METHOD AND REAGENT FOR INHIBITING HEPATITIS C VIRUS REPLICATION

Abstract: An enzymatic RNA molecule which specifically cleaves RNA of a hepatitis C virus.

Description: DESCRIPTION Method and Reagent for Inhibiting Hepatitis C Virus Replication Background of the Invention This application is a continuation-in-part of Draper, entitled "Method and Reagent For Inhibiting Hepatitis C Virus Replication", filed May 14, 1992, assigned U.S. Serial No. 07/882,888, the whole of which is hereby incorporated by reference herein. This invention relates to reagents useful as inhibitors of hepatitis C virus (HCV) replication and gene expression. The following is a discussion of relevant art, none of which is admitted to be prior art to the pending claims. The Hepatitis C virus group is responsible for most cases of non-A, non-B hepatitis. Although non-A, non-B hepatitis may be caused by many different viruses, the principal cause is HCV. The infection is transmitted through blood transfusions (25-50% of hemophiliacs have chronic hepatitis) , percutaneous infusion from illicit drug usage (25-50% of all drug users have non-A, non-B hepatitis) , renal organ transplant (where most late mortality is due to non-A, non-B hepatitis) , and maternal- neonatal transfer. Up to 20% of sporadic outbreaks of hepatitis are caused by HCV. The association of hepatitis C virus in posttransfusion hepatitis (>95% of the cases) and the subsequent observation that infection with this virus, more so than with hepatitis B virus, correlates strongly with the development of hepatocellular carcinoma and liver cirrhosis has led to intense study of the molecular biology of the viral genes. Hepatitis C virus (HCV) is a positive-stranded, enveloped virus which is evolutionarily related to the flaviviruses and pestiviruses. The HCV genome consists of a 5' untranslated region (5' UTR) , a long open reading frame of between 9030 and 9099 nucleotides and a 3' UTR. The 3' end of the genome has been reported to contain a short stretch of poly(A) in type I strains, but this has not been confirmed in type II, III or IV strains. It has been reported that sequences in the 5' UTR exhibit negative translational control over viral gene expression, but the major regulation of HCV gene expression comes from the proteolytic clevages of the polyprotein. Various proteolytic cleavages of the polyprotein are essential for the efficient expression of replication-associated viral proteins after translation. The resultant replicase proteins interact with a region of between 27 and 45 nucleotides in the 3' UTR which functions as a structural cue for the initiation of viral genomic replication. Cleavage of the polyprotein of HCV uses both cellular and virally-encoded proteases and generates at least nine proteins. A tenth viral protein (a second protease) has been reported to be generated by alternative cleavage of the polyprotein, but has not been confirmed. Confirmed virally-encoded proteins can be classified as structural or non-structural proteins. The structural proteins of the virus are the C protein (22kD) , E glycoprotein (35 kD) and the E2/NS1 glycoprotein (58 kD) . The non-structural proteins include the NS2 (53 kD) , NS3 (70 kD) , NS4a (8 kD) , NS4b (27 kD) , NS5a (58 kD) and NS5b (68 kD) . The C protein is a hydrophobic protein which constitutes the core structural component of the viral particle and may play a role in localizing the viral particle to the cellular membrane. There is also evidence from transient assays that the core protein may function as a transactivator of gene expression. This protein is essential to viral replication and appears to be highly conserved at the nucletide level of homology among known types of HCV. The envelope proteins are necessary for viral replication but their nucleotide (and amino acid) sequences diverge significantly between types of HCV. The NS3 protein functions as the major viral protease and mutations in this protein lead to inactivation of viral replication by inhibiting the processing of the polyprotein. The nucleotide sequence of the NS3 region is highly conserved among viral isolates. The level of infidelity exhibited by the HCV RNA replicase has been indirectly quantified by assessing the sequential appearance of nucleotide substitutions in the genomes of HCV samples obtained from the same patient. These studies suggested that the nucleotide divergence was minimal but it may have been an underestimate of the actual infidelity of the replicase because the recovered samples were actually pre-selected by growth in the patient. Unacceptible substitutions would have been lost during the outgrowth of the virus. The replication of HCV in hepatocytes is integrally intertwined with the replication of other hepatitis viruses. Although hepatitis delta virus (HDV) is quite distinct from HCV, the life cycles of the two viruses can be interdependent. Normally HDV depends upon the replication of Hepatitis B Virus (HBV) to supply capsid proteins and other functions necessary for the assembly of infectious HDV particles. Because HCV inhibits HBV and Hepatitis A virus (HAV) growth in co-infected cells, the replication of HCV can also inhibit the maturation of HDV. The use of HDV as a gene vector for treatment of HCV infections would not be influenced by this interference because gene expression of the HDV genome is apparently uninhibited by HCV. Summary of the Invention The invention features novel enzymatic RNA molecules, or ribozymes, and methods for their use for inhibiting HCV replication. Such ribozymes can be used in a method for treatment of diseases caused by these related viruses in man and other animals, including other primates. Ribozymes are RNA molecules having an enzymatic activity which is able to repeatedly cleave other separate RNA molecules in a nucleotide base sequence specific manner. Such enzymatic RNA molecules can be targeted to virtually any RNA transcript, and efficient cleavage achieved .in vitro. Kim et al. , 84 Proc. Nat. Acad. of Sci. USA 8788, 1987, Hazeloff et al. , 234 Nature 585, 1988, Cech, 260 JAMA 3030, 1988, and Jefferies et al . , 17 Nucleic Acid Research 1371, 1989. Ribozymes act by first binding to a target RNA. Such binding occurs through the target RNA binding portion of a ribozyme which is held in close proximity to an enzymatic portion of the RNA which acts to cleave the target RNA. Thus, the ribozyme first recognizes and then binds a target RNA through complementary base-pairing, and once bound to the correct site, acts enzymatically to cut the target RNA. Strategic cleavage of such a target RNA will destroy its ability to direct synthesis of an encoded protein. After a ribozyme has bound and cleaved its RNA target it is released from that RNA to search for another target and can repeatedly bind and cleave new targets. The enzymatic nature of a ribozyme is advantageous over other technologies, such as antisense technology (where a nucleic acid molecule simply binds to a nucleic acid target to block its translation) since the effective concentration of ribozyme necessary to effect a therapeutic treatment is lower than that of an antisense oligonucleotide. This advantage reflects the ability of the ribozyme to act enzymatically. Thus, a single ribozyme molecule is able to cleave many molecules of target RNA. In addition, the ribozyme is a highly specific inhibitor, with the specificity of inhibition depending not only on the base pairing mechanism of binding, but also on the mechanism by which the molecule inhibits the expression of the RNA to which it binds. That is, the inhibition is caused by cleavage of the RNA target and so specificity is defined as the ratio of the rate of cleavage of the targeted RNA over the rate of cleavage of non-targeted RNA. This cleavage mechanism is dependent upon factors additional to those involved in base pairing. Thus, it is thought that the specificity of action of a ribozyme is greater than that of antisense oligonucleotide binding the same RNA site. This class of chemical cleavers will exhibit a high degree of specificity for only the viral mRNA in infected cells. A ribozyme molecule targeted to a highly conserved sequence region will allow the treatment of many strains of human HCV with a single compound. No treatment exists which specifically attacks expression of the viral gene(s) of HCV. Current treatment protocols (interferon and ribavirin) consist of treating the symptoms of the disease, not the viral replication. Upon cessation of current treatment protocols, a rebound of disease ensues because the treatment does not impact the latency of the virus or actual viral replication. The cleavage of viral RNA offers a novel treatment which will reduce virus replication and establishment of latency in newly infected cells. The methods of this invention can be used to treat human hepatitis C virus infections, which include both acute and chronic virus infection and HCV-induced hepatocyte transformation. The utility can be extended to other species of HCV which infect non-human animals, where such infections are of veterinary importance. Further, the utility may be extended to other members of the pestivirus and flavivirus families. Treatment will occur at the time of active viral infection and will reduce virus loads in the infected cells and also disable viral replication. Ribozyme treatment may also be used as a means of creating defective genomes which can be used in vaccines. Thus, in the first aspect the invention features an enzymatic RNA molecule (or ribozyme) which specifically cleaves HCV RNA. Preferred cleavage sites are within regions required for viral replication, e.g.. protein synthesis, such as the 5' non-translated region of the HCV genome. This region is believed to control the translation of viral proteins in a manner which is reminiscent of the cap independent translational control of picornaviruses. Disruption of this region in the RNA results in deficient protein synthesis as well as incomplete DNA synthesis (and inhibition of transcription from the defective genomes) . Alternative regions outside of the 5' non-translated region also make suitable targets of ribozyme-mediated inhibition of HCV replication. Such targets include the [mRNA] genomic regions which encode the