Human β-defensin 3 peptide is increased and redistributed in Crohn's ileitis

Beta-defensin index: A functional biomarker for oral cancer detection

There is an unmet clinical need for a non-invasive and cost-effective test for oral squamous cell carcinoma (OSCC) that informs clinicians when a biopsy is warranted. Human beta-defensin 3 (hBD-3), an epithelial cell-derived anti-microbial peptide, is pro-tumorigenic and overexpressed in early-stage OSCC compared to hBD-2. We validate this expression dichotomy in carcinoma in situ and OSCC lesions using immunofluorescence microscopy and flow cytometry. The proportion of hBD-3/hBD-2 levels in non-invasively collected lesional cells compared to contralateral normal cells, obtained by ELISA, generates the beta-defensin index (BDI). Proof-of-principle and blinded discovery studies demonstrate that BDI discriminates OSCC from benign lesions. A multi-center validation study shows sensitivity and specificity values of 98.2% (95% confidence interval [CI] 90.3-99.9) and 82.6% (95% CI 68.6-92.2), respectively. A proof-of-principle study shows that BDI is adaptable to a point-of-care assay using microfluidics. We propose that BDI may fulfill a major unmet need in low-socioeconomic countries where pathology services are lacking.

Salivary Th17 cytokine, human β-defensin 1-3, and salivary scavenger and agglutinin levels in Crohn's disease

OBJECTIVES

Crohn's disease patients, who are prone to develop periodontal diseases, may carry genetic defects in their Th17 cytokine, human beta-defensin (hBD) 1-3, and salivary and scavenger agglutinin (SALSA) expressions. Biochemical composition of saliva reflects the oral consequences of systemic immune response modifications. Our aim was to evaluate the salivary Th17 cytokine, epithelial hBD 1-3, and SALSA levels in relation to Crohn's disease.

MATERIALS AND METHODS

This cross-sectional study included 42 Crohn's disease patients and 34 systemically healthy controls. Periodontal and dental indexes were measured, and stimulated saliva samples were collected. Salivary Th17 cytokine levels were analyzed by multiplex technique, and hBD 1-3 and SALSA levels by enzyme-linked immunosorbent assay.

RESULTS

There were 19 gingivitis and 11 initial periodontitis patients in the Crohn's disease group, and 15 gingivitis and 4 initial periodontitis in the control group. In comparison to controls, higher salivary Th17 cytokine levels were observed in Crohn's disease patients. No statistical difference was observed between Crohn's disease and control groups in terms of their salivary hBD 1-3 and SALSA levels. Based on the regression analysis, there is no independent association between Crohn's disease and salivary Th17 cytokine levels.

CONCLUSIONS

Crohn's disease does not relate to salivary antimicrobial hBD 1-3 or SALSA levels. While Crohn's disease patients have higher salivary Th17 cytokine levels in comparison to systemically healthy controls, an independent association between Crohn's disease and Th17 cytokine profile is still missing.

CLINICAL RELEVANCE

Diminished Th17 cytokine response in Crohn's disease, which might be related to genetic susceptibility, can be also visualized in saliva.

Infection and inflammation stimulate expansion of a CD74+ Paneth cell subset to regulate disease progression

Paneth cells (PCs), a specialized secretory cell type in the small intestine, are increasingly recognized as having an essential role in host responses to microbiome and environmental stresses. Whether and how commensal and pathogenic microbes modify PC composition to modulate inflammation remain unclear. Using newly developed PC-reporter mice under conventional and gnotobiotic conditions, we determined PC transcriptomic heterogeneity in response to commensal and invasive microbes at single cell level. Infection expands the pool of CD74+ PCs, whose number correlates with auto or allogeneic inflammatory disease progressions in mice. Similar correlation was found in human inflammatory disease tissues. Infection-stimulated cytokines increase production of reactive oxygen species (ROS) and expression of a PC-specific mucosal pentraxin (Mptx2) in activated PCs. A PC-specific ablation of MyD88 reduced CD74+ PC population, thus ameliorating pathogen-induced systemic disease. A similar phenotype was also observed in mice lacking Mptx2. Thus, infection stimulates expansion of a PC subset that influences disease progression.

