A cell line infectible by prion strains from different species.

It has been shown previously that ovine prion protein (PrP(C)) renders rabbit epithelial RK13 cells permissive to the multiplication of ovine prions, thus providing evidence that species barriers can be crossed in cultured cells through the expression of a relevant PrP(C). The present study significantly extended this observation by showing that mouse and bank vole prions can be propagated in RK13 cells that express the corresponding PrP(C). Importantly, the respective molecular patterns of abnormal PrP (PrP(res)) and, where examined, the neuropathological features of the infecting strains appeared to be maintained during the propagation in cell culture. These findings indicate that RK13 cells can be genetically engineered to replicate prion strains faithfully from different species. Such an approach may facilitate investigations of the molecular basis of strain identity and prion diversity.

Determinants in the envelope E protein and viral RNA helicase NS3 that influence the induction of apoptosis in response to infection with dengue type 1 virus.

One mechanism by which dengue (DEN) virus may cause cell death is apoptosis. In this study, we investigated whether the genetic determinants responsible for acquisition by DEN type 1 (DEN-1) virus of mouse neurovirulence interfere with the induction of apoptosis. Neurovirulent variant FGA/NA d1d was generated during the adaptation of the human isolate of DEN-1 virus strain FGA/89 to grow in newborn mouse brains and mosquito cells in vitro [Desprès, P. Frenkiel, M. -P. Ceccaldi, P.-E. Duarte Dos Santos, C. and Deubel, V. (1998) J. Virol., 72: 823-829]. Genetic determinants possibly responsible for mouse neurovirulence were studied by sequencing the entire genomes of both DEN-1 viruses. Three amino acid differences in the envelope E protein and one in the nonstructural NS3 protein were found. The cytotoxicity of the mouse-neurovirulent DEN-1 variant was studied in different target cells in vitro and compared with the parental strain. FGA/NA d1d was more pathogenic for mouse neuroblastoma cells and attenuated for human hepatoma cells. Changes in virus replicative functions and virus assembly may account, in a large part, for the differences in the induction of apoptosis. Our data suggest that identified amino acid substitutions in the envelope E protein and viral RNA helicase NS3 may influence DEN-1 virus pathogenicity by altering viral growth.

Alpha-glucosidase inhibitors reduce dengue virus production by affecting the initial steps of virion morphogenesis in the endoplasmic reticulum.

We report that endoplasmic reticulum alpha-glucosidase inhibitors have antiviral effects on dengue (DEN) virus. We found that glucosidase inhibition strongly affects productive folding pathways of the envelope glycoproteins prM (the intracellular glycosylated precursor of M [membrane protein]) and E (envelope protein): the proper folding of prM bearing unprocessed N-linked oligosaccharide is inefficient, and this causes delayed formation of prME heterodimer. The complexes formed between incompletely folded prM and E appear to be unstable, leading to a nonproductive pathway. Inhibition of alpha-glucosidase-mediated N-linked oligosaccharide trimming may thus prevent the assembly of DEN virus by affecting the early stages of envelope glycoprotein processing.

[Apoptotic cell death in response to dengue virus infection: what are the consequences of viral pathogenesis?]. / La mort cellulaire par apoptose en réponse à l'infection par le virus de la dengue: quelles conséquences dans la pathogénie virale?

Dengue is a human disease of viral etiology which may be fatal in its hemorragic form. It is widely spread in the tropical areas of the different continents and has been dramatically expanding over the past 30 years. Although an immunological disorder is thought to be involved in dengue physiological symptoms, the pathogenesis of dengue hemorragic fever has not yet been elucidated. Whether the immune response is deleterious or beneficial to the host remains a matter of debate. Other factors, related to virus replication in specific host cells, could also contribute to the severity of the disease. Apoptotic cell death is one of the important consequences of dengue virus infection both in vitro and in vivo. Dengue replication triggers apoptotic signals in neurons and hepatocytes although the original effectors and kinetics differ. Implications of the ongoing apoptotic processes in viral pathogenesis will be further discussed.