The truth of intrauterine infection of hepatitis B

Have been infected with HBV intrauterine neonatal hepatitis B vaccine immunization refers to the failure of the main reasons, in order to reduce neonatal prenatal HBV infection in the uterus by the increase the effect of hepatitis B vaccination in recent years, some scholars have conducted a blocking hepatitis B virus intrauterine transmission of the preliminary study.

Mother to child transmission of HBV is considered three ways: ① prenatal intrauterine infection; ② dissemination of birth; ③ postnatal horizontal transmission.
The truth of intrauterine infection of hepatitis B

Block detail "infected" HBV!

As the existence of modes of transmission of hepatitis B virus, hepatitis B prevention efforts to cause difficulties. This paper reviews recent Hepatitis B virus intrauterine infection and the control mechanism of intrauterine infection in a preliminary study. To clarify the mechanism of intrauterine infection and to take appropriate preventive measures to control the spread of hepatitis B virus has a very important significance.

Hepatitis B virus (HBV) infection is a worldwide public health problem. It is estimated that worldwide there are about 215 million carriers of HBsAg, of which Asia and the Western Pacific region, the distribution of 168 million, China has almost 120 million people, accounting for about 10% of the population. In the HBV-prone areas, mother to child transmission is the major route of HBV infection, but also chronic carriers of hepatitis B among the crowd formed a large number of important reasons.

Mother to child transmission of HBV is considered three ways: ① prenatal intrauterine infection; ② dissemination of birth; ③ postnatal horizontal transmission. For the use of the latter two modes of transmission of hepatitis B vaccine and HBIG has been basically can block [1,2], but the current spread within the uterus of preventive measures to be ineffective. Although some studies have already confirmed the presence of intrauterine infection, but on the infection mechanism of HBV intrauterine infection in the study reported very little at home and abroad, and the view was not unanimous. Therefore, to clarify the mechanism of intrauterine infection, thereby blocking to take effective measures for the control and prevention of hepatitis B is very important significance.

1. HBV intrauterine transmission of the impact of factors and mechanisms

1.1 Virus factors and HBV intrauterine infection

Due to HBV intrauterine infection resulting directly from the mother, for intrauterine infection of the baby, the mother is the source of infection. Thus, reflecting the strength of body transmitted indicators, such as HBsAg status, HBsAg titer, HBVDNA content, etc. is to study the hot issue.

With regard to the relevant factors of HBV intrauterine infection studies have shown that HBV infection in newborns lines and serum HBsAg-positive mothers has increased remarkably. On the one hand, HBsAg presence of representatives of active HBV replication, which is also highly infectious blood, and therefore more vulnerable to infection of the fetus. So that the HBsAg-positive as a risk factor for neonatal infection may be related to HBsAg-positive blood, high levels of infectious HBV strong related; On the other hand, HBsAg may be directly involved in the HBV intrauterine transmission. HBsAg in order to free state and bound state (IgG) receptor through the placenta into the fetal blood circulation. Immature fetal immune system to HBsAg tolerance. T cells to HBsAg immune tolerance may make cytotoxic T-cell function impairment, and the latter for the removal of HBV infected liver cells is necessary. Because humoral immunity required the help of Th cells, and thus humoral immunity have also been affected. Thus, HBsAg into the fetal blood circulation, it may interfere with the immune cells recognize and kill the virus, and even affect the production of specific antibodies, but not removed from the mother's HBV, resulting in fetal chronic carrier state.

HBsAg reflects the strength of indirect indicators of infectious, HBVDNA is a direct indicator of the strength reflected contagious. Maternal blood levels of HBVDNA whether and neonatal infection, Burk et al [3] In an epidemiological survey, conducted a study on this issue and found that HBsAg-positive mothers with HBVDNA serum levels are up, infant the risk of infection has gradually increased. In the HBsAg-negative mothers, high levels of serum HBVDNA babies born to mothers who are at risk of infection better than low levels of serum HBVDNA babies born to mothers (OR = 19.2), so the researchers believe that perinatal exposure to high levels of maternal blood HBVDNA leading to infant infection in the most important factor. Deng Xin-Qing to HBsAg, HBsAg-positive pregnant women for the study of 178 cases of neonatal vaccination testing HBsAg and anti-HBs, and to detect blood mother HBVDNA content, was found with elevated levels of maternal serum HBVDNA, their newborns as carriers continue to The danger was increased, leading to increased opportunities for immunization failure.

