The Transfer Of Maternal Immunity Promotes The Immune Response Of Infants About Hepatitis B Vaccine

Background:Neonatal immunity is based on passive immunity provided by the maternal antibodies, whose active immune function is not ripe yet.The immature function of the active immune has lasted for 2 to 3 months after their birth. This period of time is referred as the"window period". It's hard to get immune response so that most of the vaccinations are delayed. However, studies show that there are active immune during this period as well. Moreover, vaccination with hepatitis B vaccine at birth, have had almost adult response rate, which makes the question of whether the active immune of infants is mature to become a hot topic again. Animal experiments show that: vaccinated parent, the response rate of vaccine of its offspring is also high. The further research indicates that maternal PBMC in the colostrum can directly transfer to the offspring. Population studies have shown that: maternal PBMC can directly transfer to fetus across the placenta in vivo. As maternal PBMC from animal has active immune function in its offspring, we speculate that maternal PBMC from human should have similar active immune function. Therefore, we put forward the hypothesis: The transfer of maternal immunity promotes the immune response of infants about hepatitis B vaccine. And then we may explain the contradiction of immature active immunity and high response rate of hepatitis B vaccine.Methods:This study explores from two aspects: Animal experiment and population study.1. Animal experiment: All animal experiments were conducted between March 2009 and December 2009 in Shaanxi province,March 2010 and December 2010 in Gansu province. All Sows were free from anti-HBV before the start of the experiment detected by Enzyme-linked immunosorbent assay (ELISA) kits, and were randomly allocated to experiment group (EG) or control group (CG). Sows and piglets were ear notched or punched for identification purposes. After deliveries, the piglets were fed with their mother's milk in the first month, and then they were raised in routine method. In the first batch of animal experiments, the piglets delivered by the sows of EG were randomly assigned to vaccinated group (VG-EG) or non-vaccinated group (NVG-EG), the piglets delivered by the sows of CG were also randomly assigned to vaccinated group (VG-CG) or non-vaccinated group (NVG-CG). Based on the results of the first batch of experiment, anti-HBs of all the piglets in NVG-EG and NVG-CG were negative, so in the second batch of experiment, all the piglets received three doses of vaccination and divided into VG-EG or VG-CG. The sows of EG and the piglets of VG-EG and VG-CG were vaccinated three times with 20μg of recombinant hepatitis B vaccine intradermally in two lateral sides of the neck behind the ear. Blood samples were collected 2ml for each piglet in evacuated test tubes by venipuncture of ear vein using sterile equipment and procedures, respectively, on weeks 1, 2, 3, 4, 5, 6, 7, 8, 9 and 10 post-immunization. Anti-HBs of all the serum specimens were tested by using Enzyme-linked immunosorbent assay (ELISA) kits for anti-HBs from Kehua Company in Shanghai and Electro-Chemiluminescence Immunoassay (ECLIA) reagents for anti-HBs from Roche Diagnostics GmbH.2. Population study: The preparation of the multi-centre population study was started in January 2010 and data analysis was completed in December 2010. All field work was conducted in Wuwei city of Gansu province from May to October 2010. A total of 328 mother-baby pairs were recruited, including 74 pairs from three hospitals (Wuwei City People's Hospital, Liangzhou Hospital and the third hospital of Liangzhou distinct) and 254 pairs from Yongchang county of Gansu province. The inclusion criteria were that the mothers had no history of hepatitis B virus infection and the ages of infants were 8- 48 months. A standard questionnaire was used to compile the basic information, family history of hepatitis B virus infection, the information of breastfeeding and immunization history of mothers and infants through face to face interview with mothers. Blood samples, collected for each study subject, included 5ml for mothers and children above 2 years, or 3ml for children less than 2 years. HBs Ag of all the serum specimens were tested by using ELISA kits for HBsAg from Kehua Company in Shanghai. Anti-HBs were tested by using ELISA kits for anti-HBs from Kehua Company and ECLIA reagents for anti-HBs from Roche