Ferrets exclusively synthesize Neu5Ac and express naturally humanized influenza A virus receptors

Mammals express the sialic acids ​N-acetylneuraminic acid (​Neu5Ac) and ​N-glycolylneuraminic acid (​Neu5Gc) on cell surfaces, where they act as receptors for pathogens, including influenza A virus (IAV). ​Neu5Gc is synthesized from ​Neu5Ac by the enzyme cytidine monophosphate-N-acetylneuraminic acid hydroxylase (CMAH). In humans, this enzyme is inactive and only ​Neu5Ac is produced. Ferrets are susceptible to human-adapted IAV strains and have been the dominant animal model for IAV studies. Here we show that ferrets, like humans, do not synthesize ​Neu5Gc. Genomic analysis reveals an ancient, nine-exon deletion in the ferret CMAH gene that is shared by the Pinnipedia and Musteloidia members of the Carnivora. Interactions between two human strains of IAV with the sialyllactose receptor (sialic acid—α2,6Gal) confirm that the type of terminal sialic acid contributes significantly to IAV receptor specificity. Our results indicate that exclusive expression of ​Neu5Ac contributes to the susceptibility of ferrets to human-adapted IAV strains

The pneumococcal alpha-glycerophosphate oxidase enhances nasopharyngeal colonization through binding to host glycoconjugates

Streptococcus pneumoniae (the pneumococcus) is a major human pathogen, causing a broad spectrum of diseases including otitis media, pneumonia, bacteraemia and meningitis. Here we examined the role of a potential pneumococcal meningitis vaccine antigen, alpha-glycerophosphate oxidase (SpGlpO), in nasopharyngeal colonization. We found that serotype 4 and serotype 6A strains deficient in SpGlpO have significantly reduced capacity to colonize the nasopharynx of mice, and were significantly defective in adherence to human nasopharyngeal carcinoma cells in vitro. We also demonstrate that intranasal immunization with recombinant SpGlpO significantly protects mice against subsequent nasal colonization by wild type serotype 4 and serotype 6A strains. Furthermore, we show that SpGlpO binds strongly to lacto/neolacto/ganglio host glycan structures containing the GlcNAcβ1-3Galβ disaccharide, suggesting that SpGlpO enhances colonization of the nasopharynx through its binding to host glycoconjugates. We propose that SpGlpO is a promising vaccine candidate against pneumococcal carriage, and warrants inclusion in a multi-component protein vaccine formulation that can provide robust, serotype-independent protection against all forms of pneumococcal disease

Identification of NuoX and NuoY Ligand binding specificity in the Campylobacter Jejuni Complex I

The components of the proton pump NADH:ubiquinone (Complex I) of the respiration pathway have been identified in the C. jejuni genome. However, the paradigm genes nuoE and nuoF encoding subunits of the NADH dehydrogenase module of Complex I are absent. Instead the genes cj1575c and cj1574c encoding NuoX and NuoY are present in the loci corresponding to nuoE and nuoF, respectively. Bioinformatics analyses showed the presence of nuoX and nuoY homologues in all sequenced strains of C. jejuni and in other Campylobacter species, as well as the presence of orthologues in other ɛ-Proteobacteria. To understand the involvement of the NuoX and NuoY proteins in the respiration of C. jejuni and to characterize their ligand binding specificity and affinity, a tricarboxylic acid cycle array was developed as a tool to identify proteins that can bind to intermediates of this cycle as well as other metabolites. This array showed that NuoX bound FAD2+, and NuoY bound FAD2+ and the electron donors malate and lactate. Saturation Transfer Difference Nuclear Magnetic Resonance studies confirmed the NuoY binding ligands, and suggested that the flavin moiety of FAD2+ interacted more strongly with NuoY than the adenine moiety. Affinity data generated by Surface Plasmon Resonance indicated that NuoY bound to FAD2+ with a KD of 337 nM; NuoX and NuoY had an affinity for NADH of a KD of 403 nM and 478 nM, respectively, and a ten-fold lower affinity for both NAD+ and FAD2+. The data suggested that the flavin-adenine dinucletoide could be bound preferentially to the NAD in the Complex I of C. jejuni

Carbohydrate binding and gene expression by in vitro and in vivo propagated Campylobacter jejuni after Immunomagnetic Separation

