Advances in the study of site-specific antibody-drug conjugates / 药学学报

Antibody drug conjugates (ADCs) are an emerging class of targeted therapeutics with the potential to improve therapeutic index over the traditional chemotherapy. However, it is difficult to control the site and stoichiometry of conjugation in mAb, typically resulting in heterogeneous mixtures of ADCs that are difficult to optimize. New methods for site-specific drug attachment allow development of more homogeneous conjugates and control of the site of drug attachment. In this article, the new literature on development of ADCs and site-specific ADCs is reviewed. In addition, we summarized the various strategies in production of site-specific ADCs.

Detection of alloantibodies against Factor VIII in plasma of patients with hemophilia A and its relationship with Factor VIIIC domain / 中国实验血液学杂志

This study was purposed to detect the alloantibodies against Factor VIII (FVIII) by ELISA for estimating the incidence of the alloantibodies against Factor VIII (FVIII) in patients with hemophilia A, and to investigate the relationship between factor VIIIC domain and alloantibodies. Total of 140 patients with hemophilia A and 80 normal controls were enrolled in this study, among them plasma FVIII level of 84 patients was less than 1%, plasma FVIII level of 34 patients was between 1% and 5%, and plasma FVIII level of 22 patients was more than 5%. All patients were treated with plasma-derived FVIII concentrate or plasma before. The ELISA plate was coated with McAb (SZ-132) against FVIII prepared in our laboratory, then human recombinant FVIII concentrates were applied. After incubation in room temperature for 2 hours, diluted plasma samples and HRP-conjugated goat anti-human IgG were added successively, finally A490 was recorded. The threshold of alloantibody of patient plasma was set as mean value>3 SD more than control. The plate was coated with antibody against His, then human recombinant FVIII-C1C2 prepared in our laboratory was added. After incubation in room temperature for 2 hours, diluted plasma samples and HRP-conjugated goat anti-human IgG were added successively, finally A490 were recorded. The threshold was set as the mean value>3 SD more than control. The results showed that the alloantibodies against FVIII were found in 56 patients (40%) by ELISA, and 82.1% (46/56) of this kind of alloantibody could interact with the C domain of FVIII. It is concluded that C domain of FVIII is one of the primary binding sites for the alloantibodies against FVIII in Chinese patients with hemophilia A.

The Significance and Limitation of C4d as a Biomarker in the Transplanted Kidney / 대한이식학회지

C4d is produced from the direct interaction between antibodies and tissue injury at an antibody binding site in a graft. C4d deposition along peritubular capillaries (PTCs) in a renal allograft is a characteristic finding of antibody-mediated rejection (AMR), and is a useful diagnostic tool of AMR. The C4d along PTCs is associated with poor graft survival. Therefore C4d is regarded as a biomarker of AMR and was included in the diagnosis criteria of AMR at 2007 Banff conference. However, although C4d assay is widely used, it has several limitations. ABO-incompatible transplantations develop C4d along the PTCs in the majority of grafts but this seems to be graft accommodation rather than AMR. Recent studies reported that more than half of renal allograft biopsies with chronic AMR were C4d-negative. Without treatment, the C4d-negative AMR can cause scarring within the graft, transplant glomerulopathy (TG) or even graft loss. C4d is not a certain indicator of antibody-mediated rejection and C4d staining is not always highly sensitive for detecting AMR. Measuring endothelial gene expression in kidney graft biopsies with alloantibody can be another sensitive and specific method to diagnose AMR and predict graft outcomes. Because of these complexities, at the 2011 Banff meeting, criteria for diagnosis of chronic AMR in the kidney were refined, and the need for inclusion of C4d-negative AMR in the Banff classification was investigated.

