 peptides could kill bacteria by disrupting the bacterial cell envelope.

Conclusion

Duck LEAP-2 showed its antimicrobial activity against both gram-positive and gram-negative bacteria. Disulfide bonds were important for the powerful killing effect by disrupting the bacterial cell envelope. Therefore, duck LEAP-2 can be used for effective antibiotics alternatives.

Enrofloxacin and Probiotic Lactobacilli Influence PepT1 and LEAP-2 mRNA Expression in Poultry

Expression of peptide transporter 1 (PepT1) and liver-expressed antimicrobial peptide 2 (LEAP-2) in chickens can be influenced by food deprivation, pathological conditions and drug administration. Effect of three putative probiotic Lactobacillus strains and enrofloxacin on the expression of PepT1 and LEAP-2 mRNA was investigated in Ross 308 chickens. One-day-old chicks (n = 24) were allocated to following groups: control (without treatment); group treated with probiotics via feed; group treated with a combination of probiotics and enrofloxacin; and a group given enrofloxacin only. The drug was administered at a dose of 10 mg kg^-1, via drinking water for 5 days. Samples from liver, duodenum and jejunum were collected 126 h after the start of the treatment. Expression levels of PepT1 and LEAP-2 were determined by real-time polymerase chain reaction and were statistically evaluated by Mann-Whitney test. Enrofloxacin administered alone or in combination with probiotics provoked a statistically significant up-regulation of PepT1 mRNA levels in the measured organ sites. These changes can be attributed to a tendency of improvement in utilization of dietary peptide and in body weight gain. LEAP-2 mRNA expression levels did not change significantly in enrofloxacin-treated chickens in comparison with control group.

Expression of host defense peptides in the intestine of Eimeria-challenged chickens

Avian coccidiosis is caused by the intracellular protozoan Eimeria, which produces intestinal lesions leading to weight gain depression. Current control methods include vaccination and anticoccidial drugs. An alternative approach involves modulating the immune system. The objective of this study was to profile the expression of host defense peptides such as avian beta-defensins (AvBDs) and liver expressed antimicrobial peptide 2 (LEAP2), which are part of the innate immune system. The mRNA expression of AvBD family members 1, 6, 8, 10, 11, 12, and 13 and LEAP2 was examined in chickens challenged with either E. acervulina, E. maxima, or E. tenella. The duodenum, jejunum, ileum, and ceca were collected 7 d post challenge. In study 1, E. acervulina challenge resulted in down-regulation of AvBD1, AvBD6, AvBD10, AvBD11, AvBD12, and AvBD13 in the duodenum. E. maxima challenge caused down-regulation of AvBD6, AvBD10, and AvBD11 in the duodenum, down-regulation of AvBD10 in the jejunum, but up-regulation of AvBD8 and AvBD13 in the ceca. E. tenella challenge showed no change in AvBD expression in any tissue. In study 2, which involved challenge with only E. maxima, there was down-regulation of AvBD1 in the ileum, AvBD11 in the jejunum and ileum, and LEAP2 in all 3 segments of the small intestine. The expression of LEAP2 was further examined by in situ hybridization in the jejunum of chickens from study 2. LEAP2 mRNA was expressed similarly in the enterocytes lining the villi, but not in the crypts of control and Eimeria challenged chickens. The lengths of the villi in the Eimeria challenged chickens were less than those in the control chickens, which may in part account for the observed down-regulation of LEAP2 mRNA quantified by PCR. Overall, the AvBD response to Eimeria challenge was not consistent; whereas LEAP2 was consistently down-regulated, which suggests that LEAP2 plays an important role in modulating an Eimeria infection.

