Hepatitis B virus infection and immune response among infants born to HBV surface antigen positive mothers in Yunnan province

Objective To examine the infection prevalence of and immune response to hepatitis B virus (HBV) among infants born to HBV surface antigen (HBsAg) positive mothers in Yunnan province.Methods The HBsAg positive women were screened out from all pregnant women hospitalized for their delivery in Yunnan province between January through June 2011; then procedures for the prevention of mother-to-infant transmission (PMTCT) were implemented among the participants and their newborns.The venous blood specimens (2 milliliters for each) were collected from the participants' infants aged 7-12 months and detected for HBsAg,antibody to HB surface antigen (anti-HBs),hepatitis B e antigen (HBeAg),antibody to HB e antigen (anti-HBe),and antibody to HB core antigen (anti-HBc) with enzyme-linked immunosorbent assay (ELISA).The specimens positive to HBsAg were further quantified for HBV-DNA with PCR-fluorescent probing and those negative to HBsAg but positive to anti-HBs were detected for the quantification of anti-HBs with chemiluminescence immunoassay.Results Among a total of 3 026 infants with PMTCT,the immune response rate was 92.43% and the effective immune response rate was 80.04%,while the proportion of the infants presenting non-effective immunity was 16.09% and the failure rate of PMTCT was 3.87%.For all specimens detected,74.62% were anti-HBs positive-only; 14.44% were both anti-HBs and anti-HBc positive; 3.70% were negative for all the five indicators; and 3.37% were anti-HBs,anti-HBe and anti-HBc positive.For all the infants identified as PMTCT failure,45.30%,39.32%,and 15.38% were determined with the HBV-DNA of >5×10⁷ IU/ml,500-5×10⁷ IU/ml,and <500 IU/ml and 79.49% were HBeAg positive.Among the infants with effective immune response,80.73% were anti-HBs positive-only; 16.62% were both anti-HBs and anti-HBc positive; 3.65% were anti-HBs,anti-HBc and anti-HBe positive; and the positive rate of anti-HBc and anti-HBe were 23.20% and 3.79%,respectively.Of all the infants with effective immune response,66.93%,19.66%,and 13.41% were detected with the anti-HBs level of >1 000 mIU/ml,100-1 000 mIU/ml,and 10-99 mIU/ml.The results of statistical analyses demonstrated that immune response level was irrelevant neither to gender nor to serum positivity of anti-HBe and anti-HBc.Conclusion The implementation of PMTCT and postpartum medical follow-up play a critical role for the prevention and control of HBV infection among the infants born to HBsAg positive mothers.