Abstract:
The invention concerns the use, in the induction of an immune response, of a synthetic microparticle polymer carrying on the surface one or more covalently bonded proteins capable of carrying one or more epitopes, the densities of the protein(s) on the surface of the microparticles, and their molecular weights, being adjusted so as to direct the immune response to the induction of a humoral and cellular response or to the induction of a largely cellular response. Said microparticles have an average diameter of approximately 0.25 to 1.5 μm.

Description:
BACKGROUND OF THE INVENTION 
     The object of the present invention is microparticles carrying antigens on their surf ace and their use in the induction of humoral or cellular responses. 
     More specifically, the invention also relates to microparticles carrying a significant density of antigens on their surface. 
     The B cells which express immunoglobulin receptors specific for an individual antigen are highly effective for the presentation of this antigen (Rock et al. C., J. Exp. Med. (1984) 160; 1102; Hutchings et al., Eur. J. Immunol. (1987) 17:393). For example, specific B cells can present tetanus toxin to T cells at antigen concentrations 10 4  times lower than those required for the presentation by nonspecific B cells or peripheral blood monocytes (Lanzavecchia, Nature (1985) 314:537). 
     In addition, in vivo studies with mice deficient in B cells show that these cells are required for the activation of T cells of lymphatic ganglions (Janeway et al., J Immunol. (1987) 138:2848; Kurt-Jones et al. A.K., J. Immunol. (1987) 140:3773). 
     Mice deficient in B cells also show reduced responses with respect to specific CD4+ and CD8+ T cells from tumors, after immunization with Freund&#39;s murine leukemia virus (Schultz et al., Science, (1990) 291). 
     The capacity of B cells to modify and to present the antigen with a view to recognition by CD4+ helper T cells restricted by the class II major histocompatibility complex (MHC) forms the basis of a model for the activation of the B cells by T cells (Noelle et al., The Faseb Journal (1991) 5:2770). 
     The recognition of the peptide-class II MHC complex by CD4+ helper T cells on the surface of the B cells leads to the formation of physically stable conjugates between the T cells and the B cells (Kupfer et al. S. J., Proc. National Acad. Sci. USA (1986) 83:6080). 
     This direct recognition results in the proliferation and the differentiation of B cells in response to lymphokines such as Interleukin-2, Interleukin-4 or Interleukin-5. 
     The induction of the antibody response against an antigen requires the presentation of the antigen by the B cells. 
     The majority of the studies on antigen presentation have been carried out using soluble proteins such as tetanus toxoid, lysozyme, hemocyanin (LH). However, most of the antigens to which the immune system is exposed are contained in complex particulate structures such as bacteria or parasites. 
     It is well known that cells which are capable of phagocytosis such as the macrophages can present bacterial antigens to T cells. 
     However, it is not known whether cells which do not phagocytose, such as B cells, can present complex antigens of significant size. 
     It has recently been shown that, in vivo, bacterial antigens must be in a soluble form in order to induce an antibody-dependent response by the T cells (Leclerc et al., J. Immunol. (1990) 144:3174; Leclerc et al., J. Immunol. (1991) 147:3545). 
     However, it seemed advisable to determine also that, in vivo, bacterial protein antigens are exclusively presented to the T cells by the phagocytic cells and that the B cells cannot modify antigens in particle form. 
     SUMMARY OF THE INVENTION 
     According to the present invention, the capacity of macrophages and B cells to present the same antigen, in soluble and particulate forms, has therefore been compared. 
     In particular, protein antigens, such as lysozyme and TNP-KLH, coupled to poly(acrolein) or polystyrene microparticles of a comparable size to that of a bacterium, have been used. 
     According to the invention, it has unexpectedly been shown that B cells which present TNP-KLH or lysozyme very effectively are incapable of presenting these antigens coupled to beads. However, macrophages present both forms of the antigens to T cells. 
     The study of antigen presentation and the induction of the cellular and/or humoral T response is of particular scientific and medical importance. 
     In fact, directing the response towards a purely cellular response or a purely humoral response could allow vaccination against certain pathogens, modification of certain biological dysfunctions and curing certain pathologies. 
     For example, such direction would enable the elimination of persistent infections or the regulation of allergic responses. 
     In addition, there are two sub-populations of CD4+ T cells, Th1 and Th2, which have different capacities to produce various lymphokines (Mosmann, Cherwinski, Bond, Giedlin and Coffman, J. Immunol., 136, 2348-2357 (1986)). The induction of Th1 or Th2 plays a major role in the resistance to bacterial, parasitic or viral infections. Thus, in the case of murine cutaneous leishmaniasis, the Th1 protect from infection while the Th2 aggravate the disease. In vitro, B lymphocytes optimally stimulate the proliferation of Th2 clones while a strong proliferation of Th1 clones is observed with adherent cells (Gajewski, Pinnas, Wong and Fitch, J. Immunol., 146, 1750-1758 (1991)). 
     Directing of the antigen towards presentation by the B cells or macrophages could allow induction of Th1 or Th2 responses. 
     Various techniques have been developed in the past to achieve a better immune response. 
     The oldest method consists of activating the immune system with adjuvants. Thus, Freund&#39;s adjuvant leads to an increased intensity of the humoral and cellular responses. However, such adjuvants have major disadvantages due to their lack of specificity, toxicity, and immunological side-reactions which may be caused by their lack of purity. 
     The iscomes (immuno-stimulating complexes) are composed of an antigenic complex and an adjuvant, QuilA, which is extracted from trees. These particles have a diameter of about 35 nm and are composed of subunits of about 12 nm. They lead to the induction of an immune response but more often the antigens are encapsulated and thus then released in the external medium. In addition, the technique does not allow accurate control of the type of cells presenting these particles, and these particles therefore induce a double humoral and cellular response. 
     Lastly, from a practical standpoint, these particles are difficulty to prepare, lack stability and have significant toxicity. 
     Liposomes, which have also been tested for use in inducing an immune response, have the same disadvantages as the iscomes. 
     Biodegradable microparticles such as for example lactic and glutamic acid polymers have also been developed (Aguado and Lambert, Immuno. Biol., 184, 113-125 (1992)). These particles liberate the antigen in a soluble form during their degradation. This liberation enables presentation of the antigen by different cells and the induction of a humoral response without the possibility of direction towards a specifically cellular response. 
     Particles composed entirely of recombinant proteins have also been synthesized. Thus, French patent application FR 2.635.532 describes particles composed of a hybrid protein between HBs antigen and an immunogenic sequence presumed to induce neutralizing antibodies directed against the HIV virus. 
     Particles containing poliomyelitis toxin have also been produced. 
     These particles have significant disadvantages. Thus, it is very difficult to insert long sequences into these particles. In addition, they induce as much humoral as cellular response and it is thus not possible to obtain specifically one or the other. 
     Polyacrolein or polystyrene particles to which antibodies have been coupled have already been used for the development of separation techniques (Rembaum et al., Immunol. (1982) 52:341-351). 
     However, no use for the preparation of vaccines and in vivo immunization has been reported. The beads used have diameters of 20 to 35 nm (polyacrolein) or of 40 to 120 μm (polystyrene). 
