US 6,433,159 B1Grant
Compositions and methods for treatment of Hepatitis C virus associated diseases
Issue Date:2002-08-13
•1 Claims
Abstract
Antisense oligonucleotides are provided which are complementary to at least a portion of HCV RNA and specifically hybridizable therewith. These oligonucleotides can be administered to inhibit the replication of Hepatitis C virus in vivo or in vitro and to treat Hepatitis C virus-associated disease. These compounds can be used either prophylactically or therapeutically to reduce the severity of diseases associated with Hepatitis C virus.
Metadata
Assignee
- ISIS Pharmaceuticals, Inc.
Inventor
- Kevin P. Anderson
Application Information
Application Number:US 08/823,895
Filing Date:1997-03-17
Priority Date:1992-09-10
Art Unit:7
Classifications
IPC:
C07H 2104
Field of Search:
536 245536 231536 241536 243536 2431536 2432536 2433435 64351723514 44935 9935 11935 34
Patent Drawings
This patent does not have any drawings.
Description
[0002] This is a continuation of application Ser. No. 08/453,085, filed May 30, 1995, now abandoned which is a continuation of application Ser. No. 07/945,289, filed Sep. 10, 1972, now abandoned.
FIELD OF THE INVENTION
[0003] This invention relates to the design and synthesis of antisense oligonucleotides which can be administered to inhibit the replication of Hepatitis C virus in vivo or in vitro and to treat Hepatitis C virus-associated disease. These compounds can be used either prophylactically or therapeutically to reduce the severity of diseases associated with Hepatitis C virus. Oligonucleotides which are specifically hybridizable with RNA targets are disclosed.
BACKGROUND OF THE INVENTION
[0004] The predominant form of hepatitis currently resulting from transfusions is not related to the previously characterized Hepatitis A virus or Hepatitis B virus and has been referred to as Non-A, Non-B Hepatitis (NANBH). NANBH currently accounts for over 90% of cases of post-transfusion hepatitis. Estimates of the frequency of NANBH in transfusion recipients range from 5%-13% for those receiving volunteer blood, or 25-54% for those receiving blood from commercial sources.
[0005] Acute NANBH, while often less severe than acute disease caused by Hepatitis A or Hepatitis B viruses, occasionally leads to severe or fulminant hepatitis. Of greater concern, progression to chronic hepatitis is much more common after NANBH than after either Hepatitis A or Hepatitis B infection. Chronic NANBH has been reported in 10%-70% of infected individuals. This form of hepatitis can be transmitted even by asymptomatic patients, and frequently progresses to malignant disease such as cirrhosis and hepatocellular carcinoma. Chronic active hepatitis, with or without cirrhosis, is seen in 44%-90% of posttransfusion hepatitis cases. Of those patients who developed cirrhosis, approximately one-fourth died of liver failure.
[0006] Chronic active NANBH is a significant problem to hemophiliacs who are dependent on blood products; 5%-11% of hemophiliacs die of chronic end-stage liver disease. Cases of NANBH other than those traceable to blood or blood products are frequently associated with hospital exposure, accidental needle stick, or tattooing. Transmission through close personal contact also occurs, though this is less common for NANBH than for Hepatitis B.
