Abstract:
Provided is an antibody production method whereby it is possible to repeatedly acquire antibodies produced by fish without killing the fish. Specifically provided is an antibody production method whereby it is possible to repeatedly acquire the antibodies produced by a fish, without killing the fish, by administering antigens to fish that have blisters.

Description:
SEQUENCE LISTING 
     The instant application contains a Sequence Listing which has been submitted electronically in ASCII format and is hereby incorporated by reference in its entirety. Said ASCII copy, created on Oct. 30, 2013, is named P44483_SL.txt and is 44,184 bytes in size. 
     TECHNICAL FIELD 
     The invention relates to an antibody production method. More specifically, the invention relates to an antibody production method that includes administering an antigen to a fish bearing water vesicles, and allowing the fish to produce an antibody. 
     BACKGROUND ART 
     A technique that allows  Escherichia coli , yeast, or the like to produce a useful protein by utilizing genetic recombination technologies, and a technique that administers such a protein to a mouse or the like as an antigen, and allows the mouse or the like to produce an antibody, are widely used at present. 
     However, a protein produced by a prokaryote such as  Escherichia coli  has not been accurately subjected to multimer formation and posttranslational modification such as glycosylation. A protein produced by yeast has not been subjected to complete posttranslational modification, and may not have the original functions. 
     In order to solve the above problem, a technique that allows insect cells or mammalian cells (e.g., mouse, pig, or human) to produce a useful protein has been used. However, this technique has problems in that a considerable cost is required to culture the cells, and it takes time to obtain a useful protein. 
     In view of the above situation, use of fish as a bioreactor has recently attracted attention. This technique has an advantage in that a protein derived from fish is subjected to multimer formation and posttranslational modification such as glycosylation in the same manner as a protein derived from a mammal. Patent Document 1 discloses a technique that allows a transgenic fish to produce a glycoprotein multimer by utilizing the above advantage, and collects the glycoprotein multimer from the embryo, larva, fry, tissue, or blood. 
     Fish can be raised relatively easily and inexpensively. It is very easy to care for fish since egg laying/collection can be controlled by controlling the water temperature, feeding, the duration of sunshine, the water quality, and the like. 
     The inventors of the invention developed various techniques such as a technique that produces an antigen-producing yeast, and administers the yeast to a fish (e.g., zebrafish) as feed to allow the fish to produce a specific antibody derived from the fish, and a technique that allows a fish to produce an antibody to a membrane protein such as a G protein-coupled receptor (GPCR) (that has been considered to be difficult) (Japanese Patent Application No. 2009-83900) (see Patent Documents 2 and 3, for example). 
     However, since these techniques collect the antibody from the whole body of the fish, it is impossible to repeatedly obtain the antibody produced by the fish while keeping the fish alive. 
     In order to solve the above problem, the inventors focused on fish bearing water vesicles (e.g., Bubble Eye) in the course of the development of the invention. Such goldfish are widely grown in Japan and overseas for ornamental purpose. 
     Patent Document 4 discloses that the blister fluid of a Bubble Eye has a function of protecting fish cells or promoting cell proliferation, and makes it possible to efficiently process fish cells in a state in which the quality of unfertilized eggs is maintained, for example. 
     However, Patent Document 4 does not even suggest allowing the blister fluid to produce a useful protein (e.g., antibody), and no attempts have been made to utilize a fish bearing water vesicles for production of an antibody. 
     RELATED-ART DOCUMENT 
     Patent Document 
     
         
         Patent Document 1: JP-A-2001-86992 
         Patent Document 2: JP-A-2007-255892 
         Patent Document 3: JP-A-2009-73783 
         Patent Document 4: JP-A-2009-183151 
       
