Longitudinal T and B cell recall responses following vaccination with the Pfizer-BioNTech mRNA vaccine BNT162b2.

BACKGROUND SARS-CoV-2 caused a pandemic that resulted in the death of millions of patients. The Pfizer-BioNTech mRNA vaccine against SARS-CoV-2 (BNT162b2) induced the development of antigen-specific T and B cells, which correlated with protection from disease. However, their ability to mount a true recall response following reactivation was not addressed. OBJECTIVE To determine the longevity, intensity, and phenotype of the T and B cell recall responses following vaccination with BNT162b2. METHODS Twelve participants vaccinated with BNT162b2 were included in this study. Six blood samples were collected prior to administering the prime dose, 21 days after the prime dose, and 1, 3, 6, and 9 months post-booster dose. Antigen-specific B and T cells were stimulated ex vivo, and their abundance, longevity, phenotype, and intensity of their recall responses were analyzed. Plasma and supernatant of activated B cells were used to determine the levels, kinetics, and neutralization potential of antigen-specific immunoglobulins. RESULTS Vaccination with BNT162b2 resulted in the development of long-lasting neutralizing immunoglobulins, as well as antigen-specific memory CD4+ T cells that proliferate upon reactivation, promote a protective Th1 response, and induce IgG/IgA class switching in antigen-specific memory B cells, which are primed to secrete neutralizing antibodies upon reactivation. Additionally, antigen-specific memory CD8+ T cells proliferate upon reactivation and upregulate granzyme and perforin to eliminate infected cells. CONCLUSION Vaccination with BNT162b2 induces spike-specific memory T and B cells that are reactivated upon antigen exposure to mount a recall response that protects from SARS-CoV-2 infection for up to 9 months after immunization.