The protection effect of LEAP-2 on the mudskipper (Boleophthalmus pectinirostris) against Edwardsiella tarda infection is associated with its immunomodulatory activity on monocytes/macrophages

Liver-expressed antimicrobial peptide 2 (LEAP-2) is a cationic peptide that plays an important role in the host's innate immune system. However, the mechanism by which LEAP-2 modulates/regulates the host defense against pathogens remains largely unknown. In this study, we identified a cDNA sequence encoding LEAP-2 homolog (BpLEAP-2) in the mudskipper, Boleophthalmus pectinirostris. Sequence analysis revealed that BpLEAP-2 belonged to the fish LEAP-2A cluster and that it was closely related to ayu LEAP-2. BpLEAP-2 mRNA was detected in a wide range of tissues, with the highest level of transcripts found in the liver. Upon infection with Edwardsiella tarda, BpLEAP-2 mRNA expression was significantly increased in the liver, kidney, spleen, and gill, but decreased in the intestine. Chemically synthesized BpLEAP-2 mature peptide did not exhibit antibacterial activity against E. tarda in vitro. Intraperitoneal injection of BpLEAP-2 (1.0 or 10.0 μg/g) resulted in significantly improved survival rate and reduced tissue bacterial load in E. tarda-infected mudskippers. In E. tarda-infected fish, BpLEAP-2 (0.1, 1.0, or 10.0 μg/g) eliminated E. tarda-induced tissue mRNA expression of BpTNF-α and BpIL-1β. In monocytes/macrophages (MO/MФ), BpLEAP-2 (1.0 or 10.0 μg/ml) induced chemotaxis, enhanced respiratory burst, and inhibited E. tarda-induced mRNA expression of BpTNF-α and BpIL-1β. At a concentration of 10.0 μg/ml, BpLEAP-2 also significantly enhanced the bacterial killing efficiency of MO/MФ. No significant effect was seen in the phagocytic activity of MO/MФ upon treatment with BpLEAP-2. Our study provides evidence, for the first time, that LEAP-2 exhibited immunomodulatory effects on immune cells, and protected the host from pathogenic infections independent of direct bacterial killing function.

Expression, purification and characterization of the recombinant cysteine-rich antimicrobial peptide snakin-1 in Pichia pastoris

Snakin-1 (SN-1) is a small cysteine-rich plant antimicrobial peptide with broad spectrum antimicrobial activity which was isolated from potato (Solanum tuberosum). Here, we carried out the expression of a recombinant SN-1 in the methylotrophic yeast Pichia pastoris, along with its purification and characterization. A DNA fragment encoding the mature SN-1 was cloned into pPIC9 vector and introduced into P. pastoris. A large amount of pure recombinant SN-1 (approximately 40 mg/1L culture) was obtained from a fed-batch fermentation culture after purification with a cation exchange column followed by RP-HPLC. The identity of the recombinant SN-1 was verified by MALDI-TOF MS, CD and (1)H NMR experiments. All these data strongly indicated that the recombinant SN-1 peptide had a folding with six disulfide bonds that was identical to the native SN-1. Our findings showed that SN-1 exhibited strong antimicrobial activity against test microorganisms and produced very weak hemolysis of mammalian erythrocytes. The mechanism of its antimicrobial action against Escherichia coli was investigated by both outer membrane permeability assay and cytoplasmic membrane depolarization assay. These assays demonstrated that SN-1 is a membrane-active antimicrobial peptide which can disrupt both outer and cytoplasmic membrane integrity. This is the first report on the recombinant expression and purification of a fully active SN-1 in P. pastoris.