[0007] The causative agent of the majority of NANBH has recently been identified and is now referred to as Hepatitis C Virus (HCV). Houghton et al., EP Publication 318,216; Choo et al., Science1989, 244, 359-362. Based on serological studies using recombinant DNA-generated antigens it is now clear that HCV is the causative agent of most cases of post-transfusion NANBH. Clones of cDNA prepared from nucleic acid isolated from concentrated virus particles were originally isolated based on their ability to encode polypeptides which reacted with sera from NANBH patients. These clones hybridized with RNA, but not DNA, isolated from infected liver tissue, indicating the presence of an RNA genome. Hybridization analyses and sequencing of the cDNA clones revealed that RNA present in infected liver and particles was the same polarity as that of the coding strand of the cDNAs; in other words, the virus genome is a positive or plus-strand RNA genome. EP Publication 318,216 (Houghton et al.) disclose partial genomic sequences of HCV-1, and teach recombinant DNA methods of cloning and expressing HCV sequences and HCV polypeptides, techniques of HCV immunodiagnostics, HCV probe diagnostic techniques, anti-HCV antibodies, and methods of isolating new HCV sequences. Houghton et al. also disclose additional HCV sequences and teach application of these sequences and polypeptides in immunodiagnostics, probe diagnostics, anti-HCV antibody production, PCR technology and recombinant DNA technology. The concept of using antisense polynucleotides as inhibitors of viral replication is disclosed, but no specific targets are taught. Oligomer probes and primers based on the sequences disclosed are also provided. EP Publication 419,182 (Miyamura et al.) discloses new HCV isolates J1 and J7 and use of sequences distinct from HCV-1 sequences for screens and diagnostics.
[0008] The only treatment regimen shown to be effective for the treatment of chronic NANBH is interferon-α. Most NANBH patients show an improvement of clinical symptoms during interferon treatment, but relapse is observed in at least half of patients when treatment is interrupted. Significant improvements in antiviral therapy are therefore greatly desired.
OBJECTS OF THE INVENTION
[0009] It is an object of this invention to provide oligonucleotides which are capable of hybridizing with RNA of HCV to inhibit the synthesis or function of said RNA.
[0010] It is another object of this invention to provide oligonucleotides which are capable of hybridizing with RNA of HCV to inhibit replication of the virus.
[0011] It is a further object to provide oligonucleotides which can modulate the expression of HCV through antisense interaction with viral RNA.
[0012] Yet another object of this invention is to provide methods of prophylaxis, diagnostics and therapeutics for acute or chronic HCV infection.
[0013] A further object of this invention is to provide methods of prophylaxis, diagnostics and therapeutics for HCV-associated diseases.
[0014] Methods, materials and kits for detecting the presence or absence of HCV or HCV RNA in a sample suspected of containing it are further objects of the invention.
[0015] These and other objects will become apparent to persons of ordinary skill in the art from a review of the instant specification and appended claims.
SUMMARY OF THE INVENTION
[0016] In accordance with the present invention, compositions and methods for modulating the effects of HCV infection are provided. Oligonucleotides complementary to, and specifically hybridizable with, selected sequences of HCV RNA are provided. The HCV 5′ end hairpin loop, 5′ end 6-base-pair repeats, 5′ end untranslated region, polyprotein translation initiation codon, ORF 3 translation initiation codon, 3′-untranslated region, 3′ end palindrome region, R2 sequence and 3′ end hairpin loop are preferred targets. Methods for diagnosing or treating disease states by administering oligonucleotides, either alone or in combination with a pharmaceutically acceptable carrier, to animals suspected of having HCV-associated diseases are also provided.
[0017] The relationship between the target RNA and oligonucleotides complementary to at least a portion of the target, and specifically hybridizable with it, is commonly denoted as “antisense”. The oligonucleotides are able to inhibit the function of viral RNA by interfering with its replication, transcription into mRNA, translation into protein, packaging into viral particles or any other activity necessary to its overall biological function. The failure of the RNA to perform all or part of its function results in failure of all or a portion of the normal life cycle of the virus.
[0018] It has been found that antisense oligonucleotides designed to target viruses can be effective in diminishing viral infection. It is preferred that oligonucleotides have between about 5 and about 50 nucleotide units. It is also preferred that the oligonucleotides be specifically hybridizable with the HCV 5′ end hairpin loop, 5′ end 6-base-pair repeats, 5′ end untranslated region, polyprotein translation initiation codon, ORF 3 translation initiation codon, 3′-untranslated region, 3′ end palindrome region, R2 sequence or 3′ end hairpin loop. The oligonucleotide may be modified to increase nuclease resistance and to increase its efficacy.
