First Constraints on the Photon Coupling of Axionlike Particles from Multimessenger Studies of the Neutron Star Merger GW170817.

We use multimessenger observations of the neutron star merger event GW170817 to derive new constraints on axionlike particles (ALPs) coupling to photons. ALPs are produced via Primakoff and photon coalescence processes in the merger, escape the remnant, and decay back into two photons, giving rise to a photon signal approximately along the line of sight to the merger. We analyze the spectral and temporal information of the ALP-induced photon signal and use the Fermi Large Area Telescope (Fermi-LAT) observations of GW170817 to derive our new ALP constraints. We also show the improved prospects with future MeV γ-ray missions, taking the spectral and temporal coverage of Fermi-LAT as an example.

Blood-Flow Restricted Warm-Up Alters Muscle Hemodynamics and Oxygenation during Repeated Sprints in American Football Players.

Team-sport athletes and coaches use varied strategies to enhance repeated-sprint ability (RSA). Aside from physical training, a well-conducted warm-up enhances RSA via increased oxidative metabolism. Strategies that impede blood flow could potentiate the effects of a warm-up due to their effects on the endothelial and metabolic functions. This study investigated whether performing a warm-up combined with blood-flow restriction (WFR) induces ergogenic changes in blood volume, muscle oxygenation, and RSA. In a pair-matched, single-blind, pre-post parallel group design, 15 American football players completed an RSA test (12 × 20 m, 20 s rest), preceded by WFR or a regular warm-up (SHAM). Pressure was applied on the athletes' upper thighs for ≈15 min using elastic bands. Both legs were wrapped at a perceived pressure of 7 and 3 out of 10 in WFR and SHAM, respectively. Changes in gastrocnemius muscle oxygen saturation (SmO2) and total hemoglobin concentration ([THb]) were monitored with near-infrared spectroscopy. Cohen's effect sizes (ES) were used to estimate the impact of WFR. WFR did not clearly alter best sprint time (ES -0.25), average speed (ES 0.25), total time (ES -0.12), and percent decrement score (ES 0.39). While WFR did not meaningfully alter average SmO2 and [THb], the intervention clearly increased the maximum [THb] and the minimum and maximum SmO2 during some of the 12 sprint/recovery periods (ES 0.34-1.43). Results indicate that WFR positively alters skeletal muscle hemodynamics during an RSA test. These physiological changes did not improve short-term RSA, but could be beneficial to players during longer activities such as games.

CD160 isoforms and regulation of CD4 and CD8 T-cell responses.

BACKGROUND: Coexpression of CD160 and PD-1 on HIV-specific CD8+ T-cells defines a highly exhausted T-cell subset. CD160 binds to Herpes Virus Entry Mediator (HVEM) and blocking this interaction with HVEM antibodies reverses T-cell exhaustion. As HVEM binds both inhibitory and activatory receptors, our aim in the current study was to assess the impact of CD160-specific antibodies on the enhancement of T-cell activation. METHODS: Expression of the two CD160 isoforms; glycosylphosphatidylinositol-anchored (CD160-GPI) and the transmembrane isoforms (CD160-TM) was assessed in CD4 and CD8 primary T-cells by quantitative RT-PCR and Flow-cytometry. Binding of these isoforms to HVEM ligand and the differential capacities of CD160 and HVEM specific antibodies to inhibit this binding were further evaluated using a Time-Resolved Fluorescence assay (TRF). The impact of both CD160 and HVEM specific antibodies on enhancing T-cell functionality upon antigenic stimulation was performed in comparative ex vivo studies using primary cells from HIV-infected subjects stimulated with HIV antigens in the presence or absence of blocking antibodies to the key inhibitory receptor PD-1. RESULTS: We first show that both CD160 isoforms, CD160-GPI and CD160-TM, were expressed in human primary CD4+ and CD8+ T-cells. The two isoforms were also recognized by the HVEM ligand, although this binding was less pronounced with the CD160-TM isoform. Mechanistic studies revealed that although HVEM specific antibodies blocked its binding to CD160-GPI, surprisingly, these antibodies enhanced HVEM binding to CD160-TM, suggesting that potential antibody-mediated HVEM multimerization and/or induced conformational changes may be required for optimal CD160-TM binding. Triggering of CD160-GPI over-expressed on Jurkat cells with either bead-bound HVEM-Fc or anti-CD160 monoclonal antibodies enhanced cell activation, consistent with a positive co-stimulatory role for CD160-GPI. However, CD160-TM did not respond to this stimulation, likely due to the lack of optimal HVEM binding. Finally, ex vivo assays using PBMCs from HIV viremic subjects showed that the use of CD160-GPI-specific antibodies combined with blockade of PD-1 synergistically enhanced the proliferation of HIV-1 specific CD8+ T-cells upon antigenic stimulation. CONCLUSIONS: Antibodies targeting CD160-GPI complement the blockade of PD-1 to enhance HIV-specific T-cell responses and warrant further investigation in the development of novel immunotherapeutic approaches.

