Expression of the G glycoprotein gene of human respiratory syncytial virus in Salmonella typhimurium

The attachment protein, G, of human respiratory syncytial virus (RSV) is an M(r) 84K to 90K species which has a high content of N-linked and O-linked carbohydrates. The unglycosylated form of this protein was expressed by inserting a full-length cDNA copy of the mRNA from the A2 strain of RSV into a prokaryotic expression vector under the control of the lambda PL promoter. Salmonella typhimurium cells transformed with the G-containing plasmid synthesized a protein of M(r) 40,000 that specifically reacted with polyclonal and two neutralizing monoclonal antibodies raised against the native RSV G glycoprotein. Recombinant G protein was purified by immunoaffinity chromatography using a neutralizing monoclonal antibody. Cotton rats immunized with the recombinant G protein produced serum antibodies to the G glycoprotein that neutralized RSV in vitro. The study demonstrates that the G protein of RSV can be expressed in bacteria and that at least one neutralizing epitope is not structurally dependent on carbohydrates.