ABSTRACT
Coxsackie B1 virus infection enhances the susceptibility of in vitro cultured HEp-2 cells to invasiveness by Shigella flexneri. We have studied the effect of viral infection on two phases of the invasiveness. Only a minor part was mediated by enhanced bacterial adherence to the cells, and the intracellular multiplication was unaffected by the virus. Enhanced adherence was not dependent on the presence of the gene product of the 140 Md virulence associated plasmid. Our data indicate that enhanced invasiveness induced by viral infection is mediated by an effect on other phases of the invasiveness.
Subject(s)
Bacterial Adhesion , Enterovirus B, Human/physiology , Shigella flexneri/pathogenicity , Cytochalasin D/pharmacology , Humans , Plasmids , Shigella flexneri/growth & development , Shigella flexneri/physiology , Tumor Cells, Cultured , VirulenceABSTRACT
A model for the study of internalization of particles in mammalian cells was applied to asbestos and glass fibres. Briefly, a fluorescent fluid-phase endocytic marker, Lucifer Yellow CH (LY), was allowed to be incorporated into the lysosomal compartment of Syrian hamster embryo cells. Mineral fibres that were internalized by the cells subsequently became 'fluorescent', presumably when the fibre-containing endosome fused with the LY-containing lysosomes. This method was compared with differential interference contrast (DIC) optics. Approximately three times as many of the cell-associated fibres were determined to be internalized by the fluorescence method compared with DIC optics. Both fine and coarse glass fibres were internalized as effectively as asbestos fibres. The relative frequency of internalized (i.e. fluorescent) fibres increased until 4 hr after exposure compared with the total number of cell-associated fibres. The frequency of internalized fibres compared with the number of cell-associated fibres was constant over the range of fibre levels studied. A surface modification (octadecyldimethylchlorosilane-derivatization) of amosite fibres that decreased the carcinogenicity of the fibres, decreased slightly the number of internalized fibres relative to the number of cell-associated fibres, but this was not statistically significant. Cytoskeleton-interfering agents significantly decreased the relative number of internalized fibres.
ABSTRACT
Coxsackie B1 virus induces increased susceptibility to invasion by Shigella flexneri when HEp-2 cells are inoculated with the complete virus. When RNA from the same virus was microinjected into cells, virus RNA was synthesized and new virus particles were formed, but the transfected RNA had no effect on bacterial invasiveness. However, when the cells were prestimulated with UV-inactivated virus, the microinjected RNA induced an additional enhancement of bacterial invasiveness. Microinjected whole virus particles did not replicate and did not induce any change in bacterial invasiveness. The results indicate that an initial event in virus multiplication is necessary to achieve an effect of transfected viral RNA on invasion of S. flexneri.
Subject(s)
Enterovirus B, Human/genetics , Enterovirus B, Human/radiation effects , RNA, Viral/pharmacology , Shigella flexneri/physiology , Ultraviolet Rays , Cytosol/microbiology , Enterovirus B, Human/growth & development , Humans , Microinjections , RNA, Viral/administration & dosage , Time Factors , Transfection , Tumor Cells, Cultured , Virus Activation/radiation effectsABSTRACT
Coxsackie B1 virus did not replicate when microinjected into HEp-2 cells. Replication was assayed by production of infectious virus particles, synthesis of viral RNA, and lysis of cells. The same virus preparation initiated replication when it was inoculated into HEp-2 cells similarly to that by microinjected purified coxsackie B1 virus RNA.
