Abstract:
Polypeptide epitopes are defined herein which when used as components of vaccine compositions, induced partial immunity to Schistosoma mansoni. The epitopes are found on the surface of schistosomula. The epitopes are part of larger proteins which are immunologically cross-reactive with myosin heavy chains from other species. However, anti-myosin antibodies directed against myosin molecules of other species are not cross-reactive with the surface epitopes of S. mansoni.

Description:
The work leading to this invention was supported in part by grants from the National Institutes of Health. The U.S. government retains some rights in the invention. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates to prophylaxis against Schistosoma mansoni, which causes big belly disease or bilharziasis. 
     BACKGROUND OF THE INVENTION 
     Schistosomiasis is a parasitic infection of man which is widespread in tropical countries. Schistosomiasis, known as bilharziasis in Europe and as big belly disease in China, ranks as one of the most debilitating of tropical infections. Schistosomiasis is the result of infection with sexually mature and reproducing adult worms of any one of several closely related species of parasitic flatworms. The disease occurs where the parasite&#39;s specific snail intermediate hosts are found. Approximately 250 million people are estimated to be infected, with about 5% of those displaying severe disease symptoms. 
     Human schistosomiasis is transmitted by water contact. The cercariae, or mobil larvae, emerge from the snail host and penetrate the skin of humans, where they rapidly develop into schistosomula. The schistosomula enter the blood stream and migrate to the lungs at 4 to 14 days. The schistosomula re-enter the blood stream migrating to the mesenteric or pelvic venules where they mate and lay eggs. 
     Often, upon infection, a rash occurs at the penetration site. Other symptoms include cough, fever, eosinophilia, and asthma-like symptoms. The adult worm grows to approximately 1.5 cm and can lay up to 500 eggs a day. 
     While there are some drugs which effectively counter infection, drug resistance as well as incomplete curing of worms creates recurrence problems. Effective vaccines are needed to provide lasting protection from these infections in areas of the world where water sources will continue to remain contaminated with fecal matter. 
     OBJECTS OF THE INVENTION 
     It is an object of the invention to provide a fusion protein which can stimulate an immune response resulting in protective antibodies which recognize surface antigens of schistosomula. 
     It is another object of the invention to provide antibodies which bind to epitopes expressed on the surface of live schistosomula. 
     It is yet another object of the invention to provide polypeptides which are capable of binding to antibodies which bind to antigens on the surface of live schistosomula. 
     It is still another object of the invention to provide vaccines comprising polypeptides which bind to antibodies which bind to the surface of live schistosomula, in combination with an immune adjuvant. These and other objects of the invention are provided by one or more of the embodiments described below. 
     In one embodiment a preparation is provided comprising antibodies which bind to protein epitopes expressed on the surface of live schistosomula of S. mansoni. The protein epitopes are common to two glycoproteins of S. mansoni, of sizes 200 kDa and 38 kDa, but are not immunologically cross-reactive with antibodies raised against bovine or C. elegans myosin. 
     In another embodiment of the present invention a fusion protein is provided which, when injected into mice to stimulate an immune response, elicits production of antibodies which recognize protein epitopes expressed on the surface of live schistosomula of S. mansoni, said protein epitopes being common to a 200 kDa and a 38 kDa glycoprotein of S. mansoni; said protein epitopes are not immunologically cross-reactive with antisera raised against bovine or C. elegans myosin. 
     In another embodiment of the present invention polypeptides are provided which bind to the antibodies which bind to protein epitopes expressed of the surface of S. mansoni schistosomula. The polypeptides have a sequence corresponding to that shown in FIG. 1. The polypeptide can be synthesized chemically, or can be synthesized by a transformed host cell carrying a recombinant DNA sequence which codes for the polypeptide. Vaccines are also provided by the present invention which comprise either the polypeptide or the fusion protein of the present invention in combination with an immune adjuvant. 
     The present invention provides means of generating large quantities of protein antigens. The antigens can be synthesized either chemically or by recombinant DNA techniques to provide large quantities of immunogens for vaccine production and testing. 
