Influence of Cytokines on HIV-Specific Antibody-Dependent Cellular Cytotoxicity Activation Profile of Natural Killer Cells

There is growing interest in HIV-specific antibody-dependent cellular cytotoxicity (ADCC) as an effective immune response to prevent or control HIV infection. ADCC relies on innate immune effector cells, particularly NK cells, to mediate control of virus-infected cells. The activation of NK cells (i.e., expression of cytokines and/or degranulation) by ADCC antibodies in serum is likely subject to the influence of other factors that are also present. We observed that the HIV-specific ADCC antibodies, within serum samples from a panel of HIV-infected individuals induced divergent activation profiles of NK cells from the same donor. Some serum samples primarily induced NK cell cytokine expression (i.e., IFNγ), some primarily initiated NK cell expression of a degranulation marker (CD107a) and others initiated a similar magnitude of responses across both effector functions. We therefore evaluated a number of HIV-relevant soluble factors for their influence on the activation of NK cells by HIV-specific ADCC antibodies. Key findings were that the cytokines IL-15 and IL-10 consistently enhanced the ability of NK cells to respond to HIV-specific ADCC antibodies. Furthermore, IL-15 was demonstrated to potently activate “educated” KIR3DL1+ NK cells from individuals carrying its HLA-Bw4 ligand. The cytokine was also demonstrated to activate “uneducated” KIR3DL1+ NK cells from HLA-Bw6 homozygotes, but to a lesser extent. Our results show that cytokines influence the ability of NK cells to respond to ADCC antibodies in vitro. Manipulating the immunological environment to enhance the potency of NK cell-mediated HIV-specific ADCC effector functions could be a promising immunotherapy or vaccine strategy

Mechanical properties, flammability and char morphology of epoxy resin/montmorillonite nanocomposites

Epoxy resin/montmorillonite nanocomposites were obtained via in-situ intercalative polymerization. Na-montmorillonites modified with octaclecyl, hexadecyl and dodecyl trimethylammonium, benzyl triethylammonium and tetramethylammonium ions were used in diglycidyl ether of bisphenol-A epoxy resin. Montmorillonites modified with long alkyl ammonium ions yielded intercalated nanocomposites whereas those with benzyl or very short alkyl ammonium ions gave phase separated microcomposites. Significant improvements in flexural strength and stiffness were obtained, especially at a low clay mineral level of 0.5 mass% with octaclecyl trimethylammonium ions. Fracture toughness values double that of neat epoxy resin could be reached together with improved stiffness and strength by nanocomposite formation. The largest improvement in fracture toughness was also obtained by octadecyl trimethylammonium montmorillonite. Regarding flexural strength and fracture toughness, optimum clay mineral levels were assessed as 0.5 mass% for intercalated nanocomposites. Flammability was evaluated by oxygen index measurements with varying clay mineral level and surface modification. Largest improvement, i.e. from 20.9% to 23.2%, was attained with 2 mass% dodecyl trimethylammonium montmorillonite containing epoxy resin. Basal spacings in char residues of oxygen index tests were around 1.3 nm, irrespective of the montmorillonite content, type of modification and oxygen index performance

Effect of accelerators on the dynamics of rubber blends

Resumen del póster presentado al 8th International Discussion Meeting on Relaxations in Complex Systems: "New results, Directions and Opportunities", celebrado en Wisla (Polonia) del 23 al 28 de julio de 2017.Accelerators are fundamental ingredients in the sulfur vulcanization of rubber compounds increasing the cure rate and yield thereby allowing the cure process to proceed at lower temperatures and with higher efficiency. However, the presence of accelerators in the rubber compound can affect the segmental dynamics or even be related with slower relaxation processes. In this work we present a broadband dielectric study on the effect of accelerators on the dynamics of vulcanized styrene-butadiene rubber compounds with different accelerator structures and loading levels. The dynamics of all the samples show a main peak (besides the beta relaxation) as a sum of two relaxation processes. While the fastest relaxation corresponds to the segmental polymer dynamics, the origin of the low frequency contribution was attributed to a process arising from a component that is not covalently bonded to the polymer chain and not restricting the segmental dynamics.Peer reviewe

Effect of processing oils on the dynamics of rubber blends

Resumen del póster presentado al 8th International Discussion Meeting on Relaxations in Complex Systems: "New results, Directions and Opportunities", celebrado en Wisla (Polonia) del 23 al 28 de julio de 2017.Processing oils are used in a wide variety of industries as raw material components as well as processability improvers. When used in rubber compounds, a good compatibility of the process oil with the polymer matrix is required to obtain the desired final properties. The presence of oil can affect the dynamics of the polymers in different ways. For instance, small molecule diluents like treated distillate aromatic extract oil (TDAE) can reduce the severity of constraints on the local motion and, thereby, reducing the degree of intermolecular cooperativity. In this work, we have analysed the oil content effect on the dynamical behaviour of neat styrene-butadiene rubber, butadiene rubber and their blends by means of differential scanning calorimetry and broadband dielectric spectroscopy. In the case of butadiene rubber, we have observed that the segmental relaxation shifts to lower frequencies in the presence of the diluents, showing a glass transition temperature (Tg) increase effect, while for the styrene-butadiene rubber we observed the contrary response. The oil incorporation in rubber compounds shows a Tg decrease or increase effect, depending on the relative oil and polymer blend glass transition temperatures.Peer reviewe