Yeast β-d-glucans induced antimicrobial peptide expressions against Salmonella infection in broiler chickens

The present study was designed to investigate the effects of yeast β-d-glucans (YG) on gene expression of endogenous β-defensins (AvBDs), cathelicidins (Cath) and liver-expressed antimicrobial peptide-2 (LEAP-2) in broilers challenged with Salmonella enteritidis (SE). 240 day-old Cobb male broilers were randomly assigned to 2×2 factorial arrangements of treatments with two levels of dietary YG (0 or 200mg/kg in diet) and two levels of SE challenge (0 or 1×10(9) SE at 7-9 days of age). The results showed SE infection reduced growth performance,and increased salmonella cecal colonization and internal organs invasion, increased concentration of intestinal specific IgA and serum specific IgG antibody, as compared to uninfected birds. SE challenge differentially regulated AvBDs, Caths and LEAP-2 gene expression in the jejunum and spleen of broiler chickens during the infection period. However, YG supplementation inhibited the growth depression by SE challenge, and further increased level of serum specific IgG and intestinal specific IgA antibody. Higher level of salmonella colonization and internal organs invasion in the SE-infected birds were reduced by YG. SE-induced differentially expression patterns of AMPs genes was inhibited or changed by YG. Results indicated YG enhance chicken's resistance to salmonella infection.

Changes in expression of an antimicrobial peptide, digestive enzymes, and nutrient transporters in the intestine of E. praecox-infected chickens

Coccidiosis is a major intestinal disease of poultry, caused by several species of the protozoan Eimeria. The objective of this study was to examine changes in expression of digestive enzymes, nutrient transporters, and an antimicrobial peptide following an Eimeria praecox challenge of chickens at days 3 and 6 post-infection. Gene expression was determined by real-time PCR and analyzed by one-way ANOVA. In the duodenum, the primary site of E. praecox infection, a number of genes were downregulated at both d3 and d6 post-infection. These genes included liver expressed antimicrobial peptide 2 (LEAP2), the cationic (CAT1), anionic (EAAT3), and L-type (LAT1) amino acid transporters, the peptide transporter PepT1 and the zinc transporter ZnT1. Other transporters were downregulated either at d3 or d6. At both d3 and d6, there was downregulation of B(o)AT and CAT1 in the jejunum and downregulation of LEAP2 and LAT1 in the ileum. LEAP2, EAAT3, and ZnT1 have been found to be downregulated following challenge with other Eimeria species, suggesting a common cellular response to Eimeria.

Expression of digestive enzymes and nutrient transporters in Eimeria-challenged broilers

Avian coccidiosis is a disease caused by the intestinal protozoa Eimeria. The site of invasion and lesions in the intestine is species-specific, for example E. acervulina affects the duodenum, E. maxima the jejunum, and E. tenella the ceca. Lesions in the intestinal mucosa cause reduced feed efficiency and body weight gain. The growth reduction may be due to changes in expression of digestive enzymes and nutrient transporters in the intestine. The objective of this study was to compare the expression of digestive enzymes, nutrient transporters and an antimicrobial peptide in broilers challenged with either E. acervulina, E. maxima or E. tenella. The genes examined included digestive enzymes (APN and SI), peptide and amino acid transporters (PepT1, ASCT1, b(0,+)AT/rBAT, B(0)AT, CAT1, CAT2, EAAT3, LAT1, y(+)LAT1 and y(+)LAT2), sugar transporters (GLUT1, GLUT2, GLUT5 and SGLT1), zinc transporter (ZnT1) and an antimicrobial peptide (LEAP2). Duodenum, jejunum, ileum and ceca were collected 7 days post challenge. E. acervulina challenge resulted in downregulation of various nutrient transporters or LEAP2 in the duodenum and ceca, but not the jejunum or ileum. E. maxima challenge produced both downregulation and upregulation of nutrient transporters and LEAP2 in all three segments of the small intestine and ceca. E. tenella challenge resulted in the downregulation and upregulation of nutrient transporters and LEAP2 in the jejunum, ileum and ceca, but not the duodenum. At the respective target tissue, E. acervulina, E. maxima and E. tenella infection caused common downregulation of APN, b(0,+)AT, rBAT, EAAT3, SI, GLUT2, GLUT5, ZnT1 and LEAP2. The downregulation of nutrient transporters would result in a decrease in the efficiency of protein and polysaccharide digestion and uptake, which may partially explain the weight loss. The downregulation of nutrient transporters may also be a cellular response to reduced expression of the host defense protein LEAP2, which would diminish intracellular pools of nutrients and inhibit pathogen replication.

