Characterization of annexin A1 glycan binding reveals binding to highly sulfated glycans with preference for highly sulfated heparan sulfate and heparin

Annexin A1 is a multifunctional, calcium-dependent phospholipid binding protein involved in a host of processes including inflammation, regulation of neuroendocrine signaling, apoptosis, and membrane trafficking. Binding of annexin A1 to glycans has been implicated in cell attachment and modulation of annexin A1 function. A detailed characterization of the glycan binding preferences of annexin A1 using carbohydrate microarrays and surface plasmon resonance served as a starting point to understand the role of glycan binding in annexin A1 function. Glycan array analysis identified annexin A1 binding to a series of sulfated oligosaccharides and revealed for the first time that annexin A1 binds to sulfated non-glycosaminoglycan carbohydrates. Using heparin/heparan sulfate microarrays, highly sulfated heparan sulfate/heparin were identified as preferred ligands of annexin A1. Binding of annexin A1 to heparin/heparan sulfate is calcium- but not magnesium-dependent. An in-depth structure-activity relationship of annexin A1-heparan sulfate interactions was established using chemically defined sugars. For the first time, a calcium-dependent heparin binding protein was characterized with such an approach. N-Sulfation and 2-O-sulfation were identified as particularly important for binding.

Racial/ethnic and socioeconomic disparities in the diagnosis and treatment of sleep-disordered breathing in children

OBJECTIVE

Although racial/ethnic and socioeconomic healthcare disparities in pediatric primary care are widely documented, little is known regarding health disparities for common otolaryngic conditions. Pediatric sleep-disordered breathing (SDB) is highly prevalent, associated with significant physical and neurocognitive sequelae, and a common reason for pediatric otolaryngology referral. We sought to synthesize information from published findings related to racial/ethnic and socioeconomic disparities in children with SDB.

METHODS

Qualitative systematic review of MEDLINE database for articles reporting on racial/ethnic or socioeconomic differences in prevalence, diagnosis or surgical treatment of SDB in children over 30 years.

RESULTS

Of 210 abstracts identified, 33 met inclusion criteria. 24 articles directly addressed differences in race/ethnicity and socioeconomic status, and 10 had findings which identified a disparity. Differences were identified in prevalence, sleep patterns, and sequelae of pediatric SDB (24/33) and in access to care and utilization of adenotonsillectomy (10/33). Black children (12/33) and children with socioeconomic deprivation (17/33) were the most common minority groups studied. Although conclusions were broad, common study findings showed: (1) children in racial/ethnic and socioeconomic minorities may have higher prevalence and greater risk for SDB, and (2) In the U.S., white children or children with private insurance are more likely to undergo adenotonsillectomy.

CONCLUSIONS

Racial/ethnic and socioeconomic disparities are prevalent among children with SDB. Disparities in multiracial populations and disparities in access to care, treatment, and utilization of services for pediatric SDB require more detailed investigation. Given the potential negative impact of SDB in children, as well as its economic consequences, the evaluation of disparities should be prioritized in health policy research.

Racial/ethnic and socioeconomic disparities in the prevalence and treatment of otitis media in children in the United States

OBJECTIVES

Although racial/ethnic and socioeconomic disparities in child health are prevalent, little is known about them within common pediatric otolaryngic problems. Otitis media (OM) is a frequent diagnosis in children, and tympanostomy tube placement is the most common surgical treatment for OM. We sought to identify current knowledge regarding racial/ethnic and socioeconomic disparities in children with OM or tympanostomy tube placement.

METHODS

Qualitative systematic review of MEDLINE database for U.S.-based articles reporting on racial/ethnic or socioeconomic disparities in diagnosis or surgical treatment of OM over the last 30 years.

RESULTS

Of 428 abstracts identified, 15 met inclusion criteria. Articles addressed OM prevalence (12 of 15), risk factors (9 of 15), and tympanostomy tube insertion (4 of 15). Minority racial/ethnic groups studied were Black (11 of 15), Hispanic (6 of 15), American Indian/Alaska Native (2 of 15), and Asian (1 of 15). Predominant findings showed: 1) the most common identified risk factor for OM is socioeconomic status; 2) considerable variability exists concerning racial/ethnic disparities in disease prevalence; and 3) White children are more likely to undergo tympanostomy tube insertion compared to Black or Hispanic children.

CONCLUSIONS

Racial/ethnic and socioeconomic disparities exist for the prevalence and treatment of children with OM. Socioeconomic deprivation increases the risk of OM in children. Despite the frequency of tympanostomy tube insertion in children in the United States, few studies have addressed inequalities in access or utilization of surgical therapy. Given the changing healthcare climate and the social and economic impact of OM in children, further investigation of racial/ethnic and socioeconomic disparities targeting access to surgical treatment of OM should take precedence in health services research.

Shotgun glycomics: a microarray strategy for functional glycomics

Major challenges of glycomics are to characterize a glycome and identify functional glycans as ligands for glycan-binding proteins (GBPs). To address these issues we have developed a general strategy termed shotgun glycomics. We focus on glycosphingolipids (GSLs), a challenging class of glycoconjugates recognized by toxins, antibodies, and GBPs. We derivatized GSLs extracted from cells with a heterobifunctional fluorescent tag suitable for covalent immobilization. Fluorescent GSLs were separated by multidimensional chromatography, quantified, and coupled to glass slides to create GSL shotgun microarrays. The microarrays were interrogated with cholera toxin, antibodies, and sera from patients with Lyme disease to identify biologically relevant GSLs that were subsequently characterized by mass spectrometry. Shotgun glycomics incorporating GSLs and potentially glycoprotein-derived glycans provides an approach to accessing the complex glycomes of animal cells and offers a strategy for focusing structural analyses on functionally significant glycans.

Progesterone receptor requires a co-chaperone for signalling in uterine biology and implantation

Embryo implantation is absolutely dependent on the preparation of the uterus to the receptive stage and attainment by the blastocyst of implantation competency. Co-ordinated effects of progesterone and oestrogen are essential for these processes and determine the window of implantation. In rodents, a generalized stromal edema occurs before blastocyst attachment followed by uterine luminal closure. This leads to apposition of the blastocyst trophectoderm against the luminal epithelium and ultimately attachment. Progesterone is essential for luminal closure, which must occur for successful implantation. More importantly, progesterone is critical for almost every stage of pregnancy, including ovulation, fertilization, implantation, decidualization and pregnancy maintenance. Progesterone exerts its effects on target tissues primarily via nuclear progesterone receptor (PR) whose optimal activity is potentiated by an immunophilin co-chaperone, FK-506 binding protein 4 (FKBP52). While mice lacking PR are infertile due to complete failure of ovulation, fertilization, and implantation, female mice with targeted deletion of the Fkbp52 gene are infertile specifically because of implantation failure resulting from compromised uterine receptivity. This review highlights the evolution of knowledge about progesterone signalling during early pregnancy. Future studies are likely to provide a better understanding of FKBP52-PR signalling in promoting uterine receptivity for implantation and may reveal new targets for improving infertility.

Mutational analysis of the carbohydrate binding activity of the tobacco lectin

At present the three-dimensional structure of the tobacco lectin, further referred to as Nictaba, and its carbohydrate-binding site are unresolved. In this paper, we propose a three-dimensional model for the Nictaba domain based on the homology between Nictaba and the carbohydrate-binding module 22 of Clostridium thermocellum Xyn10B. The suggested model nicely fits with results from circular dichroism experiments, indicating that Nictaba consists mainly of β-sheet. In addition, the previously identified nuclear localization signal is located at the top of the protein as a part of a protruding loop. Judging from this model and sequence alignments with closely related proteins, conserved glutamic acid and tryptophan residues in the Nictaba sequence were selected for mutational analysis. The mutant DNA sequences as well as the original Nictaba sequence have been expressed in Pichia pastoris and the recombinant proteins were purified from the culture medium. Subsequently, the recombinant proteins were characterized and their carbohydrate binding properties analyzed with glycan array technology. It was shown that mutation of glutamic acid residues in the C-terminal half of the protein did not alter the carbohydrate-binding activity of the lectin. In contrast, mutation of tryptophan residues in the N-terminal half of the Nictaba domain resulted in a complete loss of carbohydrate binding activity. These results suggest that tryptophan residues play an important role in the carbohydrate binding site of Nictaba.

