Epitopes expressed on very low Mr Schistosoma mansoni adult tegumental antigens conform to a general pattern of life-cycle cross-reactivity.

The relationship between antigens associated with the surface of newly transformed schistosomula of Schistosoma mansoni and the tegumental surface membrane of adult S. mansoni worms has been further explored. Immunoprecipitation of detergent-solubilized 125I-tegumental surface membrane antigens of adult S. mansoni with antibodies from mice vaccinated with highly irradiated S. mansoni cercariae revealed major antigens of Mr 32, 20, 15 and 8K. The Mr 32 and 20K antigens have been previously demonstrated to be antigenically and electrophoretically identical to major antigens on the schistosomulum surface. The Mr 15 and 8K antigens, on the other hand, have not been identified by the immunoprecipitation of 125I-schistosomulum surface antigens, although a distinct schistosomulum surface antigen of Mr 15K is precipitated by antibodies from mice vaccinated with highly irradiated cercariae. Nevertheless, it was shown that antibodies to the Mr 15 and 8K antigens were specifically absorbed from vaccinated mouse serum by intact, live schistosomula, demonstrating that the Mr 15 and 8K antigens are exposed on or released from the schistosomulum surface. In contrast, absorption of the antiserum with eggs failed to remove antibody against any of the four tegumental membrane antigens examined. The Mr 15 and 8K antigens were shown to be recognized via polypeptide epitopes and not periodate-sensitive carbohydrate epitopes, further emphasizing the similarity of these to the well-characterized Mr 32 and 20K tegumental surface membrane antigens. A general relationship between schistosomulum surface, adult tegumental membrane and egg antigens was demonstrated by ELISA, using antibodies raised against the three antigenic fractions.(ABSTRACT TRUNCATED AT 250 WORDS)

Antibody to carbohydrate and polypeptide epitopes on the surface of schistosomula of Schistosoma mansoni in Egyptian patients with acute and chronic schistosomiasis.

125I-Schistosoma mansoni schistosomulum surface antigens were immunoprecipitated with human antibodies from individual Egyptian patients diagnosed as being either acutely or chronically infected with S. mansoni. Both sets of patients were found to have IgG antibodies in their sera capable of immunoprecipitating the major Mr greater than 200, 38 and 32K antigens. However, the immunoprecipitation of the Mr greater than 200K antigen was found to constitute a significantly greater proportion of the total precipitate achieved with acute sera than with chronic sera. The Mr 38 and 32K antigens were more variably precipitated by the acute sera than the chronic sera but the proportion of the total precipitation that these two antigens constituted was not found to be significantly different between the two sets of sera. Immunoprecipitation with pooled antibodies absorbed with egg and adult worm homogenates which had been treated to remove either carbohydrate or polypeptide epitopes demonstrated that the Mr greater than 200K antigen was the principal target of egg-cross-reactive anti-carbohydrate antibody amongst the antigens detected. The Mr 38 and 32K antigens were found to be precipitated by antibodies to protease-sensitive and periodate-insensitive polypeptide epitopes. These results are consistent with egg-cross-reactive anti-carbohydrate IgG antibody making a greater contribution to schistosomulum surface recognition in acute infection than in chronic infection. Indeed the presence of a higher level of egg-cross-reactive and anti-carbohydrate antibody directed against schistosomulum surface epitopes in an acute serum pool than in a chronic serum pool was confirmed by measurement of antibody binding to whole schistosomula.

Variable species and stage specificity of schistosomulum surface epitopes recognized by mice vaccinated with highly irradiated cercariae.

