Seroepidemiologic Study of Spermatozoal Transmission of Hepatitis B Virus (HBV)

Transmission of hepatitis B virus (HBV) from mother-to-infant is the predominant route in most high prevalence areas such as China. However, father-to-child transmission also plays another important role in the prevalence of hepatitis B. Children infected with HBV from their carrier fathers would be horizontally by postnatal intimate contact or vertically via male germ line. The latter is considered an intrauterine infection, however, whether it is really existed in human remains to be determined. In past decades, several experiments reported there presences of integrated HBV DNA in human spermatozoal chromosomes. Studies on embryos hybridized with mammalian ova and human spermatozoa were also confirmed that sperm-integrated HBV DNA can replicate and express the HBV protein in two-cell' hybrid embryos. All above findings demonstrated that father might transmit HBV to fetus by spermatozoa in theory. Since HBV is a blood-borne virus, the unvaccinated pregnant women would be at risk for HBV exposure if their fetuses carried the virus from fathers. On other hand, maternal antibodies can pass through the placenta and enter the fetal circulation freely. If women had been vaccinated for HBV before conception, thus some attractive questions are raised that what would happen to a maternal immune system if her fetus carried HBV from spermatozoa? Would the fetus be passive immunized by hepatitis B immunoglobulin leaked from maternal circulation? However, the literature on transmission of HBV by spermatozoa in vivo is rare, the viral replicating status and fetal immune response in uterus are unknown. Only one study had detected HBV DNA and serological makers on eight aborted fetuses suspected with HBV transmission via spermatozoa, but it is a small sample study and the maternal serological status is uncertain. Specimens applied for evaluating intrauterine infection include amniotic fluids, placental tissue and neonatal peripheral blood. Because postnatal sample is inevitably to be contaminated by maternal blood during delivery, it would be useless to determine the time when the infection was occurred (before or during the partum). A better alternative is detecting fetal infection before the partum by prenatal diagnostic technique. Comparing to the postnatal specimens, intrauterine specimens obtained from amniocentesis or cordocentesis can minimize the contamination of maternal blood. It is also a safety technique and the risk of nosocomial infection caused by invasive procedures is very low. The aim of this study was to investigate the fetal hepatitis B seroepidemiology by prenatal diagnostic technique and to find the evidence of HBV vertical transmission via spermatozoa.