Xenon Difluoride and the Nature of the Xenon-Fluorine Bond

Xenon reacts with fluorine to form XeF(2) which can be isolated before it reacts with fluorine to form XeF(4). The linear configuration of XeF(2) with the 2.00-A bond length and the vibrational force constants support the assignment of 10 electrons to the valence shell of xenon. Similar arguments support the assignment of 12 and 14 valence electrons respectively to xenon in XeF(4) and XeF(6).

Kinetics of Allosteric Inhibition In Vivo: a Quantitative Analysis with Synchronous Cultures of Blastocladiella emersonii

Negative feedback control of the arginine biosynthetic pathway of Blastocladiella emersonii was observed in vivo by conducting kinetic radioisotope incorporation experiments. Transient responses of arginine precursor pools to perturbations in the medium end product concentration allowed a quantitative description of the negative feedback associated with pathway control, indicated that the N(alpha)-acetyl-l-glutamate pool size was the controlled variable, and suggested that N(alpha)-acetyl-l-glutamate and l-ornithine were the products of a transacetylation reaction in which N(alpha)-acetyl-l-ornithine and glutamic acid were the reactants. The precursors to arginine biosynthesis were found to undergo two discrete disturbances in response to altering the exogenous arginine concentration only once. An increased supply of exogenous end product resulted in diminished radioactivity in the intracellular pools of arginine, ornithine, and acetyl-glutamate, but elevated the radioisotope content of the pool of N(alpha)-acetyl-l-ornithine. Conversely, a lowered concentration of end product in the medium caused a rise in the radioisotope content of all the precursor pools except that of N(alpha)-acetyl ornithine, in which the radioactivity fell. Examination of tracer distribution among the precursors in the absence of exogenous arginine showed the nonacetylated precursor pools to be about 30 times larger than those of the acetylated intermediates and placed upper limits on the pool sizes of two pathway members that were not isolated (N(alpha)-acetyl-l-glutamic-gamma-semialdehyde and N(alpha)-acetyl-l-glutamic-gamma-semiphosphate).

Carbohydrate recognition properties of human ficolins: glycan array screening reveals the sialic acid binding specificity of M-ficolin

Ficolins are oligomeric innate immune recognition proteins consisting of a collagen-like region and a fibrinogen-like recognition domain that bind to pathogen- and apoptotic cell-associated molecular patterns. To investigate their carbohydrate binding specificities, serum-derived L-ficolin and recombinant H- and M-ficolins were fluorescently labeled, and their carbohydrate binding ability was analyzed by glycan array screening. L-ficolin preferentially recognized disulfated N-acetyllactosamine and tri- and tetrasaccharides containing terminal galactose or N-acetylglucosamine. Binding was sensitive to the position and orientation of the bond between N-acetyllactosamine and the adjacent carbohydrate. No significant binding of H-ficolin to any of the 377 glycans probed could be detected, providing further evidence for its poor lectin activity. M-ficolin bound preferentially to 9-O-acetylated 2-6-linked sialic acid derivatives and to various glycans containing sialic acid engaged in a 2-3 linkage. To further investigate the structural basis of sialic acid recognition by M-ficolin, point mutants were produced in which three residues of the fibrinogen domain were replaced by their counterparts in L-ficolin. Mutations G221F and A256V inhibited binding to the 9-O-acetylated sialic acid derivatives, whereas Y271F abolished interaction with all sialic acid-containing glycans. The crystal structure of the Y271F mutant fibrinogen domain was solved, showing that the mutation does not alter the structure of the ligand binding pocket. These analyses reveal novel ficolin ligands such as sulfated N-acetyllactosamine (L-ficolin) and gangliosides (M-ficolin) and provide precise insights into the sialic acid binding specificity of M-ficolin, emphasizing the essential role of Tyr(271) in this respect.

Innate immune lectins kill bacteria expressing blood group antigen

The expression of ABO(H) blood group antigens causes deletion of cells that generate self anti-blood group antibodies, but this deletion limits adaptive immunity toward pathogens bearing cognate blood group antigens. To explore potential defense mechanisms against these pathogens, given such limitations in adaptive immunity, we screened for innate proteins that could recognize human blood group antigens. Here we report that two innate immune lectins, galectins-4 and -8, which are expressed in the intestinal tract, recognize and kill human blood group antigen-expressing E. coli, while failing to alter viability of other E. coli strains or other gram-negative or gram-positive organisms both in vitro and in vivo. Killing by both galectins-4 and -8 resides within their C-terminal domains, occurs rapidly and independently of complement, and is accompanied by disruption of membrane integrity. These results demonstrate that innate defense lectins can provide immunity against pathogens that display blood group self-antigens on their surface.

Use of glycan microarrays to explore specificity of glycan-binding proteins

Microarrays of defined glycans represent a high throughput approach to determining the specificity of lectins, or more generally glycan-binding proteins (GBPs). The utility of a glycan microarray is directly related to the number and variety of the glycans available on the printed surface for interrogation by GBPs. The Consortium for Functional Glycomics (CFG), funded by the National Institute of General Medical Sciences (NIGMS), has generated a glycan microarray available to the public as an investigator-driven resource, where hundreds of GBPs have been analyzed. Here we describe the methods generally used by the CFG to prepare glycan arrays and interrogate them with GBPs. We also describe our new approach to normalizing glycan microarray data derived from concentration-dependent analyses of GBP binding, and the application of this approach with the plant lectin Sambucus nigra agglutinin (SNA-I) and human galectin-8. The use of glycan microarrays with this approach readily generates a prediction of the glycan determinants required for high affinity binding by a GBP.

Antibodies against Manalpha1,2-Manalpha1,2-Man oligosaccharide structures recognize envelope glycoproteins from HIV-1 and SIV strains

Design of an envelope glycoprotein (Env)-based vaccine against human immunodeficiency virus type-1 (HIV-1) is complicated by the large number of N-linked glycans that coat the protein and serve as a barrier to antibody-mediated neutralization. Compared to normal mammalian glycoproteins, high-mannose-type glycans are disproportionately represented on the gp120 subunit of Env. These N-glycans serve as a target for a number of anti-HIV molecules that bind terminal alpha1,2-linked mannose residues, including lectins and the monoclonal antibody 2G12. We created a Saccharomyces cerevisiae glycosylation mutant, Deltamnn1Deltamnn4, to expose numerous terminal Manalpha1,2-Man residues on endogenous hypermannosylated glycoproteins in the yeast cell wall. Immunization of rabbits with whole cells from this mutant induced antibodies that bound to a broad range of Env proteins, including clade A, B, and C of HIV and simian immunodeficiency virus (SIV). The gp120 binding activity of these immune sera was due to mannose-specific immunoglobulin, as removal of high-mannose glycans and alpha1,2-linked mannoses from gp120 abrogated serum binding. Glycan array analysis with purified IgG demonstrated binding mainly to glycans with Manalpha1,2-Manalpha1,2-Man trisaccharides. Altogether, these data demonstrate the immunogenicity of exposed polyvalent Manalpha1,2-Manalpha1,2-Man structures on the yeast cell wall mannan and their ability to induce antibodies that bind to the HIV Env protein. The yeast strain and sera from this study will be useful tools for determining the type of mannose-specific response that is needed to develop neutralizing antibodies to the glycan shield of HIV.

Cation-independent mannose 6-phosphate receptor: a composite of distinct phosphomannosyl binding sites

The 300-kDa cation-independent mannose 6-phosphate receptor (CI-MPR), which contains multiple mannose 6-phosphate (Man-6-P) binding sites that map to domains 3, 5, and 9 within its 15-domain extracytoplasmic region, functions as an efficient carrier of Man-6-P-containing lysosomal enzymes. To determine the types of phosphorylated N-glycans recognized by each of the three carbohydrate binding sites of the CI-MPR, a phosphorylated glycan microarray was probed with truncated forms of the CI-MPR. Surface plasmon resonance analyses using lysosomal enzymes with defined N-glycans were performed to evaluate whether multiple domains are needed to form a stable, high affinity carbohydrate binding pocket. Like domain 3, adjacent domains increase the affinity of domain 5 for phosphomannosyl residues, with domain 5 exhibiting approximately 60-fold higher affinity for lysosomal enzymes containing the phosphodiester Man-P-GlcNAc when in the context of a construct encoding domains 5-9. In contrast, domain 9 does not require additional domains for high affinity binding. The three sites differ in their glycan specificity, with only domain 5 being capable of recognizing Man-P-GlcNAc. In addition, domain 9, unlike domains 1-3, interacts with Man(8)GlcNAc(2) and Man(9)GlcNAc(2) oligosaccharides containing a single phosphomonoester. Together, these data indicate that the assembly of three unique carbohydrate binding sites allows the CI-MPR to interact with the structurally diverse phosphorylated N-glycans it encounters on newly synthesized lysosomal enzymes.

