NEMATODE VACCINE

Abstract: A substantially purified antigen derived from a first species of parasitic nematodes, which antigen is capable of providing protection to a host from parasitism by a second nematode species, which may be the same as or different from the first nematode species, following vaccination of the host with the antigen, characterized in that the antigen is proteinaceous, has a pI between 3.8 and 4.4, can be bound by lentil lectin and Helix promatia lectin and has a molecular weight of approximately 45 kD as determined by SDS-PAGE.

Description: Nematode Vaccine Technical Field The invention relates to antigens which confer protective immunity against infection by parasitic nematodes. The invention also relates to vaccines conferring protective immunity against infection by parasitic nematodes, and to antibodies conferring passive iiπmunity to infection by parasitic nematodes. Background Art Nematodes (nema - thread; oides - resembling) , which are unsegmented roundworms with elongated, fusiform, or saclike bodies covered with cuticle, are virtually ubiquitous in nature, inhabiting soil, water and plants, and are importantly involved in a wide range of animal and plant parasitic diseases. The roundworm parasites of mammals belong to the phylum Nemathel inthes. The roundworms include the hookworm (e.g. Necator americanus and Ancylostoma duodenale) , roundworm (e.g. the common roundworm Ascaris lumbricoides) , whipworm (e.g. Trichuris trichiura) , and the pinworm or threadworm (e.g. Enterobius vermicularus) , as well as Stronqyloides stercoralis. Trichinella spiralis (infection in man and pigs) , and the filarial worm Wuchereria bancrofti. Other important roundworm parasites include Ancylostoma caninum (infections of man) , Strongylus vulqaris (infections of horses) , Trichostrongylus colubriformis (infections of sheep) , Haemonchus contortus (infections of sheep and goats) , Ostertacria ostertaαi (infections of cattle) , Ascaris suum (infections in pigs) , Toxascaris leonia or Uncinaria stenocephala (infections of dogs) , Toxocara spp (circulatory infections of man) and Dirofilaria immitis (circulatory infections of cats and dogs) . Even when symptom-free, parasitic worm infections are harmful to the host animal for a number of reasons; e.g. they deprive the host of food, injure organs or obstruct ducts, may elaborate substances toxic to the host, and provide a port of entry for other organisms. In other cases, the host may be a species raised for food and the parasite may be transmitted upon eating to infect the ingesting animal. It is highly desirable to eliminate such parasites as soon as they have been discovered. More commonly, such infections are not symptom-free. Helminth infections of mammals, particularly by parasitic nematodes, are a source of great economic loss, especially of livestock and pets, e.g. sheep, cattle, horses, pigs, goats, dogs, cats and birds, especially poultry. These animals must be regularly treated with anthelminthic chemicals in order to keep such infections under control, or else the disease may result in anaemia, diarrohea, dehydration, loss of appetite, and even death. The only currently available means for controlling helminth infections is with the use of anthelminthic chemicals, but these are only effective against resident worms present at the time of treatment. Therefore, treatment must be continuous since the animals are constantly exposed to infection; e.g. anthelminthic treatment with diethylcarbamazine is required every day or every other day most of the year to control Dirofilaria immitis or the dog heartworm. This is an expensive and labor intensive procedure. Due to the widespread use of anthelminthic chemicals, the worms may develop resistance and so new and more potent classes of chemicals must be developed. An alternative approach is clearly desirable. The development of a vaccine against parasitic nematodes would overcome many of the drawbacks inherent in chemical treatment for the prevention and curing of helminthic infections. The protection would certainly last longer, only the vaccinated animal would be affected, and the problems of toxicity and persistence of residues would be minimized or avoided. Accordingly, there have been attempts, reported in the prior art, to develop such vaccines using parasitic nematodes; unfortunately, they have met with limited success and factors such as material availability and vaccine stability have precluded their large scale use. These previous attempts are discussed in International Patent Application No. PCT/AU88/00239 (WO 89/00163) and PCT/AU89/00416 (WO 90/03433) . Recent advances in biotechnology and in particular recombinant DNA technology, realistically offer the opportunity to produce commercially-viable vaccines against a range of economically-important parasites of man and domestic animals. This approach would overcome many of the problems proposed to account for the lack of efficacy of killed vaccines using crude parasite preparations. For example, the vaccines produced by recombinant DNA techniques would not contain immunosuppressants or immunomodulators which may be found in crude extracts of parasitic nematode species. But it is necessary to first identify the antigens. Once identified and characterized, recombinant DNA technology could be used to construct microorganisms which synthesize those proteins or portions of the proteins containing protective epitopes and use the products synthesized by the recombinant organism in vaccines to protect animals from infection with the parasites. In PCT/AU88/00239 it has been demonstrated that a recombinant DNA derived antigen shown to be nematode tropomyosin, gave 50% protection in sheep against Haemonchus contortus challenge. In PCT/AU89/00416 excretory/secretory antigens from adult Trichostronσylus colubriformis have been shown to give protection to vaccinated guinea pigs. For reasons which will become clear later in the specification, these antigens are different from the antigen identified in the current specification. Description of the Invention Definitions The term "adjuvant" as used throughout the specification refers to an agent used to enhance the immune response of the immunised host to the immunising composition. The term "parenteral" as used herein includes subcutaneous injections, intraperitoneal or intramuscular injection, or infusion techniques. The term "homologue" refers to proteins or to DNA sequences coding for those proteins which are related in structure to a first protein or DNA sequence to such an extent that it is clear that the proteins are related in function. In the context of this invention, it is demonstrated that the DNA from H. contortus which codes for the antigen of the invention can be used in DNA hybridisation experiments to identify specific DNA sequences in other species of parasitic nematodes. The conditions under which the hybridisation experiments were carried out indicate that the related DNA sequences are at least 50% homologous in nucleotide sequence over 60 base pairs to that isolated from H. contortus. These related DNA segments code for antigens in those other species of parasitic nematodes which are also related in amino acid sequence to the protective antigen isolated from H contortus. It is contended that the related proteins will act as effective immunogens to protect animals from parasitism by the other species of parasites. These related DNA sequences are referred to as homologous genes and the related proteins are referred to as homologous antigens. Also, in the context of this invention, it has been demonstrated tht the protective antigen is a member of a gene family wherein the encoding polynucleotide and the gene product share an homology of the order of 50% over 60 nucleotides or 70% over 20 amino acids respectively with the encoding gene and protective antigen of this invention. These related genes and gene products are also homologues of this invention. Homologues of the invention may also be generated in vitro as hereinafter described. The term "derived" in the context of the antigens of the invention as used herein is intended to encompass antigen obtained by isolation from a parasitic nematode life stage expressing the antigen, as well as antigen obtained by manipulation of and expression from nucleotide sequences prepared from a parasitic nematode life stage, including genomic DNA, mRNA, cDNA synthesized from mRNA and synthetic nucleotides prepared to have sequences corresponding to the antigen encoding sequences. It is also intended to encompass synthetic peptide antigens prepared on the basis of the known amino acid sequences of the antigen as expressed by nematodes or cell lines expressing recombinant forms of the antigen. Disclosure It is preferable, if possible, to identify "novel" or "concealed" antigens i.e. components of the parasite which can act as effective and protective immunogens but which are not involved in naturally acquired immunity. To identify those components it is necessary to vaccinate the host with extracts from the parasite, identify fractions which give some protection, subtractionate the protective components using protein chemistry techniques, vaccinate animals with those subtractions and identify those subtractions which protect and continue with that process until a pure parasite component is used to vaccinate and protect the animal. As much as possible, the natural host should be used in such experiments. As laboratory model animals are not the natural host for the parasite they are likely to be able to reject the parasite by mechanisms of which the natural host is incapable. Thus it is possible that antigens which protect laboratory animals against particular parasites may not be effective in the natural host of the parasite. This will be more likely to be the case in situations where the natural host develops immunity to the parasite very slowly. The antigen characterised in the current work is derived from Haemonchus contortus but it is recognised that similar or related antigens, "homologues", could be identified from other species of parasitic nematode known to infect man or domestic animals and that these related antigens, would provide effective vaccines against parasitism by species of nematode. Species of parasites and hosts they may infect include for example: Trichinella spiralis or Ancylostoma caninum infections of man, Stronqylus vulcraris infections of horses, Trichostrongylus colubriformis infections of sheep, Haemonchus contortus infections of goats, Ostertacria ostertacri infections of cattle, Ascaris suum or Trichinella spiralis infections of pigs, Toxascaris leonina or Uncinaria stenocephala infections of cats and Ancylostoma caninum or Trichuris vulpis infections of dogs as well as infections of the circulatory system of man by larvae of Toxocara spp and of the circulatory system of dogs by Dirofilaria immitis as well as infections of the circulatory system, urogenital system, respiratory system, skin and subcutaneous tissues of these and other species of animal. It should be noted that this list is by no means complete. A preparation is described which gives protection against challenge infection by Haemonchus contortus. The protective components in the fraction are identified as being soluble in buffers containing low levels of zwitterionic detergents and as not being retained following chromatography on wheat-germ lectin sepharose columns. The protective antigens thus prepared are capable of being further purified by, for example, fractionation on lentil lectin (LL) chromatography or Helix pomatia lectin (HpL) chromatography, reverse phase HPLC, size exclusion chromatography or other purification methods known in the art in the presence of solubilizing detergents. According to a first embodiment of the present invention there is provided a substantially purified antigen derived from a first species of parasitic nematode, which antigen is capable of providing protection to a host from parasitism by a second nematode species, which may be the same as or different from the first nematode species, following vaccination of the host with the antigen, characterized in that the antigen is proteinaceous, has a pl in the range of 3.8-4.4, binds to lentil lectin and Helix pomatia lectin and has a molecular weight of approximately 45 kD as determined by reducing SDS-PAGE. Typically the antigen is at least 90% pure. This level of purity is demonstrated with respect to the cleanliness of the preparations used in amino acid sequencing. The invention encompasses the antigen in both glycosylated and non-glycosylated form. Typically, the first parasitic nematode species is selected from species of the genera Trichinella. Ancylostoma, Strongylus. Trichostrongylus, Haemonchus, Ostertagia, Ascaris, Toxascaris. Uncinaria, Trichuris. Dirofilaria, Toxocara, Necator. Enterobius. Strongy1oides and Wuchereria. Examples of such species include Trichinella spiralis, Ancylostoma caninu , Strongylus vulαaris, Trichostrongylus colubriformis, Haemonchus contortus, Ostertagia ostertagi. Ascaris suum, Toxascaris leonina, Uncinaria stenocephala. Trichuris vulpis, Dirofilaria immitis, Toxocara spp, Necator americanus, Ancylostoma duodenale, Ascaris lumbricoides, Trichuris trichiura. Enterobius vermicularus, Strongyloides stercoralis and Wuchereria bancrofti. Typically the protection conferred on the host is protection against a parasitic nematode species selected from species of the genera Trichinella, Ancylostoma, Strongylus, Trichostrongylus. Haemonchus, Ostertagia, Ascaris, Toxascaris, Uncinaria. Trichuris, Dirofilaria, Toxocara, Necator. Enterobius. Strongyloides and Wuchereria. Examples of such species include Trichinella