    
    
     BRIEF DESCRIPTION OF THE FIGURES 
     FIG. 1, panel A depicts the nucleotide sequence of the insert of clone IrV-5. Panel B shows the deduced amino acid sequence of clone IrV-5 insert DNA in line I, and the myosin heavy chain of C. elegans amino acid sequence in line II. Panel C shows a diagrammatic illustration of the region of homology between the deduced amino acid sequence of clone IrV-5 and C. elegans myosin heavy chain. 
     FIG. 2 shows the identification of the native protein encoded by the clone IrV-5. 
     FIG. 3 shows the identification of the surface labeled polypeptides recognized by anti-fusion protein antisera. 
     FIG. 4 shows the sequential immunoprecipitation of surface labeled polypeptides of S. mansoni. 
     FIG. 5 shows surface binding of anti-fusion protein antisera to newly transformed schistosomula. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     It has been discovered that epitopes which are common to two glycoproteins (38 kDa and 200 kDa) of schistosomula of S. mansoni are able to provide protection against infection by S. mansoni. The epitope (or epitopes) on the 38 kDa protein are exposed to the surface of the schistosomula. The epitope on the 200 kDa protein is apparently not exposed to the surface ofschistosomula. 
     The 38 kDa protein is immunologically cross-reactive with antisera to both bovine smooth uterine muscle myosin as well as C. elegans myosin. However,the particular epitopes of the present invention which are shared by the 200 and 38 kDa proteins and which are exposed to the surface of schistosomula, are not immunologically cross-reactive with the anti-myosinantisera of cows or C. elegans. In addition, other previously known antibodies which are cross-reactive with the 38 kDa glycoprotein, such as monoclonal antibody 128 (Dalton, et al., Experimental Parasitology, vol. 63, pp. 215-226, 1987) are not immunologically cross-reactive with the epitopes identified by the present invention. Previously described antibodies which recognize surface epitopes on the 38 kDa glyco-protein are directed against glycanic moieties. One benefit of the epitopes identified by the present invention (as compared to the previously identified glycanic epitopes) is that the protein epitopes can be synthesized by means of organisms containing recombinant DNA. 
     The proteinaceous character of the epitopes identified in the present invention is evident from the following fact: the epitopes are identified by antisera which were raised against lysates of bacteria infected with recombinant phage. As bacteria do not glycosylate proteins, the epitopes must be protein epitopes rather than glycanic epitopes. 
     A fusion protein according to the present invention may include portions ofany bacterial protein which is well expressed. Particularly convenient fusion proteins are made using portions of the amino terminal end of the enzyme beta-galactosidase. Other bacterial proteins are known in the art and may be used to obtain expression in bacteria. If expression in other types of host cells is desired, fusions may be made to proteins of the host cell which are conveniently expressed. In the course of constructing the particular fusion protein which is exemplified below, a lambda gt11 vector was used to create the fusion protein. S. mansoni cDNA was insertedinto the lambda gt11 DNA in order to create a library of S. mansoni genes. A description of the making of the cDNA library can be found in the Proceedings of the National Academy of Sciences U.S.A., vol. 84, page 4268, 1987. Techniques for making cDNA libraries are well known in the art. See, e.g., Maniatis et al., Molecular Cloning, pp. 211-246, Cold Spring Harbor Laboratory, 1982. 
     The clones of the present invention which contain the protein epitopes common to both the 200 kDa and the 38 kDa glycoprotein were identified using a rabbit antiserum (termed anti-IrV) which was raised against a subset of adult worm antigens, including the 200 kDa glycoprotein. The particular subset of adult worm antigens was selected based on its enhanced reactivity with sera of vaccinated as compared to chronically infected mice. The subset of antigens were purified using immunoprecipitation and immunodepletion techniques. See, Dalton et al., J.Immunology, vol. 139, pp. 2474-2481, 1987. Five clones were identified out of 20,000 plaques screened which reacted immunologically with the anti-IrVserum. 
