Magda Marchetti

Lactoferrin inhibits herpes simplex virus type 1 adsorption to Vero cells

This paper describes the ability of human and bovine lactoferrins (HLf; BLf), iron-binding proteins belonging to the non-immune defense system, to interfere with herpes simplex virus type 1 (HSV-1) infection. Since lactoferrins are known to bind to heparan sulphate proteoglycans and to low density lipoprotein receptor, which in turn act as binding sites for the initial interaction of HSV-1 with host cells, we tested the effect of these proteins on HSV-1 multiplication in Vero cells. Both HLf and BLf are found to be potent inhibitors of HSV-1 infection, the concentrations required to inhibit the vital cytopathic effect in Vero cells by 50% being 1.41 microM and 0.12 microM, respectively. HLf and BLf exerted their activity through the inhibition of adsorption of virions to the cells independently of their iron withholding property showing similar activity in the apo- and iron-saturated form. The binding of [35S]methionine-labelled HSV-1 particles to Vero cells was strongly inhibited when BLf was added during the attachment step. BLf interacts with both Vero cell surfaces and HSV-1 particles, suggesting that the hindrance of cellular receptors and/or of viral attachment proteins may be involved in its antiviral mechanism.

Inhibition of poliovirus type 1 infection by iron-, manganese-and zinc-saturated lactoferrin

Abstract In this study we investigated the inhibitory activity of different milk proteins on poliovirus infection in Vero cells. Proteins analyzed were mucin, α-lactalbumin, β-lactoglobulin, and bovine and human lactoferrin. Viral cytopathic effect was not prevented by mucin, α-lactalbumin or β-lactoglobulin, whereas the lactoferrins tested were able to inhibit the replication of poliovirus in a dose-dependent manner. Further experiments were carried out in which apo- and native lactoferrin or lactoferrin fully saturated with ferric, manganese or zinc ions were added to the cells during different phases of viral infection. Results obtained demonstrated that all lactoferrins were able to prevent viral replication when present during the entire cycle of poliovirus infection or during the viral adsorption step. Only zinc lactoferrin strongly inhibited viral infection when incubated with the cells after the viral attachment, being the inhibition directly correlated with the degree of zinc saturation. Our results demonstrated that all lactoferrins interfered with an early phase of poliovirus infection; zinc lactoferrin was the sole compound capable of inhibiting a phase of infection subsequent to virus internalization into the host cells.

Antiviral Activity of Lactoferrin

In 1976, Matthews et al.19 reported the antiviral activity of milk proteins, underlining their possible clinical importance. Only recently, this effect has been ascribed mainly to lactoferrin (Lf). Lf was initially shown to exert a protective influence in mice infected with Friend leukemia virus15. Subsequently, a potent antiviral activity has been attributed to Lf, both in vitro towards cytomegalovirus (HCMV)9,7, herpes simplex virus (HSV)17, human immunodeficiency virus (HIV)7,29 and in vivo towards HSV-16 and HCMV25. Our groups provided evidence on the antiviral activity of Lf towards HSV-218, rotavirus28, and HIV22 infections (Table 1).

Metal complexes of bovine lactoferrin inhibit in vitro replication of herpes simplex virus type 1 and 2

The inhibitory effect of bovine lactoferrin (BLf) saturated with ferric, manganese or zinc ions, on the infection of Vero cells by human herpes simplex virus type 1 (HSV1) and 2 (HSV2) was investigated. Viral infectivity determined by intracellular antigen synthesis and plaque formation was efficiently inhibited by metal saturated lactoferrins in a dose-dependent manner. Effective BLf concentrations which reduced the infection by 50% ranged from 5.2 to 31 mug ml and were far below the cytotoxicity threshold. Fe BLf and Mn BLf exhibited selectivity indexes higher than Zn BLf and apoBLf for both viruses and the effect was mainly directed towards the early steps of infection. The slight viral inhibition shown by the citrate complexes of the different metals could indicate that the antiviral effect was not significantly influenced by Fe , Mn or Zn ions delivered by BLf into the cells.

