Abstract:
The present invention relates to cDNAs encoding murine antibodies against apolipoprotein B-100, the protein moiety of low density lipoprotein(LDL) in human plasma. In addition, the present invention relates to the method of preparation of recombinant antibodies specific for human plasma apolipoprotein B-100 of LDL, and use thereof, for diagnosis and treatment of cardiovascular diseases.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is a divisional of U.S. patent application Ser. No. 08/634,783 filed Apr. 19, 1996, now U.S. Pat. No. 5,861,276. 
    
    
     TECHNICAL FIELD 
     The present invention relates to cDNAs encoding murine monoclonal antibody against apolipoprotein B-100, the protein of low-density lipoproteins(LDL) in human plasma. 
     More specifically, the present invention relates to cDNAs encoding heavy chain and light chain of murine monoclonal antibody which recognizes and binds to apolipoprotein B-100. Apolipoprotein B-100 is the major protein moiety of LDL which plays an important role in the plasma lipid metabolism, transporting cholesterol from liver to necessary peripheral tissue. 
     BACKGROUND OF ART 
     Apolipoprotein B-100, the protein of low density lipoproteins in human plasma, is reported to be a more reliable positive index than former cholesterol index of LDL-cholesterol, for diagnosis of cardiovascular diseases, such as arteriosclerosis, coronary artery disease, and the like [Brustolin, D. et al., Clin. Chem. 37: 742-747 (1991); Dona, V. et al., Giorn. It. Chim. Clin. 12: 205-214 (1987)]. 
     The specific monoclonal antibody can be used as a diagnostic agent to measure the concentration of apolipoprotein B-100 in blood conveniently and reliably for the global risk estimation of cardiovascular diseases. In addition the specific monoclonal antibody against apolipoprotein B-100 can be used for specific binding and removal of the high level of blood LDL for the treatment of cardiovascular diseases. Therefore, it is necessary to produce specific monoclonal antibodies against apolipoprotein B-100. 
     SUMMARY OF THE INVENTION 
     The object of the present invention is to provide cloned cDNAs, which encode antigen-binding fragment(Fab) of murine monoclonal antibodies binding specifically with human plasma apolipoprotein B-100. These monoclonal antibodies are MabB9 with IgG2b heavy chain and kappa light chain, and MabB23 with IgG2b heavy chain and lambda light chain. The hybridoma cells producing MabB9 and MabB23, H-MabB9 and H-MabB23, respectively, have been deposited with the Korean Collection for Type Cultures, Genetic Engineering Research Institute (&#34;GERI&#34;), KIST, P.O. Box 115, Yusong, Taejon, 305-600, Republic of Korea, as accession numbers KCTC 0104 BP (H-MabB9) and KCTC 0105 BP (H-MabB23) on Mar. 23, 1994 [Reference Patent Application #94-12084, Republic of Korea, May 31, 1994] 
     The object of the present invention is to provide cDNAs of heavy chain gene(B9H) (SEQ ID NO: 1) and light chain gene(B9L) (SEQ ID NO: 2), which encode antigen-binding fragment (Fab) of murine monoclonal antibody, MabB9, and to provide cDNAs of heavy chain gene(B23H) (SEQ ID NO: 3) and light chain gene(B23L) (SEQ ID NO: 4), which encode the Fab fragment of murine monoclonal antibody, MabB23. 
     And the object of the present invention is to provide Escherichia coli transformant, TG1/pB9HT7, containing the vector pB9HT7, in which the heavy chain gene, B9H (SEQ ID NO: 1), is inserted(depositary authority: Korean Collection for Type Cultures, Genetic Engineering Research Institute, KIST, P.O. Box 115, Yusong, Taejon, 305-600, Republic of Korea; accession number: KCTC 0197 BP; accession date: Oct. 6, 1995) and E. Coli transformant, TG1/pB9LBlue, containing the vector pB9LBlue, in which the light chain gene, B23H (SEQ ID NO: 3), is inserted(depositary authority: Korean Collection for Type Cultures, Genetic Engineering Research Institute, KIST, P.O. Box 115, Yusong, Taejon, 305-600, Republic of Korea; accession number: KCTC 0198 BP; accession date: Oct. 6, 1995). 
     And the object of the present invention is to provide E. coli transformant, TG1/pB23HT7, containing the vector pB23HT7, in which the heavy chain gene, B23H (SEQ ID NO: 3), is inserted(depositary authority: Korean Collection for Type Cultures, Genetic Engineering Research Institute, KIST, P.O. Box 115, Yusong, Taejon, 305-600, Republic of Korea; accession number: KCTC 0199 BP; accession date: Oct. 6, 1995) and E. coli transformant, TG1/pB23LBlue, containing the vector pB23LBlue, in which the former light chain gene, B23L (SEQ ID NO: 4), is inserted(depositary authority: Korean Collection for Type Cultures, Genetic Engineering Research Institute, KIST, P.O. Box 115, Yusong, Taejon, 305-600, Republic of Korea; accession number: KCTC 0199 BP; accession date: Oct. 6, 1995). 