    
     SUMMARY OF THE INVENTION 
     Technical Problem 
     An object of the invention is to provide an antibody production method that can repeatedly obtain an antibody produced by a fish while keeping the fish alive. 
     Solution to Problem 
     The inventors conducted extensive studies in order to achieve the above object. As a result, the inventors found that it is possible to repeatedly obtain an antibody produced by a fish while keeping the fish alive by administering an antigen to a fish bearing water vesicles (e.g., Bubble Eye). This finding has led to the completion of the invention. 
     Specifically, several aspects of the invention relate to the following antibody production method, an antibody produced by the antibody production method, and the like (see (1) to (8)). 
     (1) An antibody production method including administering an antigen to a fish bearing water vesicles, and allowing the fish to produce an antibody. 
     (2) The antibody production method according to (1), wherein the antigen is administered to the water vesicle. 
     (3) The antibody production method according to (1) or (2), wherein the antigen is administered together with an oil base, or administered together with an oil base and inactivated  Escherichia coli  cells. 
     (4) The antibody production method according to any one of (1) to (3), further including collecting the antibody produced by the fish from the water vesicle of the fish. 
     (5) The antibody production method according to any one of (1) to (4), wherein the fish bearing water vesicles is a Bubble Eye or a Ranchu. 
     (6) The antibody production method according to any one of (1) to (5), wherein the antigen is a protein or a glycoprotein. 
     (7) The antibody production method according to (6), wherein the antigen is enhanced green fluorescent protein (EGFP), glucoamylase, or leucine-rich repeat-containing G protein-coupled receptor 3 (LGR3). 
     (8) An antibody produced by the antibody production method according to any one of (1) to (7). 
     Advantageous Effects of the Invention 
     The antibody production method according to the aspect of the invention makes it possible to allow a fish to produce an antibody, and repeatedly obtain a large amount of antibody while keeping the fish alive. The antibody production method according to the aspect of the invention can produce a useful antibody even when using a glycoprotein or the like as the antigen. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a view showing Western blotting results (Example 1). 
         FIG. 2  is a view showing dot blotting results (Example 1), 
         FIG. 3  is a view illustrating a photograph of a Bubble Eye (Example 1). 
         FIG. 4  is a view illustrating a photograph of a tag (Example 1). 
         FIG. 5  is a view showing antigen-antibody reaction results (EGFP-His protein) Example 1). 
         FIG. 6  is a view showing antigen-antibody reaction results (the purified GA-His and the culture supernatant of GA-His) (Example 1). 
         FIG. 7  is a view illustrating the sequence of pCold-TF-hLGR3 (Example 2).  FIG. 7  discloses SEQ ID NOS 24-25, respectively, in order of appearance. 
         FIG. 8  is a view showing antigen-antibody reaction results (Example 2). 
         FIG. 9  is a view showing antigen-antibody reaction results (Example 2). 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     The term “antibody production method” used herein in connection with the embodiments of the invention refers to a method that is targeted at a fish as a living organism that produces an antibody, and includes administering an antigen to a fish, and allowing the fish to produce an antibody. 
     More specifically, the term “antibody production method” used herein in connection with the embodiments of the invention refers to a method that includes administering an antigen to a fish bearing water vesicles, and allowing the fish to produce an antibody. The antibody production method may further include an additional known step or method that is used when producing an antibody. 
     The antigen may be administered by an arbitrary method as long as it is possible to allow a fish to produce an antibody. For example, a protein, yeast, or the like that serves as the antigen may be orally administered as feed, or the antigen may be administered directly to the abdominal cavity or the water vesicle via injection or the like. It is particularly preferable to administer the antigen directly to the water vesicle. 
     The antigen may be administered independently, or may be administered together with an adjuvant. The adjuvant is not particularly limited as long as it is possible to assist the fish in producing an antibody. It is particularly preferable to use an oil base, or a combination of an oil base and inactivated  Escherichia coli  cells, as the adjuvant. 
     The antibody production method according to the embodiments of the invention may further include collecting the antibody produced by the fish. It is preferable to collect the antibody while keeping the fish alive. It is particularly preferable to collect the blister fluid including the antibody from the water vesicle of the fish, for example. In this case, the antibody produced by the fish can be collected while keeping the fish alive by inserting a syringe needle or the like directly into the water vesicle of the fish, and collecting the blister fluid. 
     The term “fish bearing water vesicles” used herein in connection with the embodiments of the invention refers to an arbitrary fish of which the skin forms a water vesicle. The water vesicle of the fish bearing water vesicles contains lymph that includes the antibody produced by the fish. When the lymph has been collected from the water vesicle using a syringe or the like, the water vesicle is filled with lymph again. Examples of the fish bearing water vesicles include goldfish such as the Bubble Eye and the Ranchu. 
     The antigen used in connection with the embodiments of the invention is not particularly limited as long as the fish can produce an antibody. Examples of the antigen include transmembrane proteins such as GPCR and LGR3, soluble proteins such as EGFP, and glycoproteins such as α-dystroglycan and glucoamylase. 
     The amount of the antigen administered to the fish is not particularly limited as long as the fish can produce an antibody. It is particularly preferable to administer the antigen (protein) in an amount of 100 μg or more. 
     The invention is further described below by way of examples. Note that the invention is not limited to the following examples. 
     Example 1 
     I. Preparation of Antigen 
     Antigen:  Aspergillus oryzae  Glucoamylase 
     1-1. Construction of Plasmid 
     1) Incorporation of Nitrate Reductase Gene Derived from  Aspergillus oryzae  (Hereinafter May be Referred to as “niaD Gene”) into  Escherichia coli  Vector 
     A primer A (SEQ ID NO: 1), a primer B (SEQ ID NO: 2), and an LA-Taq polymerase (Takara Holdings Inc.) were mixed, and subjected to PCR under the following conditions using genomic DNA derived from  Aspergillus oryzae  as a template to amplify the niaD gene (SEQ ID NO: 3). 
     The genomic DNA derived from  Aspergillus oryzae  was prepared according to the method described in Reference 1. 
     Reference 1: R. C. Garber and O. C. Yoder, Anal. Biochem., 135, 416-422 (1983) PCR conditions 
     1 cycle at 96° C. (5 min) 
     30 cycles at 96° C. (20 sec), 60° C. (30 sec), and 72° C. (5 min) 
     1 cycle at 72° C. (7 min) 
     The resulting PCR amplified product was treated with restriction enzymes (PstI-HindIII) (37° C.), and the PstI-HindIII fragment of the niaD gene was separated by agarose gel electrophoresis. A QIAquick Gel Extraction Kit (QIAGEN) was used for separation. 
     The PstI-HindIII fragment of the niaD gene was ligated to the PstI-HindIII site of  Escherichia coli  plasmid pUC119 (Takara Holdings Inc.) using a DNA Ligation Kit Ver. 1 (Takara Holdings Inc.), and transformed into the  Escherichia coli  JM109 strain to obtain  Escherichia coli  plasmid pNIA2 into which the niaD marker gene was subcloned. 
     The  Escherichia coli  plasmid pNIA2 can be introduced into both the PstI site and the Sail site as a unique site. 
     2) Incorporation of Glucoamylase B Terminator Gene Derived from  Aspergillus Oryzae  (Hereinafter May be Referred to as “glaB Terminator Gene”) into  Escherichia coli  Vector 
     A primer C (SEQ ID NO: 4), a primer C (SEQ ID NO: 5), and an LA-Taq polymerase (Takara Holdings Inc.) were mixed, and subjected to PCR under the following conditions using genomic DNA derived from  Aspergillus oryzae  as a template to amplify the glaB terminator gene (SEQ ID NO: 6). 
     PCR Conditions 
     1 cycle at 96° C. (5 min) 
     30 cycles at 96° C. (20 sec), 60° C. (30 sec), and 72° C. (5 min) 
     1 cycle at 72° C. (7 min) 
     The resulting PCR amplified product was treated with restriction enzymes (SalI-XhoI) (37° C.), and the SalI-XhoI fragment of the glaB terminator gene was separated by agarose gel electrophoresis. A QIAquick Gel Extraction Kit (QIAGEN) was used for separation. 
     The SalI-XhoI fragment of the glaB terminator gene was ligated to the SalI site of the  Escherichia coli  plasmid pNIA2 obtained in section 1) using a DNA Ligation Kit Ver. 1 (Takara Holdings Inc.), and transformed into the  Escherichia coli  JM109 strain to obtain  Escherichia coli  plasmid pNIAT into which the glaB terminator gene was subcloned. 
     The  Escherichia coli  plasmid pNIAT can be introduced into both the PstI site and the SalI site as a unique site. 
     3) Incorporation of sodM Promoter Gene Derived from  Aspergillus oryzae  (Hereinafter May be Referred to as “sodM Promoter Gene”) 
     A primer E (SEQ ID NO: 7), a primer F (SEQ ID NO: 8), and an LA-Taq polymerase (Takara Holdings Inc.) were mixed, and subjected to PCR under the following conditions using genomic DNA derived from  Aspergillus oryzae  as a template to amplify the sodM promoter gene (SEQ ID NO: 9). 
     PCR Conditions 
     1 cycle at 96° C. (5 min) 
     30 cycles at 96° C. (20 sec), 60° C. (30 sec), and 72° C. (5 min) 
     1 cycle at 72° C. (7 min) 
     The resulting PCR amplified product was treated with restriction enzymes (SalI-PstI) (37° C.), and the SalI-PstI fragment of the sodM promoter gene was separated by agarose gel electrophoresis. A QIAquick Gel Extraction Kit (QIAGEN) was used for separation. 
     The SalI-PstI fragment of the sodM promoter gene was ligated to the PstI-SalI site of the  Escherichia coli  plasmid pNIAT obtained in section 2) using a DNA Ligation Kit Ver. 1 (Takara Holdings Inc.), and transformed into the  Escherichia coli  JM109 strain to obtain  Escherichia coli  plasmid pNMB into which the sodM promoter gene was subcloned. 
     A gene that encodes the expression target protein using  Aspergillus oryzae  can be introduced into the Sail site as a unique site using the  Escherichia coli  plasmid pNMB. 
     1-2. Incorporation of Target Gene 
     1) Preparation of Vector 
     The  Escherichia coli  plasmid pNMB constructed in section 1-1 was treated with a restriction enzyme (Sail) (37° C.). After the addition of a dNTP so that the final concentration was 10 mM, the mixture was treated with a T4 DNA polymerase (Takara Holdings Inc.) for 1 hour (37° C.). The mixture was then treated with alkaline phosphatase derived from bacteria (Takara Holdings Inc.) for 30 minutes (50° C.). The resulting product was eluted using a PCR clean-up column (Promega KK) to obtain a vector. 
     2) Preparation of Insert 
     An insert subcloned into the vector was prepared using a gene that encodes the expression target protein using  Aspergillus oryzae  as the target gene. 
     The target gene was a) the glucoamylase B (glaB) gene derived from  Aspergillus oryzae  (SEQ ID NO: 10 (amino acid sequence: SEQ ID NO: 11)), orb) the glucoamylase B (glaB) gene derived from  Aspergillus oryzae  to which an His-tag gene was bound (SEQ ID NO: 12 (amino acid sequence: SEQ ID NO: 13)). 
     A sense primer (30 bp downstream from the start codon of the target gene) (5′-terminal was phosphorylated) (SEQ ID NO: 14), an antisense primer (49 bp upstream from the stop codon of the target gene) (5′-terminal was phosphorylated) (SEQ ID NO: 15), and a Pfu Taq polymerase (Toyobo Co., Ltd.) were mixed, and subjected to PCR under the following conditions using genomic DNA derived from  Aspergillus oryzae  (see section 1-1.1)) as a template to amplify the target gene. 
     The resulting PCR amplified product was eluted using a PCR clean-up column (Promega KK) to obtain an insert. 
     PCR Conditions 
     1 cycle at 96° C. (5 min) 
     30 cycles at 96° C. (20 sec), 60° C. (30 sec), and 72° C. (5 min) 
     1 cycle at 72° C. (7 min) 
     3) Ligation of Vector and Insert 
     The vector obtained in section 1) and the insert of each target gene obtained in section 2) were mixed in a molar ratio of 1:20, subjected to ligation using a DNA Ligation Kit Ver. 1 (Takara Holdings Inc.), and transformed into the  Escherichia coli  JM109 strain. 
     A transformant in which the reading frame of each target gene was subcloned in the forward direction with respect to the sodM promoter was used as a target gene expression plasmid. 
     1-3. Acquisition of Target Gene Expression Strain 
     The NiaD variant of  Aspergillus oryzae  (deposited at International Patent Organism Depositary (IPOD), National Institute of Advanced Industrial Science and Technology (accession number: FERMP-17707)) was transformed by a PEG-calcium method using the target gene expression plasmid prepared in section 1-2. 
     1) The PEG-calcium method was performed as described below in accordance with Reference 2. 
     About 10 8  spores of  Aspergillus oryzae  were inoculated onto a DPY liquid medium (100 ml), and cultured at 28° C. for 18 to 20 hours. After germination, glass beads (diameter: 0.6 cm) were added to the culture flask, followed by shaking at 30° C. and 130 rpm for 24 hours. 
     The hyphae were collected, and washed 2 to 3 times with a 0.8 M NaCl aqueous solution. After the addition of 10 ml of a fresh protoplasting solution (15 mg/ml Yatalase (Takara Bio Inc.), 10 mg/ml Cellulase Onozuka R-10 (Yakult Honsha), 0.8 M NaCl, 10 mM phosphate buffer (pH: 6.0), and 1 mM DTT), the mixture was slowly shaken at 30° C. for 3 to 4 hours to effect cell wall digestion to prepare protoplasts. 
     The resulting protoplast solution was filtered using a filter “Miracloth” (Calbiochem), and the filtrate was centrifuged (2500×g) at 4° C. for 5 minutes to collect the protoplasts. 
     The protoplasts were washed with an ice-cooled solution 1 (0.8 M NaCl, 10 mM CaCl 2 , and 10 mM Tris-HCl (pH: 8.0)), and suspended in the solution 1 (2×10 8 /ml). After the addition of a solution 2 (40% PEG4000, 50 mM CaCl 2 , 10 mM Tris-HCl (pH: 8.0)) (0.2 vol), the mixture was slowly mixed. 
     0.1 ml of the protoplast solution was put in a tube (15 ml). After the addition of 15 μl or less (3 to 7 μg) of the target DNA, the mixture was allowed to stand on ice for 30 minutes. After the addition of 0.5 ml of the solution 2, the mixture was slowly stirred, and allowed to stand at room temperature or 20 minutes. After the addition of 5 ml of the solution 1, the mixture was stirred, and centrifuged (2500×g) at 4° C. for 5 minutes. 
     A precipitate including the protoplasts was suspended in 0.1 nil of the solution 1, and the suspension was spread over a CD regeneration medium containing 0.8 M NaCl. After the addition of a CD soft agar medium cooled to 30° C., the medium was solidified, and the mixture was cultured at 28° C. for 4 to 7 days. 
     Reference 2: Mol Gen Genet, 218, 99-104, (1989) 
     2) A transformant that can be grown using a Czapek-Dox medium (2% glucose, 0.1% dipotassium hydrogen phosphate, 0.05% potassium chloride, 0.05% magnesium sulfate, 0.001% iron sulfate, and 0.3% sodium nitrate) that uses nitric acid as a single nitrogen source was selected to obtain a plurality of transformants including the target gene expression plasmid.
 