Extended Adam–Gibbs approach to describe the segmental dynamics of cross-linked miscible rubber blends

We present an extension to the Adam–Gibbs (AG) model to describe the segmental dynamics of miscible polymer blends with strong interactions. We studied the segmental dynamics of cross-linked styrene–butadiene rubber (SBR)/butadiene rubber (BR) blends of different microstructure, chain-end functionalization, and composition both unfilled and filled with precipitated silica by means of broadband dielectric spectroscopy (BDS). Contrary to what is observed for athermal miscible blends, the dynamics shows only a single segmental relaxation process due to the strong intermolecular interaction given by the cross-links. The temperature dependence of the relaxation times has been described and analyzed within the framework of a modified AG approach that takes into account the strong interactions between blend components due to the presence of the cross-links. The accuracy of the proposed model facilitates a deepened understanding of the dynamics of polymer blend systems based on the dynamics of its neat components.This work was partially Supported by the Spanish Ministry “Ministerio de Economia y Competitividad”, code: MAT2015-63704-P (MINECO/FEDER, UE).Peer reviewe

The effects of fiber silane modification on the mechanical performance of chopped basalt fiber/ABS composites

The purpose of this study was to examine the effects of silane coupling agent modifications on the mechanical performance of the basalt fiber (BF)-reinforced acrylonitrile–butadiene–styrene (ABS) composites. Three different silane coupling agents were used. The mechanical properties of the composites were determined by the tensile, flexural, impact tests, and dynamic mechanical analysis (DMA). According to the test results, the tensile strength increased with the use of (3-aminopropyl) triethoxysilane (AP) and 3-(trimethoxysilyl) propylmethacrylate (MA), while the use of (3-glycidyloxypropyl) trimethoxysilane (GP) reduced the tensile strength. All the silane modifications improved the flexural strength and modulus and the highest improvement was achieved with the use of AP. No remarkable difference was observed in impact properties with the use of silane coupling agents. The addition of BF significantly improved the elastic modulus of the ABS regardless of the modification type, while the further improvements were achieved through the use of AP and MA. In brief, AP showed the highest performance among the studied silane coupling agents due to the covalent bond formation between the amino group of AP and the nitrile group of styrene–acrylonitrile (SAN) matrix. © The Author(s) 2019

The effect of vulcanization additives on the dielectric response of styrene-butadiene rubber compounds

Rubber compounds are usually vulcanized in order to improve their mechanical properties. Although vulcanization has been largely studied in the literature, it is not completely clear how the different additives interact among them and how these affect the final properties of the compounds. Here, we present a systematic study using a combination of different experimental techniques, which allows a deeper understanding of the vulcanization mechanisms. We have studied different compounds, with and without silica filler, prepared with styrene butadiene rubber (SBR) of different microstructures and functional end groups. The dielectric response of cured and uncured samples was measured at different temperatures in a wide frequency range. In addition, we analysed the calorimetric and mechanical properties for selected compounds as well as the crosslink density. Furthermore, we performed in-situ vulcanization (in the dielectric cell) to analyse the evolution of different contributions to the dielectric spectrum during cure. Based on our results we conclude that the dielectric response of these SBR compounds is strongly affected by the presence of one of the cure accelerators used in the formulation, namely diphenyl guanidine (DPG). However, this does not affect the segmental relaxation time nor the structure of the crosslink network or the mechanical properties. This study shows the potential of broadband dielectric spectroscopy for monitoring and understanding the vulcanization mechanisms.This work was partially supported by the Elkartek program (nG17, KK-2017/00012) and Basque Government (IT-1175-19). M.M., N.A.I., C.S. and S.W. gratefully acknowledge the Goodyear Tire and Rubber Company for the permission to publish this paper

Cross-Reactive Influenza-Specific Antibody-Dependent Cellular Cytotoxicity Antibodies in the Absence of Neutralizing Antibodies

A better understanding of immunity to influenza virus is needed to generate cross-protective vaccines. Engagement of Ab-dependent cellular cytotoxicity (ADCC) Abs by NK cells leads to killing of virus-infected cells and secretion of antiviral cytokines and chemokines. ADCC Abs may target more conserved influenza virus Ags compared with neutralizing Abs. There has been minimal interest in influenza-specific ADCC in recent decades. In this study, we developed novel assays to assess the specificity and function of influenza-specific ADCC Abs. We found that healthy influenza-seropositive young adults without detectable neutralizing Abs to the hemagglutinin of the 1968 H3N2 influenza strain (A/Aichi/2/1968) almost always had ADCC Abs that triggered NK cell activation and in vitro elimination of influenza-infected human blood and respiratory epithelial cells. Furthermore, we detected ADCC in the absence of neutralization to both the recent H1N1 pandemic strain (A/California/04/2009) as well as the avian H5N1 influenza hemagglutinin (A/Anhui/01/2005). We conclude that there is a remarkable degree of cross-reactivity of influenza-specific ADCC Abs in seropositive humans. Targeting cross-reactive influenza-specific ADCC epitopes by vaccination could lead to improved influenza vaccines