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

OBJECTIVETo develop a more reliable and stable method for determining monoclonal antibody (mAb) affinity constant based on competitive antibody/antigen binding.

METHODSThe Kd value was calculated based on the relationship between the binding proportion of the antigen and the original concentration of the mAb that competed for the binding site of the antigen.

RESULTSThe Kd values measured with this improved method under two different conditions were 2.61x10(-12) mol/L and 2.39x10(-12) mol/L, and those with Friguent method in these two conditions were 5.57x10(-10) mol/L and 1.41x10(-10) mol/L, respectively.

CONCLUSIONCompared with Friguent method, the Kd values measured with this improved method are closer to the actual value, and the measurement results under different experiment conditions are more stable.

BACKGROUND/AIMS: For laboratory diagnostics in liver diseases, many enzymes have been used for the assessment of hepatocellular function. Among them, two transaminases, alanine and aspartate aminotransferase, have been regarded as the most sensitive indicators of hepatocellular damage. However, the enhanced enzyme activities of the enzymes do not exactly indicate or represent the cause and progression of diseases in the patients with liver disease. To overcome such limitations, immunological methods have been suggested as one of the alternatives for the replacement or supplement of the conventional enzymatic analysis. METHODS: In the hope of developing a new assay system for measuring the AST concentration rather than its activity, we have developed a new assay using fluorescence labeled anti-AST monoclonal antibodies. Blood was obtained from a normal population of 234 patients and 43 liver disease patients. The linearity, limit of detection, and performance of the new assay system were tested and evaluated. The comparability of assay was examined with an ELISA and biochemical assays. RESULTS: The linearity fell in the range of 0-1 mg/L of AST (R=0.995), and the analytical detection limit was 12 microgram/L of AST. The mean recovery of the control was 102.4 % in a working range. The precision of the intra- and inter-assay in a range of 50-800 microgram/L was CVs < 7% and CVs < 6%, respectively. In the normal population, the mean AST concentration was 35.5 microgram/L. The mean AST concentration in patients with liver disease was 266.5 microgram/L. The new assay system correlated well with an ELISA and biochemical assay for quantification of AST concentration (R=0.92 and 0.88, respectively; N=43). CONCLUSIONS: We have developed a new immunological assay using generated monoclonal antibodies to human cytosolic AST and used them for the development of a fluorescent assay measuring the enzyme mass. Cytosolic AST mass in sera could be measured reproducibly by the immunological method. In conclusion, this study has provided us with a new type of tool for an accurate measurement of the enzyme amount in circulation.
Antibodies, Monoclonal ; Aspartate Aminotransferase, Cytoplasmic/*blood/immunology ; Fluorescent Antibody Technique/*methods ; Humans ; Liver Diseases/diagnosis

The enzyme linked immunosorbent assay (ELISA)-inhibition test using a Clonorchis sinensis species-specific mouse monoclonal antibody(MAb), CsHyb 0605-23, showed increased specificity over the conventional ELISA used for serodiagnosis of clonorchiasis. To characterize the corresponding antigen further, the MAb was tested against polysaccharide, protein and glycolipid fractions obtained from a crude extract of C. sinensis adult worms, using chloroform, methanol and phenol extractions. Only the polysaccharide fraction was recognized by the MAb among those fractions. Mild oxidation of the antigen with sodium periodate showed decreased reactivity against the MAb. We concluded that the antigen and antigenic determinants recognized by the MAb are carbohydrates.
parasitology-helminth-trematoda ; Clonorchis sinensis ; Monoclonal antibody ; antigen ; immunology ; carbohydrate ; polysaccharide ; enzyme-linked immunosorbent assay ; diagnosis

The distribution of pemphigus subclass autoantibodies in a patient with pemphigus vulgaris (PV) has been investigated by semiquantitative indirect immunofluorescence (IIF), using the HP series monoclonal antibodies specific for four human IgG subclasses on human foreskins. IgG1 and IgG4 intercellular substance-specific autoantibodies were detected in the serum of the patient, whereas IgG2 and IgG3 autoantibodies were absent. In addition to foreskins, human tonsillar epithelia were used as substrates of IIF for detecting the PV autoantibodies and it was one of satisfactory substitutes for monkey esophagus.
Antibodies, Monoclonal ; Autoantibodies* ; Esophagus ; Fluorescent Antibody Technique, Indirect ; Foreskin ; Haplorhini ; Humans ; Immunoglobulin G* ; Pemphigus*

This study was undertaken to purify cystic fluid (CF) antigen of Taenia solium metacestodes by affinity chromatography using specific monoclonal antibody (McAb) and to characterize the antigenicity of the purified antigen. The hybridoma cell lines, prepared by fusion between mouse plasmacytoma and spleen cells from BALB/c mice immunized with CF, secrected antibodies reacting to various helminthic antigens. Majority of cell lines reacted to CF only but some also reacted to parenchymal antigen of T. solium metacestodes, adult T. saginata, sparganum, hydatid cystic fluid, Paragonimus westermani and Clonorchis sinensis, either in combination with CF, other antigens or independently. Cloned cells derived from monoclonal lines also produced antibodies reacting either to CF only or to other helminthes in combination or independently. These results indicated that CF of T. solium metacestodes contained proteins which possessed antigenic determinants not only specific to CF but also cross reactive with the afore-mentioned helminthes. CF of T. solium metacestodes was purified by affinity chromatography using the McAb which reacted to CF and parenchymal antigens. The affinity-purified antigen(A-Ag) and unbound pool(U-Ag) were separated. A-Ag showed 2 protein bands by disc-PAGE whereas CF exhibited 6 bands and U-Ag consisted of all bands CF had. The diagnostic significance of A-Ag was evaluated by ELISA in human neurocysticercosis and other helminthic and neurologic diseases. By A-Ag, the levels of the specific IgG antibody, as shown by absorbance in sera and CSF, were lower than those of CF and U-Ag. Accordingly, the sensitiviy was about 70 % of CF and U-Ag. However, the nonspecific positive reactions to CF and U-Ag, observed in sparganosis, T. saginata infection and paragonimiasis did not occur when A-Ag was used. These results indicated that the affinity-purified A-Ag had the higher specificity but the lower sensitivity as a diagnostic antigen in cysticercosis, probably because it only detected a single or limited numbers of monospecific antibodies among the diverse polyclonal antibodies produced in the patients with neurocysticercosis.
parasitology-helminth-cestoda ; Taenia solium ; cysticercus ; antigen ; affinity chromatography ; monoclonal antibody

