The polysaccharide inulin is characterized by an extensive series of periodic isoforms with varying biological actions

Abstract

In studying the molecular basis for the potent immune activity of previously described gamma and delta inulin particles and to assist in production of inulin adjuvants under Good Manufacturing Practice, we identified five new inulin isoforms, bringing the total to seven plus the amorphous form. These isoforms comprise the step-wise inulin developmental series amorphous → alpha-1 (AI-1) → alpha-2 (AI-2) → gamma (GI) → delta (DI) → zeta (ZI) → epsilon (EI) → omega (OI) in which each higher isoform can be made either by precipitating dissolved inulin or by direct conversion from its precursor, both cases using regularly increasing temperatures. At higher temperatures, the shorter inulin polymer chains are released from the particle and so the key difference between isoforms is that each higher isoform comprises longer polymer chains than its precursor. An increasing trend of degree of polymerization is confirmed by end-group analysis using 1 H nuclear magnetic resonance spectroscopy. Inulin isoforms were characterized by the critical temperatures of abrupt phase-shifts (solubilizations or precipitations) in water suspensions. Such (aqueous) "melting" or "freezing" points are diagnostic and occur in strikingly periodic steps reflecting quantal increases in noncovalent bonding strength and increments in average polymer lengths. The (dry) melting points as measured by modulated differential scanning calorimetry similarly increase in regular steps. We conclude that the isoforms differ in repeated increments of a precisely repeating structural element. Each isoform has a different spectrum of biological activities and we show the higher inulin isoforms to be more potent alternative complement pathway activators.

Enhanced pulmonary immunization with aerosolized inactivated influenza vaccine containing delta inulin adjuvant

“…and s.c. routes http://dx.doi.org/10.1016/j.ejps.2014.10.008 0928-0987/Ó 2014 Elsevier B.V. All rights reserved. (Cooper et al, 2013). d-inulin, the most immunologically active inulin polymorph , demonstrated potent adjuvant activity when co-administered i.m.…”

Inulin crystal initiation via a glucose-fructose cross-link of adjacent polymer chains: Atomic force microscopy and static molecular modelling

“…The many applications of inulin (Barclay, Ginic-Markovic, Cooper & Petrovsky, 2010) include a stable semi-crystalline form termed microparticulate inulin (MPI) currently in advanced human and veterinary clinical development as a vaccine adjuvant. It is broadly effective as the commercially produced delta isoform Advax™ adjuvant (Gordon et al, 2012; Honda-Okubo, Saade & Petrovsky, 2012; Larena, Prow, Hall, Petrovsky & Lobigs, 2013; Petrovsky et al, 2013; Saade, Honda-Okubo, Trec & Petrovsky, 2013; see also Cooper, Barclay, Ginic-Markovic, & Petrovsky, 2013, 2014a; Cooper, Barclay, Ginic-Markovic, Gerson, & Petrovsky, 2014b). We here outline a model of MPI assembly and surface structure, known to be important for its adjuvant efficacy because dissolved inulin is immunologically inactive.…”

“…Different polymorphic forms of inulin exist, distinguished by their solubility and H-bonding strengths (Cooper & Petrovsky, 2011; Cooper et al, 2013). Differences in immune actions of these forms were also noted and remain a focus of ongoing research.…”

Advax-Adjuvanted Recombinant Protective Antigen Provides Protection against Inhalational Anthrax That Is Further Enhanced by Addition of Murabutide Adjuvant

“…Inulin is a plant-derived polysaccharide that can exist as a number of different isoforms (31). The delta isoform of inulin forms a semicrystalline structure that possesses immune-modulatory activity and has been shown to enhance the immunogenicity and protection of a wide variety of vaccines, including those against Japanese encephalitis virus (32), West Nile virus (33), influenza virus (34), human immunodeficiency virus (35), and hepatitis B virus (36).…”