EP0626013A1

EP0626013A1 - RECOMBINANT $g(b)-LACTAMASE USABLE AS CARRIER MOLECULE FOR THE PREPARATION OF IMMUNOGENIC COMPOSITIONS

Info

Publication number: EP0626013A1
Application number: EP93905393A
Authority: EP
Inventors: Brigitte Gicquel; Juliano Timm; Joaquim Trias; Colette Duez; Mariagrazia Perilli; Jean Dusart; Jean-Marie Frere
Original assignee: Institut Pasteur de Lille
Current assignee: Institut Pasteur de Lille
Priority date: 1992-02-14
Filing date: 1993-02-12
Publication date: 1994-11-30
Also published as: FR2687410B1; US5830457A; WO1993017113A1; FR2687410A1

Abstract

La présente invention concerne une séquence nucléotidique, caractérisée en ce qu'elle est choisie parmi l'un des enchaînements nucléotidiques suivants: la séquence du gène codant pour une beta-lactamase, ou toute partie de ce gène, en particulier la séquence comprise entre les nucléotides 1 et 394 contenant les signaux d'expression du gène, ou la séquence codante comprenant les nucléotides 395 à 1274, ou toute séquence hybridant dans des conditions stringentes avec la séquence ci-dessus. Utilisation de la beta-lactamase comme protéine porteuse d'épitopes hétérologues, pour la préparation de compositions vaccinantes.The present invention relates to a nucleotide sequence, characterized in that it is chosen from one of the following nucleotide sequences: the sequence of the gene encoding a beta-lactamase, or any part of this gene, in particular the sequence between nucleotides 1 and 394 containing the expression signals of the gene, or the coding sequence comprising nucleotides 395 to 1274, or any sequence hybridizing under stringent conditions with the above sequence. Use of beta-lactamase as protein carrying heterologous epitopes, for the preparation of vaccine compositions.

Description

Î-lactamase recom-binante, usable as a carrier molecule for the preparation of immunogenic compositions.

The present application relates to new means for the preparation of immunogenic compositions and preferably protective vaccinating compositions, capable of being in the form of "live vaccines", of particles or molecules which can be administered to humans or animals. .

One of the aims of the present invention is to propose means for developing immunogenic compositions capable of triggering in humans or in animals a cellular and / or humoral immune response (by means of antibodies), against antigenic determinants and in particular epitopes characteristic of different pathogens. More generally, the invention proposes new means for triggering or promoting an immune response against any determined epitope for producing antibodies or a cellular immune response, and in particular when the antigenic determinants are of the hapten type and therefore incapable of triggering by themselves. same this immune response. The invention is also of interest in order to promote an immune response capable of being imparted by an antigen, and in particular to increase the level or the protective character thereof.

The invention describes in this regard new molecules capable of being used as a vector for the antigenicity of different epitopes, both in immunogenic compositions containing the hybrid (recombinant) molecules thus formed or in live vaccines. Different factors can be decisive in the choice of a molecule, in particular a protein capable of behaving as a carrier protein (also called a vector) in order to confer or improve the immunogenicity of a heterologous epitope compared to to this molecule. For example, account must be taken of the size parameters of the vector protein as such and of its size relative to that of the epitope which it must contain as well as of the size of the epitope as such. Other constraints for the development of vaccines, living or not, involving carrier molecules, are for example the antigenicity of the carrier molecule, its toxicity for a cellular host in which it would be produced or for the subject to which it would be administered. It is also necessary to determine the potential sites of insertion for the epitope, and in a very important way when this modified protein is used within the framework of the preparation of a live vaccine, its capacity to be exported or even secreted by l host that produces it, in order to be accessible to the immune system of the subject to whom the vaccine is administered.

In the context of the present invention, the inventors are interested in proteins of the / 3-lactamase family, some of the properties of which have been studied until now in a context different from that of the present invention.

3-lactamases are enzymes divided into different classes, depending on their enzymatic activity on different substrates. They are produced by different organisms and in particular by bacteria, for example bacteria of the type E. coli, Staphylococcus aureus, or by mycobacteria. These enzymes are studied for their capacity to protect bacteria against the lethal effects of antibiotics of the / 3-lactams type, and therefore their capacity to confer on certain bacteria resistance to different antibiotics. It is in this context of studying the resistance of bacteria to antibiotics that several authors have published articles describing the purification of certain β-lactamases.

For example, Choubey et al have published results describing the purification to the homogeneity of a 3-lactamase from Mycobacterium smegmatis (Microbiology, 1986, Vol. 1: 171-175). Other authors have published data relating to the characterization of the β-lactamase produced in a strain of Mycobacterium fortuitum (J. Amicosante et al, Biochem. J., 1990, 271: 729-734; L. Fattorili et al, Antimicrobial Agents and Chemotherapy, September 1991, p. 1760-1764). In this second publication, the authors recall that β-lactamases have been described as periplasmic enzymes in Gra-negative bacteria. In Grain-positive, since there is a single cell membrane, these enzymes are exported to the surface or released into the environment. Some are found in large quantities in the culture medium, others are anchored to the bacterial membrane. These enzymes have a wide spectrum of activity.

The release of this enzyme by the bacteria that produce it, would therefore be partly linked to environmental factors or factors specific to the physiology of the producer cell or structural determinants of / 3-lactamase.

Despite the known characteristics of β-lactamases, to intervene in the resistance to certain antibiotics, and despite the fact that the mode of expression and in particular the possibility of secretion of this protein by the cell which produces it were not completely characterized, the inventors were interested in the capacity of this enzyme to behave as a vector for the antigenicity of an epitope which would be heterologous to it.

By heterologous epitope is meant here an amino acid sequence characteristic of a protein and in particular of an antigen different from a / 3-lactamase, at the very least different from the / 3-lactamase chosen as carrier molecule.

According to the inventors, the known properties of different / 3-lactamases, such as the fact that they are exported and monomeric, as well as their structural properties are capable of conferring on them numerous advantages for being used as vector carriers of the antigenicity of different epitopes. They have also proved to be interesting in the context of the development of live vaccines. In order to define the conditions to be observed for the construction of recombinant proteins from / 3-lactamase, the inventors determined the sequence and the structural organization of the gene and predicted by modeling the three-dimensional structure of the protein / 3- lactamase from a mycobacterium, Mycobacterium fortuitum (hereinafter referred to as M. fortuitum). Knowledge of this gene has made it possible to locate regions capable of containing between nucleotides 395 and 1274 of this sequence.

Advantageously, sequences corresponding to the preceding definitions, are constituted by the nucleotide sequences cloned in the plasmids contained in the E. coli strains deposited at the C.N.C.M. under the numbers 1-1170 and 1-1171, as well as any nucleotide sequence hybridizing under stringent conditions with these cloned sequences.

The sequence shown in FIG. 4 contains the gene coding for M. fortuitum / 3-lactamase, as well as the non-coding parts. The nucleotide sequence of the M. fortuitum / 3-lactamase gene is not the only sequence of interest in the context of the invention; indeed fragments or part of the sequence shown in Figure 4 can be interesting.