     In addition, the object of the present invention is to provide the method of preparation of recombinant antibody against human plasma lipoprotein B-100 by expressing the cloned cDNAs via the construction of an expression vector for appropriate host cells such as E. coli. 
     In addition, the object of the present invention is to provide the use of recombinant antibody against human plasma apolipoprotein B-100 for diagnosis of cardiovascular diseases by allowing measurement of the concentration of human plasma apolipoprotein B-100. 
     In addition, the object of the present invention is to provide the use of recombinant antibody against human plasma apolipoprotein B-100 for treatment of cardiovascular diseases by allowing the specific binding and removal of the high level LDL or other apolipoprotein B-100 containing harmful substances from blood. 
     In the following, the present invention will be described in detail. 
    
    
     BRIEF DESCRIPTION OF FIGURES 
     FIG. 1 shows the structure and restriction map of pB9HT7 vector containing 690 bp cDNA SEQ. ID No. 1 of the heavy chain (B9H) of murine monoclonal antibody, MabB9, against human plasma apolipoprotein B-100, prepared according to this invention. 
     FIG. 2 shows the structure and restriction map of pB9LBlue vector containing 642 bp cDNA SEQ. ID No. 2 of the light chain (B9L) of murine monoclonal antibody, MabB9, against human plasma apolipoprotein B-100, prepared according to this invention. 
     FIG. 3 shows the structure and restriction map of pB23HT7 vector containing 693 bp cDNA SEQ. ID No. 3 of the heavy chain (B23H) of murine monoclonal antibody, MabB23, against human plasma apolipoprotein B-100, prepared according to this invention. 
     FIG. 4 shows the structure and restriction map of pB23LBlue vector containing 642 bp CDNA SEQ. ID No. 4 of the light chain (B23L) of murine monoclonal antibody, MabB23, against human plasma apolipoprotein B-100, prepared according to this invention. 
     FIG. 5 shows nucleotide sequence SEQ ID NO: 1 and deduced amino acid sequence of CDNA (B9H) encoding the heavy chain of murine monoclonal antibody, MabB9, against human plasma apolipoprotein B-100, prepared according to this invention. CDR 1, 2, 3 sequences within V-region and C H  1-region (from nucleotide No. 355) are underlined. Unusual amino acids found when compared with those of mouse heavy chain subgroup II(B) are indicated with dotted line under the very amino acid. 
     FIG. 6 shows nucleotide sequence SEQ ID NO: 2 and deduced amino acid sequence of cDNA (B9H) encoding light chain of murine monoclonal antibody, MabB9, against human plasma apolipoprotein B-100, prepared according to this invention. CDR 1, 2, 3 sequences within V-region and C K  1-region (from nucleotide No. 322) are underlined. 
     FIG. 7 shows nucleotide sequence SEQ ID NO: 3 and deduced amino acid sequence of cDNA (B23H) encoding the heavy chain of murine monoclonal antibody, MabB23, against human plasma apolipoprotein B-100, prepared according to this invention. CDR 1, 2, 3 sequences within V-region and C H  1-region (from nucleotide No. 358) are underlined. Unusual amino acids found when compared with those mouse heavy chain subgroup I(B) are indicated with dotted line under the very amino acid. 
     FIG. 8 shows nucleotide sequence SEQ ID NO: 4 and deduced amino acid sequence of cDNA (B23L) encoding the light chain of murine monoclonal antibody, MabB23, against human plasma apolipoprotein B-100, prepared according to this invention. CDR 1, 2, 3 sequences within V-region and C.sub.λ 1-region (from nucleotide No. 331) are underlined. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Hybridoma cells producing murine monoclonal antibody against human plasma apolipoprotein B-100 are cultured with optimal media, such as RPMI medium, (Sigma, R-6504) and harvested. Then, the total RNAs of the cells are extracted by acid guanidium thiocyanate-phenol-chloroform method and the like. Also, the poly(A) +   RNA is purified by oligo(dT)-cellulose chromatography method [Aviv, H. and Leder, P., Proc. Natl. Acad. Sci. USA, 69: 1408-1412, 1972]. 
     Next, the first strand of cDNA is synthesized by using reverse transcriptase and oligo(dT) 15  primer. In order to get the cDNAs encoding heavy chain and light chain of antibody, polymerase chain reaction(PCR) is performed by Taq DNA polymerase using the specific oligonucleotide primers corresponding to N-terminal and C-terminal sequences of the heavy and light chains of antibody. The N-terminal primer used is synthesized according to the data obtained from N-terminal sequencing of the purified heavy and light chain proteins of the antibody, and the C-terminal primer used is obtained according to the constant region sequences of the heavy and light chains of the antibody. 
