Human peripheral and gastric lymphocyte responses to Helicobacter pylori NapA and AphC differ in infected and uninfected individuals

CD4+ T cell count and HIV-1 viral load dynamics positively impacted by H. pylori infection in HIV-positive patients regardless of ART status in a high-burden setting

BACKGROUND

There is a widespread co-infection of HIV and Helicobacter pylori (H. pylori) globally, particularly in developing countries, and it has been suggested that this co-infection may affect the course of HIV disease. However, the interplay between H. pylori infection and HIV disease progression is not fully elucidated. In this study, we investigated the effect of H. pylori co-infection on CD4+ T cell count and HIV viral load dynamics in HIV-positive individuals in a high co-endemic setting.

METHODS

A comparative cross-sectional study was conducted among 288 HIV-positive and 175 HIV-negative individuals, both with and without H. pylori infection. Among HIV-positive participants, 195 were on antiretroviral therapy (ART) and 93 were ART-naïve. CD4+ T cell count and HIV-1 viral load were measured and compared between H. pylori-infected and -uninfected individuals, taking into account different HIV and ART status.

RESULT

Our study demonstrated that individuals infected with H. pylori had a significantly higher CD4+ T cell count compared to uninfected controls among both HIV-negative and HIV-positive participants, regardless of ART therapy. Conversely, HIV/H. pylori co-infected participants had lower HIV-1 viral load than those without H. pylori infection. Linear regression analysis further confirmed a positive association between H. pylori infection, along with other clinical factors such as BMI, ART, and duration of therapy, with CD4+ T cell count while indicating an inverse relationship with HIV-1 viral load in HIV-positive patients. Additionally, factors such as khat chewing, age and WHO clinical stage of HIV were associated with reduced CD4+ T cell count and increased HIV-1 viral load.

CONCLUSION

Our study demonstrates that H. pylori co-infection was associated with higher CD4+ T cell count and lower HIV-1 viral load in HIV-positive patients, regardless of ART status. These findings show a positive effect of H. pylori co-infection on the dynamics of HIV-related immunological and virological parameters. Further studies are needed to elucidate the underlying mechanisms of the observed effects.

The influence of Salvia cadmica Boiss. extracts on the M1/M2 polarization of macrophages primed with Helicobacter pylori lipopolysaccharide in conjunction with NF-kappa B activation, production of cytokines, phagocytic activity and total DNA methylation

ETHNOPHARMACOLOGICAL RELEVANCE

The large number of secondary derivatives have been isolated from the genus Salvia with about 700 species, and used in the pharmacopoeia throughout the world. Various biological properties of Salvia formulations have been reported including as antioxidant, antimicrobial, hypotensive, anti-hyperglycemia, anti-hyperlipidemia, anti-cancer, and skin curative. Salvia cadmica Boiss. root and aerial part extracts enriched with polyphenols are bactericidal towards gastric pathogen Helicobacter pylori (Hp) and diminish deleterious effects induced by Hp lipopolysaccharide (LPS) towards gastric epithelial cells.

AIM OF THIS STUDY

To examine the influence of S. cadmica extracts on the M1/M2 polarization of macrophages primed with Hp LPS vs standard LPS Escherichia coli (Ec), and the macrophage cytokine as well as phagocytic activity, which are affected during Hp infection.

MATERIAL AND METHODS

Macrophages derived from THP-1 human monocytes primed with LPS Hp/Ec and/or S. cadmica extracts, were examined for the biomarkers of activation (surface, cytoplasmic or soluble), and phagocytic capacity. The bone marrow macrophages of Caviaporcellus were used to determine the engulfment of Hp.

RESULTS

Priming of THP-1 cells (24h) with LPS Hp/Ec resulted in polarization of M1 macrophages, activation of nuclear factor kappa B, secretion of tumor necrosis factor (TNF)-α, interleukin (IL)-1 beta, macrophage chemotactic protein (MCP)-1, immunoregulatory IL-10, and production of reactive oxygen species. These effects were diminished after restimulation of cells with S. cadmica extracts. THP-1 macrophages exposed to studied extracts showed an increased phagocytic capacity, in conjunction with elevated CD11b/CD11d expression and enhanced production of inducible nitric oxide synthase. They also increased Hp engulfment by bone marrow macrophages. These effects were not related to a global DNA methylation.

