[Study on allelic characteristics of "homozygote" resulted from low resolution genotyping of HLA-Cw locus].

OBJECTIVE: To study the allelic characteristics of "homozygote" resulted from low resolution genotyping of HLA-Cw locus and to provide more precise typing data for clinical transplantation. METHODS: Forty three related allogeneic hematopoietic stem cell transplantation(allo-HSCT) donors and patients with HLA-Cw * 03, Cw * 07 homozygote, which were the most common gene groups in Chinese population, identified by low resolution genotyping level were retyped by high resolution PCR-SSP genotyping method, and three dimensional structure modelling was also made by using a solely developed HLA three-dimensional matching software (HLA strucMark version 1.0) to evaluate the effect of differences between two mismatched alleles and its relationship with GVHD occurrence. RESULTS: The typing results of high resolution level demonstrated that the confirmed allelic homozygotes for Cw * 03 and Cw * 07 were 14% and 43%, respectively, while the others were all heterozygotes. The ambiguous typing results could be confirmed by family data study or by high resolution typing methods when there was no family data available, Three-dimensional modeling results of the mismatched alleles undetected in low resolution typing level indicated that family data study or high resolution PCR-SSP genotyping were important in preventing graft-versus-host disease. CONCLUSIONS: When HLA-Cw homozygote results were found in low resolution genotyping method, the results should be reconfirmed by family data study or by high resolution typing methods to provide precise typing results for avoiding severe graft-versus-host disease.

[Prokaryotic expression of HLA-B * 2705 heavy chain and identification for its activity].

In order to investigate the expression of heavy chain of HLA-B * 2705 in prokaryotic system and identify its activity, the extra-membrane gene fragment of HLA-B * 2705 was amplified from full-length HLA-B*2705 cDNA by PCR and cloned into pGEM-T vector. After identification by sequencing, the prokaryotic expressing vector pET32a (+)-B * 2705 was constructed. The antigenic activity of expressed protein was identified by Western blot and antibody blocking reaction. The results indicated that the fused HLA-B * 2705 protein expression with high efficiency was obtained. The expressed product was more than 50% of the total bacteria protein. The antigenic activity of expressed protein was confirmed by Western blot and antibody blocking reaction. It is concluded that HLA-B * 2705 fusion protein are obtained as basis for the further studies.

[Haplotype and linkage analysis of HLA-I classical genes in Chinese Han population].

The aim of this study was to investigate the parameters of gene frequencies, haplotype frequencies and linkage disequilibrium of HLA-A, -B, -Cw in HLA classical I loci for Chinese Han population. HLA-A, HLA-B and HLA-Cw loci were genotyped in 1014 unrelated China people using low resolution PCR-SSP typing method, and their genetic parameters were analyzed by statistic methods. The results indicated that among all the detected HLA-I genes, A*02 (0.33), A*11 (0.24), B*15 (0.14), B*13 (0.13), Cw*03 (0.25) and Cw*07 (0.18) were the popular gene groups distributing in Chinese Han population, and A*02-B*46 (0.071), A*11-B*15 (0.051), A*02-Cw*01 (0.084), A*11-Cw*03 (0.079), B*46-Cw*01 (0.095) and B*13-Cw*03 (0.071) were the predominant haplotypes in Han population. Additionally, A*02-B*46, A*30-B*13, A*30-Cw*06, A*02-Cw*01, B*46-Cw*01 and B*58-Cw*03 were statistically significant with strong linkage disequilibrium. While A*02-B*15, A*02-B*40, A*24-Cw*03, A*02-Cw*03 and A*31-Cw*03 were in low linkage disequilibrium, among them A*24-Cw*03 appeared frequently in HLA recombination events. In addition, A*02-B*46-Cw*01 (0.075), A*30-B*13-Cw*06 (0.046), A*11-B*13-Cw*03 (0.045), A*33-B*58-Cw*03 (0.044), A*11-B*15-Cw*08 (0.027), A*02-B*38-Cw*07 (0.023) and A*11-B*40-Cw*07 (0.022) were the main extended haplotypes in Han population. In conclusions, this study investigated systematically the genetic polymorphism features of Chinese Han population, which may provide useful genetic parameters for researches in colonial evolution, clinical transplantation and disease susceptibility.

[Genetic polymorphism of HLA-Cw locus in hematopoietic stem cell transplantation patient and donor population].

