Detection of anti-protective antigen salivary IgG antibodies in recipients of the US licensed anthrax vaccine.

The immune response of anthrax vaccine recipients is not routinely monitored. For field use, a noninvasive test would be beneficial to evaluate the antibody response of anthrax-vaccinated individuals working within a high-risk area of possible exposure. The aim of this cross-sectional study was to determine whether whole saliva can be used as a surrogate matrix for the detection of 83 kDa protective antigen (PA)-specific immunoglobulin G (IgG). An enzyme-linked immunosorbent assay was used for the detection of PA-specific IgG in matched samples (serum and saliva) that were collected from vaccinated and unvaccinated participants. Specimens from 180 individuals revealed a positive correlation (r=0.73; P<0.0001) between the level of PA-specific antibody detected in the saliva and serum. The number of vaccinations influenced both the saliva and serum antibody response. On average, the concentration of serological PA-specific antibodies in the vaccinated group was nearly 1600-fold greater than that in saliva. The magnitude of the salivary anti-PA antibody response was not significantly affected by the consumption of food, beverage, or tobacco products or other factors, which could potentially affect oral fluid properties. These results suggest that an oral fluid-based immunoassay may be a feasible alternative to monitoring the serological antibody response of individuals that have been vaccinated against anthrax.