Adenovirus F protein as a delivery vehicle for botulinum B

Beata Clapp,Massimo Maddaloni,Sarah Golden,Herman F Staats,David W Pascual

doi:10.1186/1471-2172-11-36

Beata Clapp, Massimo Maddaloni + Show 3 more

Open Access

https://doi.org/10.1186/1471-2172-11-36

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Abstract

BackgroundImmunization with recombinant carboxyl-terminal domain of the heavy chain (Hc domain) of botulinum neurotoxin (BoNT) stimulates protective immunity against native BoNT challenge. Most studies developing a botulism vaccine have focused on the whole Hc; however, since the principal protective epitopes are located within β-trefoil domain (Hcβtre), we hypothesize that immunization with the Hcβtre domain is sufficient to confer protective immunity. In addition, enhancing its uptake subsequent to nasal delivery prompted development of an alternative vaccine strategy, and we hypothesize that the addition of targeting moiety adenovirus 2 fiber protein (Ad2F) may enhance such uptake during vaccination.ResultsThe Hcβtre serotype B immunogen was genetically fused to Ad2F (Hcβtre/B-Ad2F), and its immunogenicity was tested in mice. In combination with the mucosal adjuvant, cholera toxin (CT), enhanced mucosal IgA and serum IgG Ab titers were induced by nasal Hcβtre-Ad2F relative to Hcβtre alone; however, similar Ab titers were obtained upon intramuscular immunization. These BoNT/B-specific Abs induced by nasal immunization were generally supported in large part by Th2 cells, as opposed to Hcβtre-immunized mice that showed more mixed Th1 and Th2 cells. Using a mouse neutralization assay, sera from animals immunized with Hcβtre and Hcβtre-Ad2F protected mice against 2.0 LD50.ConclusionThese results demonstrate that Hcβtre-based immunogens are highly immunogenic, especially when genetically fused to Ad2F, and Ad2F can be exploited as a vaccine delivery platform to the mucosa.

Highlights

Immunization with recombinant carboxyl-terminal domain of the heavy chain (Hc domain) of botulinum neurotoxin (BoNT) stimulates protective immunity against native BoNT challenge
Significant S-IgA Ab responses were detected in fecal extracts from mice dosed nasally with Hcβtre-adenovirus 2 fiber protein (Ad2F), either in the presence or absence of cholera toxin (CT) adjuvant, as opposed to mice dosed nasally with Hcβtre, which produced weak Hcβtre-specific S-IgA Abs (Figure1A)
Mice i.n. immunized with HcβtreAd2F alone or i.m. or i.n. with Hcβtre alone exhibited only weak serum IgG responses (Figure 1B,D), mice i.m. immunized with Hcβtre-Ad2F without CT showed modest induction of serum IgG Ab responses (Figure 1D)

Summary

Introduction

Immunization with recombinant carboxyl-terminal domain of the heavy chain (Hc domain) of botulinum neurotoxin (BoNT) stimulates protective immunity against native BoNT challenge. Toxoid-based vaccines can be conveniently produced, these have a number of limitations, including isolation of active toxins, loss of essential neutralizing epitopes by formalin treatment, and multiple immunizations required to sustain elevated Ab titers [10]. To overcome these limitations, recent efforts have shifted to adapting recombinant BoNT heavy (H) chain to develop subunit vaccines [11,12], as well as employing DNA vaccine approaches [13,14]. Such approaches eliminate the reliance on handling active intact BoNTs

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