Antiadenovirus activity of milk proteins: lactoferrin prevents viral infection

Different milk proteins were analysed for their inhibitory effect on adenovirus infection in vitro. Proteins investigated were mucin, alpha-lactalbumin, beta-lactoglobulin, bovine lactoferrin, and human lactoferrin. Results obtained demonstrated that mucin, alpha-lactalbumin, and beta-lactoglobulin did not prevent the viral cytopathic effect, whereas lactoferrin was able to inhibit adenovirus replication in a dose-dependent manner. Further experiments were carried out in which lactoferrin was added to the cells during different phases of viral infection. Results obtained showed that lactoferrin was able to prevent viral replication when added both before, or during the viral adsorption step, or when present during the entire replicative cycle of adenovirus, demonstrating that its action takes place on an early phase of viral replication.

Antiviral activity of lactoferrin towards naked viruses

It is well known that lactoferrin (Lf) is a potent inhibitor towards several enveloped and naked viruses, such as rotavirus, enterovirus and adenovirus. Lf is resistant to tryptic digestion and breast-fed infants excrete high levels of faecal Lf, so that its effect on viruses replicating in the gastrointestinal tract is of great interest. In this report, we analysed the mechanism of the antiviral action of this protein in three viral models which, despite representing different genoma and replication strategies, share the ability to infect the gut. Concerning the mechanism of action against rotavirus, Lf from bovine milk (BLf) possesses a dual role, preventing virus attachment to intestinal cells by binding to viral particles, and inhibiting a post adsorption step. The BLf effect towards poliovirus is due to the interference with an early infection step but, when the BLf molecule is saturated with Zn+2 ions, it is also capable of inhibiting viral replication after the viral adsorption phase. The anti-adenovirus action of BLf takes place on virus attachment to cell membranes through competition for common glycosaminoglycan receptors and a specific interaction with viral structural polypeptides. Taken together, these findings provide further evidence that Lf is an excellent candidate in the search of natural agents against viral enteric diseases, as it mainly acts by hindering adsorption and internalisation into cells through specific binding to cell receptors and/or viral particles.

Bovine Lactoferrin Inhibits Adenovirus Infection by Interacting with Viral Structural Polypeptides

ABSTRACT We recently demonstrated that lactoferrin, an antimicrobial glycoprotein, can inhibit adenovirus infection by competing for common glycosaminoglycan receptors. This study further characterizes the antiadenovirus activity of the protein, thus demonstrating that lactoferrin neutralizes infection by binding to adenovirus particles and that its targets are viral III and IIIa structural polypeptides.

Evaluation of uptake, cytotoxicity and inflammatory effects in respiratory cells exposed to pristine and -OH and -COOH functionalized multi-wall carbon nanotubes.

Toxic effects were reported for pristine‐multi‐wall carbon nanotubes (p‐MWCNTs) while the role of the functionalization on MWCNT‐induced toxicity is not yet well defined. We evaluated on human alveolar (A549) epithelial cells and normal bronchial (BEAS‐2B) cells exposed to p‐MWCNTs, MWCNTs‐OH and MWCNTs‐COOH: uptake by TEM, cell viability by different assays, membrane damage by the LDH assay and cytokine release by ELISA. The aims of the present study were to: (i) confirm MWCNT cytotoxicity mechanisms hypothesized in our previous studies; (ii) identify the most reliable viability assay to screen MWCNT toxicity; and (iii) to test our model to clarify the role of functionalization on MWCNT‐induced toxicity. In A549 cells, p‐MWCNTs and MWCNTs‐OH were localized free in the cytoplasm and inside vacuoles whereas MWCNTs‐COOH were confined inside filled cytoplasmic vesicles. WST‐1 and Trypan blue assays showed in A549 cells a similar slight viability reduction for all MWCNTs whereas in BEAS‐2B cells WST1 showed a high viability reduction at the highest concentrations, particularly for MWCNTs‐COOH. The MTT assay showed a false cytotoxicity as a result of MWCNTs‐interference. Pristine and MWCNTs‐COOH induced membrane damage, particularly in BEAS‐2B cells. MWCNTs‐COOH induced interleukin‐6 (IL‐6) and IL‐8 release in A549 cells whereas p‐MWCNTs induced IL‐8 release in BEAS‐2B cells. MWCNTs intracellular localization in A549 cells confirms the toxicity mechanisms previously hypothesized, with p‐MWCNTs disrupting the membrane and vesicle‐confined MWCNTs‐COOH inducing inflammation. WST‐1 was more reliable than MTT to test MWCNT‐toxicity. BEAS‐2B cells were more susceptible then A549 cells, particularly to MWCNT‐COOH cytotoxicity. Our results confirm the toxicity of p‐MWCNTs and demonstrate, also for the two kinds of tested functionalized MWCNTs toxic effects with a different mechanism of action. Copyright