1-4. Preparation of Target Gene Product
 
     The transformants obtained in section 1-3 were cultured using a potato dextrose medium to form spores, and the spores were collected using sterilized water. 
     The collected spores were inoculated onto a GPY liquid medium (2% glucose, 1% polypeptone, 0.5% yeast extract, 0.1% dipotassium hydrogen phosphate, 0.05% potassium chloride, 0.05% magnesium sulfate, 0.001% iron sulfate, and 0.3% sodium nitrate) (100 ml) in a 500 ml Erlenmeyer flask so that the final spore concentration was 1×10 6 /ml. 
     The spores were cultured at 30° C. for 3 days, and a culture supernatant in which the target gene product was secreted and expressed was collected. 
     1-5. Concentration of Culture Supernatant 
     Part of the culture supernatant collected in section 1-4 was centrifuged (3000×g) using a filter unit “Centriprep 10” (Millipore, molecular weight cut-off: 10,000 NMWL), and concentrated. 
     1-6. Determination of GA Concentration in Culture Supernatant 
     The GA concentration in the culture supernatant collected in section 1-4 was estimated by separating the proteins from the culture supernatant by SDS-PAGE, and quantifying the CBB stained image using image analysis software “CS Analyzer 3.0” (ATTO). 
     Specifically, the following steps 1) to 5) were performed. 
     1) Purified GA obtained in 1-7 was dissolved in PBS (3 to 11 μg) (standard). 
     A 5× sample buffer (2.5 M Tris-HCl, 10% glycerol, 0.05% bromophenol blue, and 10% SDS) was respectively added to the purified GA solution and the 1× culture supernatant (1 to 3 μl) (final concentration: 1×), and the mixtures were boiled at 100° C. for 5 minutes to obtain samples. 
     2) Proteins were separated from the samples by SDS-PAGE (7.5% polyacrylamide gel, 200 V, 20 m A). 
     3) The gel was immersed in a CBB staining solution (0.25% CBB-R250, 50% methanol, and 5% acetic acid), and shaken at room temperature for 30 minutes to stain the proteins. 
     4) The gel was immersed in a destaining solution (25% methanol and 10% acetic acid), and shaken at room temperature to wash CBB that was not bound to the proteins. 
     5) The gel was photographed using a CCD camera (Light Capture II, ATTO), the detected band of the GA was quantified by zone densitometry analysis (CS Analyzer 3.0), and a calibration curve was drawn from the integrated value of purified GA. 
     The GA concentration in the culture supernatant (unconcentrated) estimated from the calibration curve was about 3.0 μg/μl. 
     The GA concentration in the culture supernatant that was 5-fold concentrated in section 1-5 was adjusted to 4 μg/μl based on the above result using a goldfish Ringer&#39;s solution (125 mM NaCl, 2.6 mM KCl, 10 mM 2-[4-(2-hydroxyethyl)-1-piperazinyl]ethanesulfonic acid (HEPES) (pH: 7.4)) (hereinafter may be referred to as “the culture supernatant of GA” or “the culture supernatant of GA-His”). 
     1-7. Purification of Target Gene Product 
     1) Target Gene Product 
     Ammonium sulfate (saturation concentration: 70%) was added to part of the culture supernatant collected in section 1-4, and the mixture was stirred at 4° C. overnight to precipitate proteins. The precipitate was removed by centrifugation. 
     After the addition of a resin “Toyopearl Butyl-650M” (Tosoh Corporation) to the culture supernatant, the mixture was stirred at a low temperature overnight, and the resin was collected. 
     The collected resin was washed twice with a 1.5 M ammonium sulfate solution, and the target GA protein was eluted using a 10 mM acetate buffer (pH: 5.0), and freeze-dried to obtain purified GA protein. 
     The GA concentration in purified GA protein was adjusted to 4 μg/μl using a goldfish Ringer&#39;s solution (hereinafter may be referred to as “purified GA”). 
     2) His-Tagged Target Gene Product 
     The culture supernatant including the target gene product (see section 1-4) was added to a nickel column (His GraviTrap column (GE Healthcare)), and recombinant glucoamylase bound to the column was eluted using a 20 mM sodium phosphate buffer (pH: 7.4) including 0.5 M NaCl and 400 mM imidazole. 
     The eluated fraction was transferred to a dialysis membrane, and dialyzed twice (4° C., 3 hours) using a buffer (1 l) including a 50 mM sodium acetate buffer (pH: 5.0) to purify the His-tagged target gene product. 
     The concentrated GA in the purified His-tagged target gene product was adjusted to 4 μg/μl using a goldfish Ringer&#39;s solution (hereinafter may be referred to as “purified GA-His”). 
     Antigen: EGFP-his Protein 
     2-1. Preparation of Vector (Construction of Plasmid to Incorporation of Target Gene) 
     A vector “pCold TF DNA” (Takara Bio Inc.) was modified as described below to prepare a pColdTEE-EGFP-His vector that was a construct in which a 5′-untranslated region, a translation enhancing element (TEE), an EGFP, and a His-tag (purification tag) DNA sequence (3′-terminal) were arranged downstream of a CspA promoter. 
     1) A primer G (SEQ ID NO: 18), a primer H (SEQ ID NO: 19), and a PCR Enzyme “TAKARA Ex Taq” (Takara Bio Inc.) were mixed, and subjected to PCR under the following conditions using a pXI-EGFP vector (prepared by incorporating EGFP (SEQ ID NO: 17) downstream of pXI (SEQ ID NO: 16) (see Japanese Patent Application No. 2009-107344 and Reference 3)) as a template to amplify a fragment in which the start codon of the egfp gene was converted into a restriction enzyme (SmaI) recognition sequence, and the 3′-terminal was converted into a His-tag DNA sequence.
 
Reference 3: Johnson A D, Krieg P A. pXeX, a vector for efficient expression of cloned sequences in  Xenopus  embryos. Gene. 1994 September
 
PCR Conditions
 
1 cycle at 95° C. (1 min)
 
30 cycles at 95° C. (10 sec), 55° C. (30 sec), and 72° C. (2 min)
 
1 cycle at 72° C. (5 min)
 
2) A primer G (SEQ ID NO: 18), a primer I (SEQ ID NO 20), and a PCR Enzyme “TAKARA Ex Taq” (Takara Bio Inc.) were mixed, and subjected to PCR under the above conditions (see section 1)) using the amplified product obtained in section 1) (i.e., a fragment in which the start codon of the egfp gene was converted into a restriction enzyme (SmaI) recognition sequence, and the 3′-terminal was converted into a His-tag DNA sequence as a template to amplify an egfp-his6 gene (“his6” disclosed as SEQ ID NO: 26) fragment in which a restriction enzyme (SfiI) recognition sequence was arranged downstream of the His-tag.
 
3) A primer J (SEQ ID NO: 21), a primer K (SEQ ID NO: 22), and a PCR Enzyme “TAKARA Ex Taq” (Takara Bio Inc.) were mixed, and subjected to PCR under the following conditions using a vector “pCold TF DNA” (Takara Bio Inc.) as a template to amplify a DNA fragment in which a restriction enzyme (SmaI) recognition sequence was bound to the TEE, and a restriction enzyme (SfiI) recognition sequence was arranged upstream of the transcription terminator sequence.
 
