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

Multispecific myeloid defensins

PURPOSE OF REVIEW

This review describes recent progress in our understanding of defensins and their contributions to innate immunity. Defensins are small, cysteine-rich endogenous antibiotic peptides. Human neutrophils contain large amounts of three alpha-defensins (HNP-1-HNP-3), and smaller amounts of a fourth, HNP-4. Monocytes and macrophages generally lack defensins, but they release messengers that induce the synthesis of beta-defensins in epithelial cells.

RECENT FINDINGS

In addition to their antimicrobial and immunomodulatory effects, HNP-1-HNP-3 possess antiviral and toxin-neutralizing properties. Induction of beta-defensins in epithelial cells is mediated by cell-surface Toll-like receptors or cytoplasmic peptidoglycan receptors that can recognize pathogen-associated molecules. Mutations in Nod2, a cytoplasmic peptidoglycan receptor, are associated with reduced levels of intestinal alpha-defensins and ileal Crohn's disease. Human defensin genes show marked copy-number polymorphism. High level constitutive expression of defensins may afford protection against HIV-1 and other defensin-sensitive pathogens. Theta-defensins (cyclic octadecapeptides found in nonhuman primates) have impressive antiviral and antitoxic properties.

SUMMARY

The multiple properties of defensins contribute to human innate immunity against bacteria, bacterial toxins, and viruses.

Multifunctional antimicrobial peptides: therapeutic targets in several human diseases

Antimicrobial peptides have emerged as promising agents against antibiotic-resistant pathogens. They represent essential components of the innate immunity and permit humans to resist infection by microbes. These gene-encoded peptides are found mainly in phagocytes and epithelial cells, showing a direct activity against a wide range of microorganisms. Their role has now broadened from that of simply endogenous antibiotics to multifunctional mediators, and their antimicrobial activity is probably not the only primary function. Although antimicrobial peptide deficiency, dysregulation, or overproduction is not known to be a direct cause of any single human disease, numerous studies have now provided compelling evidence for their involvement in the complex network of immune responses and inflammatory diseases, thereby influencing diverse processes including cytokine release, chemotaxis, angiogenesis, wound repair, and adaptive immune induction. The purpose of this review is to highlight recent literature, showing that antimicrobial peptides are associated with several human conditions including infectious and inflammatory diseases, and to discuss current clinical development of peptide-based therapeutics for future use.

Analysis of differential gene expression between chronic hepatitis B patients and asymptomatic hepatitis B carriers

BACKGROUND AND AIMS

Chronic hepatitis B virus (HBV) infection remains a serious global health problem, inducing a spectrum of diseases, including asymptomatic HBV carriage (ASC) and chronic hepatitis B (CHB). ASC and CHB represent different immunological states and their prognoses are diverse. To clarify molecular mechanisms underlying the two infection states, the differentially expressed genes between the two states were screened and identified.

METHODS

Subtracted complementary DNA libraries by suppression subtractive hybridization, dot blot hybridization and quantitative real-time PCR were used to identify the differentially expressed genes between subjects with CHB and those with ASC.

RESULTS

RNA from peripheral blood mononuclear cells from CHB and ASC subjects was subjected to suppression subtractive hybridization and resulted in isolation of subtracted complementary DNA clones. Eighty-eight randomly sampled clones were rescreened by dot blot hybridization, from which 29 clones were identified as differentially expressed genes. The differential expression of three genes was confirmed by real-time PCR in 23 subjects with CHB and 21 with ASC.

CONCLUSIONS

Differentially expressed genes in peripheral blood mononuclear cells between CHB and ASC have been isolated by suppression subtractive hybridization, including some new genes. Of the up-regulated genes in CHB, most are known to be responsive to inflammatory conditions. These genes might provide clues in elucidating the mechanisms of the two different HBV infection states and designing therapeutic targets for HBV infection.

Differential type I interferon activation and susceptibility of dendritic cell populations to porcine arterivirus

Dendritic cells (DCs) play a role in anti-viral immunity by providing early innate protection against viral replication and by presenting antigen to T cells for initiation of the adaptive immune response. Studies show the adaptive response to porcine reproductive and respiratory syndrome virus (PRRSV) is ineffective for complete viral elimination. Other studies describe the kinetics of the adaptive response to PRRSV, but have not investigated the early response by DCs. We hypothesize that there is an aberrant activation of DCs early in PRRSV infection; consequently, the adaptive response is triggered inadequately. The current study characterized a subtype of porcine lung DCs (L-DCs) and investigated the ability of PRRSV to infect and replicate in L-DCs and monocyte-derived DCs (MDDCs). Furthermore, the type I interferon anti-viral response to PRRSV with and without the addition of recombinant porcine IFN-alpha (rpIFN-alpha), an important cytokine that signals for anti-viral mediator activation, was analysed. Results show that PRRSV replicated in MDDCs but not L-DCs, providing evidence that these cells have followed distinct differentiation pathways. Although both cell types responded to PRRSV with an induction of IFN-beta mRNA, the magnitude and duration of the response differed between cell types. The addition of rpIFN-alpha was protective in MDDCs, and mRNA synthesis of Mx (myxovirus resistant) and PKR (double-stranded RNA dependent protein kinase) was observed in both cell types after rpIFN-alpha addition. Overall, PRRSV replicated in MDDCs but not L-DCs, and rpIFN-alpha was required for the transcription of protective anti-viral mediators. DC response to PRRSV was limited to IFN-beta transcription, which may be inadequate in triggering the adaptive immune response.