Glycan microarray analysis of P-type lectins reveals distinct phosphomannose glycan recognition

The specificity of the cation-independent and -dependent mannose 6-phosphate receptors (CI-MPR and CD-MPR) for high mannose-type N-glycans of defined structure containing zero, one, or two Man-P-GlcNAc phosphodiester or Man-6-P phosphomonoester residues was determined by analysis on a phosphorylated glycan microarray. Amine-activated glycans were covalently printed on N-hydroxysuccinimide-activated glass slides and interrogated with different concentrations of recombinant CD-MPR or soluble CI-MPR. Neither receptor bound to non-phosphorylated glycans. The CD-MPR bound weakly or undetectably to the phosphodiester derivatives, but strongly to the phosphomonoester-containing glycans with the exception of a single Man7GlcNAc2-R isomer that contained a single Man-6-P residue. By contrast, the CI-MPR bound with high affinity to glycans containing either phospho-mono- or -diesters although, like the CD-MPR, it differentially recognized isomers of phosphorylated Man7GlcNAc2-R. This differential recognition of phosphorylated glycans by the CI- and CD-MPRs has implications for understanding the biosynthesis and targeting of lysosomal hydrolases.

Changes of the receptor-binding properties of influenza B virus B/Victoria/504/2000 during adaptation in chicken eggs

Selection of high-growth virus variants of strain B/Victoria/504/2000 by serial passage in eggs resulted in three amino acid substitutions, G141E, R162M, and D196Y, in the vicinity of the receptor-binding pocket of viral hemagglutinin. Virus variants containing the identified amino acid substitutions, individually or in various combinations, were constructed using reverse genetics and analyzed for their receptor-binding properties using glycan microarray platform. Three different patterns of virus binding were revealed. A low-growth virus variant, corresponding to the original egg-derived virus B/Victoria/504/2000 prior to acquisition of amino acid changes G141E, R162M, and D196Y, had a clear preference for the oligosaccharide chains terminated with alpha2-6-linked sialic acid with very weak binding of the glycans terminated with alpha2-3-linked sialic acid. Amino acid substitutions R162M and D196Y had similar effects, resulting in viruses that bound with high efficiency almost all terminally sialylated glycans represented on the array regardless of the type of glycosidic linkage. In contrast, substitution of G141E alone, or in combinations with the other two amino acid substitutions, significantly restricted virus glycan-binding capabilities. All virus variants possessing this substitution lost the ability to bind glycans with alpha2-6 glycosidic linkage as well as most of the glycans with alpha2-3 glycosidic linkage. Linear penta- and heptasaccharide chains represented at the non-reducing end by alpha2-3 sialylated Type-II motif (LacNAc) were the only structures bound with high affinity by the virus variants with G141E substitution. In all cases when the effects on virus binding of individual amino acid substitutions differed, the effect of R162M was subordinate to the effect of either G141E or D196Y.

Fluorescent glycosylamides produced by microscale derivatization of free glycans for natural glycan microarrays

A novel strategy for creating naturally derived glycan microarrays has been developed. Glycosylamines are prepared from free reducing glycans and stabilized by reaction with acryloyl chloride to generate a glycosylamide in which the reducing monosaccharide has a closed-ring structure. Ozonolysis of the protected glycan yields an active aldehyde, to which a bifunctional fluorescent linker is coupled by reductive amination. The fluorescent derivatives are easily coupled through a residual primary alkylamine to generate glycan microarrays. This strategy preserves structural features of glycans required for antibody recognition and allows development of natural arrays of fluorescent glycans in which the cyclic pyranose structure of the reducing-end sugar residue is retained.

Generation of a natural glycan microarray using 9-fluorenylmethyl chloroformate (FmocCl) as a cleavable fluorescent tag

Glycan microarray technology has become a successful tool for studying protein-carbohydrate interactions, but a limitation has been the laborious synthesis of glycan structures by enzymatic and chemical methods. Here we describe a new method to generate quantifiable glycan libraries from natural sources by combining widely used protease digestion of glycoproteins and Fmoc chemistry. Glycoproteins including chicken ovalbumin, bovine fetuin, and horseradish peroxidase (HRP) were digested by Pronase, protected by FmocCl, and efficiently separated by 2D-HPLC. We show that glycans from HRP glycopeptides separated by HPLC and fluorescence monitoring retained their natural reducing end structures, mostly core alpha1,3-fucose and core alpha1,2-xylose. After simple Fmoc deprotection, the glycans were printed on NHS-activated glass slides. The glycans were interrogated using plant lectins and antibodies in sera from mice infected with Schistosoma mansoni, which revealed the presence of both IgM and IgG antibody responses to HRP glycopeptides. This simple approach to glycopeptide purification and conjugation allows for the development of natural glycopeptide microarrays without the need to remove and derivatize glycans and potentially compromise their reducing end determinants.

Facile preparation of fluorescent neoglycoproteins using p-nitrophenyl anthranilate as a heterobifunctional linker

A facile preparation of neoglycoconjugates has been developed with a commercially available chemical, p-nitrophenyl anthranilate (PNPA), as a heterobifunctional linker. The two functional groups of PNPA, the aromatic amine and the p-nitrophenyl ester, are fully differentiated to selectively conjugate with glycans and other biomolecules containing nucleophiles. PNPA is efficiently conjugated with free reducing glycans via reductive amination. The glycan−PNPA conjugates (GPNPAs) can be easily purified and quantified by UV absorption. The active p-nitrophenyl ester in the GPNPA conjugates readily reacts with amines under mild conditions, and the resulting conjugates acquire strong fluorescence. This approach was used to prepare several fluorescent neoglycoproteins. The neoglycoproteins were covalently printed on activated glass slides and were bound by appropriate lectins recognizing the glycans.

Intravenous immunoglobulin contains a broad repertoire of anticarbohydrate antibodies that is not restricted to the IgG2 subclass

BACKGROUND

Specificities for carbohydrate IgG antibodies, thought to be predominantly of the IgG2 subclass, have never been broadly examined in healthy human subjects.

OBJECTIVE

To examine commercial intravenous immunoglobulin (IVIG) preparations for their ability to recognize a wide range of glycans and to determine the contribution of IgG2 to the binding pattern observed.

METHODS

We used a glycan microarray to evaluate IVIG preparations and a control mix of similar proportions of human myeloma IgG1 and IgG2 for binding to 377 glycans, courtesy of the Consortium for Functional Glycomics Core H. Glycans recognized were categorized using public databases for their likely cellular sources. IgG2 was depleted from IVIG by using immunoaffinity chromatography, and depletion was confirmed by using nephelometry and surface plasmon resonance.

RESULTS

Nearly half of the glycans bound IgG. Some of the glycans with the greatest antibody binding can be found in structures of human pathogenic bacteria (eg, Streptococcus pneumoniae, Mycobacterium tuberculosis, Vibrio cholera) and nonpathogenic bacteria, including LPS and lipoteichoic acid, capsular polysaccharides, and exopolysaccharides. Surprisingly, depletion of IgG2 had only a modest effect on anticarbohydrate recognition patterns compared with the starting IVIG preparation. Little to no binding activity was detected to human endogenous glycans, including tumor-associated antigens.

CONCLUSIONS

This novel, comprehensive analysis provides evidence that IVIG contains a much wider range than previously appreciated of anticarbohydrate IgG antibodies, including those recognizing both pathogenic and non-pathogen-associated prokaryotic glycans.

Novel fluorescent glycan microarray strategy reveals ligands for galectins

Galectin-1 (Gal-1) and galectin-3 (Gal-3) are widely expressed galectins with immunoregulatory functions in animals. To explore their glycan specificity, we developed microarrays of naturally occurring glycans using a bifunctional fluorescent linker, 2-amino-N-(2-aminoethyl)-benzamide (AEAB), directly conjugated through its arylamine group by reductive amination to free glycans to form glycan-AEABs (GAEABs). Glycans from natural sources were used to prepare over 200 GAEABs, which were purified by multidimensional high-pressure liquid chromatography and covalently immobilized onto N-hydroxysuccinimide-activated glass slides via their free alkylamine. Fluorescence-based screening demonstrated that Gal-1 recognizes a wide variety of complex N-glycans, whereas Gal-3 primarily recognizes poly-N-acetyllactosamine-containing glycans independent of N-glycan presentation. GAEABs provide a general solution to glycan microarray preparation from natural sources for defining the specificity of glycan-binding proteins.