In particular, an advantageous nucleotide sequence in the context of the invention is the nucleotide sequence corresponding to the non-coding 5 'end of the β-lactamase gene, this sequence containing the expression signals for the gene for this enzyme. This 5 ′ part of the gene sequence can be used for the expression of various nucleotide sequences in cellular hosts of the mycobacteria type. It is suitable for example for the expression in mycobacteria, of / 3-lactamases originating from organisms other than mycobacteria, since it contains expression signals recognized by mycobacteria.

Other fragments of the nucleotide sequence represented in FIG. 4, which can be used in the context of the invention, are the sequences coding for a 8 truncated protein whose overall structure is preserved, compared to the native protein, in particular under conditions such that the expression product of this nucleotide sequence is stable and in particular insensitive to the cellular proteases of the host which produces it and / or possibly the subject to which it is administered.

By protein stability is meant in particular the possibility of purifying it or the possibility for this protein to be recognized by an antibody.

An advantageous nucleotide sequence is a sequence having similarities with the sequence shown in FIG. 4. By similarity is meant in particular the capacity to hybridize under stringent conditions with the sequence of FIG. 4.

To determine whether a nucleotide sequence is capable of hybridizing under stringent conditions with the coding sequence contained in the sequence represented in FIG. 4, the following test can be carried out:

One uses for example a probe determined from the coding sequence represented in FIG. 5 with which one wishes to test the hybridization of a determined sequence; this probe is labeled with ³² p (10 ⁶ cpm / ml) and it is brought into contact with the sequence tested for 16 hours at 65 ° C. in a hybridization solution (50% formamide, 5 × SSPE, sperm DNA salmon 200 μg / ml and 10 x Denhart). The membranes on which the hybridization is carried out are then washed twice for 30 minutes with a 1SSC solution, 0.1% SDS at room temperature (20 ° C.) and then washed twice with 0.1SSC, 0.1% SDS. for 30 minutes at

0.1 x SSC:

NaCl: 15 mM

Na ₃ citrate: 0.1%

According to another definition, a nucleotide sequence of the invention is characterized in that it codes for a protein of the type / 3-lactamase comprising the amino acid chain shown in FIG. 4.

The invention further relates to a recombinant nucleotide sequence characterized in that it comprises: a nucleotide sequence corresponding to one of the preceding definitions, coding for a β-lactamase, modified by at least one heterologous nucleotide sequence coding for a peptide sequence heterologous comprising at least one epitope, the modification being carried out at at least one site allowing, when the recombinant sequence is expressed, the exposure of the epitope to the surface of / 3-lactamase or its accessibility to the solvent, a nucleotide sequence meeting the previous definitions, coding for a truncated β-lactamase, modified by at least one 10 heterologous nucleotide sequence encoding a heterologous peptide sequence comprising at least one epitope, the modification being carried out at at least one site allowing, when the recombinant sequence is expressed, the exposure of the epitope to the surface of the / 3-lactamase or its accessibility to the solvent, and the expressed hybrid protein retaining the essential structural characteristics of the native / 3-lactamase, in particular those which give it its recognition by antibodies directed against the epitope (s), or its stability, when it is recombined.

The exposure at the level of the recombinant protein, of the heterologous epitope, corresponds to the accessibility of this epitope to the solvent, in particular to water molecules, or to the availability of this epitope to be presented to antibodies.

According to the definition given in the preceding paragraph, the nucleotide sequence coding for β-lactamase or for a truncated / 3-lactamase, can be modified by at least one heterologous nucleotide sequence. In fact, just as the size of the heterologous nucleotide sequence does not constitute an a priori limiting parameter, it is possible to envisage inserting several heterologous sequences within the sequence coding for / 3-lactamase or for a truncated β-lactamase .

The insertion of heterologous sequences comprising at least one epitope and having a size of a few nucleotides may appear advantageous insofar as the problems which may result from a deformation of the modified / 3-lactamase encoded by the 11 recombinant nucleotide sequence of the invention are limited. However, it is possible to insert, at one or more sites of the nucleotide sequence coding for / 3-lactamase, heterologous nucleotide sequences of longer sequences, as soon as they code for a peptide sequence including the epitope or the epitopes will be exposed on the surface of the recombinant protein formed or accessible to the solvent. Preferably, the hybrid thus formed retains the most important characteristics of its structure, in particular its capacity to be recognized by anti-/ 3-lactamase antibodies and anti-heterologous sequence antibodies, as well as its capacity to be purified.

A protein known as stable according to the invention exhibits at least one of the following properties: the enzymatic activity of / 3-lactaπtase, if necessary modified in intensity, the ability to be recognized by an antibody, in particular an anti-/ 3- antibody lactaιnase, or an antibody directed against a heterologous epitope which it contains, when it is a question of the recombinant protein or, an insensitivity to degradation by cellular proteases, the possibility of being purified.

Different heterologous nucleotide sequences can be chosen to produce the recombinant nucleotide sequences of the invention. A first group of heterologous sequences is characterized in that it comprises sequences coding for a peptide or a polypeptide, involved in the virulence of a pathogenic agent or in general for an antigen with protective potential against a 12 factor produced as a result of infection. In this regard, a sequence characteristic of a pathogenic organism is, for example, a sequence of virus, parasite, bacteria or fungus (for example of the genus Aspergillus). In particular, in the context of the present invention, the sequences of bacteria such as M. leprae, M. tuberculosis, M. intracellulare, M. africanum, M. avium, the bacilli responsible for diphtheria, tetanus, Salmonella, will be cited. treponemes, pertussis toxin, sequences of other microorganisms such as sporozoites and merozoites of plasmodium, sequences of Leishmania or Schistosoma, Shigella, Neisseria, Borrelia, sequences of viruses including the mumps virus, rubella, measles, herpes, influenza, rabies virus, polio, hepatitis, AIDS HIV, HTLV-I, HTLV-II and SIV as well as oncogenic viruses.

The nucleic acid sequence to be expressed can also code for an immunogenic sequence such as that of snake or insect venom.

By way of example, an interesting heterologous nucleotide sequence is, for example, a sequence coding for a peptide sequence of a human retrovirus antigen of HIV type, in particular an envelope, gag, nave or pol antigen of an HIV- retrovirus. 1 or HIV-2.

Other interesting sequences are the immunogenic sequences of mycobacteria, in particular proteins or fragments of proteins corresponding to genes involved in virulence and antigens with protective potential. An antigen is said to have "protective potential" when it is capable of triggering or promoting a response 13 protective immune system, in particular by production of antibodies or by induction of a cell-mediated immune response, in particular of the CTL type. Such an antigen with protective potential can consist of an epitope or even a hapten insufficient in itself to trigger the immune response.

The invention thus allows the preparation of recombinant proteins of interest in particular for the constitution of immunogenic compositions, in which the epitope exposed on the surface of the recombinant protein is characteristic for example of a hormone, or of any substance which it is sought to attenuate or even neutralize the biological effects.

Advantageously, a recombinant nucleotide sequence may consist of a nucleotide sequence coding for / 3-lactamase or a truncated β-lactamase, as described above in which a heterologous sequence coding for the peptide sequence V3 of the envelope antigen would be inserted. different HIV-1 variants or a larger sequence of the envelope of an HIV virus. This sequence has been described in the publication by K. Javaherian et al. (Proc. Natl. Acad. Sci. USA 8_6: 6768-6772, 1989). Advantageously, the heterologous sequence coding for the V3 peptide sequence is inserted at the BglII site of the sequence coding for β-lactamase.