Effects of chicken intestinal antimicrobial peptides on humoral immunity of chickens and antibody titres after vaccination with infectious bursal disease virus vaccine in chicken

Sixty chickens were randomly divided into two groups (30 chickens in each group) to determine the effect of oral administration of chicken intestinal antimicrobial peptides (CIAMP) on the humoral immune response. Chickens of both groups were fed the same diet. In the treatment group chickens received drinking water supplemented with CIAMP (1 microg/ml) right after hatching. Samples of blood, bursa of Fabricus, spleen and intestine were taken at day 1, 4, 7, 10 and 17 of experiment. CIAMP supplementation enhanced the content of IgG and IgM in serum from day 4-10 and day 10-17, respectively, (p < 0.05), IgM-forming cells in bursa of Fabricus and spleen at the age of 7 days (p < 0.05) and IgG-forming cells in bursa of Fabricus at the age of 4 days (p < 0.05). In addition, CIAMP enhanced the IgA-forming cells in caecal tonsils diffuse area at day 4 (p < 0.05). Furthermore, CIAMP enhanced the antibody response to infectious bursal disease virus vaccine (IBDV) in chickens 21 days following IBDV vaccine administration (p < 0.05). These results suggested that CIAMP could modulate the humoral immune response of chickens and increased the antibody titres of infectious bursal disease virus vaccine.

Antimicrobial peptides human beta-defensins stimulate epidermal keratinocyte migration, proliferation and production of proinflammatory cytokines and chemokines

Besides their microbicidal functions, human beta-defensins (hBD) and LL-37 activate different immune and inflammatory cells, and their expression is enhanced in inflamed skin and cutaneous wound sites. To protect against pathogens, the skin produces antimicrobial peptides including hBDs and LL-37. Therefore, the aim of our study was to investigate whether hBDs participate in cutaneous inflammation and wound healing by inducing keratinocyte migration, proliferation, and production of proinflammatory cytokines/chemokines. We found that hBD-2, -3, and -4 but not hBD-1 stimulated human keratinocytes to increase their gene expression and protein production of IL-6, IL-10, IP-10, monocyte chemoattractant protein-1, macrophage inflammatory protein-3alpha, and RANTES. This stimulatory effect was markedly suppressed by pertussis toxin and U-73122, inhibitors for G protein and phospholipase C, respectively. We also demonstrated that hBDs elicited intracellular Ca2+ mobilization, and increased keratinocyte migration, and proliferation. In addition, these peptides induced phosphorylation of EGFR, signal transducer and activator of transcription (STAT)1, and STAT3, which are intracellular signaling molecules involved in keratinocyte migration and proliferation. In our study, inhibition of these molecules significantly reduced hBD-mediated keratinocyte migration and proliferation. In conclusion, this study provides evidence that human antimicrobial peptides may be involved in skin immunity through stimulating cytokine/chemokine production, and participate in wound healing by promoting keratinocyte migration and proliferation.

Interaction of antimicrobial peptide temporin L with lipopolysaccharide in vitro and in experimental rat models of septic shock caused by gram-negative bacteria

Sepsis remains a major cause of morbidity and mortality in hospitalized patients, despite intense efforts to improve survival. The primary lead for septic shock results from activation of host effector cells by endotoxin, the lipopolysaccharide (LPS) associated with cell membranes of gram-negative bacteria. For these reasons, the quest for compounds with antiendotoxin properties is actively pursued. We investigated the efficacy of the amphibian skin antimicrobial peptide temporin L in binding Escherichia coli LPS in vitro and counteracting its effects in vivo. Temporin L strongly bound to purified E. coli LPS and lipid A in vitro, as proven by fluorescent displacement assay, and readily penetrated into E. coli LPS monolayers. Furthermore, the killing activity of temporin L against E. coli was progressively inhibited by increasing concentrations of LPS added to the medium, further confirming the peptide's affinity for endotoxin. Antimicrobial assays showed that temporin L interacted synergistically with the clinically used beta-lactam antibiotics piperacillin and imipenem. Therefore, we characterized the activity of temporin L when combined with imipenem and piperacillin in the prevention of lethality in two rat models of septic shock, measuring bacterial growth in blood and intra-abdominal fluid, endotoxin and tumor necrosis factor alpha (TNF-alpha) concentrations in plasma, and lethality. With respect to controls and single-drug treatments, the simultaneous administration of temporin L and beta-lactams produced the highest antimicrobial activities and the strongest reduction in plasma endotoxin and TNF-alpha levels, resulting in the highest survival rates.

