Neutralizing receptor antibody

Kwong PD, Wyatt R, Robinson J, Sweet RW, Sodroski J, Hendrickson WA (1998) Structure of an HIV gpl20 envelope glycoprotein in complex with the CD4 receptor and a neutralizing human antibody. Nature 393 648-659... 

Another difficulty is that a peptide may be able to bind to an existing neutralizing monoclonal antibody by an induced-fit mechanism that is somehow driven by the pre-existing structure of the antibody paratope. However, the same induced-fit process may not take place when the peptide is used as the immunogen and is confronted in the host by a large population of B cell receptors allowing a variety of other interactions. 

Schlaeppi JM, Wood JM. Targeting vascular endothelial growth factor (VEGF) for anti-tumor therapy, by anti-VEGF neutralizing monoclonal antibodies or by VEGF receptor tyrosine kinase inhibitors. Cancer Metastasis Rev 1999 18 4734-81. 

However, not all antibody detected by ELISA corresponds to the antibody molecule that blocks the biological activity or active sites of the therapeutic protein. These neutralizing (blocking) antibodies are only a small fraction of the binding antibody population. Different cell- and receptor-based neutralizing antibody assays are developed for different protein drugs. 

IL-4 Modulators/Clinical Data. Different approaches have been taken to neutralize IL-4 activity, including soluble IL-4 receptor, antibodies against IL-4, and mutated IL-4, which acts as an antagonist of the receptor. In a mouse model of airway inflammation, soluble IL-4 receptor administered intranasally, before allergen challenge, results in a reduction of eosinophil infiltration, V-CAM expression, and mucus hypersecretion (417). This treatment, however, did not change airway hyperreactivity in response to methacholine. 

HIV is not only insufficiently neutralized by antibodies, it even uses bound antibodies to get access to immune cells, such as macrophages, which carry receptors for the Fc fragment of antibodies. 

Specific nutrient transport systems in brain capillaries can be used to facilitate drug entry into the brain. L-dopa (L-3,4-dfiiydroxyphenylalanine), a metabolic precursor of dopamine, is transported across endothelial cells by the neutral amino acid transport system [5], r-dopa permeates through capillaries into the striatal tissue, where it is decarboxylated to form dopamine. Therefore, systemic administration of L-dopa is often beneficial to patients with Parkinson s disease. Certain protein modifications, such as cationization [6] and anionization [7], produce enhanced uptake in the brain. Modification of drugs [8,9] by linkage to an antitransferrin receptor antibody also appears to enhance transport into the brain. This approach depends on receptor-mediated transcytosis of transferrin-receptor complexes by brain endothehal cells substantial uptake also occurs in the Hver. 

Inhibition of inflammatory cytokines (Fig. 2) Humanized monoclonal anti-TNF antibodies (Infliximab (Remicade ), Adalimumab (Humira )) bind with high selectivity to human TNF-a and neutralize its activity. Thereby, infliximab decreases the effects of enhanced TNF levels during inflammatory disease such as production of proteases, chemokines, adhesion molecules, cyclooxygenase products (prostaglandins), and proinflammatory molecules such as interleukin-1 and -6. The antibodies may also recognize membrane-bound TNF-a on lymphocytes and other immune cells. These cells may subsequently become apoptotic or are eliminated via Fc-receptor-mediated phagocytosis. 

In addition to inhibiting cytokine synthesis by glucocorticoids, cytokine effects can be prevented by scavenging the cytokine either with neutralizing antibodies or soluble receptors or by blocking the respective cytokine plasma membrane receptors with blocking antibodies or receptor antagonists. 

Commercially available dtugs used for therapeutic therapy comprise up to date mainly injectable monoclonal antibodies like Infliximab (Remicade ) and Adalimumab (Humira ) or TNF-receptor derivatives like Etanercept (Enbrel ) (Fig. 3). One possible way of action of these reagents is the neutralization of TNF, thereby blocking its inflammatory effects and dampening (auto)immune responses [3, 4]. 

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