Alpha-defensin binding expands human adenovirus tropism.

Mammalian α-defensins are a family of abundant effector peptides of the mucosal innate immune system. Although primarily considered to be antimicrobial, α-defensins can increase rather than block infection by certain prominent bacterial and viral pathogens in cell culture and in vivo. We have shown previously that exposure of mouse and human adenoviruses (HAdVs) to α-defensins is able to overcome competitive inhibitors that block cell binding, leading us to hypothesize a defensin-mediated binding mechanism that is independent of known viral receptors. To test this hypothesis, we used genetic approaches to demonstrate that none of several primary receptors nor integrin co-receptors are needed for human α-defensin-mediated binding of HAdV to cells; however, infection remains integrin dependent. Thus, our studies have revealed a novel pathway for HAdV binding to cells that bypasses viral primary receptors. We speculate that this pathway functions in parallel with receptor-mediated entry and contributes to α-defensin-enhanced infection of susceptible cells. Remarkably, we also found that in the presence of α-defensins, HAdV tropism is expanded to non-susceptible cells, even when viruses are exposed to a mixture of both susceptible and non-susceptible cells. Therefore, we propose that in the presence of sufficient concentrations of α-defensins, such as in the lung or gut, integrin expression rather than primary receptor expression will dictate HAdV tropism in vivo. In summary, α-defensins may contribute to tissue tropism not only through the neutralization of susceptible viruses but also by allowing certain defensin-resistant viruses to bind to cells independently of previously described mechanisms.

Characterisation of defensins across the marsupial family tree.

Defensins are antimicrobial peptides involved in innate immunity, and gene number differs amongst eutherian mammals. Few studies have investigated defensins in marsupials, despite their potential involvement in immunological protection of altricial young. Here we use recently sequenced marsupial genomes and transcriptomes to annotate defensins in nine species across the marsupial family tree. We characterised 35 alpha and 286 beta defensins; gene number differed between species, although Dasyuromorphs had the largest repertoire. Defensins were encoded in three gene clusters within the genome, syntenic to eutherians, and were expressed in the pouch and mammary gland. Marsupial beta defensins were closely related to eutherians, however marsupial alpha defensins were more divergent. We identified marsupial orthologs of human DEFB3 and 6, and several marsupial-specific beta defensin lineages which may have novel functions. Marsupial predicted mature peptides were highly variable in length and sequence composition. We propose candidate peptides for future testing to elucidate the function of marsupial defensins.

Regulation of Chloride Channels by Epidermal Growth Factor Receptor-Tyrosine Kinase Inhibitor-Induced α-Defensin 5.

Epidermal growth factor receptor tyrosine kinase inhibitors (EGFR-TKIs) are used to treat non-small cell lung cancer with EGFR mutations. However, first-generation erlotinib and second-generation afatinib often cause diarrhea, which may develop because of the association between EGFR-TKIs and the chloride channel or abnormalities in the intestinal microbiota due to disruption of the intestinal immune system. As reports on the effects of EGFR-TKIs on intestinal immunity are lacking, we aimed to determine whether the intestinal immune system is involved in the molecular effects of EGFR-TKIs on chloride channels using Caco-2 cells. Initially, we evaluated the association of chloride channels with α-defensin 5 (DEFA5), a marker of intestinal immunity. Erlotinib and afatinib significantly increased the extracellularly secreted DEFA5 level and autophagy-related 16-like 1 and X-box binding protein 1 transcript levels, indicative of enhanced granule exocytosis. Conversely, intracellular DEFA5 and Toll-like receptor 4 protein expression and tumor necrosis factor-α transcript levels decreased significantly, suggesting that Toll-like receptor 4 suppression repressed DEFA5 production. Furthermore, among the chloride channels, DEFA5 was found to significantly increase the transcript levels of cystic fibrosis transmembrane conductance regulators. These results indicate that DEFA5 plays a significant role in the mechanism of chloride channel-mediated diarrhea induced by EGFR-TKIs. Therefore, we successfully elucidated the potential host action of DEFA5 in cancer therapy for the first time.