spiralis. Ancylostoma caninum, Strongylus vulgaris, Trichostrongylus colubriformis, Haemonchus contortus, Ostertagia ostertagi, Ascaris suum, Toxascaris leonina, Uncinaria stenocephala. Trichuris vulpis. Dirofilaria immitis, Toxocara spp, Necator americanus, Ancylostoma duodenale, Ascaris lumbricoides. Trichuris trichiura, Enterobius vermicularus, Strongyloides stercoralis and Wuchereria bancrofti. Preferably the first and second nematode species are selected from the genera Haemonchus, Trichostrongylus and Ostertagia. More preferably the first and second nematode species are from the genus Haemonchus. Preferred first and second nematode species are Haemonchus contortus. T ichostrongylus colubriformus and Ostertagia circumcincta. More preferably the first and second nematode species are Haemonchus contortus. The present inventors have determined that the antigen of the first embodiment is most likely a proteolytic cleavage product of a higher molecular weight nematode glycoprotein. The nematode glycoprotein could be prepared from native sources by antibody affinity chromatography using antibodies raised to the expression product of the cloned gene. The higher molecular weight glycoprotein in glycosylated and unglycosylated form is also encompassed by the present invention and is termed hereinafter the "antigen precursor". The antigen precursor in substantially purified form is also part of the first embodiment of the present invention. Typically the antigen precursor comprises the amino acid sequence illustrated in Figure 8. According to a second embodiment of the present invention there is provided a homologue of the antigen or antigen precursor of the first embodiment. Typically the homologue is at least 70% homologous over 20 amino acids to the amino acid sequence illustrated in Figure 8. According to a third embodiment of the present invention there is provided a polynucleotide molecule, excluding polynucleotide molecules as they exist in nature which encodes an antigen or an antigen precursor of the first embodiment, or a homologue of the second embodiment. Typically the polynucleotide molecule is a DNA molecule. Preferably the polynucleotide molecule is a cDNA molecule. A preferred polynucleotide molecule of the invention is a cDNA molecule having substantially the sequence illustrated in Figure 7 or 8. The invention includes within its scope DNA molecules having at least 50% homology over 60 nucleotides with the sequence illustrated in Figure 8, and encoding a protective molecule capable of conferrring immunity against parasitic nematode infection. According to a fourth embodiment of the present invention there is provided a recombinant DNA molecule comprising a DNA molecule of the third embodiment and vector DNA. Typically the vector DNA comprises plasmid, phage or viral DNA. Preferred vectors include lambda gtll, pUR290, pUR291, pUR282, pU 270, pUC8, pUC9, pZipNeo, an SV40 based vector, lambda gtlO, an EMBL vector, pBR327, pBR329, or pBR329 containing a par locus, baculovirus or vaccinia virus. According to a fifth embodiment of the invention there is provided a transformed host, carrying at least one recombinant DNA molecule according to the fourth embodiment. Typically the host is selected from bacteria, yeasts, other fungi, insect, plant and mammalian cell lines. Preferred host cells are I _ coli K12 derivatives. According to a sixth embodiment of the present invention there is provided an expression product of a transformed host of the fifth embodiment comprising an antigen or antigen precursor of the first embodiment or a homologue of the second embodiment. The expression product may be a fused expression product. According to a seventh embodiment of the present invention there is provided a synthetic polypeptide corresponding to all or part of an antigen, precursor, homologue or expression product of the invention which synthetic polypeptide when administered to a host animal is capable of inducing protective immunity against infestation of the host animal by a parasitic nematode. According to an eighth embodiment of this invention, there is provided a vaccine comprising an effective amount of at least one antigen and/or antigen precursor of the first embodiment and/or a homologue of the second embodiment and/or expression product of the sixth embodiment and/or synthetic polypeptide of the seventh embodiment together with a pharmaceutically and/or veterinarally acceptable carrier, diluent, excipient and/or adjuvant. The vaccines of the invention could alternatively comprise at least one anti-idiotypic antibody capable of protecting a host from infection by a parasitic nematode by mimicking the antigen, antigen precursor, homologue, expression product and/or synthetic polypeptide. A pharmaceutically and/or veterinarally acceptable carrier, diluent, excipient and/or adjuvant may be added to the active component. As a further alternative, the vaccine may be a whole cell vaccine comprising a transformed host of the fifth embodiment together with a pharmaceutically and/or veterinarally acceptable carrier, diluent, excipient and/or adjuvant. The cells may be live or killed. The transformed cells include those capable of expressing the expression product for mucosal presentation to a host to be vaccinated, such as, as a cell surface fusion product. According to a ninth embodiment of this invention there is provided a process for the preparation of an antigen of the first embodiment, which process comprises: a) homogenizing young adults of a parasitic nematode species to produce an homogenate; b) obtaining membranous material from the homogenate; c) extracting the membranous material with a buffer containing low levels of a zwitterionic detergent to obtain a detergent extract; d) chromatographing the detergent extract on a wheat-germ lectin sepharose column; and e) collecting flow-through from the column. Preferably, the process also comprises: f) fractionation by preparative iso-electricfocussing and collection of fractions having a pi in the range 3.8-4.4, or more preferably 4.0-4.3; g) fractionation by gel filtration chromatography to collect fractions with molecular weights in the range 10-60kD; and h) fractionation by lentil lectin and/or Helix pomatia lectin chromatography and collecting bound material. According to a tenth embodiment of this invention, there is provided a process for the preparation of a vaccine of the eighth embodiment which process comprises: admixing an effective amount of at least one antigen and/or antigen precursor of the first embodiment and/or homologue of the second embodiment and/or expression product of the sixth embodiment and/or synthetic polypeptide of the seventh embodiment and/or transformed host of the fifth embodiment and/or antiidiotype antibody with a pharmaceutically and/or veterinarally acceptable carrier, diluent, excipient and/or adjuvant. According to an eleventh embodiment of this invention, there is provided a method of protecting a host against infection by at least one parasitic nematode species which method comprises administering an effective amount of an antigen and/or antigen precursor of the first embodiment and/or homologue of the second embodiment and/or expression product of the sixth embodiment and/or synthetic polypeptide of the seventh embodiment and/or a vaccine of the eighth embodiment to the host. According to a twelfth embodiment of this invention, there is provided an antibody raised against an antigen and/or antigen precursor of the first embodiment and/or homologue of the second embodiment and/or expression product of the sixth embodiment and/or synthetic polypeptide of the seventh embodiment and/or a vaccine of the eighth embodiment. The antibody of the invention may be monoclonal or polyclonal. The invention also provides other compounds which behave in a similar manner to the antibodies of the twelfth embodiment, by binding to and altering the structure and/or function of an antigen or antigen precursor of the first embodiment, or homologue of the second embodiment, expression product of the sixth embodiment, or synthetic polypeptide of the seventh embodiment. According to a thirteenth embodiment of this invention, there is provided an antibody composition comprising an antibody of the twelfth embodiment together with a pharmaceutically and/or veterinarally acceptable carrier, diluent and/or excipient. According to a fourteenth embodiment of this invention, there is provided a process for the preparation of an antibody of the twelfth embodiment which process comprises vaccinating an immunoresponsive host with an antigen and/or antigen precursor of the first embodiment and/or homologue of the second embodiment and/or expression product of the sixth embodiment and/or synthetic polypeptide of the seventh embodiment and/or a vaccine of the eighth embodiment. According to a fifteenth embodiment of this invention, there is provided a process for the preparation of an antibody composition of the thirteenth embodiment which process comprises admixing an effective amount of an antibody of the twelfth embodiment with a pharmaceutically and/or veterinarally acceptable carrier, diluent, and/or excipient. According to a sixteenth embodiment of this invention, there is provided a method of passively vaccinating a host in need of such treatment against a parasitic nematode, which method comprises administering an effective amount of an antibody of the twelfth embodiment and/or an antibody composition of the thirteenth embodiment to the host. According to a seventeenth embodiment of the present invention there is provided a process for the preparation of a recombinant DNA molecule of the fourth embodiment which process comprises inserting a DNA molecule of the third embodiment into vector DNA. According to an eighteenth embodiment of the present invention there is provided a process for the preparation of a transformed host of the fifth embodiment which process comprises making a host competent for transformation to provide a competent host and transforming the competent host with a recombinant DNA molecule of the fourth embodiment. According to a nineteenth embodiment of the present invention there is provided a diagnostic kit comprising a sample of an antigen, antigen precursor, homologue, expression product or synthetic polypeptide of the present invention and/or an antibody of the present invention. According to a twentieth embodiment of the present invention, there is provided a process for the biosynthesis of an expression product of the sixth embodiment which process comprises providing a transformed host of the fifth embodiment, culturing the host under suitable conditions to obtain expression of the expression product and collecting the expression product from the transformed host. According to a twenty first embodiment of this invention there is provided an antiidiotype antibody corresponding to a portion of an antigen of the invention and capable of protecting a host immunised with the antiidiotype antibody from infestation by a parasitic nematode species. It is recognised that variation in amino acid and nucleotide sequences can occur between different allelic forms of a particular protein and the gene(s) encoding the protein. Further once the sequence of a particular gene or protein is known, a skilled addressee, using available techniques, would be able to manipulate those sequences in order to alter them from the specific sequences obtained to provide a gene or protein which still functions in the same way as the gene or protein to which it is related. These molecules are referred to herein as "homologues" and are intended also to be encompassed by the present invention. In this regard, a "homologue" is a polypeptide that retains the basic functional attribute, namely, the protective activity of an antigen of the invention, and that is homologous to an antigen of the invention. For purposes of this description, "homology" between two sequences connotes a likeness short of identity indicative of a derivation of the first sequence from the second. In particular, a polypeptide is "homologous" to an antigen of the invention if a comparison of amino-acid sequences between the polypeptide and the antigen, reveals an identity of greater than about 70% over 20 amino acids. Such a sequence comparison can be performed via known algorithms, such as the one described by Lipman and Pearson, Science 227: 1435 (1985) , which are readily implemented by computer. Homologues can be produced, in accordance with the present invention, by conventional site-directed mutagenesis, which is one avenue for routinely identifying residues of the molecule that can be modified without rendering the resulting polypeptide biologically inactive. Oligonucleotide-directed mutagenesis, comprising [i] synthesis of an oligonucleotide with a sequence that contains the desired nucleotide substitution (mutation) , [ii] hybridizing the oligonucleotide to a template comprising a structural sequence coding for an antigen of the invention and [iii] using T4 DNA polymerase to extend the oligonucleotide as a primer, is preferred because of its ready utility in determining the effects of particular changes to the antigen structural sequence. Its relative expense may militate in favour of an alternative, known direct-mutagenesis method. Also exemplary of antigen homologues within the present invention are molecules that correspond to a portion of the antigen, or that comprise a portion of the antigen without being coincident with the natural molecule, and that display the protective activity of an antigen of the invention. Other homologues of the present invention are fragments of the antigen that retain protective activity. Likewise within