Mechanisms and regulation of defensins in host defense

As a family of cationic host defense peptides, defensins are mainly synthesized by Paneth cells, neutrophils, and epithelial cells, contributing to host defense. Their biological functions in innate immunity, as well as their structure and activity relationships, along with their mechanisms of action and therapeutic potential, have been of great interest in recent years. To highlight the key research into the role of defensins in human and animal health, we first describe their research history, structural features, evolution, and antimicrobial mechanisms. Next, we cover the role of defensins in immune homeostasis, chemotaxis, mucosal barrier function, gut microbiota regulation, intestinal development and regulation of cell death. Further, we discuss their clinical relevance and therapeutic potential in various diseases, including infectious disease, inflammatory bowel disease, diabetes and obesity, chronic inflammatory lung disease, periodontitis and cancer. Finally, we summarize the current knowledge regarding the nutrient-dependent regulation of defensins, including fatty acids, amino acids, microelements, plant extracts, and probiotics, while considering the clinical application of such regulation. Together, the review summarizes the various biological functions, mechanism of actions and potential clinical significance of defensins, along with the challenges in developing defensins-based therapy, thus providing crucial insights into their biology and potential clinical utility.

Crohn’s disease: Why the ileum?

Crohn’s disease (CD) is an inflammatory bowel disease characterized by immune-mediated flares affecting any region of the intestine alternating with remission periods. In CD, the ileum is frequently affected and about one third of patients presents with a pure ileal type. Moreover, the ileal type of CD presents epidemiological specificities like a younger age at onset and often a strong link with smoking and genetic susceptibility genes. Most of these genes are associated with Paneth cell dysfunction, a cell type found in the intestinal crypts of the ileum. Besides, a Western-type diet is associated in epidemiological studies with CD onset and increasing evidence shows that diet can modulate the composition of bile acids and gut microbiota, which in turn modulates the susceptibility of the ileum to inflammation. Thus, the interplay between environmental factors and the histological and anatomical features of the ileum is thought to explain the specific transcriptome profile observed in CD ileitis. Indeed, both immune response and cellular healing processes harbour differences between ileal and non-ileal CD. Taken together, these findings advocate for a dedicated therapeutic approach to managing ileal CD. Currently, interventional pharmacological studies have failed to clearly demonstrate distinct response profiles according to disease site. However, the high rate of stricturing disease in ileal CD requires the identification of new therapeutic targets to significantly change the natural history of this debilitating disease.

Evaluation of human β‑defensins in the cerebrospinal fluid of suspected meningitis

Human β-defensins (HBDs) are an important class of antimicrobial peptides that have immunomodulatory functions; however, the role of HBDs have not been well explored in the pathogenesis of meningitis. A cross-sectional study was performed to explore the levels of HBD1, HBD2, HBD3, and HBD4 in the cerebrospinal fluid (CSF) of 176 suspected meningitis cases. CSF samples were first subjected to PCR analysis using a set of universal primers targeting a portion of the eubacteria 16S rRNA gene. The analysis demonstrated that 66 samples (37.5%) were PCR-positive, whilst 110 samples (62.5%) were PCR-negative. DNA sequence analysis of the PCR-positive products identified two broad categories of bacteria, Gram-negative (68.2%) and Gram-positive (31.8%). A total of 88 PCR-negative CSF samples showed abnormal leukocyte counts, glucose concentrations, and/or protein concentrations, and were considered abnormal (ABN). The remaining 22 CSF samples were considered normal (NOR). HBD1, HBD2, and HBD4 levels did not exhibit significant differences between PCR-positive, ABN, and NOR CSF samples. However, HBD3 levels were significantly higher in the ABN CSF samples than in the NOR CSF samples (P=0.005). HBD3 levels were also elevated in the PCR-positive CSF samples compared with the NOR CSF samples, but the difference was not significant (P=0.151). HBD2, HBD3, and HBD4 were correlated with leukocyte counts, glucose concentration, and protein concentration. In conclusion, HBD3 levels were significantly elevated in the CSF of suspected meningitis cases regardless of the cause of meningitis. The CSF levels of certain HBDs were affected by specific diagnostic laboratory parameters for meningitis, including leukocyte counts, glucose concentration, and protein concentration.

Inflammatory bowel disease-associated adherent-invasive Escherichia coli have elevated host-defense peptide resistance

Adherent-invasive Escherichia coli (AIEC) are isolated from inflammatory bowel disease (IBD) patients at a higher rate than from control patients. Using a collection of E. coli strains collected from Crohn's disease (CD), ulcerative colitis (UC), or non-IBD control patients, antibiotic and resistance to the antimicrobial peptides HBD-3 and LL-37 was assessed. Carriage of bacterial-encoded omptin protease genes was assessed by PCR and omptin protease activity was measured using a whole-cell based fluorescence assay. Elevated resistance to antibiotics and host defense peptides in IBD-associated AIEC were observed. IBD-associated strains showed increased (but statistically non-significant) antibiotic resistance. CD-associated strains showed greater (but statistically non-significant) resistance to HBD3-mediated killing while UC-associated strains showed statistically greater resistance to LL-37 mediated killing. High-level resistance to LL-37 was associated with carriage of omptin protease genes and with increased omptin protease activity. Antimicrobial host defense peptide resistance may be an adaptive feature of AIEC leading to enhanced pathogenesis during the initiation or progression of IBD.

