beta-Defensins: endogenous antibiotics of the innate host defense response

Evaluating the Antimicrobial Efficacy of TroLEAP2 like-27 peptide in golden pompano (Trachinotus ovatus) against Bacterial Pathogens

Amicrobial peptides are crucial components of immune system, acting as the first line of defense against microbial invasion. This study investigated the antimicrobial activity of TroLEAP2 like-27, a novel 27-amino acid peptide derived from golden pompano (Trachinotus ovatus), against Gram-positive Lactococcus garvieae and Staphylococcus epidermidis, and Gram-negative Vibrio alginolyticus and Vibrio harveyi. The 3D structure and helical wheel presentation of TroLEAP2 like-27 were consistent with typical AMP features. The hydrophobic ratio of TroLEAP2 like-27 was 47 %, and its α-helical structure suggested strong antimicrobial potential. The expression levels of the TroLEAP2 like gene in the liver and intestines tissues of T. ovatus were significantly upregulated following infection with L. garvieae and V. harveyi. The peptide induced bacterial agglutination in the presence of Ca2+ and exhibited bactericidal activity with a MIC50 of 60 μM. Transmission electron microscopy (TEM) revealed structural damage to bacterial membranes, while membrane permeability assays showed dose-dependent disruption and depolarization in all tested strains. Additionally, TroLEAP2 like-27 exhibited a potent capacity to interact with and degrade genomic DNA of all tested bacteria. The peptide treatment significantly reduced bacterial loads in the gill, liver, and intestinal tissues of the fish, with histological analysis revealing a remarkable protective effect on the tissues. Furthermore, fish treated with TroLEAP2 like-27 exhibited improved survival rates following bacterial infection. These findings suggest that TroLEAP2 like-27 is a promising antimicrobial peptide with potential therapeutic applications.

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

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

Structure and Activity of a Selective Antibiofilm Peptide SK-24 Derived from the NMR Structure of Human Cathelicidin LL-37

The deployment of the innate immune system in humans is essential to protect us from infection. Human cathelicidin LL-37 is a linear host defense peptide with both antimicrobial and immune modulatory properties. Despite years of studies of numerous peptides, SK-24, corresponding to the long hydrophobic domain (residues 9–32) in the anionic lipid-bound NMR structure of LL-37, has not been investigated. This study reports the structure and activity of SK-24. Interestingly, SK-24 is entirely helical (~100%) in phosphate buffer (PBS), more than LL-37 (84%), GI-20 (75%), and GF-17 (33%), while RI-10 and 17BIPHE2 are essentially randomly coiled (helix%: 7–10%). These results imply an important role for the additional N-terminal amino acids (likely E16) of SK-24 in stabilizing the helical conformation in PBS. It is proposed herein that SK-24 contains the minimal sequence for effective oligomerization of LL-37. Superior to LL-37 and RI-10, SK-24 shows an antimicrobial activity spectrum comparable to the major antimicrobial peptides GF-17 and GI-20 by targeting bacterial membranes and forming a helical conformation. Like the engineered peptide 17BIPHE2, SK-24 has a stronger antibiofilm activity than LL-37, GI-20, and GF-17. Nevertheless, SK-24 is least hemolytic at 200 µM compared with LL-37 and its other peptides investigated herein. Combined, these results enabled us to appreciate the elegance of the long amphipathic helix SK-24 nature deploys within LL-37 for human antimicrobial defense. SK-24 may be a useful template of therapeutic potential.

Nano- and Macroscale Imaging of Cholesterol Linoleate and Human Beta Defensin 2-Induced Changes in Pseudomonas aeruginosa Biofilms

The biofilm production of Pseudomonas aeruginosa (PA) is central to establishing chronic infection in the airways in cystic fibrosis. Epithelial cells secrete an array of innate immune factors, including antimicrobial proteins and lipids, such as human beta defensin 2 (HBD2) and cholesteryl lineolate (CL), respectively, to combat colonization by pathogens. We have recently shown that HBD2 inhibits biofilm production by PA, possibly linked to interference with the transport of biofilm precursors. Considering that both HBD2 and CL are increased in airway fluids during infection, we hypothesized that CL synergizes with HBD2 in biofilm inhibition. CL was formulated in phospholipid-based liposomes (CL-PL). As measured by atomic force microscopy of single bacteria, CL-PL alone and in combination with HBD2 significantly increased bacterial surface roughness. Additionally, extracellular structures emanated from untreated bacterial cells, but not from cells treated with CL-PL and HBD2 alone and in combination. Crystal violet staining of the biofilm revealed that CL-PL combined with HBD2 effected a significant decrease of biofilm mass and increased the number of larger biofilm particles consistent with altered cohesion of formed biofilms. These data suggest that CL and HBD2 affect PA biofilm formation at the single cell and community-wide level and that the community-wide effects of CL are enhanced by HBD2. This research may inform future novel treatments for recalcitrant infections in the airways of CF patients.

Expression of Defensin Antimicrobial Peptides in the Peritoneal Cavity of Patients on Peritoneal Dialysis

Objective

To investigate the expression and regulation of defensins in the peritoneal cavity of peritoneal dialysis (PD) patients.

Design

The presence of defensins in the peritoneal cavity was assessed using reverse transcription polymerase chain reaction (RT-PCR). In vivo defensin expression was analyzed in human peritoneal membrane biopsies and in peritoneal cavity leukocytes isolated from spent dialysate. Defensin expression in vitro was assessed in cultured human peritoneal mesothelial cells (HPMC) and confirmed with PCR Southern blot and DNA sequencing. The effect of tumor necrosis factor alpha (TNFa) and epidermal growth factor (EGF) on b2 defensin expression in HPMC was analyzed by Northern blot analysis and RT-PCR respectively.

Results

Both a and b classes of defensins are expressed in the peritoneal cavity of PD patients. Messenger RNA for the a-defensin human neutrophil peptide 3 and for b-defensin-1 (hbD-1) were found in preparations containing predominantly peritoneal leukocytes, whereas b-defensin-2 (hbD-2) is expressed by HPMC. HPMC isolated from different individuals displayed variability in both basal hbD-2 expression and in response to stimulation by TNFa. Conversely, EGF consistently downregulated the level of hbD-2 message in HPMC.

Conclusion

a- and b-defensins are expressed in the peritoneal cavity, and hbD-2 is the main defensin present in the peritoneal membrane. Variable levels of expression of hbD-2 by mesothelial cells were seen, with evidence of regulation by cytokines and growth factors. This provides evidence for a previously unknown mechanism of innate immunity at that site.

Inducible expression of defensins and cathelicidins by nutrients and associated regulatory mechanisms

Host defense peptides (HDPs) are crucial components of the body's first line of defense that protect organisms from infections and mediate immune responses. Defensins and cathelicidins are the two most important families of HDPs in mammals. In this review, we summarize the nutrients that are involved in inducible expression of endogenous defensins and cathelicidins. In addition, the mitogen-activated protein kinases (MAPK), nuclear factor kappa B (NF-κB) and histone deacetylase (HDAC) signaling pathways that play vital roles in the induction of defensin and cathelicidin expression are highlighted. Endogenous defensins and cathelicidins induced by nutrients may be potential alternatives to antibiotic treatments against infection and diseases. This review mainly focuses on the inducible expression and regulatory mechanisms of defensins and cathelicidins in multiple species by different nutrients and the potential applications of defensin- and cathelicidin-inducing nutrients.

