Expression of β-defensins pBD-1 and pBD-2 along the small intestinal tract of the pig: Lack of upregulation in vivo upon Salmonella typhimurium infection

Short-chain fatty acids modulate the IPEC-J2 cell response to pathogenic E. coli LPS-activated PBMC

Intestinal disorders can affect pigs of any age, especially when animals are young and more susceptible to infections and environmental stressors. For instance, pathogenic E. coli can alter intestinal functions, thus leading to altered nutrient adsorption by interacting with local cells through lipopolysaccharide (LPS). Among several compounds studied to counteract the negative effects on the intestine, short-chain fatty acids (SCFA) were demonstrated to exert beneficial effects on gut epithelial cells and resident immune cells. In this study, acetate and propionate were tested for their beneficial effects in a co-culture model of IPEC-J2 and porcine PBMC pre-stimulated with LPS from E. coli 0111:B4 aimed at mimicking the interaction between intestinal cells and immune cells in an inflammatory/activated status. IPEC-J2 viability was partially reduced when co-cultured with activated PBMC and nitric oxide concentration increased. IPEC-J2 up-regulated innate and inflammatory markers, namely BD-1, TLR-4, IL-8, TNF-α, NF-κB, and TGF-β. Acetate and propionate positively modulated the inflammatory condition by sustaining cell viability, reducing the oxidative stress, and down-regulating the expression of inflammatory mediators. TNF-α expression and secretion showed an opposite effect in IPEC-J2 depending on the extent of LPS stimulation of PBMC and TGF-β modulation. Therefore, SCFA proved to mediate a differential effect depending on the degree and duration of inflammation. The expression of the tight junction proteins (TJp) claudin-4 and zonula occludens-1 was up-regulated by LPS while SCFA influenced TJp with a different kinetics depending on PBMC stimulation. The co-culture model of IPEC-J2 and LPS-activated PBMC proved to be feasible to address the modulation of markers related to anti-bacterial immunity and inflammation, and intestinal epithelial barrier integrity, which are involved in the in vivo responsiveness and plasticity to infections.

Effects on the intestinal morphology, inflammatory response and microflora in piglets challenged with enterotoxigenic Escherichia coli K88

Enterotoxigenic Escherichia coli (ETEC) is an important cause of diarrhea in piglets, which leads to great economic losses. In this study, the ternary crossbred weaned piglets were orally administered with 1.5 × 10¹¹ CFU ETEC K88 for three days. The results showed the ratio of villus length to crypt depth decreased in the duodenum and ileum after ETEC K88 infection. The expression of tight junction proteins ZO-1 in the jejunum and ileum, occludin in the jejunum and colon, and claudin-1 in the colon were down-regulated. The expression of IL-8 in the duodenum and jejunum, IL-13 in the colon, and TNF-α in the jejunum and colon were up-regulated. The expression of pBD1 in the colon, pBD2 in the jejunum, and pBD3 in the duodenum increased after infection. Meanwhile, the expression of TLR4, p38 MAPK and NF-κB p65 increased in all intestinal segments. Moreover, the expression of IL-8 in superficial cervical lymph nodes (SCLN), TNF-α in mesenteric lymph nodes (MLN), and IL-13 in inguinal lymph nodes (ILN) and MLN were up-regulated. The expression of pBD1 and pBD2 in SCLN and MLN, and pBD3 in SCLN were up-regulated. Acidobacteria and Proteobacteria were the most abundant phyla in both groups by analysis of intestinal microflora using 16 s rRNA sequencing, and the relative abundances of bacteria were found to be changed by Metastats software and LEfSe analysis. Our results indicated that cytokines and pBDs had different roles in different intestinal segments or different lymph nodes against ETEC K88, and gut microbiota was influenced after infection.

Investigation of serum beta-defensin-1 levels in bovine trichophytosis cases

Background and Aim:

Antimicrobial peptides are polypeptides that are a component of innate immunity and exhibit antifungal activity. This study aimed to investigate serum beta-defensin-1 levels in cattle diagnosed with trichophytosis, which is a zoonotic skin disease that affects several animal species.

Materials and Methods:

A total of 23 young cattle, aged 2-4 months, of different breeds and sexes were selected. Of these, 16 cattle were clinically diagnosed with trichophytosis and seven were healthy.

Results:

The mean serum beta-defensin-1 levels of the infected animals were lower than those of control animals, yet the difference between the two groups was not significant (p>0.05).

Conclusion:

No significant alterations occurred in serum beta-defensin-1 levels of cattle with trichophytosis.

Investigation of serum β-defensin-1 level in calves with coccidiosis

Objective

Coccidiosis is a protozoan infection that can result in hemorrhagic diarrhea, depression, weakness, weight loss, and even mortality in young animals. β-defensin-1 is an antimicrobial peptide produced largely by epithelial cells in the skin and mucosa. It possesses antifungal, antibacterial, antiparasitic, and antiviral properties. The goal of this study was to evaluate how β-defensin-1 levels changed in coccidiosis-infected calves.

Materials and Methods

The sample included 10 coccidiosis-positive calves and 7 healthy calves, for a total of 17 calves of diverse breeds and older than 15 days. To assess the level of β-defensin-1, blood samples were obtained from the vena jugularis of the animals. The concentrations of β-defensin-1 in the serum were measured using a commercial ELISA kit.

Results

Although the serum β-defensin-1 level decreased in infected animals, the drop was not statistically significant when compared to the control group.

Conclusion

According to the study's findings, there was no significant change in the serum β-defensin-1 level in coccidiosis-infected calves. We believe that it will be advantageous to conduct additional studies with a larger sample size in order to acquire more precise results.