Expression of digestive enzymes and nutrient transporters in Eimeria acervulina-challenged layers and broilers

Avian coccidiosis is a disease caused by intestinal protozoa in the genus Eimeria. Clinical signs of coccidiosis include intestinal lesions and reduced feed efficiency and BW gain. This growth reduction may be due to changes in expression of digestive enzymes and nutrient transporters in the intestine. The objective of this study was to examine the differential expression of digestive enzymes, transporters of amino acids, peptides, sugars, and minerals, and an antimicrobial peptide in the small intestine of Eimeria acervulina-infected broilers and layers. Uninfected broilers and layers, in general, expressed these genes at comparable levels. Some differences included 3-fold and 2-fold greater expression of the peptide transporter PepT1 and the antimicrobial peptide LEAP2 (liver expressed antimicrobial peptide 2), respectively, in the jejunum of layers compared with broilers and 17-fold greater expression of LEAP2 in the duodenum of broilers compared with layers. In the duodenum of Eimeria-infected broilers and layers, there was downregulation of aminopeptidase N; sucrase-isomaltase; the neutral, cationic, and anionic amino acid transporters b(o,+)AT/rBAT, B(o)AT, CAT2, and EAAT3; the sugar transporter GLUT2; the zinc transporter ZnT1; and LEAP2. In the jejunum of infected layers there was downregulation of many of the same genes as in the duodenum plus downregulation of PepT1, b(o,+)AT/rBAT, and the y(+) L system amino acid transporters y(+) LAT1 and y(+) LAT2. In the ileum of infected layers there was downregulation of CAT2, y(+)LAT1, the L type amino acid transporter LAT1, and the sugar transporter GLUT1, and upregulation of APN, PepT1, the sodium glucose transporter SGLT4, and LEAP2. In E. acervulina-infected broilers, there were no gene expression changes in the jejunum and ileum. These changes in intestinal digestive enzyme and nutrient transporter gene expression may result in a decrease in the efficiency of protein digestion, uptake of important amino acids and sugars, and disruption of mineral balance that may affect intestinal cell metabolism and Eimeria replication.

Molecular characterization of LEAP-2 cDNA in common carp (Cyprinus carpio L.) and the differential expression upon a Vibrio anguillarum stimulus; indications for a significant immune role in skin

LEAP-2 is a cysteine-rich cationic antimicrobial peptide (AMP) playing an important role in host innate immune system. LEAP-2 genes have been identified from higher vertebrates and several fish species. Here we report the cloning and identification of two LEAP-2 cDNA sequences from the liver of common carp (Cyprinus carpio L.). The LEAP-2A cDNA was 1325 bp long and contained an ORF of 279 bp encoding a protein of 92 amino acids. The LEAP-2B cDNA was 608 bp long and contained an ORF of 276 bp encoding a protein of 91 amino acids. Both LEAP-2 proteins consisted of 41 amino acid residues and shared four cysteines at the conserved positions in the predicted mature peptides, highly similar to LEAP-2 of other species. Sequence alignment showed that LEAP-2 amino acid sequences were well conserved in different species, and the phylogenetic relation of LEAP-2 was coincident with evolution of biological species. Expression analysis data revealed that LEAP-2A and LEAP-2B mRNAs were expressed in a wide range of common carp tissues including liver, spleen, head kidney, skin, gills, hindgut and foregut. When injected intraperitoneally with Vibrio anguillarum, the expression level of common carp LEAP-2A was quickly up-regulated in liver, spleen, head kidney, skin, gills, foregut and hindgut, however, the expression level of LEAP-2B was similarly up-regulated in spleen, skin, gills and hindgut but not in liver, head kidney and foregut. Our results showed that the LEAP-2A had a markedly high constitutive expression in skin, and the LEAP-2A and the LEAP-2B had a significantly high up-regulated expression after stimulus in skin. This differential expression of LEAP-2 in common carp suggests that it may play a key role in immune responses against invading pathogens and both LEAP-2 molecules may be involved in mucosal immunity.

