Spleen-targeted DDS-based immunization: A novel platform for rapid and highly diversified antibody generation

Abstract

Monoclonal antibodies (mAbs) have emerged as a leading modality in modern drug discovery, with their global market projected to exceed USD 490 billion by 2030. Despite their success, conventional immunization techniques such as subcutaneous immunization often fail to induce antibodies against complex membrane proteins (MPs) and require long immunization periods. In response, the authors have developed a novel spleen-targeted immunization technology based on drug delivery system (DDS) principles. This “spleen immunization” method employs polyethylene glycol (PEG)-modified liposomes (PEG-Lip) as an antigen carrier to deliver antigens directly to the spleen, the central organ for systemic immune regulation. By exploiting the interaction between PEG-Lip and marginal zone B cells, this strategy induces rapid and robust humoral immune responses, producing highly diverse and high-affinity antibodies in a short timeframe. Using ovalbumin (OVA) as a model antigen, spleen immunization induced antigen-specific IgG responses within 7 days—clearly faster and stronger than conventional subcutaneous immunization. The induced antibodies exhibited broader IgG subclass diversity (IgG1, IgG2a, IgG2b, and IgG3) and higher affinity (K_D values). B-cell receptor (BCR) repertoire sequencing revealed greater diversity indices, confirming activation of a broader immune network. Furthermore, using the model membrane protein angiotensin-converting enzyme 2 (ACE2), spleen immunization successfully generated ACE2-specific antibodies that recognized native membrane-bound ACE2—a result rarely achieved by conventional methods. This DDS-based spleen-targeted immunization platform offers a breakthrough in antibody discovery, particularly for previously intractable MP antigens such as GPCRs. It provides a rapid, high-diversity, and high-affinity antibody generation route, enabling efficient development of therapeutic and diagnostic antibodies against emerging infectious diseases and cancer-related targets. The approach holds significant promise for advancing biopharmaceutical innovation and expanding the landscape of antibody-based therapeutics.