Evaluation of Potential Probiotic Properties of Lactobacillus and Bacillus Strains Derived from Various Sources for Their Potential Use in Swine Feeding

Beneficial effects of probiotics are relevant to the various potential properties of individual strains, and they may also relate to the original sources of the probiotic strains. This study aimed to characterize the potential probiotic properties of the strains originating from various sources for probiotics use in swine feeding. A total of 9 potential probiotic strains, seven lactobacilli and 2 bacilli, were examined for antimicrobial production against swine pathogens, adhesion and anti-adhesion of potential probiotic strains to IPEC-J2 cells, aggregation ability, host defense peptide expression, and hemolytic assay. The results highlight that all strains derived from different sources could exhibit probiotic properties, although different abilities were observed. L. rhamnosus SD11 exhibited the highest inhibitory effect against all pathogens compared to other strains. Bacillus licheniformis KMP-9, B. subtilis KMP-N004, and L. fermentum SD7 gave the highest internalization and that related to high abilities of exclusion, competition, and displacement inhibition to pathogens. Such strains also gave a higher co-aggregation to all pathogens compared to other potential probiotic strains. L. rhamnosus GG, L. fermentum SD7, L. rhamnosus SD4, and B. subtilis KMP-N004 had significantly higher pBD-2 mRNA expression than other strains. None of potential probiotic strains showed hemolytic activity. In conclusion, the strains derived from either humans or animals possessed desirable probiotic properties including inhibition against porcine pathogens, adhesion capacity to porcine enterocytes, anti-adhesion pathogens to porcine enterocytes, and modulated innate immunity. Results indicate that these probiotic strains may be good candidates for use in swine feeding to reduce the risk of infection.

The immunomodulatory function of the porcine β-defensin 129: Alleviate inflammatory response induced by LPS in IPEC-J2 cells

β-defensin family plays a critical role in host defense against infections. In this study, we found that pBD129 are widely expressed in porcine tissues such as the intestine, liver, and spleen. Interestingly, the expression level of pBD129 in most tissues was higher in Tibetan pigs than in DLY (Duroc × Landrace × Yorkshire) pigs (P < 0.05), and was significantly upregulated upon E. coli K88 infection (P < 0.05). The pBD129 protein was successfully expressed in E. coli and the molecule weight was estimated by SDS-PAGE to be 37.2 kDa. Mass spectrometry verified the protein as a pBD129. The protein showed antibacterial activities against Streptococcus and E. coli DH5α with a minimal inhibitory concentration (MIC) of 32 μg/mL. Hemolytic and cytotoxicity assays indicated that pBD129 had no detrimental effect on cell viability. Importantly, pBD129 significantly reduced the apoptosis of porcine intestinal epithelial cells exposure to bacterial endotoxins, which was associated with down-regulation of inflammatory cytokines such as the IL-1β, IL-6 and TNFα (P < 0.05), and down-regulation of apoptosis-related genes such as the caspase-3, caspase-8, and caspase-9 (P < 0.05). These results suggested that pBD129 is a novel modulator of innate immunity involved in mammalian inflammatory responses.

Antimicrobial peptides in domestic animals and their applications in veterinary medicine

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

Dietary polyphenol impact on gut health and microbiota

Polyphenols are naturally occurring compounds in plants and they are the most abundant antioxidants in the human diet. Due to their considerable structural diversity, this largely influences their bioavailability. Since a large proportion of polyphenols remains unabsorbed along the gastrointestinal tract, they may accumulate in the large intestine, where most of them are extensively metabolized by the intestinal microbiota. The formation of bioactive polyphenol-derived metabolites may also benefit the health status of the subjects, although the mechanisms have not been delineated. This review aims to highlight the impact of polyphenols on gut health and the modes of action could be through modulation of intestinal barrier function, innate and adaptive immune response, signaling pathways, as well as the ability to modify gut microbiota composition. The review will conclude by presenting future perspective and challenges of polyphenols application in food products to be used for preventing or treating diseases.

Isoleucine attenuates infection induced by E. coli challenge through the modulation of intestinal endogenous antimicrobial peptide expression and the inhibition of the increase in plasma endotoxin and IL-6 in weaned pigs

Enteric infection is a major cause of morbidity and mortality in both humans and animals worldwide. Immunotherapy against intestinal infection is a well-known alternative to the antibiotic strategy. Herein, we demonstrated that isoleucine significantly suppressed the multiplication of E. coli in the presence of IPEC-J2 cells. Isoleucine supplementation enhanced the concentrations of total plasma protein and IgA in pigs compared to the alanine control diet, while inhibiting the increase in plasma endotoxin and IL-6 contents induced by E. coli challenge. A significant interaction between the E. coli challenge and the diet treatment was found in the red blood cell volume. Isoleucine improved the expression of porcine β-defensin-1 (pBD-1), pBD-2, pBD-3, pBD-114 and pBD-129 in the jejunum and ileum of pigs with or without E. coli challenge. Conclusively, isoleucine attenuated the infection caused by the E. coli challenge possibly through increasing the intestinal β-defensin expression and inhibiting the increase in plasma endotoxin and IL-6 in weaned pigs.

Differential expression, molecular cloning, and characterization of porcine beta defensin 114

Background

β-defensins have attracted considerable research interest because of their roles in protecting hosts from various pathogens. This study was conducted to investigate the expression profiles of the porcine β-defensin 114 (PBD114) in different breeds and in response to infections. Moreover, the function of PBD114 protein was partially investigated.

Methods

Six Tibetan pigs (TP) and six DLY (Duroc×Landrace×Yorkshire) pigs were slaughtered to explore the expression profiles of PBD114 in different breeds and tissues. For infection models, sixteen DLY pigs were divided into two groups and challenged either with sterile saline or E. coli K88. The recombinant protein PBD114 (rPBD114) was obtained by using a heterologous expression system in E. coli.

Results

PBD114 gene was highly expressed in tissues such as the intestine, liver, spleen, and thymus. Interestingly, the expression level of PBD114 gene was higher in the TP pigs than in the DLY pigs (P < 0.05), and was significantly elevated upon E. coli K88 challenge (P < 0.05). The nucleotide sequences of PBD114 from Tibetan and DLY pigs was identical, and both showed a 210-bp open reading frame encoding a 69-amino acid mature peptide. To explaore the function of PBD114 protein, PBD114 gene was successfully expressed in E. coli Origami B (DE3) and the molecular weight of the rPBD114 was estimated by SDS-PAGE to be 25 kDa. The rPBD114 was purified and mass spectrometry verified the protein as PBD114. Importantly, rPBD114 showed antimicrobial activities against E. coli DH5α and E. coli K88, and the minimal inhibitory concentrations (MICs) were 64 and 128 μg/mL, respectively. Hemolytic and cytotoxicity assays showed that rPBD114 did not affect cell viability under physiological concentrations.

Conclusions

PBD114 is an infection response gene that is differentially-expressed between different porcine breeds and tissues. The antimicrobial activity of PBD114 protein, against pathogens such as the E. coli K88, suggested that it may serve as a candidate for the substitution of conventionally used antibiotics.

