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O/W Nanoemulsion as an Adjuvant for an Inactivated H3N2 Influenza Vaccine: Based on Particle Properties and Mode of Carrying

Authors Zhao L, Zhu Z, Ma L, Li Y

Received 1 October 2019

Accepted for publication 10 March 2020

Published 25 March 2020 Volume 2020:15 Pages 2071—2083


Checked for plagiarism Yes

Review by Single anonymous peer review

Peer reviewer comments 2

Editor who approved publication: Dr Mian Wang

Lanhua Zhao,1,2 Zhe Zhu,1 Lei Ma,1 Yingbo Li1

1Institute of Medical Biology, Chinese Academy of Medical Sciences, Peking Union Medical College, Kunming 650118, People’s Republic of China; 2Institute of Pathogenic Biology, School of Medicine, University of South China, Hengyang, 421001, People’s Republic of China

Correspondence: Yingbo Li
Tel +86 13888034695

Background and Purpose: Adjuvant can reduce vaccine dosage and acquire better immune protection to the body, which helps to deal with the frequent outbreaks of influenza. Nanoemulsion adjuvants have been proved efficient, but the relationship between their key properties and the controlled release which greatly affects immune response is still unclear. The present work explores the role of factors such as particle size, the polydispersity index (PDI), stability and the safety of nanoemulsions by optimizing the water concentration, oil phase and modes of carrying, to explain the impact of those key factors above on adjuvant effect.
Methods: Isopropyl myristate (IPM), white oil, soybean oil, and grape-kernel oil were chosen as the oil phase to explore their roles in emulsion characteristics and the adjuvant effect. ICR mice were immunized with an emulsion-inactivated H3N2 split influenza vaccine mixture, to compare the nanoemulsion’s adjuvant with traditional aluminium hydroxide or complete Freund’s adjuvant.
Results: Particle size of all the nanoemulsion formed in our experiment ranged from 20 nm to 200 nm and did not change much when diluted with water, while the PDI decreased obviously, indicating that the particles tended to become more dispersive. Formulas with 80% or 85.6% water concentration showed significant higher HAI titer than aluminium hydroxide or complete Freund’s adjuvant, and adsorption rather than capsule mode showed higher antigen delivery efficiency. As mentioned about oil phase, G (IPM), F (white oil), H (soybean oil), and I (grape-kernel oil) showed a decreasing trend in their adjuvant efficiency, and nanoemulsion G was the best adjuvant with smaller and uniform particle size.
Conclusion: Emulsions with a smaller, uniform particle size had a better adjuvant effect, and the adsorption mode was generally more efficient than the capsule mode. The potential adjuvant order of the different oils was as follows: IPM > white oil > soybean oil > grape-kernel oil.

Keywords: nanoemulsion, influenza vaccine, particle properties, mode of carrying, oil phase

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