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Q L Choo

Publications and source records attributed to Q L Choo.

At least 37 records · Page 2Linked to original sources
PubMed1992

Characterization of the hepatitis C virus E2/NS1 gene product expressed in mammalian cells.

Truncated and full-length versions of the hepatitis C virus protein domain encoding a presumptive envelope glycoprotein designated E2/NS1 were stably expressed in CHO cell lines. Characterization of the processing events involved in the maturation of E2/NS1 revealed that a high-mannose form resident in the endoplasmic reticulum was the most abundant form detected intracellularly. The ionophore carboxyl cyanide m-chlorophenyl-hydrazone was used to show that the E2/NS1 glycoprotein resided in the endoplasmic reticulum. The full-length form of E2/NS1 appeared to be cell-associated and could not be detected as a secreted product. C-terminal truncated molecules could be detected in the extracellular media as fully processed glycoproteins containing terminal sialic acid additions. These truncated glycoproteins are predicted to be biologically relevant targets of the host immune response and are therefore potential subunit vaccine candidates.

Animals↗
PubMed1992

Early antihepatitis C virus response with second-generation C200/C22 ELISA.

Detection of early antibody to hepatitis C virus (HCV) by a new second-generation C200/C22 anti-HCV enzyme-linked immunosorbent assay (ELISA) and a four-antigen recombinant immunoblot assay (4-RIBA) was compared with the first-generation anti-HCV C100 ELISA using sequential serum samples of 9 recipients who were infected with HCV, as detected by polymerase chain reaction after transfusion of blood products. Within 26 weeks after transfusion, 9/9 (100%) recipients seroconverted with C200/22 ELISA, and 6/9 (67%) seroconverted with C100 ELISA. Compared with C100 ELISA, C200/C22 ELISA seroconversion occurred simultaneously in 3 cases, 5-6 weeks earlier in 3 other cases, and 20 weeks earlier in 1 case. Seven of 9 (78%) recipients became positive, and 2/9 (22%) became indeterminate with 4-RIBA. In 8 cases with clinical posttransfusion hepatitis non-A, non-B (PTH-NANB), anti-HCV C200/C22 ELISA seroconversion occurred 2-17 (mean 6) weeks after the onset of hepatitis. In 6 cases of PTH-NANB, anti-HCV C100 ELISA seroconversion occurred 2-26 (mean 9) weeks after the onset of hepatitis. It is concluded that the second-generation C200/C22 ELISA is more sensitive than the C100 ELISA for the detection of antibody during early HCV infection. Indeterminate 4-RIBA results are found in the early phase of HCV infection.

Enzyme-Linked Immunosorbent Assay↗
PubMed1992

Enhanced sensitivity of a second generation ELISA for antibody to hepatitis C virus.

A second generation ELISA for combined detection of antibodies to three hepatitis C virus (HCV) recombinant proteins, i.e. C100, C33c and core, was compared with a first generation anti-HCV ELISA in which only antibodies to C100 are detected. The results of the ELISAs were evaluated in 225 haemophilia patients (panel A) and 44 patients with non-A, non-B (NANB) hepatitis (panel B). HCV infection was established by cDNA-polymerase chain reaction (PCR) (in panel B only) and by studying the anti-HCV reaction patterns in 4 separate ELISAs for detection of antibodies to the recombinant proteins C100, C33c, core and a combination of two synthetic peptides sp67/65 derived from the C100 region. The sensitivity for the detection of HCV infection had increased from 0.92[95% confidence interval (CI): 0.87-0.95] to 1.00 (95% CI: 0.89-1.00) in haemophiliacs and from 0.84 (95% CI: 0.66-0.95) to 1.00 (95% CI: 0.89-1.00) in NANB hepatitis patients when the second generation ELISA was used instead of the first generation ELISA. Concurrently the chance of a false negative result was reduced in panel A and B from 0.37 to 0 and from 0.28 to 0, respectively. Analysis of anti-HCV reaction patterns revealed that 172 of 206 (83.5%) anti-HCV ELISA-reactive haemophilia patients had antibodies to all 4 antigens tested. In the NANB hepatitis patients 18 of 31 (58.1%) anti-HCV ELISA-reactive subjects reacted with 4 antigens. In the PCR tested panel of NANB hepatitis patients 2 subjects who showed antibody reactivity to only one antigen and 5 patients with reactivity to 2 antigens were PCR-positive.(ABSTRACT TRUNCATED AT 250 WORDS)

Antigens, Viral↗
PubMed1991

Genetic organization and diversity of the hepatitis C virus.

