Schistosoma japonicum: the effect of serum fractions precipitated by ammonium sulfate on viability of schistosomula.

The effect of serum fractions precipitated by a saturated ammonium sulfate solution on viability of Schistosoma japonicum schistosomula was investigated. Axenized cercariae were incubated for 10 days at 37 degrees C in NCTC 109 supplemented with the 34%, 40%, 50%, 62% and 68% fractions of human or rabbit serum in an equivalent concentration to 10% serum. Only larvae cultured in media with the 68% fraction of human or rabbit serum retained the transparent feature and active motility, while the larvae cultured in other media became opaque and immotile. This was also true in media with human serum albumin or fatty acid-free human serum albumin at concentrations of 1.0 and 10.0 mg/ml of NCTC 109. On 10-day culture a part of larvae in the medium with the 68% fraction of human serum began to feed on red blood cells and the intestine was nearly closed by 21 days. These results suggest that serum fraction of 68% ammonium sulfate consisting of albumin is an important constituent in supporting the further growth of schistosomula in vitro.