MICROPARTICLE DELIVERY SYSTEM

Abstract: A particulate carrier for an agent comprising a solid core of a polysaccharide and a proteinaceous material and an organometallic polymer bonded to the core is provided. The agent has a biological activity, such as immunogenicity, and may comprise the proteinaceous material or be a separate component of the core. Polysaccharide cores include dextran, starch, cellulose and derivatives thereof and the organometallic polymer includes silicones including substituted silicones. The particulate carriers are useful for delivering agents to the immune system of a subject by mucosal or parenteral administration to produce immune responses, including antibody responses.

Description: TITLE OF INVENTION MICROPARTICLE DELIVERY SYSTEM FIELD OF INVENTION The present invention relates to a particulate carrier for delivering materials having biological activity. The term " icroparticle" as used herein refers to any particulate carrier used for delivery of a biologically-active material and includes materials which are microcapsules and icrosphereε. REFERENCE TO RELATED APPLICATION This application is a continuation-in-part of copending U.S. patent application serial no. 08/245,646, filed May 18, 1994. BACKGROUND OF THE INVENTION Vaccines have been used for many years to protect humans and animals against a wide variety of infectious diseases. Such conventional vaccines consist of attenuated pathogens (for example, polio virus) , killed pathogens (for example, Bordetella pertussis) or immunogenic components of the pathogen (for example, diphtheria toxoid) . Some antigens are highly immunogenic and are capable alone of eliciting protective immune responses. Other antigens, however, fail to induce a protective immune response or induce only a weak immune response. This low immunogenicity can be significantly improved if the antigens are co-administered with adjuvants. Adjuvants enhance the immunogenicity of an antigen but are not necessarily immunogenic themselves. Adjuvants may act by retaining the antigen locally near the site of administration to produce a depot effect facilitating a slow, sustained release of antigen to cells of the immune system. Adjuvants can also attract cells of the immune system to an antigen depot and stimulate such cells to elicit immune responses. Adjuvants have been identified that enhance the immune response to antigens delivered parenterally. Some of these adjuvants are toxic, however, and can cause undesirable side-effects, making them unsuitable for use in humans and many animals. Indeed, only aluminum hydroxide and aluminum phosphate are routinely used as adjuvants in human and veterinary vaccines. However, even these adjuvants are not suitable for use with all antigens and can also cause irritation at the site of injection. There is a clear need to develop novel adjuvants which are safe and efficacious for enhancing the immunogenicity of antigens. Immunization can also be achieved by the delivery of antigens to ucosal surfaces, such as by ingestion of the antigen. Thus, it is known that the ingestion of antigens by animals can result in the appearance of antigen-specific secretory IgA antibodies in intestinal, bronchial or nasal washings and other external secretions. For example, studies with human volunteers have shown that oral administration of influenza vaccine is effective at inducing secretory anti-influenza antibodies in nasal secretions and substances have been identified which might be useful as adjuvants for such ingested vaccines. However, most of these adjuvants are relatively poor in terms of improving immune responses to ingested antigens. Currently, some of these adjuvants have been determined to be safe and efficacious in enhancing immune responses in humans and animals to antigens that are administered via the orogastrointestinal, nasopharyngeal-respiratory and genital tracts or in the ocular orbits. However, administration of antigens via these routes is generally ineffective in eliciting an immune response. The inability to immunize at the mucosal surface is generally believed to be due to: the destruction of the antigen or a reduction in its immunogenicity in the acidic and/or enzymatically hostile environments created by secretions produced at the mucosal epithelium; the dilution of the antigen to a concentration that is below that required to induce immune responses; the carriage of antigen from the body in discharges originating at the mucosal epithelium; and the lack of suitable adjuvants which remain active at the mucosal epithelium. Clearly, there is a need to identify powerful adjuvants which are safe and efficacious for use at the mucosal epithelium in the orogastrointestinal, nasopharyngeal-respiratory and urogenital tracts and in the ocular orbits and at other mucosal sites. Sensitive antigens may be entrapped to protect them against destruction, reduction in immunogenicity or dilution. The antigen can be coated with a single wall of polymeric material or can be dispersed within a monolithic matrix. Thus, U.S. Patent 5,151,264 describes a particulate carrier of a phospholipid/ glycolipid/polysaccharide nature that has been termed Bio Vecteurε Supra Moleculaires (BVSM) . The particulate carriers are intended to transport a variety of molecules having biological activity in one of the layers thereof. However, U.S. Patent 5,151,264 does not describe particulate carriers containing antigens for immunization and particularly does not describe particulate carriers for immunization via the orogastrointestinal, nasopharyngeal-respiratory and urogenital tracts and in the ocular orbits or other mucosal sites. U.S. Patent 5,075,109 describes encapsulation of the antigens trinitrophenylated keyhole limpet hemocyanin and staphylococcal enterotoxin B in 50:50 poly (DL-lactide- co-glycolide) . Other polymers for encapsulation are suggested, such as poly(glycolide) , poly(DL-lactide-co- glycolide) , copolyoxalates, polycaprolactone, poly(lactide-co-caprolactone) , poly(estera ides) , polyorthoesters and poly 8-hydroxybutyric acid) , and polyanhydrides. The encapsulated antigen was administered to mice via gastric intubation and resulted in the appearance of significant antigen-specific IgA antibodies in saliva and git secretions and in sera. As stated in this patent, in contrast, the oral administration of the se.iiie amount of unencapsulated antigen was ineffective at inducing specific antibodies of any isotype in any of the fluids tested. Poly(DL- lactide-co-glycolide) microcapsυles were also used to administer antigen by parerrteral injection. Published PCT application WO 91/06282 describes a delivery vehicle comprisirq a plurality of bioadhesive microspheres and antigenic vaccine ingredients. The microspheres being of starch, gelatin, dextran, collagen or albumin. This delivery vehicle is particularly intended for the uptake of vaccine across the nasal mucosa. The delivery vehicle may additionally contain an absorption enhancer. The antigens are typically encapsulated within protective polymeric materials. SUMMARY OF V7HE INVENTION The present invention is directed towards the provision of a new and useful microparticle delivery system, which may be used for delivery of materials having biological activity, including antigens to a host. In accordance with cne aspect of the present invention, there is provided a particulate carrier, which comprises: a solid core comprising a polysaccharide and a proteinaceous material; and an organometallic polymer bonded to the core. Such particulate carrier generally has a particle size from about 10 nm to about 50 μm, preferably from about 1 to about 10 μm. The polysaccharide component of the core may be dextran, starch, cellulose or derivatives thereof, particularly soluble starch. The starch may be derived from a variety of onocotyledonous and dicotyledonous species, such as corn, potato or tapioca. The