Maturation-Induced Cloaking of Neutralization Epitopes on HIV-1 Particles

To become infectious, HIV-1 particles undergo a maturation process involving proteolytic cleavage of the Gag and Gag-Pol polyproteins. Immature particles contain a highly stable spherical Gag lattice and are impaired for fusion with target cells. The fusion impairment is relieved by truncation of the gp41 cytoplasmic tail (CT), indicating that an interaction between the immature viral core and gp41 within the particle represses HIV-1 fusion by an unknown mechanism. We hypothesized that the conformation of Env on the viral surface is regulated allosterically by interactions with the HIV-1 core during particle maturation. To test this, we quantified the binding of a panel of monoclonal antibodies to mature and immature HIV-1 particles by immunofluorescence imaging. Surprisingly, immature particles exhibited markedly enhanced binding of several gp41-specific antibodies, including two that recognize the membrane proximal external region (MPER) and neutralize diverse HIV-1 strains. Several of the differences in epitope exposure on mature and immature particles were abolished by truncation of the gp41 CT, thus linking the immature HIV-1 fusion defect with altered Env conformation. Our results suggest that perturbation of fusion-dependent Env conformational changes contributes to the impaired fusion of immature particles. Masking of neutralization-sensitive epitopes during particle maturation may contribute to HIV-1 immune evasion and has practical implications for vaccine strategies targeting the gp41 MPER

Women\u27s experiences on the path to a career in game development

This chapter seeks to identify whether there is a dominant, presupposed career pipeline to a career in game development and then looks for women and women’s experiences at each stage of that pipeline. It concludes that a dominant pipeline does exist and that this pathway both disadvantages women who attempt it and marginalizes other pathways. Along the way women deal with obstacles that can delegitimize their choices and experiences and/or make the assumed pathway inhospitable. This chapter relies on published literature as well as data from the 2014 and 2015 Developer Satisfaction Surveys (DSS) conducted by the International Game Developers Association (IGDA) in partnership with the authors

Immunoelectron Microscopic Evidence for Tetherin/BST2 as the Physical Bridge between HIV-1 Virions and the Plasma Membrane

Tetherin/BST2 was identified in 2008 as the cellular factor responsible for restricting HIV-1 replication at a very late stage in the lifecycle. Tetherin acts to retain virion particles on the plasma membrane after budding has been completed. Infected cells that express large amounts of tetherin display large strings of HIV virions that remain attached to the plasma membrane. Vpu is an HIV-1 accessory protein that specifically counteracts the restriction to virus release contributed by tetherin. Tetherin is an unusual Type II transmembrane protein that contains a GPI anchor at its C-terminus and is found in lipid rafts. The leading model for the mechanism of action of tetherin is that it functions as a direct physical tether bridging virions and the plasma membrane. However, evidence that tetherin functions as a physical tether has thus far been indirect. Here we demonstrate by biochemical and immunoelectron microscopic methods that endogenous tetherin is present on the viral particle and forms a bridge between virion particles and the plasma membrane. Endogenous tetherin was found on HIV particles that were released by partial proteolytic digestion. Immunoelectron microscopy performed on HIV-infected T cells demonstrated that tetherin forms an apparent physical link between virions and connects patches of virions to the plasma membrane. Linear filamentous strands that were highly enriched in tetherin bridged the space between some virions. We conclude that tetherin is the physical tether linking HIV-1 virions and the plasma membrane. The presence of filaments with which multiple molecules of tetherin interact in connecting virion particles is strongly suggested by the morphologic evidence

Antibody Responses against Xenotropic Murine Leukemia Virus-Related Virus Envelope in a Murine Model

