Analysis Of Hepatitis B Virus S Gene Immune Escape-related Mutation In Chronic Hepatitis B Patients With HBsAg And HBsAb Co-existence

Background and objective: The related liver diseases caused by chronic hepatitis B virus(HBV)infection seriously endanger human health.In China,there are 78 millions of chronic HBV-infected people,leading to death of near300,000 patients due to HBV-related diseases such as liver cancer.Hepatitis B surface antigen(HBsAg)is an important diagnostic marker of HBV infection.HBsAb is a specific protective antibody and positive HBsAb indicates the establishment of host immunity against HBV.Chronic HBV-infected patients had positive HBsAg for more than 6 months and the positivity often last in life-length.Major marker for clinical cure of chronic HBV infection is HBs Ag loss.HBsAg could be neutralized by HBsAb.However,there were about2.5%-8.9% chronic HBV-infected patients who presented HBsAg and HBsAb co-existence in clinical practice.At present,the clinical significance and mechanism of this phenomenon have not been completely understood,and may be related to multiple factors.Among them,HBV S gene mutation may be one factor that is associated with HBsAg and HBsAb co-existence in serum samples of the patients.This study aims to analyze the characteristics of the immune escape-related mutations of HBV S gene major hydrophilic regions(MHR)in chronic hepatitis B patients with HBs Ag and HBsAb co-existence.Methods:We collected chronic hepatitis B patients with HBsAg and HBs Ab co-existence(Interval at least six months,two consecutive tests confirmed)from the database in2007-2013,excluding liver cirrhosis,liver cancer,and other viral overlapping infection.A total of 89 patients with HBsAg and HBsAb co-existence and 148 HBsAg single positive chronic hepatitis B patients were included.Their clinical data were collected and their serum samples were collected from the serum Biobank.Serum HBV DNA was extracted from these patients,and HBV S genes were amplified from serum and sequenced.Forty-six well-documented immune escape-related mutations and additional N-glycosylation mutation alignments were analyzed using DNASTAR Lasergene MegAlign software.Results: There was no significant difference in age,ALT,TBIL,HBV DNA level and HBeAg positive rate between the two groups.The detection rate of immune escape-related mutations in co-existence group was 31.46%,which was significantly higher than HBs Ag single positive group(18.92%,p=0.021).The detection rates of s L110I/S mutation,sT113N/S mutation,sT131I/N/P mutation and sS143L/M/T mutation were significantly higher than those in the single positive group,and the detection rates of multiple mutation in co-existence group were also significantly higher than those in the single positive group(20.22% vs.6.08%;p=0.001).In addition,the detection rate of additional N-glycosylation mutations in co-existence group was higher than those in single positive group(7.87% vs.2.03%;p=0.030).Conclusions: Compared to that in single HBsAg-positive patients,HBV S gene in HBs Ag and HBsAb co-existence patients harbored more mutational diversity,higher detection rates of single and multiple immune escape-related mutations,and higher detection rate of additional N-glycosylation mutations.These suggest that HBV genetic mutation in S gene MHR might be a driven factor of HBsAg and HBsAb co-existence in chronic HBV-infected patients.