SARS-CoV-2 specific plasma cells acquire long-lived phenotypes in human bone marrow

Area of Science:

• Immunology
• Virology
• Cell Biology

Background:

• SARS-CoV-2 specific antibody-secreting plasma cells (PC) are found in human bone marrow (BM) after infection or vaccination.
• It was previously unclear if these PC develop memory phenotypes.

Purpose of the Study:

• To investigate the phenotypes of SARS-CoV-2 specific plasma cells in human bone marrow after mRNA vaccination.
• To determine if memory plasma cell phenotypes are established following SARS-CoV-2 vaccination.

Main Methods:

• Characterization of SARS-CoV-2-specific human bone marrow plasma cells (BMPC) using tetramer-based, antigen-specific flow cytometry.
• Utilizing FluoroSpot assay to analyze BMPC populations.

Main Results:

• SARS-CoV-2 spike-S1-specific PC were detected in all tested BM samples from vaccinated individuals, comprising 0.22% of total BMPC.
• The majority of these BMPC expressed IgG, indicating a systemic vaccination response against the spike S1 protein.
• Approximately one-fifth of SARS-CoV-2-specific BMPC exhibited memory plasma cell phenotypes (downregulated CD19, variable CD45 expression).

Conclusions:

• Phenotypically diverse SARS-CoV-2-specific PC, including memory phenotypes, are established in human bone marrow after basic mRNA immunization.
• These findings suggest that basic mRNA vaccination against SARS-CoV-2 induces durable humoral immunity.