Deletions of neuraminidase and resistance to oseltamivir may be a consequence of restricted receptor specificity in recent H3N2 influenza viruses

Background

Influenza viruses attach to cells via sialic acid receptors. The viral neuraminidase (NA) is needed to remove sialic acids so that newly budded virions can disperse. Known mechanisms of resistance to NA inhibitors include mutations in the inhibitor binding site, or mutations in the hemagglutinin that reduce avidity for sialic acid and therefore reduce the requirement for NA activity.

Results

Influenza H3N2 isolates A/Oklahoma/323/03 (Fujian-like), A/Oklahoma/1992/05 (California-like), and A/Oklahoma/309/06 (Wisconsin-like) lost NA activity on passage in MDCK cells due to internal deletions in the NA-coding RNA segment. The viruses grow efficiently in MDCK cells despite diminished NA activity. The full length NA enzyme activity is sensitive to oseltamivir but replication of A/Oklahoma/323/03 and A/Oklahoma/309/06 in MDCK cells was resistant to this inhibitor, indicating that NA is not essential for replication. There was no change in HA activity or sequence after the NA activity was lost but the three viruses show distinct, quite restricted patterns of receptor specificity by Glycan Array analysis. Extensive predicted secondary structure in RNA segment 6 that codes for NA suggests the deletions are generated by polymerase skipping over base-paired stem regions. In general the NA deletions were not carried into subsequent passages, and we were unable to plaque-purify virus with a deleted NA RNA segment.

Conclusion

H3N2 viruses from 2003 to the present have reduced requirement for NA when passaged in MDCK cells and are resistant to NA inhibitors, possibly by a novel mechanism of narrow receptor specificity such that virus particles do not self-aggregate. These viruses delete internal regions of the NA RNA during passage and are resistant to oseltamivir. However, deletions are independently generated at each passage, suggesting that virus with a full length NA RNA segment initiates the first round of infection.

Glycan reductive isotope labeling for quantitative glycomics

Many diseases and disorders are characterized by quantitative and/or qualitative changes in complex carbohydrates. Mass spectrometry methods show promise in monitoring and detecting these important biological changes. Here we report a new glycomics method, termed glycan reductive isotope labeling (GRIL), where free glycans are derivatized by reductive amination with the differentially coded stable isotope tags [(12)C(6)]aniline and [(13)C(6)]aniline. These dual-labeled aniline-tagged glycans can be recovered by reverse-phase chromatography and can be quantified based on ultraviolet (UV) absorbance and relative ion abundances. Unlike previously reported isotopically coded reagents for glycans, GRIL does not contain deuterium, which can be chromatographically resolved. Our method shows no chromatographic resolution of differentially labeled glycans. Mixtures of differentially tagged glycans can be directly compared and quantified using mass spectrometric techniques. We demonstrate the use of GRIL to determine relative differences in glycan amount and composition. We analyze free glycans and glycans enzymatically or chemically released from a variety of standard glycoproteins, as well as human and mouse serum glycoproteins, using this method. This technique allows linear relative quantitation of glycans over a 10-fold concentration range and can accurately quantify sub-picomole levels of released glycans, providing a needed advancement in the field of glycomics.

Related lectins from snowdrop and maize differ in their carbohydrate-binding specificity

Searches in an EST database from maize revealed the expression of a protein related to the Galanthus nivalis (GNA) agglutinin, referred to as GNA(maize). Heterologous expression of GNA(maize) in Pichia pastoris allowed characterization of the first nucleocytoplasmic GNA homolog from plants. GNA(maize) is a tetrameric protein which shares 64% sequence similarity with GNA. Glycan microarray analyses revealed important differences in the specificity. Unlike GNA, which binds strongly to high-mannose N-glycans, the lectin from maize reacts almost exclusively with more complex glycans. Interestingly, GNA(maize) prefers complex glycans containing beta1-2 GlcNAc residues. The obvious difference in carbohydrate-binding properties is accompanied by a 100-fold reduced anti-HIV activity. Although the sequences of GNA and GNA(maize) are clearly related they show only 28% sequence identity. Our results indicate that gene divergence within the family of GNA-related lectins leads to changes in carbohydrate-binding specificity, as shown on N-glycan arrays.

Role of cellular heparan sulfate proteoglycans in infection of human adenovirus serotype 3 and 35

Species B human adenoviruses (Ads) are increasingly associated with outbreaks of acute respiratory disease in U.S. military personnel and civil population. The initial interaction of Ads with cellular attachment receptors on host cells is via Ad fiber knob protein. Our previous studies showed that one species B Ad receptor is the complement receptor CD46 that is used by serotypes 11, 16, 21, 35, and 50 but not by serotypes 3, 7, and 14. In this study, we attempted to identify yet-unknown species B cellular receptors. For this purpose we used recombinant Ad3 and Ad35 fiber knobs in high-throughput receptor screening methods including mass spectrometry analysis and glycan arrays. Surprisingly, we found that the main interacting surface molecules of Ad3 fiber knob are cellular heparan sulfate proteoglycans (HSPGs). We subsequently found that HSPGs acted as low-affinity co-receptors for Ad3 but did not represent the main receptor of this serotype. Our study also revealed a new CD46-independent infection pathway of Ad35. This Ad35 infection mechanism is mediated by cellular HSPGs. The interaction of Ad35 with HSPGs is not via fiber knob, whereas Ad3 interacts with HSPGs via fiber knob. Both Ad3 and Ad35 interacted specifically with the sulfated regions within HSPGs that have also been implicated in binding physiologic ligands. In conclusion, our findings show that Ad3 and Ad35 directly utilize HSPGs as co-receptors for infection. Our data suggest that adenoviruses evolved to simulate the presence of physiologic HSPG ligands in order to increase infection.

In this study, we attempted to identify binding receptors that are used by the two human adenovirus (Ad) serotypes 3 and 35. Ad3 uses yet-unknown receptors and is one of the most common Ads causing epidemic conjunctivitis, and respiratory and gastrointestinal diseases. Ad35 uses the complement receptor CD46 as an attachment receptor and mainly causes infections of the kidney and urinary tract. We utilized novel high-throughput techniques in combination with the recombinant viral proteins (fiber knobs), which mediate the initial interaction of Ads with host cells. We found that both serotypes interacted with cellular heparan sulfate proteoglycans (HSPGs). In subsequent assays, we show that HSPGs were not major receptors, but acted as low-affinity co-receptors for both Ad3 and Ad35. Ad3 and Ad35 used different viral proteins in order to interact with HSPGs. Both serotypes, however, used the same regions within HSPGs that show high levels of sulfation and are important for binding of extracellular located physiologic ligands. In summary, we show that Ad3 and Ad35 evolved to “highjack” yet another class of cellular surface molecules that are essential for the function of the target host cells and are ubiquitously expressed. This provides new insights into the emerging picture of the infection mechanism of Ad3 and Ad35.

Incorporation of a non-human glycan mediates human susceptibility to a bacterial toxin

AB(5) toxins comprise an A subunit that corrupts essential eukaryotic cell functions, and pentameric B subunits that direct target-cell uptake after binding surface glycans. Subtilase cytotoxin (SubAB) is an AB(5) toxin secreted by Shiga toxigenic Escherichia coli (STEC), which causes serious gastrointestinal disease in humans. SubAB causes haemolytic uraemic syndrome-like pathology in mice through SubA-mediated cleavage of BiP/GRP78, an essential endoplasmic reticulum chaperone. Here we show that SubB has a strong preference for glycans terminating in the sialic acid N-glycolylneuraminic acid (Neu5Gc), a monosaccharide not synthesized in humans. Structures of SubB-Neu5Gc complexes revealed the basis for this specificity, and mutagenesis of key SubB residues abrogated in vitro glycan recognition, cell binding and cytotoxicity. SubAB specificity for Neu5Gc was confirmed using mouse tissues with a human-like deficiency of Neu5Gc and human cell lines fed with Neu5Gc. Despite lack of Neu5Gc biosynthesis in humans, assimilation of dietary Neu5Gc creates high-affinity receptors on human gut epithelia and kidney vasculature. This, and the lack of Neu5Gc-containing body fluid competitors in humans, confers susceptibility to the gastrointestinal and systemic toxicities of SubAB. Ironically, foods rich in Neu5Gc are the most common source of STEC contamination. Thus a bacterial toxin's receptor is generated by metabolic incorporation of an exogenous factor derived from food.

