In situ engineering of the lymph node microenvironment via intranodal injection of adjuvant-releasing polymer particles

Abstract

Recent studies have demonstrated a simple, potentially universal strategy to enhance vaccine potency, via intralymph node (i.LN) injection. To date, intranodal immunization studies have focused on the delivery of unadjuvanted vaccines (e.g., naked DNA, peptide, or protein). We hypothesized that combining i.LN vaccination with controlled release biomaterials permitting sustained dosing of molecular adjuvants to the local tissue microenvironment would further enhance this promising vaccination strategy. To test this idea, we encapsulated the Toll-like receptor-3 ligand poly(inosinic:cytidylic acid) (polyIC) in biodegradable poly(lactide-co-glycolide) microparticles (MPs) designed to remain extracellular and release polyIC in the LN over several days. Intranodal injection of MPs increased persistence of polyIC in LNs compared to the same dose of soluble polyIC or polyIC formulated in nanoparticles, leading to increased accumulation of Toll-like receptor agonist in LNresident antigen presenting cells and more enduring dendritic cell activation. Intralymph node injection of ovalbumin mixed with polyIC-releasing MPs enhanced the humoral response and expanded ovalbumin-specific T cells to frequencies as high as 18% among all CD8 þ cells following a single injection (8.2-fold greater than the same vaccine given i.m.), a response that could not be matched by antigen mixed with polyIC-loaded nanoparticles or a 10-fold greater dose of soluble polyIC. Thus, i.LN immunization with slow release-formulated adjuvants may be a broadly applicable strategy to enhance therapeutic or prophylactic vaccines.C ompared to live attenuated pathogens, vaccines based on nonreplicating viral/bacterial vectors or subunit antigens offer enhanced safety but elicit weaker, less durable immune responses. Thus, enhancing the potency of these vector/subunit vaccines without sacrificing their excellent safety profile is a central focus of vaccine development. One strategy to enhance vaccine potency is to improve the delivery of antigen and adjuvant molecules to critical antigen presenting cells (APCs) in secondary lymphoid organs. In the "geographic" view of immunity, antigen which does not reach these sites for induction of primary immune responses is ignored by the immune system (1). Following traditional vaccine injection in peripheral tissues, soluble proteins or small particles (<50 nm) drain directly to lymph nodes (LNs), while cell-associated antigen or larger antigen particles access LNs by APC uptake and trafficking (2-4). Recently, intralymph node (i.LN) vaccination-injection of antigens/adjuvants directly into LNs-has shown great promise for vaccine delivery, improving the potency of DNA, RNA, peptide, protein, and dendritic cell-based vaccines (2). Studies have demonstrated as much as 10 6 -fold reductions in antigen dose (5, 6), 100-fold reductions in adjuvant dose (7), and enhanced protection with reduced side effects relative to traditional parenteral immunizations (2). Lymph node injection in humans is readily performed using ultraso...

Enhancing Efficacy of Anticancer Vaccines by Targeted Delivery to Tumor-Draining Lymph Nodes

“…Compared with current published studies, our TRP-2-based therapeutic nanoparticle vaccine is very potent at the low doses used for antigen and adjuvant (18,39,40). Similarly, other studies have shown improved therapeutic outcomes by either conjugating the adjuvant or the antigen onto or into delivery systems, such as poly(lactideco-glycolide) particles and liposomes, but, to our knowledge, this is the first study to show enhanced co-uptake of both adjuvant and antigen by LN-resident APCs after nanoparticle conjugation (14)(15)(16)(17)(18)(19). Furthermore, it has been shown recently that encapsulating antigens or TLR agonists in nanoparticles enhanced humoral responses compared with immunization with soluble antigen or adjuvant (41,42).…”

“…4B) induced by targeting the vaccine to the tdLN led to regression of early-stage tumors and more impressively of tumors having reached the Swiss legal limit of 1 cm 3 . In the literature, cancer vaccines are usually administered when the tumors are 5 to 7 mm in diameter or even before they are detectable, and also do not usually induce this high number of TAA-specific CD8 þ T cells in the blood and the LNs (17,19,30,38,44), thus emphasizing the benefits of nanoparticle-mediated targeting of antigen and adjuvant to DCs in the tdLN (18,38,45). We noted, however, that after regressing some tumors grew back.…”

“…17, 31, 38). Our nanoparticles were in the range of 30 nm, thus smaller than particles used in many vaccination studies, hence affording enhanced lymphatic drainage and targeting of the skin-draining LNs (14)(15)(16)(17)(18)(19).…”

“…Strategies based on delivering adjuvants or antigens carried by nanoparticles or liposomes have led to improved targeting of LNs, activation of LN-resident DCs, and enhanced induction of antigen-specific CD8 þ T cells, hence better protection in tumor challenge studies (14)(15)(16)(17)(18)(19). Ultrasmall, functionalizable nanoparticles (NP) developed in our laboratory effectively target DCs in skin-draining LNs upon intradermal delivery (20,21).…”

Polymer-based nanoparticles loaded with a TLR7 ligand to target the lymph node for immunostimulation

“…This targeting has been shown to enhance cytotoxic T-cell responses when the TLR7 agonist is applied together with antigen in the context of vaccination (Jewell et al, 2011;Nuhn et al, 2016). In addition, lymph node targeting of TLR ligands can reduce systemic levels of proinflammatory cytokines (Bourquin et al, 2008).…”