Effect of oestradiol on PAMP-mediated CCL20/MIP-3 alpha production by mouse uterine epithelial cells in culture

The present study was undertaken to establish whether mouse uterine epithelial cells produce CCL20/macrophage inflammatory protein 3 alpha (CCL20/MIP-3 alpha) and to determine whether secretion is under hormonal control and influenced by pathogen-associated molecular patterns (PAMPs). In the absence of PAMPs, polarized uterine epithelial cells grown to confluence on cell culture inserts constitutively secreted CCL20/MIP-3 alpha with preferential accumulation into the apical compartment. When epithelial cells were treated with the Toll-like receptor (TLR) agonists Pam3Cys (TLR2/1), peptidoglycan (TLR2/6) or lipopolysaccharide (LPS; TLR4), CCL20/MIP-3 alpha increased rapidly (4 hr) in both apical and basolateral secretions. Time-course studies indicated that responses to PAMPs added to the apical surface persisted for 12-72 hr. Stimulation with loxoribin (TLR7) and DNA CpG motif (TLR9) increased basolateral but not apical secretion of CCL20/MIP-3 alpha. In contrast, the viral agonist Poly(I:C) (TLR3) had no effect on either apical or basolateral secretion. In other studies, we found that oestradiol added to the culture media decreased the constitutive release of CCL20/MIP-3 alpha. Moreover, when added to the culture media along with LPS, oestradiol inhibited LPS-induced increases in CCL20/MIP-3 alpha secretion into both the apical and basolateral compartments. In summary, these results indicate that CCL20/MIP-3 alpha is produced in response to PAMPs. Since CCL20/MIP-3 alpha is chemotactic for immature dendritic cells, B cells and memory T cells and has antimicrobial properties, these studies suggest that CCL20/MIP-3 alpha production by epithelial cells, an important part of the innate immune defence in the female reproductive tract, is under hormonal control and is responsive to microbial challenge.

DEFB-1 genetic polymorphism screening in HIV-1 positive pregnant women and their children

OBJECTIVE

In our study we evaluated the frequency of three SNPs (-52 G/A, -44 C/G; -20 G/A) in the 5' UTR of DEFB-1 gene, in a cohort of 130 HIV-1 infected mothers and their children, collected by the Italian group SIGO in Obstetrics and Gynecology.

METHODS

The three SNPs (-52 G/A, -44 C/G; -20 G/A) in the 5' UTR of DEFB-1 gene were genotyped by direct sequencing of PCR products.

RESULTS

The C allele at position -44 was shown to be significantly different in both HIV-1 positive mothers and their children when compared to the healthy controls. The odds ratio for -44 C allele in children born to HIV-1 infected mothers is 7.09 (confidence interval 3.38-15.3) while the odds ratio for this allele in HIV-1 infected mothers is 6.42 (confidence interval 3.14-13.4).

CONCLUSIONS

Our results evidence a high frequency of the -44 CC allele in HIV-1 infected mothers and their children with augmented potential risk of maternal fetal transmission. This potential vertical transmission risk has been successfully prevented by antiretroviral drug treatment and cesarian section of the HIV-1 positive mothers.

The human beta-defensin-3, an antibacterial peptide with multiple biological functions

A group of interesting molecules called defensins exhibit multiple functions but have been primarily recognized to possess a broad spectrum of antimicrobial activities. Studies have reported two different types of defensins (alpha and beta) from human and animals, a cyclic theta defensin from rhesus, and several defensin-like peptides from plants. There is no amino acid sequence homology between these peptides, but they all contain three Cys-Cys disulfide linkages while the connectivities are different. Human beta-defensin-3 (HbetaD-3) is the most recently discovered member of the host-defense peptide family that has attracted much attention. This molecule is expressed either constitutively or induced upon a challenge, and a growing evidence indicates the involvement of such molecules in adaptive immunity as well. It has been shown to exhibit antibacterial activities towards Gram-negative and Gram-positive bacteria as well as an ability to act as a chemo-attractant. Analysis of NMR structural data suggested a symmetrical dimeric form of this peptide in solution, which consists of three beta strands and a short helix in the N-terminal region. While the disulfide linkages are known to provide the structural stability and stability against proteases, the biological relevance of this dimeric form was contradicted by another biological study. Since there is considerable current interest in developing HbetaD-3 for possible pharmaceutical applications, studies to further our understanding on the determinants of antibacterial activities and immunomodulatory function of HbetaD-3 are considered to be highly significant. The knowledge of its biosynthetic regulation will also help in understanding the role of HbetaD-3 in immunity. This article presents an overview of the expression and regulation of HbetaD-3 in humans, and the structure-function correlations among HbetaD-3 and its modified peptides are discussed emphasizing the functional importance. The future scope for studies on HbetaD-3 and design of short potent antimicrobial peptides, based on the native HbetaD-3 molecule, that do not interfere in the immunomodulatory function is also outlined.