A top-down proteomic approach reveals a salivary protein profile able to classify Parkinson's disease with respect to Alzheimer's disease patients and to healthy controls.

Parkinson's disease (PD) is a complex neurodegenerative disease with motor and non-motor symptoms. Diagnosis is complicated by lack of reliable biomarkers. To individuate peptides and/or proteins with diagnostic potential for early diagnosis, severity and discrimination from similar pathologies, the salivary proteome in 36 PD patients was investigated in comparison with 36 healthy controls (HC) and 35 Alzheimer's disease (AD) patients. A top-down platform based on HPLC-ESI-IT-MS allowed characterizing and quantifying intact peptides, small proteins and their PTMs (overall 51). The three groups showed significantly different protein profiles, PD showed the highest levels of cystatin SA and antileukoproteinase and the lowest of cystatin SN and some statherin proteoforms. HC exhibited the lowest abundance of thymosin ß4, short S100A9, cystatin A, and dimeric cystatin B. AD patients showed the highest abundance of α-defensins and short oxidized S100A9. Moreover, different proteoforms of the same protein, as S-cysteinylated and S-glutathionylated cystatin B, showed opposite trends in the two pathological groups. Statherin, cystatins SA and SN classified accurately PD from HC and AD subjects. α-defensins, histatin 1, oxidized S100A9, and P-B fragments were the best classifying factors between PD and AD patients. Interestingly statherin and thymosin ß4 correlated with defective olfactory functions in PD patients. All these outcomes highlighted implications of specific proteoforms involved in the innate-immune response and inflammation regulation at oral and systemic level, suggesting a possible panel of molecular and clinical markers suitable to recognize subjects affected by PD.

Enteric α-Defensin Contributes to Recovery of Radiation-Induced Intestinal Injury by Modulating Gut Microbiota and Fecal Metabolites.

The effect of ionizing radiation on the gastrointestinal tract is a common complication of abdominal and pelvic radiotherapy. However, the pathological features of radiation enteropathy and its effective medical intervention regimen is still a global challenge. Here, we explored the role and mechanism of enteric alpha-defensins (EαDs) in protecting against radiation enteropathy. To address this, we utilized EαDs-deficiency mice, in which the matrix metallopeptidase 7 to activate Paneth cell α-defensins was knockout (KO) mice, and the complementary wild-type (WT) control mice for this study. Remarkably, the KO mice were more susceptible to 5.0 Gy total-body irradiation, resulting in worse clinic scores and lower survival rate, compared with the wild-type mice. Histological examination indicated that the KO mice were subjected to slow recovery of intestinal villus and mucosa function, characterized by the reduced expression of TFF3, Glut1 and Muc2. In addition, compared with the wild-type controls, the KO mice experienced serious inflammation response in intestinal tissue, indicated by the remarkably increased expression level of IL-1ß, IL-6 and IL-12. Using high-throughput sequencing analysis, we found that the intestinal bacterial community of the KO mice was more prone to dysbiosis than that of the WT mice, with significantly increased abundance of opportunistic pathogenic bacteria, such as Streptococcus sp. and Escherichia-Shigella sp., whereas remarkably decreased probiotics harboring Lactobacillus sp., Desulfovibrio sp. etc. Fecal metabolomics analysis indicated that the relative abundance of 31 metabolites arose significantly different between WT and KO mice on day 10 after radiation exposure. A subset of differential metabolites to regulate host metabolism and immunity, such as acetic acid, acetate, butanoic acid, was negatively correlated with the alteration of gut microbiota in the irradiated KO mice. This study provides new insight into EαDs contribution to the recovery of radiation-induced intestinal damage, and suggests a potential novel target to prevent the adverse effects of radiotherapy.

Alpha-defensins inhibit ERK/STAT3 signaling during monocyte-macrophage differentiation and impede macrophage function.

