Fertilization in humans is initiated by binding of spermatozoa to a selectin ligand on the egg’s extracellular matrix.

Aeromonas caviae Sch3N possesses a small genomic island that is involved in both flagellin glycosylation and lipopolysaccharide (LPS) O-antigen biosynthesis. This island appears to have been laterally acquired as it is flanked by insertion element-like sequences and has a much lower G؉C content than the average aeromonad G؉C content. Most of the gene products encoded by the island are orthologues of proteins that have been shown to be involved in pseudaminic acid biosynthesis and flagellin glycosylation in both Campylobacter jejuni and Helicobacter pylori. Two of the genes, lst and lsg, are LPS specific as mutation of them results in the loss of only a band for the LPS O-antigen. Lsg encodes a putative Wzx flippase, and mutation of Lsg affects only LPS; this finding supports the notion that flagellin glycosylation occurs within the cell before the flagellins are exported and assembled and not at the surface once the sugar has been exported. The proteins encoded by flmA, flmB, neuA, flmD, and neuB are thought to make up a pseudaminic acid biosynthetic pathway, and mutation of any of these genes resulted in the loss of motility, flagellar expression, and a band for the LPS O-antigen. Furthermore, pseudaminic acid was shown to be present on both flagellin subunits that make up the polar flagellum filament, to be present in the LPS O-antigen of the A. caviae wild-type strain, and to be absent from the A. caviae flmD mutant strain.Mesophilic Aeromonas strains are being increasingly recognized as important bacterial pathogens. They are widely distributed in the environment and cause gastrointestinal and wound infections in healthy humans and, less commonly, septicemia in immunocompromised patients (15). In particular, Aeromonas caviae is reported to be the most prevalent pediatric enteropathogenic species of the genus (30,46). A range of putative virulence factors have been described for the aeromonads, from the hemolytic toxin aerolysin and cytotonic toxins to capsules and extracellular enzymes (44). The process of adherence of aeromonads is still poorly understood, although a number of factors have been implicated, such as long wavy pili, outer membrane proteins, lipopolysaccharide (LPS) Oantigen, and the polar flagellum (1, 44). The mesophilic aeromonads are interesting as most strains express two distinct flagellum systems (10, 34). They have a polar flagellum for swimming in liquid and express separate lateral flagella for swarming over surfaces. Investigations have revealed that both the polar and lateral flagellum systems of the mesophilic aeromonads are involved in adherence to both biotic and abiotic surfaces (20).Previously, we showed that transposon mutations in the flm locus of A. caviae greatly reduced adherence of this organism to the human epithelial cell line HEp-2. In addition, mutation of this locus caused losses of motility, flagella, and the LPS O-antigen (12). In A. caviae Sch3N the flmA and flmB genes were clustered together in a locus with neuA, flmD, and neuB.

A recent analysis of the human sperm N-glycome confirmed the expression of biantennary bisecting type N-glycans and terminal Lewis(x)/Lewis(y) sequences previously implicated in the suppression of the innate and adaptive immune responses, respectively. In this study, glycomic analysis of seminal plasma glycoproteins derived from four fertile men was carried out to determine if the same sequences were expressed on the N- and O-glycome of human seminal plasma glycoproteins. Three major families of N-glycans were detected: (i) high mannose glycans (Man(5-7)GlcNAc(2)); (ii) bi-, tri-, and tetraantennary core-fucosylated complex type N-glycans with antennae terminated with Lewis(x) and/or Lewis(y) sequences; and (iii) bi-, tri-, and tetraantennary core-fucosylated complex type N-glycans with antennae capped with sialic acid. Analysis of the O-glycans revealed Core 1 and Core 2 type structures that are also fucosylated or sialylated or a combination of both. The same high mannose and polyfucosylated N-glycans associated with sperm are also present in seminal plasma. Bisecting type N-glycan expression is greatly decreased compared to sperm, while sialylated glycans are abundant in some individuals and minor in others. In summary, the glycosylation profile of seminal plasma glycoproteins is consistent with the modulation of the adaptive but not the innate arm of the human immune response.

Background:In vivo pharmacological inhibition of sialyltransferases has, to date, not been possible. Results: 3F-NeuAc acts as a global sialyltransferase inhibitor in mice and causes kidney and liver dysfunction. Conclusion: Sialoside expression can be modulated in vivo with a sialyltransferase inhibitor. Significance: Pharmacological blockade of sialoside expression will be an important tool for future exploration of sialic acid in health and disease.