Xenotropic murine leukemia virus-related virus (XMRV) was recently discovered to be the first human gammaretrovirus that is associated with chronic fatigue syndrome and prostate cancer (PC). Although a mechanism for XMRV carcinogenesis is yet to be established, this virus belongs to the family of gammaretroviruses well known for their ability to induce cancer in the infected hosts. Since its original identification XMRV has been detected in several independent investigations; however, at this time significant controversy remains regarding reports of XMRV detection/prevalence in other cohorts and cell type/tissue distribution. The potential risk of human infection, coupled with the lack of knowledge about the basic biology of XMRV, warrants further research, including investigation of adaptive immune responses. To study immunogenicity in vivo, we vaccinated mice with a combination of recombinant vectors expressing codon-optimized sequences of XMRV gag and env genes and virus-like particles (VLP) that had the size and morphology of live infectious XMRV.Immunization elicited Env-specific binding and neutralizing antibodies (NAb) against XMRV in mice. The peak titers for ELISA-binding antibodies and NAb were 1:1024 and 1:464, respectively; however, high ELISA-binding and NAb titers were not sustained and persisted for less than three weeks after immunizations.Vaccine-induced XMRV Env antibody titers were transiently high, but their duration was short. The relatively rapid diminution in antibody levels may in part explain the differing prevalences reported for XMRV in various prostate cancer and chronic fatigue syndrome cohorts. The low level of immunogenicity observed in the present study may be characteristic of a natural XMRV infection in humans

Different Pattern of Immunoglobulin Gene Usage by HIV-1 Compared to Non-HIV-1 Antibodies Derived from the Same Infected Subject

A biased usage of immunoglobulin (Ig) genes is observed in human anti-HIV-1 monoclonal antibodies (mAbs) resulting probably from compensation to reduced usage of the VH3 family genes, while the other alternative suggests that this bias usage is due to antigen requirements. If the antigen structure is responsible for the preferential usage of particular Ig genes, it may have certain implications for HIV vaccine development by the targeting of particular Ig gene-encoded B cell receptors to induce neutralizing anti-HIV-1 antibodies. To address this issue, we have produced HIV-1 specific and non-HIV-1 mAbs from an infected individual and analyzed the Ig gene usage. Green-fluorescence labeled virus-like particles (VLP) expressing HIV-1 envelope (Env) proteins of JRFL and BaL and control VLPs (without Env) were used to select single B cells for the production of 68 recombinant mAbs. Ten of these mAbs were HIV-1 Env specific with neutralizing activity against V3 and the CD4 binding site, as well as non-neutralizing mAbs to gp41. The remaining 58 mAbs were non-HIV-1 Env mAbs with undefined specificities. Analysis revealed that biased usage of Ig genes was restricted only to anti-HIV-1 but not to non-HIV-1 mAbs. The VH1 family genes were dominantly used, followed by VH3, VH4, and VH5 among anti-HIV-1 mAbs, while non-HIV-1 specific mAbs preferentially used VH3 family genes, followed by VH4, VH1 and VH5 families in a pattern identical to Abs derived from healthy individuals. This observation suggests that the biased usage of Ig genes by anti-HIV-1 mAbs is driven by structural requirements of the virus antigens rather than by compensation to any depletion of VH3 B cells due to autoreactive mechanisms, according to the gp120 superantigen hypothesis

A genetic network model of cellular responses to lithium treatment and cocaine abuse in bipolar disorder

<p>Abstract</p> <p>Background</p> <p>Lithium is an effective treatment for Bipolar Disorder (BD) and significantly reduces suicide risk, though the molecular basis of lithium's effectiveness is not well understood. We seek to improve our understanding of this effectiveness by posing hypotheses based on new experimental data as well as published data, testing these hypotheses in silico, and posing new hypotheses for validation in future studies. We initially hypothesized a gene-by-environment interaction where lithium, acting as an environmental influence, impacts signal transduction pathways leading to differential expression of genes important in the etiology of BD mania.</p> <p>Results</p> <p>Using microarray and rt-QPCR assays, we identified candidate genes that are differentially expressed with lithium treatment. We used a systems biology approach to identify interactions among these candidate genes and develop a network of genes that interact with the differentially expressed candidates. Notably, we also identified cocaine as having a potential influence on the network, consistent with the observed high rate of comorbidity for BD and cocaine abuse. The resulting network represents a novel hypothesis on how multiple genetic influences on bipolar disorder are impacted by both lithium treatment and cocaine use. Testing this network for association with BD and related phenotypes, we find that it is significantly over-represented for genes that participate in signal transduction, consistent with our hypothesized-gene-by environment interaction. In addition, it models related pharmacogenomic, psychiatric, and chemical dependence phenotypes.</p> <p>Conclusions</p> <p>We offer a network model of gene-by-environment interaction associated with lithium's effectiveness in treating BD mania, as well as the observed high rate of comorbidity of BD and cocaine abuse. We identified drug targets within this network that represent immediate candidates for therapeutic drug testing. Posing novel hypotheses for validation in future work, we prioritized SNPs near genes in the network based on functional annotation. We also developed a "concept signature" for the genes in the network and identified additional candidate genes that may influence the system because they are significantly associated with the signature.</p