     Polyacrolein particles of 2 μm diameter have also been used for the in vitro study of T response stimulation (Ziegler et al., Eur J. Immunol. (1987), 17: 1287-1296). The activity of these beads was not tested in vivo. 
     In all this work, the size of the particles was not considered to be a critical criterion. However, particles of small size (nanoparticles) such as HBs particles could be presented by B lymphocytes. On the other hand, particles with too large size (greater than 5-10 microns) could not be presented by phagocytic cells. 
     The various solutions proposed in the prior art, on the one hand to induce a significant immune response and on the other to direct this response specifically towards one of the two response routes, humoral or cellular, are thus not satisfactory. 
     The invention offers the development of products giving a good immune response with either a cellular or a humoral direction. 
     According to the invention, it has unexpectedly been found that such a response can be induced by using microparticles, of small size and having varied antigenic densities. 
     The present invention particularly relates to synthetic polymer microparticles carrying on their surface one or more proteins covalently bonded to the material of the microparticles, said protein or proteins each carrying one or more epitopes and being present at a density of between 10 4  and 5.10 5  molecules/μm 2  for each of the proteins. 
     The invention also relates to the characteristics below, considered alone or in all technically possible combinations: 
     The coupling of the antigenic proteins or microparticles must be covalent in order to avoid the liberation of the antigen in soluble form. 
     The microparticles advantageously have an average diameter of between about 0.25 μm and 1.5 μm, and preferentially of about 1 μm so as to be able to be presented to CD4+ T lymphocytes by phagocytic cells but not by B lymphocytes. 
     Said microparticles are more particularly characterized in that the covalent bond is formed by reaction between the NH 2  and/or CO groups of the proteins and the material making up the microparticle. 
     Advantageously such bond is created by using a bridging reagent as intermediate, such as for example glutaraldehyde or carbodiimide. However, any other bifunctional reagent able to form such a bond can be used. Such reagents are known, see for example Synthetic polypeptides as antigens, M. H. Von Regensmortel, J. P. Briand, S. Muller and S. Plane 1988 (Elsevier). This bond can also be formed without a bridging reagent. 
     The material of the microparticle can advantageously be a biocompatible polymer, such as an acrylic polymer, for example polyacrolein or polystyrene or the poly(alpha-hydroxy acids), copolymers of lactic and glycolic acids, or lactic acid polymers. 
     By polymer should be understood any homopolymer or hetero- or co-polymer. 
     It must allow covalent bonding of the proteins to the material and must not cause a rejection or toxic reaction by the organism into which it may be injected. Advantageously, for human therapeutic applications, it should be a biodegradable polymer, for example a polymer able to be degraded by cells containing lysosomal enzymes, such as the macrophages. 
     Such biodegradable materials can include lactic and glutamic acid polymers, starch or polymers used for biomedical applications, and in particular those used for sutures. 
     Such a microparticle can carry on its surface, in addition to the antigenic proteins, molecules able to activate the immune system, such as the interleukins, in particular gamma-interferon or interleukin 4. 
     These microparticles can carry one or more proteins which can themselves each contain one or more epitopes. Such proteins can be glycoproteins, synthetic peptides containing an epitope or several epitopes, or any other nonprotein molecule or molecule containing a protein portion able to induce an immune response. 
     The microparticles which are the object of the present invention can in addition be encapsulated in order to protect the antigens fixed to their surfaces from degradation and to transport them to their site of action. 
     They can thus comprise a nucleus formed from a polysaccharide matrix, to which are bound the antigens, an initial lipid layer bound covalently to the nucleus and a second layer of amphophilic molecules. 
     Another object of the invention is drugs or vaccines comprising the microparticles described above, as well as pharmaceutical compositions characterized in that they contain them, in combination with pharmaceutically compatible diluents or adjuvants. 
     The present invention generally relates to the use of synthetic polymer microparticles carrying on their surface one or more covalently bonded proteins, said protein or proteins each carrying one or more T or B epitopes, for the production of a drug or vaccine for inducing an immune response, according to which the densities of the protein or proteins on the microparticle surfaces are adjusted so as to direct said immune response towards a largely humoral response or a largely cellular response. 
     Another aspect of the invention has as object a process for the production of a drug or vaccine whose immune response is either largely humoral or largely cellular, of Th1 or Th2 type, said process being characterized in that at least one protein carrying one or more epitopes is covalently fixed to synthetic polymer microparticles or beads, the density of the protein fixed to the surface being varied according to the type of response required. 
     In order to induce a cellular and humoral response, microparticles should preferentially be used with a density for each of the proteins carrying an epitope of a minimum of 10 5  and preferentially of about 5.10 5  molecules/μm 2 . Such densities approximately correspond for a bead of 1 μm diameter to quantities of protein on the microparticle surface of 10 5  and 4.10 5  molecules respectively. 
     For the induction of a largely cellular response, restricted class II CD4+, microparticles should preferentially be used with a density for each of the proteins carrying an epitope of between 10 4  and 5.10 4  protein molecules/μm 2 . 
     In order to encourage the induction of this cellular response, microparticles should preferentially be used carrying on their surface proteins with molecular weights greater than 50 kD. 
     The other characteristics of these microparticles are those given above for the high-density microparticles. 
     The proteins and antigens covalently bonded to the microparticles depend on the anticipated application for said microparticles. 
     They also depend on the type of immune response required, but also on the disease or ailment to be treated or against which the patient is to be protected. 
     Examples of epitopes which may be used are the epitopes from the Pre S2 region of the HBS antigen of the viral hepatitis virus, with the following sequences: 
     T epitope: Pre S:T (120-132) 
     MQWNSTTFHQTLQ (SEQ ID NO:1) 
     B epitope: Pre S:B (132-145) 
     QDPRVRGLYFPAGG (SEQ ID NO:2) 
     Other examples are the epitopes of the VP1 protein of the poliomyelitis virus whose sequences are as follows: 
     T epitope: C3:T (103-115) 
     KLFAVWKITYKDT (SEQ ID NO:3) 
     B epitope: C3:B (93-103) 
     DNPASTTNKDK (SEQ ID NO:4) 
     Another example is the epitope of the V3 loop of the GP120 protein of the HIV1 virus whose sequence is the following: 
     T+B epitope: V3 loop 
     INCTRPNNNTRKSIRIQRGPGRAFVTIGKIGNMRQAHCNI (SEQ ID NO:5) 
     The B epitopes may preferentially be used to induce a humoral response using high-density microparticles and the T epitopes to induce a largely cellular response using microparticles with a low density of surface proteins. 
     Such microparticles may be injected into patients who are to be treated in a therapeutic or prophylactic manner in ways known to those skilled in the art, for example by subcutaneous, intra-peritoneal, or intravenous injection or by any other means for inducing an immune response. 
     This subject is discussed in Current protocols in immunology (edited by J. F. Coligen, A. M. Kruisbeek, D. H. Margulies, E. M. Shevach, W. Strober, published by Wiley-Interscience), in which the range of immunological techniques is listed. 