the present invention would be synthetic polypeptides that (i) correspond to a portion of the antigen amino-acid sequence and (ii) retain an activity characteristic of the antigen. Such synthetic polypeptides would preferably be between 6 and 30 amino residues in length. Whether a synthetic polypeptide meeting criterion (i) also satisfies criterion (ii) can be routinely determined by assaying for protective activity, in an appropriate host. The amount of antigen, antigen precursor, homologue, expression product and/or synthetic polypeptide to be combined with carrier, diluent, excipient and/or adjuvant to produce a single vaccine dosage form will vary depending upon the infection being vaccinated against, the host to be treated and the particular mode of administration. It will be understood, also, that the specific dose level for any particular host will depend upon a variety of factors including the activity of the specific antigen, antigen precursor, homologue, expression product and/or synthetic polypeptide employed, the age, body, weight, general health, sex, diet, time of administration, route of administration, rate of excretion, drug combination and the particular infection state being prevented. The vaccines of the present invention may be administered parenterally or potentially via mucosal routes in dosage unit formulations containing conventional, non-toxic, pharmaceutically and/or veterinarally acceptable carriers, diluents, adjuvants and/or excipients as desired. Injectable preparations, for example, sterile injectable aqueous or oleagenous suspensions may be formulated according to the known art using suitable dispersing or wetting agents and suspending agents. The sterile injectable preparation may also be a sterile injectable solution or suspension in a non-toxic parenterally acceptable diluent or solvent, for example, a solution in 1,3-butanediol. Among the acceptable vehicles and solvents that may be employed are water, Ringer's solution, and isotonic sodium chloride solution. In addition, sterile, fixed oils are conventionally employed as a solvent or suspending medium. For this purpose any bland fixed oil may be employed including synthetic mono- or diglycerides. In addition, fatty acids such as oleic acid find use in the preparation of injectables. At present alum is the only registered adjuvant for human use however, experimental work is being conducted on other adjuvants for human use and it is anticipated that these other adjuvants would be suitable for use in preparing compositions for human vaccination in accordance with this invention. Suitable adjuvants for the vaccination of animals include but are not limited to oil emulsions such a Freund's complete or incomplete adjuvant (not suitable for livestock use), Marcol 52: Montanide 888 (Marcol is a Trademark of Esso. Montanide is a Trademark of SEPPIC, Paris) , squalane or squalene, Adjuvant 65 (containing peanut oil, mannide monooleate and aluminium onostearate) , mineral gels such as aluminium hydroxide, aluminium phosphate, calcium phosphate and alum, surfactants such a hexadecylamine, octadecylamine, lysolecithin, dimethyldioctadecylammonium bromide, N,N-dioctadecyl-N' , N- -bis (2-hydroxyethyl) propanediamine, methoxyhexadecylglycerol and pluronic polyols, polyanions such as pyran, dextran sulfate, polyacrylic acid and carbopol, peptides and amino acids such as muramyl dipeptide, dimethylglycine, tuftsin and trehalose dimycolate. The antigens, precursors, expression products and/or synthetic polypeptides of the present invention can also be administered following incorporation into liposomes or other micro-carriers, or after conjugation to polysaccharides, proteins or polymers or in combination with Quil-A to form "Iscoms" (Immunostimulating complexes) . Other adjuvants suitable for use in the present invention include conjugates comprising the immunogen together with an integral membrane protein of prokaryotic origin, such as TraT. (See PCT/AU87/00107) . Routes of administration, dosages to be administered as well as frequency of injections are all factors which can be optimised using ordinary skill in the art. Typically, the initial vaccination is followed some weeks later by one or more "booster" vaccinations, the net effect of which is the production of vigorous immune response both cellular and humoral. Brief Description of the Drawings Fig. l shows gel filtration HPLC results for IEF 5 and 6 on SDS polyacrylamide gel stained with silver. Lanes 1-6 contain GF1-GF6; lane 7 contains Bio-Rad low and high molecular weight standards with sizes given in kilodaltons and lane 8 contains IEF 5 and 6 (pre GF HPLC) . Fig. 2 shows lectin affinity chromatography results for IEF 5 and 6 on an SDS polyacrylamide gel stained with silver. Lane 1 contains molecular weight standards. Lanes 2 and 3 contain material bound and eluted from lentil lectin Sepharose (LLS) ; lane 4, material that was bound and eluted from Helix pomatia lectin Sepharose (HpLS) after initial binding and elution from LLS and lane 5 contains material that did not bind to HpLS after initial binding and elution from LLS. Fig. 3 shows lectin affinity chromatography results for IEF 5 and 6 as a Western blot overlayed with Concanavalin A-HRP and reactive material visualized by enzymatic reaction. Lane 1 contains IEF 5 and 6; lane 2, material not binding to LLS; lane 3, material bound and eluted from LLS; lane 4, material bound and eluted from HpLS after initial binding and elution from LLS; lane 5, material not bound to HpLS after initial binding and elution from LLS; lane 6, material not bound to LLS or HpLS and lane 7, BRL high molecular weight standards. Fig. 4 shows lectin affinity chromatography results for IEF 5 and 6 as a Western blot overlayed with Helix pomatia lectin - HRP and reactive material visualized by enzymatic reaction. Lane contents are as described for Fig. 3. Fig. 5 shows reverse-phase HPLC results for IEF 5 and 6 on a PLRP-S column. The gradient used for elution consisted of 30% acetonitrile in water with 0.1% TFA to 60% acetonitrile in water with 0.1% TFA. The flow rate was 1ml/min and the absorbance monitored at 220 nm. Peak fractions indicated by numbers were collected manually. Fig. 6(a) and Fig. 6(b) shows reverse-phase HPLC results for IEF 5 and 6, as an SDS polyacrylamide gel (9-22% gradient) stained with silver. Numbers refer to peak fractions shown in Fig. 5. Lane S, Bio-Rad low and high molecular weight standards in the sizes given in kilodaltons. Fig. 7 shows the cloned DNA sequence of pBTA879 and the derived amino acid sequence of the cloned gene coding a homologue of the protective antigen. Fig. 8 shows the cloned DNA sequence of pBTA963 and the derived amino acid sequence of the cloned gene coding for the protective antigen. Fig. 9 shows a Southern blotting of DNA from H. contortus hybridised to the cDNA from pBTA879 and pBTA963 showing the presence of homologous genes within the parasite genome. Lane 1. Haemonchus contortus DNA, Hinfl digest, probed with pBTA963. Lane 2. Haemonchus contortus DNA, Hinfl digest, probed with pBTA879. Fig. 10 shows Southern blotting of DNA from T\_ colubriformis, Ostertagia circumcincta and Ostertagia ostertagi with a 45 kD antigen probe demonstrating the presence of related genes in other species of nematode. Lane 1. Haemonchus contortus DNA, Hinfl digest. Lane 2. Trichostrongylus colubriformis DNA, Hinfl digest. Lane 3. Ostertagia ostertagi DNA, Hinfl digest. Lane 4. Ostertagia circumcincta DNA, Hinfl digest. Lane 5. Plasmid pBTA963, Hinfl digest - positive control. Fig. 11(a) and Fig. 11(b) shows SDS PAGE gels and Western blots of the recombinant 45 kD antigen expressed in E coli. Fig. 11(a) Expression of 45kDa Antigen E. Coli:Samples were electrophoresed on a 12.5% SDS polyacrylamide gel. The gel was then stained with Coomassie brilliant blue. Lane 1: uninduced control; Lane 2: 1 hour post-induction; Lane 3: 3 hours post- induction; Lane 4: Biorad prestained SDS PAGE standards. Fig. 1Kb) Western Blot of Expressed 45kDa Antigen: Samples were electrophoresed as in Figure 11(a), then electrophoretically blotted onto a nitrocellulose filter. SUBSTITUTESHEET - 19A - The filter was probed with rabbit serum raised against a peptide corresponding to the truncated N-terminus of the 45kDa protein. The Promega Protoblot alkaline phosphatase system (product no. W3930) was used to develop colour. Fig. 12 shows Western blots of extracts from H. contortus and the dog heart worm D. immitis showing that antigens immunologically related to that of the invention are expressed in other species of parasitic nematode. Lane 1, D immitis extract; Lane 2, H contortus extract; Lane 3, BRL high molecular weight standards. Best Method of Carrying Out the Invention Young adults of Haemonchus contortus were homogenised in phosphate-buffered saline (PBS) and the homogenate was centrifuged in order to sediment the membranous material from the nematodes. This pellet was found to protect sheep from challenge infection following two vaccinations. The protective fraction was then extracted with a number of different detergents. Zwittergent 3-14 (Calbiochem) was found to be suitable although other detergents were also found to be effective. Efficiency of extraction was judged by the ability of the detergent used to solubilize protective antigens (as judged by vaccination/challenge experiments) SUBSTITUTESHEET - 20 - with the highest specific activity (as estimated by the number of micrograms of solubilized material required to give protection) whilst leaving an insoluble residue which failed to give significant protection following the vaccination/challenge protocol employed (42%, see Table 3) . It is acknowledged that the Zwittergent 3-14 extraction procedure may not have been completely efficient and some of the protective antigens may be found in the detergent insoluble fraction. The recombinant DNA molecules and transformed host cells of the invention are prepared using standard techniques of molecular biology. Expression products of the invention are obtained by culturing transformed host cells of the invention under standard conditions as appropriate to the particular host cell and separating the expression product from the culture by standard techniques. The expression product may be used in impure form or may be purified by standard techniques as appropriate to the expression product being produced. Where appropriate, whole cells may be used in vaccines. Synthetic polypeptides of the invention are prepared by standard techniques of peptide synthesis based on the known sequences of antigens, antigen precursors, homologues and expression products of the invention. The homologues, expression products and synthetic polypeptides can be tested for protective activity as described in the following examples. Recombinant DNA technology can be used to provide a large amount of the protective antigen or homologues described herein. The DNA segment coding for the protective antigen or the precursor for the protective antigen or homologue can be inserted into any of a number of recombinant plasmid systems to enable the molecule to be synthesised in large amounts. The recombinant systems include E. coli. yeast, and baculovirus systems and viruses such as vaccinia. The recombinant organisms can - 21 - be grown in large volumes in fermenters and the recombinant antigens purified by standard methods - solubilisation in solutions containing urea and reducing agents such as DTT or mercaptoethanol, refolding in the presence of reagents such as reduced and oxidised glutathione, purification by ion exchange, filtration and/or gel permeation chromatography, terminally sterilised by filtration and adjuvanted in any of a number of adjuvants including oils. The vaccine is prepared by mixing, preferably homogeneously mixing, an antigen, antigen precursor, homologue, expression product and/or synthetic polypeptide and/or transformed host and/or antiidiotype antibody of the invention with a pharmaceutically and/or veterinarally acceptable carrier, diluent, excipient and/or adjuvant using standard methods of pharmaceutical and/or veterinary preparation. The amount of antigen, antigen precursor, homologue, expression product, synthetic polypeptide and/or transformed host and/or antiidiotype antibody required to produce a single dosage form will vary depending upon the infection being vaccinated against, host to be treated and the particular mode of administration. The specific dose level for any particular host will depend upon a variety of factors including the age, body weight, general health, sex and diet of the host, time of administration, route of administration, rate of excretion and drug combination. The vaccine may be administered parenterally in unit dosage formulations containing conventional, non-toxic, pharmaceutically and/or veterinarally acceptable carriers, diluents, excipients and/or adjuvants as desired. Antiidiotypes are raised by vaccinating a suitable host with an antigen, precursor, expression product, homologue and/or synthetic polypeptide of the invention and using the resulting antibodies to raise antibodies - 22 - against the antigen binding region of the antibodies raised in the first vaccination. Antibodies are raised using standard vaccination regimes in appropriate hosts. The host is vaccinated with an antigen, antigen precursor, homologue, expression product, synthetic polypeptide and/or vaccine of the invention. An immune response is generated as result of vaccination. The immune response may be monitored, for example, by measurement of the levels of antibodies produced. The antibody composition is prepared by mixing, preferably homogeneously mixing, antibody with a pharmaceutically and/or