OBJECTIVE: To analyze the distribution of genes in HLA-Cw locus from Han population of China in a large scale, and to provide basic data for further study on the genetic characteristics of HLA-Cw locus of this population. METHODS: Totally 1285 unrelated Chinese Han individuals were typed by PCR-SSP, and statistics was utilized to investigate the distribution rules of detected genes. RESULTS: Twenty-three HLA-Cw alleles were identified in Chinese Han population, out of them HLA-Cw*01, *03, *07 and *08 were the commonest genes, which accounted for frequencies of 0.1529, 0.2385, 0.1747 and 0.1004, respectively. Five genes which could not be identified by serological method were deaed: HLA-Cw*12, *14, *15, *16 and *17. Hardy-Weinberg test showed that the observed genetic polymorphism distribution values were correspondent with the expected (chi-square=73.74, df=98, P>0.5). CONCLUSION: This study may serve a full-scale scientific genetic parameters of HLA-Cw genes for Chinese Han population studies.

[Therapeutic effect of a novel recombinant vaccine encoding chicken collagen type II procollagen gene on collagen-induced arthritis in rat].

OBJECTIVE: To investigate the therapeutic effect of gene vaccine encoding chicken collagen type II (CC II) on collagen-induced arthritis (CIA) comprehensively. METHODS: Three groups (CIA) were given a single intravenous injection of plasmid pcDNA-CCOL2A1 (20 microg/kg, 200 microg/kg, 400 microg/kg) respectively and one group (CIA) was injected 200 microg/kg pcDNA3.1 as a control. The effect of gene vaccine (pcDNA-CCOL2A1) was evaluated according to the arthritis score, radiological and histological examinations. RESULTS: The severity of arthritis of CIA rats which were administered 200 microg/kg pcDNA-CCOL2A1 was significantly reduced from the fifth day. According to the radiological and histological examinations, the articular cartilage as well as subchondral bone trabeculae are similar to those of the normal groups, so the bone and articular cartilage structure were protected after treatment with 200 microg/kg pcDNA-CCOL2A1 with a little synovial hyperplasia. The therapeutic effect of 200 microg/kg pcDNA-CCOL2A1 group has significant difference in comparison with that of the pcDNA3.1 group (P < 0.05) and the arthritis scores are reduced to about 50% of those in control groups, but 20 microg/kg group and 400 microg/kg group has no therapeutic effect in our observation (P > 0.05). CONCLUSION: The new gene vaccine pcDNA-CCOL2A1 has significant therapeutic effect on CIA rats, and the treatment may therefore be an effective strategy for RA patient clinically.

[An unusual recombination event occurring between HLA-B and -Cw loci within a Chinese Han family].

OBJECTIVE: To investigate the recombination event occurring between HLA-B and -Cw loci discovered in a family of Chinese Han nationality with an acute myeloid leukemia (AML) patient. METHODS: Peripheral blood samples were collected from a Chinese man with M5 type AML, aged 39, and his healthy wife and daughter, all of Han nationality. HLA class I (-A, -B, and -Cw) and II (-DRB1 and -DQB1) alleles were typed by both low and high resolution PCR with sequence specific primers (PCR-SSP) and sequence-based typing (SBT). Then the recombination sites were analyzed by family study. RESULTS: The 2 haplotypes of the patient, his daughter, and his wife were A*2402101-Cw*030401/0402-B*1301-DRB1*0406-DQR1*030302/0303 and A*02011-Cw*150201/0202-B*4002-DRB1*1405-DQB1*05031, A*02011-Cw*150201/0202-B*1301-DRB1*0406-DQB1*030302/0303 and A*2406-Cw*0602-B*1302_DRB1*070101/0102-DQB1*0202, and A*330301/0302-Cw*030201/0202-B*58-1-DRB1*17-DQB1*0202 and A*2406-Cw*0602-B*1302-DRB1*070101/0102-B*5801-DRB1*0202 respectively. Family study demonstrated that A*02011-Cw*150201/0202 recombination and B*1301-DRB1*030302/0303 recombination carried by the daughter came from the 2 isolated chromosomes of her father, indicating that the recombination event occurred between HLA-B and -Cw loci during meiosis of the father and resulted in a new HLA haplotype that was inherited by the daughter. CONCLUSION: An unusual HLA-B/Cw recombination event occurring between HLA-B and -Cw loci has been found in a Han family, which helps further study the mechanisms of HLA recombination.

