Evolution of Antibody Immunity to SARS-CoV-2

Area of Science:

• Immunology
• Virology

Background:

• Severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) infection leads to antibody production, but long-term humoral immunity, particularly memory B cell responses, remains incompletely understood.
• While antibody titers wane over time, the quality and evolution of memory B cells are critical for sustained protection against reinfection.

Approach:

• The study tracked antibody titers (IgM, IgG, IgA) and neutralizing activity in 87 individuals at 1.3 and 6.2 months post-SARS-CoV-2 infection.
• RBD-specific memory B cells were quantified and characterized for clonal turnover, somatic hypermutation, and antibody expression.
• Intestinal biopsies were analyzed for SARS-CoV-2 nucleic acids and immunoreactivity to assess potential antigen persistence.

Key Points:

• SARS-CoV-2-specific IgM and IgG antibody titers decreased significantly, while IgA remained more stable.
• Plasma neutralizing activity reduced five-fold, but the number of RBD-specific memory B cells remained constant.
• Memory B cells exhibited clonal turnover and produced antibodies with enhanced potency and resistance to RBD mutations, indicating an evolving humoral response.

Conclusions:

• The memory B cell response to SARS-CoV-2 undergoes significant evolution between 1.3 and 6.2 months post-infection.
• Evidence suggests SARS-CoV-2 antigen persistence, particularly in the small bowel, may drive this ongoing evolution of the humoral immune memory.