     The DNA fragments obtained by the polymerase chain reactions are cloned into proper vectors, such as pT7Blue(Novagen, USA) and pBluescript(Stratagene, USA). Nucleotide sequences of the cloned cDNAs are determined by chain termination method using dideoxy nucleotides and the like [Sanger, F. et al., Proc. Natl. Acad. Sci. USA, 76: 4350-4354, 1977]. 
     The following examples will further illustrate the present invention, which by no means limit the present invention. 
     EXAMPLE 1 
     mRNA purification from hybridoma cells producing monoclonal antibodies against human plasma apolipoprotein B-100 
     The hybridoma cells, H-MabB9(depositary authority: Korean Collection for Type Cultures, Genetic Engineering Research Institute, KIST, P.O. Box 115, Yusong, Taejon, 305-600, Republic of Korea; accession number: KCTC 0104 BP; accession date: Mar. 23, 1994) producing monoclonal antibody MabB9 (IgG2b, kappa) against human plasma apolipoprotein B-100, and H-MabB23(depositary authority: Korean Collection for Type Cultures, Genetic Engineering Research Institute, KIST, P.O. Box 115, Yusong, Taejon, 305-600, Republic of Korea; accession number: KCTC 0105 BP; accession date: Mar. 23, 1994) producing monoclonal antibody MabB23 (IgG2b, lambda) were made by the process, wherein pancreatic cells of Balb/c mouse and myeloma cell that has been previously immunized with human apolipoprotein B-100 were fused with the myeloma cells of Sp2/O-Ag-14 by the well-established hybridoma technique established well [Kohler, G. and Milstein, C., Nature, 256: 495-497, 1975; Galfre, G. et al., Nature, 256: 550-552, 1977]. These hybridoma cells were cultured in optimal media, such as RPMI medium (Sigma, R-6504), and harvested. 
     Then, the total cellular RNA was extracted by acid guanidium thiocyanate-phenol-chloroform method [Puissant, C. and Houdebine, L. M., Biotechnique, 8: 148-149, 1990]. 
     And the poly (A)+RNA was purified by oligo(dT)-cellulose chromatography method [Aviv, H. and Leder, P., Proc. Natl. Acad. Sci. USA, 69: 1408-1412, 1972] 
     EXAMPLE 2 
     N-terminal amino acid sequencing of heavy and in light chains of monoclonal antibody MabB9 against human plasma apolipoprotein B-100. 
     Murine monoclonal antibody MabB9 against human plasma apolipoprotein B-100 was mixed with Laemmli&#39;s sample buffer [Laemmli, E. K., Nature, 227: 680-685, 1970], including mercaptoethanol. The antibody was separated by SDS-polyacrylamide gel electrophoresis and transferred onto PVDF membrane by electroblotting method [Towbin, H. et al., Proc. Natl. Acad. Sci. USA, 76: 4350-4354, 1979). Then, about 50-kD band corresponding to the heavy chain and 25-kD band corresponding to light chain of monoclonal antibody MabB9 were cut to analyze their N-terminal amino acid sequences by amino acid sequence analyzer. 
     As a result, the N-terminal amino acid sequence of the heavy chain of monoclonal antibody MabB9 was determined as E-V-Q-L-V-E--S--G-A-E SEQ. ID No. 5 and that of the light chain of MabB9 was determined as D-I-K-M-T-Q--S--P--S--S SEQ. ID No. 6. 
     EXAMPLE 3 
     N-terminal amino acid sequencing of heavy and light chains of monoclonal antibody MabB23 against human plasma apolipoprotein B-100. 
     Murine monoclonal antibody MabB23 against human plasma apoliporotein B-100 was incubated with Laemmli&#39;s sample buffer. The antibody was separated by SDS-polyacrylamide gel electrophoresis and transferred onto PVDF membrane by electroblotting method. Then, about 50-kD band corresponding to the heavy chain and 25-kD band corresponding to light chain of monoclonal antibody MabB23 were cut to analyze their N-terminal amino acid sequences by amino acid sequence analyzer. 
     As a result, the N-terminal amino acid sequence in heavy chain of monoclonal antibody MabB23 was determined as E-V-Q-L-V-E--S--G-P-G SEQ. ID No. 7 and that in light chain of monoclonal antibody MabB23 as Q-A-V-V-T-Q-E--S--A-L SEQ. ID No. 8. 
     EXAMPLE 4 
     cDNA cloning of heavy and light chains of murine monoclonal antibody MabB9 against human plasma apolipoprotein B-100. 
