Dog-mouse heterohybridoma and gene fragment coding for constant region of canine immunoglobulins

Abstract: A gene fragment which comprises a DNA sequence coding for an amino acid sequence of a constant region of canine im­ munoglobulin lambda chain; a gene fragment which comprises a DNA sequence coding for an amino acid sequence of a constant region of canine immunoglobulin kappa chain; a gene fragment which com­ prises a DNA sequence coding for the constant region of canine immunoglobulin gamma chain; a recombinant DNA molecule coding for an amino acid sequence of a mouse-dog chimeric antibody which comprises a gene fragment coding for an amino acid sequence of a variable region of a mouse immunoglobulin and a gene fragment coding for an amino acid sequence of a constant region of a canine immunoglobulin wherein the latter gene fragment; a polypeptide of a mouse-dog chimeric antibody which is expressed from a cell transformed with an expression vector for cells wherein said recombinant DNA molecule cording for an amino acid sequence of the mouse-dog chimeric antibody is incorporated; a dog-mouse heterohybridoma which produces canine immunoglobulin; and a process for preparing a canine im­ munoglobulin gene.

Description: The present invention relates to a novel canine monoclonal antibody which is expected to be useful for diagnosis, treatment and prevention of canine diseases, especially canine infectious diseases. More particularly, it relates to a novel dog-mouse heterohybridoma capable of producing a canine immunoglobulin, gene fragments coding for constant regions of canine immunoglobulin and a canine chimeric antibody produced by utilizing said gene fragments. From ancient times, dogs have been favorably treated as a pet by humans. In modern Europe and America, they are called "Companion species" and are now becoming a member of the human society On the other hand, dogs have hitherto been used as an experimental animal in various fields including medicine, pharmacy, animal husbandry, veterinary, psychology etc. They have also been used as a SPF dog in recent years in tests for the determination of effects and safety of drugs, and hence, usefulness thereof for humans becomes greater and greater. In any case, it is earnestly desired to establish a method for more certain diagnosis, treatment and prevention of canine diseases, especially canine infectious diseases in order to keep healthy conditions thereof. There are many canine viral diseases, and among them, those caused by canine distemper virus, canine parvovirus, infectious canine hepatitis are acute diseases having a very high mortality rate. Although vaccines for prevention of these diseases have been developed, only symptomatic therapy such as antibiotics and sulfonamides which prevents secondary bacterial infections has been available for treating dogs infected and attacked by these diseases. Thus the conventional methods for treating these diseases are still insufficient. Hitherto, a hyperimmune serum and an immunoglobulin derived from serum have been utilized for treatment of these diseases and confirmed to be effective. However, with the popularity of the idea for kind treatment of animals, canine serum materials have become hard to obtain, and hence, this treatment cannot be used nowadays. Therefore, development of a monoclonal antibody capable of neutralizing the infecting viruses in place of the conventional hyperimmune sera will greatly contribute to the treatment of these viral diseases. As mentioned above, a monoclonal antibody having a neutralizing activity against viruses can be used as the alternative to the hyperimmune serum. Hitherto, basic techniques of preparing monoclonal antibodies have been established mainly for mouse monoclonal antibodies. Monoclonal antibodies produced by cells such as hybridomas can advantageously be obtained in a large amount and semipermanently and solve the problem of material insufficiency. However, the monoclonal antibody in this case should be a canine monoclonal antibody instead of a conventional mouse monoclonal antibody in order to eliminate side effects such as anaphylatic shock, serum disease, etc. caused by the use of mouse monoclonal antibodies in dogs which act as heteroproteins in dogs. Methods for preparing such a canine monoclonal antibody as a drug for treating the canine viral diseases include: (1) a method using a dog-dog hybridoma; (2) a method using a canine lymphocyte transformed with some viral or chemical agent; (3) a method using a dog-mouse heterohybridoma; (4) a method using a dog-(dog-mouse) hybridoma derived from a dog-mouse heterohybridoma; and (5) a method of obtaining by gene recombination techniques a mouse (V) - dog(C) chimeric monoclonal antibody wherein a variable (V) region which binds to an antigen is derived from a mouse monoclonal antibody having neutralizing activity against viruses and a constant (C) region which is responsible for antigenicity, immunogenicity and physiological activity is derived from a canine monoclonal antibody. However, none of the above methods has hitherto been reported to be effectively used. In the method (1), the fusion efficiency is quite low and no appropriate myeloma strain is available. In case of method (2), there is no appropriate virus corresponding to EB virus in case of humans and no appropriate chemical agent. The methods (3) and (4) provide many difficulties (for example, a stability problem) in obtaining the desired canine monoclonal antibody with high efficiency as compared with the preparation of a human monoclonal antibody. Therefore, it is expected that the method (5) using the chimeric monoclonal antibody approach is the most realizable among those five methods. The chimeric monoclonal antibody is prepared by incorporating a recombinant plasmid vector containing genes encoding a mouse (V) - dog (C) chimeric antibody into an animal host cell (e. g. mouse myeloma cell), expressing said genes in the host cell and collecting the monoclonal antibody from the supernatant of the cell culture, wherein said mouse (V) - dog (C) chimeric antibody is encoded by a V (variable) gene from a mouse-mouse hybridoma capable of producing a mouse monoclonal antibody, a C (constant) gene from a canine cell canable of producing a canine monoclonal antibody and said V gene and said C gene are linked to each other. Several reports are found as to human chimeric antibodies (Japanese Patent First Publication Nos. 155132/1985 and 47500/1986). As mentioned above, a gene coding for an amino acid sequence of a variable (V) region of an antibody molecule capable of binding to a desired antigen and a gene coding for an amino acid sequence of a constant (C) region of a canine immunoglobulin are required for preparing the canine chimeric antibody. The gene coding for the variable (V) region of the chimeric antibody is derived from a cell capable of producing a mouse monoclonal antibody having a neutralizing activity against the above mentioned various canine viruses and said cell can be prepared rather easily using the conventional mouse-mouse hybridoma technology. However, the gene coding for the constant (C) region of the chimeric antibody, i. e. the gene coding for the constant (C) region of the canine immunoglobulin is still unknown with respect to its structure and has never been cloned. Therefore, in order to prepare the canine chimeric antibody, it is inevitably required to clone the genes coding for the constant (C) regions of canine immunoglobulins. In addition, although it is difficult to obtain the monoclonal antibody showing a desired specificity with the methods (1) to (4), materials (cell lines) useful for the preparation of the chimeric antibody can effectively be provided by method (5) since any cell which produces a canine immunoglobulin can, regardless of its specificity, be employed as material for providing a gene coding for the C region of a canine immunoglobulin. Thus the technical problem underlying the present invention essentially is to provide DNA sequences for the production of antibodies which can be administered to dogs and which do not display the above mentioned undesired properties. The solution of this technical problem is achieved by providing the embodiments characterized in the claims. Accordingly, the present invention provides DNA sequences encoding constant (C) regions of canine immunoglobulins, chimeric antibodies containing C regions encoded by such DNA sequences, and hybridomas producing such chimeric antibodies. Thus, an object of the invention is to provide a hitherto unreported dog-mouse heterohybridoma capable of producing the canine immunoglobulin and a hitherto genetically unanalyzed DNA fragment coding for an amino acid sequence of the constant (C) region of the canine immunoglobulin. Another object of the invention is to provide a process for preparing the canine chimeric antibody using said DNA fragment coding for the amino acid sequence in the constant (C) region of the canine immunoglobulin, said chimeric antibody being useful as agent for diagnosis, treatment and prevention of canine diseases, especially infectious canine diseases without showing side effects. These and other objects and advantages of the invention will be apparent to those skilled in the art from the following description. The figures show: Fig. 1 shows the results of EIA using an anti-canine antibody proving that IgG produced by the dog-mouse heterohybridomas prepared by the present invention is a canine monoclonal antibody; Fig. 2 shows the results of a Western blot analysis using an anti-canine antibody proving that IgG produced by the dog-mouse heterohybridomas prepared by the present invention is a canine monoclonal antibody; Fig. 3 shows a restriction enzyme map of a DNA fragment (S6-61) coding for the constant region of a canine immunoglobulin lambda chain cloned by the