Patent Publication Number: US-2010112078-A1

Title: Polymer particles based vaccine

Description:
RELATED APPLICATION 
     This application is a continuation-in-part of International patent application Ser. No. PCT/IN2008/000198, filed Mar. 28, 2008, designating the United States and published in English as WO2008/117313 on Oct. 2, 2008, which claims priority to Indian patent application Ser. No. 678/DEL/2007, filed Mar. 28, 2007. The disclosures of each of the foregoing patent applications are incorporated herein in their entireties by this reference. 
    
    
     FIELD OF INVENTION 
     The present invention provides a vaccine composition comprising polymer particles comprising an effective amount of antigen for inducing humoral and/or cell mediated immune response. 
     BACKGROUND OF THE INVENTION 
     The current vaccine formulations elicit either humoral or cell-mediated immune response depending on the mode of delivery and adjuvant used. Although previous work in immunological delivery research has achieved delivery of strong antigens to elicit an immune response by bioneutralizing antibodies (humoral response), they fail to elicit cytotoxic T lymphocyte (CTL) response. For many infectious diseases both bioneutralizing antibody and activated T cell mediated responses are desired for immunity. For this very reason, polymer particle based delivery systems are being much sought for their application in single dose vaccines and different therapeutic applications. Such systems can be utilized to develop highly useful, effective vaccines and vaccine delivery system. 
     Polymer particle based vaccine delivery systems provide a viable alternative to multidose immunization schedule for many infectious diseases where neutralizing antibody titers provide protective immunity (Cleland J L. Single-administration vaccines: controlled-release technology to mimic repeated immunizations, Trends Biotechnol 1999; 17:25-29). Particles, particularly made from poly lactide-co-glycolide (PLGA) or PLA, not only work as a delivery system but also provide adjuvant activity (Jiang W, Gupta R K, Deshpande, M C, Schwendeman S P. Biodegradable poly (lactic-co-glycolic acid) microparticles for injectable delivery of vaccine antigens. Adv Drug Deliv Rev 2005; 57:391-410; O&#39;Hagan D T, Singh M. Microparticles as vaccine adjuvants and delivery systems. Expert Rev Vaccines 2003; 2:269-83). These polymeric particulate delivery systems have the capacity to present the antigen both by MHC class I (MHC I) and MHC class II (MHC II) pathway and thus can activate both humoral and cellular response (O&#39;Hagan D T, Singh M. Microparticles as vaccine adjuvants and delivery systems. Expert Rev Vaccines 2003; 2:269-83.; Men Y, Audran R, Thomasin C, Eberl G, Demotz S, Merkle H P, et al. MHC class II and class II-restricted processing and presentation of microencapsulated antigens. Vaccine 1999; 17:1047-56.; Carcaboso A M, Hernandez R M, Igartua M, Rosas J E, Patarroyo M E, Pedraz J L. Potent, long lasting systemic antibody levels and mixed Th1/Th2 immune response after nasal immunization with malaria antigen loaded PLGA microparticles, Vaccine 2004; 22:1423-32). Efficient targeting of particulate antigen to the APCs has been reported as a major factor contributing towards the generation of immune response, which requires that the particle size should be between 1-10 μm (Tabata Y, Ikada Y. Macrophage phagocytosis of biodegradable microspheres composed of L-lactic acid/glycolic acid homo- and copolymers. J Biomed Mater Res 1988; 22:837-58.; Eldridge J H, Staas J K, Meulbroek J A, McGhee J R, Tice T R, Gilley R M. Biodegradable microspheres as a vaccine delivery system. Mol Immunol 1991; 28:287-94.; Thiele L, Rothen-Rutishauser B, Jilek S, Wunderli-Allenspach H, Merkle H P, Walter E. Evaluation of particle uptake in human blood monocyte-derived cells in vitro. Does phagocytosis activity of dendritic cells measure up with macrophages? J Control Release 2001; 76:59-71). Nevertheless, efficient primary antibody responses have been observed with much larger and diverse range of polymer particles having size bigger than that of APCs (Hilbert A K, Fritzsche U, Kissel T. Biodegradable microspheres containing influenza A vaccine: immune response in mice. Vaccine 1999; 17:1065-73.; Tabata Y, Inoue Y, Ikada Y. Size effect on systemic and mucosal immune responses induced by oral administration of biodegradable microspheres, Vaccine 1996; 14:1677-85, Shi L, Caulfield M J, Chern R T, Wilson R A, Sanyal G, Volkin D B. Pharmaceutical and immunological evaluation of a single-shot hepatitis B vaccine formulated with PLGA microspheres. J Pharm Sci 2002; 91:1019-35). Immune responses from many polymer entrapped antigens reveal that micron sized range particles promote humoral response whereas nanoparticles (&lt;1 μm) promote cellular response (Gutierro I, Hernandez R M, Igartua M, Gascon A R, Pedraz J L. Size dependent immune response after subcutaneous, oral and intranasal administration of BSA loaded nanospheres. Vaccine 2002; 21:67-77; Harding C V, Song R. Phagocytic processing of exogenous particulate antigens by macrophages for presentation by class I MHC molecules. J Immunol 1994; 153:4925-33.; Chong C S, Cao M, Wong W W, Fischer K P, Addison W R, Kwon G S, et al. Enhancement of T helper type 1 immune responses against hepatitis B virus core antigen by PLGA nanoparticle vaccine delivery. J Control Release 2005; 102:85-99). As the humoral and cellular immune responses complement each other, size of the polymeric particulate delivery system influences both the strength and quality of immune response. 
     It is widely accepted that polymeric particle based vaccine delivery formulations are more immunogenic than soluble antigens in vivo. However, there has been much ambiguity and debate over whether this effect can be explained solely by the enhanced uptake of the particles by the professional APCs and more so over the size of particles that can be engulfed by the APCs for antigen presentation to initiate an effective immune response. It has been reported that while non-phagocytic eukaryotic cells can internalize particles &lt;1 μm in size (Rejman J, Oberle V, Zuhorn I S, Hoekstra D. Size-dependent internalization of particles via the pathways of clathrin- and caveolae-mediated endocytosis. Biochem J 2004; 377:159-69), the professional phagocytic APCs—dendritic cells (DCs) and macrophages—can internalize and present particulate antigens of size &gt;1 μm (Shen Z, Reznikoff G, Dranoff G, Rock K L. Cloned dendritic cells can present exogenous antigens on both MHC class I and class II molecules, J Immunol 1997; 158:2723-30). Most of these studies used polystyrene particles and there are enough evidences that surface chemistry of particles does influence the uptake rate (Oh Y K, Swanson J A, Different fates of phagocytosed particles after delivery into macrophage lysosomes. J Cell Biol 1996; 132:585-93; Tomazic-Jezic V J, Merritt K, Umbreit T H, Significance of the type and the size of biomaterial particles on phagocytosis and tissue distribution, J Biomed Mater Res 2001; 55:523-29.; Foged C, Brodin B, Frokjaer S, Sundblad A. Particle size and surface charge affect particle uptake by human dendritic cells in an in vitro model. Int J Pharm 2005; 298:315-22) thus a clear picture on size based cellular uptake is never observed. PLGA or PLA based nanoparticles are extensively taken up by non-phagocytic eukaryotic cells, macrophages and DCs (Lutsiak M E, Robinson D R, Coester C, Kwon G S, Samuel J. Analysis of poly(D,L-lactic-co-glycolic acid) nanosphere uptake by human dendritic cells and macrophages in vitro. Pharm Res 2002; 19:1480-87.; Panyam J, Labhasetwar V. Dynamics of endocytosis and exocytosis of poly(D,L-lactide-co-glycolide) nanoparticles in vascular smooth muscle cells. Pharm Res 2002; 20:212-20), however such clear uptake studies with large sized polymer particles have not been shown conclusively (Walter E, Dreher D, Kok M, Thiele L, Kiama S G, Gehr P, et al. Hydrophilic poly(DL-lactide-co-glycolide) microspheres for the delivery of DNA to human-derived macrophages and dendritic cells. J Control Release 2001; 76:149-68; Jones B G, Dickinson P A, Gumbleton M, Kellaway I W. The inhibition of phagocytosis of respirable microspheres by alveolar and peritoneal macrophages, Int J Pharm 2002; 236:65-79, Peyre M, Fleck R, Hockley D, Gander B, Sesardic D, In vivo uptake of an experimental microencapsulated diphtheria vaccine following subcutaneous immunisation, Vaccine 2004; 22:2430-37). As the size of PLA/PLGA particles changes from nanometer range to &gt;1 μm, drastic reduction in uptake of polymer particles by cells is observed (Desai M P, Labhasetwar V, Amidon G L, Levy R J. Gastrointestinal uptake of biodegradable microparticles: effect of particle size. Pharm Res 1996; 13:1838-45; Horisawa E, Kubota K, Tuboi I, Sato K, Yamamoto H, Takeuchi H, et al. Size-dependency of DL-lactide/glycolide copolymer particulates for intra-articular delivery system on phagocytosis in rat synovium, Pharm Res 2002; 19:132-39) and 0.5 μm has been suggested as the cut off size for efficient phagocytosis Foster K A, Yazdanian M, Audus K L. Microparticulate uptake mechanisms of in vitro cell culture models of the respiratory epithelium. J Pharm Pharmacol 2001; 53:57-66.; Lai S K, Hida K, Man S T, Chen C, Machamer C, Schroer T A, et al. Privileged delivery of polymer nanoparticles to the perinuclear region of live cells via a non-clathrin, non-degradative pathway. Biomaterials 2007; 28:2876-84.; Hirota K, Hasegawa T, Hinata H, Ito F, Inagawa H, Kochi C, et al. Optimum conditions for efficient phagocytosis of rifampicin-loaded PLGA microspheres by alveolar macrophages. J Control Release 2007; 119:69-76). It is quite possible that bigger sized particles are localized in the cell membrane (Lacasse F X, Filion M C, Phillips N C, Escher E, McMullen J N, Hildgen P. Influence of surface properties at biodegradable microsphere surfaces: effects on plasma protein adsorption and phagocytosis. Pharm Res 1998; 15:312-17) and deliver antigen into phagosomes which have the capacity to present the antigen via MHC II pathway (Ramachandra L, Song R, Harding C V. Phagosomes are fully competent antigen-processing organelles that mediate the formation of peptide:class II MHC complexes, J Immunol 1999; 162:3263-72). 
     The PCT publication WO0012125A1 describes a method of inducing a polarized TH1 response by parenteral administration of microparticle containing antigen entrapped or encapsulated by a biodegradable polymer. The document further describes a method for inducing a polarized TH2 response by parenteral administration of nanoparticles containing antigen entrapped or encapsulated by a biodegradable polymer. 
     SUMMARY OF THE INVENTION 
     The present invention provides a vaccine composition comprising an effective amount of antigen or a nucleic acid encoding antigen, encapsulated in polymeric particles, wherein said polymeric particles comprises nanoparticles, microparticles or combinations thereof, wherein the nanoparticle induces cellular response i.e Cytotoxic T lymphocyte (CTL) response or TH1 immune response and the microparticle induces humoral response or TH2 response by bioneutralizing antibodies. 
     The present invention provides a vaccine composition for therapeutic or prophylactic purposes eliciting humoral and cellular response, said composition comprising an antigen and/or a nucleic acid encoding said antigen, wherein said antigen and/or a nucleic acid is encapsulated in polymeric nanoparticles and microparticles, wherein ratio of said microparticles to nanoparticles is in the range of 1:9 to 9:1 excluding 1:1. 
     A vaccine composition for therapeutic or prophylactic purposes comprising an antigen or a nucleic acid encoding said antigen, encapsulated in polymeric particles, wherein said polymeric particles comprises nanoparticles, microparticles or combinations thereof, wherein microparticle induces humoral immune response and nanoparticle induces cell mediated immune response. 
     A method of inducing a humoral response in a subject, comprising administering to the subject an effective amount of a vaccine composition comprising an antigen or a nucleic acid encoding said antigen, encapsulated in polymeric particles, wherein said polymeric particles comprises microparticles. 
     A method of inducing a cell mediated immune response in a subject, comprising administering to the subject an effective amount of a vaccine composition comprising an antigen or a nucleic acid encoding said antigen, encapsulated in polymeric particles, wherein said polymeric particles comprises nanoparticles. 
     A method of inducing a combined humoral cell mediated immune response in a subject, comprising administering to the subject an effective amount of a vaccine composition comprising an antigen or a nucleic acid encoding said antigen, encapsulated in polymeric particles, wherein said polymeric particles comprises nanoparticles and microparticles. 
    
