SCH-C (SCH 351125), an orally bioavailable, small molecule antagonist of the chemokine receptor CCR5, is a potent inhibitor of HIV-1 infection in vitro and in vivo.

We describe here the identification and properties of SCH-C (SCH 351125), a small molecule inhibitor of HIV-1 entry via the CCR5 coreceptor. SCH-C, an oxime-piperidine compound, is a specific CCR5 antagonist as determined in multiple receptor binding and signal transduction assays. This compound specifically inhibits HIV-1 infection mediated by CCR5 in U-87 astroglioma cells but has no effect on infection of CXCR4-expressing cells. SCH-C has broad and potent antiviral activity in vitro against primary HIV-1 isolates that use CCR5 as their entry coreceptor, with mean 50% inhibitory concentrations ranging between 0.4 and 9 nM. Moreover, SCH-C strongly inhibits the replication of an R5-using HIV-1 isolate in SCID-hu Thy/Liv mice. SCH-C has a favorable pharmacokinetic profile in rodents and primates with an oral bioavailability of 50-60% and a serum half-life of 5-6 h. On the basis of its novel mechanism of action, potent antiviral activity, and in vivo pharmacokinetic profile, SCH-C is a promising new candidate for therapeutic intervention of HIV infection.

Discovery of 4-[(Z)-(4-bromophenyl)- (ethoxyimino)methyl]-1'-[(2,4-dimethyl-3- pyridinyl)carbonyl]-4'-methyl-1,4'- bipiperidine N-oxide (SCH 351125): an orally bioavailable human CCR5 antagonist for the treatment of HIV infection.

Structure-activity studies on piperidino-piperidine 3 led to the discovery of SCH 351125 (1), a selective CCR5 antagonist with potent activity against RANTES binding (K(i) = 2 nM), which possesses subnanomolar activity in blocking viral entry and has excellent antiviral potency versus a panel of primary HIV-1 viral isolates. Compound 1, which has good oral bioavailability in rats, dogs, and monkeys, is proposed as a potential therapeutic agent for the treatment of HIV-1 and has entered human clinical trials.

Piperazine-based CCR5 antagonists as HIV-1 inhibitors. II. Discovery of 1-[(2,4-dimethyl-3-pyridinyl)carbonyl]-4- methyl-4-[3(S)-methyl-4-[1(S)-[4-(trifluoromethyl)phenyl]ethyl]-1-piperazinyl]- piperidine N1-oxide (Sch-350634), an orally bioavailable, potent CCR5 antagonist.

Truncation of the original piperidino-2(S)-methyl piperazine lead structure 2, from a family of muscarinic antagonists, gave compound 8 which has improved selectivity for the HIV-1 co-receptor CCR5 over muscarinic receptors. Further optimization for pharmacokinetic properties afforded Sch-350634 (1), a prototypical piperazine-based CCR5 antagonist, which is a potent inhibitor of HIV-1 entry and replication in PBMCs. The title compound (1) has excellent oral bioavailability in rat, dog, and monkey.

Hepatitis C virus internal ribosome entry site (IRES) stem loop IIId contains a phylogenetically conserved GGG triplet essential for translation and IRES folding.

The hepatitis C virus (HCV) internal ribosome entry site (IRES) is a highly structured RNA element that directs cap-independent translation of the viral polyprotein. Morpholino antisense oligonucleotides directed towards stem loop IIId drastically reduced HCV IRES activity. Mutagenesis studies of this region showed that the GGG triplet (nucleotides 266 through 268) of the hexanucleotide apical loop of stem loop IIId is essential for IRES activity both in vitro and in vivo. Sequence comparison showed that apical loop nucleotides (UUGGGU) were absolutely conserved across HCV genotypes and the GGG triplet was strongly conserved among related Flavivirus and Pestivirus nontranslated regions. Chimeric IRES elements with IIId derived from GB virus B (GBV-B) in the context of the HCV IRES possess translational activity. Mutations within the IIId stem loop that abolish IRES activity also affect the RNA structure in RNase T(1)-probing studies, demonstrating the importance of correct RNA folding to IRES function.