present invention and the sequencinq strategy (→) Fig. 4 shows the results of a Southern hybridization analysis where a DNA fragment (S6-61) coding for the constant region of a canine immunoglobulin lambda chain cloned by the present invention is hybridized with chromosomal DNA (EcoRI digestion) of canine hepatocytes; Fig. 5 shows the results of a Northern hybridization analysis where a DNA fragment (S6-61) coding for the constant region of a canine immunoglobulin lambda chain cloned by the present invention is hybridized with poly(A)⁺ RNA of CM-S6 cells (lane 1) or CM-S1 cells (lane 2); Fig. 6 shows a nucleotide sequence coding for the constant region of the canine immunoglobulin lambda chain present in the DNA fragment (S6-61) cloned by the present invention; Fig. 7 shows the whole amino acid sequence of the constant region of the canine immunoglobulin lambda chain encoded by the DNA fragment (S6-61) cloned by the present invention; Fig. 8 shows the results of a Southern hybridization analysis where a chromosomal DNA of canine hepatocytes is hybridized with a[³²P]-labeled probe containing the human C kappa chain gene; Fig. 9 shows the results of a Northern hybridization analysis where poly(A)⁺ RNA extracted from canine spleen cells is hybridized with a [32p]-labeled DEk5a probe; Fig. 10 shows a restriction enzyme map of a DNA fragment (DEk5a) coding for the constant region of the canine immunoglobulin kappa chain cloned by the present invention and the sequencing strategy (→); Fig. 11 shows the nucleotide sequence coding for the constant region of the canine immunoglobulin kappa chain present in the DNA fragment DEk5a cloned by the present invention; Fig. 12 shows the whole amino acid sequence of the constant region of the canine immunoglobulin kappa chain encoded by a gene in the DNA fragment DEk5a cloned by the present invention; Fig. 13 shows the results of a Southern hybridization analysis where chromosomal DNA of canine hepatocytes is hybridized with a [³²P]-labeled probe containing the human C gamma 1 chain gene; Fig. 14 shows a restriction enzyme map of the chromosomal DNA fragments (DE94gamma,DB31gamma) coding for the constant regions of canine immunoglobulin gamma chains and cloned by the present invention; Fig. 15 shows the result of a Northern hybridization analysis where poly(A)⁺ RNA extracted from canine, mouse or feline spleen cells is hybridized with a [³²P]-labeled DE94gamma or DB31gamma probe; Fig. 16 shows the nucleotide sequence coding for the constant region of canine immunoglobulin gamma chain present in the DNA fragment DE94gamma cloned by the present invention; Fig. 17 shows the nucleotide sequence coding for the constant region of canine immunoglobulin gamma chain present in a DNA fragment DB31gamma cloned by the present invention; Fig. 18 shows the whole amino acid sequences of the constant regions of canine immunoglobulin gamma chains encoded by DNA fragment DE94gamma and DB31gamma cloned by the present invention; Fig. 19 shows a restriction enzyme map of a clone JP2g L4ll containing the V kappa region gene isolated from anti-CPV mouse monoclonal antibody-producing cells; Fig. 20 shows a nucleotide and an amino acid sequence of the V region gene JP2gL4ll isolated from anti-CPV mouse monoclonal antibody-producing cells; and Fig. 21 shows the construction of a gene (pSV2-EPLDCk) expressing an L chain of an anti-CPV mouse-dog chimeric antibody. There are two approaches for isolating the gene coding for the amino acid sequence of the constant (C) region of the canine immunoglobulin. That is, the first is to construct a library from a chromosomal DNA of canine cells and then to clone the gene coding for the C region according to conventional methods [for example, see T. Maniatis "Molecular Cloning" Cold Spring Harbor Lab.(1982)], and the second is to construct a library by synthesizing cDNA from a messenger RNA (mRNA) of canine cells and then to clone the C region gene according to conventional methods [for example, see "DNA cloning Vol. I" ed. by D. M. Glover, IRL Press (1985)]. For the screening procedure, mainly four methods can be used, i. e. (a) a method which comprises purifying the antibody protein produced by the canine antibody-producing cell, analyzing the amino acid sequence of said protein, synthesizing a nucleotide sequence corresponding to said amino acid sequence, and then using said nucleotide sequence as a probe for screening (hybridization); (b) a method of cross-hybridization using a probe synthesized by referring to a gene fragment of mouse and human immunoglobulin genes or nucleotide sequences thereof previously reported [for example, Sakano et al., Nature, 286, p676 (1980); E. E. Max et al., J. Biol. Chem., 256, p5116 (1981); J. W. Ellison et al., Nuc. Acids. Res., 10, p4071 (1982); and P. A. Hieter et al., Cell, 22, p197 (1980)]; (c) a method which comprises synthesizing an oligonucleotide primer based on a nucleotide sequence selected by analogy to an amino acid sequence of a canine antibody protein or a nucleotide sequence selected by analogy to the mouse and human immunoglobulin genes previously reported and then screening based on the primer using the PCR procedure [R. Orlandi et al., Proc. Natl. Acad. Sci. USA, 86, p3833 (1989)] and (d) a process which comprises expressing the canine antibody gene incorporated into an expression vector (e. g. Lambda gtll) in E. coli or in an animal cell and screening the expression products by using an antiserum (or a monoclonal antibody) directed to the canine antibody protein. In any case, the screening process using the canine antibody protein-producing cells is preferable in view of the cloning efficiency and is essential in the case of the above second process for isolating the gene using the cDNA synthesized from messenger RNA. Although it is possible to use polyclonal cells such as spleen cells or lymph node cells as the antibody-producing cells, monoclonal cells are preferable in view of the easiness of genetic analysis. There are several methods for establishing the monoclonal antibody-producing cells as cited above under (1) to (5). However, methods (1) and (2) are extremely difficult to set into practice and method (4) requires the dog-mouse heterohybridomas of method (3). In conclusion, it is most important to obtain the dog-mouse heterohybridomas using method (3). The dog-mouse heterohybridomas can be prepared by several methods previously disclosed. According to these methods, the present inventors have established dog-mouse heterohybridomas CM-S1, -S2 and -S6 which produce the canine monoclonal antibody. Among these dog-mouse heterohybridomas, CM-S6 is the most preferable for preparing the gene of the present invention and has been deposited at the Fermentation Research Instituted, Agency of Industrial Science and Technology, Japan under Budapest Treaty under the accession number FERM BP-2946. As mentioned above, the present inventors have cloned several kinds of gene fragments coding for the constant region of immunoglobulins from canine cells. The cloned gene fragments coding for the C region of canine immunoglobulin of the present invention were analyzed by comparing an amino acid sequence deduced from the nucleotide sequence thereof with the corresponding sequences of the C region genes of immunoglobulins from other animal species, and as a result, it was found that each gene fragment of the present invention contains gene fragments coding for a lambda chain, the kappa chain and gamma chains, respectively. Immunoglobulin lambda chain has already been found in human [P. A. Hieter et al., Nature, 294, p536 (1981); G. F. Hollis et al., Nature 296, p321 (1982)] and in mouse [B. Blomberg et al., Proc. Natl. Acad. Sci. USA, 79, p530 (1982); J. Miller et al., Nature, 295, p428 (1982)] and has also been reported for other animal species such as rabbit [Duvoisin, MR. M. et al., J. Immunol., 136, p4297-4302 (1986)]. However, there has never been reported the canine lambda chain of the present invention, the amino acid sequence thereof and the nucleotide sequence coding therefor. The cDNA fragment coding for the constant region of canine immunoglobulin lambda chain prepared as mentioned above has been analyzed for its nucleotide sequence. Then, the amino acid sequence of said constant region has been deduced from the nucleotide sequence and compared with the amino acid sequences of the constant regions of immunoglobulin lambda chains derived from human, mouse, rabbit etc. as previously reported. It was found that the constant region of the canine immunoglobulin lambda chain has a specific amino acid sequence at the N-terminal region which has the following amino acid sequence (A) at the N-terminal region of the first cysteine counted from the N-terminus of said polypeptide: -Gly-Ala-xxx-xxx-xxx-xxx-xxx-xxx-Cys- (A) wherein xxx means an optional amino acid residue. From comparison among the amino acid sequence of the constant region of the canine immunoglobulin lambda chain analyzed in accordance with the present invention, the amino acid sequence of the constant region of a feline immunoglobulin lambda chain separately analyzed by the present inventors and various amino acid sequences of the constant regions of immunoglobulin lambda chains derived from several animal species, it has been found that the region -Gly-Ala- present at the N-terminus of the above cysteine is a region whose amino acid sequence varies with animal species such dog, mouse, human, etc. In addition, it has been found that this region is quite well preserved among subclasses, for example, as an amino acid sequence of the constant region of human lambda chain. The above sequence (A) is supposed to be specific for the constant region of canine immunoglobulin lambda chain region cloned by the present invention and has the following amino acid sequence (A') which is one example of the preferable