Sequencing of hepatitis C virus cDNA with polymerase chain reaction directed sequencing

Interaction between hepatitis C virus core protein and translin protein- a possible molecular mechanism for hepatocellular carcinoma and lymphoma caused by hepatitis C virus

AIM: To investigate the interaction between hepatitis C virus core protein and translin protein and its role in the pathogenensis of hepatocellular carcinoma and lymphoma.

METHODS: With the components of the yeast two hybrid system 3,“ bait” plasmids of HCV core the gene was constructed. After proving that hepatitis C virus core protein could be firmly expressed in AH109 yeast strains, yeast two- hybrid screening was performed by mating AH109 with Y187 that transformed with liver cDNA library plasmids - pACT2 and then plated on quadrople dropout (QDO) medium and then assayed for α-gal activity. Sequencing analysis of the genes of library plasmids in yeast colonies that could grow on QDO with α-gal activity was performed. The interaction between HCV core protein and the protein we obtained from positive colony was further confirmed by repeating yeast two - hybrid analysis and coimmunoprecipitation in vitro.

RESULTS: A gene from a positive colony was the gene of translin, a recombination hotspot binding protein. The interaction between HCV core protein and translin protein could be proved not only in yeast, but also in vitro.

CONCLUSION: The core protein of HCV can interact with translin protein. This can partly explain the molecular mechanism for hepatocellular carcinoma and lymphoma caused by HCV.

Preparation of human single chain Fv antibody against hepatitis C virus E2 protein and its identification in immunohistochemistry

AIM: To screen human single chain Fv antibody (scFv) against hepatitis C virus E2 antigen and identify its application in immunohistochemistry.

METHODS: The phage antibody library was panned by HCV E2 antigen, which was coated in microtiter plate. After five rounds of biopanning, 56 phage clones were identified specific to HCV E2 antigen. The selected scFv clones were digested by Sfi I/Not I and DNA was sequenced. Then it was subcloned into the vector pCANTAB5E for expression as E-tagged soluble scFv. The liver tissue sections from normal person and patients with chronic hepatitis B and chronic hepatitis C were immunostained with HCV E2 scFv antibody.

RESULTS: The data of scFv-E2 DNA digestion and DNA sequencing showed that the scFv gene is composed of 750 bp. ELISA and immunohistochemistry demonstrated that the human single chain Fv antibody against hepatitis C E2 antigen has a specific binding character with hepatitis virus E2 antigen and paraffin-embedded tissue, but did not react with liver tissues from healthy persons or patients with chronic hepatitis B.

CONCLUSION: We have successfully screened and identified HCV E2 scFv and the scFv could be used in the immunostaining of liver tissue sections from patients with chronic hepatitis C.

mIL-2R, T cell subsets and hepatitis C

AIM: To study the levels of membrane interleukin-2 receptor (mIL-2R) and T cell subsets in peripheral blood mononuclear cells (PBMC) from patients with hepatitis C and their role in the pathogenesis of hepatitis C.

METHODS: The levels of mIL-2R and T cells subsets in PBMC were detected by biotin- streptatividin (BSA) technique before and after stimulation with PHA in 203 patients with hepatitis C with HCV-RNA (+), anti-HCV (+), anti-HCV (-).

RESULTS: The total expressive levels of mIL-2R before and after stimulation with PHA (0.03 ± 0.01, 0.03 ± 0.02, 0.04 ± 0.02, 0.36 ± 0.03), and T cell subsets in PBMC (0.62 ± 0.06, 0.37 ± 0.05, 0.35 ± 0.07) were all lower in patients with hepatitis C than those in normal controls (0.66 ± 0.07, 0.41 ± 0.06, 0.31 ± 0.05, P < 0.01). Among the patients, the levels of mIL-2R were lower in silence than those in situation of PHA inducting (P < 0.01). However, the levels of mIL-2R were similar in acute hepatitis C to that in chronic hepatitis C (P > 0.05). The levels of CD₃⁺, CD₄⁺, CD₄⁺/CD₈⁺ were lower and CD₈⁺ was higher in patients with acute and chronic hepatitis C with anti-HCV (+) than those in normal controls (0.62 ± 0.06, 0.37 ± 0.05, 0.35 ± 0.07, 1.18 ± 0.30, 0.61 ± 0.07, 0.37 ± 0.05, 1.39 ± 0.33, 0.31 ± 0.05, P < 0.05 - P < 0.01).

CONCLUSION: The cellular immunity is obviously changed in patients with hepatitis C. The levels of mIL-2R and activation of T cells are closely associated with chronicity of hepatitis C.