     To synthesize the first strand of cDNA, 1 μg of poly (A) +   RNA of H-MabB9 Hybridoma cell purified in Example 1 was incubated with 1 mM each of 4 dNTPs, 50 units of RNasin (Boehringer Mannheim, USA), 80 pmoles of oligo d(T) 15  primer and 15 unit of AMV reverse transcriptase in 20 μl of the reaction buffer [50 mM KCl, 50 mM Tris-Cl(pH8.3), 10 mM MgCl 2 , 1 mM spermidine, 10 mM DTT, 4 mM sodium pyrophosphate] at 42° C. for 1 hr. Then, N-terminal and C-terminal oligonucleotide primers and 2 units of Taq DNA polymerase were added to perform the polymerase chain reaction (PCR). The N-terminal oligonucleotide primers were synthesized according to the codons of N-terminal amino acid sequences determined in Example 2, and the C-terminal oligonucleotide primers were synthesized according to the constant region sequences of IgG2b heavy chain and kappa light chain of monoclonal antibody MabB9. The PCR was performed according to the steps, wherein the reaction mixture was incubated initially at 94° C. for 15 sec, at 57° C. for 10 sec and at 72° C. for 15 sec, and then at 94° C. for 5 sec, at 57° C. for 10 sec, at 72° C. for 15 sec sequentially and repeatedly for 33 cycles, and finally at 94° C. for 15 sec, at 57° C. for 10 sec and at 720C for 120 sec. As a result, 690 bp of DNA fragment corresponding to Fab region of the heavy chain of monoclonal antibody MabB9 was obtained. The DNA fragment was cloned into pT7Blue(Novagene, USA) phagemid vector to construct pB9HT7 containing B9H, the heavy chain cDNA of monoclonal antibody MabB9. The structure and restriction map of pB9HT7 is shown in FIG. 1. 
     Likewise, 642 bp DNA fragment corresponding to the light chain of monoclonal antibody MabB9 was obtained and cloned into pBluescript(Stratagene, USA) phagemid vector to construct pB9LBlue containing B9L, light chain cDNA of monoclonal antibody MabB9. The structure and restriction map of pB9LBlue is shown in FIG. 2. 
     With the above described vectors, Escherichia coli TG1 strains were transformed to obtain TG1/pB9HT7 and TG1/pB9LBlue. And the strains were deposited with the Korean Collection for Type Cultures, Genetic Engineering Research Institute, KIST, P.O. Box 115, Yusong, Taejon, 305-600, Republic of Korea, on Oct. 6, 1995(respective accession numbers: KCTC 0197 BP and KCTC 0198 BP). 
     EXAMPLE 5 
     CDNA cloning of heavy and light chains of murine monoclonal antibody MabB23 against human plasma apolipoprotein B-100 
     1 μg of poly(A) +   RNA of H-MabB23 hybridoma cell purified in Example 1 was incubated with AMV reverse transcriptase, and the same method as described in Example 4 was performed to synthesize the first strand cDNA. Then, N-terminal oligonucleotide primers synthesized according to the N-terminal amino acid sequencing data obtained in Example 3 for the heavy and light chains of monoclonal antibody MabB23, and C-terminal oligonucleotide primers synthesized according to the constant region sequences of the IgG2b heavy chain and lambda light chain, were added to perform the PCR reactions using the same reaction conditions as described in Example 4. 
     As a result, 693 bp DNA fragment corresponding to Fab region of the heavy chain of monoclonal antibody MabB23 was obtained. The DNA fragment was cloned into pT7Blue vector to construct pB23HT7 containing B23H, the heavy chain cDNA of monoclonal antibody MabB23. The structure and restriction map of pB23HT7 is shown in FIG. 3. 
     Likewise, 642 bp DNA fragment corresponding to the light chain of monoclonal antibody MabB23 was obtained, and cloned into pBluescript vector to construct pB23LBlue containing B23L, the light chain cDNA of monoclonal antibody MabB23. The structure and restriction map of pB23LBlue is shown in FIG. 4. 
     With the above-described vectors, Escherichia coli TG1 strain was transformed to obtain TG1/pB23HT7 and TG1/pB23LBlue. The strains were deposited with the Korean Collection for Type Cultures, Genetic Engineering Research Institute, KIST, P.O. Box 115, Yusong, Taejon, 305-600, Republic of Korea, on Oct. 6, 1995 (respective accession number: KCTC 0199 BP and KCTC 0200 BP) 
     EXAMPLE 6 
     Nucleotide sequencing of heavy chain CDNA of murine monoclonal antibody MabB9 against human plasma apolipoprotein B-100 
     To determine the nucleotide sequence of the heavy chain cDNA of the murine monoclonal antibody MabB9 against human plasma apolipoprotein B-100, double stranded or single stranded phagemid DNA of pB9HT7 which contains the heavy chain cDNA(B9H) cloned in Example 4 was purified by SDS-alkaline extraction method [Birnboim, H. C., Methods Enzymol., 100: 243-255, 1983]. Nucleotide sequence of the antibody cDNA was determined by chain termination method using dideoxy nucleotides [Sanger, F. et al., Proc. Natl. Acad. Sci. USA, 74: 5463-5467, 1977], wherein the nucleotide sequence was fully determined on both orientations using M13 universal primer or synthetic internal primers. 
