Macrophage activation as an immune correlate to protective immunity against schistosomiasis in mice immunized with an irradiated, cryopreserved live vaccine.
Immune responses against Schistosoma mansoni were evaluated in C57BL/6 mice injected with one of two populations of irradiated schistosomules, the larval preparations differing only in the degree of freezing-induced damage sustained upon cryopreservation. Mice injected with larvae which successfully withstood cryopreservation showed a significant reduction in worm burden following cercarial challenge. No protection was achieved in mice which received larvae damaged by a suboptimal thawing rate. Parallel comparison of several humoral and cellular responses in mice which received either inoculum revealed that induction of activated macrophages and production of macrophage-activating lymphokine activity were the strongest correlates to development of protective immunity. Protected mice also showed marginal 30-min skin test reactivity and weak but transient 24-h delayed-type hypersensitivity to a soluble adult worm preparation. In contrast, indistinguishable levels of circulating antibodies to soluble and tegumental antigens developed in the two immunization groups, and antigen-stimulated lymphocyte blastogenic responses were strong and essentially equivalent in magnitude. These studies strongly suggested that in this new model for investigating anti-schistosome effector mechanisms, responses contributing to the development of activated macrophages may be essential for induction of protective immunity.
D000818:Animals; D000906:Antibodies / Q000276:immunology; D005260:Female; D005615:Freezing; D007111:Immunity, Cellular; D008262:Macrophage Activation; D051379:Mice; D008810:Mice, Inbred C57BL; D011309:Preservation, Biological; D012550:Schistosoma mansoni / Q000276:immunology; D012555:Schistosomiasis mansoni / Q000276:immunology* / Q000517:prevention & control; D014613:Vaccines, Attenuated / Q000276:immunology*
D000906:Antibodies; D014613:Vaccines, Attenuated