Characterization of Bacillus anthracis Spore Proteins Using a Nanoscaffold Vaccine Platform.

Dina R Weilhammer,Amy Rasley,Paul D Hoeprich,Adam Driks,Sean F Gilmore,Mark Khemmani,Nicholas O Fischer,Sandra K G Peters,Tyler Boone,Craig D Blanchette,Alexis D Dunkle

doi:10.3389/fimmu.2020.01264

Abstract

Subunit vaccines are theoretically safe and easy to manufacture but require effective adjuvants and delivery systems to yield protective immunity, particularly at critical mucosal sites such as the lung. We investigated nanolipoprotein particles (NLPs) containing the Toll-like receptor 4 agonist monophosphoryl lipid A (MPLA) as a platform for intranasal vaccination against Bacillus anthracis. Modified lipids enabled attachment of disparate spore and toxin protein antigens. Intranasal vaccination of mice with B. anthracis antigen-MPLA-NLP constructs induced robust IgG and IgA responses in serum and in bronchoalveolar and nasal lavage. Typically, a single dose sufficed to induce sustained antibody titers over time. When multiple immunizations were required for sustained titers, specific antibodies were detected earlier in the boost schedule with MPLA-NLP-mediated delivery than with free MPLA. Administering combinations of constructs induced responses to multiple antigens, indicating potential for a multivalent vaccine preparation. No off-target responses to the NLP scaffold protein were detected. In summary, the NLP platform enhances humoral and mucosal responses to intranasal immunization, indicating promise for NLPs as a flexible, robust vaccine platform against B. anthracis and potentially other inhalational pathogens.

Highlights

Bacillus anthracis is an endospore forming, gram positive bacterium, and the causative agent of anthrax [1]
To investigate the potential for using spore-derived proteins as vaccine antigens, we identified seven proteins for use in our studies that have been previously identified as localized to the exosporium, spore surface, or interspace region of the B. anthracis spore, as well as two coat proteins that are exposed on the spore surface upon removal of the exosporium (Table 1)
monophosphoryl lipid A (MPLA):nickel-chelating lipids (NiNLPs) that have been successfully conjugated to individual B. anthracis antigens will collectively be referred to as MPLA:nanolipoprotein particles (NLPs):BAA throughout the remainder of the text

Summary

Introduction

Bacillus anthracis is an endospore forming, gram positive bacterium, and the causative agent of anthrax [1]. Anthrax is largely considered a disease of herbivores with humans contracting the natural disease through contact with infected animals or animal products. Anthrax in humans presents with a wide array of clinical manifestations depending on the route of exposure with inhalational (pulmonary anthrax) disease being most severe [1]. Inhalation of spores would be the most likely route of exposure in the event of a bioterror attack resulting in pulmonary anthrax with nearly 100% mortality rates if untreated [4, 5]. Given the previous use of B. anthracis as a bioweapon, coupled with the relative simplicity of large-scale spore production and ease of dissemination, this organism remains of high concern

Methods

Results

Conclusion