Immunopotentiating effect of fungal glucans as revealed by frequency limitation of postchemotherapy relapse in experimental mouse tuberculosis.

Two kinds of fungal glucan, particulate yeast glucan (PYG) and lentinan, were examined for their immunopotentiating effect illustrated by reduced frequency of post-chemotherapy relapse in experimental mouse tuberculosis. Infected mice were treated by intensive chemotherapy with a three-drug combination [Streptomycin (SM) + isoniazid (INH) + rifampicin (RFP), ethambutol (EB) + INH + RFP, or SM + INH + pyrazinamide (PZA)] for 5 months. After termination of chemotherapy, the mice of each treated group were divided into three subgroups to receive or not to receive glucan for 4 weeks and again for 4 weeks after a month interval. During this 3-month period and the succeeding 5 months, the mice were subjected to occasional sacrifice to examine the growth of latent tubercle bacilli in the lung and spleen by cultivation of tissue homogenates. The results indicated that the regimens with SM + INH + RFP and EB + INH + RFP were highly effective in eliminating persistent tubercle bacilli down to undetectable levels. However, later multiplication of the latent bacilli was observed during the advanced postchemotherapy period. The application of PYG was most effective in prevention of this type of relapse in the spleen, but not so in the lung. Lentinan effect was manifested in the lung, but not in the spleen.