viral structural protein, E2/NS1, and the regions encoding the nonstruc- tural proteins, especially the NS3 protease and NS2/NS3 hybrid proteases. Selection of particular target regions will depend upon the secondary structure of the genome. To avoid the potential of viral escape from ribozyme therapy, by random base changes in the genomic RNA, targeting of multiple regions within the 5' UTR, or the C and NS3 genes is anticipated. Multiple targeting will also minimize the ability of the virus to utilize point mutations for escape from immune surveillance. The phase variation which accompanies amino acid substitutions in the surface proteins (and result from point mutations in the genome of HCV) has been proposed to account for the viral persistance which is typical of HCV infections. Thus, two or more different ribozymes can be used in this invention for therapeutic treatment. By "gene" is meant to refer to either the protein coding regions of the cognate mRNA, or any regulatory regions in the RNA which regulate synthesis of the protein or stability of the mRNA. By "enzymatic RNA molecule" it is meant an RNA molecule which has complementarity in a substrate binding region to a specified gene target, and also has an enzymatic activity which is active to specifically cleave RNA in that target. That is, the enzymatic RNA molecule is able to intermolecularly cleave RNA and thereby inactivate a target RNA molecule. This complementarity functions to allow sufficient hybridization of the enzymatic RNA molecule to the target RNA to allow the cleavage to occur. 100% complementarity is preferred, but complementarity as low as 50-75% may also be useful in this invention. By "equivalent" RNA to HCV is meant to include those naturally occurring RNA molecules associated with viral caused diseases in various animals, including humans, and other primates. These viral RNAs have similar structures and equivalent genes to each other. In preferred embodiments, the enzymatic RNA molecule is formed in a hammerhead motif, but may also be formed in the motif of a hairpin, hepatitis delta virus, group I intron or RNaseP RNA (in association with an RNA guide sequence) . Examples of such hammerhead motifs are described by Rossi et al . , 8 AIDS RESEARCH AND HUMAN RETROVIRUSES 183, 1992, of hairpin motifs by Hampel et al., RNA CATALYST FOR CLEAVING SPECIFIC RNA SEQUENCES, filed September 20, 1989, which is a continuation-in-part of U.S. Serial No. 07/247,100 filed September 20, 1988, Hampel and Tritz, 28 Biochemistry 4929, 1989 and Hampel et al. , 18 Nucleic Acids Research 299, 1990, and an example of the hepatitis delta virus motif is described by Perrotta and Been, 31 Biochemistry 16, 1992, of the RNaseP motif by Guerrier-Takada et al. , 35 Cell 849, 1983, and of the group I intron by Cech et al. , U.S. Patent 4,987,071. These specific motifs are not limiting in the invention and those skilled in the art will recognize that all that is important in an enzymatic RNA molecule of this invention is that it has a specific substrate binding site which is complementary to one or more of the target gene RNA regions, and that it have nucleotide sequences within or surrounding that substrate binding site which impart an RNA cleaving activity to the molecule. In particularly preferred embodiments, the RNA which is cleaved by the ribozyme is in the 5' UTR of HCV genomic RNA or in the C protein or NS3 ORFs. Nucleotide numbers in the HCV genome are given to delineate the 5' ends of the target regions. Primary sequence data is taken from Tanaka et al, 23 Virus Res. 39, 1992. For comparison, the HCV sequence data of Choo et al 88 Proc. Natl. Acad. Sci. USA 2451 1991 was used. TABLE 1. HCV mRNA target sequences. Nucleotide No. Target Sequence 3 Seq. ID. NO. 27 CGACACU C CACCAUA Seq. ID. NO. 001 114 GCAGCCU C CAGGACC Seq. ID. NO. 002 128 CCCCCCU C CCGGGAG Seq. ID. NO. 003 148 UAGUGGU C UGCGGAA Seq. ID. NO. 004 165 GGUGAGU A CACCGGA Seq. ID. NO. 005 175 CCGGAAU U GCCAGGA Seq. ID. NO. 006 199 CCUUUCU U GGAUCAA Seq. ID. NO. 007 213 ACCCGCU C AAUGCCU Seq. ID. NO. 008 252 GACUGCU A GCCGAGU Seq. ID. NO. 009 260 GCCGAGU A GUGUUGG Seq. ID. NO. 010 265 GUAGUGU U GGGUCGC Seq. ID. NO. 011 270 GUUGGGU C GCGAAAG Seq. ID. NO. 012 288 UUGUGGU A CUGCCUG Seq. ID. NO. 013 298 GCCUGAU A GGGUGCU Seq. ID. NO. 014 306 GGGUGCU U GCGAGUG Seq. ID. NO. 015 325 GGGAGGU C UCGUAGA Seq. ID. NO. 016 327 GAGGUCU C GUAGACC Seq. ID. NO. 017 330 GUCUCGU A GACCGUG Seq. ID. NO. 018 407 AGGACGU C AAGUUCC Seq. ID. NO. 019 412 GUCAAGU U CCCGGGC Seq. ID. NO. 020 413 UCAAGUU C CCGGGCG Seq. ID. NO. 021 426 CGGUGGU C AGAUCGU Seq. ID. NO. 022 472 CCCACGU U GGGUGUG Seq. ID. NO. 023 489 CGCGACU A GGAAGAC Seq. ID. NO. 024 498 GAAGACU U CCGAACG Seq. ID. NO. 025 499 AAGACUU C CGAACGG Seq. ID. NO. 026 508 GAACGGU C GCAACCU Seq. ID. NO. 027 534 ACAACCU A UCCCCAA Seq. ID. NO. 028 536 AACCUAU C CCCAAGG Seq. ID. NO. 029 546 CAAGGCU C GCCGACC Seq. ID. NO. 030 561 CGAGGGU A GGGCCUG Seq. ID. NO. 031 573 CUGGGCU C AGCCUGG Seq. ID. NO. 032 583 CCUGGGU A CCCUUGG Seq. ID. NO. 033 588 GUACCCU U GGCCCCU Seq. ID. NO. 034 596 GGCCCCU C UAUGGCA Seq. ID. NO. 035 598 CCCCUCU A UGGCAAU Seq. ID. NO. 036 632 GAUGGCU C CUGUCAC Seq. ID. NO. 037 637 CUCCUGU C ACCCCGC Seq. ID. NO. 038 649 CGCGGCU C CCGGCCU Seq. ID. NO. 039 657 CCGGCCU A GUUGGGG Seq. ID. NO. 040 660 GCCUAGU U GGGGCCC Seq. ID. NO. 041 696 GCGCAAU C UGGGUAA Seq. ID. NO. 042 707 GUAAGGU C AUCGAUA Seq. ID. NO. 043 710 AGGUCAU C GAUACCC Seq. ID. NO. 044 714 CAUCGAU A CCCUCAC Seq. ID. NO. 045 730 UGCGGCU U CGCCGAC Seq. ID. NO. 046 731 GCGGCUU C GCCGACC Seq. ID. NO. 047 748 AUGGGGU A CAUUCCG Seq. ID. NO. 048 752 GGUACAU U CCGCUCG Seq. ID. NO. 049 753 GUACAUU C CGCUCGU Seq. ID. NO. 050 758 UUCCGCU C GUCGGCG Seq. ID. NO. 051 761 CGCUCGU C GGCGCCC Seq. ID. NO. 052 773 CCCCCCU A GGGGGCG Seq. ID. NO. Q53 806 AUGGUGU C CGGGUUC Seq. ID. NO. 054 812 UCCGGGU U CUGGAGG Seq. ID. NO. 055 813 CCGGGUU C UGGAGGA Seq. ID. NO. 056 832 GUGAACU A CGCAACA Seq. ID. NO. 057 847 GGGAACU U GCCCGGU Seq. ID. NO. 058 855 GCCCGGU U GCUCUUU Seq. ID. NO. 059 859 GGUUGCU C UUUCUCU Seq. ID. NO. 060 982 AUUGUGU A UGAGGCA Seq. ID. NO. 061 1001 GCAUGAU C AUGCAUA Seq. ID. NO. 062 1022 GGUGCGU A CCCUGCG Seq. ID. NO. 063 1031 CCUGCGU U CGGGAGA Seq. ID. NO. 064 1032 CUGCGUU C GGGAGAA Seq. ID. NO. 065 1048 AACGCCU C CCGUUGU Seq. ID. NO. 066 1053 CUCCCGU U GUUGGGU Seq. ID. NO. 067 1056 CCGUUGU U GGGUAGC Seq. ID. NO. 068 1061 GUUGGGU A GCGCUCA Seq. ID. NO. 069 1127 GCCACGU C GACUUGC Seq. ID. NO. 070 1132 GUCGACU U GCUCGUU Seq. ID. NO. 071 1136 ACUUGCU C GUUGGGG Seq. ID. NO. 072 1139 UGCUCGU U GGGGCGG Seq. ID. NO. 073 1153 GCCGCUU U CUGUUCC Seq. ID. NO. 074 1154 CCGCUUU C UGUUCCG Seq. ID. NO. 075 1158 UUUCUGU U CCGCCAU Seq. ID. NO. 076 1159 UUCUGUU C CGCCAUG Seq. ID. NO. 077 1168 GCCAUGU A CGUGGGG Seq. ID. NO. 078 1189 UGCGGAU C CGUUUUC Seq. ID. NO. 079 1193 GAUCCGU U UUCCUCG Seq. ID. NO. 080 1194 AUCCGUU U UCCUCGU Seq. ID. NO. 081 1195 UCCGUUU U CCUCGUC Seq. ID. NO. 082 1196 CCGUUUU C CUCGUCU Seq. ID. NO. 083 1280 GCCAUGU A UCAGGUC Seq. ID. NO. 084 1282 CAUGUAU C AGGUCAC Seq. ID. NO. 085 1287 AUCAGGU C ACCGCAU Seq. ID. NO. 086 1373 AAGCUGU C GUGGAUA Seq. ID. NO. 087 1380 CGUGGAU A UGGUGGC Seq. ID. NO. 088 1406 GGGGAGU C CUAGCGG Seq. ID. NO. 089 1409 GAGUCCU A GCGGGCC Seq. ID. NO. 090 1418 CGGGCCU U GCCUACU Seq. ID. NO. 091 1423 CUUGCCU A CUAUUCC Seq. ID. NO. 092 1426 GCCUACU A UUCCAUG Seq. ID. NO. 093 1428 CUACUAU U CCAUGGU Seq. ID. NO. 094 1429 UACUAUU C CAUGGUG Seq. ID. NO. 095 1727 GCUCCAU C GACAAGU Seq. ID. NO. 096 1735 GACAAGU U CGCUCAG Seq. ID. NO. 097 1736 ACAAGUU C GCUCAGG Seq. ID. NO. 098 1740 GUUCGCU C AGGGAUG Seq. ID. NO. 099 1757 GCCCCAU C ACCUAUA Seq. ID. NO. 100 1762 AUCACCU A UACCGAG Seq. ID. NO. 101 1795 AGGCCUU A CUGCUGG Seq. ID. NO. 102 1806 CUGGCAU U ACGCACC Seq. ID. NO. 103 1807 UGGCAUU A CGCACCU Seq. ID. NO. 104 1815 CGCACCU C GGCAGUG Seq. ID. NO. 105 1827 GUGUGGU A UCGUACC Seq. ID. NO. 106 1829 GUGGUAU C GUACCUG Seq. ID. NO. 107 1832 GUAUCGU A CCUGCGU Seq. ID. NO. 108 1840 CCUGCGU C GCAGGUG Seq. ID. NO. 109 1854 GUGUGGU C CAGUGUA Seq. ID. NO. 110 1883 GCCCUGU U GUAGUGG Seq. ID. NO. Ill 1886 CUGUUGU A GUGGGGA Seq. ID. NO. 112 1902 GACCGAU C GGUCCGG Seq. ID. NO. 113 1906 GAUCGGU C CGGUGCC Seq. ID. NO. 114 1917 UGCCCCU A CGUAUAA Seq. ID. NO. 115 1921 CCUACGU A UAACUGG Seq. ID. NO. 116 1923 UACGUAU A ACUGGGG Seq. ID. NO. 117 1990 AACUGGU U UGGCUGU Seq. ID. NO. 118 1991 ACUGGUU U GGCUGUA Seq. ID. NO. 119 1998 UGGCUGU A CAUGGAU Seq. ID. NO. 120 2043 GGGCCCU C CGUGCAA Seq. ID. NO. 121 2054 GCAACAU C GGGGGGG Seq. ID. NO. 122 2063 GGGGGGU C GGCAACC Seq. ID. NO. 123 2072 GCAACCU C ACCUUGA Seq. ID. NO. 124 2077 CUCACCU U GACCUGC Seq. ID. NO. 125 2121 GGCCACU U ACACAAA Seq. ID. NO. 126 2122 GCCACUU A CACAAAA Seq. ID. NO. 127 2137 UGUGGCU C GGGGCCA Seq. ID. NO. 128 2149 CCAUGGU U AACACCU Seq. ID. NO. 129 2150 CAUGGUU A ACACCUA Seq. ID. NO. 130 2219 UUACCAU C UUUAAGG Seq. ID. NO. 131 2221 ACCAUCU U UAAGGUU Seq. ID. NO. 132 2261 ACAGGCU U AGUGCUG Seq. ID. NO. 133 2262 CAGGCUU A GUGCUGC Seq. ID. NO. 134 2295 AGAGCGU U GCGACCU Seq. ID. NO. 135 2320 GACAGAU C GGAGCUC Seq. ID. NO. 136 2327 CGGAGCU C AGCCCGC Seq. ID. NO. 137 2344 CUGCUGU C CACGACA Seq. ID. NO. 138 2417 UCCACCU C CAUCAGA Seq. ID. NO. 139 2421 CCUCCAU C AGAACAU Seq. ID. NO. 140 2429 AGAACAU C GUGGACG Seq. ID. NO. 141 2534 CGCGCGU C UGUGCCU Seq. ID. NO. 145 2585 CCGCCCU A GAGAACC Seq. ID. NO. 143 2600 UGGUGGU C CUCAACG Seq. ID. NO. 144 2603 UGGUCCU C AACGCGG Seq. ID. NO. 145 2671 GCCUGGU A CAUCAAG Seq. ID. NO. 146 2675 GGUACAU C AAGGGCA Seq. ID. NO. 147 2690 GGCUGGU C CCUGGGG Seq. ID. NO. 148 2704 GCGGCAU A UGCUCUG Seq. ID. NO. 149 2709 AUAUGCU C UGUACGG Seq. ID. NO. 150 2713 GCUCUGU A CGGCGUG Seq. ID. NO. 151 2738 UCCUGCU C CUGCUGG Seq. ID. NO. 152 2763 ACGGGCU U ACGCCAU Seq. ID. NO. 153 2764 CGGGCUU A CGCCAUG Seq. ID. NO. 154 2878 UGGUGGU U ACAAUAC Seq. ID. NO. 155 2879 GGUGGUU A CAAUACU Seq. ID. NO. 156 2884 UUACAAU A CUUUAUC Seq. ID. NO. 157 2887 CAAUACU U UAUCACC Seq. ID. NO. 158 2888 AAUACUU U AUCACCA Seq. ID. NO. 159 2910 GGCGCAU U UGUGCGU Seq. ID. NO. 160 2911 GCGCAUU U GUGCGUG Seq. ID. NO. 161 2924 UGUGGGU C CCCCCUC Seq. ID. NO. 162 2931 CCCCCCU C UCAAUGU Seq. ID. NO. 163 2933 CCCCUCU C AAUGUCC Seq. ID. NO. 164 2939 UCAAUGU C CGGGGGG Seq. ID. NO. 165 2958 CGAUGCU A