[Establishment of purification procedure for recombinant fusion protein B7-2-PE40KDEL].

This study was aimed to establish downstream purification procedure by which the protein of interest can be purified to higher purity rapidly and efficiently. The different combinations of various purification strategies, methods and conditions were compared, including reversed phase chromatography, metal chelating chromatography, anion exchange chromatography, blue dye affinity chromatography, filtration chromatography and so on. The results showed that in reversed phase chromatography, isolated protein of interest was denatured and precipitated immediately after chromatography because methanol or acetonitrile were adopted as the organic phase. In blue dye affinity chromatography expecting to purify the protein of interest in one step, protein of interest was difficultly differentiated from mixed protein as much proteins bound to the chromatography media by non-specific affinity. While there is a translation-enhancing sequence T7-g10 in the PRSETA-B7-2-PE40KDEL expression vector, so it adds 6 histidines to the N terminus of the protein of interest, this allows to purify the protein of interest by metal chelating chromatography. Based on this characteristic, a three-step chromatography line including metal chelating chromatography, anion exchange chromatography and filtration chromatography was finally established after repeated experiments. By this way the purity of protein of interest reached 95% and the total recovery rate was 8%. The result of Western blot indicated that the expressed and purified recombinant B7-2-PE40KDEL could specifically bind with mAb against human B7-2 and multiple antibody against PEA. The cytotoxicity of the recombinant toxin tested by MTT method showed that the B7-2-PE40KDEL could selectively kill Jurkat cell line expressing CD28 receptor well and had no killing effect on the Raji cell line unexpressing CD28 receptor. It is concluded that a high efficient and speedy three-step purification procedure for the purifying recombinant protein B7-2-PE40KDEL was established, and this procedure possess selective killing activity on CD28 positive T lymphocytes.

[Recombination within the human leucocyte antigen].

Understanding with greater clearness the characteristics of recombination within the human leucocyte antigen(HLA) is of deep significance to gaining an insight into the evolutionary process of shaping HLA allelic diversity and ultimately the human resistance against diverse pathogens. Family studies and statistical analysis of recombination have provided estimations of recombination fractions across the major histocompatibility complex and have identified the potential recombination hotspots. Other characteristics such as haplotype specificity and sequence motifs have been intensively studied. The recombination fractions, hotspots and other characters are reviewed in this paper.

[A preliminary study on the expression and biological function of recombinant human SCF-TPO fusion protein].

OBJECTIVE: To study the expression of recombinant human SCF-TPO fusion protein and its biological function. METHODS: Four primers were designed according to known sequences of TPO and SCF. The functional amino acid domains of TPO and SCF were amplified by RT-PCR from fetus hepatocytes, respectively. The expression plasmid pET32a/SCF-TPO was constructed by VOE gene fusion technique and expressed in E. coli BL21(DE3) plysS as inclusion body after isopropyl-beta-D-1-thiogalactopyranoside (IPTG) induction. The fusion protein was tested by SDS-PAGE and Western blot. The biological functions of SCF-TPO fusion protein in MO7e cells was investigated by MTT method after purification with metal chelating chromatography. RESULTS: The high expression SCF-TPO fusion protein was obtained, reaching up to 30% of the total cellular protein. Western blot verified the correct fusion expression and MTT results showed the growth promoting effect of the SCF-TPO fusion protein on MO7e cells, with a higher promoting activity at 100 ng/ml. CONCLUSIONS: Expressed SCF-TPO fusion protein after renaturation has biological activity in promoting the proliferation of MO7e cells.

[Biochemical and physical properties for a recombinant IL6 Pseudomonas exotoxin fusion protein IL6D24-PE40KDEL].

The objective was to identify some biochemical and physical properties for fusion protein IL6D24-PE40KDEL. Edman degradation, SDS-PAGE, peptide mass fingerprinting, Western blot and MTT were used for identification of the protein. The results showed that the sequence of N-terminus is Met-Ile-Asp-Lys-Gln-Ile, Met was added because of prokaryotic expression system; Western blot revealed that the purified protein could react with IL6 and PEA antibody. The purified protein IL6D24-PE40KDEL could kill the multiple myeloma cell lines U266 expressing high affinity IL6R, but it could not kill the cell lines CEM which not expressed IL6R; The molecular weight was 58.7 kD measuring by SDS-PAGE; peptide mass fingerprinting (PMF) confirmed that the construction of IL6D24-PE40KDEL was correct. A novel protein by Peptident database in EXPASY web site was identified. In conclusion, IL6D24-PE40KDEL is a new targeting protein with bioactivity of specific killing effect.

