The peptide is a poly-γ-D-glutamic acid (DPGA) 10 structure, which is related to the sequence of the Bacillus anthracis capsule. γ-DPGA is an important virulence factor of Bacillus anthracis. The capsule suppresses the inherent defenses of the host through its antiphagocytosis effect. Gamma-DPGA is a bad immunogen, but when combined with carrier protein, it can trigger serum antibodies.
Kubler-Kielb, J. et al. Infect. Immun. 74, 4744 (2006).