     A particular advantage of the present invention rests in the fact that it enables the induction of a humoral or cellular immune response without the addition of adjuvants to the beads or microparticles. However, the addition of nontoxic adjuvants not causing an immune side-reaction is also envisageable within the scope of use according to the present invention. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The present invention is illustrated without being in any way restricted by the following examples in which: 
     The diagrams of FIG. 1 are the results of fluorimetric analyses (FACS) of microparticles carrying the KLH or TNP-KLH antigens. The ordinates show the antibody used (PBS-control, anti-KLH, anti-TNP). The abscissae show the type of microparticle tested: B (KLH), B (TNP-KLH), B (OVA) and B (OVA-TNP) which correspond to the microparticles on which are bonded respectively KLH, TNP-KLH, ovalbumin and ovalbumin-TNP. 
     FIGS. 2A to 2D show the capacities of spleen and macrophage cells and of TNP-specific B cells activated by LPS to present KLH, TNP-KLH, microparticles carrying KLH and microparticles carrying TNP-KLH. 
     FIG. 3 is a curve showing the proliferative responses of ganglion cells from mice immunized with soluble lysozyme and stimulated in vitro by soluble lysozyme (FIG. 3A) or by microparticles carrying lysozyme and having diameters of 0.25, 0.75 and 1.5 (FIG. 3B). The cell proliferation was measured by the incorporation of thymidine (CPM) as ordinate, with the microparticle dilution shown on the abscissa. 
     FIG. 4 shows the production of IL2/IL4 by a lysozyme-specific hybridoma after stimulation by soluble lysozyme (FIG. 4A) or by microparticles carrying lysozyme (FIG. 4B). The microparticle concentrations are shown on the abscissae while the proliferation is shown on the ordinates. 
     FIGS. 5A and 5B show the activation of the lysozyme-specific T hybridoma measured by the production of IL2/IL4 after stimulation by soluble lysozyme (FIG. 5A) or lysozyme coupled to microparticles (FIG. 5B) in the presence of splenocytes or A20 B cells as cells presenting the antigen. 
     FIGS. 6A and 6B show the in vitro proliferation after stimulation by soluble lysozyme of inguinal ganglion cells from mice immunized with respectively soluble lysozyme in complete Freund&#39;s adjuvant (FIG. 6A) and by lysozyme coupled to microparticles (FIG. 6B). 
     FIGS. 7A and 7B show the in vitro proliferation after stimulation by lysozyme of inguinal ganglion cells from mice immunized by different concentrations of soluble lysozyme (7A) or lysozyme coupled to microparticles (7B). 
     FIG. 8 shows the proliferation of ganglion cells from mice immunized with lysozyme in complete Freund&#39;s adjuvant or in PBS or in the presence of microparticles coupled to patella hemocyanin, or KLH (Keyhole Limpet Hemocyanin). 
     FIG. 9 shows the proliferative response of ganglion cells from mice immunized with soluble hemoglobin in adjuvant (Hb+CFA) or coupled to beads (B-Hb). 
     FIG. 10 shows the proliferative response of mouse cells stimulated by soluble ovalbumin (OVA+CFA) or ovalbumin coupled to beads (B-OVA). 
     The proliferative response of the hemoglobin and ovalbumin respectively was measured as ordinate by the incorporated radioactivity (CPM) as a function of the quantity of hemoglobin or ovalbumin (as abscissa) used for restimulating the cells. 
     FIG. 11 illustrates the proliferation of mouse cells after immunization with the C3 peptide as its soluble form (C3:T+CFA) or as microparticles (B-C3: T). The cells were restimulated in the presence of a quantity of soluble C3 (as abscissa) and the proliferation was measured (ordinate). 
     FIG. 12 shows the proliferation of mouse cells after immunization with the pre-S:TB peptide as its soluble form (Pre-S:TB+alum) or as microparticles (B-pre-S:TB) or the pre-S:B peptide in particulate form (B-Pre S:B) and restimulated by the Pre-S peptide. 
     FIGS. 13A and 13B represent respectively the levels of anti-lysozyme antibody (FIG. 13A) and anti-KLH antibody (FIG. 13B) of mice immunized with lysozyme and alum adjuvant, with microparticles carrying lysozyme or with microparticles carrying LH. 
     FIGS. 14 and 15 show the antibody response of mice immunized with hemoglobin (FIG. 14) or ovalbumin (FIG. 15) in soluble or particulate form. The log of the antibody titer is shown on the ordinate with time on the abscissa. 
     FIG. 16 shows the antibody response of mice immunized by soluble pre-S: TB peptide, or the pre-S: TB or pre-S: B peptides in particulate forms. The ordinate and the abscissa of this curve are as defined for FIGS. 14 and 15. 
     FIG. 17A shows the proliferation of mouse cells after immunization by injection of lysozyme with Freund&#39;s adjuvant, after in vitro stimulation by microparticles carrying different densities of lysozyme. 
     FIG. 17B shows the in vitro proliferation of mouse cells after immunization in vivo with lysozyme or with beads carrying lysozyme after stimulation by different concentrations of lysozyme. 
     FIG. 18 is a diagram illustrating the production of anti-lysozyme antibody in cells from mice immunized by injection of lysozyme and Freund&#39;s adjuvant or by lysozyme-carrying microparticles. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     EXAMPLE 1 
     Preparation of beads coupled to KLH or to ovalbumin. 
     1. Materials and methods and presentation by B cells or by macrophages. 
     The mice were 6 to 8 week old BALB/c and DBA/2 females. 
     The antigens were KLH and ovalbumin (OVA) marketed by Sigma Chemical (St Louis, USA). The trinitrophenylated hemocyanin (TNP4-KLH) was prepared as previously described (Shutze et al., J. Immunol. (1989) 142:2635). 
     1.1 Covalent coupling of antigens to poly(acrolein) microparticles. 
     Poly(acrolein) microparticles with diameter between 0.25 and 1.5 μm, marketed by Polysciences Inc. (Washington Pa.) were coupled to ovalbumin or KLH as previously described (Rembaum et al., Immunol. (1982) 52:341; Ziegler et al., Eur. J. Immunol. (1987) 17:1287). 
     1 ml of these microparticles was washed twice in PBS and resuspended in 1 ml of KLH or ovalbumin (5 mg/ml in PBS). After 3 hours&#39; incubation at ambient temperature, the microparticles were washed twice in PBS and resuspended in 2 ml of PBS containing 15 of bovine serum albumin (BSA) and antibiotics. The microparticles thus obtained were stored at 4° C. until used. 
     The microparticles carrying the TNP-OVA or TNP-KLH antigens were prepared by incubation of microparticles carrying OVA or KLH with TNBS (trinitrobenzene sulfonate). 
     2 ml of the microparticles which had been coupled to KLH or ovalbumin were washed twice in PBS and resuspended in 2 ml of cacodylate buffer containing 10 mg/ml of TNBS. The microparticles were incubated for 30 minutes in darkness at ambient temperature and washed three times in PBS. They were resuspended in 2 ml of PBS containing 1% BSA and antibiotics and stored at 4° C. 