proteinaceous material component of the core may have biological activity. An additional material having biological activity also may be included in the core. The particles then provide a delivery vehicle for the biologically-active material to a host, generally an animal, including a human. The material having biological activity, for example, immunogenicity, includes proteins (such as influenza viral protein) , peptideε, antigens, bacteria, bacterial lysates, viruses (such as, influenza virus) , virus-infected cell lysates (such as, a herpes simplex virus-infected cell lysate) , antibodies, carbohydrates, nucleic acids, lipids, haptens, pharmacologically-active materials, and combinations, derivations and mixtures thereof. The organometallic polymer bonded to the core preferably is derived from a functionalized silicone, including an end-substituted silicone. One particular class of end-substituted silicones from which the organometallic polymer may be derived are (trialkoxysilyl) alkyl-terminated polydialkylsiloxanes. In a further aspect of the present invention, there is provided an immunogenic composition formulated for mucosal or parenteral administration, comprising the particulate carrier containing an immunogenic material and a physiologically-acceptable carrier therefor. In an additional aspect, there is provided a method of producing an immune response in a host, comprising the administration thereto, generally by mucosal or parenteral administration, the immunogenic composition provided herein. The immune response produced may be an antibody response, including local and serum antibody responses. In a further aspect of the present invention, there is provided a method for producing a particulate carrier, which comprises: (a) forming an aqueous composition comprising a dissolved polysaccharide and a dispersed or dissolved proteinaceous material; (b) forming an emulsion in which the aqueous composition is the dispersed phase; (c) forming from the emulsion a particulate carrier comprising a core of said polysaccharide and proteinaceous material having bonded thereto an organometallic polymer; and (d) collecting the particulate carrier so formed. The method may optionally include a step of sonicating the suspension of microspheres to produce a fine suspension before the forming step (c) , so as to control particle size. This procedure enables the proteinaceous material to be incorporated into the icroparticles under temperature conditions which do not denature the proteinaceous material or adversely affect the biological activity thereof. Advantages of the present invention include: (a) ease and safety of microparticle manufacture; (b) biocompatability and safety of the microparticles; (c) improved immunogenicity of antigens presented to cells of the immune system by the microparticles; (d) ease of storage and administration; and (e) fabrication conditions that do not adversely affect the biological activity of proteinaceous or other material. In this application, the term "coated" microparticles is used to define microparticles that have a long chain organometallic polymer bound, bonded or otherwise associated with the core thereof. BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 shows a flow diagram for a process for the production of starch microparticles according to one embodiment of the invention. In this Figure, HSA = human serum albumin, HSV2-lysate/HSA = herpes simplex virus type-2 lysate mixed with human serum albumin, Flu X31/HSA = influenza virus strain X31 mixed with human serum albumin. Figure 2 shows scanning electron microscopy (SEM) analysis of influenza virus strain A-X31 and human serum albumin - containing microparticles that were either (A) coated with the silicone polymer s(triethoxyεilyl)propyl- terminated polydimethysiloxane (TS-PDMS) or (B) were uncoated. The SEM images represent magnification of 2500 diameters. The nominal diameter of the TD-PDMS-coated microparticles was 10 μm and that of uncoated microparticles was 10 μm. Figure 3 showε the diameter distribution of human serum albumin-containing starch microparticles coated with the silicone polymer 3-(triethoxyl) silylpropyl- terminated polydi ethylsiloxane (TS-PDMS) . HSA- containing starch particles (Δ) were fabricated and compared to polyεtyrene microεphere εtandards by flow cytometry ( -■-; 10 μm, 7 μm, 4 μm diameter) . The particles had a mean diameter of 4.18 μm and a standard deviation of plus or minus 3 μm. Figure 4 shows an immunoblot analysis of human serum albumin released from human serum albumin-containing starch microparticles that were either coated with the silicone polymer 3-(triethoxysilyl)propyl-terminated polymethylsiloxane (TS-PDMS) or uncoated following suspension of the microparticles in phosphate buffered saline (PBS). Lane 1 shows 0.5 μg of an HSA standard. Lanes 2 to 4 show HSA released from TS-PDMS coated microparticles incubated in vitro for 30 min, lh and 3h in PBS i vitro and laneε 5 to 7 show HSA released from uncoated microparticles at 30 min. , lh and 3h vitro. Figure 5 shows the anti-HSA IgG serum antibody responεeε following variouε immunization protocolε. Groupε of 6 mice were immunized intraperitoneally (I.P.) on dayε 0, 7 and 14 with 250 μL of PBS, pH 7.4, containing 100 μg of HSA incorporated into TS-PDMS-coated or uncoated starch microparticles. Sera obtained on days 21, 35, 49, 63 and 84 were evaluated for the presence of anti-HSA IgG antibodieε using an enzyme-linked immunosorbent assay (ELISA) . 1 mg of coated or uncoated microparticles contains 50 μg of HSA. Figure 6 showε the percentage of animalε developing an anti-HSA IgG serum antibody responεe following intragaεtric immunization with HSA incorporated into uncoated or TS-PDMS coated microparticles as compared to soluble HSA in free form. Figure 7 shows the anti-HSA IgG serum antibody titres in six mice immunized intragastrically with a 50 μg dose of uncoated or TS-PDMS coated microparticles. Animals were immunized on days 0, 7 and 14 with 0.5 mL of 0.2 M NaHC0 3 containing 50 μg of HSA incorporated into TS-PDMS-coated or uncoated starch microparticles or soluble HSA. Sera obtained on days 21, 35, 49, 63 and 84 were evaluated for the presence of anti-HSA IgG antibodies using an ELISA. 1 mg of coated or uncoated microparticles contains 50 μg of HSA. Figure 8 shows the anti-HSA IgG serum antibody titres in εix mice immunized intragaεtrically with a 75 μg dose of uncoated or TS-PDMS coated microparticles as compared to soluble HSA in free form. Animals were immunized on days 0, 7 and 14 with 0.5 mL of 0.2 M NaHC0 3 containing 75 μg of HSA incorporated into TS-PDMS-coated or uncoated starch microparticles or soluble HSA. Sera obtained on days 21, 35, 49, 63 and 84 were evaluated for the preεence of anti-HSA IgG antibodies using an ELISA. 