Electronic supplementary material

The online version of this article (10.1186/s40104-019-0367-0) contains supplementary material, which is available to authorized users.

β-Defensins: Farming the Microbiome for Homeostasis and Health

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

Pleiotropic Anti-Infective Effects of Defensin-Derived Antimicrobial Compounds

We identified low-molecular weight compounds derived from the antimicrobial peptide human neutrophil peptide-1 that bind to Lipid II, an essential precursor of bacterial cell wall biosynthesis. These compounds act as antibacterials on multiple biosynthesis pathways with specificity against gram-positive organisms. Here, we have tested a small subset of our most promising leads against the bacterium Clostridium perfringens and sporozoites of Eimeria tenella, an intracellular protozoan parasite that causes intestinal disease in poultry. We found one compound, 1611-0203 (2-{2,3,5,6-tetrafluoro-4-[2,3,5,6-tetrafluoro-4-(2-hydroxyphenoxy)phenyl]phenoxy}phenol), specifically to inhibit growth of both agents out of all compounds tested. Additionally, compound 1611-0203 inhibits Staphylococcus aureus and Enterococcus spp. Mechanism-of-action studies further reveal that 1611-0203 affects cell wall biosynthesis and inhibits additional biosynthetic pathways. Combined, our results indicate that compounds such as 1611-0203 have therapeutic potential to act as anti-infectives against various organisms simultaneously.

Caprylic acid and nonanoic acid upregulate endogenous host defense peptides to enhance intestinal epithelial immunological barrier function via histone deacetylase inhibition

The intestinal epithelial barrier plays a critical role in the etiopathogenesis of ulcerative colitis. This study aims to explore the potential effects and underlying mechanisms of medium chain fatty acids (caprylic acid and nonanoic acid) on intestinal epithelial barrier function. Using the porcine jejunal epithelial cell line IPEC-J2, a well-established model, challenged with Escherichia coli ATCC 43889 (O157:H7), we found that treatment with caprylic acid (C8) and nonanoic acid (C9) significantly reduced bacterial translocation, enhanced antibacterial activity, and remarkably increased the secretion of porcine β-defensins 1 (pBD-1) and pBD-2. Mechanistically, like TSA (a histone deacetylase inhibitor), C8 and C9 attenuated the activity of the classical histone deacetylase pathway to facilitate the acetylation of histone 3 lysine 9 (H3K9) at the promoters pBD-1 and pBD-2, and consequently augmented the gene expression of pBD-1 and pBD-2. In conclusion, with their combined antibacterial and defense peptide-induced roles, the use of C8 and C9 may provide a novel method to protect the intestinal barrier of animals and humans from bacterial infection.

Swine-Derived Probiotic Lactobacillus plantarum Inhibits Growth and Adhesion of Enterotoxigenic Escherichia coli and Mediates Host Defense

Weaning stress renders piglets susceptible to pathogen infection, which leads to post-weaning diarrhea, a severe condition characterized by heavy diarrhea and mortality in piglets. Enterotoxigenic Escherichia coli (ETEC) is one of typical strains associated with post-weaning diarrhea. Thus, prevention and inhibition of ETEC infection are of great concern. Probiotics possess anti-pathogenic activity and can counteract ETEC infection; however, their underlying mechanisms and modes of action have not yet been clarified. In the present study, the direct and indirect protective effects of Lactobacillus plantarum ZLP001 against ETEC infection were investigated by different methods. We found that bacterial culture and culture supernatant of L. plantarum ZLP001 prevented ETEC growth by the Oxford cup method, and ETEC growth inhibition was observed in a co-culture assay as well. This effect was suggested to be caused mainly by antimicrobial metabolites produced by L. plantarum ZLP001. In addition, adhesion capacity of L. plantarum ZLP001 to IPEC-J2 cells were observed using microscopy and counting. L. plantarum ZLP001 also exhibited a concentration-dependent ability to inhibit ETEC adhesion to IPEC-J2 cells, which mainly occurred via exclusion and competition mode. Furthermore, quantitative real time polymerase chain reaction (qPCR) analysis showed that L. plantarum ZLP001 upregulated the expression of host defense peptides (HDPs) but did not trigger an inflammatory response. In addition, L. plantarum ZLP001 induced HDP secretion, which enhanced the potential antimicrobial activity of IPEC-J2 cell-culture supernatant after incubation with L. plantarum ZLP001. Our findings demonstrate that L. plantarum ZLP001, an intestinal Lactobacillus species associated with piglet health, possesses anti-ETEC activity. L. plantarum ZLP001 might prevent ETEC growth, inhibit ETEC adhesion to the intestinal mucosa, and activate the innate immune response to secret antimicrobial peptides. L. plantarum ZLP001 is worth investigation as a potential probiotics.

Identification of transcripts involved in digestion, detoxification and immune response from transcriptome of Empoasca vitis (Hemiptera: Cicadellidae) nymphs

Tea production has been significantly impacted by the false-eye leafhopper, Empoasca vitis (Göthe), around Asia. To identify the key genes which are responsible for nutrition absorption, xenobiotic metabolism and immune response, the transcriptome of either alimentary tracts or bodies minus alimentary tract of E. vitis was sequenced and analyzed. Over 31 million reads were obtained from Illumina sequencing. De novo sequence assembly resulted in 52,182 unigenes with a mean size of 848nt. The assembled unigenes were then annotated using various databases. Transcripts of at least 566 digestion-, 224 detoxification-, and 288 immune-related putative genes in E. vitis were identified. In addition, relative expression of highly abundant transcripts was verified through quantitative real-time PCR. Results from this investigation provide genomic information about E. vitis, which will be helpful in further study of E. vitis biology and in the development of novel strategies to control this devastating pest.

Use of recombinant porcine β-defensin 2 as a medicated feed additive for weaned piglets

Post-weaning diarrhoea (PWD) in piglets is associated with colonization of the intestine with bacterial pathogens. In this study, we evaluated the use of recombinant porcine β-defensin 2 (rpBD2) as a medicated feed additive for weaned piglets. The crude extract from the culture supernatant of rpBD2-expressing Pichia pastoris was used as a medicated feed additive for weaned piglets. Dietary treatments included a positive control (basal diet + antibiotics, designated PC) and three different rpBD2 treatments without antibiotics (basal diet supplemented with 1, 5, or 15 g of crude rpBD2/kg basal diet, designated 1PD, 5PD, and 15PD, respectively). Of all the treatments, 5PD had the greatest impact on the weaned piglets. It increased their body weight, average daily weight gain, average daily feed intake, and intestinal villus height in the duodenum and jejunum, and reduced the incidence of PWD. The diversity of the cecal digesta and mucosa microflora was compared between the weaned piglets in the PC and 5PD groups. Piglets treated with 5PD had lower diversity indices and fewer bacterial pathogens in their cecal digesta and mucosa than the PC group. Our results demonstrate that crude rpBD2 could provide an alternative to the traditional antibiotic feed additives given to weaned piglets.