Alpha-1-antitrypsin deficiency (AATD) is a genetic disorder associated with a 5-tenfold decrease in lung levels of alpha-1-antitrypsin (AAT) and an increased risk for obstructive lung disease. α-defensins are cationic broad-spectrum cytotoxic and pro-inflammatory peptides found in the azurophilic granules of neutrophils. The concentration of α-defensins is less than 30 nM in the bronchoalveolar lavage fluid of healthy controls but is up to 6 µM in AATD individuals with significant lung function impairment. Alveolar macrophages are generally classified into pro-inflammatory (M1) or anti-inflammatory (M2) subsets that play distinct roles in the initiation and resolution of inflammation. Therefore, monocyte-macrophage differentiation should be tightly controlled to maintain lung integrity. In this study, we determined the effect of α-defensins on monocyte-macrophage differentiation and identified the molecular mechanism of this effect. The results of this study demonstrate that 2.5 µM of α-defensins inhibit the phosphorylation of ERK1/2 and STAT3 and suppress the expression of M2 macrophage markers, CD163 and CD206. In addition, a scratch assay shows that the high concentration of α-defensins inhibits cell movement by ~ 50%, and the phagocytosis assay using flow cytometry shows that α-defensins significantly reduce the bacterial phagocytosis rate of monocyte-derived macrophages (MDMs). To examine whether exogenous AAT is able to alleviate the inhibitory effect of α-defensins on macrophage function, we incubated MDMs with AAT prior to α-defensin treatment and demonstrate that AAT improves the migratory ability and phagocytic ability of MDMs compared with MDMs incubated only with α-defensins. Taken together, this study suggests that a high concentration of α-defensins inhibits the activation of ERK/STAT3 signaling, negatively regulates the expression of M2 macrophage markers, and impairs innate immune function of macrophages.

Molecular dynamics simulations of human α-defensin 5 (HD5) crossing gram-negative bacterial membrane.

Human α-defensin 5 (HD5) is a cationic antimicrobial peptide exhibiting a wide range of antimicrobial activities. It plays an important role in mucosal immunity of the small intestine. HD5 exerts its bactericidal activities through multiple mechanisms, one of which involves HD5 inducing the formation of pores in the bacterial membrane, subsequently allowing the peptide to enter the bacterial cytoplasm. Nevertheless, the precise molecular intricacies underlying its bactericidal mechanisms remain inadequately understood. In this work, the Potential of Mean Force (PMF) was computed to delve into the energetic properties governing the movement of HD5 across the lipopolysaccharide (LPS) membrane, which is a representative model of the gram-negative bacterial membrane. Our findings indicate that the most favorable free energy is attained when HD5 binds to the surface of the LPS membrane. This favorable interaction is primarily driven by the strong interactions between arginine residues in HD5 and the charged head groups of LPS, serving as the predominant forces facilitating the adhesion of HD5 to the membrane. Our analysis reveals that a dimeric form of HD5 alone is sufficient to create a water-filled channel in the membrane; however, achieving the complete lysis of the gram-negative bacterial membrane requires higher-order oligomerization of HD5. Our results suggest that HD5 employs the toroidal pore formation mechanism to disrupt the integrity of the LPS membrane. Furthermore, we identified that the primary energy barrier obstructing HD5 from traversing the membrane is localized within the hydrophobic core of the membrane, which is also observed for other defensins. Additionally, our study demonstrates that a mixture of HD5-LPS leads to a thinning of the membrane. Taken together, this work provides a deeper insight into the molecular intricacies governing the behavior of HD5 as it translocates through the gram-negative bacterial membrane.

FOXO inhibition rescues α-defensin expression in human intestinal organoids.

