International Journal for Parasitology VoL 16, No. 4, pp. 297-306, 1986. 0020-7519/86 $3.00+0.00 Printed in Great Britain. Pergamon Journals Ltd. © 1986 Australian Society for Parasitology IMMUNIZATION AGAINST TAENIA TAENIAEFORMIS IN MICE: IDENTIFICATION OF ONCOSPHERAL ANTIGENS IN POLYACRYLAMIDE GELS BY WESTERN BLOTTING AND ENZYME IMMUNOASSAY M. W. LIGHTOWLERS, M. D. RICKARD and G. F. MITCHELL* University of Melbourne, Veterinary Clinical Centre, Princes Highway, Werribee, Victoria 3030, Australia and *Immunoparasitology Unit, Walter and Eliza Hall Institute, Melbourne Victoria 3050, Australia (Received 28 May 1985) Abstraet--LIGHTOWLERS M. W., RICKARD M. D. and MITCHELL G. F. 1986. Immunization against Taenia taeniaeformis in mice: Identification of oncospheral antigens in polyacrylamide gels by western blotting and enzyme immunoassay. International Journal for Parasitology 16: 297-306. Oncospheral antigens of Taenia taeniaeformis were fractionated using polyacrylamide gel electrophoresis (PAGE) in the presence of sodium deoxycholate (DOC PAGE) under conditions in which their ability to vaccinate mice against infection was not destroyed. A gel cut-out fraction (DOC PAGE FII) was shown to be effec- tive in vaccinating against infection with larvae. DOC-PAGE analysis of radioactivity using 125I-labelled antigen indicated that FII represented 11 °7o of the original labelled protein. Antigens from DOC PAGE FII were eluted from gel cut-outs and shown to retain their ability to vaccinate mice against infection. In sodium dodecyl sulphate PAGE (SDS PAGE) the eluted DOC PAGE Fll components were shown to con- tain a restricted subset of polypeptides over a wide range of molecular weight. Specific oncospheral antigens were identified on western blots from DOC PAGE using enzyme immunoassay. Sera used included sera collected from mice protected against infection with larvae by vaccination with oncosphere antigen and sera from mice 28 days post infection (28 DPI) which had been shown to contain antibodies capable of passively transferring protection against infection. Four major antigens were visualized within the FII region using sera from mice vaccinated with complete oncosphere antigen or DOC PAGE FII. The principal antigen detected using 28 DPI sera was not within the FII region although a single weak antigen was detected with 28 DPI sera in FII. Using low acrylamide concentration gels (5o70monomer) the four antigens within FII were widely separated and used as gel cut-outs for immunizing mice. No frac- tions were effective in protecting against infection with larvae. Vaccination with cut-outs from 5°7o acrylamide gels containing all four FII antigens stimulated only marginal protection as did a gel cut-out from an area in which major antigens were not identified. Loss of vaccination efficacy as oncosphere antigens are fractionated in DOC PAGE suggests that other techniques will have to be used for identify- ing host-protective antigens from oncospheres beyond DOC PAGE FII. A polyclonal rabbit antiserum against DOC PAGE FII will now be used in screening expression libraries of T. taeniaeforrnis cDNA in further attempts to obtain host-protective antigens. INDEX KEY WORDS: Taenia taeniaeformis; immunization; oncospheral antigens; sodium deoxy- cholate; polyacrylamide gel electrophoresis; western blotting; enzyme immunoassay. INTRODUCTION MICE from strains highly susceptible to infection with the natural cestode parasite of rodents, Taenia taeniaeformis, can be protected against first infection by immunization with extracts from the parasite (reviewed by Rickard & Williams, 1982). Although antigen preparations from various life-cycle stages of the parasite are effective in conferring protection, antigens from oncospheres (TtO) are a potent source of protective immunogens (Rajasekariah, Rickard & Mitchell, 1980). For this reason attention has focussed on oncospherai antigens in investigations towards the development of a model defined-antigen vaccine against cystercercosis. A method for solubilizing T. taeniaeformis onco- cosphere antigens which immunize mice against infection was described by Rajasekariah, Rickard, Mitchell & Anders (1982) and immunochemical and immunoprecipitation analysis of these antigens in polyacrylamide gel electrophoresis (PAGE) (Bowtell, Mitchell, Anders, Lightowlers & Rickard, 1983; Lightowlers, Mitchell, Bowtell, Anders & Rickard, 1984) has identified a number of potential host-pro- tective antigens. Immunization with gel cut-outs from PAGE performed in the presence of the deter- gent sodium dodecyl sulphate (SDS) failed to immunize mice against infection with larvae, whereas a gel cut-out from PAGE performed in the presence 297