HBsAg和HBsAb双阳性慢性乙肝患者血清中HBV基因型与S区突变的关系

目的 探讨HBsAg和HBsAb同时阳性（HBsAg＋/HBsAb＋）慢性乙肝患者血清中HBV基因型与S区氨基酸序列突变的关系.方法 将43例HBsAg＋/HBsAb＋慢性乙肝患者作为实验组,并选取35例HBsAg＋/HBsAb-慢性乙肝患者作为对照组,对血清中HBV DNA S区基因序列进行PCR扩增和测序,根据测序结果对患者的基因型进行分型并对S区氨基酸序列突变进行比对分析.结果 实验组中B基因型8例、C基因型35例,对照组中B基因型9例、C基因型26例.实验组C基因型患者的年龄（50.2±16.3）岁]明显大于B基因型（34.4±13.4）岁]（P=0.015）;实验组B基因型和C基因型的S区氨基酸突变率分别为0.77%和1.64%（P=0.005）;而对照组的B、C两种基因型的突变率分别为0.59%和0.49%（P=0.597）.同样为C基因型的两组患者,实验组S区氨基酸突变明显多于对照组（P=0.000）,而且实验组S区氨基酸突变大多分布在主要亲水结构区域（MHR）α决定簇的第一个环状结构区内;而B基因型只有少数患者有α决定簇内的突变.结论 HBsAg＋/HbsAb＋的乙肝患者C基因型较B基因型更易发生突变;且C基因型患者的氨基酸突变大多发生于S区的α决定簇内,可能正是由于此种突变使HbsAg的抗原性发生改变,最终导致了HbsAg和HbsAb同时阳性.

Relationship between genotypes and mutations in S gene sequence of chronic hepatitis B patients with positive results for both HBsAg and HBsAb tests

Objective To analyze relationship between genotypes and mutations in S gene sequence of chronic hepatitis B patients with positive results for both HBsAg and HBsAb tests (HBsAg+/HBsAb+). Methods Specimens collected from 43 cases of chronic hepatitis B patients with HBsAg+/HBsAb+ were used as experimental group, and specimens collected from 35 cases of newly diagnosed chronic hepatitis B patients with HBsAg+/HBsAb- were used as control group. The S gene region of HBV DNA was amplified and sequenced. The amino acid sequences were classified to different genotypes and the mutations were analyzed based on the sequencing results. Results The experimental group contained 8 patients of the B genotype and 35 patients of the C genotype, whereas the control group contained 9 patients of the B genotype and 26 patients of the C genotype. In experimental group, the average age of the C genotype patients (50.2±16.3) years] was obviously older than that of the B genotype patients (34.4±13.4) years](P=0.015). The mutation rates for the B and C genotypes in the experimental group were 0.77% and 1.64%, respectively (P=0.005). Whereas the mutation rates were 0.59% and 0.49% for the B and C genotypes in control group (P=0.597). In addition, among the C genotype patients, the experimental group had a marked increase in S gene amino acid mutations, and a higher amino acid mutation rate was observed in the major hydrophobic region (MHR, aa100~169), especially in the first loop (aa124~137) of α determinant (aa124~147). However, only few patients with the B genotype had mutations in α determinant. Conclusion The C genotype patients with HBsAg+/HBsAb+ are likely to have more mutations than the B genotype patients, especially the mutations in α determinant. The mutations in this area may lead to changes of antigenicity and simultaneous HBsAg+/HBsAb+ finally.