title: Polymorphisms within Fas gene are not associated with occult hepatitis B virus infection: Polymorphisms within Fas gene in occult HBV infection.
abstract: BACKGROUND
  Occult hepatitis B infection (OBI) is a form of hepatitis in which there is an absence of detectable HBsAg, despite the presence of HBV-DNA in the peripheral blood of patients. It seems that non-effective or attenuated immune system responses against HBV lead to the development of OBI. Previous studies showed that the Fas/Fas ligand (FasL) system is an important death signaling pathway that is used by cytotoxic T lymphocytes to eradicate HBV from the liver.
  
  
  OBJECTIVE
  To investigate polymorphisms in the -670 region of the Fas gene in those with OBI.
  
  
  METHODS
  The plasma samples from 3700 blood donors were tested for HBsAg and anti-HBs by ELISA. The HBsAg-/anti-HBc(+) samples were selected and screened for HBV-DNA by PCR. Those with HBV-DNA were diagnosed as OBI and PCR-RFLP technique was performed to examine polymorphisms within their Fas gene.
  
  
  RESULTS
  352 (9.5%) of 3700 blood samples were HBsAg-/anti-HBc(+). HBV-DNA was detected in 57 (16.1%) of 352 HBsAg-/anti-HBc(+) samples. Therefore, 57 HBsAg-/anti-HBc+/HBV-DNA(+) patients were diagnosed as OBI. Patient and control groups had no significant differences in terms of the studied polymorphisms.
  
  
  CONCLUSIONS
  The functional polymorphisms in the promoter region of Fas gene are not associated with OBI. Therefore, it may be concluded that polymorphisms at the -670 position of the Fas gene do not have any critical effects on the immune response against HBV in OBI.
authors.affiliation: Department of Microbiology, Hematology and Immunology, Faculty of Medicine, Rafsanjan University of Medical Sciences, Rafsanjan, IR Iran.
authors.forename: Mohammad Kazemi
authors.initials: MK
authors.lastname: Arababadi
authors.forename: Adel
authors.initials: A
authors.lastname: Mohammadzadeh
authors.forename: Ali Akbar
authors.initials: AA
authors.lastname: Pourfathollah
authors.forename: Derek
authors.initials: D
authors.lastname: Kennedy
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