Host defense peptides in the oral cavity and the lung: similarities and differences

Dry powder measles vaccine: particle deposition, virus replication, and immune response in cotton rats following inhalation

A stable and high potency dry powder measles vaccine with a particle size distribution suitable for inhalation was manufactured by CO(2)-Assisted Nebulization with a Bubble Dryer(®) (CAN-BD) process from bulk liquid Edmonston-Zagreb live attenuated measles virus vaccine supplied by the Serum Institute of India. A novel dry powder inhaler, the PuffHaler(®) was adapted for use in evaluating the utility of cotton rats to study the vaccine deposition, vaccine virus replication, and immune response following inhalation of the dry powder measles vaccine. Vaccine deposition in the lungs of cotton rats and subsequent viral replication was detected by measles-specific RT-PCR, and viral replication was confined to the lungs. Inhalation delivery resulted in an immune response comparable to that following injection. The cotton rat model is useful for evaluating new measles vaccine formulations and delivery devices.

Sex differences in dental caries experience: clinical evidence, complex etiology

A sex difference in oral health has been widely documented through time and across cultures. Women's oral health declines more rapidly than men's with the onset of agriculture and the associated rise in fertility. The magnitude of this disparity in oral health by sex increases during ontogeny: from childhood, to adolescence, and through the reproductive years. Representative studies of sex differences in caries, tooth loss, and periodontal disease are critically reviewed. Surveys conducted in Hungary, India, and in an isolated traditional Brazilian sample provide additional support for a significant sex bias in dental caries, especially in mature adults. Compounding hormonal and reproductive factors, the sex difference in oral health in India appears to involve social and religious causes such as son preference, ritual fasting, and dietary restrictions during pregnancy. Like the sex difference in caries, tooth loss in women is greater than in men and has been linked to caries and parity. Results of genome wide association studies have found caries susceptible and caries protective loci that influence variation in taste, saliva, and enamel proteins, affecting the oral environment and the micro-structure of enamel. Genetic variation, some of which is X-linked, may partly explain how sex differences in oral health originate. A primary, but neglected, factor in explaining the sex differential in oral health is the complex and synergistic changes associated with female sex hormones, pregnancy, and women's reproductive life history. Caries etiology is complex and impacts understanding of the sex difference in oral health. Both biological (genetics, hormones, and reproductive history) and anthropological (behavioral) factors such culture-based division of labor and gender-based dietary preferences play a role.

Differential and coordinated expression of defensins and cytokines by gingival epithelial cells and dendritic cells in response to oral bacteria

Background

Epithelial cells and dendritic cells (DCs) both initiate and contribute to innate immune responses to bacteria. However, much less is known about the coordinated regulation of innate immune responses between GECs and immune cells, particularly DCs in the oral cavity. The present study was conducted to investigate whether their responses are coordinated and are bacteria-specific in the oral cavity.

Results

The β-defensin antimicrobial peptides hBD1, hBD2 and hBD3 were expressed by immature DCs as well as gingival epithelial cells (GECs). HBD1, hBD2 and hBD3 are upregulated in DCs while hBD2 and hBD3 are upregulated in GECs in response to bacterial stimulation. Responses of both cell types were bacteria-specific, as demonstrated by distinctive profiles of hBDs mRNA expression and secreted cytokines and chemokines in response to cell wall preparations of various bacteria of different pathogenicity: Fusobacterium nucleatum, Actinomyces naeslundii and Porphyromonas gingivalis. The regulation of expression of hBD2, IL-8, CXCL2/GROβ and CCL-20/MIP3α by GECs was greatly enhanced by conditioned medium from bacterially activated DCs. This enhancement was primarily mediated via IL-1β, since induction was largely attenuated by IL-1 receptor antagonist. In addition, the defensins influence DCs by eliciting differential cytokine and chemokine secretion. HBD2 significantly induced IL-6, while hBD3 induced MCP-1 to approximately the same extent as LPS, suggesting a unique role in immune responses.

Conclusions

The results suggest that cytokines, chemokines and β-defensins are involved in interaction of these two cell types, and the responses are bacteria-specific. Differential and coordinated regulation between GECs and DCs may be important in regulation of innate immune homeostasis and response to pathogens in the oral cavity.

