PROTECTIVE EFFECT OF BETA-GLUCAN AGAINST MYCOBACTERIUM-BOVIS, BCG INFECTION IN BALB C MICE/

beta-1,3-Glucan is a potent stimulator of macrophage functions and has a protective effect against a range of infections in rodent models. W e examined whether the agent could also protect against the intracellu lar Mycobacterium bovis, bacillus Calmette-Guerin (BCG) infection in m ice. BCG-susceptible BALB/c mice were injected intravenously (i.v.) wi th beta-glucan or vehicle 3 days before, or with beta-glucan 7 days af ter i.v. challenge with Live BCG bacilli. The animals were killed 4 or 8 weeks later, their organs were homogenized and applied to object sl ides and stained with auramin for counting of bacilli, or seeded onto agar in Petri dishes. Mice treated with beta-glucan both pre- and post challenge had significantly lower numbers of BCG bacilli and BCG colon y-forming units in spleen homogenates compared with controls 4 weeks a fter challenge. A similar, but not statistically significant, tendency was observed in spleen homogenates from mice killed 8 weeks after cha llenge. In homogenates of liver and lungs there were similar findings, but less pronounced. There was a dose-dependent effect of beta-glucan injected before BCG challenge on the number of BCG bacilli found in s pleen and liver homogenates. In addition, antibody cross-reactivity wa s demonstrated between M. tuberculosis cell wall and beta-glucan. The results suggest that beta-glucan has a protective effect against M. bo vis, BCG infection in susceptible mice.