Hepatitis C virus (HCV) is a serious worldwide health problem. The mRNA of HCV is uncapped and thus requires a different mechanism than cellular genes for translation. Translation of HCV mRNA is controlled through an element in the viral RNA known as IRES (Internal Ribosome Entry Site). The IRES sequence functions in the complete absence of additional viral gene expression, and therefore must be dependent on factors expressed by cellular genes.Scientists at Immusol have developed a method for gene identification, based on function inside living cells, that would allow the specific, directed identification and cloning of HCV-IRES regulators. We have created a highly complex library of ribozyme genes that can be stably introduced into mammalian cells using viral gene transfer. By generating cell lines with a counter-selectable reporter gene (HSVTK) expressed in an HCV-IRES dependent fashion, we can select for cells with decreased expression of HSVTK, and thus isolate ribozymes that inactivate cellular genes involved in HCV-IRES dependent translation. Once specific ribozymes are selected and verified, their target recognition binding sequences can be used as tags to identify and clone the corresponding target genes.
Imusol's commercial development plans are two-fold. We plan to develop a ribozyme or ribozyme gene therapy approach to treat Hepatitis C virus infections by interfering with a translation virus-specific mechanism for RNA. Secondly, we plan to use the isolated ribozymes and their target binding sequences to identify and clone the cellular genes that are involved in this process. These genes can then be used as targets for conventional drug development.