specific amino acid sequences present in the constant region of canine immunoglobulin lambda chain. -Gly-Ala-Asn-Lys-Ala-Thr-Leu-Val-Cys- (A') The dog-mouse heterohybridoma of the present invention produces canine immunoglobulin containing a peptide of a lambda chain C region having the above amino acid sequence (A) or (A'). The gene fragment coding for the constant region of canine immunoglobulin lambda chain of the present invention also contains a DNA fragment coding for the above amino acid sequence (A) or (A'). Such amino acid sequence contained in the above lambda chain is believed to be an important amino acid sequence for determining the C region of canine immunoglobulin lambda chain and is firstly disclosed by the present invention. In the constant region polypeptide of canine lambda chain, the 11th - 9th amino acid sequence at the N-terminal region from the second cystein residue counted from the C-terminus is deemed to be the region whose amino acid sequence varies with species such as dog, cat, human, mouse, etc. as mentioned above, and it is found that the constant region of canine immunoglobulin lambda chain of the present invention has the corresponding specific sequence of -Pro-Asp-Lys-. One preferable example of the gene coding for the constant region of canine immunoglobulin lambda chain is a gene fragment coding for the amino acid sequence as shown in Fig. 7 and one example of the nucleotide sequence of said gene is as shown in Fig. 6. On the analogy of the case of human and mouse [P. A. Hieter et al., Nature, 294, p536 (1981); G. F. Hollis et al., Nature, 296, p321 (1982); B. Blomberg et al., Proc. Natl. Acad. Sci. USA, 79, p530 (1982); J. Miller et al., Nature, 295, p428 (1982)], there is expected an existence of several subclasses in canine lambda chain. In fact, Southern hybridization using the lambda chain gene of the present invention shows an existence of C lambda region genes of several subclasses belonging to the same canine lambda chain gene in addition to the lambda chain of the present invention (Fig 4). That is, there exist genes of different subclasses having a quite similar sequence to that of the gene fragment coding for the constant region of canine immunoglobulin lambda chain of the present invention. The canine lambda chain gene of the present invention is believed to have sequences which cover also such gene fragments coding for amino acid sequences of different subclasses. Therefore, such gene fragments coding for different subclasses can also be used as the canine lambda chain gene as far as they have substantially the same sequences as that of the gene of the present invention. Cloning of such C genes of different subclasses can be carried out by using a part of the nucleotide sequence disclosed in the present invention as a probe. Alternatively, a chromosomal gene coding for the canine lambda chain can also be cloned from canine cells using the canine immunoglobulin lambda chain of the present invention as a probe. Kappa chain of immunoglobulin has also already been found in human and mouse [P. A. Hieter et al., Cell, 22, p197 (1980); H. Sakano et al., Nature 280, p288-294 (1979)] and also reported for other animal species such as rabbit [L. Emorine et al., Proc. Natl. Acad. Sci. USA, 80, p5709-5713 (1983)]. However, there has never been reported for the canine kappa chain of the present invention, an amino acid thereof and a nucleotide sequence coding therefor. The present inventors have obtained a chromosomal DNA fragment which will code for the constant region of canine immunoglobulin kappa chain by the above-mentioned procedure. The present inventors have also analyzed the nucleotide sequence of the chromosomal DNA fragment and have determined an amino acid sequence of the kappa constant region. As a result of comparison of the amino acid sequence with those of the constant region of immunoglobulin kappa chain derived from human, mouse, rabbit, etc., it has been found that the gene fragment of the present invention is a gene fragment coding for the constant region of immunoglobulin kappa chain. The gene fragment coding for the constant region of canine immunoglobulin kappa chain of the present invention is a DNA sequence coding for a peptide comprising 109 amino acids and characterized in that five amino acids at the C-terminus thereof are -Cys-Gln-Arg-Val-Asp. It is known that the C-terminus of the amino acid sequence of human or mouse kappa chain constant region is Cys (cystein) residue as previously reported. It is very rare that the amino acid sequence of the constant region contains additional four amino acids subsequent to the Cys residue present at the C-terminus like in the gene of the present invention coding for the constant region of canine immunoglobulin kappa chain which is characteristic to the constant region of canine immunoglobulin kappa chain of the present invention. The gene coding for the constant region of canine immunoglobulin kappa chain of the present invention contains the gene fragment as shown by the restriction enzyme map of Fig. 10. Among the genes coding for the constant region of canine immunoglobulin kappa chain of the present invention, one of the preferable examples is the gene fragment coding for the amino acid sequence as shown in Fig. 12. Such amino acid sequence has hitherto never been reported. One example of the nucleotide sequence of the gene coding for the C region of canine immunoglobulin kappa chain of the present invention is as shown in Fig. 11. cDNA coding for the C region of immunoglobulin kappa chain can be cloned from a cDNA library of canine antibody-producing cells using the canine immunoglobulin kappa chain of the present invention as a probe. Gamma chain of immunoglobulin has also already been found in human and mouse [e. g. A. Shimizu et al., Cell, 29, p121 (1982); N. Takahashi et al., Cell, 29, p671 (1982)] and also reported for other animal species such as rabbit [C. L. Martens et al., Proc. Natl. Acad. Sci. USA, 79, p6018 (1982)] and bovine [K. L. Knight et al., J. Immunol, 140, p3654 (1988)]. However, there has never been any report concerning the canine immunoglobulin gamma chain. The present inventors have obtained two chromosomal gene fragments (DE94gamma and DB31gamma )which will code for the constant region of canine immunoglobulin gamma chain by the aforementioned procedure. The cloned gene fragments have genetically been analyzed by comparing amino acid sequences deduced from the nucleotide sequence of these gene fragments with those of the genes derived from other animal species coding for the C region of immunoglobulin, and as a result, it has been found that the gene fragments obtained by the present invention are gene fragments coding for the constant region of different subclasses of the immunoglobulin gamma chain. The amino acid sequences of each canine gamma chain have been compared with previously reported amino acid sequences of the constant region of immunoglobulin gamma chain derived from human, mouse, rabbit, etc. As a result, it has been found that the amino acid sequence specific for the constant region of canine immunoglobulin gamma chain includes the following amino acid sequence (B) in the vicinity of the second cysteine residue counted from the C-terminus of CHl domain of the constant region of the gamma chain: -Ala-Cys-xxx-xxx-Ser- (B) wherein xxx represents an optional amino acid. The present inventors have found that an amino acid sequence of the above region -Ala-Cys-xxx-xxx-Ser- present in the vicinity of the above-mentioned cysteine varies with animal species such as dog, cat, mouse, human, etc. by comparing the amino acid sequence of the constant region of canine immunoglobulin gamma chain analyzed by the present invention with the previously analyzed amino acid sequences of the constant region of immunoglobulin gamma chain derived from various animals. The present inventors have also found that this region is quite well preserved among subclasses(DE94 gamma and DB31gamma) of canine gamma chain and also preserved among those of human, rabbit and mouse. The above sequence (B) is supposed to be specific for the constant region of canine immunoglobulin gamma chain. Similar sequences specific for the constant region of canine immunoglobulin gamma chain have also been found in the vicinity of cystein at the N-terminal region of CH3 domain (C): -Cys-xxx-Ile-xxx-Asp-xxx-Phe-xxx-Pro- (C) wherein xxx represents an optional amino acid. The amino acid sequences of these regions cloned by the present invention have the following sequences (B') and (C') which are each one of the preferable examples of specific amino acid sequences present in the constant region of canine immunoglobulin gamma chain. -Ala-Cys-Leu-Val-Ser- (B') -Cys-Leu-Ile-Lys-Asp-Phe-Phe-Pro-Pro- (C') The gene fragments coding for the constant region of canine immunoglobulin gamma chain of the present invention are characterized by that they contain a DNA sequence coding for the above amino acid sequence (B), (C), (B') or (C'). These amino acid sequences contained in the gamma chain , which are quite important for determining the C region of canine immunoglobulin gamma chain, have been found by the present inventors for the first time. Preferable examples of the constant region of canine immunoglobulin gamma chain containing these amino acid sequences have an amino acid sequence as shown in Fig. 18. Such amino acid sequences and nucleotide sequences coding therefor have never been reported until the present invention. An example of the nucleotide sequences of the gene coding for the C region of canine immunoglobulin gamma chain of the present invention include the sequences as shown in Fig. 16 and Fig. 17. On the analogy of the human and mouse cases [for example, A. Shimizu et al., Cell, 29, p121 (1982); N. Takahashi et al., Cell, 29, p671 (1982)], the canine