Lei Wang1, Hua Liu, Xiaoxiao Ning, Feng Gao. 1. Clinical Laboratory, the Sixth People's Hospital, Affiliated to Shanghai Jiao Tong University, Shanghai, China.
Abstract
AIMS: To study the characteristics of mutation in the amino acids coded by the S gene region in the HBV DNA sequence and to comprehensively explore and analyze the cause of the double positive result phenomena in both HBsAg and HBsAb tests. METHODS: Specimens collected from 43 cases of chronic hepatitis B patients with positive results for both HBsAg and HBsAb tests were used as the experimental group; specimens collected from 43 cases randomly picked from all patients with chronic hepatitis B with a single positive result for HBsAg test were used as the control group. In HBV DNA, the S gene region was amplified and sequenced. Amino acid sequences were grouped, and mutations were analyzed based on the sequencing results. RESULTS: The patients were infected with HBV of the genotype B and C and those who with genotype C show more mutations than genotype B carriers. Compared with the control group, the experimental group had a marked increase in S gene amino acid mutations; a higher amino acid mutation rate was observed in the first loop (aa124-137) of the a-determinant (aa124-147) and there was a statistical difference (genotype B: 2.68% vs. 0.00%, P = 0.041; genotype C: 7.14% vs. 2.01%, P < 0.001). CONCLUSION: The first loop in a-determinant of S gene sequence possesses a large numbers of mutated amino acids, leading to changes of antigenicity and simultaneous positive results in both HBsAg and HBsAb tests finally.
AIMS: To study the characteristics of mutation in the amino acids coded by the S gene region in the HBV DNA sequence and to comprehensively explore and analyze the cause of the double positive result phenomena in both HBsAg and HBsAb tests. METHODS: Specimens collected from 43 cases of chronic hepatitis Bpatients with positive results for both HBsAg and HBsAb tests were used as the experimental group; specimens collected from 43 cases randomly picked from all patients with chronic hepatitis B with a single positive result for HBsAg test were used as the control group. In HBV DNA, the S gene region was amplified and sequenced. Amino acid sequences were grouped, and mutations were analyzed based on the sequencing results. RESULTS: The patients were infected with HBV of the genotype B and C and those who with genotype C show more mutations than genotype B carriers. Compared with the control group, the experimental group had a marked increase in S gene amino acid mutations; a higher amino acid mutation rate was observed in the first loop (aa124-137) of the a-determinant (aa124-147) and there was a statistical difference (genotype B: 2.68% vs. 0.00%, P = 0.041; genotype C: 7.14% vs. 2.01%, P < 0.001). CONCLUSION: The first loop in a-determinant of S gene sequence possesses a large numbers of mutated amino acids, leading to changes of antigenicity and simultaneous positive results in both HBsAg and HBsAb tests finally.