Patent Grant
8298778
The present application is a 35 U.S.C. §371 National Stage patent application of International patent application PCT/JP2009/052091, filed on Feb. 6, 2009, which claims priority to Japanese patent application JP 2008-029589, filed on Feb. 8, 2008.
The present invention relates to a method and a kit for detecting an antibody to Avibacterium paragallinarum. Specifically, the present invention relates to a method for detecting an antibody to Avibacterium paragallinarum (hereinafter also refer to as “A.pg”; previously referred to as Haemophilus paragallinarum) which comprises detecting an antibody induced by an outer-membrane protein (hereinafter also refer to as “HMT p210 polypeptide”) of Avibacterium paragallinarum serotype A and/or serotype C by ELISA with a solid phase to which a peptide consisting of an amino acid sequence of non-homologous region of said outer-membrane protein or a portion thereof is immobilized, and a detection kit used for said method. Although a peptide is referred to as dipeptide, tripeptide, oligopeptide, polypeptide, and the like depending on the number of amino acid residues constituting of said peptide, a peptide as used herein is defined merely as “peptide” as encompassing any of these peptides.
Avian infectious coryza caused by infection with A.pg is known as important respiratory diseases in poultry. Poultry suffering from avian infectious coryza have a running nose, swelling of the face and epiphora as cardinal symptoms. Avian infectious coryza brings about a great economical damage since it leads to decrease in the breeding rate of poultry, retarding of egg laying, decrease in egg production or failure of egg laying.
Page et al. classified A.pg into three serotypes A, B and C (Non-patent reference 1) whereas Sawata et al. classified into two serotypes 1 and 2 (Non-patent reference 2). Subsequently, Kume et al. reported that serotype A by Page corresponds to serotype 1 by Sawata et al. whereas serotype C by Page corresponds to serotype 2 by Sawata et al. (Non-patent references 3 and 4). Nowadays, serotype A (serotype 1) of A.pg (hereinafter also refer to as “A.pg-A”) and serotype C (serotype 2) of A.pg (hereinafter also refer to as “A.pg-C”) are considered to be a main causative agent of avian infectious coryza.
For protection from avian infectious coryza, an inactivated vaccine has hitherto been used widely which is obtained by inactivating the cells of A.pg-A or A.pg-C with formalin, thimerosal, and the like. However, adverse side effects caused by such an inactivated vaccine has been an issue as it was reported that local necrotic lesions are formed in the inoculated chicken when the vaccine is administered (Non-patent reference 5), and hence, development of a highly safe vaccine is earnestly desired.
Under the circumstances, there have been developed or are under development a component vaccine where only a protective antigen, i.e. an effective component, obtained from bacterial cells or culture supernatant is used; a recombinant vaccine where a gene coding for a protective antigen is cloned by genetic recombination technique and expressed in bacteria, yeast, animal cells, plant cells, insect cells, and the like, and a product expressed in a large amount is purified and used; and a vector vaccine where a gene coding for a protective antigen is inserted into a viral vector, and the like.
For instance, Tokunaga et al. have successfully purified, from culture of A.pg-A, a polypeptide having about 130 kd of molecular weight from said A.pg-A, said polypeptide inducing production of a hemagglutination-inhibition antibody (HI antibody) and protecting against avian infectious coryza by A.pg-A (Patent reference 1). Furthermore, they have cloned a DNA fragment coding for said 130 Kd polypeptide and expressed said gene fragment in E. coli to find that the produced polypeptide could protect from avian infectious coryza caused by Avibacterium paragallinarum serotype A. Besides, they used said DNA fragment coding for the 130 Kd polypeptide as a probe to identify an HMT p210 gene coding for serotype A HMT p210 polypeptide, an outer-membrane protein having a hemagglutination activity, consisting of 2,042 amino acids. They also cloned from Avibacterium paragallinarum serotype C a DNA fragment hybridizable with said DNA fragment to obtain serotype C HMT p210 gene (Patent reference 2). They compared nucleotide sequences of open reading frame of HMT p210 genes of Avibacterium paragallinarum serotypes A and C to report that homology between both genes was about 80% as a whole, and that a region of about 3.4 kbp at the 5′-end (hereinafter refer to as “Region 1”) and a region of about 1.2 kbp at the 3′-end (hereinafter refer to as “Region 3”) had a very high homology while a region of about 1.5 kbp flanked by the two regions (hereinafter refer to as “Region 2”) had a low homology (Patent reference 2).
It was also reported by Noro et al. that the HMT p210 gene discovered by Tokunaga et al. is important for a target region of a serotype specific vaccine. Noro et al. reported that, by immunizing poultry with a peptide encoded by a DNA fragment of from 4,801 bp to 5,157 bp, which is a portion of HMT p210 gene coding for the A.pg-A HMT p210 polypeptide, said peptide induced an HI antibody and had a vaccinal effect against A.pg-A (Patent reference 3). Noro et al. also reported in the 143rd Meeting of the Japanese Society of Veterinary Science held on Apr. 3-5, 2007, Japan that, by immunizing poultry with a peptide encoded by a DNA fragment of 5.5 kbp, which is a portion of HMT p210 gene coding for the A.pg-C HMT p210 polypeptide, said peptide induced an HI antibody and had a vaccinal effect against A.pg-C.
