Hepatitis B-specific T helper cell responses in uninfected infants born to HBsAg^(+)/HBeAg^(-) mothers

Vertically transmitted hepatitis B virus(HBV)usually causes chronic infection.While combined active–passive immunoprophylaxis in neonates of hepatitis B surface antigen-positive(HBsAg1)mothers at birth prevents vertical transmission,it is not yet clear whether neonates encounter the virus or its products in the absence of hepatitis B e antigen(HBeAg).This study was undertaken to investigate HBV antigen-specific T-cell responses in vaccinated neonates of HBsAg1/HBeAg2 mothers.Blood was collected from 46 HBsAg1 mothers and their neonates(subjects)as well as 24 age-matched controls.All neonates of HBsAg1 mothers received appropriate immunoprophylaxis,and HBsAg and hepatitis B surface antibody(anti-HBs)antibody titers were determined after completion of the vaccination course.Peripheral blood mononuclear cells(PBMCs)from infants at birth,1 and 6 months of age were stimulated with recombinant HBsAg,hepatitis B core antigen(HBcAg)and mitogen,and interferon(IFN)-c concentrations were determined by ELISA.HBsAg-induced production of IL-2,IL-5,IL-6 and IL-10 was assessed using a cytometric bead array kit on cells from 6-month-old neonates post-vaccination.All neonates were HBsAg2 and responded to vaccination.Increased IFN-c production following HBcAg stimulation was seen in 30.4%of neonates born to HBsAg1/HBeAg2 mothers.Subjects demonstrated significantly higher IL-2 production post-HBsAg stimulation,whereas IL-5,IL-6 and IL-10 cytokine responses were not significantly different.Almost one-third of uninfected neonates developed viral antigen-induced IFN-c production,suggesting that they had been exposed to virions or viral derivatives.This encounter,however,did not impair their T-cell responses to vaccination.