The in vitro activity of selected defensins against an isolate of Pseudomonas in the presence of human tears

BACKGROUND/AIMS

Pseudomonas aeruginosa is a major cause of severe bacterial keratitis and remains a difficult clinical entity to treat successfully with the current arsenal of antimicrobial agents. Defensins are small cationic peptides with broad in vitro antimicrobial activity and are potential ocular therapeutic agents. The authors characterised the in vitro activity of defensins NP-1 and NP-3a against P aeruginosa in the presence of human tears.

METHODS

A clinical Pseudomonas isolate was grown to mid-log phase, and 1 x 10(6 )colony forming units were exposed to the peptides (200 microg/ml) for up to 2 hours in the presence of varying concentrations (10-70%) of human tears.

RESULTS

For both peptides in the presence of 10% tears, >3 log units of killing was achieved within 30 minutes. In 70% tears, NP-1 produced >1 log unit of killing at 2 hours, indicating that, although reduced, its activity remained significant. In 20% tears, NP-3a demonstrated 2 log units of killing at 2 hours; however, the antimicrobial activity of this defensin was completely inhibited in the presence of 70% tears.

CONCLUSION

These in vitro data suggest that while the microbicidal activity of some defensins may be diminished at the ocular surface in vivo, significant activity is still possible with certain peptides.

Human beta-defensin 2 induces a vigorous cytokine response in peripheral blood mononuclear cells

beta-Defensins are a family of small cationic peptides involved in the innate response to microbial infection. Although their role in microbial killing is well established, the mechanisms through which this occurs remain largely undefined. Here, using protein array technology, we describe a role for human beta-defensins in the induction of an inflammatory cytokine response by human peripheral blood mononuclear cells (PBMCs). Human beta-defensins 1, 2, and 3 were examined for induction of an array of cytokines and chemokines. Some cytokines, such as interleukin 8 (IL-8) and monocyte chemoattractant protein 1, were up-regulated by all three defensins, while others, such as IL-6 and IL-10, were induced more selectively. It was notable that each defensin induced a unique pattern of cytokines. This report documents, for the first time, an analysis of the composite cytokine response of human PBMCs to beta-defensins. The induction or up-regulation of a number of cytokines involved in the adaptive immune response suggests a possible role for these defensins in linking innate and acquired immunity.

Diesel exhaust particles increase IL-1beta-induced human beta-defensin expression via NF-kappaB-mediated pathway in human lung epithelial cells

Background

Human β-defensin (hBD)-2, antimicrobial peptide primarily induced in epithelial cells, is a key factor in the innate immune response of the respiratory tract. Several studies showed increased defensin levels in both inflammatory lung diseases, such as cystic fibrosis, diffuse panbronchiolitis, idiopathic pulmonary fibrosis and acute respiratory distress syndrome, and infectious diseases. Recently, epidemiologic studies have demonstrated acute and serious adverse effects of particulate air pollution on respiratory health, especially in people with pre-existing inflammatory lung disease. To elucidate the effect of diesel exhaust particles (DEP) on pulmonary innate immune response, we investigated the hBD-2 and interleukin-8 (IL-8) expression to DEP exposure in interleukin-1 beta (IL-1β)-stimulated A549 cells.

Results

IL-1β markedly up-regulated the hBD-2 promoter activity, and the subsequent DEP exposure increased dose-dependently the expression of hBD-2 and inflammatory cytokine IL-8 at the transcriptional level. In addition, DEP further induced the NF-κB activation in IL-1β-stimulated A549 cells more rapidly than in unstimulated control cells, which was showed by nuclear translocation of p65 NF-κB and degradation of IκB-α. The experiment using two NF-κB inhibitors, PDTC and MG132, confirmed that this increase of hBD-2 expression following DEP exposure was regulated through NF-κB-mediated pathway.

Conclusion

These results demonstrated that DEP exposure increases the expression of antimicrobial peptide and inflammatory cytokine at the transcriptional level in IL-1β-primed A549 epithelial cells and suggested that the increase is mediated at least partially through NF-κB activation. Therefore, DEP exposure may contribute to enhance the airway-responsiveness especially on the patients suffering from chronic respiratory disease.

