Cellular immunity in experimental Echinococcus multilocularis infection. I. Sequential and comparative study of specific in vivo delayed-type hypersensitivity against E. multilocularis antigens in resistant and sensitive mice.

Species- or strain-related differences in receptivity of intermediate hosts to E. multilocularis larvae could be related to differences in specific cellular immune response of the host. In order to test this hypothesis, we assessed the delayed-type hypersensitivity (DTH) to E. multilocularis antigens (EmAg) in mice of three strains differing by their sensitivity (AKR and C57BL.6) or resistance (C57BL.10) to E. multilocularis infection. DTH was determined by measuring in vivo the foot-pad response 24 h after an EmAg antigenic challenge. The level of positive response was evaluated in immunized mice; however, a typical DTH response was only observed by immunizing mice with a strong adjuvant schedule. Course of DTH in the immunized mice was shown to be somewhat different in sensitive and resistant mice. The differences were much more marked in mice infected with proliferative E. multilocularis larvae. The levels of the footpad response was significantly higher in resistant mice, although the peak of the reaction was obtained later than in sensitive mice. DTH, expressed by the foot-pad response against EmAg, remained significant for the entire period of observation in sensitive as well as in resistant mice. There was no correlation between receptivity of the murine hosts and levels of specific antibodies against EmAg. These results suggest a relationship between resistance to E. multilocularis infection and intensity and/or course of DTH in mice. The resistance could be mediated by some particularities of the in situ cellular immune response in the periparasitic granuloma.