[Fusion construction, prokaryotic expression and structure characteristics prediction of bimolecular thrombopoietin].

AIM: Design, construction, expression in E coli and protein characteristics prediction of bimolecular thrombopoietin (T-T) with more stability, efficiency, and lower toxicity. METHODS: The expression vectors of TPO and T-T, pET32 a(+)/TPO and pET32 a (+)/T-T, had been constructed by molecular cloning methods. Then, they were expressed in host bacterium. Their products were identified by Western blot. The protein characteristics, such as second structure, antigenicity, hydrophilicity, flexibility and isoelectric point, were predicted by DS Gene and Protscale software. RESULTS: The expressing vectors pET32a(+)/TPO and T-T were constituted correctly and expressed in origami (DE3), and their expression efficiency were more than 40 percent of total protein. T-T was identified correctly by Western blot. DS Gene and Protscale software predict the protein characteristics of TPO sequences in T-T molecule were no change, there was high flexibility in the linker domain. But two amino acids in T-T molecule have been mutated, and an insert fragment with 34 amino acids following the linker had antigenicity, hydrophilicity, and beta-sheet structure. CONCLUSION: We have constructed correctly and expressed T-T with high level in E Coli. Protein characteristics prediction of T-T accords with our design.

[Molecular design and construction of IL6D24-PE40KDEL, a novel recombinant interleukin6-pseudomonas exotoxin fusion protein, having targeted cytotoxicity for leukemias expressing interleukin6 receptors].

OBJECTIVE: A novel recombinant interleukin6-Pseudomonas exotoxin fusion protein, having targeted cytotoxicity for leukemic cells highly expressing IL6R has been molecularly designed and constructed in this study. METHODS: Firstly, REDLK at C-terminus of Pseudomonas exotoxin PE40 was replaced with KDEL using point mutagenesis technology. Secondly, a cDNA encoding interleukin-6 devoid of N-terminal 24 amino acids [IL6D24] was fused to 5' terminus of PE40KDEL DNA by the method of gene splicing by overlap extension, which could generate recombinant IL6D24-PE40KDEL and IL6D24-Linker-PE40KDEL fusion genes. Thirdly, recombinant fusion genes IL6D24-PE40KDEL and IL6D24-Linker-PE40KDEL were ligated into the EcoR I and Sma I cloning sites in the pBV220 plasmids respectively and then transformed into E.coli HB101 cells. The expressed recombinant exotoxin fusion proteins were purified to electrophoresis purity by Mono Q column chromatography. Its selectively killing was tested by the MTS colorimetric method using both U937 and CEM cells lines. RESULTS: Recombinant exotoxin fusion proteins IL6D24-PE40KDEL was expressed as a form of inclusion bodies at higher level of 40% approximately of total proteins in bacterial cells. Western blot showed that the purified products could react specifically with IL6 monoclonal antibody and PEA antiserum, respectively. IL6D24-PE40KDEL was selectively cytotoxic to U937 cells expressing IL6R-positive with ID50 of 250 ng/ml, and but not CEM cells expressing IL6R-negative. CONCLUSIONS: Two novel recombinant interleukin6-Pseudomonas exotoxin fusion proteins IL6D24-PE40KDEL and IL6D24-Linker-PE40KDEL have been successfully constructed and they can selectively kill the leukemic cells expressing highly IL6R.

[Clinical application for reference strand mediated conformation analysis system in HLA-A genotyping].

