Circulating antigens, antibodies and immune complexes in experimental Taenia pisiformis infections of rabbits.

Circulating antigen has been detected in the serum of rabbits experimentally infected with Taenia pisiformis. A rabbit antiserum against an antigen preparation derived from the in vitro maintenance of living metacestodes of T. pisiformis was used in a double-antibody enzyme-linked immunosorbent assay (ELISA). Antigen was detected in infected rabbit serum 48 h after infection and peak levels were recorded at 2 weeks post-infection or post-challenge. The pattern of circulating immune complex formation followed closely that of circulating antigen, and infected rabbit serum contained both anti-metacestode and antioncospheral antibodies. Serum antigen levels were just detectable (0.4-0.8 micrograms protein/ml) over the period (greater than 2 weeks post-infection) of peritoneal cyst development. The circulating antigen probably has antigenic determinants in common with the oncosphere, juvenile and mature metacestode stages. Possible reasons for the temporal variation in serum antigen levels are discussed.