Identification of the IgE-binding epitopes in main dust mite allergen Der p 1 / 南方医科大学学报

<p><b>OBJECTIVE</b>To identify the IgE-binding epitopes in the allergen Der p 1 of main house dust mites, which can be recognized by the specific IgE in the sera from allergic individuals, and obtain a hypoallergen derived from the T-B epitope fused peptide for potential use in specific immunotherapy (SIT).</p><p><b>METHODS</b>Thirty-one peptides containing 15 amino acids each, which covered the full 222 amino acids of Der p 1 protein sequence, were synthesized on the cellulous membrane by solid-phase peptide (SPOTs) synthesis, with 8 overlapping amino acids between every two neighboring peptides. The membrane bearing the spots of the synthesized peptides were incubated with the allergic serum pools consisting of the sera from 5 allergic individuals. The membrane was then probed with HRP-conjugated anti-human IgE, followed by enhanced chemiluminescence (ECL) for visualization and gray scale analysis of the positive peptide spots.</p><p><b>RESULTS</b>Three strong IgE-binding epitopes were identified in the amino acid sequence of Der p 1 molecule, namely Ep1 (amino acids 85-99), Ep2 (amino acids 106-120) and Ep3 (amino acids 190-204).</p><p><b>CONCLUSION</b>The 3 IgE-binding epitopes (B cell epitopes) identified in Der p 1 confirm the presence of linear epitopes in Der p 1, suggesting the possibility of constructing T/B epitope-fused hypoallergens.</p>

Distribution and force spectroscopy of CD20 antigen-antibody binding on the B cell surface / 生物工程学报

The lower expression of CD20 antigen molecules on the B cell membrane is the primary characteristic of B-chronic lymphocytic leukemia (B-CLL). In this paper, we combined laser scanning confocal microscopy (LSCM) and quantum dots labeling to detect the expression and distribution of CD20 molecules on CD20+B lymphocyte surface. Simultaneously, we investigated the morphology and ultrastructure of the B lymphocytes that belonged to the normal persons and B-CLL patients through utilizing the atomic force microscope (AFM). In addition, we measured the force spectroscopy of CD20 antigen-antibody binding using the AFM tips modified with CD20 antibody. The fluorescent images indicated that the density of CD20 of normal CD20+B lymphocytes was much higher than that of B-CLL CD20+B cells. The AFM data show that ultrastructure of B-CLL CD20+B lymphocytes became more complicated. Moreover, the single molecular force spectroscopy data show that the special force of CD20 antigen-antibody was four times bigger than the nonspecific force between the naked AFM tip and cell surface. The force map showed that CD20 molecules distributed homogeneously on the normal CD20+B lymphocytes, whereas, the CD20 molecules distributed heterogenous on B-CLL CD20+B lymphocytes. Our data provide visualized evidence for the phenomenon of low-response to rituximab therapy on clinical. Meanwhile, AFM is possible to be a powerful tool for development and screening of drugs for pharmacology use.

Prokaryotic expression of recombinant Streptococcus suis IgG binding protein and its binding activity with IgG / 生物工程学报

Streptococcus suis (S. suis) IgG-binding protein (SPG) was present in all S. suis strains examined. It showed binding activities with IgG from various host species. Little was known about the biological role of this protein, but it was commonly believed that it acted as virulence factor. In this study, the genes encoding SPG were amplified respectively from the total DNA of the S. suis serotype 1/2, 1, 2 and 9 with PCR and expressed in Escherichia coli BL21 by plasmid pET28a as vector. The recombinant proteins were first purified with affinity chromatography (Ni-NTA), and further purified by sephadexG-200 gel chromatography. The recombinant SPG proteins were identified to have binding activities with IgG of different host species, and for human and porcine IgG they showed better binding activities. But the SPG from different serotypes of S. suis showed no great differences in their binding activities with IgG from the same host species.

Analysis of monoclonal antibody binding sites in ovine prion protein / 生物工程学报

Binding sites of five monoclonal antibodies were obtained by reinforceable method of overlapping recombinant prion protein and synthetic peptide. Overlapping peptides of PrP core were expressed in Escherichia coli by insertion of serial PCR amplicons of ovine PrP gene fragments into pET32a. The expressed fusion peptides were then tested for the binding activity to PrP monoclonal antibodies in Western blotting. The binding sites of 5 monoclonal antibodies of ovine PrP were located respectively as follows: 2H3 in 199 aa-213 aa, 4C6, 5F11 and 7F11 in 139 aa-168 aa and 7F1 in 214 aa-227 aa. There oligo peptides were synthesized and used in ELISA test for more accurate localization of the binding sites. The binding sites of 4C6, 5F11 and 7F11 were further confirmed to be in 149 aa-158 aa. This conclusion may contribute to the research for pathogenesis and diagnostic method of scrapie and bovine transmissible spongiform encephalopathy.