     The determined nucleotide sequence SEQ ID NO: 1 of MabB9 heavy chain cDNA in MabB9 is shown in FIG. 5. When compared with the reported immunoglobulin heavy chain cDNA sequences, it was found that the heavy chain CDNA of MabB9, B9H, belongs to mouse heavy chain subgroup II(B) [Kabat, E. A. et al., Sequences of Proteins of Immunological Interest, 5th ed., US Department of Human Services, Public Health Service, National Institute of Health, Bethesda, Md., 1991]. The V(variable)-region was located between amino acid number(No.) 1 and No. 118 and CH1-region located from No. 119. And V-region also contained unique CDR(complementarity determining sequences) 1, 2, 3 sequences, located between amino acid No. 31 and No. 35 (CDR 1), between No. 50 and No. 66 (CDR 2) and between No. 99 and No. 107 (CDR 3), which confer antigen- binding specificity. 7 Cysteine residues were found at amino acid numbers 22, 96, 133, 145, 200, 227 and 230, which would participate in disulfide bonding to form Fab structure of antibody. 
     When compared with the V-region sequence profiles of mouse heavy chain subgroup II(B) [Harris, L. and Bajorath, J., Protein Sci. 4: 306-310, 1995], some unusual amino acids were found at the following locations: Met (No. 13), Thr(No. 25), Thr(No. 48) and Phe (No. 70). 
     EXAMPLE 7 
     Nucleotide sequencing of light chain cDNA of murine monoclonal antibody MabB9 against human plasma apolipoprotein B-100. 
     To determine the nucleotide sequence of the light chain cDNA of the murine monoclonal antibody MabB9 against human plasma apolipoprotein B-100, double stranded or single stranded phagemid DNA of pB9LBlue which contains the light chain cDNA (B9L) cloned in Example 4 was purified by the SDS-alkaline extration method [Birnboim, H. C., 1983]. Nucleotide sequence of the antibody cDNA was determined by the chain termination method using dideoxy nucleotides [Sanger, F. et al., 1977], wherein the nucleotide sequence was fully determined on both orientations using M13 universal primer or synthetic internal primers. 
     The nucleotide sequence SEQ ID NO: 2 of MabB9 light chain cDNA is shown in FIG. 6. When compared with the reported immunoglobulin light chain cDNA sequences, it was found that the light chain cDNA of MabB9, B9L, belongs to mouse kappa chain subgroup V [Kabat, E. A. et al., 1991]. The V-region was located between amino acid No. 1 and No. 107 and C K  -region located from No. 108. And V-region also contained unique CDR 1,2,3 sequences, located between amino acid No. 24 and No. 34 (CDR 1), between No. 50 and No. 56 (CDR 2) and between No. 89 and No. 97 (CDR 3), which confer antigen-binding specificity. 5 Cysteins were found at amino acid numbers 23, 88, 134, 194 and 214, which would participate in disulfide bonding to form Fab structure of antibody. 
     As illustrated in Example 6 and Example 7, cDNAs encoding the heavy chain and light chain of the antigen-binding fragment (Fab) of monoclonal antibody MabB9 (IgG2b, kappa) against apolipoprotein B-100, the protein moiety of low-density lipoproteins(LDL) was shown to have all the requirements of antibody. Unique CDR sequences and some unusual amino acids were also found. These results strongly suggest that the cDNAs are functional. 
     The sequences were submitted to the GenBank/EMBL Data Libraries and have acquired the accession numbers of U28968 (heavy chain CDNA of MabB9; B9H, SEQ ID NO: 1) and U28969 (light chain cDNA of MabB9; B9L, SEQ ID NO: 2)(The sequences release date is Jan. 1, 1997). 
     EXAMPLE 8 
     Nucleotide sequencing of heavy chain CDNA of murine monoclonal antibody MabB23 against human plasma apolipoprotein B-100. 
     To determine the nucleotide sequence of heavy chain CDNA, B23H in murine monoclonal antibody MabB23 against human plasma apolipoprotein B-100, double stranded or single stranded phagemid DNA of pB23HT7 which contains the heavy chain cDNA (B23H) cloned in Example 5 was purified. Then, the same method as described in Example 6 was performed for nucleotide sequencing SEQ ID NO: 3. 
     The determined nucleotide sequence of MabB23 heavy chain cDNA in MabB23 is shown in FIG. 7. When compared with the reported immunoglobulin heavy chain cDNA sequences, it was found that the heavy chain cDNA of MabB23, B23H, belongs to mouse heavy chain subgroup I(B) [Kabat, E. A. et al., 1991]. The V-region was located between amino acid No. 1 and No. 119 and C H  1-region located from No. 120. And the V-region contained unique CDR 1,2,3 sequences, located between amino acid No. 31 and No. 35 (CDR 1), between No. 50 and No. 65 (CDR 2) and between No. 98 and No. 108 (CDR 3), which confer antigen-binding specificity. 7 Cysteins were found at amino acid numbers 22, 95, 134, 146, 201, 228 and 231, which would participate in disulfide bonding to form Fab structure of antibody. 