[0019] In accordance with preferred embodiments, the viral RNA is interfered with to an extent sufficient to inhibit HCV infection and/or HCV replication. Thus, oligonucleotides which are capable of interacting with portions of HCV RNA are comprehended. Animals suspected of having HCV-associated disease are contacted with an oligonucleotide made in accordance with this invention. In particular, the present invention is believed to be effective in the treatment of acute and chronic HCV infections and HCV-associated disease, either prophylactically or therapeutically.
[0020] It is to be expected that differences in the RNA of HCV from different strains and from different types within a strain exist. Thus, it is believed, for example, that the regions of the various HCV strains serve essentially the same function for the respective strains and that interference with expression of the genetic information will afford similar results in the various strains. This is believed to be so even though differences in the nucleotide sequences among the strains exist.
[0021] Accordingly, nucleotide sequences set forth in the present specification will be understood to be representational for the particular strain being described. Homologous or analogous sequences for different strains of HCV are specifically contemplated as being within the scope of this invention.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
[0022] Antisense oligonucleotides hold great promise as therapeutic agents for the treatment of many human diseases. In most cases, oligonucleotides complementary to specific RNA target sequences bind by Watson-Crick base pairing to pre-mRNA or mature mRNA, inhibiting the flow of genetic information from DNA to protein. In the case of RNA viruses such as HCV, oligonucleotides are designed to specifically hybridize to viral genomic RNA, mRNA, or replicative intermediate RNA, interfering with the function of the RNA such that viral replication or protein expression is modulated.
[0023] Numerous recent studies have documented the utility of antisense oligonucleotides as biochemical tools for studying target proteins. Rothenberg et al., J. Natl. Cancer Inst.1989, 81, 1539-1544; Zon, G. Pharmaceutical Res.1987, 5, 539-549. Because of recent advances in oligonucleotide chemistry, synthesis of nuclease-resistant oligonucleotides, and availability of types of oligonucleotides which exhibit enhanced cell uptake, it is now possible to consider the use of antisense oligonucleotides as a novel form of therapeutics.
[0024] For therapeutics, an animal suspected of having an HCV infection or HCV-associated disease is treated by administering oligonucleotides in accordance with this invention. Oligonucleotides may be formulated in a pharmaceutical composition, which may include carriers, thickeners, diluents, buffers, preservatives, surface active agents and the like in addition to the oligonucleotide. Pharmaceutical compositions may also include one or more active ingredients such as, for example, antimicrobial agents, antiinflammatory agents, anesthetics, and the like in addition to oligonucleotide.
[0025] The pharmaceutical composition may be administered in a number of ways depending on whether local or systemic treatment is desired, and on the area to be treated. Administration may be topically (including ophthalmically, vaginally, rectally, intranasally), orally, by inhalation, or parenterally, for example by intravenous drip, subcutaneous, intraperitoneal or intramuscular injection.
[0026] Formulations for topical administration may include ointments, lotions, creams, gels, drops, suppositories, sprays, liquids and powders. Conventional pharmaceutical carriers, aqueous, powder or oily bases, thickeners and the like may be necessary or desirable. Coated condoms may also be useful.
[0027] Compositions for oral administration include powders or granules, suspensions or solutions in water or non-aqueous media, capsules, sachets, or tablets. Thickeners, flavorings, diluents, emulsifiers, dispersing aids or binders may be desirable.
[0028] Formulations for parenteral administration may include sterile aqueous solutions which may also contain buffers, diluents and other suitable additives.
[0029] Dosing is dependent on severity and responsiveness of the condition to be treated, but will normally be one or more doses per day, with course of treatment lasting from several days to several months or until a cure is effected or a diminution of disease state is achieved. Dosage and frequency will vary depending on, for example, body weight of patient and means of administration. Individual doses will normally range from about 0.001 mg to 500 mg, but may be higher or lower. Persons of ordinary skill can easily determine optimum dosages, dosing methodologies and repetition rates.