1 mg of coated or uncoated microparticleε containε 50 μg of HSA. Figure 9 εhowε the anti-HSA IgG and IgA εerum antibody titre in groupε of 15 mice immunized intragaεtrically with 50 ,ug (Panelε A and B) or 10 μg (Panelε C and D) of HSA containing microparticleε. Animalε were immunized on dayε 0, 7, 14 and 70 with HSA incorporated into TS-PD^S-grafted (εolid barε) or ungrafted (hatched barε) microparticleε. Sera obtained on days 35, 49, 63 and 77 were evaluated for the presence anti-HSA IgG (Panels A anό C) or IgA (Panels B and D) using an ELISA. Figure 10 shows the anti-Flu X31 (i.e. influenza virus type A εtrain X31) S_r m an ib dy titreε in mice immunized by the intraperitoneal route with εoluble Flu X31/HSA, Flu X31/HSA mixed with microparticleε coated with TS-PDMS or Flu X31/HSA entrapped in TS-PDMS-coated microparticleε. Figure 11 εhowε the anii-HSA antibody titreε in the εera of mice immunized by the intraperitoneal route with εoluble Flu X31/HSA, Flu X3 /HSA in buffer or mixed with microparticles coated with TS-PDMS or Flu X31/HSA entrapped in TS-PDMS-coated microparticles. Figure 12 εhowε the anti-Flu X31 antibody titreε in the εera of mice immunized by the intranaεal route with εoluble Flu X31/HSA or Flu X31/HSA entrapped in TS-PDMS- coated microparticleε. Figure 13 εhowε the anti-HSA antibody titres in the sera of mice immunized by the intranasal route with soluble Flu X31/HSA or Flu X31/HSA entrapped in TS-PDMS- coated microparticles. Figure 14 and 15 shows, for two different experiments (Expt φl and Expt #2 respectively) , the anti- HSV-2 antibody titres in the sera of mice immunized by the intraperitoneal route with herpes simplex virus type 2 (HSV-2) infected cell lysate adminiεtered in a variety of formε. CT = cholera toxin, UN = uncoated, TK = thymidine kinase. Figure 16 showε the εerum IgG reεponεes in mice immunized intraperitoneally by the 47kDa membrane protein from Haemophilus influenzae (Hin47 MP) in a variety of forms. EL = eluate, SOL = soluble, FCA = Freund's Complete Adjuvant, Ex 1 = experiment 1, Ex 2 = experiment 2. GENERAL DESCRIPTION OF THE INVENTION As noted above, the preεent invention relates to a particulate carrier or microparticle, which is useful for the delivery of biologically-active materials to a vertebrate, generally an animal including humans, including the delivery of antigenε to the immune εyεtem, by mucoεal or parenteral ad iniεtration. The particulate carrier compriεes two components, namely a solid core and an organometallic polymer bonded to the core. The solid core comprises at least two components, namely a polysaccharide and a proteinaceouε material. The polyεaccharide may be one of a wide range of such materials, preferably starch, particularly starch which has been treated as to be "soluble" starch (i.e. a starch which has been treated to provide a εtarch which iε εoluble in water) . However, other polyεaccharide materials may be used, including dextran and cellulose, aε well aε derivatives and mixtures of two or more polyεaccharideε. The particulate carrier may have a particle εize which generally ranges from about 10 nm to about 50 μm and preferably about 1 to about 10 μm for mucosal administration of antigens. The proteinaceous material may be any desired proteinaceous material and may itself have biological activity. Examples of proteinaceouε materialε which may be used are proteins derived from a variety of viruεeε and bacteria including tetanus toxoid, diphtheria toxoid, cholera toxoid and subunitε thereof, pertuεsiε toxoid, viral εubunitε, such as rubella virus proteins El, E2 and C, bacterial subunitε, εuch aε the P41, OεpA and OspB proteins of B. burσdorferi. protein-polysaccharide conjugates, protozoan subunits, such aε T. σondi P30, anticoagulants, venoms, such aε εnake venom, cytokines, such aε interleukinε 4, 5, 6 and 12, interferonε, tumour necroεiε factor, and albuminε, such aε human serum albumin, bovine serum albumin and ovalbumin, as well aε recombinant proteinε, peptideε and lipopeptideε and analogε thereto, including muramyl dipeptide, lipopolyεaccharide and lipid A or analogues of εuch proteinε or of immunologic regionε of εuch proteinε. Where the proteinaceous material has biological activity, an additional biologically-active material may or may not be included in the core. Where the proteinaceouε material lackε biological activity, a material having biological activity may be incorporated into the core, εo that the proteinaceous material actε aε a carrier for the biologically-active material. Both the polyεaccharide and proteinaceous material are required to be present for microparticle formation and organometallic polymer coating. In the absence of one of the components, it has not been posεible to obtain the particulate carrier of the invention. The proportion of the core compriεing proteinaceouε material may vary up to about 33 wt% of the core, generally from about 0.5 wt% to about 10 wt%. Where a biologically-active material iε preεent in the core other than in the form of the proteinaceouε material, εuch material may compriεe from about 0.5 to about 30 wt% of the core, preferably from about 0.5 to about 5.0 wt%. Such biologically-active material may be any member of the various clasεes of known biologically- active materials, including proteins, peptideε, antigens. antibodieε, immunotargeting moleculeε, bacteria, bacterial lyεateε, viruεes, viruε-infected cell lyεateε, antibodieε, carbohydrateε, nucleic acidε, lipidε, glycolipidε, haptenε, pharmacologically-activematerialε, aε well aε combinationε, derivatives and mixtures thereof. Specific examples of such materials include influenza viruεeε, parainfluenza viruεeε, reεpiratory viruses, measleε viruεeε, mumps viruεeε, human immunodeficiency viruεes, polio viruεeε, rubella viruεeε, herpex εi plex viruεeε type 1 and 2, hepatitiε viruεeε typeε A, B and C, yellow fever viruεeε, ε allpox viruεeε, rabieε viruεeε, vaccinia viruses, reo viruses, rhinoviruseε, Coxεackie viruεeε, Echoviruεeε, rotaviruεeε, papilloma viruεeε, paravoviruεes and adenoviruses; E. coli, V. cholera. BCG. C. diphtheria. Y. pestiε. S. tvphi. B. pertuεεiε. S. aureus, S. pneumoniae. S. pyoσenes. S. mutanε, Myocoplasmas, Yeastε, C. tetani. meningococci fN. menincritiε. , Shiσella εpp, Campylobacter εpp, proteuε εpp, Neiεseria gonorrhoea, and Haemoohilus influenzae; aε well aε proteinε obtained from εuch viruses and bacteria. The solid core has an organometallic polymer bonded to thereto. Such organometallic compounds may include linear, branched or crosε-linked εilicones which are bonded at the ends of polymer chains to the core, although the polymer may be bonded to the core at locationε along the length of the chain. Such polyεiloxanes may vary in molecular weight from about 400 up to about 1,000,000 Daltons and preferably from about 700 to about 60,000 Daltons. A variety of polyεiloxaneε may be employed. For the purpose of bonding the polyεiloxane to the εolid core, the polyεiloxanes preferably are derived from functionalized materials which have functional groups at the endε of the polymer chain which facilitate bonding the endε of the polyεiloxane chain to the solid core. Preferably, however, where such functional groups are present, they are joined to the polyεiloxane chain through end-blocking groupε. Suitable functionalized εiliconeε uεeful for forming the productε of the invention include (trialkoxyεilyl) alky1-terminated polydialkylsiloxanes and trialkoxysilylterminated polydialkylsiloxanes. One uεeful member of thiε group of compoundε iε 3- (triethoxyεilyl) propyl-ter inated polydimethylεiloxane (herein abbreviated aε TS-PDMS) . The organometallic polymer iε preεent in the particulate carrier in relatively minor amountε, generally from about 0.5 to about 5 wt% of the εolid core. The presence of the organometallic polymer, particularly a silicone, bonded to the solid core enables biologically-active materials to be adminiεtered to a hoεt, particularly by mucoεal adminiεtration, to achieve an enhanced biological response to such material, for example, an enhanced immune response to an antigen, in comparison to delivery of the material by the same particulate material without the organometallic polymer bonded thereto, as seen from the data presented herein. The particulate carrier provided herein may be formed in any convenient manner permitting coated particle formation. One preferred procedure is described below with reference to Figure 1. DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to Figure 1, there is shown a method for preparing starch microparticles according to one embodiment of the present invention. Antigen-containing starch microparticles are manufactured by mixing starch and the antigen in solventε, forming an emulεion in oil, and then dispersing the emulsion into an acetone solution with vigorous stirring and collecting the particles formed. The starch or other polysaccharide first is disεolved in a εolvent εuitable for the polysaccharide. For εtarch, dimethylsulfoxide