CONCLUSIONS

S. cadmica extracts possess an immunomodulating activity, which might be useful in control of H. pylori LPS driven activity of macrophages.

Helicobacter pylori infection: Beyond gastric manifestations

Helicobacter pylori (H. pylori) is a bacterium that infects more than a half of world’s population. Although it is mainly related to the development of gastroduodenal diseases, several studies have shown that such infection may also influence the development and severity of various extragastric diseases. According to the current evidence, whereas this bacterium is a risk factor for some of these manifestations, it might play a protective role in other pathological conditions. In that context, when considered the gastrointestinal tract, H. pylori positivity have been related to Inflammatory Bowel Disease, Gastroesophageal Reflux Disease, Non-Alcoholic Fatty Liver Disease, Hepatic Carcinoma, Cholelithiasis, and Cholecystitis. Moreover, lower serum levels of iron and vitamin B12 have been found in patients with H. pylori infection, leading to the emergence of anemias in a portion of them. With regards to neurological manifestations, a growing number of studies have associated that bacterium with multiple sclerosis, Alzheimer’s disease, Parkinson’s disease, and Guillain-Barré syndrome. Interestingly, the risk of developing cardiovascular disorders, such as atherosclerosis, is also influenced by the infection. Besides that, the H. pylori-associated inflammation may also lead to increased insulin resistance, leading to a higher risk of diabetes mellitus among infected individuals. Finally, the occurrence of dermatological and ophthalmic disorders have also been related to that microorganism. In this sense, this minireview aims to gather the main studies associating H. pylori infection with extragastric conditions, and also to explore the main mechanisms that may explain the role of H. pylori in those diseases.

Gut-brain Axis and migraine headache: a comprehensive review

The terminology "gut-brain axis "points out a bidirectional relationship between the GI system and the central nervous system (CNS). To date, several researches have shown that migraine is associated with some gastrointestinal (GI) disorders such as Helicobacter pylori (HP) infection, irritable bowel syndrome (IBS), and celiac disease (CD). The present review article aims to discuss the direct and indirect evidence suggesting relationships between migraine and the gut-brain axis. However, the mechanisms explaining how the gut and the brain may interact in patients with migraine are not entirely clear. Studies suggest that this interaction seems to be influenced by multiple factors such as inflammatory mediators (IL-1β, IL-6, IL-8, and TNF-α), gut microbiota profile, neuropeptides and serotonin pathway, stress hormones and nutritional substances. Neuropeptides including CGRP, SP, VIP, NPY are thought to have antimicrobial impact on a variety of the gut bacterial strains and thus speculated to be involved in the bidirectional relationship between the gut and the brain. According to the current knowledge, migraine headache in patients harboring HP might be improved following the bacteria eradication. Migraineurs with long headache history and high headache frequency have a higher chance of being diagnosed with IBS. IBS and migraine share some similarities and can alter gut microflora composition and thereby may affect the gut-brain axis and inflammatory status. Migraine has been also associated with CD and the condition should be searched particularly in patients with migraine with occipital and parieto-occipital calcification at brain neuroimaging. In those patients, gluten-free diet can also be effective in reducing migraine frequency. It has also been proposed that migraine may be improved by dietary approaches with beneficial effects on gut microbiota and gut-brain axis including appropriate consumption of fiber per day, adhering to a low glycemic index diet, supplementation with vitamin D, omega-3 and probiotics as well as weight loss dietary plans for overweight and obese patients.

Differential modulation of Helicobacter pylori lipopolysaccharide-mediated TLR2 signaling by individual Pellino proteins

BACKGROUND

Eradication rates for current H. pylori therapies have fallen in recent years, in line with the emergence of antibiotic resistant infections. The development of therapeutic alternatives to antibiotics, such as immunomodulatory therapy and vaccines, requires a more lucid understanding of host-pathogen interactions, including the relationships between the organism and the innate immune response. Pellino proteins are emerging as key regulators of immune signaling, including the Toll-like receptor pathways known to be regulated by H. pylori. The aim of this study was to characterize the role of Pellino proteins in the innate immune response to H. pylori lipopolysaccharide.

