Optimization of an efficient cell culture hepatitis B infection system for assessment of hepatitis B virus neutralizing monoclonal antibodies

Background: Human polyclonal plasma-derived hepatitis B immunoglobulin (HBIG) is currently used for immunoprophylaxis of HBV infection. The development of virus-neutralizing monoclonal antibodies (MAbs) requires the use of optimized cell culture systems supporting HBV infection. Objective: This study aims to optimize the hepatitis B virus infectivity of NTCP-reconstituted HepG2 (HepG2-NTCP) cells to establish an efficient system to evaluate the HBV-neutralizing effect of anti-HBs MAbs. Methods: Serum-derived HBV (sHBV) and cell culture-derived HBV (ccHBV) were simultaneously used for the optimization of HBV infection in HepG2-NTCP cells by applying different modifications. Results: Our results for the first time showed that in addition to human serum, monkey serum could significantly improve ccHBV infection, while fetal and adult bovine serum as well as duck and sheep serum did not have a promotive effect. In addition, sHBV and ccHBV infectivity are largely similar except that adding 5% of PEG, which is commonly used to improve in vitro infection of ccHBV, significantly reduced sHBV infection. We showed that a combination of spinoculation, trypsinization, and also adding human or monkey serum to HBV inoculum could significantly improve the permissivity of HepG2-NTCP cells to HBV infection compared with individual strategies. All anti-HBs MAbs were able to successfully neutralize both ccHBV and sHBV infection in our optimized in vitro system. Conclusion: Our study suggests different strategies for improving ccHBV and sHBV infection in HepG2-NTCP cells. This cell culture-based system allows assessment of HBV neutralizing MAbs and may also prove to be valuable for the analysis of other HBV neutralizing therapeutics.