Tang, etc. Fortunately, a study, 11 cases of HBsAg-positive pregnant women in eight cases of HBVDNA-positive pregnant women in eight cases of HBVDNA positive (72.7%), 10 patients with anti-HBe-positive pregnant women only 1 case HBVDNA positive (10.0%), and serum Studies testing and molecular hybridization results showed that HBsAg and / or HBVDNA positive pregnant women in labor induction in cases of fetal intrauterine infection rate was significantly higher than anti-HBe positive group. Turn and from two cases of intrauterine infection that HBV infection of the fetus through the placental barrier, or the first infection of placental tissue and in which the copy, and then infect the fetus.

The study shows that high levels of maternal blood HBVDNA infectious cause of strong risk factors for neonatal infections.

1.2 Theory of placental leakage

As early as in 1987, Ohto and Lin examined 32 cases of HBsAg-positive pregnant women and the resulting baby's umbilical cord blood after birth measured at 1 month follow-up infant venous blood in the HBsAg. The results found in 5 cases of intrauterine infection in the baby's mother, 27, only two cases had symptoms of threatened premature labor. The researchers therefore believe that threatened abortion or threatened premature labor, because of the strong uterine muscle contraction can lead to a slight placenta tear maternal blood infiltration of fetal blood, due to HBsAg-positive mother's blood, HBV high concentration, and thus a small amount of mother Blood mixed with intrauterine infection can be caused by the fetus. The researchers further pointed out that the placenta did not occur if the leakage can not be the placenta into the fetus in maternal blood circulation, even in the presence of high titer maternal HBsAg and HBsAg intrauterine infection also does not occur. Door can be such a case-control study, 8 cases of intrauterine infection in infants, 3 infants of mothers with threatened premature labor during pregnancy history, and 224 cases of intrauterine infection in infants has not taken place, only 6 cases the baby's mother had threatened premature labor history, the OR value of 21.8, suggesting threatened premature labor is a risk factor for intrauterine infection, results support the Ohto and Lin point of view.

1.3 placenta and infect the doctrine of

Fetus in intrauterine infection, necessarily involve HBV or HBV-infected cells through the placenta, therefore, the placenta in the role of intrauterine infection is a very important issue. Yan Yongping and other pairs of HBsAg-positive pregnant women during pregnancy, the placenta of different HBsAg, HBcAg presence and distribution were studied. In the 18 cases of HBsAg-positive pregnant women were not the early detection of HBsAg and HBsAg-positive staining was found. In the six cases of second trimester placenta, there is one cases were positive for HBsAg and HBsAg. In the 62 cases of full-term delivery of the placenta, there are 21 cases detected HBsAg, the researchers believe that HBV via the placenta is the main way invasive fetal blood and / or cell transmission methods and realized. Namely, first of all through the villi in maternal HBV clearance and / or infection of decidual cells, and then infected with the adjacent villi, including the villous trophoblast cells and stromal cells, and further invasion of villous fetal capillary endothelial cells, ultimately infect the fetus. On this basis, the researchers then used a case-control method to analyze the risk of transmission of hepatitis B virus intrauterine factors, from the placental barrier in trophoblast cells (TC), villous stromal cells (VSC), and villous capillary endothelial cells (VCEC) of infection caused the intrauterine transmission of the relative risk odds ratio (OR), respectively 9.113,11.68 and 43.50, OR the value of the home side from the placenta to the fetus there is a gradual upward trend surface, indicating placental barrier in TC, VSC, VECE of infection is another risk factor for intrauterine transmission.