MATERIALS AND METHODS

Gain-of-function and loss-of-function approaches were utilized to elucidate the role of individual Pellino proteins in the Toll-like receptor 2-mediated response to H. pylori LPS by monitoring NF-ĸB activation and the induction of proinflammatory chemokines. Expression of Pellino family members was investigated in gastric epithelial cells and gastric tissue biopsy material.

RESULTS

Pellino1 and Pellino2 positively regulated Toll-like receptor 2-driven responses to H. pylori LPS, whereas Pellino3 exerted a negative modulatory role. Expression of Pellino1 was significantly higher than Pellino3 in gastric epithelial cells and gastric tissue. Furthermore, Pellino1 expression was further augmented in gastric epithelial cells in response to infection with H. pylori or stimulation with H. pylori LPS.

CONCLUSIONS

The combination of low Pellino3 levels together with high and inducible Pellino1 expression may be an important determinant of the degree of inflammation triggered upon Toll-like receptor 2 engagement by H. pylori and/or its components, contributing to H. pylori-associated pathogenesis by directing the incoming signal toward an NF-kB-mediated proinflammatory response.

Dual role of Helicobacter and Campylobacter species in IBD: a systematic review and meta-analysis

OBJECTIVE

To conduct a comprehensive global systematic review and meta-analysis on the association between Helicobacter pylori infection and IBD. As bacterial antigen cross-reactivity has been postulated to be involved in this association, published data on enterohepatic Helicobacter spp (EHS) and Campylobacter spp and IBD was also analysed.

DESIGN

Electronic databases were searched up to July 2015 for all case-control studies on H. pylori infection/EHS/Campylobacter spp and IBD. Pooled ORs (P-OR) and 95% CIs were obtained using the random effects model. Heterogeneity, sensitivity and stratified analyses were performed.

RESULTS

Analyses comprising patients with Crohn's disease (CD), UC and IBD unclassified (IBDU), showed a consistent negative association between gastric H. pylori infection and IBD (P-OR: 0.43, p value <1e-10). This association appears to be stronger in patients with CD (P-OR: 0.38, p value <1e-10) and IBDU (P-OR: 0.43, p value=0.008) than UC (P-OR: 0.53, p value <1e-10). Stratification by age, ethnicity and medications showed significant results. In contrast to gastric H. pylori, non H. pylori-EHS (P-OR: 2.62, p value=0.001) and Campylobacter spp, in particular C. concisus (P-OR: 3.76, p value=0.006) and C. showae (P-OR: 2.39, p value=0.027), increase IBD risk.

CONCLUSIONS

H. pylori infection is negatively associated with IBD regardless of ethnicity, age, H. pylori detection methods and previous use of aminosalicylates and corticosteroids. Antibiotics influenced the magnitude of this association. Closely related bacteria including EHS and Campylobacter spp increase the risk of IBD. These results infer that H. pylori might exert an immunomodulatory effect in IBD.

Helicobacter pylori-Mediated Protection from Allergy Is Associated with IL-10-Secreting Peripheral Blood Regulatory T Cells

