Different serotypes of dengue viruses differently regulate the expression of the host cell antigen processing machinery
ACTA TROPICA
Authors: Gan, Chye Sheng; Yusof, Rohana; Othman, Shatrah
Abstract
Dengue virus (DV) infection demonstrates an intriguing virus-induced intracellular membrane alteration that results in the augmentation of major histocompatibility complex (MHC) class I-restricted antigen presentation. As oppose to its biological function in attracting CD8(+) T-cells, this phenomenon appears to facilitate the immune evasion. However, the molecular events that attribute to the dysregulation of the antigen presenting mechanism (APM) by DV remain obscure. In this study, we aimed to characterize the host cell APM upon infection with all serotypes of whole DV. Cellular RNA were isolated from infected cells and the gene expressions of LMP2, LMP7, TAP1, TAP2, TAPBP, CALR, CANX, PDIA3, HLA-A and HLA-B were analyzed via quantitative PCR. The profiles of the gene expression were further validated. We showed that all four DV serotypes modulate host APM at the proteasomal level with DV2 showing the most prominent expression profile. (C) 2015 Elsevier B.V. All rights reserved.
A Comparative Study of SBAS Systems for Navigation in Geostationary Orbit
PROCEEDINGS OF THE 28TH INTERNATIONAL TECHNICAL MEETING OF THE SATELLITE DIVISION OF THE INSTITUTE OF NAVIGATION (ION GNSS+ 2015)
Authors: Kahr, Erin; Montenbruck, Oliver; O'Keefe, Kyle
Abstract
Real data has been collected from space demonstrating the CanX-2 receiver's ability to track the WAAS, EGNOS, GAGAN, and MSAS systems. Two types of analysis were performed, in order to assess the suitability of SBAS ranging measurements as a source of positioning information for users in geostationary and other higher orbits, in which SBAS satellites may be permanently in view while GPS visibility is severely limited by the shape of the transmit gain patterns. The first analysis, of the transmit gain patterns of the EGNOS, WAAS, MSAS and GAGAN systems, revealed that all the SBAS satellites transmit enough power to be tracked over the earth's limb. It was revealed that GAGAN has a narrower gain pattern than the other SBAS systems. WAAS and EGNOS appear to have similar gain patterns but WAAS has a higher transmit power by 2-4 dB, and MSAS appears to transmit lower signal power than the other systems but uses an antenna design providing more even global coverage which results in and stronger power transmitted towards the edge of the earth. The second study determined that the SBAS ranging capability was useable in space, provided that the fast correction data transmitted by the SBAS satellites is applied in addition to the MT9 broadcast ephemeris. The SBAS ranging residuals were assessed compared to GPS single point position solutions in space and on the ground, and were found to agree to within +/- 10 m in most cases for WAAS and +/- 20 m for MSAS and GAGAN. EGNOS does not support ranging. Provided the lower accuracy compared to GPS is taken into account, the SBAS systems could be used to provide positioning and timing information to users in GEO or other orbits above the MEO GNSS constellations.