To mediate critical host-microbe interactions in the human small intestine, Paneth cells constitutively produce abundant levels of α-defensins and other antimicrobials. We report that the expression profile of these antimicrobials is dramatically askew in human small intestinal organoids (enteroids) as compared to that in paired tissue from which they are derived, with a reduction of α-defensins to nearly undetectable levels. Murine enteroids, however, recapitulate the expression profile of Paneth cell α-defensins seen in tissue. WNT/TCF signaling has been found to be instrumental in the regulation of α-defensins, yet in human enteroids exogenous stimulation of WNT signaling appears insufficient to rescue α-defensin expression. By stark contrast, forkhead box O (FOXO) inhibitor AS1842856 induced the expression of α-defensin mRNA in enteroids by >100,000-fold, restoring DEFA5 and DEFA6 to levels comparable to those found in primary human tissue. These results newly identify FOXO signaling as a pathway of biological and potentially therapeutic relevance for the regulation of human Paneth cell α-defensins in health and disease.

Regulation of dermal fibroblasts by human neutrophil peptides.

Human neutrophil peptides (HNPs) can induce cell proliferation and activation so their growth promoting activities may have potential clinical benefit. This study investigated the effects of HNPs on human dermal fibroblasts. Differential gene expression in HNP-treated cells and genes involved in regulating intracellular pathways were explored. Dermal fibroblasts were isolated from healthy neonatal foreskin and treated with HNPs in 2D and 3D cell culture systems. The expression of cell proliferation (Ki-67) gene and cell activation (COL1A1) gene plus their proteins was measured. Differential gene expression was determined using RNA-seq, and upregulated and downregulated genes were mapped onto intracellular pathways by KEGG analysis and Gene Ontology databases. HNPs significantly increased cell proliferation without cytotoxicity whilst HNP1 enhanced expression of COL1A1 and type I collagen production in 2D cells and 3D spheroids. RNA-sequencing analysis showed gene clustering with clear separation between HNP1-treated and control groups. A heatmap of top 50 differentially expressed genes was consistent among HNP1-treated samples. Most upregulated genes were associated with cell proliferation and activation as mapped into intracellular pathways whilst most downregulated genes belonged to steroid/arachidonic acid metabolism and inflammatory signaling pathways. HNP1 increased cell proliferation and activation but reduced lipid metabolism and inflammation.

The Function and Modification of Human Defensin 5.

The antibacterial and antiviral functions of human defensin 5 lay the foundation for its role as a core host protective component. In addition, HD5 also has the function of inhibiting tumor proliferation and immune regulation. However, everything has two sides; cytotoxic and proinflammatory properties may exist, while HD5 performs physiological functions. Accordingly, the modification and engineering of HD5 are particularly important. Therefore, this review summarizes the role of HD5 in various aspects of host defense, as well as modification of HD5 to ameliorate the biological activity, with a view to promoting the clinical use of HD5.

Novel diagnostic markers for periprosthetic joint infection: a systematic review.

Background: Identifying novel biomarkers that are both specific and sensitive to periprosthetic joint infection (PJI) has the potential to improve diagnostic accuracy and ultimately enhance patient outcomes. Therefore, the aim of this systematic review is to identify and evaluate the effectiveness of novel biomarkers for the diagnosis of PJI. Methods: We searched the MEDLINE, EMBASE, PubMed, and Cochrane Library databases from January 1, 2018, to September 30, 2022, using the search terms "periprosthetic joint infection," "prosthetic joint infection," or "periprosthetic infection" as the diagnosis of interest and the target index, combined with the term "marker." We excluded articles that mentioned established biomarkers such as CRP, ESR, Interleukin 6, Alpha defensin, PCT (procalcitonin), and LC (leucocyte cell count). We used the MSIS, ICM, or EBJS criteria for PJI as the reference standard during quality assessment. Results: We collected 19 studies that analyzed fourteen different novel biomarkers. Proteins were the most commonly analyzed biomarkers (nine studies), followed by molecules (three studies), exosomes (two studies), DNA (two studies), interleukins (one study), and lysosomes (one study). Calprotectin was a frequently analyzed and promising marker. In the scenario where the threshold was set at ≥50-mg/mL, the calprotectin point-of-care (POC) performance showed a high sensitivity of 98.1% and a specificity of 95.7%. Conclusion: None of the analyzed biomarkers demonstrated outstanding performance compared to the established parameters used for standardized treatment based on established PJI definitions. Further studies are needed to determine the benefit and usefulness of implementing new biomarkers in diagnostic PJI settings.

