Autonomous Targeting Research Articles

Inflation Targeting Monetary and Fiscal Policies in a Two-Country Stock-Flow Consistent Model

This paper develops a simple two-country stock-flow consistent model based on that of Godley and Lavoie (2007b). In order to motivate the use of stabilisation policies, persistent inflationary pressure and endogenous economic cycles are introduced into the model. Three scenarios are then simulated: a step decrease in real exports from country B, increased wage pressure in country B and an income tax cut in country A. In all cases, monetary and fiscal policies in isolation enjoy little success but a combined monetary and fiscal approach to stabilisation proves highly effective. Moreover, the model suggests that the pursuit of autonomous inflation targeting in each country introduces excessive exchange rate volatility relative to an alternative rule in which one central bank takes a leading role in interest rate setting.

Autonomous Targeting of Infectious Superspreaders Using Engineered Transmissible Therapies

Infectious disease treatments, both pharmaceutical and vaccine, face three universal challenges: the difficulty of targeting treatments to high-risk ‘superspreader’ populations who drive the great majority of disease spread, behavioral barriers in the host population (such as poor compliance and risk disinhibition), and the evolution of pathogen resistance. Here, we describe a proposed intervention that would overcome these challenges by capitalizing upon Therapeutic Interfering Particles (TIPs) that are engineered to replicate conditionally in the presence of the pathogen and spread between individuals — analogous to ‘transmissible immunization’ that occurs with live-attenuated vaccines (but without the potential for reversion to virulence). Building on analyses of HIV field data from sub-Saharan Africa, we construct a multi-scale model, beginning at the single-cell level, to predict the effect of TIPs on individual patient viral loads and ultimately population-level disease prevalence. Our results show that a TIP, engineered with properties based on a recent HIV gene-therapy trial, could stably lower HIV/AIDS prevalence by ∼30-fold within 50 years and could complement current therapies. In contrast, optimistic antiretroviral therapy or vaccination campaigns alone could only lower HIV/AIDS prevalence by <2-fold over 50 years. The TIP's efficacy arises from its exploitation of the same risk factors as the pathogen, allowing it to autonomously penetrate superspreader populations, maintain efficacy despite behavioral disinhibition, and limit viral resistance. While demonstrated here for HIV, the TIP concept could apply broadly to many viral infectious diseases and would represent a new paradigm for disease control, away from pathogen eradication but toward robust disease suppression.

Saying ‘No!’ to Lethal Autonomous Targeting

Plans to automate killing by using robots armed with lethal weapons have been a prominent feature of most US military forces’ roadmaps since 2004. The idea is to have a staged move from ‘man-in-the-loop’ to ‘man-on-the-loop’ to full autonomy. While this may result in considerable military advantages, the policy raises ethical concerns with regard to potential breaches of International Humanitarian Law, including the Principle of Distinction and the Principle of Proportionality. Current applications of remote piloted robot planes or drones offer lessons about how automated weapons platforms could be misused by extending the range of legally questionable, targeted killings by security and intelligence forces. Moreover, the alleged moral disengagement by remote pilots will only be exacerbated by the use of autonomous robots. Leaders in the international community need to address the difficult legal and moral issues now, before the current mass proliferation of development reaches fruition.

Onboard Autonomous Targeting for the Trans-Earth Phase of Orion

The present investigation focuses on one aspect of the autonomous targeting process used onboard during the Orion trans-Earth injection phase, specifically, a fast and robust algorithm that identifies a feasible return trajectory, one that meets the entry constraints without exceeding the fuel available. Unlike earlier Apollo missions, Orion seeks to land near the polar regions of the moon. Thus, a substantial plane change maneuver is required before returning to Earth. To reduce the fuel expenditure associated with this plane change, a three-maneuver sequence is employed during the return phase. An autonomous onboard targeting process for precision entry (one that incorporates multiple coordinated trans-Earth maneuvers) is sought in the event of loss of communication with the ground. The latter scenario presents a very unique challenge: one never before required of any Apollo vehicle. The Apollo missions also benefited from flexible entry requirements in contrast to Orion. Precision targeting in multibody regimes has only been previously demonstrated in unmanned sample return missions such as Genesis. The formulation presented here ensures that the entry constraints are met without violating the available fuel budget.

