Immunization studies with attenuated strains of Bacillus anthracis

Abstract

Live, attenuated strains of Bacillus anthracis lacking either the capsule plasmid pXO2, the toxin plasmid pXO1, or both were tested for their efficacy as vaccines against intravenous challenge with anthrax toxin in Fischer 344 rats and against aerosol or intramuscular challenge with virulent anthrax spores in Hartley guinea pigs. Animals immunized with toxigenic, nonencapsulated (pXO1+, pXO2-) strains survived toxin and spore challenge and demonstrated postimmunization antibody titers to the three components of anthrax toxin (protective antigen, lethal factor, and edema factor). Immunization with two nontoxigenic, encapsulated (pXO1-, pXO2+), Pasteur vaccine strains neither provided protection nor elicited titers to any of the toxin components. Therefore, to immunize successfully against anthrax toxin or spore challenge, attenuated, live strains of B. anthracis must produce the toxin components specified by the pXO1 plasmid.

Antigen delivery by attenuated Bacillus anthracis: new prospects in veterinary vaccines

“…This toxinogenic and capsulated strain is virulent for guinea-pigs since less than 100 spores are sufficient to cause lethal anthrax in naïve animals. As previously observed, the Sterne stain induced an antibody response to PA and LF and protected 100% of animals compared with a pX01-cured strain (Ivins et al 1986). RPL686 and RPL686Dcya were able to stimulate immunity against anthrax as efficient as the Sterne strain.…”

Rapid and sensitive identification of pathogenic and apathogenic Bacillus anthracis by real-time PCR

“…In our opinion this approach is essential for the risk assessment when analyzing material from a potential anthrax attack. Apathogenic B. anthracis strains lacking either one or both plasmids have been isolated from the environment [21] and strains with just the pX01 have been used for vaccination [26,27]. A vaccine strain has been used in an anthrax attack in Japan, but without casualities.…”

Investigation of spore surface antigens in the genus Bacillus by the use of polyclonal antibodies in immunofluorescence tests

“…Anthrax strains generously provided by Dr J. Ezzell of the US Army Medical Research Institute of Infectious Diseases (USAMRIID) included Pasteur strains and strains produced at USAMRIID (A strains) also believed to be cured of the pXOl toxin plasmid (Ezzell et a/. 1984;Ivins et al 1986) and therefore avirulent for guinea-pigs. Of the remaining avirulent anthrax strains, Sterne and the Soviet vaccine strain ST1 are not encapsulated and are believed to lack the pX02 plasmid (Ivins et al 1986); the basis of the avirulence of strain B1 is unknown.…”