肝细胞癌患者B和C基因型乙型肝炎病毒X蛋白的变异特点

背景与目的：X蛋白是乙型肝炎病毒(hepatitis B virus,HBV)最重要的致病因子之一,它在HBV相关性肝细胞癌(hepatocellular carcinoma,HCC)的发生发展中起着重要作用。目前已知B、C基因型HBV相关性HCC的临床及病理表现不尽相同,但目前尚不清楚这种差别是否与B、C基因型HBV X基因之间的差别有关。因此本实验拟研究B、C基因型间HBV X蛋白氨基酸差异及其在HCC患者中的变异及特点,初步探讨其与HCC发生、发展的关系。方法：PCR扩增22份乙型肝炎病毒表面抗原(HBsAg)阳性HCC患者血清HBV X基因,克隆、测序并以Vector NTI6．0软件分析其基因型。以DNAMAN软件对标准HBV及HCC来源的HBV X蛋白进行氨基酸同源分析。结果：检测的22个HBV X基因片段均属于B或C基因型。B、C基因型HBV X蛋白之间存在14个氨基酸的差异,HCC患者来源的B、C型HBV X蛋白存在4个氨基酸的共有变异,C型HBV X蛋白尚有6个型特异性变异。这些差异或变异氨基酸均位于X蛋白B、T细胞表位或反式激活区及调节区内。结论：B、C基因型HBV X蛋白之间存在氨基酸差异,且在HCC中发生基因型特异性变异,这些差异或变异氨基酸可能导致X蛋白免疫学功能及反式激活功能的不同。

X protein variations of genotype B and C hepatitis B virus isolated from the patients with hepatocellular carcinoma

BACKGROUND & OBJECTIVE: X protein was one of the most important pathogens of hepatitis B virus (HBV), and was crucial in the carcinogenesis of HBV related hepatocellular carcinoma (HCC). It was demonstrated that the infection of genotype B or C HBV would result in different clinical manifestations and pathological characteristics in HCC patients, however, it was under elucidation whether these differences related to different genotypes of HBV X protein. This study was designed to investigate the amino acid differentiations of X proteins in standard genotype B or C HBV strains and the variations in HBV isolated from the HCC patients, and elucidate preliminarily the relationship between the genotype of HBV and carcinogenesis of HCC. METHODS: HBV X genes from the serum of twenty two HBsAg positive HCC patients were amplified, cloned and sequenced. Genotyping of the X gene was carried out by Vector NTI6.0 software and the amino acid alignment among the standard and HCC originated X protein were done by DNAMAN software. RESULTS: Twenty two HBV X genes were obtained and all of them could be categorized into genotype B or C. Besides of 14 amino acid differentiations within X protein between standard B and C HBV strains, HCC originated X protein of B and C genotype showed 4 consensus amino acid variations, and genotype C X protein showed additional 6 genotype specific variations. All these differentiated and varied amino acids were located in the B, T cell epitopes and transactive or related regulatory regions. CONCLUSIONS: In addition to amino acid differentiations, X protein of genotype B or C HBV also showed genotype specific variations in HCC patients. Amino acid differentiations and variations may result in the different immunocompetence and transactivation capacity between X proteins of genotype B and C.