Association between α-defensin 5 and the expression and function of P-glycoprotein in differentiated intestinal Caco-2 cells.

α-Defensin 5 is known to be secreted by Paneth cells in the small intestine and plays an important role in eliminating pathogenic microorganisms. It has been reported that a decrease in α-defensin 5 level in the human small intestine is a risk of inflammatory bowel disease (IBD). Furthermore, P-glycoprotein (P-gp), a member of the ATP-binding cassette transporter superfamily, encoded by the ABCB1/MDR1 gene, plays an important role in the front line of host defense by protecting the gastrointestinal barrier from xenobiotic accumulation and may contribute to the development and persistence of IBD. Therefore, we examined the relationship between α-defensin 5 and the expression and function of P-gp using a human gastrointestinal model cell line (Caco-2). We found that MDR1 mRNA and P-gp protein level were increased in Caco-2 cells as well as α-defensin 5 secretion corresponded with the duration of cell culture. Exposure to α-defensin 5 peptide and recombinant tumor necrosis factor-α (TNF-α) significantly increased the expression and function P-gp. The mRNA levels of interleukin (IL)-8, IL-6, TNF-α, IL-1ß, and IL-2 were also increased following exposure to TNF-α, similar to α-defensin 5 treatment. These results suggest that α-defensin 5 regulates P-gp expression and function by increasing TNF-α expression in Caco-2 cells.

Alleviation of Hepatic Steatosis by Alpha-Defensin Is Associated with Enhanced Lipolysis.

Background and Objectives: The neutrophilic peptide, alpha-defensin, is considered an evolving risk factor intimately linked with lipid mobilization. It was previously linked to augmented liver fibrosis. Here, we assess a potential association between alpha-defensin and fatty liver. Materials and Methods: A cohort of transgenic C57BL/6JDef+/+ male mice that overexpress the human neutrophil-derived alpha-defensin in their polymorphonuclear neutrophils (PMNs) were assessed for liver steatosis and fibrosis development. Wild type (C57BL/6JDef.Wt) and transgenic (C57BL/6JDef+/+) mice were maintained on a standard rodent chow diet for 8.5 months. At the termination of the experiment, systemic metabolic indices and hepatic immunological cell profiling were assessed. Results: The Def+/+ transgenic mice exhibited lower body and liver weights, lower serum fasting glucose and cholesterol, and significantly lower liver fat content. These results were associated with impaired liver lymphocytes count and function (lower CD8, NK cells, and killing marker CD107a). The metabolic cage demonstrated dominant fat utilization with a comparable food intake in the Def+/+ mice. Conclusions: Chronic physiological expression of alpha-defensin induces favorable blood metabolic profile, increased systemic lipolysis, and decreased hepatic fat accumulation. Further studies are needed to characterize the defensin net liver effect.

Intestinal α-Defensins Play a Minor Role in Modulating the Small Intestinal Microbiota Composition as Compared to Diet.

