DNA vaccination against anthrax in mice - combination of anti-spore and anti-toxin components

The predominant antigen in human anthrax vaccines is the protective antigen (PA) of Bacillus anthracis. To address the question whether immune responses against B. anthracis spores can improve the protectivity of a PA-based DNA vaccine against anthrax, we designed a eucaryotic expression plasmid encoding the exosporium antigen BcIA, which is a collagen-like surface protein. This plasmid, pSecTag BcIA, carries a secretion signal for the recombinant antigen. Using NMRI mice we compared the effects of immunisation with a combination of PA- and BcIA-encoding plasmid DNA, to immunisations with either PA- or BcIA-encoding pDNA. After three immunisations the mice were infected with 25 x LD50 of B. anthracis Ames spores. The plasmid pSecTag BcIA, induced high BcIA-specific antibody responses. Vaccination with a combination of PA- and BcIA-encoding pDNA led to significantly better survival than immunisation with only PA- or only BcIA-encoding plasmids. (c) 2005 Elsevier Ltd. All rights reserved.