Chromogranin A detection in saliva of type 2 diabetes patients

Chromogranin A is present in secretion granules of nerve, endocrine and immune cells and is a precursor of several peptides with antibacterial and antifungal properties at micromolar concentrations.Our aim in this prospective, double blind study, was to determine the expression of chromogranin A and its peptides at protein level in saliva of type 2 diabetic patients and thereby to obtain a new non-invasive diagnostic means for the future.Saliva was taken from 30 type 2 diabetic patients and 30 healthy individuals at the same time interval in the morning without any oral stimuli. Circadianic periodics in protein productions have been avoided. The presence of chromogranin A and its derived peptides was determined in whole saliva, after centrifugation at 40C for 12 min at 14 000 rpm, by SDS-PAGE electrophoresis and Immunoblotting (Western Blot). To ensure same protein concentrations Bradford protein quantification assay has been performed before.For the first time, we have determined an overexpression of chromogranin A in saliva of diabetic patients in 100% of the individuals. Chromogranin A, a circulating biomarker for epithelial tumours, is also overexpressed in saliva of type 2 diabetic patients. To confirm our results, more studies with a large amount of patients is necessary.

Epithelial cells and innate antifungal defense

The human pathogenic fungus Candida albicans is the predominant cause of both superficial and invasive forms of candidiasis. Clinical observations indicate that mucocutaneous Candida infections are commonly associated with defective cell-mediated immune responses. The importance of the innate immune system as a first-line defense against pathogenic challenge has long been recognized. Over the last decade, many key molecules mediating innate host defense have been identified. Central to these developments is the discovery of pattern recognition receptors such as Toll-like receptors and C-type lectin-receptors that induce innate immune responses and also modulate cellular and humoral adaptive immunity during Candida infections. Although a large amount of information is now available in systemic infections, little is known about localized infections. We address the most relevant pattern recognition receptors and their signaling mechanisms in oral epithelial cells, to gain a better understanding of their contributions to antifungal innate immunity.

Measuring antimicrobial peptide activity on epithelial surfaces in cell culture

To more accurately assess the activity and role of epithelial cell-derived antimicrobial peptides in their native settings, it is essential to perform assays at the surfaces under relevant conditions. In order to carry this out, we utilize three-dimensional cultures of airway and gingival epithelium, which are grown at an air-liquid interface. Under these conditions, the cultures can be subjected to challenge with a variety of factors known to cause an increase in antimicrobial peptide gene expression. The functional relevance of this induction can then be assessed by quantifying antibacterial activity either directly on the surface of the cells or using the fluid secreted onto the apical surface of the cultures. The relative contribution of the peptides can also be measured by pre-incubation of the secreted fluid with specific inhibitory antibodies. Thus, a relatively inexpensive in vitro model can be used to evaluate the role of antimicrobial peptides in mucosal epithelium.

Flagellin-induced corneal antimicrobial peptide production and wound repair involve a novel NF-kappaB-independent and EGFR-dependent pathway

Background

The bacterial protein flagellin plays a major role in stimulating mucosal surface innate immune response to bacterial infection and uniquely induces profound cytoprotection against pathogens, chemicals, and radiation. This study sought to determine signaling pathways responsible for the flagellin-induced inflammatory and cytoprotective effects on human corneal epithelial cells (HCECs).

Methodology/Principal Findings

Flagellin purified from Pseudomonas aeruginosa (strain PAK) or live bacteria were used to challenge cultured HCECs. The activation of signaling pathways was assessed with Western blot, and the secretion of cytokine/chemokine and production of antimicrobial peptides (AMPs) were measured with ELISA and dot blot, respectively. Effects of flagellin on wound healing were assessed in cultured porcine corneas. L94A (a site mutation in TLR5 binding region) flagellin and PAK expressing L94A flagellin were unable to stimulate NF-κB activation, but were potent in eliciting EGFR signaling in a TGF-α–related pathway in HCECs. Concomitant with the lack of NF-κB activation, L94A flagellin was ineffective in inducing IL-6 and IL-8 production in HCECs. Surprisingly, the secretion of two inducible AMPs, LL-37 and hBD2, was not affected by L94A mutation. Similar to wild-type flagellin, L94A induced epithelial wound closure in cultured porcine cornea through maintaining EGFR-mediated signaling.

Conclusions/Significance

Our data suggest that inflammatory response mediated by NF-κB can be uncoupled from epithelial innate defense machinery (i.e., AMP expression) and major epithelial proliferation/repair pathways mediated by EGFR, and that flagellin and its derivatives may have broad therapeutic applications in cytoprotection and in controlling infection in the cornea and other mucosal tissues.

