Effect of HSV-2 Infection on the Expression of HPV 16 Genes in Caski Cells

Human papillomaviruses (HPVs) have been proposed to be the most important etiological factors for cervical cancer although different agents may act in conjunction. Herpes simplex virus type 2 (HSV-2) infection is considered as a possible cofactor to malignant transformation. To examine the influence of HSV-2 infection on the HPV genes expression, CaSki cells bearing 60 to 600 copies of HPV-16 DNA per cell were used as a model system. Twenty hours post HSV-2 infection the mRNA transcripts for HPV-16 early (E1, E2 and E6) and late (L1) genes were analysed by RT-PCR assay. Results indicated that the level of transcription of E1, E2 and E6 genes was up to 3-fold enhanced in HSV-2 infected CaSki cells suggesting that HSV-2 infection could increase the risk of cervical cancer by overexpression of both HPV regulatory and oncogenic genes.

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.

Virulence Traits in Escherichia Coli Strains Isolated from Outpatients with Urinary Tract Infections

This study aims to characterize phenotypic and genotypic virulence traits in Escherichia coli strains, isolated from outpatients with urinary tract infections, comparing with those obtained from inpatients. Information on the pathogenic behavior of the uropathogenic strains was obtained by monitoring different biological properties, such as autoagglutination, hemagglutination, adhesiveness to and invasion of human bladder (HT1376) cells, biofilm formation, phylogenetic grouping, and virulence-related genes. The results show similar behavior in the two groups concerning autoagglutination, hemagglutination, and biofilm formation. None of the strains examined was invasive. However, in strains from outpatients there was an increased adhesion to HT1376 cells compared with clinical strains, a significant higher presence of genes codifying for adhesins and cell protection factors, and a lower proportion of strains belonging to B1 group. These findings add further information on the pathogenic traits of community E. coli, since strains isolated from the outpatients' group were differently “armed” in comparison with those of clinical cases, and more suitable to infect healthy individuals.

Invasive pathway of Listeria ivanovii in human amnion-derived WISH cells

Among Listeria genus, only two species, Listeria ivanovii and Listeria monocytogenes, are pathogenic. L. ivanovii is almost only associated with infections in animals, mainly sheep and cattle, and has rarely been associated with human infections, whereas L. monocytogenes causes severe illnesses in both humans and animals. To further investigate the pathogenetic features of L. ivanovii in humans, we undertook a study in which the intracellular behaviour of this pathogen was analysed in WISH cells, a cell line derived from human amniotic tissue, and compared to that of L. monocytogenes. Using microbiological, biochemical, and ultrastructural approaches, we demonstrate that L. ivanovii can adhere to and invade human amniotic cells, lyse the phagosomal membrane, polymerize host cell actin, and spread from cell to cell more efficiently than L. monocytogenes. However, although L. ivanovii is capable of specifically infecting and replicating in human amnion cells, its survival in cytoplasm is limited compared to that of L. monocytogenes.

Acid adaptation and survival of Listeria monocytogenes in Italian-style soft cheeses

AIMS

The ability of Listeria monocytogenes to survive and grow at high salt concentrations and low pH makes it a potential hazard after the consumption of milk and dairy products, often implicated in severe outbreaks of listeriosis. This study was designed to evaluate the behaviour of L. monocytogenes in traditional acid and salted Italian-style soft cheeses and to investigate whether Listeria occurrence and growth in these environments may represent a potential increase of hazard.

METHODS AND RESULTS

A first approach was addressed to in vitro evaluate survival, acid tolerance response, ability to produce biofilm, and capability to invade intestinal-like cells of a L. monocytogenes strain grown under experimental conditions mimicking environmental features that this pathogen encounters in soft cheeses (such as acid pH and high NaCl content). A second set of experiments was performed to monitor, during the storage at 4 degrees C, the survival of acid-adapted and nonadapted Listeriae in artificially contaminated soft cheeses. Both acid tolerance response and invasion efficiency of acid-adapted bacteria resulted in an increase, even when bacteria were simultaneously pre-exposed to increasing salt stress. The contamination of cheeses with acid-adapted and nonadapted bacteria evidenced in all products a good survival. A significant increased survival, the recovery of bacterial cells highly resistant to lethal pH exposure, and the prevalence of filamentous structures were observed in crescenza cheese during the storage.

CONCLUSIONS

The Listeria survival and acid pH tolerance observed during refrigerated storage are probably related to the intrinsic acid and saline features of soft cheeses analysed.

SIGNIFICANCE AND IMPACT OF THE STUDY

Italian soft cheeses tested may represent a potential hazard for the recovery of acid-adapted L. monocytogenes cells with enhanced ability to adhere to inert surfaces and/or to penetrate host cells.

Gut-associated bacterial microbiota in paediatric patients with inflammatory bowel disease

BACKGROUND

Clinical and experimental observations in animal models indicate that intestinal commensal bacteria are involved in the initiation and amplification of inflammatory bowel disease (IBD). No paediatric reports are available on intestinal endogenous microflora in IBD.

AIMS

To investigate and characterise the predominant composition of the mucosa-associated intestinal microflora in colonoscopic biopsy specimens of paediatric patients with newly diagnosed IBD.

