Immunization of mice with the antigen A60 oi Mycobacterium bovis BCG

Antigen 60 (A60) is a thermostable component of the cytoplasm of Mycobacterium tuberculosis and BCG which can be fractionated into at least 15 protein bands when analysed by Western blot. Normal B6D2 mice were immunized subcutaneously with 20 μg of the A60 protein suspended in Freund's incomplete adjuvant (FIA) or in saline. Three weeks later the mice received a second dose of vaccine followed 2 weeks later by an aerogenic challenge with approximately 10³ CFU of M. tuberculosis Erdman. The mice receiving the adjuvanled A60 showed a significant reduction (P < 0·05) in the number of viable organisms recovered from the lungs and the spleen 3 weeks after challenge. However, this response was less than that seen in BCG vaccinated controls.