Abstract
Recombinant Sindbis viruses were engineered to express alternative forms of the protective antigen (PA) of Bacillus anthracis. The recombinant viruses induced PA-specific immunoglobulin G and neutralizing antibodies in Swiss Webster mice. Vaccination with the recombinant viruses induced immunity that offered some protection from a lethal Ames strain spore challenge and synergized the protective effects of ciprofloxacin.