UCAUCCU Seq. ID. NO. 166 2960 AUGCUAU C AUCCUCC Seq. ID. NO. 167 2963 CUAUCAU C CUCCUCA Seq. ID. NO. 168 2966 UCAUCCU C CUCACAU Seq. ID. NO. 169 2969 UCCUCCU C ACAUGUG Seq. ID. NO. 170 3059 CUGCCAU A ACUGCGA Seq. ID. NO. 171 3138 AGGCCAU U ACGUCCA Seq. ID. NO. 172 3139 GGCCAUU A CGUCCAA Seq. ID. NO. 173 3143 AUUACGU C CAAAUGG Seq. ID. NO. 174 3154 AUGGCCU U CAUGAAG Seq. ID. NO. 175 3155 UGGCCUU C AUGAAGC Seq. ID. NO. 176 3209 CCCCGCU A CAGGAUU Seq. ID. NO. 177 3216 ACAGGAU U GGGCCCA Seq. ID. NO. 178 3233 CGGGCCU A CGAGACC Seq. ID. NO. 179 3242 GAGACCU U GCGGUGG Seq. ID. NO. 180 3263 AGCCCGU C GUCUUCU Seq. ID. NO. 181 3266 CCGUCGU C UUCUCUG Seq. ID. NO. 182 3268 GUCGUCU U CUCUGAC Seq. ID. NO. 183 3290 CCAAGAU C AUCACCU Seq. ID. NO. 184 3293 AGAUCAU C ACCUGGG Seq. ID. NO. 185 3329 GGGACAU C AUCUUGG Seq. ID. NO. 186 3332 ACAUCAU C UUGGGAC Seq. ID. NO. 187 3334 AUCAUCU U GGGACUG Seq. ID. NO. 188 3347 UGCCCGU C UCCGCCC Seq. ID. NO. 189 3349 CCCGUCU C CGCCCGA Seq. ID. NO. 190 3371 GGGAGAU A CUUCUGG Seq. ID. NO. 191 3416 GGCGACU C CUUGCCC Seq. ID. NO. 192 3419 GACUCCU U GCCCCCA Seq. ID. NO. 193 3428 CCCCCAU C ACGGCCU Seq. ID. NO. 194 3482 CUAGCCU C ACAGGCC Seq. ID. NO. 195 3518 GGGAGGU U CAAGUGG Seq. ID. NO. 196 3519 . GGAGGUU C AAGUGGU Seq. ID. NO. 197 3527 AAGUGGU U UCCACCG Seq. ID. NO. 198 3528 AGUGGUU U CCACCGC Seq. ID. NO. 199 3529 GUGGUUU C CACCGCA Seq. ID. NO. 200 3576 UGUGUGU U GGACCGU Seq. ID. NO. 201 3601 GCCGGCU C AAAGACC Seq. ID. NO. 202 3611 AGACCCU A GCCGGCC Seq. ID. NO. 203 3684 UGCGCCU C CCGGGGC Seq. ID. NO. 204 3696 GGCGCGU U CCCUUAC Seq. ID. NO. 205 3697 GCGCGUU C CCUUACA Seq. ID. NO. 206 3701 GUUCCCU U ACACCAU Seq. ID. NO. 207 3702 UUCCCUU A CACCAUG Seq. ID. NO. 208 3724 GGUAGCU C GGACCUC Seq. ID. NO. 209 3731 CGGACCU C UAUCUGG Seq. ID. NO. 210 3733 GACCUCU A UCUGGUC Seq. ID. NO. 211 3735 CCUCUAU C UGGUCAC Seq. ID. NO. 212 3740 AUCUGGU C ACGAGAC Seq. ID. NO. 213 3761 ACGUCAU U CCGGUGC Seq. ID. NO. 214 3762 CGUCAUU C CGGUGCG Seq. ID. NO. 215 3786 UGACGGU C GGGGGAG Seq. ID. NO. 216 3797 GGAGCCU A CUGUCCC Seq. ID. NO. 217 3802 CUACUGU C CCCCAGA Seq. ID. NO. 218 3835 GGCUCUU C GGGUGGC Seq. ID. NO. 219 3851 CACUGCU C UGCCCUU Seq. ID. NO. 220 3858 CUGCCCU U CGGGGCA Seq. ID. NO. 221 3859 UGCCCUU C GGGGCAC Seq. ID. NO. 222 3872 ACGCUGU A GGCAUCU Seq. ID. NO. 223 3878 UAGGCAU C UUCCGGG Seq. ID. NO. 224 3880 GGCAUCU U CCGGGCU Seq. ID. NO. 225 3881 GCAUCUU C CGGGCUG Seq. ID. NO. 226 3908 GGGGGGU U GCGAAGG Seq. ID. NO. 227 4056 GAGCACU A AAGUGCC Seq. ID. NO. 228 4072 GCUGCGU A CGCAGCC Seq. ID. NO. 229 4087 CAAGGGU A CAAGGUA Seq. ID. NO. 230 4115 CAUCUGU U GCCGCCA Seq. ID. NO. 231 4175 CCAACAU C AGAACUG Seq. ID. NO. 232 4187 CUGGGGU A AGGACCA Seq. ID. NO. 233 4228 UCCACCU A UGGUAAG Seq. ID. NO. 234 4233 CUAUGGU A AGUUCCU Seq. ID. NO. 235 4237 GGUAAGU U CCUUGCC Seq. ID. NO. 236 4238 GUAAGUU C CUUGCCG Seq. ID. NO. 237 4241 AGUUCCU U GCCGACG Seq. ID. NO. 238 4280 AUAUCAU A AUAUGUG Seq. ID. NO. 239 4283 UCAUAAU A UGUGAUG Seq. ID. NO. 240 4337 GCACAGU C CUGGACC Seq. ID. NO. 241 4370 CGCGGCU C GUCGUGC Seq. ID. NO. 242 4373 GGCUCGU C GUGCUCG Seq. ID. NO. 243 4379 UCGUGCU C GCCACCG Seq. ID. NO. 244 4425 CCCAAAU A UUGAGGA Seq. ID. NO. 245 4444 GCUCUGU C CAACACU Seq. ID. NO. 246 4460 GAGAGAU C CCCUUCU Seq. ID. NO. 243 4481 AGGCCAU C CCCCUCG Seq. ID. NO. 248 4487 UCCCCCU C GAGGCCA Seq. ID. NO. 249 4496 AGGCCAU C AAGGGGG Seq. ID. NO. 250 4528 UGCCACU C CAAGAAG Seq. ID. NO. 251 4577 UCGGAAU C AAUGCCG Seq. ID. NO. 252 4586 AUGCCGU A GCGUAUU Seq. ID. NO. 253 4591 GUAGCGU A UUACCGG Seq. ID. NO. 254 4593 AGCGUAU U ACCGGGG Seq. ID. NO. 255 4594 GCGUAUU A CCGGGGU Seq. ID. NO. 256 4616 UGUCCGU C AUACCGA Seq. ID. NO. 257 4619 CCGUCAU A CCGACUA Seq. ID. NO. 258 4626 ACCGACU A GCGGAGA Seq. ID. NO. 259 4672 ACGGGCU A CACCGGU Seq. ID. NO. 260 4697 CGGUGAU C GACUGCA Seq. ID. NO. 261 4789 GCGGUGU C GCGCUCA Seq. ID. NO. 162 4795 UCGCGCU C ACAACGG Seq. ID. NO. 263 4920 CUGUGCU U GGUAUGA Seq. ID. NO. 264 4924 GCUUGGU A UGAGCUC Seq. ID. NO. 265 4931 AUGAGCU C ACGCCCG Seq. ID. NO. 266 4947 UGAGACU A CAGUCAG Seq. ID. NO. 267 4952 CUACAGU C AGGUUGC Seq. ID. NO. 268 4957 GUCAGGU U GCGGGCU Seq. ID. NO. 269 4965 GCGGGCU U ACCUGAA Seq. ID. NO. 270 4966 CGGGCUU A CCUGAAU Seq. ID. NO. 271 4974 CCUGAAU A CACCAGG Seq. ID. NO. 272 4984 CCAGGGU U GCCCGUC Seq. ID. NO. 273 4991 UGCCCGU C UGCCAGG Seq. ID. NO. 274 5004 GGACCAU C UGGAGUU Seq. ID. NO. 275 5102 ACCUGGU A GCAUACC Seq. ID. NO. 276 5107 GUAGCAU A CCAAGCC Seq. ID. NO. 277 5133 CAGGGCU C AGGCUCC Seq. ID. NO. 278 5218 CUGCUGU A UAGGCUA Seq. ID. NO. 279 5220 GCUGUAU A GGCUAGG Seq. ID. NO. 280 5306 UGGAGGU C GUCACUA Seq. ID. NO. 281 5309 AGGUCGU C ACUAGCA Seq. ID. NO. 282 5313 CGUCACU A GCACCUG Seq. ID. NO. 283 5330 UGCUGGU A GGCGGAG Seq. ID. NO. 284 5339 GCGGAGU C CUUGCAG Seq. ID. NO. 285 5342 GAGUCCU U GCAGCUC Seq. ID. NO. 286 5359 GCCGCAU A UUGCCUG Seq. ID. NO. 287 5361 CGCAUAU U GCCUGAC Seq. ID. NO. 288 5376 AACCGGU A GUGUGGU Seq. ID. NO. 289 5399 GUAGGAU C AUUUUGU Seq. ID. NO. 290 5423 CGGCUGU U GUUCCCG Seq. ID. NO. 291 5426 CUGUUGU U CCCGACA Seq. ID. NO. 292 5427 UGUUGUU C CCGACAG Seq. ID. NO. 293 5524 GAGCAGU U CAAGCAG Seq. ID. NO. 294 5525 AGCAGUU C AAGCAGA Seq. ID. NO. 295 5583 CGCUGCU C CCGUGGU Seq. ID. NO. 296 5596 GUGGAGU C CAGGUGG Seq. ID. NO. 297 5612 GGGCCCU U GAGGCCU Seq. ID. NO. 298 5620 GAGGCCU U CUGGGCA Seq. ID. NO. 299 5621 AGGCCUU C UGGGCAA Seq. ID. NO. 300 5674 GCAGGCU U AUCCACU Seq. ID. NO. 301 5675 CAGGCUU A UCCACUC Seq. ID. NO. 302 5767 CUCCUGU U CAACAUC Seq. ID. NO. 303 5768 UCCUGUU C AACAUCU Seq. ID. NO. 304 5801 CUCAACU C GCUCCUC Seq. ID. NO. 305 5805 ACUCGCU C CUCCCAG Seq. ID. NO. 306 5821 GCUGCUU C GGCCUUC Seq. ID. NO. 307 5827 UCGGCCU U CGUGGGC Seq. ID. NO. 308 5828 CGGCCUU C GUGGGCG Seq. ID. NO. 309 5843 CCGGCAU U GCCGGUG Seq. ID. NO. 310 5858 CGGCCAU U GGCAGCA Seq. ID. NO. 311 5867 GCAGCAU A GGCCUUG Seq. ID. NO. 312 5873 UAGGCCU U GGGAAGG Seq. ID. NO. 313 5905 GCGGGCU A UGGAGCG Seq. ID. NO. 314 5930 GUGCACU C GUGGCUU Seq. ID. NO. 315 5937 CGUGGCU U UUAAGGU Seq. ID. NO. 316 5938 GUGGCUU U UAAGGUC Seq. ID. NO. 317 5939 UGGCUUU U AAGGUCA Seq. ID. NO. 318 5940 GGCUUUU A AGGUCAU Seq. ID. NO. 319 5945 UUAAGGU C AUGAGCG Seq. ID. NO. 320 5965 GCGCCCU C CGCCGAG Seq. ID. NO. 321 5981 ACCUGGU U AACUUGC Seq. ID. NO. 322 5982 CCUGGUU A ACUUGCU Seq. ID. NO. 323 5990 ACUUGCU C CCUGCCA Seq. ID. NO. 324 6004 AUCCUCU C CCCCGGC Seq. ID. NO. 325 6020 CCCUGGU C GUCGGGG Seq. ID. NO. 326 6023 UGGUCGU C GGGGUCG Seq. ID. NO. 327 6029 UCGGGGU C GUGUGUG Seq. ID. NO. 328 6044 CAGCAAU C CUGCGUC Seq. ID. NO. 329 6051 CCUGCGU C GGCACGU Seq. ID. NO. 340 6106 AUAGCGU U CGCUUCG Seq. ID. NO. 341 6107 UAGCGUU C GCUUCGC Seq. ID. NO. 342 6111 GUUCGCU U CGCGGGG Seq. ID. NO. 343 6413 ACGGCAU C AUGCAAA Seq. ID. NO. 344 6574 CCGAACU A UUCCAGG Seq. ID. NO. 345 6576 GAACUAU U CCAGGGC Seq. ID. NO. 346 6577 AACUAUU C CAGGGCG Seq. ID. NO. 347 6637 GGGGACU U CCACUAC Seq. ID. NO. 348 6638 GGGACUU C CACUACG Seq. ID. NO. 349 6643 UUCCACU A CGUGACG Seq. ID. NO. 350 6671 ACAACGU A AAAUGCC Seq. ID. NO. 351 6703 CCCGAAU U CUUCACC Seq. ID. NO. 352 6704 CCGAAUU C UUCACCG Seq. ID. NO. 353 6706 GAAUUCU U CACCGAA Seq. ID. NO. 354 6707 AAUUCUU C ACCGAAU Seq. ID. NO. 355 6715 ACCGAAU U GGACGGG Seq. ID. NO. 356 6730 GUGCGGU U GCACAGG Seq. ID. NO. 357 6739 CACAGGU A CGCUCCG Seq. ID. NO. 358 6744 GUACGCU C CGGCGUG Seq. ID. NO. 359 6759 CAGACCU C UCCUACG Seq. ID. NO. 360 6761 GACCUCU C CUACGGG Seq. ID. NO. 361 6764 CUCUCCU A CGGGAGG Seq. ID. NO. 362 6776 AGGAUGU C ACAUUCC Seq. ID. NO. 363 6782 UCACAUU C CAGGUCG Seq. ID. NO. 364 6788 UCCAGGU C GGGCUCA Seq. ID. NO. 365 6794 UCGGGCU C AACCAAU Seq. ID. NO. 366 6802 AACCAAU A CCUGGUU Seq. ID. NO. 367 6809 ACCUGGU U GGGUCAC Seq. ID. NO. 368 6814 GUUGGGU C ACAGCUC Seq. ID. NO. 369 6821 CACAGCU C CCAUGCG Seq. ID. NO. 370 6906. UAAACGU A GGCUGGC Seq. ID. NO. 371 6922 AGGGGGU C UCCCCCC Seq. ID. NO. 372 6924 GGGGUCU C CCCCCUC Seq. ID. NO. 373 6931 CCCCCCU C CUUGGCC Seq. ID. NO. 374 6934 CCCUCCU U GGCCAGC Seq. ID. NO. 375 6943 GCCAGCU C UUCAGCU Seq. ID. NO. 376 6958 AGCCAAU U GUCUGCG Seq. ID. NO. 377 6961 CAAUUGU C UGCGCCU Seq. ID. NO. 378 7034 CCAACCU C CUGUGGC Seq. ID. NO. 379 7118 ACCCGCU U CGAGCGG Seq. ID. NO. 380 7119 CCCGCUU C GAGCGGA Seq. ID. NO. 381 7145 GGGAAGU A UCCGUUG Seq. ID. NO. 382 7195 CCCGCGU U GCCCAUA Seq. ID. NO. 383 7202 UGCCCAU A UGGGCAC Seq. ID. NO. 384 7218 CCCGGAU U ACAACCC Seq. ID. NO. 385 7219 CCGGAUU A CAACCCU Seq. ID. NO. 386 7234 CCACUGU U AGAGUCC Seq. ID. NO. 387 7235 CACUGUU A GAGUCCU Seq. ID. NO. 388 7251 GAAAAGU C CGGACUA Seq. ID. NO. 389 7258 CCGGACU A CGUCCCU Seq. ID. NO. 390 7262 ACUACGU C CCUCCGG Seq. ID. NO. 391 7266 CGUCCCU C CGGCGGU Seq. ID. NO. 392 7288 UGCCCAU U GCCGCCU Seq. ID. NO. 393 7296 GCCGCCU A CCACGGG Seq. ID. NO. 394 7354 ACAGAGU C CACCGUG Seq. ID. NO. 395 7386 GCUGGCU A CUAAGAC Seq. ID. NO. 396 7389 GGCUACU A AGACUUU Seq. ID. NO. 397 7395 UAAGACU U UCGGCAG Seq. ID. NO. 398 7396 AAGACUU U CGGCAGC Seq. ID. NO. 399 7397 AGACUUU C GGCAGCU Seq. ID. NO. 400 7411 UCCGGAU C GUCGGCC Seq. ID. NO. 410 7414 GGAUCGU C GGCCGUU Seq. ID. NO. 402 7421 CGGCCGU U GACAGCG Seq. ID. NO. 403 7498 UCGUACU C CUCCAUG Seq. ID. NO. 404 7501 UACUCCU C CAUGCCC Seq. ID. NO. 405 7514 CCCCCCU U GAGGGGG Seq. ID. NO. 406 7539 CCCUGAU C UCAGCGA Seq. ID. NO. 407 7541 CUGAUCU C AGCGACG Seq. ID. NO. 408 7552 GACGGGU C UUGGUCU Seq. ID. NO. 409 7554 CGGGUCU U GGUCUAC Seq. ID. NO. 410 7558 UCUUGGU C UACCGUG Seq. ID. NO. 411 7560 UUGGUCU A CCGUGAG Seq. ID. NO. 412 7589 ACGACAU C GUCUGCU Seq. ID. NO. 413 7592 ACAUCGU C UGCUGCU Seq. ID. NO. 414 7600 UGCUGCU C AAUGUCC Seq. ID. NO. 415 7606 UCAAUGU C CUACACA Seq. ID. NO. 416 7667 UGCCCAU C AACGCGU Seq. ID. NO. 417 7723 ACAACAU C CCGCAGU Seq. ID. NO. 418 7775 UGCAAGU C CUGGACG Seq. ID. NO. 419 7789 GACCACU A CCGGGAC Seq. ID. NO. 420 7839 UAAGGCU A AACUUCU Seq. ID. NO. 421 7847 AACUUCU A UCCGUAG Seq. ID. NO. 422 7849 CUUCUAU C CGUAGAA Seq. ID. NO. 423 7853 UAUCCGU A GAAGAAG Seq. ID. NO. 424 7894 GCCAAAU C UAAAUUU Seq. ID. NO. 425 7896 CAAAUCU A AAUUUGG Seq. ID. NO. 426 7900 UCUAAAU U UGGCUAU Seq. ID. NO. 427 7901 CUAAAUU U GGCUAUG Seq. ID. NO. 428 7906 UUUGGCU A UGGGGCA Seq. ID. NO. 429 7955 ACCACAU C CGCUCCG Seq. ID. NO. 430 7960 AUCCGCU C CGUGUGG Seq. ID. NO. 431 8075 CUCGCCU U AUCGUAU Seq. ID. NO. 432 8076 UCGCCUU A UCGUAUU Seq. ID. NO. 433 8078 GCCUUAU C GUAUUCC Seq. ID. NO. 