Association of exon 9 but not intron 8 VDR polymorphisms with occult HBV infection in south-eastern Iranian patients

Background and Aim: Occult hepatitis B infection (OBI) is characterized as a form of hepatitis in which, despite the absence of detectable hepatitis B surface antigen (HBsAg), hepatitis B virus DNA (HBV-DNA) is present in a patient's peripheral blood. Investigators believe that divergent genetics and immunological parameters vary between resistant individuals and patients with OBI. Vitamin D3 and its known receptor appear to be involved in antiviral immune responses. Therefore, because OBI is a form of viral infection, the aim of this study was to investigate the association between polymorphisms in intron 8 and exon 9 of the vitamin D receptor (VDR) with OBI. Methods: In this experimental study, the plasma samples of 3700 blood donors were collected and tested for HBsAg and anti-HBs using ELISA. The HBsAg-/anti-HBc+ samples were selected and screened for HBV-DNA using polymerase chain reaction (PCR). HBV-DNA-positive samples assigned as OBI cases and PCR-restricted fragment length polymorphism. Results: The results of the current study demonstrated that 352 (9.5%) of 3700 blood samples were HbsAg-/anti-HBc+. HBV-DNA was detected in 57/352 (16.1%) of HBsAg-/anti-HBc+ samples. Our results showed a significant difference in the T/T allele of exon 9 of VDR, but any differences were also observed in the other examined alleles. Conclusion: The polymorphisms in the T/T allele of exon 9 of VDR is possibly associated with OBI, thus it can be concluded that VDR and its functional polymorphisms are likely to be related to sensitivity and resistance of the immune system to HBV in OBI patients.