is a preferred solvent, in which starch, for example, "soluble" starch, is diεεolved at a elevated temperature, for example, a temperature of about 50 * to about 100 * C, preferably about 75 * to about 90 ° C and then cooled to a lower temperature, particularly to a temperature below about 35 * C, without precipitating therefrom. Alternative polar εolventε which may be uεed aε εolvents for the starch, including dimethylformamide as well aε various alcoholε. The εtarch solution is mixed with an aqueous εolution and/or dispersion of a proteinaceous material, in the illustrated embodiment, human serum albumin (HSA) , which may be used alone aε an antigen or combined with other antigenic material, for example, a herpeε εimplex viruε type 2 (HSV-2) infected cell lysate or a whole influenza strain X31 (Flu X31) , in which event the HSA acts also as a carrier protein. Mixing of the εtarch εolution and antigen compoεition generally produces by stirring, a highly viscouε mixture, which then is added dropwise into vegetable oil, or other water-immiscible fluid which is capable of forming a water-in-oil emulsion, including silicone oils or derivatives thereof or mixtures thereof, with vigorous stirring to promote the formation of a water-in-oil emulsion, in which droplets of the starch- proteinaceous material composition are diεperεed in the vegetable oil. This step of the process, therefore, involves forming an emulsion in which the aqueous compoεition iε the diεperεed phaεe. The particle size of the liquid droplets, which determineε the εize of the ultimate carrier microparticleε, iε determined by the volumetric ratio of aqueouε phaεe to oil phaεe, by the degree of εtirring of the water-in-oil emulεion and may further be controlled by εonication. Additional control of particle εize may be achieved by employing a surfactant in the oil, such as non-ionic surfactantε of the TWEEN or SPAN type. The water-in-oil emulεion then may be added dropwiεe to a εolvent for the oil and aqueous medium containing the εtarch, proteinaceous material and antigen, to result in microparticle formation. In the procedure of the present invention, the solvent alεo containε a εilicone polymer material which can bond to the εolid core produced by the εolvent. Alternatively, εo e or all the εilicone oil can be included in the vegetable oil or εilicone oil can replace all or part of the vegetable oil. (Figure 1 also illuεtrateε an alternative procedure, employed in the Exampleε below to produce particulate carrier lacking the εilicone polymer, for comparative experimentation.) The εolvent which may be employed for εuch deεiccation and oil diεεolution may be any organic εolvent iεcible with the oil and water phaεeε of the emulεion and in which the starch and proteinaceouε material are εubεtantially inεoluble. Such εolventε include but are not limited to ketoneε, εuch as acetone and methyl ethyl ketone. The silicone polymer disεolved in the solvent may be a functionalized polysiloxane, particularly end- functionalized, to permit bonding of the polyεiloxane to the εolid core of the particulate material. Such functionalized polysiloxane may include 3- (trialkoxyεilyl) alkyl-terminated polydialkylεiloxaneε, particularly 3-triethoxyεilyl) propyl-ter inated polydimethylpolyεiloxane (TS-PDMS) . The resulting particulate material may be harvested from the residual medium by any convenient meanε, including centrifugation, εeparated and dried. The particulate material reεulting from thiε procedure then iε in a εuitable form for formulation for adminiεtration of the biologically-active material. It iε clearly apparent to one εkilled in the art, that the variouε e bodimentε of the preεent invention have many applicationε in the fieldε of medicine and in particular vaccination, diagnoεiε and treatment of infectionε with pathogenε including bacteria and viruεeε. A further non-limiting discuεεion of such uεeε iε further presented below. Vaccine Preparation and Use In an embodiment, immunogenic compositionε, εuitable to be uεed aε, for example, vaccineε, may be prepared from microparticles as disclosed herein. The immunogenic composition elicits an immune response by the host to which it is administered including the production of antibodies by the host. The immunogenic composition may be prepared aε injectableε, aε liquid solutions or emulsionε. The microparticleε may be mixed with phyεiologically acceptable carrierε which are compatible with the microparticleε. Theεe may include, water, εaline, dextroεe, glycerol, ethanol and combinationε thereof. The vaccine may further contain auxiliary εubstances such as wetting or emulεifying agentε, pH buffering agentε, or adjuvants to further enhance the effectiveness of the vaccines. Vaccines may be administered by injection subcutaneously or intramuscularly. Alternatively, and in a preferred embodiment, the immunogenic compoεitionε compriεingmicroparticleε formed according to the preεent invention, may be delivered in a manner to evoke an immune response at mucosal εurfaceε. Thuε, the immunogenic compoεition may be adminiεtered to mucoεal εurfaceε by, for example, the naεal or oral (intragaεtric) routeε. Alternatively, other modes of administration including suppositories may be desirable. For suppoεitorieε, binderε and carrierε may include, for example, polyalkylene glycolε and triglycerideε. Oral formulations may include normally employed incipients, εuch aε pharmaceutical grades of saccharin, cellulose and magnesium carbonate. These compositionε may take the form of solutions, suspensions, tablets, pills, capεuleε, εuεtained releaεe formulationε or powderε and contain 1 to 95% of the microparticles of the present invention. In order to protect the microparticles and the material having biological activity contained within the core of the microparticle, from gastric acidity when administered by the oral route, an acidic neutralizing preparation (such as a sodium bicarbonate preparation) is advantageously administered before, concomitant with or directly after administration. The vaccines are adminiεtered in a manner compatible with the doεage formulation, and in εuch amount aε to be therapeutically effective, protective and immunogenic. the quantity to be adminiεtered depends on the subject to be treated, including, for example, the capacity of the subject's immune system to syntheεize antibodies, and if needed, to produce a cell-mediated immune responεe. Preciεe amountε of microparticle and material having biological activity required to be adminiεtered depend on the judgement of the practitioner. However, suitable dosage rangeε are readily determinable by one skilled in the art and may be of the order of micrograms to milligrams. Suitable regimes for initial administration and booster doses are also variable, but may include an initial administration followed by subεequent ad iniεtrationε. The dosage of the vaccine may also depend on the route of administration and will vary according to the εize of the hoεt. EXAMPLES The above disclosure generally describes the present invention. A more complete understanding can be obtained by reference to the following specific Examples. These Exampleε are deεcribed εolely for purpoεes of illustration and are not intended to limit the scope of the invention. Changes in form and εubεtitution of equivalentε are contemplated as circumstanceε may εuggeεt or render expedient. Although εpecific termε have been employed herein, εuch termε are intended in a deεcriptive sense and not for purposes of limitations. Example 1 This Example describeε the production of antigen- containing εtarch microparticles. A flow diagram summariεing the proceεs of starch microparticle production effected herein is shown in Figure 1. Antigen-containing starch microparticleε were manufactured by mixing εtarch and the antigen in εolventε, forming an emulεion in oil, and then diεpersing the emulsion into an