    
     
       BRIEF DESCRIPTION OF ACCOMPANYING DRAWINGS 
         FIG. 1 : Shows size based anti-HBsAg IgG antibody response from HBsAg entrapped PLA particles. (▪) Alum absorbed HBsAg, () Microparticles, (▴) Microparticle with alum, (▾) Nanoparticles, and (♦) Nanoparticles with alum. Error bars represent mean±standard deviation (n=8). 
         FIG. 2 : Demonstrates particle uptake in murine macrophage cell line J774A.1 using different sized 6-coumarin entrapped PLA particles in vitro at various time points. (A-D) Nanoparticles uptake in murine macrophage cell line J774A.1. (E-H) Microparticles uptake in murine macrophage cell line J774A.1. Each bar represents 25 μm. 
         FIG. 3 : Demonstrates Fluorescence quenching. A, B and C show uptake of FITC-BSA entrapped nanoparticles in macrophages in vitro at 24 hours. D, E and F show uptake of FITC-BSA entrapped microparticles in macrophages in vitro at 24 hours. Each bar indicates 10 μm. 
         FIG. 4 : CLSM images showing intracellular uptake and localization of 6-coumarin entrapped PLA nanoparticles and surface attachment of microparticles in murine macrophage cell line J774A.1 in vitro. (A) An overview of 6-coumarin entrapped nanoparticles phagocytosed by macrophages in vitro at 24 hours is shown. (B) Optical sections (z-sections) of the same macrophage showing phagocytosed nanoparticles at different sections. Each optical section represents a particular plane of focus and nanoparticles have different plane of focus indicating that they are internalized completely. (C) An overview of 6-coumarin based microparticle adhering to a macrophage in vitro at 24 hours is shown. (D) Optical sections (z-sections) of the same macrophage showing an adherent microparticle. The data shown here is a representative of a minimum of three individual experiments done at same experimental conditions. Each bar represents 5 μm. 
         FIG. 5 : (A) T cell proliferation assay of mice immunized with HBsAg entrapped PLA microparticles and nanoparticles. (B, C) Cytokine assay from the culture supernatants of T cell proliferation assay (A) for the analysis of mouse IFN-γ (B) and mouse IL-4 (C). Error bars represent mean±standard deviation of triplicate wells. 
         FIG. 6 : Groups of animals (n=8) immunized with either nanoparticles or microparticles with or without alum as a single dose; or with standard dose of alum adsorbed HBsAg containing 1 μg of HBsAg. Serum samples were collected at specific time intervals and analyzed for anti-HBsAg IgG1 and IgG2a antibody titers. The data was expressed as a ratio between IgG1 and IgG2a absorbance values. 
         FIG. 7 : Analysis of surface MHC class I levels (left) and MHC class II levels (right) on APCs (macrophages) treated with different sized HBsAg particles at 24 h in vitro. Particle size is indicated by color bars as: (−) 200 nm; (−) 600 nm; (−) 2-8 μm; (−) 20 μm; (−) 50 μm; (−) untreated cells; and (−) control. 
         FIG. 8 : Western blot analysis showing continuous release of HBsAg from microparticles into APCs resulting in its higher accumulation with time. Each lane depicts the intracellular HBsAg content after treatment with a particular size of HBsAg entrapped PLA particles. Untreated cell lysates were taken as negative control (−ve ctl) whereas soluble HBsAg (2-3 μg) was taken as positive control (+ve ctl). RB indicates lane for Rainbow marker. 
         FIG. 9 : Modulation of Anti HBsAg IgG response using different sized polylactide particles 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The present invention provides a vaccine composition comprising an effective amount of antigen or a nucleic acid encoding antigen, encapsulated in polymeric particles, wherein said polymeric particles comprises nanoparticles, microparticles or combinations thereof, wherein the nanoparticle induces cellular response i.e Cytotoxic T lymphocyte (CTL) response or TH1 immune response and the microparticle induces humoral response or TH2 response by bioneutralizing antibodies. 
     The present invention provides a vaccine composition (or vaccine loaded polymer particle delivery system) that allows single-shot vaccine formulations to be produced for antigens which would otherwise require multiple injections to elicit an immune response. 
     The present invention provides a vaccine composition (or vaccine loaded polymer particle delivery system) comprising the microparticle, nanoparticle or combination thereof wherein the nanoparticle induces cellular response i.e Cytotoxic T lymphocyte (CTL) response or TH1 immune response and the microparticle induces humoral response or TH2 response by bioneutralizing antibodies, wherein said composition allows single-shot vaccine formulations to be produced for antigens which would otherwise require multiple injections to elicit an immune response. 
     In accordance with the present invention, one embodiment provides a vaccine composition for inducing humoral and/or cell mediated immune response comprising antigen or a nucleic acid encoding said antigen, encapsulated in a polymeric particles, wherein said polymeric particles comprises nanoparticles, microparticles or combinations thereof, wherein the nanoparticle size ranges from 200-600 nm and microparticle size ranges from 2-8 μm. 
     The vaccine composition provided in the present invention is useful against various diseases where humoral and/or cellular immune response is required for such as malaria, tuberculosis, hepatitis, diphtheria, tetanus, cancer and human immunodeficiency virus infection. 
     The vaccine composition disclosed in the present invention can be useful against other diseases such as AIDS-AIDS related complex, chickenpox, common cold—Influenza (Flu), dengue fever, foot and mouth disease, hepatitis, herpes simplex, HPV, Lassa fever, measles, mumps, poliomyelitis, rabies, SARS, Smallpox, viral encephalitis, viral gastroenteritis, viral meningitis, viral pneumonia, West Nile disease and Yellow fever. 
     The vaccine composition disclosed in the present invention can be useful against other bacterial diseases such as Anthrax, Bacterial Meningitis, Botulism, Brucellosis, Cat Scratch Disease, Cholera, Diphtheria, Epidemic Typhus, Gonorrhea, Impetigo, Leprosy (Hansen&#39;s Disease), Listeriosis, Rheumatic Fever; Nocardiosis, Pertussis (Whooping Cough), Plague, Pneumococcal pneumonia, Psittacosis, Q fever, Rocky Mountain Spotted Fever (RMSF), Salmonellosis, Scarlet Fever, Shigellosis, Syphilis, Tetanus, Trachoma, Tuberculosis, Tularemia, Typhoid Fever, Typhus and Urinary Tract Infections. 
     The vaccine composition disclosed in the present invention can be useful against other parasitic diseases such as African trypanosomiasis, Amebiasis, Ascariasis, Babesiosis, Chagas Disease, Clonorchiasis, Cryptosporidiosis, Cysticercosis, Diphyllobothriasis, Dracunculiasis, Echinococcosis, Enterobiasis, Fascioliasis, Fasciolopsiasis, Filariasis, Free-living amebic infection, Giardiasis, Gnathostomiasis, Hymenolepiasis, Isosporiasis, Kala-azar, Leishmaniasis, Malaria, Metagonimiasis, Myiasis, Onchocerciasis, Pediculosis, Pinworm Infection, Scabies, Schistosomiasis, Taeniasis, Toxocariasis, Toxoplasmosis, Trichinellosis, Trichinosis, Trichuriasis, Trichomoniasis and Trypaonsomiasis. 
     The vaccine composition disclosed in the present invention can be useful against other fungal diseases such as Aspergillosis, Blastomycosis, Candidiasis, Coccidioidomycosis, Cryptococcosis, Histoplasmosis and Tinea pedis. 
     The vaccine composition disclosed in the present invention can be useful against diseases such as transmissible spongiform encephalopathy, Bovine spongiform encephalopathy and Creutzfeldt-Jakob disease. 
     One embodiment of the invention provides a vaccine composition for therapeutic or prophylactic purposes comprising an antigen or a nucleic acid encoding said antigen, encapsulated in polymeric particles, wherein said polymeric particles comprises nanoparticles, microparticles or combinations thereof, wherein microparticle induces humoral immune response and nanoparticle induces cell mediated immune response. 
     One embodiment of the invention provides a vaccine composition for therapeutic or prophylactic purposes eliciting humoral and cellular response, said composition comprising an antigen and/or a nucleic acid encoding said antigen, wherein said antigen and/or a nucleic acid is encapsulated in polymeric nanoparticles and microparticles, wherein ratio of said microparticles to nanoparticles is in the range of 1:9 to 9:1 excluding 1:1. 
     Another embodiment of the invention provides a vaccine composition, wherein the antigen is derived from an organism selected from a group consisting of rotavirus, paramyxovirus, mumps virus, rubella virus, polio virus, hepatitis virus, herpes viruses, human immunodeficiency virus,  Haemophilus influenza, Clostridium tetani, Corynebacterium diphtheria , and  Neisseria gonorrhea.    
     Another embodiment of the invention provides a vaccine composition, wherein, said antigen is selected from a group of Hepatitis B surface antigen, tetanus toxoid and Diphtheria toxin. 
     Another embodiment of the invention provides a vaccine composition, wherein the antigen is selected from a group consisting of proteins, polysaccharides, glycoproteins, glycolipids, nucleic acid and combinations thereof. 
     Another embodiment of the invention provides a vaccine composition, wherein size of said nanoparticle ranges from 200-600 nm. 
     Another embodiment of the invention provides a vaccine composition, wherein size of said microparticle ranges from 2-8 μm. 
     Another embodiment of the invention provides a vaccine composition, wherein said polymeric particle is a biodegradable polymer. 
     Another embodiment of the invention provides a vaccine composition, wherein said biodegradable polymer is selected from a group of poly(lactide-co-glycolide), polylactide or polyglycolide. 
