MHC-linked Ir gene control of T cell responses: GAT-specific proliferating T cells and helper T cells are elicited in nonresponder mice immunized with soluble GAT

The immune response to the synthetic terpolymer GAT is controlled by MHC-linked Ir gene(s). We show in this paper that antigen-presenting cells and T cells from mice belonging to two nonresponder strains (SJL and DBA/1) can present and recognize GAT, respectively. This has been measured with a T cell proliferation assay of GAT-primed lymph node cells. In order to detect T cell proliferation among GAT-primed lymph node cells from DBA/1 mice, it is necessary to treat the cells with monoclonal anti-Lyt-2 antibodies and complement (C) before the assay. These conclusions were further verified with SJL mice, when a T cell line derived from LN cells was used. We have shown that after immunization with GAT, specific T helper cells can be generated in the lymph nodes of SJL mice but not in the lymph nodes of DBA/1 mice. Furthermore, GAT-specific T helper cells can be detected in the spleen of SJL mice after immunizations with GAT, provided these spleen cells are pretreated with monoclonal anti-Lyt-2 antibodies + C or mild irradiation. Together, these results support the general idea that nonresponsiveness can be explained by a regulatory imbalance rather than by discrete cellular "defects."     

Factors Associated with Post-Seasonal Serological Titer and Risk Factors for Infection with the Pandemic A/H1N1 Virus in the French General Population

The CoPanFlu-France cohort of households was set up in 2009 to study the risk factors for infection by the pandemic influenza virus (H1N1pdm) in the French general population. The authors developed an integrative data-driven approach to identify individual, collective and environmental factors associated with the post-seasonal serological H1N1pdm geometric mean titer, and derived a nested case-control analysis to identify risk factors for infection during the first season. This analysis included 1377 subjects (601 households). The GMT for the general population was 47.1 (95% confidence interval (CI): 45.1, 49.2). According to a multivariable analysis, pandemic vaccination, seasonal vaccination in 2009, recent history of influenza-like illness, asthma, chronic obstructive pulmonary disease, social contacts at school and use of public transports by the local population were associated with a higher GMT, whereas history of smoking was associated with a lower GMT. Additionally, young age at inclusion and risk perception of exposure to the virus at work were identified as possible risk factors, whereas presence of an air humidifier in the living room was a possible protective factor. These findings will be interpreted in light of the longitudinal analyses of this ongoing cohort.     

6-Bromoindolglyoxylamido derivatives as antimicrobial agents and antibiotic enhancers

The combination of increased incidence of drug-resistant strains of bacteria and a lack of novel drugs in development creates an urgency for the search for new antimicrobials. Initial screening of compounds from an in-house library identified two 6-bromoindolglyoxylamide polyamine derivatives (3 and 4) that exhibited intrinsic antimicrobial activity towards Gram-positive bacteria, Staphylococcus aureus and S. intermedius with polyamine 3 also displaying in vitro antibiotic enhancing properties against the resistant Gram-negative bacterium Pseudomonas aeruginosa. A series of 6-bromo derivatives (5–15) were prepared and biologically evaluated, identifying analogues with enhanced antibacterial activity towards Escherichia coli and with moderate to excellent antifungal properties. Polyamine 3, which includes a spermine chain, was the most potent of the series – its mechanism of action was attributed to rapid membrane permeabilization and depolarization in both Gram-positive and Gram-negative bacteria.     

Integrin cytoplasmic domain-associated protein 1alpha (ICAP-1alpha ) interacts directly with the metastasis suppressor nm23-H2, and both proteins are targeted to newly formed cell adhesion sites upon integrin engagement