The invention also relates to a recombinant • cloning and / or expression, replicative or integrative vector characterized in that it is modified, in one of its non-essential sites for its replication or its integration, by a nucleotide sequence recombinant described above. 14

Interestingly, the recombinant nucleotide sequence contained in the vector is under the control of the expression promoter of / 3-lactamase corresponding to the sequence.

When this vector is modified by the coding sequence alone or by a partial coding sequence for / 3-lactamase, it may also include expression, translation and even secretion signals, of origin different from that of β- lactamase, chosen according to the host in which one seeks to clone or express this recombinant vector.

By way of example of a vector for the preparation of recombinant vectors according to the invention, mention may be made of plasids, folds or transposons.

In particular, a plasmid of the invention is the plasmid pACYC184BlaM containing the SphI fragment of the sequence of the / 3-lactamase of M. fortuitum presented in FIG. 4, and which is deposited at the C.N.C.M. (National Collection of Microorganisms, Paris, France) in an E.coli HB101 strain (pACYC184BlaM), under the number 1-1171 deposited on February 11, 1992.

The plasmid pACYC184BlaM contains the Sphl / SphI fragment, of about 4.7 kb, of the genomic DNA of M. fortuitum D316 hybridizing with the BlaOl probe. This fragment carries the first 834 bases of the gene coding for a class A / 3-lactamase, as well as its regulatory regions.

The culture medium recommended for this strain is an L-Broth medium plus chloramphenicol (30 μg / ml) and the seeding is carried out on L-Broth medium, the incubation temperature being approximately 37 ° C. with stirring.

Another preferred plasmid according to 1 ^st invention contains the gene of the / 3-lactamase M. fortuitum; he 15 This is the plasmid pIPJ39 contained in a strain of E.coli MC1061 (pIPJ39), deposited at the CNCM on February 11, 1992 under the number 1-1170.

Plasmid pIPJ39 contains the approximately 6 kb BamHI / BamIII fragment of the genomic DNA of M. fortuitum FC1 hybridizing with the BlaOl probe. This fragment carries the gene coding for a class A / 3-lactamase, as well as flanking regions.

The culture medium recommended for this strain is an L-Broth medium plus ampicillin (100 μg / ml) and the seeding is carried out with an L-Broth medium and the incubation temperature is approximately 37 ° C. with stirring.

The subject of the invention is also a recombinant cellular host, characterized in that it is transformed by a recombinant nucleotide sequence described above or by a recombinant vector above, under conditions allowing the expression of the recombinant nucleotide sequence under the form of a stable fusion protein and its exposure or export to the surface of the host or its secretion into the extracellular medium.

Many cellular hosts can be modified by a recombinant nucleotide sequence or a recombinant vector according to the invention.

A suitable method for the preparation of recombinant cellular hosts according to the invention is for example 1 electroporation, in accordance with the description of Snapper S. et al (1988, PNAS USA 85: 6985-6991) or the conjugation according for example the technique of Lazraq R. et al (1990, FEMS Microbiol. Lett. 69_: 135-138), or according to the technique of Gormley EP and Davies J. (J. Bacteriol, 173: 6705-6708). 16

Advantageously, mycobacteria will be used when the sequence coding for β-lactamase is a sequence originating in mycobacterium. In fact in this case the transfer into a strain of mycobacteria of the gene coding for a / 3-lactamase of mycobacterium makes it possible to facilitate the expression of this sequence, insofar as the recognition and expression, and even secretion, signals contained in the β-lactamase gene are recognized by the host mycobacteria. In general, a strain of Actinomycetes and in particular an avirulent or made avirulent strain can be used, ensuring that the recognition signals are suitable for the expression of the recombinant sequence or of the recombinant vector introduced into the strain. .

Particularly preferably for carrying out the invention, use will be made of the BCG strain. The invention therefore relates to a strain of BCG, transformed by a recombinant nucleotide sequence or a recombinant vector of the invention allowing exposure to the surface of the cell of a recombinant protein (hybrid protein), under conditions ensuring the exposure of the epitope or epitopes against which one seeks to induce an immune response.

A hybrid protein is said to be exposed when it is extracellular but remains anchored at a point on the surface of the cell that produces it. Particularly advantageously, the nucleotide sequences of the invention will be expressed in such a way that the expression products are secreted outside the cell which produces them and consequently released into the medium. 17

Other cellular hosts according to the invention are bacteria, a non-virulent E. coli strain, or a non-virulent strain of enterobacterium such as avirulent salmonella, since the recombinant nucleotide sequence or the above recombinant vector , transforming the bacteria, is placed under the control of expression signals recognized by this bacteria.

Other interesting icroorganisms are for example fungi such as Aspergillus.

In the case of the use as a cellular host, of prokaryotic or eukaryotic cells not belonging to the group of mycobacteria, recourse will be had to the use of expression signals recognizable by the host cell, in order to obtain the expression or even the secretion of the recombinant protein containing the / 3-lactamase or a truncated β-lactamase as well as the heterologous peptide sequence.

Other systems for the expression of the recombinant β-lactamase according to the invention can for example be constituted by animal cells, for example insect cells or mammalian cells such as CHO cells. In this case, the vectors specific to the insertion of DNA or 1ΑDNC or even RNA into these cells can be viruses, or plasmids. Other systems such as yeast systems such as Saccharomyces Cerevisiae may also be suitable.

By exposed site is meant a site which allows access or recognition of the heterologous peptide sequence and in particular access to the epitope or epitopes or their recognition, in order to obtain an immune response. An exposed site is 18 either a site on the surface of the protein / 3-lactamase or a site contained in this protein whose epitope remains recognized by the antibodies, for example even when the protein is denatured.

By way of example, it is possible to mention the possibility that the heterologous peptide sequence is inserted upstream of a site normally not exposed on the surface of the β-lactamase protein, this site being exposed due to the insertion of the heterologous sequence, for example following a folding resulting from interactions between the protein / 3-lactamase and the heterologous sequence. By choosing the site of insertion into the protein / 3-lactamase, it will be advantageous to select sites which make it possible to conserve the overall structure of the protein and therefore its stability.

The knowledge acquired by the inventors on the sequence of the M. fortuitum / 3-lactamase gene enabled them to locate the different regions of the α-helix and β-sheet type responsible for the three-dimensional conformation of this protein. Consequently, the inventors were able to determine, using the three-dimensional structure of the / 3-lactamase from S. aureus and from S. albus G, which could be the suitable domains for the insertion of heterologous peptide sequences. , avoiding alteration of the structure of the native protein under conditions which would have adversely affected its usefulness as a carrier molecule. Thus, the inventors have established the possibility of preferably inserting heterologous peptide sequences in a domain of a β-lactamase outside the regions structured in α helices or in β sheets. 19

As a preference, a heterologous peptide sequence is inserted into the M. fortuitum β-lactamase in the region forming the junction between the α2 helix and the α3 helix of the β-lactamase.

Other preferred insertion sites are formed by the regions between the β2 sheet and the α2 helix, between the o: 3 helix and the α4 helix or even between the β4 sheet and the β5 sheet.

