Abstract
Vaccine development requires innovative approaches to improve immune responses while reducing the number of immunizations. In this study, we explore the impact of controlled antigen release on immune activation and regulation using programmable infusion pumps and biodegradable biomaterials in OT-II and wild-type mice to understand the adaptive immune response through controlled antigen delivery in the absence of adjuvant. Ovalbumin (OVA) was delivered via an exponentially decreasing profile, mimicking clearance of infection, and an exponentially increasing profile, mimicking induction of infection. Exponentially decreasing OVA delivery through infusion pumps promoted regulatory T-cell (Treg) activation in secondary lymphoid organs and suppressed pro-inflammatory T-helper type 17 (Th17) responses in blood. An exponentially increasing OVA profile enhanced central memory T-cell (TCM) populations in submandibular blood and humoral immune responses in cardiac blood serum, demonstrating distinct immune modulation based on release kinetics. OVA was also delivered using a biodegradable PLGA-PEG-PLGA (PPP) depot, which provided controlled OVA release in an exponentially decreasing pattern. PPP-OVA treatment significantly reduced the frequency of pro-inflammatory T-helper type 1 (Th1) cells while increasing CD25(+)FOXP3(+) Treg cells in the spleen. Moreover, to identify T-cell populations that most accurately characterize the divergence in Treg and T-helper response to OVA kinetics, a Sequential Feature Selection (SFS) algorithm with Machine Learning (ML) models was used. ML algorithms identified gMFI of RORγt(+) as a key feature in submandibular blood and the ratio of gMFI of FOXP3(+) to GATA3(+) as the marker that was significantly changed by treatments in inguinal lymph nodes (iLN) when infusion pumps were used to deliver OVA. In addition, ML-based SFS identified CD25(+)FOXP3(+) regulatory T cells as the most important feature, influencing the expression of other cell types in both inguinal lymph nodes (iLN) and spleen when PPP was used to deliver OVA. This finding suggests that the exponentially decreasing profile may generate anti-inflammatory responses. Overall, these findings suggest that controlled antigen delivery enhances immune regulation and memory T cells, providing new insights into immune responses mediated by the release kinetics.