434 8170 UCCUCGU A CGGAUUC Seq. ID. NO. 435 8176 UACGGAU U CCAGUAC Seq. ID. NO. 436 8182 UUCCAGU A CUCUCCU Seq. ID. NO. 437 8187 GUACUCU C CUGGGCA Seq. ID. NO. 438 8201 AGCGGGU U GAGUUCC Seq. ID. NO. 439 8206 GUUGAGU U CCUGGUG Seq. ID. NO. 440 8207 UUGAGUU C CUGGUGA Seq. ID. NO. 441 8227 UGGAAAU C AAAGAAA Seq. ID. NO. 442 8357 AGGCCAU A AAGUCGC Seq. ID. NO. 443 8362 AUAAAGU C GCUCACG Seq. ID. NO. 444 8366 AGUCGCU C ACGGAGC Seq. ID. NO. 445 8378 AGCGGCU C UACAUCG Seq. ID. NO. 446 8380 CGGCUCU A CAUCGGG Seq. ID. NO. 447 8384 UCUACAU C GGGGGCC Seq. ID. NO. 448 8424 CUGCGGU U AUCGCCG Seq. ID. NO. 449 8425 UGCGGUU A UCGCCGG Seq. ID. NO. 450 8427 CGGUUAU C GCCGGUG Seq. ID. NO. 451 8460 GACGACU A GCUGCGG Seq. ID. NO. 452 8508 GGCCUGU C GAGCUGC Seq. ID. NO. 453 8522 CAAAGCU C CAGGACU Seq. ID. NO. 454 8540 CGAUGCU C GUGAACG Seq. ID. NO. 454 8558 ACGACCU U GUCGUUA Seq. ID. NO. 455 8561 ACCUUGU C GUUAUCU Seq. ID. NO. 456 8564 UUGUCGU U AUCUGUG Seq. ID. NO. 457 8638 AGGUACU C UGCCCCC Seq. ID. NO. 458 8671 CCAGAAU A CGACUUG Seq. ID. NO. 459 8698 UCAUGCU C CUCCAAC Seq. ID. NO. 460 8701 UGCUCCU C CAACGUG Seq. ID. NO. 461 8728 GACGCAU C CGGCAAA Seq. ID. NO. 462 8774 CCCCCCU U GCACGGG Seq. ID. NO. 463 8842 AUCAUGU A UGCGCCC Seq. ID. NO. 464 8854 CCCACCU U AUGGGCA Seq. ID. NO. 465 8855 CCACCUU A UGGGCAA Seq. ID. NO. 466 8871 GAUGAUU U UGAUGAC Seq. ID. NO. 467 8880 GAUGACU C ACUUCUU Seq. ID. NO. 468 8931 CCUGGAU U GUCAGAU Seq. ID. NO. 469 8934 GGAUUGU C AGAUCUA Seq. ID. NO. 470 8939 GUCAGAU C UACGGGG Seq. ID. NO. 471 8941 CAGAUCU A CGGGGCC Seq. ID. NO. 472 9065 CAUGCCU C AGGAAAC Seq. ID. NO. 473 9074 GGAAACU U GGGGUAC Seq. ID. NO. 474 9080 UUGGGGU A CCGCCCU Seq. ID. NO. 475 9088 CCGCCCU U GCGAGUC Seq. ID. NO. 476 9095 UGCGAGU C UGGAGAC Seq. ID. NO. 477 9119 GAAGUGU C CGCGCUA Seq. ID. NO. 478 9126 CCGCGCU A GGCUACU Seq. ID. NO. 479 9131 CUAGGCU A CUGUCCC Seq. ID. NO. 480 9136 CUACUGU C CCAAGGG Seq. ID. NO. 481 9226 GCCGCGU C CCAGCUG Seq. ID. NO. 482 9238 CUGGACU U GUCCAGC Seq. ID. NO. 483 9241 GACUUGU C CAGCUGG Seq. ID. NO. 484 9250 AGCUGGU U CGUUGCU Seq. ID. NO. 485 9251 GCUGGUU C GUUGCUG Seq. ID. NO. 486 9254 GGUUCGU U GCUGGUU Seq. ID. NO. 487 9278 GAGACAU A UAUCACA Seq. ID. NO. 488 9280 GACAUAU A UCACAGC Seq. ID. NO. 489 9282 CAUAUAU C ACAGCCU Seq. ID. NO. 490 9292 AGCCUGU C UCGUGCC Seq. ID. NO. 491 9326 GGUGCCU A CUCCUAC Seq. ID. NO. 492 9329 GCCUACU C CUACUUU Seq. ID. NO. 493 9332 UACUCCU A CUUUCCG Seq. ID. NO. 494 9335 UCCUACU U UCCGUAG Seq. ID. NO. 495 9336 CCUACUU U CCGUAGG Seq. ID. NO. 496 9337 CUACUUU C CGUAGGG Seq. ID. NO. 497 9341 UUUCCGU A GGGGUAG Seq. ID. NO. 498 9347 UAGGGGU A GGCAUCU Seq. ID. NO. 499 9353. UAGGCAU C UACCUGC Seq. ID. NO. 500 9355 GGCAUCU A CCUGCUC Seq. ID. NO. 501 9362 ACCUGCU C CCCAACC Seq. ID. NO. 502 9385 GGGAGCU A AUCACUC Seq. ID. NO. 503 9388 AGCUAAU C ACUCCAG Seq. ID. NO. 504 9392 AAUCACU C CAGGCCA Seq. ID. NO. 505 9402 GGCCAAU A GGCCAUC Seq. ID. NO. 506 a Sequences which exhibit perfect homology between the two genomes are highlighted in bold face type. Methods for preparation of ribozymes useful in this invention are generally described by Draper, entitled, "Method and Reagent For Treatment of Arthritic Conditions", filed November 12, 1993, and assigned U.S. Serial No. 08/152,487, the whole of which is hereby incorporated by reference herein. In a second related aspect, the invention features a mammalian cell which includes an enzymatic RNA molecule as described above. Preferably, the mammalian cell is a human or other primate cell. In a third related aspect, the invention features an expression vector which includes nucleic acid encoding the enzymatic RNA molecules described above, located in the vector, e.g., in a manner which allows expression of that enzymatic RNA molecule within a mammalian cell. In a fourth related aspect, the invention features a method for treatment of an HCV-caused disease by administering to a patient an enzymatic RNA molecule which cleaves HCV RNA in the regions discussed above. The invention provides a class of chemical cleaving agents which exhibit a high degree of specificity for the viral RNA of HCV type infected cells. The ribozyme molecule is preferably targeted to a highly conserved sequence region of HCV such that all types and strains of this virus can be treated with a single ribozyme. Such enzymatic RNA molecules can be delivered exogenously to infected cells. In the preferred hammerhead motif the small size (less than 40 nucleotides, preferably between 32 and 36 nucleotides in length) of the molecule allows the cost of treatment to be reduced compared to other ribozyme motifs. Synthesis of ribozymes greater than 100 nucleotides in length is very difficult using automated methods, and the therapeutic cost of such molecules is prohibitive. Delivery of ribozymes by expression vectors is primarily feasible using only ex vivo treatments. This limits the utility of this approach. In this invention, small ribozyme motifs (e.g. , of the hammerhead structure, shown g enerally in Fig. 1) are used for exogenous delivery. The simple structure of these molecules also increases the ability of the ribozyme to invade targeted regions of the mRNA structure. Thus, unlike the situation when the hammerhead structure is included within longer transcripts, there are no non-ribozyme flanking sequences to interfere with correct folding of the ribozyme structure or with complementary binding of the ribozyme to the mRNA target region. The enzymatic RNA molecules of this invention can be used to treat HCV virus infections. Infected animals can be treated at the time of productive infection. This timing of treatment will reduce viral loads in infected cells and disable viral replication in any subsequent rounds of infection. This is possible because the preferred ribozymes disable those structures required for successful initiation of viral protein synthesis. For treatment of transformed hepatocytes, the methods of this invention allow inhibition of the expression of viral genes thought to cause cell transformation. The preferred targets of the present invention are advantageous over other targets since they do not act only at the time of viral absorption or genomic replication during infection. In addition, viral particles which are released during a first round of infection in the presence of such ribozymes will still be immunogenic by virtue of having their capsids intact. Thus, one method of this invention allows the creation of defective but immunogenic viral particles, and thus a continued possibility of initiation of an immune response in a treated animal. In addition, the enzymatic RNA molecules of this invention can be used in vitro in a cell culture infected with HCV viruses to produce viral particles which have intact capsids and defective genomic RNA. These particles can then be used for instigation of immune responses in a prophylactic manner, or as a treatment of infected animals. Other features and advantages of the invention will be apparent from the following description of the preferred embodiments thereof, and from the claims. Description of the Preferred Embodiments The drawing will first briefly be described. Drawing Fig. 1 is a diagrammatic representation of a hammerhead motif ribozyme showing stems I, II and III (marked (I) , (II) and (III) respectively) interacting with an HCV target region. The 5' and 3' ends of both ribozyme and target are shown. Dashes indicate base-paired nucleotides. Target Sites The genome of HCV may be subject to rapid genetic drift by virtue of its RNA content and the nature of errors in genomic replication. Those regions (genes) of the genome which are essential for virus replication, however, are expected to maintain a constant sequence (i.e. , are conserved) over extensive periods of time. These regions are preferred target sites in this invention since they are more likely to be conserved between different types or strains of HCV viruses, and thus only one ribozyme is needed to destroy all such viruses. Thus, one ribozyme may be used to target all HCV viruses . We have selected several such regions in the genomes of these viruses, and examined their nucleotide sequences for the presence of regions which may be cleaved by ribozymes targeted to those regions. One region analyzed in detail is the 5' non-translated region; other regions (such as the C or NS1 protein ORFs) can be analyzed in a manner similar to that described below. Ribozymes targeting selected regions of the HCV genome are preferably chosen to cleave the target RNA in a manner which inhibits translation of the RNA. Genes are selected such that such viral replication is inhibited, e.g., by inhibiting protein synthesis. Selection of effective target sites within these critical regions of viral RNA entails testing the accessibility of the target RNA to hybridization with various oligonucleotide probes. These studies can be performed using RNA probes and assaying accessibility by cleaving the hybrid molecule with RNaseH (see below) . Alternatively, such a study can use ribozyme probes designed from secondary structure predictions of the RNAs, and assaying cleavage products by polyacrylamide gel electrophoresis (PAGE) , to detect the presence of cleaved and uncleaved molecules. The following is but one example of a method by which suitable target sites can be identified and is not limiting in this invention. Generally, the method involves identifying potential cleavage sites for a hammerhead ribozyme, and then testing each of these sites to determine their suitability as targets by ensuring that secondary structure formation is minimal. The mRNA sequences of the virus are folded using RΝAfold computer analyses. The regions of the mRΝA, in this case the 5' nucleotides of the HCV genome, which are predicted to have weak or non-base paired nucleotides are searched for putative ribozyme recognition motifs. These sites represent the preferred sites for hammerhead or other ribozyme cleavage within these target RΝAs. Short RΝA substrates corresponding to each of the gene sites are designed. Each substrate is composed of two to three nucleotides at the 5' and 3' ends that will not base pair with a corresponding ribozyme recognition region. The unpaired regions flank a central region of 12-14 nucleotides