Inhibition of in vitro Infection of Hepatitis B Virus by Human Breastmilk

Background: Despite the presence of hepatitis B virus (HBV) in human breastmilk of mothers infected with HBV, breastfeeding does not increase the risk of mother-to-child transmission (MTCT) of HBV. We hypothesized that human breastmilk may contain active component(s) that binds to HBV and inhibits the infectivity of HBV. Methods: Competitive inhibition immunoassays and far-Western blotting were used to test the binding of human whey to hepatitis B surface antigen (HBsAg). The identity of the component(s) responsible for the binding was determined by protein mass spectrometry. The inhibition of human whey and binding component on the infectivity of HBV was evaluated in an HBV culture system based on HepG2 cells that stably express sodium-taurocholate co-transporter polypeptide (NTCP). Results: Human whey significantly inhibited the binding of HBsAg to anti-HBs in competitive inhibition immunoassays. The far-Western blotting showed that HBsAg bound to a protein at approximately 80 kD, which was identified to be lactoferrin by mass spectrometry. Competitive inhibition immunoassays further demonstrated that human and bovine lactoferrin bound to HBsAg. Human whey from HBsAg-negative or -positive mothers, natural human lactoferrin, recombinant human lactoferrin, and bovine lactoferrin each significantly inhibited the infectivity of HBV in HepG2-NTCP cells. Interpretation: Our results indicate that human breastmilk can bind to HBsAg and inhibit the infectivity of HBV and the active component is lactoferrin. The findings may explain the reason that breastfeeding has no additional risk for MTCT of HBV, although human breastmilk contains HBV. Funding Information: National Natural Science Foundation of China (81672002), the Science and Technology Department of Jiangsu Province (BK20161105), and the Jiangsu Provincial Department of Health (H201537), China. Declaration of Interests: The authors who have taken part in this study declared that they do not have anything to disclose regarding conflict of interest with respect to this manuscript. Ethics Approval Statement: This study was approved by the institutional review boards of Nanjing Drum Tower Hospital.