Relationship Between Precore/core Promoter Mutations Of HBV And Intrauterine Infection Or Interruption At Third Trimester Of Pregnancy

Hepatitis B virus (HBV) infection is still one of primary problems in China and the world. The most important route of transmission of HBV is mother-to-infant transmission in Asia. And intrauterine infection is the main reason of immunoprophylaxis failure. Several studies in China have shown that HBV infection in the uterus may be interrupted with pregnant women of asymptomatic carriers receiving hepatitis B immune globulin(HBIG) intramuscularly 200 IU—400 IU once every four weeks from being pregnant for 28 weeks to delivery. Both HBV S region wild and mutant strains can infect foetus and it may be one of the important reasons of immunoprophylaxis failure. Precore (PC) and core promoter (CP) regions of HBV are the targets of host immunization and play an important role in the viral replication. Some reports have shown that high dose of HBIG can cause HBV escape mutations in the S region. Recently our study has shown that there is no relationship between HBV S region mutations and interruption with HBIG at third trimester of pregnancy and HBV S region mutations are not the main reason of intrauterine infection. However there is no mother-newborn paired study on the relationship between precore/core promoter mutations of HBV and intrauterine infection. And there is no report about the relationship between precore/core promoter mutations and interruption with HBIG at third trimester of pregnancy. In this study we investigated the relationship between precore/basic core promoter(BCP) mutations of HBV and both intrauterine infection andinterruption with HBIG at third trimester of pregnancy.Section 1 Relationship between precore/core promoter mutations of HBV and intrauterine infectionObjective: To explore the possible relationship between precore/basic core promoter mutations of HBV and intrauterine infection.Methods: 99 pregnant women who were asymptomatic carriers of HBV (HBIG group 58 and no HBIG group 41) and their newborn infants were investigated. HBV DNA quantification in serum was determined using real-time PCR. Relevant serum markers (HBeAg, HBsAg or anti-HBs) of HBV were measured by EIA. Precore(PC) and basicl core promoter(BCP) regions of HBV DNA were amplified by polymerase chain reaction and then subjected to direct sequencing.Results: The rate of HBV intrauterine infection of newborns in the HBIG group(22.4%)was lower than that control group(40.9%) (x~2=5.15, p=0.023). Of 22 newborns in HBIG group, 9 (40.9%) were anti-HBs positive. Precore and basic core promoter regions of HBV DNA were amplified and sequenced susscessfully in 82 mothers. 1896G→A, 1762A→T, 1764G→A, 1752A→G and 1799C→ G were the most commen mutations. There was no significant difference between the rate of HBV intrauterine infection of newborns of women in 1896G → A group (25.0%) and without 1896G→A group (37.0%) (x~2=0.236 , p=0.627). And there was no significant difference between the rate of HBV intrauterine infection of newborns in 1762A→T/1764G→A double mutation group (22.2%) and without 1762A→T/1764G→A double mutation group (37.2%) (Fisher's exact test p=0. 470). The rate of HBV intrauterine infection of newborns in 1752A→ G— 1799C→G double mutation group(26. 3%) was lower than the rate without 1752A→G/1799C→G double mutation group,but there was no significant difference (x~2=0. 297, p= 0.586). The rate of HBV intrauterine infection of newborns of in 1799C →G group (45.6%) was higer than without 1799C→G group (32.4%), but there was no significant difference (x~2=0. 258, p=0. 611). And there was also no significant difference among 1896G→A, 1762A → T-1764G→A, 1752A →G-1799C→G and 1799C → G mutation groups. Surpringly there was great difference between mothers' and newborns' sepuence in precore and basic core promoter regions of HBV DNA in 60 mother-newborn pairs.Conclusion: Injectting HBIG intramuscularly at third trimester of pregnancy can decrease the rate of HBV intrauterine infection and the fetus acquiring passive immunization may be the important mechanism of it. The common mutations in precore and basic core promoter regions of HBV DNA may not affect the rate of HBV intrauterine infection. Both HBV mutant strains and wild strains in precore and basic core promoter regions can infect fetus. Mutant and wild strains in precore and basic core promoter regions may infect individuals according to their bionomics.Section 2 The impact of injecting HBIG at third trimester of pregnancy on the mutations of precore and core promoter regions of HBV DNAObjective:To investigate the impact of injectting HBIG at third trimester of pregnancy on precore and basic core promoter regions of HBV DNA. Methods: 120 pregnant women (HBIG group 67 and no HBIG group 53) were studied. HBV DNA quantification in serum was determined using real-time PCR. Relevant serum markers (HBeAg, HBsAg) of HBV were measured by EIA. Precore and basic core promoter(BCP) regions of HBV DNA were amplified by polymerase chain reaction and then subjected to direct sequencing.Results:(1)Serums of 33 women of HBIG group were collected before interruption with HBIG and at delivery. There was no significant difference between the level of HBV DNA at delivery and that before interruption (t=0.375, p=0.709). Precore and basic core promoter regions of HBV DNA were amplified and sequenced susscessfully in double serums of 23 of 33 women. The rate of total nucleotide substitute in precore and BCP regions before interruption and at delivery was not different significantly (p>0.05). However the rate of total mutations of hot points such as 1896G→A, 1899G→A, 1762A→T, 1764G→A was significant lower at delivery than before interruption (x~2=5.717, p=0.017). The prevalence of 1896G→A or 1899G→A or 1762A→T or 1764G → A mutation was lower atdelivery than before interruption, but no significant difference (p>0.05). (2) The rate of total nucleotide substitute in precore and BCP region at delivery in 53 HBIG group women was not different significantly from 47 no HBIG goup women (p>0. 05). The rate of total mutations of hot points in HBIG group was lower than that in no HBIG group, but no significant difference (p>0.05). Also the prevalance of 1896G→A or 1899G→A or 1762A→T or 1764G→A was lower in HBIG group than that in no HBIG group , but no significant difference (p>0.05). Conclusion: The level of HBV DNA in pregnant women could not decrease by injectting the dose of HBIG for interruption of HBV intrauterine infection at third trimester of pregnancy. Interruption of HBV intrauterine infection at third trimester of pregnancy using HBIG may not raise the mutations in the precore and basic core promoter regions of HBV DNA. Contrarily injectting HBIG at third trimester of pregnancy can decrease mutations of hot points in the precore and basic core promoter regions of HBV DNA, but more researches are required.