to which complementary arms in the ribozyme are designed. The structure of each substrate sequence is predicted using a PC fold computer program. Sequences which give a positive free energy of binding are accepted. Sequences which give a negative free energy are modified by trimming one or two bases from each of the ends. If the modified sequences are still predicted to have a strong secondary structure, they are rejected. After substrates are chosen, ribozymes are designed to each of the RNA substrates. Ribozyme folding is also analyzed using PC fold. Ribozyme molecules are sought which form hammerhead motif stem II (see Fig. 1) regions and contain flanking arms which are devoid of intramolecular base pairing. Often the ribozymes are modified by trimming a base from the ends of the ribozyme, or by introducing additional base pairs in stem II to achieve the desired fold. Ribozymes with incorrect folding are rejected. After substrate/ribozyme pairs are found to contain correct intramolecular structures, the molecules are folded together to predict intermolecular interactions. A schematic representation of a ribozyme with its coordinate base pairing to its cognate target sequence is shown in Figure 1. Using such analyses, the following predictions of effective target sites in the HCV genomic RNA, based upon computer generated RNA structure analysis, were obtained (see Table 1) . The target nucleotide is listed with the genomic nucleotide number (in the HCV genome) given to the left of the sequence. Flanking nucleotides are given for reference. Those targets thought to be useful as ribozyme targets can be tested to determine accessibility to nucleic acid probes in a ribonuclease H assay (see below) . This assay provides a quick test of the use of the target site without requiring synthesis of a ribozyme. It can be used to screen for sites most suited for ribozyme attack. Synthesis of Ribozymes Ribozymes useful in this invention can be produced by gene transcription as described by Cech, supra, or by chemical synthesis. Chemical synthesis of RNA is similar to that for DNA synthesis. The additional 2' -OH group in RNA, however, requires a different protecting group strategy to deal with selective 3' -5' internucleotide bond formation, and with RNA susceptibility to degradation in the presence of bases. The recently developed method of RNA synthesis utilizing the t-butyldimethylsilyl group for the protection of the 2' hydroxyl is the most reliable method for synthesis of ribozymes. The method repro- ducibly yields RNA with the correct 3' -5' internucleotide linkages, with average coupling yields in excess of 99%, and requires only a two-step deprotection of the polymer. A method based upon H-phosphonate chemistry gives a relatively lower coupling efficiency than a method based upon phosphoramidite chemistry. This is a problem for synthesis of DNA as well. A promising approach to scale- up of automatic oligonucleotide synthesis has been described recently for the H-phosphonates. A combination of a proper coupling time and additional capping of "failure" sequences gave high yields in the synthesis of oligodeoxynucleotides in scales in the range of 14 micromoles with as little as 2 equivalents of a monomer in the coupling step. Another alternative approach is to use soluble polymeric supports (e.g. , polyethylene glycols) , instead of the conventional solid supports. This method can yield short oligonucleotides in hundred milligram quantities per batch utilizing about 3 equivalents of a monomer in a coupling step. Various modifications to ribozyme structure can be made to enhance the utility of ribozymes. Such modifications will enhance shelf-life, half-life .in vitro, stability, and ease of introduction of such ribozymes to the target site, e.g., to enhance penetration of cellular membranes, and confer the ability to recognize and bind to targeted cells. Exogenous delivery of ribozymes benefits from chemical modification of the backbone, e.g., by the overall negative charge of the ribozyme molecule being reduced to facilitate diffusion across the cell membrane. The present strategies for reducing the oligonucleotide charge include: modification of internucleotide linkages by ethylphosphonates, use of phosphoramidites, linking oligonucleotides to positively charged molecules, and creating complex packages composed of oligonucleotides, lipids and specific receptors or effectors for targeted cells. Examples of such modifications include sulfur- containing ribozymes containing phosphorothioates and phosphorodithioates as internucleotide linkages in RNA. Synthesis of such sulfur-modified ribozymes is achieved by use of the sulfur-transfer reagent, 3 H-1,2-benzenedithiol- 3-one 1,1-dioxide. Ribozymes may also contain ribose modified ribonucleotides. Pyrimidine analogues are prepared from uridine using a procedure employing diethylamino sulphur trifluoride (DAST) as a starting reagent. Ribozymes can also be either electrostatically or covalently attached to polymeric cations for the purpose of reducing charge. The polymer can be attached to the ribozyme by simply converting the 3'-end to a ribonucleoside dialdehyde which is obtained by a periodate cleavage of the terminal 2',3'-cis diol system. Depending on the specific requirements for delivery systems, other possible modifications may include different linker arms containing carboxyl, amino or thiol functionalities. Yet further examples include use of methylphosphonates and 2' - o-methylribose and 5' or 3' capping or blocking with m 7 GpppG or m 3 2,2 ' 7 GpppG. For example, a kinased ribozyme is contacted with guanosine triphosphate and guanyltransferase to add a m 3 G cap to the ribozyme. After such synthesis, the ribozyme can be gel purified using standard procedure. To ensure that the ribozyme has the desired activity, it may be tested with and without the 5' cap using standard procedures to assay both its enzymatic activity and its stability. Synthetic ribozymes, including those containing various modifiers, can be purified by high pressure liquid chromatography (HPLC) . Other liquid chromatography techniques, employing reverse phase columns and anion exchangers on silica and polymeric supports may also be used. There follows an example of the synthesis of one ribozyme. A solid phase phosphoramidite chemistry is employed. Monomers used are 2' -tert-butyl-dimethylsilyl cyanoethylphosphoramidities of uridine, N-benzoyl- cytosine, N-phenoxyacetyl adenosine and guanosine (Glen Research, Sterling, VA) . Solid phase synthesis is carried out on either an ABI 394 or 38OB DNA/RNA synthesizer using the standard protocol provided with each machine. The only exception is that the coupling step is increased from 10 to 12 minutes. The phosphoramidite concentration is 0.1M. Synthesis is done on a lμmole scale using a lμmole RNA reaction column (Glen Research) . The average coupling efficiencies are between 97% and 98% for the 394 model, and between 97% and 99% for the 380B model, as determined by a calorimetric measurement of the released trityl cation. Blocked ribozymes are cleaved from the solid support (e.g. , CPG) , and the bases and diphosphoester moiety deprotected in a sterile vial by dry ethanolic ammonia (2 mL) at 55°C for 16 hours. The reaction mixture is cooled on dry ice. Later, the cold liquid is transferred into a sterile screw cap vial and lyophilized. To remove the 2' -tert-butyl-dimethylsilyl groups from the ribozyme, the residue is suspended in 1 M tetra-n- butylammonium fluoride in dry THF (TBAF) , using a 20 fold excess of the reagent for every silyl group, for 16 hours at ambient temperature (about 15-25°C) . The reaction is quenched by adding an equal volume of sterile 1 M triethylamine acetate, pH 6.5. The sample is cooled and concentrated on a SpeedVac to half the initial volume. The ribozymes are purified in two steps by HPLC on a C4 300 μ 5 mm DeltaPak column in an acetonitrile gradient. The first step, or "trityl on" step, is a separation of 5' -DMT-protected ribozyme (s) from failure sequences lacking a 5' -DMT group. Solvents used for this step are: A (0.1 M triethylammonium acetate, pH 6.8) and B (acetonitrile) . The elution profile is: 20% B for 10 minutes, followed by a linear gradient of 20% B to 50% B over 50 minutes, 50% B for 10 minutes, a linear gradient of 50% B to 100% B over 10 minutes, and a linear gradient of 100% B to 0% B over 10 minutes. The second step is a purification of a completely deblocked ribozyme by a treatment of 2% trifluoroacetic acid on a C4 300 μ 5 mm DeltaPak column in an acetonitrile gradient. Solvents used for this second step are: A (0.1 M Triethylammonium acetate, pH 6.8) and B (80% acetonitrile, 0.1 M triethylammonium acetate, pH 6.8) . The elution profile is: 5% B for 5 minutes, a linear gradient of 5% B to 15% B over 60 minutes, 15% B for 10 minutes, and a linear gradient of 15% B to 0% B over 10 minutes. The fraction containing ribozyme is cooled and lyophilized on a SpeedVac. Solid residue is dissolved in a minimum amount of ethanol and sodium perchlorate in acetone. The ribozyme is collected by centrifugation, washed three times with acetone, and lyophilized. Expression Vector While synthetic ribozymes are preferred in this invention, those produced by expression vectors can also be used. In designing a suitable ribozyme expression vector the following factors are important to consider. The final ribozyme must be kept as small as possible to minimize unwanted secondary structure within the ribozyme. A promoter (e.g. , the human cytomegalovirus immediate early promoter) should be chosen to be a relatively strong promoter, and expressible both in vitro and in vivo. Such a promoter should express the ribozyme at a level suitable to effect production of enough ribozyme to destroy a target RNA, but not at too high a level to prevent other cellular activities from occurring (unless cell death itself is desired) . A hairpin at the 5' end of the ribozyme is useful to protect the ribozyme from 5' -3' exonucleases. A selected hairpin at the 3' end of the ribozyme is useful because it acts as a protection from 3' -5' exonucleases. Such hairpins can be inserted within the vector sequences to allow standard ribozymes to be placed in an appropriate orientation