Transferrin increases adherence of iron-deprived Neisseria gonorrhoeae to human endometrial cells

Holo and apo-transferrins interfere with adherence to abiotic surfaces and with adhesion/invasion to HeLa cells in Staphylococcus spp

Staphylococcus aureus and Staphylococcus epidermidis are the major cause of infections associated with implanted medical devices. Colonization on abiotic and biotic surfaces is often sustained by biofilm forming strains. Human natural defenses can interfere with this virulence factor. We investigated the effect of human apo-transferrin (apo-Tf, the iron-free form of transferrin, Tf) and holo-transferrin (holo-Tf, the iron-saturated form) on biofilm formation by CA-MRSA S. aureus USA300 type (ST8-IV) and S. epidermidis (a clinical isolate and ATCC 35984 strain). Furthermore S. aureus adhesion and invasion assays were performed in a eukaryotic cell line. A strong reduction in biofilm formation with both Tfs was obtained albeit at very different concentrations. In particular, the reduction in biofilm formation was higher with apo-Tf rather than obtained with holo-Tf. Furthermore, while S. aureus adhesion to eukaryotic cells was not appreciably affected, their invasion was highly inhibited in the presence of holo-Tf, and partially inhibited by the apo form. Our results suggest that Tfs could be used as antibacterial adjuvant therapy in infection sustained by staphylococci to strongly reduce their virulence related to adhesion and cellular invasion.

Interaction of primary human endometrial cells with Neisseria gonorrhoeae expressing green fluorescent protein

Infection of the endometrium by Neisseria gonorrhoeae is a pivotal stage in the development of pelvic inflammatory disease in women. An ex vivo model of cultures of primary human endometrial cells was developed to study gonococcal-host cell interactions. To facilitate these studies, gonococci were transformed with a hybrid shuttle vector containing the gfp gene from Aequoria victoria, encoding the green fluorescent protein (GFP), to produce intrinsically fluorescent bacteria. The model demonstrated that both pili and Opa proteins were important for both mediating gonococcal interactions with endometrial cells and inducing the secretion of pro-inflammatory cytokines and chemokines. Pil+ gonococci showed high levels of adherence and invasion, regardless of Opa expression, which was associated with increased secretion of IL-8 chemokine and reduced secretion of IL-6 cytokine. Gonococcal challenge also caused increased secretion of TNF-alpha cytokine, but this did not correlate with expression of pili or Opa, suggesting that release of components from non-adherent bacteria may be involved in TNF-alpha induction. Thus, the use of cultured primary endometrial cells, together with gonococci expressing green fluorescent protein, has the potential to extend significantly our knowledge, at the molecular level, of the role of this important human pathogen in the immunobiology of pelvic inflammatory disease.

Gonococcal invasion of epithelial cells driven by P.IA, a bacterial ion channel with GTP binding properties

The neisserial porin P.I is a GTP binding protein that forms a voltage-gated channel that translocates into mammalian cell membranes and modulates host cell signaling events. Here, we report that P.I confers invasion of the bacterial pathogen Neisseria gonorrhoeae into Chang epithelial cells and that this event is controlled by GTP, as well as other phosphorus-containing compounds. Bacterial invasion was observed only for strains carrying the P.IA subtype of porin, which is typically associated with the development of disseminated neisserial disease, and did not require opacity outer membrane proteins, previously recognized as gonococcal invasins. Allelic replacement studies showed that bacterial invasiveness cotransferred with the P.IA (por1A) gene. Mutation of the P.I-associated protein Rmp did not alter the invasive properties. Cross-linking of labeled GTP to the porin revealed more efficient GTP binding to the P.IA than P.IB porin subtype. GTP binding was inhibited by an excess of unlabeled GTP, ATP, and GDP, as well as inorganic phosphate, but not by UTP or beta-glycerophosphate, fully in line with the respective invasion-inhibitory activities observed for these compounds. The P.IA-mediated cellular invasion may explain the more invasive behavior of P.IA strains in the natural infection and may broaden the basis for the development of a P.I-based gonococcal vaccine.

Gonococcal arthritis

Disseminated gonococcal infection is the most common systemic complication of acute gonorrhea and occurs in 0.5% to 3.0% of patients with untreated mucosal infection. It is also the most common cause of septic arthritis in patients less than 30 years of age. Fortunately, the incidence of gonorrhea is decreasing dramatically in the United States and Western Europe, although it is still high in developing countries. Increasing resistance to antibiotics requires continuous surveillance of antimicrobial susceptibilities to determine the efficacy of current therapeutic measures.

Isolation and analysis of a fur mutant of Neisseria gonorrhoeae

The pathogenic Neisseria spp. produce a number of iron-regulated gene products that are thought to be important in virulence. Iron-responsive regulation of these gene products has been attributed to the presence in Neisseria spp. of the Fur (ferric uptake regulation) protein. Evidence for the role of Fur in neisserial iron regulation has been indirect because of the inability to make fur null mutations. To circumvent this problem, we used manganese selection to isolate missense mutations of Neisseria gonorrhoeae fur. We show that a mutation in gonococcal fur resulted in reduced modulation of expression of four well-studied iron-repressed genes and affected the iron regulation of a broad range of other genes as judged by two-dimensional polyacrylamide gel electrophoresis (PAGE). All 15 of the iron-repressed spots observed by two-dimensional PAGE were at least partially derepressed in the fur mutant, and 17 of the 45 iron-induced spots were affected by the fur mutation. Thus, Fur plays a central role in regulation of iron-repressed gonococcal genes and appears to be involved in regulation of many iron-induced genes. The size and complexity of the iron regulons in N. gonorrhoeae are much greater than previously recognized.