Swedish Defence Research Agency

About: Swedish Defence Research Agency is a government organization based out in Stockholm, Sweden. It is known for research contribution in the topics: Radar & Laser. The organization has 1413 authors who have published 2731 publications receiving 56083 citations. The organization is also known as: Totalförsvarets forskningsinstitut.

Reverse genetics for crimean-congo hemorrhagic fever virus.

Abstract: The widespread geographical distribution of Crimean-Congo hemorrhagic fever (CCHF) virus (more than 30 countries) and its ability to produce severe human disease with high mortality rates (up to 60%) make CCHF a major public health concern worldwide. We describe here the successful establishment of a reverse genetics technology for CCHF virus, a member of the genus Nairovirus, family BUNYAVIRIDAE: The RNA polymerase I (pol I) system was used to generate artificial viral RNA genome segments (minigenomes), which contained different reporter genes in antisense (virus RNA) or sense (virus-complementary RNA) orientation flanked by the noncoding regions of the CCHF virus S segment. Reporter gene expression was observed in different eukaryotic cell lines following transfection and subsequent superinfection with CCHF virus, confirming encapsidation, transcription, and replication of the pol I-derived minigenomes. The successful transfer of reporter gene activity to fresh cells demonstrated the generation of recombinant CCHF viruses, thereby confirming the packaging of the pol I-derived minigenomes into progeny viruses. The system offers a unique opportunity to study the biology of nairoviruses and to develop therapeutic and prophylactic measures against CCHF infections. In addition, we demonstrated for the first time that the human pol I system can be used to develop reverse genetics approaches for viruses in the family BUNYAVIRIDAE: This is important since it might facilitate the manipulation of bunyaviruses with cell and host tropisms restricted to primates.

Aging of Cholinesterases Phosphylated by Tabun Proceeds through O-Dealkylation.

Abstract: Human butyrylcholinesterase (hBChE) hydrolyzes or scavenges a wide range of toxic esters, including heroin, cocaine, carbamate pesticides, organophosphorus pesticides, and nerve agents. Organophosphates (OPs) exert their acute toxicity through inhibition of acetylcholinesterase (AChE) by phosphorylation of the catalytic serine. Phosphylated cholinesterase (ChE) can undergo a spontaneous, time-dependent process called "aging", during which the OP-ChE conjugate is dealkylated. This leads to irreversible inhibition of the enzyme. The inhibition of ChEs by tabun and the subsequent aging reaction are of particular interest, because tabun-ChE conjugates display an extraordinary resistance toward most current oxime reactivators. We investigated the structural basis of oxime resistance for phosphoramidated ChE conjugates by determining the crystal structures of the non-aged and aged forms of hBChE inhibited by tabun, and by updating the refinement of non-aged and aged tabun-inhibited mouse AChE (mAChE). Structures for non-aged and aged tabun-hBChE were refined to 2.3 and 2.1 A, respectively. The refined structures of aged ChE conjugates clearly show that the aging reaction proceeds through O-dealkylation of the P(R) enantiomer of tabun. After dealkylation, the negatively charged oxygen forms a strong salt bridge with protonated His438N epsilon2 that prevents reactivation. Mass spectrometric analysis of the aged tabun-inhibited hBChE showed that both the dimethylamine and ethoxy side chains were missing from the phosphorus. Loss of the ethoxy is consistent with the crystallography results. Loss of the dimethylamine is consistent with acid-catalyzed deamidation during the preparation of the aged adduct for mass spectrometry. The reported 3D data will help in the design of new oximes capable of reactivating tabun-ChE conjugates.

Hfq, a novel pleiotropic regulator of virulence-associated genes in Francisella tularensis.

Abstract: Francisella tularensis is a highly infectious pathogen that infects animals and humans, causing tularemia. The ability to replicate within macrophages is central for virulence and relies on expression of genes located in the Francisella pathogenicity island (FPI), as well as expression of other genes. Regulation of FPI-encoded virulence gene expression in F. tularensis involves at least four regulatory proteins and is not fully understood. Here we studied the RNA-binding protein Hfq in F. tularensis and particularly the role that it plays as a global regulator of gene expression in stress tolerance and pathogenesis. We demonstrate that Hfq promotes resistance to several cellular stresses (including osmotic and membrane stresses). Furthermore, we show that Hfq is important for the ability of the F. tularensis vaccine strain LVS to induce disease and persist in organs of infected mice. We also demonstrate that Hfq is important for stress tolerance and full virulence in a virulent clinical isolate of F. tularensis, FSC200. Finally, microarray analyses revealed that Hfq regulates expression of numerous genes, including genes located in the FPI. Strikingly, Hfq negatively regulates only one of two divergently expressed putative operons in the FPI, in contrast to the other known regulators, which regulate the entire FPI. Hfq thus appears to be a new pleiotropic regulator of virulence in F. tularensis, acting mostly as a repressor, in contrast to the other regulators identified so far. Moreover, the results obtained suggest a novel regulatory mechanism for a subset of FPI genes.

Engineering Method for Prediction of Impact Response and Damage in Sandwich Panels

Abstract: An engineering method is suggested for prediction of impact response and damage of flat sandwich panels. The approach accounts for local core crushing, delamination and large face sheet deflections and does not rely on empirical indentation laws. Different models are suggested depending upon the impactor mass being either larger or significantly smaller than the mass of the impacted panel. The solution for large mass impact is based on closed form expressions. The solution for small mass impact is obtained from a dimensionless two-parameter integral equation. The validity of the approach is demonstrated on a number of static indentation experiments and impacts on sandwich panels.

Potential source of Francisella tularensis live vaccine strain attenuation determined by genome comparison.

Abstract: Francisella tularensis is a bacterial pathogen that causes the zoonotic disease tularemia and is important to biodefense. Currently, the only vaccine known to confer protection against tularemia is a specific live vaccine strain (designated LVS) derived from a virulent isolate of Francisella tularensis subsp. holarctica. The origin and source of attenuation of this strain are not known. To assist with the design of a defined live vaccine strain, we sought to determine the genetic basis of the attenuation of LVS. This analysis relied primarily on the comparison between the genome of LVS and Francisella tularensis holarctica strain FSC200, which differ by only 0.08% of their nucleotide sequences. Under the assumption that the attenuation was due to a loss of function(s), only coding regions were examined in this comparison. To complement this analysis, the coding regions of two slightly more distantly related Francisella tularensis strains were also compared against the LVS coding regions. Thirty-five genes show unique sequence variations predicted to alter the protein sequence in LVS compared to the other Francisella tularensis strains. Due to these polymorphisms, the functions of 15 of these genes are very likely lost or impaired. Seven of these genes were demonstrated to be under stronger selective constraints, suggesting that they are the most probable to be the source of LVS attenuation and useful for a newly defined vaccine.