Analysis of anti-protective antigen IgG subclass distribution in recipients of anthrax vaccine adsorbed (AVA) and patients with cutaneous and inhalation anthrax

The anti-PA IgG1, IgG2, IgG3, and IgG4 subclass responses to clinical anthrax and to different numbers of anthrax vaccine adsorbed (AVA, BioThrax®) injections were determined in a cross-sectional study of sera from 63 vaccinees and 13 clinical anthrax patients. The data show that both vaccination with three AVA injections and clinical anthrax elicit anti-PA IgG1, IgG2, and IgG3 subclass responses. An anti-PA IgG4 response was detected in AVA recipients after the fourth injection. The anthrax lethal toxin (LTx) neutralization efficacy of sera from recipients who received 4 to ≥10 AVA injections did not vary significantly in relation to changes in distribution of anti-PA IgG1 and IgG4 subclasses.