     The DNA fragment amplified in section 3) and the egfp-his6 gene (“his6” disclosed as SEQ ID NO: 26) fragment digested by the restriction enzymes SmaI and SfiI (see section 2)) were subjected to ligation using the DNA Ligation Kit Mighty Mix (Takara Bio inc.) to prepare a pColdTEE-EGFP-His vector. 
     2-2. Preparation of Target Gene Product 
     The pColdTEE-EGFP-His vector prepared in section 2-1 was transformed into  Escherichia coli  BL21, smeared on an LB plate medium containing ampicillin sodium (final concentration: 50 μg/ml), and cultured at 37° C. overnight. Note that a product manufactured by Wako Pure Chemical Industries, Ltd. was used as the reagent unless otherwise indicated. 
     1) The resulting colony was inoculated onto an LB-ampicillin liquid medium, and cultured at 37° C. for 12 hours with shaking. The culture supernatant was inoculated onto a 2×YT-ampicillin liquid medium (50 μg/ml ampicillin sodium, 1.6% Bacto Trypton (BD), 1% dry yeast extract (Nacalai Tesque, Inc.), and 0.5% NaCl (pH: 7.0)), and cultured at 37° C. with shaking until the absorbance at a wavelength of 600 nm reached 0.4 to 0.5. 
     After allowing the culture supernatant to stand at 15° C. for 30 minutes, 0.1 mM isopropyl β-D-1-thiogalactopyranoside (IPTG) was added in an amount of 1/1000 of that of the culture supernatant, and expression of the EGFP-His protein was induced at 15° C. for 24 hours with shaking. 
     After confirming expression of the EGFP-His protein with the naked eye, the mixture was centrifuged (3000×g) at 4° C. for 15 minutes to collect fungus bodies. The fungus bodies were washed twice with a cooled 1× phosphate buffered saline (PBS) (137 mM NaCl, 2.7 mM KCl, 1.5 mM KH 2 PO 4 , and 8.1 mM Na 2 HPO 4 ) to remove residual medium components. 
     2) After the addition of 40 ml of an Ni column elution buffer A (20 mM sodium phosphate, 0.5 M NaCl, and 20 mM imidazol (pH: 7.4)), the fungus bodies were crushed using an ultrasonic cell disrupter (MICROSON XL 2000 (MISONIX)). 
     The mixture was then centrifuged (12,000×g) at 4° C. for 30 minutes to collect a supernatant, and impurities were removed using a filter having a pore size of 0.20 μm (ADVANTEC) to prepare an  Escherichia coli - expressed  protein extract. 
     The  Escherichia coli - expressed  protein extract was added to an Ni column (GE healthcare) charged with an Ni Sepharose medium (GE healthcare) using a peristaltic pump (BioRad) to bind the EGFP-His protein to the medium. 
     3) An EGFP-His protein was eluted from the column using the Ni column elution buffer A (20 mM sodium phosphate, 0.5 M NaCl, and 20 mM imidazol (pH: 7.4)) and the Ni column elution buffer B (20 mM sodium phosphate, 0.5 M NaCl, and 500 mM imidazol (pH: 7.4)) by utilizing the continuous concentration gradient of imidazol (20 to 500 mM).
 
4) The Ni column elution buffer contained in the EGFP-His protein fraction was replaced with a DEAE column elution buffer A (20 mM 2-amino-2-(hydroxymethyl)propane-1,3-diol (Tris)-HCl (pH: 8.0)) using an ultrafiltration membrane (Millipore) to prepare a sample. The sample was added to an anion-exchange column changed with a DEAE Sepharose Fast Flow medium (GE healthcare) using a low-pressure chromatography system (AKTAprime plus (GE healthcare)) to bind EGFP-His protein to the medium, and EGFP-His protein was eluted using the DEAE column elution buffer A (20 mM Tris-HCl (pH: 8.0)) and a DEAE column elution buffer B (20 mM Tris-HCl, 1 M NaCl (pH: 8.0)) by utilizing the continuous concentration gradient of NaCl (0 to 1 M).
 
5) The solvent contained in the fraction including EGFP-His protein eluted from the column (see section 4)) was replaced with a divalent ion-free goldfish Ringer&#39;s solution (125 mM NaCl, 2.6 mM KCl, 10 mM 2-[4-(2-hydroxyethyl)-1-piperazinyl]ethanesulfonic acid (HEPES) (pH: 7.4)) so that an EGFP-His protein concentration was 4 μg/μl.
 
     II. Determination of Antigen-Antibody Reaction 
     The antigens (purified GA, purified GA-His, and EGFP-His proteins) prepared in section I were allowed to react with an antibody, and the presence or absence of an antigen-antibody reaction was determined by Western blotting or dot blotting. 
     1. Antibody 
     1) Anti-his Antibody 
     Anti-His Antibody (Amersham Biosciences) 
     2) Anti-GlaB Antibody 
     A peptide (SEQ ID NO: 11) of a fall-length glucoamylase protein was designed, and synthesized by chemosynthesis. A rabbit was immunized with the peptide (antigen) conjugated to keyhole limpet hemocyanin (KLH) as a carrier protein to obtain an antibody (custom antibody production (Invitrogen)). 
     2. Western Blotting 
     1) A 5× sample buffer (2.5 M Tris, 10% glycerol, 0.05% bromophenol blue, and 10% SDS) was respectively added to EGFP-His protein, purified GA, and purified GA-His prepared in section I (final concentration: 1×), and the mixtures were boiled at 100° C. for 5 minutes to obtain samples. 
     The samples were subjected to electrophoresis (10% polyacrylamide gel, 200 V, 20 mA) to separate the proteins. 
     2) The proteins were transferred to a PVDF membrane (ATTO) using a semi-dry blotter, and the PVDF membrane was rinsed twice with 0.5% Tween20/PBS (0.5% PBST), for 1 hour with shaking to block the PVDF membrane. 
     The PVDF membrane was thus blocked and rinsed twice with PBST, washed once with 0.5% PBST for 15 minutes, and washed twice with 0.5% PBST for 5 minutes to remove extra blocking reagents. 
     3) The anti-His antibody and the anti-GlaB antibody (see section 1) were diluted (1/3000 and 1/1000, respectively) with a Can Get Signal (TOYOBO) solution 1. The PVDF membrane was immersed therein, and reacted at room temperature for 1 hour with shaking. The PVDF membrane was then washed three times with 0.5% PBST for 10 minutes to remove extra antibody solution.
 
4) An anti-mouse IgG HRP labeled secondary antibody and an anti-rabbit IgG HRP labeled secondary antibody were diluted (1/25,000 and 1/100,000, respectively) with a Can Get Signal Solution 2. The PVDF membrane was immersed therein, and reacted at room temperature for 1 hour with shaking.
 
5) The PVDF membrane was then washed three times with PBST for 10 minutes, immersed in an Amersham ECL plus Western Blotting Detection Reagent (GE healthcare), reacted at room temperature for 5 minutes, photographed using a CCD camera (Light Capture (ATTO)), and luminescence was detected using a CS Analyzer 3.0 (ATTO).
 
     As shown in  FIG. 1  (see (A) (i.e., the PVDF membrane reacted with the anti-His antibody)), an EGFP-His protein (EGFP-His in  FIG. 1 ) and purified GA-His (glaB-His in  FIG. 1 ) were detected from the PVDF membrane reacted with the anti-His antibody. 
     As shown in  FIG. 1  (see (B) (i.e., the PVDF membrane reacted with the anti-GlaB antibody)), purified GA (glaB in  FIG. 1 ) and purified GA-His (glaB-His in  FIG. 1 ) were detected from the PVDF membrane reacted with the anti-GlaB antibody. 
     It was confirmed from the above results that purified GA-His can be detected using the anti-GlaB antibody and the anti-His antibody. 
     In  FIG. 1 , the amount of the sample in each lane, the primary antibody, the secondary antibody, and the dilution ratio are shown in the upper part of each photograph (M: Prestained SDS-PAGE Standards (Broad Range) (BioRad)). 
     2. Dot Blotting 
     1) An EGFP-His protein, purified GA, and purified GA-His prepared in section I were respectively diluted with PBS (range: 250 μg/μ1 to 250 ng/μl) to obtain the samples. 
     2) A PVDF membrane was immersed in methanol for 5 minutes with shaking, immersed in ultrapure water twice for 10 minutes with shaking, and immersed in PBS for 10 minutes or more with shaking to equilibrate the PVDF membrane. 
     3) The PVDF membrane was sandwiched between the sheets of Elleair Prowipe (DAIO PAPER Co.) immediately before the dropwise addition of the sample to remove unnecessary PBS. The sample (2 μl) was added dropwise to the PVDF membrane placed on a Parafilm, and the PVDF membrane was air-dried.
 