[0030] The present invention employs oligonucleotides complementary to specific regions of HCV. RNA for antisense inhibition of HCV. In the context of this invention, the term “oligonucleotide” refers to an oligomer or polymer of ribonucleic acid or deoxyribonucleic acid. This term includes oligomers consisting of naturally occurring bases, sugars and intersugar (backbone) linkages as well as oligomers having non-naturally occurring portions which function similarly. Such modified or substituted oligonucleotides are often preferred over native forms because of properties such as, for example, enhanced cellular uptake and increased stability in the presence of nucleases.
[0031] Specific examples of some preferred oligonucleotides envisioned for this invention may contain phosphorothioates, phosphotriesters, methyl phosphonates, chain alkyl or cycloalkyl intersugar linkages or short chain heteroatomic or heterocyclic intersugar linkages. Most preferred are those with CH2—NH—O—CH2, CH2—N(CH3)—O—CH2, CH2—O—N(CH3)—CH2, CH2—N(CH3)—N(CH3)—CH2and O—N(CH3)—CH2—CH2backbones (where phosphodiester is O—P—O—CH2). Also preferred are oligonucleotides having morpholino backbone structures. Summerton, J. E. and Weller, D. D. U.S. Pat. No. 5,034,506. In other preferred embodiments, such as the protein-nucleic acid (PNA) backbone, the phosphodiester backbone of the oligonucleotide may be replaced with a polyamide backbone, the bases being bound directly or indirectly to the aza nitrogen atoms of the polyamide backbone. P. E. Nielsen, M. Egholm, R. H. Berg, O. Buchardt, Science1991, 254, 1497. Other preferred oligonucleotides may contain alkyl and halogen-substituted sugar moieties comprising one of the following at the 2′ position: OH, SH, SCH3, F, OCN, O(CH2)nNH2or O(CH2)nCH3where n is from 1 to about 10; C1to C10lower alkyl, substituted lower alkyl, alkaryl or aralkyl; Cl; Br; CN; CF3; OCF3; O-, S-, or N-alkyl; O-, S-, or N-alkenyl; SOCH3; SO2CH3; ONO2; NO2; N3; NH2; heterocycloalkyl; heterocycloalkaryl; aminoalkylamino; polyalkylamino; substituted silyl; an RNA cleaving group; a conjugate; a reporter group; an intercalator; a group for improving the pharmacokinetic properties of an oligonucleotide; or a group for improving the pharmacodynamic properties of an oligonucleotide and other substituents having similar properties. Oligonucleotides may also have sugar mimetics such as cyclobutyls in place of the pentofuranosyl group.
[0032] All such oligonucleotides are comprehended by this invention so long as they function effectively to hybridize with HCV RNA. The oligonucleotides in accordance with this invention preferably comprise from about 5 to about 50 nucleic acid base units. It is more preferred that such oligonucleotides comprise from about 8 to 30 nucleic acid base units, and still more preferred to have from about 12 to 25 nucleic acid base units. As will be appreciated, a nucleic acid base unit is a base-sugar combination suitably bound to adjacent nucleic acid base unit through phosphodiester or other bonds.
[0033] The oligonucleotides used in accordance with this invention may be conveniently and routinely made through the well-known technique of solid phase synthesis. Equipment for such synthesis is sold by several vendors including Applied Biosystems. Any other means for such synthesis may also be employed, however the actual synthesis of the oligonucleotides are well within the talents of the routineer. It is also well known to use similar techniques to prepare other oligonucleotides such as the phosphorothioates and alkylated derivatives.
[0034] In accordance with this invention, persons of ordinary skill in the art will understand that messenger RNA includes not only the sequence information to encode a protein using the three letter genetic code, but also associated ribonucleotides which form regions known to such persons as the 5′-untranslated region, the 3′-untranslated region, and the 5′ cap region, as well as ribonucleotides which form various secondary structures. Thus, oligonucleotides may be formulated in accordance with this invention which are targeted wholly or in part to these associated ribonucleotides as well as to the coding ribonucleotides. In preferred embodiments, the oligonucleotide is specifically hybridizable with the HCV 5′ end hairpin loop, 5′ end 6-base-pair repeats, ORF 3 translation initiation codon (all of which are contained in the 5′-untranslated region), polyprotein translation initiation codon, 3′-untranslated region, R2 region, 3′ hairpin loop or 3′ end palindrome region.