LFA-1 antagonists as agents limiting human immunodeficiency virus type 1 infection and transmission and potentiating the effect of the fusion inhibitor T-20.

Adhesion molecules are known to play major roles in the initiation and stabilization of cell-to-cell contacts during the immunological response. Human immunodeficiency virus type 1 (HIV-1) exploits those interactions to facilitate infection and propagation processes. The primary objective of the present study was to investigate the ability of antagonists specific for lymphocyte function-associated antigen 1 (LFA-1) to diminish HIV-1 infection and transmission. We demonstrate here that LFA-1 antagonists can significantly reduce HIV-1 replication in primary human cells and virus propagation by affecting cell-to-cell interactions. Moreover, the inhibition of LFA-1-mediated adhesion events also potentiates the antiviral efficacy of the peptide fusion inhibitor T-20. Altogether, our data suggest that LFA-1 antagonists represent promising antiviral agents. Antiadhesion therapy could be considered a complementary strategy targeting cellular functions essential for HIV-1 spreading and against which the combined therapy currently used displays a limited efficacy.

The ERK mitogen-activated protein kinase pathway contributes to Ebola virus glycoprotein-induced cytotoxicity.

Ebola virus is a highly lethal pathogen that causes hemorrhagic fever in humans and nonhuman primates. Among the seven known viral gene products, the envelope glycoprotein (GP) alone induces cell rounding and detachment that ultimately leads to cell death. Cellular cytoxicity is not seen with comparable levels of expression of a mutant form of GP lacking a mucin-like domain (GPDeltamuc). GP-induced cell death is nonapoptotic and is preceded by downmodulation of cell surface molecules involved in signaling pathways, including certain integrins and epidermal growth factor receptor. To investigate the mechanism of GP-induced cellular toxicity, we analyzed the activation of several signal transduction pathways involved in cell growth and survival. The active form of extracellular signal-regulated kinases types 1 and 2 (ERK1/2), phospho-ERK1/2, was reduced in cells expressing GP compared to those expressing GPDeltamuc as determined by flow cytometry, in contrast to the case for several other signaling proteins. Subsequent analysis of the activation states and kinase activities of related kinases revealed a more pronounced effect on the ERK2 kinase isoform. Disruption of ERK2 activity by a dominant negative ERK or by small interfering RNA-mediated ERK2 knockdown potentiated the decrease in alphaV integrin expression associated with toxicity. Conversely, activation of the pathway through the expression of a constitutively active form of ERK2 significantly protected against this effect. These results indicate that the ERK signaling cascade mediates GP-mediated cytotoxicity and plays a role in pathogenicity induced by this gene product.

T-cell tropism and the role of ORF66 protein in pathogenesis of varicella-zoster virus infection.

The pathogenesis of varicella-zoster virus (VZV) involves a cell-associated viremia during which infectious virus is carried from sites of respiratory mucosal inoculation to the skin. We now demonstrate that VZV infection of T cells is associated with robust virion production and modulation of the apoptosis and interferon pathways within these cells. The VZV serine/threonine protein kinase encoded by ORF66 is essential for the efficient replication of VZV in T cells. Preventing ORF66 protein expression by stop codon insertion (pOka66S) impaired the growth of the parent Oka (pOka) strain in T cells in SCID-hu T-cell xenografts in vivo and reduced formation of VZV virions. The lack of ORF66 protein also increased the susceptibility of infected T cells to apoptosis and reduced the capacity of the virus to interfere with induction of the interferon (IFN) signaling pathway following exposure to IFN-gamma. However, preventing ORF66 protein expression only slightly reduced growth in melanoma cells in culture and did not diminish virion formation in these cells. The pOka66S virus showed only a slight defect in growth in SCID-hu skin implants compared with intact pOka. These observations suggest that the ORF66 kinase plays a unique role during infection of T cells and supports VZV T-cell tropism by contributing to immune evasion and enhancing survival of infected T cells.

