Objective: To determine the actual hepatitis B virus (HBV) infection rate, occult HBV infection (OBI) rate, and molecular evolutionary characteristics of the OBI virus S gene in the adolescent population living in rural and pastoral areas of Xinjiang Province.
Methods: A cross-sectional questionnaire survey was conducted among the adolescent population living in the farming and herding areas. Venous blood samples (3-5 mL) were collected from eligible students in three central schools located in Banfanggou Township, Shuixigou Village, and Miaolgou Village, all in Urumqi County, in the nine-year compulsory system. Clustersampling in a population was adopted, and informed consent was obtained from the participating students. All serum samples were qualitatively tested for hepatitis B surface antigen (HBsAg) by electrochemiluminescence. Subsequently, the HBV S gene was amplified by nested polymerase chain reaction (PCR), and the positive PCR products were purified; the target gene sequences were then amplified. Molecular evolutionary characterization of the target gene sequences was performed using MEGA 11software.
Results: Overall, 1712 subjects were enrolled. The HBsAg carrier rate and OBI infection rate were 1.93% (33/1712) and 6.13% (103/1679), respectively. HBsAg (-) samples included 103 OBI strains, of which B-genotype strains accounted for 80.58% (83/103; 1 case of ayw1 serotype and 82 cases of adw2 serotype), C-genotype strains accounted for 14.56% (15/103; 1 case of adw2 serotype and 14 cases of adrq+serotype), and D-genotype strains accounted for 4.85% (5/103; 1 case of adw2 serotype and 4 cases of ayw2 serotype). Mutations were detected in the "a" determinant region of the following genes: P127S, G130R, and N146S (B-genotype OBI strains); T126I and T143S (C-genotype OBI strains); T126I, P127S, F134Y, and T143S (D-genotype OBI strains).
Conclusion: A certain proportion of young people are infected with OBI strains. The B-genotype of OBI strains is the possible dominant genotype. OBI strains have amino acid mutations in the "a" determinant region, and they are likely to undergo a change in their antigenicity and immunogenicity. More attention must be paid to prevent problems due to OBI.
Keywords: Adolescent population; Molecular evolution; Occult hepatitis B virus infection (OBI); S gene.
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