Serum diagnosis has not been performed for avian infectious coryza since, in addition to acute progress of the disease, poultry infected with A.pg are not likely to induce an antibody even after onset of the disease. On the other hand, poultry undergone vaccination induce an antibody to Hemagglutinin (hereinafter also referred to as “HA”) on the surface of the A.pg cells and, for estimation of vaccinal effect in vitro, a hemagglutination-inhibition test (hereinafter also referred to as “HI test”) with an anti-HA antibody has been performed. HI test, where fresh chicken erythrocytes or chicken erythrocytes fixed with glutaraldehyde are used, is indicated to have defects: (1) since fresh chicken erythrocytes are necessary for estimation of vaccinal effect of A.pg-A, it is troublesome and laborsome such as obtaining chickens for blood (breeding and managing chickens under condition of separation from pathogens), bleeding, blood treatment, and the like, (2) stable results are not likely to be obtained since the results may be influenced by the lots of chickens erythrocytes and estimation of an antibody titer is made by subjectivity of a person who measures.
On the other hand, Sun et al. reported, for alternative serum diagnostic of HI test, blocking ELISA (B-ELISA) using a serotype specific monoclonal antibody (Non-patent reference 6). B-ELISA is ELISA where serotype A or C cells disrupted by sonication were used as an antigen and monoclonal antibodies reactive with the respective serotypes were used to competitively detect antibodies in sera. This method is advantageous in that it has a higher sensitivity than HI test and may treat multiple antibodies. However, it requires four steps, i.e. addition of sera, addition of monoclonal antibodies, addition of anti-mouse IgG-HRP labeled antibody and addition of a substrate for development, one more step than in ordinary ELISA, rendering troublesome procedures. Also, for this method, serotype specific monoclonal antibodies need be obtained. For manufacturing a kit, it will take trouble of preparing and adding a plate immobilized with an antigen and reference serum as well as monoclonal antibodies. Besides, it is noted that said B-ELISA is a system that detects an antibody to only an antigenic epitope recognized by a single monoclonal antibody for the respective serotypes. With a system that detects an antibody to a single epitope, however, when said epitope is lost due to mutation of A.pg, it is highly liable not to detect its infection or an antibody induced by vaccination.
An object of the present invention is to provide a method for detecting antibodies, distinctively antibodies to A.pg serotype A and to serotype C, respectively. Specifically, a method for detecting antibodies is provided that is characterized by using a recombinant antigenic peptide with which antibodies to A.pg serotype A and to serotype C, respectively, may be distinguished from each other. More specifically, a method for detecting antibodies is provided that is characterized by using a recombinant antigenic peptide comprising an amino acid sequence within a region having low homology between outer-membrane proteins of A.pg serotype A and serotype C.
Under the circumstances, the present inventors have assiduously investigated so as to attain the objects mentioned above, and as a result, have found that an amino acid sequence homologous between A.pg-A and A.pg-C is included in the amino acid sequence of Region 2, as separately located, of p 210 polypeptide encoded by HMT p210 gene, an important vaccinal antigen, (among 31 amino acid residues of amino acids Nos. 243-273 of SEQ ID NO: 1 for A.pg-A and of amino acids Nos. 38-68 of SEQ ID NO: 2 for A.pg-C, 29 amino acid residues are identical; cf.
Thus, the present invention includes the followings:
(1) A method for detection of an antibody to Avibacterium paragallinarum characterized by that said method comprises antibody measurement by reacting at least one antigen of Peptide A or Peptide B below with a sample:
Peptide A:
which is a peptide which consists of a portion of the amino acid sequence of SEQ ID NO: 1, consists of a peptide chain of 6 or more amino acid residues, and does not include an amino acid sequence of amino acids Nos. 243-273 of SEQ ID NO: 1;
Peptide B:
which is a peptide which consists of a portion of the amino acid sequence of SEQ ID NO: 2, consists of a peptide chain of 6 or more amino acid residues, and does not include an amino acid sequence of amino acids Nos. 38-68 of SEQ ID NO: 2.
(2) The method for detection of (1) above wherein Peptide A or Peptide B is a peptide chain of 10 or more amino acid residues.
(3) The method for detection of (1) above wherein Peptide A or Peptide B is a peptide chain of 20 or more amino acid residues.
(4) The method for detection of (1) above wherein Peptide A or Peptide B is a peptide chain as follows:
Peptide A:
which is a peptide which consists of a portion of the amino acid sequence of SEQ ID NO: 1, comprises an amino acid sequence of amino acids Nos. 8-236 of SEQ ID NO: 1, and does not include an amino acid sequence of amino acids Nos. 243-273 of SEQ ID NO: 1;
Peptide B:
which is a peptide which consists of a portion of the amino acid sequence of SEQ ID NO: 2, comprises an amino acid sequence of amino acids Nos. 69-452 of SEQ ID NO: 2, and does not include an amino acid sequence of amino acids Nos. 38-68 of SEQ ID NO: 2.
(5) The method for detection of (1) above wherein Peptide A or Peptide B is a peptide chain as follows:
Peptide A:
which is a peptide consisting of an amino acid sequence of amino acids Nos. 8-236 of SEQ ID NO: 1;
Peptide B:
which is a peptide consisting of an amino acid sequence of amino acids Nos. 69-452 of SEQ ID NO: 2.