Overexpression of Porcine Beta-Defensin 2 Enhances Resistance to Actinobacillus pleuropneumoniae Infection in Pigs

To reduce the need for antibiotics in animal production, alternative approaches are needed to control infection. We hypothesized that overexpression of native defensin genes will provide food animals with enhanced resistance to bacterial infections. In this study, recombinant porcine beta-defensin 2 (PBD-2) was overexpressed in stably transfected PK-15 porcine kidney cells. PBD-2 antibacterial activities against Actinobacillus pleuropneumoniae, an important respiratory pathogen causing porcine contagious pleuropneumonia, were evaluated on agar plates. Transgenic pigs constitutively overexpressing PBD-2 were produced by a somatic cell cloning method, and their resistance to bacterial infection was evaluated by direct or cohabitation infection with A. pleuropneumoniae. Recombinant PBD-2 peptide that was overexpressed in the PK-15 cells showed antibacterial activity against A. pleuropneumoniae. PBD-2 was overexpressed in the heart, liver, spleen, lungs, kidneys, and jejunum of the transgenic pigs, which showed significantly lower bacterial loads in the lungs and reduced lung lesions after direct or cohabitation infection with A. pleuropneumoniae. The results demonstrate that transgenic overexpression of PBD-2 in pigs confers enhanced resistance against A. pleuropneumoniae infection.

Porcine β-defensin 2 attenuates inflammation and mucosal lesions in dextran sodium sulfate-induced colitis

Intestinal permeability plays a critical role in the etiopathogenesis of ulcerative colitis. Defensins, including porcine β-defensin (pBD)2, are crucial antimicrobial peptides for gut protection owing to their antibacterial and immunomodulatory activities. The purpose of this study was to investigate the protective effects of pBD2 on mucosal injury and the disruption of the epithelial barrier during the pathological process of dextran sodium sulfate (DSS)-induced colitis. The effects and mechanism of pBD2 were evaluated both using a DSS-induced C57BL/6 mouse model and, in vitro, using Caco-2 and RAW264.7 cells. DSS-induced colitis was characterized by higher disease activity index, shortened colon length, elevated activities of myeloperoxidase and eosinophil peroxidase, histologic evidence of inflammation, and increased expression levels of TNF-α, IL-6, and IL-8. pBD2 increased the expression of zonula occludens-1, zonula occludens-2, claudin-1, mucin-1, and mucin-2 mRNA and proteins, and it decreased permeability to FITC-D, as well as apoptosis, in DSS-treated mice. pBD2 also decreased inflammatory infiltrates of the colon epithelium. In Caco-2 cells, pBD2 increased transepithelial electrical resistance and mucin mRNA expression, and it decreased the permeability of FITC-D while preserving the structural integrity of the tight junctions. The effects of pBD2 appeared to be through upregulation of the expression of genes associated with tight junctions and mucins, and by suppressing DSS-induced increases in inflammation, inducible NO synthase, cyclooxygenase-2, and apoptosis. These results show that pBD2 improves DSS-induced changes in mucosal lesions and paracellular permeability, possibly by affecting the activation of NF-κB signaling. The present study demonstrates that intrarectal administration of pBD2 may be a novel preventive option for ulcerative colitis.

Fluorescent labeling for clonal selection of Marc 145 cells secreting high levels of recombinant protein PBD-1

Despite the powerful impact gene expression markers like the green fluorescent protein (GFP) or enhanced GFP (EGFP) exert on linking the expression of recombinant protein for selection of high producers in recent years, there is still a strong incentive to develop more economical and efficient methods for isolating mammalian cell clones secreting high levels of recombinant proteins. Here we present a new method based on the co-expression of EGFP that allows clonal selection in standard 96-well cell culture plates. The genes encoding the EGFP protein and the related protein are linked by an internal ribosome entry site and thus are transcribed into the same mRNA in an independent translation process. Since both proteins arise from a common mRNA, the EGFP expression level correlates with the expression level of the therapeutic protein in each clone. By expressing recombinant porcine β-defensin 1 in Marc 145 cells, we demonstrate the robustness and performance of this technique. The method can be served as an alternative to identify high-producer clones with various cell sorting methods.

A competitive chemiluminescence enzyme immunoassay method for β-defensin-2 detection in transgenic mice

A competitive chemiluminescence enzyme immunoassay (CLEIA) method for porcine β-defensin-2 (pBD-2) detection in transgenic mice was established. Several factors that affect detection, including luminol, p-iodophenol and hydrogen peroxide concentrations, as well as pH, were studied and optimized. The linear range of the proposed method for pBD-2 detection under optimal conditions was 0.05-80 ng/mL with a correlation coefficient of 0.9960. Eleven detections of a 30 ng/mL pBD-2 standard sample were performed. Reproducible results were obtained with a relative standard deviation of 3.94%. The limit of detection of the method for pBD-2 was 3.5 pg/mL (3σ). The proposed method was applied to determine pBD-2 expression levels in the tissues of pBD-2 transgenic mice, and compared with LC-MS/MS and quantitative real-time reverse-transcriptase polymerase chain reaction. This suggests that the CLEIA can be used as a valuable method to detect and quantify pBD-2.

