Anti-Invasive Activity of Bovine Lactoferrin against Listeria monocytogenes.

We have investigated the possible role of bovine lactoferrin in protecting the intestinal epithelium from bacterial infections, using as an in vitro model enterocyte-like cell lines HT-39 and Caco-2 infected with a food-borne pathogen, Listeria monocytogenes . When infection occurred in the presence of 1 mg/ml of bovine lactoferrin, in the form of apolactoferrin or iron- or manganese-saturated forms, the adhesion of bacteria to eukaryotk cells was unaffected, but the number of internalized bacteria was reduced by 42- to 125-fold. The possibility of a toxic effect of lactoferrin was excluded, because bovine lactoferrin was used at nonbactericidal and noncytotoxic concentrations

Influence of iron-limiting conditions on E. coli HB101(pRI203) invasion

Availability of iron has been shwn to affect the virulence of different microorganisms, including enteroinvasive bacteria. In our research we studied the influence of ferric ions availability on bacteria able to penetrate epithelial cells

HUMAN SERUM NON-ANTIBODY INHIBITORS TOWARDS SA-11 ROTAVIRUS HEMAGGLUTINATION

In the present work the non-antibody inhibitory activity of human serum towards SA-11 rotavirus hemagglutination (HA) has been studied. Among human serum protein components, inhibitory activity was recovered in fractions III (beta-globulin), IV (alpha-globulin) and IV (glycoprotein). Additional experiments performed with purified lipo-protein sub-classes and their lipid and apolipoprotein moieties demonstrated the ability of HDL and, HDL1 to prevent SA-11 HA

Lactoferrin functions. Current status and perspectives

Lactoferrin, an iron-binding glycoprotein synthesized by neutrophils and exocrine glands, plays an important role in human innate defense mechanisms against bacteria, fungi, and viruses. First, a bacteriostatic activity of lactoferrin, depending on iron withholding to bacteria, and successively a bactericidal iron-independent effect, related to its binding on bacterial surfaces, was recognized. Many other functions have been ascribed to this cationic protein, including the inhibiting action toward bacterial adhesion and invasion of target host cells. Recent research also reported the lactoferrin influence on bacterial aggregation and biofilm development of Pseudomonas aeruginosa and Streptococcus mutans. The different lactoferrin functions can be justified by different physicochemical properties of the molecule, which include the iron-binding capability, the binding to anionic cell surfaces and molecules, and serine protease activity

Effect of inhibitors of HeLa cell structures and functions on Escherichia coli HB101 (PRI203) entry process.

We investigated the effect of some eucaryotic cytoplasmic structure and function inhibitors on the entry into HeLa cells of the Escherichia coli HB101 K12 strain, harbouring the recombinant plasmid pRI203, in which is cloned a 3.2 Kb chromosomal fragment of Yersinia pseudotuberculosis. Substances impairing microfilament structures and functions (cytochalasin B and trifluoroperazine) significantly reduced invasion ability whereas microtubule organization inhibitors (colchicine and vinblastine) were ineffective. Data obtained with a lipophilic weak base (methylamine), which raises the pH of intracellular vesicles, demonstrated that, in entry pathway of E. coli HB101 (pRI203), endosome acidification is not required. Host cell energy has been shown to contribute to bacterial internalization since the presence of oxidative phosphorylation and glycolysis inhibitors (sodium azide, 2-dinitrophenol and 2-deoxy-D-glucose) during the invasion process, affected bacterial entry

NECROTIC CELL DEATH IN HUMAN AMNIOTIC CELLS INFECTED BY LISTERIA MONOCYTOGENES

Listeria monocytogenes can cause a placental-foetal infection that results in spontaneous abortion, premature labour, stillbirth, or neonatal sepsis and meningitis. Bacteria cross the maternofoetal barrier at the villous syncytiotrophoblast level and subsequently spread from the placenta to the fetus. L. monocytogenes is able to induce different kinds of death in a variety of cells. Murine hepatocytes, murine T and human B lymphocytes, and murine dendritic cells die by apoptosis, whereas bacterial infection of murine and human macrophages leads mainly to necrotic cell death. As we previously described the efficient infection and growth of L. monocytogenes in a human amniotic cell line, we investigated the fate of these cells in order to analyse the mode of cell death. Our results provide biochemical and morphological evidence of necrotic death induced by L. monocytogenes infection

Heterogeneity of virulence-related properties in Listeria monocytogenes strains isolated from patients with haematological malignancies

Listeria monocytogenes is an intracellular foodborne pathogen of humans and animals for which there are indications of virulence differences among strains. Various virulence properties related to different phases of infection process were investigated in L. monocytogenes strains isolated from patients affected by haematological malignancies. In these isolates, besides to the clinical history, we analysed the haemolysin production, the survival to acidic pH, the ability to enter and proliferate in human intestinal-like and human macrophagic-like cells, as well as the allelic polymorphism of the actA gene involved in intracellular movement. A general heterogeneity in the virulence properties was detected which did not appear correlated with the clinical outcome of listeriosis but more probably was influenced by the status of the immune defence of the host