Lipid-mediated resistance of Gram-negative bacteria against various pore-forming antimicrobial peptides

Lipopolysaccharides (LPSs) play a dual role as target and as effector molecules. The knowledge of the LPS-induced activation of human immune cells is increasing; however, surprisingly, much less effort seems to be directed towards the understanding of the mechanisms leading to the killing of the bacterial organisms, which eventually results in the release of LPS from the bacterial surface into the blood circulation. We demonstrate mechanisms of interaction of peptides of the innate immune system ( e.g. defensins and cathelicidins) as well as of externally administered antibiotics ( e.g. Polymyxin B) with Gram-negative bacteria. The main focus is directed on data derived from electrical measurements on a reconstitution system of the outer membrane as an asymmetric bilayer composed on one side of LPS and on the other of phospholipids. All these antimicrobial peptides (AMPs) are membrane-active and induce the permeabilization of the reconstituted membranes by the formation of lesions. We found that differences in the activity of the AMPs against various sensitive and resistant Gram-negative bacteria can be explained solely by variations in the chemical structure of LPS, e.g. in the composition of the sugar head group. A reduction of the net negative charge of LPS is responsible for a reduced interaction with the polycationic AMPs and thus for resistance. A most important side effect of positively charged AMPs is the neutralization of the negatively charged LPS released from the bacterial surface as a consequence of AMP-induced killing.

Cystic fibrosis--what are the prospects for a cure?

Significant improvements in the treatment of cystic fibrosis over the last few decades have altered this lethal disease in children to a multisystem disorder with survival into adult life now common. In most developed countries the numbers of adult cystic fibrosis patients outnumber children. This is mainly due to improvements in care during early life. The principal cause of morbidity and mortality is pulmonary disease, and so the focus of new treatments has targeted the lungs. Identification of the underlying gene defect in the cystic fibrosis transmembrane conductance regulator has ushered in a new era in cystic fibrosis research, with prospects of a cure. In this article, we review the most exciting recent advances that correct defects in cellular processing, chloride channel function and gene therapy.

Clinical application of human β-defensin and CD14 gene polymorphism in evaluating the status of chronic inflammation

Background

Periodontitis is a common disease that affects the periodontal tissue supporting the teeth. This disease is attributed to multiple risk factors, including diabetes, cigarette smoking, alcohol, pathogenic microorganisms, genetics and others. Human beta-defensin-1 (hBD-1) is a cationic antimicrobial peptide with cysteine-rich ß-sheets and broad-spectrum antimicrobial activity. CD14 is a protein involved in the detection of bacterial lipopolysaccharide (LPS) and has also been associated with periodontitis. This study investigates the single nucleotide polymorphic (SNP) region, -1654(V38I), of the human beta-defensin-1 (hBD-1) gene as well as the -159 region of the CD14 gene in subjects with chronic periodontitis.

Methods

Blood samples from periodontally healthy subjects and periodontitis patients were obtained. DNA was extracted from the blood and was used to perform restriction digest at the polymorphic G1654A site of DEFB1 with the enzyme HincII. The polymorphic site 159TT of CD14 was digested with the enzyme AvaII. Enzyme-linked immunosorbent assay (ELISA) was performed on soluble samples to determine the protein expressions.

Results

The control and patient groups expressed 35% and 38% 1654 A/A genotype of DEFB1, respectively. The A allele frequency of the control group was 40%, while the patient blood group was 54%. The mean hBD-1 protein levels of the control and patient samples were 102.83 pg/mL and 252.09 pg/mL, respectively. The genotype distribution of CD14 in healthy subjects was 16% for C/C, 26% for T/T and 58% for C/T. The genotype frequencies of CD14 in periodontitis patients were 10% for C/C, 43% for T/T and 47% for C/T. The CD14 protein expression determined by ELISA showed a mean protein level of the control samples at 76.28ng/mL and the patient blood samples at 179.27ng/mL with a p value of 0.001.

Our study demonstrated that patients suffering from chronic periodontitis present more commonly with the 1654A/A genotype on the DEFB1 gene and the 159T/T genotype on the CD14 gene.

Conclusions

This study purely investigated the association between periodontitis and one polymorphic site on both DEFB1 and CD14 gene, with the purpose of expanding knowledge for the future development in diagnostic markers or therapeutic interventions to combat this disease.

Regulation of antimicrobial peptide gene expression by nutrients and by-products of microbial metabolism

BACKGROUND

Antimicrobial peptides (AMPs) are synthesized and secreted by immune and epithelial cells that are constantly exposed to environmental microbes. AMPs are essential for barrier defense, and deficiencies lead to increased susceptibility to infection. In addition to their ability to disrupt the integrity of bacterial, viral and fungal membranes, AMPs bind lipopolysaccharides, act as chemoattractants for immune cells and bind to cellular receptors and modulate the expression of cytokines and chemokines. These additional biological activities may explain the role of AMPs in inflammatory diseases and cancer. Modulating the endogenous expression of AMPs offers potential therapeutic treatments for infection and disease.

METHODS

The present review examines the published data from both in vitro and in vivo studies reporting the effects of nutrients and by-products of microbial metabolism on the expression of antimicrobial peptide genes in order to highlight an emerging appreciation for the role of dietary compounds in modulating the innate immune response.

RESULTS

Vitamins A and D, dietary histone deacetylases and by-products of intestinal microbial metabolism (butyrate and secondary bile acids) have been found to regulate the expression of AMPs in humans. Vitamin D deficiency correlates with increased susceptibility to infection, and supplementation studies indicate an improvement in defense against infection. Animal and human clinical studies with butyrate indicate that increasing expression of AMPs in the colon protects against infection.

CONCLUSION

These findings suggest that diet and/or consumption of nutritional supplements may be used to improve and/or modulate immune function. In addition, by-products of gut microbe metabolism could be important for communicating with intestinal epithelial and immune cells, thus affecting the expression of AMPs. This interaction may help establish a mucosal barrier to prevent invasion of the intestinal epithelium by either mutualistic or pathogenic microorganisms.

The synthetic peptides bovine enteric β-defensin (EBD), bovine neutrophil β-defensin (BNBD) 9 and BNBD 3 are chemotactic for immature bovine dendritic cells

Human and murine immature DCs (iDCs) are highly efficient in antigen capture and processing, while as mature cells they present antigen and are potent initiators of cell-mediated immune responses. Consequently, iDCs are logical targets for vaccine antigens. Originally discovered for their antimicrobial activity, and thought of as strictly part of the innate immune system, studies with defensins such as human β (beta)-defensin 2 (hBD2) and murine β-defensin 2 (mBD2) have shown that they can function as chemo-attractant for iDCs and, in vaccination strategies, can enhance antigen-specific adaptive immune responses. Most studies to date have been conducted in mice. In contrast, little is known about defensins in cattle. To expand our understanding of the role of defensins in modulating immune responses in cattle, DCs were generated from bovine monocytes and the immature state of these bovine DCs was characterized phenotypically and through functional assays. By day 3 (DC3), bovine monocyte-derived DCs stained positively for DC-specific receptors CD1, CD80/86, CD205, DC-Lamp and MMR. When compared to conventional 6-day DC cultures or DCs cultured for 10 days with and without maturation factors, these DC3 were functionally at their most immature stage. Fourteen of the 16 known bovine β-defensins were synthesized and the synthetic peptides were screened for their ability to attract bovine iDCs. Bovine DC3 were consistently attracted to BNBD3, an analog of BNBD3 (aBNBD3), BNBD9 and bovine EBD in vitro and to aBNBD3 in vivo. These results are the first to describe chemotactic ability of synthetic bovine β-defensins for immature bovine monocyte-derived DCs.

