Echinostoma revolutum in mice; dynamics of the antibody attack to the surface of an intestinal trematode

Abstract

Echinostoma revolutum in mice: Dynamics of the antibody attack to the surface of an intestinal trematode. International Journal for Parasitology 16: 475–482. Two weeks after infection of mice with the intestinal trematode Echinostoma revolutum, sera became positive for antibodies (IgG, IgM, IgA) to the surface of in vitro excysted juveniles, as tested by IFAT, coinciding with development of immunity to reinfection. Juveniles also bound C3 when incubated in normal serum in vitro. Antibody- or C3-covered juveniles were attacked by cells in an in vitro peritoneal-cell-adherence test, but antibodies, C3 or cells had no effect on the survival of juveniles in vitro after 24 h. In vivo excysted juveniles, recovered from the intestine of immune mice 2 h after reinfection with metacercariae, were covered with IgG and IgA, but IgM, C3 or cells were not observed on their surface. A high degree of specificity of the E. revolutum surface antibodies was observed, with no cross reactions to schistosomulae of Schistosoma mansoni or vice versa. IFAT with sections of 1–4-week-old flukes incubated in immune serum indicated, that antibody also bound to the surface of older flukes. Juveniles completely lost the surface-bound antibodies within 5 h of being transferred to medium, but reexposure to immune serum made them positive again. It is suggested, that shedding of surface-bound antibodies may be an adaptation of these flukes to withstand the hosts immune attack.