Alternatively spliced N-terminal exons in tropomyosin isoforms do not act as autonomous targeting signals

Tropomyosin (Tm) polymerises head-to-tail to form a continuous polymer located in the major groove of the actin filament. Multiple Tm isoforms are generated by alternative splicing of four genes, and individual isoforms show specific localisation patterns in many cell types, and can have differing effects on the actin cytoskeleton. Fluorescently-tagged Tm isoforms and mutants were expressed in C2C12 cells to investigate the mechanisms of alternative localisation of high molecular weight (HMW) and low molecular weight (LMW) Tms. Fluorescently-tagged Tm constructs show similar localisation to endogenous Tms as observed by antibodies, with the HMW Tm3 relatively diminished at the periphery of cells compared to LMW isoforms Tm5b or Tm5NM1. Tm3 and Tm5b only differ in their N-terminal exons, but these N-terminal exons do not independently direct localisation within the cell, as chimeric mutants Tm3-Tm5NM1 and Tm5b-Tm5NM1 show an increased peripheral localisation similar to Tm5NM1. The lower abundance of Tm3 at the periphery of the cell is not a result of different protein dynamics, as Tm3 and Tm5b show similar recovery after photobleaching. The relative exclusion of Tm3 from the periphery of cells does, however, require interaction with the actin filament, as mutants with truncations at either the N-terminus or the C-terminus are unable to localise to actin stress fibres, and are present in the most peripheral regions of the cell. We conclude that it is the entire Tm molecule which is the unit of sorting, and that the alternatively spliced N-terminal exons do not act as autonomous targeting signals.

T lymphocytes as potential therapeutic drug carrier for cancer treatment

The aim of our research is the application of human immune cells (T lymphocytes) as target directed drug carrier. Thereby, the inclusion of therapeutical nanoparticles into immune cells is a new strategy for a localized chemotherapy. The autonomous targeting of diseased sites makes immune cells to perfectly controlled drug delivery systems. The study's aim was to demonstrate the feasibility to mobilise immune cells as therapeutic drug carrier systems which can be combined with existing immunotherapies. Therefore, Jurkat cells as well as T lymphocytes were used to identify the smoothest procedure for loading nanoparticles into immune cells. Different loading processes, incubation times and nanoparticle concentrations were compared. Nanoparticles coated with cytotoxic antibiotic doxorubicin were used in first release experiments. A time dependent liberation of doxorubicin from carrier cells was discussed as first therapeutic approach.

Autonomous Navigation for the Deep Impact Mission Encounter with Comet Tempel 1

The engineering goal of the Deep Impact mission is to impact comet Tempel 1 on July 4, 2005, with a 370 kg active Impactor spacecraft (s/c). The impact velocity will be just over 10 km/s and is expected to excavate a crater approximately 20 m deep and 100 m wide. The Impactor s/c will be delivered to the vicinity of Tempel 1 by the Flyby s/c, which is also the key observing platform for the event. Following Impactor release, the Flyby will change course to pass the nucleus at an altitude of 500 km and at the same time slow down in order to allow approximately 800 s of observation of the impact event, ejecta plume expansion, and crater formation. Deep Impact will use the autonomous optical navigation (AutoNav) software system to guide the Impactor s/c to intercept the nucleus of Tempel 1 at a location that is illuminated and viewable from the Flyby. The Flyby s/c uses identical software to determine its comet-relative trajectory and provide the attitude determination and control system (ADCS) with the relative position information necessary to point the High Resolution Imager (HRI) and Medium Resolution Imager (MRI) instruments at the impact site during the encounter. This paper describes the Impactor s/c autonomous targeting design and the Flyby s/c autonomous tracking design, including image processing and navigation (trajectory estimation and maneuver computation). We also discuss the analysis that led to the current design, the expected system performance as compared to the key mission requirements and the sensitivity to various s/c subsystems and Tempel 1 environmental factors.