     1.2 Analysis by flow cytofluorimetry. 
     50 μl of microparticles were washed twice in PBS containing 1% of BSA and incubated for 40 minutes at 4° C. with mouse anti-KLH or anti-TNP serum. After two washes the microparticles were incubated with goat antibody coupled to FITC (fluoroisothiocyanate) directed against mouse immunoglobulins (Biosys, Compiegne, France) for 40 minutes at 4° C. 
     After four washes the microparticles were resuspended in 1 ml of PBS containing 1% of BSA. 
     The fluorescence intensity was measured by use of a FACSAN flow cytometer (Becton Dickinson, Mountain View, Calif.). 
     1.3 Culture medium. 
     The lymphocytes were cultured in RPMI 1640 (Seromed, Munich, FRG) complemented with 2 mM L-glutamine, 10% of FCS (fetal calf serum) inactivated by heat, 50 μM of 2-ME and antibiotics. 
     1.4 Establishment of the KLH-specific T cell line. 
     This cell line was established and maintained according to the method described by Taylor et al. (IRL Press, New York) and Galelli et al. (J. Immunol. (1990) 145:2397). 
     Inguinal ganglion cells (4 10 6  /ml) from DBA/2 mice which 8 days before removal of the cells had received an injection at the base of the tail of 100 μg of KLH in emulsion in complete Freund&#39;s adjuvant were cultured for 4 days in the culture medium in the presence of KLH (100 μg/ml). 
     The cultures were incubated in a humid atmosphere under 7.5% of CO 2  at 37° C. 
     A cell line was established from this initial culture by serial passage of T cells purified on Ficoll (2.10 5  /ml) in the presence of DBA/2 mouse spleen cells which had been irradiated (3000 rads) for 6 to 8 days (rest period) or with irradiated spleen cells plus KLH (100 μg/ml) for 4 days (stimulation period). 
     The T cells used in these experiments were collected 8 to 10 days after their last contact with KLH. 
     1.5 Estimation of the T cell proliferation. 
     Cultures in triplicate containing 5.10 4  T cells purified on Ficoll, and 5.10 4  purified and irradiated (900 rad) TNP-specific memory B cells, or 5.10 5  irradiated (3000 rad) entire spleen cells, or 10 5  irradiated (3300 rad) adherent spleen cells, or 10 5  irradiated (3300 rad) A20 B cell lymphoma cells positive for class II MHC (Kim et al., J. Immunol. (1979) 122:549), or 10 5  TNP-specific virgin B cells activated by LPS as source of the cells presenting the antigens, and different concentrations of antigen were incubated in flat-bottomed microculture plates (Corning, Cambridge, Mass.) under a total volume of 0.2 ml/well of complete medium. The T cell proliferation was estimated by incorporation of tritiated thymidine during the final eight hours of 3 days&#39; culture. 
     The results are expressed as the geometric mean of three cultures, after elimination of background noise. The standard deviation was less than 15% of the mean. 
     1.6 TNP-Specific B cells. 
     The TNP-specific B cells from normal mice were purified by adsorption and elution on TNP8-gelatin according to the method described by Haas and Layton J. E., J. Exp. Med. (1975) 141:1004. 
     This method was modified in order to obtain populations enriched in TNP-specific memory B cells from spleens from previously immunized mice, as described previously (Galelli et al., J. Immunol. (1990) 145:2397)). The TNP-specific memory B cells were selected on the gelatin carrying a hapten (TNP2-gelatin), by testing the affinity of TNP receptors by comparison with virgin B cells, and the capacity to secrete large quantities of anti-TNP immunoglobulin G in the presence of low antigen concentrations. 
     10 8  spleen cells containing neither erythrocytes nor dead cells were suspended in 3 ml of HEPES (50 mM) buffered with DMEM (Seromed, Munich, Germany) and incubated in plastic Petri dishes covered with TNP2-gelatin. The dishes were gently agitated for 15 minutes at 4° C., then washed 10 times with DMEM at ice temperature. The adherent cells were eluted by the addition of 5 ml of DMEM reheated to 37° C. and the bonded TNP-gelatin was eliminated by digestion with collagenase (CLSIII Collagenase from Worthington Biochemicals, Freehold, N.J., 100 U/ml) for 15 minutes at 37° C. 
     This method gives an overall yield, expressed as a percentage of the original number of spleen cells, of 0.3 to 0.6% of cells bonding to TNP from the immunized mouse spleen. The cells were cultured overnight, before the addition of other cells and reagents, in order to enable the reexpression of surface immunoglobulins modified by the treatment with the collagenase. The presence of free TNP receptors on the cells was evaluated from their capacity to bind erythrocytes carrying TNP on their surface. 
     55 to 76% of the cells obtained from the immunized mice formed rosettes with the mouse spleen B cells modified by the TNP. These cells did not proliferate in response to concanavalin A but were 20 times enriched, for the cells which secreted anti-TNP immunoglobulin G after stimulation by TNP-LH, by comparison with non-fractionated spleen cells. 
     1.7 TNP-Specific virgin B cells activated by LPS. 
     TNP-Specific virgin B cells from non-immunized mice were purified by adsorption and elution on TNP8 gelatine as described previously. These cells were cultured to a density of 2.10 6  per ml in a medium containing 50 μg/ml of LPS (Salmonella enteriditis, Difco Laboratories, Detroit, Mich.) for 3 days. The non-adherent lymphoblasts were purified by use of Ficolle-Hypaque (Pharmacia, Piscataway, N.J.), then washed and used as secondary cells. 
     1.8 Macrophages. 
     The macrophages were obtained from non-immunized spleen cells by adhesion for 4 hours at 37° C. followed by washing of the cells in order to eliminate the non-adherent cells as previously described (Kakiochi et al., J. Immunol. (1983) 131:109). 
     2. Results. 
     2.1 Verification of antigen coupling to the microparticles. 
     The KLH was covalently bonded to polyacrolein microparticles with diameter between 0.25 and 1.5 μm. The coupling of the KLH to the microparticles was checked by flow cytofluorimetric analysis using anti-KLH mouse serum. 
     The results obtained with 1.5 μm microparticles are shown in FIG. 1. 
     The 1.5 μm microparticles were coupled to ovalbumin (B OVA) or KLH (B-KLH). The TNP-OVA or TNP-KLH microparticles (designated respectively B(TNP-OVA) and B(TNP-KLH)) were prepared by incubation of microparticles carrying OVA or KLH with TNBS. The cytofluorimetric analysis was carried out on microparticles incubated in the presence of PBS or anti-KLH or anti-TNP mouse serum. After washing, the microparticles were incubated with goat antibodies bonded to FITC directed against mouse immunoglobulins and were analyzed by flow cytometry. 
     Similar results were obtained with 0.25 and 0.75 μm microparticles. 
     Control microparticles coupled to ovalbumin were not recognized by the anti-KLH serum. 
     2.2 Comparison of the ability of different splenocyte populations to present soluble or particulate antigens. 
     The ability of non-fractionated splenocytes, macrophages, and TNP-specific virgin B cells was compared for presentation of soluble or particulate KLH and TNP-KLH to KLH-specific T cells. 