acetone εolution with vigorouε stirring and collecting the particles formed. Starch microparticles were separately manufactured containing the antigens, human serum albumin (HSA) , tetanus toxoid (TT) , ovalbumin (OVA), Hin47, herpes simplex virus type 2 (HSV-2) - infected cell lysate and whole influenza virus. To form the tetanuε toxoid, Hin47, HSV-2 and influenza viruε-containing εtarch microparticles, HSA was included aε a "filler" protein. Specifically, 1 g of soluble potato starch was added to 2 L of dimethylsulfoxide (DMSO) while stirring the mixture. The starch was diεεolved by heating the mixture to 85 * C for 5 minuteε. The following amountε (Table 1) of antigen were prepared to form the antigen-containing microparticleε indicated: TABLE 1 When the εtarch solution had cooled to a temperature of lesε than 37 * C, the antigen preparation indicated above waε added to the cooled εolution and the mixture εtirred (500 rpm) at room for 20 minuteε to form a highly viεcouε mixture. This viscous mixture was added dropwiεe to 30.0 mL of vegetable oil and εtirred vigorouεly (1500 rpm) for 15 minutes at room temperature to produce a water-in-oil emulsion. This water-in-oil emulsion was sonicated on ice for 60 seconds with stirring. The emulsion was then added dropwise with stirring (1000 rpm) to 400 mL of acetone containing 0.125% v/v Tween 80. The resultant particleε, of approximately 4.18 ±3μ were collected by centrifugation, (200 xg, 5 minuteε) , waεhed twice with acetone and dried by expoεure to air at room temperature for 48 hourε. Example 2 Thiε Example deεcribeε the coating of antigen- containing εtarch microparticleε. The microparticleε formed in Example 1 may be coated with a variety of εilicones via bonded interactions at the surface including polydimethylsiloxaneε (PDMS) with different molecular weights and varied end blocks. A convenient end-functionalized silicone was 3- (triethoxyεilyl)propyl-terminated polydimethylεiloxane (abbreviated to TS-PDMS) . The TS-PDMS waε εyntheεiεed by the hydroεilylative addition of hydrogen-terminated PDMS to allyltriethoxyεilane under the catalyεiε of H 2 PtCl 6 aε followε. To a mixture of 17.0 mL hydrogen-terminated PDMS (Hiilε, PDMS H , viscosity 1,000 cs) and 0.8 mL allyltriethoxyεilane (Aldrich) (molar ratio of the functional groupε PDMS H : H 2 C=CH 1:3) waε added 0.05 mL of a 0.1 M hydrogen hexachloroplatinate(IV) hydrate εolution (H 2 PtCl 6 ) in i-propanol (Caledon) with εtirring under the protection of nitrogen at 0°C. The εolution waε allowed to return to room temperature overnight. The i-propanol and unreacted allyltriethoxyεilane were evaporated under reduced preεεure and elevated temperature up to 140 * C for 6 hourε until gaε ceaεed to bubble from the viεcouε fluid. The reεidue waε εubjected to further waεhing with diεtilled water four timeε to remove any impuritieε. The product waε characterized by 'H NMR, w Si NMR, GPC and IR. The reaction involved iε illuεtrated by the following equation: where n iε the number of εiloxane groupε. The uεe of an end-functionalized εilicone resulted in the formation of chemical bonds to the εtarch surface. To produce particles coated with TS-PDMS and having antigens entrapped within them, the sonicated water-in- oil emulsion produced by the procedure described above in Example 1 was added dropwiεe with εtirring (1000 rpm) to 400 mL of acetone containing 0.125% v/v TS-PDMS (1,000 c.ε.) in place of the Tween 80. The reεulting coated particleε were harveεted and dried aε described in Example 1. Example 3 This Example describeε an analysiε of the antigen- containing εtarch microparticleε. Size diεtributionε of the antigen-containing εtarch microparticleε prepared aε deεcribed in Exampleε 1 and 2 were obtained by εcanning electron microεcopy and flow cytometry uεing polyεtyrene microparticle standards. Figure 2 showε a εcanning electron microεcope analyεiε of HSA-containing microparticleε that were either coated with TS-PDMS or were uncoated. The microparticleε ranged in εize from 1 to 100 μm and had a mean diameter of 4 to 5 μm as determined by flow cytometry (Figure 3). The efficiency of antigen incorporation into starch microparticles was between 70 and 90%. The antigen content of HSA-loaded microparticles (termed herein "core loading") waε determined by incorporating an 125 I-HSA tracer of known specific activity in the antigen preparation prior to microparticle formation. Protein core loading of HSA in starch microparticles was found to be about 5 to 6% by weight. The core loading of TT in the microparticle waε eliminated by ELISA to be 0.34% w/w with a total protein core loading of 14.1% w/w. The core loading of OVA in the microparticleε waε eεtimated to be 7.75% w/w uεing a spectrophotometer at an O.D. 2g0 . The core loading of Hin47 in the microparticle was estimated by ELISA to be 0.03% w/w with a total protein core loading of 14% w/w. "Core-loading" of microparticles containing whole influenza viruε waε thuε eεtimated by the releaεe of viruε by degradation of the microparticleε by acid hydrolyεiε with HC1 or enzymatic hydrolysis with human saliva. Enzymatic hydrolysis of microparticles with human saliva was originally the preferred method as it was not anticipated to appreciably alter the antigenic integrity of the viral proteinε. Microparticleε were digeεted with 250 μL of centrifugally clarified saliva overnight at 37 ° C. Suεpensions were centrifuged at 5000 xg for 10 minuteε and the εupernatantε diluted 1:10 with Triε Baεe buffered εaline (TBS, pH 7.2) containing 0.1% NaN 3 and εtored at 4 ° C until analyzed by SDS-PAGE. "Core-loading" was determined by acid-hydrolysiε of the microparticleε. Thus, microparticles were incubated in 0.1 M HC1 for 24 hours at 37 * C. Supernatants were clarified by centrifugatic at 3000 rpm and filtered through a 0.45 μ filter. The solution was neutralized with 1 M NaOH. Protein r<-ϊleaεed from acid hydrolyεed microparticleε were detected uεing an ELISA. The Flu X31/HSA microparticleε were eεtimated to contain about 0.3 to 0.5% of Flu X31 and about 5 to 6% of HSA (w/w) . Although HSA ι__ay be incorporated into the microparticleε preferentially to Flu X31, attemptε to fabricate coated micropart.icleε without protein were unsuccessful. Example 4 This Example describes the effects upon antigens of their entrapment in starch microparticles. The time courεe εampleε from the antigen releaεe εtudieε deεcribed for HSA containing microparticleε deεcribed in Example 3 were alεo analyzed by Weεtern (immunoblot) analysis using an HSA-specific polyclonal antiseru . For immunodetection analysiε of releaεed HSA, the gel waε equilibrated in tranεfer buffer (0.2 M glycine, 15% methanol, 0.025 M Triε Baεe, pH 8.3) for 15 minutes along with nitrocelluloεe (NC) membraneε and filter paper, both of which were cut to the εame εize as the gel. The immunoblot apparatus was then placed in the transblot device and electrophoretic tranεfer waε performed overnight at 30 voltε. After tranεfer, the NC membrane waε incubated with agitation in 100 mL of blocking buffer (5% w/v skim milk powder in PBS) for 2 hourε. The NC membrane was then incubated with 100 mL of a 1:500 dilution of alkaline phosphatase-conjugated goat anti-HSA in blocking buffer for 2 hourε at room temperature, on a tilting platform. The NC membrane waε washed 3 times (10 minutes each) with PBS, and proteins were visualized by incubating the membrane with 30 mL of developing buffer (100 mM Tris Baεe, 100 mM NaCl, 5 mM MgCl 2 , pH 9.5) containing 200 μL of 50 mg/mL nitroblue tetrazolium and 100 μL of 50 mg/mL 5-bromo-4-chloro-3- indolylphoεphate for 60 minutes. The membrane was rinsed 3 times with H 2 0 and air dried. The resultε of the immunoblot analyεiε are εhown in Figure 4. Thiε analysis showed that HSA released into the supernatants by HC1 treatment or incubation of the microparticles in PBS was detectable by an HSA-specific polyclonal antiεerum. The