In situ detection of mutated hepatitis B virus in microdissected, formalin-fixed liver tissues from patients with chronic hepatitis B

Hepatitis B virus mutations associated with in situ expression of hepatitis B core antigen, viral load and prognosis in chronic hepatitis B patients

In this retrospective study, we investigated the prevalence and significance of mutations in part of the hepatitis B virus (HBV) x gene, and tried to clarify their relationship with clinicopathological or histopathological characteristics and prognosis in patients with chronic hepatitis B (CHB). A total of 83 consecutive CHB patients (1986-1994) were chosen for the present study. Sequence analysis was performed using polymerase chain reaction (PCR) and the direct sequencing method. The histological activity index was described using Scheuer scores. Two-step immunohistochemical staining showed the expression of viral antigens in situ. Tissue HBV DNA levels were determined by fluorescence quantitative real-time PCR. For the prognostic study, all the patients were followed up using clinical and laboratory data. Mutation at nt1726-1730 correlated significantly with decreased expression of HBcAg in situ (P = 0.006) and with lower HBV DNA levels in the liver (P = 0.004). In particular, the CTGAC mutation showed the strongest decrease of the viral load (P = 0.007). By contrast, nt1762/1764 mutation correlated with increased HBcAg (P = 0.005) and higher HBV DNA levels (P = 0.006). The mutants with the wild-type of nt1726-1730 or nt1762/1764 mutation were more prevalent in hepatocellular carcinoma (HCC) patients than in CHB patients. Although the mutations did not correlate with cirrhosis, the frequency of nt1762/1764 mutation in patients with hepatocarcinogenesis was significantly higher than in those without hepatocarcinogenesis (P = 0.011). Mutations at nt1726-1730 and nt1762/1764 are associated with in situ expression of HBcAg and viral load. Higher HBV DNA levels in the liver may be associated with hepatocarcinogenesis. Mutation at nt1762/1764 remarkably increases the risk of hepatocarcinogenesis.

Association of p16INK4A hypermethylation with hepatitis B virus X protein expression in the early stage of HBV-associated hepatocarcinogenesis

The aim of the present study was to explore the relationship between methylation status of the p16(INK4A) promoter and some HBV-related factors, and the role of these factors in p16(INK4A) hypermethylation and hepatocellular carcinoma (HCC) progression. Twenty-three cases of surgically resected HBV-associated HCC and 25 fine-needle aspiration biopsy cases of chronic hepatitis B (CHB) were studied. The methylation status of the p16(INK4A) promoter was determined by methylation-specific polymerase chain reaction (PCR). Two-step immunohistochemical staining showed the expression of viral antigens in situ. Tissue HBV-DNA levels were determined by fluorescence quantitative real-time PCR. PCR and the direct sequencing method were used for mutation analysis. In peritumoral tissues (P = 0.025) and CHB samples (P = 0.029), the expression of hepatitis B virus X protein (HBx) was higher in methylated groups of p16(INK4A) promoter than in unmethylated groups. Other HBV factors including hepatitis B surface antigen and hepatitis B core antigen, tissue HBV-DNA levels and HBV x gene mutations had no relation to the methylation status of p16(INK4A) promoter. The data indicate that p16(INK4A) promoter hypermethylation correlated closely with higher HBx expression in the precancerous lesions, suggesting that HBx may play an important role in the early stage of HBV-associated hepatocarcinogenesis via induction of hypermethylation of p16(INK4A) promoter.

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Study on definition of pre-x region in hepatitis B virus genome

AIM

To identify the pre-X gene in HBV strains of Chinese patients.

METHODS

The whole HBV genome was amplified by long-distance and accurate polymerase chain reaction (LA-PCR) method from the serum of 2 patients with chronic HBV infection, and then the PCR products were cloned into pGEM Teasy vectors. Five clones of HBV genome were sequenced. Sequences of our finding were compared with other HBV genome sequence deposited in GenBank.

RESULTS

Pre-X region was found in the HBV genome of these 5 clones, just upstream to the X gene. The pre-X gene is 168 bp long, and can be translated with X gene in frame. The amino acids sequence of pre-X gene was as the following: MGLGYWPSPPAWNLCGSSADPYCGTPSSLFCS QPVWSETYRNRQLCCPLSQIHLLS.

CONCLUSION

Pre-X region may be a serotype-specific coding gene.

Study on definition of pre-pre-S region in hepatitis B virus genome

AIM

To investigate the new open reading frame (ORF) in hepatitis B virus (HBV) genome.

