Attachment of nontypable Haemophilus influenzae to human pharyngeal epithelial cells mediated by a ganglioside receptor

Anti-GD2 immunotherapy for neuroblastoma

INTRODUCTION

Current therapeutic approaches for high-risk neuroblastoma (HR-NB) include high-dose chemotherapy, surgery and radiotherapy; interventions that are associated with long and short-term toxicities. Effective immunotherapy holds particular promise for improving survival and quality of life by reducing exposure to cytotoxic agents. GD2, a surface glycolipid is the most common target for immunotherapy. Areas covered: We review the status of anti-GD2 immunotherapies currently in clinical use for neuroblastomas and novel GD2-targeted strategies in preclinical development. Expert commentary: Anti-GD2 monoclonal antibodies are associated with improved survival in patients in their first remission and are increasingly being used for chemorefractory and relapsed neuroblastoma. As protein engineering technology has become more accessible, newer antibody constructs are being tested. GD2 is also being targeted by natural killer cells and T-cells. Active immunity can be elicited by anti-GD2 vaccines. The rational combination of currently available and soon-to-emerge immunotherapeutic approaches, and their integration into conventional multimodality therapies will require further investigation to optimize their use for HR-NB.

Biofilm-specific extracellular matrix proteins of nontypeable Haemophilus influenzae

Nontypeable Haemophilus influenzae (NTHi), a human respiratory tract pathogen, can form colony biofilms in vitro. Bacterial cells and the amorphous extracellular matrix (ECM) constituting the biofilm can be separated using sonication. The ECM from 24- and 96-h NTHi biofilms contained polysaccharides and proteinaceous components as detected by nuclear magnetic resonance (NMR) and Fourier transform infrared spectroscopy (FTIR) spectroscopy. More conventional chemical assays on the biofilm ECM confirmed the presence of these components and also DNA. Proteomics revealed eighteen proteins present in biofilm ECM that were not detected in planktonic bacteria. One ECM protein was unique to 24-h biofilms, two were found only in 96-h biofilms, and fifteen were present in the ECM of both 24- and 96-h NTHi biofilms. All proteins identified were either associated with bacterial membranes or cytoplasmic proteins. Immunocytochemistry showed two of the identified proteins, a DNA-directed RNA polymerase and the outer membrane protein OMP P2, associated with bacteria and biofilm ECM. Identification of biofilm-specific proteins present in immature biofilms is an important step in understanding the in vitro process of NTHi biofilm formation. The presence of a cytoplasmic protein and a membrane protein in the biofilm ECM of immature NTHi biofilms suggests that bacterial cell lysis may be a feature of early biofilm formation.

A mouse model of lethal synergism between influenza virus and Haemophilus influenzae

Secondary bacterial infections that follow infection with influenza virus result in considerable morbidity and mortality in young children, the elderly, and immunocompromised individuals and may also significantly increase mortality in normal healthy adults during influenza pandemics. We herein describe a mouse model for investigating the interaction between influenza virus and the bacterium Haemophilus influenzae. Sequential infection with sublethal doses of influenza and H. influenzae resulted in synergy between the two pathogens and caused mortality in immunocompetent adult wild-type mice. Lethality was dependent on the interval between administration of the bacteria and virus, and bacterial growth was prolonged in the lungs of dual-infected mice, although influenza virus titers were unaffected. Dual infection induced severe damage to the airway epithelium and confluent pneumonia, similar to that observed in victims of the 1918 global influenza pandemic. Increased bronchial epithelial cell death was observed as early as 1 day after bacterial inoculation in the dual-infected mice. Studies using knockout mice indicated that lethality occurs via a mechanism that is not dependent on Fas, CCR2, CXCR3, interleukin-6, tumor necrosis factor, or Toll-like receptor-4 and does not require T or B cells. This model suggests that infection with virulent strains of influenza may predispose even immunocompetent individuals to severe illness on secondary infection with H. influenzae by a mechanism that involves innate immunity, but does not require tumor necrosis factor, interleukin-6, or signaling via Toll-like receptor-4.

Sialidase fusion protein as a novel broad-spectrum inhibitor of influenza virus infection

Influenza is a highly infectious disease characterized by recurrent annual epidemics and unpredictable major worldwide pandemics. Rapid spread of the highly pathogenic avian H5N1 strain and escalating human infections by the virus have set off the alarm for a global pandemic. To provide an urgently needed alternative treatment modality for influenza, we have generated a recombinant fusion protein composed of a sialidase catalytic domain derived from Actinomyces viscosus fused with a cell surface-anchoring sequence. The sialidase fusion protein is to be applied topically as an inhalant to remove the influenza viral receptors, sialic acids, from the airway epithelium. We demonstrate that a sialidase fusion construct, DAS181, effectively cleaves sialic acid receptors used by both human and avian influenza viruses. The treatment provides long-lasting effect and is nontoxic to the cells. DAS181 demonstrated potent antiviral and cell protective efficacies against a panel of laboratory strains and clinical isolates of IFV A and IFV B, with virus replication inhibition 50% effective concentrations in the range of 0.04 to 0.9 nM. Mouse and ferret studies confirmed significant in vivo efficacy of the sialidase fusion in both prophylactic and treatment modes.

