Immunity to tapeworms: intraspecific cross-protective interactions between Hymenolepis citelli, H. diminuta and H. microstoma in mice.

Interactions between tapeworm species in a single host offer intriguing opportunities for immunological studies that attempt to identify the mechanism(s) underlying protection against cestode infections. Mice that are immunized against Hymenolepis citelli infections were shown to be refractory to subsequent H. diminuta challenge infections. The reciprocity of the response was also demonstrated, although the protection recorded for H. diminuta when mice are sensitized with H. citelli is weaker than that observed when mice are primed with H. diminuta against H. citelli challenge. H. citelli was also shown to be expelled simultaneously during the rejection phase of H. diminuta in concurrent infections, indicating the susceptibility of the former tapeworm to the rejection mechanism initiated by the latter. H. microstoma-immunized mice were shown to be strongly protected against heterologous H. citelli challenge. However, mice primed against H. citelli were not as strongly protected against H. microstoma challenge infections: a statistically significant protection was obtained only after a 12-cysticercoid H. citelli primary infection, although a 6-cyst infection did stunt the growth of H. microstoma challenge worms. It is presently suggested that the cross-protective responses observed in the study between H. citelli, H. diminuta and H. microstoma may have emanated from a specific immunological cross-reactivity due to the sharing of similar immunogens.