     When compared with V-region sequence profiles of mouse heavy chain subgroup I(B) [Harris, L. and Bajorath, 1995], some unusual amino acids were found at the following locations: Glu (No. 1), Val (No. 5) and Val (No. 96). A new amino acid in the heavy chain constant region, Arg(AGG) at amino acid No. 133 instead of Gly(GGG) was found, which has not been hitherto reported. 
     EXAMPLE 9 
     Nucleotide sequencing of light chain cDNA of murine monoclonal antibody MabB23 against human plasma apolipoprotein B-100. 
     To determine the nucleotide sequence of light chain cDNA of the murine monoclonal antibody MabB23 against human plasma apolipoprotein B-100, double stranded or single stranded phagemid DNA of pB23LBlue which contains light chain CDNA (B23L) cloned in Example 5 was purified. Then the same method as described in Example 6 was performed for nucleotide sequencing. 
     The determined nucleotide sequence SEQ ID NO: 4 of MabB23 light chain cDNA is shown in FIG. 8. When compared with the reported immunoglobulin light chain cDNA sequence, it was found that the light chain cDNA of MabB23, B23L belongs to a typical mouse lambda chain [Kabat, E. A. et al., 1991]. The V-region was located between amino acid No. 1 and No. 110 and C.sub.λ -region located from No. 111. And the V-region contained unique CDR 1,2,3 sequences, located between amino acid No. 23 and No. 36 (CDR 1), between No. 52 and No. 58 (CDR 2), and between No. 91 and No. 99 (CDR 3), which confer antigen- binding specificity. 5 Cysteins were found at amino acid numbers 22, 90, 137, 196 and 214, which would participate in disulfide bonding to form Fab structure of antibody. 
     As illustrated in Example 8 and Example 9, cDNAs encoding the heavy chain and light chain of the antigen-binding fragment (Fab) of monoclonal antibody MabB23 (IgG2b, lambda) against apolipoprotein B-100, the protein moiety of low-density lipoproteins(LDL) were shown to have all the sequence requirements of antibody. Unique CDR sequences and some unusual amino acids were also found. These results strongly suggest that the cDNAs are functional. 
     The sequences were submitted to the GenBank/EMBL Data Libraries and have acquired the accession numbers of U28970 (heavy chain cDNA of MabB23; B23H SEQ ID NO: 3) and U28967 (light chain cDNA of MabB23; B23L SEQ ID NO: 4)(The sequences release date is Jan. 1, 1997). 
     cDNAs of the present invention can be used for expression in microorganisms of the recombinant Fab antibodies specific for human plasma apolipoprotein B-100 of LDL. The recombinant antibodies can be utilized as a diagnostic agent to measure the concentration of plasma apolipoprotein B-100, a positive index for cardiovascular diseases and in global risk assessment of the disease. In addition, the recombinant antibodies can be used for development of an immunotherapeutic protein which can specifically bind with the harmful LDL-containing substances in blood for subsequent removal from circulation in relation to the development of arterosclerosis. 
     