The intestinal microbiota is at the interface between the host and its environment and thus under constant exposure to host-derived and external modulators. While diet is considered to be an important external factor modulating microbiota composition, intestinal defensins, one of the major classes of antimicrobial peptides, have been described as key host effectors that shape the gut microbial community. However, since dietary compounds can affect defensin expression, thereby indirectly modulating the intestinal microbiota, their individual contribution to shaping gut microbiota composition remains to be defined. To disentangle the complex interaction among diet, defensins, and small-intestinal microbiota, we fed wild-type (WT) mice and mice lacking functionally active α-defensins (Mmp7-/- mice) either a control diet or a Western-style diet (WSD) that is rich in saturated fat and simple carbohydrates but low in dietary fiber. 16S rDNA sequencing and robust statistical analyses identified that bacterial composition was strongly affected by diet while defensins had only a minor impact. These findings were independent of sample location, with consistent results between the lumen and mucosa of the jejunum and ileum, in both mouse genotypes. However, distinct microbial taxa were also modulated by α-defensins, which was supported by differential antimicrobial activity of ileal protein extracts. As the combination of WSD and defensin deficiency exacerbated glucose metabolism, we conclude that defensins only have a fine-tuning role in shaping the small-intestinal bacterial composition and might instead be important in protecting the host against the development of diet-induced metabolic dysfunction. IMPORTANCE Alterations in the gut microbial community composition are associated with many diseases, and therefore identifying factors that shape the microbial community under homeostatic and diseased conditions may contribute to the development of strategies to correct a dysbiotic microbiota. Here, we demonstrate that a Western-style diet, as an extrinsic parameter, had a stronger impact on shaping the small intestinal bacterial composition than intestinal defensins, as an intrinsic parameter. While defensins have been previously shown to modulate bacterial composition in young mice, our study supplements these findings by showing that defensins may be less important in adult mice that harbor a mature microbial community. Nevertheless, we observed that defensins did affect the abundance of distinct bacterial taxa in adult mice and protected the host from aggravated diet-induced glucose impairments. Consequently, our study uncovers a new angle on the role of intestinal defensins in the development of metabolic diseases in adult mice.

A Single Surface-Exposed Amino Acid Determines Differential Neutralization of AAV1 and AAV6 by Human Alpha-Defensins.

Adeno-associated viruses (AAVs) are being developed as gene therapy vectors due to their low pathogenicity and tissue tropism properties. However, the efficacy of these vectors is impeded by interactions with the host immune system. One potential immune barrier to vector transduction is innate immune host defense peptides, such as alpha-defensins, which are potent antiviral agents against other nonenveloped viruses. To investigate the interaction between AAVs and alpha-defensins, we utilized two closely related AAV serotypes, AAV1 and AAV6. Although their capsids differ by only six residues, these two serotypes exhibit markedly different tissue tropisms and transduction efficiencies. Using two abundant human alpha-defensins, enteric human defensin 5 (HD5) and myeloid human neutrophil peptide 1 (HNP1), we found both serotype-specific and defensin-specific effects on AAV infection. AAV6 infection was uniformly neutralized by both defensins at low micromolar concentrations; however, inhibition of AAV1 infection was profoundly influenced by the timing of defensin exposure to the virus relative to viral attachment to the cell. Remarkably, these differences in the defensin-dependent infection phenotype between the viruses are completely dictated by the identity of a single, surface-exposed amino acid (position 531) that varies between the two serotypes. These findings reveal a determinant for defensin activity against a virus with unprecedented precision. Furthermore, they provide a rationale for the investigation of other AAV serotypes not only to understand the mechanism of neutralization of defensins against AAVs but also to design more efficient vectors. IMPORTANCE The ability of adeno-associated viruses (AAVs) to infect and deliver genetic material to a range of cell types makes them favorable gene therapy vectors. However, AAV vectors encounter a wide variety of host immune factors throughout the body, which can impede efficient gene delivery. One such group of factors is the alpha-defensins, which are a key component of the innate immune system that can directly block viral infection. By studying the impact that alpha-defensins have on AAV infection, we found that two similar AAV serotypes (AAV1 and AAV6) have different sensitivities to inhibition. We also identified a single amino acid (position 531) that differs between the two AAV serotypes and is responsible for mediating their defensin sensitivity. By investigating the effects that host immune factors have on AAV infection, more efficient vectors may be developed to evade intervention by the immune system prior to gene delivery.

Human Neutrophil α-Defensins 1-3 Are Upregulated in the Microenvironment of Fibrotic Liver.