The Cytoplasmic Domain of Vamp4 and Vamp5 Is Responsible for Their Correct Subcellular Targeting: THE N-TERMINAL EXTENSION OF VAMP4 CONTAINS A DOMINANT AUTONOMOUS TARGETING SIGNAL FOR THE TRANS-GOLGI NETWORK

SNAREs represent a superfamily of proteins responsible for the last stage of docking and subsequent fusion in diverse intracellular membrane transport events. The Vamp subfamily of SNAREs contains 7 members (Vamp1, Vamp2, Vamp3/cellubrevin, Vamp4, Vamp5, Vamp7/Ti-Vamp, and Vamp8/endobrevin) that are distributed in various post-Golgi structures. Vamp4 and Vamp5 are distributed predominantly in the trans-Golgi network (TGN) and the plasma membrane, respectively. When C-terminally tagged with enhanced green fluorescent protein, the majority of Vamp4 and Vamp5 is correctly targeted to the TGN and plasma membrane, respectively. Swapping the N-terminal cytoplasmic region and the C-terminal membrane anchor domain between Vamp4 and Vamp5 demonstrates that the N-terminal cytoplasmic region of these two SNAREs contains the correct subcellular targeting information. As compared with Vamp5, Vamp4 contains an N-terminal extension of 51 residues. Appending this 51-residue N-terminal extension onto the N terminus of Vamp5 results in targeting of the chimeric protein to the TGN, suggesting that this N-terminal extension of Vamp4 contains a dominant and autonomous targeting signal for the TGN. Analysis of deletion mutants of this N-terminal region suggests that this TGN-targeting signal is encompassed within a smaller region consisting of a di-Leu motif followed by two acidic clusters. The essential role of the di-Leu motif and the second acidic cluster was then established by site-directed mutagenesis.

The FcγRIa (CD64) Ligand Binding Chain Triggers Major Histocompatibility Complex Class II Antigen Presentation Independently of Its Associated FcR γ-Chain

AbstractWithin multi-subunit Ig receptors, the FcR γ-chain immunoreceptor tyrosine-based activation motif (ITAM) plays a crucial role in enabling antigen presentation. This process involves antigen-capture and targeting to specific degradation and major histocompatibility complex (MHC) class II loading compartments. Antigenic epitopes are then presented by MHC class II molecules to specific T cells. The high-affinity receptor for IgG, hFcγRIa, is exclusively expressed on myeloid lineage cells and depends on the FcR γ-chain for surface expression, efficient ligand binding, and most phagocytic effector functions. However, we show in this report, using the IIA1.6 cell model, that hFcγRIa can potentiate MHC class II antigen presentation, independently of a functional FcR γ-chain ITAM. Immunoelectron microscopic analyses documented hFcγRIa α-chain/rabbit IgG-Ovalbumin complexes to be internalized and to migrate via sorting endosomes to MHC class II-containing late endosomes. Radical deletion of the hFcγRIa α-chain cytoplasmic tail did not affect internalization of rabbit IgG-Ovalbumin complexes. Importantly, however, this resulted in diversion of receptor-ligand complexes to the recycling pathway and decreased antigen presentation. These results show the hFcγRIa cytoplasmic tail to contain autonomous targeting information for intracellular trafficking of receptor-antigen complexes, although deficient in canonical tyrosine- or dileucine-targeting motifs. This is the first documentation of autonomous targeting by a member of the multichain FcR family that may critically impact the immunoregulatory role proposed for hFcγRIa (CD64).

The FcγRIa (CD64) Ligand Binding Chain Triggers Major Histocompatibility Complex Class II Antigen Presentation Independently of Its Associated FcR γ-Chain