[0035] The size of the HCV genome is approximately 9400 nucleotides, with a single translational reading frame encoding a polyprotein which is subsequently processed to several structural and non-structural proteins.
[0036] Several regions of the HCV genome have been identified as antisense targets in the present invention. It should be noted that sequence availability and nucleotide numbering schemes vary from strain to strain. The 5′ untranslated region of HCV consists of approximately 350 nucleotides upstream of the polyprotein translation initiation codon. A hairpin loop present at nucleotides 1-22 at the 5′ end of the genome (HCV-1) identified herein as the “5′ end hairpin loop” is believed to serve as a recognition signal for the viral replicase or nucleocapsid proteins. Han et al., Proc. Natl. Acad. Sci.1991, 88, 1711-1715.
[0037] Three small (12-16 amino acids each) open reading frames (ORFs) are located in the 5′-untranslated region of HCV RNA. These ORFs may be involved in control of translation. The ORF 3 translation initiation codon as denominated herein is found at nucleotides 315-317 of HCV-1 according to the scheme of Han et al., Proc. Natl. Acad. Sci.1991, 88, 1711-1715; and at nucleotides-127 to -125 according to the scheme of Choo et al., Proc. Natl. Acad. Sci.1991, 88, 2451-2455 and depicted in SEQ ID NO: 25.
[0038] The polyprotein translation initiation codon as denominated herein is an AUG sequence located at nucleotides 342-344 of HCV-1 according to Han et al., Proc. Natl. Acad. Sci.1991, 88, 1711-1715 or at nucleotide 1-3 according to the HCV-1 numbering scheme of Choo et al., Proc. Natl. Acad. Sci.1991, 88, 2451-2455 and SEQ ID NO: 25.
[0039] The 3′ untranslated region, as denominated herein, consists of nucleotides downstream of the polyprotein translation termination site (ending at nt 9037 according to Choo et al. and SEQ ID NO: 25; nt 9377 according to schemes of Han and Inchauspe as depicted in SEQ ID NO: 26). Nucleotides 9697-9716 (numbering scheme of Inchauspe for HCV-H which is depicted in SEQ ID NO: 26) at the 3′ terminus of the genome within the 3′ untranslated region can be organized into a stable hairpin loop structure identified herein as the 3′ hairpin loop. A short nucleotide stretch (R2) immediately upstream (nt 9691-9696 of HCV-H depicted in SEQ ID NO: 26) of the 3′ hairpin, and denominated herein “the R2 sequence”, is thought to play a role in cyclization of the viral RNA, possibly in combination with a set of 5′ end 6-base-pair repeats of the same sequence at nt 23-28 and 38-43. (Inchauspe et al., Proc. Natl. Acad. Sci.1991, 88, 10292-10296) is identified herein as “5′ end 6-base-pair repeat”. Palindrome sequences present near the 3′ end of the genome (nucleotides 9312-9342 according to the scheme of Takamizawa et al., J. Virol.1991, 65, 1105-1113 depicted in SEQ ID NO: 27) are capable of forming a stable secondary structure. This is referred to herein as the 3′ end palindrome region.