Complete genome sequence of a serotype 11A, ST62 Streptococcus pneumoniae invasive isolate

BackgroundStreptococcus pneumoniae is an important human pathogen representing a major cause of morbidity and mortality worldwide. We sequenced the genome of a serotype 11A, ST62 S. pneumoniae invasive isolate (AP200), that was erythromycin-resistant due to the presence of the erm(TR) determinant, and carried out analysis of the genome organization and comparison with other pneumococcal genomes.ResultsThe genome sequence of S. pneumoniae AP200 is 2,130,580 base pair in length. The genome carries 2216 coding sequences (CDS), 56 tRNA, and 12 rRNA genes. Of the CDSs, 72.9% have a predicted biological known function. AP200 contains the pilus islet 2 and, although its phenotype corresponds to serotype 11A, it contains an 11D capsular locus. Chromosomal rearrangements resulting from a large inversion across the replication axis, and horizontal gene transfer events were observed. The chromosomal inversion is likely implicated in the rebalance of the chromosomal architecture affected by the insertions of two large exogenous elements, the erm(TR)-carrying Tn1806 and a functional prophage designated ϕSpn_200. Tn1806 is 52,457 bp in size and comprises 49 ORFs. Comparative analysis of Tn1806 revealed the presence of a similar genetic element or part of it in related species such as Streptococcus pyogenes and also in the anaerobic species Finegoldia magna, Anaerococcus prevotii and Clostridium difficile. The genome of ϕSpn_200 is 35,989 bp in size and is organized in 47 ORFs grouped into five functional modules. Prophages similar to ϕSpn_200 were found in pneumococci and in other streptococcal species, showing a high degree of exchange of functional modules. ϕSpn_200 viral particles have morphologic characteristics typical of the Siphoviridae family and are capable of infecting a pneumococcal recipient strain.ConclusionsThe sequence of S. pneumoniae AP200 chromosome revealed a dynamic genome, characterized by chromosomal rearrangements and horizontal gene transfers. The overall diversity of AP200 is driven mainly by the presence of the exogenous elements Tn1806 and ϕSpn_200 that show large gene exchanges with other genetic elements of different bacterial species. These genetic elements likely provide AP200 with additional genes, such as those conferring antibiotic-resistance, promoting its adaptation to the environment.

Inhibition of herpes simplex, rabies and rubella viruses by lectins with different specificities

A series of eleven lectins were investigated for their inhibiting activity towards herpes simplex type 1, rabies and rubella viruses. Herpes simplex virus adsorption was inhibited by Limulus polyphemus (LPA), Canavalia ensiformis (ConA) and wheat germ (WGA) agglutinins, whereas Bauhinia purpurea (BPA) and soybean agglutinins were more effective if present during viral replication; rabies virus attachment to susceptible cells was prevented by LPA and Narcissus pseudonarcissus (NPA) agglutinin whereas WGA and BPA were inhibitory at a later step; rubella virus multiplication was affected only after the attachment step by NPA, ConA and WGA.