Haptenation of Adult Schistosoma mansoni and Assessment of Humorally Mediated Damage In vitro

Abstract

Adult Schistosoma mansoni were haptenated with DNP under mild conditions using DNP-liposomes, as devised by Levi-Schaffer et al. (1983, Am. J. Trop. Med. Hyg. 32: 343) for haptenating schistosomula. The effects of complement, alone or with anti-DNP antibodies, on tegumental morphology of DNP-haptenated adult worms were assessed by both scanning and transmission electron microscopy, as a simple model system for possible in vitro effects of complement and anti-schistosomal antibodies on normal adult worms. Complement-mediated cytotoxicity, as measured by tegumental changes in both normal and haptenated worms, was observed and indicates a possible role for complement in humorally mediated damage of adult schistosomes. The damage to haptenated adults in the presence of both complement and anti-DNP was greater than that to nonhaptenated worms similarly treated. However, anti-DNP plus complement caused less damage to normal worms than did complement alone, perhaps the result of blocking by antibodies bound to the tegument via Fc receptors. Evidence herein presented implicates both classical and alternative complement activation by the adult worm's tegument. Tegumental tubercle smoothing was one manifestation of damage, as assessed by SEM. Smoothing appears to progress from spine blunting to disappearance, arguing for resorption rather than shedding as the mechanism for spine loss. Because the spines are mostly actin bundles, we suggest that complement-mediated intrategumental calcium ion flux could lead to spine resorption resulting from actin filament depolymerization and/or calcium-induced severing of actin filaments and dissociation of actin filament cross-linking proteins. This process could have adaptive value to the adult worm, in that the spines may be a repository of readily mobilizable actin molecules for tegumental maintenance and repair.