Functional characterization of HFR1, a high-mannose N-glycan-specific wheat lectin induced by Hessian fly larvae

We previously cloned and characterized a novel jacalin-like lectin gene from wheat (Triticum aestivum) plants that responds to infestation by Hessian fly (Mayetiola destructor) larvae, a major dipteran pest of this crop. The infested resistant plants accumulated higher levels of Hfr-1 (for Hessian fly-responsive gene 1) transcripts compared with uninfested or susceptible plants. Here, we characterize the soluble and active recombinant His(6)-HFR1 protein isolated from Escherichia coli. Functional characterization of the protein using hemagglutination assays revealed lectin activity. Glycan microarray-binding assays indicated strong affinity of His(6)-HFR1 to Manalpha1-6(Manalpha1-3)Man trisaccharide structures. Resistant wheat plants accumulated high levels of HFR1 at the larval feeding sites, as revealed by immunodetection, but the avirulent larvae were deterred from feeding and consumed only small amounts of the lectin. Behavioral studies revealed that avirulent Hessian fly larvae on resistant plants exhibited prolonged searching and writhing behaviors as they unsuccessfully attempted to establish feeding sites. During His(6)-HFR1 feeding bioassays, Drosophila melanogaster larvae experienced significant delays in growth and pupation, while percentage mortality increased with progressively higher concentrations of His(6)-HFR1 in the diet. Thus, HFR1 is an antinutrient to dipteran larvae and may play a significant role in deterring Hessian fly larvae from feeding on resistant wheat plants.

The "old" Euonymus europaeus agglutinin represents a novel family of ubiquitous plant proteins

Molecular cloning of the "old" but still unclassified Euonymus europaeus agglutinin (EEA) demonstrated that the lectin is a homodimeric protein composed of 152 residue subunits. Analysis of the deduced sequence indicated that EEA is synthesized without a signal peptide and undergoes no posttranslational processing apart from the removal of a six-residue N-terminal peptide. Glycan array screening confirmed the previously reported high reactivity of EEA toward blood group B oligosaccharides but also revealed binding to high mannose N-glycans, providing firm evidence for the occurrence of a plant carbohydrate-binding domain that can interact with structurally different glycans. Basic Local Alignment Search Tool searches indicated that EEA shares no detectable sequence similarity with any other lectin but is closely related evolutionarily to a domain that was first identified in some abscisic acid- and salt stress-responsive rice (Oryza sativa) proteins, and, according to the available sequence data, might be ubiquitous in Spermatophyta. Hence, EEA can be considered the prototype of a novel family of presumably cytoplasmic/nuclear proteins that are apparently ubiquitous in plants. Taking into account that some of these proteins are definitely stress related, the present identification of the EEA lectin domain might be a first step in the recognition of the involvement and importance of protein-glycoconjugate interactions in some essential cellular processes in Embryophyta.

Characterization of a streptococcal cholesterol-dependent cytolysin with a lewis y and b specific lectin domain

The cholesterol-dependent cytolysins (CDCs) are a large family of pore-forming toxins that often exhibit distinct structural changes that modify their pore-forming activity. A soluble platelet aggregation factor from Streptococcus mitis (Sm-hPAF) was characterized and shown to be a functional CDC with an amino-terminal fucose-binding lectin domain. Sm-hPAF, or lectinolysin (LLY) as renamed herein, is most closely related to CDCs from Streptococcus intermedius (ILY) and Streptococcus pneumoniae (pneumolysin or PLY). The LLY gene was identified in strains of S. mitis, S. pneumoniae, and Streptococcus pseudopneumoniae. LLY induces pore-dependent changes in the light scattering properties of the platelets that mimic those induced by platelet aggregation but does not induce platelet aggregation. LLY monomers form the typical large homooligomeric membrane pore complex observed for the CDCs. The pore-forming activity of LLY on platelets is modulated by the amino-terminal lectin domain, a structure that is not present in other CDCs. Glycan microarray analysis showed the lectin domain is specific for difucosylated glycans within Lewis b (Le (b)) and Lewis y (Le (y)) antigens. The glycan-binding site is occluded in the soluble monomer of LLY but is apparently exposed after cell binding, since it significantly increases LLY pore-forming activity in a glycan-dependent manner. Hence, LLY represents a new class of CDC whose pore-forming mechanism is modulated by a glycan-binding domain.

Dimeric Galectin-8 induces phosphatidylserine exposure in leukocytes through polylactosamine recognition by the C-terminal domain

Human galectins have distinct and overlapping biological roles in immunological homeostasis. However, the underlying differences among galectins in glycan binding specificity regulating these functions are unclear. Galectin-8 (Gal-8), a tandem repeat galectin, has two distinct carbohydrate recognition domains (CRDs) that may cross-link cell surface counter receptors. Here we report that each Gal-8 CRD has differential glycan binding specificity and that cell signaling activity resides in the C-terminal CRD. Full-length Gal-8 and recombinant individual domains (Gal-8N and Gal-8C) bound to human HL60 cells, but only full-length Gal-8 signaled phosphatidylserine (PS) exposure in cells, which occurred independently of apoptosis. Although desialylation of cells did not alter Gal-8 binding, it enhanced cellular sensitivity to Gal-8-induced PS exposure. By contrast, HL60 cell desialylation increased binding by Gal-8C but reduced Gal-8N binding. Enzymatic reduction in surface poly-N-acetyllactosamine (polyLacNAc) glycans in HL60 cells reduced cell surface binding by Gal-8C but did not alter Gal-8N binding. Cross-linking and light scattering studies showed that Gal-8 is dimeric, and studies on individual subunits indicate that dimerization occurs through the Gal-8N domain. Mutations of individual domains within full-length Gal-8 showed that signaling activity toward HL60 cells resides in the C-terminal domain. In glycan microarray analyses, each CRD of Gal-8 showed different binding, with Gal-8N recognizing sulfated and sialylated glycans and Gal-8C recognizing blood group antigens and polyLacNAc glycans. These results demonstrate that Gal-8 dimerization promotes functional bivalency of each CRD, which allows Gal-8 to signal PS exposure in leukocytes entirely through C-terminal domain recognition of polyLacNAc glycans.

Minireview: the intersection of steroid receptors with molecular chaperones: observations and questions

An involvement of molecular chaperones in the action and well-being of steroid receptors was recognized early in the molecular era of hormone research. However, this has continued to be a topic of much enquiry and some confusion. All steroid receptors associate with heat shock protein 90, the main character of a series of multiprotein chaperone complexes generally referred to as the "heat shock protein 90 chaperoning machine." Receptor association with chaperones occurs in an ordered, step-wise fashion and is necessary for the maintenance of unliganded receptor in a state ready to bind and respond to hormone. Chaperones additionally modulate how receptors respond to hormone and activate target genes. Although much is known about the participants in this chaperoning process and the consequences of chaperoning, many key questions remain unanswered, particularly those concerning molecular mechanisms, cellular dynamics, and the functions of an array of cochaperone proteins. Here, we point out several areas in need of investigation to encourage new ideas and participants in this burgeoning field.

Transgenic Leishmania and the immune response to infection

Genetic manipulation of single-celled organisms such as the Leishmania parasite enables in depth analysis of the consequences of genotypic change on biological function. In probing the immune responses to infection, use of transgenic Leishmania has the potential to unravel both the contribution of the parasite to the infection process and the cellular interactions and mechanisms that characterize the innate and adaptive immune responses of the host. Here, we briefly review recent technical advances in parasite genetics and explore how these methods are being used to investigate parasite virulence factors, elucidate immune regulatory mechanisms and contribute to the development of novel therapeutics for the leishmaniases. Recent developments in imaging technology, such as bioluminescence and intravital imaging, combined with parasite transfection with fluorescent or enzyme-encoding marker genes, provides a rich opportunity for novel assessment of intimate, real-time host-parasite interactions at a previously unexplored level. Further advances in transgenic technology, such as the introduction of robust inducible gene cassettes for expression in intracellular parasite stages or the development of RNA interference methods for down-regulation of parasite gene expression in the host, will further advance our ability to probe host-parasite interactions and unravel disease-promoting mechanisms in the leishmaniases.