According to an advantageous embodiment of the invention, the heterologous sequence can also be inserted into the C-terminal part of the sequence of β-lactamase.

For the preparation of recombinant proteins involving β-lactamases of different origin, the location of the α helices and β sheets giving them their structure will advantageously be determined, relative to the data obtained for the β-lactamase from S. aureus.

Preferably, the insertion is carried out in such a way that the heterologous peptide sequence is accessible to the water molecules of the environment.

The heterologous sequences capable of being inserted into the β-lactamase or into a truncated β-lactamase are the sequences which have been described above in the part which relates to the nucleotide sequences. These are, for example, sequences of the HIV retrovirus, in particular sequences of the envelope glycoprotein, the gag, nef or pol proteins, of an HIV-1 or HIV-2 retrovirus. By way of example, mention may be made of the V3 peptide of the HIV-1 envelope.

The invention allows the production of recombinant β-lactamase proteins in which the insertion of the heterologous sequence comprising the epitope is accompanied by a deletion of part of the β- 20 lactamase. The invention also allows, according to an advantageous embodiment, the insertion of the heterologous sequence without deletion at the level of β-lactamase.

For example, this insertion can be carried out at the C-terminal end of the β-lactamase, without deletion at the level of the sequence of the latter.

The invention also relates to an immunogenic composition characterized in that it comprises a recombinant BCG strain described above, in combination with a pharmaceutical vehicle ent suitable for its administration to humans or animals.

Such a composition is capable of constituting a live vaccine. It can be administered by injection or by any other suitable route. Such an immunogenic composition can be used to trigger the immune response, for example to trigger the cellular response and optionally to trigger the production of protective antibodies, or even to contribute to the production of these antibodies in a host to which it is administered. The invention relates not only to the manufacture of vaccinating compositions which can be administered to humans but also to the preparation of compositions for the purposes of vaccination in veterinary medicine.

The immunogenic composition of the invention can also be used as a booster composition to stimulate the production of antibodies initiated by the administration of a protein or of another constituent of the pathogenic agent or more generally of The agent against which an immune response is sought.

Preferably, the invention relates to an immunogenic composition characterized in that the strain 21 recombinant it contains as active ingredient is a strain M. bovis type BCG meeting the definitions given above. A particular BCG strain is the avirulent strain of INSTITUT PASTEUR No. 1137P2, used for the commercialized vaccine against tuberculosis.

As a pharmaceutical vehicle suitable for the production of the immunogenic compositions of the invention, mention may be made of the physiological excipients that are usually acceptable, in particular neutral or acid excipients and for example magnesium stearate, polyvinyl pyrrolidone or alcohols. This immunogenic composition can also comprise adjuvants of the immune response such as Freund's complete or incomplete adjuvant, aluminum hydroxide, muramyl dipeptide derivatives, a metabolizing oil such as squalene.

If a live vaccine is used, the usual doses for BCG vaccination may be used.

Another immunogenic composition of the invention is characterized in that it comprises a recombinant protein corresponding to the above definitions, in combination with a pharmaceutical vehicle suitable for its administration. This composition, like the immunogenic composition forming the live vaccine, can be used to trigger the immune response or in the form of a booster composition.

Other advantages and characteristics of the invention appear in the examples which follow and in the figures which are described below. 22 LEGEND OF FIGURES

Figure 1 :

BlotMl nucleotide sequence

Figure 2:

Plasmid pACYC184 recombined with an insert of approximately 4.7 kb from the β lactamase gene,

Figure 3:

Plasmid pIPJ39 recombined with the β lactamase gene,

Figure 4:

Sequence of the genetic region carrying the gene coding for M. fortuitum β-lactamase.

The nucleotide sequence is indicated in capital letters and is numbered in the right column. The peptide sequence of β-lactamase is indicated with the three-letter code under the corresponding nucleotide sequence. The numbering is indicated below the sequence.

The nucleotide sequence from ntl to ntl061 was determined from the plasmid pIPJ319.

Figure 5:

MF: Mycobacterium fortuitum SA: Streptomyces albus AU: Staphylococcus aureus

The position of the insertions to be made is indicated by dotted lines.

The position of the a and β helices is indicated under the sequence of S. aureus. 23

The structural predictions of M. fortuitum are given above its sequence.

Figure 6:

Position of predicted structural motifs for M. fortuitum β-lactamase

The different α helices and β sheets are indicated by rectangles. This figure also shows the nucleotide sequence and the position of several restriction sites.

Figure 7 - Construction of the plasmid pIPJ46

The plasmid pAL817 is a derivative of pAL5000 and is described in the publication Ranes et al, J. Bacteriol. 172: 2793-2797 (1990). The cassette containing the kanamycin resistance gene of the transposon Tn903 and the plasmid pSL1180 come from the company Pharmacia.

Figure 8 - Construction of plasmids pIPJ64 and pIPJ65

The amplification of the V3 fragment is made from the plasmid pTG5167 supplied by Transgene. The plasmid pIPJ42 is a derivative of pIPJ39 where the BglII / BamHI fragment, corresponding to the promoter and the aminoterminal fragment of the gene coding for the beta-lactamase of Mycobacterium fortui tum FC1, has been replaced by the BglII / BglII fragment of pACYC184 promoter and to the aminoterminal fragment of the gene coding for the beta-lactamase of Mycobacterium fortuitum D316. The plasmid pTG5167 is a derivative of pTG186poly (Guy et al, 1987) where a BglII-EcoRI fragment carrying the gene coding for the GP160 protein of HIV1 / MN has been cloned in the polylinker. 24 Figure 9 - Construction of the plasmids pRJ27 and pRJ28

The amplification of the gag11 fragment is made from the plasmid pTG2103 supplied by Transgene. The plasmid pTG2103 is a derivative of pTG959 (Guy et al, 1987) where a BglII / EcoRI fragment carrying the gene coding for the P24 protein of HIV1 / LAI has been cloned in the polylinker.

Figure 10 - Construction of plasmids pRJ33 and pRJ34

The amplification of the Gag fragment p24 is made from the plasmid pTG2103 supplied by Transgene.

Figure 11 - Construction of plasmids pSA1.5 and pSAIl.5

The amplification of the gene coding for the GP63 protein of Leishmania major is made directly from the chromosome of this parasite.

Figure 12 - Western type analysis of the expression of the beta-lactamase-V3 polypeptide. The molecular weight markers are indicated to the left of line 1.

Lane 1: gpl20 protein; lane 2: standard BCG supernatant; lane 3: extract of standard BCG; lane 4: supernatant of recombinant BCG carrying the plasmid pIPJ64; lane 5: extract of recombinant BCG carrying the plasmid pIPJ64.

Figure 13 - Western type analysis of beta-lactamase-GaglI polypeptide expression 25

Lane 1: molecular weight markers; lane 2: Gag P24 protein; lane 3: extract of standard BCG; lanes 4 and 5: extracts of recombinant BCG carrying the plasmid pRJ28; lanes 6 and 7: extracts of recombinant BCG carrying the plasmid pRJ27.

Figure 14 - Western type analysis of the expression of the beta-lactamase-Gag P24 polypeptide

Line 1: extract of standard BCG; lane 2: Gag P24 protein; lane 3: molecular weight markers; lanes 4 and 5: extracts of recombinant BCG carrying the plasmid pRJ33 and pRJ34, respectively.