(6) The method for detection of (4) above wherein Peptide A is a peptide chain as follows:
Peptide A:
which is a peptide which consists of a portion of the amino acid sequence of SEQ ID NO: 1, comprises an amino acid sequence of amino acids Nos. 274-445 of SEQ ID NO: 1, and does not include an amino acid sequence of amino acids Nos. 243-273 of SEQ ID NO: 1.
(7) The method for detection of (5) above wherein Peptide A is a peptide chain as follows:
Peptide A:
which is a peptide consisting of an amino acid sequence of amino acids Nos. 274-445 of SEQ ID NO: 1.
(8) The method for detection of any of (1) to (7) above wherein Peptide A or Peptide B is a peptide having an amino acid sequence wherein 1 or several amino acid residues therein are deleted, added or substituted.
(9) The method for detection of any of (1) to (8) above wherein the antibody measurement is selected from the group consisting of ELISA, Western blot and dot blot.
(10) The method for detection of any of (1) to (9) above wherein the sample is sera from chickens infected with Avibacterium paragallinarum or sera from chickens to which Avibacterium paragallinarum vaccine is administered.
(11) A kit for measurement of an antibody to Avibacterium paragallinarum characterized by that at least one of Peptide A or Peptide B below is used as an antigen:
Peptide A:
which is a peptide which consists of a portion of the amino acid sequence of SEQ ID NO: 1, consists of a peptide chain of 6 or more amino acid residues, and does not include an amino acid sequence of amino acids Nos. 243-273 of SEQ ID NO: 1;
Peptide B:
which is a peptide which consists of a portion of the amino acid sequence of SEQ ID NO: 2, consists of a peptide chain of 6 or more amino acid residues, and does not include an amino acid sequence of amino acids Nos. 38-68 of SEQ ID NO: 2.
(12) The kit for measurement of an antibody of (11) above wherein Peptide A or Peptide B is a peptide chain of 10 or more amino acid residues.
(13) The kit for measurement of an antibody of (11) above wherein Peptide A or Peptide B is a peptide chain of 20 or more amino acid residues.
(14) The kit for measurement of an antibody of (11) above wherein Peptide A or Peptide B is a peptide chain as follows:
Peptide A:
which is a peptide which consists of a portion of the amino acid sequence of SEQ ID NO: 1, comprises an amino acid sequence of amino acids Nos. 8-236 of SEQ ID NO: 1, and does not include an amino acid sequence of amino acids Nos. 243-273 of SEQ ID NO: 1;
Peptide B:
which is a peptide which consists of a portion of the amino acid sequence of SEQ ID NO: 2, comprises an amino acid sequence of amino acids Nos. 69-452 of SEQ ID NO: 2, and does not include an amino acid sequence of amino acids Nos. 38-68 of SEQ ID NO: 2.
(15) The kit for measurement of an antibody of (11) above wherein Peptide A or Peptide B is a peptide chain as follows:
Peptide A:
which is a peptide consisting of an amino acid sequence of amino acids Nos. 8-236 of SEQ ID NO: 1;
Peptide B:
which is a peptide consisting of an amino acid sequence of amino acids Nos. 69-452 of SEQ ID NO: 2.
(16) The kit for measurement of an antibody of (14) above wherein Peptide A is a peptide chain as follows:
Peptide A:
which is a peptide which consists of a portion of the amino acid sequence of SEQ ID NO: 1, comprises an amino acid sequence of amino acids Nos. 274-445 of SEQ ID NO: 1, and does not include an amino acid sequence of amino acids Nos. 243-273 of SEQ ID NO: 1.
(17) The kit for measurement of an antibody of (15) above wherein Peptide A is a peptide chain as follows:
Peptide A:
which is a peptide consisting of an amino acid sequence of amino acids Nos. 274-445 of SEQ ID NO: 1.
(18) The kit for measurement of an antibody of any of (11) to (17) above wherein Peptide A or Peptide B is a peptide having an amino acid sequence wherein 1 or several amino acid residues therein are deleted, added or substituted.
(19) The kit for measurement of an antibody of any of (11) to (18) above wherein the antibody measurement is selected from the group consisting of ELISA, Western blot and dot blot.
(20) The kit for measurement of an antibody of any of (11) to (19) above wherein the sample is sera from chickens infected with Avibacterium paragallinarum or sera from chickens to which Avibacterium paragallinarum vaccine is administered.
In accordance with the present invention, a method and a kit for detecting an antibody to Avibacterium paragallinarum are provided. The peptides from A.pg-A and from A.pg-C as used herein do not include an amino acid sequence homologous to each other and therefore may specifically bind to an antibody induced by a vaccine from A.pg-A and an antibody induced by a vaccine from A.pg-C, respectively. Accordingly, a method and a kit for detection of the present invention enables to distinctly measure an antibody titer for the respective antibodies to vaccines from A.pg-A and A.pg-C in chicken sera not only when the respective vaccines are separately administered to chickens but also when a mixture of the vaccines is administered.
Furthermore, the present invention, as using a purified recombinant antigen, allows for immobilization of a higher concentration of an antigen than the prior art using cell debris of A.pg and hence allows for construction of a system for measuring an antibody with higher detection sensitivity. The method for detecting an antibody of the present invention, as using the antigenic peptide which is capable of distinguishing a serotype of A.pg, detects an antibody more simply and, in view of antigenic mutation of A.pg, more reliably than B-ELISA using a serotype specific monoclonal antibody.