and expressed with such sequences attached. Poly(A) tails are also useful to protect the 3' end of the ribozyme. These can be provided by either including a poly(A) signal site in the expression vector (to signal a cell to add the poly(A) tail in vivo) , or by introducing a poly(A) sequence directly into the expression vector. In the first approach the signal must be located to prevent unwanted secondary structure formation with other parts of the ribozyme. In the second approach, the poly(A) stretch may reduce in size over time when expressed in vivo, and thus the vector may need to be checked over time. Care must be taken in addition of a poly(A) tail which binds poly(A) binding proteins which prevent the ribozyme from acting upon their target sequence. Ribozyme Testing Once the desired ribozymes are selected, synthesized and purified, they are tested in kinetic and other experiments to determine their utility. An example of such a procedure is provided below. Preparation of Ribozyme Crude synthetic ribozyme (typically 350 μg at a time) is purified by separation on a 15% denaturing polyacrylamide gel (0.75 mm thick, 40 cm long) and visualized by UV shadowing. Once excised, gel slices containing full length ribozyme are soaked in 5 ml gel elution buffer (0.5 M NH 4 OAc, 1 mM EDTA) overnight with shaking at 4°C. The eluent is desalted over a C-18 matrix (Sep-Pak cartridges, Millipore, Milford, MA) and vacuum dried. The dried RNA is resuspended in 50-100 μl TE (TRIS 10 mM, EDTA 1 mM, pH 7.2) . An aliquot of this solution is diluted 100 fold into 1 ml TE, half of which was used to spectrophotometrically quantitate the ribozyme solution. The concentration of this dilute stock is typically 150- 800 nM. Purity of the ribozyme is confirmed by the presence of a single band on a denaturing polyacrylamide gel. A ribozyme may advantageously be synthesized in two or more portions. Each portion of a ribozyme will generally have only limited or no enzymatic activity, and the activity will increase substantially (by at least 5-10 fold) when all portions are ligated (or otherwise juxtaposed) together. A specific example of hammerhead ribozyme synthesis is provided below. The method involves synthesis of two (or more) shorter "half" ribozymes and ligation of them together using T4 RNA ligase. For example, to make a 34 mer ribozyme, two 17 mers are synthesized, one is phosphorylated, and both are gel purified. These purified 17 mers are then annealed to a DNA splint strand complementary to the two 17 mers. This DNA splint has a sequence designed to locate the two 17 mer portions with one end of each adjacent each other. The juxtaposed RNA molecules are then treated with T4 RNA ligase in the presence of ATP. The 34 mer RNA so formed is then HPLC purified. Preparation of Substrates Approximately 10-30 pmoles of unpurified substrate is radioactively 5' end-labelled with T4 polynucleotide kinase using 25 pmoles of [Letter to client re action proposed γ- 32 P] ATP. The entire labelling mix is separated on a 20% denaturing polyacrylamide gel and visualized by autoradiography. The full length band is excised and soaked overnight at 4°C in 100 μl of TE (10 mM Tris-HCl pH 7.6, 0.1 mM EDTA) . Kinetics Reactions For reactions using short substrates (between 8 and 16 bases) a substrate solution is made IX in assay buffer (75 mM Tris-HCl, pH 7.6; 0.1 mM EDTA, 10 mM MgCl 2 ) such that the concentration of substrate is less than InM. A ribozyme solution (typically 20 nM) is made IX in assay buffer and four dilutions are made using IX assay buffer. Fifteen μl of each ribozyme dilution (i.e. , 20, 16, 12, 8 and 4 nM) is placed in a separate tube. These tubes and the substrate tube are pre-incubated at 37°C for at least five minutes. The reaction is started by mixing 15 μl of substrate into each ribozyme tube by rapid pipetting (note that final ribozyme concentrations are 10, 8, 6, 4, 2 nM) . 5 μl aliquots are removed at 15 or 30 second intervals and quenched with 5 μl stop solution (95% formamide, 20 mM EDTA xylene cyanol, and bromphenol blue dyes) . Following the final ribozyme time point, an aliquot of the remaining substrate is removed as a zero ribozyme control. The samples are separated on either 15% or 20% polyacrylamide gels. Each gel is visualized and quantitated with an Ambis beta scanner (Ambis Systems, San Diego, CA) . For the most active ribozymes, kinetic analyses are performed in substrate excess to determine K,„ and K cat values. For kinetic reactions with long RNA substrates (greater than 15 bases in length) the substrates are prepared by transcription using T7 RNA polymerase and defined templates containing a T7 promoter, and DNA encoding appropriate nucleotides of the viral RNA. The substrate solution is made IX in assay buffer (75 mM Tris- HCl, pH 7.6; 0.1 mM EDTA; 10 mM MgCl 2 ) and contains 58 nanomolar concentration of the long RNA molecules. The reaction is started by addition of gel purified ribozymes to 1 μM concentration. Aliquots are removed at 20, 40, 60, 80 and 100 minutes, then quenched by the addition of 5 μl stop solution. Cleavage products are separated using denaturing PAGE. The bands are visualized and quantitated with an Ambis beta scanner. Kinetic Analysis A simple reaction mechanism for ribozyme-mediated cleavage is: R + S t * [R : S] [R : P] → R + P k.! where R = ribozyme, S = substrate, and P = products. The boxed step is important only in substrate excess. Because ribozyme concentration is in excess over substrate concentration, the concentration of the ribozyme-substrate complex ( [R:S] ) is constant over time except during the very brief time when the complex is being initially formed, i.e. , : d[R:Sl = 0 dt where t = time, and thus: (R) (S)ki = (RS) (k 2 + k j. ) . The rate of the reaction is the rate of disappearance of substrate with time: Rate = -d(S) = k 2 (RS) dt Substituting these expressions : (R) (S)k- . = l/k 2 -d(S) (k 2 + k.) dt or: Integrating this expression with respect to time yields: -In S_ = kj^, (R) t S 0 (k 2 + where S 0 = initial substrate. Therefore, a plot of the negative log of fraction substrate uncut versus time (in minutes) yields a straight line with slope: slope = k-k 2 (R) = k obs (k 2 + k where k obE - observed rate constant. A plot of slope (k obs ) versus ribozyme concentration yields a straight line with a slope which is: slope = k-jsj which is k,, at (k 2 + k x ) K„ Using these equations the data obtained from the kinetic experiments provides the necessary information to determine which ribozyme tested is most useful, or active. Such ribozymes can be selected and tested in in. vivo or ex vivo systems. Liposome Preparation Lipid molecules are dissolved in a volatile organic solvent (CHC1 3 , methanol, diethylether, ethanol, etc.) . The organic solvent is removed by evaporation. The lipid is hydrated into suspension with 0.Ix phosphate buffered saline (PBS) , then freeze-thawed 3x using liquid nitrogen and incubation at room temperature. The suspension is extruded sequentially through a 0.4 μm, 0.2μm and 0.lμm polycarbonate filters at maximum pressure of 800 psi. The ribozyme is mixed with the extruded liposome suspension and lyophilized to dryness. The lipid/ribozyme powder is rehydrated with water to one-tenth the original volume. The suspension is diluted to the minimum volume required for extrusion (0.4ml for 1.5ml barrel and 1.5ml for 10ml barrel) with lxPBS and re-extruded through 0.4μm, 0.2μm, O.lμm polycarbonate filters. The liposome entrapped ribozyme is separated from untrapped ribozyme by gel filtration chromatography (SEPHAROSE CL-4B, BIOGEL A5M) . The liposome extractions are pooled and sterilized by filtration through a 0.2μm filter. The free ribozyme is pooled and recovered by ethanol precipitation. The liposome concentration is determined by incorporation of a radioactive lipid. The ribozyme concentration is determined by labeling with 32 P. Rossi et al. , 1992 supra (and references cited therein) describe other methods suitable for preparation of liposomes. In Vivo Assay The efficacy of action of a chosen ribozyme may be tested in vivo by use of cell cultures sensitive to HCV using standard procedures. For example, monolayer cultures of HCV-sensitive HepG2 cells are grown in 6 or 96 well tissue culture plates. Prior to transduction with HCV expression plasmids, cultures are treated for three to 24 hours with ribozyme-containing liposomes or cationic lipid/ribozyme complexes. Cells are then rinsed with phosphate buffered saline (PBS) and transduced or transfected with HCV expression plasmids. The cells are treated for three to five days with appropriate ribozyme preparations in fresh changes of medium. Total cellular RNA is harvested by the guanidine isothiocyanate technique and the amount of HCV mRNA is quantified and assessed for ribozyme-mediated cleavage using the ribonuclease protection assay. Alternatively, cellular lysates can be prepared and the core particles of HCV could be immunoprecipitated using polyclonal anti-core antiserum adsorbed to protein A-Sepharose according to manufacturers directions. The precipitated cores are treated with ribonuclease to digest any non-encapsidated RNAs and the core protein is digested with proteinase K/phenol extraction. Usually one-half of the total RNA and one- half of the extracted RNA is analyzed using the ribonuclease protection assay. Ribonuclease Protection Assay The accumulation of target mRNA in cells or the cleavage of the RNA by ribozymes or RNaseH (in vitro or in vivo) can be quantified using an RNase protection assay. In this method, antisense riboprobes are transcribed from template DNA using T7 RNA polymerase (U.S. Biochemicals) in 20 μl reactions containing IX transcription buffer (supplied by the manufacturer) , 0.2mM ATP, GTP and UTP, 1 U/μl pancreatic RNase inhibitor (Boehringer Mannheim Biochemicals) and 200 μCi 3 P-labeled CTP (800 Ci/mmol, New England Nuclear) for 1 h at 37°C. Template DNA is digested with 1 U RNase-free DNase I (U.S. Biochemicals, Cleveland, OH) at 37°C for 15 minutes and unincorporated nucleotides removed by G-50 SEPHADEX spin chromatography. In a manner similar to the transcription of antisense probe, the target RNA can be transcribed in vitro using a suitable DNA template. The transcript is purified