Xu Hong-mei, Ren Hong, Peng Ming-li, Ling Ning, Qing Yu-ling
The Institute of Viral Hepatitis, Chongqing University of Medical Sciences, Chongqing 400010, China.
Zhonghua Nei Ke Za Zhi. 2003 Jun;42(6):388-91.
To investigate the characteristics of mutations in pre S/S gene of HBV in asymptomatic carrier (AsC) children infected through mother-to-infant transmission and their AsC mothers with different degree of viremia.
According to the levels of viremia in every pair of mother and child, 15 pairs of child and mother were divided into three groups 5 pairs in each group in this study: group I (both children and mothers had high viremia), group II (children had high and mothers had low viremia) and group III (children had low and mothers had high viremia). pre S/S gene was amplified by PCR and cloned into pGEM-T vector with T-A cloning technique. The recombinant plasmid pGEM- preS/S was confirmed by digestion with restriction enzyme ApaI and SacI. Tow clones were selected to be sequenced in each patient. The mutations of preS/S were compared with HBV DNA consensus sequence of Chongqing.
In each group the subtypes of HBV were B/adw2 in 4 pairs and C/adrq+ in one pair. The preS/S clones in patients infected with subtype B/adw2 HBV were analyzed. It was shown that there was no difference among the four high viremic groups or between the two low viremic groups in the number of mutation and the mutational position. However, there was significant difference between the high viremic group and low viremic group. The mutation was not related to age. In the two low viremic groups (the mothers of group II and the children of group III), there were 86-94 mutational positions in 13/16 clones. There were 86 same mutational positions causing 37 amino acid changes in 11/13 clones and 90 same mutational positions causing 38 amino acid changes in 2/13 clones. Most of the changed amino acids were located within T and B cell epitopes of the envelope protein or/and the surrounding regions. Sixty-two mutational positions that resulted in 28 amino acid changes were same in these two mutational sequences.
The mutation of HBV is not associated with the duration of infection. There are many differences of mutation when HBV comes from a same strain in hosts with different degrees of viremia. There are some regular patterns in the mutation of HBV after occurrence of HBeAg seroconversion. The mutation could be related to the escape of the attack of host's immunity.
研究母婴传播感染的无症状乙肝病毒携带者（AsC）儿童及其不同病毒血症程度的AsC母亲的乙肝病毒前S/S基因变异特征。
本研究根据每对母婴的病毒血症水平，将15对母婴分为三组，每组5对：I组（儿童和母亲均有高病毒血症）、II组（儿童有高病毒血症而母亲有低病毒血症）和III组（儿童有低病毒血症而母亲有高病毒血症）。采用PCR扩增前S/S基因，并利用T-A克隆技术将其克隆到pGEM-T载体中。用限制性内切酶ApaI和SacI酶切鉴定重组质粒pGEM-preS/S。每位患者选择两个克隆进行测序。将前S/S的变异与重庆地区乙肝病毒DNA一致序列进行比较。
每组中，4对乙肝病毒亚型为B/adw2，1对为C/adrq+。对感染B/adw2亚型乙肝病毒患者的前S/S克隆进行分析。结果显示，四个高病毒血症组之间或两个低病毒血症组之间在变异数量和变异位置上无差异。然而，高病毒血症组和低病毒血症组之间存在显著差异。变异与年龄无关。在两个低病毒血症组（II组的母亲和III组的儿童）中，16个克隆中有13个克隆存在86 - 94个变异位点。13个克隆中有11个克隆存在86个相同变异位点导致37个氨基酸改变，2个克隆中有90个相同变异位点导致38个氨基酸改变。大多数改变的氨基酸位于包膜蛋白的T和B细胞表位内及/或其周围区域。这两个变异序列中有62个变异位点导致28个氨基酸改变是相同的。
乙肝病毒变异与感染持续时间无关。当乙肝病毒来自同一毒株时，在不同病毒血症程度的宿主中变异存在许多差异。HBeAg血清学转换后乙肝病毒变异存在一些规律模式。变异可能与宿主免疫攻击的逃逸有关。