Novel polysulfated galactose-derivatized dendrimers as binding antagonists of human immunodeficiency virus type 1 infection

Evidence indicates that galactosyl ceramide (GalCer) and its 3'-sulfated derivative, sulfatide (SGalCer), may act as alternate coreceptors for human immunodeficiency virus type 1 (HIV-1) in CD4(-) cells. Glycosphingolipids (GSLs) may also be necessary for fusion of HIV-1 and host cell membranes. Using an enzyme-linked immunosorbent assay to determine which GSL was the best ligand for both recombinant and virus-associated gp120, we found that SGalCer was the best ligand for each rgp120 and HIV-1 isolate tested. Therefore, novel multivalent glycodendrimers, which mimic the carbohydrate clustering reportedly found in lipid rafts, were synthesized based on the carbohydrate moiety of SGalCer. Here we describe the synthesis of a polysulfated galactose functionalized, fifth generation DAB dendrimer (PS Gal 64mer), containing on average two sulfate groups per galactose residue. Its ability to inhibit HIV-1 infection of cultured indicator cells was compared to that of dextran sulfate (DxS), a known, potent, binding inhibitor of HIV-1. The results indicate that the PS Gal 64mer inhibited infection by the HIV-1 isolates tested as well as DxS.

Acid aspiration induces bacterial pneumonia by enhanced bacterial adherence in mice

The issue of whether acid aspiration facilitates bacterial pneumonia caused by Pseudomonas aeruginosa by enhanced bacterial adherence was examined in mice. Survival or the number of bacteria in lung tissues was evaluated after an intratracheal challenge of hydrochloric acid (HCl), a sublethal dose of P. aeruginosa, or both in mice. Bacterial adherence to the tracheal epithelium after acid aspiration was also examined by scanning electron microscopy. A simultaneous intratracheal challenge of 50 microl of 10(-1) N HCl, but not 10(-2) to 10(-4) N HCl, combined with a sublethal dose of P. aeruginosa significantly increased the number of bacteria in the lung tissues and decreased survival, while all mice that received either HCl or P. aeruginosa survived. Significantly higher numbers of adherent bacteria on the tracheal epithelium were found in mice that received 10(-1)N HCl, compared with mice that received HCl (10(-2) to 10(-4) N) or saline. These data indicate that acid aspiration induced airway epithelial injury and enhanced P. aeruginosa adherence to the epithelium, and led to the subsequent development of bacterial pneumonia in mice. Enhanced bacterial adherence on the acid-injured epithelium may explain fatal bacterial pneumonias in patients with respiratory aspiration of gastric contents.

Modulating effects of mucoregulating drugs on the attachment of Haemophilus influenzae

Non-typable Haemophilus influenzae (NTHI) is one of the three major pathogens implicated in human respiratory infections. The ability to attach with pharyngeal epithelial cells is an important factor for infection and virulence. In the present study we describe the effects of two mucoregulating drugs, S-carboxymethylcysteine (S-CMC) and ambroxol, on the attachment of NTHI to pharyngeal epithelial cells. There was a significant (P < 0.0001, < 0.001 and <0.01) decrease of attachment (8.8 +/ 2.4, 9.2+/-2.5 and 15.4 +/- 5.7 bactreria/cell) compared with the control (17.5 +/- 2.9, 15.5 +/- 3.1 and 18.8 +/- 6.8 bacteria/cell) after cells were treated wth S-CMC at a dose of 100, 10 and 1 microg/ml. After attachment assay, cells treated with S-CMC (100 microg/ml) showed a significant decrease (P < 0.01) of attached bacteria (3.1 +/- 0.8 bacteria/cell) compared with the control (5.9 +/- 1.8 bacteria/cell). Treatment of cells with ambroxol did not influence bacterial attachment. By scanning electron microscopic observation it was found that NTHI attaches to the surface elevations (microplicae) of human pharyngeal epithelial cells. Atomic force microscopic observation revealed that the surface potential of microplicae decreased significantly in cells treated with S-CMC compared with the untreated control cells. As bacteria with negative surface charge attach to the positively charged domain, i.e. microplicae of human pharyngeal epithelial cells, this study suggests that the decrease of attachment of NTHI with epithelial cells after treatment with S-CMC was possibly due to the decrease of surface charge. This study suggests that S-CMC decreases the episodes of respiratory infections in patients with respiratory diseases both by inhibiting the attachment of bacteria to the upper respiratory tract, and by detaching the adherent one.