34 PP
IMMUNOGENIC POWER OF CELLULAR AND EXTRACELLULAR ANTIGENS OF CLOSTRIDIUM CHAUVOEI STRAINS ISOLATED IN SAN LUIS, ARGENTINA.

Mattar, M.A.*, Cortiñas, T.I, DiGenaro, M.S, and Guzmán A.M.S.
Area Microbiología, Universidad Nacional de San Luis, San Luis, ARGENTINA

Clostridium chauvoei is the pathogenic agent of blackleg, a disease causing serious toxemia and high mortality in cattle and sheep. It is considered as the most important clostridium producing economic losses in livestock. The control of this disease is done by comercial vaccines consisting of whole formolized cultures. Immunity to C. chauvoei is considered to be mainly anticellular, being somatic and flagellar antigens the most widely studied. However, C. chauvoei possesses an invasive infection mechanism assisted by toxins with local activity and extracellular spreading factors, the protective immunogenicity of which is considered to be of low importance. The purpose of this work was to study the protective immunogenic power of different cellular and acellular antigenic compounds obtained from two strains isolated from infected animals of San Luis raising livestock areas. Protection assays were performed by challenging lots of mice immunized with different antigenic compounds (alkaline extracts, sonicated cells and whole formolyzed cultures). No significant differences were found between the reference strain and the regional ones at the dilutions assayed (p less than/equal 0.05), being the whole formolyzed culture the one with the least protective power (p less than/equal 0.0001). Passive immunity tests using sera from mice immunized with different antigens showed 75-100% protection for the assayed strains. On the other hand adoptive immunity gave very poor protection results (0-25%). For both, the reference and regional strains, high protection levels were obtained in animals immunized intraperitoneally with freeze dried supernatants (between 83 and 100%). By immunoblotting of sera from animals immunized with extracellular proteins, we demonstrate the presence of inmunogenic bands corresponding to different soluble antigens as well as cellular antigens. The results obtained in the immunogenic study of regional strains demonstrate that these strains display a protective power similar to that of the reference strain. Such protective power can be enhanced by the use of cellular antigenic compounds different from commercial vaccines. The protection is principally antibody mediated. Besides if suitable immunization schedules and routes of administration are employed, the contribution of soluble antigens to the protective immunity of vaccines becomes important.