Cross-genotypic interaction between hepatitis C virus NS3 protease domains and NS4A cofactors.

BACKGROUND/AIMS: Hepatitis C virus (HCV) nonstructural protein 3 (NS3) protease requires NS4A as a cofactor. This cofactor activity has been mapped to the central region of NS4A which interacts with the N-terminus of NS3 protease. To investigate whether this interaction is conserved among different genotypes of HCV cross-genotypic characterization were performed to delineate the importance of NS4A cofactor function in relation to the molecular evolution of HCV METHODS: Active NS3 protease domains of genotype 1-3 (representing five subtypes: la, 1b, 2a, 2b and 3a) were produced and purified from bacterial cells. NS4A cofactor-dependent in vitro trans cleavage assays were established using the in vitro translated recombinant protein substrates. These substrates contained the junction site of NS4A/NS4B, NS4B/NS5A or NS5A/NS5B. RESULTS: Our data revealed that NS3 proteases cross-interacted with NS4A cofactors derived from different genotypes, although the genotype 2 cofactor was less efficient, which could be due to greater genetic variations in this region. Furthermore, the corresponding region in hepatitis G virus (HGV) NS4A was found to provide weak cofactor activity for HCV NS3 protease. Surprisingly, a synthetic substrate peptide from the NS4B/NS5A junction was also found to enhance HCV NS3 protease activity in a dose-dependent manner. CONCLUSION: Our study suggests that the NS4A cofactor function is well conserved among HCV It is likely that other HCV-related viruses may have developed similar strategies to regulate their protease activity.

Virus-specific cofactor requirement and chimeric hepatitis C virus/GB virus B nonstructural protein 3.

GB virus B (GBV-B) is closely related to hepatitis C virus (HCV) and causes acute hepatitis in tamarins (Saguinus species), making it an attractive surrogate virus for in vivo testing of anti-HCV inhibitors in a small monkey model. It has been reported that the nonstructural protein 3 (NS3) serine protease of GBV-B shares similar substrate specificity with its counterpart in HCV. Authentic proteolytic processing of the HCV polyprotein junctions (NS4A/4B, NS4B/5A, and NS5A/5B) can be accomplished by the GBV-B NS3 protease in an HCV NS4A cofactor-independent fashion. We further characterized the protease activity of a full-length GBV-B NS3 protein and its cofactor requirement using in vitro-translated GBV-B substrates. Cleavages at the NS4A/4B and NS5A/5B junctions were readily detectable only in the presence of a cofactor peptide derived from the central region of GBV-B NS4A. Interestingly, the GBV-B substrates could also be cleaved by the HCV NS3 protease in an HCV NS4A cofactor-dependent manner, supporting the notion that HCV and GBV-B share similar NS3 protease specificity while retaining a virus-specific cofactor requirement. This finding of a strict virus-specific cofactor requirement is consistent with the lack of sequence homology in the NS4A cofactor regions of HCV and GBV-B. The minimum cofactor region that supported GBV-B protease activity was mapped to a central region of GBV-B NS4A (between amino acids Phe22 and Val36) which overlapped with the cofactor region of HCV. Alanine substitution analysis demonstrated that two amino acids, Val27 and Trp31, were essential for the cofactor activity, a finding reminiscent of the two critical residues in the HCV NS4A cofactor, Ile25 and Ile29. A model for the GBV-B NS3 protease domain and NS4A cofactor complex revealed that GBV-B might have developed a similar structural strategy in the activation and regulation of its NS3 protease activity. Finally, a chimeric HCV/GBV-B bifunctional NS3, consisting of an N-terminal HCV protease domain and a C-terminal GBV-B RNA helicase domain, was engineered. Both enzymatic activities were retained by the chimeric protein, which could lead to the development of a chimeric GBV-B virus that depends on HCV protease function.

Generation of transmissible hepatitis C virions from a molecular clone in chimpanzees.