Line 15 - Western type analysis of the expression of the beta-lactamase-GP63 polypeptide.

Line 1: extract of standard BCG; lane 2: molecular weight markers; lane 3: extract of recombinant BCG carrying pSAIl.5

Figure 16 - Proliferative responses of cells extracted from the lymph nodes of mice inoculated with BCG carrying the plasmid pRJ28.

4 Balb / c mice receive an intradermal injection of 10 ⁷ cfu of BCG-pRJ28, 4 others receive standard BCG 1173P2. After 14 days, the peripheral lymph nodes are removed for the proliferation test.

The HIV1-LAI Gag P24 protein is used to induce the proliferation of ganglion cells which have been in contact with the BlaM-V3 fusion protein produced by recombinant BCG. 26 EXPERIMENTAL PART

In the example which follows, a mycobacterial β-lactamase was used, for its expression in M. bovis BCG, the expression signals being adapted to the mycobacterial context.

A M. fortuitum β-lactamase was previously purified by Amicosante et al and Fattorili et al from a mutant strain producing this enzyme in large quantities. The N-terminal sequence of β-lactamase was determined by Amicosante et al:

APIDDQLAELERRDNVLIGLYAANLQSGRRITHRPDEMFAMXSTFKGYV X corresponds to an indeterminacy.

In order to isolate the gene coding for this protein, a DNA probe, BlaM1 corresponding to the gene fragment coding for this N-terminal part of the protein was synthesized by PCR. For this, two mixtures of oligonucleotides were synthesized using the degeneration of the genetic code, and the preferential use of codons in mycobacteria (J. Dale and A. Pakti, Molecular Biology of the Mycobacteria, Surrey University Press, Guilford, U, 1990, p. 173-198). The amino acid sequence APIDDQ is therefore probably encoded by a family of DNA sequences whose formula is indicated by the following consensus:

5 'GC (CθUG) CC (GouC) ATC GA (CouT) GA (COUT) CAG 3'

The nucleotides are indicated in capital letters; each oligonucleotide belonging to the family is determined by choosing one of the nucleotides indicated in parentheses. The mixture of these oligonucleotides, called Moligol, has been chemically synthesized by incorporating one or other of the nucleotides indicated in parentheses. We have a heterologous nucleotide sequence coding for a peptide or a polypeptide carrying at least one epitope against which it is sought to obtain an immune response and to envisage the preparation of recombinant proteins. This research also made it possible to define which sequences coded for a β-lactamase and the signals necessary for the expression of fusion products with β-lactamase, in which the β-lactamase is in stable form, and also the signals necessary for the export, even for the secretion, of the recombinant protein produced in a cellular host.

In addition, obtaining the sequence of the M. fortuitum β-lactamase gene makes it possible to provide for the use of other β-lactamases of comparable structure, in particular at the level of their three-dimensional structure, for producing recombinant proteins in the scope of the invention.

In the context of the specific application of these recombinant proteins to the development of live vaccines, the inventors have taken an interest in mycobacteria. An interesting candidate for the development of such vaccines is the mycobacterium M. bovis BCG (Bacillus Calmette et Guérin), also referred to hereinafter as BCG, used until now as a vaccine to protect against tuberculosis. BCG is an avirulent bacterium, which presents a tropism for macrophages and is capable of inducing at the same time a cellular response B, T and CTL (by cytotoxic T lymphocytes) of high amplitude. Its cell wall functions as a very effective adjuvant and a single inoculation can trigger long-lasting immunity. The present invention has made it possible to demonstrate that the use of a vector protein such as β-lactamase can promote the cloning and expression in mycobacteria, in particular in BCG, of heterologous antigenic determinants. Advantageously, in the case of the use of BCG as a cellular host for the expression of β-lactamase, use will be made of an exogenous β-lactamase compared to those which naturally preexist in BCG, in order to avoid or to minimize the phenomena of recombination.

The invention therefore relates to a nucleotide sequence characterized in that it is chosen from one of the following nucleotide sequences:

the sequence of the gene coding for a β-lactamase, comprising the sequence represented in FIG. 4,

- any part of the nucleotide sequence represented in FIG. 4, participating in the structure of β-lactamase, or necessary for its expression in an appropriate cellular host, in particular the sequence between nucleotides 1 and 394 of the sequence of FIG. 4 containing the gene expression signals, the coding sequence contained in the sequence represented in FIG. 4, and comprising the nucleotides 395 to 1274,

- any sequence hybridizing under stringent conditions with the sequence of FIG. 4 and in particular with the sequence comprised between nucleotides 1 and 394 or with the sequence used the Cyclone oligonucleotide synthesizer (Biosearch USA).

The second mixture of oligonucleotides, called Moligo2, consists of oligonucleotides corresponding to the complementary strands of the DNA sequences coding for the C-terminal part of the N-terminal fragment indicated above, that is to say: STFKGYV.

With the same nomenclature as above, the oligonucleotides constituting the Moligo2 mixture respond to the consensus:

5'AG (CθUG) TG (COUG) AAG TTC CC (GOUA) AT (AouG) CA (GouC) 3 '