Antibodies from mice vaccinated with highly irradiated Schistosoma mansoni or S. haematobium cercariae were used to characterize schistosomulum surface epitopes which were found to be diverse in their species and stage specificities. The epitopes recognized on the Mr greater than 200,000 and 15,000 schistosomulum surface antigens of S. mansoni and the Mr greater than 200,000 schistosomulum surface antigen of S. haematobium were found to be cross-specific whereas those on the Mr 38,000, 32,000 and 20,000 schistosomulum surface antigens of S. mansoni and the Mr 35,000, 30,000 and 24,000 schistosomulum surface antigens of S. haematobium were only immunoprecipitated by homologous antibody and are thus possible targets of the protective species-specific immunity stimulated by highly irradiated cercariae. The epitopes recognized on the Mr greater than 200,000 and 38,000 antigens of S. mansoni were shown to cross-react with both the egg and the adult worm whereas those on the Mr 32,000 and 20,000 antigens only cross-reacted with the adult worm, and those on the Mr 15,000 antigen cross-reacted with neither the adult worm nor the egg. In addition the epitopes on the Mr 38,000 and 32,000 antigens were demonstrated to be polypeptide in nature. Those on the Mr greater than 200,000, 20,000 and 15,000 antigens, on the other hand, could not be conclusively defined.

Analysis of the anti-Schistosoma mansoni surface antibody response during murine infection and its potential contribution to protective immunity.

Absorption of serum from chronically infected mice with homogenized schistosome eggs reduced antibody binding to the schistosomulum surface by 94%, indicating that almost all schistosomulum surface recognition during chronic infection is due to epitopes shared with the egg. Absorption of the serum with egg homogenate from which protein antigens had been removed by boiling and digestion with proteinase K resulted in a similar reduction of antisurface antibody demonstrating that all the shared epitopes that are recognized are carbohydrate in nature. Analysis of the time course of anticarbohydrate antibody production and the levels of antibody in mice infected with a single sex of schistosome indicated that eggs directly stimulated this response. Mouse mAb were identified that bound at very high levels to the schistosomulum surface and that recognized carbohydrate epitopes shared with the egg. Three of these had previously been demonstrated to passively transfer resistance, indicating that these surface carbohydrates are potential targets of protective immunity in the mouse. All the anticarbohydrate mAb also bound to the surface of schistosomula of other schistosome species. Thus, the strong immune response against these epitopes in chronic infection could account for the cross-specific immunity observed. Mice vaccinated with irradiated cercariae lacked high levels of anticarbohydrate antibodies and their recognition of the surface was largely due to antibody to species-specific polypeptide epitopes. With respect to the Mr greater than 200,000 and 38,000 antigens, it was demonstrated that these epitopes were present on the same antigens that bear the carbohydrate moieties recognized by antibodies from chronically infected mice. This specific polypeptide recognition is also reflected in the immunity generated by exposure to irradiated cercariae.

Surface antigens of and cross-protection between two geographical isolates of Schistosoma mansoni.

Two isolates of Schistosoma mansoni from Puerto Rico and Egypt were examined to determine if there were differences in surface antigens of the schistosomulum and to assess the ability of the two isolates to induce protection against one another in vivo. Immune mouse and human patient antisera recognized the same antigens on the schistosomulum surface of both isolates. However, mice immunized with schistosomula-released products from the Egyptian isolate recognized an additional antigen of Mr 13K on the Egyptian schistosomulum surface which was not present in the Puerto Rican isolate. In quantitative radioimmunoassay, sera from mice vaccinated with irradiated Egyptian cercariae bound more strongly to Egyptian schistosomula than to Puerto Rican parasites. Both isolates cross-protected against each other, but mice were less immune to challenge with Egyptian cercariae after being immunized with Puerto Rican irradiated cercariae. There was no difference in immunity to challenge when Egyptian irradiated cercariae were used to immunize. Although this evidence suggested some heterogeneity within the Egyptian isolate, cloned cercariae of the Egyptian isolate did not vary in their ability to cross-protect against each other. Furthermore, antisera from mice immunized with clones of Egyptian cercariae recognized the same schistosomulum surface antigens. The results reported here indicate that although there were small differences between the two isolates the major surface antigens are conserved.

