Analysis of antigenic variation in cysticerci of Taenia-solium

By studying the reactions and cross-reactions of antigen extracts from different collections of Taenia solium with their respective hyperimmune antisera, and by using numerical taxonomy to analyze the results, a measure of antigenic diversification within T. solium was established. Results varied somewhat depending on the immunological method employed. Double immunodiffusion and immunoelectrophoresis agreed in that all cysticerci were not identical, but shared approximately one third of their antigens. Double immunodiffusion recognized two groups of identical cysticerci: one included 50% of the cysticerci and the other, 21%. Immunoelectrophoresis was more discriminatory in that it recognized few extracts as identical. Electrophoretic data revealed that the most frequently shared antigen among cysticerci corresponded to that most frequently detected by immunologically responsive humans with cerebral cysticercosis. Antigen diversification of T. solium may provide a possible explanation of the pleomorphic immune response of man to this parasite. The role of the immune response in parasitic diseases of man is little understood. Of the many problems presented by parasitoses, host and parasite diversification is prominent. Although variation in pathogenicity within bacterial and viral species is well documented (Smith, 1968, 1972) and the participation of histocompatibility and other genotypic traits of the host in the outcome of viral and bacterial infections is possible (McDevitt et al., 1974; Fine et al., 1979), little is known about host or parasite variants in most parasitic diseases of man (Afchain, 1978; Braun, 1979; Vadas, 1980). Although cysticercosis is no exception, some observations (Flisser et al., 1980), made under the assumption that all cysticerci are antigenically identical, used variation in the host immune response to natural infection by T. solium to explain: (1) the large fraction of infected humans without detectable circulating antibodies; (2) the variation in the number and type of antigens that were recognized by those patients with detectable antibodies; (3) the presence or absence of IgE among the anticysticercus antibodies; and (4) the fact that 40% of autopsy cases were asymptomatic (Marquez-Monter and Austria, 1969). Received 4 November 1980; revised 11 May 1981; accepted 17 August 1981. * Departamento de Inmunologia, Instituto de Investigaciones Biom6dicas, Universidad Nacional Aut6noma de Mexico, M6xico 20, D.F., Mexico. t Centro de Investigaciones Ecol6gicas del Sureste, San Crist6bal Las Casas, Chiapas. In addition to the differences in the immune response among humans, antigenic differences in the parasite could also account for such a pleomorphic host-parasite relationship as is seen in human cysticercosis. The few immunological studies reported, using cysticerci from humans, point to the existence of cross-reacting antigens among cysticerci (Biagi and Tay, 1958; Biagi et al., 1961). There are also reports of cross-reactions among cysticerci and other parasites (Gemmell, 1964; Capron et al., 1968; Leid and Williams, 1975; Rydzeweski et al., 1975). However, these experiments were not designed to classify systematically T. solium with respect to its antigen content and therefore cannot be used to determine the existence of antigenic variants in T. solium. An immunotaxonomy of parasites, which would establish both similarities and differences within members of the same species or between species, would help resolve this problem and be useful in the development of immunodiagnostic techniques if serological reactions are to recognize all or, at least, most of the variants of the parasites. Likewise, the eventual development of a vaccine would require a thorough classification of the antigens of the pathogen lest it be ineffective against common variants. Clearly, antigenic taxonomy of T. soliumand, in fact, of all parasites affecting man-is necessary for research, diagnosis, and prevention of disease. Here we present data on the antigenic similarities and differences among 15 different collections of T. solium as revealed by hyperimmune mouse antisera, and