The host defense peptide beta-defensin 1 confers protection against Bordetella pertussis in newborn piglets

Innate immunity plays an important role in protection against respiratory infections in humans and animals. Host defense peptides such as beta-defensins represent major components of innate immunity. We recently developed a novel porcine model of pertussis, an important respiratory disease of young children and infants worldwide. Here, we investigated the role of porcine beta-defensin 1 (pBD-1), a porcine defensin homologue of human beta-defensin 2, in conferring protection against respiratory infection with Bordetella pertussis. In this model, newborn piglets were fully susceptible to infection and developed severe bronchopneumonia. In contrast, piglets older than 4 weeks of age were protected against infection with B. pertussis. Protection was associated with the expression of pBD-1 in the upper respiratory tract. In fact, pBD-1 expression was developmentally regulated, and the absence of pBD-1 was thought to contribute to the increased susceptibility of newborn piglets to infection with B. pertussis. Bronchoalveolar lavage specimens collected from older animals as well as chemically synthesized pBD-1 displayed strong antimicrobial activity against B. pertussis in vitro. Furthermore, in vivo treatment of newborn piglets with only 500 mug pBD-1 at the time of challenge conferred protection against infection with B. pertussis. Interestingly, pBD-1 displayed no bactericidal activity in vitro against Bordetella bronchiseptica, a closely related natural pathogen of pigs. Our results demonstrate that host defense peptides play an important role in protection against pertussis and are essential in modulating innate immune responses against respiratory infections.

Antimicrobial peptides: effectors of innate immunity in the skin

The ability of the cutaneous barrier to help defend the body against pathogens relies on both acquired and innate immune responses. Recently, a large body of research has suggested that a critical component of the innate immune response in the skin is 3 antimicrobial peptides: the cathelicidins, defensins, and dermcidins. These 3 classes of peptides have been shown to act as antimicrobials by directly inhibiting pathogen growth as well as potentiating other branches of the innate, humoral, and cell-mediated immune system. Here, we review the antimicrobial peptides with an emphasis on their role in the cutaneous immune response. We present an overview of defensin, cathelicidin, and dermcidin physiology, elucidating their various functions. In addition, we delve into the role of these peptides in specific dermatologic conditions including wound healing, atopy, and microbial infection. Finally, we discuss the future of antimicrobial peptide research including therapeutic options.

Antibacterial peptides and proteins with multiple cellular targets

Native antimicrobial peptides and proteins represent bridges between innate and adaptive immunity in mammals. On the one hand they possess direct bacterial killing properties, partly by disintegrating bacterial membranes, and some also by inhibiting functions of intracellular biopolymers. On the other, native antimicrobial peptides and proteins upregulate the host defense as chemoattractants or by various additional immunostimulatory effects. Structure-activity relationship studies indicate that residues responsible for the activities on bacterial membranes or for the secondary functions do not perfectly overlap. In reality, in spite of the relatively short size (18-20 amino acid residues) of some of these molecules, the functional domains can frequently be separated, with the cell-penetrating fragments located at the C-termini and the protein binding domains found upstream. As a cumulative effect, multifunctional and target-specific (agonist or antagonist) antimicrobial peptides and proteins interfere with more than one bacterial function at low concentrations, eliminating toxicity concerns of the earlier generations of antibacterial peptides observed in the clinical setting.

Protective roles of the skin against infection: Implication of naturally occurring human antimicrobial agents β-defensins, cathelicidin LL-37 and lysozyme

Beside its physical barrier against invading microorganisms, the skin has the ability to produce a number of antimicrobial peptides and proteins, including human beta-defensins, cathelicidin LL-37 and lysozyme that participate in the innate host defense. These antimicrobial agents are strongly active against a wide spectrum of various pathogens such as bacteria, viruses and fungi. Thus, antimicrobial agents are proposed to be promising candidates for innovative anti-infective drugs, and some antimicrobial peptides are currently used in clinical trials for treatment of various skin infections. In addition to their direct antimicrobial functions against invading pathogenic microorganisms, antimicrobial agents have also multiple roles as mediators of inflammation with the effects on epithelial and inflammatory cells, influencing cell proliferation, wound healing, cytokine/chemokine production and chemotaxis. This review describes the biology of these antimicrobial molecules and discusses their structure, expression and functions. Understanding the actions of antimicrobial agents in skin will provide further insight into the mechanism of innate cutaneous disease control, and yield novel therapeutic approaches to the treatment of skin disorders.

Chemokines: key players in innate and adaptive immunity

Healthy individuals initiate an immediate immune response to microbes by using a set of germline-encoded receptors that recognize common molecular patterns found on the surface of pathogens that are distinct from self-antigens. This innate immune response is the first line of defense against microorganisms in vertebrates, and constitutes the only immune response in plants and invertebrates. The innate immune system includes cellular components, as well as a host of soluble products (antimicrobial peptides, complement fragments, cytokines, and chemokines). The adaptive immune response, which provides long-lasting protection, takes days to develop and requires somatic mutations leading to the development of antigen-specific T cell receptors (cell-mediated immunity) and immunoglobulins (humoral immunity). Members of the chemokine superfamily are crucially involved in both innate and adaptive responses. We review the biological actions of the chemokine superfamily, focusing on several functions that are relevant for both immune responses, such as cell recruitment, microbicidal activity, cell activation, polarization of CD4+ T cells, and effects on structural cells. In particular, we will illustrate the central role that chemokines play in host defense, best demonstrated by the tremendous number of chemokine and chemokine receptor homologs found in microbial genomes, which deflect the immune response of the host.