One of the mixtures contains oligonucleotides of identical or very similar sequence to the 5 'part of BlaM1, the second mixture contains oligonucleotides complementary to the 3' part of BlaMl. These two mixtures are used to synthesize the BlaM1 probe by PCR from the DNA that we have extracted from M. fortuitum FC1 (C. Martin et al, Nature Vol. 345: 739-743, 1990). The BlaMl probe was sequenced (Figure 1). From this sequence, the oligonucleotide, BlaOl: 5 'CTTGAAGGTCGAGCACATCGCGAACAT3' was synthesized and radioactively labeled in order to use it as a probe to locate in a gene bank of M. fortuitum D316 (Amicosante et al) a clone having a fragment carrying the gene coding for β-lactamase. This library was constructed by cutting the chromosomal DNA of M. fortuitum D316 by the restriction enzyme SphI and by cloning the fragments at random in the vector pACYC184. The SphI fragments were inserted at the SphI site of pACYC184 and the HB101 strain of E. coli was transformed by this ligation mixture in the presence of calcium chloride. The transforming strains were selected on a LB medium containing 30 μg / ml of chloramphenicol. The resistant strains obtained were subcultured on solid LB medium containing 25 μg / ml of tetracycline and only those sensitive to this antibiotic were retained. A transforming clone containing a fragment hybridizing with BlaOl was isolated. This clone contains a plasmid pACYC184 recombinant with an insert of approximately 4.7 kb hybridizing with BlaOl. The restriction map of this plasmid was carried out (FIG. 2) and the region hybridizing with BlaOl was sequenced. The nucleotide sequence is indicated in FIG. 4. The analysis of this sequence shows a reading phase having similarities with other class β-lactamases. We therefore concluded that it must have been the gene for structure of M. fortuitum β-lactamase. The SphI sequence fragment contains only part of the gene. A BglII-SphI restriction fragment (shown in thick lines in FIG. 2) internal to the gene, called Bla02, was used as probe; The whole gene was cloned from a library of M. fortuitum FC1. This library was constructed by cloning 4 to 10 kb BamHI chromosomal fragments isolated by electrophoresis on an agarose gel and cloned into the BamHI site of the plasmid pUC18 linearized by cleavage at this site and dephosphorylated. The transforming clones were selected on a box of LB medium containing 100 μg / ml of ampicillin. A transforming clone hybridizing with the Bla02 probe was isolated. It contains a recombinant plasmid carrying an insert of approximately 6 kb hybridizing with the Bla02 probe. The restriction map of this insert was performed (FIG. 3) and the region hybridizing with the probe was sequenced. It contains the C-terminus of the gene (Figure 4). The two gene fragments obtained from the SphI and BamHI have a common part which allows to reconstitute the whole gene; it is represented in FIG. 4 with the amino acid sequence of the protein deduced from the nucleotide sequence. The amino acid sequence has similarities to the sequences of other known class A β-lactamases. An alignment of the sequences of the β-lactamases of M. fortuitum, of S. albus, of S. aureus is proposed in FIG. 5. The position of the different structural patterns, helices and β sheet determined for the β-lactamase of S. aureus is indicated on the primary structure of this enzyme in the same figure. According to the similarities between the primary structure of the β-lacta ase of M. fortuitum which we have just deduced from the gene whose structure we have just determined, and that of S. aureus, the position of the structural motifs is proposed to the FIG. 5. In FIG. 6, the structural motifs of the M. fortuitum β-lactamase as well as the nucleotide sequence of the gene are also shown. A region forming the junction between helix 2 and the α3 helix should correspond to an extended region inside which epitopes can be introduced without modifying the general structure of the protein. The fragment of the gene coding for this region, nt648 to nt719 contains a unique BglII site which will be used for the insertion of foreign DNA fragments coding for various epitopes. Three other regions appear interesting for the insertion of epitopes: the region nt585 to nt613, allowing an insertion between the sheet β2 and the helix α2, the region nt744 to nt748, allowing an insertion between the helices α3 and 4, and ntll52 to ntll67 which will allow the insertion of epitopes between the β4 and β5 sheets. The insertion of epitopes at the C-terminal position of the protein, ie close to nucleotide 1043, could also be of interest.

To analyze the expression of the BlaM gene, it was fused with β-galactosidase, an enzyme that is easy to measure and whose expression in bacteria is easily spotted on a Petri dish. To do this, a BglII-Pstl fragment of 1598 bp, containing a part of the blaM gene and of the upstream region, was isolated and inserted between the BamHI and Pst1 sites of the plasmid pNM482. The resulting blaM-lacZ fusion was then transferred to an E. coli mycobacterium shuttle vector and this construct was used to electroporate E.coli and M. smegmatis.

The expression of the lacZ gene has been observed only in M. smegmatis. These results show that the cloned region located upstream of the blaM gene is sufficient to induce expression of the gene and that it must therefore contain most of the signals for initiating transcription and translation. These signals are specific for mycobacteria. They can therefore therefore advantageously be used for the expression of any cloned gene under their control, in the form of an operon fusion or a protein fusion.

The fact that the blaM-lacZ fusion is functional shows that the blaM system can be used for the expression of various heterologous genes or fragments of genes in mycobacteria. Depending on the gene fusions carried out, the resulting fusion proteins may have a cytoplasmic localization, be exported outside the bacteria into the culture medium, or remain anchored to the external membrane. Examples of the use of the Pbla promoter associated with all or part of the gene coding for the beta-lactamase which it controls: expression of antigens or fragments of viral or parasitic antigens and induction of specific immune responses by the BCG expressing the one of these antigens.

The Pbla promoter (β-lactamase promoter) associated with the gene coding for beta-lactamase has been used to express several viral antigenic motifs of HIV1. (The sequences are given in relation to the publication "Hu an retrovirus and AIDS 1991" a compilation and analysis of nucleic acid and aminoacid sequences, edited by Myers G. et al., Published by Theoretical Biology and Physics, Group T-10, Mail Stop K710, Los Alamos National Laboratory, Los Alamos, New Mexico 877545 USA) or Leishmania GP63 antigen. (The sequences are given in relation to the publication: Button, LL and Me Master, WR (1988) Molecular cloning of the major surface antigen of Leishmania. J. Exp. 167. 724-729) in M. smegmatis and / or the BCG.

The V3 antigenic motif of HIV1 strain MN and an env fragment of this same strain were expressed in M. smegmatis and / or BCG.

The Gag P24 antigen of HIV1 strain LAI as well as a fragment of the latter (Gag11) were expressed in BCG. The major surface protein of Leishmania major and Leishmania infantum GP63 were also expressed by BCG.

Only the results of the immune responses directed against Gag in the case of Expression of the Gag11 fragment. A specific cellular response has been observed.

1) The fragment of the env gene coding for the determinant V3 of amino acid 303 to amino acid 338 (HIV strain MN) was inserted at the BglII site of the gene coding for beta-lactamase on the plasmid pIPJ42. To do this, a fragment coding for this determinant was synthesized by PCR. Two V3I oligonucleotides

(ATTGGATCCTGGTACCCGAGGAGTGTACAAGACCCAACTACAATAA) and V3II

(TTTGGATCCCTCTAGACCCGTCGCCACAATGTGCTTGTCTTATAGTTCCT) were synthesized by the company GENSET. They served to amplify the env fragment from the plasmid pTG5167 carrying it and originating from TRANSGENE. (Figure 8). The amplified fragment carries the BamHI restriction site at its ends. It is cut by the corresponding restriction enzyme and cloned into the plasmid pIPJ42. The recombinant plasmid carrying the fragment coding for the determinant V3 is called pIPJ52. In this plasmid, a cassette containing the origin of replication in mycobacteria (ori myco of pAL5000) and the kanamycin resistance gene of Tn903 was inserted between the SplI and BamHI sites. This cassette is the EcoRV / Hpal fragment isolated from the plasmid pIPJ46 (FIG. 8). the plasmids resulting from the insertion of the EcoRV / Hpal fragment in pIPJ52 in either of the orientations are pIPJ64 and pIPJ65.

Plasmids pIPJ64 and pIPJ65 were transferred to M. smegmatis and BCG by electroporation. The fusion polypeptide expressed by the plasmids pIPJ64 and pIPJ65 consists of the insertion of the V3 motif between the propellers 2 and 3 of beta-lactamase. This polypeptide is identified in the culture medium of the strains of M. smegmatis and BCG transformed by the plasmids pIPJ64 and pIPJ65, by Western blot using the monoclonal antibody F5-5 of 1, 'Hybridolab of the Pasteur Institute.