Mixed-ligand organometallic polymers containing the "Pd(2)(dmb)2(2+)" fragment: properties of the [Pd2(dmb)2(diphos)2+](n) polymers/oligomers in solution and in the solid state.

The 1:1 reaction between the d(9)-d(9) Pd(2)(dmb)(2)Cl(2) complex (dmb = 1,8-diisocyano-p-menthane) and the diphosphine ligands (diphos) bis(diphenylphosphino)butane (5, dppb), bis(diphenylphosphino)pentane (6, dpppen), bis(diphenylphosphino)hexane (7, dpph), and bis(diphenylphosphino)acetylene (8, dpa) in the presence of LiClO(4) leads to the [[Pd(2)(dmb)(2)(diphos)](ClO(4))(2)](n) polymers. These new materials are characterized by NMR ((1)H, (13)C, (31)P), IR, Raman, and UV-vis spectroscopies (466 < lambda(max)(dsigma-dsigma*) < 480 nm), by ATG, XRD, and DSC methods, and by the capacity to make stand-alone films. From the measurements of the intrinsic viscosity in acetonitrile, the M(n) ranges from 16000 to 18400 (12 to 16 units). The dinuclear model complex [Pd(2)(dmb)(2)(PPh(3))(2)](ClO(4))(2) (4) is prepared and investigated as well. The molecular dynamic of the title polymers in acetonitrile solution is investigated by means of (13)C spin-lattice relaxation time (T(1)) and nuclear Overhauser enhancement methods (NOE). The number of units determined by T(1)/NOE methods is 3 to 4 times less than that found from the measurements of intrinsic viscosity, and is due to flexibility in the polymer backbone, even for bridging ligands containing only one (dmb) or two C-C single bonds (dpa). During the course of this study, the starting material Pd(2)(dmb)(2)Cl(2) was reinvestigated after evidence for oligomers in the MALDI-TOF spectrum was noticed. In solution, this d(9)-d(9) species is a binuclear complex (T(1)/NOE). This result suggests that the structure of the title polymers in solution and in the solid state may not be the same either. Finally, these polymers are strongly luminescent in PrCN glasses at 77 K, and the photophysical data (emission lifetimes, 1.50 < tau(e) < 2.75 ns; quantum yields, 0.026 < Phi(e) < 0.17) are presented. X-ray data for [Pd(2)(dppe)(2)(dmb)(2)](PF(6))(4): monoclinic, space group C2/c, a = 24.3735 A, b = 21.8576(13) A, c = 18.0034(9) A, b = 119.775(1) degrees, V = 8325.0(8) A(3), Z = 4.

Hyper-responsiveness to stimulation of human immunodeficiency virus-infected CD4+ T cells requires Nef and Tat virus gene products and results from higher NFAT, NF-kappaB, and AP-1 induction.

A chronic state of immune hyperactivation is a feature of human immunodeficiency virus type-1 (HIV-1) infection. Studies on the molecular mechanisms by which HIV-1 can modulate the activation state of T cells indicate that both Nef and Tat can alter T cell activation. However, the vast majority of data has been obtained from experiments performed with vectors encoding a single virus protein. We demonstrate that infection of human CD4(+) T lymphocytes with fully infectious HIV-1 leads to a hyper-responsiveness of the interleukin-2 promoter. Hypersensitivity in HIV-1-infected T cells was observed upon stimulation with various agents that are engaging different signal transduction pathways. Experiments performed with recombinant heat stable antigen-encoding HIV-1 indicated that the virus-infected cells are the cells with an enhanced response. Both Nef and Tat are involved in this virus-mediated enhancing effect on interleukin-2 promoter activity. Interestingly, whereas Nef seems to be acting mainly through hyperactivation of nuclear factor of activated T cells (NFAT), Tat acts in an NFAT-independent manner. Mobility shift experiments demonstrated that the HIV-1-associated priming of human T cells for stimulation results in a greater induction of transcription factors recognized as essential players in T cell activation, i.e. NFAT, NF-kappaB, and AP-1. A hyper-responsive state was also established upon HIV-1 infection of a more natural cellular reservoir, i.e. primary CD4(+) T lymphocytes. Considering that the HIV-1 life cycle is tightly regulated by the T cell signaling machinery, the priming for activation of a major viral reservoir represents a means by which this retrovirus can create an ideal cellular microenvironment for its propagation and maintenance.

Virion-bound ICAM-1 and activated LFA-1: a combination of factors conferring resistance to neutralization by sera from human immunodeficiency virus type 1-infected individuals independently of the disease status and phase.

