In our study, IFN-γ secreting T-cell response detected by ICS was lower in both OBI and CHB but higher when measured by ELISpot than in spontaneously resolved infection and non-infected individuals suggesting that IFN-γ secreting T-cell response played a significant role but might not be a critical factor contributing to the outcome of OBI or chronic HBV infection. This evidence concerns the gene IFNG and infection.