Helicobacter pylori infections are usually established in early childhood and continuously stimulate immunity, including T-helper 1 (Th1), Th17, and regulatory T-cell (Treg) responses, throughout life. Although known to be the major cause of peptic ulcer disease and gastric cancer, disease occurs in a minority of those who are infected. Recently, there has been much interest in beneficial effects arising from infection with this pathogen. Published data robustly show that the infection is protective against asthma in mouse models. Epidemiological studies show that H. pylori is inversely associated with human allergy and asthma, but there is a paucity of mechanistic data to explain this. Since Th1 and Treg responses are reported to protect against allergic responses, we investigated if there were links between the human systemic Th1 and Treg response to H. pylori and allergen-specific IgE levels. The human cytokine and T-cell responses were examined using peripheral blood mononuclear cells (PBMCs) from 49 infected and 58 uninfected adult patients. Concentrations of total and allergen-specific plasma IgE were determined by ELISA and ImmunoCAP assays. These responses were analyzed according to major virulence factor genotypes of the patients' colonizing H. pylori strains. An in vitro assay was employed, using PBMCs from infected and uninfected donors, to determine the role of Treg cytokines in the suppression of IgE. Significantly higher frequencies of IL-10-secreting CD4(+)CD25(hi) Tregs, but not H. pylori-specific Th1 cells, were present in the peripheral blood of infected patients. Total and allergen-specific IgE concentrations were lower when there was a strong Treg response, and blocking IL-10 in vitro dramatically restored IgE responses. IgE concentrations were also significantly lower when patients were infected with CagA(+) strains or those expressing the more active i1 form of VacA. The systemic IL-10(+) Treg response is therefore likely to play a role in H. pylori-mediated protection against allergy in humans.

Activation of Helicobacter Pylori Causes Either Autoimmune Thyroid Diseases or Carcinogenesis in the Digestive Tract

Helicobacter pylori has been implicated in stimulation of immune system, development of autoimmune endocrinopathies as autoimmune thyroiditis (AT) and on other hand induction of immunosupresion activates gastric and extra-gastric diseases such as gastric ulcer or cancer. It causes persistent lifelong infection despite local and systemic immune response. Our results indicate that Helicobacter pylori might cause inhibition of the specific cellular immune response in Helicobacter pylori-infected patients with or without autoimmune diseases such as AT. We cannot also declare the carcinogenic effect in oropharynx. However the association of any infection agents and cancerogenesis exists. The adherence of Helicobacter pylori expression and enlargement of benign lymphatic tissue and the high incidence of the DNA of Helicobacter pylori in laryngopharyngeal and oropharyngeal cancer is reality. LTT appears to be a good tool for detection of immune memory cellular response in patients with Helicobacter pylori infection and AT. All these complications of Helicobacter pylori infection can be abrogated by successful eradication of Helicobacter pylori.

Role of Toll-like receptors in Helicobacter pylori infection and immunity

The gram-negative bacterium Helicobacter pylori (H. pylori) infects the stomachs of approximately half of the world’s population. Although infection induces an immune response that contributes to chronic gastric inflammation, the response is not sufficient to eliminate the bacterium. H. pylori infection causes peptic ulcers, gastric cancer and mucosa-associated lymphoid tissue lymphoma. Disease outcome is linked to the severity of the host inflammatory response. Gastric epithelial cells represent the first line of innate immune defence against H. pylori, and respond to infection by initiating numerous cell signalling cascades, resulting in cytokine induction and the subsequent recruitment of inflammatory cells to the gastric mucosa. Pathogen recognition receptors of the Toll-like receptor (TLR) family mediate many of these cell signalling events. This review discusses recent findings on the role of various TLRs in the recognition of H. pylori in distinct cell types, describes the TLRs responsible for the recognition of individual H. pylori components and outlines the influence of innate immune activation on the subsequent development of the adaptive immune response. The mechanistic identification of host mediators of H. pylori-induced pathogenesis has the potential to reveal drug targets and opportunities for therapeutic intervention or prevention of H. pylori-associated disease by means of vaccines or immunomodulatory therapy.

Investigation of interleukin-10 promoter polymorphisms and interleukin-10 levels in children with irritable bowel syndrome

Background/Aims

The aim of this study was to investigate whether genetic variations at positions -1082, -819, and -592 in the interleukin (IL)-10 promoter affect IL-10 production in children with irritable bowel syndrome (IBS).

Methods

Ninety-four children with IBS and 102 children as healthy controls (HCs) were enrolled. Genomic DNA was extracted, and IL-10 -1082, -819, and -592 polymorphisms were detected by direct sequencing from all participants. Peripheral blood mononuclear cells (PBMCs) from 46 IBS children and 38 HCs were isolated and cultured with and without 5 ng/mL Escherichia coli lipopolysaccharide (LPS). IL-10 levels in the culture supernatants were measured by enzyme-linked immunosorbent assay.

