Protective and dysregulated T cell immunity in RSV infection

- T cell responses play an important role in clearance of RSV, and probably in protective immunity.
- T cells are also responsible for immune-mediated tissue damage in RSV infection and in vaccine-enhanced disease.
- RSV possesses multiple immune evasion strategies that inhibit T cell function via soluble factors and dendritic cells.
- Dysregulated immune responses to RSV infection may partly account for severe disease.
- Therapeutic strategies aimed at boosting regulatory T cell responses might be beneficial.

Respiratory syncytial virus (RSV) is the most important cause of infantile bronchiolitis and a major pathogen in elderly and immunosuppressed persons. Although RSV shows limited antigenic diversity, repeated infections occur throughout life. Vaccine development has been delayed by poor immunogenicity, production issues and the fear of causing enhanced disease. T cells assist in viral clearance, but immune regulation serves to limit these responses and to prevent the exaggerated inflammatory response to RSV infection seen in children with bronchiolitis. Severe RSV disease can therefore be regarded as a dysregulated response to an otherwise trivial infection. Further insights into the role of T cells (including Th17) are needed to enable the rational design of safe, effective vaccines and novel treatments.