Besides, by the method for detection of the present invention, antibodies are distinguished not only in chicken sera after vaccination but also in sera from chickens infected with A.pg.
The present invention is characterized by a method and a kit for detection of an antibody to Avibacterium paragallinarum by antibody measurement using as an antigen peptides obtained by removing a homologous amino acid sequence between A.pg-A and A.pg-C slightly present in a non-homologous region of the amino acid sequence encoded by A.pg-derived HMT p210 gene.
For the method for detection of an antibody to Avibacterium paragallinarum of the present invention, a non-homologous region or a portion thereof of the amino acid sequence encoded by A.pg-A- and/or A.pg-C-derived HMT p210 gene is used as an antigen. A non-homologous region as used herein is defined as a region of about 1.3 kbp (SEQ ID NO: 1 for A.pg-A and SEQ ID NO: 2 for A.pg-C) which is obtained by removing a homologous sequence at the C-terminal from the amino acid sequence encoded by a DNA region of about 1.5 kbp (Region 2) flanked by the amino acid sequence encoded by a DNA region of about 3.4 kbp (Region 1) at the 5′-end and the amino acid sequence encoded by a DNA region of about 1.2 kbp (Region 3) at the 3′-end (cf.
For three A.pg-A strains (221 strain, 053 strain and W strain) isolated from A.pg-infected chickens, the nucleotide sequence corresponding to a non-homologous region of HMT p210 gene is perfectly consistent between 053 strain and W strain and differs only one nucleotide between these two strains and 221 strain. On the other hand, for three A.pg-C strains (53-47 strain, Modest strain and NK-1 strain), said nucleotide is such that Modest strain and NK-1 strain had deletion of 3 nucleotides (1 amino acid) as compared to 53-47 strain. Accordingly, it may be said that a non-homologous region of the same serotype is highly conserved and thus any strain of the same serotype may be used for the present invention.
An A.pg-1.3 gene and a DNA fragment containing said gene may be obtained as described below. For growth of A.pg, a culture medium may be used which appropriately contains polypeptone, glucose, casamino acid, sodium glutamate, yeast extract, sodium chloride, chicken broth, βNAD, chicken serum, and the like. For the present invention, a broth supplemented with chicken serum, containing 5 g polypeptone, 1 g casamino acid, 5 g sodium chloride, 5 g sodium L-glutamate, 1 g glucose, 10 g yeast extract, 175 mL chicken broth, 25 mL chicken serum and 0.025% nicotineamide adenine dinucleotide (β-NAD) in 1000 mL culture medium, was used for growth of a small to medium amount of the cells. Culture condition may be set at the temperature 37° C. and the duration in a range of 16-24 hours but may suitably be adjusted depending on the purpose of use, the format of culture, the amount of cells inoculated, the scale of culture medium, and the like.
The cells in culture may be recovered in a precipitate by centrifuge (8,000 rpm, 20 minutes). An HMT p210 gene may be prepared, using as a starting material a whole RNA, mRNA or a genomic DNA extracted from the cells, by a general genetic recombination technique as taught by Sambrook et al. (Molecular Cloning, A Laboratory Manual Second Edition. Cold Spring Harbor Laboratory Press, N.Y., 1989). In practice, a commercially available kit may be used. For instance, reagents such as TRIzol reagent (Invitrogen), ISOGEN (NIPPON GENE CO., LTD.), StrataPrep Total RNA Purification Kit (TOYOBO) for extraction of RNA, SepaGene kit (Sanko Junyaku Co., Ltd.), ISOPLANT (Wako Pure Chemical Industries, Ltd.) for extraction of chromosomal DNA, a kit such as mRNA Purification Kit (Amersham Bioscience), Poly(A) Quick mRNA Isolation Kit (TOYOBO), mRNA Separator Kit (Clontech) for purification of mRNA, SuperScript plasmid system for cDNA synthesis and plasmid cloning (Invitrogen), cDNA Synthesis Kit (TAKARA SHUZO CO., LTD.), SMART PCR cDNA Synthesis & Library Construction Kits (Clontech), Directionary cDNA Library Construction systems (Novagen Inc.), GeneAmp PCR Gold (Applied Biosystems) for conversion into cDNA may be used.
More specifically, a chromosomal DNA may be extracted from cells recovered by centrifuge, using SepaGene kit (Sanko Junyaku Co., Ltd.), and the like, cleaved with an adequate restriction enzyme, preferably EcoRI, inserted into a commercially available cloning vector, e.g. λgt11; New England Biolabs (NEB) to prepare a DNA library. Using the obtained DNA fragments as a template, PCR may be performed to amplify DNA fragments in various sizes using, LA Taq (TAKARA BIO Inc.) in accordance with protocol attached thereto. Primers for use in PCR may be designed based on the nucleotide sequences of A.pg-A- and A.pg-C-derived HMT p210 genes as Tokunaga et al. disclosed (Patent reference 1). Primers for PCR may be readily available if asked to DNA synthesis contractor services (e.g. Sigma Genosys Japan K.K.). When designed, nucleotide sequences of appropriate restriction enzyme cleavage sites may be added at the 5′-end of upstream Primer and at the 5′-end of downstream Primer. Products amplified by PCR may be cloned into a gene cloning vector, pCR-XL-TOPO (Invitrogen) to prepare plasmid pCRDNT into which various DNA fragments are inserted. A nucleotide sequence of the obtained DNA fragments, after cloned into pBluescript II SK+ (Stratagene) or pCR2.1-TOPO (Invitrogen), may be determined with a DNA sequencer (ABI Prism 377; Applied Biosystems).
