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

Area of Science:

• Immunology
• Microbiology
• Vaccinology

Background:

• Edema toxin (ET) from Bacillus anthracis, comprising edema factor (EF) and protective antigen (PA), is a key virulence factor.
• Anthrax vaccine precipitated (AVP) contains low levels of EF and can induce EF-specific antibodies.

Purpose of the Study:

• To compare humoral responses to ET in recipients of AVP versus anthrax vaccine adsorbed (AVA).
• To determine if EF antibodies elicited by AVP contribute to ET neutralization.

Main Methods:

• Comparative analysis of antibody titers (IgG) against EF and PA in human vaccine recipients.
• Luciferase-based cyclic AMP reporter assay for ET neutralization.
• Analysis of antibody binding to EF decapeptides.

Main Results:

• AVP induced significantly higher incidence and titers of EF antibodies compared to AVA.
• PA IgG levels and ET neutralization capacity were comparable between AVP and AVA groups.
• Purified EF antibodies from AVP sera demonstrated ET neutralization capabilities.

Conclusions:

• While PA antibodies are the primary neutralizers of ET, EF antibodies elicited by AVP can also neutralize ET.
• The presence of EF in AVP contributes to its immunogenicity.
• Further investigation into incorporating EF components could enhance next-generation PA-based anthrax vaccines.