Fecal HBD-2 and Claudin-3 may be potential biomarkers to predict the deterioration of necrotizing enterocolitis: A prospective study

BACKGROUND AND PURPOSE

Necrotizing enterocolitis (NEC) is a critical gastrointestinal disease. We aim to explore the value of fecal human β-defensin 2 (HBD-2), Claudin-3, high-mobility group box-1 protein (HMGB-1), and resistin-like molecule β (Relmβ) as well as some laboratory metrics to predict the deterioration of NEC.

METHODS

Infants diagnosed with NEC at Stage II were enrolled in our study. Those who progressed to Stage III were included in the Stage III group and the rest were included in the Stage II group. Clinical data and laboratory metrics of the infants were collected. Fecal samples of HBD2, HMGB-1, Claudin-3, and Relmβ collected during their enrollment were determined by using enzyme-linked immunosorbent assay (ELISA) kits. Student's t-test, the Mann-Whitney U test, the chi-square test, receiver operating characteristic (ROC), and logistic regression analysis were performed.

RESULTS

Sixty infants diagnosed with NEC at Stage II were enrolled in our study, with 27 in the Stage III group (n = 27) and 33 in the Stage II group (n = 33). Although many of these NEC cases were late preterm and term infants, the infants in the Stage III group had a lower gestational age (P < 0.05). The incidence of gestational diabetes mellitus, peritonitis, intestinal adhesion, and sepsis was higher and more infants in the Stage III group underwent surgeries (P < 0.05). The levels of HBD-2 and Claudin-3 were higher and neutrophil count was lower in the Stage III group than in the Stage II Group, and the area under the curve (AUC) was 0.754, 0,755, and 0.666, respectively (P < 0.05). HBD-2 ≥ 1649.02 ng/g and Claudin-3 ≥ 2488.71 pg/g were included in the multivariate stepwise logistic regression analysis (P < 0.05), and the AUC of the model was 0.805 (95% CI: 0.688-0.922).

CONCLUSION

Fecal HBD-2 and Claudin-3 may be potential biomarkers to predict the deterioration of NEC from Stage II to Stage III.

Human β-Defensin 2 and Its Postulated Role in Modulation of the Immune Response

Studies described so far suggest that human β-defensin 2 is an important protein of innate immune response which provides protection for the human organism against invading pathogens of bacterial, viral, fungal, as well as parasitical origin. Its pivotal role in enhancing immunity was proved in infants. It may also be considered a marker of inflammation. Its therapeutic administration has been suggested for maintenance of the balance of systemic homeostasis based on the appropriate composition of the microbiota. It has been suggested that it may be an important therapeutic tool for modulating the response of the immune system in many inflammatory diseases, offering new treatment modalities. For this reason, its properties and role in the human body discussed in this review should be studied in more detail.

Dysregulation of human beta-defensin-3 expression in the peripheral blood of patients with sepsis

Objectives:

Sepsis is a serious medical condition caused by the body’s systemic inflammatory response to infections. The antimicrobial peptides, human beta-defensins, play a key role in modulating host immune responses, and aberrant expression of human beta-defensins has been implicated in many infections and inflammatory diseases. However, little is known about the expression of human beta-defensin-3 in systemic infectious diseases.

Methods:

We investigated the gene expression and protein level of human beta-defensin-3 in peripheral whole blood from 107 participants—67 patients with sepsis and 40 healthy controls—and evaluated the feasibility of human beta-defensin-3 as an indicator for sepsis. Total RNA was extracted from peripheral blood samples, and relative mRNA expression of human beta-defensin-3 was determined by reverse transcription-quantitative polymerase chain reaction. Plasma concentration of human beta-defensin-3 was measured by enzyme-linked immunosorbent assay. Pearson’s correlation analysis was performed to assess the relationship between human beta-defensin-3 mRNA and protein levels. Receiver operating characteristic analysis was performed to evaluate the value of human beta-defensin-3 as a biomarker for sepsis.

Results:

Human beta-defensin-3 mRNA expression was significantly downregulated in sepsis patients compared to controls (p = 0.001). The mean fold change of mRNA expression (±standard error) was 0.82 ± 0.63 in sepsis patients and 1.39 ± 1.09 in controls. Plasma concentration of human beta-defensin-3 (pg/mL) was significantly lower in sepsis patients compared to healthy controls (p = 0.039). The mean protein concentration (±standard error) was 539.6 ± 39.4 in sepsis patients and 715.5 ± 53 in controls. There was a significant correlation between human beta-defensin-3 mRNA expression and the corresponding protein level in sepsis patients (r = 0.358, p = 0.04), but not in healthy controls (r = 0.124, p = 0.51). For discriminating sepsis patients from healthy controls, the area under the receiver operating characteristic curve was 0.722 (95% confidence interval: 0.597–0.847, p = 0.002) for human beta-defensin-3 mRNA and 0.689 (95% confidence interval: 0.557–0.827, p = 0.009) for human beta-defensin-3 protein.