As described below, insofar that sensitivity is not decreased or non-specific reaction is not increased, a peptide to which amino acid mutation is introduced may be used as an antigen for the antibody measurement in the present invention. For introducing mutation at a specific amino acid in a peptide, site-directed mutagenesis may usually be employed where mutation is introduced to a nucleotide sequence of a DNA fragment coding for said peptide. In practice, site-directed mutagenesis may be performed with commercially available kits in which this technique is applied, such as Site-Directed Mutagenesis System (Mutan-Super Express Km, Mutan-Express Km, Mutan-K, and the like) by Takara, QuickChange Multi Site-Directed Mutagenesis Kit, QuickChange XL Site-Directed Mutagenesis Kit by Stratagene, GeneTailor Site-Directed Mutagenesis System by Invitrogen, in accordance with protocol attached thereto.
For obtaining DNA fragments coding for an amino acid sequence of various peptides that do not contain an amino acid sequence homologous between A.pg-A and A.pg-C, so that the homologous sequence as described above would not be contained, an ordinary PCR may be performed using primers designed from non-homologous region (the nucleotide sequence depicted in SEQ ID NO: 3 for A.pg-A and the nucleotide sequence depicted in SEQ ID NO: 4 for A.pg-C) and the A.pg-1.3 gene and a DNA fragment comprising the gene as a template. In case of a short amino acid sequence, its DNA fragment may also be prepared by artificial synthesis. The DNA fragments and the primers prepared in the present invention are shown in Table 1.
The thus obtained DNA fragments may be incorporated into an appropriate expression vector, which may then be introduced into a host for expression of each of the DNA fragments. For an expression vector, pQE30 (QIAGEN) or pET22b (Novagen Inc. or TAKARA BIO Inc.), and the like may be used, as appropriately selected. For expression of a heterologous protein or peptide, bacteria, yeasts, animal cells, plant cells, insect cells, and the like may normally be used, as appropriately selected depending on the purpose of use. For transformation of a host cell, methods known in the art may be used. For instance, calcium phosphate, DEAE dextran, approach using liposome of lipofectin, polyethylene glycol fusion of protoplast, electroporation, and the like may be used, as appropriately selected depending on a host cell as used. For expression of each of the DNA fragments of the present invention, E. coli may be used which allows for expression in a large amount. For expression in E. coli, various expression vectors having trp promoter, T7 promoter, cspA promoter, and the like have been developed and commercially available and may be used as appropriate. Depending on an expression vector, suitable E. coli such as BL21, HMS174, DH5α, HB101, JM109, and the like may be selected as a host. Transformation of E. coli may be conducted using commercially available competent cells in accordance with protocol attached thereto. Thus, recombinant E. coli producing the desired polypeptide may be obtained. For culture medium (e.g. LB, SOC, SOB, and the like) used for culture of E. coli, reagents used for selection of transformant (e.g. ampicillin) and reagents used for induced expression (e.g. indole acetic acid (IAA), isopropylthio-β-D-galactoside (IPTG), and the like), commercially available ones may be used. A pH of a culture medium may be within a range suitable for growth of E. coli (pH 6 to 8).
Screening of recombinant E. coli expressing a desired peptide (the object) may be carried out as described below. Cells cultured and grown in the presence of an expression inducer (IPTG was used in an expression system in the present invention) are collected by centrifuge (10,000 rpm, 5 minutes), suspended in a fixed volume of distilled water, disrupted by sonication or a homogenizer such as French press or Manton Golin and subject to centrifuge (15,000 rpm, 15 minutes) for separation and recovery in precipitate or supernatant. To distilled water may appropriately be added a surfactant (e.g. Triton X 100), a chelating agent (e.g. EDTA), liposome, and the like. A fixed amount of expressed products recovered in supernatant and precipitate may be subject to SDS-polyacrylamide gel electrophoresis, and after staining with Coomassie Brilliant Blue, expression of the object may be confirmed by a molecular size and stained image. For confirmation (or detection) of the object, approach based on an antigen-antibody reaction such as ELISA, Western blot, dot blot, and the like may also be used other than approach based on a molecular size as described above. All of these approaches are commonly used for detecting a heterologous protein or polypeptide expressed in E. coli and may be selected as appropriate.
For purifying the object from recombinant E. coli, a combination of the methods commonly used in the field of protein chemistry may be used such as e.g. centrifuge, salting-out, ultrafiltration, isoelectric focusing, electrophoresis, ion exchange chromatography, gel filtration chromatography, affinity chromatography, hydrophobic chromatography, hydroxyapatite chromatography, and the like. An amount of the obtained protein or polypeptide may be measured with a reagent for protein measurement such as BCA Protein Assay Reagent Kit (Pierce Biotechnology, Inc), Protein Assay Kit (BIO-RAD, Inc), and the like.