Mucosal treatments for herpes simplex virus: insights on targeted immunoprophylaxis and therapy

Herpes simplex virus (HSV) serotypes 1 and 2 establish lifelong infections that can produce reactivated pools of virus at mucosal sites where primary infections were initiated. No approved vaccines are available. To break the transmission cycle, interventions must either prevent infection or reduce infectivity at mucosal sites. This article discusses the recent experimental successes of immunoprophylactic and therapeutic compounds that enhance resistance and/or reduce viral loads at genital and ocular mucosa. Current data indicate Toll-like receptor agonists and selected immunomodulating compounds effectively increase the HSV infection threshold and hold promise for genital prophylaxis. Similarly, immunization at genital and extragenital mucosal sites is discussed. Finally, preclinical success with novel immunotherapies for ocular HSV that address herpetic keratitis and corneal blindness is reviewed.

Defensins as anti-inflammatory compounds and mucosal adjuvants

Human neutrophil peptide alpha-defensins and human beta-defensins are small, well-characterized peptides with broad antimicrobial activities. In mixtures with microbial antigens, defensins attenuate proinflammatory cytokine responses by dendritic cells in culture, attenuate proinflammatory cytokine responses in the nasal fluids of exposed mice and enhance antibody responses in the serum of vaccinated mice. Although the exact mechanisms are unknown, defensins first start by binding to microbial antigens and adhesins, often attenuating toxic or inflammatory-inducing capacities. Binding is not generic; it appears to be both defensin-specific and antigen-specific with high affinities. Binding of defensins to antigens may, in turn, alter the interaction of antigens with epithelial cells and antigen-presenting cells attenuating the production of proinflammatory cytokines. The binding of defensins to antigens may also facilitate the delivery of bound antigen to antigen-presenting cells in some cases via specific receptors. These interactions enhance the immunogenicity of the bound antigen in an adjuvant-like fashion. Future research will determine the extent to which defensins can suppress early events in inflammation and enhance systemic antibody responses, a very recent and exciting concept that could be exploited to develop therapeutics to prevent or treat a variety of oral mucosal infections, particularly where inflammation plays a role in the pathogenesis of disease and its long-term sequelae.

Defensins attenuate cytokine responses yet enhance antibody responses to Porphyromonas gingivalis adhesins in mice

AIM

Our aim is to assess the ability of human neutrophil peptide alpha-defensins (HNPs) and human beta-defensins (HBDs) to attenuate proinflammatory cytokine responses and enhance antibody responses to recombinant hemagglutinin B (rHagB) or recombinant fimbrillin A (rFimA) from Porphyromonas gingivalis 381 in mice.

MATERIALS & METHODS

In the first study, C57BL/6 mice were given 10 microg rHagB or rFimA without and with 1 microg HNP1, HNP2, HBD1, HBD2 or HBD3. At 24 h, mice were euthanized and cytokine concentrations were determined in nasal wash fluid (NWF), bronchoalveolar lavage fluids, saliva and serum. In the second study, C57BL/6 mice were given 10 microg rHagB or rFimA without and with 1 microg HNPs or HBDs similarly on days 0, 7 and 14. At 21 days, mice were euthanized and rHagB- and rFimA-specific antibody responses were determined in NWF, bronchoalveolar lavage fluids, saliva and serum.

RESULTS

Mice given rHagB + HNP2, rHagB + HBD1 and rHagB + HBD3 produced significantly lower (p < 0.05) IL-6 responses than mice given rHagB alone. Mice given rHagB + HNP1, rHagB + HNP2, rHagB + HBD1 and rHagB + HBD3 produced significantly lower (p < 0.05) keratinocyte-derived chemokine responses than mice given rHagB alone. Mice given rFimA produced very low levels of IL-6 and only moderate levels of keratinocyte-derived chemokine in NWF that were not attenuated by prior incubation of rFimA with any defensin. Mice given rHagB + HNP1 produced a significantly higher (p < 0.05) serum IgG antibody response than mice given rHagB alone and mice given rFimA + HNP2 produced a higher, but not significant, antibody response.

CONCLUSION

The ability of HNPs and HBDs to attenuate proinflammatory cytokine responses in murine NWF and enhance IgG antibody responses in serum was dependent upon both the defensin and antigen of P. gingivalis.

Expression of human beta-defensin-2 in intratumoral vascular endothelium and in endothelial cells induced by transforming growth factor beta

Human beta-defensin-2 (hBD-2) is a small cationic peptide originally identified from psoriatic skin lesions as an antimicrobial agent of the innate immune system. The expression of hBD-2 is believed to be induced exclusively in epithelial cells by microbial components and certain proinflammatory cytokines, such as interleukin-1 beta (IL-1 beta). In this study, we report, for the first time, that hBD-2 is expressed in vascular endothelial cells associated with oral squamous cell carcinoma (OSCC) and Kaposi's sarcoma lesions, but not in that of normal stroma. Expression of hBD-2 in vascular endothelial cells was further substantiated by in vitro experiments using cultured human umbilical vein endothelial cells (HUVECs). Transforming growth factor beta1 (TGF beta 1) and IL-1 beta, two well-known tumorigenic inflammatory mediators, induce hBD-2 transcript and peptide expression in HUVECs. However, TGF beta 1 does not stimulate hBD-2 expression in oral epithelial cells. In addition, proinflammatory cytokines and microbial reagents do not induce the expression of hBD-1 and hBD-3 in HUVECs. Since hBD-2 has been shown to modulate migration, proliferation, and tube formation of HUVECs in vitro and participate in immune cell trafficking, its expression in vascular endothelial cells located within malignant lesions may play a role in tumor angiogenesis and cancer metastasis.