Comparison of predicted binders in Rhipicephalus (Boophilus) microplus intestine protein variants BM86 Campo Grande strain, BM86 and BM95 / Comparação da previsão de ligação das variantes de proteína de intestino de Rhipicephalus (Boophilus) microplus Bm86 cepa Campo Grande, Bm86 e Bm95

This paper reports the sequence analysis of Bm86 Campo Grande strain comparing it with Bm86 and Bm95 antigens from the preparations TickGardPLUS and GavacTM, respectively. The PCR product was cloned into pMOSBlue and sequenced. The secondary structure prediction tool PSIPRED was used to calculate alpha helices and beta strand contents of the predicted polypeptide. The hydrophobicity profile was calculated using the algorithms from the Hopp and Woods method, in addition to identification of potential MHC class-I binding regions in the antigens. Pair-wise alignment revealed that the similarity between Bm86 Campo Grande strain and Bm86 is 0.2 percent higher than that between Bm86 Campo Grande strain and Bm95 antigens. The identities were 96.5 percent and 96.3 percent respectively. Major suggestive differences in hydrophobicity were predicted among the sequences in two specific regions.

O objetivo deste estudo foi analisar a seqüência de Bm86 cepa Campo Grande comparando-a com os antígenos Bm86 e Bm95 das preparações TickGardPLUS e GavacTM, respectivamente. O produto de PCR foi clonado em PMOSBlue e seqüenciado. Para calcular os conteúdos de alfa-hélice e fita beta do polipeptídio previsto, foi utilizada a ferramenta de prognóstico de estrutura secundária PSIPRED. O perfil de hidrofobicidade foi calculado usando os algoritmos de Hopp e Woods, além da identificação das possíveis regiões de ligação com MHC classe I nos antígenos. O alinhamento "pair-wise" revelou que a similaridade entre Bm86 cepa Campo Grande e Bm86 é 0,2 por cento maior que aquela entre Bm86 cepa Campo Grande e Bm95. As identidades foram de 96,5 por cento e 96,3 por cento, respectivamente. Com relação à hidrofobicidade, os resultados sugerem que a maior diferença entre as seqüências está localizada em duas regiões específicas.

Comparison of antigenic sites of the envelope glycoprotein of the Iranian isolate of human T-cell leukemia virus type 1 with different subtypes of the virus

Human T-cell leukemia virus type 1 [HTLV-1] is an enveloped retrovirus, which is associated with a T-cell malignancy known as adult T-cell leukemia [ATL]. Variation in the HTLV-1 envelope nucleotide sequence has been extensively documented and has been used to classify HTLV-1 isolates into different subtypes. The virus occurs in at least 3 subtypes, which have been named A, B, and C. We conducted this study to compare the antigenic proprieties of the Iranian isolate of HTLV-1 with the homologous region of different subtypes of the virus. This study took place in the Department of Biology, College of Sciences, Shiraz University, Iran in 2005. The predicted antigenic sites and secondary structure of the envelope glycoprotein of HTLV-1, present in Iran, have been compared with the antigenic sites and secondary structure of the homologous domains in subtypes A, B, C of the virus. To predict the epitopes of glycoproteins, 21 different scales were used. The number of helices in the Iranian isolate was equal to the number of these regions in all 3 subtypes, but the number of beta-sheets was more than other viruses. One potential glycosylation site, on all these studied envelope glycoproteins, was predicted. Antigenic sites in the Iranian isolate were almost similar to subtype A of the virus and the Iranian isolate of HTLV-1 may be belongs to subtype A. Our results indicate the similarities and differences between the Iranian and other subtypes of HTLV-1. Antigenic sites represent potential candidates for use in a peptide vaccine against HTLV-1 glycoproteins and since most of the properties of a particular protein depend on its structural properties, this type of study can help in better understanding of HTLV-1 isolates present in Iran

Epitope mapping from real time kinetic studies - role of crosslinked disulphides and incidental interacting regions in affinity measurements: study with human chorionic gonadotropin and monoclonal antibodies.