To facilitate purification of the object, it may be expressed in a fusion with other polypeptide or peptide. A vector for expressing such a fusion protein includes His-tag expression system (Novagen Inc.) which allows for addition of oligohistidine, a system capable of expression of a fusion protein with FLAG tag (Sigma), GST fusion protein purification system (Amersham Pharmacia) which allows for production of a fusion protein with glutathione S-transferase (GST), MagneHis Protein Purification System (Promega), and the like. For instance, as carried out in the working examples of the invention, after expression as a fusion protein with oligohistidine, a polypeptide of interest may be specifically purified with nickel affinity column (GE Healthcare Bioscience).
The thus obtained various peptides not containing a homologous amino acid sequence between A.pg-A and A.pg-C may be used in antibody measurement for detection of an antibody induced by avian infectious coryza vaccine or for serological diagnosis of A.pg-infected chickens. Specifically, antibody measurement such as ELISA, Western blot, dot blot, and the like may be applied. In case that many antibodies are to be handled, ELISA with a microtiter plate to which peptides are immobilized may preferably be used.
For a peptide to be immobilized to a microtiter plate, a peptide consisting of a non-homologous region in the amino acid sequence encoded by A.pg-1.3 gene, or a portion of said peptide, may be used. Since it is established that 6 to 10 or thereabout amino acids may form an epitope recognizable by an antibody (it is published on-line (http://www.genosys.jp/products/spots/spots_faq.html) that 3 to 6 amino acids are sufficient for forming an epitope recognizable by an antibody), a peptide which is a portion of a non-homologous region and consists of an amino acid sequence of 6 or more consecutive amino acids may be used in the present invention. For enhancing specificity, preferably a peptide which is a portion of a non-homologous region and consists of an amino acid sequence of 10 or more consecutive amino acids, or more preferably, 20 or more consecutive amino acids, may form an epitope.
Most preferably, a polypeptide encoded by AΔ6b-2# (P-AΔ6b-2#), a polypeptide encoded by CΔ6b-1b (P-CΔ6b-1b) and a polypeptide encoded by AΔ7b-1b (P-AΔ7b-1b), and a portion of a peptide consisting of a non-homologous region in the amino acid sequence encoded by A.pg-1.3 gene which may encompass the above polypeptides may be used. Besides, insofar that decreased sensitivity or increased non-specific reaction, which may interfere with detection of an antibody, is not provided, a mutated peptide may also be used where amino acid mutation is introduced. Two or more of these peptides may be used in combination therewith as occasion demands. For instance, when a causative agent of avian infectious coryza is to be identified, each of the respective peptides may preferably be used separately, or a mixture of A.pg-A-derived peptides or a mixture of A.pg-C-derived peptides may preferably be used separately. In case that merely epidemiology of avian infectious coryza infection or survey of efficacy of avian infectious coryza vaccine is aimed, a mixture of A.pg-A-derived peptides and a mixture of A.pg-C-derived peptides may further be mixed together for use.
Immunized sera after vaccination may be obtained by administering subcutaneously, intradermally or intraperitoneally a mixture of the above peptide and an adjuvant to an appropriate animal once to thrice at an interval of 2 to 4 weeks, taking blood subsequently from the animal and centrifuging blood (14,000 rpm, 5 minutes). Adjuvant may include Freund's complete adjuvant, Freund's incomplete adjuvant, aluminum hydroxide (e.g. ImjectAlum (Pearce)), and the like.
Similarly, sera of Avibacterium paragallinarum-infected animal may also be obtained by centrifuge of blood.
More specifically, any of various formats of ELISA may be conducted. For instance, a sample (immunized sera or A.pg-infected sera) may be initially added to a microtiter plate with an immobilized peptide, and after washing, a labeled anti-chicken antibody as a secondary antibody may be added to the plate. Alternatively, in combination with an antibody to a peptide-specific antibody, competitive ELISA may also be performed where a sample and a labeled anti-peptide (immobilized antigen) antibody are added simultaneously or separately or, in case that an anti-peptide antibody is not labeled, a labeled secondary antibody to an anti-peptide antibody is added.
Immobilization of a peptide on a microtiter plate may be carried out by letting the peptide left to stand at an amount of an antigen of 1-10 μg/ml at room temperature (around 25° C.) for 30 minutes to 2 hours or at a lower temperature (around 4° C.) for 12 to 24 hours. A blocking reagent for preventing a non-specific reaction may include Block Ace (SNOW BRAND MILK PRODUCTS CO., LTD.), blocking reagent for ELISA (Roche Diagnostics K.K.), a bovine serum albumin solution, a skim milk solution, and the like and may appropriately be selected. For washing after each of the reactions, PBS, TBS, or their mixture with Polysolbate (Tween 20) or a conservative (sodium azide) may be used and, for stopping the reaction, 2 to 3 molar sulfuric acid may be used. A secondary antibody may be an anti-chicken IgG labeled with HRP, fluorescent, RI or biotin. For instance, an anti-chicken IgG-HRP (Bethyl Laboratories, Inc.) as commercially available may be used. For instance, a substrate of HRP may include OPD (orthophenylenediamine) and TMBZ (3,3′,5,5′-tetramethylbendizine) where absorbance is measured at 492 nm and 450 nm, respectively.