4) The PVDF membrane was dried and then equilibrated and blocked with 5% skimmed milk/0.05% Tween 20 in TBS (20 mM Tris-HCl and 150 mM NaCl, pH: 7.5) (0.05% TBST).
 
5) The PVDF membrane was rinsed twice with 0.05% TBST, washed for 10 minutes with shaking, and washed twice for 5 minutes with shaking to remove unnecessary skimmed milk solution.
 
6) The anti-His antibody, an anti-GFP antibody (MBL), and the anti-GlaB antibody (see section 1) were respectively diluted (1/3000) with a Can Get Signal solution 1. The PVDF membrane was immersed therein, and reacted at room temperature for 2 hours with shaking.
 
     The PVDF membrane was then washed three times with 0.05% TBST for 10 minutes to remove unnecessary antibody solution. 
     7) An anti-mouse IgG HRP labeled secondary antibody and an anti-rabbit IgG HRP labeled secondary antibody were diluted (1/25,000 and 1/100,000, respectively) with a Can Get Signal solution 2. The PVDF membrane was immersed therein, and reacted at room temperature for 1 hour with shaking.
 
8) The PVDF membrane was washed three times with 0.05% TBST for 10 minutes, reacted with an Amersham ECL plus Western Blotting Detection Reagent, and luminescence was detected in the same manner as in the case of using Western blotting.
 
     As shown in  FIG. 2  (left), when detecting the EGFP-His protein, the purified GA, and the purified GA-His using the anti-GFP antibody, a reaction was observed in the spots of EGFP-His protein (GFP-His in  FIG. 2 ) from 10 to 500 ng. 
     As shown in  FIG. 2  (center), when detecting the EGFP-His protein, the purified GA, and the purified GA-His using the anti-His antibody, a reaction was observed in the spots of purified GA-His (glaB-His in  FIG. 2 ) from 10 to 500 ng, and the spots of EGFP-His protein (GFP-His in  FIG. 2 ) from 50 to 500 ng. 
     As shown in  FIG. 2  (right), when detecting the EGFP-His protein, the purified GA, and the purified GA-His using the anti-GlaB antibody, a reaction was observed in the spots of purified GA (glaB in  FIG. 2 ) and the spots of purified GA-His (glaB-His in  FIG. 2 ) from 500 μg to 500 ng. 
     It was confirmed from the above results that purified GA-His can be detected using the anti-GlaB antibody and the anti-His antibody. 
     It was also confirmed that 500 pg or more of the purified GA and the purified GA-His can be detected using the 1/1000-fold diluted anti-GlaB antibody, 10 ng or more of the purified GA-His and 50 ng or more of the EGFP-His protein can be detected using the 1/3000-fold diluted anti-His antibody, and 10 ng or more of the EGFP-His protein can be detected using the 1/3000-fold diluted anti-GFP antibody. 
     In  FIG. 2 , the type of proteins added dropwise to each lane, the primary antibody, the secondary antibody, and the dilution ratio are shown in the upper part of each photograph. The amount of protein added dropwise to each lane is shown on the left side of the photographs. 
     III. Production of Antibody by Fish Bearing Water Vesicles 
     1. Sample 
     1) Fish Bearing Water Vesicles 
     Bubble Eyes purchased from Maruteru. Fish Farm (Yatomi-shi, Aichi Prefecture) were used as fish bearing water vesicles. The Bubble Eyes were kept in tap water (water temperature: 20 to 25° C.) in which the residual chlorine was neutralized by adding a neutralizer for goldfish/killifish (Nichido Co., Ltd.).  FIG. 3  illustrates a photograph of one of the Bubble Eyes used. 
     2) Reagent 
     A product manufactured by Wako Pure Chemical Industries, Ltd. was used as the reagent unless otherwise indicated. 
     3) Antigen 
     The EGFP-His protein, the purified GA-His, or the culture supernatant of GA-His prepared in section I was used as an antigen. 
     4) Adjuvant 
     The following adjuvants (A) to (D) were prepared, and used. 
     (A) Oil base including a lecithin 
     (B) Oil base including inactivated  Mycobacterium tuberculosis  cells 
     (C) Oil base including inactivated  Aspergillus oryzae  cells 
     (D) Oil base including inactivated  Escherichia coli  cells 
     (1) Preparation of Oil Base 
     The oil base was prepared as described below by modifying the method described in Reference 4. 
     Specifically, 0.1 g of egg-yolk lecithin was added to 10 g of glycerol, and the mixture was stirred at 60° C. using a stirrer. After the gradual addition of 10 g of arachis oil (Nacalai Tesque, Inc.), the mixture was stirred until a homogenous mixture was obtained to prepare an oil base. 
     Reference 4: J. A. REYNOLDS et al. 1980 (Adjuvant activity of a novel metabolizable lipid emulsion with inactivated viral vaccines. Reynolds J A, Harrington D Q Crabbs C L, Peters C J, Di Luzio N R. Infect Immun. 1980 June; 28 (3): 937-943. 
     (2) Preparation of Inactivated  Escherichia coli  Cells and Inactivated  Aspergillus oryzae  Cells 
     The  Escherichia coli  DH5α strain was inoculated onto an LB medium, and cultured at 37° C. for 16 hours with shaking. 
     The  Aspergillus oryzae  OSI-1013 strain was inoculated onto a DPY liquid medium, and cultured at 28° C. for 18 to 20 hours. 
     The bacteria were crushed using a sonicator to obtain inactivated  Escherichia coli  cells and inactivated  Aspergillus oryzae  cells. 
     (3) Inactivated  Mycobacterium tuberculosis  Cells 
       Mycobacterium tuberculosis  H37 Ra (dry, Difco Laboratories) was used as inactivated  Mycobacterium tuberculosis  cells. 
     (4) Mixing of Oil Base with Inactivated  Escherichia coli  Cells, Inactivated  Mycobacterium Tuberculosis  Cells, or Inactivated  Aspergillus oryzae  Cells 
     Inactivated  Escherichia coli  cells, inactivated  Mycobacterium tuberculosis  cells, or inactivated  Aspergillus oryzae  cells was added to the oil base in an amount of 0.5 mg/ml. 
     (5) Mixing of Antigen with Adjuvant 
     Each of the adjuvants (A) to (D) and the antigen solution were mixed in a volume ratio of 1:1 using a syringe (volume: 1 ml) (Terumo Corporation) and a 18G reagent mixing needle (Sansyo Co., Ltd.) to prepare a water-in-oil emulsion. The water-in-oil emulsion was used for immunization. The adjuvant including the cells was used only for initial immunization, and only the oil base was subsequently used as the adjuvant. 
     2. Production of Antibody 
     Experimental groups A to E in which the EGFP-His protein was used as the antigen, experimental groups F to J in which the purified GA-His was used as the antigen, experimental groups K and L in which the culture supernatant of GA-His was used as the antigen, and a control experimental group M were provided. Six Bubble Eyes were used for each experimental group. Table 1 shows the combination of the antigen and the adjuvant in each experimental group. 
     36 Bubble Eyes used for the experimental groups A to E (in which the EGFP-His protein was used as the antigen) and the control experimental group M were individually kept in a fish tank (61) (identical water system). 36 Bubble Eyes used for the experimental groups F to J (in which the purified GA-His was used as the antigen) and the experimental groups K and L (in which the culture supernatant of GA-His was used as the antigen) were provided with an identification tag ((A) in  FIG. 4 ) on their peduncle ((B) in  FIG. 4 ), and kept in a fish tank (601) on an experimental group basis (i.e., six Bubble Eyes per fish tank). 
     Each Bubble Eye was immunized by injecting only the antigen, or an emulsion prepared by mixing the antigen and the adjuvant, into the right water vesicle in an amount of 100 μg. Each Bubble Eye was immunized every 14 days over 70 days. 
     50 to 100 μl of the blister fluid was collected from the left water vesicle of each Bubble Eye before immunization and on the day of immunization. When collecting the blister fluid on the day of immunization, the blister fluid was collected after immunization. 
     The collected blister fluid was centrifuged (1500×g) at 4° C. for 10 minutes to collect a supernatant, which was used as an antibody titer measurement sample. Note that the sample was stored at −20° C. until the sample was used to detect an antigen-specific antibody. 
                             TABLE 1               Experimental               group   Antigen   Adjuvant                   A   EGFP-His protein   No       B       Oil base       C       Oil base +               inactivated  Escherichia coli         D       Oil base +               inactivated                 Mycobacterium tuberculosis         E       Oil base +               inactivated  Aspergillus oryzae         F   Purified GA-His   No       G       Oil base       H       Oil base +               inactivated  Escherichia coli         I       Oil base +               inactivated  Mycobacterium                   tuberculosis         J       Oil base +               inactivated  Aspergillus oryzae         K   Culture supernatant of   No       L   GA-His   Oil base       M   No (only goldfish   Oil base           Ringer&#39;s solution)                    
3. Antibody Detection by Dot Blotting
 