Conclusion:

This is the first study to show the downregulation of human beta-defensin-3 gene expression and protein level in sepsis, which may contribute to the complex immunological imbalance in sepsis. The significant correlation between human beta-defensin-3 mRNA expression and protein concentration suggests that mRNA expression could be used to predict protein level. Our study also showed a potential role of human beta-defensin-3 as a blood-based biomarker for sepsis. More studies on the clinical significance of human beta-defensin-3 in sepsis could further support a biomarker development.

Beta defensin 3 enhances ovarian granulosa cell proliferation and migration via ERK1/2 pathway in vitro†

Antimicrobial peptides (AMPs) are regarded as host defense peptides that possess bactericidal activity as well as immunomodulatory function. However, the role of AMP in the mammalian ovary is unknown. In the present study, porcine granulosa cells were utilized in a cell model to study the role of porcine beta defensin 2 (pBD2; pDEFB4B) and 3 (pBD3; pDEFB103A) during ovarian follicular development. Granulosa cells were cultured in the absence and presence of 1, 10, and 50 μg/ml of pDEFB4B or pDEFB103A. After 24 h of treatment, pDEFB103A but not pDEFB4B stimulated granulosa cell proliferation in a concentration-dependent manner (P < 0.05). This effect was dependent on the stage of follicular development. In addition, transwell cell migration assay showed that in the presence of pDEFB103A (10 μg/ml), a 2.5-fold increase in cell migration was achieved. Furthermore, further study revealed that pDEFB103A increased the mRNA levels of cyclin D1 (CCND1) and proliferating cell nuclear antigen (PCNA), both associated with cell proliferation. To study the potential pathway involved in pDEFB103A-induced cell proliferation and migration, western blots were performed. It was found that pDEFB103A significantly increased the phosphorylated-ERK1/2 to nonphosphorylated ratio. Moreover, pretreatment with the U0126, a specific ERK1/2 phosphorylation inhibitor, suppressed PDEFB103A inducing GCs ERK1/2 phosphorylation, as well as proliferation and migration, suggesting that PDEFB103A may act via activating the ERK1/2 pathway. Furthermore, using a signal transduction pathway Elk-1 trans-reporting system, the activation of ERK1/2 pathway by PDEFB103A was further confirmed. Our data suggest that AMP may play a physiological role in the mammalian ovary.

Adaptation of adherent-invasive E. coli to gut environment: Impact on flagellum expression and bacterial colonization ability

The pathogenesis of Crohn's disease (CD) is multifactorial and involves genetic susceptibility, environmental triggers and intestinal microbiota. Adherent-invasive Escherichia coli (AIEC) are flagellated bacteria more prevalent in CD patients than in healthy subjects and promote chronic intestinal inflammation. We aim at deciphering the role of flagella and flagellin modulation by intestinal conditions. AIEC flagellum expression is required for optimal adhesion to and invasion of intestinal epithelial cells. Interestingly, differential flagellin regulation was observed between commensal E. coli (HS) and AIEC (LF82) strains: flagellum expression by AIEC bacteria, in contrast to that of commensal E. coli, is enhanced under intestinal conditions (the presence of bile acids and mucins). Flagella are involved in the ability of the AIEC LF82 strain to cross a mucus layer in vitro and in vivo, conferring a selective advantage in penetrating the mucus layer and reaching the epithelial surface. In a CEABAC10 mouse model, a non-motile mutant (LF82-ΔfliC) exhibits reduced colonization that is restored by a dextran sodium sulfate treatment that alters mucus layer integrity. Moreover, a mutant that continuously secretes flagellin (LF82-ΔflgM) triggers a stronger inflammatory response than the wild-type strain, and the mutant's ability to colonize the CEABAC10 mouse model is decreased. Overexpression of flagellin in bacteria in contact with epithelial cells can be detrimental to their virulence by inducing acute inflammation that enhances AIEC clearance. AIEC pathobionts must finely modulate flagellum expression during the infection process, taking advantage of their specific virulence gene regulation to improve their adaptability and flexibility within the gut environment.

