Effect of viable or dead Lactobacillus casei organisms administered orallyto mice on resistance against Trichinella spiralis infection

The capacity of viable, dead Lactobacillus casei and supernatant from L. ca sei culture, administered by oral route, to induce resistance in mice again st Trichinella spiralis infection was evaluated. The percentage of adult wo rm reduction in the intestine five days after T. spiralis infection as comp ared with the worm burden in the control group fluctuated between between 5 3.1 and 58 % in mice treated with viable L. casei, while reductions in anim als treated with dead lactobacilli or supernatant from L. casei culture wer e of 44 and 32.5 % respectively. The percentage of larvae per gram of muscl e tissue reductions, as compared with controls, obtained 30 days after infe ction ranged from 48.4 to 70.7 % in rodents which ingested viable L. casei compared with the percentage reductions of 65.9 and 24 % obtained respectiv ely in mice treated with dead lactobacilli or with L, casei supernatant. Th e protective response observed in the present study may be explained on the basis of 1) lactobacilli colonization of the intestine, 2) macrophage proc essing of dead lactobacilli in local immune tissues and presentation of I. casei antigens to Th1 cells which, in turn, produced IL-2 to activate B cel ls and other T cells.