Effects of sexual maturation and Salmonella infection on the expression of avian β-defensin genes in the chicken testis

Rooster infertility is a major concern in the poultry industry and protection of the male reproductive organs from pathogens is an essential aspect of reproductive physiology. During the last years, research on antimicrobial protection has elucidated the critical role of the antimicrobial peptides avian β-defensins (AvBDs) in the innate immunity in chickens. AvBDs have been reported to be expressed in the hen reproductive organs, providing protection against microbial pathogens including Salmonella Enteritidis (SE). However, mechanisms of antimicrobial protection of rooster reproductive organs and especially the testis, mediated by AvBDs are poorly understood. The aim of this study was to investigate the expression of the complete family of the 14 AvBD genes, in the rooster testis in vivo, to determine whether sexual maturation affects their testicular mRNA abundance and to investigate whether SE infection alters their expression. Expression analysis revealed that 9 members of the AvBD family, namely AvBD1, 2, 4, 5, 6, 9, 10, 12 and 14 were expressed in the testis. Quantitative real-time PCR analysis revealed that the mRNA abundance of three AvBDs was up regulated and of three AvBDs was down regulated with respect to sexual maturation. In addition, SE infection resulted in a significant induction of AvBD4, 10, 12 and 14 in the testis of sexually mature roosters. These findings provide strong evidence to suggest that an AvBD-mediated immune response mechanism exists in the rooster testis providing protection against bacterial pathogens including Salmonella species.

Molecular cloning and expression analysis of liver-expressed antimicrobial peptide 1 (LEAP-1) and LEAP-2 genes in the blunt snout bream (Megalobrama amblycephala)

Liver-expressed antimicrobial peptide 1 (LEAP-1) and LEAP-2 are widespread in fish and extremely important components of the host innate immune system. In this study, full-length cDNAs of LEAP-1 and LEAP-2 were cloned and sequenced from blunt snout bream, Megalobrama amblycephala. The open reading frames (ORF) of LEAP-1 and LEAP-2 genes encode putative peptides of 94 and 92 amino acids, which possess eight and four conserved cysteine residues, respectively. The homologous identities of deduced amino acid sequences show that the LEAP-1 and LEAP-2 of blunt snout bream share considerable similarity with those of grass carp. The mRNA expressions of LEAP-1 and LEAP-2 were detectable at different early developmental stages of blunt snout bream and varied with embryonic and larval growth. LEAP-1 and LEAP-2 were expressed in a wide range of adult tissues, with the highest expression levels in the liver and midgut, respectively. Bacterial challenge experiments showed that the levels of LEAP-1 and LEAP-2 mRNA expression were up-regulated in the liver, spleen, gill and brain of juvenile blunt snout bream. These results indicate that the LEAP-1 and LEAP-2 may play important roles in early development of embryos and fry, and may contribute to the defense against the pathogenic bacterial invasion. This study will further our understanding of the function of LEAP-1 and LEAP-2 and the molecular mechanism of innate immunity in teleosts.

Cyprinid herpesvirus 3 infection disrupts the skin barrier of common carp (Cyprinus carpio L.)

