Immunity against conserved epitopes dominates after two consecutive exposures to SARS-CoV-2 Omicron BA.1.

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) exposure histories become increasingly complex through original and variant-adapted vaccines and infections with viral variants. Upon exposure to the highly altered Omicron spike glycoprotein, pre-immunized individuals predominantly mount recall responses of Wuhan-Hu-1 (wild-type)-imprinted memory B (B) cells mostly targeting conserved non-neutralizing epitopes, leading to diminished Omicron neutralization. We investigated the impact of imprinting in individuals double/triple vaccinated with a wild-type-strain-based mRNA vaccine who, thereafter, had two consecutive exposures to Omicron BA.

Exposure to BA.4/5 S protein drives neutralization of Omicron BA.1, BA.2, BA.2.12.1, and BA.4/5 in vaccine-experienced humans and mice.

The SARS-CoV-2 Omicron variant and its sublineages show pronounced viral escape from neutralizing antibodies elicited by vaccination or prior SARS-CoV-2 variant infection owing to over 30-amino acid alterations within the spike (S) glycoprotein. Breakthrough infection of vaccinated individuals with Omicron sublineages BA.1 and BA.

Omicron BA.2 breakthrough infection enhances cross-neutralization of BA.2.12.1 and BA.4/BA.5.

BNT162b2-vaccinated individuals after Omicron BA.1 breakthrough infection have strong serum-neutralizing activity against Omicron BA.1, BA.

Omicron BA.1 breakthrough infection drives cross-variant neutralization and memory B cell formation against conserved epitopes.

Omicron is the evolutionarily most distinct severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) variant of concern (VOC) to date. We report that Omicron BA.1 breakthrough infection in BNT162b2-vaccinated individuals resulted in strong neutralizing activity against Omicron BA.

Neutralization of SARS-CoV-2 Omicron by BNT162b2 mRNA vaccine-elicited human sera.

The globally circulating severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) variant of concern Omicron (B.1.1.

Paracrine orchestration of intestinal tumorigenesis by a mesenchymal niche.

The initiation of an intestinal tumour is a probabilistic process that depends on the competition between mutant and normal epithelial stem cells in crypts. Intestinal stem cells are closely associated with a diverse but poorly characterized network of mesenchymal cell types. However, whether the physiological mesenchymal microenvironment of mutant stem cells affects tumour initiation remains unknown.