Abstract B cells play a central role in antiviral and antiparasitic immunity, not only as producers of antibodies, but also as APCs and mediators of inflammation In this study, we used 16-color flow cytometry analysis to investigate the frequency, differentiation, and activation status of peripheral B cells of patients with SARS-CoV-2 infection or acute Plasmodium falciparum malaria compared with the healthy individuals As a main result, we observed an increase of the frequency of (CD27?, CD21?) atypical memory B cells and (CD19+, CD27+, CD38+) plasmablasts in malaria and COVID-19 patients Additionally, CD86, PD-1, CXCR3, and CD39 expression was up-regulated, whereas CD73 was down-regulated on plasmablasts of COVID-19 and malaria patients compared with the bulk B cell population In particular, there was a more pronounced loss of CD73+ B cells in malaria The frequency of plasmablasts positively correlated with serum levels of CRP, IL-6, and LDH of COVID-19 patients In the longitudinal course of COVID-19, a rapid normalization of the frequency of atypical memory B cells was observed The role and function of plasmablasts and atypical memory B cells in COVID-19 and other acute infections remain to be further investigated The role of B cells as either ?driver or passenger? of hyperinflammation during COVID-19 needs to be clarified
B cell analysis in SARS-CoV-2 versus malaria: Increased frequencies of plasmablasts and atypical memory B cells in COVID-19