Durability of B and T cell responses against a spike protein of SARS-CoV2 elicited by mRNA vaccines

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AAI Annual Meeting; May 6-10; Portland, OR. 2022


oregon; chiles; covid-19


The pandemic of SARS-CoV2 had resulted in over 266 million infections and over 5.2 million deaths throughout the world as of early-December 2021. Pfizer and Moderna mRNA vaccines were approved for Emergency Use Authorization by the US FDA. Even though 8.2 billion doses of vaccine have been administered, the world continues to see wide-spread SARS-CoV2 infection. Therefore, it is important to understand the durability of anti-SARS-CoV2 immune responses. Serum and PBMC samples were collected from vaccinated volunteers (N=40, Age 22-67, median age 41, Male/Female = 14/26, Moderna/Pfizer = 37/3) over 8 months (pre-vaccination baseline: TP1, 2 weeks-, 3 months-, and 8 months-post full vaccination: TP2, TP3, and TP4, respectively). First, we found robust induction of anti-S IgG and IgA for all subjects at TP2, which was higher than those from Covid-19 patients. Follow up samples (TP3 and TP4) showed steady decay of antibody levels over 8 months post-vaccination. Next, we evaluated memory B cell response using flow cytometry. We detected S-protein specific B cells by using flag-tagged S-protein. The frequency of S-protein specific B cells varied among donors and was weakly associated with the level of serum anti-S IgG antibody. Lastly, we assessed T cell responses. PBMCs were stimulated with an overlapping 15-mer peptide mix that covers the entire S-protein. Antigen-specific activation of T cells were detected based upon IFN-γ and TNF-α production. We found induction of robust CD4 T cell response at TP2 but a clear reduction at TP3. TP4 showed equivalent levels of T cell responses as TP3. Together, we found that B and T cell responses against the spike protein of SARS-CoV2 induced by mRNA vaccines are not durable.


Earle A. Chiles Research Institute


Infectious Diseases


Hamilton LT, Koguchi Y, Christie T, Shimada T, Iwamoto N, Fox B, Redmond W, Piening B

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