Background and Objectives: Neutrophil infiltration is an established signature of Non-Alcoholic Fatty Liver Disease (NAFLD) and Steatohepatitis (NASH). The most abundant neutrophilic peptide, alpha-defensin, is considered a new evolving risk factor in the inflammatory milieu, intimately involved in lipid mobilization. Our objective is to assess for potential association between alpha-defensin immunostains and NAFLD severity. Materials and Methods: We retrospectively investigated the liver biopsies of NAFLD/NASH patients, obtained at Hillel Yaffe Medical center between the years 2012 and 2016. Patients' characteristics were recorded, including relevant blood tests at the time of biopsy. Each biopsy was semi-quantitatively scored using NAFLD Activity Score (NAS) and NASH fibrosis stage. The biopsies were immunostained for alpha-defensin. The precipitation of alpha-defensin was correlated to NAS and fibrosis. Results: A total of 80 biopsies were evaluated: male ratio 53.2%, mean age 44.9 ± 13.2 years, 54 had fibrosis grades 0-2, and 26 were grade 3-4. Conventional metabolic risk factors were more frequent in the high-grade fibrosis group. Immunostaining for alpha-defensin disclosed higher intensity (a.u.) in grade 3-4 fibrosis relative to grades 0-2, 25% vs. 6.5%, p < 0.05, respectively. Moreover, alpha-defensin staining was nicely co-localized with fibrosis. Conclusions: In our group of NASH/NAFLD patients, higher metabolic risk profile was associated with higher fibrosis grade. Immunostaining for alpha-defensin showed patchy intense staining concordant with high fibrosis, nicely co-localized with histological fibrosis. Whether alpha-defensin is a profibrotic risk factor or merely risk marker for fibrosis must be clarified in future studies.

Role of Defensins in Tumor Biology.

Defensins have long been considered as merely antimicrobial peptides. Throughout the years, more immune-related functions have been discovered for both the α-defensin and ß-defensin subfamily. This review provides insights into the role of defensins in tumor immunity. Since defensins are present and differentially expressed in certain cancer types, researchers started to unravel their role in the tumor microenvironment. The human neutrophil peptides have been demonstrated to be directly oncolytic by permealizing the cell membrane. Further, defensins can inflict DNA damage and induce apoptosis of tumor cells. In the tumor microenvironment, defensins can act as chemoattractants for subsets of immune cells, such as T cells, immature dendritic cells, monocytes and mast cells. Additionally, by activating the targeted leukocytes, defensins generate pro-inflammatory signals. Moreover, immuno-adjuvant effects have been reported in a variety of models. Therefore, the action of defensins reaches beyond their direct antimicrobial effect, i.e., the lysis of microbes invading the mucosal surfaces. By causing an increase in pro-inflammatory signaling events, cell lysis (generating antigens) and attraction and activation of antigen presenting cells, defensins could have a relevant role in activating the adaptive immune system and generating anti-tumor immunity, and could thus contribute to the success of immune therapy.

Efficient recombinant production of mouse-derived cryptdin family peptides by a novel facilitation strategy for inclusion body formation.

BACKGROUND: A number of antimicrobial peptides (AMPs) hold promise as new drugs owing to their potent bactericidal activity and because they are often refractory to the development of drug resistance. Cryptdins (Crps) are a family of antimicrobial peptides found in the small intestine of mice, comprising six isoforms containing three sets of disulfide bonds. Although Crp4 is actively being investigated, there have been few studies to date on the other Crp isoforms. A prerequisite for detailed characterization of the other Crp isoforms is establishment of efficient sample preparation methods. RESULTS: To avoid degradation during recombinant expression of Crps in E. coli, co-expression of Crps with the aggregation-prone protein human α-lactalbumin (HLA) was used to promote the formation of stable inclusion bodies. Using this method, the production of Crp4 and Crp6 by the BL21 strain was effective, but the expression of other Crp isoforms was not as efficient. The results of a cell-free system study suggested that Crps were degraded, even though a substantial amounts of Crps were synthesized. Therefore, using the Origami™ B strain, we were able to significantly increase the expression efficiency of Crps by promoting the formation of erroneous intermolecular disulfide bonds between HLA and Crps, thereby promoting protein aggregation and inclusion body formation, which prevented degradation. The various Crp isoforms were successfully refolded in vitro and purified using reversed-phase HPLC. In addition, the yield was further improved by deformylation of formyl-Crps. We measured the antibacterial activity of Crps against both Gram-positive and Gram-negative bacteria. Each Crp isoform exhibited a completely different trend in antimicrobial activity, although conformational analysis by circular dichroism did not reveal any significant steric differences. CONCLUSION: In this study, we established a novel and efficient method for the production of the cryptdin family of cysteine-containing antimicrobial peptides. Additionally, we found that there were notable differences in the antibacterial activities of the various Crp family members. The expression system established in this study is expected to provide new insights regarding the mechanisms underlying the different antibacterial activities of the Crp family of peptides.

