e抗原陽性慢性B型肝炎患者接受干安能治療結束後，precore/basal core promoter 基因突變和e抗原持久陰轉之相關性研究
Relationship between precore/basal core promoter gene mutant and sustained HBeAg seroconversion in chronic hepatitis B patient with lamivudine therapy
Date Issued
2006
Date
2006
Author(s)
Chen, Guann-Jou
DOI
zh-TW
Abstract
Background：Hepatitis B virus (HBV) infection is a major cause of acute and chronic liver disease worldwide, persistent hepatitis B virus infection is closely associated with the development of cirrhosis and hepatocellular carcinoma in Taiwan. Learning from nature history of hepatitis B infection, seroconvesion from HBeAg to anti-HBe usually indicates lower viral loads, resolved hepatitis activity and improved long-term outcome. Lamivudine is the first nucleoside analogue for the treatment of chronic hepatitis B, which has been shown to increase hepatitis B e antigen（HBeAg） seroconversion and reduce progression of hepatic fibrosis. Nevertheless, the relapse rate is high after cessation of lamivudine therapy unless HBeAg seroconversion occurs. Most of the published studies have shown that full HBeAg seroconversion response was durable in Western patients. However, it was not durable in Oriental countries, such as Korea and Taiwan. Hepatitis B e antigen (HBeAg) and an antibody（anti-HBe）are closely related to the level of hepatitis B virus replication and thus frequently used in assessing the activity of liver disease and monitoring the response to antiviral therapy.Therefore, it is important to identify factors associated with the development of HBeAg seroconversion in patients with HBeAg-positive chronic hepatitis B. The molecular basis of HBeAg is only partly clarified. From the viral replication’s point of view, when the precore region and core gene in HBV DNA are transcribed and translated, HBeAg is produced and secreted into the circulation. A point mutation from G to A at nucleotide (nt) 1896（A1896）converts codon 28 in the precore region from TGG for tryptophan to TAG for a stop codon and aborts the synthesis of HBeAg at the translation level. Likewise, a double mutation in the basal core promoter（BCP）changing nt 1762 and 1764 from A to T and G to A（T1762/A1764）,respectively, reduces the production of HBeAg by down-regulating the transcription of precore mRNAs. Convincing lines of evidence have indicated a close association of HBeAg seroconversion with the appearance of precore and BCP mutations as well as a decrease in the serum viral load. Another study revealed that precore 1896 wild vs. mutant strains ratio also played a role in the seroconversion of HBeAg and severity of disease activity. Liu et al reported that non-sustained HBeAg seroconversion might be due to the lack of sustained precore and BCP mutations after seroconversion. Lin et al reported that lamivudine therapy might result in the rapid selection of basal core promoter mutation of hepatitis B, but this mutation might revert to wild type gradually after cessation of therapy. The results of the present study have shown the genotype, age, and additional lamivudine therapy after HBeAg seroconversion are independent factors of sustained response to lamivudine therapy. However, the role of precore and BCP mutations in the development of sustained HBeAg seroconversion, either spontaneous or after lamivudine therapy remained unknown.
Aim：Are the precore and/or BCP mutations of hepatitis B virus,either spontaneous or after lamivudine therapy associated with sustained HBeAg seroconversion？Hypothesis one is that the precore and/or BCP mutations of hepatitis B virus could determine the appearance of anti-HBe in the spontaneous HBeAg seroconversion. Hypothesis two is that the precore and/or BCP mutations of hepatitis B at the time of HBeAg loss or end of therapy in patient serum could determine the sustained e seroconversion after lamivudine treatment.
Methods：We studied the factors in 25 patients with sustained HBeAg seroconversion as well as appearance of anti-HBe and 7 patients with sustained loss of HBeAg in the first part. We determined viral factors and status of precore and BCP mutations in the serum obtained 1 year before, 6 months before, 3 months before, at the time of , 6 months after and 1 year after HBeAg seroconversion or HBeAg loss. Secondly, both of host and viral factors as well as the drug factors were compared between 34 patients with sustained HBeAg seroconversion and 11 patients whose response was no sustained. All of patients with HBeAg positive and ALT level more than 5 times of normal upper limit without hepatitis C; hepatitis D and HIV were enrolled before therapy. All of them received a mean period 15 months（range, 6-35months）lamivudine therapy and had achieved complete responses（HBeAg seroconversion plus HBV DNA seroclearance by hybrid capture assay and normal alanine aminotransferase）and were followed-up for 6 months after end point of therapy. Stepwise logistic regression model was used to estimate the sustained response on the presence of the following variables: age; gender; genotype; pretherapy maximal ALT; the status of cirrhosis; time to HBeAg seroconversion; additional lamivudine treatment after HBeAg seroconversion; total duration of treatment; as well as HBV DNA level and status of precore mutation; basal core promoter mutation at the different time points which are of pretherapy, e antigen loss and end of therapy. The precore and basal core promoter regions were amplified and directly sequenced by polymerase chain reaction（PCR）-based assays. Besides, viral titer was checked by LightCycler real time PCR amplification machine.
Results：We found that decline of serum viral load, frequently accompanied by hepatitis exacerbation, occurred since 1 year before HBeAg seroconversion. The proportions of precore and BCP mutations also increased gradually throughout the process of HBeAg seroconversion. The virologic features and proportions of precore and BCP mutations were similar between HBeAg seroconversion with anti-HBe group and HBeAg loss group. Before HBeAg seroconversion or loss, genotype B patients had higher serum viral loads（p=0.03~0.61）and lower proportions of BCP mutation（p=0.004~0.03）compared with genotype C patients. Secondly, no significant determinant was noted by step logistic regression analysis before lamivudine therapy between sustained and non-sustained HBeAg seroconversion groups. The mixed type and mutant type of precore region were replaced by wild type at the end of therapy and HBeAg seroconversion. The wild type（G1896）became dominant strain after lamivudine therapy, that was different from status of spontaneous HBeAg seroconversion.
Conclusion: our data showed that to clarify the role of the sustained precore mutant strain in the sustained HBeAg seroconversion, it was possible to increase case number for improving the statistic power in the future. Besides, there is little PCR product amplified from the BCP region due to lower viral load after lamivudine therapy. We need a more sensitive method to detect the BCP mutation in the future.
Subjects
B型肝炎
干安能
核前區和核心啟動子變異
e抗原持久陰轉
Hepatitis B
lamivudine
precore and basal core promoter mutations
sustained e seroconversion
SDGs
Type
other
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