     Another embodiment of the invention provides a vaccine composition, wherein said polymeric particle is polylactide (PLA) polymer. 
     Another embodiment of the invention provides a vaccine composition, wherein the polymeric particle is polyglycolide. 
     Another embodiment of the invention provides a vaccine composition, wherein the ratio of microparticles to nanoparticles is 9:1, wherein said composition elicits high humoral response. 
     Another embodiment of the invention provides a vaccine composition, wherein the ratio of microparticles to nanoparticles is 8:2, wherein said composition elicits high humoral response. 
     Another embodiment of the invention provides a vaccine composition, wherein the ratio of microparticles to nanoparticles is 1:9, wherein said composition elicits high cellular response. Another embodiment of the invention provides a vaccine composition, wherein the ratio of microparticles to nanoparticles is 2:8, wherein said composition elicits high cellular response. 
     Another embodiment of the invention provides a vaccine composition, wherein said composition is used for treating diseases selected from a group consisting of malaria, tuberculosis, and human immunodeficiency virus infection. 
     One embodiment of the invention provides a method of inducing a humoral response in a subject, comprising administering to the subject an effective amount of a vaccine composition comprising an antigen or a nucleic acid encoding said antigen, encapsulated in polymeric particles, wherein said polymeric particles comprises microparticles. 
     One embodiment of the invention provides a method of inducing a cell mediated immune response in a subject, comprising administering to the subject an effective amount of a vaccine composition comprising an antigen or a nucleic acid encoding said antigen, encapsulated in polymeric particles, wherein said polymeric particles comprises nanoparticles. 
     One embodiment of the invention provides a method of inducing a combined humoral cell mediated immune response in a subject, comprising administering to the subject an effective amount of a vaccine composition comprising an antigen or a nucleic acid encoding said antigen, encapsulated in polymeric particles, wherein said polymeric particles comprises nanoparticles and microparticles. 
     One embodiment of the present invention provides a vaccine composition comprising combination of microparticle and nanoparticle polymer comprising a suitable antigen. 
     One embodiment of the present invention provides a vaccine composition for eliciting humoral (bioneutralizing antibody) and, cellular response or cell-mediated immune response (CTL, T helper cell) in a subject, comprising administering to the subject an effective amount of a composition comprising an antigen or a nucleic acid encoding the antigen, loaded in a polymeric composition, wherein the polymeric composition comprises polymer of poly(lactide-co-glycolide), polylactide or polyglycolide. 
     Another embodiment of the present invention provides a vaccine loaded polymer particles comprising polylactide (PLA) polymer particles loaded antigen or a nucleic acid encoding the antigen. 
     One embodiment of the present invention provides vaccine loaded polymer particles, wherein the microparticle and nanoparticle polymer loaded the same antigen promoting both humoral and cell mediated responses in a balanced manner or in a manner as desired. 
     One embodiment of the present invention provides a vaccine loaded polymer particles that is useful against diseases or clinical manifestations that require both bioneutralizing antibodies and T cell mediated responses. The vaccine loaded polymer particle can be used for various diseases such as malaria, tuberculosis, cancer and human immunodeficiency virus infection. 
     One embodiment of the present invention provides biodegradable polylactide (PLA) polymer particles as vaccine delivery systems to elicit either or both humoral and cell mediated immune responses from the same antigen. The difference in size and release pattern of polymer entrapped antigen(s) are known to influence the way the antigen(s) is/are presented by antigen presenting cells (APCs) to activate naïve CD4 + T cells which differentiate upon activation into either Th1 or Th2 cells resulting in either cell mediated or humoral immune responses respectively. Th1 cells are associated with IFN-γ, IL-12 and TNF-α whereas Th2 cells typically produce IL-4, IL-5, IL-10 and IL-13. The present invention provides antibody response and T cell mediated response in an animal model from different sized PLA polymer particles with entrapped HBsAg. 
     One embodiment of the present invention provides a size based design of vaccine delivery system for modulation of immune response from the same antigen. The particulate antigen acts as an effective immunogen for therapeutic, prophylactic and vaccination purposes with possibility of eliciting both humoral and cell mediated responses in a balanced manner. Generation of different magnitudes and kinetics of immune response from microparticles, nanoparticles and their physical mixture with and without adjuvants like alum suggests that particle size is an important parameter influencing the immune response. 
     The exact amount of such compositions required will vary from subject to subject, depending on the species, age, weight and general condition of the subject, the severity of the disease, infection or condition that is being treated or prevented, the particular compound used, its mode of administration, and the like. Thus, it is not possible to specify an exact amount. However, an appropriate amount may be determined by one of ordinary skill in the art using only routine experimentation given the teachings herein. 
     One embodiment of the present invention provides a single shot vaccine delivery systems that can be delivered parenterally, intrapertonially, orally, topically, transdermally, intradermally, rectally, vaginally or nasally. 
     One embodiment of the present invention provides preparation of polymer particles and characterization of particle size and surface morphology. The details are provided in Example 1 and Example 2. 
     Another embodiment of the present invention provides immunogenicity evaluation of PLA particles containing HBsAg. Immunization of rats with HBsAg encapsulated in micro particle and nanoparticle of PLA with or without alum is shown in  FIG. 9  and described in Example 3.  FIG. 9  shows Immune response from physical mixture of nanoparticles and microparticle. It can be deduced from the figure that by varying the ratio of nanoparticles and microparticles, immune response can be modulated. For dominant humoral response, mixture containing nanoparticles (0-20%) and microparticles (100-80%) will be ideal. For cellular response mixture containing nanoparticles (100-80%) and microparticles (0-20%) will be ideal. Depending on the requirement for both type of immune response for a particular disease, the physical mixture combinations can be optimized to provide protective immunity. Immunization with different sized HBsAg entrapped particles result in varied antibody response ( FIG. 1 ). HBsAg entrapped microparticles (2-8 μm) elicit better antibody titer (peak titer value 1803±150 mIU/mL) than nanoparticles (peak titer value 1010±191 mIU/mL). Admixture of microparticles and alum improve the antibody titers considerably. Immunization with microparticles and alum (MP+Alum) elicit antibody titers (peak titer value 4941±100 mIU/mL) better than from alum adsorbed HBsAg (peak titer value 3999±150 mIU/mL). The data is provided in  FIG. 1  and table 1. 
     Another embodiment of the present invention provides estimation of HBsAg antibody titer by performing ELISA. The details for ELISA are provided in Example 4. 
     One embodiment of the invention provides Tell cell proliferation and cytokine assay as shown in Example 5. The microparticles which give rise to higher antibody response promote IL-4 secretion; whereas nanoparticles favor IFN-γ secretion. This data is provided in  FIG. 5  and table 2, 3 and 4. This is in concurrence with the concept that microparticles promote humoral response where as nanoparticles promote cellular response. The nanoparticles escape into the cell cytoplasm and deliver the antigen in the cytosol which gets acted upon by MHC class I presentation machinery thereby promoting more of Th1 type response where as immunization with microparticles results in antigen presentation via the classical MHC II presentation on the APCs and thus promote Th2 response. Analysis of surface MHC levels on APCs in vitro further supports this fact. In case of macrophages treated with nanoparticles (200-600 nm), surface MHC class I levels are greatly upregulated at 24 hours. But in case of macrophages treated with microparticles (2-8 μm and beyond), MHC class II levels are significantly upregulated than MHC I as shown in  FIG. 7 . 
     Another embodiment of the present invention provides that microparticles promote humoral response where as nanoparticles promote cellular response. Accordingly, microparticles promote Th2 response and nanoparticles promote TH1 response. This is a surprising result of the present invention as; this result is in contradiction to the earlier teachings that disclose that microparticles promote Th1 response and nanoparticles promote TH2 response. 
     One embodiment of the present invention provides In vitro and Ex vivo analysis such as Phagocytic uptake, Fluorescence quenching, Confocal laser scanning microscopy (CLSM) and flow cytometric analysis of fluorescent particles as shown in Example 6. 
