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An In vitro Model to Study Immune Responses of Human Peripheral Blood Mononuclear Cells to Human Respiratory Syncytial Virus Infection
Published on: December 10, 2013
Structure-Based Design and Antigenic Validation of Respiratory Syncytial Virus G Immunogens
Ana M Nuñez Castrejon1, Sara M O'Rourke2, Lawrence M Kauvar3
1Department of Microbiology and Environmental Toxicology, University of California Santa Cruz, Santa Cruz, California, USA.
Insights
An engineered Respiratory Syncytial Virus (RSV) G protein mutant, RSV G S177Q, shows promise as a vaccine antigen. It retains high-affinity binding to protective antibodies and maintains its structure, addressing previous immunogenicity and safety concerns for RSV G vaccine development.
Area of Science:
- Virology and Immunology
- Vaccine Development
Background:
- Respiratory Syncytial Virus (RSV) is a major cause of severe respiratory illness in vulnerable populations, with no current FDA-approved vaccines.
- The RSV G glycoprotein mediates viral attachment and immune evasion but has been challenging to develop as a vaccine antigen due to poor immunogenicity and safety concerns.
- Previous engineering of RSV G proteins introduced mutations to enhance immunogenicity and safety, but their impact on protein structure and epitope display was unclear.
Purpose of the Study:
- To investigate whether engineered single-point mutant RSV G proteins retain their antigenic structure and binding to protective antibodies.
- To validate the potential of an engineered RSV G protein, specifically RSV G S177Q, as a vaccine immunogen.
Main Methods:
- Assessed the binding affinity of the engineered RSV G S177Q protein to protective human and mouse monoclonal antibodies.
- Evaluated the reactivity of RSV G S177Q with human reference immunoglobulin to RSV.
- Determined the high-resolution crystal structure of the RSV G S177Q protein in complex with the anti-RSV G antibody 3G12.
Main Results:
- The RSV G S177Q protein demonstrated high-affinity binding to protective monoclonal antibodies against RSV.
- RSV G S177Q exhibited comparable reactivity to wild-type RSV G protein with human anti-RSV antibodies.
- The crystal structure revealed that RSV G S177Q maintains its antigenic structure, validating its conformational epitopes.
Conclusions:
- The engineered RSV G S177Q protein successfully retains high-affinity binding to protective antibodies and its native antigenic structure.
- These findings support the further development of RSV G S177Q as a viable vaccine immunogen, addressing prior limitations.
- Structure-guided design of RSV G mutants offers a promising strategy for developing effective RSV vaccines.
Abstract:
Respiratory syncytial virus (RSV) is a leading cause of severe lower respiratory tract disease of children, the elderly, and immunocompromised individuals. Currently, there are no FDA-approved RSV vaccines. The RSV G glycoprotein is used for viral attachment to host cells and impairment of host immunity by interacting with the human chemokine receptor CX3CR1. Antibodies that disrupt this interaction are protective against infection and disease. Nevertheless, development of an RSV G vaccine antigen has been hindered by its low immunogenicity and safety concerns. A previous study described three engineered RSV G proteins containing single-point mutations that induce higher levels of IgG antibodies and have improved safety profiles compared to wild-type RSV G (H. C. Bergeron, J. Murray, A. M. Nuñez Castrejon, et al., Viruses 13:352, 2021, https://doi.org/10.3390/v13020352). However, it is unclear if the mutations affect RSV G protein folding and display of its conformational epitopes. In this study, we show that the RSV G S177Q protein retains high-affinity binding to protective human and mouse monoclonal antibodies and has equal reactivity as wild-type RSV G protein to human reference immunoglobulin to RSV. Additionally, we determined the high-resolution crystal structure of RSV G S177Q protein in complex with the anti-RSV G antibody 3G12, further validating its antigenic structure. These studies show for the first time that an engineered RSV G protein with increased immunogenicity and safety retains conformational epitopes to high-affinity protective antibodies, supporting its further development as an RSV vaccine immunogen. IMPORTANCE Respiratory syncytial virus (RSV) causes severe lower respiratory diseases of children, the elderly, and immunocompromised populations. There currently are no FDA-approved RSV vaccines. Most vaccine development efforts have focused on the RSV F protein, and the field has generally overlooked the receptor-binding antigen RSV G due to its poor immunogenicity and safety concerns. However, single-point mutant RSV G proteins have been previously identified that have increased immunogenicity and safety. In this study, we investigate the antibody reactivities of three known RSV G mutant proteins. We show that one mutant RSV G protein retains high-affinity binding to protective monoclonal antibodies, is equally recognized by anti-RSV antibodies in human sera, and forms the same three-dimensional structure as the wild-type RSV G protein. Our study validates the structure-guided design of the RSV G protein as an RSV vaccine antigen.