Real time kinetic studies were used to map conformational epitopes in human chorionic gonadotropin (hCG) for two monoclonal antibodies (MAbs). The epitopes were identified in the regions (alpha 5--14 and alpha 55--62). The association rate constant (k+1) was found to be altered by chemical modification of hCG, and the ionic strength of the reaction medium. Based on these changes, we propose the presence of additional interactions away from the epitope- paratope region in the hCG-MAb reaction. We have identified such incidental interacting regions (IIRs) in hCG to be the loop region alpha 35--47 and alpha 60--84. The IIRs contribute significantly towards the KA of the interaction. Therefore, in a macromolecular interaction of hCG and its MAb, KA is determined not only by epitopeparatope interaction but also by the interaction of the nonepitopic-nonparatopic IIRs. However, the specificity of the interaction resides exclusively with the epitope-paratope pair.

Construction of a human Fab phage display library from antibody repertoires of osteosarcoma patients

Osteosarcoma is the commonest type of primary malignant bone tumor, frequently found in adolescents at sites of rapid bone growth. Despite current management protocols, up to half of the patients succumb to this disease. Moreover, there is no well-characterized molecular marker for diagnosis and prognosis. Since phage display methodology allows the selection of human antibody fragments with potential use in clinical applications, we applied this procedure to construct a recombinant Fab (antigen binding fragment) library from patients with osteosarcoma. We used peripheral blood lymphocyte total RNA from 11 osteosarcoma patients and cloned recombinant Fab representing the micro, gamma and kappa chain antibody repertoires of these individuals. The resulting library was cloned in the pComb3X vector and attained 1.45 x 10(8) different functional forms. BstO I fingerprinting and DNA sequencing analysis of randomly selected clones revealed the diversity of the library, demonstrating that Fab harbors Vkappa chains from subgroups I to V, biased towards the A27 fragment, as normally reported for the human repertoire. Analysis of the VH repertoire revealed that our library has a slight bias towards the VH4 family, instead of the usually reported VH3. This is the first description of a phage display library from osteosarcoma patients. We believe these human Fab fragments will provide a valuable tool for the study of this neoplasia and could also contribute to improvements in the diagnosis of this disease.

Progress in single-domain antibody derived from heavy-chain antibody / 生物工程学报

Functional heavy-chain antibodies (HCAbs) lacking light chains occur naturally in camels. The variable domain of heavy chain of heavy-chain antibody is referred to VHH. The VHH gene family is homologous to human VH subgroup III. The single-domain VHH antibodies are constructed by cloning the variable domains of HCAbs. Compared to human VHs, VHH germ-line sequences contain some hallmark substitutions in framework region 2, including V37F(Y), G44 E, L45 R, W47G. The substitutions at positions 44, 45, 47 are often used to camelise the human VHs. Being a small binders, VHH antibodies are well expressed, extremely stable and very soluble. Camelised human VHs are proved to exhibit the same qualities as those of VHH antibodies. The single-domain VHH antibodies will be useful in the drug development and basic research.

Antigenic analysis of the common recombinant mutant types of HBsAg / 中华实验和临床病毒学杂志

<p><b>BACKGROUND</b>To study the difference between the mutant types and the wild type of HBsAg on the binding efficiency with antibodies in order to find some methods to detect the mutants.</p><p><b>METHODS</b>The recombinant wild type of HBsAg and the mutants including 145 R, 133 T, 126 S, 141 E, 126 S+133 T, 126 S+133 T+145 R and 126 S+133 T+141 E were cloned, respectively. Then the expression vector containing the wild or mutant gene was transfected into COS7 cells, and the recombinant proteins were expressed. The proteins were detected with the routine HBsAg kits.</p><p><b>RESULTS</b>The binding efficiency with monoclonal antibodies of HBsAg expressed by 126 S was higher than that of the wild type, while the results of 145 R, 141 E, 126 S+133 T+145 R and 126 S+133 T+141 E were lower than that of the wild, and 133 T was similar to the wild. But most of the mutants had the same reactivity with the polyclonal antibody.</p><p><b>CONCLUSIONS</b>The effect of mutations on antibody binding differs depending on the amino acid involved and on the location within the "a" loop. So it is necessary to use polyclonal antibody or to find new kits to detect the mutants of HBsAg.</p>

Effect of serum dilution in diagnosis of malaria in community.