METHODS

Mucosa-associated bacteria were quantified and isolated from biopsy specimens of the ileum, caecum and rectum obtained at colonoscopy in 12 patients with Crohn's disease, 7 with ulcerative colitis, 6 with indeterminate colitis, 10 with lymphonodular hyperplasia of the distal ileum and in 7 controls. Isolation and characterisation were carried out by conventional culture techniques for aerobic and facultative-anaerobic microorganisms, and molecular analysis (16S rRNA-based amplification and real-time polymerase chain reaction assays) for the detection of anaerobic bacterial groups or species.

RESULTS

A higher number of mucosa-associated aerobic and facultative-anaerobic bacteria were found in biopsy specimens of children with IBD than in controls. An overall decrease in some bacterial species or groups belonging to the normal anaerobic intestinal flora was suggested by molecular approaches; in particular, occurrence of Bacteroides vulgatus was low in Crohn's disease, ulcerative colitis and indeterminate colitis specimens.

CONCLUSION

This is the first paediatric report investigating the intestinal mucosa-associated microflora in patients of the IBD spectrum. These results, although limited by the sample size, allow a better understanding of changes in mucosa-associated bacterial flora in these patients, showing either a predominance of some potentially harmful bacterial groups or a decrease in beneficial bacterial species. These data underline the central role of mucosa-adherent bacteria in IBD.

Apoptotic death of Listeria monocytogenes-infected human macrophages induced by lactoferricin B, a bovine lactoferrin-derived peptide

Listeria monocytogenes, an intracellular facultative food-borne pathogen, was reported to induce apoptosis in vitro and in vivo in a variety of cell types with the exception of murine macrophages. These cells represent the predominant compartment of bacterial multiplication and die as a result of necrosis. In this study we showed that human non-activated and IFN-gamma-activated macrophagic-like (THP-1) cells infected with L. monocytogenes, mainly die by necrosis rather than by an apoptotic process. Two natural products derived from bovine milk, lactoferrin and its derivative peptide lactoferricin B, are capable of regulating the fate of infected human macrophages. Bovine lactoferrin treatment of macrophages protects them from L. monocytogenes-induced death whereas lactoferricin B, its derivative peptide, determines a shifting of the equilibrium from necrosis to apoptosis.

Infectious agents in tissues from spontaneous abortions in the first trimester of pregnancy

Some evidence suggests that intrauterine infection plays a major role in the pathogenesis of early pregnancy loss, but the implication and prevalence of microrganisms in the aetiology of spontaneous abortion during the first trimester of pregnancy has not yet been well established. In this study, we analysed the tissues relative to the product of conception from abortions during the first trimester (51 spontaneous abortions and 56 voluntary pregnancy interruptions) in women attending the Gynecological Sciences Perinatology and Puericulture Department of "Policlinico Umberto I". Specimens were investigated by cultural methods for the presence of yeasts, gram positive, gram negative bacteria, and genital mycoplasma. By molecular diagnostic procedures, DNA sequences of Chlamydia trachomatis, herpes simplex viruses, adenovirus, human papillomaviruses and human polyomaviruses BK and JC were searched. None of these agents could be found in voluntary pregnancy interruption samples, with the exception of 3.6% of specimens positive for adenovirus, whereas spontaneous abortion tissues were positive for at least one microrganism by 31.5%. Data analysis showed the occurrence of both monomicrobial and polymicrobial infections.

Detection of Listeria monocytogenes in Italian-style soft cheeses

AIMS

A rapid detection system specific for Listeria monocytogenes and based on the polymerase chain reaction (PCR) was developed.

METHODS AND RESULTS

Primers annealing to the coding region of the actA gene, critically involved in virulence and capable of discrimination between two different alleles naturally occurring in L. monocytogenes, have been utilized. The procedure was applied to recover L. monocytogenes cells in artificially contaminated fresh Italian soft cheeses (mozzarella, crescenza and ricotta). Low levels of L. monocytogenes were detected in mozzarella and crescenza homogenates (0.04-0.4 and 4 CFU g(-1), respectively) whereas in ricotta the detection limit was higher (40 CFU g(-1)).

CONCLUSIONS

This PCR-based assay is highly specific as primers used recognize the DNA from different L. monocytogenes strains of clinical and food origin, while no amplification products result with any other Listeria spp. strains.

SIGNIFICANCE AND IMPACT OF THE STUDY

This study highlighted a low-cost and rapid procedure that can be appropriated for the detection in real time of low L. monocytogenes levels in soft cheese.

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 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.

Involvement of herpes simplex type 2 in modulation of gene expression of human papillomavirus type 18

Human papillomaviruses (HPVs) and herpes simplex virus type 2 (HSV-2) can establish latent or persistent infections in the host, and are involved in the aetiology of benign and/or malignant lesions of the urogenital tract. To investigate the putative interaction between these DNA viruses when a double infection occurs, we have studied the effect of HSV-2 infection in HeLa 229 cells containing 10-50 copies of HPV type 18 genomic DNA. Twenty hours post HSV-2 infection, the analysis of mRNA transcripts from E1, E2, E6 early and L1 late HPV18 genes was performed in HeLa cells by a semi-quantitative RT-PCR assay. A modulation of HPV18 E1 and E6 early genes was observed, resulting in a 9-fold and 3-fold increased transcription respectively.