     In one embodiment of the invention cellular interactions of different sized PLA particles with macrophages are analyzed to visualize particle uptake by macrophages, cells are incubated with different sized PLA particles for various time points both in vitro and ex vivo as shown in Example 6. Fluorescence microscopy shows that most of the nanoparticles were localized intracellularly and maximum uptake is observed between 6-24 hours. It is also observed that nanoparticles get continuously endocytosed and exocytosed from the cells ( FIG. 2A-D ). The most interesting observation was that PLA microparticles of size 2-8 μm and above were found to be attached to the surface of APCs for a considerable period of time ( FIG. 2E-H ). Intracellular accumulation of nanoparticles was associated with 2-3 times enlargement of cell size ( FIG. 21 ) where as association of microparticles did not alter the cell size ( FIG. 2J ). It has been documented that size and surface chemistry of particles do influence particle uptake and in particular, hydrophobic polymer particles have the tendency to adhere to the cell surface. Higher sized particles (20-50 μm) which have been reported previously to elicit antibody titer upon immunization were also found to be attached to the cell surface ( FIG. 2K ). 
     In one embodiment of the invention attachment of PLA microparticles on cell surface of macrophages are analyzed to confirm that fluorescence emitted from the microparticles are indeed extracellular and hence the microparticles are cell surface attached, 0.1% (w/v) crystal violet or 0.4% (w/v) trypan blue is used to quench the extracellular fluorescence. Under such conditions only intracellular fluorescence signal would be emitted and captured and any extracellular signal would get nullified by the quenching dye. FITC-BSA entrapped nanoparticles are efficiently up taken by macrophages and appeared green under FITC filter ( FIGS. 3 , A-C). In case of FITC-BSA entrapped microparticles, fluorescence is quenched by the dye confirming that they are cell surface associated ( FIGS. 3 , D-F). Also, in case of FITC-BSA entrapped microparticles, green fluorescence is only seen intracellularly and not inside the particles ( FIGS. 3 , E and F). This can be explained by the fact that microparticles remain cell surface adherent non-specifically and constantly release the fluorescent antigen (BSA) into the cell. This results in intracellular accumulation of antigen as reflected in higher levels of fluorescence. In such cases, the positions on the cell surface where the microparticles are attached do not show any fluorescence instead certain specific areas within the cell appear green under the FITC filter. The uptake of particles is quantified as cell-associated fluorescence intensity by cytometric analysis using a BD-LSR flow cytometer (FACS). The fluorescence quenching for 6-coumarin entrapped PLA microparticles both in absence and presence of a phagocytic inhibitor cytochalasin D. It is observed that very low percentage of cells show fluorescence at all time points upon quenching. Since the extracellular fluorescence is quenched by trypan blue (≧85%), it indicates that these microparticles are extracellular and cell surface attached. Similar results are observed in the presence of cytochalasin D (20 μg/1×10 6  cells). Percentage of fluorescence labeled cells drastically reduced from as high as 25.4% to 2.2% at 24 hours, and 15.9% to 0.4% at 48 hours when quenched with trypan blue. Since cytochalasin D, only prevents phagocytosis but not cell surface attachment per se, these results prove that microparticles (2-8 μm) are indeed attached to the cell surface. Similar observations are found for bigger sized (&gt;10 μm) particles. However, 6-coumarin entrapped PLA nanoparticles are efficiently taken up by macrophages in a time bound manner indicated by an increase in fluorescence intensity which saturates and decreases at later time points in the presence of trypan blue ( FIG. 4B ). Even after quenching, fluorescence of 6-coumarin entrapped nanoparticle increase from 1.8% (1 hour) to 36.6% (at 24 hours) but decrease at later time points (18.4% at 48 hours). This reduction in nanoparticle uptake at higher time point may be attributed to the exocytosed nanoparticles which are quenched by the dye after a long period of incubation. However, in the presence of cytochalasin D, a drastic decrease in percentage fluorescence of nanoparticles is observed ( FIG. 4B , lower panel). Most of the fluorescence associated with nanoparticles is quenched and is around 1-2% at all the time points. Cytochalasin D prevents the phagocytosis of nanoparticles and hence the fluorescence from extracellular nanoparticles is quenched. 
     One embodiment of the present invention provides an analysis of In vitro localization of different sized PLA particles in macrophages by CLSM. Intracellular localization of nanoparticles and surface attachment of microparticles is confirmed by CLSM. In case of macrophages incubated with fluorescent nanoparticles, a number of nanoparticles are found present in different optical sections (z-sections) of the same cell. This implies that nanoparticles are indeed phagocytosed by the cell and localized at different locations ( FIGS. 4A  and B). In case of macrophages incubated with microparticles, the same microparticle is visible in all optical sections. Microparticles appear in focus in the initial sections much before the cell actually can be focused with respect to the optical sectioning done for a particular cell sample indicating that microparticles are cell surface associated and not internalized ( FIGS. 4C  and D). For analyzing intracellular localization of particles, cells are later incubated with organelle-specific contrasting fluorescent dye, 50 nM Lyso Tracker™ Red (Molecular Probes) for 30 minutes at 37° C. and washed three times with sterile 50 mM phosphate-buffered saline (PBS). The endo-lysosomes appear red in color when labelled with 50 nM Lyso Tracker™ Red and visualized under RITC filter. A series of z-sections are performed using CLSM following which the co-localization of the nanoparticles within the endo-lysosomal compartments at different sections of the cells can be visualized under both FITC and RITC filters. The co-localization shows yellow fluorescence in the overlay between green fluorescent nanoparticles and red fluorescent vesicles at various time points. No such co-localization of the fluorescent microparticles is observed within the labelled cells though they are seen to be attached to the surface of the cells. The cellular attachment of microparticles is evident even after vigorous washing of the particles treated cells with 50 mm PBS. 
     Another embodiment of the present invention provides analysis of cytokine secretion pattern; antibody isotyping; and surface MHC levels on interaction of different sized antigen loaded PLA particles with macrophages. As the modulation of the immune response is regulated by cytokines, their secretion pattern is analyzed from T cells, isolated from mice immunized with different sized PLA particles entrapping HBsAg. Cytokine levels are quantitated from the culture supernatants of T-cell proliferation assay ( FIG. 5A ). It is observed that nanoparticles favor IFN-γ secretion ( FIG. 5B ) much higher (4-5 times) in comparison to microparticles. Microparticles, on the other hand, favor IL-4 secretion which is better than that from nanoparticles ( FIG. 5C ). This supports the observation that nanoparticles do enter the cells and somehow escape to the cell cytoplasm to promote Th1 response. Microparticles remain outside the cell and promote Th2 response. This is further confirmed from the antibody isotyping in rats immunized with different sized HBsAg encapsulated PLA particles over a period of one month. Groups immunized with microparticles show higher IgG1/IgG2a ratio than those immunized with nanoparticles ( FIG. 6 ). IgG1 is an indicator of Th2 type response whereas IgG2a favors Th1 type response. Alum is a known Th2 favoring adjuvant thus immunization with only alum favored highest IgG1/IgG2a ratio. Immunization with admixture of microparticles and alum favors three times more IgG1/IgG2a ratio than that observed with nanoparticle and alum immunization. Nanoparticles alone result in lowest IgG1/IgG2a ratio suggesting the preferential elicitation of cellular immune response. Improvement in antibody titer as well as IgG1/IgG2a ratio with admixture of alum and nanoparticles are not as significant as it is observed with microparticle and alum based immunization ( FIG. 1  and  FIG. 6 ). Different sized PLA particles entrapping the same antigen (HBsAg) thus elicit immune response of varied strength and quality. Modulation of immune response from different sized HBsAg particles is further characterized by analysis of surface MHC levels on macrophages in vitro ( FIG. 7 ). HBsAg microparticles (2-8 μm, 20 μm and 50 μm) upregulate MHC class II molecules significantly and correlate with high IL-4 secretion and higher antibody titers. Polylactide nanoparticles (size range 200 nm-600 nm) upregulate higher levels of surface MHC class I molecules in comparison to MHC class II molecules. This analysis is done in a size specific manner rather than antigen specific manner and it further supports the observations obtained from cytokine analysis and antibody isotyping using different sized HBsAg particles. Therefore the present disclosure shows unexpected result of eliciting Th2 and TH1 response by microparticles and nanoparticles respectively. This surprising finding of the present invention is exemplified by using microparticles of size 2-8 μm and nanoparticles of size 200 nm-600 nm. 
