Serum-Free Culturing of Adult Schistosoma mansoni in Dialysis Bags for the Production of Excretory/Secretory Antigens

Antigenic excretory/secretory (E/S) products from Schistosoma mansoni are potentially important in the development of diagnostic assays used to detect circulating antigens in schistosomiasis. The E/S products to be used as antigen(s) for this development must, by necessity, be free of exogenous proteins. The ability to extend serum-free in vitro culture of adult worms is, therefore, essential. Adult worms were perfused from mice, washed in serum-free RPMI-1640 with antibiotics, and placed in sterile dialysis bags, molecular weight cut-off 10 kDa, at a concentration of 100 worms in 1 ml of serum-free, supplemented RPMI-1640. Each bag was then placed in a flask of supplemented RPMI-1640 with 10% fetal calf serum in a humidified incubator at 37 C, 7% CO2. At days 1, 3, 5, 8, and 12, worms were collected; E/S culture medium was analyzed by sodium dodecyl sulfate polyacrylamide gel electrophoresis. Worm survival rates were 85% after 1 day in culture, dropping gradually to 65% on day 8, and then to 38% on day 12. Silver stain for total protein and immunoblot exposed to positive human infection serum showed E/S culture media from days 3 and 5 having the least complex banding pattern. The quantitative specific activity of E/S, as measured by antigen-limiting Falcon assay screening test system-enzyme-linked immunosorbent assays against human infection serum, indicates E/S antigenicity closely follows the attrition of worms and, therefore, may be directed against the release of somatic antigens by dead worms. Culturing S. mansoni in dialysis tubing is useful in deriving E/S products.