     One clone, identified as IrV-5, contains S. mansoni sequences which share 48% identity with the amino acid sequence of the heavy chain of C. elegansmyosin. However, the identity is located in a region of the sequence distinct from that region which contains the protein epitopes shared by the 200 kDa and the 38 kDa glycoproteins of S. mansoni. Thus the epitopes identified in the present invention are not cross-reactive with anti-myosin antisera directed against either bovine or C. elegans myosin. 
     Polyclonal antibodies against bovine uterine smooth muscle myosin and a monoclonal antibody (12.1.1) against the S2 region of myosin heavy chain of C. elegans immunoreact with the fusion polypeptide. However, the anti-bovine and anti-C. elegans antibodies do not immunoreact with surfaceepitopes of schistosomula. In contrast, antisera raised against the native fusion protein encoded by clone IrV-5, are able to specifically immunoprecipitate a 38 kDa component from an extract of radio-iodinated, surface labeled schistosomula. Thus, anti-schistosome myosin antibodies define epitopes exposed on the surface of live schistosomula, and these epitopes are not recognized by antibodies against myosin derived from other species. 
     A fusion protein, according to the present invention, can be synthesized inany heterologous host cell. As is known in the art, vectors for particular host cells are available and can be used to maximize protein production. Suitable host cells include yeast cells, E. coli cells, and other readily culturable cells. 
     Surface expression of the epitopes of the present invention can be detectedusing indirect immunofluorescence analysis. Surface integrity of schistosomula during the course of the immunofluorescence assays can be verified using diamidinophenylindole, a fluorochrome specifically taken upby damaged schistosomula. Antibodies raised against the fusion protein of the present invention as well as monoclonal antibody 128 show strong binding to the surface of live newly transformed schistosomula. 
     Surface binding can be detected in the following way. Live schistosomula can be incubated for about one hour on ice with the test antibody. Antibody which binds to the surface of the schistosomula can be detected using antibody raised against immunoglobulin of the species of the first antibody. Rhodamine-conjugated protein A can be used to identify the boundantibodies. Alternatively, the anti-immunoglobulin antibody can itself be conjugated to a fluor such as fluorescein isothiocyanate. The schistosomula are washed three times after each antibody incubation. Immunofluorescence using frozen sections can be carried out as described in The Journal of Immunology, vol. 137, page 3593, 1986. Other means of detecting surface binding are known in the art and can be used as is convenient. 
     An alternative method for identifying surface epitopes is to radio-iodinatesurface polypeptides. Surface labeling can be accomplished using the Iodo-Gen method described in The Journal of Immunology, vol. 139, page 2474, 1987. The surface labeled proteins can be extracted with a detergentfor example 1% NP 40, and immunoprecipitated, as described in The Journal of Immunology, vol. 136, page 4689, 1986. The extracted proteins can be separated on polyacrylamide gels by means of electrophoresis, and identified immunologically by means of immunoblotting. 
     Antibody to be used for testing polypeptides to determine whether they contain the protein epitopes according to the present invention include those directed against bovine smooth uterine muscle myosin, which can be obtained from ICN ImmunoBiologicals, Lisle, Ill. Antibody directed againstmyosin of C. elegans is described in Miller et al., Proceeding of the National Academy of Sciences U.S.A., vol. 83, page 2305, 1986. 
     The polypeptides of the present invention can be synthesized chemically according to methods which are well known in the art. The polypeptide neednot contain all of the amino acids shown in FIG. 1, as many may be unnecessary for the epitope structure claimed herein. Polypeptides can be synthesized according to the Merrifield solid phase procedure, which is well known in the art. Alternatively the polypeptide can be synthesized ina recombinant DNA containing organism, as described above. It is most convenient to synthesize the polypeptide of the present invention as a fusion protein. The critical characteristic of the polypeptides of the present invention is that they are able to bind to the antibodies which are immunoreactive with protein epitopes expressed on the surface of live schistosomula of S. mansoni. The surface epitopes bound by the antibodies are common to both the 200 kDa and the 38 kDa glycoproteins, and these epitopes are not immunoreactive with antibodies directed against bovine orC. elegans myosin. 