by standard methods and digested with ribozyme at 37°C according to methods described later. Alternatively, virus-infected cells are harvested into 1 ml of PBS, transferred to a 1.5 ml EPPENDORF tube, pelleted for 30 seconds at low speed in a microcentrifuge, and lysed in 70 μl of hybridization buffer (4 M guanidine isothiocyanate, 0.1% sarcosyl, 25 mM sodium citrate, pH 7.5) . Cell lysate (45μl) or defined amounts of in vitro transcript (also in hybridization buffer) is then combined with 5 μl of hybridization buffer containing 5 x 10 5 cpm of each antisense riboprobe in 0.5 ml EPPENDORF tubes, overlaid with 25 μl mineral oil, and hybridization accomplished by heating overnight at 55°C. The hybridization reactions are diluted into 0.5 ml RNase solution (20 U/ml RNase A, 2 U/ml RNase Tl, 10 U/ml RNase- free DNAse I in 0.4 M NaCl) , heated for 30 minutes at 37°C, and 10 μl of 20% SDS and 10 μl of Proteinase K (10 mg/ml) added, followed by an additional 30 minutes incubation at 37°C. Hybrids are partially purified by extraction with 0.5 ml of a 1:1 mixture of phenol/chloroform; aqueous phases are combined with 0.5 ml isopropanol, and RNase-resistant hybrids pelleted for 10 minutes at room temperature (about 20°C) in a microcentrifuge. Pellets are dissolved in 10 μl loading buffer (95% formamide, IX TBE, 0.1% bromophenol blue, 0.1% xylene cylanol) , heated to 95°C for five minutes, cooled on ice, and analyzed on 4% polyacrylamide/7 M urea gels under denaturing conditions. Ribozyme Stability The chosen ribozyme can be tested to determine its stability, and thus its potential utility. Such a test can also be used to determine the effect of various chemical modifications (e.g. , addition of a poly(A) tail) on the ribozyme stability and thus aid selection of a more stable ribozyme. For example, a reaction mixture contains 1 to 5 pmoles of 5' (kinased) and/or 3' labeled ribozyme, 15 μg of cytosolic extract and 2.5 mM MgCl 2 in a total volume of lOOμl. The reaction is incubated at 37°C. Eight μl aliquots are taken at timed intervals and mixed with 8μl of a stop mix (20 mM EDTA, 95% formamide) . Samples are separated on a 15% acrylamide sequencing gel, exposed to film, and scanned with an Ambis. A 3' -labelled ribozyme can be formed by incorporation of the 32 P-labeled cordycepin at the 3' OH using poly(A) polymerase. For example, the poly(A) polymerase reaction contains 40 mM Tris, pH 8, 10 mM MgCl 2 , 250 mM NaCl, 2.5 mM MnCl 2 , ; 3 μl P 32 cordycepin, 500 Ci/mM; and 6 units poly(A) polymerase in a total volume of 50 μl. The reaction mixture was incubated for 30 minutes at 37°C. Effect of base substitution upon Ribozyme Activity To determine which primary structural characteristics could change ribozyme cleavage of substrate, minor base changes can be made in the substrate cleavage region recognized by a specific ribozyme. For example, the substrate sequences can be changed at the central "C" nucleotide, changing the cleavage site from a GUC to a GUA motif. The K^/IC,,. values for cleavage using each substrate are then analyzed to determine if such a change increases ribozyme cleavage rates. Similar experiments can be performed to address the effects of changing bases complementary to the ribozyme binding arms. Changes predicted to maintain strong binding to the complementary substrate are preferred. Minor changes in nucleotide content can alter ribozyme/substrate interactions in ways which are unpredictable based upon binding strength alone. Structures in ' the catalytic core region of the ribozyme recognize trivial changes in either substrate structure or the three dimensional structure of the ribozyme/substrate comple . To begin optimizing ribozyme design, the cleavage rates of ribozymes containing varied arm lengths, but targeted to the same length of short RNA substrate can be tested. Minimal arm lengths are required and effective cleavage varies with ribozyme/substrate combinations. The cleavage activity of selected ribozymes can be assessed using HCV-homologous substrates or HCV genomic RNA. The assays are performed in ribozyme excess and approximate K^/K^ values obtained. Comparison of values obtained with short and long substrates indicates utility in vivo of a ribozyme. Intracellular Stability of liposome-delivered ribozymes To test the stability of a chosen ribozyme in vivo the following test is useful. Ribozymes are 32 P-end labeled, entrapped in liposomes and delivered to HCV sensitive cells for three hours. The cells are fractionated and purified by phenol/chloroform extraction. Cells (lxlO 7 , T- 175 flask) are scraped from the surface of the flask and washed twice with cold PBS. The cells are homogenized by douncing 35 times in 4 ml of TSE (10 mM Tris, pH 7.4, 0.25 M Sucrose, mM EDTA) . Nuclei are pelleted at lOOxg for 10 minutes. Subcellular organelles (the membrane fraction) are pelleted at 200,000xg for two hours using an SW60 rotor. The pellet is resuspended in 1 ml of H buffer (0.25 M Sucrose, 50 mM HEPES, pH 7.4) . The supernatant contains the cytoplasmic fraction (in approximately 3.7 ml) . The nuclear pellet is resuspended in 1 ml of 65% sucrose in TM (50 mM Tris, pH 74. , 2.5 mM MgCl 2 ) and banded on a sucrose step gradient (1 ml nuclei in 65% sucrose TM, 1 ml 60% sucrose TM, 1 ml 55% sucrose TM, 50% sucrose TM, 300 ul 25% sucrose TM) for one hour at 37,000xg with an SW60 rotor. The nuclear band is harvested and diluted to 10% sucrose with TM buffer. Nuclei are pelleted at 37,000xg using an SW60 rotor for 15 minutes and the pellet resuspended in 1 ml of TM buffer. Aliquots are size fractionated on denaturing polyacrylamide gels and the intracellular localization determined. By comparison to the migration rate of newly synthesized ribozyme, the various fraction containing intact ribozyme can be determined. To investigate modifications which would lengthen the half-life of ribozyme molecules intracellularly, the cells may be fractioned as above and the purity of each fraction assessed by assaying enzyme activity known to exist in that fraction. The various cell fractions are frozen at -70°C and used to determine relative nuclease resistances of modified ribozyme molecules. Ribozyme molecules may be synthesized with 5 phosphorothioate (ps) , or 2'-0-methyl (2'-0Me) modifications at each end of the molecule. These molecules and a phosphodiester version of the ribozyme are end-labeled with 32 P and ATP using T4 polynucleotide kinase. Equal concentrations are added to the cell cytoplasmic extracts and aliquots of each taken at 10 minute intervals. The samples are size fractionated by denaturing PAGE and relative rates of nuclease resistance analyzed by scanning the gel with an Ambis scanner. The results show whether the ribozymes are digested by the cytoplasmic extract, and which versions are relatively more nuclease resistant. Modified ribozymes generally maintain 80-90% of the catalytic activity of the native ribozyme when short RNA substrates are employed. Unlabeled, 5' end-labeled or 3' end-labeled ribozymes can be used in the assays. These experiments can also be performed with human cell extracts to verify the observations. Administration of Ribozyme Selected ribozymes can be administered prophylacti- cally, or to virus infected patients, e.g., by exogenous delivery of the ribozyme to an infected tissue by means of an appropriate delivery vehicle, e.g., a liposome, a controlled release vehicle, by use of iontophoresis, electroporation or ion paired molecules, or covalently attached adducts, and other pharmacologically approved methods of delivery. Routes of administration include intramuscular, aerosol, oral (tablet or pill form) , topical, systemic, ocular, intraperitoneal and/or intrathecal. Expression vectors for immunization with ribozymes and/or delivery of ribozymes are also suitable. See Draper, U.S. Serial No. 08/152,487, filed November 12, 1993, the whole of which including drawings is hereby incorporated herein by reference. See, also, Sullivan, U.S. Serial No. 08/155,474, the whole of which including drawings is hereby incorporated herein by reference. The specific delivery route of any selected ribozyme will depend on the use of the ribozyme. Generally, a specific delivery program for each ribozyme will focus on naked ribozyme uptake with regard to intracellular localization, followed by demonstration of efficacy. Alternatively, delivery to these same cells in an organ or tissue of an animal can be pursued. Uptake studies will include uptake assays to evaluate cellular ribozyme uptake, regardless of the delivery vehicle or strategy. Such assays will also determine the intracellular localization of the ribozyme following uptake, ultimately establishing the requirements for maintenance of steady- state concentrations within the cellular compartment containing the target sequence (nucleus and/or cytoplasm) . Efficacy and cytotoxicity can then be tested. Toxicity will not only include cell viability but also cell function. Some methods of delivery that may be used include: a. encapsulation in liposomes, b. transduction by retroviral vectors, c. conjugation with cholesterol, d. localization to nuclear compartment utilizing antigen binding site found on most snRNAs, e. neutralization of charge of ribozyme by using nucleotide derivatives, and f. use of blood stem cells to distribute ribozymes throughout the body. At least three types of delivery strategies are useful in the present invention, including: ribozyme modifications, particle carrier drug delivery vehicles, and viral expression vectors. Unmodified ribozymes and antisense oligonucleotides, like most small molecules, are taken up by cells, albeit slowly. To enhance cellular uptake, the ribozyme may be modified essentially at random, in ways which reduces its charge but maintains specific functional groups. This results in a molecule which is able to diffuse across the cell membrane, thus removing the permeability barrier. Modification of ribozymes to reduce charge is just one approach to enhance the cellular uptake of these larger molecules. The random approach, however, is not advisable since ribozymes are structurally and functionally more complex than small drug molecules. The structural requirements necessary to maintain ribozyme catalytic activity are