Gracia1,2, Angus Johnston1,2, Christopher JH Porter1,2 and Natalie L Trevaskis1*

 

1Drug Delivery, Disposition and Dynamics, Monash Institute of Pharmaceutical Sciences, Monash University, 381 Royal Parade, Parkville 3052, Melbourne, VIC, Australia
2
ARC Centre of Excellence in Convergent Bio-Nano Science and Technology

 

Improving the delivery of immunotherapies and vaccines to target cells in the lymphatics has the potential to enhance efficacy and lower off-target side effects. Nano-sized carriers are known to promote access to the lymphatic system following interstitial (SC, IM) administration and are therefore being increasingly utilized for this purpose1. Recent studies have demonstrated that an endogenous nanostructure, high density lipoprotein (HDL), is returned from peripheral tissues to the systemic circulation via the lymphatic system2,3. This intrinsic lymph-targeting property suggests the potential to use HDL as biocompatible drug delivery carriers for immunotherapies and vaccines. The current study aimed to determine the impact of HDL characteristics on lymphatic uptake and lymph node (LN) retention profiles. Endogenous HDLs were isolated from biological fluids (rat lymph, rat plasma and human plasma) by density gradient ultracentrifugation and separated into two subclasses (D-HDL of density ~1.10-1.18 g/ml and L-HDL of density ~1.06-1.10 g/ml). Synthetic HDLs (rHDLs) were prepared by lipids and apolipoprotein A-I (the main protein component of HDL). All HDLs were characterized for physical properties (size, shape, surface charge). HDLs were radiolabelled and SC administered into the hind leg of thoracic lymph-cannulated female Sprague-Dawley rats. Endogenous HDLs of the same density range had comparable size (~10 or ~20 nm for D-HDLs and L-HDLs, respectively) regardless of source and all appeared spherical (Fig. 1A). The sizes were successfully mimicked by the prepared rHDLs which appeared discoidal in shape. Overall, all HDLs and rHDLs had slightly negative surface charge. When lymphatic transport was assessed, all HDLs were directly transported into the lymph and not blood circulation as suggested by the high lymph to plasma concentration ratios (up to 100:1) of the associated radiolabels during the first 12 hours post-dose. This was further confirmed by specific accumulation of the radiolabel dose in the LN draining the injection side of the leg but not on the opposite side. Comparing the various HDL types, certain endogenous HDLs displayed significantly higher lymphatic transport (Fig. 1B) and LN retention when compared to the other HDLs despite similarity in size, shape and surface charge. Further studies will investigate whether this was due to variation in the composition of the HDLs, which may alter their interaction with surrounding cells at the injection site or within LN. Overall, the data confirmed the lymph and LN targeting properties of HDL. Understanding the HDL characteristics that enhance lymph uptake and LN retention is relevant for optimizing the design of HDL as a lymph-targeting carrier for immunotherapies and vaccines.

Figure 1 (A) Representative TEM of endogenous human plasma D-HDL; (B) Lymph uptake of various HDLs and rHDLs, expressed as cumulative %dose transported in lymph over 34 hours in thoracic-lymph cannulated rats (n=3-5)

1Trevaskis et al, Nat. Rev. Drug. Discov., 2015, 14, 781-803

2Martel et al, JCI 2013, 123(4), 1571-1579

3Lim et al, Cell Metabolism 2013, 17, 671-684

 

Biographic Details

Miss Gracia

Monash University, Australia

Phone: +613 9903 9742 

Email: gracia.gracia@monash.edu

Research interests: lymphatic drug delivery, vaccine technologies

Venue

Room: 
AEB Auditorium