Experimental field trial with an immunostimulating complex (ISCOM) vaccine against contagious bovine pleuropneumonia.

The experimental field trial with an immunostimulating complex (ISCOM) vaccine has been an occasion to explore the role of a Th1 response in the pathogenesis caused by Mycoplasma mycoides subsp. mycoides small colony (MmmSC) and in immune protection. The ISCOM complex is known to promote Th1 response. Antibodies to MmmSC were detected by indirect enzyme-linked immunosorbent assay (ELISA) in the vaccinated cattle, although the levels were lower than in a previous study. No antibodies were detected by complement fixation test (CF). After the challenge infection, vaccinated animals developed CF antibody response. They showed significantly reduced mortality compared with controls. However, gross pathological and histopathological score for vaccinated animals was as high as for the non-vaccinated, characterized by a high inflammatory reaction with histopathology dominated by interlobular pneumonia with vasculitis.