A persistent question in the field of antibody imaging and therapy is whether increased affinity is advantageous for the targeting of tumors. We have addressed this issue by using a manipulatable ...model system to investigate the impact of affinity and antigen density on antibody localization. In vitro enzyme-linked immunosorbent assays and bead-binding assays were carried out using BSA conjugated with high and low densities (HD and LD, respectively) of the chemical hapten rho-azophenyl-arsonate as an antigen. Isotype-matched monoclonal antibodies (mAbs) 36-65 and 36-71, with identical epitope specificity but 200-fold differences in affinity, were chosen as targeting agents. The relative in vitro binding of 36-65 and 36-71 was compared with an artificial "tumor" model in vivo using antigen-substituted beads s.c. implanted into SCID mice. Nonsubstituted BSA beads were implanted in the contralateral groin as a nonspecific control. The efficacy of the targeting of 125I-labeled antibodies was assessed by the imaging of animals on a gamma-scintillation camera using quantitative region-of-interest image analysis over the course of 2 weeks and by postmortem tissue counting. In vitro, both antibodies bound well to the HD antigen, whereas only the high-affinity mAb 36-71 bound effectively to the LD antigen. In vivo, high-affinity mAb 36-71 bound appreciably to both LD and HD beads. In contrast, there was no specific localization of low-affinity mAb 36-65 to LD antigen beads, although the antibody did bind to the beads with the HD antigen. Whereas the high-affinity mAb 36-71 increased its binding to HD beads throughout the 14 days of observation, binding of the high affinity antibody to LD beads and of the low affinity antibody to HD beads plateaued between 10-14 days. These in vitro and in vivo findings demonstrate that the need for a high-affinity antibody is dependent on the density of the target antigen. High-affinity antibodies bind effectively even with a single antigen-Fab interaction, irrespective of the antigen density. In contrast, low-affinity antibodies, because of weak individual antigen-Fab interactions, require the avidity conferred by divalent binding for effective attachment, which can only occur if antigen density is above a certain threshold. An understanding of the differential behavior of high- and low-affinity antibodies and the impact of avidity is useful in predicting the binding of monovalent antibody fragments and engineered antibody constructs and underlies the trend toward development of multivalent immunological moieties. Consideration of the relative density of the antigen on the tumor and the background tissues may enable and even favor targeting with low-affinity antibodies in selected situations.
Investigations on the impact of pellet size on the cellular oxygen uptake and accumulation of ganoderic acid (GA) suggested the favorable effect of oxygen limitation on GA formation by the higher ...fungus Ganoderma lucidum. A two‐stage fermentation process was thus proposed for enhanced GA production by combining conventional shake‐flask fermentation with static culture. A high cell density of 20.9 g of DW/L (DW = dry cell weight) was achieved through a 4‐day shake‐flask fermentation followed by a 12‐day static culture. A change in the cell morphology and a decrease in the sugar consumption rate were observed during the static culture. The GA production in the new two‐stage process was considerably enhanced with its content increased from 1.36 (control) to 3.19 mg/100 mg of DW, which was much higher than previously observed.
The purpose of the paper is twofold, first to suggest a general method, called the second variation-convex analysis mixed method, for analysis of nonlinear functionals. As an application of the ...approach, a strictly dual complementary variational principle of Reissner plates with the local form
1 and the existing criterion of variational solution have been studied. The study shows that the principle and the criterion
1 can be improved into a global form by using the novel approach. In contrast with existing methods (Jin
1 and Gao and Stang
2), this method will be able to analyze general nonlinear problems,
1 rather than geometrically nonlinear ones.
2 Our second purpose is to present a new approach to the derivation of the exact boundary integral equation for the analysis of nonlinear Reissner plates and to the derivation of the criterion for the solution of the boundary integral equation. Subsequently, the boundary and the domain of the plate are discretized to solve the nonlinear problems. All unknown variables are at the boundary. Numerical results are presented to illustrate the method and demonstrate its effectiveness and accuracy.
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