2) The fragment of the gene coding for the part of Gag (HIV1 strain LAI) from amino acid 233 to amino acid 307 (Gagll) was inserted at the PstI site of the gene coding for beta-lactamase on the plasmid pIPJ42 . To do this, a fragment containing the part of the gag gene coding for Gag11 was synthesized in vitro by PCR. Two NG1 oligonucleotides

(AAACTGCAGGGATCCATGGGAAGTGACATAGCA) and NG2 (CCCTGAAGCTTACTCGGCTCTTAGAGTTTT) were synthesized on a CYCLONE DNA synthesizer. They were used to amplify the fragment coding for Gag11 from the plasmid pTG2103 carrying it and originating from TRANSGENE. The amplified fragment carries the PstI and HindIII sites. It is cut by the corresponding enzymes and cloned in the plasmid pIPJ42 between the PstI and HindIII sites. The resulting plasmid is called pRJ20. From this plasmid, the Kpnl / Hin dm fragment coding for the beta-lactamase-GaglI fusion was inserted at the Seal site of pRR3 (Ranes, MG, Rauzier, J., Lagranderie, M., Georghiu, M. and Gicquel , B. (1990) Functional analysis of pAL5000, a plasmid from Mycobacterium fortui tum: construction of a "mini" Mycobacterium- escherichia coli shuttle vector. J. Bacteriol. 172. 2793-2797) in both directions. The resulting plasmids were called pRJ27 and pRJ28. Plasmids pRJ27 and pRJ28 were transferred to M. smegmatis and BCG by electroporation.

The fusion polypeptide expressed by the plasmids pR 27 and pRJ28 consists of the fusion between an amino-terminal fragment of 24 amino acids of beta-lactamase with the fragment gagll since a stop codon is located at the end of gagll. The beta-lactamase-GagII fusion polypeptide is not found in the culture medium of M. smegmatis or of BCG transformed by pRJ27 and pRJ28, but in the cytoplasm of these bacteria. It is identified by western blot in the bacterial extracts (produced according to Winter, N., Lagranderie, M., Rauzier, J., Ti m, J., Lecrec, C., Guy, B., Kieny, MP, Gheorghiu, M., Gicquel, B. (1991) Expression of heterologous genes in Mycobacterium bovis BCG: induction of a cellular response against HIV1 Nef protein. Gene 190, 47-54) using the monoclonal antibody 1542 of Hybridolab Pastor Institute.

After inoculation of Balb / c mice with BCG expressing the beta-lactamase-GaglI fusion, a cell-type immune response directed against Gag was observed using tests of proliferation of lymph node cells after stimulation with the protein Gag P24. The protocol used is similar to that described by Winter et al. Details are shown in Figure 13.

It is likely to be T (CD4) and T (CD8) lymphocytes

3) The Gag P24 protein of HIV1 strain LAI.

The fragment coding for the protein GagP24 was inserted at the BglII site of the gene coding for beta-lactamase on the plasmid pIPJ42. To do this, a fragment coding for Gag P24 was synthesized in vitro by PCR from the plasmid pTG2103, originating from TRANSGENE, using the oligonucleotides JGAG1.

(CGAATTCAGATCTCAACTTTAAATGCATGGGTA) and EML5 (GTTCGAATTCTCACAAACTCTTGC), previously synthesized on a CYCLONE synthesizer. The amplified fragment carries the BglII and BamHI sites. It is cut by the corresponding enzymes and cloned into the plasmid pIPJ42 between the BglII and BamHI sites. The resulting plasmid is called pRJ22. As in the case of the construction of the plasmids pIPJ64 and pIPJ65, the cassette containing the origin of replication in mycobacteria (ori yco of pAL5000) and the kanamycin resistance gene of Tn903 was inserted between the SplI and BamHI sites. It is the EcoRV / Hpal fragment isolated from the plasmid pIPJ46 (Figure 10). These plasmids resulting from the insertion of the EcoRV / Hpal fragment are called pRJ33 and pRJ34.

Plasmids pRJ33 and pRJ34 were transferred to M. smegmatis and BCG by electroporation. The fusion polypeptide expressed by the plasmids pRJ33 and pRJ34 consists of an amino-terminal fragment of 60 amino acids of beta-lactamase with the protein GagP24 since a stop codon is located at the end of the Gag P24 gene cloned here. Analogously to the beta-lactamase-GagII fusion, the beta-lacatamase-Gag P24 fusion polypeptide is not found in the culture medium but in the cytoplasm. It is identified by Western blot using the 1113 monoclonal antibody from the Hybridolab of the Institut Pasteur.

4) The GP63 surface antigen of Leishmania infantum and Leishmania major. The fragment coding for the GP63 protein lacking the C-terminal transmembrane part was inserted at the BglII site of the gene coding for beta-lactamase on the plasmid pIPJ42. To do this, a fragment coding for the GP63 antigen was synthesized in vitro by PCR. Two GP631 oligonucleotides

(GCGGGATCCTTATGCATGTGCGCGACGTGAACTGGGGC) and GP632 (CCGAATTCAAGCTTCTACGCCGTGTTGCCGCCGTCCTT) were used to amplify this fragment from the chromosomal DNA of the strains of Leishmania infantum and Leishmania major. The ends of the amplified fragments have the BamH and HindIII sites. They are cut by the corresponding enzymes and inserted between the BglII and HindIII sites of pIPJ42. The resulting plasmid is called pLMl.5.

As in the case of the construction of the plasmids pIPJ64 and pIPJ65, the cassette containing the origin of replication in mycobacteria (oriMyco of pAL5000) and the kanamycin resistance gene of Tn903 was inserted between the SplI and BamHI sites.

It is the EcoRV / Hpal fragment isolated from the plasmid pIPJ46 (FIG. 11).

The plasmids resulting from the insertion of the EcoRV / Hpal fragment in one or the other of the orientations are called pSA1.5 and pSAI1.5.

Plasmids pSA1.5 and pSAIl.5 were transferred to M. smegmatis and BCG by electroporation. The fusion polypeptides expressed by these plasmids consist of the fusion between an amino¬ terminal fragment of 60 amino acids of beta-lactamase with the protein GP63 deleted from the C-terminal transmembrane part. The beta-lactamase-Protein GP63 fusion polypeptides are as in the case of Gag fusions found in the cytoplasm of M. smegmatis and BCG transformed by the plasmids pSA1.5 and pSAI1.5. They are identified by a monoclonal antibody directed against the protein GP63 purified from extracts of a recombinant E. coli strain expressing this protein. This monoclonal antibody has been described by Hand an, L. Button, and RW McMaster [(1990) Leishmania major; Production of recombinant gp63, its antigernicity and immunogenicity in mice Exp. Parasitol. 70, 427-435] (Figure 15).

Claims

1. Nucleotide sequence, characterized in that it is chosen from one of the following nucleotide sequences:

- any part of the nucleotide sequence represented in FIG. 4, participating in the structure of β-lactamase, or necessary for its expression in an appropriate cellular host, in particular the sequence between nucleotides 1 and 394 of the sequence in FIG. 4 containing the gene expression signals,

the coding sequence contained in the sequence represented in FIG. 4, and comprising nucleotides 395 to 1274,

any sequence hybridizing under stringent conditions with the sequence of FIG. 4 and in particular with the sequence included between nucleotides 1 and 394, or with the sequence included between nucleotides 395 and 1274 of this sequence.

2. Nucleotide sequence, characterized in that it codes for a protein of the β-lactamase type comprising the chain of amino acids represented in FIG. 4.

