Understanding the T cell immune response in SARS coronavirus infection

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

There are very few studies of T cell response to other SARS-CoV proteins. Nonetheless, animal studies using DNA vaccines suggest that the M protein may induce T cell response, albeit to a lesser degree than the S and N proteins. 38 Yang et al. demonstrated that it was possible to induce recall T cell response from the PBMCs of SARS patients who have recovered for more than 1 year by using overlapping peptides spanning the entire M protein. 41 In this study, four human T cell immunodominant peptides, M21-44, M65-91, M117-140 and M200-220, were subsequently identified. Similarly, Li et al. also reported that 9% of their SARS subjects had T cell response against the M peptide region, M146-160. 34 The largest accessory protein of SARS-CoV is the 3a protein of 274 amino acids. However, other than Li et al.'s report, there had been no demonstration of T cell responses against this protein. The 3a protein peptide 3a36-50 was one of the three most frequently recognized T cell epitopes identified in their study. 34 Similar to the results reported by Li et al. our data showed that the 3a protein peptide 3a6-20 was able to elicit both CD8 1 and CD4 1 responses. 33 Interestingly, mice immunized with 3a DNA vaccine were shown to have high levels of humoral response as well as Th1 response. 42 These observations indicated that the accessory 3a protein is immunogenic and able to induce T cell response.