Nonglycosylated RSV F protein elicited protective immunity in mice

Abstract Human respiratory syncytial virus (RSV) is the primary cause of severe respiratory tract disease in infants and young children, but no vaccine is yet on the market. The fusion (F) protein of RSV, especially the prefusion F protein (pre-F), is the best antigen for eliciting a protective immunity and neutralizing antibody response in the host. In this study, we constructed and purified the nonglycosylated pre-F protein using Escherichia coli BL21, called pre-RBF. We found that pre-RBF could be produced at high levels with stable trimer conformations. Importantly, pre-RBF was shown to bind 5C4, a monoclonal antibody specific for the pre-F. Compared to mice immunized with formalin-inactivated RSV (FI-RSV), mice immunized with different doses of pre-RBF all showed superior protective immunity, which was confirmed by serum-neutralizing activity and viral clearance after challenge. Pre-RBF induced a balanced Th1-biased immunity response, whereas FI-RSV induced Th2-biased immune responses. So pre-RBF represents a potential vaccine candidate for the prevention of human infection with RSV.