Partial purification of antigens collected during in vitro cultivation of the larval stages of Taenia pisiformis.

Larvae of Taenia pisiformis were cultured in vitro in medium containing 2-5, 5 or 20% (v/v) of normal rabbit serum (NRS). Greatest development occurred in 20% NRS, and the potency of antigens collected in medium from each culture tested by intradermal (2/d) skin tests in infected rabbits paralleled the in vitro growth rate of larvae. 'Culture' antigens from 5% NRS stimulated good immunity in rabbits to a challenge infection with T. pisiformis eggs, although they were poorly reactive in skin tests. T. pisiformis larvae were also cultured in 10% (v/v) of filtrates of serum reduced to one-half of its volume by passage through 300 000 MW cut off (XM300F) or 100 000 MW cut off (XM100F) ultrafiltration membranes. Larvae cultured using XM300F had growth rates comparable with those cultured in 20% NRS, and the antigens release into the culture medium had equal potency in i/d tests and in stimulating protective immunity in rabbits. Larvae did not develop in XM100F or produce skin-reactive or protective antigens. Crude 'culture' antigen from cultures in 20% NRS was separated into 4 fractions by filtration on Sephadex G200. All of these fractions gave i/d skin reactions in infected rabbits. Fraction 3 (F3) was the most active, but was shown by acrylamide gel electrophoresis and immunoelectrophoresis to be highly contaminated with rabbit serum proteins. F3 was separated into fractions on DEAE-Sephadex A50, and the third fraction from this was as active as the original culture medium in i/d skin tests, but had only 5% of the original protein concentration. Electrophoresis demonstrated few serum contaminants, and 2 indistinct protein bands that were not present in a similar fraction of NRS. Neither Sephadex G200 F3 nor DEAE-Sephadex F3 stimulated protective immunity in rabbits, suggesting that antigens stimulating immunity against the establishment of T. pisiformis in rabbits and those provoking cell-mediated immune reactions may be different.