well understood by those in the art. These requirements are taken into consideration when designing modifications to enhance cellular delivery. The modifications are also designed to reduce susceptibility to nuclease degradation. Both of these characteristics should greatly improve the efficacy of the ribozyme. Cellular uptake can be increased by several orders of magnitude without having to alter the phosphodiester linkages necessary for ribozyme cleavage activity. Chemical modifications of the phosphate backbone will reduce the negative charge allowing free diffusion across the membrane. This principle has been successfully demonstrated for antisense DNA technology. The similarities in chemical composition between DNA and RNA make this a feasible approach. In the body, maintenance of an external concentration will be necessary to drive the diffusion of the modified ribozyme into the cells of the tissue. Administration routes which allow the diseased tissue to be exposed to a transient high concentration of the drug, which is slowly dissipated by systemic adsorption are preferred. Intravenous administration with a drug carrier designed to increase the circulation half-life of the ribozyme can be used. The size and composition of the drug carrier restricts rapid clearance from the blood stream. The carrier, made to accumulate at the site of infection, can protect the ribozyme from degradative processes. Drug delivery vehicles are effective for both systemic and topical administration. They can be designed to serve as a slow release reservoir, or to deliver their contents directly to the target cell. An advantage of using direct delivery drug vehicles is that multiple molecules are delivered per uptake. Such vehicles have been shown to increase the circulation half-life of drugs which would otherwise be rapidly cleared from the blood stream. Some examples of such specialized drug delivery vehicles which fall into this category are liposomes, hydrogels, cyclodextrins, biodegradable nanocapsules, and bioadhesive microspheres. From this category of delivery systems, liposomes are preferred. Liposomes increase intracellular stability, increase uptake efficiency and improve biological activity. Liposomes are hollow spherical vesicles composed of lipids arranged in a similar fashion as those lipids which make up the cell membrane. They have an internal aqueous space for entrapping water soluble compounds and range in size from 0.05 to several microns in diameter. Several studies have shown that liposomes can deliver RNA to cells and that the RNA remains biologically active. For example, a liposome delivery vehicle originally designed as a research tool, Lipofectin, has been shown to deliver intact mRNA molecules to cells yielding production of the corresponding protein. Liposomes offer several advantages : They are non- toxic and biodegradable in composition; they display long circulation half-lives; and recognition molecules can be readily attached to their surface for targeting to tissues. Finally, cost effective manufacture of liposome- based pharmaceuticals, either in a liquid suspension or lyophilized product, has demonstrated the viability of this technology as an acceptable drug delivery system. Other controlled release drug delivery systems, such as nonoparticles and hydrogels may be potential delivery vehicles for a ribozyme. These carriers have been developed for chemotherapeutic agents and protein-based pharmaceuticals, and consequently, can be adapted for ribozyme delivery. Topical administration of ribozymes is advantageous since it allows localized concentration at the site of administration with minimal systemic adsorption. This simplifies the delivery strategy of the ribozyme to the disease site and reduces the extent of toxicological characterization. Furthermore, the amount of material to be applied is far less than that required for other administration routes. Effective delivery requires the ribozyme to diffuse into the infected cells. Chemical modification of the ribozyme to neutralize negative charge may be all that is required for penetration. However, in the event that charge neutralization is insufficient, the modified ribozyme can be co-formulated with permeability enhancers, such as Azone or oleic acid, in a liposome. The liposomes can either represent a slow release presentation vehicle in which the modified ribozyme and permeability enhancer transfer from the liposome into the infected cell, or the liposome phospholipids can participate directly with the modified ribozyme and permeability enhancer in facilitating cellular delivery. In some cases, both the ribozyme and permeability enhancer can be formulated into a suppository formulation for slow release. Ribozymes may also be systemically administered. Systemic absorption refers to the accumulation of drugs in the blood stream followed by distribution throughout the entire body. Administration routes which lead to systemic absorption include: intravenous, subcutaneous, intraperitoneal, intranasal, intrathecal and ophthalmic. Each of these administration routes expose the ribozyme to an accessible diseased tissue. Subcutaneous administration drains into a localized lymph node which proceeds through the lymphatic network into the circulation. The rate of entry into the circulation has been shown to be a function of molecular weight or size. The use of a liposome or other drug carrier localizes the ribozyme at the lymph node. The ribozyme can be modified to diffuse into the cell, or the liposome can directly participate in the delivery of either the unmodified or modified ribozyme to the cell. Intraperitoneal administration also leads to entry into the circulation, with once again, the molecular weight or size controlling the rate of entry. Liposomes injected intravenously show accumulation in the liver, lung and spleen. The composition and size can be adjusted so that this accumulation represents 30% to 40% of the injected dose. The rest is left to circulate in the blood stream for up to 24 hours. The chosen method of delivery should result in cytoplasmic accumulation and molecules should have some nuclease-resistance for optimal dosing. Nuclear delivery may be used but is less preferable. Most preferred delivery methods include liposomes (10-400 nm) , hydrogels, controlled-release polymers, microinjection or electroporation (for ex vivo treatments) and other pharmaceutically applicable vehicles. The dosage will depend upon the disease indication and the route of administration but should be between 100-200 mg/kg of body weight/day. The duration of treatment will extend through the course of the disease symptoms, usually at least 14-16 days and possibly continuously. Multiple daily doses-'are anticipated for topical applications, ocular applications and vaginal applications. The number of doses will depend upon disease delivery vehicle and efficacy data from clinical trials. Establishment of therapeutic levels of ribozyme within the cell is dependent upon the rate of uptake and degradation. Decreasing the degree of degradation will prolong the intracellular half-life of the ribozyme. Thus, chemically modified ribozymes, e.g. , with modification of the phosphate backbone, or capping of the 5' and 3' ends of the ribozyme with nucleotide analogs may require different dosaging. Descriptions of useful systems are provided in the art cited above, all of which is hereby incorporated by reference herein. The claimed ribozymes are also useful as diagnostic tools to specifically or non-specifically detect the presence of a target RNA in a sample. That is, the target RNA, if present in the sample, will be specifically cleaved by the ribozyme, and thus can be readily and specifically detected as smaller RNA species. The presence of such smaller RNA species is indicative of the presence of the target RNA in the sample. Other embodiments are within the following claims.

Claims: Claims 1. An enzymatic RNA molecule which is active to specifically cleave RNA of HCV. 2. The enzymatic RNA molecule of claim 1 which cleaves RNA of HCV in the 5' non-translated region, RNA encoding the core (c) region or the proteases NS3 or NS2/NS3. 3. The enzymatic RNA molecule of claim 1 wherein said RNA molecule is in a hammerhead motif. 4. The enzymatic RNA molecule of claim 1 wherein said RNA molecule is in a hairpin, hepatitis Delta virus, group 1 intron, or RNaseP RNA motif. 5. The enzymatic RNA molecule of claim 1 which cleaves the sequence shown as any of SEQ. ID. NOS. 1-8. 6. A mammalian cell including an enzymatic RNA molecule of any of claims 1-5. 7. The cell of claim 6, wherein said cell is a human cell. 8. An expression vector including nucleic acid encoding the enzymatic RNA molecule of any of claims 1-5, in a manner which allow expression of that enzymatic RNA molecule within a mammalian cell. 9. A method for treatment of a disease caused by an HCV or expression of an HCV gene or portion of an HCV gene by administering to a patient an enzymatic RNA molecule of any of claims 1-5. 10. The method of claim 9 wherein said patient is a human, or non-human primate. 11. A method for providing defective viral particles comprising the step of contacting a cell infected with an HCV with an enzymatic RNA molecule active to cleave a gene required for viral replication. 12. The method of claim 11 wherein said molecule is active to cleave a nucleic acid required for viral protein synthesis. 13. The method of claim 11 wherein said nucleic acid is in the 5' non-translated region of HCV. 14. Defective viral particles produced by contacting a cell infected with an HCV with an enzymatic RNA molecule active to cleave a gene required for viral replication. 15. A method for inducing an immune response or for inducing production of anti-HCV immunoglobulin in a human, comprising the step of administering a defective viral particle produced by contacting a cell infected with an HCV with an enzymatic RNA molecule active to cleave a gene required for viral replication.

Inventors: DRAPER KENNETH G, DRAPER, KENNETH, G.
Applicants: RIBOZYME PHARM INC, RIBOZYME PHARMACEUTICALS, INC.
Application year: 1995
Main classification: C12N9
IPC codes: A61K35, A61K38, A61K39, A61K48, A61P1, A61P31, C07H21, C12N5, C12N7, C12N9, C12N15