     In these experiments the splenocyte populations were prepared from non-immunized mice. After purification, the TNP-specific B cells were activated for three days by LPS; it is known that the lymphoblasts induced by LPS are extremely efficient for antigen presentation (Kakiochi et al., J. Immunol. (1983) 131:109). 
     The results are illustrated in FIG. 2 for which 5.10 8  irradiated splenocytes, 10 5  adherent cells or 10 5  TNP-specific virgin B cells activated by LPS were cultured with 5.10 4  KLH-specific T cells in the presence of different quantities of soluble KLH (A), soluble TNP-KLH (B), or fixed on microparticles (B KLH) (C), or (B TNP-KLH) (D). The T cell proliferation was estimated on day 3. 
     As shown in FIG. 2 (2A and 2B) the macrophages and the B cells activated by LPS efficiently stimulated the T cells when they were incubated with soluble KLH or TNP-LH. 
     In contrast to these results, only the macrophages, and not the LPS-activated TNP-specific B cells, were able to stimulate the KLH-specific T cells (FIGS. 2C and D) when the microparticles carrying KLH or TNP-KLH were used. 
     These results show that the macrophages are responsible for the activity of spleen cell antigen presentation when particulate antigens are used. 
     The inability of the TNP-specific B cells to present the particulate antigen has thus been demonstrated. 
     EXAMPLE 2 
     Induction of a lysozyme specific CD4+ T-proliferative response in vivo and in vitro by lysozyme-coupled microparticles. 
     1. MATERIALS AND METHODS. 
     1.1 Antigens. 
     The lysozyme (LYSO) and the Limulus hemocyanin (LH) were from Sigma Laboratories. 
     1.2 Coupling of the antigen to the microparticles. 
     The soluble antigen was made particulate by coupling to microparticles (Polysciences) of between 0.2 and 1 μm diameter. Two coupling methods were used: 
     1.2 a) Direct covalent coupling without activating agent. 
     The polyacrolein beads or microparticles possess aldehyde groups capable of spontaneous reaction with the amine functions of the proteins. 
     1 ml of beads were washed 4 times in PBS and then taken up in 1 ml of antigen at 5 mg/ml concentration. After 3 hours&#39; incubation at ambient temperature, the beads were washed 3 times in PBS and incubated for 30 minutes in 1 ml of PBS-1% human albumin in order to saturate the free reactive groups on the beads. After washing, the particles were then taken up in 2 ml of PBS-1% human albumin-1% antibiotic and stored at +4° C. 
     b) Covalent coupling by glutaraldehyde. 
     The antigen was coupled to polystyrene beads by glutaraldehyde, which was capable of forming a Schiff&#39;s base with the protein amine groups. 
     0.5 ml of beads were washed 3 times in PBS and taken up in 0.5 ml of 8% glutaraldehyde. After 6 hours&#39; incubation at ambient temperature, the beads were washed twice and then taken up in 1 ml of antigen at concentration 400 μg/ml. After incubation overnight at ambient temperature, the beads were washed and incubated with 1 ml of 0.2M ethanolamlne for 30 minutes in order to block the free aldehyde functions of the glutaraldehyde. 
     After a final washing, the particles were taken up in 1 ml of PBS-1% human albumin-1% antibiotic then stored at +4° C. 
     This coupling method enabled the quantity of proteins coupled to the microparticles to be determined by spectrophotometry. The absorbances of the 400 μg/ml protein solution and the supernatant obtained after incubation of the beads with this protein solution were measured at 280 nm. Given the number of beads used for the coupling, the difference between the quantity of protein before coupling and the residual quantity after coupling could be used to estimate the quantity of lysozyme coupled per particle. 
     1.3 Immunization protocol. 
     BALB/c females, haplotype h-2 d , aged 6 to 9 weeks (reared in the Institut Pasteur) were used. 
     immunization by intra-peritoneal route: 100 μg of lysozyme with 1 mg of alum were injected, or different quantities of antigen coupled to beads without adjuvant, 
     immunization by subcutaneous route: 100 μg of lysozyme in emulsion with complete Freund&#39;s adjuvant were injected at the base of the tail, or different quantities of antigen coupled to beads. 
     The serum of each mouse was sampled 7 to 14 days after injection. The antibody strength of the serum was measured by the ELISA assay. 
     The cell proliferative response was measured on inguinal ganglions and/or on the spleen, sampled 7 and/or 14 days after each injection. 
     1.4 Detection of antibodies by ELISA. 
     The antigen (lysozyme) was incubated at a concentration of 5 μg/ml in 50 mM pH 9.6 carbonate buffer in the microplates (Nunc) for one night at 4° C. After washing with a 0.01% PBS-Tween 20 buffer, the different serum dilutions to be tested, in 1% BSA buffer, were incubated for 1 hour at 37° C. After washing, 100 μl of a mouse anti-Ig conjugate (complete anti-Ig supplied by Diagnostics Pasteur and specific anti-Ig by Sigma) were placed in each well, marked with goat peroxidase; this was incubated for 1 hour at 37° C. After washing, a substrate solution was added freshly prepared as follows: 0.5 mg/ml of orthophenylenediamine (Sigma) in a 0.1M citric acid-0.2M disodium phosphate buffer, pH 5, to which was added H 2  O 2  to 1/2500. 
     A yellow coloration revealed the presence of specific antibodies; the enzyme reaction was stopped 8 minutes later by the addition of 50 μl of 11.5% H 2  SO 4 . 
     The absorbance of each well was measured at 492 nm by an optical density reader (Dynatech). The negative control was made with 1:100 serum from non-immunized BALB/c mice. The results are expressed either in OD×1000 from measured absorbance, corrected for the absorbance in absence of serum, or by the antibody titer calculated from the linear regression based on the absorbance obtained with the serum from the non-immunized BALB/c mice. 
     When the antigen was in particulate form, the ELISA assay was carried out in tubes. The serum dilutions to be tested were incubated directly with the antigen coupled to the beads (8.10 8  particles/ml). 
     Washings were made by centrifuging in 0.1% PBS-Tween 20 buffer. When the enzyme reaction had finished, 200 μl from each tube was transferred onto a microplate and the absorbance then measured. 
     1.5 Inhibition of the fixation of the anti-lysozyme antibody by the ELISA assay. 
     The ELISA assay measured the fixation of specific antibodies present in the serum of the immunized BALB/c mice by the lysozyme. This fixation was reduced if the serum was preincubated (before the ELISA assay) with the antigen: soluble lysozyme or lysozyme coupled to beads, which then behaved as an inhibitor. 
     The anti-lysozyme serum was preincubated with soluble lysozyme or lysozyme coupled to beads for 1 hour at 37° C., then for 1 night at 4° C.; the reaction was carried out in the tubes. The fixation of antibodies not bonded to the inhibitor was evaluated by the ELISA assay (triplicates) on microplates, in which the wells were covered with 5 μg/ml of lysozyme. The absorbance of each well was measured at 492 nm, and corrected for the absorbance in the absence of serum. The negative control was carried out with 1:100 serum from non-immunized BALB/c mice. The absorbance without inhibitor during the preincubation of the serum corresponded to the maximum anti-lysozyme antibody fixation. 