veterinarally acceptable carrier, diluent, and/or excipient using standard methods of pharmaceutical and/or veterinary preparation. The amount of antibody required to produce a single dosage form will vary depending upon the infection being vaccinated against, host to be treated and the particular mode of administration. The specific dose level for any particular host will depend upon a variety of factors including the age, body weight, general health, sex, and diet of the host, time of administration, route of administration, rate of excretion, drug combination and the severity of the infection undergoing treatment. The antibody composition may be administered parenterally, in unit dosage formulations containing conventional, non-toxic, pharmaceutically and/or veterinarally acceptable carriers, diluents, and/or excipients as desired, to passively protect hosts against nematode infestation. Diagnostic kits are prepared by formulating expression product, antibodies, antigen, antigen precursor, homologue or synthetic polypeptide at appropriate concentration to the substance(s) to be detected with a pharmaceutically and/or veterinarally acceptable carrier, diluent and/or excipient. A positive control standard of a known concentration of the substance to be detected is prepared similarly. The - 23 - negative standard comprises carrier, diluent and/or excipient alone. The invention is further described with reference to the following examples, which are not limiting on the scope of the present invention. Example 1 Young H. contortus nematodes were recovered from infected sheep. The nematodes were washed three times in PBS and homogenised in PBS. The homogenate was centrifuged at 500xg for 10 min to remove large and unbroken worm material. The supernatant was then centrifuged at 120,000 x g av for 2 hours at 4°C. The pelleted material was suspended in PBS and then used to vaccinate sheep subcutaneously in the absence of adjuvant on two occasions four weeks apart, each vaccination containing approximately 50mg worm wet weight equivalent per kg body weight of the sheep. Three weeks after the second vaccination the sheep and five non-vaccinated infection controls were challenged with 10,000 infective larvae of Haemonchus contortus. On days 23, 27, 28, 33, 36 and 40 post infection, faecal egg counts were performed on all sheep. The results (eggs/g faeces) are presented in Table 1. 24 - Table 1 Faecal Egg Counts Eggs/g Faeces Animal Day 23 27 29 33 36 40 It is clear that four of the five vaccinated animals were well protected from infection (p < 0.02 for the vaccinated group vs control group) . Example 2 A series of experiments was conducted in which female guinea pigs were vaccinated with homogenates of adult H. contortus and with 120,000 xg pellets and supernatants derived from those homogenates (prepared essentially as described in Example 1) . The guinea pigs received two vaccinations mtraperitoneally in the absence of adjuvant three to four weeks apart and were challenged three to four weeks after the second vaccination with 1,000 infective larvae of H. contortus. Five to six days following infection, the animals were sacrificed and worm counts performed. Table 2 summarises the results of these experiments showing the worms recovered from the vaccinates as a percentage of those recovered from control non-vaccinated animals receiving the same challenge infection. - 25 - Table 2 Fraction % Protection Experiment No. Homogenate 61 163 Homogenate (3 groups) 45, 55, 45 165 120,000 x g pellet 59 196 120,000 x g pellet 34* 171 120,000 x g supernatant 29 196 120,000 x g supernatant 15* 149 * These animals only received one vaccination. It is clear from these results that fractions derived from homogenates of adult H. contortus are capable of giving significant protection to guinea pigs, particularly the particulate material found in the 120,000 x g pellet. Example 3 Young adult H. contortus were homogenised in Tris buffered saline and a 120,000 x g pellet prepared as described in Example 2. The pellet was resuspended in Tris buffered saline (TBS) containing 1% (W/V) Zwittergent SB-14 (Sigma) by sonication and shaking at 4°C for 1 hour. The extract was centrifuged at 50,000 x gav for 30 minutes to pellet the detergent insoluble material. The supernatant fraction was passed over an affinity column of wheat germ lectin-sepharose 6MB (Sigma) on two occasions to separate glycoproteins containing terminal N-acetyl-glucosamine residues. The five fractions derived from this procedure were used to vaccinate guinea pigs as described in Example 2. The results (Table 3) clearly demonstrate that a significant portion of the protective material was solubilized in the detergent, but the majority of the protective antigen(s) failed to bind to wheat germ lectin. - 26 - Table 3 Fraction μg/animal % Protection SB-14 insoluble material SB-14 soluble material SB-14 soluble WGA + SB-14 soluble WGA " WGA + is wheat germ agglutinin binding material WGA " is wheat germ agglutinin non-binding material SB-14 is Zwittergent SB-14 (Calbiochem) . Material contained in a particulate preparation derived from a homogenate of H. contortus, when used to vaccinate guinea pigs or sheep, is capable of promoting an immune response in the vaccinated animals which gives rise to reduced parasitism in those animals when they are infected with the parasite. The protective antigens are largely soluble in detergents such as Zwittergent SB-14 and do not bind to wheat germ agglutinin under the conditions employed in the above examples. Example 4 A Zwittergent SB-14 extract was prepared from 10-15g wet weight of young adult H. contortus as described in Example 3, and used to vaccinate sheep in two experiments. The animals received two vaccinations three weeks apart, the first in Freund's complete adjuvant and the second in Freund's incomplete adjuvant. Three weeks after the second vaccination, the sheep were challenged per os with 10,000 larvae of H. contortus. Faecal egg counts were performed twice per week starting 21 days post infection for the next ' 4 weeks at which time the animals were slaughtered for worm counts (Table 4a and 4b) . It is clear that the Zwittergent SB-14 extract contained antigens which were capable of giving - 27 - significant protection in sheep against infection as measured by either faecal egg counts or worm counts, in spite of the fact that the amount of protein used to vaccinate each animal in the experiment was very small (10 ± 2.5mg) and the extract contained a large number of components as judged by SDS polyacrylamide gel electrophoresis. Table 4a Challenge SB-14 in SB-14 Controls Adjuvant Extract of 28 Table 4b Example 5 For the same experiment as in Example 3, five times more material was prepared than that used in that Example. The remaining Zwittergent SB-14 extract (approximately 63mg of protein) was fractionated by preparative isoelectric focussing in a 4% Ultrodex resin (LKB) containing Pharmalyte 3-10 ampholines and 0.5% CHAPS detergent (Calbiochem) . Following electrophoresis for 10000 Vh, the bed was scraped into 30 fractions and the material in each fraction was eluted in 0.1% CHAPS. The pH of each fraction was determined and each fraction was then concentrated to 1ml on a YM10 membrane. An aliquot of each fraction was analysed by SDS polyacrylamide gel electrophoresis and stained with Coomassie brilliant blue. Aliquots (approximately 1/8) of each fraction were pooled based on the components visualised on the SDS gel giving a total of 5 fractions which were used to vaccinate guinea pigs as described in - 29 - Example 2. Worm counts (Table 5) show that the majority of the protective antigen(s) is contained in Fractions 1-10 of the IEF gel which covers the pi range of 3.3-4.6. Other fractions also contained material which resulted in a decrease in worm burdens and these are also of interest in this application. Table 5A Experiment #229 Fraction pi Worm Counts Protection Controls 467 ± 190 SB-14 Extract 226 ± 62 52^ IEF 1-10 3.3-4.6 233 ± 155 50*, IEF 11-14 4.7-5.3 341 ± 112 37! IEF 15-18 5.4-6.2 323 ± 107 31! IEF 19-22 6.6-7.5 528 + 33 0 IEF 23-30 7.7-9.3 347 + 247 26! Table 5B Experiment #250 Fraction pi Worm Counts Protection Controls 664 ± 152 SB-14 Extract 254 ± 111 62 s , IEF 1-10 3-4 238 ± 67 64! IEF 11-14 7-5 274 ± 287 59! IEF 15-18 4-6 455 ± 251 31! IEF 19-22 6-7 474 ± 427 28! IEF 23-30 5-9 356 + 100 463 For the second experiment in Example 4, the results of which are presented in Table 4b, groups of sheep were vaccinated with similar broad range IEF fractions as in the above example. The results are presented in Table 5c. - 30 Table 5c Protection cf Group Average adjuvant Fraction controls Worms Adjuvant controls 75600 2117 SB-14 Extract IEF 1-10 IEF11-14 IEF 15-18 IEF 19-22 IEF 23-30 This data corroborates that obtained in the guinea pig vaccination and challenge experiments in that it clearly demonstrates that there are antigens in the IEF fractions 1-10 which are capable of providing significant degrees of protection to sheep against H. contortus challenge infections. It is ^ also clear from these data that there are additional protective components in the other IEF fractions examined in this experiment and these are of interest in this application as well as those contained in IEF fractions 1-10. Example 6 Half of the first 10 IEF fractions used in Example 5 were pooled in pairs and used to vaccinate guinea pigs. The worm counts (Table 6) show the majority of the protective material was contained in fractions 5 and 6 from the original IEF gel which contains material with a pi of 3.8-4.4. 31 - Table 6 Fraction pi Worm Counts Protection When aliquots of the IEF fractions were electrophoresed on SDS polyacrylamide gels and stained with silver, a number of components could be visualized which seemed to be enriched in the pl 3.8-4.4 fractions. Some of these were not sharp bands and are presumably glycoproteins. The apparent molecular weight of these compounds compared with BRL high molecular weight protein standards were 100-120kD, 40-55kD, a cluster of perhaps 5 components in the 14-20kD range and material not resolved by the gel at molecular weight less than 15kD. In addition there was a sharp doublet of proteins with apparent molecular weights of 32-36kD which were more abundant however in neighbouring less protective fractions and are therefore considered unlikely to be the antigens responsible for the protective immune responses. The IEF fractions were also used in "Western blots" using serum from sheep vaccinated in Example 4 as indicator serum. All of the components in the pi 3.8-4.4 range which were observed in the silver stained gels reacted with the sheep serum and are therefore capable of eliciting an immune response in sheep under the vaccination regime carried out in that experiment. These results indicate that potentially protective antigens can be isolated from young adult H. contortus which are particulate, solubilized at least in part with - 32 - 1% Zwittergent SB-14, have a pi in the range of 3.8-4.4 and may have apparent molecular weights of 100-120kD, 40-55kD, 14-20kD or less than 15kD as estimated by SDS gel electrophoresis and compared with BRL high molecular weight markers. Example 7 IEF fractions 5 and 6 were dialysed against 50mM sodium phosphate buffer pH 6.6 containing 0.6% CHAPS and concentrated six-fold on a YM-10 membrane. 0.2 ml aliquots were fractionated by HPLC gel filtration using a Bio-Sil TSK-400 column (30 x 0.75 cm.) (Bio-Rad) in the same buffer at a flow rate of 0.2ml/min and eluent absorbance monitored at 280 n . Fractions were collected and pooled on the basis of eluent absorbance profile. The fractions present in the last eluting peak were pooled and re-chromatographed on a TSK-SW 3000 G gel filtration column (Toyo Soda) using the conditions described above. A total of six pools were used to vaccinate guinea pigs as described in Example 2; each pool contained the equivalent of 4ml IEF 5 and 6. Worm counts (Table 7) show that the majority of the protective antigen(s) is contained in GF 5 and GF 6 which include antigens in an approximate molecular weight range from < lOkD to 60kD. - 33 - Table 7 Fraction M.W. Range Worm Counts % Protection (kD) Controls -- 436 + 123 When aliquots of the gel filtration pools were electrophoresed on SDS polyacrylamide gels and stained with silver, a number of components could be visualized which seemed to be enriched in GF 5 and GF 6 (Fig. 1) . The apparent molecular weight of these compared with Bio-Rad low molecular weight standards were 45kD, perhaps four indistinct components in the 25-30kD range and perhaps five proteins in the 14-20kD range. There are also other components that are unresolved on this gel and co-migrate at the buffer front. Components resident in GF 5 and GF 6 could be more highly resolved by several means. The methods described in Examples 8 and 9 are by way of illustration only. T x-a-mpl e> ft 6ml IEF 5 and 6 was diluted with an equal volume of lOOmM Tris/250mM sodium chloride pH 7 and stirred with 0.5ml of lentil lectin-Sepharose 4B (Pharmacia) for 16h at 4°C. The Sepharose conjugate was removed by centrifugation for l min at 3,000 xg, washed four times with 50mM Tris-saline buffer pH 7 containing 0.1% - 34 - Zwittergent SB-14 (TSZ buffer) then eluted with the same buffer to which had been added 0.3M methyl-α-D-mannopyranoside. Half of the lentil lectin bound fraction was stirred with 0.5ml Helix pomatia lectin-Sepharose 6MB (Pharmacia) for 16h at 4°C, the conjugate washed four times in TSZ buffer and then eluted in TSZ buffer containing 0.2M N-acetyl-D-galactosamine. Aliquots of all fractions were run in triplicate on SDS polyacrylamide gels before 1) staining with silver (Fig. 2) or Western transfer and 2) staining with Concanavalin A horse radish peroxidase (HRP) conjugate (Sigma) (Fig. 3) or 3) staining with Helix pomatia lectin-HRP (Sigma) (Fig. 4) . The silver stained gel shows a predominant protein of 45kD which binds to both lentil and Helix pomatia lectins; the latter does not bind minor contaminant proteins. These observations are confirmed by the two lectin blots (Concanavalin A has the same sugar specificity as lentil lectin) . Guinea pigs were vaccinated as described in Example 2 with samples of the fractions of IEF 5 and 6 following fractionation by lectin affinity chromatography as outlined above. Worm counts at slaughter (Table 8) showed that protection was afforded by the lectin-bound fraction. Other fractions also afforded some protection in this experiment. This could be due to incomplete removal of the 45kD component from the IEF fraction 5 & 6 by the lectins as the antigen may exist in various forms with different degrees of glycosylation (although little material of this molecular weight can be seen on the SDS gel profiles of the Helix pomatia lectin unbound fraction) . The protection obtained with the other fractions could also be due to the presence in those fractions of other protective antigens. These other antigens are of interest, here. - 35 - Table 8 bound 221 + 150 52 LL + , Helix pomatia lectin unbound 218 + 114 53 Example 9 IEF 5 and 6 was dialysed against 20mM Tris/lmM EDTA pH 7.5 and then concentrated ten-fold using a YM-10 membrane. 