A major role for carbohydrate epitopes preferentially recognized by chronically infected mice in the determination of Schistosoma mansoni schistosomulum surface antigenicity.

A radioimmunoassay that makes use of whole schistosomula and 125I-labeled protein A has been used to characterize and to quantify the binding of antisera to the surface of 3 hr mechanically transformed schistosomula of Schistosoma mansoni. This technique facilitates the determination of epitopes on the schistosomula in addition to those detected by surface labeling and immunoprecipitation. By using this technique, it has been demonstrated that there is a much greater binding to the parasite surface of antibodies from chronically infected mice (CMS) than of antibodies from mice infected with highly irradiated cercariae (VMS), and CMS recognizes epitopes that VMS does not. Treatment of the surface of the schistosomula with trifluoromethanesulphonic acid and sodium metaperiodate has suggested that the discrepancy of the binding between the two sera is due to the recognition of a large number of additional epitopes by CMS, which are carbohydrate in nature. Some of the carbohydrate epitopes are expressed on the previously described surface glycoprotein antigens of Mr 200,000, 38,000, and 17,000.

IgM antibodies recognizing carbohydrate epitopes shared between schistosomula and miracidia of Schistosoma mansoni that block in vitro killing.

A series of monoclonal antibodies (mAb) was raised in mice against Schistosoma mansoni, which recognized a carbohydrate determinant on a major Mr greater than 200,000 schistosomulum surface antigen. These mAb cross-reacted with the surface of cercariae and miracidia and with schistosomula of S. haematobium and S. bovis. Other mAb were generated that only recognized a Mr 20,000 schistosomulum surface antigen; they did not cross-react with eggs or miracidia and were species specific. The anti-Mr 20,000 mAb of the IgG1 isotype exhibited high levels of complement-dependent cytotoxicity to schistosomula in vitro. IgM mAb that recognized carbohydrate epitopes of the Mr greater than 200,000 surface antigen blocked the lethal activity of the anti-Mr 20,000 mAb. The IgM anti-Mr greater than 200,000 mAb also reduced complement-dependent cytotoxicity of serum from mice vaccinated with irradiated cercariae.

The recognition of Schistosoma mansoni surface antigens by antibodies from patients infected with S. mansoni and S. haematobium.

Polypeptide surface antigens of Schistosoma mansoni recognized by schistosomiasis patients have been identified and their strain and species specificity investigated. Antibodies from individuals infected with S. mansoni were used in immunoprecipitation assays of 125I-labelled schistosomulum surface antigens. All individuals surveyed from St. Lucia strongly precipitated antigens of approximately Mr 38,000 to 32,000 and 20,000. These antigens were shown by two-dimensional gel electrophoresis to be the same as those recognized by experimentally immunized mice. Although individuals showed a highly heterogeneous response against total polypeptide antigens synthesized in vitro by cell-free translation of adult S. mansoni mRNA, all individuals recognized the same surface antigens. Immunoprecipitation with sera from patients infected with S. mansoni in many different parts of Africa resulted in generally the same antigens being precipitated, although a very high molecular weight antigen(s), not strongly recognized by the St. Lucian sera was also precipitated by most of the African patient sera. One serum from Ghana precipitated the high molecular weight antigen but not the low molecular weight antigens, raising the possibility of the existence of S. mansoni strain(s) exhibiting some diversity in surface antigens. The surface of S. mansoni schistosomula was found to bind strongly antibodies from individuals infected with S. haematobium, demonstrating that most surface antigens are cross-reactive. Immunoprecipitation demonstrated, however, that of the polypeptide surface antigens only the very high molecular weight antigen was recognized by anti-S. haematobium antibodies and that the 38,000 to 32,000 and 20,000 Mr antigens were species-specific. Immunoprecipitation of the polypeptide antigens derived from purified adult surface membranes demonstrated recognition of the same 32,000, 25,000 and 20,000 Mr antigens recognized by chronically infected mice. Again these antigens were found to be species-specific.