     Results are expressed as a percentage of the inhibition of the antibody fixation and calculated according to the ratio: ##EQU1## 
     The graphical representation of the soluble lysozyme concentration necessary for 50% inhibition, together with the number of beads coupled to lysozyme, enabled estimation of the quantity of lysozyme fixed per particle. 
     1.6 Stimulation of a lysozyme-specific T hybridoma 
     A T hybridoma was produced by immunization of BALB/c mice with lysozyme. It specifically recognized peptide 108-116 of lysozyme, in combination with molecules of the class II I-E d  Major Histocompatibility Complex. 
     10 5  T hybridoma cells were stimulated by increasing antigen concentrations: lysozyme or coupled beads, in the presence of different cells presenting the antigen: 5.10 5  irradiated splenocytes (3000 rad) of BALB/c mice or 10 5  cells of B lymphoma A20, restricted by Class II MHC molecules. The cells were cultured (in triplicate) in a complete RPMI medium (SEROMED) supplemented with 10% decomplemented fetal calf serum, 50 μM β-mercaptoethanol, 2 mM glutamine, 100 UI/ml penicillin and 100 μg/ml streptomycin, on flat-bottomed microplates (Corning 25860). The positive control was performed by stimulation of the hybridoma by the T lymphocyte mitogen:concanavalin A at 5 μg/ml. 
     The supernatant was removed after 24 h culture at 37° C. (7.5% CO 2 ), then frozen to -20° C. for a minimum of 16 h. The stimulation of the hybridoma was measured by the IL2 concentration of the supernatant in a CTL-L cell proliferation test. Standard deviations have not been given as the error was lower than 10% of the mean of the triplicates. 
     1.7 Determination of IL2 and IL4 
     The CTL-L line is dependent on Interleukin 2 and Interleukin 4; it was maintained in culture in complete medium enriched with 20% of rat splenocyte supernatant, incubated 36 h with 2.5 μg/ml of concanavalin A. 
     After thawing, the culture supernatants (tested 1/2) were incubated in the presence of 2.25.10 4  CTL-L cells, previously washed three times in RPMI 1640 medium, for 3 days at 37° C. (7.5% CO 2 ). 
     The cell proliferation was measured by the addition of tritiated thymidine with specific activity 1 Ci/mmole, at a level of 2 μCi/ml of culture, for the last 16 hours of culture. 
     The cell DNA was recovered after cell lysis and filtration using a &#34;Skatron&#34;. Radioactivity incorporation was counted by scintillation using a beta counter. 
     The results are expressed in cpm based on the mean of the triplicates, corrected for the radioactivity incorporated in the absence of antigen. 
     1.8 Proliferation test 
     The spleen and/or the inguinal ganglions were removed under sterile conditions 7 or 14 days after immunization of the mice (see immunization protocol). 8.10 5  Cells were incubated in the presence of different concentrations of antigen, soluble or coupled to beads. The cells were cultured (in triplicate) in RPMI 1640 medium (SEROMED) supplemented with 1.5% decomplemented fetal calf serum, 0.5% normal mouse serum, 50 μM β-mercaptoethanol, 2 mM glutamine, 100 UI/ml penicillin and 100 μg/ml streptomycin, on microplates (Corning 25860) for 4 days at 37° C. (7.5% CO 2 ). 
     The cell proliferation was measured by the incorporation of tritiated thymidine with specific activity 25 Ci/mmole, at a level of 2 μCi/ml of culture, for the last 16 hours of culture. The cell DNA was recovered after cell lysis and filtration using a Skatron. Radioactivity incorporation was counted by scintillation using a beta counter. 
     The results are expressed in cpm based on the mean of the triplicates, corrected for the radioactivity incorporated in the absence of antigen. 
     2--RESULTS. 
     2.1. Stimulation of ganglion cells from mice immunized with lysozyme by lysozyme coupled to microparticles. 
     In the tests illustrated by FIGS. 3A and 3B, BALB/c mice were immunized by subcutaneous injection at the base of the tail of soluble lysozyme complemented with Freund&#39;s adjuvant (CFA). 
     After 14 days, the inguinal ganglions were removed, and the proliferative response of these cells was tested in vitro against different concentrations of lysozyme or against different concentrations of microparticles coupled to lysozyme. The results are expressed in cpm corrected for the value obtained without antigen. 
     Soluble lysozyme induced substantial proliferation of cells from mice immunized by this antigen in Freund&#39;s adjuvant (3A). The in vitro stimulation of these cells by lysozyme-microparticles revealed that the latter are able to induce a very strong cell proliferation (FIG. 3B). The microparticles with very large diameter, 0.81 and 0.96 μm (spontaneous coupling), were very effective. 
     2.2. Stimulation of T hybridoma by lysozyme coupled to beads 
     FIGS. 4A and 4B correspond to the results for stimulation of lysozyme-specific T hybridoma by soluble lysozyme (4A) or lysozyme coupled to microparticles (4B). The degree of stimulation of the hybridoma was measured by the level of IL-2/IL-4 produced. 
     In the presence of irradiated splenocytes, the T hybridoma was strongly stimulated by soluble lysozyme (FIG. 4A). In the presence of these cells, the large lysozyme-microparticles (0.81 and 0.96 μm) also caused substantial production of IL-2/IL-4 (FIG. 4B), in contrast to the 0.5 and 0.25 μm microparticles which were not able to stimulate the specific T hybridoma. 
     2.3. Inability of B lymphoma A20 cells to present lysozyme coupled to beads to lysozyme-specific T hybridoma. 
     It is known that B cell tumors carrying Ia receptors can be used as antigen-presenting cells for antigens which do not react with the Ig receptor but which are fixed by B cell tumors by nonspecific mechanisms (Walker et al., J. Immunol. (1982) 128:2164; Glimcher et al. J. Exp. Med (1981) 155:445; MacKean et al. J. Exp. Med. (1981) 154:1419). 
     The capacity of one of these B cell tumors, the A20 line, to present lysozyme in soluble or particulate form was thus tested. 
     The presentation of soluble or particulate lysozyme was compared using two sources of antigen-presenting cells: either a heterogenous source, irradiated entire splenocytes, or B cells from the A20 lymphoma. When the antigen was in soluble form (FIG. 5A), it could stimulate the T hybridoma equally well in the presence of splenocytes as of A20 B cells. However, particulate lysozyme was presented only by splenocytes and not by A20 B cells (FIG. 5B). 
     These results confirm that splenocytes can present an antigen to T cells, either in soluble or particulate form. However, B lymphocytes were not able to present an antigen rendered particulate by coupling to a bead of a size of the order of a micron. 
     2.4 Induction of T proliferative responses by injection of lysozyme coupled to microparticles to mice. 
     The in vivo immunogenicity of the antigen coupled to microparticles was analyzed by immunizing BALB/c mice with lysozyme in complete Freund&#39;s adjuvant or with this antigen coupled to polyacrolein beads. After 14 days, cells from draining ganglions of these animals were stimulated in vitro by different concentrations of soluble lysozyme. 