Modulation of human beta-defensin-1 (hBD-1) in plasmacytoid dendritic cells (PDC), monocytes, and epithelial cells by influenza virus, Herpes simplex virus, and Sendai virus and its possible role in innate immunity

hBD comprise a family of antimicrobial peptides that plays a role in bridging the innate and adaptive immune responses to infection. The expression of hBD-2 increases upon stimulation of numerous cell types with LPS and proinflammatory cytokines. In contrast, hBD-1 remains constitutively expressed in most cells in spite of cytokine or LPS stimulation; however, its presence in human PDC suggests it plays a role in viral host defense. To examine this, we characterized the expression of hBD-1 in innate immune cells in response to viral challenge. PDC and monocytes increased production of hBD-1 peptide and mRNA as early as 2 h following infection of purified cells and PBMCs with PR8, HSV-1, and Sendai virus. However, treatment of primary NHBE cells with influenza resulted in a 50% decrease in hBD-1 mRNA levels, as measured by qRT-PCR at 3 h following infection. A similar inhibition occurred with HSV-1 challenge of human gingival epithelial cells. Studies with HSV-1 showed that replication occurred in epithelial cells but not in PDC. Together, these results suggest that hBD-1 may play a role in preventing viral replication in immune cells. To test this, we infected C57BL/6 WT mice and mBD-1((-/-)) mice with mouse-adapted HK18 (300 PFU/mouse). mBD-1((-/-)) mice lost weight earlier and died sooner than WT mice (P=0.0276), suggesting that BD-1 plays a role in early innate immune responses against influenza in vivo. However, lung virus titers were equal between the two mouse strains. Histopathology showed a greater inflammatory influx in the lungs of mBD-1((-/-)) mice at Day 3 postinfection compared with WT C57BL/6 mice. The results suggest that BD-1 protects mice from influenza pathogenesis with a mechanism other than inhibition of viral replication.

Intestinal epithelial cells and their role in innate mucosal immunity

The mucosal surfaces of the respiratory, gastrointestinal and urogenital tracts are covered by a layer of epithelial cells that are responsible for sensing and promoting a host immune response in order to establish the limits not only for commensal microorganisms but also for foreign organisms or particles. This is a remarkable task as the human body represents a composite of about 10 trillion human-self cells plus non-self cells from autochthonous or indigenous microbes that outnumber human cells 10:1. Hence, the homeostasis of epithelial cells that line mucosal surfaces relies on a fine-tuned immune system that patrols the boundaries between human and microbial cells. In the case of the intestine, the epithelial layer is composed of at least six epithelial cell lineages that act as a physiological barrier in addition to aiding digestion and the absorption of nutrients, water and electrolytes. In this review, we highlight the immense role of the intestinal epithelium in coordinating the mucosal innate immune response.

The structural parameters for antimicrobial activity, human epithelial cell cytotoxicity and killing mechanism of synthetic monomer and dimer analogues derived from hBD3 C-terminal region

Understanding the molecular mechanisms of antimicrobial peptide-membrane interactions is crucial in predicting the design of useful synthetic antimicrobial peptide analogues. Defensins are small (3-5 kDa) cysteine-rich cationic proteins which constitute the front line of host innate immunity. In this study, a series of eight 10 AA C-terminal analogues of hBD3 [sequence: RGRKXXRRKK, X = W, F, Y, V, L, I, H, C(Acm); net charge = +7, coded as W2, F2, Y2, V2, L2, I2, H2, and C2] and covalent V2-dimer [(RGRKVVRR)(2)KK] (18 AA, net charge = +11) were synthesized using solid phase peptide synthesis (SPPS) in Fmoc chemistry. Wild-type hBD3 was used as a control in all analyses. W2, V2, and especially Y2 showed high activity selectively against Gram-negative bacteria Pseudomonas aeruginosa in the concentration range of 4.3-9.7 microM. The covalent dimeric form of V2-monomer, V2-dimer, showed increased antibacterial killing compared to the monomeric form, V2-monomer. Cytotoxicity assays on a human conjunctival epithelial cell line (IOBA-NHC cells) showed that no change in viable cell number 24 h after constant exposure to all the eight peptide analogues even at concentrations up to 200 microg/ml. Fluorescence correlation spectroscopy (FCS) was used to study the interaction of these peptides against POPC vesicles (neutral; mammalian cell membrane mimic) and POPG vesicles (negatively charged; bacterial cell membrane mimic). Using FCS, significant aggregation and some leakage of Rhodamine dye were observed with POPG with Y2, W2 and V2 at the concentration of 5-10 mmicroM and no significant aggregation or disruption of vesicles was observed for all peptide analogues tested against POPC. V2-dimer induced more leakage and aggregation than the monomeric form. Overall, V2-dimer is the most effective antimicrobial peptide, with aggregation of POPG vesicles observed at concentrations as low as 1 microM. The concentration of 5-10 microM for Y2 from FCS correlated with the concentration of 5 microM (6.25 microg/ml), at which Y2 showed a cooperative increase in the activity. This suggests a structural transition of Y2 in the 2.5-5 microM concentration range resulting in the correlated increased antimicrobial activity. These results and the FCS together with previous NMR and molecular dynamics (MD) suggested that the charge density-based binding affinity, stable covalent dimerization, the ability to dimerize or even oligomerize and adopt a well-defined structure are important physicochemical properties distinguishing more effective cationic antimicrobial peptides.

The potent adjuvant effects of chicken beta-defensin-1 when genetically fused with infectious bursal disease virus VP2 gene

Defensins are fundamental components of innate immune response. Current data favor that defensins play vital roles on both innate and adaptive immune responses. The aim of the present study was to investigate whether the chicken beta-defensin-1 (also named avian beta-defensin-1, AvBD1) has the potent adjuvant effects on DNA vaccine encoding IBDV VP2 gene, when genetically fused with VP2 gene. The recombinant vectors pcDNA3.1(+)-VP2 and pcDNA3.1(+)-AvBD1-VP2 were constructed as the DNA vaccines. Four groups of 14-day-old chickens were intramuscularly injected with PBS buffer, empty vector pcDNA3.1(+), recombinant pcDNA3.1(+)-VP2 and pcDNA3.1(+)-AvBD1-VP2. Results showed that VP2-specific antibody levels significantly increased following two recombinant DNA vaccine administrations (p<0.05), compared with the group of PBS and empty vector. The antibody level of group immunized with pcDNA3.1(+)-AvBD1-VP2 was significantly higher than that of group immunized with pcDNA3.1(+)-VP2 after second vaccination (p<0.05). The percentages of CD3+, CD4+ and CD8+ T-cell subtypes between groups of pcDNA3.1(+)-VP2 and pcDNA3.1(+)-AvBD1-VP2 obtained significantly different (p<0.05), the latter was higher, at 7 days post-booster. The protection from IBD challenged by immunized chickens with DNA vaccines encoding IBDV VP2 gene alone was lower than that by immunized IBDV VP2 gene together with AvBD1 gene. The results indicated that AvBD1 has an adjuvant effects on improvement the IBDV VP2-DNA vaccine effectiveness.

Defensins in the oral cavity: distribution and biological role

The oral cavity outreaches as a particular environment in which there is a continuous interplay between bacteria, fungi and viruses, and the epithelial barrier. Among the innate mechanisms that aim to establish a regulated equilibrium between health and disease, natural antimicrobial peptides, especially those part of the defensins' family, have emerged as fundamental mediators. Their biological role is emphasized by the large number of expressed genes, as well as the multiplicity of the individual molecules present on biological tissues and fluids, in physiological and pathological conditions. Furthermore, the direct antimicrobial action, defensins may play a pivotal role in the orchestration of the innate response and contribute to the interplay between the innate and adaptive immunity. This review focuses on the specificities of defensins' structure, expression and biological role in the oral environment, enlightening their relevance in physiological and pathological conditions.