[0040] Oligonucleotides useful in the invention are complementary to HCV RNA. Thus, the oligonucleotides in accordance with the invention preferably have one of the sequences shown in Table 1, or an effective portion thereof. It is preferred to employ any of these oligonucleotides as set forth above or any of the similar oligonucleotides, which persons of ordinary skill in the art can prepare from knowledge of the preferred antisense targets for the modulation of HCV infection.
| TABLE 1 |
|---|
| RNA SEQUENCE TARGETS AND ANTISENSE |
| OLIGONUCLEOTIDES FOR HCV |
| [Sequences are from HCV-1 (US) and HCV-J (Japan)] |
[0041] The oligonucleotides of this invention can be used in diagnostics, therapeutics and as research reagents and kits. Since the oligonucleotides of this invention hybridize to RNA from HCV, sandwich and other assays can easily be constructed to exploit this fact. Provision of means for detecting hybridization of oligonucleotide with HCV or HCV RNA present in a sample suspected of containing it can routinely be accomplished. Such provision may include enzyme conjugation, radiolabelling or any other suitable detection systems. Kits for detecting the presence or absence of HCV may also be prepared.
[0042] The following specific examples are given for illustrative purposes only and are not intended to limit the invention.
EXAMPLES
Example 1
[0043] Oligonucleotide Synthesis
[0044] Unmodified DNA oligonucleotides are synthesized on an automated DNA synthesizer (Applied Biosystems model 380B) using standard phosphoramidite chemistry with oxidation by iodine. β-cyanoethyldiisopropyl-phosphoramidites are purchased from Applied Biosystems (Foster City, Calif.). For phosphorothioate oligonucleotides, the standard oxidation bottle is replaced by a 0.2 M solution of 3H-1,2-benzodithiole-3-one 1,1-dioxide in acetonitrile for the stepwise thiation of the phosphite linkages. The thiation cycle wait step is increased to 68 seconds and is followed by the capping step.
[0045] After cleavage from the controlled pore glass column (Applied Biosystems) and deblocking in concentrated ammonium hydroxide at 55° C. for 18 hours, the oligonucleotides are purified by precipitation twice out of 0.5 M NaCl with 2.5 volumes ethanol. Analytical gel electrophoresis is accomplished in 20% acrylamide, 8 M urea, 45 mM Tris-borate buffer, pH 7.0.
Example 2
[0046] Transcription and Translation of HCV RNA in Genetically Engineered Cells
[0047] A recombinant DNA vector capable of expressing HCV genes in mammalian cells is constructed using standard genetic engineering methods. A cDNA fragment representing the HCV mRNA or genomic transcript is placed behind an inducible eukaryotic promotor such as the LTR from mouse mammary tumor virus in such a way that transcription of the HCV cDNA begins at the appropriate nucleotide position. At the 3′ end of the gene, a polyadenylation signal is incorporated to ensure termination at the appropriate nucleotide position. It may be advantageous to modify the coding sequence by insertion of an in-frame reporter domain (e.g., the enzymatically active domain of the firefly luciferase gene) which can simplify detection procedures for expression of the fusion protein. The vector also contains one or more selectable genetic markers such as neomycin resistance.
[0048] The described vector is introduced into mammalian cells using a standard calcium chloride transfection procedure. Cells containing transfected DNA are identified by growth in the presence of selective agents such as neomycin, and cloned by limiting dilution. Expression of HCV RNA in cloned transfectants can be verified using any one of a number of assays such as northern blots, RNA polymerase chain reaction, or nuclease protection. Protein expression can be verified using western blotting or immune precipitation with specific HCV antibodies, or by monitoring for the presence of detectable enzymatic activity resulting from the incorporation of an assayable reporter domain. If an inducible promotor such as the MMTV LTR is used in construction of the vector, a glucocorticoid inducer such as dexamethasone should be added to the transfected cells prior to assays in order to induce gene expression.
Example 3
[0049] Evaluation of Antisense Oligonucleotide Inhibition of HCV Gene Expression from Genetically Engineered Cells
[0050] Mammalian cells transfected with expression vectors such as those described in Example 2 are incubated overnight in medium containing antisense oligonucleotides. After oligonucleotide treatment, cells are treated with dexamethasone in order to induce expression of HCV gene products. After a suitable incubation period (4-24 hours) cells are harvested, and expression of specific HCV polypeptide can be detected immunologically using specific antisera in a western blot or immunoprecipitation assay. If the cells contain a vector containing a reporter domain, such as that for firefly luciferase, fused in-frame with the HCV polyprotein, cell extracts can be harvested and evaluated for enzymatic activity of the reporter domain.