gamma chain is also expected to have several subclasses. It is known that there are at least four subclasses of canine gamma chain [J. S. Johnson et al., J. Immunol., 98, p923 (1966)], and the genes of the present invention appear to code for two of these four subclasses. In fact, Southern hybridization using the genes of the present invention and a canine chromosomal DNA showed the existence of several genes coding for the C regions of other subclasses of canine gamma chain in addition to the gamma chains of the present invention. That is , there are genes coding for different subclasses having extremely similar sequences to that of the gene of the present invention. In fact, DE94gamma and Db31gamma chain share striking homology with each other, except for the hinge regions. It is believed that the canine gamma chain genes of the present invention have sequences which cover also such gene fragments coding for amino acid sequences of different subclasses. Therefore, such gene fragments coding for amino acid sequences of different subclasses can also be used as canine gamma chain gene as far as they have substantially the same sequence as that of the gene of the present invention. Such genes coding for C regions of different subclasses can be cloned by using a part of the nucleotide sequence of the present invention as a probe. As far as the constant region of immunoglobulin is concerned, it is also reported that a genetic analysis of immunoglobulins derived from human, rabbit, etc. showed the existence of an allotype which differs in one to several amino acids within the same class or subclass. Therefore, the gene coding for the constant region of canine immunoglobulin lambda chain, kappa chain or gamma chain of the present invention is not limited to the gene fragments coding for the above-mentioned amino acid sequences but includes those genes coding for the constant region of different allotypes which have almost the same sequence as the above sequences though containing a partial substitution of an amino acid. The thus prepared gene coding for the constant region of canine immunoglobulin of the present invention allows for preparation of the canine chimeric antibody using the conventional process for preparing an chimeric antibody [for example, Watanabe et al., Cancer Research, 47, p999-1005 (1987); Japanese Patent First Publication No. 20255/1988]. That is, the chimeric gene can basically be constructed by linking two kinds of gene fragments, i. e. the V region gene and the C region gene, to each other. Since the gene can be classified into mainly two categories depending on a way of isolation, the chimeric antibody can be constructed by using either a combination of V and C region genes isolated from a chromosomal DNA or a combination of V and C region genes isolated from cDNA. The chimeric antibody can be expressed in any expression system such as an animal cell expression system, an E. coli expression system, an yeast expression system, etc. using different expression vectors. In a combination of the V region and the constant region for preparing the chimeric antibody, a preferable combination is the VH region with the constant region derived from canine H chain such as gamma chain, the V kappa region with the constant region of canine kappa chain, and the V lambda region with the constant region of canine lambda chain, but other combinations can also be used. There can be used any V region including those derived from mouse, dog, or other animals, and CDR graft V region [M. Verhoeyen, C. Milstein, G. Winter, Science, 239, p1539 (1987)], as far as it is effective for treating canine diseases (e. g. viral canine diseases). Thus, although it is described as to the mouse-dog chimeric antibody against canine parvovirus to exemplify the canine chimeric antibody of the present invention, the V region is not limited to that used therein. The gene fragment coding for canine immunoglobulin provided by the present invention discloses the specific amino acid sequence or DNA sequence in the constant region of canine immunoglobulin, and hence, allows for isolating those genes coding for the constant regions belonging to different subclasses or allotypes. By using the gene coding for the constant region of canine immunoglobulin of the present invention, a canine chimeric antibody can be prepared for the first time. chimeric antibody prepared according to the present invention can be used as agents for diagnosis, prevention and treatment of canine diseases which have hitherto never been developed. The present invention is illustrated by the following Examples in more detail but should not be construed to be limited thereto. Example 1 : Preparation of canine monoclonal antibody-producing cells: (1) Immunization and preparation of canine lymphocytes: In order to efficiently obtain activated canine B cells, a complete Freund's adjuvant (CFAa: manufactured by Difco)(5ml) was injected to dogs subcutaneously and intraperitoneally for several times at an interval of 2 to 3 weeks for nonspecific immunization. Two to three weeks after the final immunization, spleen and lymphnodes were taken out and a suspension of canine lymphocytes was obtained by crushing with a pincette and pipetting. One dog gave 1 to 3 x 10⁹ cells from spleen and 1 to 3 x 10⁸ from lymphonode. These lymphocytes were suspended in a complete medium of RPMI 1640 plus 10% fetal calf serum (manufactured by Flow Laboratories) supplemented with L-glutamine (manufactured by Flow Laboratories) at a concentration of 5 to 10 x 10⁵ cells/ml and thereto was added poke-weed mitogen (PWM: manufactured by Gibco)(2.5µg/ml), followed by culturing the cells in the presence of 5% CO₂ at 37° C for 2 to 5 days for activation. (2) Preparation of mouse myeloma cells: The myeloma cells employed in the present invention are those derived from Balb/c mice as described in Köhler et al., Nature 256, p495 (1975) and Eur. J. Immunol., 6, p511 (1976), especially cell lines X63-Ag8-6.5.3 , P3-X63-Ag8-U1 and SP2/0Ag12. These cells were cultured and grown in a complete medium of RPMI 1640 supplemented with glutamine plus 10 % fetal calf serum. They were collected just before cell fusion, washed twice with RPMI 1640 medium and resuspended in the same medium for use in cell fusion. (3) Cell fusion of the canine lymphocytes and the mouse myeloma cells: The above canine lymphocytes and mouse myeloma cells were mixed at a ratio of 10:1 or 5:1 (canine lymphocytes : myeloma cells; canine lymphocytes = 1 x 10⁸ cells) and centrifuged at 1,500 rpm for 5 minutes. To the obtained cell pellet was added a 45% polyethylene glycol solution (manufactured by Sigma, pH 7.6, MW 3,650, or manufactured by Celba, pH 7.6, MW 4,000) diluted with RPMI 1640 (1ml) at room temperature over 1 minute. After the mixture was allowed to stand at 37°C for 5 to 10 minutes, the cells were resuspended by adding RPMI 1640 (40 ml) to the mixture over 6 minutes to quench the cell fusion. The cells were then centrifuged at 1,000 rpm for 10 minutes, the supernatant was removed by suction and the resulting cell pellet was resuspended in RPMI 1640 + 10% fetal calf serum + HAT (H: hypoxanthine 13.0 µg/ml, A: aminopterin 0.18 µg/ml, T: thymidine 3.87 µg/ml; all manufactured by Sigma)supplemented with glutamine at a concentration of 2 to 10 x 10⁵ lymphocytes/ml. The suspension was poured into each well of a 96-well microtiter plate at 200 µl/well and was cultured in the presence of 5% CO₂ at 37°C. After 5 to 7 days, 50% of medium was exchanged with the same fresh medium and thereafter the medium exchange was repeated for 5 to 6 times after 10 to 28 days from the cell fusion. By this procedure, only hybridomas were grown, and thereafter the cell culture was continued until screening assay. (4) Screening assay and cloning of hybridoma: Screening assay was conducted to detect a clone which produces a canine IgG antibody using enzyme immunoassay (EIA). A 96-well plate was coated with a goat anti- canine IgG antibody (manufactured by Cappel) and treated with bovine serum albumin (manufactured by Sigma) to block non-specific adsorption. To each well was added the culture supernatant (50 µl) from each well of the hybridoma culture plate. After incubating the plate at 37°C for 1 to 2 hours, washing was carried out with PBS-T {0.01% Tween manufactured by Katayama Kagaku K.K., 0.01M phosphate buffer, pH 7.2, 0.15M NaCl} four times, a peroxydase-labelled goat anti-canine IgG antibody (manufactured by Cappel, 10,000 fold dilution)(50 µl) was added to each well and the plate was incubated at 37°C for 1 hour. After washing with PBS-T five times, TMBZ substrate solution (TMBZ: manufactured by Dojin Kagaku K.K., 0.4 mg/ml, hydrogen peroxide: manufactured by Mitsubisi Gasu Kagaku K.K., 0.006%) (50µl) was added in order to develop a color reaction. After 10 to 15 minutes, 0.3N H₂SO₄ (manufactured by Katayama Kagaku K.K.)(50µl) was added to each well to quench the reaction and each color development was quantitated with a spectrophotometer (wavelength: 450nm). The canine IgG-producing hybridomas in the thus selected wells were then cloned by a limiting dilution procedure. After growth of the clones in each well of the 96-well plate, the above enzyme immunoassay (EIA) was repeated to detect the canine IgG-producing clones. This cloning procedure was repeated at least 3 times to give the dog-mouse hybridoma clone which stably produce canine IgG. This hybridoma clone was successively subjected to an extensive culture and was kept in the freezed state with a cell-freezing medium of RPMI 1640 + HAT + 10% DMSO supplemented with glutamine in liquid nitrogen. (5) Characterization of the established hybridoma clone and canine IgG monoclonal antibody produced therefrom: Measurement with an EIA procedure of an amount of the produced canine antibody confirmed that the established dog-mouse hybridomas were capable of stably producing the canine IgG monoclonal antibody in an amount of 1.0 to 3.0 µg/ml for 1 year or more and no abnormality was observed in their ability of producing the antibody. The canine monoclonal antibody produced by the established dog-mouse hybridoma was proven to be canine IgG by an immunoprecipitation method {cf. "Meneki Jikken Sosaho (Immunological Experimentation)" ed. Jap. Soc. Immunol.