Campylobacter jejuni is an important human food-borne intestinal pathogen, however relatively little is known about its mechanisms of pathogenesis or pathogen-host interactions. To monitor changes in gene expression and glycan binding of C. jejuni within a common avian host, an immunomagnetic separation technique (IMS) was utilised to directly isolate infecting C. jejuni 81116 from a chicken host. An average of 105 cells/g was re-isolated from chicken caecal samples by IMS technique. The in vivo passaged strains were used successfully in evaluation of carbohydrate binding through the use of a glycan array and were further suitable for transcriptome analysis. The glycan microarray analysis demonstrated differences in binding to negatively charged glycans of laboratory grown strains of C. jejuni compared with strains isolated after in vivo passage. The in vivo passaged strains showed marked up-regulation of chemotaxis receptors and toxin genes. The optimised Campylobacter IMS technique described in this study allowed isolation directly from an animal host. Changes in gene expression and glycan binding at an in vivo level can also be identified by using this method. © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

Variation of chemosensory receptor content of <it>Campylobacter jejuni</it> strains and modulation of receptor gene expression under different <it>in vivo</it> and <it>in vitro</it> growth conditions

<p>Abstract</p> <p>Background</p> <p>Chemotaxis is crucial for the colonisation/infection of hosts with <it>Campylobacter jejuni.</it> Central to chemotaxis are the group A chemotaxis genes that are responsible for sensing the external environment. The distribution of group A chemoreceptor genes, as found in the <it>C. jejuni</it> sequenced strains, <it>tlp1-4, 7, 10</it> and <it>11</it> were determined in 33 clinical human and avian isolates.</p> <p>Results</p> <p>Group A <it>tlp</it> gene content varied among the strains with genes encoding <it>tlp1</it> (aspartate receptor, <it>ccaA</it>) and <it>tlp7</it> present in all strains tested, where as <it>tlp11</it> was present in only one of our international collection clinical isolates, <it>C. jejuni</it> 520, but was more prevalent (9/13) in the freshly isolated clinical stains from patients who required hospitalisation due to <it>C. jejuni</it> infection (GCH1-17). Relative expression levels of the group A <it>tlp</it> genes were also determined in <it>C. jejuni</it> reference strains NCTC 11168-GS, 11168-O and 81116 using cells grown <it>in vitro</it> at 37°C, 42°C and maintained at room temperature and with cells isolated directly from murine and avian hosts by immune magnetic separation without subsequent culture. Gene expression of <it>tlp</it> genes was varied based on strain, growth conditions and <it>in vivo</it> isolation source. <it>Tlp1,</it> although the most conserved, showed the lowest and most varied mRNA expression and protein production under laboratory conditions. <it>Tlp7</it> was highly expressed at most conditions tested, and gene expression was not influenced by the <it>tlp7</it> gene encoding a full length protein or one expressed as separate periplasmic and cytoplasmic domains.</p> <p>Conclusion</p> <p>We have shown that chemosensory receptor set variation exists among <it>C. jejuni</it> strains, but is not dependent on the isolation source.</p

The glycointeractome of serogroup B Neisseria meningitidis strain MC58

Neisseria meningitidis express numerous virulence factors that enable it to interact with diverse microenvironments within the host, during both asymptomatic nasopharyngeal colonization and invasive disease. Many of these interactions involve bacterial or host glycans. In order to characterise the meningococcal glycointeractome, glycan arrays representative of structures found on human cells, were used as a screening tool to investigate host glycans bound by N. meningitidis. Arrays probed with fluorescently labelled wild-type MC58 revealed binding to 223 glycans, including blood group antigens, mucins, gangliosides and glycosaminoglycans. Mutant strains lacking surface components, including capsule, lipooligosaccharide (LOS), Opc and pili, were investigated to identify the factors responsible for glycan binding. Surface plasmon resonance and isothermal calorimetry were used to confirm binding and determine affinities between surface components and host glycans. We observed that the L3 LOS immunotype (whole cells and purified LOS) bound 26 structures, while L8 only bound 5 structures. We further demonstrated a direct glycan-glycan interaction between purified L3 LOS and Thomsen–Friedenreich (TF) antigen, with a KD of 13 nM. This is the highest affinity glycan-glycan interaction reported to date. These findings highlight the diverse glycointeractions that may occur during different stages of meningococcal disease, which could be exploited for development of novel preventative and therapeutic strategies.Office of the Snr Dep Vice Chancellor, Institute for GlycomicsFull Tex

Lectin activity of the TcdA and TcdB toxins of Clostridium difficile

Clostridium difficile is a major cause of hospital-acquired antibioticassociated diarrhea. C. difficile produces two cytotoxins, TcdA and TcdB; both toxins are multidomain proteins that lead to cytotoxicity through the modification and inactivation of small GTPases of the Rho/Rac family. Previous studies have indicated that host glycans are targets for TcdA and TcdB, with interactions thought to be with both - and -linked galactose. In the current study, screening of glycan arrays with different domains of TcdA and TcdB revealed that the binding regions of both toxins interact with a wider range of host glycoconjugates than just terminal - and -linked galactose, including blood groups, Lewis antigens, N-acetylglucosamine, mannose, and glycosaminoglycans. The interactions of TcdA and TcdB with ABO blood group and Lewis antigens were assessed by surface plasmon resonance (SPR). The blood group A antigen was the highest-affinity ligand for both toxins. Free glycans alone or in combination were unable to abolish Vero cell cytotoxicity by TcdB. SPR competition assays indicate that there is more than one glycan binding site on TcdB. Host glycoconjugates are common targets of bacterial toxins, but typically this binding is to a specific structure or related structures. The binding of TcdA and TcdB is to a wide range of host glycans providing a wide range of target cells and tissues in vivo.Full Tex

A drug delivery strategy: binding enkephalin to asialoglycoprotein receptor by enzymatic galactosylation.

