Durable SARS-CoV-2 B cell immunity after mild or severe disease

Area of Science:

• Immunology
• Virology
• Infectious Diseases

Background:

• Antibody levels against SARS-CoV-2 wane over time post-infection.
• This waning immunity raises concerns about the durability of humoral immunity and potential reinfection risk.
• Memory B cells (MBCs) are crucial for long-term immunity and may persist even when antibody titers decline.

Purpose of the Study:

• To investigate the presence and characteristics of SARS-CoV-2-specific memory B cells (MBCs) in individuals recovering from COVID-19.
• To determine if MBCs contribute to durable humoral immunity following SARS-CoV-2 infection.
• To compare MBC responses in patients with mild versus moderate-to-severe COVID-19.

Main Methods:

• Multidimensional flow cytometry was used to analyze S protein receptor binding domain-specific (S-RBD-specific) MBCs.
• Cohorts included ambulatory patients with mild COVID-19 (n=7) and hospitalized patients with moderate-to-severe disease (n=7).
• Analysis was performed at a median of 54 days post-symptom onset.

Main Results:

• S-RBD-specific class-switched MBCs were detected in 13 out of 14 participants.
• Resting MBCs (rMBCs) constituted the majority of S-RBD-specific MBCs.
• FCRL5 upregulation on rMBCs was more pronounced after mild infection compared to severe infection.

Conclusions:

• Most individuals infected with SARS-CoV-2 develop S-RBD-specific, class-switched resting MBCs.
• These MBCs resemble those induced by vaccination against other pathogens, suggesting durable B cell-mediated immunity.
• The findings provide evidence for lasting humoral immunity against SARS-CoV-2 following both mild and severe disease.