Screening and identification of hepatitis B surface antigen binding to lactoferrin in human milk / 中华围产医学杂志

ABSTRACT

Objective Human milk of mothers with positive hepatitis B surface antigen (HBsAg) contains hepatitis B virus (HBV). However, breastfeeding does not increase the risk of mother-to-infant transmission of HBV. Previous investigations demonstrated that breast milk has a property of binding with HBsAg. This study aimed to identify the component in human milk that can bind to HBsAg. Methods This study was performed in Nanjing Drum Tower Hospital, the Affiliated Hospital of Nanjing University Medical School, from June 2015 to February 2017. Human milk samples from two postpartum women with negative HBV markers and two control samples of cow milk and goat milk were analyzed by Far-Western blot, in which highly purified recombinant yeast HBsAg was used to bind with whey proteins. Based on the results of mass-spectrum analysis, competition inhibition test was used to confirm the functioning component. Results Far-Western blot showed remarkable protein bands at the relative molecular weight of about 80 000 in both lanes of human milk, but none in the lane of cow or goat milk. Mass-spectrum analysis of the protein band indicated there were proteins sharing 28.4%-93.4% homology in amino acid sequences with five proteins with the highest homology to lactoferrin (93.4%). Further Far-Western blot with purified recombinant lactoferrin showed that lactoferrin could bind to the recombinant HBsAg. Competition inhibition test suggested that the purified recombinant lactoferrin inhibited the binding of HBsAg to its antibody in a dose-dependent manner. Conclusions This study confirms the capability of lactoferrin in human milk to combine with HBsAg, suggesting that lactoferrin can bind to HBV. Further study on whether lactoferrin can inhibit the infectivity of HBV would be valuable to clarify the reason for not increasing the risk of mother-to-infant transmission of HBV by breastfeeding.