1) Sample
 
     The blister fluid collected in section 2 was defrosted, and centrifuged (10,000×g) at 4° C. for 10 minutes to remove a precipitate to obtain a sample. 
     An anti-myc tag antibody (SANTACRUZ) was used as a negative control, and an anti-His antibody (Amersham Biosciences) that was 1/100 to 1/5000-fold diluted with PBS was used as a positive control. 
     2) Antigen 
     The EGFP-His protein and the purified GA-His prepared in section I, of which the solvent was replaced with PBS, were used as the antigen. 
     3) Dot Blotting 
     An antigen-antibody reaction was detected by dot blotting using a sandwich technique (see (1) to (6)). 
     (1) A PVDF membrane (ATTO) was immersed in methanol for 5 minutes with shaking, immersed in ultrapure water twice for 10 minutes with shaking, and immersed in PBS for 10 minutes or more with shaking to equilibrate the PVDF membrane. The PVDF membrane was sandwiched between sheets of Elleair Prowipe (DAIO PAPER Co.) immediately before the dropwise addition of the sample to remove unnecessary PBS. The sample (2 μl) was added dropwise to the PVDF membrane placed on a Parafilm, and the PVDF membrane was air-dried.
 
(2) The dried PVDF membrane was equilibrated and blocked with 5% skimmed milk/0.05% Tween 20 in TBS (20 mM Tris-HCl and 150 mM NaCl (pH: 7.5)) (0.05% TBST).
 
     The PVDF membrane was then rinsed twice with 0.05% TBST, washed for 10 minutes with shaking, and washed twice for 5 minutes with shaking to remove unnecessary skimmed milk solution. 
     (3) EGFP-His protein or the purified GA-His (antigen) was diluted to 5 or 10 ng/μl with a Can Get Signal (TOYOBO) solution 1. The PVDF membrane was immersed therein, and reacted at room temperature for 2 hours with shaking. The PVDF membrane was then washed three times with 0.05% TBST for 10 minutes to remove unnecessary antigen solution.
 
(4) An anti-GFP antibody (MBL) or an anti-GA antibody (provided by Gekkeikan Sake Co., Ltd.) was diluted (1/3000) with a Can Get Signal solution 1. The PVDF membrane was immersed therein, and reacted at room temperature for 1 hour with shaking. The PVDF membrane was then washed three times with 0.05% TBST for 10 minutes to remove unnecessary antibody solution.
 
(5) An anti-rabbit IgG HRP labeled secondary antibody was diluted (1/100,000) with a Can Get Signal solution 2. The PVDF membrane was immersed therein, and reacted at room temperature for 1 hour with shaking. The PVDF membrane was then washed three times with 0.05% TBST for 10 minutes to remove unnecessary antibody solution.
 
(6) The PVDF membrane was then washed three times with PBST for 10 minutes, immersed in an Amersham ECL plus Western Blotting Detection Reagent (GE healthcare), and reacted at room temperature for 5 minutes, and luminescence was detected using a CCD camera.
 
       FIG. 5  and Table 2 show the results for the experimental groups in which the EGFP-His protein was administered, and  FIG. 6  and Table 3 show the results for the experimental groups in which the purified GA-His or the culture supernatant of GA-His was administered. 
     
       
         
               
               
               
               
               
               
               
             
               
               
               
               
               
               
               
               
             
           
               
                   
                 TABLE 2 
               
               
                   
                   
               
               
                   
                   
                 After 
                 After 
                 After 
                 After 
                 After 
               
               
                   
                 pre 
                 14 days 
                 28 days 
                 42 days 
                 56 days 
                 70 days 
               
               
                   
                   
               
             
             
               
                   
               
             
          
           
               
                 A 
                 1 
                 − 
                 − 
                 − 
                 − 
                 − 
                 − 
               
               
                   
                 2 
                 − 
                 − 
                 − 
                 − 
                 − 
               
               
                   
                 3 
                 − 
                 − 
                 − 
                 − 
                 − 
                 − 
               
               
                   
                 4 
                 − 
                 − 
                 − 
                 − 
                 − 
                 − 
               
               
                   
                 5 
                 − 
                 − 
                 − 
                 − 
                 − 
                 − 
               
               
                   
                 6 
                 − 
                 − 
                 − 
                 − 
                 − 
                 − 
               
               
                 B 
                 1 
                 − 
                 − 
                 − 
                 − 
                 − 
                 − 
               
               
                   
                 2 
                 − 
                 − 
                 − 
                 − 
                 − 
                 − 
               
               
                   
                 3 
                 − 
                 − 
                 − 
                 + 
                 + 
                 + 
               
               
                   
                 4 
                 − 
                 − 
                 − 
                 − 
                 − 
                 − 
               
               
                   
                 5 
                 − 
                 − 
                 − 
                 − 
                 − 
                 − 
               
               
                   
                 6 
                 − 
                 − 
                 − 
                 + 
                 + 
                 − 
               
               
                 C 
                 1 
                 − 
                 − 
                 − 
                 − 
                 − 
                 − 
               
               
                   
                 2 
                 − 
                 − 
                 − 
                 − 
                 − 
                 − 
               
               
                   
                 3 
                 − 
                 − 
                 − 
                 + 
                 + 
                 + 
               
               
                   
                 4 
                 − 
                 − 
                 − 
                 − 
                 − 
                 − 
               
               
                   
                 5 
                 − 
                 − 
                 − 
                 − 
                 − 
                 − 
               
               
                   
                 6 
                 − 
                 − 
                 − 
                 + 
                 + 
                 + 
               
               
                 D 
                 1 
                 − 
                 − 
                 − 
                 − 
                 − 
                 − 
               
               
                   
                 2 
                 − 
                 − 
                 − 
                 − 
                 − 
                 − 
               
               
                   
                 3 
                 − 
                 − 
                 − 
                 − 
                 − 
                 − 
               
               
                   
                 4 
                 − 
                 − 
                 − 
                 − 
                 − 
                 − 
               
               
                   
                 5 
                 − 
                 − 
                 − 
                 − 
                 − 
                 − 
               
               
                   
                 6 
                 − 
                 − 
                 − 
                 − 
                 − 
                 − 
               
               
                 E 
                 1 
                 − 
                 − 
                 − 
                 − 
                 − 
                 − 
               
               
                   
                 2 
                 − 
                 − 
                 − 
                 − 
                 − 
                 − 
               
               
                   
                 3 
                 − 
                 − 
                 − 
                 − 
                 − 
                 − 
               
               
                   
                 4 
                 − 
                 − 
                 − 
                 − 
                 − 
                 − 
               
               
                   
                 5 
                 − 
                 − 
                 − 
                 − 
                 − 
                 − 
               
               
                   
                 6 
                 − 
                 − 
                 − 
                 − 
                 − 
                 − 
               
               
                 M 
                 1 
                 − 
                 − 
                 − 
                 − 
                 − 
                 − 
               
               
                   
                 2 
                 − 
                 − 
                 − 
                 − 
                 − 
                 − 
               
               
                   
                 3 
                 − 
                 − 
                 − 
                 − 
                 − 
                 − 
               
               
                   
                 4 
                 − 
                 − 
                 − 
                 − 
                 − 
                 − 
               
               
                   
                 5 
                 − 
                 − 
                 − 
                 − 
                 − 
                 − 
               
               
                   
                 6 
                 − 
                 − 
                 − 
                 − 
                 − 
                 − 
               
               
                   
               
             
          
         
       
     