     Vaccines according to the present invention are composed of the polypeptidewhich contains the protein epitopes shared by the 200 kDa and the 38 kDa proteins and an immune adjuvant. The adjuvant can be any which is known inthe art of immunization. These include C. parvum, and Freund&#39;s adjuvant. A particularly preferred vaccine contains the polypeptide complexed to Quil A (saponin extract from Quillajabark Araloside A) produced according to K.Dalsgaard, Saponin Adjuvants III, Archiv fur die Gesamte Virus Forschung, vol. 44, pp. 243-254, 1974, which has been centrifuged to form iscoms, as described in Morein et al., Nature, vol. 308, page 457, 1984. The dosage of antigen given for immunizations will generally be between about 10 ug and 1 mg. The vaccines can be administered in any physiologically acceptable diluent. 
     The DNA preparations according to the present invention are any which when transcribed and translated, in vitro or in vivo, yield a sequence as shownin FIG. 1, panel B, line I. As is understood, it is only necessary that theregions of the sequence necessary to form the protein epitopes which are common to the 200 kDa and the 38 kDa proteins be present. It is not necessary that the exact coding sequence of DNA isolated from schistosomula be present, but only those sequences which lead to the same amino acid sequence or functionally equivalent amino acid sequences which are able to bind to the antibodies of the present invention. 
     EXAMPLE 1 
     This example demonstrates the purification of antigens which are specific to vaccinated mice by sequential immunoaffinity chromatography. In addition, the use of these antigens to make a polyclonal antiserum is demonstrated. 
     Immunodepletion permitted identification of a subset of schistosomula and adult worm glycoproteins that can be defined as &#34;vaccine-specific.&#34; These vaccine-specific antigens from adult worms were purified using preparativesequential immunochromatography. The resulting glycoproteins constitute only a very minor fraction of the total proteins. These glycoproteins wereused to immunize and raise antiserum in a rabbit. This antiserum is termed anti-IrV, which stands for anti-irradiated-vaccinated serum. Schistosomulaand adult worm glycoproteins metabolically labeled with  35  S-methionine were first immunodepleted with sera from patently infected mice before immunoprecipitation with sera from vaccinated mice. All of theantigens detected by this technique bound to concanavalin A and are therefore glycosylated. 
     Immunoprecipitations were carried out as described in Norden et al., Experimental Parasitology, vol. 58, page 333, 1984 and vol. 57, page 110, 1984. Sequential immunoprecipitations were carried out using serum from patently infected and once or twice vaccinated mice. Immunodepletion with antiserum from patently infected mice was performed as follows: 50,000 dpmof methionine-labeled schistosomula or adult worm polypeptide preparations were incubated for 18 hours with 2 ul of serum from patently infected mice. To assure precipitation of all classes and isotopes of Ig, 10 ul of affinity-purified rabbit IgG reactive with mice IgG, IgM, IgA, and IgD (Jackson Immuno Research Laboratories, Inc., Avondale, Pa.) were then added. After a further four hour incubation, immune complexes were precipitated with 5 ul of a 50% suspension of Staphylococcus aureus. The supernatant was collected and the precipitation reaction repeated twice with the same antiserum (from patently infected mice). The final supernatant was transferred to a fresh tube and then precipitated with 2 ul of the other antiserum. Reciprocal immunodepletion experiments in whichincubation with antiserum from once or twice vaccinated mice was followed by precipitation with antiserum from patently infected mice were carried out in the same manner. 