Results

There were no significant differences in the distribution of IL-10 -1082, -819, and -592 polymorphisms or in the allele and haplotype frequencies between IBS children and HCs. PBMCs from children with IBS had significantly lower IL-10 levels after LPS stimulation than PBMCs from HCs (p=0.011); however, LPS-induced IL-10 levels in PBMCs with different genotypes of -819 and -592 polymorphisms were not significantly different between IBS patients and HCs.

Conclusions

Although significantly lower LPS-induced IL-10 production by PBMCs was noted, it is unlikely that IL-10 production was fully genetically determined in our IBS children. ClinicalTrials.gov identifier: NCT01131442.

The immunomodulatory properties of Helicobacter pylori confer protection against allergic and chronic inflammatory disorders

Chronic infection with the gastric bacterial pathogen Helicobacter pylori causes gastritis and predisposes carriers to a high risk of developing gastric and duodenal ulcers, gastric cancer, and gastric lymphoma, but has also recently been shown to protect against certain allergic and chronic inflammatory disorders. The immunomodulatory properties that allow the bacteria to persist for decades in infected individuals in the face of a vigorous, yet ultimately non-protective, innate, and adaptive immune response may at the same time confer protection against allergies, asthma, and inflammatory bowel diseases. Experimental evidence from mouse models suggests that H. pylori has evolved to skew the adaptive immune response toward immune tolerance rather than immunity, which promotes persistent infection on the one hand, and inhibits auto-aggressive and allergic T-cell responses on the other. Regulatory T-cells mediating peripheral immune tolerance have emerged as key cellular players in facilitating persistent infection as well as protection from allergies, in both observational studies in humans and experimental work in mice. Recent data suggest that H. pylori actively targets dendritic cells to promote tolerance induction. The findings discussed in this review raise the possibility of harnessing the immunomodulatory properties of H. pylori for the prevention and treatment of allergic and auto-immune diseases, and also provide new insights relevant for H. pylori-specific vaccine development.

Immunosuppressive proteins isolated from spiral and coccoid cytoplasmic solutions of Helicobacter pylori

The aim of this study was to investigate the antiproliferative proteins that probably have a role in Helicobacter pylori evade of immune response and cause chronic infection disease and also to see if coccoid form had a role in its chronicity. H. pylori strain VacA s2/m2 positive and CagA negative, from a gastric biopsy of a patient with peptic ulcer disease, was isolated and cultured in brucella agar. Both spiral and coccoid forms were harvested and ruptured by sonication. The cytoplasmic solutions of both forms were collected and their fractions obtained by gel chromatography and preparative polyacrylamide gel electrophoresis. The fractions were analyzed by MTT assay for their antiproliferative activity. We isolated two proteins with a significant dose dependent antiproliferative activity that analyzed with sodium dodecyl sulfate-polyacrylamide gel electrophoresis, one of them that was urease positive showed two bands with 61 and 27 kDa, which is resumed to urease of H. pylori, another consist of 57 and 63 kDa. Helicobacterpylori secret some proteins like urease that inhibit immune cells proliferation response against its antigens.

Small bowel homing T cells are associated with symptoms and delayed gastric emptying in functional dyspepsia

OBJECTIVES

Immune activation may have an important pathogenic role in the irritable bowel syndrome (IBS). While little is known about immunologic function in functional dyspepsia (FD), we have observed an association between cytokine secretion by peripheral blood mononuclear cells (PBMCs) and symptoms in IBS. Upper gastrointestinal inflammatory diseases are characterized by enhanced small bowel homing α4-, β7-integrin, chemokine receptor 9 (CCR9) positive T lymphocytes. We hypothesized that increased cytokine release and elevated circulating small bowel homing T cells are linked to the severity of symptoms in patients with FD. Thus, we aimed to (i) compare cytokine release in FD and healthy controls (HCs), (ii) quantify "gut homing" T cells in FD compared with HC and patients with IBS, and (iii) correlate the findings to symptom severity and gastric emptying.