     In the presence of soluble lysozyme, the ganglion cells proliferated strongly, whether originating from mice immunized with soluble lysozyme or lysozyme-microparticles (FIG. 6A). This shows that in both cases lysozyme-specific T cells were sensitized in vivo. After injection of LH-microparticles to mice, representing the specificity control, the ganglion cells of these animals were not able to proliferate in response to stimulation by soluble lysozyme in vitro (FIG. 6B). The cellular response in vivo is thus specific to the protein antigen coupled to microparticles, used during immunization of the mice. 
     The proliferative response of the cells sensitized by 10 9  lysozyme-microparticles (corresponding to 1 μg of lysozyme), in the absence of adjuvant, was as high as that of cells from animals immunized with 100 μg of lysozyme in Freund&#39;s adjuvant (CFA) (FIG. 6A). In order to confirm and clarify this result, proliferative responses of ganglion cells from animals having received different doses of lysozyme in CFA or different concentrations of coupled microparticles were compared, after in vitro stimulation by soluble lysozyme. 
     In the case of FIGS. 7A and 7B, the mice had been immunized by subcutaneous injection at the base of the tail of soluble lysozyme and complete Freund&#39;s adjuvant (CFA) (FIG. 7A) or beads coupled to antigen without adjuvant (FIG. 7B). 
     After 14 days, the inguinal ganglions were removed, and the proliferative response of these cells was tested in vitro against different lysozyme concentrations. The results are expressed in cpm corrected for the value obtained without antigen. 
     In FIG. 7B, it should be noted that the designations 10 9 , 10 8 , 10 7  and 10 6  B-LYSO correspond respectively to weights of 1; 0.1; 0.01 and 0.001 μg of lysozyme. 
     These results show that the ganglion cells from animals immunized with lysozyme-carrying microparticles proliferate in vitro after contact with lysozyme, thus demonstrating sensitization of the T cells specific for this antigen. 
     Comparison of the concentration effects (FIG. 7) shows that 1 μg of lysozyme coupled to beads gives a response quasi-equivalent to that of 1 μg of antigen injected in CFA. 
     FIG. 8 represents the proliferative response of cells from mice immunized with lysozyme in complete Freund&#39;s adjuvant (CFA) or in PBS with microparticles coupled to LH. The addition of LH beads to lysozyme did not lead to induction of high proliferative responses, which shows that the lysozyme must be covalently coupled to the microparticles to induce T-proliferative responses. 
     2.5--Induction of T-proliferative responses by injection of mice with hemoglobin or ovalbumin coupled to microparticles 
     Mice were immunized with hemoglobin or ovalbumin in complete Freund&#39;s adjuvant, or with these proteins covalently coupled to the same type of particles as in the previous examples (polystyrene, 1 μm diameter). 
     The ganglion cells from these animals were restimulated in vitro by the soluble proteins and the cell proliferation was measured. 
     The results obtained for hemoglobin (Hb) are shown in FIG. 9, while FIG. 10 shows the results obtained for ovalbumin (OVA). 
     These results overall show that these proteins coupled to microparticles are able to sensitize CD4+ T lymphocytes specific to these proteins in vivo, in the absence of adjuvant. 
     2.6--Induction of T-proliferative responses by injection of synthetic peptides 
     2.6.1--T Epitope from region C3 of the VP1 protein The T epitope of the C3 region (C3: T, 103-115) of the poliovirus protein was synthesized and covalently coupled to 1 μm beads. These beads were injected into BALB/C mice. 
     The results in FIG. 11 clearly show that the T epitope coupled to the beads (B-C3:T) induced a strong T-proliferative response for quantities of the order of 10 9  beads injected per mouse. 
     2.6.2--Pre-S:T peptide of the HBS antigen 
     The pre-S:T peptide (120-132) of the HBS antigen was synthesized and covalently coupled by glutaraldehyde to beads of 1 μm diameter. 
     FIG. 12 shows that the injection of 10 9  beads to DBA/1 mice induced a strong T-proliferative response, stronger than that obtained with the peptide in CFA. The injection of beads not containing the B epitope did not induce a proliferative response, showing the specificity of the response. 
     EXAMPLE 3 
     Induction of antibody response by microparticles carrying an antigen. 
     The materials and methods were similar to those of Example 2. 
     1. Lysozyme or Limulus hemocyanin 
     For FIGS. 13A and 13B, BALB/c mice were immunized by intra-peritoneal injection with 100 μg of soluble lysozyme in adjuvant (alum) or with beads coupled to antigen: lysozyme or Limulus hemocyanin (LH), without adjuvant. 
     The injections were carried out at D0, D21, D42, the serums were taken at D20, D31, D40 and D52 and assayed by ELISA for their antibody content. The results are expressed in log10 of the titer of anti-lysozyme antibody (FIG. 13A) and anti-KLH antibody (FIG. 13B). 
     Three antigen injections were performed i.p. at days 0, 21 and 42. The lysozyme-microparticles gave very good antibody responses while no antibody response was induced by the LH microparticles. These microparticles moreover very efficiently stimulated T responses. 
     One of the differences between LH and lysozyme is their molecular weights (14500 for lysozyme and 71000 for LH). 
     At equal concentrations of coupled antigen, the density of LH molecules on the beads is thus about 5 times lower. This could explain the absence of stimulation of antibody responses if these are due to T-independent direct stimulation by the antigen present at high density on the microparticles. 
     2. Hemoglobin and ovalbumin 
     Mice were immunized with soluble antigen in alum adjuvant or with the same antigen in particulate form, in the absence of adjuvant. Antibody appearance was then monitored over several weeks. 
     In the case of hemoglobin (Hb), the mice were immunized with 100 μg of protein or 10 9  beads coupled with the protein at different densities (2.10 4  and 2.10 5  molecules/μm 2 ). The beads carrying ovalbumin (OVA) were tested at two densities, 7.10 3  and 7.10 4  molecules/μm 2 . 
     An initial injection was carried out, followed by two more injections on the 21st and 40th days. Serums were taken at the 20th day, the 31st day, the 41st day and the 52nd day, then assayed by ELISA for their IgG antibody levels. The results are expressed in log of the antibody titer. 
     The results in FIG. 14 show that hemoglobin coupled to beads did not induce an antibody response. For ovalbumin (FIG. 15) antibodies were detectable after several injections if the antigen was coupled at high density, but these responses were weak. These results show that proteins of high molecular weight such as hemoglobin are not able to induce an antibody response, even if they are coupled at a high density on the beads. 
     These results, similar to those obtained with lysozyme and limulus hemocyanin, confirm that beads carrying high-molecular-weight proteins induce T-proliferative responses in the absence of any antibody production. 
     Likewise, proteins of low or medium molecular weight (less than 50 000) can induce the appearance of antibodies if they are coupled to the beads at high densities. 
     3. Synthetic peptides 
     The peptides pre-S:TB (120-145) and pre-S:B corresponding to the portions of the HBS antigen containing respectively a T epitope and a B epitope or only the B epitope were covalently coupled to 1 μm beads with glutaraldehyde (B-pre-S:TB and B-pre-S:B). 