High-level expression, purification and characterisation of porcine β-defensin 2 in Pichia pastoris and its potential as a cost-efficient growth promoter in porcine feed

Porcine β-defensin 2 (pBD2), a recently discovered porcine defensin that is produced by the intestine, exerts antimicrobial activities and innate immune effects that are linked to intestinal diseases in pigs. Here, we report a codon-optimised protein corresponding to mature pBD2 cDNA that was expressed and purified in Pichia pastoris yeast. The highest amount of secreted protein (3,694.0 mg/L) was reached 144 h into a 150-h induction during high-density cultivation. Precipitation followed by gel exclusion chromatography yielded 383.7 mg/L purified recombinant pBD2 (rpBD2) with a purity of ~93.7 %. Two recombinant proteins of 5,458.5 and 5,258.4 Da were detected in the mass spectrum due to variation in the amino-terminus. The rpBD2 exhibited high antimicrobial activity against a broad range of pig pathogenic bacteria (minimal inhibitory concentration [MIC] 32-128 μg/mL); the highest activity was observed against Salmonella choleraesuis, Staphylococcus aureus and Streptococcus suis (MIC 32-64 μg/mL). However, rpBD2 also inhibited the growth of probiotics such as Lactobacillus plantarum, Bacillus subtilis and Saccharomyces cerevisiae, but at lower efficacies than the pathogens. Purified or unpurified rpBD2 also maintained high activity over a wide range of pH values (2.0-10.0), a high thermal stability at 100 °C for 40 min and significant resistance to papain, pepsin and trypsin. In addition, the activity of rpBD2 towards S. aureus was unaffected by 10 mM dithiothreitol (DTT) and 20 % dimethyl sulphoxide (DMSO). Our results suggest that pBD2 could be produced efficiently in large quantities in P. pastoris and be a substitute for traditional antibiotics for growth promotion in the porcine industry.

Modulation of porcine β-defensins 1 and 2 upon individual and combined Fusarium toxin exposure in a swine jejunal epithelial cell line

Defensins are small antimicrobial peptides (AMPs) that play an important role in the innate immune system of mammals. Since the effect of mycotoxin contamination of food and feed on the secretion of intestinal AMPs is poorly understood, the aim of this study was to elucidate the individual and combined effects of four common Fusarium toxins, deoxynivalenol (DON), nivalenol (NIV), zearalenone (ZEA), and fumonisin B1 (FB1), on the mRNA expression, protein secretion, and corresponding antimicrobial effects of porcine β-defensins 1 and 2 (pBD-1 and pBD-2) using a porcine jejunal epithelial cell line, IPEC-J2. In general, upregulation of pBD-1 and pBD-2 mRNA expression occurred following exposure to Fusarium toxins, individually and in mixtures (P < 0.05). However, no significant increase in secreted pBD-1 and pBD-2 protein levels was observed, as measured by enzyme-linked immunosorbent assay (ELISA). Supernatants from IPEC-J2 cells exposed to toxins, singly or in combination, however, possessed significantly less antimicrobial activity against Escherichia coli than untreated supernatants. When single toxins and two-toxin combinations were assessed, toxicity effects were shown to be nonadditive (including synergism, potentiation, and antagonism), suggesting interactive toxin effects when cells are exposed to mycotoxin combinations. The results show that Fusarium toxins, individually and in mixtures, activate distinct antimicrobial defense mechanisms possessing the potential to alter the intestinal microbiota through diminished antimicrobial effects. Moreover, by evaluating toxin mixtures, this improved understanding of toxin effects will enable more effective risk assessments for common mycotoxin combinations observed in contaminated food and feed.

Genome-level identification, gene expression, and comparative analysis of porcine ß-defensin genes

BACKGROUND

Beta-defensins (β-defensins) are innate immune peptides with evolutionary conservation across a wide range of species and has been suggested to play important roles in innate immune reactions against pathogens. However, the complete β-defensin repertoire in the pig has not been fully addressed.

RESULT

A BLAST analysis was performed against the available pig genomic sequence in the NCBI database to identify β-defensin-related sequences using previously reported β-defensin sequences of pigs, humans, and cattle. The porcine β-defensin gene clusters were mapped to chromosomes 7, 14, 15 and 17. The gene expression analysis of 17 newly annotated porcine β-defensin genes across 15 tissues using semi-quantitative reverse transcription polymerase chain reaction (RT-PCR) showed differences in their tissue distribution, with the kidney and testis having the largest pBD expression repertoire. We also analyzed single nucleotide polymorphisms (SNPs) in the mature peptide region of pBD genes from 35 pigs of 7 breeds. We found 8 cSNPs in 7 pBDs.

CONCLUSION

We identified 29 porcine β-defensin (pBD) gene-like sequences, including 17 unreported pBDs in the porcine genome. Comparative analysis of β-defensin genes in the pig genome with those in human and cattle genomes showed structural conservation of β-defensin syntenic regions among these species.

Co-administration of Bacillus subtilis RJGP16 and Lactobacillus salivarius B1 strongly enhances the intestinal mucosal immunity of piglets

Probiotics, including Bacillus spp. and Lactobacillus, are potential replacements for low dose in-feed antibiotics for pig. This study aimed to evaluate the effect of the co-administration of Bacillus subtilis RJGP16 and Lactobacillus salivarius B1 as potential probiotics to stimulate local immune responses. Thirty two newborn piglets were divided into four groups and orally administrated with different combination of probiotics (none; RJGP16; B1; RJGP16 and B1) at the age of 0, 7 and 11 days. We analysed the parameters of the mucosal immunity of piglets a week after weaning. Our results showed that the gene expression of interleukin (IL)-6 in the duodenum and ileum, porcine beta-defensins (pBD)-2 in the duodenum were significantly increased (p<0.01) with co-administration of the RJGP16 and B1. Also the expression and release of TLR-2 and the number of immunoglobulin (Ig) A producing cells were increased (p<0.01). The results demonstrate that the co-administration of the two bacteria stimulate a more intense mucosal immunity than the administration of each bacterium alone.