Multiple alignments of hepatitis C virus (HCV) polyproteins from six different genotypes identified a total of 22 nonconsensus mutations in a clone derived from the Hutchinson (H77) isolate. These mutations, collectively, may have contributed to the failure in generating a "functionally correct" or "infectious" clone in earlier attempts. A consensus clone was constructed after systematic repair of these mutations, which yielded infectious virions in a chimpanzee after direct intrahepatic inoculation of in vitro transcribed RNAs. This RNA-infected chimpanzee has developed hepatitis and remained HCV positive for more than 11 months. To further verify this RNA-derived infectivity, a second naive chimpanzee was injected intravenously with serum collected from the first chimpanzee. Infectivity analysis of the second chimpanzee demonstrated that the HCV infection was successfully transmitted, which validated unequivocally the infectivity of our repaired molecular clone. Amino acid sequence comparisons revealed that our repaired infectious clone had 4 mismatches with the isogenic clone reported by Kolykhalov et al. (1997, Science 277, 570-574) and 8 mismatches with that reported by Yanagi et al. (1997, Proc. Natl. Acad. Sci. USA 94, 8738-8743). At the RNA level, more mismatches (43 and 67, respectively) were identified; most of them were synonymous substitutions. Further comparisons with 16 isolates from different genotypes demonstrated that our repaired clone shares greater consensus than the reported isogenic clones. This approach of generating infectious HCV RNA validates the importance of amino acid sequence consensus in relation to the biology of HCV.

Characterization of soluble hepatitis C virus RNA-dependent RNA polymerase expressed in Escherichia coli.

Production of soluble full-length nonstructural protein 5B (NS5B) of hepatitis C virus (HCV) has been shown to be problematic and requires the addition of salts, glycerol, and detergents. In an effort to improve the solubility of NS5B, the hydrophobic C terminus containing 21 amino acids was removed, yielding a truncated NS5B (NS5BDeltaCT) which is highly soluble and monodispersed in the absence of detergents. Fine deletional analysis of this region revealed that a four-leucine motif (LLLL) in the hydrophobic domain is responsible for the solubility profile of the full-length NS5B. Enzymatic characterization revealed that the RNA-dependent RNA polymerase (RdRp) activity of this truncated NS5B was comparable to those reported previously by others. For optimal enzyme activity, divalent manganese ions (Mn2+) are preferred rather than magnesium ions (Mg2+), whereas zinc ions (Zn2+) inhibit the RdRp activity. Gliotoxin, a known poliovirus 3D RdRp inhibitor, inhibited HCV NS5B RdRp in a dose-dependent manner. Kinetic analysis revealed that HCV NS5B has a rather low processivity compared to those of other known polymerases.

Genetic analysis of human immunodeficiency virus type 1 envelope V3 region isolates from mothers and infants after perinatal transmission.

The human immunodeficiency virus type 1 (HIV-1) sequences from variable region 3 (V3) of the envelope gene were analyzed from seven infected mother-infant pairs following perinatal transmission. The V3 region sequences directly derived from the DNA of the uncultured peripheral blood mononuclear cells from infected mothers displayed a heterogeneous population. In contrast, the infants' sequences were less diverse than those of their mothers. In addition, the sequences from the younger infants' peripheral blood mononuclear cell DNA were more homogeneous than the older infants' sequences. All infants' sequences were different but displayed patterns similar to those seen in their mothers. In the mother-infant pair sequences analyzed, a minor genotype or subtype found in the mothers predominated in their infants. The conserved N-linked glycosylation site proximal to the first cysteine of the V3 loop was absent only in one infant's sequence set and in some variants of two other infants' sequences. Furthermore, the HIV-1 sequences of the epidemiologically linked mother-infant pairs were closer than the sequences of epidemiologically unlinked individuals, suggesting that the sequence comparison of mother-infant pairs done in order to identify genetic variants transmitted from mother to infant could be performed even in older infants. There was no evidence for transmission of a major genotype or multiple genotypes from mother to infant. In conclusion, a minor genotype of maternal virus is transmitted to the infants, and this finding could be useful in developing strategies to prevent maternal transmission of HIV-1 by means of perinatal interventions.

Absence of hepatitis B and C viruses in pediatric idiopathic membranoproliferative glomerulonephritis.

