Human memory T cell responses to SARS-CoV E protein

E protein is a membrane component of severe acute respiratory syndrome coronavirus (SARS-CoV). Disruption of E protein may reduce viral infectivity. Thus, the SARS-CoV E protein is considered a potential target for the development of antiviral drugs. However, the cellular immune responses to E protein remain unclear in humans. In this study, we found that peripheral blood mononuclear cells (PBMCs) from fully recovered SARS individuals rapidly produced IFN-γ and IL-2 following stimulation with a pool of 9 peptides overlapping the entire E protein sequence. Analysis of the immune responses by flow cytometry showed that both CD4(+) and CD8(+)T cells were involved in the SARS-CoV E-specific immune responses after stimulation with SARS-CoV E peptides. Moreover, the majority of IFN-γ(+)CD4(+)T cells were central memory cells expressing CD45RO(+)CCR7(+)CD62L(−); whereas IFN-γ(+)CD8(+) memory T cells were mostly effector memory cells expressing CD45RO(−)CCR7(−)CD62L(−). The results of T-cell responses to 9 individual peptides indicated that the E protein contained at least two major T cell epitopes (E2 amino acid [aa] 9–26 and E5–6: aa 33–57) which were important in eliciting cellular immune response to SARS-CoV E protein in humans.