}. This antibody was found to be canine IgG since it did not form precipitates with goat anti-mouse IgG serum and goat anti-human IgG serum but did form a precipitate with goat anti-canine IgG serum. EIA further proved that the monoclonal antibody was canine IgG antibody since it specifically reacted only with the anti-canine IgG antibody but reacted with neither the anti-human IgG antibody nor the anti-mouse IgG antibody (Fig. 1). Furthermore, Western blotting assay proved that both the heavy chain (H chain) fragment and the light chain (L chain) fragment of the monoclonal antibody specifically react only with the anti-canine IgG antibody but did not react with the anti-human IgG antibody or anti-mouse IgG antibody and that the H chain fragment and L chain fragment of the monoclonal antibody were identical to those fragments of standard canine IgG antibody in view of molecular weight, showing that the monoclonal antibody is a complete canine IgG monoclonal antibody having both the H chain and L chain fragments of the canine IgG antibody (Fig.2). In addition, cytoplasmic synthesis of canine IgG antibody was studied by fluorescent antibody dyeing assay of the hybridoma clone. As a result, each clone was intracytoplasmically dyed specifically only with the anti-canine IgG antibody but was not dyed with the anti-human IgG antibody and the anti-mouse IgG antibody, proving that the hybridoma clones intracytoplasmically synthesized a complete canine IgG monoclonal antibody. The dog mouse heterohybridoma CM-S6 cells producing this canine monoclonal antibody have been deposited under accession number BP-2946 as mentioned hereinbefore. The CM-S6 cells were used in the following Experiment to isolate the constant region of canine immunoglobulin. Example 2 Cloning of the gene coding for the constant region of canine immunoglobulin lambda chain (1) Construction of a cDNA library: Total RNA was separated from the heterohybridoma CM-S6 using a guanidinium@ thiocyanate method {J. M. Ghirgwin et al., Biochemistry, 18, p5294 (1979)} and poly(A)⁺ RNA was purified using an oligo(dT)column (Pharmacia). cDNA of the CM-S6 cells was synthesized from the purified poly(A)⁺ RNA using the cDNA synthesis system Plus (Amersham). EcoRI sites of the synthesized cDNA were methylated with EcoRI methylase (manufactured by Takara Shuzo Co. Ltd., the reagents used hereinafter are manufactured by Takara Shuzo Co. Ltd., or Toyobo Co. Ltd., unless otherwise mentioned) and then EcoRI linkers were added to the cDNA with T4 DNA ligase. This cDNA was completely digested with the restriction enzyme EcoRI and cDNA having an EcoRI linker was purified with a Bio Gel A50m column (Bio-Rad). The obtained cDNA was ligated to EcoRI arms of λgt11 vector DNA (Stratagene) with T4 DNA ligase and then an in vitro packaging reaction was carried out using kits (manufactured by Stratagene) to give a cDNA library of CM-S6 cells. (2) Screening of the canine immunoglobulin gene with anti-canine antibody: Using the cDNA library of CM-S6 cells constructed as mentioned above, E. coli Y1090 cells infected with the phage λgt11 were poured onto an LB plate {laboratory dish of No.2 square manufactured by Eiken Kizai charged with 1.5% Bacto-agar manufactured by Difco, 1% Bacto-tryptone manufactured by Difco 0.5% Bacto-yeast extract manufactured by Difco, 0.25% NaCl manufactured by Wako Pure Chemical Industries, pH 7.5} so that 50,000 plaques per plate of the λgt11 phage were formed and cultured at 42°C for 3 hours. After laying a nitrocellulose filter (NC filter: Code BA85 manufactured by S&S) soaked with 10 mM IPTG (manufactured by Wako Pure Chemical Industries) on the plate, the culturing was continued at 37°C for additional 4 hours. The NC filter was peeled off the plate, wash with a W buffer {WB: 7 mM Tris buffer, pH 7.2, 150mM NaCl, 0.005% Tween 20} and immersed in BLOTTO {5% skim milk, 10 µl/100ml Antifoam A} at 4°C over night. Then the BLOTTO was exchanged with a BLOTTO containing an anti-canine IgG antibody {manufactured by Cappel; 10 µg/ml; treated with a 1% E. coli lysate (manufactured by BioRad) at 4°C overnight} and the reaction was conducted at room temperature for 2 hours. After washing the NC filter with WB five times, the NC filter was immersed in an incubation buffer {PBS, pH 7.2, 0.005% Tween 20, 1% BSA} containing a peroxydase-labelled goat IgG antibody {manufactured by Cappel; treated with a 1% E. coli lysate( manufactured by Bio-Rad) at 4°C overnight} and the reaction was conducted at room temperature for 2 hours. After washing the NC filter with WB five times, the NC filter was immersed in a color development solution containing 5 % HRP color development reagent (manufactured by Bio-Rad) and 0.5% H₂O₂ (manufactured by Wako Pure Chemical Industries) to proceed color development. After selection based on the color development on the NC filter, the phage was further cloned. The clone was selected by way of reaction with the anti-canine IgG antibody and finally clone S6-61 was obtained. This clone had a size of 0.7 kb and seemed to contain a gene coding for the lambda chain in accordance with the nucleotide sequence analysis as described hereinafter. Fig. 3 shows a restriction enzyme map of this clone. (3) Southern blotting and Northern blotting analysis using S6-61: Southern blotting analysis was carried out using S6-61 DNA. Chromosomal DNA (10 µg) from canine, feline and mouse hepatocytes was digested with the restriction enzyme EcoRI and the obtained DNA fragments were subjected to electrophoresis using a 0.7% agarose gel. After transfer to a nylon membrane filter (Gene Screen Plus, NEN Research Product), the Southern hybridization was carried out with a {³²P}-labeled S6-61 probe containing the constant region of a canine lambda chain. The Southern hybridization was carried out in accordance with a manual delivered with the Gene Screen Plus membrane. The molecular size was calculated based on the marker DNA which was prepared by digesting λ phage DNA with Hind III. As shown in Fig. 4, several bands having various sizes from about 2 to about 20 kb were detected. This suggests that the gene coding for the C region of canine lambda chain has several subclasses, which can also be estimated by analogy to human and mouse {P. A. Hieter et al., Nature, 294, p536 (1981); G.F. Hollis et al., Nature, 296, p321 (1982); B. Blomberg et al., Proc. Natl. Acad. Sci. USA, 79, p53 (1982); J. Miller et al., Nature, 295, p428 (1982)}. Since it is known that the gene coding for the lambda C region is amplified in wild mice {C. L. Scott et al., Nature, 300, p757 (1982)}, the gene coding for the C region of canine lambda chains can also presumably be subjected to amplification. Northern blotting was then conducted. The RNA used for the hybridization was prepared by isolating total RNA from CM-S1 and CM-S6 cells according to the guanidinium thiocyanate method {J. M. Ghirgwin et al., Biochemistry, 18, p5294 (1979)} and purifying poly(A)⁺ RNA using an oligo dT column (Pharmacia). The RNA (2µg) was electrophoresed using an 0.75% agarose gel containing 3% formaldehyde. After transfer to a nylon membrane filter (Gene Screen Plus), a Northern hybridization was carried out in accordance with a protocol delivered with the Gene Screen Plus membrane. As a result, this probe detected a band at about 1.3 kb in both mRNAs(Fig. 5). This size is almost the same as that of the genes coding for mouse and human immunoglobulin lambda chains. From the above two results, the S6-61 gene was presumed to be an active gene coding for a functional canine lambda C region. (4) Nucleotide sequence and amino acid sequence of S6-61 : In order to determine the nucleotide sequence of S6-61, small EcoRI-SacI, SacI-AccII, AccII-EcoRI, StuI-EcoRI and EcoRI-HhaI DNA fragments were prepared (Fig. 3). These small fragments were blunt-ended with T4-DNA polymerase and inserted into the SmaI site of a M13mp19 vector using a Takara ligation kit. Competent JM109 cells were prepared in accordance with a Toyobo Instruction Manual and transformed with M13mp19 DNA wherein the C lambda gene was inserted. The DNA sequence was determined using a Takara M13 Sequencing kit and Fuji Genser Gel System. The direction of determination of the nucleotide sequence is shown in Fig. 3. As a result of the determination of the nucleotide sequence, it was confirmed that the canine lambda chain gene consisted of a V, J and C region (Fig. 6). Fig. 7 shows the result thereof. The amino acid sequence encoded by the open reading frame suggested that this gene is not a pseudogene. A homology search with the nucleotide sequence of S6-61 was carried out using the LASL and EMBL data bases, and using genetic analysis software (Genetyx Ver. 6 manufactured by Software Kaihatsu, K.K.). The DNA sequence had the highest degree of homology with the human immunoglobulin lambda chain gene but no homology was found with genes other than the immunoglobulin lambda C chain gene. Comparison of the C lambda region of the S6-61 gene with those of mouse and human showed 75.2% homology with mouse and 84.8% homology with human on the nucleic acid level and 73.1% homology with mouse and 84.6% homology with human on the amino acid level. As is clear from the above results, the S6-61 gene is certainly a gene coding for the canine C lambda chain which can be used for the preparation of a chimeric antibody. Example 3 Cloning of the gene coding for the constant region of canine kappa chain: (1) Conditions of