Gaia is a cornerstone mission in the science programme of the European Space Agency (ESA). The spacecraft construction was approved in 2006, following a study in which the original interferometric concept was changed to a direct-imaging approach. Both the spacecraft and the payload were built by European industry. The involvement of the scientific community focusses on data processing for which the international Gaia Data Processing and Analysis Consortium (DPAC) was selected in 2007. Gaia was launched on 19 December 2013 and arrived at its operating point, the second Lagrange point of the Sun-Earth-Moon system, a few weeks later. The commissioning of the spacecraft and payload was completed on 19 July 2014. The nominal five-year mission started with four weeks of special, ecliptic-pole scanning and subsequently transferred into full-sky scanning mode. We recall the scientific goals of Gaia and give a description of the as-built spacecraft that is currently (mid-2016) being operated to achieve these goals. We pay special attention to the payload module, the performance of which is closely related to the scientific performance of the mission. We provide a summary of the commissioning activities and findings, followed by a description of the routine operational mode. We summarise scientific performance estimates on the basis of in-orbit operations. Several intermediate Gaia data releases are planned and the data can be retrieved from the Gaia Archive, which is available through the Gaia home page.

Gene therapy for cystic fibrosis (CF) lung disease requires efficient gene transfer to airway epithelial cells after intralumenal delivery. Most gene transfer vectors so far tested have not provided the efficiency required. Although human respiratory syncytial virus (RSV), a common respiratory virus, is known to infect the respiratory epithelium, the mechanism of infection and the epithelial cell type targeted by RSV have not been determined. We have utilized human primary airway epithelial cell cultures that generate a well-differentiated pseudostratified mucociliary epithelium to investigate whether RSV infects airway epithelium via the lumenal (apical) surface. A recombinant RSV expressing green fluorescent protein (rgRSV) infected epithelial cell cultures with high gene transfer efficiency when applied to the apical surface but not after basolateral inoculation. Analyses of the cell types infected by RSV revealed that lumenal columnar cells, specifically ciliated epithelial cells, were targeted by RSV and that cultures became susceptible to infection as they differentiated into a ciliated phenotype. In addition to infection of ciliated cells via the apical membrane, RSV was shed exclusively from the apical surface and spread to neighboring ciliated cells by the motion of the cilial beat. Gross histological examination of cultures infected with RSV revealed no evidence of obvious cytopathology, suggesting that RSV infection in the absence of an immune response can be tolerated for >3 months. Therefore, rgRSV efficiently transduced the airway epithelium via the lumenal surface and specifically targeted ciliated airway epithelial cells. Since rgRSV appears to breach the lumenal barriers encountered by other gene transfer vectors in the airway, this virus may be a good candidate for the development of a gene transfer vector for CF lung disease.Human respiratory syncytial virus (RSV) is the most important viral agent causing serious pediatric respiratory disease worldwide (5). RSV infection causes common-cold-like symptoms that progress to lower respiratory tract disease in 25 to 40% of infected infants and results in hospitalization for 0.1 to 1.0% of those infected. Almost everyone has been infected by RSV by 2 years of age. The immunity induced by RSV infection typically is incomplete, and reinfection is common, although subsequent infections are partially restricted and the disease severity is reduced (5).There is a relative lack of direct, detailed information on the characteristics of RSV infection, spread, and pathology in the upper and lower respiratory tract of humans. RSV infects the superficial layer of the respiratory epithelium and has the capacity to spread throughout the conducting airways. However, the details of RSV infection remain unclear, including whether there is a cell specificity to infection, the extent of virus infection and its relationship to disease manifestation and severity, the extent and cause of tissue damage, and whether the formation of syncytia that are so prominent in nonpola...

Two major antigenic subgroups (designated A and B) have been described for human respiratory syncytial virus (RSV). Previously, on the basis of reactivity patterns with monoclonal antibodies, the greatest intersubgroup variation was shown to occur in the G protein, the putative attachment glycoprotein. To delineate the molecular basis for this variation, we have determined the nucleotide and deduced amino acid sequences of the G mRNAs and proteins representing a subgroup A (Long strain) and a subgroup B (18537 strain) virus. These sequences were compared to the available G mRNA sequence for another subgroup A (A2 strain) virus. The Long G protein shared 94% amino acid identity with the A2 G protein. In contrast, the 18537 G protein shared only 53% amino acid identity with the A2 sequence; interestingly, most of the sequence divergence occurred in the proposed extracellular domain of the G protein. This extensive divergence for the G protein was significantly greater than that observed for other