         __________________________________________________________________________#             SEQUENCE LISTING  - -  - - (1) GENERAL INFORMATION:  - -    (iii) NUMBER OF SEQUENCES: 8  - -  - - (2) INFORMATION FOR SEQ ID NO:1:  - -      (i) SEQUENCE CHARACTERISTICS:      (A) LENGTH: 690 base - #pairs      (B) TYPE: nucleic acid      (C) STRANDEDNESS: double      (D) TOPOLOGY: linear  - -     (ii) MOLECULE TYPE: cDNA  - -     (xi) SEQUENCE DESCRIPTION: SEQ ID NO:1:  - - GAGGTGCAGC TGGTGGAGTC TGGAGCTGAG CTGATGAAGC CTGGGGCCTC AG -#TGAAGATA     60   - - TCCTGCAAGG CTACTGGCTA CACATTCAGT AGCTACTGGA TAGAGTGGAT AA -#AGCAGAGG    120   - - CCTGGACATG GCCTTGAGTG GACTGGAGAG ATTTTACCTG GAAGTGGTAC TA -#CTAAATAC    180   - - AATGAGAAGT TCAAGGACAA GGCCACATTC ACTGCAGATA CATCCTCCAA CA -#CAGCCTAC    240   - - ATGCAACTCA GCAGCCTGAC ATCTGAGGAC TCTGCCGTCT ATTACTGTGC AA -#GATCGTAT    300   - - AGGTACGCCC CTATGGACTA CTGGGGTCAA GGAACCTCAG TCACCGTCTC CT -#CAGCCAAA    360   - - ACAACACCCC CATCAGTCTA TCCACTGGCC CCTGGGTGTG GAGATACAAC TG -#GTTCCTCC    420   - - GTGACTCTGG GATGCCTGGT CAAGGGCTAC TTCCCTGAGT CAGTGACTGT GA -#CTTGGAAC    480   - - TCTGGATCCC TGTCCAGCAG TGTGCACACC TTCCCAGCTC TCCTGCAGTC TG -#GACTCTAC    540   - - ACTATGAGCA GCTCAGTGAC TGTCCCCTCC AGCACCTGGC CAAGTCAGAC CG -#TCACCTGC    600   - - AGCGTTGCTC ACCCAGCCAG CAGCACCACG GTGGACAAAA AACTTGAGCC CA -#GCGGGCCC    660   - - ATTTCAACAA TCAACCCCTG TCCTCCATGC         - #                  - #   690  - -  - - (2) INFORMATION FOR SEQ ID NO:2:  - -      (i) SEQUENCE CHARACTERISTICS:      (A) LENGTH: 642 base - #pairs      (B) TYPE: nucleic acid      (C) STRANDEDNESS: double      (D) TOPOLOGY: linear  - -     (ii) MOLECULE TYPE: cDNA  - -     (xi) SEQUENCE DESCRIPTION: SEQ ID NO:2:  - - GATATCAAGA TGACCCAGTC TCCATCTTCC ATGTATGCAT CTCTAGGAGA GA -#GAGTCACT     60   - - ATCACTTGCA AGGCGAGTCA GGACATTTAT AGCTATTTAA GCTGGTTCCA GC -#AGAAACCA    120   - - GGGAAATCTC CTAAGACCCT GATCTATCGT GCAAACAGAT TGGTCGATGG GG -#TCCCATCA    180   - - AGGTTCAGTG GCAGTGGATC TGGGCAAGAT TATTCTCTCA CCATCAGCAG CC -#TGGAGTAT    240   - - GAAGATCTGG GAATTTATTA TTGTCTACAG TTTGATGAGT TTCCGTACAC GT -#TCGGAGGG    300   - - GGGACCAAGC TGGAAATAAA ACGGGCTGAT GCTGCACCAA CTGTATCCAT CT -#TCCCACCA    360   - - TCCAGTGAGC AGTTAACATC TGGAGGTGCC TCAGTCGTGT GCTTCTTGAA CA -#ACTTCTAC    420   - - CCCAAAGACA TCAATGTCAA GTGGAAGATT GATGGCAGTG AACGACAAAA TG -#GCGTCCTG    480   - - AACAGTTGGA CTGATCAGGA CAGCAAAGAC AGCACCTACA GCATGAGCAG CA -#CCCTCACG    540   - - TTGACCAAGG ACGAGTATGA ACGACATAAC AGCTATACCT GTGAGGCCAC TC -#ACAAGACA    600   - - TCAACTTCAC CCATTGTCAA GAGCTTCAAC AGGAATGAGT GT    - #    - # 642  - -  - - (2) INFORMATION FOR SEQ ID NO:3:  - -      (i) SEQUENCE CHARACTERISTICS:      (A) LENGTH: 693 base - #pairs      (B) TYPE: nucleic acid      (C) STRANDEDNESS: double      (D) TOPOLOGY: linear  - -     (ii) MOLECULE TYPE: cDNA  - -     (xi) SEQUENCE DESCRIPTION: SEQ ID NO:3:  - - GAGGTGCAGC TGGTGGAGTC AGGACCTGGC CTGGTGGCGC CCTCACAGAG CC -#TGTCCATC     60   - - ACGTGCACTG TCTCAGGGTT CTCATTAACC GACTATGGTG TAAGCTGGAT TC -#GCCAGCCT    120   - - CCAGGAAAGG GTCTGGAGTG GCTGGGAGTA ATTTGGGCTG GTGGAAGCAC AT -#TCTATAAT    180   - - TCAGCTCTCA AGTCCAGACT GAGCATCAAC AAGGACAACT CCAAGAGCCA AG -#TTTTCTTA    240   - - AAAATGAACA GTCTGCACAC TGATGACACA GCCATGTACT ACTGTGTCAA AC -#ATGAGGAT    300   - - AGGTACGACT GGTACTTCGA TGTCTGGGGC GCAGGGACCA CGGTCACCGT CT -#CCTCAGCC    360   - - AAAACAACAC