Within multi-subunit Ig receptors, the FcR γ-chain immunoreceptor tyrosine-based activation motif (ITAM) plays a crucial role in enabling antigen presentation. This process involves antigen-capture and targeting to specific degradation and major histocompatibility complex (MHC) class II loading compartments. Antigenic epitopes are then presented by MHC class II molecules to specific T cells. The high-affinity receptor for IgG, hFcγRIa, is exclusively expressed on myeloid lineage cells and depends on the FcR γ-chain for surface expression, efficient ligand binding, and most phagocytic effector functions. However, we show in this report, using the IIA1.6 cell model, that hFcγRIa can potentiate MHC class II antigen presentation, independently of a functional FcR γ-chain ITAM. Immunoelectron microscopic analyses documented hFcγRIa -chain/rabbit IgG-Ovalbumin complexes to be internalized and to migrate via sorting endosomes to MHC class II-containing late endosomes. Radical deletion of the hFcγRIa -chain cytoplasmic tail did not affect internalization of rabbit IgG-Ovalbumin complexes. Importantly, however, this resulted in diversion of receptor-ligand complexes to the recycling pathway and decreased antigen presentation. These results show the hFcγRIa cytoplasmic tail to contain autonomous targeting information for intracellular trafficking of receptor-antigen complexes, although deficient in canonical tyrosine- or dileucine-targeting motifs. This is the first documentation of autonomous targeting by a member of the multichain FcR family that may critically impact the immunoregulatory role proposed for hFcγRIa (CD64).

Intracellular trafficking of the vacuolar H+-ATPase accessory subunit Ac45.

Ac45 is a type I transmembrane protein associated with vacuolar H+-ATPase, a proton pump mediating the acidification of multiple intracellular organelles. In this study, we examined the intracellular routing of Ac45 in transfected CV-1 fibroblasts. Steady state immunolabeling showed that Ac45 is located on the plasma membrane and in a vacuolar compartment in the juxtanuclear region. Antibody internalization experiments revealed that Ac45 is rapidly retrieved from the cell surface and is targeted to the vacuolar structures. The 26-residue cytoplasmic tail of Ac45 was intrinsically capable of mediating endocytosis of the cell surface protein Tac, indicating that the tail contains an autonomous internalization signal. Immunolocalization studies on cells expressing carboxy-terminally truncated Ac45 mutants showed the presence of essential routing information in the membrane-distal region of the cytoplasmic tail. Further mutational analysis of this region, which lacks the recognized tyrosine- or di-leucine-based sorting motifs, suggested that multiple sites rather than a short linear sequence are responsible for the internalization. Collectively, our results indicate that the cytoplasmic tail of Ac45 contains autonomous targeting information distinct from previously described routing determinants.

Intracellular trafficking of the vacuolar H+-ATPase accessory subunit Ac45

ABSTRACT Ac45 is a type I transmembrane protein associated with vacuolar H+-ATPase, a proton pump mediating the acidification of multiple intracellular organelles. In this study, we examined the intracellular routing of Ac45 in transfected CV-1 fibroblasts. Steady state immunolabeling showed that Ac45 is located on the plasma membrane and in a vacuolar compartment in the juxtanuclear region. Antibody internalization experiments revealed that Ac45 is rapidly retrieved from the cell surface and is targeted to the vacuolar structures. The 26-residue cytoplasmic tail of Ac45 was intrinsically capable of mediating endocytosis of the cell surface protein Tac, indicating that the tail contains an autonomous internalization signal. Immunolocalization studies on cells expressing carboxy-terminally truncated Ac45 mutants showed the presence of essential routing information in the membrane-distal region of the cytoplasmic tail. Further mutational analysis of this region, which lacks the recognized tyrosine- or di-leucine-based sorting motifs, suggested that multiple sites rather than a short linear sequence are responsible for the internalization. Collectively, our results indicate that the cytoplasmic tail of Ac45 contains autonomous targeting information distinct from previously described routing determinants.

TGN38 is maintained in the trans-Golgi network by a tyrosine-containing motif in the cytoplasmic domain.

Sorting of proteins destined for different plasma membrane domains, lysosomes and secretory pathways takes place in the trans-Golgi network (TGN). TGN38 is an integral membrane protein found in this intracellular compartment. We show that TGN38 contains an autonomous targeting signal within its cytoplasmic domain which determines its intracellular location. Deletion analysis and site-directed mutagenesis of this domain demonstrate that a tyrosine motif homologous to the internalization signal of surface receptors is necessary and sufficient for correct localization. These findings suggest that TGN38 is maintained in the TGN by retrieval from the plasma membrane and employs a different mechanism for retention from that of the transferase enzymes of the trans-Golgi.