Herpes simplex virus type 2 modulates the susceptibility of human bladder cells to uropathogenic bacteria

The present study analyses the susceptibility of human bladder-derived cells (HT-1376) to the infection by herpes simplex virus type 2 (HSV-2) and Chlamydia trachomatis, as well as to the adhesiveness of uropathogenic bacteria. HT-1376 cells were efficiently infected by HSV-2 strain 333, as demonstrated by immunofluorescence staining of viral antigens, titration of cytopathic effect, and visualisation by transmission electron microscopy. This cell model was also prone to C. trachomatis (serovar E, Bour strain) replication and to the adherence of clinical uropathogenic isolates of Escherichia coli, Pseudomonas aeruginosa, Proteus vulgaris and Enterococcus faecalis. The pre-infection of HT-1376 cells with HSV-2 caused a tenfold increased adherence of an E. coli strain (U1), isolated from a patient affected by severe haemorrhagic cystitis, whereas in HSV-2 pre-infected cells the number of C. trachomatis inclusion bodies was significantly reduced. Our findings indicate that these cells are a suitable in vitro model for studying infection and super-infection of the lower urinary tract by viruses and bacteria.

Involvement of bovine lactoferrin moieties in the inhibition of herpes simplex virus type 1 infection

Bovine lactoferrin (BLf) is an iron binding protein folded in two lobes, N- and C-lobes. In this study we have reported the inhibitory activity towards herpes simplex virus type 1 (HSV-1) in vitro infection of BLf tryptic digested N- and C-lobes in comparison with the whole protein. The N-lobe and C-lobe exerted an anti-herpesvirus activity 50- and 10-fold lower than native BLf, respectively. In order to assess the phase of viral replication affected, lactoferrin-derived lobes were added to the cells at different non cytotoxic concentrations, during the whole cycle of viral infection or during viral attachment step, demonstrating that both lobes interfered with the early phases of infection. Among the BLf tryptic digested fragments, two negatively-charged small peptides deriving from N-lobe, previously shown effective towards HSV-1, have been further studied. We assessed that the net negative charge of these peptides was not responsible for the antiviral activity since their activity was not modified when the aspartic and glutamic acidic residues of these peptides were replaced with asparagine and glutamine, respectively. The experiments here reported confirm a pivotal role of N-lobe in inhibiting viral infection. However, the residual inhibiting activity of C-lobe and the similar efficacy shown by negatively or positively charged peptides strongly support the idea that the antiviral activity of bovine lactoferrin cannot be fully explained simply on the basis of competition between the protein and viral recognition sites for binding to glycosaminoglycans.

Infection of human enterocyte-like cells with rotavirus enhances invasiveness of Yersinia enterocolitica and Y. pseudotuberculosis

Mixed infection with rotavirus and either Yersinia enterocolitica or Y. pseudotuberculosis was analysed in Caco-2 cells, an enterocyte-like cell line highly susceptible to these pathogens. Results showed an increase of bacterial adhesion and internalisation in rotavirus-infected cells. Increased internalisation was also seen with Escherichia coli strain HB101 (pRI203), harbouring the inv gene from Y. pseudotuberculosis, which is involved in the invasion process of host cells. In contrast, the superinfection with bacteria of Caco-2 cells pre-infected with rotavirus resulted in decreased viral antigen synthesis. Transmission electron microscopy confirmed the dual infection of enterocytes. These data suggest that rotavirus infection enhances the early interaction between host cell surfaces and enteroinvasive Yersinia spp.

Acid tolerance in Listeria monocytogenes influences invasiveness of enterocyte-like cells and macrophage-like cells

Clinical and food Listeria monocytogenes isolates, pre-exposed to mild acidic conditions, were able to readily develop acid tolerance, irrespective of their origin. We attempted to investigate the influence of acid tolerance mechanisms, either constitutive or induced, on the invasive behaviour of this facultative food-borne pathogen. Entry efficiency and intracellular growth of acid-tolerant strains were evaluated in in vitro cell models capable to mimic in vivo target cells, such as enterocytes and macrophages. An acid-adapted L. monocytogenes wild-type strain and a constitutively acid-tolerant mutant were able to enter enterocyte-like (Caco-2) cells as well as to survive and proliferate intracellularly in lipopolysaccharide-treated macrophage-like (J774.A1) cells, at a significant increased extent by respect of the non acid-adapted wild-type strain. These findings add new information about the influence of the acid tolerance response on L. monocytogenes virulence, suggesting that in acid-adapted bacteria the early events of pathogenesis which allow the colonization and the spread of bacteria in the host may be highly promoted.

Modulation of actA gene expression in Listeria monocytogenes by iron

This study analysed the invasiveness of Listeria monocytogenes into enterocyte-like Caco-2 cells in which iron depletion was achieved by picolinic acid treatment. Both entry and intracellular multiplication varied depending on the endogenous iron content of bacterial and eukaryotic cells. The behaviour within enterocytes was correlated with a 10-fold increased transcription of the actA gene observed in bacterial cells grown under conditions of iron stress.

