Susceptibility of human and non-human cell lines to HCV infection as determined by the centrifugation-facilitated method

Inhibition of hepatitis C virus genotype 3a by siRNAs targeting envelope genes

Hepatitis C virus (HCV) genotype 3a is considered a significant risk factor for the development of liver diseases and hepatocellular carcinoma for most of the cases in Pakistan. Because of the limited efficiency of the current therapy, RNA interference (RNAi), which results in sequence-specific degradation of HCV RNA, has potential as a powerful alternative molecular therapeutic approach. The envelope genes (E1 and E2) of HCV come in immediate contact with cells during infection and therefore might be a relevant target for new drug development. In the present study, the expression of E1 and E2 genes of HCV genotype 3a was dramatically reduced at both the mRNA and protein level using gene-specific small interfering RNAs (siRNA) when compared to mock-transfected and cells treated with control siRNAs. The potential of siRNAs to inhibit HCV-3a replication in serum-infected Huh-7 cells was also demonstrated by combined treatment of siRNAs against the E1 and E2 genes, which resulted in a significant decrease in HCV viral copy number. This clearly demonstrates that the RNAi-mediated silencing of HCV E1 and E2 is among the first of its type for the development of an effective siRNA-based therapeutic option against HCV-3a.

Coxsackie B4 virus infection of beta cells and natural killer cell insulitis in recent-onset type 1 diabetic patients

Type 1 diabetes is characterized by T cell-mediated autoimmune destruction of pancreatic beta cells. Several studies have suggested an association between Coxsackie enterovirus seroconversion and onset of disease. However, a direct link between beta cell viral infection and islet inflammation has not been established. We analyzed pancreatic tissue from six type 1 diabetic and 26 control organ donors. Immunohistochemical, electron microscopy, whole-genome ex vivo nucleotide sequencing, cell culture, and immunological studies demonstrated Coxsackie B4 enterovirus in specimens from three of the six diabetic patients. Infection was specific of beta cells, which showed nondestructive islet inflammation mediated mainly by natural killer cells. Islets from enterovirus-positive samples displayed reduced insulin secretion in response to glucose and other secretagogues. In addition, virus extracted from positive islets was able to infect beta cells from human islets of nondiabetic donors, causing viral inclusions and signs of pyknosis. None of the control organ donors showed signs of viral infection. These studies provide direct evidence that enterovirus can infect beta cells in patients with type 1 diabetes and that infection is associated with inflammation and functional impairment.

An in vitro system combined with an in-house quantitation assay for screening hepatitis C virus inhibitors

Hepatitis C virus (HCV) infection is a serious global health problem. Interferon-alpha (IFN-alpha) and ribavirin have demonstrated efficacy in the treatment of HCV infection; however, these therapies display many side effects. To screen the anti-HCV compounds from plants, we established an in vitro model for inoculation of HCV by centrifugation-facilitated method. The HCV RNA molecules were then quantitated by nested competitive reverse transcription-polymerase chain reaction (cRT-PCR) using fluorescein-labeled primers, and analyzed by ABI Prism 310. The positive and negative strands of HCV RNA were detectable in Vero cells on Day 7 post-infection, suggesting that the HCV RNA was present in the cell model system. The cell culture system was further used to screen the anti-HCV activities of 4 Chinese herbal formulas and 15 formula components. IFN-alpha showed an antiviral effect. The formulas exhibited no anti-HCV activities, while Arnebia euchroma, Thlaspi arvense, and Poncirus trifoliata displayed anti-HCV activities. Therefore, these results pointed out the possibility by using the cell culture system established in this study to screen the herb extracts for their anti-HCV activities.

Expression of human CD81 in transgenic mice does not confer susceptibility to hepatitis C virus infection

We previously demonstrated that hepatitis C virus (HCV) binds to human CD81 through the E2 glycoprotein. Therefore, expression of the human CD81 molecule in transgenic mice was expected to provide a new tool to study HCV infection in vivo, as the chimpanzee is the only species currently available as a laboratory animal model that can be infected with HCV. We produced transgenic mice expressing the human CD81 protein in a wide variety of tissues. We confirmed binding of recombinant E2 glycoprotein to the liver tissue as well as to thymocytes and splenic lymphocytes in the transgenic mice. We inoculated chimpanzee plasma infected with HCV into these animals. None of these transgenic animals showed evidence of viral replication. Furthermore, human CD81 transgenic mice that lack expression of endogenous mouse CD81 were also resistant to HCV infection. We conclude that expression of human CD81 alone is insufficient to confer susceptibility to HCV infection in the mouse. The presence of additional possible factors for HCV infection is discussed.

TT virus (TTV) loads associated with different peripheral blood cell types and evidence for TTV replication in activated mononuclear cells

TT virus (TTV) loads associated with the peripheral blood cells of seven patients known to carry the virus in plasma were investigated by real-time PCR. Whereas red cells/platelets were uniformly negative, six and four patients yielded positive peripheral blood mononuclear cells (PBMCs) and polymorphonuclear leukocytes, respectively, but viral titres were generally low. Fractionation of PBMCs into monocyte- and B, T4, and T8 lymphocyte-enriched subpopulations showed no pattern in the viral loads that might suggest the preferential association of TTV to one or more specific cell types. TTV-negative PBMCs absorbed measurable amounts of virus when incubated with infected plasma at 4 degrees C. Furthermore, cultures of TTV-negative phytohaemagglutinin-stimulated PBMCs exposed in vitro to virus-positive plasma and faecal extracts released considerable levels of infectious TTV into the supernatant fluid and the same was true for TTV-positive stimulated PBMCs. These results indicate that, whereas freshly harvested resting PBMCs seem to produce little, if any TTV, stimulated PBMCs actively replicate the virus.

[Hepatitis C virus culture systems]

Hepatitis C virus pathogenesis and cycle are difficult to study because of the lack of culture system able to replicate efficiently the virus. Furthermore such a system will permit screen new antiviral drugs. Studies were realized to select cell culture system able to allow hepatitis C virus replication. Primary cell cultures and cell lines were used to performed HCV culture. Most of these works used lymphocyte and hepatocyte primary cultures or cell lines because of HCV tropism in these cells in vivo. Animals and arthropods cell lines were used as well for their capacity to bind and replicate HCV. The aim of this review is to present the different cell systems used to replicate HCV in culture and the results obtained.