Hepatitis B Molecular Laboratory, Department of Virology, School of Public Health, Tehran University of Medical Sciences, Tehran, Iran.
Occult hepatitis B virus (HBV) infection is a well-recognized clinical entity characterized by the detection of HBV DNA in serum and/or in liver in the absence of detectable hepatitis B surface antigen (HBsAg). The frequency of the diagnosis depends on the relative sensitivity of both HBsAg and HBV DNA assays.
To determine the prevalence of occult HBV infection in a high risk group of children who developed HBV infection despite immunoprophylaxis.
the sera of 75 children born to HBsAg-positive mothers previously immunized by HBIG and prophylaxic vaccine regimen were assayed for HBV DNA by real-time PCR. Subsequently, the samples were tested by a sensitive standard PCR employing independent set of primers for all HBV genes and analyzed by direct sequencing.
HBV DNA was detected in 21/75 (28%) of children, ranged between 77 and 9240 copies/mL. All were positive for anti-HBs. 5 (24%) were found to be positive for anti-HBc, and anti-HBc-only positive individual were not observed. 8 isolates (38%) did not contain any mutation. Other 13 infected children (62%) contained at least one mutation in regions known to be involved in functional and/or immune epitope activity. 10 were contained G145R mutations.
HBV occult infection seems to be relatively frequent in immunized children born to HBsAg-positive mothers. HBsAg negativity is not sufficient to completely exclude HBV DNA presence. These findings emphasize the consideration of occult HBV infection in hypo endemic areas.