     IgG molecules capable of binding to staphylococcal protein A were isolated from sera of normal, patently infected, and vaccinated mice using protein A-Sepharose CL-4B (Pharmacia Fine Chemicals, Piscataway, N.J.). These purified mice IgGs were then separately coupled to cyanogen bromide-activated Sepharose 4B (Pharmacia) following the manufacturer&#39;s instructions. Approximately 10 mg of S. mansoni adult worm concanavalin A-binding glycoproteins, isolated as described above, were applied to the normal mouse IgG affinity column. The unbound fraction was then applied and recycled six times over an immunoaffinity column prepared with IgG from patently infected mice. The antigens that did not bind to these two columns were applied and recycled six times over a third immunoaffinity column prepared with IgG from sera of mice vaccinated twice with irradiated cercariae. This column was then washed extensively with 20 mM tris(hydroxymethyl)aminomethane-HCl, pH 8.0, containing 1 mM EDTA, 0.1M sodium chloride, 2.5M potassium chloride and 0.1% N octyl-beta-D-glucopyranoside (washing buffer) and the bound antigens were eluted with 0.05M diethylamine, pH 11.5. The eluted fractions were immediately neutralized with 1M sodium bicarbonate, pH 8.0, and dialyzed and concentrated against phosphate-buffered saline, pH 7.3, containing 0.1% N-octyl-beta-D glucopyranoside. 
     A New Zealand white rabbit was immunized with approximately 1 ug of immunoaffinity-purified antigens at two subcutaneous sites every three weeks for a total of four immunizations. Muramyl dipeptide-threonine, provided by Dr. A. Allison (Syntex Laboratories, Inc., Palo Alto, Calif.),was used as an adjuvant. The rabbit was bled by cardiac puncture three weeks after the last immunization and the serum separated. 
     The rabbit antiserum (anti-IrV) raised against vaccine-specific antigens was reactive with each of the glycoproteins used for immunization. It immunoprecipitated metabolically labeled schistosomula and adult worm glycoproteins identical to those antigens showing a unique or enhanced immunoactivity with sera from twice-vaccinated mice, as assessed by two-dimensional SDS-PAGE analysis. The rabbit antiserum also reacted with the major surface-iodinated antigens of newly transformed schistosomula and schistosomula cultured for three to six hours in vitro. The anti-IrV antiserum immunoprecipitated six surface-labeled polypeptides of newly transformed schistosomula. The greatest reactivity was directed towards polypeptides of the following sizes: greater than 300, 200, 150 (a doublet), and 32-38 kDa. 
     EXAMPLE 2 
     This example demonstrates recombinant cDNA expression clones reactive with anti-IrV sera and the nucleotide sequence determined therefrom. 
     In order to obtain large quantities of schistosomular antigens necessary for active vaccination experiments, we have constructed an adult worm cDNAexpression library in lambda-gt11 and have screened this library with the anti-IrV sera. Clones were identified which were reactive with the antiserum. Southern blots probed with radio-labeled transcripts of the cDNA inserts of each clone confirm the presence of homologous sequences ofDNA in the genome of S. mansoni. Northern blots probed in the same manner showed that the clones hybridized to an mRNA transcript of approximately 8kb. 
     The nucleotide sequence of the insert of one of these clones, termed clone IrV-5, is shown in FIG. 1a. The deduced amino acid sequence of the insert DNA is shown in FIG. 1b, line I. The DNA sequence was determined by the dideoxy-chain termination method of Sanger et al. Proceedings of the National Academy of Sciences U.S.A., vol. 74, page 5463 (1977). The 1583 basepair sequence contains one large open reading frame encoding a polypeptide of 62 kDa. 
     A computerized comparison of the predicted amino acid sequence shown in FIG. 1b of the IrV-5 clone with that of other sequences in the National Biomedical Research Foundation Library revealed 48% identity with the amino acid sequence of the myosin heavy chain of the nematode C. elegans. The similar region partially overlaps the S-1, S-2, and rod regions of C. elegans myosin heavy chain (residues 727 to 1256). Residues 121 through 572 of IrV-5, similar to the rod region of C. elegans myosin, shows the high predicted alpha-helix probability profile and a periodic seven-residue pattern with hydrophobic residues concentrated at positions 1 and 4, characteristic of alpha-helical coiled-coil proteins. These results suggest that clone IrV-5 partially encodes a schistosome myosin. 
