Isolation and characterization of monoclonal antibodies that inhibit hepatitis C virus NS3 protease

A series of mouse monoclonal antibodies (MAbs) to the nonstructural protein 3 (NS3) of hepatitis C virus was prepared. One of these MAbs, designated 8 D4, was found to inhibit NS3 pretense activity. This inhibition was competi tive with respect to the substrate peptide (K-i = 39 nM) but was significan tly decreased by the addition of the NS4A peptide, a coactivator of the NS3 protease. 8D4 also showed marked inhibition of the NS3-dependent cis proce ssing of the NS3/4A polyprotein but had virtually no effect on the succeedi ng NS3/4A-dependent trans processing of the NS5A/5B polyprotein in vitro. E pitope mapping of 8D4 with a random peptide library revealed a consensus se quence, DxDLV, that matched residues 79 to 83 (DQDLV) of NS3, a region cont aining the catalytic residue Asp-81. Furthermore, synthetic peptides includ ing this sequence were shown to block the ability of 8D4 to bind to NS3, in dicating that 8D4 interacts with the catalytic region of NS3. The data show ing decreased inhibition potency of 8D4 against the NS3/4A complex suggest that 8D4 recognizes the conformational state of the protease active site ca used by the association of NS4A with the protease.