Effect of oral administration of lysozyme or digested bacterial cell walls on immunostimulation in guinea pigs

The effect of oral administration of bacteriolytic enzymes and enzymatically digested bacterial cell walls on immunostimulation in guinea pigs was studied. Guinea pigs were given lysozyme or pronase or both orally for a period of 8 days, and on day 7 they were primed with hepatitis B surface antigen. Circulating antibody titers to the antigen in the enzyme-treated group were significantly higher (four to six times, P less than 0.05) than those in nontreated control groups on day 16 after immunization. Stimulation of cellular immunity in the group receiving both lysozyme and pronase simultaneously was significantly increased compared with the group receiving only one of them. The humoral immune response was enhanced by oral administration of enzymatically digested cell walls isolated from Bifidobacterium longum. The result suggested that intestinal bacteria might be solubilized by oral administration of bacteriolytic enzymes and that the absorbable fragment of peptidoglycan released from the bacterial cell walls might be responsible for the enhanced host immune responses.