Trefoil factor 2 (TFF2) deficiency in murine digestive tract influences the immune system

BACKGROUND AND AIMS

The gastrointestinal trefoil factor family (TFF1, TFF2, TFF3) peptides are considered to play an important role in maintaining the integrity of the mucosa. The physiological role of TFF2 in the protection of the GI tract was investigated in TFF2 deficiency.

METHODS

TFF2-/- mice were generated and differential expression of various genes was assessed by using a mouse expression microarray, quantitative real time PCR, Northern blots or immunohistochemistry.

RESULTS

On an mRNA level we found 128 differentially expressed genes. We observed modulation of a number of crucial genes involved in innate and adaptive immunity in the TFF2-/- mice. Expression of proteasomal subunits genes (LMP2, LMP7 and PSMB5) involved in the MHC class I presentation pathway were modulated indicating the formation of immunoproteasomes improving antigen presentation. Expression of one subunit of a transporter (TAP1) responsible for importing degraded antigens into ER was increased, similarly to the BAG2 gene that modulates chaperone activity in ER helping proper loading on MHC class I molecules. Several mouse defensin (cryptdin) genes coding important intestinal microbicidal proteins were up-regulated as a consequence of TFF2 deficiency. Normally moderate expression of TFF3 was highly increased in stomach.

Innate host defense of the lung: effects of lung-lining fluid pH

Lung-lining fluid (LLF) is a primary constituent of the pulmonary host defense system. It is distributed continuously throughout the respiratory tract but is heterogeneous regarding its chemistry and physiology between the conducting airways and alveoli. The conducting airways are lined with airway surface liquid (ASL), a mucus gel-aqueous sol complex that interacts functionally with epithelial cilia as the mucociliary escalator. The alveoli are lined with alveolar subphase fluid (AVSF) and pulmonary surfactant. AVSF sterility is maintained in part by the phagocytic activity of resident alveolar macrophages. Normal ASL and AVSF are both more acidic than blood plasma. However, the details of acid-base regulation differ between the two media. Appreciable transepithelial acid-base flux is possible across the airway epithelium, whereas the alveolar epithelium is relatively impermeable to transepithelial acid-base flux. Moreover, one must consider the influence of resident macrophages on AVSF pH. Resident macrophages occupy a sizable fraction of AVSF by volume and are a substantial source of metabolic H+. The buffering capacities of ASL and AVSF probably are largely due to secreted peptides (e.g., ASL mucins and AVSF surfactant proteins). Acid-base exchange between the extracellular hydrophase and intracellular buffering systems of resident macrophages represents an additional buffer pool for AVSF. The pH of ASL and AVSF can be depressed by disease or inflammation. Low pH is predicted to suppress microbe clearance from the airways and alveoli, increase pathogen survival in both regions, and alter mediator release by resident macrophages and recruited leukocytes thereby increasing the propensity for bystander cell injury. Overall, ASL/AVSF pH is expected to be a major determinant of lung host defense responses.

Recent developments in immunomodulatory peptides in juvenile rheumatic diseases: from trigger to dimmer?

PURPOSE OF REVIEW

Current therapy for juvenile rheumatic diseases is based on general immune suppression or blocking inflammatory pathways. These treatments do not induce long-term disease remission and have a risk of side effects; this is especially unfavorable in children. It is better to focus on induction of tolerance mechanisms than on suppression of inflammation. This promotes epitope specific immunotherapy as a possible safe treatment option.

RECENT FINDINGS

In the search for specific peptides for immunotherapy in autoimmunity, the focus is shifting from purported triggers of disease to peptides that regulate the ongoing inflammation. These so-called 'immunomodulatory peptides' are important in every healthy immune system. Several juvenile rheumatic diseases have been linked to certain immunomodulatory peptides. In juvenile dermatomyositis, peptides from human skeletal myosin play a role in the perpetuation of the disease. In systemic lupus erythematosus, the focus is mostly on DNA-derived peptides and peptides from anti-DNA antibodies. In juvenile idiopathic arthritis, heat shock proteins have been shown to contain important immunomodulatory epitopes.

SUMMARY

Immunomodulatory peptides play an important role in juvenile rheumatic diseases. Promising candidates for immunotherapy have been identified. This opens the possibility of clinical testing in rheumatic diseases of childhood.