ELISA by two-antibody sandwich may also be used where an antibody to a peptide is initially immobilized on a microtiter plate and the peptide is bound to said antibody. For this ELISA, either a polyclonal antibody or a monoclonal antibody to the peptide may be used. A polyclonal antibody may be obtained by the same procedure as described for immunized sera above. An animal for use in immunization may include chicken, rat, guinea pig, hamster, dog, monkey, and the like. A monoclonal antibody may be obtained by isolating antibody-producing cells such as splenocytes or lymphocytes from an animal immunized with A.pg cells or a polypeptide, and fusing these cells with myeloma cells in accordance with Milstein et al. (Method Enzymol., 73, 3-46, 1981) to prepare hybridomas producing an antibody to the peptide for use in the present invention. Also, a technique for preparing an antibody with the use of phage display library (Phage Display of Peptides and Proteins: A Laboratory Manual Edited by Brian K. Kay et al., Antibody Engineering: A PRACTICAL APPROACH Edited by J. McCAFFERTY et al., ANTIBODY ENGINEERING second edition edited by Carl A. K. BORREBAECK) may be utilized to prepare an antibody to the peptide for use in the present invention.
A method for measuring an anti-A.pg antibody by the thus established ELISA may be used for detecting an antibody induced by a vaccine or A.pg infection. The present invention is explained in more detail by means of the following Examples but should not be construed to be limited thereto.
Genomic DNA libraries were prepared from A.pg-A 221 strain and A.pg-C 53-47 strain in accordance with the method of Tokunaga et al. (Japanese Patent Publication No. 10-84969). Briefly, chromosomal DNAs were extracted from cells collected by centrifuge (8,000 rpm, 20 minutes) using SepaGene kit (Sanko Junyaku Co., Ltd.), and digested with restriction enzyme Sau3AI to prepare DNA libraries. Using DNA fragments from the DNA libraries as a template, PCR was performed with LA Taq (TAKARA BIO Inc.) in accordance with protocol attached thereto to amplify fragments each consisting of a portion of the A.pg-1.3 gene. PCR reaction was carried out with LA PCR kit vert (TAKARA SHUZO CO., LTD.) at 96° C. for 1 minute; then 30 cycles of at 96° C. for 40 seconds, at 56° C. for 60 seconds, and at 72° C. for 120 seconds; and at 72° C. for 10 minutes.
Each of the DNA fragments obtained in Example 1 was digested with suitable restriction enzymes and after separation on 0.8% agarose electrophoresis the amplified fragments were eluted and recovered with Quantum Prep Freeze N Squeeze DNA Gel Extraction Spin Co kit. The obtained fragments were ligated to plasmid pQE30 (QIAGEN: 6 His-tag sequences (SEQ ID NO: 23) are present immediate downstream the initiation codon) or pET22b, which has been digested with the same restriction enzymes as above and the 5′-end of which has been dephosphorylated. The resulting plasmids were used to transform E. coli JM109 strain. E. coli comprising the amplified fragments was cultured overnight in Circle Grow medium (Funakoshi Co., Ltd.) supplemented with ampicillin and on the next day IPTG was added at a final concentration of 1 mM for further culture for 2.5 hours. After centrifuge (10,000 rpm, 5 minutes), supernatant was discarded and precipitate was suspended in an amount of 1/10 relative to the culture of Lysis Buffer A (8 M urine, 100 mM NaH2PO4, 10 mM Tris, 10 mM Imidazole, pH 8.0) to dissolve the cells. After centrifuge (15,000 rpm, 15 minutes), supernatant of cell lysate was collected. The collected supernatant of cell lysate was mixed with 1 mL of Ni-NTA agarose gel for absorption to the gel and filled in a column attached with a bottom stopper. After washing the column, a fraction eluted with an eluate (8 M urine, 100 mM NaH2PO4, 10 mM Tris, 100 mM Imidazole, pH 8.0) was collected and sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) was conducted. Among the A.pg-A- and A.pg-C-derived fragments,
The polypeptide P-AΔ5-1 obtained in Example 2 was diluted with PBS to 10 μg/dose and added with aluminum hydroxide at a final concentration of 20%. The resultant mixture was administered subcutaneously to SPF chickens of 5 weeks old at the neck twice at an interval of 3 weeks for immunization. For the other polypeptides P-AΔ3-0, P-AΔ5-0, P-CΔ5-1 and P-CΔ6-0, they were diluted with PBS to 10 μg/dose and emulsified with an oil adjuvant (0.01 g antigen, 0.001 mL or less formalin, 0.01 mL Polysolbate 80, 0.04 mL sorbitan sesquioleate, 0.36 mL light liquid paraffin, the remainder phosphate buffer per dose (0.5 mL)) and the resultant mixture was once administered subcutaneously to SPF chickens of 5 weeks old at the neck. The chickens at 9-11 weeks old were bled to give immunized sera to each of the polypeptides.
