Effect of promoter region polymorphisms in the interferon gamma-i̇nducible Protein-10 (IP-10) gene on Hepatitis B surface antigen loss in chronic Hepatitis b patients

Introduction and Objective: Although chronic hepatitis B infection is a vaccine-preventable disease, it still remains an important cause of liver disease-related morbidity and mortality. The ideal endpoint that can be achieved with current treatments is the loss of hepatitis B surface antigen (HBsAg). It has been shown that the loss of HBsAg significantly reduces the possibility of liver-related mortality due to complications such as cirrhosis and hepatocellular carcinoma (HCC). Factors affecting HBsAg loss have been one of the focal points of previous studies on hepatitis B. In this context, our study aimed to investigate the promoter region polymorphisms of the IP-10 (CXCL10) molecule, an important proinflammatory chemokine that may have an effect on HBsAg loss. Materials and Methods: The study was conducted on 60 patients with HBsAg loss who were retrospectively screened among 1950 chronic hepatitis B patients who applied to the Infectious Diseases and Clinical Microbiology outpatient clinic of Çukurova University Hospital between 2005 and 2022 and who met the inclusion criteria and 60 control group patients who were HBsAg positive. The laboratory results of the patients were accessed through the hospital automation system. Afterwards, patients were called and peripheral blood samples were taken, deoxyribonucleic acid (DNA) was isolated to look for IP-10 polymorphisms and the relevant gene region was amplified by Polymerase Chain Reaction (PCR) method. Sanger sequencing was performed. In the sequenced IP-10 (the region between chr4:76,022,698-76,023,698 according to GRCh38/hg38) promoter, exon 1, intron 1 and exon 2 region; 3 variants were identified by scanning the GWAS database and literature. The obtained sequence data (ab1) were analyzed in the CLC Genomic Workbench 24 program. Results: It was observed that there were c.-135C>T(rs56061981), c.85C>T(rs11548618), c.83T>G polymorphisms in the IP-10 promoter and exon 2 regions. No significant difference was found between the case and control groups in terms of genotype and allele frequencies of these 3 polymorphisms (p>0,05). The HBsAg loss rate between 2005-2022 was found to be 5,33%. The mean age at the beginning was 38,1±12,0 years in the HBsAg loss group and 34,9±14,5 years in the HBsAg positive group, but this difference was not statistically significant (p=0,105). The mean age of HBsAg loss in the case group was 53,2±11,3 years. Basal and maximum HBsAg levels, maximum hepatitis B virus (HBV) DNA levels, baseline Hepatitis B e antigen (HBeAg) serology, and antiviral treatment use were different in these 2 groups. While basal and maximum HBsAg (p<0,001), and maximum HBV DNA (p=0,002) were lower in the case group, basal HBeAg negativity (p=0,015), and antiviral non-use (p<0,001) rates were higher in the case group. Interferon (IFN) and nucleoside/nucleotide analogs (NA) use (p=0,042), only NA use (p<0,001), duration of IFN and NA use (p=0,011), and only NA use (p=0,01) were significantly higher in the control group. The cut-off value of baseline HBsAg to predict HBsAg loss was determined as <1559 S/CO (77,2% AUC, 58,33% sensitive, 86,67% specificity, p<0,001). Conclusion: Based on the results obtained from our study, we can say that c.-135C>T, c.85C>T, c.83T>C polymorphisms have no effect on HBsAg loss. We can suggest that low baseline and follow-up maximum HBsAg levels, low follow-up maximum HBV DNA, baseline HBeAg seronegativity, and not using antiviral treatment may predict HBsAg loss. Keywords: Chronic HBV infection, HBsAg loss, IP-10, CXCL10, Polymorphism