Risks associated with high-dose Lactobacillus rhamnosus in an Escherichia coli model of piglet diarrhoea: intestinal microbiota and immune imbalances

Probiotic could be a promising alternative to antibiotics for the prevention of enteric infections; however, further information on the dose effects is required. In this study, weanling piglets were orally administered low- or high-dose Lactobacillus rhamnosus ACTT 7469 (10¹⁰ CFU/d or 10¹² CFU/d) for 1 week before F4 (K88)-positive Escherichia coli challenge. The compositions of faecal and gastrointestinal microbiota were recorded; gene expression in the intestines was assessed by real-time PCR; serum tumour necrosis factor-α (TNF-α) concentrations and intestinal Toll-like receptor 4 (TLR4) were detected by ELISA and immunohistochemistry, respectively. Unexpectedly, high-dose administration increased the incidence of diarrhoea before F4⁺ETEC challenge, despite the fact that both doses ameliorated F4⁺ETEC-induced diarrhoea with increased Lactobacillus and Bifidobacterium counts accompanied by reduced coliform shedding in faeces. Interestingly, L. rhamnosus administration reduced Lactobacillus and Bifidobacterium counts in the colonic contents, and the high-dose piglets also had lower Lactobacillius and Bacteroides counts in the ileal contents. An increase in the concentration of serum TNF-α induced by F4⁺ETEC was observed, but the increase was delayed by L. rhamnosus. In piglets exposed to F4⁺ETEC, jejunal TLR4 expression increased at the mRNA and protein levels, while jejunal interleukin (IL)-8 and ileal porcine β-defensins 2 (pBD2) mRNA expression increased; however, these increases were attenuated by administration of L. rhamnosus. Notably, expression of jejunal TLR2, ileal TLR9, Nod-like receptor NOD1 and TNF-α mRNA was upregulated in the low-dose piglets after F4⁺ETEC challenge, but not in the high-dose piglets. These findings indicate that pretreatment with a low dose of L. rhamnosus might be more effective than a high dose at ameliorating diarrhoea. There is a risk that high-dose L. rhamnosus pretreatment may negate the preventative effects, thus decreasing the prophylactic benefits against potential enteric pathogens. Our data suggest a safe threshold for preventative use of probiotics in clinical practice.

Small intestinal segment perfusion test in piglets: future applications in studying probiotics-gut crosstalk in infectious diarrhoea?

Worldwide infectious diarrhoea, mainly caused by rotavirus and enterotoxigenic Escherichia coli (ETEC), accounts for a large part of deaths in children. ETEC is also the main cause of traveller's diarrhoea. Probiotics are promising for prevention and treatment of diarrhoea, but there is insufficient evidence to support the use of any specific probiotic or probiotics in general. Because of the sensitivity of suckling and weaned piglets for ETEC, piglets are a good model for infectious diarrhoea in infants and traveller's diarrhoea. Just as in human the efficacy of probiotics in diminishing diarrhoea and improving growth in suckling and weaned piglets is not uniform. A piglet model of infectious diarrhoea provides access to intestinal compartments that are not easily accessible in infants. In an in situ piglet model of secretory diarrhoea, the functional physiological response to ETEC and the concomitant host genome response to ETEC and probiotics may be tested. This will provide new insights in the complex crosstalk between ETEC, probiotics and the gut in the future.

A new Beta defensin from sika deer: molecular cloning and sequence characterization

The beta-defensins are small, well-characterized peptides with broad antimicrobial activities. Here we report the identification of a novel β-defensin, sika deer β-defensin-1 (siBD-1), from sika deer tissues with a pair of PCR primers according to the conserved cDNA sequences of known ruminant β-defensins. Total RNA was extracted from the tongue epithelia of a sika deer and the 418 bp cDNA encoding siBD-1 was amplified by the reverse transcription PCR (RT-PCR), 5'- and 3'-RACE. The cDNA contained an open reading frame (ORF) of 192 bases which encoded a 64 amino acid prepro-peptide. The prepro-peptide contained six invariantly spaced cysteine residues, which is the β defensin consensus sequence. The putative mature peptide of the siBD-1 contained nine positively charged residues (5 arginine-R, 3 lysine-K, and 1 histidine-H). The sequence homology shows that siBD-1 has 73.0-90.6% amino-acid identity and 74.6-90.6% cDNA identity with other ruminant beta-defensins, sharing the greatest identity with buffalo enteric β-defensin in both amino acid and nucleotide sequences.

Recombinant PBD-1 (porcine beta-defensin 1) expressed in the milk by transplanting transgenic mES-like-derived cells into mouse mammary gland

ES (embryonic stem)-derived cells have been investigated in many animal models of severe injury and degenerative disease. However, few studies have examined the ability of ES-derived cells to improve functional outcome following partially damaged breast and also the modification of mammary tissue to produce costly proteins. This study investigates the feasibility of implanting mES-dK (mouse ES-derived keratinocytes-like) cells stably transfected with a mammary gland special expression vector for the PBD-1 (porcine beta-defensin 1) in developing mammary glands. Our aim was to assess the ability of cell grafting to improve functional outcome following partial damage of the breast, also on the breast modification mammary tissue in mice for the production of PBD-1 protein secreted in the milk. Our results showed that the ratios of the surviving cells labelled with the myoepithelial or luminal cell markers, EMA (epithelial membrane antigen) and CALLA, were 41.7 +/- 15.2% and 28.4 +/- 9.6%, respectively, which revealed that transplanted mES-dK cells survived, integrated in vivo and differentiated into myoepithelial or luminal cells. In addition, Western blot analysis showed that 37.5% (3 out of 8) female transplanted mice had PBD-1 expression in their milk and reached 0.4998, 0.5229 and 0.5195 microg/ml, respectively.

Quantitative analysis of the immune response upon Salmonella typhimurium infection along the porcine intestinal gut

Salmonella enterica serovar Typhimurium causes enteric disease and compromises food safety. In pigs, the molecular response of the intestine to S. typhimurium has been traditionally characterized by in vitro models that do not reflect the actual immunological competence of the intestinal mucosa. In this work, we performed an oral S. typhimurium infection study to obtain insight into the in vitro response in three different sections (jejunum, ileum and colon) of the porcine intestine. For this, samples from one-month-old infected piglets were collected during a time course comprising 1, 2, and 6 days post inoculation to evaluate the intestinal response by quantifying the mRNA expression of gene coding for 28 innate immune system molecules using quantitative real-time PCR assays. In addition, samples from non-infected control animals were also employed to establish differences in the steady state gene expression between intestinal sections. The panel of quantified molecules included an assortment of cytokines, chemokines, pattern-recognition receptors, intracellular signaling molecules, transcription factors and antimicrobial molecules. Changes in gene expression occurred in the three different parts of the intestine and during the course of the S. typhimurium infection. Moreover, the high variation observed in expression patterns of genes coding for inflammatory mediators could indicate that each intestinal section responds differently to the infection. Thus, on the contrary to findings in the jejunum and colon, a down-regulation and lack of induction of some proinflammatory cytokine transcripts was observed in the ileum. Nevertheless, all chemoattractant cytokines assayed were up-regulated in the ileum and jejunum whereas only interleukin-8 and MIP-1α mRNA were over expressed in the colon. In conclusion, our results reveal regional differences in gene expression profiles along the porcine intestinal gut as well as regional differences in the inflammatory response to S. typhimurium infection. Taken together, these data should provide a basis for a complete understanding of the porcine intestinal response to bacterial infection.