CCCCATCAGT CTATCCACTG GCCCCTAGGT GTGGAGATAC AA -#CTGGTTCC    420   - - TCCGTGACTC TGGGATGCCT GGTCAAGGGC TACTTCCCTG AGTCAGTGAC TG -#TGACTTGG    480   - - AACTCTGGAT CCCTGTCCAG CAGTGTGCAC ACCTTCCCAG CTCTCCTGCA GT -#CTGGACTC    540   - - TACACTATGA GCAGCTCAGT GACTGTCCCC TCCAGCACCT GGCCAAGTCA GA -#CCGTCACC    600   - - TGCAGCGTTG CTCACCCAGC CAGCAGCACC ACGGTGGACA AAAAACTTGA GC -#CCAGCGGG    660   - - CCCATTTCAA CAATCAACCC CTGTCCTCCA TGC       - #                  -#        693   - -  - - (2) INFORMATION FOR SEQ ID NO:4:   - -      (i) SEQUENCE CHARACTERISTICS:       (A) LENGTH: 642 base - #pairs       (B) TYPE: nucleic acid       (C) STRANDEDNESS: double       (D) TOPOLOGY: linear   - -     (ii) MOLECULE TYPE: cDNA   - -     (xi) SEQUENCE DESCRIPTION: SEQ ID NO:4:   - - CAGGCTGTTG TGACTCAGGA ATCTGCACTC ACCACATCAC CTGGTGAAAC AG -#TCACACTC     60   - - ACTTGTCGCT CAAATACTGG GGCAGTTACA ACTAGTAACT ATGCCAGCTG GG -#TCCAAGAA    120   - - AAACCAGATC ATTTATTCAC TGGTCTAATA GGTGGTACCA ACAACCGAGT TC -#CAGGTGTT    180   - - CCTGCCAGGT TCTCAGGCTC CCTGATTGGA GACAAGGCTG CCCTCACCAT CA -#CAGGGGCA    240   - - CAGACTGAGG ATGAGGCAAT ATATTTCTGT GCTCTATGGA ACAGCAACCA CT -#GGGTGTTC    300   - - GGTGGAGGAA CCAAACTGAC TGTCCTAGGC CAGCCCAAGT CTTCGCCATC AG -#TCACCCTG    360   - - TTTCCACCTT CCTCTGAAGA GCTCGAGACT AACAAGGCCA CACTGGTGTG TA -#CGATCACT    420   - - GATTTCTACC CAGGTGTGGT GACAGTGGAC TGGAAGGTAG ATGGTACCCC TG -#TCACTCAG    480   - - GGTATGGAGA CAACCCAGCC TTCCAAACAG AGCAACAACA AGTACATGGC TA -#GCAGCTAC    540   - - CTGACCCTGA CAGCAAGAGC ATGGGAAAGG CATAGCAGTT ACAGCTGCCA GG -#TCACTCAT    600   - - GAAGGTCACA CTGTGGAGAA GAGTCTGTCT CGTGCTGACT GT    - #    - # 642  - -  - - (2) INFORMATION FOR SEQ ID NO:5:  - -      (i) SEQUENCE CHARACTERISTICS:      (A) LENGTH: 10 amino - #acids      (B) TYPE: amino acid      (C) STRANDEDNESS: single      (D) TOPOLOGY: unknown  - -     (ii) MOLECULE TYPE: peptide  - -     (xi) SEQUENCE DESCRIPTION: SEQ ID NO:5:  - - Glu Val Gln Leu Val Glu Ser Gly Ala Glu 1               5   - #                10  - -  - - (2) INFORMATION FOR SEQ ID NO:6:  - -      (i) SEQUENCE CHARACTERISTICS:      (A) LENGTH: 10 amino - #acids      (B) TYPE: amino acid      (C) STRANDEDNESS: single      (D) TOPOLOGY: unknown  - -     (ii) MOLECULE TYPE: peptide  - -     (xi) SEQUENCE DESCRIPTION: SEQ ID NO:6:  - - Asp Ile Lys Met Thr Gln Ser Pro Ser Ser 1               5   - #                10  - -  - - (2) INFORMATION FOR SEQ ID NO:7:  - -      (i) SEQUENCE CHARACTERISTICS:      (A) LENGTH: 10 amino - #acids      (B) TYPE: amino acid      (C) STRANDEDNESS: single      (D) TOPOLOGY: unknown  - -     (ii) MOLECULE TYPE: peptide  - -     (xi) SEQUENCE DESCRIPTION: SEQ ID NO:7:  - - Glu Val Gln Leu Val Glu Ser Gly Pro Gly 1               5   - #                10  - -  - - (2) INFORMATION FOR SEQ ID NO:8:  - -      (i) SEQUENCE CHARACTERISTICS:      (A) LENGTH: 10 amino - #acids      (B) TYPE: amino acid      (C) STRANDEDNESS: single      (D) TOPOLOGY: unknown  - -     (ii) MOLECULE TYPE: peptide  - -     (xi) SEQUENCE DESCRIPTION: SEQ ID NO:8:  - - Gln Ala Val Val Thr Gln Glu Ser Ala Leu 1               5   - #                10__________________________________________________________________________