Understanding the T cell immune response in SARS coronavirus infection

Janice Oh, Hsueh-Ling; Ken-En Gan, Samuel; Bertoletti, Antonio; Tan, Yee-Joo

Amongst the SARS-CoV structural proteins, the S protein has been found to elicit neutralizing antibodies 17,18 with its major immunodominant epitope found between residues 441 to 700. Using an online database and with verification from T2 binding assays, the first two HLA-A*02:01-restricted T cell epitopes (S1203-1211 and S978-986) were identified in the S protein of SARS-CoV. 19 They were immunogenic and elicited high IFNc-specific T cell response in patients who have recovered from SARS. In comparison, the homologous peptide from HCoV229e did not elicit a significant response. A third CTL epitope, S1167-1175 (also known as SSp-1) was reported shortly after by another group. 20 This peptide was able to induce CTL response in HLA-A*02:01 transgenic mice immunized with peptide loaded dendritic cells (DCs). At the same time, they were able to generate peptidespecific CD8 1 CTL in peripheral blood mononuclear cells (PBMCs) from healthy human donor. The same group also showed that heat inactivated SARS-CoV particles elicited CTL response to all three S epitopes (SSp-1, S978 and S1202) in patients' PBMCs one year postinfection. 21 Interestingly, 5 healthy individuals without contact history with SARS-CoV also exhibited SSp-1-specific responses in their PBMCs but exhibited lower cytotoxic activity and cytokine release when compared to the recovered SARS patients.