Bovine lactoferrin peptidic fragments involved in inhibition of herpes simplex virus type 1 infection

Bovine lactoferrin (BLf) prevents the infection of some enveloped and naked viruses. To identify BLf sequences responsible for the antiviral activity, we tested 31 HPLC fractions, derived from tryptic digestion of BLf, toward herpes simplex virus type 1 (HSV-1). Only a few HPLC purified fragments were active against HSV-1, even if at lower extent than the native undigested BLf. Two large fragments, one corresponding to the C-lobe (amino acid sequence 345-689) and the other corresponding to a large portion of the N-lobe (1-280), were inhibitors of HSV-1 infection, while a smaller part of the N-lobe (86-258) was ineffective. Among the low-molecular-weight fragments, only two small peptides, which coeluted in a single chromatographic peak, were effective towards HSV-1. These peptides, both present in the N-lobe, were identified as peptides 222-230 (ADRDQYELL) and 264-269 (EDLIWK). The same peptides, chemically synthesised, were able to inhibit HSV-1 infection only when they were assayed in association.

The anti-invasive effect of bovine lactoferrin requires an interaction with surface proteins of Listeria Monocytogenes

The anti-invasive effect of bovine lactoferrin (BLf) and of bovine transferrin (BTf) towards L. monocytogenes, an intracellular facultative food-borne pathogen, was assayed in the enterocyte-like cell line Caco-2. When 0.5 mg/ml BLf were added during the infection time or preincubated with bacteria the number of internalized bacteria was noticeably decreased whereas BLf was ineffective when preincubated with the enterocytes or added post infection. BTf was deprived of any effect. Results from direct binding and Western blotting assays provided evidence that two L. monocytogenes surface proteins, of approximately 80 and 60 kDa, specifically reacted with BLf. These findings strongly support the hypothesis that the antiinvasive mechanism of BLf is due to its interaction with bacterial surfaces, but not to its binding with eukaryotic cells.

Detection of viral and bacterial infections in women with normal and abnormal colposcopy

Signs and symptoms of sexually-transmitted diseases (STD) do not allow any etiological diagnosis in women. Colposcopic findings are seldom pathognomic. Consequently, the microbiology laboratory with the recent availability of molecular diagnostic tools is required to detect the infectious bacterial and/or viral agents involved in STD. In cervical samples of women submitted to gynaecological screening for past or present signs and symptoms of inflammation and with different colposcopic findings, we searched by molecular approaches Chlamydia trachomatis, Mycoplasma genitalium, herpes simplex virus type 1 and 2, adenovirus and 45 genotypes of papillomaviruses and, by cultural methods Mycoplasma hominis and Ureaplasma urealyticum. Colposcopy permitted us to divide the studied population into three groups: 48 women had negative colposcopic findings, 50 presented signs of flogosis and 100 resulted positive for an abnormal transformation zone (ANTZ) and/or for HPV colposcopic findings. Results obtained by microbiological assays indicated that the prevalence of infectious agents did not always correlate with colposcopy. Double and triple infections were found in groups 2 and 3, with mycoplasmas being the most common microrganisms present in association and quite almost copresent with papillomaviruses.

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

In this study we investigated the inhibitory activity of different milk proteins on poliovirus infection in Vero cells. Proteins analyzed were mucin, alpha-lactalbumin, beta-lactoglobulin, and bovine and human lactoferrin. Viral cytopathic effect was not prevented by mucin, alpha-lactalbumin or beta-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.

Natural milk fatty acids affect survival and invasiveness of Listeria monocytogenes

The effects of 12 fatty acids, naturally occurring in milk from several mammalian species, on the survival and invasion ability of Listeria monocytogenes, a food-borne pathogen, were determined. The survival was tested in the presence of 200 micrograms ml-1 fatty acids suspended in brain hearth infusion broth or in storage conditioning solution (NaCl 1%) of Mozzarella cheese, an Italian soft unripened cheese, at pH 7.0 or 5.0. Lauric (C12:0), linoleic (C18:2) and linolenic (C18:3) acids exerted the strongest bactericidal activity. The invasive efficiency of L. monocytogenes, determined in the Caco-2 enterocyte-like cell line, was strongly decreased in the presence of the fatty acids tested (from about 20 to 500-fold). This research suggests that naturally occurring fatty acids of milk, supplemented in milk derivatives, could affect both bacterial growth and invasiveness and consequently, could serve as barriers towards L. monocytogenes infection.

Simultaneous detection of HPV and other sexually transmitted agents in chronic urethritis

BACKGROUND

Many pathogens may be responsible of Non Gonococcal Urethritis (NGU) with the possible occurrence of symptomatic and asymptomatic mixed viral and bacterial infections. In particular, genital papillomaviruses (HPVs) have been searched since they are linked to both benign and malignant lesions of the penis and urethra and the presence of a potential male carried state has received limited scrutiny while the screening of sexually active females has received substantial attention.

METHODS

In male patients affected by chronic NGU, the presence of DNA of Chlamydia trachomatis, herpes simplex virus (HSV) type 1 and 2 and human papillomaviruses by PCR and the occurrence of Gram positive and Gram negative micro-organisms, of Mycoplasma hominis and Ureaplasma urealyticum, by conventional cultural methods have been investigated.

RESULTS

Results obtained indicated a high percentage of mixed infections, up to 36%. Genital HPV DNA was detected in 31% of specimens positive for two or more agents, and HSV DNA was detected in 10% of studied population.