The nucleotide sequence of the RNA genome of the human hepatitis C virus (HCV) has been determined from overlapping cDNA clones. The sequence (9379 nucleotides) has a single large open reading frame that could encode a viral polyprotein precursor of 3011 amino acids. While there as little overall amino acid and nucleotide sequence homology with other viruses, the 5' HCV nucleotide sequence upstream of this large open reading frame has substantial similarity to the 5' termini of pestiviral genomes. The polyprotein also has significant sequence similarity to helicases encoded by animal pestiviruses, plant potyviruses, and human flaviviruses, and it contains sequence motifs widely conserved among viral replicases and trypsin-like proteases. A basic, presumed nucleocapsid domain is located at the N terminus upstream of a region containing numerous potential N-linked glycosylation sites. These HCV domains are located in the same relative position as observed in the pestiviruses and flaviviruses and the hydrophobic profiles of all three viral polyproteins are similar. These combined data indicate that HCV is an unusual virus that is most related to the pestiviruses. Significant genome diversity is apparent within the putative 5' structural gene region of different HCV isolates, suggesting the presence of closely related but distinct viral genotypes.

Amino Acid Sequence↗
PubMed1991

Characterization of the terminal regions of hepatitis C viral RNA: identification of conserved sequences in the 5' untranslated region and poly(A) tails at the 3' end.

We have determined the nucleotide sequence at the extreme 5' and 3' termini of the hepatitis C virus (HCV) genome. Our analyses of these sequences show (i) the nucleotide sequence in the 5' untranslated region is highly conserved among HCV isolates of widely varying geographical origin, (ii) within this region, there are blocks of nucleotide sequence homology with pestiviruses but not with other viruses, (iii) the relative position of short open reading frames present in the same region of the HCV genome is similar to that of the pestiviral genome, (iv) RNAs truncated at the 5' and 3' ends are found, but the origin and functions of these RNAs are unknown, and (v) poly(A) tails appear to be present on 3' subgenomic RNAs. These data differentiate HCV from the flaviviruses and indicate a closer evolutionary relationship of HCV with the pestiviruses. However, HCV also appears to be substantially different from other known pestiviruses. These data are consistent with the assignment of HCV to a separate viral genus.

Amino Acid Sequence↗
PubMed1991

A high prevalence of antibody to the hepatitis C virus in patients with hepatocellular carcinoma in Japan.

In Japan, hepatocellular carcinoma (HCC) is one of the most prevalent cancers, with a reported fatality rate showing a consistent and significant increase in the last decade. At most, only 25% of HCC cases are positive for the hepatitis B surface antigen (HBsAg). To investigate a potential role for hepatitis C virus (HCV) in the development of HCC, sera from 105 HBsAg-negative HCC patients were collected from five districts of Japan and assayed for antibody to HCV antigen (HCVAb). A large number of these patients (76.2%) were found to be positive for the HCVAb in comparison with the reported prevalence in sera from blood donors (1.1%). A history of blood transfusion was found in 39.6% of the cases positive for HCVAb, which was significantly different to the lower rate (4.7%) observed in HCC patients who were both positive for HBsAg and negative for HCVAb (P less than 0.001).

Blood Transfusion↗
PubMed1991

Hepatitis C virus antibodies in acute icteric and chronic non-A, non-B hepatitis.

Hepatitis C virus antibodies were measured in 213 patients who had acute (n = 122) and chronic (n = 91) non-A, non-B hepatitis. In acute infection, anti-hepatitis C virus was detected in 61% of IV drug abusers, in 33% of patients with transfusion-associated hepatitis, and in 22% of patients with sporadic infections (P less than 0.0005, drug abusers vs. sporadic). Mean time to seroconversion was 11.6 weeks (range, 1-80 weeks). Anti-hepatitis C virus was more common in chronic infection (P less than 0.001) and was more often detected in IV drug users (89%; P less than 0.0001) and after transfusion (71%; P less than 0.005) compared with chronic sporadic infection (27%). Antibody persisted for up to 8 years. Six chronic case patients (8.3%) later lost antibody (mean, 24 months; range, 12-48 months).

Acute Disease↗
PubMed1991

Variable and hypervariable domains are found in the regions of HCV corresponding to the flavivirus envelope and NS1 proteins and the pestivirus envelope glycoproteins.