crosshybridization: Most of the canine immunoglobulin light chains are lambda chains {L. Hood et al., Cold Spring Harbor Symp. Quant. Biol. 32, p133 (1967)}, and hence, it is foreseeable that only few lymphocytes express kappa chains. In fact, the dog-mouse heterohybridoma as described above were lambda chain producing cells. Therefore, it is very difficult to obtain the desired gene from mRNAs of polyclonal antibody-producing cells by a cDNA cloning procedure. Therefore, the present inventors have tried to isolate the desired gene fragment for the constant region of the canine immunoglobulin kappa chain from a chromosomal DNA gene bank of canine hepatocytes under crosshybridization conditions using the constant region of human kappa chain (human C kappa) as a probe. For cloning of the canine kappa chain gene by a crosshybridization procedure, conditions of crosshybridization with the human kappa chain were studied. The gene coding for the human C kappa region used for the crosshybridization was a gene cloned from a human cell line ARH77 {ATCC CRT 1621} which is available from professor Takesi Watanabe, Department of Molecular Immunology, Medical Institute of Bioregulation, Kyushyu University {cf. Kudo et al., Gene, 33, p181, (1985); Nishimura et al., Cancer Res., 47, p999 (1987)}. From this human C kappa gene, an EcoRI-EcoRI fragment containing the C kappa exon was obtained and used as a probe. Chromosomal DNA was isolated from canine hepatocytes according to N. Blin and D. W. Stafford [Nuc. Acids. Res., 3, p2303 (1976)] and 10 µg of the chromosomal DNA was digested with the restriction enzyme EcoRI. DNA fragments obtained by the restriction enzyme digestion were subjected to electrophoresis using an 0.7% agarose gel. The DNA was transferred to a nitrocellulose membrane filter (BA85 manufactured by S&S) and then Southern hybridization was carried out with a [³²P]-labeled DNA probe containing the human C kappa region gene. The Southern hybridization was carried out in 6xSSC [0.09 M Na₃C₆H₅O₇x2H₂O, 0.9 M NaCl , 10 mM EDTA, manufactured by Dojin Kagaku] and 0.5% SDS [manufactured by Bio-Rad] at 65°C overnight. The final washing of the filter was conducted with a solution of 0.1xSSC and 0.1% SDS at 45°C for 15 minutes. Autoradiography of this filter showed a band of about 5 kb as shown in Fig. 8. The molecular size was calculated from a marker DNA prepared by digesting λ phage DNA with HindIII. This DNA fragment of 5 kb appears to contain the gene coding for the canine kappa chain and was used for cloning. (2) Isolation of the gene coding for canine kappa chain: Chromosomal DNA (100 µg) from canine hepatocytes was completely digested with EcoRI and DNA fragments of 5 kb were prepared by a sucrose density gradient centrifugation [sucrose 10 to 40% (wt/vol), 26,000 rpm, 18 hours, 15°C]. The obtained DNA fragments were then ligated to EcoRI arms of λgt11 vector DNA (manufactured by Stratagene) with T4 DNA ligase and an in vitro packaging reaction was carried out using a kit available from Stratagene to give a canine hepetocyte gene library containing the gene for the kappa constant region. Plaque hybridization [W.D. Benton, R.W. Davis, Science, 196, p180 (1977)] was conducted using a human C kappa probe under the same conditions as those of the above crosshybridization and clone DEk5a containing a canine C kappa chain exon was isolated from the library. Fig. 10 shows a restriction enzyme map of this clone. (3) Southern blotting and Northern blotting analysis using DEk5a: Chromosomal DNA (10 µg) from canine hepatocytes was digested with the restriction enzyme EcoRI and Southern blotting analysis was conducted in the same manner as described in Example 2(3) using clone DEk5a. The pattern of the bands was compared with that from the crosshybridization previously conducted using a human C kappa chain probe, and as a result, a band was observed at the same position at about 5 kb. This result presumably shows that there is a single canine C kappa region gene without any other subtypes. This is also suggested by analogy to human and mouse [P. A. Hieter et al., Cell, 22, p197 (1989); E. E. Max et al., Proc. Natl. Acad. Sci. USA, 76, p3450 (1979)]. Northern blotting analysis was then carried out in the same manner as described in Example 2(3) using the DEk5a clone. The probe detected a band at about 1.3 kb with mRNA from canine spleen cells (Fig. 9). This is almost the same size as that of the mouse and human immunoglobulin kappa chain genes but the signal of the band is weaker than in the case of lambda. This shows that only a few lymphocytes express kappa light chains. These results presumably show that the DEk5a contains an active gene coding for a functional canine C kappa region. (4) Nucleic acid and amino acid sequences of DEk5a: In order to determine the nucleic acid sequence of the gene coding for the canine C kappa region, a PstI fragment of about 2.0 kb containing the C kappa region was isolated from the clone DEk5a and subcloned into the PstI site of pUC18. The resulting plasmid (pDEK5aPst) was prepared in a large amount using a conventional method [for example, T. Maniatis "Molecular Cloning " Cold Spring Harbor Lab. (1982)] and from the PstI-PstI fragment small DNA fragments (PstI-PstI, HaeIII-RsaI, RsaI-RsaI, RsaI-HaeIII, HaeIII-PstI) were prepared. These small DNA fragments were blunt-ended with T4-DNA polymerase and then inserted into the SmaI site of M13mp19 using the Takara Ligation Kit. The nucleotide sequence was determined in the same manner as described in Example 2 (4). The direction of determination of the nucleotide sequence is shown in Fig. 10. As a result of the DNA sequence determination, it was confirmed that the C kappa gene comprises a single exon (Fig. 11). The amino acid sequence encoded by the open reading frame suggested that this gene is not a pseudogene (Fig. 12). A homology search with the nucleotide sequence of DEk5a was carried out using the LASL and EMBL data bases and using genetic analysis software (Genetyx manufactured by Software Kaihatsu, K.K.). The DNA sequence had a high degree of homology with genes coding for human and mouse immunoglobulins kappa chains but no homology was found with genes other than the immunoglobulin kappa chain genes. Comparison of the C kappa region of the DEk5a gene with the mouse and human C kappa regions showed 70.0% homology with mouse and 70.1% homology with human C kappa regions on the nucleic acid level and 59.0% homology with mouse and 59.6% homology with human genes on the amino acid level. As is clear from the above results, the DEk5a gene is certainly a gene coding for the canine C kappa chain which can be used for the preparation of a dog-mouse chimeric antibody. Example 4 Cloning of the gene coding for constant region of canine gamma chain: (1) Conditions of crosshybridization: It was then tried to isolate the canine gamma chain gene by cloning using a crosshybridization procedure as in the case of kappa chain gene. In the same manner as in Example 3 (1), crosshybridization was carried out using chromosomal DNA (10 µg) from canine hepatocytes digested with the restriction enzymes BamHI, EcoRI and HindIII and a human C gamma 1 gene as a probe. The gene coding for the human C gamma 1 region used for the crosshybridization was a gene cloned from a human cell line 1 ARH77 [ATCC CRL 1621] which is available from professor Takeshi Watanabe, Kyushu University, Seitai Bogyo Igaku Kenkyuusho [Kudo et al., Gene, 33, p181 (1985); Nishimura et al.,Cancer Res., 47, p999 (1987)]. Computerized analysis of homology between mouse, human and rabbit gamma chains showed an extremely high homology at the region containing the CH2-CH3 exons. Therefore, a PstI-SphI fragment containing the CH2-CH3 exons was obtained from the human C gamma 1 gene and used as a probe. The result of the autoradiography showed four bands at about 2.0, 1.9, 1.3 and 1.05 kb as shown in Fig. 13 (BamHI digest). These bands were targeted for cloning. (2) Isolation of the canine gamma chain gene: Chromosomal DNA (100 µg) from canine hepatocytes was partially digested with MboI and then DNA fragments corresponding to the above 20 kb and 25 kb were prepared by a sucrose density gradient centrifugation [sucrose 10 to 40% (wt/vol), 26,000 rpm, 18 hours, 15°C]. Then, the obtained DNA fragments were ligated to BamHI-digested λEMBL3 vector DNA (manufactured by Nippon Gene) with T4 DNA ligase and an in vitro packaging reaction was carried out using a kit available from Stratagene. E.coli P2392 (Stratagene) was then infected with the phages containing recombinant DNA and canine hepatocytes gene library containing the genes for the C gamma chains was obtained. Plaque hybridization [W. D. Benton, R. W. Davis, Science, 196, p180 (1977)] was conducted under the same conditions as those of the above described crosshybridization. Six different clones were obtained after screening 2.0 x 10⁶ recombinant phages. Southern blot analysis and restriction cleavage mapping have revealed that these clones represent two different canine gamma gene. The restriction maps of two canine gamma gene clones, DE94gamma and a DB31gamma, are shown in Fig. 14. A BamHI fragment (2.0kbp) of DE94gamma and a BamHI fragment (1.3kbp) of DB31gamma contain canine C gamma chain exons. These BamHI fragments were used in the following Examples. (3) Southern and Northern blotting analysis using DE94gamma and DB31gamma: Chromosomal DNA (10 µg) from canine hepatocytes was digested with the restriction enzyme BamHI and Southern blotting analysis was conducted using clones DE94gamma and DB31gamma in the same manner a described in Example 2 (3). Comparison of the pattern of bands with that of the crosshybridization previously conducted using the human C gamma 1 gene probe showed a band at the same position (the same result as shown in Fig.13). This result showed the existence of several C gamma