CONCLUSIONS

The concomitant presence of different infectious agents could determine latent, sub-clinical or chronic infections with periodic reactivation. In particular results suggest that HPV and HSV may stimulate cytokine production which can up regulate the expression of other infectious agents and may be responsible for latent chlamydial infections characterised by the persistence of this micro-organism in an altered form, viable but in a culture negative state. Therefore an increased awareness of mixed infections is relevant to define the management and treatment of chronic urethritis.

Antiviral effect of bovine lactoferrin saturated with metal ions on early steps of human immunodeficiency virus type 1 infection

Lactoferrin is a mammalian iron-binding glycoprotein present in many biological secretions, such as milk, tears, semen and plasma and a major component of the specific granules of polymorphonuclear leucocytes. The effect of bovine lactoferrin (BLf) in apo-form or saturated with ferric, manganese or zinc ions, on human immunodeficiency virus type 1 (HIV-1) infection in the C8166 T-cell line was studied. Both HIV-1 replication and syncytium formation were efficiently inhibited, in a dose-dependent manner, by lactoferrins. BLf in apo and saturated forms markedly inhibited HIV-1 replication when added prior to HIV infection or during the virus adsorption step, thus suggesting a mechanism of action on the HIV binding to or entry into C8166 cells. Likewise, the addition of Fe3+BLf prior to HIV infection and during the attachment step resulted in a marked reduction of the HIV-1 DNA in C8166 cells 20 h after infection. The potent antiviral effect and the high selectivity index exhibited by BLf suggest for this protein, in apo or saturated forms, an important role in inhibiting the early HIV-cell interaction, even though a post adsorption effect cannot be ruled out.

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 micrograms ml-1 and were far below the cytotoxicity threshold. Fe3+BLf and Mn2+BLf exhibited selectivity indexes higher than Zn2+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 Fe3+, Mn2+ or Zn2+ ions delivered by BLf into the cells.

Antirotaviral activity of milk proteins: lactoferrin prevents rotavirus infection in the enterocyte-like cell line HT-29

Different milk proteins were analyzed for their inhibitory effect on either rotavirus-mediated agglutination of human erythrocytes or rotavirus infection of the human enterocyte-like cell line HT-29. Proteins investigated were alpha-lactalbumin, beta-lactoglobulin, apo-lactoferrin, and Fe(3+)-lactoferrin, and their antiviral action was compared with the activity of mucin, a milk glycoprotein known to affect rotavirus infection. Results obtained demonstrated that beta-lactoglobulin, apo- and Fe(3+)-lactoferrin are able to inhibit the replication of rotavirus in a dose-dependent manner, apo-lactoferrin being the most active. It was shown that apo-lactoferrin hinders virus attachment to cell receptors since it is able to bind the viral particles and to prevent both rotavirus haemagglutination and viral binding to susceptible cells. Moreover, this protein markedly inhibited rotavirus antigen synthesis and yield in HT-29 cells when added during the viral adsorption step or when it was present in the first hours of infection, suggesting that this protein interferes with the early phases of rotavirus infection.

Identification of Listeria monocytogenes by colony hybridization test using the virulence-associated hly and inlA genes as probes

We developed a method of identification of Listeria monocytogenes based on colony hybridization with nonradioactively labeled DNA probes, represented by the hly and inlA virulence-associated genes. The procedure described in this paper results simple, rapid, specific and reproducible. Since it can be performed in a short time, the above technique can be applied to detect L. monocytogenes from different source and constitutes a noteworthy and alternative tool to identify this gram-positive pathogenic bacterium.

In vitro effect of natural and semi-synthetic carbohydrate polymers on Chlamydia trachomatis infection

The effect of different natural and semi-synthetic polysaccharides on Chlamydia trachomatis multiplication in Hela 229 cells was evaluated. Some neutral, negatively and positively charged carbohydrates were able, in a dose-dependent fashion, to inhibit chlamydial infection by interfering mainly with the adsorption process. The inhibiting compounds, whose effect was shown within the concentration range of 8-200 micrograms/ml, were in order of action: dextran sulphate > glyloid sulphate 4327 > glycogen sulphate 4427 > arabic gum = glyloid > chitosan > glycogen. Data obtained suggested that antichlamydial activity was not only related to the electric charge of these molecules but could also be attributed to other features of their polymeric backbone. Since carbohydrate polymers have also been shown to inhibit the early stages of infection by viral agents causing sexually transmitted diseases, the employment of these molecules for prevention or treatment of mixed viral-C. trachomatis infections can be hypothesized.

Superinfection by Listeria monocytogenes of cultured human enterocyte-like cells infected with poliovirus or rotavirus

A mixed infection with either rotavirus or poliovirus and Listeria monocytogenes was analysed in Caco-2 cells, a tumour-derived cell line, highly susceptible to these pathogens. The multiplication of these pathogens, whose usual site of entry and/or replication is the intestine, was also followed by electron microscopy. Results obtained showed an increase of L. monocytogenes internalisation in cells infected with rotavirus, whereas the preinfection with poliovirus had only a slight interfering effect on bacterial entry. Analysis of L. monocytogenes multiplication in virus-infected cells revealed that rotavirus also promoted bacterial replication, which poliovirus hampered replication. Concerning the effect of Caco-2 cell invasion by L. monocytogenes on viral replication, we observed an increase in rotavirus antigen synthesis but no significant effect on poliovirus yield under our experimental conditions.

