Occult HBV Infection May Be Transmitted Through Close Contant

Background:Our country is an high endemic area of HBV infection in the world, According to the report, the prevalence rate of hepatitis B surface antigen in our country was 7.18%, it is estimated that the number of hepatitis B surface antigen carriers in our country is about 93 million.Over the past decade, occult hepatitis B virus infection (OBI) has been paied more and more attention by the researchers and clinical workers. A latent form of infection is defined as the surface antigen negative, but HBV DNA positive. The mechanism of occult hepatitis B virus infection is complex, it’s related to the low levels of the virus replication, viral gene mutation, a host of individual differences, Whether merging of other viral infections, it’s the result of various factors. At present, the research on the transmission mode of occult hepatitis B infection is mainly concentrated in the blood transmission and mother to child transmission, and the research on the family close contact with this transmission is relatively few.Objective:To search for the infectious source of hepatitis B virus (HBV) for a child,who had received the standard vaccination regimen at birth and produced protective antibody.Methods:Serum samples were obtained from a child and his parents. Sera were tested for HBV serological markers and viral loads.HBV DNA was extracted using phenol-chloroform.The surface gene of HBV was amplified by nested PCR and the amplicons were cloned and sequenced.Phylogenetic analysis was carried out using Mega 6.0 and Bioedit 7.0.Results:Both parents had occult infections. Twelve, eleven and nine clones, from the father, mother and son, respectively, were sequenced. Serotypes adrq+, aywl,ayw,ayr and genotype B,subgenotype C2,a recombinant B/C were identified in the father.Serotypes aywl,adw2,adwq+and genotype B,subgenotype C5,two recombinants B/C、a recombinant C/G were identified in the mother. adrq+was the only serotype in son. Subgenotype C2 was the only genotype identified in son. A phylogenetic tree showed that all of the child’s sequences and most of the father’s sequences clustered together. However, none of mother’s sequences clustered with those of the child. The surface gene from the child and his father had the same amino acid substitution pattern (T118K, T123N and G145A).Conclusions:(1) The father was the source of the son’s HBV infection, suggesting that occult HBV infection may be transmitted through close contact. (2) Occult HBV may manifest as an overt infection following transmission. (3) Monitoring of the levels of anti-HBs among vaccinated subjects for booster vaccination is necessary in regions where HBV is endemic. (4) Nucleic acid testing for occult HBV infection (OBI) should be considered for non-responders to the vaccine.