Cell adhesion-dependent signaling implicates cytoplasmic proteins interacting with the intracellular tails of integrins. Among those, the integrin cytoplasmic domain-associated protein 1alpha (ICAP-1alpha) has been shown to interact specifically with the beta(1) integrin cytoplasmic domain. Although it is likely that this protein plays an important role in controlling cell adhesion and migration, little is known about its actual function. To search for potential ICAP-1alpha-binding proteins, we used a yeast two-hybrid screen and identified the human metastatic suppressor protein nm23-H2 as a new partner of ICAP-1alpha. This direct interaction was confirmed in vitro, using purified recombinant ICAP-1alpha and nm23-H2, and by co-immunoprecipitation from CHO cell lysates over-expressing ICAP-1alpha. The physiological relevance of this interaction is provided by confocal fluorescence microscopy, which shows that ICAP-1alpha and nm23-H2 are co-localized in lamellipodia during the early stages of cell spreading. These adhesion sites are enriched in occupied beta(1) integrins and precede the formation of focal adhesions devoid of ICAP-1alpha and nm23-H2, indicating the dynamic segregation of components of matrix adhesions. This peripheral staining of ICAP-1alpha and nm23-H2 is only observed in cells spreading on fibronectin and collagen and is absent in cells spreading on poly-l-lysine, vitronectin, or laminin. This is consistent with the fact that targeting of both ICAP-1alpha and nm23-H2 to the cell periphery is dependent on beta(1) integrin engagement rather than being a consequence of cell adhesion. This finding represents the first evidence that the tumor suppressor nm23-H2 could act on beta(1) integrin-mediated cell adhesion by interacting with one of the integrin partners, ICAP-1alpha.     

Escape of HIV-1-Infected Dendritic Cells from TRAIL-Mediated NK Cell Cytotoxicity during NK-DC Cross-Talk—A Pivotal Role of HMGB1

Early stages of Human Immunodeficiency Virus-1 (HIV-1) infection are associated with local recruitment and activation of important effectors of innate immunity, i.e. natural killer (NK) cells and dendritic cells (DCs). Immature DCs (iDCs) capture HIV-1 through specific receptors and can disseminate the infection to lymphoid tissues following their migration, which is associated to a maturation process. This process is dependent on NK cells, whose role is to keep in check the quality and the quantity of DCs undergoing maturation. If DC maturation is inappropriate, NK cells will kill them (“editing process”) at sites of tissue inflammation, thus optimizing the adaptive immunity. In the context of a viral infection, NK-dependent killing of infected-DCs is a crucial event required for early elimination of infected target cells. Here, we report that NK-mediated editing of iDCs is impaired if DCs are infected with HIV-1. We first addressed the question of the mechanisms involved in iDC editing, and we show that cognate NK-iDC interaction triggers apoptosis via the TNF-related apoptosis-inducing ligand (TRAIL)-Death Receptor 4 (DR4) pathway and not via the perforin pathway. Nevertheless, once infected with HIV-1, DC_HIV become resistant to NK-induced TRAIL-mediated apoptosis. This resistance occurs despite normal amounts of TRAIL released by NK cells and comparable DR4 expression on DC_HIV. The escape of DC_HIV from NK killing is due to the upregulation of two anti-apoptotic molecules, the cellular-Flice like inhibitory protein (c-FLIP) and the cellular inhibitor of apoptosis 2 (c-IAP2), induced by NK-DC_HIV cognate interaction. High-mobility group box 1 (HMGB1), an alarmin and a key mediator of NK-DC cross-talk, was found to play a pivotal role in NK-dependent upregulation of c-FLIP and c-IAP2 in DC_HIV. Finally, we demonstrate that restoration of DC_HIV susceptibility to NK-induced TRAIL killing can be obtained either by silencing c-FLIP and c-IAP2 by specific siRNA, or by inhibiting HMGB1 with blocking antibodies or glycyrrhizin, arguing for a key role of HMGB1 in TRAIL resistance and DC_HIV survival. These findings provide evidence for a new strategy developed by HIV to escape immune attack, they challenge the question of the involvement of HMGB1 in the establishment of viral reservoirs in DCs, and they identify potential therapeutic targets to eliminate infected DCs.     