Iron availability affects entry of Listeria monocytogenes into the enterocytelike cell line Caco-2

The influence of iron on the entry of Listeria monocytogenes into Caco-2 cells was studied. Iron availability was found to modify the surface hydrophobicity and protein profile of L. monocytogenes, with the result that cell invasion strongly increased upon bacterial growth in iron-rich medium. The enhanced invasive capability of iron-overloaded L. monocytogenes cells correlates to the higher-level expression of the inlAB virulence genes, which were positively iron regulated at the transcriptional level.

In vitro study of a double infection by herpes simplex virus type 2 and Chlamydia trachomatis

Sexually transmitted diseases (STDs) may recognize multiple etiological agents. Among them, Chlamydia trachomatis (Ct) and herpes simplex virus type 2 (HSV-2) cause symptomatic, subclinical and asymptomatic infections of the urogenital tract which can lead to serious sequelae. In the present study the coinfection and superinfection by Ct and HSV-2 in epithelial cultured cells from human cervix (HeLa 229) are described. A double infection, followed by the intracellular synthesis of chlamydial and viral antigens, was established. Both synergistic and interfering phenomena were recorded: viral antigen synthesis resulted increased whereas Ct inclusion bodies were produced to a lower extent.

The effects of inhibitors of vacuolar acidification on the release of Listeria monocytogenes from phagosomes of Caco-2 cells

To evaluate the role of the acidic pH of phagosomes on the invasive ability and fate of Listeria monocytogenes within host cells, entry and replication of this gram-positive bacterium in a human enterocyte-like cell line (Caco-2) were investigated by a combination of biochemical and ultrastructural approaches. The effects of inhibitors of vacuolar acidification--the lipophilic weak base ammonium chloride, the carboxylic ionophore monensin and the vacuolar proton ATPase inhibitor bafilomycin A1--on the bacterial invasion pathway were analysed. These agents, which raise the intracellular vesicle acidic pH of living cells by different mechanisms, affected L. monocytogenes replication in Caco-2 cells. Bacteria internalised by bafilomycin-treated cells were unable to escape from phagosomes, as demonstrated by electronmicroscopy. The results provide evidence that low pH is required for efficient intracellular growth of L. monocytogenes.

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.

Invasion of cultured human cells by Streptococcus pyogenes

The invasive capacity of streptococcal strains belonging to groups A and B was evaluated by infecting human epithelial and endothelial cells and monitoring the number of viable intracellular bacteria at different times postinfection. All strains tested entered eukaryotic cells (HeLa, HEp2 and HUVE), with Streptococcus pyogenes exhibiting a higher invasion efficiency than group B streptococci (GBS). No intracellular multiplication was observed, and GBS remained viable 24 h postinfection, whereas S. pyogenes were gradually killed. We found that cytochalasin D almost completely inhibited internalization of all bacterial strains, whereas colchicine had no effect, indicating that host microfilaments play a major role in bacterial internalization. Moreover, the use of the lysosomotropic agent ammonium chloride enabled us to demonstrate that a pH increase in the intracellular vesicles did not affect streptococcal entry. These results were documented by electron microscopic observations which revealed the different steps in the invasion pathway, including a fusion event between phagosomes containing S. pyogenes and lysosomes.

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.

Inhibition of herpes simplex virus infection by negatively charged and neutral carbohydrate polymers

Different natural and semisynthetic polysaccharides were evaluated for their inhibitory effect on in vitro replication of herpes simplex virus (HSV) types 1 and 2. Some neutral and negatively charged carbohydrates were able to inhibit viral infection by interfering mainly with the adsorption process showing a dose-dependent relationship. Their effect was shown within the concentration range of 200-0.8 micrograms/ml, and the inhibiting compounds were in order of action: dextran sulfate = scleroglucan = lambda carrageenan > glyloid sulfate 4324 > locust beam gum towards HSV-1 and dextran sulfate = glyloid sulfate 4324 = lambda carrageenan > scleroglucan > glycogen sulfate 4435 towards HSV-2. The data obtained indicate that the antiviral activity of polysaccharides was not only related to their electric charge. Other characteristics of the molecules such as the polymeric backbone, the carbohydrate moieties and the degree of polymerization could play a role in influencing their antiviral properties.

Enhancement of rotavirus infectivity by saturated fatty acids

The effect of different saturated fatty acids from 10 to 16 carbon atom chains and some derivatives on the infectivity of SA-11 rotavirus was examined. Both fatty acids and derivatives induced an increase of rotavirus infected LLC-MK2 cells when present during viral absorption to host cells. Capric acid and palmitic acid were the most effective with a dose-dependent relationship. These last lipids, in the same experimental conditions, failed to restore the susceptibility to infection of LLC-MK2 cells made resistant by neuraminidase treatment or to allow cell infection by non-infectious single-shelled viral particles. Results obtained suggest that the enhancing effect on viral infectivity by saturated fatty acids requires previous binding of rotaviral outer capsid proteins to sialic acid containing cell receptors.