An Update Review on the Paneth Cell as Key to Ileal Crohn's Disease

The Paneth cells reside in the small intestine at the bottom of the crypts of Lieberkühn, intermingled with stem cells, and provide a niche for their neighbors by secreting growth and Wnt-factors as well as different antimicrobial peptides including defensins, lysozyme and others. The most abundant are the human Paneth cell α-defensin 5 and 6 that keep the crypt sterile and control the local microbiome. In ileal Crohn's disease various mechanisms including established genetic risk factors contribute to defects in the production and ordered secretion of these peptides. In addition, life-style risk factors for Crohn's disease like tobacco smoking also impact on Paneth cell function. Taken together, current evidence suggest that defective Paneth cells may play the key role in initiating inflammation in ileal, and maybe ileocecal, Crohn's disease by allowing bacterial attachment and invasion.

Cervical Gene Delivery of the Antimicrobial Peptide, Human β-Defensin (HBD)-3, in a Mouse Model of Ascending Infection-Related Preterm Birth

Approximately 40% of preterm births are preceded by microbial invasion of the intrauterine space; ascent from the vagina being the most common pathway. Within the cervical canal, antimicrobial peptides and proteins (AMPs) are important components of the cervical barrier which help to prevent ascending vaginal infection. We investigated whether expression of the AMP, human β-defensin-3 (HBD3), in the cervical mucosa of pregnant mice could prevent bacterial ascent from the vagina into the uterine cavity. An adeno-associated virus vector containing both the HBD3 gene and GFP transgene (AAV8 HBD3.GFP) or control AAV8 GFP, was administered intravaginally into E13.5 pregnant mice. Ascending infection was induced at E16.5 using bioluminescent Escherichia coli (E. coli K1 A192PP-lux2). Bioluminescence imaging showed bacterial ascent into the uterine cavity, inflammatory events that led to premature delivery and a reduction in pups born alive, compared with uninfected controls. Interestingly, a significant reduction in uterine bioluminescence in the AAV8 HBD3.GFP-treated mice was observed 24 h post-E. coli infection, compared to AAV8 GFP treated mice, signifying reduced bacterial ascent in AAV8 HBD3.GFP-treated mice. Furthermore, there was a significant increase in the number of living pups in AAV HBD3.GFP-treated mice. We propose that HBD3 may be a potential candidate for augmenting cervical innate immunity to prevent ascending infection-related preterm birth and its associated neonatal consequences.

Specific gut microbiome members are associated with distinct immune markers in pediatric allogeneic hematopoietic stem cell transplantation

BACKGROUND

Increasing evidence reveals the importance of the microbiome in health and disease and inseparable host-microbial dependencies. Host-microbe interactions are highly relevant in patients receiving allogeneic hematopoietic stem cell transplantation (HSCT), i.e., a replacement of the cellular components of the patients' immune system with that of a foreign donor. HSCT is employed as curative immunotherapy for a number of non-malignant and malignant hematologic conditions, including cancers such as acute lymphoblastic leukemia. The procedure can be accompanied by severe side effects such as infections, acute graft-versus-host disease (aGvHD), and death. Here, we performed a longitudinal analysis of immunological markers, immune reconstitution and gut microbiota composition in relation to clinical outcomes in children undergoing HSCT. Such an analysis could reveal biomarkers, e.g., at the time point prior to HSCT, that in the future could be used to predict which patients are of high risk in relation to side effects and clinical outcomes and guide treatment strategies accordingly.

RESULTS

In two multivariate analyses (sparse partial least squares regression and canonical correspondence analysis), we identified three consistent clusters: (1) high concentrations of the antimicrobial peptide human beta-defensin 2 (hBD2) prior to the transplantation in patients with high abundances of Lactobacillaceae, who later developed moderate or severe aGvHD and exhibited high mortality. (2) Rapid reconstitution of NK and B cells in patients with high abundances of obligate anaerobes such as Ruminococcaceae, who developed no or mild aGvHD and exhibited low mortality. (3) High inflammation, indicated by high levels of C-reactive protein, in patients with high abundances of facultative anaerobic bacteria such as Enterobacteriaceae. Furthermore, we observed that antibiotic treatment influenced the bacterial community state.

CONCLUSIONS

We identify multivariate associations between specific microbial taxa, host immune markers, immune cell reconstitution, and clinical outcomes in relation to HSCT. Our findings encourage further investigations into establishing longitudinal surveillance of the intestinal microbiome and relevant immune markers, such as hBD2, in HSCT patients. Profiling of the microbiome may prove useful as a prognostic tool that could help identify patients at risk of poor immune reconstitution and adverse outcomes, such as aGvHD and death, upon HSCT, providing actionable information in guiding precision medicine.