Glycosylation of biopharmaceuticals can mediate cell specific delivery by targeting carbohydrate receptors. Additionally, glycosylation can improve the physico-chemical (drug-like) properties of peptide based drug candidates. The main purpose of this study was to examine if glycosylation of the peptide enkephalin could facilitate its binding to the carbohydrate receptor, asialoglycoprotein. Firstly, we described the one-pot enzymatic galactosylation of lactose modified enkephalin in the presence of uridine-5'-diphosphogalactose 4-epimerase and lipopolysaccharyl α-1,4-galactosyltransferase. Stability experiments using human plasma and Caco-2 cell homogenates showed that glycosylation considerably improved the stability of enkephalin (at least 60% remained stable after a 2 hr incubation at 37°C). In vitro permeability experiments using Caco-2 cells revealed that the permeability of mono- and trisaccharide conjugated enkephalins was 14 and 28 times higher, respectively, than that of enkephalin alone (Papp 3.1×10-8 cm/s). By the methods of surface plasmon resonance and molecular modeling, we demonstrated that the enzymatic glycosylation of enkephalin enabled binding the asialoglycoprotein receptor. The addition of a trisaccharide moiety to enkephalin improved the binding of enkephalin to the asialoglycoprotein receptor two fold (KD = 91 µM). The docking scores from molecular modeling showed that the binding modes and affinities of the glycosylated enkephalin derivatives to the asialoglycoprotein receptor complemented the results from the surface plasmon resonance experiments

Nontypeable Haemophilus influenzae Has Evolved Preferential Use of N-Acetylneuraminic Acid as a Host Adaptation

Host-adapted bacterial pathogens such as NTHi cannot survive out of their host environment and have evolved host-specific mechanisms to obtain nutrients and evade the immune response. Relatively few of these host adaptations have been characterized at the molecular level. NTHi utilizes sialic acid as a nutrient and also incorporates this sugar into LOS, which is important in biofilm formation and immune evasion. In the present study, we showed that NTHi has evolved to preferentially utilize the Neu5Ac form of sialic acid. This adaptation is due to the substrate preference of the enzyme CMP-Neu5Ac synthetase, which synthesizes the activated form of Neu5Ac for macromolecule biosynthesis. This adaptation allows NTHi to evade killing by a human antibody response against the nonhuman sialic acid Neu5Gc.Nontypeable Haemophilus influenzae (NTHi) is a Gram-negative bacterial pathogen that is adapted exclusively to human hosts. NTHi utilizes sialic acid from the host as a carbon source and as a terminal sugar on the outer membrane glycolipid lipooligosaccharide (LOS). Sialic acid expressed on LOS is critical in NTHi biofilm formation and immune evasion. There are two major forms of sialic acids in most mammals, N-acetylneuraminic acid (Neu5Ac) and N-glycolylneuraminic acid (Neu5Gc), the latter of which is derived from Neu5Ac. Humans lack the enzyme to convert Neu5Ac to Neu5Gc and do not express Neu5Gc in normal tissues; instead, Neu5Gc is recognized as a foreign antigen. A recent study showed that dietary Neu5Gc can be acquired by NTHi colonizing humans and then presented on LOS, which acts as an antigen for the initial induction of anti-Neu5Gc antibodies. Here we examined Neu5Gc uptake and presentation on NTHi LOS. We show that, although Neu5Gc and Neu5Ac are utilized equally well as sole carbon sources, Neu5Gc is not incorporated efficiently into LOS. When equal amounts of Neu5Gc and Neu5Ac are provided in culture media, there is ∼4-fold more Neu5Ac incorporated into LOS, suggesting a bias in a step of the LOS biosynthetic pathway. CMP-Neu5Ac synthetase (SiaB) was shown to have ∼4,000-fold-higher catalytic efficiency for Neu5Ac than for Neu5Gc. These data suggest that NTHi has adapted preferential utilization of Neu5Ac, thus avoiding presentation of the nonhuman Neu5Gc in the bacterial cell surface. The selective pressure for this adaptation may represent the human antibody response to the Neu5Gc xenoantigen