     As shown in  FIG. 5  and Table 2, an antibody to the EGFP-His protein (EGFP-His in  FIG. 5  (hereinafter the same)) was detected, and an increase in antibody titer was observed in two Bubble Eyes in the experimental group B in which the oil base was administered as the adjuvant together with the antigen, and two Bubble Eyes in the experimental group C in which the oil base including inactivated  Escherichia coli  cells was administered together with the antigen. 
     In contrast, an increase in antibody titer with respect to the EGFP-His protein was not observed in the Bubble Eyes in the experimental group D in which the oil base including  Mycobacterium tuberculosis  cells was administered together with the antigen and the Bubble Eyes in the experimental group E in which the oil base including  Aspergillus oryzae  cells was administered together with the antigen. An increase in antibody titer was also not observed in the Bubble Eyes in the experimental group A in which only the antigen was administered. 
     Bubble Eye No. 3 in the experimental group B that showed an increase in antibody titer with respect to EGFP-His protein indicated an increase in an antibody titer in the blister fluid when 42 days had elapsed after the first immunization. In particular, the antibody titer gradually increased from the 56th day to the 70th day after the first immunization. Bubble Eye No. 6 showed a slight increase in antibody titer when 42 days had elapsed after the first immunization, and the antibody titer further increased when 56 days had elapsed after the first immunization. 
     Bubble Eye No. 3 in the experimental group C that showed an increase in antibody titer with respect to EGFP-His protein indicated a significant increase in antibody titer when 42 days had elapsed after the first immunization. Bubble Eye No. 6 showed an increase in antibody titer from the 42nd day to the 70th day after the first immunization. 
     Note that  FIG. 5  also shows the results for the positive control (+) in which the anti-His antibody was reacted, and the results for the negative control (−) in which the anti-myctag antibody was reacted (upper left) (dilution ratio: 1/100 to 1/5000). 
     In  FIG. 5 , the alphabetical character shown above each PVDF membrane indicates the experimental group, the numerals (1 to 6) shown above each PVDF membrane indicate the identification numbers of the Bubble Eyes, and the immunization conditions (OB: oil base) for each experimental group are shown on the right of the alphabetical character. The sample (blister fluid) collection day (i.e., the number of days elapsed after the first immunization) (“pre” indicates before immunization) is shown on the right of each PVDF membrane. 
     
       
         
               
               
               
               
               
               
               
             
               
               
               
               
               
               
               
               
             
           
               
                   
                 TABLE 3 
               
               
                   
                   
               
               
                   
                   
                 After 
                 After 
                 After 
                 After 
                 After 
               
               
                   
                 pre 
                 14 days 
                 28 days 
                 42 days 
                 56 days 
                 70 days 
               
               
                   
                   
               
             
             
               
                   
               
             
          
           
               
                 F 
                 1 
                 − 
                 − 
                 − 
                   
                   
                   
               
               
                   
                 2 
                 − 
                 − 
                 − 
                 − 
                 − 
               
               
                   
                 3 
                 − 
                 − 
                 − 
                 − 
                 − 
               
               
                   
                 4 
                 − 
                 − 
                 − 
                 − 
               
               
                   
                 5 
                 − 
                 − 
                 − 
                 − 
                 − 
               
               
                   
                 6 
                 − 
                 − 
                 − 
                 − 
                 − 
               
               
                 G 
                 1 
                 − 
                 − 
                 − 
                 − 
               
               
                   
                 2 
                 − 
                 − 
                 + 
               
               
                   
                 3 
                 − 
                 − 
                 − 
                 − 
               
               
                   
                 4 
                 − 
                 − 
                 − 
               
               
                   
                 5 
                 − 
                 − 
                 − 
                 − 
                 + 
                 + 
               
               
                   
                 6 
                 − 
                 − 
                 + 
               
               
                 H 
                 1 
                 − 
                 − 
                 − 
               
               
                   
                 2 
                 − 
                 − 
                 − 
                 − 
                 − 
               
               
                   
                 3 
                 − 
                 − 
                 − 
                 − 
               
               
                   
                 4 
                 − 
                 − 
                 − 
                 − 
               
               
                   
                 5 
                 − 
                 − 
                 − 
                 − 
                 − 
                 − 
               
               
                   
                 6 
                 − 
                 − 
                 − 
                 − 
                 − 
                 − 
               
               
                 I 
                 1 
                 − 
                 − 
                 − 
               
               
                   
                 2 
                 − 
                 − 
                 − 
                 − 
               
               
                   
                 3 
                 − 
                 − 
                 − 
                 − 
                 − 
                 − 
               
               
                   
                 4 
                 − 
                 − 
                 − 
                 − 
               
               
                   
                 5 
                 − 
                 − 
                 − 
                 − 
                 − 
               
               
                   
                 6 
                 − 
                 − 
                 − 
                 − 
               
               
                 J 
                 1 
                 − 
                 − 
                 − 
                 − 
                 − 
                 − 
               
               
                   
                 2 
                 − 
                 − 
                 − 
                 − 
                 − 
               
               
                   
                 3 
                 − 
                 − 
                 − 
                 − 
               
               
                   
                 4 
                 − 
                 − 
                 − 
                 − 
                 − 
               
               
                   
                 5 
                 − 
                 − 
                 − 
                 − 
                 − 
               
               
                   
                 6 
                 − 
                 − 
                 − 
                 − 
                 − 
               
               
                 K 
                 1 
                 − 
                 − 
                 − 
                 + 
                 + 
                 + 
               
               
                   
                 2 
                 − 
                 − 
                 − 
                 − 
                 − 
                 − 
               
               
                   
                 3 
                 − 
                 − 
                 − 
                 − 
               
               
                   
                 4 
                 − 
                 − 
                 − 
                 − 
                 − 
                 + 
               
               
                   
                 5 
                 − 
                 − 
                 − 
                 − 
               
               
                   
                 6 
                 − 
                 − 
                 + 
               
               
                 L 
                 1 
                 − 
                 − 
                 − 
                 − 
               
               
                   
                 2 
                 − 
                 − 
                 − 
                 − 
               
               
                   
                 3 
                 − 
                 − 
               
               
                   
                 4 
                 − 
                 − 
                 − 
                 − 
               
               
                   
                 5 
                 − 
                 − 
                 − 
               
               
                   
                 6 
                 − 
                 − 
                 − 
                 + 
                 + 
                 + 
               
               
                 M 
                 1 
                 − 
                 − 
                 − 
                 − 
                 − 
                 − 
               
               
                   
                 2 
                 − 
                 − 
                 − 
                 − 
                 − 
                 − 
               
               
                   
                 3 
                 − 
                 − 
                 − 
                 − 
                 − 
                 − 
               
               
                   
                 4 
                 − 
                 − 
                 − 
                 − 
                 − 
                 − 
               
               
                   
                 5 
                 − 
                 − 
                 − 
                 − 
                 − 
                 − 
               
               
                   
                 6 
                 − 
                 − 
                 − 
                 − 
                 − 
                 − 
               
               
                   
               
             
          
         
       
     