Cyprinid herpesvirus-3 (CyHV-3) is recognised as a pathogen which causes mass mortality in populations of carp, Cyprinus carpio. One of the characteristic symptoms of the disease associated with CyHV-3 infection is the occurrence of skin lesions, sloughing off the epithelium and a lack of mucus. Furthermore, fish then seem to be more susceptible to secondary infections by bacterial, parasitic or fungal pathogens which may cause further mortality within the population. The observed pathological alterations lead to the assumption that the carp skin barrier is strongly challenged during CyHV-3 associated disease. Therefore we examined mRNA expression of genes encoding inflammatory mediators, type I interferons, and the following skin defence molecules: antimicrobial peptides, claudins, and mucin. In addition, we monitored changes in the bacterial flora of the skin during disease conditions. Our results show that CyHV-3 associated disease in the skin of common carp leads to a reduction in mRNA expression of genes encoding several important components of the mucosal barrier, in particular mucin 5B, beta defensin 1 and 2, and the tight junction proteins claudin 23 and 30. This caused changes in the bacterial flora and the development of secondary bacterial infection among some individual fish. To our knowledge this is the first report showing that under disease conditions associated with virus infection, the mucosal barrier of fish skin is disrupted resulting in a higher susceptibility to secondary infections. The reported clinical signs of CyHV-3 skin infection can now be explained by our results at the molecular level, although the mechanism of a probable virus induced immunomodulation has to be investigated further.

Streptococcus pyogenes infection of tonsil explants is associated with a human β-defensin 1 response from control but not recurrent acute tonsillitis patients

Host defence peptides (HDP), including the defensins and hCAP-18, function as part of the innate immune defences, protecting the host epithelia from microbial attachment and invasion. Recurrent acute tonsillitis (RAT), in which patients suffer repeated symptomatic tonsil infections, is linked to Streptococcus pyogenes, a group A streptococcus, and may reflect the impaired expression of such peptides. To address this, the defensin and hCAP-18 messenger RNA expression profiles of 54 tonsils excised from control and RAT patients undergoing tonsillectomy were quantified and compared. Marked variation in expression was observed between individuals from the two groups, but statistically no significant differences were identified, suggesting that at the time of surgery the tonsil epithelial HDP barrier was not compromised in RAT subjects. Surgical removal of the tonsils occurs in a quiescent phase of disease, and so to assess the effects of an active bacterial infection, HaCaT cells an in vitro model of the tonsil epithelium, and explants of patient tonsils maintained in vitro were challenged with S. pyogenes. The HaCaT data supported the reduced expression of hCAP-18/LL-37, human β-defensin 1 (HBD1;P < 0.01) and HBD2 (P < 0.05), consistent with decreased protection of the epithelial barrier. The tonsil explant data, although not as definitive, showed similar trends apart from HBD1 expression, which in the control tonsils but not the RAT patient tonsils was characterized by increased expression (P < 0.01). These data suggest that in vivo HBD1 may play a critical role in protecting the tonsil epithelia from S. pyogenes.

The activity of antimicrobial peptide S-thanatin is independent on multidrug-resistant spectrum of bacteria

In this study, the activity of S-thanatin (an analog of antimicrobial peptide derived from thanatin) against different bacterial pathogens frequently which can cause therapeutic problems was tested. The result showed minimal inhibitory concentrations (MICs) of S-thanatin against all isolates of the Escherichia coli, Klebsiella pneumoniae, Enterobacter cloacae, Enterobacter aerogenes, Klebsiella ornithinolytica and Klebsiella oxytoca were in the range of 4-16μg/ml, no matter which antibiotic the bacterial was resistant or susceptible, while almost all MICs to Gram-positive bacterial were >128μg/ml except Enterococcus faecium. S-thanatin was more effective toward Gram-negative strains, especially for Enterobacter and Klebsiella. The MICs of S-thanatin were no significantly different in the same species regardless of antibiotic sensitive or -resistant isolates to single or multiple antibiotic (P>0.05). Likewise, no notable difference could be observed between E. coli, K. pneumoniae, E. cloacae, E. aerogenes, K. ornithinolytica which were sensitive to S-thanatin (P>0.05). It was implied that the antimicrobial activity of S-thanatin was independent on multi-drug resistance spectrum of bacteria.

