Sortase-conjugation generates a capsule vaccine that protects guinea pigs against Bacillus anthracis

► Sortase forms a single covalent bond between a carrier protein and a capsule antigen. ► PDGA-D4 vaccine includes polyglutamate and the D4 domain of protective antigen. ► PDGA-D4 elicits immunity against Bacillus anthracis challenge in guinea pigs. ► PDGA-D4 elicits immunity against pagA mutant Bacillus anthracis. ► Sortase-conjugation may be broadly useful to generate conjugate vaccines.