METHODS

PBMC from 45 (Helicobacter pylori negative) patients with FD (Rome II) and 35 matched HC were isolated by density gradient centrifugation and cultured for 24 h. Cytokine production (tumor necrosis factor (TNF)-α, interleukin (IL)-1β, IL-6, IL-10) was measured by enzyme-linked immunosorbent assay. CD4+ α4β7+CCR9+ T cells were quantified by flow cytometry in FD, HC and 23 patients with IBS. Gastric emptying was measured by scintigraphy. Symptom severity was assessed utilizing the standardized Gastrointestinal Symptom Score.

RESULTS

FD patients had significantly higher TNF-α (107.2 ± 42.8 vs. 58.7 ± 7.4 pg/ml), IL-1β (204.8 ± 71.5 vs. 80.2 ± 17.4 pg/ml), and IL-10 (218 ± 63.3 vs. 110.9 ± 18.5 pg/ml) levels compared with HC, and enhanced gut homing lymphocytes compared with HC or IBS. Cytokine release and CD4+α4β7+CCR9+ lymphocytes were correlated with the symptom intensity of pain, cramps, nausea, and vomiting. Delayed gastric emptying was significantly associated (r = 0.78, P = 0.021) with CD4+α4β7+CCR9+ lymphocytes and IL-1β, TNF-α, and IL-10 secretion.

CONCLUSIONS

Cellular immune activation with increased small bowel homing T cells may be key factors in the clinical manifestations of H. pylori-negative FD.

Decreased interleukin-10 secretion by peripheral blood mononuclear cells in children with irritable bowel syndrome

BACKGROUND AND AIMS

The aim of the present study was to evaluate proinflammatory and anti-inflammatory cytokine levels in children with irritable bowel syndrome (IBS).

PATIENTS AND METHODS

Thirty-five children with IBS (17 diarrhea-predominant, 7 constipation-predominant, and 11 mixed type) and 25 healthy children as healthy controls (HCs) were enrolled. All of the participants completed a questionnaire recording the duration, severity, and associated academic and social influences. Peripheral blood mononuclear cells were isolated and cultured for 24 hours with and without 1 or 5 ng/mL Escherichia coli lipopolysaccharide (LPS). Cytokine production including tumor necrosis factor-α (TNF-α), interleukin (IL)-6, and IL-10 was measured using enzyme-linked immunosorbent assays.

RESULTS

Children with IBS revealed lower baseline and significantly lower IL-10 levels after LPS stimulation compared with HCs (P = 0.001). Although not to a significant level, TNF-α and IL-6 levels were higher in children with IBS compared with HCs. The IL-10 levels in patients with IBS with strong pain intensity were lower both in baseline and under 1 ng/mL LPS stimulation. The levels became significantly lower under 5 ng/mL LPS stimulation compared with those experiencing mild and moderate pain intensity (P = 0.025).

CONCLUSIONS

Our study suggests that children with IBS tend to produce lower amounts of the anti-inflammatory cytokine IL-10 at baseline and after LPS stimulation, implying that defects in immune modulation may contribute to IBS in children.

Lymphocyte proliferative response to Helicobacter pylori antigens in H. pylori-infected patients

Helicobacter pylori (Hp) contributes to the development of gastric and extra-gastric diseases such as autoimmune thyroiditis (AT), and causes persistent life-long infection despite local and systemic immune response. We determined the specific cellular immune response to Hp antigens and PWM (control mitogen) in two groups of Hp infected patients--group A (n = 21), involving patients with autoimmune thyroiditis and group B (n = 13) of patients without AT--using modified lymphocyte transformation test before and after eradication therapy in comparison with healthy controls (group C, n = 15). Immune reactivity to the majority of Hp antigens (aHp, hHp, HpAg, CagA) was significantly lower in group B before eradication therapy in comparison with healthy Hp negative controls. A significant increase in immune reactivity was observed in group B to certain Hp antigens after successful eradication. The same levels (but insignificant) of immune reactivity were shown in group A. Our results indicate that Hp can cause the inhibition of the specific cellular immune response in Hp infected patients with or without autoimmune diseases such as AT, which can be abrogated by successful eradication of Hp. Lymphocyte transformation test appears to be a good tool for detection of immune memory cellular response in patients with Hp infection.