     The antibody response induced by these beads was compared with that induced by 10 μg of soluble pre-S:TB peptide in alum adjuvant. 
     The results in FIG. 16 show that the beads coupled to the TB peptide, containing a T epitope and a B epitope, induced strong antibody responses, which confirms that antigens of low molecular weight coupled to beads are able to induce an antibody reaction in the absence of adjuvant. It may be noted that these responses are as good as those obtained with the free peptide in the presence of alum adjuvant. 
     EXAMPLE 4 
     Effect of the lysozyme density on the microparticle surface on their immunogenicity 
     The materials and methods used were similar to those for Example 2. 
     The immunogenicity of beads coupled to lysozyme with different numbers of molecules on their surface was tested in experiments illustrated in FIGS. 17 and 18. 
     For FIG. 17A, BALB/c mice were immunized by subcutaneous injection of 100 μg of lysozyme in CFA. After 14 days, the inguinal ganglions were removed and the cells tested in vitro against beads carrying different densities of lysozyme (from 1100 to 950 000 molecules of lysozyme on 1 μm diameter beads). The results are expressed in cpm corrected for the value obtained without antigen. 
     For FIG. 17B, BALB/c mice were immunized by subcutaneous injection at the base of the tail with soluble lysozyme with adjuvant (CFA) or 10 9  beads carrying different densities of lysozyme without adjuvant. 
     After 14 days, the inguinal ganglions were removed and the proliferative response of these cells was tested in vitro against different concentrations of lysozyme or beads. The results are expressed in cpm corrected for the value obtained without antigen. 
     The proliferation of ganglion cells originating from animals immunized by soluble lysozyme in CFA was tested in vitro after stimulation by different lysozyme-microparticles. The proliferative response of these cells increased as the density of lysozyme on the microparticle surface increased. No proliferation of the ganglion cells was obtained after stimulation by microparticles with a density of 1100 lysozyme molecules per microparticle (FIG. 17A). 
     In the experiment shown in FIG. 17B, the immunogenicity of these microparticles was tested in vivo. BALB/c mice were immunized by the different microparticles, without adjuvant, and the ganglion cells of these animals were stimulated in vitro by different concentrations of soluble lysozyme. 
     The proliferation of ganglion cells originating from animals immunized by microparticles coupled to lysozyme at high density (950 000 and 210 000) was high, and comparable to the response of cells sensitized by 100 μg of lysozyme in CFA. After immunization by microparticles carrying a medium density of lysozyme (45 000), the cells proliferated in response to lysozyme in vitro at concentrations from 10 -1  μg/ml. Lower-density microparticles did not sensitize T cells in vivo, since no proliferation was observed in the presence of lysozyme, even at high concentration (FIG. 17B). 
     It should be noted that 10 9  microparticles coupled to lysozyme at high density correspond to 23 μg (1-950 000-G) and 5 μg (1-210 000-G) of coupled lysozyme, nevertheless the cell proliferation was as high as that after injection with 100 μg of lysozyme in CFA. 
     For FIG. 18, BALB/c mice were immunized by subcutaneous injection of lysozyme with adjuvant (CFA) or of 10 9  microparticles carrying different densities of lysozyme (950 000; 210 000, 45 000 and 1100 molecules respectively on a 1 μm diameter microparticle). 
     After 14 days, serums were taken and assayed by ELISA for their level of anti-lysozyme antibody. The results are expressed in log10 of the antibody titer. 
     The humoral response of the mice immunized by these microparticles with different lysozyme densities were studied. Injection of 100 μg of lysozyme in CFA induced a high level of anti-lysozyme antibody (FIG. 18). Fourteen days after immunization, the beads coupled to the highest density of lysozyme (950 000) had induced significant antibody production, while beads of lower density had not stimulated the induction of a significant anti-lysozyme antibody response. In particular it should be noted that the beads with density 210 000, which had induced an excellent specific proliferation of the ganglion cells, did not stimulate antibody production. These results show that T cell proliferation is induced with lysozyme densities of between 45 000 and 950 000 molecules per microparticle, while antibody production requires a high density of protein coupled to the microparticles. 
     Within the meaning of the present description, the expression &#34;microparticles&#34; refers to particles which may have various geometric and spatial configurations. In practice, they are preferentially microspheres or beads, such as are obtained by conventional polymer manufacturing techniques. 
     
         __________________________________________________________________________SEQUENCE LISTING(1) GENERAL INFORMATION:(iii) NUMBER OF SEQUENCES: 5(2) INFORMATION FOR SEQ ID NO:1:(i) SEQUENCE CHARACTERISTICS:(A) LENGTH: 13(B) TYPE: AMINO ACID(C) STRANDEDNESS: UNKNOWN(D) TOPOLOGY: UNKNOWN(ii) MOLECULE TYPE: PEPTIDE(xi) SEQUENCE DESCRIPTION: SEQ ID NO:1:MetGlnTrpAsnSerThrThrPheHisGlnThrLeu510Gln(2) INFORMATION FOR SEQ ID NO:2:(i) SEQUENCE CHARACTERISTICS:(A) LENGTH: 14(B) TYPE: AMINO ACID(C) STRANDEDNESS: UNKNOWN(D) TOPOLOGY: UNKNOWN(ii) MOLECULE TYPE: PEPTIDE(xi) SEQUENCE DESCRIPTION: SEQ ID NO:2:GlnAspProArgValArgGlyLeuTyrPheProAla510GlyGly(2) INFORMATION FOR SEQ ID NO:3:(i) SEQUENCE CHARACTERISTICS:(A) LENGTH: 13(B) TYPE: AMINO ACID(C) STRANDEDNESS: UNKNOWN(D) TOPOLOGY: UNKNOWN(ii) MOLECULE TYPE: PEPTIDE(xi) SEQUENCE DESCRIPTION: SEQ ID NO:3:LysLeuPheAlaValTrpLysIleThrTyrLysAsp510Thr(2) INFORMATION FOR SEQ ID NO:4:(i) SEQUENCE CHARACTERISTICS:(A) LENGTH: 11(B) TYPE: AMINO ACID(C) STRANDEDNESS: UNKNOWN(D) TOPOLOGY: UNKNOWN(ii) MOLECULE TYPE: PEPTIDE(xi) SEQUENCE DESCRIPTION: SEQ ID NO:4:AspAsnProAlaSerThrThrAsnLysAspLys510(2) INFORMATION FOR SEQ ID NO:5:(i) SEQUENCE CHARACTERISTICS:(A) LENGTH: 40(B) TYPE: AMINO ACID(C) STRANDEDNESS: UNKNOWN(D) TOPOLOGY: UNKNOWN(ii) MOLECULE TYPE: PEPTIDE(xi) SEQUENCE DESCRIPTION: SEQ ID NO:5:IleAsnCysThrArgProAsnAsnAsnThrArg510LysSerIleArgIleGlnArgGlyProGlyArg1520AlaPheValThrIleGlyLysIleGlyAsnMet2530ArgGlnAlaHisCysAsnIle3540__________________________________________________________________________