     FIG. 1b, line II displays the amino acid sequence of the myosin heavy chainof C. elegans. Four dots between the residues of line I and line II represent identical amino acids. Two dots between the amino acid residues represent conservative amino acid substitutions, as ranked by the FASTP Program of Lipman and Pearson. Gaps introduced in the amino acid sequence to allow maximal alignment between the two sequences are indicated as -. Asterisks represent potential N-linked glycosylation sites in the sequenceof IrV-5. FIG. 1c diagrammatically represents the areas of homology betweenthe schistosome and C. elegans myosin molecules. 
     EXAMPLE 3 
     This example demonstrates the immunological similarity between the expression product of the clone IrV-5 and myosins of other species. 
     The 185 kDa fusion polypeptide consisting of schistosome sequences linked to beta-galactosidase sequences was recognized by polyclonal antibodies directed against bovine uterine smooth muscle myosin and by a monoclonal antibody against the S-2 region of the myosin heavy chain of C. elegans. 
     Antisera were raised against highly purified fusion polypeptide from clone IrV-5. The antisera were prepared in C56BL/6 mice as follows: E. coli CAG456 were infected with recombinant phage IrV-5, induced with isoprophyl-beta-D-thiogalactopyranoside, grown for three hours and lysed. Proteins were resolved by 10% SDS-PAGE, and the IrV-5 fusion protein was purified to apparent homogeneity by electroelution. The protein was complexed to Quil A, then centrifuged to form iscoms (immunostimulatory complexes) according to the method of Morein et al., Nature, vol. 308, page 457 (1984). Mice were immunized three times subcutaneously with a total of 45 ug. Antisera against bacterial lysates infected with parental lambda-gt11 (anti-beta-galactosidase sera) were similarly prepared. 
     The anti-fusion protein antisera recognized a single component of 200 kDa in immunoblots of extracts from both schistosomula and adult worms. Concanavalin A affinity-purified glycoprotein fractions from both developmental stages gave an identical result. Results are shown in FIG. 2. 
     Glycoproteins obtained as described in Dalton, et al. Journal of Immunology, vol. 136, page 4689, 1986, from extracts of adult worms (lanes1 and 2) and newly transformed schistosomula (lane 3) were electroblotted to nitrocellulose as described in Harn et al., Journal of Experimental Medicine, vol. 159, page 1371, 1984. Filters were probed with antiserum against beta-galactosidase (lane 1) or against IrV-5 fusion proteins (lanes 2 and 3). Bound antibody was detected by use of biotinylated anti-mouse or anti-rabbit IgG followed by avidinconjugated horseradish peroxidase (Vector Laboratories, Burlingame, Calif.). 
     EXAMPLE 4 
     This example demonstrates the recognition of surface proteins by the anti-fusion protein antisera. 
     Newly transformed schistosomula were surface-labeled with radio-iodine using the Iodo-Gen method (see Dalton et al. Journal of Immunology, vol. 139, page 2474, 1987). The labeled proteins were extracted with 1% NP 40, and immunoprecipitated as described in Dalton et al. Journal of Immunology, vol. 136, 1986, except that Sepharose CL 4B-protein A was usedas the immunoadsorbant. The immunoprecipitated, labeled proteins were separated on 5%-15% SDS-PAGE, and autoradiographed. 
     In FIG. 3, lane 1, polypeptides were immunoprecipitated with anti-beta-galactosidase antiserum. In lane 2 sera of mice vaccinated twicewith radiation-attenuated cercariae were used to precipitate the radio-labeled proteins. In lane 3 anti-fusion protein antiserum was used to precipitate the radio labeled proteins. In lane 4 monoclonal antibody 12.1.1 directed against C. elegans myosin was used to immunoprecipitate radio-labeled proteins. In lane 5 anti-bovine myosin antiserum was used toimmunoprecipitate. In lane 6, normal rabbit serum was used to precipitate labeled proteins. 