Association of Brain Natriuretic Peptide Levels at Time of Injury with Morbidity and Mortality in Patients with Surgically Treated Hip Fractures

Background:. An elevated brain natriuretic peptide (BNP) level has been shown to be associated with mortality and cardiac events in cardiac surgery, but its utility in the prediction of morbidity and mortality in hip fracture surgery is unknown. The primary aim of this study was to determine if there is a difference in BNP level at the time of injury between patients who do and do not develop complications after hip fracture surgery. The secondary aim was to determine if there is a predictive relationship between complications associated with the initial BNP level and mortality. Methods:. A retrospective chart review of 455 hip fractures in patients ≥60 years old that were operatively treated between February 2014 and July 2018 was performed. Patients were included if they had a BNP level within 48 hours after injury (BNPi). Specific perioperative (≤7 days), 30-day, 1-year, and 2-year postoperative complications were recorded. Wilcoxon rank-sum tests were used to determine if higher BNPi values were associated with greater morbidity. The complications associated with higher BNPi values were further analyzed to assess if they were predictive of mortality, using univariate and multivariable analyses. Results:. Higher BNPi was significantly associated with greater morbidity at all postoperative time points and with higher mortality at 1 and 2 years postoperatively. Furthermore, several complications including cardiac failure or exacerbation and altered mental status were associated with mortality at all time points in univariate analysis and at many time points in multivariable analysis. Conclusions:. Patients with higher BNPi levels were more likely to develop complications up to 1 year postoperatively, and several of these complications were associated with increased mortality. Future studies to determine if delaying surgery until BNP levels are normalized or lowered may help guide management, and may be useful in determining the need for further medical optimization. Future studies aimed at defining a threshold BNP value at the time of injury may also help in better managing patients preoperatively. Level of Evidence:. Prognostic Level III. See Instructions for Authors for a complete description of levels of evidence

Outcomes in patients undergoing cardiac catheterization and therapeutic hypothermia after cardiac arrest

BACKGROUND: We aimed to elucidate the post-hospitalization outcomes in patients undergoing therapeutic hypothermia and cardiac catheterization after sudden cardiac arrest (SCA). METHODS: A retrospective, tertiary-center study consisted of 173 consecutive patients who met inclusion criteria between January 2008 and March 2015. Major adverse cardiac events (MACE) were defined as death, myocardial infarction, revascularization, and heart failure or arrhythmia- related hospitalization. RESULTS: Ninety-nine of 173 patients (57.2%) survived to discharge. Univariate analysis showed that shockable rhythm and initial lactate level were independent predictors of survival to discharge (p-value \u3c0.001). The patients who survived were followed for 43.9±25 months after discharge; 63.6% of patients were discharged home and 36.4% of patients were to nursing homes or to long-term acute care facilities. MACE is presented in Figure 1. During the follow-up period, 53.3% of patients who survived remained free from MACE. CONCLUSIONS: In our real-world study population, 57.2% of patients were alive to discharge after undergoing catheterization and hypothermia for SCA. About half the patients who survived to discharge had MACE in an average follow-up of 3.7 years. These findings highlight the importance of close clinical follow-up for patients who survive SCA. Open full size imag