OBJECTIVE: To establish and stabilize a new HLA typing strategy, reference strand mediated conformation analysis (RSCA), and to conform its advantages by using HLA-A as target gene. METHODS: 20 standard DNA samples from international RSCA cooperative team were used to establish and stabilize RSCA. 84 DNA samples of related hematopoietic stem cell transplant donor-recipients were extracted from peripheral blood cells. HLA-A loci were typed both by RSCA and PCR-SSP. RESULTS: RSCA results of 20 standard samples were identical to those of international RSCA cooperative team, and the accuracy and replication rate were both 100%. Among the 84 samples, 82/84 (97.6%) cases could be designated definitely, and 33/84 (39%) cases could be typed to allelic level. In addition, 2/84 (2.4%) cases could not be detected by RSCA for their poor PCR results. 20 samples were randomly selected to identify the replication rate of RSCA, and the results demonstrated that the replication rate was 100%. Among the PCR-SSP typing results, there were about 10% samples needed to be typed for 1 - 3 times to confirm their types. CONCLUSION: RSCA has some advantages compared with the PCR-SSP typing method, which are high resolution, high sensitivity, high accuracy, high replication, capability to find new alleles, high throughput, low cost and suitability for unrelated hematopoietic stem cell transplant donor-recipient HLA typing. But there are still some defects in this new strategy, which are time-consuming for only one sample a time and higher DNA quality requirement. In addition, RSCA database needs to be further improved.

[Cloning, expression and biological activity identification of a cDNA encoding the extracellular region of human b7-2].

As one important member of B7/CD28/CTLA-4 costimulatory signal pathway, B7-2 molecule plays a critical role in regulating T-cell response. In order to further explore its effects on regulation of T cell activation, proliferation and associated signal pathways, the cDNA encoding extracellular region of human B7-2 was amplified via PCR and subcloned into some prokaryotic expression vectors to express target protein in host strains. The expressed protein was identified with Western blot and MTT. Results showed that after screening, the expression level of the protein of interest attained the yield of over 20% total bacterial protein by using pGEX-4T-2 vector and E. coli BL21 (DE3)-CodonPlus-RIL host cells. The recombinant protein could specially react with B7-2 McAb and could stimulate T-cell proliferation combined with anti-CD3 antibody. In conclusion, the recombinant protein was bioactive, therefore the study will make it possible for the research of relationship between B7-2 structure and its function.

[Selection of donor in mismatched hematopoietic stem cell transplantation by CREG, residue match and HLA three-dimensional structure].

After search at hematopoietic stem cell banks for transplant donors, there may be several donors matched with given standards. To determine the most appropriate donor for a specific patient, the potential donors were analyzed and compared by three methods. The first is cross-reactive group (CREG) antigens, which defined as the public antigens that shared specific serological reaction patterns. The second is residue match theory, which concerned the three residues oriented upward toward the T-cell receptor. The third is comparing HLA three-dimensional structure models. The results of the three methods were not completely accorded in our case. However, some less matched donors could be excluded from the candidates and the range of selection was further reduced. It is concluded that combined application of three methods would contribute in selecting donor for hematopoietic stem cell transplantation in clinics.

[The probability of microbiological contamination during the collection and processing of umbilical cord blood].

To study the pathogens incidences in cord blood and the efficiency of different detective methods, 60 samples were drawn and reserved from collected and processed cord blood, respectively. The BACTEC 9050 system, improved Martin/thioglycollate broth (22 degrees C) and thioglycollate broth (35 degrees C) were employed to detected bacteria (including fungus) at the same time. Two hundred and six cord blood serum samples were used to detect the HBV DNA and HCV RNA by molecular biology technique, HBsAg, Anti-HBC, Anti-HCV, Anti-HCMV-IgM, HTLV-1, HTLV-2, HIV-1 and HIV-2 by ELISA and RBC agglutination test were used to detect the TPHA. Results showed that using BACTEC 9050 system, the incidence of bacteria and fungus was 3.33% and 0% respectively in collected cord blood; in processed cord blood, the rates increased to 6.67% and 1.67%, respectively. The sensitivity of BACTEC 9050 was higher than that of Martin/thioglycollate broth (22 degrees C/35 degrees C) culture. In 206 serum samples, the positive rate of HBV DNA was 5.8%, HCV RNA was 2.4%, HBsAg was 2.4%, HCMV-IgM was 1.89%, HCV was 2.4% and Anti-HBC was 29.4%. In those samples that Anti-HBC was positive, the positive rate of HBV DNA was 6.7%. It was concluded that the incidences of microbiological contamination in cord blood were high. The routine culture system would lead to false negative results of obligate anaerobes. It was necessary to replace the current culture system with improved system, such as BACTEC 9050 system. The molecular biology technique would make up for the default of ELISA.