The role of the supplementary interaction between virion-bound host ICAM-1 and LFA-1 on target cells in sensitivity to neutralization of human immunodeficiency virus type 1 (HIV-1) is poorly studied. Serum samples from four long-term nonprogressors (LTNPs) and sequential sera from one progressor were used to assess neutralization sensitivity of isogenic ICAM-1-negative and ICAM-1-bearing HIV-1(NL4-3), a prototype of T-cell-line-adapted viruses. We found that virus neutralization sensitivity to the studied sera is not modified by the additional interaction between virally embedded ICAM-1 and LFA-1 under an inactive state. However, expression on the target cell surface of an activated LFA-1 form renders ICAM-1-bearing virus particles, but not viruses devoid of ICAM-1, more refractory to neutralization by sera from three out of four LTNPs and all sequential sera from the person who has experienced a progression of the HIV-1-associated disease. Although no conclusive correlation could be drawn between virus susceptibility to neutralization and the disease status or stages of HIV-1 infection, these findings demonstrate that other nonspecific virus-cell interactions mediated by virion-anchored host proteins and their normal cognate ligands on target cells represent factors that can affect the mechanism of HIV-1 neutralization.

The immunosuppressant rapamycin represses human immunodeficiency virus type 1 replication.

The immunosuppressive macrolide rapamycin is used in humans to prevent graft rejection. This drug acts by selectively repressing the translation of proteins that are encoded by an mRNA bearing a 5'-polypyrimidine tract (e.g., ribosomal proteins, elongation factors). The human immunodeficiency virus type 1 (HIV-1) carries a polypyrimidine motif that is located within the tat exon 2. Treatment of human T lymphoid cells with rapamycin resulted in a marked diminution of HIV-1 transcription when infection was performed with luciferase reporter T-tropic and macrophage-tropic viruses. Replication of fully infectious HIV-1 particles was abolished by rapamycin treatment. The rapamycin-mediated inhibitory effect on HIV-1 production was reversed by FK506. The anti-HIV-1 effect of rapamycin was also seen in primary human cells (i.e., peripheral blood lymphocytes) from different healthy donors. Rapamycin was shown to diminish basal HIV-1 long terminal repeat gene expression, and the observed effect of rapamycin on HIV-1 replication seems to be independent of the virus-specific transactivating Tat protein. A constitutive beta-actin promoter-based reporter gene vector was unaffected by rapamycin treatment. Kinetic virus infection studies and exposure to reporter viruses pseudotyped with heterologous envelope proteins (i.e., amphotropic murine leukemia virus and vesicular stomatitis virus G) suggested that rapamycin is primarily affecting the life cycle of HIV-1 at a transcriptional level. Northern blot analysis confirmed that this compound is selectively targeting HIV-1 mRNA synthesis.

Recognizing a something when your library sees it.

Advances are needed in random-display technologies to more tightly link drug actions and functions to the genes that control physiological processes. The reports discussed here explore two sides of these issues-generating new library formats and identifying the targets of drug ligands.

Nuclear factor of activated T cells is a driving force for preferential productive HIV-1 infection of CD45RO-expressing CD4+ T cells.

Human immunodeficiency virus type-1 (HIV-1) preferentially replicates in CD4-expressing T cells bearing a "memory" (CD45RO+) rather than a "naive" (CD45RA+/CD62L+) phenotype. Yet the basis for the higher susceptibility of these cells to HIV-1 infection remains unclear. Because the nature of the CD45 isoform itself can affect biochemical events in T cells, we set out to determine whether these isoforms could differently modulate HIV-1 long terminal repeat (LTR) activity and thereby replication. Through the use of CD4+ Jurkat T cells specifically expressing distinct CD45 isoforms (i.e. CD45RABC or CD45RO), we demonstrated that a difference in CD45 isoform expression conferred preferential replication of HIV-1 to CD45RO-expressing T cell clones following a physiological CD3/CD28 stimulation. Closer analysis indicated that higher HIV-1 LTR activation levels were consistently observed in CD45RO-positive cells, which was paralleled by more pronounced nuclear factor of activated T cells (NFAT) activation in these same cells. Specific involvement of NFAT1 was revealed in studied Jurkat clones by mobility shift analyses. In addition, preferential activation of the LTR and viral replication in CD45RO T cells was FK506- and cyclosporin A-sensitive. These results underscore the importance of NFAT in HIV-1 regulation and for the first time identify the role of the CD45 isoform in limiting productive HIV-1 replication to the human CD4 memory T cell subset.