Recently, it has been shown that immunological methods can be used for the diagnosis of malaria other than sero-epidemiology. A study has been done to investigate optimum binding capacity of antigen-antibody (Ag-Ab) at different serum dilutions. For validating antigen-antibody (Ag-Ab) reaction at 1:100, 1:1000 and 1:1000 serum dilutions, have been tested in two different laboratories to establish validation of the ELISA method. Inter laboratory test on synthetic peptide (RI) ELISA was found comparable and meaningful for assessing malaria transmission in defined locality at 1:100 dilution. Results also showed that 1:1000 serum dilution can be useful for diagnostic purpose.

Serologic heterogeneity of HLA-A24 correlates with allelic types in the Korean population

HLA-A24 is the second most frequently expressed HLA-A type in Koreans (GF 22.8%). Four different serologic reaction patterns were observed in Korean A24 positive samples using a commercial serologic typing kit. To clarify the nature of serologic heterogeneity, thirteen A24 positive DNA samples representing the four different serologic reaction patterns were subjected to DNA sequencing analysis of the amplified HLA-A genes from each sample. Four A*24 alleles (A*2402101, A*2403, A*2408, and A*2421) were associated with the four unique serologic reaction patterns. During this study, a novel allele, A*2421, was characterized. The new sequence is similar to A*2402101, differing at codon 127 (AAA-->AAC; K-->N). By comparing putative amino acid sequences and serologic reaction patterns of A*24 allelic products identified in this study, several crucial sites for A24- and A9-specific antibody binding were predicted: 127K for A24 antibody binding, and 62E-65G and 166D-167G for A9 antibody binding. This information will be helpful for accurately assigning HLA-A24 types by serology and for predicting serologic types of new alleles.

Distribution of bradykinin B2 receptors in target cells of kinin action: visualization of the receptor protein in A431 cells, neutrophils and kidney sections

Peptides corresponding to sequences derived from predicted extra- and intracellular loops of the rat bradykinin receptor were analyzed for interspecies homology as well as for matches within the present dataset of protein sequences to provide a theoretical basis for the specific recognition of the native cognate protein by antibodies raised against these antigens. Apllication of polyclonal antibodies raised against the selected peptides allowed the immunocytochemical localization of the native receptor protein in cells of rat and human origin. The detection of the molecule was achieved by different immunohisto- and immunocytochemical methods in combination with light, fluorescence, confocal optical laser and electron microscopy. These results were compared to localization studies by autoradiography. Distribution and subcellular localization were determined in human neutrophils, human epithelial carcinoma cells (A431) and in rat kidney tissue

Competitive antibody binding inhibition ELISA for the detection of Plasmodium falciparum antigen.

A competitive antibody binding inhibition ELISA to detect Plasmodium falciparum-infected cells in clinical specimens was developed. Optimum conditions developed included: 12.5 micrograms/ml of P. falciparum antigen for plate coating, 25 micrograms/ml of polyclonal rabbit anti-P. falciparum IgG, 30 minute incubation of a mixture of infected red blood cell extract with anti-P. falciparum IgG, dilution of 1:500 of alkaline phosphatase-conjugated anti-rabbit IgG, and reading of the absorbance values 60 min after adding the p-nitrophenyl phosphate substrate. Reproducibility of the assay against cultured P. falciparum-infected red blood cells varied according to parasitemia, the higher the parasitemia, the better the reproducibility. The sensitivity of the assay was approximately 110 parasites/10(6) red blood cells. The assay was applied to field conditions involving 103 cases with falciparum malaria, 38 cases with vivax malaria and 30 healthy controls. With the 10% antibody binding inhibition as a cutoff, 87.4% of falciparum cases and 26.3% of vivax cases were positive. After treatment, the majority of cases became parasitologically negative with the corresponding negative assay. Regression analysis showed only weak but statistically significant correlation between the percent inhibition with parasitemia (r = 0.38, p less than 0.001), and this was more clearly shown in patients with high parasitemia.

Receptor de membrana de linfócito T humano para eritrócitos de carneiro (CD2) / Membrane receptor of human T lymphocyte for sheep erythrocyte CD2

Esta revisäo trata inicialmente das características do receptor CD2 e suas funçöes em linfócitos T e da açäo dos anticorpos monoclonais dirigidos contra essa estrutura em linfócitos T. Finalmente säo feitas algumas consideraçöes sobre os receptores na forma solúvel