Use of real-time, label-free analysis in revealing low-affinity binding to blood group antigens by Helicobacter pylori.

Infectious diseases are often initiated by microbial adherence that is mediated by the binding of attachment molecules, termed adhesins, to cell surface receptors on host cells. We present an experimental system, oblique-incidence reflectivity difference (OI-RD) microscopy, which allows the detection of novel, low-affinity microbial attachment mechanisms that may be essential for infectious processes. OI-RD microscopy was used to analyze direct binding of the oncopathogen, Helicobacter pylori ( H. pylori ) to immobilized glycoconjugates in real time with no need for labeling tags. The results suggest the presence of additional Lewis b blood group antigen (Le(b)) binding adhesins that have not been detected previously. OI-RD microscopy also confirmed the high-affinity binding of H. pylori outer-membrane protein BabA to Le(b). The OI-RD microscopy method is broadly applicable to real-time characterization of intact microbial binding to host receptors and offers new strategies to elucidate the molecular interactions of infectious agents with human host cells.

Placental site trophoblastic tumor presenting as a friable cervical mass.

PURPOSE OF INVESTIGATION: Placental site trophoblastic tumor (PSTT) is a rare variant of gestational trophoblastic neoplasia (GTN) and primarily composed of intermediate trophoblasts. In contrast to other forms of GTN, PSTT presents with only mildly elevated levels of beta-hCG and immunohistochemical staining of tissue samples is a helpful tool for diagnosis. CASE AND RESULTS: A 38-year-old gravida 3, parity 3 female presented to the emergency department after three weeks of abnormal vaginal bleeding. The uterus was mildly enlarged, midline, and mobile with minimal discomfort. A necrotic, friable mass was protruding through the cervical os and biopsies were obtained. The serum beta-hCG was 13 mIU/ml. Computed tomography revealed a mass within the endometrial cavity and cervix but no significant lymphatic adenopathy or metastasis. Immunohistochemical staining was positive for cytokeratin AE1/AE3, E-cadherin, human placental lactogen (hPL), and alpha inhibin. Surgery was considered curative. CONCLUSION: PSTT presenting as a friable cervical mass is uncommon. Biopsies of this mass lead to the correct diagnosis. Several immunohistochemical stains are suggested in the literature to evaluate for PSTT. Clinically, it is prudent for physicians to differentiate PSTT from other forms of GTN because of the poor response of PSTT to chemotherapy.

Attachment of Helicobacter pylori to human gastric epithelium mediated by blood group antigens.

Helicobacter pylori is associated with development of gastritis, gastric ulcers, and adenocarcinomas in humans. The Lewis(b) (Le(b)) blood group antigen mediates H. pylori attachment to human gastric mucosa. Soluble glycoproteins presenting the Leb antigen or antibodies to the Leb antigen inhibited bacterial binding. Gastric tissue lacking Leb expression did not bind H. pylori. Bacteria did not bind to Leb antigen substituted with a terminal GalNAc alpha 1-3 residue (blood group A determinant), suggesting that the availability of H. pylori receptors might be reduced in individuals of blood group A and B phenotypes, as compared with blood group O individuals.

Helicobacter pylori adhesin binding fucosylated histo-blood group antigens revealed by retagging.

The bacterium Helicobacter pylori is the causative agent for peptic ulcer disease. Bacterial adherence to the human gastric epithelial lining is mediated by the fucosylated Lewis b (Leb) histo-blood group antigen. The Leb-binding adhesin, BabA, was purified by receptor activity-directed affinity tagging. The bacterial Leb-binding phenotype was associated with the presence of the cag pathogenicity island among clinical isolates of H. pylori. A vaccine strategy based on the BabA adhesin might serve as a means to target the virulent type I strains of H. pylori.

[Subcutaneous gammaglobulin in common variable immunodeficiency. First experience in Spain]. / Gammaglobulina subcutánea en inmunodeficiencia común variable. Primera experiencia en España.