Th17 cytokines and host-pathogen interactions at the mucosa: dichotomies of help and harm

The mucosal surfaces are often the first site of interaction between pathogenic microorganisms and the host. Activation of the mucosal immune response has the important function of containing an infection and preventing dissemination of pathogens to systemic sites (barrier function). Numerous lines of evidence suggest that the barrier function is orchestrated by a subset of cytokines (interleukin (IL-)17 and IL-22), which belong to the Th17 family. IL-17 and IL-22 induce expression of antimicrobial peptides and neutrophil chemoattractants at mucosal sites, and thus play an important role in controlling mucosal infections. However, there is increasing evidence that mucosal pathogens achieve greater colonization during inflammation because they are resistant to a subset of these antimicrobial responses. In this review we compare the antimicrobial responses elicited by Th17 cytokines during mucosal infections with four different pathogens: Klebsiella pneumoniae, Citrobacter rodentium, Candida albicans and Salmonella typhimurium. We will then discuss which responses may constitute the mucosal barrier, thus providing a benefit to the host, and which ones may promote the colonization of pathogens, thereby providing a benefit to the microbes.

Factors that deregulate the protective immune response in tuberculosis

Tuberculosis (TB) is a chronic infectious disease which essentially affects the lungs and produces profound abnormalities on the immune system. Although most people infected by the tubercle bacillus (90%) do not develop the disease during their lifetime, when there are alterations in the immune system, such as co-infection with HIV, malnutrition, or diabetes, the risk of developing active disease increases considerably. Interestingly, during the course of active disease, even in the absence of immunosuppressive conditions, there is a profound and prolonged suppression of Mycobacterium tuberculosis-specific protective immune responses. Several immune factors can contribute to downregulate the protective immunity, permitting disease progression. In general, many of these factors are potent anti-inflammatory molecules that are probably overproduced with the intention to protect against tissue damage, but the consequence of this response is a decline in protective immunity facilitating bacilli growth and disease progression. Here the most significant participants in protective immunity are reviewed, in particular the factors that deregulate protective immunity in TB. Their manipulation as novel forms of immunotherapy are also briefly commented.

Asthma and atopy are associated with DEFB1 polymorphisms in Chinese children

Human beta-defensin (HBD)-1 is constitutively expressed in the airway, and hBD-1 plays crucial roles in innate immunity against respiratory pathogens. Asthma was associated with DEFB1 polymorphisms in Caucasians. This study investigates whether three single nucleotide polymorphisms (SNPs) in 5'-untranslated region of DEFB1 are associated with asthma phenotypes in Chinese children. Subjects aged 5-18 years were recruited from general pediatric clinics. Plasma IgE concentrations were measured by immunoassays. DEFB1 SNPs were characterized by restriction fragment length polymorphism. In all, 305 asthmatics and 156 controls were recruited. For asthma diagnosis, atopy and plasma total IgE, higher percentages of subjects with these outcomes had the minor alleles -20A and -52G (P = 0.041-0.0002). For log-transformed total IgE, the covariate was positive and significant for G-20A under recessive model (P = 0.001) and for G-52A under both recessive and codominant models (P = 0.008 and 0.035). The recessive model covariate was also positive and significant (P = 0.020) for C-44G on peripheral blood eosinophil count. The GCA haplotype of DEFB1 was significantly associated with asthma (odds ratio (95% confidence interval): 1.64 (1.05-2.57); P = 0.029). These results suggest that DEFB1 is a candidate gene for asthma and atopy in children.

Intein-mediated expression is an effective approach in the study of β-defensins

Mammalian beta-defensins are an important family of host defense peptides with diverse functions. Surprisingly most of the mammalian beta-defensin genes are revealed preferentially expressed in the male organs. There is a pressing need to understand how the ample defensin repertoires work in both host defense and fertility with an aim to overcome antibiotic resistance of pathogens and reproductive problems. The biggest obstacle is the production of beta-defensin peptides as beta-defensins are small, antimicrobial and multi-disulfide molecules. In this study, the well documented HBD2, function-unknown RBD1 and function-partly-known rBin1b are successfully expressed and assayed. This approach overcomes the difficulties in beta-defensin production and provides a convenient and economical peptide-production platform to elucidate the antimicrobial activities and clinical prospects of beta-defensins. In the strategy of recombinant expression, this approach may be the best to develop the "natural" peptide pools for both host defense and fertility in a cost-effective manner.

Menstrual hemocidin HbB115-146 is an acidophilic antibacterial peptide potentiating the activity of human defensins, cathelicidin and lysozyme

PROBLEM

Our recent studies proved that menstrual discharge is exceptionally rich in bactericidal hemoglobin peptides (hemocidins). Of special interest is the behavior of hemocidins in low pH of the vagina, in different ionic strengths, and in the presence of other specialized antibacterial molecules acting in this organ.

METHODS OF STUDY

We studied the activity of a model representative of menstrual hemocidin: the peptide from human beta-globin, spanning residues 115-146 (HbB115-146). The bactericidal action of this peptide in different physicochemical conditions, as well as the evaluation of the synergistic effect of the peptide with mixtures of neutrophil alpha-defensin HNP-1, epithelial beta-defensin HBD-1, cathelicidin LL-37 and lysozyme were studied using the bacterial membrane permeability test.

RESULTS

The HbB115-146 is a salt-resistant antibiotic molecule strongly potentiating its activity in acidic conditions (pH 4.4-5.0), characteristic for the vagina. Hemocidin HbB115-146 is also an effective factor stimulating the activity of other antibacterial polypeptides present in the female urogenital tract. The observed synergistic effect is preserved or enhanced at lower pH and, with the exception of HBD-1, is observed also at physiological salt concentrations.

CONCLUSION

The results of this study clearly demonstrate that hemocidins are important polypeptide factors involved in maintaining vaginal immunity during normal menstrual bleedings.

Gene-environment interactions in asthma: with apologies to William of Ockham

Many environmental factors and a large number of genetic polymorphisms have been reported to be associated with asthma risk in different locales and at different ages. It seems that what we call asthma is a heterogeneous set of conditions for which the only common feature is recurrent airway obstruction that is at least partially responsive to usual asthma therapy. Recent studies in which environmental factors and genetic variants were studied concomitantly have suggested a potential unifying concept for the disease. It seems that asthma is a genetically mediated development dysregulation of diverse immune and airway responses to a variety of specific and nonspecific exposures. It thus seems improbable that most genetic variants associated with asthma influence the disease regardless of which environmental factors trigger it and at which lifetime phase they are present. More likely, the most important gene variants for asthma are polymorphisms that exert their influence on the network system controlling biological responses to asthma-related exposures.

Associations between defensin polymorphism and somatic cell count in milk and milk utility traits in Jersey dairy cows

The aim of the study was to investigate associations between combined defensin genotypes (CDGs) and somatic cell count (SCC) in Jersey cows. The study included a herd of 184 dairy Jersey cows from Wielkopolska region in Poland. Polymerase chain reaction-restriction fragment length polymorphism analysis with TaqI restrictase established the existence of 12 CDGs with a frequency of over 1%. The most frequent were A1A2B1B2C1C2 and A1A2B1B2C1- genotypes with a frequency of 56.9783% and 12.5% respectively. The study also confirmed the existence of a statistically significant association between SCC and the year of study, season, lactation stage and cow. The highest SCC (transformed into a logarithmic scale) was found in the milk of cows with A1-B1-C1C2 genotype, whereas the lowest one in cows with A2-B1B2C1C2 genotype. Another aim of the project was to study the association between CDG and milk production traits, such as daily milk yield and fat and protein content. CDG was found to be a significant factor affecting daily milk yield and non-significant for fat and protein content. The highest daily milk yield was observed in cows with CDGs A1A2B1B2C2- and -A2-B1B2C1-, whereas the lowest one was characteristic of -A2-B1-C1C2 and A1A2B1-C1- animals. Fat content was found to be related to CDG genotype in the opposite way; the highest values were recorded in animals with -A2-B1B2C1- genotype, the lowest - in animals with -A2-B1-C1C2 genotype. Similar results were observed in protein content in milk -A2-B1B2C1-, the highest content and -A2-B1-C1C2, the lowest content. The results confirm the hypothesis of using CDG as an SCC marker. However, further studies should be conducted to confirm these results before CDG can be used as a marker in a mass selection of dairy cows.