Galectin-1, -2, and -3 exhibit differential recognition of sialylated glycans and blood group antigens

Human galectins have functionally divergent roles, although most of the members of the galectin family bind weakly to the simple disaccharide lactose (Galbeta1-4Glc). To assess the specificity of galectin-glycan interactions in more detail, we explored the binding of several important galectins (Gal-1, Gal-2, and Gal-3) using a dose-response approach toward a glycan microarray containing hundreds of structurally diverse glycans, and we compared these results to binding determinants on cells. All three galectins exhibited differences in glycan binding characteristics. On both the microarray and on cells, Gal-2 and Gal-3 exhibited higher binding than Gal-1 to fucose-containing A and B blood group antigens. Gal-2 exhibited significantly reduced binding to all sialylated glycans, whereas Gal-1 bound alpha2-3- but not alpha2-6-sialylated glycans, and Gal-3 bound to some glycans terminating in either alpha2-3- or alpha2-6-sialic acid. The effects of sialylation on Gal-1, Gal-2, and Gal-3 binding to cells also reflected differences in cellular sensitivity to Gal-1-, Gal-2-, and Gal-3-induced phosphatidylserine exposure. Each galectin exhibited higher binding for glycans with poly-N-acetyllactosamine (poly(LacNAc)) sequences (Galbeta1-4GlcNAc)(n) when compared with N-acetyllactosamine (LacNAc) glycans (Galbeta1-4GlcNAc). However, only Gal-3 bound internal LacNAc within poly(LacNAc). These results demonstrate that each of these galectins mechanistically differ in their binding to glycans on the microarrays and that these differences are reflected in the determinants required for cell binding and signaling. The specific glycan recognition by each galectin underscores the basis for differences in their biological activities.

A novel mechanism for LSECtin binding to Ebola virus surface glycoprotein through truncated glycans

LSECtin is a member of the C-type lectin family of glycan-binding receptors that is expressed on sinusoidal endothelial cells of the liver and lymph nodes. To compare the sugar and pathogen binding properties of LSECtin with those of related but more extensively characterized receptors, such as DC-SIGN, a soluble fragment of LSECtin consisting of the C-terminal carbohydrate-recognition domain has been expressed in bacteria. A biotin-tagged version of the protein was also generated and complexed with streptavidin to create tetramers. These forms of the carbohydrate-recognition domain were used to probe a glycan array and to characterize binding to oligosaccharide and glycoprotein ligands. LSECtin binds with high selectivity to glycoproteins terminating in GlcNAcbeta1-2Man. The inhibition constant for this disaccharide is 3.5 microm, making it one of the best low molecular weight ligands known for any C-type lectin. As a result of the selective binding of this disaccharide unit, the receptor recognizes glycoproteins with a truncated complex and hybrid N-linked glycans on glycoproteins. Glycan analysis of the surface glycoprotein of Ebola virus reveals the presence of such truncated glycans, explaining the ability of LSECtin to facilitate infection by Ebola virus. High mannose glycans are also present on the viral glycoprotein, which explains why DC-SIGN also binds to this virus. Thus, multiple receptors interact with surface glycoproteins of enveloped viruses that bear different types of relatively poorly processed glycans.

Deficiency of co-chaperone immunophilin FKBP52 compromises sperm fertilizing capacity

FKBP52 is a member of the FK506-binding family of immunophilins and serves as a co-chaperone for steroid hormone nuclear receptors to govern appropriate hormone action in target tissues. Male mice missing Fkbp52 are infertile, and this infertility has been ascribed to compromised sensitivity of the anterior prostate, external genitalia, and other accessory sex organs to androgen. Here, we show additional defects contributing to infertility. We found that epididymal Fkbp52(-/-) sperm are sparse often with aberrant morphology, and they have reduced fertilizing capacity. This phenotype, initially observed in null males on a C57BL/6/129 background, is also maintained on a CD1 background. Expression studies show that while FKBP52 and androgen receptor are co-expressed in similar cell types in the epididymis, FKBP52 is also present in epididymal sperm flagella. Collectively, our results suggest that reduced number and abnormal morphology contribute to compromised fertilizing capacity of Fkbp52(-/-) sperm. This study is clinically relevant because unraveling the role of immunophilin signaling in male fertility will help identify new targets for male contraceptives and/or alleviate male infertility.

A randomised controlled trial examining the longer-term outcomes of standard versus new antiepileptic drugs. The SANAD trial

OBJECTIVES

To compare clinicians' choice of one of the standard epilepsy drug treatments (carbamazepine or valproate) versus appropriate comparator new drugs.

DESIGN

A clinical trial comprising two arms, one comparing new drugs in carbamazepine and the other with valproate.

SETTING

A multicentre study recruiting patients with epilepsy from hospital outpatient clinics.

PARTICIPANTS

Patients with an adequately documented history of two or more clinically definite unprovoked epileptic seizures within the last year for whom treatment with a single antiepileptic drug represented the best therapeutic option.

INTERVENTIONS

Arm A was carbamazepine (CBZ) versus gabapentin (GBP) versus lamotrigine (LTG) versus oxcarbazepine (OXC) versus topiramate (TPM). Arm B valproate (VPS) versus LTG versus TPM.

MAIN OUTCOME MEASURES

Time to treatment failure (withdrawal of the randomised drug for reasons of unacceptable adverse events or inadequate seizure control or a combination of the two) and time to achieve a 12-month remission of seizures. Time from randomisation to first seizure, 24-month remission of seizures, incidence of clinically important adverse events, quality of life (QoL) outcomes and health economic outcomes were also considered.

RESULTS

Arm A recruited 1721 patients (88% with symptomatic or cryptogenic partial epilepsy and 10% with unclassified epilepsy). Arm B recruited 716 patients (63% with idiopathic generalised epilepsy and 25% with unclassified epilepsy). In Arm A LTG had the lowest incidence of treatment failure and was statistically superior to all drugs for this outcome with the exception of OXC. Some 12% and 8% fewer patients experienced treatment failure on LTG than CBZ, the standard drug, at 1 and 2 years after randomisation, respectively. The superiority of LTG over CBZ was due to its better tolerability but there is satisfactory evidence indicating that LTG is not clinically inferior to CBZ for measures of its efficacy. No consistent differences in QoL outcomes were found between treatment groups. Health economic analysis supported LTG being preferred to CBZ for both cost per seizure avoided and cost per quality-adjusted life-year gained. In Arm B for time to treatment failure, VPS, the standard drug, was preferred to both TPM and LTG, as it was the drug least likely to be associated with treatment failure for inadequate seizure control and was the preferred drug for time to achieving a 12-month remission. QoL assessments did not show any between-treatment differences. The health economic assessment supported the conclusion that VPS should remain the drug of first choice for idiopathic generalised or unclassified epilepsy, although there is a suggestion that TPM is a cost-effective alternative to VPS.

CONCLUSIONS

The evidence suggests that LTG may be a clinical and cost-effective alternative to the existing standard drug treatment, CBZ, for patients diagnosed as having partial seizures. For patients with idiopathic generalised epilepsy or difficult to classify epilepsy, VPS remains the clinically most effective drug, although TPM may be a cost-effective alternative for some patients. Three new antiepileptic drugs have recently been licensed in the UK for the treatment of epilepsy (levetiracetam, zonisamide and pregabalin), therefore these drugs should be compared in a similarly designed trial.

FKBP52 deficiency-conferred uterine progesterone resistance is genetic background and pregnancy stage specific

Immunophilin FKBP52 serves as a cochaperone to govern normal progesterone (P(4)) receptor (PR) function. Using Fkbp52(-/-) mice, we show intriguing aspects of uterine P(4)/PR signaling during pregnancy. Implantation failure is the major phenotype found in these null females, which is conserved on both C57BL6/129 and CD1 backgrounds. However, P(4) supplementation rescued implantation and subsequent decidualization in CD1, but not C57BL6/129, null females. Surprisingly, experimentally induced decidualization in the absence of blastocysts failed in Fkbp52(-/-) mice on either background even with P(4) supplementation, suggesting that embryonic signals complement uterine signaling for this event. Another interesting finding was that while P(4) at higher than normal pregnancy levels conferred PR signaling sufficient for implantation in CD1 null females, these levels were inefficient in maintaining pregnancy to full term. However, elevating P(4) levels further restored PR signaling to a level optimal for successful term pregnancy with normal litter size. Collectively, the results show that the indispensability of FKBP52 in uterine P(4)/PR signaling is a function of genetic disparity and is pregnancy stage specific. Since there is evidence for a correlation between P(4) supplementation and reduced risks of P(4)-resistant recurrent miscarriages and remission of endometriosis, these findings have clinical implications for genetically diverse populations of women.