Transcriptomics of enterotoxigenic Escherichia coli infection. Individual variation in intestinal gene expression correlates with intestinal function

Acute secretory diarrhea is a major cause of morbidity and mortality in young animals and humans. Deaths result from excessive fluid and electrolyte losses. The disease is caused by non-invasive bacteria such as Vibrio cholerae and Escherichia coli which produce enterotoxins, however, much less is known about the role of individual host responses. Here we report the response of intact porcine small intestinal mucosa to infection with enterotoxigenic E. coli (ETEC). Jejunal segments in four piglets were infused with or without ETEC, and perfused for 8h, and net absorption measured. Microarray analysis at 8h post-infection showed significant differential regulation of on average fifteen transcripts in mucosa, with considerable individual variation. Differential net absorption varied between animals, and correlated negatively with the number of up regulated genes, and with one individual gene (THO complex 4). This shows that quantitative differences in gene regulation can be functionally linked to the physiological response in these four animals.

Different messenger RNA expression for the antimicrobial peptides beta-defensins between Meishan and crossbred pigs

beta-Defensins are cysteine-rich endogenously produced antimicrobial peptides that play an important role in innate immunity. In this study, the expressions of genes porcine beta-defensins-1(pBD-1), pBD-2 and pBD-3 were determined using real-time PCR for Chinese Meishan pigs and Crossbred (Duroc x Yorkshire x Landrace) pigs of 7 days old in various tissues. The results showed that expressions of pBD-1, 2 and 3 of Meishan pigs in most tissues were higher than those of crossbred pigs and main expression sites for pBD-1 and pBD-3 were tongue and oral mucosa in two varieties of pigs, whereas pBD-2 of crossbred pig was mainly expressed in kidney and liver, and pBD-2 of Meishan pigs mainly in tongue and oral mucosa. The higher expression of pBDs might be the reason of Meishan pigs has higher immunity and disease resistance. The mechanisms of this need a further research.

Effects of pig antibacterial peptides on growth performance and intestine mucosal immune of broiler chickens

Currently, substitutions for antibiotic growth promoters in animals are attracting interest. This study investigated the effects of pig antibacterial peptides (PABP) on growth performance and small intestine mucosal immune responses in broilers. Three hundred 1-d-old Arbor Acre male broiler chickens were randomly allocated to 5 groups with 60 birds per group. The groups were control group; PABP administered in drinking water at 20 and 30 mg/L of water; or PABP supplemented in feed at 150 and 200 mg/kg of diet. The birds were fed a corn-soybean based diet for 6 wk. Chickens were weighed weekly and killed after 42 d of feeding, and growth performance was measured. Samples of the duodenum and jejunum were collected. The villus height, mucosa thickness, alkaline phosphatase activity, and numbers of secreting IgA and goblet cells were evaluated. The PABP-treated groups had greater BW and average daily gain, greater height of villus and thickness of gut mucosa, greater activity of alkaline phosphatase, higher ratio of secreting IgA, and a greater number of goblet cells compared with the control group (P<0.05). In conclusion, PABP can improve the growth performance, increase the intestinal ability to absorb nutrients, and improve the mucosal immunity of the intestine.

The mucosal immune system: recent developments and future directions in the pig

In most animals, the mucosal immune system effectively controls expression of active immune responses to pathogen and tolerance to harmless antigens. Our understanding of the function and control of the mucosal immune system has advanced as a result of studies in rodents and humans. The discoveries of regulatory T-cells and T-helper-17 cells, and studies on the interactions between epithelial and dendritic cells, demonstrate its complexity. In pigs, some of the systems and reagents for determining the relevance of these mechanisms are present, and indicate lines for future work. However, many empirical studies of the effect of manipulation of the mucosal immune system in the pig by prebiotics, probiotics and feed additives have been carried out. Interpretation of these results needs to be made with care, since manipulation of the mucosal immune system may improve its efficiency under a specific set of environmental and husbandry conditions, but impair it under others.

Porcine host defense peptides: expanding repertoire and functions

Host defense peptides (HDPs) are a large group of innate immune effectors that are also termed antimicrobial peptides. Because of the rapid progress that has been made in completing several animal genomes, many HDPs have been systemically defined using bioinformatic analysis and partially characterized using reverse genomic approaches. In pigs, about 30 HDPs have been identified and partially characterized relative to structure and function. Antimicrobial activity of porcine HDPs has been extensively evaluated against a broad spectrum of microorganisms in vitro and evaluated for their protective role in vivo. Increasing evidence indicates that HDPs are functionally differentiated during posttranslational and postsecretory processing, and that the structural units for antimicrobial and immunoregulatory functions are separate. These findings suggest promising new avenues for therapeutic drug design based on HDPs, including porcine HDPs. This review summarizes and discusses advances in porcine HDPs research during the last decade with an emphasis on the rapidly expanding profiles and biological functions.

Early immune response following Salmonella enterica subspecies enterica serovar Typhimurium infection in porcine jejunal gut loops

Salmonella enterica subspecies enterica serovar Typhimurium, commonly called S. Typhimurium, can cause intestinal infections in humans and various animal species such as swine. To analyze the host response to Salmonella infection in the pig we used an in vivo gut loop model, which allows the analysis of multiple immune responses within the same animal. Four jejunal gut-loops were each inoculated with 3×10⁸ cfu of S. Typhimurium in 3 one-month-old piglets and mRNA expressions of various cytokines, chemokines, transcription factors, antimicrobial peptides, toll like and chemokine receptors were assessed by quantitative real-time PCR in the Peyer’s patch and the gut wall after 24 h. Several genes such as the newly cloned CCRL1/CCX-CKR were assessed for the first time in the pig at the mRNA level. Pro-inflammatory and T-helper type-1 (Th1) cytokine mRNA were expressed at higher levels in infected compared to non-infected control loops. Similarly, some B cell activation genes, NOD2 and toll like receptor 2 and 4 transcripts were more expressed in both tissues while TLR5 mRNA was down-regulated. Interestingly, CCL25 mRNA expression as well as the mRNA expressions of its receptors CCR9 and CCRL1 were decreased both in the Peyer’s patch and gut wall suggesting a potential Salmonella strategy to reduce lymphocyte homing to the intestine. In conclusion, these results provide insight into the porcine innate mucosal immune response to infection with entero-invasive microorganisms such as S. Typhimurium. In the future, this knowledge should help in the development of improved prophylactic and therapeutic approaches against porcine intestinal S. Typhimurium infections.