0.3ml aliquots were acidified by the addition of trifluoroacetic acid (TFA) to a concentration of 0.1% and then centrifuged to remove any precipitate. The supernatant was injected onto a PLRP-S reverse phase HPLC column (Polymer Laboratories) equilibrated in 30% acetonitrile/0.1% TFA and developed with a linear gradient over 30 min until 60% acetonitrile/0.1% TFA was achieved. Eluent absorbance was monitored at 220nm (Fig. 5) and fractions collected across the gradient. Selected fractions were run on SDS polyacrylamide gels and stained with silver (Fig. 6) to show that most of the proteins present in the starting material were recovered and were highly resolved. These data demonstrate that the antigens in the protective fraction could be well resolved by reverse phase HPLC but further studies demonstrated that the material was no longer protective to guinea pigs following vaccination. Presumably treatment of the antigen fraction with the solvents used on the reverse phase HPLC denatured the antigens so that they no longer resembled the structure of the native antigens. - 36 - Example 10 In order to remove the detergent, concentrate the sample, remove salts and exchange the antigen into a buffer suitable for amino acid sequence analysis, the lentil lectin bound, Helix pomatia bound antigen of approximately 45kD was fractionated by reverse phase HPLC on a Polypore phenyl RP (30x2.lmm) column and resolved over 20 minutes with a gradient of from 0.1% TFA/10% acetonitrile to 0.07% TFA/70% acetonitrile (flow rate 200ul/min) . The 45kD antigen was eluted toward the centre of the gradient as a major peak with a small shoulder. The two fractions were collected separately but appear to be composed of the same polypeptide based on the N-terminal amino acid sequence data obtained. The N-terminal amino acid sequence of the fractions was determined by gas phase sequencing on an Applied Biosysterns model 470A amino acid sequencer. The following sequence was obtained: A F X P G S N N G M (T) D E I R Q I F (V) (D) (K) (Y) (H) (D) (N) (S) (G) (G) (P) (P) (P) (D) In addition, samples of the 45 kD antigen were purified by electrophoresis on SDS polyacrylamide gels, transferred to nitrocellulose, stained with Ponceau S, the areas of the nitrocellulose which contained the 45 kD antigen were cut out and incubated with Endoproteinase Lys-C. Peptides which resulted from the digestion were separated by reverse phase HPLC and sequenced as above. The following sequences were obtained: (K) X X (P) (D) X E V E A N (T) A A Y A (N) E (E) (Y) (S) (K) D N E Y R S L I A X X (Q) (Q) (L) X (S) (E) (H) (G) - 37 - (K) (L) (D) (G) F A P K X (D) (G) (D) (G) (A) (A) ( ) (H) N E Y R (S ) I (L) (A) ( ) (P) X (L) (N) X (S ) ( I) (T) (G) (K) X (P) Y (D) X (D) V X A (D) X X (T) (P) (P) X (G) (K) (P) (T) (T) (D) (E) X indicates that no amino acid could be ascribed to that particular position. Residues in brackets are ascribed with less confidence than the other residues. In some cases, it was not possible to differentiate between two or three residues in a particular cycle in which case, they are listed beneath one another. The first residue in each peptide is assumed to be a lysine ( ) based on the specificity of Endoproteinase Lys-C. These sequences are suitable for the design of oligonucleotide sequences which would be suitable to use as hybridisation probes to identify the gene coding for the antigen in gene libraries generated using H. contortus RNA (complementary DNA libraries) or DNA (genomic libraries) or as primers for the polymerase chain reaction (PCR) . Example 11 Molecular cloning of the 45 kD gene (a) Oligonucleotide synthesis From the amino acid sequence described in Example 10, oligonucleotides were prepared that could be used to screen cDNA and genomic libraries to identify the gene(s) encoding the 45 kD antigen. In addition, the oligonucleotide could be used in conjunction with oligo (dT) in PCR (Saiki et al., 1988) to amplify the DNA encoding the 45 kD protein. - 38 - The following multiply-degenerate primers were designed and synthesized on an Applied Biosystem Model 380A automated DNA synthesizer. Nucleotides additional to those necessary to encode the required amino acid sequence were included on the 5' ends of the oligonucleotides. These sequences encode sites for the restriction enzymes, Eco RI and Sma I in order to assist in the cloning of PCR amplified DNA into appropriate vectors. An oligo (dT) primer for use in PCR was also synthesized. The primer also contained Eco RI and Sma I restriction sites. A112/301 GCGAATTCCCGGG . GCA . TTT . CAT . CCG . GGG . AAC . AAC . AAC . GGG . ATG . ACG . GAC . G T C C A A T T T A A T C T T T T C C C C A112 /302 GCGAATTCCCGGG.GCA.TTT.CAT.CCG.GGG.TCG.AAC.AAC.GGG.ATG.ACG.GAC.G T C C A A AGA T T A A T C T T T T T C C C C C A112/302 is identical to A112/301 except for the sixth codon from the 5' end. This was altered from AAC/T to T/AC/GG/A/T/C to account for the mixed signal seen in the amino terminal sequence, viz. asparagine (A112/301) or serine (A112/302) . (b) RNA isolation and cDNA library construction Total RNA was isolated from 1 g (wet weight) of H. contortus using an RNA extraction kit purchased from Pharmacia (Cat # XY-016-00-01) . Larvae were obtained from the abomasum of sheep 15 days after infestation with exsheathed L3 stage parasites and stored a -70°C after snap freezing in liquid nitrogen. In order to extract RNA, the frozen worms were pulverized under liquid nitrogen, added to 7 ml extraction solution (which is a buffered aqueous solution containing guanidine thiocyanate, N-lauryl sarcosine and EDTA; density at 25°C - 39 - = 1.15 g/ml) and then layered over 2 x 1.25 ml cushions of CsTFA (buffered aqueous solution containing CsTFA; density at 25°C = 1.51 g/ml) in 13 x 51 mm polyallomer tubes. The gradients were centrifuged at 31,000 rpm for 16 hours at 15°C using an SW 50.1 rotor in an L8-70 Beckman ultracentrifuge. After centrifugation, pellets of RNA were dissolved in TE buffer (10 mM Tris-HCl, pH 7.5, 1 mM EDTA) and reprecipitated from ethanol at -20°C. The sedimented RNA was then dissolved again in TE and further purified by centrifugation through an oligo (dT) -cellulose column (Pharmacia mRNA Purification Kit Cat, # XY-012-00-02) as described by the manufacturer. The resulting purified poly(A) + RNA was used to construct cDNA libraries using a Pharmacia cDNA Synthesis Kit (Cat # XY-003-00-03) . Briefly, polyadenylated RNA purified from 325 μg total RNA was treated with the Moloney Murine Leukaemia Virus Reverse Transcriptase in the presence of oligo (ά τ )i2-i8* Second strand synthesis was accomplished using RNase H and E. coli DNA polymerase I. The double stranded cDNA was treated with the Klenow fragment of DNA polymerase and ligated to Eco RI/Not I adaptors. The cDNA was then treated with T4 polynucleotide kinase to phosphorylate it and ligated into Eco RI digested, dephosphorylated lambda gt 10 arms and packaged in vitro into infectious bacteriophage particles (Protoclone lambda gt 10 System and Packagene System, Promega) as described by the supplier. The packaged cDNA was transfected into E. coli C600 Hfl and plated on Luria agar plates using Luria top agar containing 10 mM MgS0 4 . A total of 6 x 10 7 p.f.u. were obtained of which 98 % were recombinants. The average insert size was 2.0 kbp. (c) Preparation of DNA probes for screening recombinant libraries. A 45 kD antigen-specific double stranded DNA probe was prepared using PCR. The procedure used was based on that described by Saiki et al. (1985) and used a cloned form of Tag polymerase (Perkin Elmer Cetus) . 2μg total - 40 - RNA was annealed to 100 ng oligo (dT) PCR primer in 6μl water by heating to 70°C for 5 minutes and then leaving to cool to room temperature. The annealed RNA-oligo (dT) was then incubated with 200 units reverse transcriptase (BRL) in the presence of 50 mM Tris-HCl (pH 8.3), 75 mM KC1, 10 mM MgCl 2 , 5 mM spermidine, 10 mM DTT, 1 unit RNasin for 1 hour at 37°C in a final volume of 25 μl. A similar reaction from which reverse transcriptase was omitted served as a negative control for the PCR reaction. PCR was performed on cDNA produced as described above. The reaction mixture contained first strand cDNA synthesized from lμg total RNA, lμM each of one of A112/301 or A112/302 and lμM oligo (dT) PCR primer, 200μM of each dNTP, 50 mM KC1, 10 mM Tris-HCl (pH 9.0), 2 mM MgCl 2 . 0.01 % gelatin, 0.01 % Triton X-100 and 2 units of Tag polymerase in a total volume of lOOμl. Amplification was carried out over 25 cycles, each of which consisted of denaturation for 1 minute at 94°C, annealing for 2 minutes at 40°C and extension for 3 minutes at 72°C. Samples of each PCR reaction were analyzed on a 0.8 % agarose gel at the end of the reactions. In the reaction containing primer A112/301 and oligo (dT) , a unique band of approximately 650 bp was observed. Several other bands were present but these were also seen in the reaction in which oligo (dT) only was used. The approximately 650 bp band was not seen when primer A112/302 was used. No bands were seen in the negative control reaction from which reverse transcriptase was omitted. The approximately 650 bp PCR product was digested with Eco RI, purified by electrophoresis on an agarose gel, ligated into pBluescript SK- (Stratagene) using conventional techniques (Maniatis et al. , 1982) and sequenced using the dideoxy chain termination procedure (Amersham Microtitre Plate Sequencing Kit, Cat # RPN.1590). Sequence analysis of the ends of the clone confirmed that it contained the sequence of primer - 41 - A112/301 at the 5' end and a poly (A) stretch at the 3' end. Furthermore, 14 out of the 18 nucleotides immediately downstream from the 3' end of the region corresponding to the primer A112/301 corresponded to those predicted from the amino acid sequence of the purified protein. This is an homology of 86 % at the amino acid level (18 amino acids out of the 21 returned from N terminal sequencing) . The differences between the amino acid sequence obtained from the purified antigen and that predicted from the DNA sequence of the PCR clone could be accounted for by ambiguities in the amino terminal sequence analysis of the purified protein and/or PCR incorporation errors although this is an unlikely explanation given the large number of differences. The PCR clone was grown, DNA was isolated, digested with Eco RI and the insert purified for use as a hybridisation probe to screen the cDNA library described in (b) of this example. Approximately 10 5 p.f.u. were screened by hybridization of nitrocellulose filter replicas of the library at 55°C in a solution containing 2 x 10 5 cpm/ml probe, 5 x SSPE, 5 x Denhardt's solution, 0.5 % (w/v) SDS and 20 μg/ml sheared, denatured salmon sperm DNA. After washing the filters at 60°C in 0.5 x SSC, 0.1 % SDS and autoradiography, 16 positive plaques were identified. Of these, 8 were picked for subsequent purification and analysis. Eco RI inserts were isolated from the purified phage DNA and subcloned into pBluescript SK- for further analysis. The sequence of one of these clones, pBTA879, is shown in Fig. 7. There is a single long open reading frame of 1336 nucleotides followed by a translation stop codon, TGA. The open reading frame of this clone extends from the 5' end of the clone. There is no methionine initiation codon present in this region of the sequence so this clone probably does not represent the complete coding region. - 42 - Close examination of the amino acid sequence derived from the cDNA sequence (Fig 7) reveals a region of homology with the amino terminal sequence of the purified 45 kD protein commmencing at nucleotide 65 from the 5' end of the cDNA clone where 11 of the predicted amino acids occur over the following 16 residues. In addition, there is a second region with homology with the N- terminal sequence commencing at nucleotide 773 of the sequence. Of 19 amino acids, 14 residues are identical with those determined from the protein sequence. The level of homology was 73.7% at the amino acid level. It appears that there may be repetitive domains within the molecule. Both of these regions of homology are indicated in Fig. 7 by double underlining. Other regions within the predicted amino acid sequence which