The polypeptides P-AΔ6b-1b, P-AΔ6b-2#, P-AΔ7b-1b and P-CΔ6b-1b obtained in Example 2 were diluted with 50 mM bicarbonate buffer to 1.0-2.5 μg/mL and each 100 μL of the solution was added to 96-well plate for immobilization. After absorption at room temperature for 1 hour, the reaction solution was discarded, and the plate was washed with 200 μL of PBS-T (8.1 mM disodium hydrogenphosphate, 1.5 mM potassium dihydrogenphosphate, 137 mM sodium chloride, 2.7 mM potassium chloride, 0.05% Tween 20) and added with 200 μL of PBS-T supplemented with 5% skim milk for blocking. The blocking solution was discarded. Serum was diluted with PBS-T supplemented with 1% skim milk to 50- to 100-fold and each 100 μL of the solution was added to each well for reaction at room temperature for 1 hour. After removing the reaction solution, the plate was washed with PBS-T three times. An anti-chicken IgG-HRP-labeled antibody was diluted with PBS-T supplemented with 1% skim milk to 10,000- to 20.000-fold and each 100 μL of the solution was added to each well for reaction at room temperature for 1 hour in the dark. After removing the reaction solution, the plate was washed with PBS-T three times. Each 100 μL of a substrate solution (100 mM citrate, 200 mM disodium hydrogenphosphate, 0.004% orthophenylenediamine, hydrogen peroxide) was added for reaction at room temperature for 30 minutes. Each 100 μL of 3M sulfuric acid was added to stop the reaction. Absorbance at the wavelength of 492 nm was measured with 96-well plate reader (Molecular Devices Japan). The results are shown in Table 2.
The polypeptide P-AΔ6b-1b which comprises an amino acid sequence homologous between the amino acid sequence of amino acids Nos. 243-271 of SEQ ID NO: 1 from Region 2 of A.pg-A and the amino acid sequence of amino acids Nos. 38-68 of SEQ ID NO: 2 from Region 2 of A.pg-C (among 31 amino acid residues, 30 amino acid residues are common; cf.
A commercially available oil adjuvant vaccine with an inactivated cell (Oilvacks 7; Juridical Foundation The Chemo-Sero-Therapeutic Research Institute) and a vaccine of the same composition as Oilvacks 7 excepting that A.pg antigen (inactivated A.pg-A and A.pg-C) was replaced with the polypeptides AΔ5-1 and CΔ5-1 obtained in Example 2 were prepared and subcutaneously injected once to SPF chickens of 5 weeks old at the neck. For the commercially available vaccine, in addition to 1 dose, its dilutions to 1/100 and 1/1,000 were also administered. For the polypeptides, a vaccine containing a mixture of the A.pg-A- and A.pg-C-derived polypeptides, each diluted to 3, 0.3 and 0.03 μg/chicken, was administered. After blood was taken from the chickens at 9 weeks old, 0.2 mL of a solution of A.pg-A 211 strain (1.5×109 CFU/mL) or A.pg-C 53-47 strain (5.0×109 CFU/mL) was administered intranasally to the chickens and clinical symptoms such as swelling of the face, a running nose and epiphora were observed for 1 week.
The obtained sera were subject to ELISA value as described below. The polypeptides P-AΔ6b-2# and P-CΔ6b-1b obtained in Example 2 were diluted with 50 mM bicarbonate buffer to 1.0 μg/mL and each 50 μL of the solution was added to 96-well plate for immobilization. After absorption at 4° C. overnight, the reaction solution was discarded, and the plate was washed with 300 μL of PBS-T (8.1 mM disodium hydrogenphosphate, 1.5 mM potassium dihydrogenphosphate, 137 mM sodium chloride, 2.7 mM potassium chloride, 0.05% Tween 20) and added with 300 μL of PBS-T supplemented with 5% skim milk for blocking. The blocking solution was discarded. Serum was diluted with PBS-T supplemented with 5% skim milk to 1,000-fold and each 50 μL of the solution was added to each well for reaction at room temperature for 1 hour. After removing the reaction solution, the plate was washed with PBS-T three times. An anti-chicken IgG-HRP-labeled antibody was diluted with PBS-T supplemented with 5% skim milk to 25,000-fold and each 50 μL of the solution was added to each well for reaction at room temperature for 30 minutes in the dark. After removing the reaction solution, the plate was washed with PBS-T three times. Each 100 μL of a substrate solution (TMB+substrate-chromogen; DAKO Corp.) was added for reaction at room temperature for 15 minutes. Each 100 μL of 3M sulfuric acid was added to stop the reaction. Absorbance at the wavelength of 450 nm was measured with 96-well plate reader (Molecular Devices Japan).
As shown in
The method for detection of the present invention may be used for testing immune condition of chickens immunized with a vaccine consisting of a polypeptide comprising the amino acid sequence as used in the present invention. Also, the method for detection of the present invention may be used for studying a mechanism of outbreak of disease or epidemiology by measuring sera from chickens suffering from avian infectious coryza through infection with A.pg.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2008-029589 | Feb 2008 | JP | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/JP2009/052091 | 2/6/2009 | WO | 00 | 8/9/2010 |
| Publishing Document | Publishing Date | Country | Kind |
|---|---|---|---|
| WO2009/099204 | 8/13/2009 | WO | A |
| Number | Name | Date | Kind |
|---|---|---|---|
| 6544519 | Tokunaga et al. | Apr 2003 | B1 |
| 20030027987 | Tokunaga et al. | Feb 2003 | A1 |
| Number | Date | Country |
|---|---|---|
| 64-467 | Jan 1989 | JP |
| 10-84969 | Apr 1998 | JP |
| 2002-154983 | May 2002 | JP |
| 2005-218414 | Aug 2005 | JP |
| WO 9812331 | Mar 1998 | WO |
| Number | Date | Country | |
|---|---|---|---|
| 20110201034 A1 | Aug 2011 | US |