Diagnostics GmbH. Retrospective cohort study was used for analyzing the differences between anti-HBs titers of the infants whose mothers had different anti-HBs titers.3. Statistical Analysis: Data were input in duplicates into the database with SPSS 16.0. All statistical analysis was performed using SPSS version 16.0 and SAS version 9.1. Figures were performed using Microsoft office excel 2007. The t test (or t'test), Correlation, the Chi-square (χ2)-test (or Fisher's exact test), Repetitive measure analysis of variance, Wilcoxon rank sum test were used in the statistical treatment.Results:1. Animal experiment: There are 9 sows and 79 piglets (53 survived, the survival rate is 67.1%). The qualitative results of ELISA demonstrated that the piglets of VG-EG had a significantly higher anti-HBs positive rates when compared with the piglets of VG-CG (P<0.01). The quantitative results of ECLIA demonstrated that the piglets of VG-EG had a significantly higher anti-HBs titers compared with the piglets of VG-CG on weeks 4 and 5 post-immunization (P<0.05); weeks 1, 2, 3, 6, 7, 8, 9 and 10 post-immunization (P<0.01). Moreover, the results of repetitive measure analysis of variance also showed the anti-HBs titers of the piglets of VG-EG were significantly higher (F=14.89,P<0.001). The anti-HBs positive rates (anti-HBs titers≥10 mIU/mL) and anti-HBs high positive rates (anti-HBs titers≥100 mIU/mL) of the piglets of VG-EG at ten different times after immunization were high than the rates of VG-CG.2. Population study: The quantitative results (n=285 pairs) showed: 56.8% (162/285) mothers and 33.0% (94/285) infants were anti-HBs negative (anti-HBs titers<10 mIU/mL);43.2% (123/285) mothers and 67.0% (191/285) infants were anti-HBs positive (anti-HBs titers≥10 mIU/mL). All infants received hepatitis B vaccine in three doses. However, the rates of the first dose, the second dose and the third dose of hepatitis B vaccine which were vaccinated on time were 96.8%, 84.2% and 60.0% seperately. Totally 44.6% (127/285) of the infants were vaccinated delayed (≥one of the three doses of hepatitis B vaccine were delayed). The results of retrospective cohort study demonstrated that the anti-HBs titers of the infants delivered by mothers who were anti-HBs positive (anti-HBs titers≥10 mIU/mL) were significantly higher compared with the infants delivered by mothers who were anti-HBs negative (anti-HBs titers<10 mIU/mL) (P<0.05). Moreover, anti-HBs positive rate of the infants who were breastfed by their mothers was significantly higher than the infants who were formula-fed (69.5% versus 28.6%, P<0.05). In addition, we chose the mothers who had immunity history of hepatitis B vaccine before their delivering. Then we compare the anti-HBs titer, qualitatively and quantitatively, between the infants whose mothers were anti-HBs positive and those whose are negative. The results show that there were no significant differences in the anti-HBs positive rate and titers (P>0.05).Conclusion:1. We found that the transfer from maternal hepatitis B vaccine-specific immunity to offsprings in pigs for the first time all over the world: The anti-HBs titers of the piglets of VG-EG, delivered by the sows vaccinated with hepatitis B vaccine, were significantly higher compared with the piglets which were delivered by unvaccined sows.2. The study results supported the hypothesis we put forward by using retrospective cohort study: The transfer of maternal immunity promotes the immune response of infants about hepatitis B vaccine. The anti-HBs titers of the infants delivered by mothers who were anti-HBs positive were significantly higher than the infants delivered by mothers who were anti-HBs negative; anti-HBs positive rate of the infants who were breastfed by their mothers was significantly higher compared with the infants who were formula-fed. However, when we analyze the results of mothers who had immunity history of hepatitis B vaccine, for an insufficient sample size, we could not rule out the Genetic susceptibility of hepatitis B which may have influence on our results.3. If mothers were immunited with hepatitis B vaccine, active immunity can be transferred from mothers to their infants and promote the immune response against hepatitis B vaccine of infants. The immunity of hepatitis B vaccine and the detection of HBV markers for women of childbearing age should be paid more attention, which can reduce the incidence of weak or non-response of hepatitis B vaccine of infants and improve the hepatitis B vaccine immunization programs.