3. Recombinant nucleotide sequence, characterized in that it comprises:

- A nucleotide sequence according to any one of claims 1 to 2 coding for β-lactamase, modified by at least one sequence heterologous nucleotide encoding a heterologous peptide sequence comprising at least one epitope, the modification being carried out at at least one site allowing, when the recombinant sequence is expressed, the exposure of the epitope to the surface of β-lactamase, or its accessibility to the solvent, a nucleotide sequence according to any one of claims 1 or 2, coding for a truncated β-lactamase, modified by at least one heterologous nucleotide sequence coding for a heterologous peptide sequence comprising at least one epitope, the modification being carried out at least one site allowing, when the recombinant sequence is expressed, the exposure of the epitope to the surface of β-lactamase or its accessibility to the solvent, and the expressed hybrid protein retaining the essential structural characteristics of β-lactamase native, in particular those which give it its stability, in particular its recognition growth by antibodies.

4. Recombinant nucleotide sequence according to claim 3, characterized in that the heterologous nucleotide sequence which contains code for a peptide sequence involved in the virulence of a pathogenic agent, or for an antigen with protective potential.

5. Recombinant nucleotide sequence according to any one of claims 3 or 4, characterized in that the heterologous nucleotide sequence which it contains codes for a peptide sequence of an antigen of a human retrovirus of HIV type, in particular an envelope, gag, nave, or pol antigen of an HIV-1 or HIV-2 retro virus.

6. Recombinant nucleotide sequence according to any one of claims 3 to 5, characterized in that the heterologous nucleotide sequence which it contains codes for the peptide sequence V3 of the HIV-1 envelope antigen.

7. Recombinant cloning and / or expression vector, characterized in that it is modified by one of its non-essential sites for its replication or its integration, by a nucleotide sequence according to any one of claims 1 to 6.

8. Recombinant vector according to claim 7, characterized in that the nucleotide sequence which it contains is placed under the control of the promoter of the β-lactamase gene from which the abovementioned nucleotide sequence originates.

9. Recombinant vector according to claim 7 or 8, characterized in that it is a plasmid, a phage or a transposon.

10. Recombinant vector according to any one of claims 7 to 9, characterized in that it is the plasmid pACYC184 BlaM containing the SphI fragment of the sequence represented in FIG. 4, contained in a strain of E. coli filed with the CNCM on February 11, 1992 under number 1-1171.

11. Recombinant vector according to any one of claims 7 to 9, characterized in that it is the plasmid pIPJ39, containing the gene for the β-lactamase of M. fortuitum, this plasmid being contained in a strain of E .coli deposited at the CNCM on February 11, 1992 under the number 1-1170.

12. Recombinant cell host, characterized in that it is transformed by a nucleotide sequence according to any one of claims 1 to 6 or by a recombinant vector according to any one of claims 7 to 11, under conditions allowing expression of the recombinant nucleotide sequence in the form of a stable fusion protein or preferably its export to the surface of the host or its secretion into the medium.

13. Cell host according to claim 12, characterized in that it is a strain of Actinomycete, preferably a strain of mycobacterium, avirulent or rendered avirulent.

14. Recombinant cell host according to claim 13, characterized in that it is M. bovis BCG.

15. Recombinant cell host according to claim 12, characterized in that it is a bacterium, for example of a non-virulent E. coli strain, or of a non-virulent strain of enterobacterium such as Avirulent salmonella, since the recombinant nucleotide sequence or the recombinant vector according to any one of Claims 3 to 11, which it contains, is placed under the control of expression signals recognized by this bacterium.

16. Recombinant cell host according to claim 12, characterized in that it is a fungus, for example of the genus Aspergillus therefore guue the recombinant nucleotide sequence or the recombinant vector according to any one of claims 3 to 11 , which it contains, is placed under the control of expression signals recognized by this fungus.

17. Recombinant protein, characterized in that it is a β-lactamase encoded by a nucleotide sequence according to any one of the claims 1 or 2 modified at an exposed site, by at least one heterologous peptide sequence comprising at least one antigenic epitope under conditions such that the recombinant protein is capable of inducing an immune response against the heterologous polypeptide (s) ) in animals or humans.

18. Recombinant protein according to claim 17, characterized in that the structure of β-lactamase is essentially conserved, so that the recombinant protein is stable, and in particular that it is insensitive to cellular proteases.

19. Protein according to any one of claims 17 or 18, characterized in that the β-lactamase is a class A β-lactamase.

20. Recombinant protein according to claim 1 or claim 2, characterized in that the β-lactamase is that of M. fortuitum.

21. Recombinant protein according to any one of claims 17 to 20, characterized in that the β-lactamase is in active form.

22. Recombinant β-lactamase protein according to any one of claims 17 to 21, characterized in that the heterologous peptide sequence which it contains, is accessible to the solvent.

23. Recombinant β-lactamase protein according to any one of claims 17 to 21, characterized in that it contains at least one heterologous peptide sequence comprising at least one epitope, inserted at a site present in a region of the β- lactamase outside regions structured in α helices or β sheets.

24. Recombinant β-lactamase protein according to any one of claims 17 to 23, characterized in that it contains at least one peptide sequence heterologous comprising at least one epitope inserted in the region forming the junction between helix 2 and helix c-3 of β-lactamase.

25. Recombinant β-lactamase protein according to any one of claims 17 to 23, characterized in that it contains at least one heterologous peptide sequence comprising at least one epitope inserted in the region forming the junction between the α3 helix and l α4 helix of β-lactamase.

26. Recombinant β-lactamase protein according to any one of claims 17 to 23, characterized in that it contains at least one heterologous peptide sequence comprising at least one epitope inserted in the region forming the junction between the β4 sheet and the sheet. β5 of β-lactamase.

27. Recombinant β-lactamase protein according to any one of claims 17 to 23, characterized in that it contains at least one heterologous peptide sequence comprising at least one epitope inserted in the exposed region of the C-terminal sequence of β - lactamase.

28. Recombinant β-lactamase protein according to any one of claims 17 to 27, characterized in that it contains, as heterologous peptide sequence, a peptide sequence of the HIV retrovirus, in particular a sequence of the envelope glycoprotein, or gag, nef, pol proteins of an HIV-1 or HIV-2 retrovirus.

29. Recombinant β-lactamase protein according to any one of claims 17 to 27, characterized in that it contains, as heterologous peptide sequence, the peptide V3 of the HIV-1 envelope, preferably inserted at its site BgpII.

30. Immunogenic composition, characterized in that it comprises a recombinant, avirulent cell host according to any one of claims 12 to 16 and a pharmaceutical vehicle suitable for administration.

31. Immunogenic composition according to claim 30, characterized in that it comprises a recombinant strain M. bovis BCG, in combination with a pharmaceutically suitable vehicle for administration.

32. Immunogenic composition, characterized in that it comprises a recombinant protein according to any one of claims 17 to 29, in combination with a pharmaceutical vehicle suitable for administration.

33. Recombinant nucleotide sequence according to any one of claims 3 to 6, characterized in that the heterologous nucleotide sequence is inserted in a region between the α helices and the β sheets of the sequence of the β-lactamase represented in the figure 6.

34. Recombinant nucleotide sequence according to claim 33, characterized in that the insertion site is contained in a region of the sequence of FIG. 6 chosen from: the region between the β2 sheet and the α2 helix corresponding to nucleotides 585 to 613, the region between the helices α2 and α3, corresponding to nucleotides 648 to 719, in particular the BglII site, the region between the helices α3 and α4 corresponding to nucleotides 744 to 748, - the region between the sheets β4 and β5 corresponding to nucleotides 1152 to 1167.