In a recent study posted to bioRxiv*, researchers at Washington University School of Medicine, St. Louis, demonstrated that severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) vaccine booster elicits robust germinal center (GC) B cell responses.
Several studies have reported that coronavirus disease 2019 (COVID-19) vaccine boosters enhance immune responses to ancestral SARS-CoV-2 and emergent variants of concern. Besides, new vaccines based on circulating SARS-CoV-2 variants are being developed to augment antibody responses.
Moreover, recent evidence suggests that a booster dose based on the Beta variant results in higher titers of neutralizing antibodies (nAbs) against Beta and Omicron variants than wildtype-based booster or bivalent vaccines encoding wildtype and Omicron spike proteins. Nonetheless, it remains unclear whether booster doses induce GC reactions.
Study: SARS-CoV-2 Omicron boosting induces de novo B cell response in humans. Image Credit: NIAID
The study and findings
In the present study, researchers evaluated the immune responses of SARS-CoV-2 infection-naïve healthy, vaccinated adults. Participants completed primary vaccination with Pfizer’s BNT162b2 or Moderna’s mRNA-1273 vaccine. They were boosted with a single dose of mRNA-1273 or the bivalent mRNA-1273.213 (based on the spike proteins of Beta and Delta variants). Forty-six individuals were recruited; seven were boosted with the mRNA-1273, while 31 received the variant-specific vaccine.
Enzyme-linked immunosorbent spot (ELISpot) assay was used to quantify circulating spike-specific plasmablasts. The authors detected spike-specific IgA- and IgG-producing plasmablasts in all mRNA-1273 recipients a week after boosting. Similarly, they observed IgG-producing plasmablasts against the spike protein of ancestral strain, Beta, and Delta variants. In addition, fine needle aspirates (FNAs) and bone marrow aspirates were collected from some individuals…