Human Spleen Organoids as a Preclinical Platform for Evaluating Vaccine-Induced Antibody Responses 2261165

Abstract Introduction Human spleen organoids represent a promising ex vivo model that recapitulates the cellular diversity, spatial architecture, and immune functionality of secondary lymphoid tissues. These organoids offer a human-relevant platform for preclinical vaccine evaluation, potentially improving translational insight into immunogenicity. While recent studies have demonstrated antigen-specific immune responses to live-attenuated vaccines in spleen organoids, it remains unclear whether such responses extend to subunit-based immunogens, which form the basis of many modern vaccines. To address this, we evaluated the ability of spleen organoids to generate antibody responses to protein subunit immunogens. Methods Organoids were stimulated with wild-type SARS-CoV-2 spike and receptor-binding domain (RBD) proteins multimerized on mi3 nanoparticles, both with and without adjuvant formulations. Antigen-specific B cell activation was monitored by flow cytometry and ELISA, and antibody maturation was evaluated through single B cell sorting and sequencing. Results Consistent with waning immune memory observed in post-pandemic human populations, baseline responses to wild-type immunogens were modest. However, booster formulations and adjuvanted constructs enhanced antigen-specific responses, highlighting the platform’s sensitivity to immunogen design and immune memory dynamics. Conclusion Together, these results suggest that human spleen organoids can model both the baseline and augmented humoral responses to protein subunit vaccines, underscoring their potential as a human-derived platform for preclinical vaccine testing and immune response modeling. Funding Source Gates Foundation Topic Categories Vaccines and Immunotherapy (VAC)