region genes of different subclasses belonging to the same canine gamma chain in addition to the DE94gamma and DB31gamma. The existence of several subclasses in the canine gamma chain is also suggested by analogy to human and mouse [for example, A. Shimizu et al., Cell, 29, p121 (1982); N. Takahashi et al., Cell, 29, p671 (1982)]. It is known that at least four serologically different subclasses of the canine gamma chain exist [J. S. Johnson, J. Immunol., 98, p923 (1966)]. The DE94gamma and DB31gamma genes seem to code for two of the four canine IgG subclasses. Then, Northern blotting analysis was carried out in the same manners described in Example 2(3) using the DE94gamma(a) and DB31gamma(b) clones. The probes specifically detected a band at about 1.8 kb with mRNAs from dog (Fig. 15). This band has almost the same size as that of mouse and human immunoglobulin gamma chain genes. These two results presumably show that the DE94gamma and DB31gamma clones contain genes coding for a functional canine C gamma region. (4) Nucleic acid and amino acid sequences of the DE94gamma and DB31gamma genes: The nucleotide sequences were determined in the same manner as described in Example 2 (4). The direction of determination of the nucleotide sequences is shown in Fig. 14. These C gamma genes share a striking homology (Fig. 16 and 17). The amino acid sequences encoded by the open reading frames suggested that these genes are not pseudogenes (Fig. 18). A homology search with the nucleotide sequences of DE94gamma and DB31gamma was carried out using the LASL and EMBL data bases and using genetic analysis software (Genetyx manufactured by software Kaihatsu, K.K.). The DNA sequences had a high degree of homology with genes coding for human and mouse immunoglobulin gamma chains but no homology was found with genes other than the immunoglobulin gamma chain genes. Comparison of the C gamma region of the DE94gamma gene with the mouse and human C gamma 1 regions showed 61.0% homology with mouse, 70.4% homology with human and 80.7% homology with DB31gamma genes an the amino acid level. On the other hand, the DB31gamma gene showed 64.7% homology with mouse and 67.6% homology with human genes on the amino acid level. As is clear from the above results, the DE94gamma and DB31gamma genes are certainly genes coding for canine gamma chain which can be used for the preparation of a dog-mouse chimeric antibody. Example 5 Preparation of mouse-dog chimeric antibody: (1)Isolation of gene coding for mouse immunoglobulin kappa chain variable (V kappa) region: In order to show usefulness of the thus isolated genes coding for the constant regions of canine immunoglobulins in the preparation of a chimeric antibody, a chimeric antibody comprising one of said genes and a gene coding for the variable region of mouse antibody JP-2 having a neutralization activity against canine parvovirus (CPV) was prepared. The gene coding for the V kappa region of antibody JP-2 was isolated first. Chromosomal DNA (100 µg) isolated from hybridoma JP-2 (gamma 1,kappa) producing an anti-CPV antibody was digested with the restricted enzyme HindIII. The resulting DNA fragments were then ligated to λL47 vector DNA (Amersham) with T4 DNA ligase and a chromosomal DNA library of JP-2 cells was obtained. A clone JP-2gL411 containing the V kappa region gene of the anti-CPV antibody was isolated from the library using the plaque hybridization procedure [W.D. Benton, R.W. Davis, Science, 196, p180 (1977)] and a mouse J kappa region [E.E. Max et al., J. Biol. Chem., 256, p5116 (1981)]. Fig. 19 shows restriction enzyme map thereof. From this gene fragment a BamHI-HindIII fragment was prepared containing a V kappa exon and the fragment was subjected to Northern hybridization with mRNA from JP-2 and the parental line P3X63Ag8.U1 to detect a JP-2 specific band at 1.3 kbp. The nucleotide sequence was determined (Fig. 20). The direction of sequencing is shown by arrows (Fig. 19). The open reading frame (Fig. 20) shows that the gene codes for a functional immunoglobulin V kappa chain. Based on these results, this V kappa gene was used for preparation of an L chain for a mouse - dog chimeric antibody. (2) Preparation of the genes coding for the L chain of mouse - dog chimeric antibody (pSV2-EPLDCk): The plasmid pDEk5aPst prepared in Example 3 (2) was digested with HindIII and EcoRI to prepare a 2 kbp HindIII DNA fragment containing a gene coding for the canine immunoglobulin C kappa chain. On the other hand, plasmid pJP2gL411 containing the gene coding for a mouse immunoglobulin V kappa chain as prepared in Example 5 (1) was digested with BamHI and HindIII to prepare a 4.4 kbp DNA fragment containing a mouse immunoglobulin V kappa-J kappa region. These genes were ligated to each other using a Takara LigationKit in the pSV2-neo vector [P.J. Southern et al., J. mol. Appl. Genet., 1. p327 (1982)] which was ditested with EcoRI and BamHI resulting in plasmid pSV2-PLDCk. The human heavy chain enhancer element was inserted into the HpaI site of this plasmid to prepare plasmid pSV2-EPLDCk (Fig. 21). (3) Expression of mouse - dog chimeric antibody: The plasmid pSV2-EPLDCk was introduced into the mouse B lymphoma line Sp2/0-Ag12 (ATCC CRT 1581) using a DEAE-dextran method previously reported by Maeda et al. [Japanese Patent First Publication No. 20255/1988]. The cells were transformed with the plasmid pSV2-EPLDCk to yield cells which produce the desired L chain of the mouse - dog chimeric antibody. As mentioned above, only the use of the gene coding for the constant region of canine immunoglobulin as cloned by the present inventors makes it possible to prepare the canine chimeric antibody. The thus prepared canine chimeric antibody can be used as agent for diagnosis, prevention and treatment of canine diseases,especially canine infectious diseases.

Claims: Claims for the following Contracting States : AT, BE, CH, DE, DK, FR, GB, GR, IT, NL, SE, LU A gene fragment which comprises a DNA sequence coding for an amino acid sequence of a constant region of a canine immunoglobulin lambda chain. The gene fragment according to Claim 1 wherein the amino acid sequence of the constant region includes the following amino acid sequence at the N-terminal region of the first cysteine counted from the N-terminus of polypeptide of the constant region of said lambda chain: -Gly-Ala-xxx-xxx-xxx-xxx-xxx-xxx-Cys- in which xxx represents an optional amino acid residue. The gene fragment according to Claim 2 wherein the amino acid sequence at the N-terminal region of the first cysteine counted from the N-terminus of the polypeptide of the constant region of said lambda chain is as follows: -Gly-Ala-Asn-Lys-Ala-Thr-Leu-Val-Cys- The gene fragment according to any one of Claims 1-3, wherein the amino acid sequence of the constant region includes the following amino acid sequence of from the 11th to 9th amino acid position of the N-terminal region of the second cysteine of the C-terminus of the polypeptide of the constant region of said lambda chain: -Pro-Asp-Lys-. The gene fragment according to any one of Claims 1-4, wherein the constant region comprises a polypeptide comprising the following amino acid sequence: The gene fragment according to Claim 5 which contains following DNA sequence: A gene fragment which comprises a DNA sequence coding for an amino acid sequence of a constant region of a canine immunoglobulin kappa chain. The gene fragment according to Claim 7 wherein the constant region comprises a polypeptide comprising 109 amino acids and the amino acid sequence of the five C-terminal amino acids. is -Cys-Gln-Arg-Val-Asp. The gene fragment according to Claim 7 or 8, wherein the polypeptide of constant region has following amino acid sequence: The gene fragment according to Claim 9 which comprises the following DNA sequence: A recombinant DNA molecule containing a DNA sequence coding for an amino acid sequence of an L chain of a mouse - dog chimeric antibody which comprises a gene fragment coding for an amino acid sequence of a variable region of a mouse immunoglobulin L chain and a gene fragment coding for an amino acid sequence of a constant region of canine immunoglobulin L chain wherein the latter gene fragment is linked to the 3' site of the former gene fragment. The recombinant DNA molecule according to Claim 11 wherein the gene fragment coding for the amino acid sequence of the constant region of the canine immunoglobulin L chain is a gene fragment according to any one of Claims 1 to 10. The recombinant DNA molecule according to Claim 11 wherein the gene fragment coding for the amino acid sequence of the variable region codes for an amino acid sequence which is specifically reactive with canine parvovirus. The recombinant DNA molecule according to Claim 13 wherein the gene fragment encodes the following amino acid sequence of the variable region: A polypeptide of a mouse-dog chimeric antibody L chain which is expressed in cells transformed with an expression vector wherein a recombinant DNA molecule according to any one of claims 11 to 14 is incorporated. A gene fragment which comprises a DNA sequence coding for an amino acid sequence of a polypeptide of a constant region of a canine immunoglobulin gamma chain. The gene fragment according to Claim 16 wherein the amino acid sequence of the constant region includes the following amino acid sequence in the vicinity of the second cystein (Cys) counted from the C-terminal region of the CH1 domain of the polypeptide of the constant region: -Ala-Cys-xxx-xxx-Ser-, in which xxx represents an optional amino acid residue. The gene fragment according to Claim 16 or 17, wherein the amino acid sequence of the constant region includes the following amino acid sequence in the vicinity of the second cystein (Cys) counted from the C-terminal region of CH1 domain of the polypeptide of the constant region: -Ala-Cys-Leu-Val-Ser-. The gene fragment according to any one of Claims 16 to 18, wherein the amino acid sequence in the vicinity of the cystein (Cys) at the C-terminal region of the CH3 domain of the polypeptide of the constant region is as follows: -Cys-xxx-Ile-xxx-Asp-xxx-Phe-xxx-Pro-, in which xxx represents an optional amino acid residue. The gene fragment according to any one of Claims 16 to 19, wherein the amino acid sequence in the vicinity of the cystein (Cys) at the C-terminal region of the CH3 domain of the polypeptide of the constant region is as follows: -Cys-Leu-Ile-Lys-Asp-Phe-Phe-Pro-Pro-. The gene fragment according to any one of Claims 16 to 20, wherein the constant region comprises the following amino acid sequence: The gene fragment according to any one of Claims 16-20, wherein the constant region comprises the following amino acid sequence: A recombinant DNA molecule coding for a mouse-dog chimeric antibody H chain which comprises a gene fragment according to any one of Claims 16 - 22 which codes for an amino acid sequence of a constant region of a canine immunoglobulin gamma chain and a gene fragment coding for an amino acid sequence of a variable region of a mouse immunoglobulin H chain wherein the former gene fragment is linked to the 3' site of the latter gene fragment. A process for preparing a mouse-dog chimeric antibody H chain which comprises incorporating the recombinant DNA molecule according to Claim 23 into an expression vector, culturing cells transformed with said recombinant vector, and collecting the expressed mouse-dog chimeric antibody H chain. A polypeptide of a mouse-dog chimeric antibody H chain as prepared in accordance with the process of Claim 24. A dog-mouse heterohybridoma which produces a canine immunoglobulin. The hybridoma according to Claim 26 wherein the L chain of the produced canine immunoglobulin is a lambda chain encoded by a gene fragment according to any one of Claims 1 to 6. The hybridoma according to claim 26, wherein the L chain of the produced canine immunoglobulin is a kappa chain encoded by a gene fragment according to any one of claims 7 to 10. The hybridoma according to claim 26 wherein the H chain of the produced canine immunoglobulin is a gamma chain encoded by a gene fragment according to any one of claims 16 to 22. A process for preparing a canine immunoglobulin gene which comprises synthesizing cDNAs from poly(A)⁺ RNA of dog-mouse heterohybridomas, transforming a host cell with a vector in which said cDNAs are incorporated, obtaining expression products in each host cell, and screening a transformant which produces the canine immunoglobulin with an anti-canine immunoglobulin antibody. Claims for the following Contracting State : ES A process for preparing a canine immunoglobulin gene or gene fragment which comprises synthesizing cDNAs from poly(A)⁺ RNA of dog-mouse heterohybridomas, transforming a host cell with a vector in which said cDNAs are incorporated, obtaining expression products in each host cell, and screening a transformant which produces the canine immunoglobulin with an anti-canine immunoglobulin antibody. A process according to claim 1 wherein the gene fragment comprises a DNA sequence coding for an amino acid sequence of a constant region of a canine immunoglobulin lambda chain. The process according to Claim 2 wherein the amino acid sequence of the constant region includes the following amino acid sequence at the N-terminal region of the first cysteine counted from the N-terminus of polypeptide of the constant region of said lambda chain: -Gly-Ala-xxx-xxx-xxx-xxx-xxx-xxx-Cys- in which xxx represents an optional amino acid residue. The process according to Claim 3 wherein the amino acid sequence at the N-terminal region of the first cysteine counted from the N-terminus of the polypeptide of the constant region of said lambda chain is as follows: -Gly-Ala-Asn-Lys-Ala-Thr-Leu-Val-Cys- The process according to any one of claims 2-4, wherein the amino acid sequence of the constant region includes the following amino acid sequence of from the 11th to 9th amino acid position of the N-terminal region of the second cysteine of the C-terminus of the polypeptide of the constant region of said lambda chain: -Pro-Asp-Lys-. The process according to any one of Claims 2-5, wherein the constant region comprises a polypeptide comprising the following amino acid sequence: The process according to Claim 6 wherein the gene fragment contains the following DNA sequence: A process according to claim 1 wherein the gene fragment comprises a DNA sequence coding for an amino acid sequence of a constant region of a canine immunoglobulin kappa chain. The process according to Claim 8 wherein the constant region comprises a polypeptide comprising 109 amino acids and the amino acid sequence of the five C-terminal amino acids is -Cys-Gln-Arg-Val-Asp. The process according to Claim 8 or 9, wherein the polypeptide of the constant region has the following amino acid sequence: The process according to Claim 10 wherein the gene fragment comprises the following DNA sequence: A process for the preparation of a recombinant DNA molecule containing a DNA sequence coding for an amino acid sequence of an L chain of a mouse - dog chimeric antibody which comprises combining a gene fragment coding for an amino acid sequence of a variable region of a mouse immunoglobulin L chain and a gene fragment coding for an amino acid sequence of a constant region of canine immunoglobulin L chain wherein the latter gene fragment is linked to the 3' site of the former gene fragment. The process according to Claim 12 wherein the gene fragment coding for the amino acid sequence of the constant region of the canine immunoglobulin L chain is a gene fragment obtained according to any one of Claims 2 to 11. The process according to Claim 12 wherein the gene fragment coding for the amino acid sequence of the variable region codes for an amino acid sequence which is specifically reactive with canine parvovirus. The process according to Claim 14 wherein the gene fragment encodes the following amino acid sequence of the variable region: A process for the preparation of a polypeptide of a mouse-dog chimeric antibody L chain which comprises incorporating the recombinant DNA molecule obtained according to any one of claims 12 to 15 into an expression vector, culturing cells transformed with said recombinant vector, and collecting the expressed mouse-dog chimeric antibody L chain. A process according to claim 1 wherein the gene fragment comprises a DNA sequence coding for an amino acid sequence of a polypeptide of a constant region of a canine immunoglobulin gamma chain. The process according to Claim 17 wherein the amino acid sequence of the constant region includes the following amino acid sequence in the vicinity of the second cystein (Cys) counted from the C-terminal region of the CH1 domain of the polypeptide of the constant region: -Ala-Cys-xxx-xxx-Ser-. in which xxx represents an optional amino acid residue. The process according to Claim 17 or 18, wherein the amino acid sequence of the constant region includes the following amino acid sequence in the vicinity of the second cystein (Cys) counted from the C-terminal region of CH1 domain of the polypeptide of the constant region: -Ala-Cys-Leu-Val-Ser-. The process according to any one of Claims 17 to 19, wherein the amino acid sequence in the vicinity of the cystein (Cys) at the C-terminal region of the CH3 domain of the polypeptide of the constant region is as follows: -Cys-xxx-Ile-xxx-Asp-xxx-Phe-xxx-Pro-. in which xxx represents an optional amino acid residue. The process according to any one of Claims 17 to 20, wherein the amino acid sequence in the vicinity of the cystein (Cys) at the C-terminal region of the CH3 domain of the polypeptide of the constant region is as follows: -Cys-Leu-Ile-Lys-Asp-Phe-Phe-Pro-Pro-. The process according to any one of Claims 17 to 21, wherein the constant region comprises the following amino acid sequence: The process according to any one of Claims 17-21, wherein the constant region comprises the following amino acid sequence: A process for the preparation of a recombinant DNA molecule coding for a mouse-dog chimeric antibody H chain which comprises combining a gene fragment obtained according to any one of Claims 17-23 which codes for an amino acid sequence of a constant region of a canine immunoglobulin gamma chain and a gene fragment coding for an amino acid sequence of a variable region of a mouse immunoglobulin H chain wherein the former gene fragment is linked to the 3' site of the latter gene fragment. A process for preparing a mouse-dog chimeric antibody H chain which comprises incorporating the recombinant DNA molecule according to Claim 24 into an expression vector, culturing cells transformed with said recombinant vector, and collecting the expressed mouse-dog chimeric antibody H chain. A dog-mouse heterohybridoma which produces a canine immunoglobulin. The hybridoma according to Claim 26 wherein the L chain of the produced canine immunoglobulin is a lambda chain encoded by a gene fragment obtained according to any one of Claims 2 to 7. The hybridoma according to claim 26, wherein the L chain of the produced canine immunoglobulin is a kappa chain encoded by a gene fragment according to any one of claims 8 to 11. The hybridoma according to claim 26 wherein the H chain of the produced canine immunoglobulin is a gamma chain encoded by a gene fragment according to any one of claims 17 to 23.

Inventors: EDA YASUYUKI, KIMACHI KAZUHIKO, MAEDA HIROAKI, ONO YOICHI, TOKIYOSHI SACHIO, EDA, YASUYUKI, KIMACHI, KAZUHIKO, MAEDA, HIROAKI, ONO, YOICHI, TOKIYOSHI, SACHIO
Applicants: CHEMO SERO THERAPEUT RES INST, JURIDICAL FOUNDATION THE CHEMO-SERO-THERAPEUTIC RESEARCH INSTITUTE
Application year: 1990
Main classification: C12N15
IPC codes: A61K39, C12N15, C12N5, C07K16