Alpha-defensins (α-Defs) in Crohn's disease: decrease of ileal α-Def 5 via permanent methylation and increase in plasma α-Def 1-3 concentrations offering biomarker utility

An impaired expression of α-defensins (α-Defs) in the ileal mucosa and, conversely, increased levels in plasma, have been reported in Crohn's disease (CD). However, the specificity and correlation of these findings with the degree of inflammation are unclear. We aimed to characterize the concentration and utility of ileal and plasma α-Defs in CD and to analyse a potential epigenetic mechanism of α-Def expression. Peripheral blood samples and ileal biopsies were obtained from patients at disease onset (aCD), from those who achieved remission (iCD) and from two control groups (healthy controls and non-CD-aetiology ileitis patients). Plasma α-Defs 1-3 and 4 were detected by enzyme-linked immunosorbent assay (ELISA); α-Def 5 by immunolocalization. Methylation analysis of the α-Def 5 gene was performed using the MassARRAY EpiTYPER system. Plasma α-Defs 1-3 concentrations were significantly higher in aCD with ileal involvement (L1, L3) versus iCD or the control groups. The α-Defs 1-3 concentrations were also similar to healthy controls in patients with non-CD ileitis. There was a significant positive correlation between plasma α-Defs 1-3 levels in aCD and the endoscopic index, as well as with C-reactive protein (CRP) levels. The immunopositivity scoring showed significantly reduced α-Def 5 expression in ileal inflamed (aCD) versus non-inflamed mucosa (iCD and healthy controls). The α-Def 5 gene showed a higher methylation status in CD patients than controls, regardless of the inflammation. Plasma α-Defs 1-3 concentrations correlate with the degree of inflammation and appear to be specific biomarkers of ileal-CD at diagnosis. Ileal α-Def 5 expression is down-regulated permanently by methylation.

Early type I Interferon response induces upregulation of human β-defensin 1 during acute HIV-1 infection

HIV-1 is able to evade innate antiviral responses during acute infection to establish a chronic systemic infection which, in the absence of antiretroviral therapy (ART), typically progresses to severe immunodeficiency. Understanding these early innate immune responses against HIV-1 and their mechanisms of failure is relevant to the development of interventions to better prevent HIV-1 transmission. Human beta defensins (HBDs) are antibacterial peptides but have recently also been associated with control of viral replication. HBD1 and 2 are expressed in PBMCs as well as intestinal tissue, but their expression in vivo during HIV-1 infection has not been characterized. We demonstrate that during acute HIV-1 infection, HBD1 but not HBD2 is highly upregulated in circulating monocytes but returns to baseline levels during chronic infection. HBD1 expression in monocytes can be induced by HIV-1 in vitro, although direct infection may not entirely account for the increase in HBD1 during acute infection. We provide evidence that HIV-1 triggers antiviral IFN-α responses, which act as a potent inducer of HBD1. Our results show the first characterization of induction of an HBD during acute and chronic viral infection in humans. HBD1 has been reported to have low activity against HIV-1 compared to other defensins, suggesting that in vivo induced defensins may not significantly contribute to the robust early antiviral response against HIV-1. These data provide important insight into the in vivo kinetics of HBD expression, the mechanism of HBD1 induction by HIV-1, and the role of HBDs in the early innate response to HIV-1 during acute infection.

Acute Infectious Gastroenteritis Potentiates a Crohn's Disease Pathobiont to Fuel Ongoing Inflammation in the Post-Infectious Period

Crohn’s disease (CD) is a chronic inflammatory condition of diverse etiology. Exposure to foodborne pathogens causing acute gastroenteritis produces a long-term risk of CD well into the post-infectious period but the mechanistic basis for this ongoing relationship to disease onset is unknown. We developed two novel models to study the comorbidity of acute gastroenteritis caused by Salmonella Typhimurium or Citrobacter rodentium in mice colonized with adherent-invasive Escherichia coli (AIEC), a bacterial pathobiont linked to CD. Here, we show that disease activity in the post-infectious period after gastroenteritis is driven by the tissue-associated expansion of the resident AIEC pathobiont, with an attendant increase in immunopathology, barrier defects, and delays in mucosal restitution following pathogen clearance. These features required AIEC resistance to host defense peptides and a fulminant inflammatory response to the enteric pathogen. Our results suggest that individuals colonized by AIEC at the time of acute infectious gastroenteritis may be at greater risk for CD onset. Importantly, our data identify AIEC as a tractable disease modifier, a finding that could be exploited in the development of therapeutic interventions following infectious gastroenteritis in at-risk individuals.

Western societies have a disproportionately high rate of inflammatory bowel disease (IBD), with growing incidence especially in the adolescent population. A large body of evidence supports the view that bacteria in the gut participate in the pathophysiology of human bowel diseases. The unifying concept is chronic inflammation that is driven by microbial stimulation of the mucosal immune system. However, the mechanisms by which pathogenic or commensal microbes work in concert with each other and with host responses to perpetuate this inflammation is not well known. Adherent-invasive E. coli (AIEC) are Crohn’s disease (CD)-associated bacteria that are implicated in disease pathology. AIEC are pro-inflammatory and may play a central role in maintaining chronic inflammation in response to other CD risk factors, such as acute infectious gastroenteritis. Here, we show that indeed, acute infectious gastroenteritis creates an inflammatory environment in the gut that drives AIEC expansion and worsens disease severity. The increase in disease severity strictly correlates with this AIEC bloom because blocking this bloom by sensitizing AIEC to host defenses also improves the health status of the host. The long time period between recovery from acute gastroenteritis and new onset CD may allow for targeted interventions to mitigate the risk of CD in AIEC-positive individuals.