Human β-defensin-3 induction in H pylori-infected gastric mucosal tissues

AIM: To examine human β-defensin-3 (hBD-3) expression in inflamed gastric mucosal tissues or MKN45 gastric cancer cells with or without H pylori infection for better understanding the innate immune response to H pylori.

METHODS: We used reverse transcription-polymerase chain reactions and immunohistochemistry to examine hBD-3 expression in inflamed gastric mucosal tissues or MKN45 gastric cancer cells with or without H pylori. Effects of hBD-3 against H pylori were also evaluated.

RESULTS: The mean mRNA expression of hBD-3 in H pylori-positive specimens was significantly higher than that in H pylori-negative specimens (P = 0.0002, Mann-Whitney). In addition, unlike uninfected samples, 8 of 15 (53.33%) infected mucosal samples expressed hBD-3 protein. H pylori dose-dependently induced mRNA expression of hBD-3 in MKN45 cells, an effect inhibited by adding anti-toll-like receptor (TLR)-4 antibody. HBD-3 protein completely inhibited H pylori growth.

CONCLUSION: Our results suggest that like hBD-2, hBD-3 may be involved in the pathophysiology of H pylori-induced gastritis.

α-Defensins from blood leukocytes of the monkey Papio hamadryas

Three antimicrobial peptides named PHD1-3 (Papio hamadryas defensin) have been isolated from hamadryas baboon blood leukocytes using preparative electrophoresis and reverse-phase HPLC. The primary structures of these peptides have been determined by automated Edman degradation and mass-spectrometry. The results suggest that the peptides belong to the alpha-defensin family. Structural homology analysis reveals that among alpha-defensins from other animal species, PHD3 is the most closely related to RMAD5 (rhesus macaque alpha-defensin) (90% homology) from rhesus macaque leukocytes and also highly similar to human alpha-defensin HD5 (60% homology), which is produced by intestinal Paneth cells. The homology of PHD3 with human neutrophil alpha-defensin HNP1 (human natural peptide) was 30%. The primary structures of PHD1 and PHD2 are most similar to RED1 (rhesus enteral defensin), one of six enteral alpha-defensins of rhesus monkeys. PHD1-3 have been shown to be active against the Gram-positive bacteria Listeria monocytogenes and Staphylococcus aureus, the Gram-negative bacterium Escherichia coli, and the fungus Candida albicans, similarly to the human HNP1 defensin.

Paneth cell defensins: key effector molecules of innate immunity

Antimicrobial peptides are fundamental effector molecules of innate immunity, utilized in host defence by virtually all organisms studied. These gene-encoded peptides have direct antibiotic activity against a wide range of bacteria and other microbes. In humans and other mammals, defensins are a predominant class of such peptides. In the mammalian small intestine, Paneth cells, specialized secretory epithelial cells located at the base of the crypt invaginations lining the intestinal wall, produce defensins and other antibiotic proteins. Recent investigations in murine models provide compelling support for the hypothesis that enteric defensins play a pivotal role in defence from food- and water-borne pathogens in the intestinal lumen. Investigations by others indicate that intestinal commensal bacteria are key factors in the pathogenesis of IBD (inflammatory bowel disease) in genetically susceptible humans. Recent studies provide evidence that reduced expression of Paneth cell defensins may be a key factor in the pathogenesis of ileal Crohn's disease, a subgroup of IBD. Future studies to further define the function and regulation of Paneth cell defensins will enhance our understanding of normal small bowel physiology, and probably contribute to a better understanding of the pathogenesis of inflammatory and infectious diseases of the bowel. Such knowledge may provide new therapeutic targets and strategies.

Molecular and functional characterization of bovine beta-defensin-1

We report the biochemical and functional properties of a novel bovine beta-defensin (bBD-1). Cloned from bovine mammary papillary duct epithelia, the bBD-1 cDNA predicts a 69 amino acid propeptide that is much more similar to human beta-defensin-1 (hBD-1) than to other bovine defensins. The bBD-1 gene contains two exons and one 8.5 kb intron. Using RT-PCR, we detected the bBD-1 transcript in the teat mucosa, kidney, vagina, ovary, oviduct, and colon. A synthetic bBD-1 peptide demonstrates potent antibacterial activity against Escherichia coli. The widespread expression of bBD-1 mRNA indicates that bBD-1 may play an important role in the bovine host defense against infections.

Contribution of alpha- and beta-defensins to lung function decline and infection in smokers: an association study

Background

Alpha-defensins, which are major constituents of neutrophil azurophilic granules, and beta-defensins, which are expressed in airway epithelial cells, could contribute to the pathogenesis of chronic obstructive pulmonary disease by amplifying cigarette smoke-induced and infection-induced inflammatory reactions leading to lung injury. In Japanese and Chinese populations, two different beta-defensin-1 polymorphisms have been associated with chronic obstructive pulmonary disease phenotypes. We conducted population-based association studies to test whether alpha-defensin and beta-defensin polymorphisms influenced smokers' susceptibility to lung function decline and susceptibility to lower respiratory infection in two groups of white participants in the Lung Health Study (275 = fast decline in lung function and 304 = no decline in lung function).

Methods

Subjects were genotyped for the alpha-defensin-1/alpha-defensin-3 copy number polymorphism and four beta-defensin-1 polymorphisms (G-20A, C-44G, G-52A and Val38Ile).

Results

There were no associations between individual polymorphisms or imputed haplotypes and rate of decline in lung function or susceptibility to infection.

Conclusion

These findings suggest that, in a white population, the defensin polymorphisms tested may not be of importance in determining who develops abnormally rapid lung function decline or is susceptible to developing lower respiratory infections.

Cross-species analysis of the mammalian β-defensin gene family: presence of syntenic gene clusters and preferential expression in the male reproductive tract

Mammalian β-defensins are an important family of innate host defense peptides with pleiotropic activities. As a first step to study the evolutionary relationship and biological role of the β-defensin family, we identified their complete repertoires in the human, chimpanzee, mouse, rat, and dog following systemic, genome-wide computational searches. Although most β-defensin genes are composed of two exons separated by an intron of variable length, some contain an additional one or two exons encoding an internal pro-sequence, a segment of carboxy-terminal mature sequences or untranslated regions. Alternatively, spliced isoforms have also been found with several β-defensins. Furthermore, all β-defensin genes are densely clustered in four to five syntenic chromosomal regions, with each cluster spanning <1.2 Mb across the five species. Phylogenetic analysis indicated that, although the majority of β-defensins are evolutionarily conserved across species, subgroups of gene lineages exist that are specific in certain species, implying that some β-defensins originated after divergence of these mammals from each other, while most others arose before the last common ancestor of mammals. Surprisingly, RT-PCR revealed that all but one rat β-defensin transcript are preferentially expressed in the male reproductive tract, particularly in epididymis and testis, except that Defb4, a human β-defensin-2 ortholog, is more restricted to the respiratory and upper gastrointestinal tracts. Moreover, most β-defensins expressed in the reproductive tract are developmentally regulated, with enhanced expression during sexual maturation. Existence of such a vast array of β-defensins in the male reproductive tract suggests that these genes may play a dual role in both fertility and host defense.