     The anti-fusion protein antisera specifically immunoprecipitated a 38-kDa component from an extract of surface-labeled schistosomula. This 38 kDa component was also immunoprecipitated by antibodies against bovine myosin and C. elegans myosin and by sera of mice vaccinated twice with radiation-attenuated cercariae. No 38 kDa component was detected by immunoblotting, perhaps due to a low concentration of this surface polypeptide relative to total glycoproteins. (See previous Example). 
     EXAMPLE 5 
     This example demonstrates that the 38 kDa glycoprotein recognized by the anti-fusion protein antisera was the same 38 kDa molecule as that precipitated by various monoclonal antibodies described in the literature. 
     Sequential immunoprecipitations were carried out using a monoclonal antibody designated 128. This monoclonal antibody which is described in Dalton et al. Experimental Parasitology, vol. 63, pages 215-226 (1987) recognizes glycanic epitopes on a 38 kDa polypeptide of schistosomula. As demonstrated in FIG. 4, monoclonal antibody 128 and the anti-fusion protein antisera recognize the same component. 
     Schistosomula, surface-iodinated and extracted as above, were incubated with monoclonal antibody 128 or with normal mouse sera cross-linked to Sepharose 4B beads. Following extensive washing the specifically bound fractions were eluted with 0.05M diethylanolamine, pH 11.5, and neutralized. Aliquots of the supernatants were then immunoprecipitated andprocessed as described above. 
     Lane 1 shows the result of a primary incubation with monoclonal antibody 128 and secondary precipitation with monoclonal antibody 128. The lane 2 shows a primary incubation with monoclonal antibody 128 and a secondary incubation with anti-fusion protein antiserum. In lanes 3 to 5 the primaryincubation was with normal mouse serum. In lane 3 the secondary precipitation was with monoclonal antibody 128. In lane 4 the secondary precipitation was with anti-fusion protein. And in lane 5 the secondary precipitation was with normal mouse serum. These experiments demonstrate that monoclonal antibody 128 and the anti-fusion protein antiserum recognize the same component. 
     EXAMPLE 6 
     This example demonstrates that anti-fusion protein antiserum binds to the surface of newly transformed schistosomula. 
     Live schistosomula were incubated for one hour on ice with monoclonal antibody 128 (FIG. 5 panels A and B); anti-fusion protein antiserum (panels C and D); and anti-beta-galactosidase antiserum (panels E and F). Bound antibody was detected using affinity purified rabbit anti-mouse IgG obtained from Jackson Immuno Research, followed by Rhodamine-conjugated protein A (Cappel Scientific Division, Cooper Biomedical Inc., Malvern, Pa.) panels A, C, and E); and phase contrast views of the schistosomula are shown in panels B, D and F. Surface integrity of schistosomula during the course of the immunofluorescence assays was verified by use of diamidinophenylindole, a fluorochrome specifically taken up by damaged schistosomula. 
     Both the anti-fusion protein antiserum and monoclonal antibody 128 showed strong binding to the surface of live, newly transformed schistosomula. However no surface binding was detected using the antibodies against bovine or C. elegans myosin or antiserum raised against purified beta-galactosidase. Thus the anti-fusion protein antiserum defines epitopes exposed on the surface of live schistosomula, and these epitopes are not recognized by antibodies against myosin derived from other species. 
     EXAMPLE 7 
     This example demonstrates the immunoprophylactic potential of the IrV-5 fusion protein. 
     Groups of mice (8 mice per group) were immunized with 5 to 20 ug of purified IrV-5 fusion protein, administered either in the form of immuno-stimulatory complexes (Iscoms) using Quil A or mixed with Corynebacterium parvum or Freund&#39;s adjuvant. The mice were immunized subcutaneously on days 0, 14 and 28. On day 38 the mice were challenged with 125 cercariae and on day 94 mice were perfused and the number of worms in the perfusate was counted. Table 1 shows the results obtained. The reduction in worm burden particularly with iscoms and C. parvum is notable.