Schistosoma mansoni: Adsorption of Human Blood Group A and B Antigens by Schistosomula

Abstract

Immediately following skin penetration, schistosomula of Schistosoma mansoni were found capable of passively adsorbing human A and B blood group antigens onto their surfaces. The antigens were adsorbed from intact erythrocytes, boiled human saliva, or alcohol extracts of erythrocyte membranes. Evidence is presented suggesting that a glycosphingolipid structure may be important in the binding of erythrocyte antigens to schistosomes. No uptake of various other blood group antigens could be demonstrated. Mouse erythrocyte antigens have been demonstrated on the surface of adult Schistosoma mansoni reared in mice (Smithers, Terry, and Hockley, 1969; Clegg, Smithers, and Terry, 1971a), and it has been shown that at least one such antigen is passively adsorbed by schistosomula (Dean, 1971; Sell and Dean, 1972; Dean and Sell, 1972). Clegg, Smithers, and Terry (1971b) reported that young schistosomes reared in a culture medium containing human erythrocytes were destroyed following surgical transfer into monkeys which had been immunized against human erythrocytes, indicating that human antigens are also acquired by schistosomes. In one experiment, the erythrocytes used to immunize recipient monkeys differed from the erythrocytes in the worm cultures with respect to five major blood group antigens. Fewer worms were killed upon transfer to monkeys so immunized than was the case with homologous transfers, and this led the authors to conclude that blood group antigens might be acquired by schistosomula. The present study was carried out to deReceived for publication 13 September 1973. * Supported by the Bureau of Medicine and Surgery Work Unit No. MR041.05.01.0023A6GI. The opinions or assertions contained herein are the private ones of the author and are not to be construed as official or reflecting the views of the Navy Department or the naval service at large. The experiments reported herein were conducted according to the principles outlined in the Animal Welfare Act (PL 89-544 as amended) and followed the guidelines prescribed in DHEW Publication No. (NIH) 72-23, formerly PHS Publication No. 1024, Guide for Laboratory Animal Facilities and Care. termine which, if any, human blood group antigens are adsorbed onto the surfaces of schistosomula in vitro. MATERIALS AND METHODS Schistosomula were prepared from Puerto Ricanstrain cercariae of S. mansoni by allowing them to penetrate excised rat skins into Hanks' Balanced Salt Solution (HBSS), by methods described previously (Stirewalt and Uy, 1969; Clegg and Smithers, 1972). Alcohol extracts of erythrocyte membranes were prepared by the method of Koscielak (1963). Wet membranes prepared by hypotonic lysis (Dodge, Mitchell, and Hanahan, 1963) were mixed with ethanol to a final alcohol concentration of 85%, mixed on a shaker at room temperature for 3 days, centrifuged, and the superatant fluid stored at -15 C for 3 days. The resulting precipitate was collected by centrifugation and stored at -70 C. Koscielak showed that the blood group active molecules in these preparations are glycosphingolipids. Saliva of a known secretor of soluble blood group A substance was boiled and centrifuged, and the supernatant fluid employed in appropriate experiments. Neutr AB is a commercial preparation (Dade Reagents, Miami, Florida) containing both A and B blood group activities. The source of this preparation (equine gastric mucin) and the method of preparation (Dade Reagents, pers. comm.) indicate that the active molecules are probably glycoproteins rather than glycosphingolipids (Baer, Kabat, and Knaub, 1950; Kabat, 1956). Specific activities of alcohol-extracted antigens and Neutr AB were measured by means of the hemagglutination inhibition (HI) assay. Serial double dilutions of antigen were prepared in Vbottom wells of Microtiter plates (Cooke Engineering Company, Alexandria, Virginia). Dilutions were made in pH 7.4 phosphate-buffered saline (PBS) at a final volume of 0.05 ml per well. An equal volume of blood group typing antiserum