METHODS

The whole HBV genome was amplified by long-distance and accurate polymerase chain reaction (LA-PCR) method from the serum of 2 patients with chronic HBV infection, and then the PCR products were ligased into pGEM Teasy vectors. Five clones of HBV genome were sequenced. Sequences of our finding were compared with other HBV genome sequence deposited in GenBank.

RESULTS

A new ORF was found in HBV genome, just before Pre-S1 region. It was defined as pre-pre-S region. The pre-pre-S ORF was deduced to be translated with Pre-S1, Pre-S2 and S gene in frame. Its amino acids sequence was as the following: MQLIITSKLGIIYILCGRLVFYIREKLHAV PHFVGHHILGNKSYS. There was a TA-rich region before the ATG of pre-pre-S ORF, indicating a possible promoter for its transcription.

CONCLUSION

There is a new ORF pre-pre-S located upstream to pre-S1 region.

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The effects of hepatitis B virus core promoter mutations on hepatitis B core antigen distribution in hepatocytes as detected by laser-assisted microdissection

BACKGROUND/AIMS

The severity of liver damage in patients with chronic hepatitis B is dependent on several factors such as subcellular localization of hepatitis B core antigen (HBcAg) and mutation of hepatitis B virus (HBV) DNA. Here we studied the interrelationship between these two factors both in situ and in vitro.

METHODS

Hepatocytes from liver biopsies showing expression of HBcAg only in the cytoplasm (n=6), only in the nucleus (n=4) and in both cytoplasms or nucleus of different hepatocytes (n=5) were picked up by laser-assisted microdissection and were checked for nucleotide sequences of core promoter region of HBV DNA. HepG2 and Huh7 cell lines transfected with wild and mutant HBV DNA were checked for localization of HBcAg.

RESULTS

The frequencies of core promoter mutations at nucleotide (nt) 1762 and nt 1764 was significantly higher in hepatocytes with cytoplasmic expression of HBcAg compared to that of nuclear expression of HBcAg (P<0.05). Cytoplasmic expression of HBcAg was observed more frequently in HepG2 and Huh7 cells transfected with HBV mutant type (nt 1762 and 1764) than HBV wild type (P<0.05).

CONCLUSIONS

Cytoplasmic localization of HBcAg was associated with HBV DNA mutations at nt 1762 and 1764.

Influence of RNA titre and amino acid changes in the NS5A region of GB virus c/hepatitis G virus on the effectiveness of interferon therapy

BACKGROUND

A relationship between the pretreatment RNA titre of GB virus C/hepatitis G virus (GBV-C/HGV) and the effectiveness of interferon (IFN) therapy has been reported previously. However, the influence of changes in the amino acid sequence of the NS5A region of GBV-C/HGV on the effectiveness of IFN therapy has not been examined, although this influence has been explored in patients with chronic hepatitis caused by hepatitis C virus. We examined the relationship between changes in the amino-acid sequence of the NS5A region and the effectiveness of IFN therapy.

METHODS

The subjects were 10 patients with chronic hepatitis C coinfected with GBV-C/HGV and treated with IFN. The pretreatment level of GBV-C/HGV-RNA (copies/mL) in their sera was measured by real-time detection polymerase chain reaction (PCR) assay. At 6 months after cessation of therapy, four of 10 patients had become negative for GBV-C/HGV-RNA (CR, complete response) and six patients were still positive for GBV-C/HGV-RNA (NR, non-response). We determined the nucleotide sequence of the NS5A region (amino acid residues 1865-2279; NS5A1865-2279) of pretreatment GBVC/HGV-RNA by direct sequencing.

RESULTS

The pretreatment GBV-C/HGV-RNA level of CR patients (7.8 x 10(4) - 6.2 x 10(5), mean 3.30 x 10(5)) was significantly lower than that of NR patients (6.3 x 10(7) - 7.2 x 10(8), mean 3.55 x 10(8); P< 0.01). The number of amino acid substitutions in NS5A1865-2279 was five to seven (mean 5.8 +/- 1.0) in CR patients, and four to eight (mean 6.8 +/- 1.6) in NR patients, a difference that is not significant. Moreover, there were no amino acid substitutions or sites of substitution in NS5A1865-2279 that were specific to either group.

CONCLUSIONS

The effectiveness of IFN therapy for GBV-C/HGV is strongly related to the pretreatment GBV-C/HGV-RNA level, but is not related to changes in NS5A1865-2279.