Characterisation of Antibody Interactions with the G Protein of Vesicular Stomatitis Virus Indiana Strain and Other Vesiculovirus G Proteins

Vesicular stomatitis virus Indiana strain G protein (VSVind.G) is the most commonly used envelope glycoprotein to pseudotype lentiviral vectors (LV) for experimental and clinical applications. Recently, G proteins derived from other vesiculoviruses (VesG), for example Cocal virus, have been proposed as alternative LV envelopes with possible advantages compared to VSVind.G. Well-characterised antibodies that recognise VesG will be useful for vesiculovirus research, development of G protein-containing advanced therapy medicinal products (ATMPs), and deployment of VSVind-based vaccine vectors. Here we show that one commercially available monoclonal antibody, 8G5F11, binds to and neutralises G proteins from three strains of VSV as well as Cocal, and Maraba viruses, whereas the other commercially available monoclonal anti-VSVind.G antibody, IE9F9, binds to and neutralises only VSVind.G. Using a combination of G protein chimeras and site-directed mutations, we mapped the binding epitopes of IE9F9 and 8G5F11 on VSVind.G. IE9F9 binds close to the receptor binding site and competes with soluble low-density lipoprotein receptor (LDLR) for binding to VSVind.G, explaining its mechanism of neutralisation. In contrast, 8G5F11 binds close to a region known to undergo conformational changes when the G protein moves to its post-fusion structure, and we propose that 8G5F11 cross-neutralises VesGs by inhibiting this.\n\nIMPORTANCEVSVind.G is currently regarded as the gold-standard envelope to pseudotype lentiviral vectors. However, recently other G proteins derived from vesiculoviruses have been proposed as alternative envelopes. Here, we investigated two anti-VSVind.G monoclonal antibodies for their ability to cross-react with other vesiculovirus G proteins, and identified the epitopes they recognise, and explored the mechanisms behind their neutralisation activity. Understanding how cross-neutralising antibodies interact with other G proteins may be of interest in the context of host-pathogen interaction and co-evolution as well as providing the opportunity to modify the G proteins and improve G protein-containing medicinal products and vaccine vectors.