INTRODUCTION AND AIM: Weekly home-based subcutaneous immunoglobulin (SCIg) therapy is an alternative to intravenous immunoglobulin (IVIg) in the treatment of patients with primary antibody deficiencies. The objective of this study was to investigate the efficacy, safety, related quality of life and cost effectiveness of SCIg in our area. MATERIALS AND METHODS: Observational and descriptive study including paediatric patients with common variable immunodeficiency (CVID) receiving SCIg in our hospital (November 2006 to April 2008). Obtained data were compared with those from the last year with IVIg. RESULTS: Eleven patients with CVID were included. Median age was 15 years. The median trough serum IgG level was 622 mg/dl with IVIg. In patients in whom the SCIg dose was maintained or reduced compared to IVIg, the median trough serum IgG level was 850 mg/dl (p < 0.0005). Annual rate of infection was 2.22 per patient-year, without significant differences to IVIg (p = 0.212). There were 58 treatment-related adverse events (AE) reported with SCIg (45 local AE and 13 systemic AE). The most frequent treatment-related adverse event was infusion-site reaction. Switching to home-based subcutaneous IgG treatment led to significant improvements in quality of life and substantial cost savings. CONCLUSIONS: We conclude that subcutaneous administration of 16% SCIg is a safe and cost-effective alternative to IVIg for replacement therapy of primary antibody deficiencies. Median trough serum IgG levels were higher with SCIg. Local AE were common but mild and the incidence decreased over time. Quality of life is significantly improved.

Helicobacter pylori: molecular basis for host recognition and bacterial adherence.

The bacterium Helicobacter pylori is tropic for epithelial cells and the mucus layer in the stomach lining, and is associated with the development of gastritis, ulcers and possibly also gastric malignancies. Adherence to the gastric epithelial cells is mediated by fucosylated blood-group antigens associated with blood-group O phenotype, which could explain the higher prevalence of ulcerative disease in individuals with this blood group.

Glycine codon discrimination and the nucleotide in position 32 of the anticodon loop.

Using an in vitro protein-synthesizing system that allowed us to monitor separately the reading of each glycine codon, we have previously shown, that in constructs based on glycine tRNA1 from Escherichia coli the nature of the nucleotide in position 32 determines the ability of the anticodon UCC to discriminate between the glycine codons. Thus, with a U in position 32 the anticodon UCC discriminated according to the wobble rules, but with a C in this position it had lost its ability to discriminate. In the present paper we show that the same is true also for constructs based on mycoplasma glycine tRNA. When C32 in the wild type was changed to U32, the anticodon UCC discriminated between the glycine codons, while in wild type mycoplasma glycine tRNA it did not. Furthermore, when U32 was changed to C32 in glycine tRNA1(CCC), the anticodon CCC loses its ability to discriminate. We therefore conclude that the nature of the nucleotide in position 32 determines the discriminatory ability of both anticodons UCC and CCC in the glycine tRNA1 structural background, and that the same is true for the anticodon UCC in the mycoplasma glycine tRNA background.

Undiscriminating codon reading with adenosine in the wobble position.

To investigate the reading properties of adenosine in the wobble position we have used site-directed mutagenesis of the Escherichia coli glycine tRNA1(CCC) gene to substitute the nucleotide A in the wobble position of the corresponding tRNA. The effect of this change on the ability of the tRNA to discriminate between the nucleotides in the third position of the glycine codons has been investigated. We have compared the ability of the mutant glycine tRNA1(UCC) and glycine tRNA1(ACC) as well as the mycoplasma glycine tRNA(UCC) to read the glycine codons. The results showed that glycine tRNA1(ACC) unlike glycine tRNA1(UCC) did not fully discriminate between the glycine codons. These experiments were carried out using a new in vitro protein synthesizing system that allows us to monitor the reading of all four glycine codons. In the present paper we give a detailed description of this new in vitro system.

Codon reading properties of an unmodified transfer RNA.

We have previously shown that the Mycoplasma mycoides glycine tRNA (anticodon UCC) effectively reads the codons GGU and GGC in violation of the classic codon reading rules. We have attempted to elucidate what structural elements in this tRNA molecule confer this translational property and in the course of this investigation T7 RNA polymerase transcription of the corresponding gene was used to produce a tRNA devoid of modified nucleosides. Using an in vitro translation system the ability of this tRNA to read the 4 glycine codons (GGU, GGC, and GGG) was tested and it was shown to be as efficient as its normal, fully modified counterpart in the reading of all four codons. This result demonstrates that a tRNA devoid of modified nucleosides is able to efficiently sustain protein synthesis in vitro and, furthermore, that the normal modification pattern of the Mycoplasma glycine tRNA is not essential for the ability of this tRNA to read the glycine codons GGU and GGC effectively.