Listeria monocytogenes infection of Caco-2 cells: role of growth temperature

The aim of the present study was to evaluate the role of temperature in the virulence of Listeria monocytogenes, a Gram-positive facultative intracellular food-borne pathogen. The capacity of bacteria grown at 37, 25 and 4 degrees C to develop haemolytic activity, to enter the Caco-2 enterocyte-like cell line and to multiply intracellularly was investigated. We demonstrated that L. monocytogenes penetration was not significantly influenced by the growth temperature of cultures and that bacteria grown at low temperature were capable of synthesizing internalin and, during the infection process, of restoring the haemolytic phenotype which is normally lacking in the extracellular environment at 4 and 25 degrees C. It can be concluded that L. monocytogenes, frequently present in numerous environmental sources and also in refrigerated food products, produces at low temperature, the virulence factors necessary to invade intestinal cells.

Effect of lactoferricin B, a pepsin-generated peptide of bovine lactoferrin, on Escherichia coli HB101 (pRI203) entry into HeLa cells

Bovine lactoferrin and a pepsin-generated peptide of bovine lactoferrin, known as lactoferricin B, were tested for an ability to influence the cell-invasive properties of an Escherichia coli HB101 strain carrying the plasmid pRI203, which encodes the Yersinia pseudotuberculosis inv gene. At non-cytotoxic and non-bactericidal concentration (0.5 mg/ml) lactoferricin B lowered by about tenfold the cell invasion capability of E. coli HB101 (pRI203), whereas no effect was observed when bovine lactoferrin was added during the infection of HeLa cell monolayers. The step of the invasion process affected by lactoferrin B was the internalization since the adhesion of bacteria to HeLa cells was unaltered in the presence of the peptide. Latex beads coated with lactoferrin B bound to HeLa cell monolayers and induced the agglutination of bacterial cells, indicating that this highly cationic peptide interacts directly with both eukaryotic and bacterial surfaces. Moreover, we demonstrated that the anti-invasive effect induced by lactoferrin B was reversed when the medium was supplemented with Ca2+, Mg2+ and Fe2+ ions which diminished its affinity binding. Our findings suggest that lactoferrin B effectiveness towards E. coli HB101 (pRI203) invasion is correlated to its binding capability on the eukaryotic and bacterial cell surfaces.

The effect of iron on the invasiveness of Escherichia coli carrying the inv gene of Yersinia pseudotuberculosis

The effect of growth in iron-excess or iron-limitation conditions on the invasiveness for HeLa cells of Escherichia coli HB101 carrying plasmid pRI203 which bears the invasion gene of Yersinia pseudotuberculosis was examined. Iron-limitation reduced adhesion and the number of organisms internalised by HeLa cells by about 100-fold. The reduced adhesion of iron-starved bacteria correlated with reduced hydrophobicity and the reduced invasiveness appeared to depend on the plasmid copy number, which was 3.5-fold less than in bacteria grown in iron excess.

Rotavirus and poliovirus co-infection in HT-29 cells

The effect of a mixed poliovirus-rotavirus infection in HT-29 cells, a gut tumour derived cell line highly susceptible to both viruses, has been analyzed. The obtained results showed an increase of poliovirus multiplication in cells super-infected or co-infected with rotavirus, whereas the pre-infection with poliovirus had an interfering effect on rotavirus replication.

Invasiveness of Shigella flexneri in poliovirus infected HT-29 cells

In this paper we report the effect in HT-29 cells of mixed infections with poliovirus type 1 and Shigella flexneri serotype 5 strain M90T and derivative strains differing in adhesive as well as invasive properties. HT-29 epithelial intestinal cells derived from a human colon adenocarcinoma are a good model for coinfection studies because they are susceptible both to poliovirus replication and to S. flexneri invasion. The results show that 48 h after infection by poliovirus the invasiveness of wild-type S. flexneri M90T and of its adherent and invasive derivative M90T (pIL22) is increased. However, the alterations produced in HT-29 cells at the later stage of poliovirus infection are not sufficient to promote the internalization of simply non invasive, or non invasive but adherent, isogenic derivative bacterial strains.

Influence of lactoferrin on the entry process of Escherichia coli HB101 (pRI203) in HeLa cells

Lactoferrin (Lf) is an iron-binding protein which plays an important role in the host defense systems of different mucosal surfaces including the intestinal mucosa. In the present research the role of apo-Lf and iron-saturated Lf in the invasion process of enteroinvasive bacteria, grown in iron stress or excess, was investigated. As enteroinvasive bacterium, Escherichia coli HB101 strain harboring a plasmid which contains the chromosomal inv gene from Yersinia pseudotuberculosis was utilized. The product of this gene (invasin) enables this microorganism to invade human epithelial cultured cells (HeLa). The results obtained showed that apo-Lf and iron-saturated Lf added at physiological concentration during the infection exerted a significant inhibition of adhesion (3.2 x 10(5) instead 3.4 x 10(6) adherent bacteria grown in iron excess; 1.6 x 10(3) instead of 2.3 x 10(4) adherent bacteria grown in iron-limited medium) and internalization (4.0 x 10(5) instead of 3.7 x 10(6) internalized bacteria grown in iron excess; 2.1 x 10(3) instead 2.8 x 10(4) internalized bacteria grown in iron-limited medium). It has also been demonstrated that in these experimental conditions Lf binds to HeLa cell membrane as well as to bacterial outer membrane. It is likely that this binding interfere with the early events of interaction between bacteria and eukaryotic cells. This inhibiting effect of Lf on the invasion efficiency of E. coli HB101 (pRI203) could be related to the cationic nature of the molecule, although other mechanisms cannot be ruled out.

