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

Abstract

bSubunit vaccines against anthrax based on recombinant protective antigen (PA) potentially offer more consistent and less reactogenic anthrax vaccines but require adjuvants to achieve optimal immunogenicity. This study sought to determine in a murine model of pulmonary anthrax infection whether the polysaccharide adjuvant Advax or the innate immune adjuvant murabutide alone or together could enhance PA immunogenicity by comparison to an alum adjuvant. A single immunization with PA plus Advax adjuvant afforded significantly greater protection against aerosolized Bacillus anthracis Sterne strain 7702 than three immunizations with PA alone. Murabutide had a weaker adjuvant effect than Advax when used alone, but when murabutide was formulated together with Advax, an additive effect on immunogenicity and protection was observed, with complete protection after just two doses. The combined adjuvant formulation stimulated a robust, long-lasting B-cell memory response that protected mice against an aerosol challenge 18 months postimmunization with acceleration of the kinetics of the anamnestic IgG response to B. anthracis as reflected by ϳ4-fold-higher anti-PA IgG titers by day 2 postchallenge versus mice that received PA with Alhydrogel. In addition, the combination of Advax plus murabutide induced approximately 3-fold-less inflammation than Alhydrogel as measured by in vivo imaging of cathepsin cleavage resulting from injection of ProSense 750. Thus, the combination of Advax and murabutide provided enhanced protection against inhalational anthrax with reduced localized inflammation, making this a promising next-generation anthrax vaccine adjuvanting strategy.

Immunogenicity and safety of Advax™, a novel polysaccharide adjuvant based on delta inulin, when formulated with hepatitis B surface antigen: A randomized controlled Phase 1 study

“…Similarly, there was no evidence of any adverse safety signals from analysis of safety blood tests and in particular, there was no evidence of excess inflammatory effects as reflected by changes in ESR, CRP, globulins, complement levels or white blood cell counts post-immunization. This is consistent with the lack of inflammatory side effects of Advax evidenced in non-clinical studies[22]. This distinguishes Advax from other classes of adjuvants including oil emulsions (e.g.…”

“…Delta inulin is distinguished from earlier described inulin isoforms (alpha, beta and gamma) by being relatively insoluble at mammalian body temperature bestowing it with unique immunological properties including potent adjuvant properties, not exhibited by more soluble inulin forms. In animal studies, Advax enhanced adaptive immune responses to a wide variety of viral and bacterial antigens including influenza [16, 17], Japanese encephalitis[18, 19], West Nile virus[20], HIV [21]and anthrax vaccines[22]. Mice immunized with HBsAg with Advax exhibited enhanced HBsAb titers along with antigen dose-sparing and enhanced cellular immune responses including CD4 and CD8 T-cell proliferation and Th1, Th2 and Th17 cytokine production [23].…”

Physical characterization and in silico modeling of inulin polymer conformation during vaccine adjuvant particle formation

“…This polysaccharide is biocompatible and biodegradable and specific semicrystalline particulate forms of inulin have immunomodulatory properties (Cooper & Petrovsky, 2011). The utility of γ- and δ-inulin isoforms as vaccine adjuvants has been demonstrated in both animal (Feinen, Petrovsky, Verma & Merkel, 2014; Honda-Okubo, Kolpe, Li & Petrovsky, 2014; Saade, Honda-Okubo, Trec & Petrovsky, 2013) and human (Gordon, Kelley, Heinzel, Cooper & Petrovsky, 2014; Gordon, Sajkov, Woodman & Honda-Okubo, 2012) studies. However, to fully realize the vaccine adjuvant benefit of inulin particles there is a need to better understand how inulin polymer chains assemble to form the adjuvant-active inulin particles.…”

Anthrax Vaccine Precipitated Induces Edema Toxin-Neutralizing, Edema Factor-Specific Antibodies in Human Recipients

“…However, work from our group has previously shown that the toxin-neutralizing quality of PA antibodies from AVA recipients is highly variable (42). This has led to research seeking to develop more effective anthrax vaccines, including recombinant PA (43)(44)(45)(46), alternative adjuvants (47,48), and additional vaccine targets (49)(50)(51).…”