T-Cell Responses in Adults During Natural Respiratory Syncytial Virus Infection

Background. The pathogenesis of respiratory syncytial virus (RSV) in older adults may be due to age-related T-cell immunosenescence. Thus, we evaluated CD4 and CD8 T-cell responses during RSV infection in adults across the age spectrum. Methods. Peripheral blood mononuclear cells collected during RSV infection in adults, age 26-96 years, were stimulated with live RSV and peptide pools representing F, M, NP, and G proteins and analyzed by flow cytometry. Results. There were no significant age-related differences in frequency of CD4(+) T cells synthesizing interferon (IFN)gamma, interleukin (IL) 2, IL4, IL10, or tumor necrosis factor (TNF)alpha or in CD8(+) IFN gamma(+) T cells. IL4(+) CD4(+) T-cell numbers were low, as were IL13 and IL17 responses. However, in univariate analysis, CD4 T-cell IFN gamma, IL2, IL4, IL10, and TNF alpha responses and CD8(+) IFN gamma(+) T cells were significantly increased with more severe illness requiring hospitalization. In multivariate analysis, viral load was also associated with increased T-cell responses. Conclusions. We found no evidence of diminished RSV-specific CD4 or CD8 T-cell responses in adults infected with RSV. However, adults with severe disease seemed to have more robust CD4 and CD8 T-cell responses during infection, suggesting that disease severity may have a greater association with T-cell responses than age.