Example 4
[0051] Transcription and Translation of HCV RNA from Cytoplasmic Virus Vectors
[0052] A cDNA fragment representing the HCV mRNA or genomic transcript is placed behind a Vaccinia virus promotor in such a way that transcription of the HCV cDNA begins at the appropriate nucleotide position. At the 3′ end of the gene, a polyadenylation signal is incorporated to ensure termination at the appropriate nucleotide position. It may be advantageous in some instances to modify the coding sequence by insertion of an in-frame reporter domain (e.g., the enzymatically active domain of the firefly luciferase gene) which can simplify detection procedures for expression of the fusion protein.
[0053] Incorporation of the expression unit into the genome of a cytoplasmic replicating DNA virus such as Vaccinia is facilitated by inclusion of sequences upstream and downstream of the expression unit which are homologous to the Vaccinia virus genome. Co-transfection of vector into Vaccinia virus-infected mammalian cells can result in homologous recombination of vector with Vaccinia. If a suitable enzymatic marker such as β-galactosidase is present at the appropriate recombination site in the virus, then recombinant plaques can be identified by a lack of color under appropriate substrate conditions. Cloned virus can be propagated in appropriate host mammalian cell lines and expression of HCV gene products verified as described in Example 2.
Example 5
[0054] Evaluation of Antisense Oligonucleotide Inhibition of HCV Gene Expression from Cytoplasmic Virus Vectors in Mammalian Cells
[0055] Mammalian cells are incubated overnight in medium containing antisense oligonucleotides. After oligonucleotide treatment, cells are infected with recombinant Vaccinia virus expressing HCV gene products. After a suitable incubation period (4-24 hours) cells are harvested, and expression of specific HCV polypeptide can be detected immunologically using specific antisera in a western blot or immunoprecipitation assay. If the cells contain a vector containing a reporter domain, such as that for firefly luciferase, fused in-frame with the HCV polyprotein, cell extracts can be harvested and evaluated for enzymatic activity of the reporter domain.
Example 6
[0056] Evaluation of Antisense Oligonucleotide Inhibition of HCV Particle Assembly in Cells Transfected with HCV Genes or Infected with Cytoplasmic Virus Vectors Expressing HCV Genes
[0057] HCV genomic RNA and protein are expressed in cells transfected with HCV cDNA expression vectors, or in cells infected with Vaccinia virus vectors expressing the HCV cDNA. It is likely that the RNA genomes and proteins will associate to form HCV-like particles. The presence of these particles can be verified using electron microscopy. To evaluate the effects of oligonucleotides complementary to presumed packaging signals of the viral RNA on particle assembly, specific biochemical assays can be developed to measure the appearance of extracellular particles containing both HCV nucleic acid and proteins.
[0058] Mammalian cells transfected with expression vectors such as those described in Example 2 are incubated overnight in medium containing antisense oligonucleotides. After oligonucleotide treatment, cells are treated with dexamethasone in order to induce expression of HCV gene products. After a suitable incubation period (4-24 hours) extracellular fluid from treated cells is harvested, and particles are concentrated by pelleting in the ultracentrifuge. Proteins and nucleic acids are extracted from the pellet and quantitated by northern blot and western blot analysis respectively as described in Examples 4 and 5. A similar procedure could be used to monitor effects of oligonucleotide treatment on virus particle assembly resulting from infection of cells with recombinant Vaccinia virus expressing the HCV polyprotein.
Claims
What is claimed is:
1. An oligonucleotide 12-25 nucleotides in length which has a nucleotide sequence complementary to at least a portion of a polyprotein translation initiation region of HCV genomic or messenger RNA, said oligonucleotide which inhibits the translation of said RNA.
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