releaεed HSA from uncoated and TS-PDMS coated microparticleε, waε not fragmented by the fabrication proceεε. and waε not altered in εuch a way aε to preclude itε detection by HSA-εpecific antibodieε. Example 5 This Example describes the immunogenicity of HSA entrapped in microparticles in mice immunised intraperitonea1ly. To examine the immunogenicity of HSA entrapped in starch microparticles formed in accordance with the preεent invention, groupε of six, 6 to 8 week old female BALB/c mice (Charles River Breeding Laboratories, Wilmington, MA) were immunized intraperitoneally (IP) with the following amounts of antigen in 250 μL of PBS (pH 7.4) on days 0, 7 and 14: 2 mg of TS-PDMS coated microparticles prepared as described in Examples 1 and 2 containing 100 μg of HSA; and 2 mg of uncoated microparticles containing 100 μg of HSA. The mice showed no grosε pathologieε or behaviourial changeε after receiving either uncoated or TS-PDMS coated microparticleε. Sera were obtained on dayε +21, +35, +49, +63 and +84 and were evaluated for the preεence of anti-HSA IgG antibodies by antigen specific ELISA. All sampleε were analyzed in duplicate. Microtiter plate wellε were incubated overnight at 4 * C with 100 μL of 10 μg/mL HSA in TBS. The plates were washed with Tris-T buffer (0.05% Tween 20 in 0.02 M Triε Base, pH 7.4, containing 0.15 M NaCl and 0.005 M KC1) . Wells were incubated with 200 μL of 0.1% gelatin in 0.02 M Tris- buffered saline (TBS), pH 7.4 (operationally defined as blocking buffer) . After waεhing with Triε-T, the plateε were incubated for 2 h at 37 ° C with 100 μL of εample εerially diluted in blocking buffer. Wellε were washed with Tris-T and 100 μL of alkaline phosphataεe-conjugated goat anti-mouεe IgG in blocking buffer, were added to each well. After 2 hourε incubation at 37 * C, the wellε were waεhed with Tris-T and 100 μL of 1.0 M diethanolamine buffer, pH 9.8, containing 0.05 M MgCl 2 and 1.0 mg/mL of p-nitrophenylphosphate were added to each well. After 30 minuteε incubation at room temperature, the optical density of the fluid in each well waε determined at 405 nm using a icroplate reader. A normal mouse sera pool was used to establish baseline optical density values in the assay. Hyperimmune mouse HSA antiserum waε used as a positive control. The serum antibody titreε following immunization are shown in Figure 5. The resultε of immunizationε with a convenient test antigen (HSA) indicate that antigen preεented to the immune εyεtem entrapped in TS-PDMS εtarch microparticleε is substantially more immunogenic than soluble antigen or antigen entrapped in uncoated starch microparticles. Example 6 This Example deεcribeε the immunogenicity of HSA entrapped in starch microparticles in mice immunized by the intragaεtric route. To examine the immunogenicity of HSA entrapped in εtarch microparticleε formed in accordance with the preεent invention, groupε of εix, 6 to 8 week old female BALB/c mice, were immunized by the intragaεtric route (IG) with HSA-containing microparticleε, prepared aε deεcribed in Exampleε 1 (uncoated) and 2 (coated) above, (Table II) on days 0 +7 and +14: TABLE GrouD: Microparticle ' Tv e: mσ Darticle: μσ HSA A TS-PDMS coated 15 750 B TS-PDMS coated 10 500 C TS-PDMS coated 3 150 D TS-PDMS coated 1.5 75 B TS-PDMS coated 1 50 F uncoated 15 750 G uncoated 10 500 H uncoated 3 150 I uncoated 1.5 75 J uncoated 1 50 K none 0 0 N none - - 0 none - 750 P none - 500 Q none - 150 R none - 75 S none - 50 1 mg of TS-PDMS coated microparticle contains 50 μg of HSA. Sera were examined for the presence of HSA-specific antibodieε on days +21, +35 and +49. Sera and intestinal washes were examined for the presence of HSA-specific antibodies. To detect and quantify anti-HSA slgA in the inteεtinal lumen, mice were εacrificed by cervical dislocation, their small intestineε removed and examined for the preεence of antigen-specific antibodies. Individual small intestines were detached from the pyloric sphincter to the caecum and everted over capillary tubeε. The everted inteεtines were incubated in 5 mL of ice cold enzyme inhibitor solution (0.15 M NaCl, 0.01 M Na 2 HP0 4 , 0.005 M EDTA, 0.002 M PMSF, 0.05 U/mL Aprotinin, and 0.02% v/v NaN 3 ) for 4 hours. Intestines were removed and the εupernatantε clarified by centrifugation (1000 xg, 20 minutes) and stored at 0 ° C until assayed. Anti-HSA slgA titres in samples were determined by HSA-specific ELISA as described above but a goat anti-mouse IgA antiserum waε uεed in place of the goat anti-mouse IgG antiεerum. The percentage of mice immunologically responding to the intragastric immunization iε εhown in Figure 6. These results show that a much higher proportion of animals immunologically respond to the test antigen (HSA) when delivered using PDMS-coated microparticles compared to uncoated microparticles at phyεiologically relevant doses, for example, 75 μg or lesε. The εerum IgG HSA-εpecific antibody titres following IG immunization are shown in Figures 7 (50 μg of HSA) and 8 (75 μg of HSA) . Theεe reεults indicate that a test antigen (HSA) incorporated into PDMS-coated microparticles iε substantially more immunogenic than antigen incorporated into uncoated particles when delivered by the intragastric route. Example 7 The procedure of Example 6 waε repeated with groupε of 15 mice being immunized intragaεtrically with 50 μg and 10 μg of aminoencapεulated HSA, prepared as described in Example 1 (uncoated) and Example 2 (coated) above. Animals were immunized on days 0, 7, 14 and 70 with the HSA-containing microcapsules (MP) . Sera was examined for the presence of HSA-specific antibodies on dayε 35, 49, 63 and 77. The reεultε for IgG (Panelε A and C) and IgA (Panelε B and D) responses are given in Figure 4. Figure 4 showε that, at variouε timeε after tertiary IG immunization, anti-HSA IgG εera titreε induced by IG adminiεtration of 50 μg (Panelε A and B) or 10 μg (Panel C) of HSA-containing TS-PDMS-grafted MP (εolid barε) were significantly higher when compared to IgG responseε elicited following immunization with ungrafted MP (hatched barε) (p<0.005). Sera IgG induced by IG immunization were almost excluεively IgG, with very little IgG or IgGa, and no IgG 3 antibodieε. Further, IG adminiεtration of 50 μg (Panel B) or 10 μg (Panel D) of HSA in TS-PDMS-grafted MP, εtimulated εtronger anti-HSA εera IgA responses, with sera IgA responseε being significantly higher when animals were immunized with 50 μg of HSA-containing ungrafted MP (P<0.001). At all ti eε, animalε immunized IG with εoluble HSA failed to produce any detectable anti-HSA εera IgG or IgA. Following an IG boost on day 70, anti-HSA sera IgG titres induced with 50 μg of HSA contained in TS-PDMS- grafted MP were εignificantly enhanced over pre-boost titreε (P<0.001) . Theεe results demonstrate the efficacy of IG immunization with TS-PDMS MP in stimulating vigorouε circulating antibody response. In contrast to the failure of soluble HSA to provoke an appreciable IgA response in intestinal secretions when administered IG, the delivery of equal amounts of HSA entrapped in TS-PDMS-grafted or ungrafted MP resulted in HSA-specific IgA responεeε in gut secretions (P<0.001). Example 8 This Example describes the immunogenicity of herpes simplex type 2 virus (HSV-2) antigenε entrapped in microparticleε in mice immunized by the intraperitoneal and intragaεtric routeε. To examine the εtimulation of virus-specific immune responseε by viral antigenε entrapped in microparticles, mice were immunized IP and IG with HSV-2 infected cell lysates entrapped within TS-PDMS coated microparticles containing HSA aε a carrier protein. Groupε of 5, 6-8 week old female BALB/c mice were immunized by the intraperitoneal (IP) and intragastric (IG) routeε with the following materials on dayε 0, +7 and +14: 1. 125 μg of HSV-2 infected cell lyεate protein in 250 μL of PBS (IP) or 500 μL of NaHC0 3 (IG) . 2. 