Salmonella serovar specific upregulation of porcine defensins 1 and 2 in a jejunal epithelial cell line

Defensins are important antimicrobial effector peptides of the innate immune system, which provides protection against bacterial infections in the intestine. Salmonella Choleraesuis and Salmonella Typhimurium are the most commonly isolated serovars in pig, but disease outcome is dependent on the Salmonella serovar. These infections are a serious problem for the swine industry and are also posing a major threat to public health because of Salmonella-related food-borne illnesses in human. To understand the innate immune response of pigs upon Salmonella infections, we studied the effect of these Salmonella serovars on defensin gene expression in the porcine ileal epithelial cell line IPEC-J2. With the use of scanning electron microscopy, we first visualized the surface characteristics of this cell line, and captured the invasion of Salmonella into the epithelial cell. Gene expression levels of porcine beta-defensin 1 and 2 were both induced upon S. Typhimurium infection but S. Choleraesuis had no effect. Invasion, adhesion and defensin susceptibility of both serovars were similar, which could not explain the observed difference in host response to these Salmonellae. In addition, induction of defensins was dependent on viability of S. Typhimurium, since Salmonella cell- or secreted components had no effect on defensin gene expression. These results provide further insight into the porcine innate immune response towards Salmonella infections, and could partially explain the different epidemiology of Salmonella infections in pig.

Non-typhoidal Salmonella infections in pigs: a closer look at epidemiology, pathogenesis and control

Contaminated pork is an important source of Salmonella infections in humans. The increasing multiple antimicrobial resistance associated with pork-related serotypes such as Salmonella Typhimurium and Salmonella Derby may become a serious human health hazard in the near future. Governments try to anticipate the issue of non-typhoidal Salmonella infections in pork by starting monitoring programmes and coordinating control measures worldwide. A thorough knowledge of how these serotypes interact with the porcine host should form the basis for the development and optimisation of these monitoring and control programmes. During recent years, many researchers have focussed on different aspects of the pathogenesis of non-typhoidal Salmonella infections in pigs. The present manuscript reviews the importance of pigs and pork as a source for salmonellosis in humans and discusses commonly accepted and recent insights in the pathogenesis of non-typhoidal Salmonella infections in pigs, with emphasis on Salmonella Typhimurium, and to relate this knowledge to possible control measures.

Porcine beta-defensin 2 displays broad antimicrobial activity against pathogenic intestinal bacteria

Defensins are small antimicrobial peptides that play an important role in the innate immune system of mammals. Here, we describe the antimicrobial activity of pBD-2, a recently discovered new porcine defensin that is produced in the intestine. A synthetic peptide corresponding to the mature protein showed high antimicrobial activity against a broad range of pathogenic bacteria, while it only showed limited hemolytic activity against porcine red blood cells. Highest activity was observed against Salmonella typhimurium, Listeria monocytogenes and Erysipelothrix rhusiopathiae. pBD-2 (4-8microM) killed these pathogens within 3h. The activity of pBD-2 against S. typhimurium was studied in more detail. At the minimum bactericidal concentration (MBC) of pBD-2, complete killing of S. typhimurium was relatively fast with no viable bacteria left after 90 min. However, antimicrobial activity of pBD-2 was decreased at higher ionic strengths with no residual activity at 150mM NaCl. Transmission electron microscopy of pBD-2 treated S. typhimurium indicated that relatively low doses of pBD-2 caused a retraction of the cytoplasmic membrane, while pBD-2 concentrations close to the MBC led to cytoplasm leakage and complete lysis of bacterial cells. Considering the site of production and the activity, pBD-2 may be an important defense molecule for intestinal health.

Differential regulation of porcine beta-defensins 1 and 2 upon Salmonella infection in the intestinal epithelial cell line IPI-2I

Intestinal epithelial cells represent the first line of defence against pathogenic bacteria in the lumen of the gut. Besides acting as a physical barrier, epithelial cells orchestrate the immune response through the production of several innate immune mediator molecules including beta-defensins. Here, we establish the porcine intestinal cell line IPI-2I as a new model system to test the regulation of porcine beta-defensins 1 and 2. Gene expression of both defensins was highly upregulated by foetal calf serum components in normal growth medium. In serum-free medium, baseline expression remained low, but pBD-2 gene expression was increased 10-fold upon infection with Salmonella Typhimurium. Arcobacter cryaerophilus and Salmonella Enteritidis, pathogenic bacteria with comparable adhesion and invasion characteristics, failed to increase pBD-2 mRNA levels. Heat killed or colistin-treated Salmonella Typhimurium had no effect, showing that the upregulation of pBD-2 was dependent on the viability of the Salmonella Typhimurium. Gene expression of pBD-1 was regulated differently since an increase in pBD-1 mRNA was observed by Salmonella Enteritidis infection. We conclude that the IPI-2I cells can serve as a new model to study porcine beta-defensin regulation and that pBD-1 and pBD-2 are differentially regulated in this cell line.

The early transcriptional response of pig small intestinal mucosa to invasion by Salmonella enterica serovar typhimurium DT104

Salmonella enterica serovar typhimurium (S. typhimurium) species are a leading cause of human invasive gastroenteritis. There is increasing in vitro evidence about Salmonella interaction with isolated cells or cell lines (macrophages, and enterocytes) on the molecular level, however, very little is known about in vivo interactions during actual invasion. We investigated the early interaction of S. typhimurium with intact small intestinal mucosa, in a pig model. Intestinal segments were infected with or without S. typhimurium DT104, and perfused. Whole mucosal gene expression was analyzed by cDNA array on 0, 2, 4, and 8h post-infection. Invasion resulted in the upregulation of only eight transcripts in jejunal mucosa, among those the proinflammatory IL-8 (at 4h only), and the antiinflammatory STAT3 (at 4 and 8h). The limited number of differentially expressed genes found here in vivo compared to in vitro is most likely due to the presence of multiple, heterogenous cell interactions in intact mucosa. Furthermore, it is concluded that S. typhimurium evades strong host responses by downregulating the local inflammatory response.