Biophysical characterization of polydisperse liposomal adjuvant formulations

Pushpendra Singh; Gary R Matyas; Alexander Anderson; Zoltan Beck

doi:10.1016/j.bbrc.2020.05.156

Biophysical characterization of polydisperse liposomal adjuvant formulations

Biochem Biophys Res Commun. 2020 Aug 20;529(2):362-365. doi: 10.1016/j.bbrc.2020.05.156. Epub 2020 Jul 1.

Authors

Pushpendra Singh¹, Gary R Matyas², Alexander Anderson³, Zoltan Beck⁴

Affiliations

¹ U.S. Military HIV Research Program, Walter Reed Army Institute of Research, 503 Robert Grant Ave, Silver Spring, MD, 20910, USA; Henry M. Jackson Foundation for the Advancement of Military Medicine, 6720A Rockledge Drive, Bethesda, MD, 20817, USA. Electronic address: pstjnu@gmail.com.
² U.S. Military HIV Research Program, Walter Reed Army Institute of Research, 503 Robert Grant Ave, Silver Spring, MD, 20910, USA. Electronic address: gmatyas@hivresearch.org.
³ U.S. Military HIV Research Program, Walter Reed Army Institute of Research, 503 Robert Grant Ave, Silver Spring, MD, 20910, USA. Electronic address: aanderson@hivresearch.org.
⁴ U.S. Military HIV Research Program, Walter Reed Army Institute of Research, 503 Robert Grant Ave, Silver Spring, MD, 20910, USA; Henry M. Jackson Foundation for the Advancement of Military Medicine, 6720A Rockledge Drive, Bethesda, MD, 20817, USA. Electronic address: zbeck@hivresearch.org.

PMID: 32703436
DOI: 10.1016/j.bbrc.2020.05.156

Abstract

Army Liposome Formulations (ALF) are potent adjuvants, of which there are two primary forms, lyophilized ALF (ALFlyo) containing monophosphoryl lipid A (MPLA) and ALF containing MPLA and QS21 (ALFQ). ALFlyo and ALFQ adjuvants are essential constituents of candidate vaccines for bacterial, viral, and parasitic diseases. They have been widely used in preclinical immunogenicity studies in small animals and non-human primates and are progressing to phase I/IIa clinical trials. ALFQ was prepared by adding saponin QS21 to small unilamellar liposome vesicles (SUVs) of ALF55 that contain 55 mol% cholesterol, whereas ALFlyo was created by reconstituting lyophilized SUVs of ALF43, consisting of 43 mol% cholesterol, in aqueous buffer solution. These formulations display heterogenous particle size distribution. Since biophysical characteristics of liposomes may impact their adjuvant potential, we characterized the particle size distribution and lamellarity of the individual liposome particles in ALFlyo and ALFQ formulations using cryo-electron microscopy and a newly developed MANTA technology. ALFlyo and ALFQ exhibited similar particle size distributions with liposomes ranging from 50 nm to several μm. However, fundamental differences were observed in the lamellar structures of the liposomes. ALFlyo displayed a greater number of multilamellar and multivesicular liposome particles, as compared to that in ALFQ, which was predominately unilamellar.

Keywords: ALF; ALFQ; Abbreviations; Army liposome formulation; Cryo-electron microscopy; Multispectral advanced nanoparticle tracking analysis.

Publication types

Research Support, Non-U.S. Gov't
Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

Adjuvants, Immunologic / chemistry*
Cholesterol / chemistry
Cryoelectron Microscopy
Freeze Drying
Lipid A / analogs & derivatives*
Lipid A / chemistry
Liposomes / chemistry*
Liposomes / ultrastructure
Particle Size
Saponins / chemistry*

Substances

Adjuvants, Immunologic
Lipid A
Liposomes
Saponins
saponin QA-21V1
Cholesterol
monophosphoryl lipid A