Mannosylated poly(beta-amino esters) for targeted antigen presenting cell immune modulation

Abstract

Given the rise of antibiotic resistance and other difficult-to-treat diseases, genetic vaccination is a promising preventative approach that can be tailored and scaled according to the vector chosen for gene delivery. However, most vectors currently utilized rely on ubiquitous delivery mechanisms that ineffectively target important immune effectors such as antigen presenting cells (APCs). As such, APC targeting allows the option for tuning the direction (humoral vs cell-mediated) and strength of the resulting immune responses. In this work, we present the development and assessment of a library of mannosylated poly(beta-amino esters) (PBAEs) that represent a new class of easily synthesized APC-targeting cationic polymers. Polymeric characterization and assessment methodologies were designed to provide a more realistic physiochemical profile prior to in vivo evaluation. Gene delivery assessment in vitro showed significant improvement upon PBAE mannosylation and suggested that mannose-mediated uptake and processing influence the magnitude of gene delivery. Furthermore, mannosylated PBAEs demonstrated a strong, efficient, and safe in vivo humoral immune response without use of adjuvants when compared to genetic and protein control antigens. In summary, the gene delivery effectiveness provided by mannosylated PBAE vectors offers specificity and potency in directing APC activation and subsequent immune responses.

Structure–Function Assessment of Mannosylated Poly(β-amino esters) upon Targeted Antigen Presenting Cell Gene Delivery

“…12 Although both nonmannosylated and mannosylated D4A4 polymers elicited strong immune responses, only D4A4-Man was able to evoke a response statistically higher than the commercial controls. Furthermore, the structure-function analysis presented in the previous work was limited but provided a polymer chemical background basis for engineering polyplex gene delivery specific for APCs.…”

“…12 Specifically, 50:1, 100:1, and 200:1 were used in initial gene delivery experiments; whereas, only 200:1 was used during inhibition and structure-function studies (to be described later). To assess the biophysical properties associated with polyplexes, DLS was used to measure the particle effective diameter and zeta potential in both 25 mM NaOAc and PBS ( Figure 2).…”

“…This may be the result of a shielding effect conferred by the attachment of mannose combined with increased colloidal pressure (derived from increased negatively-charged serum) driving the compaction of polyplexes.Gene Delivery Studies. Previously, we identified that mannosylation (either by chemical grafting or free addition) positively affected gene delivery in direct response to binding and processing through a CD206-dependent mechanism 12. However, despite successful transfection data, clear molecular weight trends were not observed due to the narrow range of molecular weights evaluated.…”

“…11 Specificity has also been achieved by engineering the PBAE component via grafting of cell-homing ligands, 12 tuning of the polyplex physical characteristics, 13,14 or the 4 inclusion of stimulus-driven release. 15 We previously demonstrated the ability to simultaneously restrict and increase delivery to antigen presenting cells (APCs; macrophages and dendritic cells)…”

“…12,16 Mannose was selected as the grafting ligand due to the upregulation of the corresponding receptor (CD206) on the surface of APCs. 17 CD206 is a member of the calcium-dependent lectin family that selectively recognizes polysaccharides (mannose, fucose, and N-acetylglucoseamine) which are commonly present on pathogens.…”