A new method to visualize the Helicobacter pylori-associated Lewis(b)-binding adhesin utilizing SDS-digested freeze-fracture replica labeling.

Freeze-fracture replica labeling has become a versatile tool to visualize both membrane components and other cell structures using SDS-replica cleaning before specific immunogold labeling of proteins or lipids. We report here for the first time the adoption and optimization of the method to studies of bacterial envelopes, as applied to structural analysis of the distribution of the unique BabA-adhesin of the gastric pathogen Helicobacter pylori. BabA is important for bacterial adherence to the human epithelial cell lining of the stomach. The adhesin was found to be distributed all over the bacterial cell surfaces. Our results suggest that the SDS-replica labeling allows assessment of protein localization to distinct cell compartments and analysis of co-localization with neighboring membrane structures.

Biochemical aspects of Helicobacter pylori colonization of the human gastric mucosa.

Unlike Helicobacter felis and other Helicobacter species of animal origin, Helicobacter pylori colonizes the lower gastric mucin layer of the stomach and adheres to human gastric epithelial cells. It is still an open question if H. pylori can interact with specific glycoconjugates in the gastric mucin layer. It is possible that colonization of the oral cavity is a first step of a complex infectious process. Most likely resting or slow growing cells of H. pylori interact with Lewis blood group substances in the gastric mucin layer and on the epithelium. This initial colonization is probably followed by binding to specific cell surface glycoconjugates (glycoproteins and glycolipids such as GM3) and specific sialylated or highly sulphated molecules such as cell surface sulphatides and heparan sulphate. H. pylori may also bind to specific phospholipid molecules such as phosphatidylethanolamine on the gastric cells. The adhesion process of certain strains can stimulate 'close' cell adhesion including pedestal formation similar to the phenomenon typical for a special class of enterovirulent Escherichia coli called attaching effacing E. coli. After gastric cell destruction by ammonia and H. pylori toxins (such as the vacuolating toxin) H. pylori may colonize the extracellular matrix (ECM). This phenomenon seems to include binding of cell surface sialic acid specific haemagglutinin to one ECM component, i.e. laminin. It is also likely that H. pylori may use similar events to penetrate intercellular junctions of gastric epithelial cells. These adhesion-penetration phenomena also involve coating of the microbe with host proteins to escape the host immune system and initiate a chronic lifelong infection process.

pH-dependent binding of Helicobacter pylori to pig gastric mucins.

A microtiter-based assay was developed to study the binding of Helicobacter pylori to pig gastric mucins purified by density-gradient centrifugation in CsCl/4 M guanidinium chloride. Binding of H. pylori was observed over the 'mucin' band as well as with 'low-density' components in the gradients, and binding to the latter was more pronounced when incubations were performed at 37 degrees C as compared to 20 degrees C. At a lower pH, binding of H. pylori (strain SVA 40) to the 'high-density' mucins from pig antrum was increased but binding to the 'low-density' ones was decreased. Binding of the P466 strain (Le(b)-specific) was mainly associated with the 'mucin' band, whereas the MO19 strain reacted preferentially with the 'low-density' components. In summary, H. pylori may bind to gastric mucins and the binding is influenced by temperature, pH and the repertoire of bacterial adhesins.

Secretory immunoglobulin A heavy chain presents Galbeta1-3GalNAc binding structures for Actinomyces naeslundii genospecies 1.