share homology with the Endoproteinase Lys-C peptide sequences derived from the purified protein are indicated in Fig. 7 (by single underlining) . These regions all lie within the carboxy-terminal half of the molecule; all in the portion which is carboxy-terminal to amino acid 253. In addition, there is a region immediately preceding the sequence starting at nucleotide 773 which is similar to peptide sequences which have been hypothesised as being highly susceptible to proteinase digestion. The amino acid sequence N-terminal to that starting at nucleotide 65 is very hydrophobic and contains amino acids similar to those recognised by signal peptidases. The most likely explanation of these analyses is that the cDNA clone which is described in Fig. 7 encodes a glycoprotein which is related to, but not identical to, the native glycoprotein isolated from H. contortus. The cDNA clone does not code for the full length protein; at least a complete signal peptide precedes that shown in Fig.7 and it is possible that further amino acids may also be present in the full-length native molecule. In order to isolate a cDNA clone coding for the full length native 45 kD antigen, cDNA libraries were screened - 43 - with the fragment isolated from pBTA879. The cDNA library described in (b) of this example was again screened using the Eco RI band of pBTA 879 as hybridisation probe. Approximately lO^p.f.u. were screened using the same conditions as outlined earlier. After washing the filters at 60"C in 0.5 x SSC, 0.1% SDS and autoradiography, 15 positive plaques were identified. Of these 11 Eco RI inserts were purified and subcloned into pBluescript SK- for further analysis. The sequence of one of these clones, pBTA 963, is shown in Fig. 8. This contains an open reading frame of 1320 nucleotides followed by a translation stop codon, TAA. Once again, this clone does not contain an initiation methionine, however, 16 out of 18 amino acids coded for by the 5' sequence of this clone are identical to the original N-terminal amino acid sequence. This region of homology starts at base 50 or amino acid 12 and a second repeat can be found starting at base 722. Both regions are shown with double underlining. The other peptide sequences can also be located in the translated amino acid sequence from pBTA 963. These have a much greater homology with the peptide sequences than is seen with pBTA 879. In most cases this homology is 100%. The other characteristics of the two protein sequences are very similar. Both contain a hydrophobic leader sequence segment, both contain the peptidase sensitive region toward the middle of the molecules and both are of similar molecular weight and overall charge. However, the two share only approximately 54% homology in amino acid sequence overall although the homology is much higher in some places, particularly those from which the peptide sequences were derived. To try to ensure that the cloned gene codes for the purified antigen, the Eco RI fragment was isolated from the original PCR clone and was inserted into an IPTG inducible bacterial expression vector. The gene product was isolated, purified and used to vaccinate sheep. Sera obtained from these sheep were used to probe Western - 44 - blots of the purified 45 kD glycoprotein and homogenates of H. contortus. In both instances, an antigen with an apparent molecular weight of 45 kD in IEF fractions 1-10 was found to react specifically with the antisera. Antibodies generated against a 24 amino acid long peptide with a sequence predicted from the DNA sequence also reacted with the 45 kD antigen in IEF fractions 1-10. Close inspection of the Western blots of whole parasite homogenates and each broad range IEF fraction resolved with serum from sheep vaccinated with the recombinant antigen reveals that there are in fact higher molecular weight parasite components which specifically react with the post vaccination serum. These higher molecular weight components are likely to be products of the same gene family to that of the isolated antigen. They are located in IEF fractions 2, 3 and 4 in particular and appear to smear across the isoelectric focussing gels. This phenomenon of not focussing as sharp band upon fractionation by IEF is a characteristic of glycoproteins; the variable carbohydrate residues introduce a heterogeneity of charge on the molecules and a heterogeneity in pl of the population of molecules. It therefore appears that the native 45 kD antigen isolated from the parasite is a member of a class of proteins which share similar amino acid sequences over portions of the molecules. This is further supported by Southern blot analysis of H. contortus genomic DNA using both Eco RI inserts (Fig 9) . These show pBTA 963 hybridising to many bands with varying intensity. The bands at 1480, 890 and 740 base pairs are the most strongly hybridising. The same blot screened with pBTA 879 however lights up a band at 1350 base pairs with the 890 and 740 bands still binding weakly with this probe. From the Western blots it appears that some members of the protein family may have a molecular weight in excess of 65 kD. It is also possible that the protection afforded to vaccinated sheep and guinea pigs by the IEF fraction 2, 3 and 4 in Examples 4 and 5 of this - 45 - specification are due to the presence of the larger molecular weight forms of the protective antigen described herein. No DNA or protein sequences with significant homology to that of this clone could be found after searching the Genbank, EMBL or PIR computer data bases. Example 12 Homologous genes related to that of the protective antigen are present in other species of parasitic nematode DNA hybridisation (or Southern blot analysis) was carried out using standard techniques (Maniatis et al. , 1982) to determine whether other species of parasitic nematodes have genes which are "homologous" to those coding for the H. contortus protective antigen. The Eco RI insert of the cDNA clone pBTA963 described in Example 11 (Fig. 8) was used as a hybridisation probe to DNA isolated from a number of other species of parasitic nematodes. As well as hybridizing strongly to several restriction fragments in the DNA isolated from the homologous species, i.e., H. contortus. as expected, the probe also hybridized to specific restriction fragments in DNA isolated from Ostertagia circumcincta. Ostertagia ostertagi and Trichostrongylus colubriformis. The blots were washed at a stringency that suggested that the level of homology was about 70 %. (Fig. 10) . This clearly demonstrates that there are genes which are closely related to that coding for the protective antigen in these other species of parasitic nematodes and, by extension, in all species of parasitic nematodes. These genes could be isolated using standard molecular biological techniques, and recombinant organisms could be made which synthesise those related or homologous antigens from the other species of parasitic nematode. The present inventors consider that the related antigens will serve as effective immunogens to provide protection to vaccinated animals against infection by the other species of parasite. In addition, related antigens - 46 - isolated from a broad range of parasitic nematodes could be isolated and provide effective protective immunogens to protect animals against infestation by an extensive range of such nematodes. It has already been demonstrated that this approach can be successful (International application No. PCT/AU88/00239) . That patent application describes how an antigen was purified from an homogenate of T. colubriformis based on the ability of that antigen to provide protection to guinea pigs against challenge infections by T. colubriformis. Amino acid sequence information was determined for this antigen which enabled the gene coding for the antigen to be isolated from recombinant DNA libraries. The DNA coding for the T. colubriformis gene was then used as a hybridisation probe to identify recombinant organisms coding for the "homologous" gene from H. contortus. Recombinant organisms were then constructed which synthesised the H. contortus antigen which was then used in vaccination and challenge trials in sheep and guinea pigs. The H. contortus recombinant antigen provided protection to vaccinated sheep against infestation by H. contortus and provided protection to guinea pigs against challenge infection by T. colubriformis. This demonstrates that it is possible, given the DNA sequence homology demonstrated in the above hybridisation experiments, to use the cloned DNA sequence coding for protective antigen from one species of parasitic nematode to identify clones coding for the homologous gene products from other species of parasitic nematodes, engineer those recombinant organisms to express the homologous antigen and use this in a vaccine to provide protection against the other species of parasitic nematode. It is considered that a natural extension of the results presented here is to do so with the DNA sequences of the present invention. It is to be understood that the nucleotide sequence of the homologous genes and the amino acid sequence of - 47 - the homologous antigens may not be identical to those of the first target species but will be related by at least 50 % over a stretch of at least 60 base pairs and preferably the relationship would be 70% or more over this same region with the homology at the amino acid level being at least 70% over 20 amino acids. In most cases, this degree of homology would be sufficient to enable an unambiguous identification of the relatedness of the two genes or proteins. Example 13 Expression of the 45 kD Antigen in E.coli A number of systems could be used to express the recombinant 45 kD antigen, e.g. mammalian cells, virus- infected insect cells, yeasts, or bacteria. As an example, the gene was expressed in E.coli. The full cDNA fragment from pBTA 963 was isolated as a 1386 base pair Bam HI/Hind III fragment, and was subcloned into E.coli expression vector pBTA 954. pBTA 954 is a pUR-based vector containing the lac promoter, the initiating amino acids for the β-galactosidase gene and multiple cloning sites. When expression was induced by addition of ImM IPTG, this yielded a fusion protein with 11 N-terminal amino acids encoded by the vector, fused to the 45 kD protein. The apparent molecular weight of the fusion protein was approximately 61 kD (Fig. lla) . The fusion protein was recognised by rabbit serum raised against a peptide corresponding to the truncated N-terminus of the 45 kD protein (Fig. lib) . This serum had previously been shown to recognise the dominant protein in the native extract, IEF fraction 1. The fusion protein could be purified by standard techniques known in the art, formulated with a suitable adjuvant and used to vaccinate the host such as sheep and provide protection against parasite infection. - 48 - Example 14 Immunological Cross-Reactivity between Antibodies to the 45 kD antigen and Dirofilaria immitis proteins Rabbits were vaccinated with a synthetic peptide derived from the sequence of the N-terminal region of the 45 kD antigen. Antisera from these rabbits was used to probe a Western blot of extracts from both adult D. immitis and H. contortus. After development with a second antibody conjugated to alkaline phosphatase two antigens from each species were shown to be reactive. Components of 45 kD and 27 kD were detected in the H. contortus extract and 52 and 32kD in the D. immitis extract (Fig. 12) . This result supports other observations (Example 12) using DNA hybridisation techniques, that proteins related to the 45 kD antigen are present and are expressed in D. immitis. Example 15 Scale up of Manufacturing for Commercial Vaccines The production and purification techniques so far described are carried out at laboratory scale. For commercial production of the antigens of the invention, large scale fermentation of transformed hosts is required. The large scale fermentations are performed according to standard techniques, the particular techniques selected being appropriate to the transformed host used for production of the antigen. DEPOSITION OF MICROORGANISMS Strain BTA 2033, which is E. coli JM101 containing the plasmid pBTA 879, has been deposited with Australian Government Analytical Laboratories of 1 Suakin Street, Pymble 2073, New South Wales, Australia in accordance with the provisions of the Budapest Treaty on 29 January 1992 under accession number N92/4387. The genotype of E. coli JM101 is: Δ(pro-lac) . F- lacJ? ΔM15, traDl , λ " . pBTA 879 is pBLUESCRIPT-SK-minus (Stratagene, San Diego, CA, USA) containing a 1400 base - 49 - pair Eco RI insertion coding for a portion of an antigenic protein from the gasto-intestinal nematode, Haemonchus contortus. Strain BTA 2125, which is E. coli SURE strain containing the plasmid pBTA 963, has been deposited with Australian Government Analytical Laboratories of 1 Suakin Street, Pymble 2073, New South Wales, Australia in accordance with the provisions of the Budapest Treaty on 29 January 1992 under accession number N92/4388. The genotype of E. coli SURE is BTA2125 is: E. coli SURETM strain (Stratagene, San Diego, CA, USA), genotype: mcrA, Δ(mrr, hsd RMS mcrBC) , endAl, supE44, thi-1, λ " , gyrA96, relAl, lac, recB, recJ, sbcC, umuC: :Tnr(kan R ) , uvrC, {F' proAB, lacl1ZΔM15, TnlO (tet R ) }. Plasmid pBTA 963 is pBLUESCRIPT-SK-minus (Stratagene, San Diego, CA, USA) , containing a 1386 base pair Eco RI insertion coding for a portion of an antigenic protein from the gastro-intestinal nematode Haemonchus contortus. INDUSTRIAL APPLICATIONS The present invention is of use in providing antigens, vaccines, and antibodies suitable for protecting animals against infection by parasitic nematodes.