     One embodiment of the present invention provides intracellular protein analysis by western blot of cell lysates of macrophages treated with different sized HBsAg entrapped PLA microparticles show increased intracellular concentration of soluble HBsAg with time ( FIGS. 8A ,  8 B and  8 C). The detail of the Western blot protocol followed is described in Example 6. Even after 24 hours of incubation with microparticles, macrophages show increased intracellular levels of HBsAg in comparison to nanoparticles. In case of nanoparticles, level of HBsAg detected is prominent in the initial time point ( FIG. 8A ) but was more or less constant at later time points ( FIGS. 8B ,  8 C). These results further corroborate with higher levels of FITC-BSA accumulation inside APCs released from microparticles in comparison to nanoparticles at similar time points ( FIGS. 3E  and F). This observation offered a clue as to how the interaction between the APCs and antigen loaded PLA microparticles elicits higher antibody response. 
     The present invention clarifies the ambiguity relating to whether the vaccine loaded hydrophobic PLA microparticles elicit antibody response without being phagocytosed by the APCs and how different sized antigen loaded polymer particles modulate immune response. In the earlier studies it has been reported that as the particle size decreases from micrometer range to nanometer range, antibody titer decreases. Similar differences in antibody titers are observed while immunization with different sized HBsAg particles. Immunization with microparticles result in long lasting antibody titers in comparison to nanoparticles from single point immunization. Large sized particles (larger than APCs) do not get phagocytosed but still elicit antibody response from single point immunization. This suggests that uptake of the particulate antigen through phagocytosis and subsequent processing through classical MHC II presentation pathway may not be operating for such immunization modalities. Even though extensive research reports on phagocytosis of nanoparticles are available, uptake of different sized particles (micron sized) have never been correlated with antibody response. 
     The role of particle size in antigen presentation leading to generation of antibody response is assessed by carrying out cellular uptake with different sized fluorescent PLA particles. Nanoparticle endocytosis and its intracellular localization are conclusively proved by CLSM. Fluorescence quenching in presence and absence of cytochalasin D indicated that nanoparticles are uptaken by APCs through phagocytosis but microparticles are surface attached. Since the localization using CLSM show that nanoparticles are internalized and located in different compartments within the cell, it is safe to assume that most of the entrapped antigen is released into different intracellular compartments. Continuous endocytosis and exocytosis of nanoparticles from APCs probably results in low concentration of intracellular antigen with time as observed in western blots. Immunization with antigen loaded nanoparticles is associated with secretion of IFN-γ and upregulation of MHC class I molecules. Nanoparticle thus delivers antigen intracellularly and promotes more of cellular response. As both arms of immune system are complementary to each other this results in lower IgG antibody titers with nanoparticle based immunization in comparison to microparticle based immunization. However, to our surprise, micro particles (2-8 μm size) that elicit optimal antibody titer upon immunization are not taken up by the APCs. More over, they are found to be attached to the cell surface for a considerable period of time non-specifically as observed by confocal as well as flow cytometric analysis. Particle surface chemistry and size play an important role in deciding the cellular localization of polymer particles. It has been shown that hydrophobic particles of size around 1 μm remain associated with early endosome and thus never get phagocytosed to lysosome. The hydrophobic nature of PLA microparticles helps in stronger attachments to cell membrane and large size (&gt;1 μm) prevents the internalization of PLA microparticles. This results in cell surface attachment of PLA microparticles for a considerable period of time from where the entrapped antigen is released continuously into the cell. This is confirmed by the presence of higher levels of intracellular HBsAg from western blot analysis. Microparticles thus deliver the antigen slowly but persistently which results in improved antibody response in comparison to nanoparticle based immunization. However, it must be noted that the compartmentalization of the released antigen is not assessed per say but these results stress the point that there is continuous release of antigen from the microparticles into the cells for a longer period of time. This is further supported by the observation that similar sized particles having high load of antigen elicits higher antibody response from PLA particle based immunization. Since these particles are not taken up by APCs, surface attachment and continuous release of antigen from microparticles at high concentration influences the immunogenicity of polymer entrapped antigen. Higher secretion of IL-4 and upregulation of MHC II molecules induced by microparticles preferentially favor the processing and presentation of antigen through MHC class II pathway resulting in dominant humoral response. An optimal size of microparticles thus improves antibody response from single point immunization using polylactide particles. As the particle size increases beyond 2-8 μm, the available surface area of the antigen loaded particles for attachment to APC decreases resulting in low antibody titers. 
     The results in the present invention show that uptake of microparticles is not an absolute requirement for efficient antibody generation from PLA particle based immunization. Uptake of a pathogen or antigen normally takes either of three pathways. Firstly, APCs are capable to engulf particles or microorganisms non-specifically. Secondly, phagocytes are equipped with several cell-surface receptors that recognize pathogen surfaces for receptor-mediated endocytosis. Thirdly, phagocytic cells can take up soluble substances in pinocytic vacuoles by a process called macropinocytosis. For presentation of extra cellular antigen, it needs presentation and processing along with MHC II binding. The extra cellular antigen can bind to MHC II molecules present in the plasma membrane, MHC II molecules generated in early phagosomes or those generated by late endocytic pathways. For antibody generation, it is essential that the peptide fragment of the antigen binds to the MHC II molecule. This can happen either to membrane bound, recycled or nascent MHC II molecules. Even though membrane bound MHC constitute around 30% of the total molecules present in the cell for antigen presentation, these molecules are sufficient for generation of antibody response from polymer entrapped antigen. As disclosed by previous publications particulate involving latex beads where the antigen is covalently linked, PLA particles continuously release the antigen. Thus, in case of micron sized polymer particle, there is continuous release of antigen from the particles attached to the plasma membrane of the APCs for a considerable period of time. Plasma membrane has the capacity to process and present antigen and this may be the dominant mechanism for antigen presentation following immunization with PLA entrapped microparticles. 
     The results in the present invention show that these higher sized polymer particles remain attached to the APCs for a considerable time and help in presentation of antigen via MHC II pathway which was conclusively proved. It is possible that particle entrapped antigen is directly presented to B cells through antibody like receptor on its surface. Continuous release of antigen in the vicinity of APCs has been reported to be enough for presentation through membrane bound MHC II molecules. High concentration of soluble antigen near the extra cellular space of the APCs can lead to direct loading of the antigen onto MHC II molecule for presentation or can be transported by fluid phase macropinocytosis for further processing and presentation. Apart from macrophages, DCs and B cells are other APCs which may be involved in presentation of polymer entrapped antigen for improved immune response. DCs are considered to be the most important APCs; however contradictory reports exist about the ability of PLGA polymer particles to cause maturation of DCs into antigen presenting cells. These polymer particles do not possess any pathogen associated molecular patterns (PAMP) to activate DCs. However, DCs help in prolonging presentation of antigen from polymer entrapped particles. Recent studies suggest that the improved immunogenicity of the polymer entrapped antigen is mostly because of passive targeting of entrapped antigen into APCs. 
     The results in the present invention show that immunogenic potential of different sized particles by analysis of interactions between antigen loaded polymer particles with macrophages. Based on the in vitro and ex vivo uptake example in murine macrophage cell line J774A.1 and murine peritoneal exudate cells; and particle size based immunization in vivo it is concluded that: (i) Hydrophobic PLA microparticles (2-8 μm size) preferentially attach to the cell surface of APCs (macrophages) and continuously release the entrapped antigen resulting in higher antibody response than nanoparticles (&lt;1 (ii) PLA nanoparticles (&lt;1 μm) are efficiently phagocytosed by APCs (macrophages) and promote cell mediated immune response thus it elicits lower antibody titers upon immunization. (iii) Intracellular uptake of antigen loaded PLA microparticles is not necessary for improved antibody response from single point immunization. (iv) Polymer particle entrapped antigen are probably presented and processed in multiple ways for improved immune response, however passive targeting remains one of the major advantages of such system. (v) Size of polymer particle based antigen delivery system thus provides an exciting possibility for modulation of immune response via differential interactions with macrophages. 
