Enhancement of hepatitis A propagation in tissue culture with 5,6-dichloro-1-beta-D-ribofuranosylbenzimidazole

Synthesis and Biological Evaluation of New 5,6-dichlorobenzimidazole Nucleoside Derivatives

Novel 5,6-dichlorobenzimidazole nucleoside analogues structurally related to the well-known riboside DRB have been synthesized. The 1′,2′- trans nucleosides were prepared by condensation of peracylated sugars with 5,6-dichlorobenzimidazole, whereas the 1′,2′- cis β-D-arabinofuranosyl and β-D-lyxofuranosyl nucleosides were obtained by inversion of configuration on the sugar moiety. Chiral acyclic derivatives were stereospecifically prepared by ring-opening of furano- or pyrano-nucleosides by means of periodate oxidation, followed by borohydride reduction. The in vitro activities against a range of DNA and RNA viruses, as well as the cytotoxicities in human T-lymphocyte MT-4 cells, have been determined for these novel compounds and for DRB. No truly selective activity (i.e. clearly below the cytotoxic concentration) was observed against any of the viruses used. Some of the compounds, including DRB, were cytotoxic to MT-4 cells at CC50 values of less than 10 μg ml−1.

cDNA clone of hepatitis A virus encoding a virulent virus: induction of viral hepatitis by direct nucleic acid transfection of marmosets

Direct inoculation of marmoset livers with an in vitro transcription mixture containing cDNA and full-length genomic RNA transcripts of hepatitis A virus resulted in acute viral hepatitis. Elevations in serum levels of liver enzymes were correlated with appearance of antibody to hepatitis A virus. Genomes of infectious hepatitis A virus isolated from the feces of transfected marmosets contained the same mutation as the cDNA template used for transfection. Liver biopsies confirmed that the virus encoded by the cDNA clone induced histopathological changes equivalent to those caused by virulent wild-type virus.

Restricted replication of hepatitis A virus in cell culture: encapsidation of viral RNA depletes the pool of RNA available for replication

The replication of hepatitis A virus (HAV) in BS-C-1 cells was examined under single-cycle growth conditions by using strand-specific probes for detection of viral RNA species. No measurable lag phase was demonstrated between accumulation of positive-strand HAV RNA and production of infectious virions, indicating that replication of virion RNA is rate limiting for the production of infectious virus. Intracellular viral RNA was further analyzed by using 2 M LiCl to fractionate the insoluble nonvirion 35S RNA and replicative intermediates (RI) from the soluble virions and double-stranded replicative forms, in conjunction with sucrose density gradient ultracentrifugation to separate the different forms of viral RNA. Throughout the productive phase of HAV infection, 95 to 97% of positive-strand HAV RNA was soluble in 2 M LiCl and was shown to be contained in mature virions. Of the LiCl-insoluble HAV RNA, more than 99% was positive-stranded 35S RNA, whereas 0.4% was negative stranded and had the sedimentation and partial RNase resistance characteristics of RI. The pattern of RNA accumulation in HAV-infected cells is thus very different from that seen in poliovirus-infected cells, where large pools of RI and mRNA are produced before RNA is sequestered into mature virions. The results of this study suggest that encapsidation of positive-strand HAV RNA inhibits transcription at all times during the growth cycle, thereby reducing the pool of replicating RNA and the final yield of infectious HAV.