     As shown in  FIG. 6  and Table 3, an antibody to the EGFP-His protein was detected, and an increase in antibody titer was observed in three Bubble Eyes in the experimental group G in which the oil base was administered as the adjuvant together with the antigen. 
     In contrast, an increase in antibody titer with respect to the purified GA-His was not observed in Bubble Eyes in the experimental group H in which the oil base including inactivated  Escherichia coli  cells was administered together with the antigen, the Bubble Eyes in the experimental group I in which the oil base including inactivated  Mycobacterium tuberculosis  cells was administered together with the antigen, and the Bubble Eyes in the experimental group J in which the oil base including inactivated  Aspergillus oryzae  cells was administered together with the antigen. An increase in antibody titer was also not observed in the Bubble Eyes in the experimental group F in which only the antigen was administered. 
     An increase in antibody titer with respect to the culture supernatant of GA-His (GA  Aspergillus oryzae  culture supernatant in  FIG. 6  (hereinafter the same)) was observed in three Bubble Eyes in the experimental group K in which only the antigen was administered, and one Bubble Eye in the experimental group L in which the oil base was administered together with the antigen. 
     Bubble Eye No. 1 in the experimental group K that showed an increase in antibody titer with respect to culture supernatant GA-His showed an increase in antibody titer when 42 days had elapsed after the first immunization. An increase in antibody titer was observed from the 42nd day to the 70th day after the first immunization. 
     Bubble Eye No. 4 showed a slight increase in antibody titer when 70 days had elapsed after the first immunization, and Bubble Eye No. 6 showed an increase in antibody titer when 28 days had elapsed after the first immunization. Bubble Eye No. 6 in the experimental group L that showed an increase in antibody titer with respect to the culture supernatant of GA-His, showed a slight increase in antibody titer when 42 days had elapsed after the first immunization, and the antibody titer further increased when 56 days had elapsed after the first immunization. An increase in antibody titer was observed from the 42nd day to the 70th day after the first immunization. 
     The Bubble Eyes in the control experimental group M in which the oil base was administered together with the goldfish Ringer&#39;s solution, did not show an increase in antibody titer with respect to the EGFP-His protein, the purified GA-His, and the culture supernatant of GA-His. 
     Note that  FIG. 6  also shows the results for the positive control (+) in which the anti-His antibody was reacted, and the results for the negative control (−) in which the anti-myctag antibody was reacted (upper left) (dilution ratio: 1/100 to 1/5000). 
     In  FIG. 6 , the alphabetical character shown above each PVDF membrane indicates the experimental group, the numerals (1 to 6) shown above each PVDF membrane indicate the identification numbers of the Bubble Eyes, and the immunization conditions (OB: oil base) for each experimental group are shown on the right of the alphabetical character. The sample (blister fluid) collection day (i.e., the number of days elapsed after the first immunization) (“pre” refers to “before immunization”) is shown on the right of each PVDF membrane. 
     Example 2 
     I. Preparation of Antigen 
     Antigen: LGR3 
     1-1. Preparation of Vector (Construction of Plasmid to Incorporation of Target Gene) 
     A vector “pCold TF DNA” (Takara Bio Inc.) was modified as described below to prepare an expression vector “pCold-TEE-His-hLGR3-LRR”. In order to remove the trigger factor (TF) sequence of the vector “pCold TF DNA” (Takara Bio Inc.), PCR was performed using primers having a restriction enzyme (Sural or SfiI) recognition sequence utilizing the vector “pCold TF DNA” as a template to amplify the vector. 
     Likewise, PCR was performed using primers having a restriction enzyme (SmaI or SfiI) recognition sequence utilizing a vector “pCR4-TOPO-hLGR3” (Invitrogen) as a template to amplify the leucine-rich region (LRR) (SEQ ID NO: 23) of a human leucine-rich repeat-containing G protein-coupled receptor 3 (hLGR3) gene (see the hLGR marker part in  FIG. 7  (base: 1695 to 2173)). 
     The amplified product was purified, and treated with a restriction enzyme, and an expression vector “pCold-TEE-His-hLGR3-LRR” was constructed using a DNA Ligation Kit (Takara Bio Inc.). A construct was prepared using  Escherichia coli  HST08 strain, and the base sequence of the expression vector “pCold-TEE-His-hLGR3-LRR” was determined. The base sequence completely coincided with the expected base sequence. It was confirmed from the above result that the construct was properly obtained. 
     II. Determination of Antigen-Antibody Reaction 
     The construct (expression vector “pCold-TEE-His-hLGR3-LRR”) prepared in section I was transformed into the  Escherichia coli  Origami strain. 
     The strain for which transformation was confirmed by direct PCR was inoculated onto an LB medium (5 ml) (to which ampicillin was added so that the final concentration was 100 μg/ml), and pre-cultured at 37° C. and 180 rpm for 6 hours. 
     1 ml of the preculture solution was inoculated onto a 2×YT medium (250 ml), cultured at 37° C. and 130 rpm until OD 600 -0.45 to 0.5 was reached, then promptly cooled to 15° C., and kept for 30 minutes. After the addition of IPTG so that the final concentration was 0.1 mM, the mixture was cultured at 15° C. and 130 rpm for 24 hours. 
     The cells were collected, suspended in a 20 mM phosphate buffer (pH: 7.4, 20 mM imidazole and 1.5 M NaCl), subjected to sonication, and centrifuged (20,000×g) at 4° C. for 30 minutes. 
     The supernatant was collected as a soluble fraction, and the precipitate was prepared as a solubilized insoluble fraction using 6 M urea. Each fraction was purified using an Ni Sepharose column, and concentrated (Amicon Ultra (Millipore)), and the degree of purification was determined by SDS-PAGE. 
     The purified and concentrated soluble fraction and solubilized insoluble fraction were separated by SDS-PAGE, and detected using an anti-His antibody (Amersham Biosciences). As shown in  FIG. 8 , a band was detected in the soluble fraction and the solubilized insoluble fraction at the target molecular weight position (see the arrow in  FIG. 8 ). It was thus confirmed that LRR of the target hLGR3 protein was expressed. In  FIG. 8 , M indicates the marker, S indicates the soluble fraction, and P indicates the solubilized insoluble fraction. 
     III. Production of Antibody by Fish Bearing Water Vesicles 
     1. Sample 
     Five healthy Bubble Eyes (length: about 8 to 10 cm) were purchased, and kept for 2 months or more in the same manner as in Example 1, and the same reagents as those used in Example 1 were used as samples. 
     The soluble fraction (LRR of hLGR3 protein) (0.6 μg/pi) and the insoluble fraction (LRR of hLGR3 protein) (0.1 μg/μl) prepared in section II were used as antigens. An oil base prepared by homogenously mixing the components shown in Table 4 was used as an adjuvant. 
                                                 TABLE 4                   Oil base                Component   Amount (g)                            Glycerol   10.0           Lecithin   0.1           Peanut oil   10.0                        
2. Production of Antibody
 
     An antibody was produced by the following steps (1) to (5). 
     (1) 100 μl of the blister fluid was collected from each Bubble Eye before immunization. 
     (2) An emulsion prepared by mixing 90 μl of the antigen (soluble fraction (0.6 μg/μl)) prepared in section II with 90 μl of the oil base was injected into the water vesicle of each Bubble Eye. 
     (3) 100 μl of the blister fluid was collected from each Bubble Eye when 1 week had elapsed after the first immunization (see (2)), and an emulsion prepared by mixing 100 μl of the antigen (solubilized insoluble fraction (0.1 μg/μl)) prepared in section II with 100 μl of the oil base was immediately injected into the water vesicle of each Bubble Eye.
 
(4) 100 μl of the blister fluid was collected from each Bubble Eye when 1 week had elapsed after the second immunization (see (3)) (second sampling).
 
(5) 100 μl of the blister fluid was collected from each Bubble Eye when 1 week had elapsed after the second sampling (see (4)) (third sampling).
 
     The collected blister fluid was centrifuged (1500×g) at 4° C. for 10 minutes to collect a supernatant, which was used as an antibody titer measurement sample. The sample was stored at 4° C. until the sample was used to detect an antigen-specific antibody. Note that no Bubble Eye died during the immunization period. 
     3. Antibody Detection by Dot Blotting 
     1) Sample 
     The blister fluid collected from each Bubble Eye (see section 1) was diluted (dilution ratio: 1/2, 1/10, 1/20, 1/100, 1/200, 1/1000, or 1/2000) to obtain samples. 
     An anti-His antibody was used as a detection primary antibody, an anti-TF antibody (GenScript) was used as a positive control, and an anti-AIF antibody (rabbit polyclonal antibody) (PromoKine) was used as a negative control. 
     2) Antigen 
     His-TF-hLGR3 (see  FIG. 7 , base: 278 to 295, Trigger Factor (base: 296 to 1657), and hLGR marker (base: 1695 to 2173)) that was prepared in the same manner as in sections I and II and adjusted to a final concentration of 5 ng/μl using PBS, was used as an antigen. 
     3) Dot Blotting 
     An antigen-antibody reaction was detected by dot blotting using a sandwich technique (see Example 1). 
     The sample (2 μl) prepared in section 1) was added dropwise to a PVDF membrane (see  FIG. 9 ). The PVDF membrane was reacted with the antigen (see 2)), and then reacted with the detection primary antibody, the negative control, or the positive control (see 1)). An anti-mouse IgG HRP labeled secondary antibody (Cell Signaling) was diluted (1/25,000), and reacted with the PVDF membrane. 
     After completion of the reaction, the PVDF membrane was washed, immersed in an Amersham ECL plus Western Blotting Detection Reagent (GE healthcare), and reacted at room temperature for 5 minutes, and luminescence was detected using a CCD camera. 
     As shown in  FIG. 9 , when using the anti-His antibody as the detection primary antibody, the sample prepared by 1/2-fold diluting the blister fluid showed an increase in signal (before immunization&lt;second sampling&lt;third sampling). The above results suggest that an antibody to the antigen was produced in the blister fluid as a result of administering the antigen to the Bubble Eye. 
     In  FIG. 9 , reference signs B1 to B5 indicate the Bubble Eyes from which each sample is derived. “0” indicates the blister fluid before immunization, “2” indicates the blister fluid collected by the second sampling, and “3” indicates the blister fluid collected by the third sampling. The blister fluid dilution ratio (1/2 to 1/2000) is shown on the left. “P” indicates the positive control, and “N” indicates the negative control. Each control was diluted in a dilution ratio of 1/100, 1/200, 1/500, 1/1000, 1/2000, and 1/5000, and solid-phased. 
     It was confirmed from the above results that it is possible to produce an antibody using a fish bearing water vesicles. It was also confirmed that an antigen can be administered directly to the water vesicle of a fish bearing water vesicles, and the antibody produced by the fish can be collected directly from the water vesicle. 
     Since 1 to 5 ml of lymph can be collected directly from the water vesicle at one time, it is possible to collect a large amount of antibody produced by a single antigen administration. Since the lymph including the antibody could be collected while keeping the Bubble Eye alive, it was possible to repeatedly collect the lymph including the antibody from the Bubble Eye. 
     INDUSTRIAL APPLICABILITY 
     According to the embodiments of the invention, it is possible to repeatedly obtain a large amount of antibody produced by a fish while keeping the fish alive. The antibody according to the embodiments of the invention may be an antibody to a glycoprotein or the like, and may be widely used in the same manner as an antibody intended for mammals and the like.