Quantifiable fluorescent glycan microarrays

A glycan microarray was developed by using 2,6-diaminopyridine (DAP) as a fluorescent linker and printing of the glycan-DAP conjugates (GDAPs) on epoxy-activated glass slides. Importantly, all coupled GDAPs showed a detectable level of concentration-dependent GDAP fluorescence under blue laser excitation (495 nm) that can be used for both grid location and on-slide quantification. A glycan array including a large number of GDAP's derived from natural and commercially available free glycans was constructed and glycan interactions with various plant lectins were investigated. In addition, binding parameters of lectins to glycans were obtained by varying both the amount of GDAPs on the array and the lectin concentration in analyses. These data demonstrate the general utility of GDAP microarrays for functional glycomic analyses and for determining binding parameters of glycan binding proteins (GBPs).

Immunization by avian H5 influenza hemagglutinin mutants with altered receptor binding specificity

Influenza virus entry is mediated by the receptor binding domain (RBD) of its spike, the hemagglutinin (HA). Adaptation of avian viruses to humans is associated with HA specificity for alpha2,6- rather than alpha2,3-linked sialic acid (SA) receptors. Here, we define mutations in influenza A subtype H5N1 (avian) HA that alter its specificity for SA either by decreasing alpha2,3- or increasing alpha2,6-SA recognition. RBD mutants were used to develop vaccines and monoclonal antibodies that neutralized new variants. Structure-based modification of HA specificity can guide the development of preemptive vaccines and therapeutic monoclonal antibodies that can be evaluated before the emergence of human-adapted H5N1 strains.

FK506-binding protein 52 phosphorylation: a potential mechanism for regulating steroid hormone receptor activity

Functional maturation of steroid hormone receptors requires ordered assembly into a large multichaperone complex consisting of receptor monomer, an Hsp90 dimer, the p23 cochaperone, and an FK506-binding protein (FKBP) family member or alternate peptidylprolyl isomerase-related cochaperone. Previous cellular studies demonstrated that FKBP52 can potentiate receptor function. These results have been confirmed in fkbp4 gene knockout mice in which males are partially androgen insensitive and females display characteristics of progesterone insensitivity. Conversely, FKBP51, which has a high degree of similarity to FKBP52, antagonizes FKBP52-mediated potentiation. Both proteins consist of three domains: two FKBP12-like domains termed FK1 and FK2 and a tetratricopeptide repeat domain that targets binding to Hsp90. To help understand why the two FKBPs behave differently and to gain insight into FKBP52 potentiation activity, we have analyzed the loop structure that links FK1 and FK2. Within the FK linker of FKBP52 is the sequence TEEED, which forms a consensus casein kinase II phosphorylation site; the corresponding sequence in FKBP51 is FED. We demonstrate that the distinct FK linker sequences per se do not account for lack of potentiation activity by FKBP51. However, phosphorylation of the FK linker appears to be an important regulatory determinant of FKBP52-mediated potentiation of steroid receptor activity.

Food panics in history: corned beef, typhoid and "risk society"

An outline of the "risk society" thesis of the German social theorist Ulrich Beck is given, and some points that he has taken from food safety examples are discussed. The potential for exploring the viability and utility of the thesis, via a comparative study of historical food safety episodes is illustrated through an account and discussion of the large corned beef-associated typhoid outbreak which occurred in 1964 in Aberdeen, Scotland. The outcome of the Aberdeen affair, in terms of public and political interest in food safety, and impact on the official food safety system, is compared with the outcome and impact of the series of food safety episodes of the 1980s and 1990s. The interactions between the latter episodes and the new food movement, the proactive responses of corporate interests, and the dramatic changes in the food safety regime represented by the formation of the Food Standards Agency in Britain, are contrasted with the relative lack of impact of the Aberdeen outbreak. Despite criticisms of Beck's thesis, this comparative study highlights, in particular, the value of his concept of "subpolitics", and his expectation that the transition to risk society will involve the emergence of new social institutions. Such insights may help orientate epidemiologists and community health specialists who are currently active in food safety and regulation.

Immunization with H1, HASPB1 and MML Leishmania proteins in a vaccine trial against experimental canine leishmaniasis

The protective capabilities of three Leishmania recombinant proteins – histone 1 (H1) and hydrophilic acylated surface protein B1 (HASPB1) immunized singly, or together as a protein cocktail vaccine with Montanide™, and the polyprotein MML immunized with MPL^®-SE adjuvant – were assessed in beagle dogs. Clinical examination of the dogs was carried out periodically under blinded conditions and the condition of the dogs defined as asymptomatic or symptomatic. At the end of the trial, we were able to confirm that following infection with L. infantum promastigotes, five out of eight dogs immunized with H1 Montanide™, and four out of eight dogs immunized with either the combination of HASPB1 with Montanide™ or the combination of H1 + HASPB1 with Montanide™, remained free of clinical signs, compared with two out of seven dogs immunized with the polyprotein MML and adjuvant MPL^®-SE, and two out of eight dogs in the control group. The results demonstrate that HASPB1 and H1 antigens in combination with Montanide™ were able to induce partial protection against canine leishmaniasis, even under extreme experimental challenge conditions.

Human parainfluenza viruses hPIV1 and hPIV3 bind oligosaccharides with alpha2-3-linked sialic acids that are distinct from those bound by H5 avian influenza virus hemagglutinin

We investigated the binding of human parainfluenza virus types 1 and 3 (hPIV1 and hPIV3, respectively) to the glycan array of the Consortium for Functional Glycomics and binding and their release from erythrocytes under conditions where neuraminidase is inactive or active. hPIV1 and hPIV3 bind modifications of Neu5Acalpha2-3Galbeta1-4GlcNAc, including the sialyl-Lewis(x) motif and structures containing 6-sulfogalactose. hPIV1 and hPIV3 thus bind typical N-linked glycans, in contrast to avian influenza virus H5 hemagglutinin (J. Stevens, O. Blixt, T. M. Tumpey, J. K. Taubenberger, J. C. Paulson, and I. A. Wilson, Science 312:404-410, 2006), which binds less-common motifs. While the receptor is not the sole determinant of tropism, hPIV or H5 influenza virus infection of specific cells that express receptors may contribute to their different pathologies.

Phylogenetic and specificity studies of two-domain GNA-related lectins: generation of multispecificity through domain duplication and divergent evolution

A re-investigation of the occurrence and taxonomic distribution of proteins built up of protomers consisting of two tandem arrayed domains equivalent to the GNA [Galanthus nivalis (snowdrop) agglutinin] revealed that these are widespread among monotyledonous plants. Phylogenetic analysis of the available sequences indicated that these proteins do not represent a monophylogenetic group but most probably result from multiple independent domain duplication/in tandem insertion events. To corroborate the relationship between inter-domain sequence divergence and the widening of specificity range, a detailed comparative analysis was made of the sequences and specificity of a set of two-domain GNA-related lectins. Glycan microarray analyses, frontal affinity chromatography and surface plasmon resonance measurements demonstrated that the two-domain GNA-related lectins acquired a marked diversity in carbohydrate-binding specificity that strikingly contrasts the canonical exclusive specificity of their single domain counterparts towards mannose. Moreover, it appears that most two-domain GNA-related lectins interact with both high mannose and complex N-glycans and that this dual specificity relies on the simultaneous presence of at least two different independently acting binding sites. The combined phylogenetic, specificity and structural data strongly suggest that plants used domain duplication followed by divergent evolution as a mechanism to generate multispecific lectins from a single mannose-binding domain. Taking into account that the shift in specificity of some binding sites from high mannose to complex type N-glycans implies that the two-domain GNA-related lectins are primarily directed against typical animal glycans, it is tempting to speculate that plants developed two-domain GNA-related lectins for defence purposes.

Receptor binding specificity of recent human H3N2 influenza viruses

Background

Human influenza viruses are known to bind to sialic acid linked α2-6 to galactose, but the binding specificity beyond that linkage has not been systematically examined. H3N2 human influenza isolates lost binding to chicken red cells in the 1990s but viruses isolated since 2003 have re-acquired the ability to agglutinate chicken erythrocytes. We have investigated specificity of binding, changes in hemagglutinin sequence of the recent viruses and the role of sialic acid in productive infection.

