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Updated: Nov 17, 2025
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
Immunogenicity and inflammatory properties of respiratory syncytial virus attachment G protein in cotton rats
Margaret E Martinez1, Cristina Capella Gonzalez2, Devra Huey1
1Department of Veterinary Biosciences, The Ohio State University College of Veterinary Medicine, Columbus, Ohio, United States of America.
Insights
Respiratory Syncytial Virus (RSV) G protein does not directly cause lung inflammation. Expressing RSV G protein via AAV in cotton rats induced immunity and partial protection against RSV challenge.
Area of Science:
- Virology
- Immunology
- Respiratory Medicine
Background:
- Human respiratory syncytial virus (RSV) is a major cause of infant respiratory infections.
- The RSV G protein, in membrane-bound (mG) and secreted (sG) forms, binds to cellular receptors via a CX3C motif.
- Previous studies suggested RSV G protein mimics CX3CL1, potentially increasing pulmonary inflammation, but this was not directly tested independently of viral replication.
Purpose of the Study:
- To investigate the direct immunomodulatory effects of RSV G protein (mG, sG, or both) on pulmonary inflammation, independent of viral replication.
- To assess the potential of G protein expression using adeno-associated virus (AAV) vectors to induce protective immunity against RSV challenge.
Main Methods:
- Adeno-associated virus (AAV) vectors were used to express membrane-bound G protein (mG), secreted G protein (sG), or both (G) in cotton rat lungs.
- Pulmonary inflammation was assessed via histology and bronchoalveolar lavage.
- Immune responses (antibodies, CD8 T cells) and protection against RSV challenge were evaluated after AAV-G expression.
Main Results:
- AAV-mediated expression of mG, sG, or G did not increase pulmonary inflammation.
- Long-term AAV-G expression induced non-neutralizing antibodies and CD8 T cell responses.
- AAV-G expression conferred partial protection against RSV challenge, enhanced by co-immunization with interferon-α.
Conclusions:
- The RSV G protein, when expressed independently of viral replication, does not directly induce pulmonary inflammation.
- AAV-mediated expression of RSV G protein can elicit adaptive immune responses and provide partial protection against RSV infection.
- Combined AAV-G and interferon-α immunization achieved complete protection, suggesting a potential vaccine strategy.
Abstract:
Human respiratory syncytial virus (RSV) is a leading cause of lower respiratory tract infection in infants and young children worldwide. The attachment (G) protein of RSV is synthesized by infected cells in both a membrane bound (mG) and secreted form (sG) and uses a CX3C motif for binding to its cellular receptor. Cell culture and mouse studies suggest that the G protein mimics the cytokine CX3CL1 by binding to CX3CR1 on immune cells, which is thought to cause increased pulmonary inflammation in vivo. However, because these studies have used RSV lacking its G protein gene or blockade of the G protein with a G protein specific monoclonal antibody, the observed reduction in inflammation may be due to reduced virus replication and spread, and not to a direct role for G protein as a viral chemokine. In order to more directly determine the influence of the soluble and the membrane-bound forms of G protein on the immune system independent of its attachment function for the virion, we expressed the G protein in cotton rat lungs using adeno-associated virus (AAV), a vector system which does not itself induce inflammation. We found no increase in pulmonary inflammation as determined by histology and bronchoalveolar lavage after inoculation of AAVs expressing the membrane bound G protein, the secreted G protein or the complete G protein gene which expresses both forms. The long-term low-level expression of AAV-G did, however, result in the induction of non-neutralizing antibodies, CD8 T cells and partial protection from challenge with RSV. Complete protection was accomplished through co-immunization with AAV-G and an AAV expressing cotton rat interferon α.
