Preferential expansion of cross-reactive pre-existing switched memory B cells that recognize the SARS-CoV-2 Omicron variant Spike protein

In previously unvaccinated and uninfected individuals, non-RBD SARS-CoV-2 spike-specific B cells were prominent in two distinct, durable, resting, cross-reactive, "pre-existing" switched memory B cell compartments. While pre-existing RBD-specific B cells were extremely rare in uninfected and unvaccinated individuals, these two pre-existing switched memory B cell compartments were molded by vaccination and infection to become the primary source of RBD-specific B cells that are triggered by vaccine boosting. The frequency of wild-type RBD-binding memory B cells that cross-react with the Omicron variant RBD did not alter with boosting. In contrast, after a boost, B cells recognizing the full-length Omicron variant spike protein expanded, with pre-existing resting memory B cells differentiating almost quantitatively into effector B cell populations. B cells derived from "ancient" pre-existing memory cells and that recognize the full-length wild-type spike with the highest avidity after boosting are the B cells that also bind the Omicron variant spike protein. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=141 SRC="FIGDIR/small/21268554v1_ufig1.gif" ALT="Figure 1"> View larger version (32K): org.highwire.dtl.DTLVardef@1de97acorg.highwire.dtl.DTLVardef@b7ab7forg.highwire.dtl.DTLVardef@5c38dcorg.highwire.dtl.DTLVardef@99106c_HPS_FORMAT_FIGEXP M_FIG C_FIG

Immunogenicity of mRNA-1273, BNT162b2 and Ad26.COV2.S COVID-19 vaccines

BackgroundUnderstanding immunogenicity and effectiveness of SARS-CoV-2 vaccines is critical to guide rational use. MethodsWe compared the immunogenicity of mRNA-1273, BNT-162b2 or Ad26.COV2.S in ambulatory adults in Massachusetts, USA. To correlate immunogenicity with effectiveness of the three vaccines, we performed an inverse-variance meta-analysis of population level effectiveness from public health reports in >40 million individuals. ResultsA single dose of either mRNA vaccine yielded comparable antibody and neutralization titers to convalescent individuals. Ad26.COV2.S yielded lower antibody concentrations and frequently negative neutralization titers. Bulk and cytotoxic T-cell responses were higher in mRNA1273 and BNT162b2 than Ad26.COV2.S recipients, and <50% of vaccinees demonstrate CD8+ T-cell responses to spike peptides. Antibody concentrations and neutralization titers increased comparably after the first dose of either vaccine, and further in recipients of a second dose. Prior infection was associated with high antibody concentrations and neutralization even after a single dose and regardless of vaccine. Neutralization of beta, gamma and delta strains were poorer regardless of vaccine. Relative to mRNA1273, the effectiveness of BNT162b2 was lower against infection and hospitalization; and Ad26COV2.S was lower against infection, hospitalization and death. ConclusionsVariation in the immunogenicity correlates with variable effectiveness of the three FDA EUA vaccines deployed in the USA.