Intra-Lymph Node Crosslinking of Antigen-Bearing Polymers Enhances Humoral Immunity and Dendritic Cell Activation

Lymph node (LN)-resident dendritic cells (DCs) are a promising target for vaccination given their professional antigen-presenting capabilities and proximity to a high concentration of immune cells. Direct intra-LN injection has been shown to greatly enhance the immune response to vaccine antigens compared to traditional intramuscular injection but is infeasible to implement clinically. Employing the passive lymphatic flow of antigens to target LNs has been shown to increase total antigen uptake by DCs more than inflammatory adjuvants, which recruit peripheral DCs. Herein, we describe a novel vaccination platform in which two complementary multi-arm poly(ethylene glycol) (PEG) polymers--one covalently bound to the model antigen ovalbumin (OVA)--are injected subcutaneously into two distinct sites that drain to the same LN through different lymphatic vessels and, upon meeting in the LN, rapidly crosslink. This system improves OVA delivery to, and residence time within, the draining LN compared to all control groups, with the crosslinking of the two PEG components improving humoral immunity without the need for any pathogen-mimicking adjuvants. Further, we observed a significant increase in non-B/T lymphocytes in LNs cross-presenting the OVA peptide SIINFEKL on MHC I over a dose-matched control containing alum, the most common clinical adjuvant, as well as an increase in DC activation in the LN. These data suggest that this platform can be used to deliver antigens to LN-resident immune cells to produce a stronger humoral and cellular immune response over materials-matched controls without the use of traditional adjuvants. Translational Impact StatementVaccines save millions of lives each year; however, they often require more than one injection to confer protection and do not always provide long-term immunity. Transitioning from intramuscular injections to intra-lymph node injections has been shown to greatly increase immunity conferred by vaccination but is infeasible to implement clinically. Herein, we present a biomaterial-based vaccination strategy that delivers antigen to the lymph nodes after a pair of remote injections, which increases the duration of immune cell exposure to the vaccine and, consequently, enhances humoral immunity.