Psoriasis: dysregulation of innate immunity

The current understanding of the function of natural killer (NK) T cells in innate immunity and their potential to control acquired specific immunity, as well as the remarkable efficacy of antitumour necrosis factor-alpha biological treatments in psoriasis, forces us to refine the current T-cell hypothesis of psoriasis pathogenesis, and to give credit to the role of innate immunity. Psoriasis might be envisioned to be a genetically determined triggered state of otherwise dormant innate immunity. This aggravated state of innate immunity is represented by the activity of NK T cells, dendritic cells, neutrophils and keratinocytes, leading to the recruitment and activation of preferentially type 1 T cells, possibly in an antigen-independent way. Keratinocytes in psoriasis then are sensitive to the effects of T-cell activation and cytokine production, interferon (IFN)-gamma, by responding with psoriasiform hyperplasia. The chronic inflammation of psoriatic lesions suggests that this might be due to a deficiency in downregulation processes (e.g. a defect in the regulatory T-cell repertoire) and/or the persistence of an unknown trigger resulting in an exaggerated innate immune response.

Microbial compounds induce the expression of pro-inflammatory cytokines, chemokines and human beta-defensin-2 in vaginal epithelial cells

Vaginal epithelium has a powerful innate immune system that protects the female reproductive organs from bacterial and fungal infections. In the present study, we aimed to explore whether the Toll-like receptor (TLR) signaling pathway and the induction of pro-inflammatory cytokines and antimicrobial peptides could contribute to the protection against pathogenic microorganisms in vaginal epithelia, using an immortalized vaginal epithelial cell line PK E6/E7 as a model. We found that TLR2 and TLR4 receptors are expressed in vivo in the vaginal epithelia and in vitro in PK E6/E7 vaginal epithelial cell line. The Gram-negative cell wall compound lipopolysaccharide (LPS), the Gram-positive compound peptidoglycan (PGN), heat-killed Candida albicans and zymosan significantly (P<0.05) induced the expression of pro-inflammatory cytokines and chemokines such as TNF-alpha and IL-8/CXCL8 in vaginal epithelial cells. Furthermore, the expression and production of human beta-defensin-2 (hBD2), an antimicrobial peptide with chemotactic functions, was also up-regulated in PK E6/E7 cells after treatment with LPS, PGN or C. albicans. Treatment of vaginal epithelial cells with microbial compounds induced the activation and nuclear translocation of NF-kappaB transcription factor, a key element of innate and adaptive immune responses. In our work, we provide evidence that microbial compounds induce the production of pro-inflammatory cytokines, chemokines and antimicrobial peptides in vaginal epithelial cells. In vivo, vaginal epithelial cell-derived inflammatory mediators and antimicrobial peptides may play important roles in vaginal immune responses and in the elimination of pathogens from the female reproductive tract.

Concentrations of α- and β-defensins in gastric juice of patients with various gastroduodenal diseases

AIM: To determine the concentration of α- and β-defensins in gastric juice of patients with various gastroduodenal diseases.

METHODS: Concentrations of human neutrophil peptides (HNPs) 1-3, the major forms of α-defensins, and human β-defensin (HBD)-1 and HBD-2 were measured by radioimmunoassay in plasma and gastric juice of 84 subjects, consisting of 54 Helicobacter pylori-infected and 30 uninfected subjects. They included 33 patients with chronic gastritis (CG), 12 with gastric ulcer (GU), 11 with duodenal ulcer (DU), 11 with benign gastric polyp (BGP) and 16 with normal mucosa (N group) on upper endoscopy. Plasma pepsinogen I and II levels, biomarkers for gastric mucosal inflammation and atrophy, were also measured.

RESULTS: Gastric juice HNPs 1-3 levels in patients with CG, GU and BGP were significantly higher than those in patients with DU and N. Gastric juice HBD-2 concentrations in patients with CG and GU were significantly higher than those in the N group, but were significantly lower in DU patients than in GU patients. Gastric juice HBD-1 levels and plasma levels of these peptides were similar in the patient groups. Concentrations of gastric juice HNPs 1-3 and HBD-2 of in H pylori-infected patients were significantly different from those in uninfected subjects. HNPs 1-3 concentrations in gastric juice correlated negatively with plasma pepsinogen I levels and I/II ratios. HBD-2 levels in gastric juice correlated positively and negatively with plasma pepsinogen II concentrations and I/II ratios, respectively.

CONCLUSION: HNPs 1-3 and HBD-2 levels in gastric juice are diverse among various gastrointestinal diseases, reflecting the inflammatory and atrophic events of the background gastric mucosa affected by H pylori.

