Rapid identification of antigen-specific monoclonal antibodies from HIV-1 elite controllers using the Beacon platform

Elite controllers (ECs) are rare human immunodeficiency virus (HIV)-infected individuals who manage viral replication without antiretroviral therapy. While their cellular immunity is well characterized, humoral responses remain limited, which provides an uncommon window into antibody responses to HIV-1. Using single-cell functional screening, this study aimed to isolate and characterize HIV-1 envelope (Env)-specific monoclonal antibodies (mAbs) from ECs. The Beacon platform was used for enrichment, activation, and screening of cluster of differentiation 27⁺ (CD27⁺) memory B cells. Among ~ 12,000 single B cells, 40 Env-specific IgG-secreting cells were identified. Although 18 mAbs were recovered, six showed high-affinity binding to multiple Env trimers (average EC50 < 100 ng/mL). Notably, one mAb (#2) demonstrated broad reactivity, neutralizing 15 of the 17 pseudoviruses, albeit with limited potency (geometric mean IC50 of 46.53 μg/mL). Sequence analysis revealed predominant usage of IGHV1-69 and varied somatic hypermutation levels. However, the high binding affinity could not consistently predict neutralization potency. This study demonstrated the utility of integrated single-cell screening for rapid discovery of antibodies from rare donors. This study also highlights the need for functional assessment in HIV-1 antibody development and identification of mAb candidates for potential therapeutic applications.