NM23 and metastasis suppressor genes: update

Metastatic dissemination represents a leading cause of death in cancer patients. Elucidating the mechanisms of the metastatic process is therefore essential to control it. Since 1988, when the NME (NM23) gene was discovered, several genes specifically suppressing the metastatic potential of tumor cells, have been identified. These metastasis suppressor genes, which exhibit a reduced expression in metastatic tumor cells, are defined by their capacity to suppress metastatic dissemination in vivo without inhibiting primary tumor growth when transfected into metastatic cell lines and injected into experimental animals. Their decreased expression in a subset of human tumor cohorts is associated with a high metastatic potential, thus confirming the data obtained in experimental models. Most of these genes affect key signal transduction pathways, including mitogen-activated protein kinases, Rho-GTPases and G-protein-coupled receptors. These signaling categories control cell-cell and cell-matrix interactions, which are important in monitoring adhesion, invasion and migration properties of metastatic tumor cells. Reduced expression of metastasis suppressor genes is most often due to epigenetic mechanisms, suggesting that their re-expression could constitute a new anti-metastatic therapy. In this paper, we review the literature on metastasis suppressor genes, with a particular focus on NM23.     

Clonal Growth Strategies Along Flooding and Grazing Gradients in Atlantic Coastal Meadows

Specific composition and species clonal traits were characterized along combined flooding and grazing gradients to answer two questions. i) To what extent does the interaction of flooding and grazing influence the clonal characteristics of the vegetation? ii) Are the effects of both environmental factors independent or interactive? This study was carried out in a wet meadow along the Atlantic coast (France). Three plant communities (hygrophilous, meso-hygrophilous and mesophilous) were distinguished along a flooding gradient and five levels of grazing pressure were controlled through an experimental design (from no grazing to heavy grazing). We monitored species composition and retrieved, for each species, the type of clonal growth organs (CGOs) and clonal traits from the CLO-PLA3 database. We identified two syndromes of clonal traits: ??above-ground splitters?? and ??below-ground integrators??. Clonal traits played a key role in plant assembly in the studied meadows. The interaction of both environmental factors selected for particular syndromes of clonal traits; however, flooding had a stronger filtering effect than grazing. The hygrophilous community was dominated by above-ground splitters, whereas the meso-hygrophilous vegetation was dominated by below-ground integrators. In the mesophilous community, clonal composition was the most diverse and shared clonal traits with the vegetation of both the hygrophilous and meso-hygrophilous communities. Grazing impact on CGOs and clonal traits differed between plant communities, i.e., the effect of grazing was modulated by the flooding regime. This study confirmed that vegetation responses to grazing might depend on the pool of traits, primarily filtered by environmental factors such as flooding.     

Influence of fermentation medium composition on physicochemical surface properties of Lactobacillus acidophilus

The effect of the simple and complex basic components of a fermentation medium on the surface properties of Lactobacillus acidophilus NCC2628 is studied by physicochemical methods, such as electrophoresis, interfacial adhesion, and X-ray photonelectron spectroscopy, and by transmission electron microscopy. Starting from an optimized complete medium, the effect of carbohydrates, peptones, and yeast extracts on the physicochemical properties of the cell wall is systematically investigated by consecutively omitting one of the principal components from the fermentation medium at the time. The physicochemical properties and structure of the bacterial cell wall remain largely unchanged if the carbohydrate content of the fermentation medium is strongly reduced, although the concentration of surface proteins increases slightly. Both peptone and yeast extract have a considerable influence on the bacterial cell wall, as witnessed by changes in surface charge, hydrophobicity, and the nitrogen-to-carbon ratio. Both zeta potential and the cell wall hydrophobicity show a positive correlation with the nitrogen-to-carbon ratio of the bacterial surfaces, indicative of the important role of surface proteins in the overall surface physical chemistry. The hydrophobicity of the cell wall, which is low for the cultures grown in the complete medium and in the absence of carbohydrates, becomes fairly high for the cultures grown in the medium without peptones and the medium without yeast extract. UV spectrophotometry and sodium dodecyl sulfate-polyacrylamide gel electrophoresis combined with liquid chromatography-tandem mass spectrometry are used to analyze the effect of medium composition on LiCl-extractable cell wall proteins, confirming the major change in protein composition of the cell wall for the culture fermented in the medium without peptones. In particular, it is found that expression of the S-layer protein is dependent on the protein source of the fermentation medium.