Claims: - 50 - REFERENCES Maniatis T, Fritsch EF and Sambrook J (eds) (1982) Molecular cloning: A laboratory manual CSH Laboratory, Cold Spring Harbor. Saiki RK, Gelfand DH, Stoffels, Scharf SJ, Higuchi R, Horn GT, Mullis KB and Erlich HA (1988) Primer directed amplification of DNA with a thermostable DNA polymerase Science 239: 487-491. - 51 - CLAIMS 1. A substantially purified antigen derived from a first species of parasitic nematodes, which antigen is capable of providing protection to a host from parasitism by a second nematode species, which may be the same as or different from the first nematode species, following vaccination of the host with the antigen, characterized in that the antigen is proteinaceous, has a pl between 3.8 and 4.4, can be bound by lentil lectin and Helix pomatia lectin and has a molecular weight of approximately 45 kD as determined by SDS-PAGE. 2. An antigen according to claim 1 wherein the antigen is at least 90% pure. 3. An antigen according to claim 1 in non- glycosylated form. 4. An antigen according to any one of claims 1 to 3 wherein the first parasitic nematode species is selected from species of the genera Trichinella. Ancylostoma, Strongylus, Trichostrongylus. Haemonchus. Ostertagia, Ascaris, Toxascaris. Uncinaria. Trichuris, Dirofilaria, Toxocar , Necator, Enterobius, Strongyloides and Wuchereria. 5. An antigen according to claim 4 wherein the first parasitic nematode species is selected from Trichinella spiralis, Ancylostoma caninum. Strongylus vulgaris, Trichostrongylus colubriformus, Haemonchus contortus, Ostertagia ostertagi, Ascaris suum, Toxascaris leonina, Uncinaria stenocephala, Trichuris vulpis, Dirofilaria immitis. Toxocara species, Necator americanus. Ancylostoma duodenale, Ascaris lumbricoides, Trichuris trichiura. Enterobius vermicularus, Strongyloides stercoralis, Wuchereria bancrofti and Ostertagia circumcincta. - 52 - 6. An antigen according to claim 1 wherein the second nematode species is selected from species of the genera Trichinella. Ancylostoma, Strongylus, Trichostrongylus, Haemonchus. Ostertagia, Ascaris, Toxascaris, Uncinaria, Trichuris. Dirofilaria, Toxocara, Necator. Enterobius. Strongyloides, and Wuchereria. 7. An antigen according to claim 6, wherein the second nematode species is selected from Trichinella spiralis. Ancylostoma caninum. Strongylus vulgaris, Trichostrongylus colubriformis. Haemonchus contortus, Ostertagia ostertagi, Ascaris suum. Toxascaris leonina, Uncinaria stenocephala. Trichuris vulpis, Dirofilaria immitis. Toxocara spp. Necator americanus. Ancylostoma duodenale. Ascaris lumbricoides, Trichuris trichiura, Enterobius vermicularus. Strongyloides stercoralis, Wuchereria bancrofti and Ostertagia circumcincta. 8. An antigen according to claim 1, wherein the first and second nematode species are selected from the genus Haemonchus. 9. An antigen according to claim 8, wherein the first and seond nematode species are Haemonchus contortus. 10. An antigen precursor of an antigen according to any one of claims 1 to 9, in substantially purified form. 11. An antigen precursor according to claim 10 having a purity of at least 90%. 12. An antigen precursor according to claim 10 or 11 in unglycosylated form. 13. An antigen precursor comprising substantially the amino acid sequence illustrated in Figure 8, in glycosylated or non-glycosylated form, excluding the antigen precursor as it exists in nature. 14. An antigen having substantially the amino acid sequence consisting of .amino acids 12 to 440 of the amino acid sequence illustrated in Figure 8, in glycosylated or non-glycosylated form, excluding the antigen as it exists in nature. - 53 - 15. A homologue of an antigen or an antigen precursor according to any one of claims 1 to 14. 16. A homologue according to claim 15, which is at least 70% homologous over 20 amino acids to the amino acid sequence illustrated in Figure 8. 17. A homologue according to claim 15 comprising substantially: the amino acid sequence illustrated in Figure 7; or amino acids 17 to 454 of the amino acid sequence illustrated in Figure 7. 18. A polynucleotide molecule, exluding a polynucleotide molecule as it exists in nature, which polynucleotide molecule encodes an antigen, antigen precursor or homologue according to any one of claims 1 to 17. 19. A polynucleotide molecule according to claim 18 which polynucleotide molecule is a DNA molecule. 20. A polynucleotide molecule according to claim 19, which polynucleotide is a cDNA molecule. 21. A polynucleotide molecule according to claim 18, selected from: a polynucleotide molecule comprising substantially the nucleotide sequence illustrated in Figure 7 or Figure 8; and a polynucleotide having a nucleotide sequence corresponding substantially to nucleotide 65 to 1381 of Figure 7 or nucleotides 50 to 1339 of Figure 8. 22. A DNA molecule, excluding DNA molecules as they exist in nature having at least 50% homology with the sequence illustrated in Figure 8, and encoding a protective molecule capable of conferring immunity against parasitic nematode infection. 23. A recombinant DNA molecule comprising a polynucleotide molecule according to any one of claim 18 to 22, which polynucleotide molecule is a DNA molecule, and vector DNA. 24. A recombinant DNA molecule according to claim 23, wherein the vector DNA comprises plasmid, phage or viral DNA. - 54 - 25. A recombinant DNA molecule according to claim 24 wherein the vector DNA is selected from lambda gtll, pUR290, pUR291, pUR282, pUK270, pUC8, pUC9, pZipNeo, an SV40 based vector, lambda gtlO, an EMBL vector, pBR327, pBR329, pBR329 containing a par locus, baculovirus and vaccinia virus. 26. pBTA879 and pBTA963 as hereinbefore defined. 27. A transformant host, carrying at least one recombinant DNA molecule according to any one of claims 23 to 26. 28. A transformed host according to claim 27, wherein the host is selected from bacteria, yeasts, other fungi, insect, plant and mammalian cell lines. 29. A transformed host according to claim 28, wherein the host is an E. coli K12 derivative. 30. BTA 2033 and BTA 2125 as hereinbefore defined. 31. An expression product of a transformed host according to claim 27, comprising an antigen, antigen precursor or homologue according to any one of claims 1 to 17. 32. An expression product according to claim 31, which expression product is a fused expression product. 33. A synthetic polypeptide corresponding to all or part of an antigen, precursor or homologue according to any one of claims 1 to 17, or an expression product according to claim 31 or 32, which synthetic polypeptide, when administered to a host animal, is capable of inducing protective immunity against infestation of the host animal by a parasitic nematode. 34. A vaccine comprising an effective amount of at least one antigen, precursor or homologue according to any one of claims 1 to 17, expression product according to claim 31 or 32, and/or synthetic polypeptide according to claim 33 together with a pharmaceutically and/or veterinarally acceptable carrier, diluent and/or adjuvant. - 55 - 35. A whole cell vaccine in live or killed form comprising a transformed host according to any one of claims 27 to 30 together with a pharmaceutically and/or veterinarally acceptable carrier, diluent, excipient and/or adjuvant. 36. A whole cell vaccine according to claim 35 wherein the transformed host is capable of expressing an antigen, precursor or homologue according to any one of claims l to 17 for mucosal presentation to a host to be vaccinated. 37. A process for preparing an antigen according to claim 1, which process comprises: a) homogenzing young adults of a parasitic nematode species to produce an homogenate; b) obtaining membranous material from the homogenate; c) extracting the membranous material with a buffer containing low levels of a Zwitterionic detergent to obtain a detergent extract; d) chromatographing the detergent extract on a wheat-germ lectin sepharose column; and e) collecting flow-through from the column. 38. The process according to claim 37 which also comprises: fractionation by preparative iso-electric focussing and collection of fractions having a pi in the range 3.8-4.4, or preferably 4.0-4.3; fractionation by gel filtration chromatography to collect fractions with molecular weights in the range 10-60kD; and fractionation by lentil lectin or Helix pomatia lectin chromatography and collecting bound material. 39. A process for preparing a vaccine according to claim 34 which process comprises: admixing an effective amount of at least one antigen, antigen precursor, or homologue according to any one of claims 1 to 17; - 56 - expression product according to claim 31 or 32 and/or synthetic polypeptide according to claim 33 with a pharmaceutically and/or veterinarally acceptable carrier, diluent, excipient and/or adjuvant. 40. A method of protecting a host against infection by at least one parasitic nematode species which method comprises administering an effective amount of at least one antigen, antigen precursor, or homologue according to any one of claims 1 to 17, expression product according to claim 31 or 32, synthetic polypeptide according to claim 33, and/or vaccine according to claim 34 or 35, to the host. 41. An antibody raised against an antigen, antigen precursor, or homologue according to any one of claims 1 to 17, an expression product according to claim 31 or 32, a synthetic polypeptide according to claim 33, or a vaccine according to claim 34 or 35. 42. An antibody composition comprising at least one antibody according to claim 41 together with a pharmaceutically and/or veterinarally acceptable carrier, diluent and/or excipient. 43. A process for preparing an antibody according to claim 41 which process comprises vaccinating an immunoresponsive host with an antigen, an antigen precursor or a homologue according to any one of claims 1 to 17, an expresson product according to claim 31 or 32, a synthetic polypeptide according to claim 33 and/or a vaccine according to claim 34 or 35. 44. A process for preparing an antibody composition according to claim 42 which process comprises admixing an effective amount of an antibody according to claim 41 with a pharmaceutically and/or veterinarally acceptable carrier, diluent and/or excipient. 45. A process for preparing a recombinant DNA molecule according to claim 23 which process comprises inserting a DNA molecule according to claim 19 or 20 into vector DNA. - 57 - 46. A process for preparing a transformed host according to claim 27, which process comprises making a host competent for transformation to provide a competent host and transforming the competent host with a recombinant DNA molecule according to claim 23. 47. A diagnostic kit comprising a sample of an antigen, antigen precursor or homologue according to any one of claims 1 to 17, an expression product according to claim 31 or 32 or a synthetic polypeptide according to claim 33 and/or an antibody according to claim 41. 48. A process for biosynthesis of an expression product according to claim 31 or 32 which process comprises providing a transformed host according to claim 27, culturing the host under suitable condition to obtain expression of the expression product and collecting the expression product from the transformed host. 49. An antiidiotype antibody corresponding to a portion of an antigen according to claim 1, and capable of protecting a host immunized with the antiidiotype antibody from infestation with a parasitic nematode species. 50. A vaccine comprising an antiidotype antibody according to claim 49 together with pharmaceutically and/or veterinarally acceptable carrier, diluent, excipient and/or adjuvant. 