Methodologic research on TIMP-1, TIMP-2 detection as a new diagnostic index for hepatic fibrosis and its significance

AIM

To set up a new method to detect tissue inhibitors of metalloproteinase-1 and -2(TIMP-1 and TIMP-2) in sera of patients with hepatic cirrhosis, and to investigate the expression and location of TIMP-1 and TIMP-2 in liver tissue of patients with hepatic cirrhosis, and the correlation between TIMPs in liver and those in sera so as to discuss whether TIMPs can be used as a diagnosis index of hepatic fibrosis.

METHODS

The monoclonal antibodies (McAbs) of TIMP-1 and TIMP-2 were used to sensitize erythrocytes, and solid-phase absorption to sensitized erythrocytes (SPASE) was used to detect TIMP-1 and TIMP-2 in the sera of patients with hepatic cirrhosis. Meanwhile, with the method of in situ hybridization and immunohistochemistry, we studied the mRNA expression and antigen location of TIMP-1 and TIMP-2 in the livers of 40 hepatic cirrhosis patients with pathologic diagnosis.

RESULTS

With SPASE, they were 16.4% higher in the acute hepatitis group, 33.3% higher in the chronic hepatitis group, and the positive rates were 73.6% and 61.2% respectively in sera of hepatic cirrhosis patients, which were remarkably higher than those in chronic hepatitis and acute hepatitis group (P<0.001). In 40 samples of hepatic cirrhosis tissues, all of them showed positive expression of TIMP-1 and TIMP-2 mRNA detected with immunohistochemistry or in situ hybridization (positive rate was 100%). Expression of TIMPs in different degrees could be found in liver tissue with cirrhosis. TIMPs were located in cytoplasm of liver cells of patients with hepatic cirrhosis. There was a significant correlation between serum TIMPs level and liver TIMPs level.

CONCLUSION

SPASE is a useful method to detect the TIMP-1 and TIMP-2 in sera of patients with hepatic cirrhosis, and TIMP-1 and TIMP-2 can be considered as a useful diagnostic index of hepatic fibrosis, especially TIMP-1.

Hepatitis C virus infection of human hepatoma cell line 7721 in vitro

AIM: To establish a cell culture system with long-term replication of hepatitis C virus in vitro.

METHODS: Human hepatoma cell line 7721 was tested for its susceptibility to HCV by incubating with a serum from a patient with chronic hepatitis C. Cells and supernatant were harvested at various phases during the culturing periods. The presence of HCV RNA, the expression of HCV antigens in cells and/or supernatant were examined by RT-PCR, in situ hybridization and immunohisto-chemistry respectively.

RESULTS: The intracellular HCV RNA was first detected on d2 after infection and then could be intermittently detected in both cells and supernatant over a period of at least three months. The expression of HCV NS₃, CP₁₀ antigens could be observed in cells. The fresh cells could be infected by supernatant from cultured infected cells and the transmission of viral genome from HCV-infected 7721 cells to PBMCs was also observed.

CONCLUSION: The hepatoma line 7721 is not only susceptible to HCV but also supports its long-term replication in vitro.

Hepatitis G virus infection in patients with chronic non-A–E hepatitis

AIM: To elucidate the role of hepatitis G virus (HGV) infection in chronic non-A–E hepatitis and sequence the partial NS5 genome of HGV isolated from the serum of a Chinese patient with chronic non-A–E hepatitis

METHODS: Serum samples of patients with chronic non-A–E hepatitis were collected and total nucleic acids were extracted and subjected to reverse transcriptase-nested-polymerase chain reaction (RT-nested-PCR) using primers from the putative NS5 region of HGV genome. Then, 994bp cDNA was prepared from the positive serum, purified with electrophoresis of polyacrylamide gels, and directly sequenced using the dideoxy-mediated chain-termination method.

RESULTS: HGV-RNA was detected in 1 of the 35 patients with chronic non-A–E hepatitis. Compared with the 2 HGV isolates (PNF2161 and R10291) obtained from American patients, the HGV NS5 gene of this Beijing isolate (HG-G) showed homology of 88.0% and 89.2% respectively. On the other hand, in comparison with the West African isolate (GBV-C), the Beijing isolate showed homology of 93.5%. The patient showed persistent increase of alanine transaminase, but normal levels were achieved after interferon therapy with persistent positive HGV RNA.

CONCLUSION: HGV is one of the causes of chronic non-A–E hepatitis, but it may not be a very important cause. The nucleotide sequence of partial NS5 gene of HG-G was found to be highly homologous to the West Africa isolate.