     The results in the present invention show that, for antibody response, hydrophobic PLA particles are better than hydrophilic polymer particles and microparticles (2-8 μm size) entrapping tetanus toxoid elicit optimal antibody titers. Immunization with higher sized polymeric particles (&gt;10 μm and &lt;50 μm) as well as nanoparticles also elicit comparable antibody titers but lower than that observed for microparticles of 2-8 μm size. 
     The results in the present invention show that intracellular uptake of PLA microparticles per se is not an absolute requirement for effective and improved antibody response from particle based immunization. Instead, the continuous release of high concentration of antigen from PLA microparticles attached to the surface of APCs for a considerable period of time results in improved antibody response. Size of the polymeric particulate antigen delivery system and its subsequent interaction with macrophages is crucial for modulating immune response from single point immunization. 
     The results in the present invention suggest that it is possible to modulate the type of immune response from the same antigen varying concentration of the different size of the polymer particles as per requirement of humoral and cell mediated response. 
     It should also be understood that the foregoing describes various embodiments of the present invention and that numerous changes may be made therein without departing from the scope of the invention. The invention is further illustrated by the following examples, which are not to be construed in any way as imposing limitations upon the scope thereof. On the contrary, it is to be clearly understood that resort may be had to various other embodiments, modifications, and equivalents thereof, which, after reading the description herein, may suggest themselves to those skilled in the art without departing from the spirit of the present invention and/or the scope of the appended claims. 
     EXAMPLES 
     The following examples are put forth so as to provide those of ordinary skill in the art with a complete invention and the description of how to make and use the present invention, and are not intended to limit the scope of what the inventors regard as their invention nor are they intended to represent that the experiments below are all and only experiments performed. 
     PLA (45 kDa) was purchased from Birmingham Polymer Inc. USA. Recombinant HBsAg was from Shantha Biotechnics Pvt. Ltd, Hyderabad, India. Alum (2% w/v Al-hydrogel) was from Superfos Biosector, Denmark. Fluorescein isothiocyanate conjugated bovine serum albumin (FITC-BSA) [A-9771], rat serum albumin (RSA) [A-6272], cytochalasin D [C-8273] and polyvinyl alcohol, MW 30,000 (PVA) were from Sigma Chemicals, USA. 6-coumarin (8037L) was from Polysciences, Warrington, Pa. Dulbecco&#39;s modified Eagle&#39;s medium (DMEM), fetal calf serum (FCS) and Roswell Park Memorial Institute (RPMI-1640) medium were from Biological Industries, Israel. Micro BCA protein assay kit was from Pierce, USA. Seratec EIA hepatitis B antibody kit was from Seratec Inc. Germany. Goat anti-HBsAg antibody was from Novus Biologicals, Inc. USA and HRP conjugated anti-Goat IgG antibody was from Bio-Rad, USA. HRP conjugated anti-rat IgG1 and anti-rat IgG2a antibodies were from AbD Seratec, USA. Cell Tracker™ Red and Lyso Tracker™ Red were from Molecular Probes, Eugene, Oreg., USA. Mouse IL-4 ready-set go ELISA kit, PE labeled anti-mouse CD 11b and PE labeled anti-mouse MHC class I, H-2K d /H-2D d  antibodies were from eBiosciences, Inc. Mouse IFN-γ BD OptEIA™ ELISA set and FITC labeled anti-mouse MHC class II (I-A/I-E) were from BD Biosciences, San Diego, Calif. Brewer Thioglycollate medium (M019) was from HiMedia Lab., India. Glass fibre filter, printed filtermat A, was from Wallac, Finland. Western blot reagents and hyper film were from Amersham Biosciences, USA. 
     Example 1 
     Preparation of Polymer Particles 
     Polylactide polymer particles were prepared using w/o/w double emulsion solvent evaporation method (Katare Y K, Muthukumaran T, Panda A K. Influence of particle size, antigen load, dose and additional adjuvant on the immune response from antigen loaded PLA microparticles. Int J Pharm 2005; 301:149-60.). Briefly, primary emulsion between internal aqueous phase (IAP) containing HBsAg (10 mg/ml) and organic phase (OP) (50 mg/mL PLA solution in dichloromethane) was prepared by sonication (20 watts, 40% duty cycle, 20 cycles) (Branson Sonifier 450, USA). Resulting primary emulsion was added drop wise to external aqueous phase (EAP) containing 1% (w/v) PVA and 10% sucrose (w/v) solution in MQ water and homogenized (10,000 rpm for 10 minutes) using a homogenizer (Virtis, Cyclone I.Q., USA) for microparticle and macroparticle preparation; and sonicated (20 watts, 40% duty cycle, 20 cycles) for nanoparticle preparation. The resulting particles were collected by centrifugation (15,000 rpm, 20 minutes), and lyophilized to get free flowing powder. For the preparation of 6-coumarin fluorescent particles, size ranging from &lt;1 μm to &gt;25 μm, 50 μL of 6-coumarin dye (1 mg/mL in dichloromethane) was also added to OP during primary emulsion step. Similarly for the preparation of FITC conjugated BSA particles, FITC-BSA (10 mg/mL) was taken in IAP as the antigen. Different sized fluorescent and HBsAg entrapped PLA particles were prepared by varying energy input and OP to EAP volume ratio (Katare Y K, Muthukumaran T, Panda A K. Influence of particle size, antigen load, dose and additional adjuvant on the immune response from antigen loaded PLA microparticles. Int J Pharm 2005; 301:149-60.). 
     Example 2 
     Characterization of Particle Size and Surface Morphology 
     Size distribution of the particles was determined using Malvern mastersizer 2000 particle size analyzer (Malvern, UK). Surface morphology was analyzed by using a scanning electron microscope (SEM)—JEOL (JSM 6100, Tokyo, Japan)—after coating the particle surface with gold-palladium over an aluminium stub; and also by a transmission electron microscope (TEM)—CM 10, Philips, Holland—after coating the particles with 1% uranyl acetate over a copper grid (Polysciences, Warrington, Pa.). TEM images were obtained by using digital imaging software—AMT image capture engine (version 5.42.391). To measure the protein content of particles, accurately weighed particles were dissolved in acetonitrile to solubilize the polymer while precipitating the encapsulated protein. Precipitated protein was dissolved in 1% SDS solution and estimated using micro BCA assay. Protein extracted from particles was resolved in SDS-PAGE gel and the amount of protein in the mixture was determined by densitometry scanning of gel picture. Protein loading was calculated as the percent weight of protein per unit weight of polymer. 
     Example 3 
     Immunogenicity Evaluation of PLA Particles Containing HbsAg 
     Immunogenicity of PLA particles containing HBsAg was evaluated in Wistar rats (eight female out bred Wistar rats per group). Animals were maintained according to the guidelines established by the Institute Animal Ethics Committee (IAEC) of the National Institute of Immunology, New Delhi. Required dose of particles were weighed and suspended in saline just before immunization. Immunization of admixture of particles and alum were carried out by adding 25 μL of alum (Aluminium hydroxide gel, 2% w/v) to the required dose of polymer particles per animal. Single dose of alum adsorbed antigen (1 μg HBsAg) was used as control. Rats were immunized intramuscularly with 1 μg of HBsAg encapsulated in micro- and nano-sized PLA particles with or without alum. Animals were bled at different time intervals through retro-orbital plexus and serum antibody titers were determined by ELISA. 
     Example 4 
     Estimation of HBsAg Antibody Titer by ELISA 
     For the estimation of anti-HBsAg IgG antibody titers in serum samples, SERATEC (GmbH, Germany) HBsAg EIA kit was used. Briefly, 50 μL of each serum sample dilution was added in duplicates in a 96-well microtiter plate pre-coated with HBsAg. Antibody standards, ranging from 10 to 150 mIU/mL, were loaded in duplicates. Immediately, 50 μL conjugate (HRP-labeled HBsAg) was added to each well and microplate was incubated for 30 minutes at 37° C. Microplate was then washed five times with wash buffer. This was followed by addition of 50 μL of chromogen A (containing hydrogen peroxide) and 50 μL of chromogen B (containing TMB (tetra methyl benzidine)) in each well and mixed properly. Microplate was again incubated at 37° C. for 15 minutes. Reaction was stopped by adding 5NH 2 SO 4  (50 μL/well) and absorbance was measured at 450 nm. Antibody titers were defined as the serum anti-HBsAg IgG antibody levels in mIU/mL. Anti-HBsAg IgG antibody titers were estimated in duplicates and their concentrations (mIU/mL) were determined as geometric mean (n=8). Analysis of immune response modulation was performed by qualitative estimation of anti-rat IgG1 and anti-rat IgG2a antibody titers in the serum samples of rats immunized with different sized particles entrapping 1 μg HBsAg. Briefly, 96-well high binding flat-bottom EIA/RIA plates (Nunc) were coated with 200 ng HBsAg/100 μl per well for 1½ hours at 37° C. Plates were washed once with wash buffer (PBS-T) and then blocked using blocking solution (1% BSA in PBST) for 1½ hours at 37° C. After washing, serum samples were loaded in duplicates and incubated again for 1½ hours at 37° C. Plates were then extensively washed four times with wash buffer. This was followed with addition of secondary anti-rat IgG1*HRP or IgG2a*HRP conjugate antibody and incubated for 1 hour at 37° C. Finally, 100 μL of O-phenyl diamine (OPD) dissolved in citrate-phosphate buffer (pH 4.5) along with H 2 O 2  was added to each well and incubated for 20 minutes at room temperature. Reaction was then stopped using 50 μl per well of 2NH 2 SO 4  as the stop solution and absorbance was read at 492 nm using an ELISA reader. Ratio between IgG1 and IgG2a absorbance values for different size particle were analyzed. 