Functional impacts of the intestinal microbiome in the pathogenesis of inflammatory bowel disease

: The human intestinal microbiome plays a critical role in human health and disease, including the pathogenesis of inflammatory bowel disease (IBD). Numerous studies have identified altered bacterial diversity and abundance at varying taxonomic levels through biopsies and fecal samples of patients with IBD and diseased model animals. However, inconsistent observations regarding the microbial compositions of such patients have hindered the efforts in assessing the etiological role of specific bacterial species in the pathophysiology of IBD. These observations highlight the importance of minimizing the confounding factors associated with IBD and the need for a standardized methodology to analyze well-defined microbial sampling sources in early IBD diagnosis. Furthermore, establishing the linkage between microbiota compositions with their function within the host system can provide new insights on the pathogenesis of IBD. Such research has been greatly facilitated by technological advances that include functional metagenomics coupled with proteomic and metabolomic profiling. This review provides updates on the composition of the microbiome in IBD and emphasizes microbiota dysbiosis-involved mechanisms. We highlight functional roles of specific bacterial groups in the development and management of IBD. Functional analyses of the microbiome may be the key to understanding the role of microbiota in the development and chronicity of IBD and reveal new strategies for therapeutic intervention.

Human β-defensin-3 promotes intestinal epithelial cell migration and reduces the development of necrotizing enterocolitis in a neonatal rat model

BACKGROUND

The aim of this study was to investigate the effects of human β-defensin-3 (hBD3) on intestinal wound healing and in a neonatal rat model of necrotizing enterocolitis (NEC).

METHODS

Enterocyte migration and proliferation were detected in vitro and in vivo. The role of chemokine receptor CCR6 and its downstream signaling pathway was assessed. Newborn Sprague-Dawley rats were randomly divided into four groups: Control+NS, Control+hBD3, NEC+NS, and NEC+hBD3. Body weight, histological score, survival time, cytokines expression, and mucosal integrity were evaluated.

RESULTS

hBD3 could stimulate enterocyte migration, but not proliferation, both in cultured enterocytes and in the NEC model. Neutralizing antibody and small interfering RNA confirmed this stimulatory effect was mediated by CCR6. Furthermore, hBD3 induced Rho activation, myosin light chain 2 phosphorylation, and F-actin accumulation. The bactericidal activity of hBD3 was maintained throughout a broad pH range. Strikingly, hBD3 administration decreased the incidence of NEC, increased the survival rate, and reduced the severity of NEC. Moreover, hBD3 reduced the proinflammatory cytokines expression in ileum and serum and preserved the intestinal barrier integrity.

CONCLUSION

This study provided evidence that the antimicrobial peptide hBD3 might participate in intestinal wound healing by promoting enterocyte migration and show beneficial effects on newborn rats with NEC.

Amelioration of DSS-induced murine colitis by VSL#3 supplementation is primarily associated with changes in ileal microbiota composition

Inflammatory bowel diseases encompass gastrointestinal illnesses typified by chronic inflammation, loss of epithelial integrity and gastrointestinal microbiota dysbiosis. In an effort to counteract these characteristic perturbations, we used stem cells and/or a probiotic therapy in a murine model of Dextran Sodium Sulfate induced colitis to examine both their efficacy in ameliorating disease and impact on niche-specific microbial communities of the lower GI tract. Colitis was induced in C57BL/6 mice by administering 3% DSS in drinking water for 10 days prior to administering one of three treatment plans: daily probiotic (VSL#3) supplementation for 3 days, a single tail vein injection of 1x10 (6) murine mesenchymal stem cells, or both. Ileal, cecal and colonic sections were collected for microbiota and histological analyses. Microbiota profiling revealed distinct bacterial community compositions in the ileum, cecum and colon of control untreated animals, all of which were predicted in silico to be enriched for a number of discrete KEGG pathways, indicating compositional and functional niche specificity in healthy animals. DSS-treatment perturbed community composition in all three niches with ileal communities exhibiting the greatest change relative to control animals. Each treatment group exhibited treatment-specific alterations in microbiota composition in the lower GI tract, though disease scores were only improved in VSL#3-treated animals. The ileal microbiota were most profoundly altered in composition in this group of animals and characterized by significant Enterobacteriaceae enrichment compared with colitic mice (P<0.05).

