Twenty-year persistence of SARS-CoV-1 immune imprinting shapes antibody responses to SARS-CoV-2 infection.

Antibody imprinting is well recognized, yet its long-term dynamics and epitope specificity remain poorly understood. Here, we studied individuals sequentially infected with SARS-CoV-1 (SARS-1) and SARS-CoV-2 (SARS-2) over two decades and found durable imprinting of antibody responses following SARS-2 BF.7 breakthrough infection. Approximately 60% of isolated monoclonal antibodies were SARS-1 imprinted and targeted conserved receptor-binding domain regions, whereas 37% overcame imprinting to recognize the SARS-2 receptor-binding motif overlapping the ACE2-binding site. Notably, some SARS-1-only antibodies retained germline-like features and neutralizing activity 20 years after infection. One exceptionally imprinted broadly neutralizing antibody, THZ937, protected hamsters against contact and airborne transmission of Omicron EG.5.1, demonstrating the functional relevance of durable imprinted antibodies. Together, these findings define the remarkable longevity and molecular basis of antibody imprinting and provide insights for pan-sarbecovirus vaccine design.