Research Alert
Newswise — The COVID-19 pandemic has resulted in rapid development of several novel vaccine platforms, including the mRNA-based Pfizer/BioNTech vaccine. As of October 2022, more than 3.8 billion Pfizer/BioNTech vaccines were administrated to people in 180 countries. Meanwhile, the total number of COVID-19 cases has reached 627 million globally.
We recently developed a new antigen-specific T cell staining toolー "spheromer" that is able to label T cells more efficiently and capture a broader swath of the repertoire than any other available platform. Using spheromers loaded with SARS-CoV-2 peptides, we applied a panel covers 49 epitopes spanning the entire genome to characterize the magnitude and durability of antigen-specific T cell responses at single epitope resolution.
Using very sensitive "spheromer'' peptide-MHC multimer reagents, we analyzed healthy subjects receiving two doses of the Pfizer/BioNTech BNT162b2 vaccine. Vaccination resulted in very robust peripheral blood responses to predicted SARS-CoV-2 spike peptides bound to either class-I or class-II MHC alleles. These peaked at 9.8% and 7.5% for the dominant CD4+ (HLA-DRB1*15:01/S191) and CD8+ (HLA-A*02/S691) T cell epitopes. Interestingly, the antigen-specific CD4+ and CD8+ T cell responses were asynchronous, with the peak CD4+ T cell responses occurring one week post the second vaccination (boost), whereas CD8+ T cells didn't peak until two weeks later. These responses were much higher than in COVID-19 patients. We also found that prior SARS-CoV-2 infection decreased the CD8+ T cell response post vaccination by 2.4 to 41.4-fold at peak, and that the remaining cells were less responsive, suggesting that the virus can profoundly damage an individuals' CD8+ T cell response.
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