Based on the flavi- and pestivirus model of genome organization for the hepatitis C virus (HCV) (1-5), the nucleotide and deduced amino acid sequences of the putative envelope (E1) and the junction between the E1 and NS1/envelope 2 (E2) region from six different human isolates of HCV were compared with the nucleotide and predicted amino acid sequences of the prototype hepatitis C virus (HCV-1) (5). The overall percentage of nucleotide and amino acid changes among all six isolates, including HCV-1, from nucleotide 713 to 1630 (amino acid 129 to 437) was between 3 and 7%, which is comparable to that seen in some flaviviruses (6-8). An analysis of the number of nucleotide and deduced amino acid sequence changes among all six isolates and HCV-1 revealed a moderately variable domain of approximately 40 amino acids in the E1 region and a hypervariable domain (Region V) of approximately 28 amino acids, which is directly downstream from a putative signal peptide sequence, in the junction between E1 and NS1/E2. A similar hypervariable domain is not found in the C-terminus of the envelope polypeptide or in the N-terminus of the NS1 polypeptide domain of the flaviviruses. These findings suggest that the mature NS1/E2 polypeptide starts about amino acid 380 and that the NS1/E2 domain may correspond to a second envelope glycoprotein as in the case of the pestivirus. The observed heterogeneity in the putative structural proteins of HCV may have important ramifications for future vaccine development.

Amino Acid Sequence↗
PubMed1991

Hepatitis C virus replication in 'autoimmune' chronic hepatitis.

Both high and low anti-hepatitis C virus antibody (anti-HCV) prevalence has been reported in autoimmune chronic active hepatitis. Therefore, we studied 15 consecutive HBsAg-negative, ELISA anti-HCV-positive, autoantibody-positive patients with biopsy proven chronic active hepatitis in order to confirm ELISA specificity by immunoblot test (RIBA-HCV), and to evaluate HCV replication by serum HCV-RNA. Nine patients were anti-nuclear, three type 1 anti-liver-kidney microsomal and three anti-smooth muscle antibody positive. None had associated autoimmune disease. All cases showed mild clinical disease and only moderate necroinflammatory activity. Response to prednisone was poor. RIBA-HCV confirmed ELISA results in all patients. HCV-RNA was found in the serum from 10 patients. Institution of alpha-interferon treatment in three steroid non-responsive patients was followed by prompt normalization of transaminases. Thus, a subgroup of autoantibody-positive chronic active hepatitis can be recognized as HCV-related and should be clinically and etiologically distinguished from autoimmune chronic active hepatitis. Trials of alpha-interferon treatment are worthwhile in this condition.

Autoantibodies↗
PubMed1991

Risk factors in hepatitis C virus-infected blood donors.

Risk factors of parenteral and nonparenteral exposure to hepatitis C virus (HCV) infection were studied in 125 blood donors in The Netherlands who were positive for anti-HCV on enzyme-linked immunosorbent assay (ELISA). Risk factors were related to confirmatory test results of four-antigen recombinant immunoblot assay (4-RIBA) and polymerase chain reaction (PCR) of the HCV 5' untranslated region. Twelve (10%) of the 125 anti-HCV C100 ELISA-positive blood donors were 4-RIBA positive. Eleven (92%) of 12 4-RIBA-positive blood donors were PCR positive, and all 113 remaining 4-RIBA-negative or -indeterminate donors were PCR negative. Eleven (92%) of 12 4-RIBA-positive blood donors had a risk factor of parenteral exposure, as compared to 17 (15%) of 113 4-RIBA-negative or -indeterminate donors. The prevalence of confirmed HCV infection among Amsterdam blood donors is calculated at 0.04 percent; parenteral exposure appears to be the major risk factor for HCV infection.

Blood Donors↗
PubMed1991

Antibody to the hepatitis C virus in acute hepatitis and chronic liver diseases in Japan.

In a 6-month follow-up study of acute hepatitis in Japan, 31 out of 41 (75.6%) cases of post-transfusion non-A and non-B hepatitis (NANB-PTH) and 14 out of 40 (35.0%) cases of sporadic non-A non-B hepatitis (NANB-SPO) were found to be positive for antibody to the hepatitis C virus (HCVAb). After 12 months of follow-up, 30 cases (81.1%) became chronic among 37 HCVAb positive acute NANB hepatitis cases. This figure shows a significantly higher rate of chronicity as compared with HCVAb negative acute NANB hepatitis. The prevalences of HCVAb in hepatitis B surface antigen (HBsAg) negative cases of chronic hepatitis and liver cirrhosis were 76.3% (200/262) and 66.7% (106/159), respectively, which were significantly different from the values of 5.1% (13/255) and 10.6% (13/123) observed in HBsAg positive cases. Of chronic liver disease cases positive for HCVAb, 45.8% (152/332) had a history of blood transfusion, in contrast to the value of 3.7% (13/352) observed in HBsAg positive cases of chronic liver disease that were negative for HCVAb.

Enzyme-Linked Immunosorbent Assay↗
PubMed1991

Use of a signature nucleotide sequence of hepatitis C virus for detection of viral RNA in human serum and plasma.

