Detection of a premature stop codon in the surface gene of hepatitis B virus from an HBsAg and antiHBc negative blood donor.
BACKGROUND
In blood donors, HBV infection is detected by the presence of serum hepatitis B surface antigen (HBsAg). However, some mutations in the surface gene region may result in altered or truncated HBsAg that can escape from immunoassay-based diagnosis. Such diagnostic escape mutants pose a potential risk for blood transfusion services.


RESULTS
In the present study, we report a blood donor seronegative for HBsAg and antiHBc, but positive for antiHBs who was HBV DNA positive by PCR. Sequencing of the HBsAg gene revealed presence of a point mutation (T-A) at 207th nucleotide of the HBsAg ORF, which resulted in a premature stop codon at position 69. This results in a truncated HBsAg gene lacking the entire 'a' determinant region. However, follow-up of the donor after 2 years revealed clearance of HBV DNA from the serum.


CONCLUSIONS
The case illustrates an unusual mutation, which causes HBsAg negativity. The finding emphasizes the importance of molecular assays in reducing the possibility of HBV transmission through blood transfusion. However, developing more sensitive serological assays, capable of detecting HBV mutants, is an alternative to expensive and complex amplification-based assays for developing countries.
Datta
Sibnarayan
S
ICMR Virus Unit, Kolkata, ID and BG Hospital Campus, Kolkata, West Bengal, India.
Banerjee
Arup
A
Chandra
Partha K
PK
Chakraborty
Subhasis
S
Basu
Subir Kumar
SK
Chakravarty
Runu
R
D000328:Adult; D001782:Blood Donors; D018388:Codon, Terminator / Q000235:genetics*; D004279:DNA, Viral / Q000032:analysis / Q000097:blood; D006509:Hepatitis B / Q000821:virology*; D006510:Hepatitis B Antibodies / Q000097:blood*; D006512:Hepatitis B Core Antigens / Q000235:genetics / Q000276:immunology*; D006514:Hepatitis B Surface Antigens / Q000097:blood / Q000235:genetics; D006515:Hepatitis B virus / Q000235:genetics / Q000302:isolation & purification; D006801:Humans; D008297:Male; D008969:Molecular Sequence Data; D009154:Mutation; D010802:Phylogeny; D016133:Polymerase Chain Reaction / Q000379:methods; D017422:Sequence Analysis, DNA
D018388:Codon, Terminator; D004279:DNA, Viral; D006510:Hepatitis B Antibodies; D006512:Hepatitis B Core Antigens; D006514:Hepatitis B Surface Antigens