Roles Of The Fc Receptor Gamma-Chain In Inducing Protective Immune Responses After Heterologous Vaccination Against Respiratory Syncytial Virus Infection

The roles of the Fc receptor (FcR) in protection or inflammatory disease after respiratory syncytial virus (RSV) vaccination and infection remain unknown. Virus-like particles containing RSV fusion proteins (RSV F-VLPs) induce T-helper type 1 antibody responses and protection against RSV. Heterologous RSV F-VLP prime and formalin-inactivated RSV (FI-RSV) boost vaccination has been reported to be effective in providing protection without inflammatory disease. Here, we investigated whether the FcR gamma-chain is important for immune protection by the heterologous F-VLP and FI-RSV vaccination using FcR gamma-chain knockout (-/-) mice. RSV F-VLP-primed and FI-RSV-boosted FcR gamma -/- mice displayed less protective efficacy, as shown by higher lung viral titers upon RSV challenge, compared to RSV F-VLP-primed and FI-RSV-boosted immunized wild-type mice. RSV F-VLP and FI-RSV immunization induced lower levels of neutralizing activity and interferon-gamma-producing CD8 T-cells in the bronchoalveolar lavage cells of FcR gamma -/- mice than in those of wild-type mice. In addition, FcR gamma -/- mice displayed a trend of enhancing lung histopathology after RSV vaccination and infection. This study suggests that the FcR gamma-chain plays an important role in inducing antiviral protection and CD8 T-cell responses in RSV F-VLP prime and FI-RSV boost vaccination after RSV infections.