Enhancement of HIV vaccine efficacy via lipid nanoparticle-based adjuvants

• Main Author: Hanson, Melissa C. (Melissa Catherine)
• Other Authors: Darrell J. Irvine.
• Format: Others
• Language: English
• Published: Massachusetts Institute of Technology 2015
• Subjects: Biological Engineering.
• Online Access: http://hdl.handle.net/1721.1/97975

Thesis: Ph. D., Massachusetts Institute of Technology, Department of Biological Engineering, February 2015.. === Cataloged from PDF version of thesis. "December 2014." === Includes bibliographical references (pages 93-108). === Adjuvants are immunomodulators and/or formulations/delivery vehicles which enhance immune responses to vaccines. The lack of progress in the development of an HIV humoral vaccine is due, in part, to the absence of available adjuvants which can be sufficiently potent with minimal adverse side effects. The main goal of this thesis was to develop nanoparticles as HIV vaccine adjuvants. Building upon previous work in the Irvine lab, we determined the potency of lipid-coated microparticles was due in part to the in situ generation of antigen-displaying liposomes. Synthetic liposomes were nearly as potent as lipid-coated microparticles, but with a 10-fold greater antigen conjugation efficiency. We subsequently optimized unilamellar liposomes as delivery vehicles for surface-displayed HIV antigens. For vaccines with a recombinant gpl20 monomer (part of the HIV envelope trimer), immunization at 0 and 6 weeks with 65 nm or 150 nm diameter liposomes with 7.5 pmol gpl20 was found to induce strong anti-gp120 titers which competed with the broadly-neutralizing antibody VRC01. The second HIV antigen used was a peptide derived from the membrane proximal external region (MPER) of the gp41 protein. High-titer IgG responses to MPER required the presentation of MPER on liposomes and the inclusion of molecular adjuvants such as monophosphoryl lipid A. Anti-MPER humoral responses were further enhanced optimizing the MPER density to a mean distance of -10-15 nm between peptides on the liposomes surfaces. Lastly, we explored the adjuvant potential of cyclic dinucleotides (CDNs) with MPER liposome vaccines. Encapsulation of CDN in PEGylated liposomes enhanced its accumulation in draining lymph nodes (dLNs) 15-fold compared to unformulated cyclic dinucleotide. Liposomal CDN robustly induced type I interferon in dLNs, and promoted durable antibody titers comparable to a 30-fold larger dose of unformulated CDN without the systemic toxicity of the latter. This work defines several key properties of liposome formulations that promote durable, high-titer antibody responses against HIV antigens and demonstrates the humoral immunity efficacy of nanoparticulate delivery of cyclic dinucleotides, which is an approach broadly applicable to small molecule immunomodulators of interest for vaccines and immunotherapy. === by Melissa C. Hanson. === Ph. D.