Abstract: The present invention provides an assay for the detection of the NS2/3 cleavage products NS2 or NS3 in the presence of uncleaved NS2/3. Following self-cleavage of NS2/3 to generate NS2 and NS3 cleavage products, a sample is incubated with a ligand specific for the recognition of NS2 or NS3 cleavage product in the presence of uncleaved NS2/3. There is provided a method for detecting a NS2/3 autocleavage product in a sample containing NS2/3 protease, whereby the amount of bound ligand detected correlates with the NS2/3 autocleavage activity. A further aspect of the present invention concerns ligands selectively recognizing one of the NS2 cleavage product or the NS3 cleavage product with minimal cross-reactivity with the uncleaved NS2/3 and the other cleaved product. The present invention provides antibodies that selectively recognize one of cleaved NS2 product or cleaved NS3 product with minimal cross-reactivity with the uncleaved NS2/3 and the other cleaved product.

Abstract: An inhibitor-resistant HCV NS3 protease is provided which is useful to screen for compounds having therapeutic value against drug resistant HCV strains. In particular, the inhibitor-resistant HCV NS3 protease comprises an amino acid sequence which is mutated in the substrate binding pocket thereof rendering the protease resistant to inhibitor. In a specific aspect of the present invention, at least one of the amino acids at position 155, 156 and 168 of the HCV NS3 protease is mutated to yield an inhibitor-resistant protease.