Suppression of NF-kappaB-mediated beta-defensin gene expression in the mammalian airway by the Bordetella type III secretion system

Expression of innate immune genes such as beta-defensins is induced in airway epithelium by bacterial components via activation of NF-kappaB. We show here that live Gram-negative bacteria can similarly stimulate this pathway, resulting in upregulation of the beta-defensin tracheal antimicrobial peptide (TAP) in primary cultures of bovine tracheal epithelial cells (TECs), by a Toll-like receptor 4 (TLR4)-mediated pathway. The Gram-negative airway pathogen Bordetella bronchiseptica possesses a type III secretion system previously suggested to inhibit the nuclear translocation of NF-kappaB in a cell line by immunohistochemistry. We therefore hypothesized that this pathogen might interfere in the innate immune response of the epithelium. Exposure of TECs to wild-type B. bronchiseptica suppressed the activation of NF-kappaB and the subsequent induction of TAP mRNA levels, whereas a type III secretion-defective strain did not. These results suggest a mechanism for bacterial evasion of the innate immune response in the airway, which could allow for the observed persistent colonization of this pathogen.

Evolution of caprine and ovine β-defensin genes

Defensins comprise an important family of anti-microbial peptides. Among vertebrates, numerous defensin genes have been detected, but their evolutionary background is still discussed. We investigated the molecular evolution and variability of beta-defensins of Caprini via sequence analyses of defensin introns. Screening of several domestic and wild species of Caprini revealed a total of 13 discrete beta-defensin coding sequences, with three of them described before this study. Phylogenetic analyses revealed that the array of newly described defensin genes is of monophyletic origin and has arisen in numerous independent duplication events after separation of the ancestral defensins. As a result of that scenario, recent defensin genes are distributed in a species-specific manner. Values of synonymous and non-synonymous substitutions demonstrated that both modes of evolutionary pressure, positive as well as negative selection, have acted. In addition, conservation of some beta-defensin exons is demonstrated. Discrimination of certain beta-defensin genes was possible only due to intron-specific differences. Therefore, sequence analyses restricted to the exons would result in underestimation of the number of beta-defensin genes. Our study shows that for reconstruction of the phylogenetic history data of defensin introns are more appropriated. Comparisons among the amino acid sequences show moderate substitutions without changing the net charge of the mature peptides.

Lipopolysaccharide and lipoteichoic acid induce different innate immune responses in bovine mammary epithelial cells

The objective of the present study was to characterize the innate immune responses induced by in vitro stimulation of bovine primary mammary epithelial cells (bMEC) using gram-negative lipopolysaccharide (LPS) and gram-positive lipoteichoic acid (LTA) bacterial cell wall components. Quantitative real-time PCR (qRT-PCR) was employed to examine the mRNA expression of a panel of 22 cytokines, chemokines, beta-defensins and components of the Toll-Like Receptor signaling pathway. Stimulation of bMEC with LPS for 24h elicited a marked increase in mRNA expression for IL-1beta, IL-8, TNFalpha, CXCL6 and beta-defensin while members of the Toll-Like Receptor pathway, although present, were largely unaffected. Surprisingly, stimulation of these cells with LTA for 24 h did not significantly alter the expression of these genes. A time course of the expression of IL-1beta, IL-8, TNFalpha, CXCL6 and beta-defensin was subsequently performed. The mRNA levels of all genes increased rapidly after stimulation for 2-4 h with both LPS and LTA but only the former treatment resulted in sustained responses. In contrast, the increased gene expression for LTA stimulated cells returned to resting levels after 8-16 h with the exception of beta-defensin, which remained up-regulated. The limited and unsustained cytokine response to LTA may explain why mastitis caused by gram-positive bacteria has greater potential for chronic intra-mammary infection than gram-negative infection. It was concluded that bovine mammary epithelial cells have a strong but differential capacity to mount innate immune responses to bacterial cell wall components.

Epithelial cells in the female reproductive tract: a central role as sentinels of immune protection

The continued presence of bacterial and viral antigens in the lumen of the vagina coupled with the periodic presence of antigens in the lumen of the upper reproductive tract provide an ongoing challenge that can compromise female reproductive health and threaten life. Separating underlying tissues from luminal antigens, polarized epithelial cells of the cervix, uterus and Fallopian tubes have evolved to protect against potential pathogens. Once thought to function exclusively by providing a crucial barrier, mucosal epithelial cells are now known to function as sentinels that recognize antigens, respond in ways that lead to bacterial and viral killing, as well as signal to underlying immune cells when pathogenic challenge exceeds their protective capacity. Unique to epithelial cells of the female reproductive tract is the regulatory control of the female sex hormones. Acting both directly and indirectly through underlying stromal cells, estradiol and progesterone regulate epithelial cell innate and adaptive immune functions to protect against potential pathogens while providing an environment that supports an allogeneic fetus. In this article, we will outline how polarized epithelial cells function as the first line of defense against potential pathogens in the female reproductive tract.

Engineering disulfide bonds of the novel human beta-defensins hBD-27 and hBD-28: differences in disulfide formation and biological activity among human beta-defensins

Human beta-defensins comprise a large number of peptides that play a functional role in the innate and adaptive immune system. Recently, clusters of new beta-defensin genes with predominant expression in testicular tissue have been discovered on different chromosomes by bioinformatics. beta-Defensins share a common pattern of three disulfides that are essential for their biological effects. Here we report for the first time the chemical synthesis of the new fully disulfide-bonded beta-defensins hBD-27 and hBD-28, and compare the results with synthetic procedures to obtain the known hBD-2 and hBD-3. While hBD-27 was readily converted into a product with the desired disulfide pattern by oxidative folding, hBD-28 required a selective protective group strategy to introduce the three disulfide bonds. The established synthetic processes were applied to the synthesis of hBD-2, which, like hBD-27, was accessible by oxidative folding, whereas hBD-3 required a selective strategy comparable to hBD-28. Experimental work demonstrated that trityl, acetamidomethyl, and t-butyl are superior to other protection strategies. However, the suitable pairwise arrangement of the protective groups can be different, as shown here for hBD-3 and hBD-28. Determination of the minimum inhibitory concentration against different bacteria revealed that hBD-27, in contrast to other beta-defensins tested, has virtually no antimicrobial activity. Compared to the other peptides tested, hBD-27 showed almost no cytotoxic activity, measured by hemoglobin release of erythrocytes. This might be due to the low positive net charge, which is significantly higher for hBD-2, hBD-3, and hBD-28.

Expression of an antimicrobial peptide identified in the male reproductive system of rats

Bin1b is a beta-defensins-like molecule originally isolated from the rat epididymis. Owing to its bactericidal activity, Bin1b may have therapeutic properties suitable for the treatment of sexually transmitted diseases. The amino terminus of the mature Bin1b peptide contains a conserved myristoylated Gly residue. We studied the requirement of the terminal myristoylated Gly residue in the bactericidal activity of Bin1b and found that the terminal myristoylated Gly residue is not essential for the bactericidal activity. In addition, we expressed the tandem repeats of Bin1b in Escherichia coli and found that two tandem repeats of Bin1b protein were successfully expressed. The bacterially expressed tandem Bin1b repeats may be used in a diverse array of biochemical and cell biological studies.

