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.
Antibodies, Monoclonal ; chemistry ; Antibody Specificity ; Binding Sites, Antibody ; Immunoconjugates ; chemistry

Protein A and protein G are two well-defined immunoglobulin (Ig)-binding proteins (IBPs), which show affinity for specific sites on Ig of mammalian hosts. Protein A and protein G contained several highly homologous IgG-binding domains which had been demonstrated to have function to bind to IgG. Whether combinations of Ig-binding domains of various IBPs could produce useful novel binding properties remains interesting. We constructed a combinatorial phage library which displayed randomly-rearranged A, B, C, D and E domains of protein A, B2 and B3 domains of protein G. Four rounds molecular evolution of this library directed by all four human IgG subclasses respectively generated a common arrangement of D-C respectively which didn't exist in SpA. The dynamic loss of control phages and increase of the phages displaying two or more binding domains, especially the selective enrichment of D-C and strict selection of its linking peptides demonstrated the efficient molecular evolutions and the significance of the selected D-C arrangement. The phage binding assays confirmed that D-C possessed a binding advantage with four human IgG subclasses compared to SpA. In this work, a novel combination of Ig-binding domains, D-C, was obtained and presented the novel Ig binding properties which provided a novel candidate molecule for the purification, production and detection of IgG antibodies and a new approach for the further study of structures and functions of IBPs.
Amino Acid Sequence ; Antibody Specificity ; Bacterial Proteins ; immunology ; metabolism ; Binding Sites ; Binding, Competitive ; Evolution, Molecular ; Immunoglobulin G ; immunology ; metabolism ; Molecular Sequence Data ; Peptide Library ; Sequence Alignment ; Staphylococcal Protein A ; immunology ; metabolism

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.
Antibodies ; Binding Sites, Antibody ; Biopsy ; Capillaries ; Cicatrix ; Factor IX ; Gene Expression ; Graft Survival ; Kidney ; Rejection (Psychology) ; Transplantation, Homologous ; Transplants

Proteases are widely found in organisms participating in the decomposition of proteins to maintain the organisms' normal life activities. Protease inhibitors regulate the activities of target proteases by binding to their active sites, thereby affecting protein metabolism. The key amino acid mutations in proteases and protease inhibitors can affect their physiological functions, stability, catalytic activity, and inhibition specificity. More active, stable, specific, environmentally friendly and cheap proteases and protease inhibitors might be obtained by excavating various natural mutants of proteases and protease inhibitors, analyzing their key active sites by using protein engineering methods. Here, we review the studies on proteases' key active sites and protease inhibitors to deepen the understanding of the active mechanism of proteases and their inhibitors.
Binding Sites ; Catalytic Domain ; Endopeptidases ; Peptide Hydrolases/genetics* ; Protease Inhibitors ; Proteins

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.
Alleles ; Base Sequence ; Binding Sites, Antibody ; DNA, Complementary ; Female ; Genetic Heterogeneity ; HLA-A Antigens/immunology* ; HLA-A Antigens/genetics* ; Human ; Korea ; Male ; Molecular Sequence Data ; Pedigree

BACKGROUNDTo 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.

METHODSThe 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.

RESULTSThe 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.

CONCLUSIONSThe 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.

Binding Sites, Antibody ; Epitopes ; Gene Transfer Techniques ; Genetic Vectors ; Hepatitis B Surface Antigens ; genetics ; immunology ; Hepatitis B virus ; genetics ; immunology ; Humans ; Mutation ; Recombinant Proteins ; genetics ; immunology

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.
Bacterial Proteins ; genetics ; metabolism ; Binding Sites, Antibody ; genetics ; Escherichia coli ; genetics ; metabolism ; Immunoglobulin G ; immunology ; Recombinant Proteins ; genetics ; immunology ; metabolism ; Streptococcus suis ; immunology

OBJECTIVETo 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).

METHODSThirty-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.

RESULTSThree 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).

CONCLUSIONThe 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.

Amino Acid Sequence ; Animals ; Antigens, Dermatophagoides ; immunology ; Arthropod Proteins ; immunology ; Binding Sites, Antibody ; Cysteine Endopeptidases ; immunology ; Epitopes ; immunology ; Immunoglobulin E ; immunology ; Lymphokines ; immunology ; Mites ; immunology ; Molecular Sequence Data

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.
Animals ; Binding Sites, Antibody ; Camelus ; immunology ; metabolism ; Genes, Immunoglobulin ; Humans ; Immunoglobulin Heavy Chains ; genetics ; Immunoglobulin Variable Region ; genetics ; Protein Engineering ; Recombinant Proteins ; biosynthesis ; genetics ; immunology

OBJECTIVETo determine the affinity of new opioid receptor ligands to cloned mu opioid receptors stably expressed in CHO cell.

METHODSThe binding characteristics of the opioid ligand [3H] diprenorphine (3H-dip) were studied by cellular biological techniques and radioligands binding in cloned mu opioid receptors stably expressed in CHO cells in saturation binding experiments, and were followed by competition binding experiments with a variety of new synthesized opioid receptor ligands.

RESULTSThe Kd and Bmax of [3H] diprenorphine bound to mu receptors were 1.06 nmol/L and 930 fmol/mg protein, respectively. Competition binding experiments revealed that ligand 3# and 12# displayed much higher affinity than DAMGO and Morphine for the cloned mu opioid receptor. However, the affinities of ligands 2#, 6#, 8# and 9# were lower than DAMGO and Morphine.

CONCLUSIONThe present results suggest that the new ligands 3# and 12# have higher affinity to mu opioid receptors. However, ligands 2#, 6#, 8# and 9# have lower affinity to mu opioid receptors.

Animals ; Binding Sites ; Binding, Competitive ; CHO Cells ; metabolism ; Cloning, Molecular ; Cricetinae ; Diprenorphine ; pharmacology ; Ligands ; Receptors, Opioid, mu ; biosynthesis ; genetics ; metabolism