The nucleic acid sequence of the putative 5'-untranslated (5PUT) region of hepatitis C virus (HCV), determined for samples obtained from a variety of geographic origins, was found to be over 98% conserved among all isolates. On the basis of this signature sequence for HCV, a viral RNA assay was developed by using cDNA synthesis with reverse transcriptase, followed by polymerase chain reaction (PCR). The new assay was compared with the Ortho-Chiron C100-3 HCV enzyme-linked immunosorbent assay to research radioimmunoassays for antibodies to the C33c and C22 HCV antigens and to the first reported set of HCV PCR primers designed from the NS3 domain. Plasma samples from 16 Japanese patients with non-A, non-B hepatitis (NANBH) and 16 immunoassay-positive blood donors from the United States were investigated. The 5PUT PCR primers were found to be superior to the NS3 primers in sensitivity and specificity (15 of 25 versus 3 of 25 of the C100 enzyme-linked immunosorbent assay-positive samples, respectively). Samples from two C100-negative patients with acute NANBH were found to react with the 5PUT primers but not with the NS3 primers. Also, two of three patients with chronic NANBH converted from reverse transcriptase PCR positive to negative after interferon treatment. Although the clinical significance of the presence or absence of HCV RNA in samples from patients is not fully understood, the use of probes and primers from the 5PUT region (as opposed to primers from other segments) should not lead to false-negative results due to nucleic acid sequence variations in viral isolates.

Base Sequence↗
PubMed1991

Role of hepatitis C virus in non-B chronic liver disease.

To assess the contribution of the recently identified hepatitis C virus to chronic liver diseases of unknown cause and chronic hepatitis attributed by exclusion to non-A, non-B hepatitis, we tested for antibody to hepatitis C in hepatitis B surface antigen-negative patients with a spectrum of chronic liver diseases. Antibody to hepatitis C virus, a marker of hepatitis C infection, was detected with a first-generation radioimmunoassay at the following frequencies in the following patient groups: 69% of transfusion-associated non-A, non-B hepatitis; 53% of non-transfusion-associated non-A, non-B hepatitis; 26% of hepatitis B surface antigen-negative hepatocellular carcinoma; 8% of cryptogenic cirrhosis; 5% to 7% of autoimmune chronic liver diseases; 19% of patients with miscellaneous types of chronic liver disease; and 0.67% of healthy controls. Among non-transfusion-associated cases, 81% with a history of intravenous drug use but only 18% with occupational exposure as health workers had antibody to hepatitis C virus. Among cases of hepatocellular carcinoma, 63% of Japanese patients but only 11% of American patients had evidence of hepatitis C infection. Comparison in a subgroup of 79 serum samples of a second-generation radioimmunoassay with the first-generation assay demonstrated a 12% increase in antibody frequency from 30% to 42%. We conclude that hepatitis C plays a substantial role in transfusion-associated and non-transfusion-associated non-A, non-B hepatitis as well as in hepatocellular carcinoma, especially in Japan, a limited role in cryptogenic cirrhosis, and essentially no role in autoimmune chronic liver diseases. Application of more sensitive immunoassays will increase the frequency of antibody seropositivity in all subgroups, but relative distinctions among risk groups are likely to remain.

Asian↗
PubMed1991

The role of chronic viral hepatitis in hepatocellular carcinoma in the United States.

Although hepatocellular carcinoma is a relatively uncommon tumor in the United States, it is quite common in sub-Saharan Africa and the Far East, where most cases are associated with infection with the hepatitis B virus. We have studied 99 American patients with hepatocellular carcinoma for evidence of hepatitis B or hepatitis C viral infection and compared these findings to those in a group of matched controls with other cancers. The two groups differed in proportion, with hepatitis B surface antigen in serum being significantly higher in patients with hepatocellular carcinoma (7% vs. 0%, p = 0.009). Antibody to hepatitis C virus was also found more frequently in patients with hepatocellular carcinoma (13% vs. 2%, p = 0.002). The relative risk for hepatocellular carcinoma in hepatitis B surface antigen-positive patients was calculated to be 17.3 and for antibody to hepatitis C virus to be 7.3. The attributable fraction of cases related to the hepatitis B surface antigen carrier state was 6.7% and for patients infected with the hepatitis C virus was 11.4%. Approximately three quarters of cases of hepatocellular carcinoma did not have evidence of either hepatitis C or hepatitis B virus infection. These findings provide strong evidence that hepatitis C virus infection is associated with the development of hepatocellular carcinoma, and in the United States may even play a more important role than the hepatitis B virus.

Adolescent↗