Human respiratory syncytial virus (RSV) was first isolated in 1956 from a laboratory chimpanzee with upper respiratory tract disease (for general reviews, see references 21, 57, 102, and 145). RSV was quickly determined to be of human origin and was shown to be the leading worldwide viral agent of serious pediatric respiratory tract disease. In a 13-year prospective study of infants and children in the United States, RSV was detected in 43%, 25%, 11%, and 10% of pediatric hospitalizations for bronchiolitis, pneumonia, bronchitis, and croup, respectively (110). Approximately two-thirds of infants are infected with RSV during the first year of life, and 90% have been infected one or more times by 2 years of age. The rate of hospitalization for primary infection is approximately 0.5% but can vary by situation and ethnic group and can be as high as 25% (77).RSV also is a significant cause of morbidity and mortality in the elderly, with an impact approaching that of nonpandemic influenza virus (39). RSV readily infects severely immunocompromised individuals, most notably allogeneic bone marrow transplant recipients, causing high mortality. RSV also makes a substantial contribution to upper respiratory tract disease in individuals of all ages (59,65 Although RSV has a single serotype, reinfection can occur throughout life. RSV in yearly winter/early spring epidemics in temperate regions; elsewhere, the timing of RSV activity can vary widely with the locale. The RSV reservoir in the offseason is unknown. Strains circulate quickly around the earth (150). Neither a vaccine nor an effective antiviral therapy is available, although there is active research in both areas (23,78,138). However, infants at high risk for serious disease can receive passive immunoprophylaxis during the epidemic season by a monthly injection of a commercial RSV-neutralizing monoclonal antibody, palivizumab (Synagis), which provides a 55% reduction in RSV-associated hospitalization (17). THE VIRUSRSV (family Paramyxoviridae, order Mononegavirales) is an enveloped virus with a single-stranded negative-sense RNA genome of 15.2 kb (21). There are animal versions of RSV, including bovine RSV (BRSV) and pneumonia virus of mice (PVM), suggesting that species jumping occurred during the evolution of these viruses. However, there is no animal reservoir for human RSV.Efficient infection by RSV of established cell lines in vitro involves binding to cell-surface glycosaminoglycans (62). However, it is not known how closely this binding models attachment in vivo or whether it is an initial interaction that is followed by a second, higher-affinity step that remains to be identified. The nucleocapsid gains entry to the cytoplasm by membrane fusion; surprisingly, this may involve clathrin-mediated endocytosis rather than surface fusion typical of paramyxoviruses (85). Viral gene expression and RNA replication occur in the cytoplasm, and virions acquire a lipid envelope by budding through the plasmid membrane (Fig. 1). Virions are pleomorphic and include spheres ...

No abstract

Human respiratory syncytial virus (RSV) is a ubiquitous pathogen that infects everyone worldwide early in life and is a leading cause of severe lower respiratory tract disease in the pediatric population as well as in the elderly and in profoundly immunosuppressed individuals. RSV is an enveloped, nonsegmented negative-sense RNA virus that is classified in Family Paramyxoviridae and is one of its more complex members. Although the replicative cycle of RSV follows the general pattern of the Paramyxoviridae, it encodes additional proteins. Two of these (NS1 and NS2) inhibit the host type I and type III interferon (IFN) responses, among other functions, and another gene encodes two novel RNA synthesis factors (M2-1 and M2-2). The attachment (G) glycoprotein also exhibits unusual features, such as high sequence variability, extensive glycosylation, cytokine mimicry, and a shed form that helps the virus evade neutralizing antibodies. RSV is notable for being able to efficiently infect early in life, with the peak of hospitalization at 2–3 months of age. It also is notable for the ability to reinfect symptomatically throughout life without need for significant antigenic change, although immunity from prior infection reduces disease. It is widely thought that re-infection is due to an ability of RSV to inhibit or subvert the host immune response. Mechanisms of viral pathogenesis remain controversial. RSV is notable for a historic, tragic pediatric vaccine failure involving a formalin-inactivated virus preparation that was evaluated in the 1960’s and that was poorly protective and paradoxically primed for enhanced RSV disease. RSV also is notable for the development of a successful strategy for passive immunoprophylaxis of high-risk infants using RSV-neutralizing antibodies. Vaccines and new antiviral drugs are in pre-clinical and clinical development, but controlling RSV remains a formidable challenge.

No abstract

No abstract