     Example 5 
     T Cell Proliferation and Cytokine Assay 
     For T-cell proliferation assay, pathogen-free 6-8 weeks old inbred male BALB/c mice (n=3) were subcutaneously immunized with either HBsAg encapsulated nanoparticles; microparticles; or alum adsorbed soluble HBsAg containing 10 μg HBsAg suspended in 125 μL saline per animal. Non-immunized group of animals was taken as control. One week after immunization, T cells were isolated from popliteal and inguinal lymph nodes of the euthanized animals. A single-cell suspension was prepared by smearing cell aggregates/lymph nodes between two sterile frosted slides in sterile RPMI medium. T cells (0.3×10 6  cells per well) were incubated in triplicates with serially double diluted soluble HBsAg as the recall antigen ranging from 10 μg/100 μL downwards at 37° C. and 5% CO 2 . No antigen was added for the control group. After 72 hours post incubation, 50 μL culture supernatant was removed from each well for cytokine assay and 0.5 μCi  3 H-thymidine/50 μL RPMI medium was added to each well and incubated for a further 14-16 hours after which the plates were harvested on to a glass fibre filter, printed filtermat A, using a Strakon cell harvester and then incorporated radioactivity was measured in a liquid scintillation counter (Wallac 1205 Betaplate counter). 
     Cell culture supernatants collected from T-cell proliferation assay were analyzed for mouse IL-4 and/or IFN-γ using eBioscience and BD ELISA kits respectively. Briefly, 96-well microtiter plates were coated with recombinant capture antibody at a dilution of 1/250 (50 μL/well), anti-mouse IL-4 and anti-mouse IFN-γ for quantitative detection of mouse IL-4 and IFN-γ respectively, and incubated at 4° C. overnight. Plates were then washed two times with PBS-T and once with PBS and then blocked using blocking buffer (200 μL/well) at 37° C. for 1-2 hours. Sets of standard serial dilution of recombinant mouse IL-4 (1 μg/mL) and IFN-γ (90 ng/mL) were prepared and added to the corresponding microplates along with the pooled test samples in individual wells (50 μL/well) and incubated for 1-2 hours. The mouse IL-4 standards ranged from a top standard of 500 pg/mL to serially diluted bottom standard of 15 pg/mL whereas the mouse IFN-γ standards ranged from 1000 pg/mL to 31 pg/mL. All dilutions were made using RPMI-1640 cell culture medium. Detection was performed using 50 μL/well of biotinylated anti-mouse IL-4 and IFN-γ antibodies respectively at 1/250 dilution followed by addition of avidin-HRP enzyme at a dilution of 1/250. TMB was used as the substrate. After 15 minutes incubation at room temperature, reaction was stopped using 2N H 2 SO 4  and absorbance was read at 450 nm. 
     Example 6 
     In Vitro and Ex Vivo Analysis 
     Phagocytic Uptake 
     In vitro and ex vivo phagocytic uptake and trafficking analysis were carried out using 6-coumarin and FITC-BSA encapsulated polymer particles in murine macrophage cell line J774A.1 and murine peritoneal exudate cells. For in vitro analysis, 25 μL (1 mg/mL) of different sized fluorescent particles—400 nm, 2-8 μm or &gt;10 μm—was added to 0.5×10 6  cells/3 mL of DMEM medium supplemented with 10% FCS, 100 U/mL penicillin, 100 μg/mL streptomycin and 0.25 μg/mL amphotericin B plated in sterile standard tissue culture grade 6-well plates (Falcon, Becton Dickinson, Franklin Lakes, N.J.) and incubated at 37° C., 5% CO 2  for various time points. Cells were washed three times with sterile 50 mM PBS and observed using a fluorescent microscope. For ex vivo analysis, 6-8 weeks old male BALB/c mice were each administered with 1 mL of 4% thioglycollate solution intraperitoneally. After three days, mice were euthanized by cervical dislocation and peritoneal macrophages were collected by flushing out the peritoneal cavity with 10 mL of ice cold RPMI-1640 medium. Cell suspension was centrifuged at 1,200 rpm for 5 minutes at 4° C. and resuspended in RPMI-1640 medium supplemented with 10% FCS, 100 U/mL penicillin, 100 μg/mL streptomycin and 0.25 μg/mL amphotericin B. Only adherent cells, 95% of which constitute macrophages, were treated with fluorescent particles and processed as described above. 
     Fluorescence Quenching 
     The presence of fluorescent particles in macrophages were tracked using a Nikon ECLIPSE TE 2000-U fluorescent microscope fitted with a digital camera (1200 DXM) and the images were obtained using Image Pro-Plus 5.1 software program. Briefly, 6-well plates containing macrophages were treated with different sized FITC-BSA based fluorescent PLA particles for different time points and washed with sterile PBS solution. Quenching of extra cellular fluorescence was achieved using 0.1% (w/v) crystal violet or 0.4% (w/v) trypan blue solution [Rejman J, Oberle V, Zuhorn I S, Hoekstra D. Size-dependent internalization of particles via the pathways of clathrin- and caveolae-mediated endocytosis. Biochem J 2004; 377:159-69.; Hed J, Hallden G, Johansson S G, Larsson P. The use of fluorescence quenching in flow cytofluorometry to measure the attachment and ingestion phases in phagocytosis in peripheral blood without prior cell separation. J Immunol Methods 1987; 101:119-25]. Images were captured using 40× objective lens under FITC filter and also under bright light in monochrome mode. Fluorescence mode images and monochrome mode images were then merged using Image Pro-Plus software. 
     Confocal Laser Scanning Microscopy (CLSM) 
     CLSM images were obtained by simultaneous scanning of contrasting double-labeled specimens using a Zeiss Confocal LSM510 microscope equipped with Argon-Krypton laser (Carl Zeiss Micro imaging, Inc., NY, USA). Macrophages were grown on cover slips inside sterile 6-well tissue culture grade plates and incubated with fluorescent nanoparticles or microparticles at 37° C., 5% CO 2  for various time points; washed with 50 mM sterile PBS and then labeled with 50 nM Cell Tracker™ Red or 50 nM Lyso Tracker™ Red at 37° C. for 30 minutes and again washed three times with 50 mM sterile PBS. The cover slip was then placed on the stage of confocal microscope. A representative cell was selected at random and a series of optical sections (z-sections) were taken in dual filter mode. Images captured in RITC, FITC and dual mode were overlaid to determine localization and co-localization of fluorescent particles. 
     Flow Cytometric Analysis of Fluorescent Particles 
     Cytometric acquisition of fluorescent particle uptake analysis was performed using a BD-LSR flow cytometer (BD Biosciences, San Jose, USA) and Cell Quest program. The data was analyzed using WinMDI 2.8 (Joseph Trotter, Scripps Institute, La Jolla, Calif.). Macrophage cell suspension (0.5×10 6  cells) pre-incubated with fluorescent nanoparticles (25 μg) or microparticles (25 μg) for various time points (at 37° C., 5% CO 2 ) was analyzed for presence or absence of internalized fluorescent particles. Extra-cellular fluorescence was quenched using an appropriate dye (0.1% w/v crystal violet or 0.4% w/v trypan blue). Particle uptake inhibition analysis was done using cytochalasin D. For this, macrophages were pre-incubated with cytochalasin D (20 μg/1×10 6  cells) 30 minutes before the start of the experiment and continued till the end. 
     Effect of particle size was also analyzed in terms of surface MHC levels on APCs—murine macrophage cell line J774A.1—in vitro. Briefly, 0.5×10 6  cells were cultured in complete DMEM medium and incubated with different sized particles encapsulating 1 μg HBsAg for different time points. After washing with sterile PBS, cells were incubated with PE anti-mouse MHC class I and FITC anti-mouse MHC class II (I-A/I-E) on ice for 30 minutes. Untreated cells were used as control. Surface MHC class I and MHC class II levels on APCs were acquired using a BD-LSR flow cytometer and data was analyzed using WinMDI 2.8. 
     Intracellular Protein Analysis by Western Blot 
     Intracellular protein released from particles was analyzed after incubation of murine macrophage cell line J774A.1 with different sized HBsAg loaded PLA particles in vitro. 0.5×10 6  cells per well were cultured in sterile 6-well plates at 37° C., 5% CO 2 . Different sized particles containing 1 μg HBsAg were added to individual wells at around 70% confluence and incubated for three different time points—1 hour, 6 hours, and 24 hours. After each incubations, cells were washed with sterile PBS and pelleted at 1200 rpm for 5 minutes at room temperature. Cell lysates were analyzed for presence of HBsAg by western blotting using chemiluminescence method. 
     Example 7 
     Statistical Analysis 
     For statistical analysis, anti-TT antibody titers were defined as μg of antibody per ml of the sera employing affinity purified antibody as a reference in ELISA. Antibody titers of individual animal (n=8) were estimated in duplicates and their concentrations (μg/ml) were determined as geometric mean. Anti-HBsAg antibody titers were estimated in duplicates and their concentrations (mIU/ml) were also determined as geometric mean (n=6). Cytokine concentrations in the cell culture supernatants were determined from the standard curve (regression coefficient, r=0.99 or better). The comparison between groups were made using Student&#39;s t test at 95% confidence level. 
     
