ABSTRACT
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.
Subject(s)
Apoptosis , Dengue Virus/pathogenicity , RNA Helicases/chemistry , RNA Helicases/metabolism , Viral Envelope Proteins/chemistry , Viral Envelope Proteins/metabolism , Amino Acid Sequence , Animals , Base Sequence , Cell Line , Chlorocebus aethiops , Culicidae , Dengue Virus/enzymology , Dengue Virus/genetics , Dengue Virus/growth & development , Epithelial Cells/pathology , Epithelial Cells/virology , Glycoproteins/metabolism , Humans , Kinetics , Membrane Fusion , Models, Molecular , Molecular Sequence Data , Mutation/genetics , Neurons/pathology , Neurons/virology , Protein Conformation , Protein Processing, Post-Translational , RNA Helicases/genetics , RNA, Viral/biosynthesis , Viral Envelope Proteins/genetics , Viral Proteins/biosynthesis , Viral Proteins/metabolism , Virulence , Virus ReplicationABSTRACT
Two Aedes albopictus strains are infected by one of the four presently known mosquito spiroplasma strains, the CUAS-1 strain isolated from Culex annulus from Taïwan. An infection by intra-thoracic inoculation leads to a pathogenic effect, dose-dependent, the longevity of mosquitoes being shortened. This pathogenicity is observed at various time after inoculation depending of the mosquito strain. On the other hand, an oral infection has no consequence on the longevity of infected females. However, the replication of spiroplasma has been demonstrated with both infection procedures.
