Surface Plasmon Resonance Analysis of Binding Kinetics and Affinity of Serum Protective Antigen Antibodies in Non‐Human Primates Following Vaccination and Anthrax Aerosol Challenge

Abstract

The immune response to anthrax protective antigen (PA) in the non-human primate (NHP) was characterized by anti-PA IgG ELISA, toxin neutralization assay (TNA), and antibody binding kinetics and affinity after vaccination and challenge. NHPs were vaccinated twice with AVA or recombinant PA (rPA) vaccine administered four weeks apart and aerosol challenged with Bacillus anthracis Ames spores 10 weeks post initial vaccination. Serum samples were collected every two weeks throughout the vaccination and challenge time periods. Serum immunoglobulins were analyzed for anti-PA binding kinetics and affinity on a Biacore 3000 at five concentrations against rPA covalently attached to a CM4 chip. The general trend for both vaccine groups was a decrease in both kd and ka immediately after vaccination and challenge. The net effect of both vaccination and aerosol challenge on binding affinity for PA was a decrease in KD (higher affinity). The average KD values for the AVA and rPA vaccinated NHPs post aerosol challenge (day 100) were 2.5 nM and 3.0 nM respectively. Data will be presented that demonstrate the effect of multiple exposures to PA (via vaccine and/or challenge) on anti-PA antibody maturation. This work was supported by NIAID Contract No. N01-AI-30061.