16 mg of TS-PDMS coated microparticleε containing about 125 , μg of HSV-2 infected cell lyεate. 3. 8 mg of TS-PDMS coated microparticles containing about 63 μg of HSV-2 infected cell lysate protein. Sera were examined for the presence of HSV-2 specific IgG antibodies and demonεtrated that viral proteinε may be entrapped within TS-PDMS coated εtarch microparticleε without reduction in immunogenicity. Example 9 Thiε Example deεcribeε the immunogenicity of whole influenza viruε entrapped in microparticleε in mice immunized IP. To examine the immunogenicity of Flu X31/HSA TS-PDMS coated microparticleε, prepared aε deεcribed in Example 2, groups of six Balb/c mice were immunized by intraperitoneal (IP) route with the following materials: 1. 5 μg of Flu X31 and 15 μg of HSA in soluble form. 2. 5 μg of Flu X31 and 15 μg of HSA mixed with TS- PDMS coated microparticles. 3. Flu X31/HSA TS-PDMS coated microparticles containing 5 μg of Flu X31 and 15 μg of HSA. The mice received a single immunization IP on day 0 and were bled at days +20 and +35. The sera obtained were asεayed for anti-Flu X31 and anti-HSA IgG antibodieε by antigen-εpecific ELISA. The anti-Flu X31 ELISA waε performed aε deεcribed above but the plates were coated overnight at 4 * C with 100 μL of whole influenza virus at 5 μg per mL in place of the HSA and an anti-Flu antibody was used as a positive control. These antibody titres are shown in Figures 10 and 11 for Flu X31 and HSA immunized mice respectively. As described in Example 5 above, HSA alone or HSA mixed with TS-PDMS coated microparticles were poorly immunogenic. In contrast, HSA entrapped in TS-PDMS coated microparticles elicited high antibody titres. Mice immunized IP with all three preparations εhowed εimilar εerum IgG anti-Flu X31 antibody reεponses on day +20. At day +35 the IgG anti-Flu X31 antibody titre in the serum of mice immunized IP with Flu X31/HSA incorporated in TS-PDMS coated microparticles waε about 10-fold greater than the titreε obtained following immunization with εoluble Flu X31 or Flu X31 mixed with TS-PDMS coated microparticleε. The studies presented in this Example demonstrate that viral antigens from influenza virus can be made more immunogenic and elicit high levels of serum IgG antibodieε, when the antigens are entrapped in microparticles formed in accordance with the present invention. Example 10 This Example describes the immunogenicity of whole influenza virus entrapped in microparticleε in mice immunized IN. To examine the immunogenicity of Flu X31/HSA TS-PDMS coated microparticleε, prepared as described in Example 2, groups of six Balb/c mice were immunized by the intranasal (IN) route with the following materials: 1. 10 μg of Flu X31 and 30 μg of HSA in εoluble form. 2. Flu X31/HSA TS-PDMS coated microparticleε containing 10 μg of Flu X31 and 30 μg of HSA. Mice were immunized IN on dayε 0 +7 and +14 and bled on dayε +20 and +35. The sera obtained were assayed for anti-Flu X31 and anti-HSA IgG antibodies by antigen- specific ELISA as described above. These εerum antibody titreε are εhown in Figureε 12 and 13 for HSA and Flu X31 reεpectively. Mice immunized IN with εoluble antigen had undetectable levels of HSA-specific serum IgG antibodies. Mice immunized with Flu X31/HSA TS-PDMS coated microparticleε εhowed a εerum anti-HSA antibody response. The anti-Flu X31 antibody titres in mice immunized IN are shown in Figure 13 and show that the highest titres were obtained following immunization with Flu X31/HSA TS-PDMS coated microparticles. The reεultε of the IN immunizationε deεcribed in thiε Example εhow that the immunogenicity of an antigen (HSA) and a mixture of influenza viruε antigens can be enhanced by entrapment in microparticles formed in accordance with the present invention. In particular, the normally non-immunogenic antigen HSA following incorporation into microparticles waε made immunogenic. Example 11 Thiε Example deεcribeε the immunogenicity of HSV-2 entrapped in microparticleε in mice immunized intragastrically (IG) . TS-PDMS-grafted (CT) or ungrafted (UN) microparticles (MP) were fabricated to contain HSV-2- infected VERO cell lyεate and HSA, aε deεcribed in Examples 1 and 2. In a first set of experimentε, using the core loading data as determined in Example 2, groupε of 10 mice each were immunized intragaεtrically (IG) on days 0, 7, 14 and 77 with 25 μg of HSV-2 infected cell lysate entrapped in grafted or ungrafted MP (CT HSV-2 MP and UN HSV-2 MP respectively) , 25 μg of HSV-2 infected cell lysate εuεpended in buffer (Soluble HSV-2) or buffer alone (Buffer) . Mice were bled on day 77 via the retroorbital plexuε and their sera asεayed for the preεence of HSV-2 εpecific IgG. The reεultε obtained are expresεed aε reciprocal end-point titreε and illuεtrated in Figure 14. ("Expt. l") . Aε may be εeen in thiε Figure, HSV-2-infected cell lyεate entrapped in CT MP waε εignificantly more proficient at εtimulating HSV-2-εpecific IgG antibodieε than HSV-2-entrapped UN MP or εoluble HSV-2. In a εecond εet of experimentε, groupε of 10 mice were immunized intraperitoneally (IP) on dayε 0, 7 and 14 with one of the following preparationε: - 5 μg of HSV-2-infected cell lysate entrapped in CT MP (CT HSV-2 MP) 5 μg of εoluble HSV-2 dissolved in buffer (Soluble HSV-2) 5 μg soluble HSV-2 disεolved in buffer and mixed with HSA-containing CT MP (Sol. HSV-2 + MP) 1 x 10 s , plaque-forming unitε (PFU) of ΔTKΗSV-2 (an attenuated, non-lethal HSV-2 mutant which iε highly immunogenic) (TKΗSV-2) 1 x 10 5 PFU ΔTKΗSV-2 mixed with HSA-containing CT MP (TK-HSV-2 + MP) . On day 21, the mice were bled and their εera assayed for HSV-2-specific IgG antibodieε. The reεults obtained are expressed as reciprocal end-point titres and illustrated in Figure 15 ("Expt. 2"). As may be εeen from theεe reεultε, CT HSV-2 MP elicited the εtrongeεt HSV-2-εpecific IgG antibody reεponses, higher than stimulated by the "gold standard", ΔTKΗSV-2. Mixing HSA CT MP and either ΔT HSV-2 or soluble HSV-2 neither enhanced nor diminished the observed antibody response, demonstrating that the i munopotentiating effect of encapsulated HSV-2 required entrapment of antigen inside particles. Example 12 This Example deεcribeε the immunogenicity of Hin47 entrapped in microparticles in mice immunized intraperitoneally (IP) . Microparticles containing Hin47 antigen were prepared as described in Example 2. Using the Hin47 core loading data aε determined in Example 2, groupε of 6 to 10 mice were given intraperitoneal injectionε of 3 μg per mouse on days 0 , 7 and 1 . Mice were bled via the retrobital plexuε on day 5 and their sera waε aεεayed for anti-Hin47 IgG. The results obtained are εhown in Figure 13. Aε may be seen in Figure 16, soluble (3 μg) Hin47 in buffer (Hin47 sol) elicited IgG responses of approximately 1000 units- Hin47 (3 μg) in conjunction with FCA produced IgG responses of approximately 18,000 units. By comparison, Hin47 in silicone-grafted microparticles (Hin47 MP Ex l and Hin47 MP Ex. 2) elicited responses of about 15,000 units, i.e. about 84% of that noted with FCA. In another experiment, the Hin47 microparticles were extracted with buffer in vitro for 18 hourε at 37°C, clarified by centrifugaticn and filtration and 3 μg of Hin47 contained in the extract waε administered IP. As seen in Figure 16, thiε preparation (Hin47 MP EL) elicited IgG responseε of approximately 9,000 unitε. SUMMARY OF THE DISCLOSURE In εummary of thiε disclosure, the present invention provideε a particulate carrier for an agent, particularly one having biological activity, compriεing a core of polyεaccharide and proteinaceouε material and an organometallic polymer bonded to the core. The particulate carriers in the form of microparticles are able to efficiently deliver agents to the cellε of the immune system of a subject following mucosal or parenteral administration to produce an immune response. Modifications are poεεible within the scope of this invention.

