Mother-to-child transmission of a hepatitis C virus variant with an insertional mutation in its hypervariable region

Background/Aims: We have analyzed the molecular basis of mother-to-child transmission of hepatitis C virus. Methods/Results: Healthy pregnant women are screened for anti-HCV antibody and babies born to hepatitis C virus carrier mothers were prospectively investigated. Among the 35 pairs studied, the hepatitis C virus genome was detectable in only one baby, who did not show any significant symptoms of hepatitis. The viral load in the blood of the mother was one of the highest of the 35, and the population of the hepatitis C virus genome was heterogeneous. Furthermore, she was found to have a mixed infection with type 1a and type 1b hepatitis C virus. However, the hepatitis C virus genome obtained from the baby was only from type 1b, less heterogeneous and composed of the clones which were detected in the blood of the mother. The selected hepatitis C virus had a 12-nucleotide insertion in the amino-terminus of the E2 hypervariable region of the genome. Conclusions: The incidence of mother-to-child transmission of hepatitis C virus from carrier mothers was shown by this prospective study to be low. The presence of selection pressure during transmission was suggested. The biological significance of the virus with 12-nucleotide insertion has to be determined.