Alum and squalene-oil-in-water emulsion enhance the titer and avidity of anti-Aβ antibodies induced by multimeric protein antigen (1-11)E2, preserving the Igg1-skewed isotype distribution.

Francesca Mantile,Maria Trovato,Simone Ottonello,Pasquale Barba,Andrea Santoni,Antonella Prisco,Piergiuseppe De Berardinis,Paulo Lee Ho

doi:10.1371/journal.pone.0101474

Francesca Mantile, Maria Trovato + Show 6 more

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https://doi.org/10.1371/journal.pone.0101474

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Abstract

The development of active immunotherapy for Alzheimer's disease (AD) requires the identification of immunogens that can ensure a high titer antibody response toward Aβ, while minimizing the risks of adverse reactions. Multimeric protein (1–11)E2 induces a robust and persistent antibody response to Aβ in mice, when formulated in Freund's adjuvant. The goal of this translational study was to evaluate the immunogenicity of (1–11)E2 formulated in alum (Alhydrogel 2%), or in a squalene oil-in-water emulsion (AddaVax), or without adjuvant. A IgG1-skewed isotype distribution was observed for the anti-Aβ antibodies generated in mice immunized with either the non-adjuvanted or the adjuvanted vaccine, indicating that (1–11)E2 induces a Th2-like response in all tested conditions. Both Alhydrogel 2% and AddaVax enhanced the titer and avidity of the anti-Aβ response elicited by (1–11)E2. We conclude that (1–11)E2 is a promising candidate for anti-Aβ immunization protocols that include alum or squalene-oil-in-water emulsion, or no adjuvant.

Highlights

Active and passive immunization studies performed in transgenic mouse models of Alzheimer’s disease have demonstrated that antibodies against Ab are able to reduce plaques and improve cognition
We have previously described a multimeric protein antigen for the induction of an antibody response to Ab that consists of a domain of the bacterial protein E2 able to self-assemble into a particle consisting of 60 monomers [9]
As Complete Freund’s Adjuvant (CFA)-IFA is a very strong and reactogenic adjuvant that is not suitable for human use, we set out to profile the immunogenicity of (1–11)E2 in the absence of adjuvants. (1–11)E2 is produced in E. coli, and chromatography-purified preparations are invariably contaminated by traces of LPS, an activator of innate immunity that can have an adjuvant effect

Summary

Introduction

Active and passive immunization studies performed in transgenic mouse models of Alzheimer’s disease have demonstrated that antibodies against Ab are able to reduce plaques and improve cognition (reviewed in [1,2,3]). In mouse models of AD and in clinical trials, induction of high titer anti-Ab antibodies correlated with the reduction in brain Ab [4,5,6,7]. The development of a vaccine for the prevention or therapy of Alzheimer’s Disease faces two challenges, namely, overcoming the low immunogenicity of the Ab peptide and avoiding detrimental inflammatory reactions in the brain [1]. Balb/c mice receiving (1–11)E2 formulated in Complete Freund’s Adjuvant (CFA) developed immune memory to Ab after a single dose, as demonstrated by the fact that a booster dose, administered 6 months after the first dose, induced a very high serum concentration of anti-Ab antibodies (above 1 mg/ml) [9,10,11]. Vaccination with (1–11)E2 in Complete Freund’s Adjuvant Incomplete Freund’s Adjuvant (CFA-IFA) polarizes the immune response toward the production of the anti-inflammatory cytokine Interleukin-4 and does not induce a T cell response to Ab [9]

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