Design and expression of peptide antibiotic hPAB-beta as tandem multimers in Escherichia coli

Peptide antibiotics are small peptides encoded by organism genomic DNA. They are recognized to play important roles in the innate host defense of most living organisms. The growing resistance of bacteria to conventional antibiotics and the need for discovery of new antibiotics have stimulated great interest in the development of peptide antibiotics as human therapeutics. However, preparation of peptide antibiotics at a large scale is a great challenge in developing these commercial products. In this study, tandem repeat multimers of peptide antibiotic hPAB-beta were designed and the recombinant plasmids containing one to eight copies of hPAB-beta gene were generated. Eight genetic engineered bacteria harboring pQE-hPAB-beta1-8 recombinant were able to express the repetitive hPAB-beta multimers of interest in inclusion bodies, respectively. The expressed proteins could reach 2.6-28% of the total proteins. The hPAB-beta trimer construct was selected out for the subsequent study based on its higher expression level (27.8%), which yields in wet cell weights (3.15+/-0.45 g/l) and the fusion protein inclusion bodies was able to completely dissolve in 8 M urea. The tandem trimers could easily be captured by Ni-NTA affinity chromatography and cleaved into monomers by hydroxylamine. Then, the monomer hPAB-beta of interest was purified to 95% homogeneity by reverse phase chromatography and gel filtration. The final yield of purified recombinant monomer hPAB-beta was 680+/-12 mg/100 g wet cells. The minimum inhibitory concentrations (MICs) of the purified recombinant hPAB-beta against type or clinical strains of microorganisms were about 31-250 microg/ml and these results showed that the recombinant hPAB-beta could retain its bioactivity.

Effect of preservative-free artificial tears on the antimicrobial activity of human beta-defensin-2 and cathelicidin LL-37 in vitro

PURPOSE

Human beta-defensin-2 (hBD-2) and cathelicidin LL-37 are salt-sensitive cationic antimicrobial peptides expressed by ocular surface epithelia. The goal of this study was to investigate the effect of preservative-free artificial tears on hBD-2 and LL-37 antimicrobial activity against Pseudomonas aeruginosa.

METHODS

P. aeruginosa was incubated with hBD-2 or LL-37 in the absence or presence (70% vol/vol) of different preservative-free artificial tears--Visine Tears (300 mOsm/kg), Tears Naturale Free (261 mOsm/kg), TheraTears (185 mOsm/kg), and Refresh Plus (325 mOsm/kg)--for 2 hours at 37 degrees C. In some experiments, P. aeruginosa was incubated with hBD-2 or LL-37 and Visine Tears or Tears Naturale Free with or without carboxymethylcellulose (0.5% vol/vol final concentration). Plates were inoculated with samples of each reaction mixture and then incubated for 24 hours at 37 degrees C.

RESULTS

Visine Tears and Tears Naturale Free had little or no effect on the antimicrobial activity of 100 microg/mL hBD-2 or LL-37. In the presence of Refresh Plus and TheraTears, the activity of 100 microg/mL hBD-2 or LL-37 was reduced by 90% to 100%. Carboxymethylcellulose, at a concentration comparable to that present in Refresh Plus, reduced the effectiveness of hBD-2 or LL-37 by 40% to 90% in the presence of Tears Naturale Free and Visine Tears.

CONCLUSION

Human beta-defensin-2 and cathelicidin LL-37 inhibit the growth of P. aeruginosa in vitro, but this activity is markedly reduced in the presence of Refresh Plus and TheraTears. These results suggest that carboxymethylcellulose-containing artificial tears may reduce the activity of the endogenously produced antimicrobial peptides.

Association of defensin beta-1 gene polymorphisms with asthma

BACKGROUND

Defensins are antimicrobial peptides that may take part in airway inflammation and hyperresponsiveness.

OBJECTIVE

We characterized the genetic diversity in the defensin beta-1 (DEFB1) locus and tested for an association between common genetic variants and asthma diagnosis.

METHODS

To identify single nucleotide polymorphisms (SNPs), we resequenced this gene in 23 self-defined European Americans and 24 African Americans. To test whether DEFB1 genetic variants are associated with asthma, we genotyped 4 haplotype-tag SNPs in 517 asthmatic and 519 control samples from the Nurses' Health Study (NHS) and performed a case-control association analysis. To replicate these findings, we evaluated the DEFB1 polymorphisms in a second cohort from the Childhood Asthma Management Program.

RESULTS

Within the NHS, single SNP testing suggested an association between asthma diagnosis and a 5' genomic SNP (g.-1816 T>C; P = .025) and intronic SNP (IVS+692 G>A; P = .054). A significant association between haplotype (Adenine, Cytosine, Thymine, Adenine [ACTA]) and asthma ( P = .024) was also identified. Associations between asthma diagnosis and both DEFB1 polymorphisms were observed in Childhood Asthma Management Program, a second cohort: g.-1816 T>C and IVS+692 G>A demonstrated significant transmission distortion ( P = .05 and .007, respectively). Transmission distortion was not observed in male subjects. The rare alleles (-1816C and +692A) were undertransmitted to offspring with asthma, suggesting a protective effect, contrary to the findings in the NHS cohort. Similar effects were evident at the haplotype level: ACTA was undertransmitted ( P = .04) and was more prominent in female subjects ( P = .007).

CONCLUSION

Variation in DEFB1 contributes to asthma diagnosis, with apparent gender-specific effects.

Sex hormone regulation of anti-bacterial activity in rat uterine secretions and apical release of anti-bacterial factor(s) by uterine epithelial cells in culture

In mature female rats, sex hormones regulate the reproductive (estrous) cycle to optimize mating and fertility. During the part of the estrous cycle when mating occurs, and when estrogen is the dominant sex hormone, the uterus is susceptible to infection with bacteria that can be deleterious for survival and fertility. The present study investigated whether sex hormones regulate innate immunity in the female reproductive tract by affecting the secretion of an anti-bacterial factor(s) in the rat uterus. Uterine fluids from intact rats at the proestrous stage of the estrous cycle significantly inhibited Staphylococcus aureus growth. When ovariectomized rats were treated with estradiol, anti-bacterial activity against both S. aureus and Escherichia coli increased in uterine secretions with hormone treatment. In contrast, rats injected with either progesterone and estradiol or progesterone alone displayed no bactericidal activity indicating that progesterone reversed the stimulatory effect of estradiol on anti-bacterial activity. In other studies, isolated uterine epithelial cells from intact animals were grown to confluence and high transepithelial resistance on cell inserts. Analysis of apical secretions indicated that a soluble factor(s) is released by polarized epithelial cells which inhibits bacterial growth. These results demonstrate that sex hormones influence the presence of a broad-spectrum bactericidal factor(s) in luminal secretions of the rat uterus. Further these studies suggest that epithelial cells which line the uterine lumen are a primary source of anti-bacterial activity.

Variability and evolution of bovine β-defensin genes

Defensins comprise an important family of antimicrobial peptides. Among vertebrates numerous defensin genes have been detected, but their evolutionary background is still discussed. We investigated the molecular evolution of bovine defensins via screening of different bovine species including the extinct ancestor of domestic cattle (Bos primigenius) for beta-defensin encoding genes. We detected a large variability of new defensin encoding sequences similar to previously published bovine neutrophil beta-defensin (bnbd), neutrophil beta-defensin 12 (nbd12), enteric beta-defensin (ebd), lingual antimicrobial peptide (lap), and tracheal antimicrobial peptide (tap). Our data suggest that variants of the same so-called subfamily (tap, lap, ebd, and nbd12) each share a common ancestry independent of their species origin, implicating several duplication events of tap, lap, ebd, and nbd12 before the different bovine lineages diverged. Variants of bovine neutrophil beta-defensins bnbd5 and bnbd9 were detected exclusively in domestic cattle and aurochs. Values of synonymous and nonsynonymous substitutions demonstrated lap, bnbd5, bnbd9 and nbd12 evolving under positive selection, whereas amino-acid altering substitutions among variants of ebd and tap are purified. Comparison of the amino-acid sequences with available structures of human and murine defensins suggested conservation of the typical secondary elements of defensins in the absence of high sequence similarity.