The blood-borne hepatitis viruses, hepatitis B virus (HBV) and hepatitis C virus (HCV), have similar epidemiological features. The association of chronic HBV infection and glomerulonephritis is well established, particularly in children. Recent reports have shown an association between HCV infection and glomerulonephritis in adults. In order to assess the role of these hepatotropic viruses in membranoproliferative glomerulonephritis (MPGN) we screened 34 children with idiopathic MPGN for the presence of HBV and HCV infection using highly sensitive polymerase chain reaction techniques for the detection of HBV DNA and HCV RNA. Also, enzyme-linked immunosorbent assays were used to detect the presence of antibody to hepatitis B surface antigen and antibody to HCV. No evidence of HBV or HCV infection was demonstrated in any of the patients. We conclude that HBV and HCV are not significant causes of idiopathic MPGN in children in the United States.

The prevalence of hepatitis C virus (HCV) in infants and children after liver transplantation.

Hepatitis C virus (HCV) is an important cause of liver injury following liver transplantation in adults. We hypothesized that the prevalence of HCV infection in children following liver transplantation would be lower than the prevalence in adults after liver transplantation because HCV-related liver disease leading to liver transplantation in children is low and children require less blood products than adults during transplantation. We therefore performed a cross-sectional study to determine the prevalence of HCV infection in children who had undergone liver transplantation. Serum samples were obtained from 62 of 65 (95.4%) consecutive patients surviving for more than six months after transplantation. Using a second-generation enzyme-linked, immunosorbent assay (ELISA-2) and a second-generation recombinant immunoblot assay (RIBA-II), antibodies to HCV were detected in 5.1% (3 of 59) of the subjects. Using a single-step, polymerase chain reaction (PCR), HCV RNA was detected in 6.2% (4 of 62). All HCV-positive children had undergone liver transplantation before the initiation of routine screening for HCV in blood donors; overall 30 patients were transplanted prior to routine screening of blood products for HCV. The prevalence of HCV in infants and children after liver transplantation in our study is substantially less than the rates reported in adults. This difference may be due, in part, to the lower volume of blood product exposure and to the fact that children, as opposed to adults, rarely have chronic HCV infection as a cause of end-stage liver disease.

Detection of viremia by a one step polymerase chain reaction method in hepatitis C virus infection.

A simple, sensitive, and specific one step polymerase chain reaction (PCR) method for the detection of hepatitis C virus (HCV) RNA in infected patients' serum or plasma samples is described. We performed the one step PCR amplification in combination with the initial step of reverse transcription by using oligonucleotide primers derived from the conserved 5'-untranslated region (5'-UTR) of the HCV genome. By utilizing this strategy, there was no need for nested or second stage PCR amplification. The PCR products (cDNAs) were easily visualized by agarose gel electrophoresis and ethidium bromide staining. Furthermore, the PCR products were characterized by Southern blot hybridization and DNA sequencing. We then used the one step PCR amplification method to detect the presence of HCV RNA in several infected patients' samples with acute and chronic infections. There was a 100% concordance between the results of PCR and second generation recombinant immunoblot assay (RIBA II). In addition, this method was found to be useful in determining viremia in HCV infected patients with indeterminate RIBA II results. The 5'-UTR of the HCV genome, being the most conserved region among different viral isolates, could be amplified by PCR for the detection of HCV RNA, as shown here, as well as serving as a potential target for antiviral agents.

A ribonuclease protection assay for the direct detection and quantitation of hepatitis C virus RNA.

A ribonuclease protection assay (RPA) was developed for the direct detection and quantitation of HCV RNA in infected patients' sera or plasma using HCV [(32)P]RNA from the conserved 5'-untranslated region (5'-UTR) as a probe. We were able to directly detect the presence of HCV RNA by RPA in several infected patients' samples. The viremic status of HCV infected patients with indeterminate recombinant immunoblot assay (RIBA II) was also determined by this assay. Polymerase chain reaction (PCR) was also performed on all these samples and were found to be positive with a concordance of 100% between the results of PCR and RPA. The RPA was able to detect approximately 1 pg of HCV RNA. A limited sequence heterogeneity among HCV isolates was also observed by this assay, suggesting that this may be a faster method of detecting heterogeneous HCV sequences in patients' samples. This simple and specific method could be used to quantitate HCV RNA in order to better determine viremia and follow the course of HCV infection especially when RIBA II results are indeterminate.