Orientia tsutsugamushi, the causative agent of scrub typhus, is an obligate intracellular bacterium that replicates slowly in the host cytoplasm. To investigate the changes of antigen expression during six days of in vitro growth, the reactivity of various monoclonal antibodies (MAbs) was examined in time course. Using immunofluorescence staining, some antigens were shown to be differentially expressed in contrast to 56-kDa protein that was produced at a constant level throughout culture. Three MAbs (NT1, M716B and M716G) revealed antigens, appearing only at 3 days after infection. MAb NT19 recognized an antigen that appeared mainly at the late stage of infection whereas two MAbs (M686-13 and M686-20) demonstrated antigens, being expressed at the early infection stage and showing distinct morphology under immunofluorescence staining. In addition, when cells were infected and then treated with chloramphenicol, granular cytoplasmic bodies were detected and the bacterial development was inhibited. These results show that O. tsutsugamushi changes the antigenic expression to adapt to and replicate in host cells.
Antibodies, Monoclonal* ; Chloramphenicol ; Cytoplasm ; Fluorescent Antibody Technique ; Orientia tsutsugamushi* ; Scrub Typhus

A new approach to enhancing the effectiveness of vaccines is to deliver antigens selectively to dendritic cells (DC) in situ, via monoclonal antibodies specific for particular DC surface molecules. This can markedly enhance CTL responses and, via helper T cells, also enhance antibody responses. DC activation agents or adjuvants must also be administered for effective CTL responses, but in some cases good antibody responses can be obtained without adjuvants. Here we review the role of different DC subsets and different DC target molecules in obtaining enhanced immune responses.
Antibodies, Monoclonal/immunology ; Antibody Formation ; Antigens/*administration & dosage/immunology ; Dendritic Cells/cytology/*immunology ; Humans ; Vaccines/*immunology

A new approach to enhancing the effectiveness of vaccines is to deliver antigens selectively to dendritic cells (DC) in situ, via monoclonal antibodies specific for particular DC surface molecules. This can markedly enhance CTL responses and, via helper T cells, also enhance antibody responses. DC activation agents or adjuvants must also be administered for effective CTL responses, but in some cases good antibody responses can be obtained without adjuvants. Here we review the role of different DC subsets and different DC target molecules in obtaining enhanced immune responses.
Antibodies, Monoclonal/immunology ; Antibody Formation ; Antigens/*administration & dosage/immunology ; Dendritic Cells/cytology/*immunology ; Humans ; Vaccines/*immunology

In recent years, as increasing of monoclonal antibody application in clinic, the antitumor effect of antibody dependent cell-mediated cytotoxicity (ADCC) get increasing attention. The natural killer (NK) cells are the most important effector cells mediating specific antitumor of ADCC; the phagocytes, T-cells and granulocytes have the definite effect on antitumor of ADCC. ADCC is confirmed as the important mechanism and means for clinically treating the cancers with monoclonal antibodies. The IgG antibody firstly combines with target cells (tumor cells) through antigen-binding sites, and then FcγR on effector cells identifies its Fc fragment and mediates ADCC. Today many kinds of monoclonal antibodies have been put into clinical application such as rituximab and other new anti-CD20 monoclonal antibodies including trastuzumab, erbitux, cetuximab, edrecolomab, nimotuzumab, gemtuzumab ozogamicin and so on, which all can mediate ADCC. The antitumor effects of ADCC mediated by monoclonal antibody can be influenced by IgG Fc receptor gene polymorphism, tumor cell antigen, serum antibody levels, cytokines and drugs etc. As to peripheral blood mononuclear cells, ADCC efficacies of FcγRIIIa-158V/V and FcγRIIa-131H/H are higher than that of other genotypes, while increasing the level of tumor antigen and decreasing the level of serum antibody or adding some cytokines (IL-2, IL-21, IL-15, etc) may elevate the ADCC effect mediated by monoclonal antibodies. Avoiding use of certain drugs (dexamethasone, TNF antagonist) or appropriately using of ondansetron and clemastine also can enhance the anti-tumor effect of ADCC mediated by monoclonal antibodies. In short, ADCC is very important in clinical application for anti-tumor treatment, but its efficacy may be impacted by multiple factors.In this article, the killing mechanisms of ADCC, the clinical use of monoclonal antibodies with antitumor effect of ADCC, the factors influencing anti-tumor efficacy of ADCC, and the antitumor effects of ADCC by other cells are reviewed.
Antibodies, Monoclonal ; therapeutic use ; Antibody-Dependent Cell Cytotoxicity ; Humans ; Immunotherapy ; Killer Cells, Natural ; Neoplasms ; therapy