Adherence of Actinomyces naeslundii ATCC 12104 to hydroxyapatite beads coated with protein fractions of parotid saliva, obtained by gel filtration on S-200 HR columns, showed GalNAcbeta1-3Galalpha-O-ethyl-inhibitable binding to high-molecular-weight proteins (Strömberg et al., 1992). The present study investigates the nature of these high-molecular-weight binding proteins and determines their specific ability to mediate adherence to representative strains of Actinomyces species. Strain ATCC 12104 bound specifically in a lactose-inhibitable manner to the heavy chain of secretory immunoglobulin A (S-IgA), contained within a high-molecular-weight parotid protein fraction separated on SDS-PAGE and transferred to a solid membrane support. Lactose-inhibitable binding to the heavy chain of S-IgA from human colostrum was also demonstrated. Peanut agglutinin bound to the heavy chain of parotid and colostrum S-IgAs contained on solid support membranes, confirming the presence of Galbeta1-3GalNAc residues on these molecules. Both salivary and colostrum S-IgA aggregated with strain ATCC 12104 in a GalNAcbeta1-3Galalpha-O-ethyl-inhibitable fashion. Further separation of high-molecular-weight salivary proteins on S-500 HR columns showed GalNAcbeta1-3Galalpha-O-ethyl-inhibitable binding to both mucin- and S-IgA-containing fractions. The presence of S-IgA in salivary pellicles formed in vivo on teeth was demonstrated by Western blot analysis of pellicle extracts with anti-IgA antibodies. Among strains representing A. naeslundii genospecies 1 and 2 and A. odontolyticus, only those of genospecies 1 with a particular adherence profile showed efficient GalNAcbeta1-3Galalpha-O-ethyl-inhibitable binding to S-IgA. Thus, oligosaccharides on S-IgA may promote bacterial aggregation (or adherence) and provide a mechanism by which S-IgA can interact with bacteria without prior immunological challenge.

Methods for the Identification of H. pylori Host Receptors.

Bacterial attachment to host receptors is a prerequisite for colonization of epithelial cell surfaces, in particular, continuously renewing mucosal surfaces, such as the gastrointestinal tract. Microbes express adhesion molecules for interactions with eukaryotic cell surface proteins or glycoconjugates, such as glycoproteins and glycolipids (1). The combination of high receptor specificity (2) and restricted receptor distribution will target bacteria to specific tissues, i.e., cell populations. This is referred to as tissue tropism and partly determines the niche a bacterium is able to occupy. In addition, competition between bacterial species for space and nutrients selects for bacteria able to colonize specific niches. Bacteria unable to adhere to the epithelial cells and mucus lining will be exposed to the local nonspecific host defense mechanisms (such as peristalsis and turnover of the epithelial cell populations and the mucus layer) and eventually removed. The biological relevance of adherence as an initial step in the infectious process has focused interest to the structures involved in these processes. Bacterial adhesins and host receptors are both potential targets for novel antimicrobial drug design (3). Antimicrobial agents could be chemically coupled to soluble high-affinity receptor analogs and kill pathogens, such as H. pylori, once they are targeted by the complex. Soluble receptor analogs would competitively interfere with bacterial attachment, utilizing the same mechanism as naturally occurring scavenger molecules in human secretions, such as milk and saliva. Receptor analogs could be developed for high-affinity interactions and would thereby be efficient inhibitors at low concentrations. Both drug targeting and competitive adhesion inhibition receptor analogs could exhibit a higher specificity for the pathogenic microbes, circumventing the negative effects of broad spectrum antibiotics.

Atomic force microscopy measurements reveal multiple bonds between Helicobacter pylori blood group antigen binding adhesin and Lewis b ligand.

The strength of binding between the Helicobacter pylori blood group antigen-binding adhesin (BabA) and its cognate glycan receptor, the Lewis b blood group antigen (Le(b)), was measured by means of atomic force microscopy. High-resolution measurements of rupture forces between single receptor-ligand pairs were performed between the purified BabA and immobilized Le(b) structures on self-assembled monolayers. Dynamic force spectroscopy revealed two similar but statistically different bond populations. These findings suggest that the BabA may form different adhesive attachments to the gastric mucosa in ways that enhance the efficiency and stability of bacterial adhesion.

Oral administration of live Shigella vaccine candidates in rhesus monkeys show no evidence of competition for colonization and immunogenicity between different serotypes.

Live oral monovalent Shigella flexneri 2a vaccine candidates as well as bivalent formulations with Shigella sonnei were evaluated in a rhesus monkey model for colonization and immunogenicity. Freshly harvested suspensions of S. flexneri 2a vaccine candidates WRSf2G12 and WRSf2G15 as well as S. sonnei vaccine candidate WRSs3 were nasogastrically administered to groups of rhesus monkeys, Macaca mulatta, either in a monovalent form or when combined with each other. The animals were monitored daily for physical well-being, stools were subjected to quantitative colony immunoblot assays for bacterial excretion and blood and stools were evaluated for humoral and mucosal immune responses. No clinical symptoms were noted in any group of animals and the vaccine candidates were excreted robustly for 48-72h without significant changes in either the magnitude or duration of excretion when given as a monovalent or as bivalent mixtures. Similarly, immunological interferences were not apparent in the magnitude of humoral and mucosal immune responses observed toward Shigella-specific antigens when monkeys were fed monovalent or bivalent formulations. These results predict that a multivalent live oral vaccine of more than one serotype can have a favorable outcome for protection against shigellosis.