Identification of putative orthologs of clinically relevant antimicrobial peptides in the equine ocular surface and amniotic membrane.

OBJECTIVES: This study aimed to define the antimicrobial peptide (AMP) expression pattern of the equine ocular surface and amniotic membrane using a targeted qPCR approach and 3'Tag-sequencing. It will serve as a reference for future studies of ocular surface innate immunity and amniotic membrane therapies. PROCEDURES: A targeted qPCR approach was used to investigate the presence of orthologs for three of the most highly expressed beta-defensins (DEFB1, DEFB4B, and DEFB103A) of the human ocular surface and amniotic membrane in equine corneal epithelium, conjunctiva, and amniotic membrane. 3'Tag-sequencing was performed on RNA from one sample of corneal epithelium, conjunctiva, and amniotic membrane to further characterize their AMP expression. RESULTS: Equine corneal epithelium, conjunctiva, and amniotic membrane expressed DEFB1, DEFB4B, and DEFB103A. DEFB103A was expressed at the highest amounts in corneal epithelium, while DEFB4B was most highly expressed in conjunctiva and amniotic membrane. 3'Tag-sequencing from all three tissues confirmed these findings and identified expression of five additional beta-defensins, 11 alpha-defensins and two cathelicidins, with the alpha-defensins showing higher normalized read counts than the beta-defensins. CONCLUSIONS: This study identified AMP expression in the equine cornea and conjunctiva, suggesting that they play a key role in the protection of the equine eye, similar to the human ocular surface. We also determined that equine amniotic membrane expresses a substantial number of AMPs suggesting it could potentiate an antimicrobial effect as a corneal graft material. Future studies will focus on defining the antimicrobial activity of these AMPs and determining their role in microbial keratitis.

Salivary Proteomics Reveals Significant Changes in Relation to Alzheimer's Disease and Aging.

BACKGROUND: Aging is a risk factor for several pathologies as Alzheimer's disease (AD). Great interest exists, therefore, in discovering diagnostic biomarkers and indicators discriminating biological aging and health status. To this aim, omic investigations of biological matrices, as saliva, whose sampling is easy and non-invasive, offer great potential. OBJECTIVE: Investigate the salivary proteome through a statistical comparison of the proteomic data by several approaches to highlight quali-/quantitative variations associated specifically either to aging or to AD occurrence, and, thus, able to classify the subjects. METHODS: Salivary proteomic data of healthy controls under-70 (adults) and over-70 (elderly) years old, and over-70 AD patients, obtained by liquid chromatography/mass spectrometry, were analyzed by multiple Mann-Whitney test, Kendall correlation, and Random-Forest (RF) analysis. RESULTS: Almost all the investigated proteins/peptides significantly decreased in relation to aging in elderly subjects, with or without AD, in comparison with adults. AD subjects exhibited the highest levels of α-defensins, thymosin ß4, cystatin B, S100A8 and A9. Correlation tests also highlighted age/disease associated differences. RF analysis individuated quali-/quantitative variations in 20 components, as oxidized S100A8 and S100A9, α-defensin 3, P-B peptide, able to classify with great accuracy the subjects into the three groups. CONCLUSION: The findings demonstrated a strong change of the salivary protein profile in relation to the aging. Potential biomarkers candidates of AD were individuated in peptides/proteins involved in antimicrobial defense, innate immune system, inflammation, and in oxidative stress. RF analysis revealed the feasibility of the salivary proteome to discriminate groups of subjects based on age and health status.