Host defense peptide resistance contributes to colonization and maximal intestinal pathology by Crohn's disease-associated adherent-invasive Escherichia coli

Host defense peptides secreted by colonocytes and Paneth cells play a key role in innate host defenses in the gut. In Crohn's disease, the burden of tissue-associated Escherichia coli commonly increases at epithelial surfaces where host defense peptides concentrate, suggesting that this bacterial population might actively resist this mechanism of bacterial killing. Adherent-invasive E. coli (AIEC) is associated with Crohn's disease; however, the colonization determinants of AIEC in the inflamed gut are undefined. Here, we establish that host defense peptide resistance contributes to host colonization by Crohn's-associated AIEC. We identified a plasmid-encoded genomic island (called PI-6) in AIEC strain NRG857c that confers high-level resistance to α-helical cationic peptides and α- and β-defensins. Deletion of PI-6 sensitized strain NRG857c to these host defense molecules, reduced its competitive fitness in a mouse model of infection, and attenuated its ability to induce cecal pathology. This phenotype is due to two genes in PI-6, arlA, which encodes a Mig-14 family protein implicated in defensin resistance, and arlC, an OmpT family outer membrane protease. Implicit in these findings are new bacterial targets whose inhibition might limit AIEC burden and disease in the gut.

Spatial and temporal stability of paneth cell phenotypes in Crohn's disease: implications for prognostic cellular biomarker development

BACKGROUND

We previously demonstrated that morphologic defects of ileal Paneth cells correlate with multiple susceptible genetic variants, the presence of granuloma, and clinical outcome in Crohn's disease. These studies were performed using uninvolved areas of resection specimens. To develop Paneth cell phenotype as a prognostic biomarker in Crohn's disease, further characterization is necessary. Specifically, effects of disease activity, phenotype duration, and the minimal crypt number that would allow for accurate Paneth cell phenotyping are unknown.

METHODS

We compared Paneth cell phenotypes in (1) 46 cases with paired involved and uninvolved sections; (2) 36 cases with multiple ileal resections over time; (3) "virtual biopsies" by randomly selecting 10 to 60 crypts from 85 surgical cases where 250 crypts had been analyzed; and (4) 26 cases with resection and biopsy performed within 1 year.

RESULTS

In paired resection specimens, the Paneth cell phenotypes in the uninvolved areas correlated with those seen in involved areas (P < 0.0001) and also predicted the presence of granuloma (P = 0.042). Importantly, the Paneth cell phenotype remained stable over time (P < 0.0001). By mathematical analyses, a minimum of 40 crypts was required to generate results equivalent to those using resection specimens. Finally, there was good correlation in Paneth cell phenotypes in biopsy specimens and resection specimens obtained within 1 year (P = 0.0004).

CONCLUSIONS

Accurate Paneth cell phenotypes can be assessed using biopsy materials with the caveat that sufficient well-oriented crypts exist in the specimen. This advance will extend the potential clinical application of this novel stratification platform.

Human β-defensin 3 induces STAT1 phosphorylation, tyrosine phosphatase activity, and cytokine synthesis in T cells

The AMP hBD-3 stimulates numerous immune effector functions in myeloid cells and keratinocytes, predominantly through the MAPK signaling cascade. In contrast, hBD-3 was reported to neutralize the activation of T cells by antagonizing MAPK signaling initiated by SDF-1α through CXCR4. With the use of complementary proteomic and immunochemical approaches, we investigated possible stimulatory effects of hBD-3 on T cells and demonstrate that hBD-3 induces STAT1 tyrosine phosphorylation within 5 min yet is unable to induce MAPK activation. Inclusion of a PTPase inhibitor increased hBD-3-induced phosphorylation dramatically, suggesting that hBD-3 also stimulates PTPase activity concurrently. The increase in PTPase activity was confirmed by demonstrating that hBD-3 suppresses IFN-γ-induced STAT1 tyrosine phosphorylation but not STAT1 serine and ERK1/2 threonine phosphorylation and stimulates the translocation of SHP-2 into the nucleus within 15 min. The signaling pathways initiated by hBD-3 may lead to the observed enhancement of distinct T cell effector functions during TCR activation, such as the increase in IL-2 and IL-10, but not IFN-γ secretion. Thus, hBD-3 initiates distinct lineage-specific signaling cascades in various cells involved in host defense and induces a concurrent tyrosine kinase and tyrosine phosphatase signaling cascade that may activate simultaneously the targeted T cells and inhibit their response to other immune mediators. Furthermore, these results suggest that this evolutionarily conserved peptide, which exhibits a broad spectrum of antimicrobial and immunomodulatory activities, serves to integrate innate and adaptive immunity.