Characterization of SARS-CoV-specific memory T cells from recovered individuals 4 years after infection

SARS-CoV infection of human results in antigen-specific cellular and humoral immune responses. However, it is critical to determine whether SARS-CoV-specific memory T cells can persist for long periods of time. In this study, we analyzed the cellular immune response from 21 SARS-recovered individuals who had been diagnosed with SARS in 2003 by using ELISA, CBA, ELISpot and multiparameter flow cytometry assays. Our results demonstrated that low levels of specific memory T cell responses to SARS-CoV S, M, E and N peptides were detected in a proportion of SARS-recovered patients, and IFN-γ was the predominant cytokine produced by T cells after stimulation with peptides. Cytometry analysis indicated that the majority of memory CD8(+) T cells produced IFN-γ, whereas memory CD4(+) T cells produced IFN-γ, IL-2 or TNF-α. These results might provide valuable information on the cellular immune response in recovered SARS-CoV patients for the rational design of vaccines against SARS-CoV infection.