Production and characterization of mouse monoclonal antibodies recognizing multiple subclasses of human IgG

Different IgG subclass profiles are produced in response to different antigenic stimuli in a variety of diseases. IgG subclass levels may reflect disease severity. Quantification of IgG subclasses depends on the availability of specific Monoclonal antibodies (MAbs). In the present study seven hybridoma clones producing MAbs reactive with multiple subclasses of human IgG were established. Splenocytes from Balb/c mice immunized with Fc fractions of human IgG1 or IgG2 myeloma proteins were fused with mouse myeloma cells. Fused cells were selected and cloned by limiting dilution assay. Antibody secreting cells were screened by Enzyme-linked immunosorbent assay (ELISA) and the specificity of secreted MAbs was further analyzed, using a panel of purified human myeloma paraproteins of different IgG subclasses by ELISA and immunoblotting. Cross-reactivity to immunoglobulins (Igs) of other species was studied by indirect ELISA using serum samples collected from 9 animals. The MAbs were found to react with triple IgG subclasses, including IgG1,2,4 (n=4) and IgG1,2,3 (n=3). Immunoblotting studies revealed recognition of linear (n=4) or conformational (n=3) epitopes by these MAbs. The most abundant cross-reactivity (71.4%) was observed with monkey Ig while no cross-reactivity was detected with hen and cat sera. The MAbs mostly displayed a restricted pattern of cross-reactivity and one of them did not bind to any of the animal sera tested. The affinity constant of 3 MAbs was measured by ELISA. Based on the data obtained from this study, mouse MAbs reactive with multiple human IgG subclasses are directed to a variety of immunogenic epitopes, mostly shared with IgG of other species. These MAbs are valuable tools for purification of non-reactive IgG subclasses through negative affinity chromatography. These MAbs could also provide an opportunity for epitope mapping of the Fc region of IgG, as well as serological phylogenetic studies.

Generation and Characterization of Mouse Hybridomas Secreting Monoclonal Antibodies Specific for Human IgG3

Mammalians express several subclasses of the IgG molecule. In human being there are four homologous IgG subclasses, each of which is structurally unique and has different functions. Quantification of IgG subclasses is fundamental to clinical assessment and diagnosis of many diseases as such assessments depends on the availability of subclassspecific antibodies (Abs), particularly monoclonal antibodies (MAbs). In the present study, we produced and characterized two murine MAbs specific for human IgG3 molecule. These MAbs were obtained by the fusion of myeloma cells with splenocytes from Balb/c mice immunized with heavy chain of a human IgG3 myeloma protein. Fused cells were selected in hypoxanthine, aminopterine and thymidine (HAT) medium and cloned by limiting dilution assay. Ab-secreting cells were screened by enzyme-linked immunosorbent assay (ELISA) and the specificity of secreted MAbs was further analyzed, using a panel of purified myeloma proteins by ELISA and immunoblotting. Two stable hybridomas designated 1F18G7 and 1F18A11 were obtained secreting MAbs specific for Fc fragment of human IgG3. None of these MAbs showed cross-reactivity with other immunoglobulin isotypes derived from human and nine other animals, except 1F18A11 which displayed a weak cross-reactivity with only dog serum. Immunoblotting results indicate that these MAbs react with linear epitope(s) located in the heavy chain of human IgG3 molecules. The affinity constant of 1F18G7 and 1F18A11 MAbs was found to be 0.81×10(9) Mol (-1) and 0.71×10(9) Mol (-1), respectively, as measured by ELISA. These two MAbs with relatively high affinity can be useful tools for quantification of IgG3 subclass levels in human serum.

