association of mutations in the basal core promoter and pre-core regions of the hepatitis b viral genome and longitudinal changes in hbv level in hbeag negative individuals: results from a cohort study in northern iran

background although certain hbv mutations are known to affect the expression of hepatitis e antigen, their association with hbv viral level or clinical outcomes is less clear. objectives we evaluated associations between different mutations in the basal core promoter (bcp) and pre-core (pc) regions of hbv genome and subsequent changes in hbv viral dna level over seven years in a population of untreated hbeag negative chronic hepatitis b (chb) participants in northeast of iran. patients and methods participants in the current study were drawn from the golestan hepatitis b cohort study (ghbcs), a cohort of approximately 2590 hbsag positive subjects (living in gonbad city) embedded in the golestan cohort study (gcs). at baseline, hbsag was measured in all participants and revealed 2590 hbsag positive cases. we randomly selected 304 participants who their blood sample were taken at both baseline and seven years later in follow-up and had not been treated for hbv during this time. hbv viral load were assessed at baseline and at year 7. the bcp and pc regions of the hbv dna, at baseline, were amplified via hemi-nested pcr and sequenced by cycle sequencing. at year 7, liver stiffness was assessed by fibroscan; also, other parameters of liver disease were assessed following standard clinical protocols. associations were assessed via tabulation, chi-square, t-tests and logistic regression. p values < 0.05 were considered statistically significant and all tests were two-sided. results among 304 hbsag positive participants, 99 had detectable hbv dna at study baseline. of these, 61.6% had pc mutations (48.5% a1896 and 25.2% g1899). in contrast to other mutations, a1896 was associated with a higher proportion of detectable hbv dna at year 7 (39.6%) compared to patients with the wild type (13.7%) (or: 4.36, ci95% = 1.63-11.70; p value = 0.002). although participants with the a1896 mutation had higher year-7 hbv viral load than participants with g1896 (2.30 ± 1.66 iu/ml vs. 1.76 ± 1 iu/ml among patients with detectable hbv; p value = 0.052), no association was observed with either serum level alt or liver stiffness. interestingly, mutations in the basal core promoter (bcp) region had no significant effect on virus dna detection. conclusions in this population with chronic hbeag negative hepatitis b, an association was observed between the g1896a mutation in the pre-core region of hbv and subsequent level of hbv dna seven years later, which indicated that mutations in this region of hbv genome may contribute to disease progression in these patients and play an important role in hbv natural course of disease.