Effect of natural and semisynthetic polymers on rabies virus infection in CER cells

Different natural and semisynthetic polymeric carbohydrates inhibited rabies virus infection in chicken-embryo-related cells by interfering with the virus adsorption process; a dose-dependent relationship was exhibited. Among polysaccharides tested, the neutral polymer Scleroglucan and the negatively charged Keltrol, glyloid sulphate 4324, glyloid sulphate 4327 and alginic acid were the most effective and remained active at concentrations far below the cytotoxicity threshold. Data obtained indicated that the inhibition mechanism of polymers may be related to the ability of these compounds to bind to viral envelopes, although their interaction with cell surfaces cannot be excluded. The charge density and the polymeric backbone of the molecules seem to play a role in influencing the antiviral properties, whereas other features such as the sugar moieties do not appear to be relevant.

Effect of enterovirus infection on susceptibility of HeLa cells to Shigella flexneri invasivity

Invasiveness of Shigella flexneri M90T in HeLa cells was significantly increased when cells were preinfected with poliovirus 1, coxsackievirus B3 and echovirus 6. This effect was dependent on the dose of virus used, evident at early stages of viral infection and lasted hours before the appearance of a cytopathic effect. An increase of bacterial invasion ability was also noticed when HeLa cells were incubated with UV-inactivated enteroviruses. This enhancing effect obtained with both viable and UV-inactivated enteroviruses was not observed when in coinfection experiments HN555, a mutant of S. flexneri M90T which lacked invasive properties, was used. The data presented here suggest that the early steps of enterovirus infection induce some alterations of HeLa cells which are responsible for the enhancing of the invasiveness of S. flexneri M90T, but not sufficient to promote internalization of a non-invasive strain.

SA-11 rotavirus binding to human serum lipoproteins

An investigation of SA-11 rotavirus binding to human serum lipoproteins was carried out. Various subclasses of lipoproteins, purified by ultracentrifugal flotation, and apoproteins were tested for their activity in inhibiting viral infectivity and hemagglutination. All tested lipoprotein subclasses (very low, low and high density, lipoproteins; VLDL, LDL, HDL, HDL1) were shown to interact with SA-11 rotavirus: VLDL and LDL were the most active in preventing rotavirus replication, whereas HDL and HDL1 inhibited viral hemagglutination to a greater extent. Moreover, A1 and A2 apoproteins were effective towards both viral infectivity and hemagglutination. Results obtained are in agreement with a preferential interaction of VP7 or VP4 proteolytic products with low density lipoproteins and of VP8* with high density lipoproteins. Binding of SA-11 to lipoproteins or apoproteins was also quantified by an enzyme-linked immunosorbent assay procedure and lipoproteins-virus interaction was visualized by electron microscopy.

Involvement of membrane carbohydrates of HeLa cells in the E. coli HB101 (pRI203) invasive pathway

The recombinant plasmid pRI203 carries a Yersinia pseudotuberculosis chromosomal gene that makes E. coli K-12 HB101 strain able to synthetize an outer membrane protein, invasin, which interacts with integrin receptors of eukaryotic cells, enabling this microorganism to penetrate human cultured animal cells. In this study we evaluated the involvement of HeLa cell membrane structural components in the early phases of the invasive pathway of E. coli HB101 (pRI203). When HeLa cell monolayers were treated with several enzymes we showed that trypsin-, proteinase K- and neuraminidase-sensitive components are required for bacterial invasion. Comparison of the ability of simple and complex carbohydrates to inhibit bacterial invasion indicated that N-acetyl neuraminic acid, N-acetyl glucosamine and mucin were the most effective competitive inhibitors. Among glycolipids, gangliosides enhanced bacterial entry in HeLa cells. The results obtained suggest that N-acetyl neuraminic acid and N-acetyl glucosamine-containing glycoproteins and/or glycolipids participate as putative HeLa cell binding sites for the penetration process of E. coli HB101 (pRI203).

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.

Influence of polyions on the early steps of enterovirus infection

The influence of electric charged molecules on the early phases of enterovirus infection was studied in order to select antiviral compounds able to prevent viral attachment. The effect of different polyelectrolytes on the multiplication of coxsackie virus B3, echovirus 6 and hepatitis A virus was investigated in susceptible cells by adding the drug before, during or after the viral adsorption period. Among polyanions, the polysaccharides heparin and dextran sulfate inhibited viral infectivity, dextran sulfate being the most effective mainly towards hepatitis A virus infection. DEAE-dextran and protamine sulfate, generally recognized as enhancers of infectivity of naked and enveloped viruses, exhibited an inhibitory effect towards the three picornaviruses tested. Only in the case of hepatitis A did DEAE-dextran slightly improve viral antigen synthesis. The inhibitory effect shown by compounds belonging to positive and negative polyions suggests that the electric charge is not sufficient by itself to explain the antiviral activity of these drugs.