       
         
           
               
             
               
                 TABLE 1 
               
             
            
               
                   
               
               
                 Serum anti-HBsAg IgG antibody titers in Rats based on size of HBsAg entrapped 
               
               
                 polymer particle 
               
            
           
           
               
               
               
               
               
               
               
               
               
               
               
            
               
                   
                 Alum 
                   
                   
                   
                 HBsAg 
                   
                   
                   
                 HBsAg 
                   
               
               
                   
                 Adsorbed 
                   
                 HBsAg 
                   
                 MP + 
                   
                 HBsAg 
                   
                 NP + 
               
               
                 Time 
                 HBsAg 
                   
                 MP 
                   
                 Alum 
                   
                 NP 
                   
                 Alum 
                   
               
               
                 (Days) 
                 (mIU/ml) 
                 S.E. 
                 (mIU/ml) 
                 S.E. 
                 (mIU/ml) 
                 S.E. 
                 (mIU/ml) 
                 S.E. 
                 (mIU/ml) 
                 S.E. 
               
               
                   
               
            
           
           
               
               
               
               
               
               
               
               
               
               
               
            
               
                 0 
                 0 
                 0 
                 0 
                 0 
                 0 
                 0 
                 0 
                 0 
                 0 
                 0 
               
               
                 30 
                 1368.25 
                 918.18 
                 328.52 
                 150 
                 1767.2 
                 523.95 
                 172.04 
                 126.7 
                 959.17 
                 347.1 
               
               
                 60 
                 2649.5 
                 100 
                 598.3 
                 160.9 
                 3682.4 
                 150 
                 1009.8 
                 191.2 
                 1909.3 
                 100 
               
               
                 90 
                 3998.6 
                 150 
                 1803.3 
                 150 
                 4940.9 
                 100 
                 757.4 
                 307 
                 2065.5 
                 100 
               
               
                 120 
                 3649.9 
                 100 
                 1651.03 
                 330.37 
                 4435.07 
                 237.96 
                 699.59 
                 150 
                 1714.4 
                 250.58 
               
               
                 180 
                 1398.31 
                 399.3 
                 907.42 
                 0.43 
                 1814 
                 0.17 
                 203.5 
                 101.45 
                 1276.7 
                 731.64 
               
               
                   
               
               
                 MP: Microparticles; 
               
               
                 NP: Nanoparticles; 
               
               
                 S.E.: Standard error 
               
            
           
         
       
     
     
       
         
           
               
             
               
                 TABLE 2 
               
             
            
               
                   
               
               
                 T-cell proliferation assay in BALB/c mice using different sized HBsAg entrapped 
               
               
                 particles in vivo 
               
            
           
           
               
               
               
               
               
               
               
               
               
               
               
            
               
                 Soluble 
                   
                   
                   
                   
                   
                   
                   
                   
                   
                   
               
               
                 HBsAg 
                 HBsAg 
                   
                 HBsAg 
                   
                 HBsAg 
               
               
                 (Recall 
                 Nano 
                   
                 Nano 
                   
                 Micro 
                   
                 Soluble 
               
               
                 Ag) 
                 (200 nm) 
                   
                 (400 nm) 
                   
                 (2-8 μm) 
                   
                 HBsAg 
                   
                 Control 
               
               
                 (μg/ml) 
                 (CCPM) 
                 S.E. 
                 (CCPM) 
                 S.E. 
                 (CCPM) 
                 S.E. 
                 (CCPM) 
                 S.E. 
                 (CCPM) 
                 S.E. 
               
               
                   
               
            
           
           
               
               
               
               
               
               
               
               
               
               
               
            
               
                 10 
                 25077.5 
                 171.5 
                 51248.5 
                 2273.5 
                 48140 
                 3681 
                 3125 
                 8 
                 2852.5 
                 339.5 
               
               
                 5 
                 24954.5 
                 4869.5 
                 42301 
                 5707 
                 70341.5 
                 2189.5 
                 2379 
                 48 
                 1968.5 
                 68.5 
               
               
                 2.5 
                 24841 
                 1299 
                 39426 
                 0 
                 32592 
                 3192 
                 3221.5 
                 743.5 
                 1890 
                 153 
               
               
                 1.25 
                 26277 
                 0 
                 33030 
                 0 
                 32154 
                 0 
                 3369 
                 307 
                 1895 
                 0 
               
               
                 0.63 
                 21797 
                 0 
                 15411 
                 456 
                 21823 
                 0 
                 3494.5 
                 453.5 
                 1895 
                 0 
               
               
                 0.31 
                 15056 
                 0 
                 11335.5 
                 1810.5 
                 21159 
                 0 
                 3417 
                 0 
                 1895 
                 0 
               
               
                 0.15 
                 10622 
                 1416 
                 7661.5 
                 1091.5 
                 22318 
                 0 
                 2652 
                 125 
                 1895 
                 0 
               
               
                 0.08 
                 11922.5 
                 4636.5 
                 6308.5 
                 176.5 
                 22566 
                 0 
                 3085 
                 568 
                 1895 
                 0 
               
               
                   
               
               
                 S.E.: Standard error; 
               
               
                 CCPM: Cell count per minute 
               
            
           
         
       
     
     
       
         
           
               
             
               
                 TABLE 3 
               
             
            
               
                   
               
               
                 Cytokine assay for the quantitative analysis of mouse IFN-γ in culture 
               
               
                 supernatants from T-cell proliferation assay (top) 
               
            
           
           
               
               
               
               
               
               
            
               
                 Soluble 
                 HBsAg 
                 HBsAg 
                   
                   
                   
               
               
                 HBsAg 
                 Nano 
                 Nano 
                 HBsAg 
                 Soluble 
               
               
                 (Recall Ag) 
                 (200 nm) 
                 (400 nm) 
                 Micro (2-8 μm) 
                 HBsAg 
                 Control 
               
               
                 (μg/ml) 
                 (pg/ml) 
                 (pg/ml) 
                 (pg/ml) 
                 (pg/ml) 
                 (pg/ml) 
               
               
                   
               
            
           
           
               
               
               
               
               
               
            
               
                 10 
                 474.9 
                 718.20 
                 153.87 
                 99.75 
                 94.69 
               
               
                 5 
                 227.07 
                 1305.11 
                 280.89 
                 94.69 
                 89.68 
               
               
                 2.5 
                 287.9 
                 648.53 
                 220.63 
                 94.69 
                 84.74 
               
               
                 1.25 
                 165.44 
                 728.41 
                 369.13 
                 89.68 
                 84.74 
               
               
                 0.63 
                 136.98 
                 2569.89 
                 246.79 
                 99.75 
                 0 
               
               
                 0.31 
                 136.98 
                 1200.68 
                 183.28 
                 89.68 
                 0 
               
               
                 0.16 
                 126.03 
                 189.34 
                 120.65 
                 89.68 
                 0 
               
               
                 0.08 
                 104.88 
                 253.48 
                 159.62 
                 89.68 
                 0 
               
               
                   
               
            
           
         
       
     
     
       
         
           
               
             
               
                 TABLE 4 
               
             
            
               
                   
               
               
                 Cytokine assay for the quantitative analysis of mouse IL-4 in culture 
               
               
                 supernatants from T-cell proliferation assay (top) 
               
            
           
           
               
               
               
               
               
               
            
               
                 Soluble 
                 HBsAg 
                 HBsAg 
                   
                   
                   
               
               
                 HBsAg 
                 Nano 
                 Nano 
                 HBsAg 
                 Soluble 
               
               
                 (Recall Ag) 
                 (200 nm) 
                 (400 nm) 
                 Micro (2-8 μm) 
                 HBsAg 
                 Control 
               
               
                 (μg/ml) 
                 (pg/ml) 
                 (pg/ml) 
                 (pg/ml) 
                 (pg/ml) 
                 (pg/ml) 
               
               
                   
               
            
           
           
               
               
               
               
               
               
            
               
                 10 
                 24.14 
                 22.78 
                 77.32 
                 30.63 
                 30.63 
               
               
                 5 
                 24.78 
                 22.32 
                 115.59 
                 30.63 
                 30.63 
               
               
                 2.5 
                 26.99 
                 21.09 
                 100.80 
                 30.63 
                 30.63 
               
               
                 1.25 
                 26.99 
                 24.14 
                 55.98 
                 30.63 
                 30.63 
               
               
                 0.63 
                 21.09 
                 26.20 
                 38.27 
                 30.63 
                 30.63 
               
               
                 0.31 
                 21.38 
                 26.20 
                 29.18 
                 29.64 
                 30.63 
               
               
                 0.16 
                 24.78 
                 27.82 
                 34.49 
                 31.66 
                 30.63 
               
               
                 0.08 
                 24.78 
                 28.71 
                 39.63 
                 30.63 
                 30.63 
               
               
                   
               
            
           
         
       
     
     INCORPORATION BY REFERENCE 
     The contents of all references (including literature references, issued patents, published patent applications, and co-pending patent applications) cited throughout this application are hereby expressly incorporated herein in their entireties by reference. 
     EQUIVALENTS 
     Those skilled in the art will recognize, or be able to ascertain using no more than routine experimentation, many equivalents of the specific embodiments of the invention described herein. Such equivalents are intended to be encompassed by the following claims.