Results

Viruses that agglutinate, or do not agglutinate, chicken red cells show identical binding to a Glycan Array of 264 oligosaccharides, binding exclusively to a subset of α2-6-sialylsaccharides. We identified an amino acid change in hemagglutinin that seemed to correlate with chicken red cell binding but when tested by mutagenesis there was no effect. Recombinant hemagglutinins expressed on Sf-9 cells bound chicken red cells but the released recombinant baculoviruses agglutinated only human red cells. Similarly, an isolate that does not agglutinate chicken red cells show hemadsorption of chicken red cells to infected MDCK cells. We suggest that binding of chicken red cells to cell surface hemagglutinin but not to virions is due to a more favorable hemagglutinin density on the cell surface. We investigated whether a virus specific for α2-6 sialyloligosaccharides shows differential entry into cells that have varying proportions of α2-6 and α2-3 sialic acids, including human A549 and HeLa cells with high levels of α2-6 sialic acid, and CHO cells that have only α2-3 sialic acid. We found that the virus enters all cell types tested and synthesizes viral nucleoprotein, localized in the nucleus, and hemagglutinin, transported to the cell surface, but infectious progeny viruses were released only from MDCK cells.

Conclusion

Agglutination of chicken red cells does not correlate with altered binding to any oligosaccharide on the Glycan Array, and may result from increased avidity due to density of hemagglutinin and not increased affinity. Absence of α2-6 sialic acid does not protect a cell from influenza infection and the presence of high levels of α2-6-sialic acids on a cell surface does not guarantee productive replication of a virus with α2-6 receptor specificity.

The SANAD study of effectiveness of carbamazepine, gabapentin, lamotrigine, oxcarbazepine, or topiramate for treatment of partial epilepsy: an unblinded randomised controlled trial

BACKGROUND

Carbamazepine is widely accepted as a drug of first choice for patients with partial onset seizures. Several newer drugs possess efficacy against these seizure types but previous randomised controlled trials have failed to inform a choice between these drugs. We aimed to assess efficacy with regards to longer-term outcomes, quality of life, and health economic outcomes.

METHODS

SANAD was an unblinded randomised controlled trial in hospital-based outpatient clinics in the UK. Arm A recruited 1721 patients for whom carbamazepine was deemed to be standard treatment, and they were randomly assigned to receive carbamazepine, gabapentin, lamotrigine, oxcarbazepine, or topiramate. Primary outcomes were time to treatment failure, and time to 12-months remission, and assessment was by both intention to treat and per protocol. This study is registered as an International Standard Randomised Controlled Trial, number ISRCTN38354748.

FINDINGS

For time to treatment failure, lamotrigine was significantly better than carbamazepine (hazard ratio [HR] 0.78 [95% CI 0.63-0.97]), gabapentin (0.65 [0.52-0.80]), and topiramate (0.64 [0.52-0.79]), and had a non-significant advantage compared with oxcarbazepine (1.15 [0.86-1.54]). For time to 12-month remission carbamazepine was significantly better than gabapentin (0.75 [0.63-0.90]), and estimates suggest a non-significant advantage for carbamazepine against lamotrigine (0.91 [0.77-1.09]), topiramate (0.86 [0.72-1.03]), and oxcarbazepine (0.92 [0.73-1.18]). In a per-protocol analysis, at 2 and 4 years the difference (95% CI) in the proportion achieving a 12-month remission (lamotrigine-carbamazepine) is 0 (-8 to 7) and 5 (-3 to 12), suggesting non-inferiority of lamotrigine compared with carbamazepine.

INTERPRETATION

Lamotrigine is clinically better than carbamazepine, the standard drug treatment, for time to treatment failure outcomes and is therefore a cost-effective alternative for patients diagnosed with partial onset seizures.

The SANAD study of effectiveness of valproate, lamotrigine, or topiramate for generalised and unclassifiable epilepsy: an unblinded randomised controlled trial

BACKGROUND

Valproate is widely accepted as a drug of first choice for patients with generalised onset seizures, and its broad spectrum of efficacy means it is recommended for patients with seizures that are difficult to classify. Lamotrigine and topiramate are also thought to possess broad spectrum activity. The SANAD study aimed to compare the longer-term effects of these drugs in patients with generalised onset seizures or seizures that are difficult to classify.

METHODS

SANAD was an unblinded randomised controlled trial in hospital-based outpatient clinics in the UK. Arm B of the study recruited 716 patients for whom valproate was considered to be standard treatment. Patients were randomly assigned to valproate, lamotrigine, or topiramate between Jan 12, 1999, and Aug 31, 2004, and follow-up data were obtained up to Jan 13, 2006. Primary outcomes were time to treatment failure, and time to 1-year remission, and analysis was by both intention to treat and per protocol. This study is registered as an International Standard Randomised Controlled Trial, number ISRCTN38354748.

FINDINGS

For time to treatment failure, valproate was significantly better than topiramate (hazard ratio 1.57 [95% CI 1.19-2.08]), but there was no significant difference between valproate and lamotrigine (1.25 [0.94-1.68]). For patients with an idiopathic generalised epilepsy, valproate was significantly better than both lamotrigine (1.55 [1.07-2.24] and topiramate (1.89 [1.32-2.70]). For time to 12-month remission valproate was significantly better than lamotrigine overall (0.76 [0.62-0.94]), and for the subgroup with an idiopathic generalised epilepsy 0.68 (0.53-0.89). But there was no significant difference between valproate and topiramate in either the analysis overall or for the subgroup with an idiopathic generalised epilepsy.

INTERPRETATION

Valproate is better tolerated than topiramate and more efficacious than lamotrigine, and should remain the drug of first choice for many patients with generalised and unclassified epilepsies. However, because of known potential adverse effects of valproate during pregnancy, the benefits for seizure control in women of childbearing years should be considered.

Short-term changes in maternal and neonatal urinary iodine excretion

Investigation of maternal urinary iodine (UI) excretion in the immediate antenatal and early postpartum periods showed a precipitous fall in median values from 93 microg/L antenatally to 36 microg/L at delivery subsequently rising to 49 microg/L and 63 microg/L at days 3 and 10 postpartum respectively. The fate of ingested iodine not appearing in the maternal urine is unknown but measurement of UI in babies born to nursing mothers suggested transfer from the mother with median neonatal values of 117 and 159 microg/L being recorded at days 3 and 10. While maternal UI seemed to relatively unaffected by breast feeding, median UI from breast feeding babies (148 microg/L) was significantly greater than in those bottle feeding (50 microg/L). This was also reflected by the finding that no breast feeding baby had a UI values < 50 microg/L in comparison to 50% of bottle feeders. The depressed values in mothers and relatively high values in their infants could present a false picture and suggest the need to defer any investigations of iodine status at this time. The findings do however suggest a need for further investigations aimed at determining the fate of iodine ingested perinatally and its possible physiological significance in maintaining thyroid status in the mother and neonate.

Alpha 2,3-sialyltransferase-IV is essential for L-selectin ligand function in inflammation

L-selectin belongs to the C-type lectin family of glycoproteins and is constitutively expressed on most leukocytes. L-selectin mediates leukocyte rolling in inflamed microvessels and high endothelial venules (HEV) via binding to specific carbohydrate structures on selectin ligands. Previous studies using sialidase treatment suggested a role of sialic acid residues in L-selectin-dependent rolling. To investigate the role of the alpha2,3-sialyltransferase (ST3Gal)-IV on L-selectin ligand activity in vivo, we studied leukocyte rolling in inflamed venules of the cremaster muscle and in Peyer's patch HEV of ST3Gal-IV-deficient mice and littermate control mice. In cremaster muscle venules with or without TNF-alpha treatment, L-selectin-dependent rolling was almost completely abolished in ST3Gal-IV(-/-) mice. In both models, L-selectin interacts with P-selectin glycoprotein ligand-1 (PSGL-1) presented by adherent leukocytes and leukocyte fragments, but not with endothelial L-selectin ligands. In contrast, L-selectin-dependent rolling in Peyer's patch HEV, which is mediated by unknown endothelial L-selectin ligands, was not impaired in the absence of ST3Gal-IV. Our in vivo data show that PSGL-1, the molecule responsible for L-selectin-mediated leukocyte interactions in inflammation, is dependent on ST3Gal-IV, while alpha2,3-sialylation by ST3Gal-IV is not necessary for L-selectin ligand activity on high endothelial cells of Peyer's patch HEV.