RC-101, a retrocyclin-1 analogue with enhanced activity against primary HIV type 1 isolates

Rhesus macaques express three theta-defensins (RTDs 1-3), cyclic octadecapeptides with antiviral and lectin-like properties. Corresponding theta-defensin genes exist and are expressed in humans, but a signal sequence mutation prevents the formation of mature theta-defensin peptides. Retrocyclin-1 is a theta-defensin peptide whose precursor is encoded by human theta-defensin pseudogenes. It can protect human peripheral blood lymphocytes from infection by R5 and X4 strains of HIV-1, and provides a molecular template for designing novel antiviral agents. In this study, we used JC53-BL reporter cells to assess the activity of retrocyclin-1 (RC-100) and several analogues against primary HIV-1 isolates, including R5 and R5X4 strains of subtypes A-D, CRF-01_AE, and recombinants. Each analogue differed from retrocyclin-1 by a single amino acid substitution: Gly --> Tyr in RC-106, RC-115, and RC-116, and Arg --> Lys in RC-101. Although the modification in RC-101 was chemically conservative, this peptide was significantly more potent than retrocyclin-1 across the panel of primary isolates. We performed surface plasmon resonance binding studies, using recombinant gp120 and CD4 produced in insect cells. Although RC-100 and RC-101 bound gp120 LAV/IIIB with a K(d) of 30-35 nM, they bound gp120 from CRF-01_AE strains (CM 235 and 93TH975.15) with K(d) values of 200-750 nM. Overall, our findings suggest that clade-related differences in gp120 glycosylation impact the ability of retrocyclin-1 to bind this viral glycoprotein, and modulate the peptides' ability to prevent HIV-1 infection. The performance of RC-101 suggests that additional "engineering" could further enhance the antiviral properties of theta-defensins.

Degranulation of paneth cells via toll-like receptor 9

The release of antimicrobial peptides and growth factors by Paneth cells is thought to play an important role in protecting the small intestine, but the mechanisms involved have remained obscure. Immunohistochemistry and immunofluorescence showed that Paneth cells express Toll-like receptor 9 (TLR9) in the granules. Injection of mice with oligonucleotides containing CpG sequence (CpG-ODNs) led to a down-modulation of TLR9 and a striking decrease in the number of large secretory granules, consistent with degranulation. Moreover CpG-ODN treatment increased resistance to oral challenge with virulent Salmonella typhimurium. Moreover, our findings demonstrate a sentinel role for Paneth cells through TLR9.

Calcium triggers beta-defensin (hBD-2 and hBD-3) and chemokine macrophage inflammatory protein-3 alpha (MIP-3alpha/CCL20) expression in monolayers of activated human keratinocytes

The inducible epidermal beta-defensins and the chemokine macrophage inflammatory protein-3alpha (MIP-3alpha/CCL20) are important mediators involved in innate and adaptive immunity and in the recruitment of immune cells. The aim of our study was to determine whether calcium could trigger the induction of beta-defensins (hBD-2 and hBD-3) mRNA and the release of MIP-3alpha by normal human keratinocyte monolayers. Epidermal cells derived from foreskin were cultured in defined medium supplemented with different calcium levels (0.09, 0.8 and 1.7 mM) and were stimulated or not with the pro-inflammatory cytokines tumor necrosis factor-alpha (TNF-alpha 1-500 ng/ml) or interferon-gamma (INF-gamma 1-100 ng/ml). A high calcium concentration (1.7 mM) alone applied in culture medium for 4 days was sufficient to induce hBD-2 and hBD-3 mRNA expression. Whatever interindividual variability in the expression of hBD-2 and hBD-3 mRNA and MIP-3alpha secretion, the addition of TNF-alpha for a short duration (26h), initiated a dose-dependent and coordinated up-regulation of hBD-2 and hBD-3 mRNA and MIP-3alpha release in keratinocyte cultures. Unlike hBD-2 and hBD-3 mRNA was preferentially stimulated by IFN-gamma rather than TNF-alpha. In our experimental conditions, L-isoleucine, described to stimulate beta-defensin in bovine epithelial cells, did not exert any effect either on hBD-2 and hBD-3 transcripts or MIP-3alpha protein. Taken together, these results confirm the major role of the maturation/differentiation process of normal human keratinocytes in the induction of inducible beta-defensins and MIP-3alpha chemokine, which contribute in vivo to the immunosurveillance of the skin barrier function.

Distribution of TFF peptides in corneal disease and pterygium

The central cornea of 10 cadavers and 33 patients suffering from keratoconus, herpetic keratitis, Fuchs' dystrophy and pterygium were analysed focusing on the expression of TFF peptides by means of reverse transcription polymerase chain reaction and immunohistochemistry. TFF1 and TFF3 transcripts were detected in healthy corneae as well as in pterygia. Only TFF3 mRNA was transcribed in keratoconus, Fuchs' dystrophy and herpetic keratitis. Immunohistochemistry revealed absence of all three TFF peptides in healthy corneae but production of TFF3 in each of the diseased corneae. In pterygia both TFF1 and TFF3 synthesis was detectable in goblet cells. The absence of TFF peptide production in the healthy cornea indicates that TFF3 secretion is induced in different corneal diseases by yet unknown stimuli. Here TFF3 synthesis can be interpreted as a protection mechanism, because all corneal diseases analysed are characterized by progressive tissue destruction. TFF1 and TFF3 production by goblet cells in pterygia is comparable to the healthy conjunctiva suggesting that TFF peptides do not play a significant role in the pathogenesis of pterygia.

Defensins and acne

Acne a disease of the pilosebaceous unit is characterised by hypercornification and hyperkeratosis of outer root sheath (ORS) and sebaceous duct and perilesional infiltrate. Lesions may be characterised as "non"-inflammatory versus inflammatory. Hypercornification of the distal ORS and the pilosebaceous duct in concert with increased sebum production and abnormalities of the microbial flora are considered to be major factors in the pathogenesis of acne vulgaris. However, the basic mechanisms involved in the development of inflammation during acne vulgaris remain unclear. We have investigated the expression patterns of two antimicrobial peptides, human beta-defensin 1 (hBD1) and human beta-defensin 2 (hBD2) in healthy human hair follicles as well as in peri- and intralesional skin of acne vulgaris lesions such as comedones, papules and pustules. Strong hBD1 and hBD2 immunoreactivity was found in all suprabasal layers of the epidermis, and all permanent compartments of the hair follicle including the distal ORS of the hair follicle and the pilosebaceous duct. Moreover, marked hBD1 and hBD2 expression was also detected in the hair follicle stem cell compartment. In contrast, the proximal follicle bulb which undergoes apoptotic regression and is also able to regenerate following injury did not express hBD1 or hBD2. The majority of acne biopsies displayed a marked upregulation of hBD2 IR in the lesional and perilesional epithelium; in particular in pustules, and a less marked upregulation of hBD1 IR. The upregulation of beta-defensins expression in acne vulgaris lesions when compared to controls suggests that beta-defensins may be involved in the pathogenesis of acne vulgaris.

Detection of HBD1 peptide in peripheral blood mononuclear cell subpopulations by intracellular flow cytometry

Production of human beta-defensin1 (HBD1) in response to LPS in monocytes, myeloid dendritic cells and plasmacytoid dendritic cells (PDC) was examined. Since PDC make up only 0.1-0.5% of the peripheral blood mononuclear cell population, we developed a method to determine HBD1 peptide levels using four-color flow cytometry, which can examine several cell surface or intracellular markers at once. Coupled with intracellular flow cytometry, we determined that PDC and monocytes only made significant amounts of HBD1 when exposed to >50ng/ml LPS for 2h. This response was limited to monocytes when ultrapure LPS was used, and was inhibited in PDC by chloroquine treatment.