Peroxiredoxins in bacterial antioxidant defense

Peroxiredoxins constitute an important component of the bacterial defense against toxic peroxides. These enzymes use reactive cysteine thiols to reduce peroxides with electrons ultimately derived from reduced pyridine dinucleotides. Studies examining the regulation and physiological roles of AhpC, Tpx, Ohr and OsmC reveal the multilayered nature of bacterial peroxide defense. AhpC is localized in the cytoplasm and has a wide substrate range that includes H2O2, organic peroxides and peroxynitrite. This enzyme functions in both the control of endogenous peroxides, as well as in the inducible defense response to exogenous peroxides or general stresses. Ohr, OsmC and Tpx are organic peroxide specific. Tpx is localized to the periplasm and can be involved in either constitutive peroxide defense or participate in oxidative stress inducible responses depending on the organism. Ohr is an organic peroxide specific defense system that is under the control of the organic peroxide sensing repressor OhrR. In some organisms Ohr homologs are regulated in response to general stress. Clear evidence indicates that AhpC, Tpx and Ohr are involved in virulence. The role of OsmC is less clear. Regulation of OsmC expression is not oxidative stress inducible, but is controlled by multiple general stress responsive regulators.

Immune activation in patients with irritable bowel syndrome

BACKGROUND AND AIMS

We set out to test the hypothesis that irritable bowel syndrome (IBS) is characterized by an augmented cellular immune response with enhanced production of proinflammatory cytokines. We further aimed to explore whether symptoms and psychiatric comorbidity in IBS are linked to the release of proinflammatory cytokines.

METHODS

We characterized basal and Escherichia coli lipopolysaccharide (LPS)-induced cytokine production in peripheral blood mononuclear cells (PBMCs) from 55 IBS patients (18 mixed-, 17 constipation-, 20 diarrhea-predominant) and 36 healthy controls (HCs). PBMCs were isolated by density gradient centrifugation and cultured for 24 hours with or without (1 ng/mL) LPS. Cytokine production (tumor necrosis factor [TNF]-alpha, interleukin [IL]-1beta, and IL-6) was measured by enzyme-linked immunosorbent assay. Abdominal symptoms and psychiatric comorbidities were assessed by using the validated Bowel Disease Questionnaire and the Hospital Anxiety and Depression Scale.

RESULTS

IBS patients showed significantly (P < .017) higher baseline TNF-alpha, IL-1beta, IL-6, and LPS-induced IL-6 levels compared with HCs. Analyzing IBS subgroups, all cytokine levels were significantly (P < .05) higher in diarrhea-predominant IBS (D-IBS) patients, whereas constipation-predominant IBS patients showed increased LPS-induced IL-1beta levels compared with HCs. Baseline TNF-alpha and LPS-induced TNF-alpha and IL-6 levels were significantly higher in patients reporting more than 3 bowel movements per day, urgency, watery stools, and pain associated with diarrhea compared with patients without these symptoms (all P < .05). LPS-induced TNF-alpha production was associated significantly (r = 0.59, P < .001) with anxiety in patients with IBS.

CONCLUSIONS

Patients with D-IBS display enhanced proinflammatory cytokine release, and this may be associated with symptoms and anxiety.

Regulation of Th-1 T cell-dominated immunity to Neisseria meningitidis within the human mucosa

Neisseria meningitidis is commonly carried asymptomatically in the upper respiratory tract and only occasionally invades the bloodstream and meninges to cause disease. Naturally acquired immunity appears protective but the nature of the cellular immune response within the mucosa is uncertain. We show that following in vitro stimulation with N. meningitidis serogroup B (MenB) antigens, approximately 66% of the dividing mucosal CD4(+)CD45RO(+) memory population express the Th1-associated IL18-R while the remainder express CRTH2, a Th2-associated marker. The pro-inflammatory bias of this anti-MenB response is not evident in blood, demonstrating compartmentalization at the induction site; and occurs in the presence or absence of lipopolysacharide indicating that these responses are already fully committed. Depletion of CD25(+) cells reveals suppression of the effector CD4(+) T cell response restricted to the mucosa and most marked in children (i.e. those at greatest risk of disease). Mucosal T-regulatory cell (Treg) activity is partially overcome by blocking the human glucocorticoid-induced TNF receptor (GITR) and is not seen following stimulation with antigens from another mucosal pathogen, influenza virus. Pro-inflammatory, antimeningococcal T cell responses may limit invasive disease at the mucosa but Treg induction while reducing immunopathological damage, may also restrict the effectiveness of the protective response, particularly in children.