Bioengineered surfaces promote specific protein-glycan mediated binding of the gastric pathogen Helicobacter pylori.

Helicobacter pylori colonizes the gastric mucosa of half of the worlds population and persistent infection is related with an increase in the risk of gastric cancer. Adhesion of H. pylori to the gastric epithelium, which is essential for infection, is mediated by bacterial adhesin proteins that recognize specific glycan structures (Gly-R) expressed in the gastric mucosa. The blood group antigen binding adhesin (BabA) recognizes difucosylated antigens such as Lewis B (Leb), while the sialic acid binding adhesin (SabA) recognizes sialylated glycoproteins and glycolipids, such as sialyl-Lewis x (sLex). This work aimed to investigate whether these Gly-Rs (Leb and sLex) can attract and specifically bind H. pylori after immobilization on synthetic surfaces (self-assembled monolayers (SAMs) of alkanethiols on gold). Functional bacterial adhesion assays for (Gly-R)-SAMs were performed using H. pylori strains with different adhesin protein profiles. The results demonstrate that H. pylori binding to surfaces occurs via interaction between its adhesins and cognate (Gly-R)-SAMs and bound H. pylori maintains its characteristic rod-shaped morphology only during conditions of specific adhesin-glycan binding. These results offer new insights into innovative strategies against H. pylori infection based on the scavenging of bacteria from the stomach using specific H. pylori chelating biomaterials.

[Spectrum of primary immunodeficiencies in a tertiary hospital over a period of 10 years]. / Espectro de las inmunodeficiencias primarias en un hospital de tercer nivel en un periodo de 10 años.

INTRODUCTION: More than 200 primary immunodeficiencies (PID) have been described and about 60% present during childhood. Early diagnosis and treatment have been shown to improve patient outcome. AIM: Analysis of patients with a PID diagnosed in a paediatric tertiary care hospital-referral centre over a period of 10 years. PATIENTS AND METHODS: Medical records of all paediatric patients followed up in our unit were retrospectively reviewed. Clinical and epidemiological features, laboratory tests, therapy and outcome were analysed. RESULTS: One hundred and eighty nine patients were followed up in this period of time. Antibody disorders were the most common diagnosis. In our series, clinical presentation at diagnosis were: recurrent respiratory infections in selective IgA deficiency and common variable immunodeficiency (CVID) patients, failure to thrive and opportunistic infections (mainly viral infections) in patients with severe combined immunodeficiency (SCID), skin abscesses (Staphylococcus aureus, Serratia spp.) and complicated pneumonia (Aspergillus spp., Rhodococcus equi) in chronic granulomatous disease, congenital heart disease and consistent phenotype in 22q11 deletion syndrome, skin abscesses and ecthyma gangrenosum in severe congenital neutropenia and opportunistic infections and sepsis (Pseudomonas aeruginosa) in children with X-linked agammaglobulinaemia (XLA). Lymphoproliferative disorders were common in CVID. No malignancies were observed during this period. One patient with XLA developed chronic encephalitis. All patients with CVID and XLA were receiving immunoglobulin replacement therapy (8 intravenous and 14 (since 2006) subcutaneous route) and in all but two SCID patients, stem cell transplantation was performed. Outcome was good in most of them except 8 SCID (2 prior and 6 after transplantation), 3 Wiskott-Aldrich syndrome, 1 complete DiGeorge, 1 chronic granulomatous disease and 1 ataxia-telangiectasia patients who died during follow-up. CONCLUSION: The vast majority of patients included in this series presented with typical clinical features; therefore, basic knowledge of these entities in primary care and collaboration with hospital referral centres should allow a large number of PID in children to be diagnosed at an early stage, leading to proper treatment and monitoring, and therefore improvement of patient prognosis.