Resistance to human beta-defensins is common among oral treponemes

BACKGROUND/AIMS

Oral treponemes are implicated in the pathogenesis of periodontal disease. We have previously shown that Treponema denticola ATCC type strains and strain GM-1 are resistant to killing by human beta-defensins (hbetaD)-1 and -2. We hypothesize that resistance to beta-defensins is a common feature of oral treponemes, which allows colonization and persistence in the oral cavity. In this study, we tested additional isolates of T. denticola, as well as six other species of treponemes, for resistance to hbetaD-1, -2 and -3. We also examined the four ATCC strains of T. denticola and strain GM-1 for resistance to hbetaD-3.

METHODS

Resistance was determined by motility and Alamar Blue assays for metabolic activity.

RESULTS

All T. denticola strains tested were resistant to hbetaD-1, -2 and -3, with the exception of strain Ambigua, which was sensitive to hbetaD-2 and -3. All other treponemes except Treponema vincentii were resistant to hbetaD-1. Treponema pectinovorum was sensitive to hbetaD-2, while T. vincentii, T. pectinovorum and Treponema maltophilum were sensitive to hbetaD-3. Escherichia coli was used as a control organism and was killed by all three defensins.

CONCLUSION

Resistance to the constitutively expressed hbetaD-1 may assist treponemes in initial colonization of epithelial surfaces, while resistance to the inducible hbetaD-2 and -3 would allow some treponemes to survive in active periodontal lesions.

Primate defensins

Defensins are endogenous, cysteine-rich antimicrobial peptides that contribute to host defence against bacterial, fungal and viral infections. There are three subfamilies of defensins in primates: alpha-defensins are most common in neutrophils and Paneth cells of the small intestine; beta-defensins protect the skin and the mucous membranes of the respiratory, genitourinary and gastrointestinal tracts; and theta-defensins, which are expressed only in Old World monkeys, lesser apes and orangutans, are lectins with broad-spectrum antiviral efficacy. Here, their discovery and recent advances in understanding their properties and functions are described.

Suppression of human prostate tumor growth in mice by a cytolytic D-, L-amino Acid Peptide: membrane lysis, increased necrosis, and inhibition of prostate-specific antigen secretion

Gene-encoded host defense peptides are used as part of the innate immunity, and many of them act by directly lysing the cell membrane of the pathogen. A few of these peptides showed anticancer activity in vitro but could not be used in vivo because of their inactivation by serum. We designed a 15-amino acid peptide, composed of D- and L-amino acids (diastereomer), which targets both androgen-independent and androgen-dependent human prostate carcinoma cell lines (CL1, 22RV1, and LNCaP). Most importantly, we observed a complete arrest of growth in CL1 and 22RV1 xenografts treated intratumorally with the diastereomer. This was also accompanied by a lowering of prostate-specific antigen serum levels secreted by the 22RV1 xenograft. Furthermore, the diastereomer synergized with conventional chemotherapeutics. In contrast, the parental all l-amino acids peptide was highly active only in vitro and could not discriminate between tumor and nontumor cells. Fluorescent confocal microscopy, histopathologic examination, and cell permeability studies (depolarization of transmembrane potential and release of an encapsulated dye) suggest a necrotic mechanism of killing, after a threshold concentration of peptide has been reached. Its destructive killing effect and the simple sequence of the diastereomer make it an attractive chemotherapeutic candidate possessing a new mode of action, with potential to be developed additionally for the treatment of prostate carcinoma.

Innate host defense of the lung: effects of lung-lining fluid pH

Lung-lining fluid (LLF) is a primary constituent of the pulmonary host defense system. It is distributed continuously throughout the respiratory tract but is heterogeneous regarding its chemistry and physiology between the conducting airways and alveoli. The conducting airways are lined with airway surface liquid (ASL), a mucus gel-aqueous sol complex that interacts functionally with epithelial cilia as the mucociliary escalator. The alveoli are lined with alveolar subphase fluid (AVSF) and pulmonary surfactant. AVSF sterility is maintained in part by the phagocytic activity of resident alveolar macrophages. Normal ASL and AVSF are both more acidic than blood plasma. However, the details of acid-base regulation differ between the two media. Appreciable transepithelial acid-base flux is possible across the airway epithelium, whereas the alveolar epithelium is relatively impermeable to transepithelial acid-base flux. Moreover, one must consider the influence of resident macrophages on AVSF pH. Resident macrophages occupy a sizable fraction of AVSF by volume and are a substantial source of metabolic H+. The buffering capacities of ASL and AVSF probably are largely due to secreted peptides (e.g., ASL mucins and AVSF surfactant proteins). Acid-base exchange between the extracellular hydrophase and intracellular buffering systems of resident macrophages represents an additional buffer pool for AVSF. The pH of ASL and AVSF can be depressed by disease or inflammation. Low pH is predicted to suppress microbe clearance from the airways and alveoli, increase pathogen survival in both regions, and alter mediator release by resident macrophages and recruited leukocytes thereby increasing the propensity for bystander cell injury. Overall, ASL/AVSF pH is expected to be a major determinant of lung host defense responses.