Human defensins and LL-37 in mucosal immunity

Defensins are widespread in nature and have activity against a broad range of pathogens. Defensins have direct antimicrobial effects and also modulate innate and adaptive immune responses. We consider the role of human defensins and the cathelicidin LL-37 in defense of respiratory, gastrointestinal, and genitourinary tracts and the oral cavity, skin, and eye. Human beta-defensins (hBDs) and human defensins 5 and 6 (HD5 and -6) are involved most obviously in mucosal responses, as they are produced principally by epithelial cells. Human alpha-defensins 1-4 (or HNPs 1-4) are produced principally by neutrophils recruited to the mucosa. Understanding the biology of defensins and LL-37 is the beginning to clarify the pathophysiology of mucosal inflammatory and infectious diseases (e.g., Crohn's disease, atopic dermatitis, lung or urinary infections). Challenges for these studies are the redundancy of innate defense mechanisms and the presence and interactions of many innate defense proteins in mucosal secretions.

The roles of antimicrobial peptides in innate host defense

Antimicrobial peptides (AMPs) are multi-functional peptides whose fundamental biological role in vivo has been proposed to be the elimination of pathogenic microorganisms, including Gram-positive and -negative bacteria, fungi, and viruses. Genes encoding these peptides are expressed in a variety of cells in the host, including circulating phagocytic cells and mucosal epithelial cells, demonstrating a wide range of utility in the innate immune system. Expression of these genes is tightly regulated; they are induced by pathogens and cytokines as part of the host defense response, and they can be suppressed by bacterial virulence factors and environmental factors which can lead to increased susceptibility to infection. New research has also cast light on alternative functionalities, including immunomodulatory activities, which are related to their unique structural characteristics. These peptides represent not only an important component of innate host defense against microbial colonization and a link between innate and adaptive immunity, but also form a foundation for the development of new therapeutic agents.

Association of a genetic polymorphism (-44 C/G SNP) in the human DEFB1 gene with expression and inducibility of multiple beta-defensins in gingival keratinocytes

Background

Human β-defensins (hBDs) are antimicrobial peptides with a role in innate immune defense. Our laboratory previously showed that a single nucleotide polymorphism (SNP) in the 5' untranslated region of the hBD1 gene (DEFB1), denoted -44 (rs1800972), is correlated with protection from oral Candida. Because this SNP alters the putative mRNA structure, we hypothesized that it alters hBD1 expression.

Methods

Transfection of reporter constructs and evaluation of antimicrobial activity and mRNA expression levels in keratinocytes from multiple donors were used to evaluate the effect of this SNP on constitutive and induced levels of expression.

Results

Transfection of CAT reporter constructs containing the 5' untranslated region showed that the -44 G allele yielded a 2-fold increase in CAT protein compared to other common haplotypes suggesting a cis effect on transcription or translation. The constitutive hBD1 mRNA level in human oral keratinocytes was significantly greater in cells from donors with the -44 GG genotype compared to those with the common CC genotype. Surprisingly, the hBD3 mRNA level as well as antimicrobial activity of keratinocyte extracts also correlated with the -44 G allele. Induced levels of hBD1, hBD2, and hBD3 mRNA were evaluated in keratinocytes challenged with Toll-like receptor 2 and 4 ligands, interleukin-1β, TNFα, and interferon-γ (IFNγ). In contrast to constitutive expression levels, IFNγ-induced keratinocyte hBD1 and hBD3 mRNA expression was significantly greater in cells with the common CC genotype, but there was no clear correlation of genotype with hBD2 expression.

Conclusion

The DEFB1 -44 G allele is associated with an increase in overall constitutive antimicrobial activity and expression of hBD1 and hBD3 in a manner that is consistent with protection from candidiasis, while the more common C allele is associated with IFNγ inducibility of these β-defensins and is likely to be more protective in conditions that enhance IFNγ expression such as chronic periodontitis. These results suggest a complex relationship between genetics and defensin expression that may influence periodontal health and innate immune responses.