High Density Lipoprotein Composition Influences Lymphatic Transport After Subcutaneous Administration

Mol Pharm. 2020 Jun 16. doi: 10.1021/acs.molpharmaceut.0c00348. Online ahead of print.

Abstract

Interstitial administration (e.g. subcutaneous (SC) administration) of immunotherapies and vaccines within nanoparticles can improve access to lymph-resident immune cells leading to enhanced efficacy and reduced off-target effects. Recently, endogenous high-density lipoproteins (HDLs) were found to return from peripheral tissue back to the systemic circulation via the lymphatic vessels and nodes. This suggests the potential utility of HDLs as biocompatible lymphatic-targeted therapeutic carriers. However, we have limited understanding of the mechanisms that drive HDL uptake into peripheral lymphatics from the interstitium. This study investigated the influence of HDL physicochemical properties on lymphatic transport and lymph node (LN) retention of HDL after SC administration. A range of HDL particles were prepared and characterised. Spherical-shaped endogenous HDLs were isolated from biological fluids (rat lymph, rat plasma and human plasma) and separated into two subclasses based on the density. Discoidal-shaped synthetic (reconstituted) HDLs (rHDLs) of similar sizes were assembled from lipids and apolipoprotein A-I. All HDLs had similar sizes of 10-20 nm and slight negative surface charge. All HDLs were radiolabelled with 3H-cholesteryl ester (3H-CE) and/or 14C-free cholesterol (14C FC) and administered SC into the hind leg of thoracic lymph-cannulated rats. The recovery of radiolabels in lymph, plasma, LN and tissues was determined. From the interstitial injection site, all HDLs were preferentially transported into the lymph and not blood vessels as indicated by high lymph-to-plasma concentration ratios of the radiolabels (up to 100:1 during the absorption phase) and greater radiolabel recovery in LNs draining the injection site compared to the contralateral side. Several HDLs with unique composition demonstrated significantly higher lymphatic transport compared to other HDLs despite possessing similar physical properties, suggesting that HDL lymphatic transport is less influenced by physical properties. The LN retention of HDL was positively correlated to increasing negative charge of HDL, which was related to surface composition. Overall, this study informs the optimal design of HDL-based nanoparticles to promote lymphatic targeting of immunotherapies and vaccines.