Immunological characterization of the equine airway epithelium and of a primary equine airway epithelial cell culture model

Our understanding of innate immunity within the equine respiratory tract is limited despite growing evidence for its key role in both the immediate defense and the shaping of downstream adaptive immune responses to respiratory disease. As the first interface to undergo pathogen invasion, the respiratory epithelium is a key player in these early events and our goal was to examine the innate immune characteristics of equine respiratory epithelia and compare them to an in vitro equine respiratory epithelial cell model cultured at the air-fluid interface (AFI). Respiratory epithelial tissues, isolated epithelial cells, and four-week old cultured differentiated airway epithelial cells collected from five locations of the equine respiratory tract were examined for the expression of toll-like receptors (TLRs) and host defense peptides (HDPs) using conventional polymerase chain reaction (PCR). Cultured, differentiated, respiratory epithelial cells and freshly isolated respiratory epithelial cells were also examined for the expression of TLR3, TLR9 and major histocompatibility complex (MHC) class I and class II using fluorescence-activated cell sorting (FACS) analysis. In addition, cytokine and chemokine profiles from respiratory epithelial tissues, freshly isolated respiratory epithelial cells, and cultured, differentiated, epithelial cells from the upper respiratory tract were examined using real-time PCR. We found that respiratory epithelial tissues and isolated epithelial cells expressed TLRs 1-4 and 6-10 as well as HDPs, MxA, 2'5' OAS, β-defensin-1, and lactoferrin. In contrast, epithelial cells cultured at the AFI expressed TLRs 1-4 and 6 and 7 as well as MxA, 2'5' OAS, β-defensin-1, but had lost expression of TLRs 8-10 and lactoferrin. In addition, MHC-I and MHC-II surface expression decreased in epithelial cells cultured at the AFI compared to isolated epithelial cells whereas TLR3 and TLR9 were expressed at similar levels. Lastly, we found that equine respiratory epithelial cells express an array of pro-inflammatory, antiviral and regulatory cytokines and that after four weeks of in vitro growth conditions, equine respiratory epithelial cells cultured at the AFI retained expression of GM-CSF, IL-10, IL-8, TGF-β, TNF-α, and IL-6. In summary, we describe the development of an in vitro equine respiratory epithelial cell culture model that is morphologically similar to the equine airway epithelium and retains several key immunological properties. In the future this model will be a used to study equine respiratory viral pathogenesis and cell-to-cell interactions.

Expression of chicken LEAP-2 in the reproductive organs and embryos and in response to Salmonella enterica infection

In recent years host antimicrobial peptides and proteins have been recognised as key mediators of the innate immune response in many vertebrate species, providing the first line of defense against potential pathogens. In chickens a number of cationic antimicrobial peptides have been recently identified. However, although these peptides have been studied extensively in the avian gastrointestinal tract, little is known about their function in the chicken reproductive organs and embryos. Chicken Liver Expressed Antimicrobial Peptide-2 (cLEAP-2) has been previously reported to function in protecting birds against microbial attack. The aim of this study was to investigate the expression of cLEAP-2 gene in the chicken reproductive organs, as well as in chicken embryos during embryonic development, and to determine whether cLEAP-2 expression in the chicken reproductive organs was constitutive or induced as a response to Salmonella enteritidis infection. RNA was extracted from ovary, oviduct, testis and epididymis of sexually mature healthy and Salmonella infected birds, as well as from chicken embryos until day ten of embryonic development. Expression analysis data revealed that cLEAP-2 was expressed in the chicken ovary, testis and epididymis as well as in embryos during early embryonic development. Quantitative real-time PCR analysis revealed that cLEAP-2 expression was constitutive in the chicken epididymis, but was significantly up regulated in the chicken gonads, following Salmonella infection. In addition, expression of cLEAP-2 during chicken embryogenesis appeared to be developmentally regulated. These data provide evidence to suggest a key role of cLEAP-2 in the protection of the chicken reproductive organs and the developing embryos from Salmonella colonization.