Tracking antigen presenting cells to uncover the intrinsic immunostimulatory properties of microarray vaccine patches using a fluosphere-based assay

The Vaccine Innovation Priority Strategy has identified microarray patch (MAP) devices as a top global priority for advancing equitable vaccine distribution. However, understanding the intrinsic immune-enhancing mechanisms of MAPs remains critical to guiding their optimisation. In this study, we focus on the immunological impact of MAP application, demonstrating that MAPs more effectively recruit antigen-presenting cells, particularly key dendritic cell (DC) subsets, including migratory DCs and lymphatic sinus DCs, to the draining lymph nodes compared to intradermal and intramuscular needle-and-syringe delivery. To facilitate this analysis, we developed a fluosphere-based method that allowed precise tracking of antigen-engaged DCs. This approach highlights that MAPs do not merely serve as an alternative delivery platform, but actively enhance early innate immune engagement by targeting multiple DC subsets known to drive robust and rapid adaptive responses. Together, these findings establish a practical framework to dissect MAP-specific immune mechanisms and support their refinement. • Dendritic cell (DC) subsets targeted by microarray patches (MAPs) are identified. • Fluospheres-based assay was developed to track these responses. • The assay enables rapid testing of delivery methods within the same animal. • MAPs activate more DC subsets than needle and syringe vaccination.