51. A method of passively protecting a host against infestation by a parasitic nematode species which method comprises administering an effective amount of at least one antibody, according to claim 41 or antibody composition according to claim 42 to the host. —58— AMENDED CLAIMS [received by the International Bureau on 21 July 1992 (21.07.92 ) ; original claim 1 amended; new claims 40 and 41 added; claims 4_7 t 8-41 and 42-51 amended and renumbered as claims 4 and 5, 6-39 and 42-51 other claims unchanged (7 pages)] 1. A substantially purified antigen derived from a first parasitic nematode species wherein said antigen is proteinaceous, has a pi between 3.8 and 4.4, can be bound by lentil lectin and Helix pomatia lectin and has an apparent molecular weight of 45 kD as determined by SDS-PAGE under reducing conditions, and said antigen, when administered to a host animal, stimulates an immune response by the host animal which protects the host animal from infestation by a second parasitic nematode species, wherein the first and second parasitic nematode species may be the same or different. 2. An antigen according to claim 1 wherein the antigen is at least 90% pure. 3. An antigen according to claim 1 in non- glycosylated form. 4. An antigen according to any one of claims l to 3 wherein the first and second parasitic nematode species are selected from species of the genera Trichinella. Ancylostoma. Strongylus. Trichostrongylus. Haemonchus. Ostertagia. Ascaris. Toxascaris. Uncinaria. Trichuris. Dirofilaria. Toxocara. Necator. Enterobius. Strongyloides and Wuchereria. 5. An antigen according to claim 4 wherein the first and second parasitic nematode species are selected from Trichinella spiralis. Ancylostoma caninum. Strongylus vulgaris. Trichostrongylus colubriformus. Haemonchus contortus. Ostertagia ostertagi, Ascaris suum. Toxascaris leonina. Uncinaria stenocephala. Trichuris vulpis. Dirofilaria immitis. Toxocara species, Necator americanus. Ancylostoma duodenale. Ascaris lumbricoides, Trichuris trichiura, Enterobius vermicularus, Strongyloides stercoralis. Wuchereria bancrofti and Ostertagia circumcincta. 6. An antigen according to claim 1, wherein the first and second parasitic nematode species are selected from the genus Haemonchus. 7. An antigen according to claim 6, wherein the first and second parasitic nematode species are Haemonchus contortus. 8. An antigen precursor of an antigen according to 5 any one of claims 1 to 7, in substantially purified form. 9. An antigen precursor according to claim 8 having a purity of at least 90%. 10. An antigen precursor according to claim 8 or 9 in non-glycosylated form. 0 11. An antigen precursor comprising substantially the amino acid sequence illustrated in Figure 8, in glycosylated or non-glycosylated form, but excluding the antigen precursor as it exists in nature. 12. An antigen comprising substantially the amino 5 acid sequence defined by residues 12 to 440 inclusive of the amino acid sequence illustrated in Figure 8, in glycosylated or non-glycosylated form, but excluding the antigen as it exists in nature. 13. A homologue of an antigen or an antigen 0 precursor according to any one of claims 1 to 12, which homologue, when administered to a host animal, stimulates an immune response by the host animal which protects the host animal from infestation by a parasitic nematodes species. 5 14. A homologue according to claim 13, which is at least 70% homologous over 20 amino acids to the amino acid sequence illustrated in Figure 8. 15. A homologue according to claim 13 comprising substantially the amino acid sequence illustrated in C Figure 7; or the amino acid sequence defined by residues 17 to 454 inclusive of the amino acid sequence illustrated in Figure 7. 16. A polynucleotide molecule, excluding a polynucleotide molecule as it exists in nature, which 5 polynucleotide molecule encodes an antigen, antigen precursor or homologue according to any one of claims to 15. - - 17. A polynucleotide molecule according to claim 16 which polynucleotide molecule is a DNA molecule. 18. A polynucleotide molecule according to claim 17, which polynucleotide is a cDNA molecule. 19. A polynucleotide molecule according to claim 16, selected from: a polynucleotide molecule comprising substantially the nucleotide sequence illustrated in Figure 7 or Figure 8; and a polynucleotide molecule comprising substantially the nucleotide sequence defined by nucleotides 65 to 1381 inclusive of Figure 7 or nucleotides 50 to 1339 inclusive of Figure 8. 20. A DNA molecule, excluding DNA molecules as they exist in nature, having at least 50% homology over 60 nucleotides with the sequence illustrated in Figure 8, and encoding a protective molecule which confers immunity against parasitic nematode infestation. 21. A recombinant DNA molecule comprising a polynucleotide molecule according to claim 17 and vector DNA. 22. A recombinant DNA molecule according to claim 21, wherein the vector DNA comprises plasmid, phage or viral DNA. 23. A recombinant DNA molecule according to claim 22 wherein the vector DNA is selected from lambda gtll, pUR290, pUR291, pUR282, pUK270, pUC8, pUC9, pZipNeo, an SV40 based vector, lambda gtlO, an EMBL vector, pBR327, pBR329, pBR329 containing a par locus, baculovirus and vaccinia virus. 24. pBTA879 and pBTA963 as hereinbefore defined. 25. A transformed host transformed with at least one recombinant DNA molecule according to any one of claims 21 to 24. 26. A transformed host according to claim 25, wherein the host is selected from bacteria, yeasts, other fungi, insect, plant and mammalian cell lines. 27. A transformed host according to claim 26, wherein the host is an E. coli K12 derivative. -61- 28. BTA 2033 and BTA 2125 as hereinbefore defined. 29. An expression product of a transformed host according to claim 25, comprising an antigen, antigen precursor or homologue according to any one of claims 1 to 15. 30. An expression product according to claim 29, wherein said expression product is a fusion product. 31. A synthetic polypeptide corresponding to all or part of an antigen, antigen precursor or homologue according to any one of claims l to 15, or an expression product according to claim 29 or claim 30, which synthetic polypeptide, when administered to a host animal, stimulates an immune response by the host animal which protects the host animal from infestation by a parasitic nematode species. 32. A vaccine comprising an effective amount of at least one antigen, antigen precursor or homologue according to any one of claims 1 to 15, expression product according to claim 29 or claim 30, and/or synthetic polypeptide according to claim 31 together with a pharmaceutically and/or veterinarally acceptable carrier, diluent and/or adjuvant. 33. A whole cell vaccine in live or killed form comprising a transformed host according to any one of claims 25 to 28 together with a pharmaceutically and/or veterinarally acceptable carrier, diluent, excipient and/or adjuvant. 34. A whole cell vaccine according to claim 33 wherein the transformed host is capable of expressing an antigen, antigen precursor or homologue according to any one of claims 1 to 15 for mucosal presentation to a host to be vaccinated. 35. A process for preparing an antigen according to claim 1, which process comprises: a) homogenzing young a.dults of a parasitic nematode species to produce an homogenate; b) obtaining membranous material from the homogenate; -62- c) extracting the membranous material with a buffer containing low levels of a Zwitterionic detergent to obtain a detergent extract; d) chromatographing the detergent extract on a wheat-germ lectin sepharose column; and e) collecting flow-through from the column. 36. The process according to claim 35 which also comprises: fractionation by preparative iso-electric focussing and collection of fractions having a pi in the range 3.8-4.4, or preferably 4.0-4.3; fractionation by gel filtration chromatography to collect fractions with molecular weights in the range 10-60kD; and fractionation by lentil lectin or Helix pomatia lectin chromatography and collecting bound material. 37. A process for preparing a vaccine according to claim 32 which process comprises: admixing an effective amount of at least one: antigen, antigen precursor, or homologue according to any one of claims 1 to 15; expression product according to claim 29 or claim 30; and/or synthetic polypeptide according to claim 31, with a pharmaceutically and/or veterinarally acceptable carrier, diluent, excipient and/or adjuvant. 38. A method of protecting a host against infestation by at least one parasitic nematode species which method comprises administering an effective amount of at least one antigen, antigen precursor, or homologue according to any one of claims l to 15, expression product according to claim 29 or claim 30, synthetic polypeptide according to claim 31, and/or vaccine according to claim 32 or claim 33, to the host. 39. An antibody raised against an antigen, antigen precursor, or homologue according to any one of claims to 15, an expression product according to claim 29 or claim 30, a synthetic polypeptide according to claim 31, or a vaccine according to claim 32 or claim 33. -63- 40. An antibody according to claim 39, wherein said antibody is a polyclonal antibody. 41. An antibody according to claim 39, wherein said antibody is a monoclonal antibody. 42. An antibody composition comprising at least one antibody according to any one of claims 39 to 41 together with a pharmaceutically and/or veterinarally acceptable carrier, diluent and/or excipient. 43. A process for preparing an antibody according to claim 39 which process comprises vaccinating an immunoresponsive host with an antigen, an antigen precursor or a homologue according to any one of claims 1 to 15, an expression product according to claim 29 or 30, a synthetic polypeptide according to claim 31 and/or a vaccine according to claim 32 or claim 33. 44. A process for preparing an antibody composition according to claim 42 which process comprises admixing an effective amount of an antibody according to any one of claims 39 to 41 with a pharmaceutically and/or veterinarally acceptable carrier, diluent and/or excipient. 45. A process for preparing a recombinant DNA molecule according to claim 21 which process comprises inserting a DNA molecule according to claim 17 or claim 18 into vector DNA. 46. A process for preparing a transformed host according to claim 25, which process comprises making a host competent for transformation to provide a competent host and transforming the competent host with a recombinant DNA molecule according to claim 21. 47. A diagnostic kit comprising a sample of an antigen, antigen precursor or homologue according to any one of claims 1 to 15, an expression product according to claim 29 or claim 30, or a synthetic polypeptide according to claim 31 and/or an antibody according to claim 39. 48. A process for biosynthesis of an expression product according to claim 29 or claim 30 which process -64- comprises providing a transformed host according to claim 25, culturing the host under suitable conditions to obtain expression of the expression product and collecting the expression product from the transformed host. 49. An antiidiotype antibody corresponding to a portion of an antigen according to claim 1, which protects a host immunized with the antiidiotype antibody from infestation by a parasitic nematode species. 50. A vaccine comprising an antiidiotype antibody according to claim 49 together with a pharmaceutically and/or veterinarally acceptable carrier, diluent, excipient and/or adjuvant. 51. A method of passively vaccinating a host against infestation by a parasitic nematode species which method comprises administering an effective amount of at least one antibody according to claim 39 or antibody composition according to claim 42 to the host.

Inventors: COBON GARY STEWART, SHARP PHILLIP JOHN, WAGLAND BARRY MAXWELL, COBON, GARY, STEWART, SHARP, PHILLIP, JOHN, WAGLAND, BARRY, MAXWELL
Applicants: BIOTECH AUSTRALIA PTY LTD, COMMW SCIENT IND RES ORG, BIOTECH AUSTRALIA PTY. LIMITED, COMMONWEALTH SCIENTIFIC AND INDUSTRIAL RESEARCH OR
Application year: 1992
Main classification: C12N15
IPC codes: A61K38, A61K39, A61P33, C07K1, C07K14, C07K16, C12N15, C12P21