Claims: CLAIMS What we claim is: 1. A particulate carrier, which compriseε: a εolid core compriεing a polyεaccharide and a proteinaceouε material, and an organometallic polymer bonded to the core. 2. The particulate carrier of claim 1 wherein the polyεaccharide iε selected from the group consisting of dextran, starch, cellulose, derivatives and mixtureε thereof. 3. The particulate carrier of claim 1 wherein the polysaccharide is a soluble starch. 4. The particulate carrier of claim 2 wherein the proteinaceous material is a material having biological activity. 5. The particulate carrier of claim 1 wherein said core contains a material having biological activity. 6. The particulate carrier of claim 5 wherein the material having biological activity iε εelected from the group conεisting of proteins, peptideε, antigenε, bacteria, bacterial lysates, viruseε, virus-infected cell lysateε, antibodieε, carbohydrateε, nucleic acids, lipids, glycolipidε haptens, pharmacologically-active materials, and combinations, derivatives and mixtures thereof. 7. The particulate carrier of claim 4 or 5 wherein the material having biological activity iε immunogenic. 8. The particulate carrier of claim 4 or 5 wherein the material having biological activity compriεeε human serum albumin, herpes simplex virus type 2 - infected cell lysate, an influenza virus, or an influenza viral protein. 9. The particulate carrier of claim 1 wherein the organometallic polymer is derived from a functionalized εilicone. 10. The particulate carrier of claim 9 wherein the functionalized silicone compriseε an end-εubεtituted εilicone. 11. The particulate carrier of claim 10 wherein the end- εubεtituted εilicone iε (trialkoxyεilyl)alkyl-terminated polydialkylεiloxane. 12. The particulate carrier of claim 11 wherein the end- εubεtituted εilicone iε 3-(triethoxyεilyl)propyl- terminated polydimethylεiloxane. 13. The particulate carrier of claim 12 wherein εaid εilicone haε a molecular weight of from about 400 to about 1,000,000 Daltonε. 14. A particulate carrier, which compriεeε: a εolid core having a particle εize of about 10 nm to about 50 μm compriεing a polyεaccharide and up to about 33 wt% of a proteinaceouε material, and an organometallic polymer in an amount of about 0.5 to about 5 wt% of εaid core bonded to the core. 15. The particulate carrier of claim 14 wherein εaid proteinaceouε material compriεeε from about 0.5 to about 10 wt% of εaid core. 16. The particulate carrier of claim 14 wherein εaid core further compriεeε about 0.5 to about 30 wt% of a biologically-active material. 17. The particulate carrier of claim 16 wherein εaid biologically-active material compriεes about 0.5 to about 5.0 wt%. 18. The particulate carrier of claim 15 wherein said organometallic polymer compriseε a polysiloxane having a molecular weight of from about 400 to 1,000,000 Daltons. 19. The particulate carrier of claim 18, wherein εaid polysiloxane has a molecular weight of from about 700 to about 60,000 Daltonε. 20. The particulate carrier of claim 14 which haε a particle εize of about 1 to about 10 μm. 21. A method for producing a particulate carrier, which compriseε: (a) forming an aqueouε compoεition compriεing a diεεolved polyεaccharide and a dispersed or dissolved proteinaceous material; (b) forming an emulsion in which the aqueous compoεition iε the diεperεed phaεe; (c) forming from εaid emulsion a particulate carrier comprising a core of said polysaccharide and proteinaceous material having bonded thereto an organometallic polymer; and (d) collecting the particulate carrier so formed. 22. The method of claim 21 wherein said aqueous composition iε formed by dissolving said polysaccharide in a polar solvent therefor to form a solution thereof, disεolving or diεperεing εaid proteinaceous material in an aqueous solvent therefor to form a solution or disperεion thereof, and mixing the resulting media. 23. The method of claim 22 wherein εaid polyεaccharide iε εtarch and εaid εolvent for said starch iε dimethylεulfoxide. 24. The method of claim 22 wherein εaid emulεion iε formed by diεperεing εaid aqueous composition in a water- immiεcible fluid capable of forming a water-in-oil emulεion. 25. The method of claim 24 wherein εaid water-immiεcible fluid compriεeε a vegetable oil. 26. The method of claim 24 wherein εaid oil-in-water emulεion alεo contains a surfactant. 27. The method of claim 24 wherein said particulate carrier iε formed by adding εaid water-in-oil emulεion dropwiεe to a solvent for water and said water-immiscible fluid containing a functionalized organometallic polymer. 28. The method of claim 27 wherein εaid functionalized organometallic polymer compriεeε an end-εubεtituted εilicone. 29. The method of claim 27 wherein said solvent compriseε a ketone. 30. The method of claim 29 wherein εaid ketone iε acetone. 31. The method of claim 21 which iε carried out under conditions which are not conducive to denaturation of said proteinaceous material. 32. An immunogenic composition formulated for mucoεal or parenteral adminiεtration, compriεing the particulate carrier of claim 7 and a phyεiological acceptable carrier therefor. 33. A method of producing an immune reεponεe in a εubject, comprising administering the immunogenic compoεition of claim 32 thereto. 34. The method of claim 33 wherein the composition is adminiεtered by mucosal or parenteral administration. 35. The method of claim 34 wherein the immune response is an antibody reεponεe. 36. The method of claim 35 wherein the antibody response is a local or serum antibody responεe.

Inventors: BROOK MICHAEL A, HERITAGE PHILIPPA L, JIANG JIANXIONG, LOOMES LESLEY M, MCDERMOTT MARK R, UNDERDOWN BRIAN J, BROOK, MICHAEL, A., HERITAGE, PHILIPPA, L., JIANG, JIANXIONG, LOOMES, LESLEY, M., MCDERMOTT, MARK, R., UNDERDOWN, BRIAN, J.
Applicants: BROOK MICHAEL A, HERITAGE PHILIPPA L, JIANG JIANXIONG, LOOMES LESLEY M, MCDERMOTT MARK R, UNDERDOWN BRIAN J, UNIV MCMASTER, BROOK, MICHAEL, A., HERITAGE, PHILIPPA, L., JIANG, JIANXIONG, LOOMES, LESLEY, M., MCDERMOTT, MARK, R., MCMASTER UNIVERSITY, UNDERDOWN, BRIAN, J.
Application year: 1995
Main classification: A61K9
IPC codes: A61K9, A61K39, C07K17, C12N11