Detection of hepatitis C virus-specific antigens in semen from non-A, non-B hepatitis patients.

Semen samples from nine patients clinically diagnosed as having non-A, non-B hepatitis (NANBH) were tested by an ELISA using antibodies raised in rabbits against HCV-specific antigens. The semen from all nine patients had elevated levels of HCV-specific antigen in comparison to semen from five healthy donors. Semen from five of the nine patients had significant levels of the HCV-specific antigen. Seven of the eight serum samples from these patients were reactive with the standard C-100 HCV ELISA. Eight of these nine patients had serum reactive for HCV-specific antibodies in our ELISA using HCV-specific antigens. This more direct evidence for viral presence supports the earlier epidemiological data suggesting that HCV could be transmitted sexually.

Detection of acute hepatitis C virus infection by ELISA using a synthetic peptide comprising a structural epitope.

An enzyme-linked immunosorbent assay (ELISA) was developed by using a synthetic polypeptide (SP) whose sequence was derived from the structural region of hepatitis C virus (HCV). Results of several coded panels of sera obtained from volunteer blood donors and patients with apparent non-A, non-B hepatitis and/or hepatitis B virus used in this ELISA were compared with those of a commercially available first-generation C-100 ELISA (using nonstructural HCV antigens), an experimental second-generation C-200/C-22 ELISA (using both structural and nonstructural HCV antigens), and recombinant immunoblot assays RIBA-I and RIBA-II. In the majority of cases, the results obtained with the HCV-SP ELISA correlated well with those obtained by RIBA-II and C-200/C-22 ELISA. In contrast, many samples that were repeatedly reactive in the C-100 ELISA results were nonreactive with RIBA and HCV-SP ELISA. In addition, HCV-SP detected HCV-specific antibody that appeared within a month of infection and coincided with the earliest increase in alanine aminotransferase. In summary, we have developed an ELISA based on a structural HCV synthetic polypeptide, HCV-SP, that has high specificity and sensitivity and is capable of detecting specific antibodies in the acute phase of HCV infection.

The novel tertiary structure in delta RNA may function as a ribozyme control element.

The viroid-like domain making up the lefthand end of the delta hepatitis genome (Branch et al., 1989) has structural elements whose interactions may be essential for replication. This portion of the genome is highly conserved in primary sequence and contains two well-defined types of structural features: sites capable of self-cleavage, and those forming a UV-sensitive element of local tertiary structure which is very stable and contains non-Watson:Crick bonds that may form a distinctive surface for binding specific proteins. The proximity of the tertiary structure to the genomic self-cleavage site suggests that the photoreactive element may regulate the ribozyme. This element's stability would limit "breathing" in this region of the circular genome, maintaining the ribozyme in the "off" conformation; its tight structure could be relieved by protein binding at the time of replication. We previously mapped a novel local tertiary structure to a highly conserved portion of the viroid genome (Branch et al., 1985). The many additional properties shared by viroids, related infectious circular RNAs of plants, and the delta agent are discussed in a recent article (Branch et al., in press-a).

Riboprobe assay for HDV RNA: a sensitive method for the detection of the HDV genome in clinical serum samples.

We have used a new hybridization assay for the detection of the genome of hepatitis delta virus (HDV) in serum using a strand-specific RNA probe obtained by transcription of a recombinant riboprobe. This assay was tested on a panel of 30 sera from HBsAg carriers with hepatitis delta antigen (HDAg) in the liver. The riboprobe assay detected HDV RNA in the serum of 83% of the patients, while 63% were positive using the DNA hybridization assay. HDAg was detected in 73% of the same sera by immunoblotting. The riboprobe assay was also compared to other assays on serial samples from an experimentally infected chimpanzee. These results demonstrate that the Northern blot assay using the RNA probe is more sensitive than the homologous DNA probe for the detection of HDV in serum and is also more sensitive than the immunoblot assay for HDAg. The riboprobe assay is the most sensitive of currently available methods to measure HD viremia.