High Environmental Stability of Hepatitis B Virus and Inactivation Requirements for Chemical Biocides

Than, Thoa Thi; Jo, Eunji; Todt, Daniel; Nguyen, Phuong Hong; Steinmann, Jochen; Steinmann, Eike; Windisch, Marc P

In this study, we analyzed the stability of the HBV by using a recently developed cell culture system fully susceptible and permissive to HBV infection and replication with high titer virus stocks. The high environmental stability of HBV observed in this study was also previously observed in an in vivo model system. Bond et al demonstrated in 1981 that HBV-positive human plasma, which was dried for 1 week and inoculated in chimpanzees, resulted in an active infection [12] . This infection system is based on human hepatoma cells and viruses generated in vitro, which might differ from primary human hepatocytes and patient-derived viral particles in some aspects. However, given the recent progress that has been made in HBV research using this system, cell culture-derived HBV particles are considered the best tool to address the questions described here [13] . However, other time points and long-term storage of plasma ex vivo were not investigated. For HCV, another blood-borne virus that belongs to the family of Flaviviridae, the environmental stability was much lower, with a half-life of 6 hours at 37°C and 11 days at 4°C [9] . Regarding the inactivation profiles for HBV with different alcohols, 1-propanol could be identified as the most effective alcohol in a quantitative suspension test, in line what has been described for HCV [9] . The concentrations of the tested alcohols required for virucidal activity were slightly higher than those required for the often-used DHBV [4] , but side-by-side comparisons using the experimental procedure have not been conducted. Importantly, 5 different alcohol-based, commercially available hand disinfectants were able to inactivate HBV after exposure for 30 seconds in a suspension test. Dilution of these products abrogated the susceptibility of HBV, but under practical conditions hand antiseptics are not diluted, precluding a recommendation for a specific product. Two WHO-recommended formulations that have been proposed as alcohol-based hand rubs to reduce the transmission of pathogens [10] were able to completely inactivate HBV. Importantly, in comparison to the enveloped viruses EBOV, HCV, influenza A(H1N1) virus, MERS-CoV, and MVA, HBV demonstrated the highest stability. The degree of susceptibility of the different viruses to the WHO formulation likely depends on the specific surface properties of the lipophilic envelope of the respective virus [14] . HBV subviral particles display a fluid bilayer membrane and were shown to have a strong resistance to freeze drying [15] . However, further investigations are required in the future, ideally with serum-derived HBV, to analyze this phenomenon in more detail.