Peptide-antibody complex

Fig. 6 Evaluation of phosvitin binding to monoclonal anti-phosphoserine antibody by ACE using mobility-shift analysis and UV detection. Peaks M, internal peptide marker mAb, free monoclonal anti-phosphoserine antibody mAb-hpAg complex, monoclonal anti-phosphoserine antibody complexed with homopolyvalent phosvitin antigen. The buffer contained phosvitin within a concentration from 0 to 60 /xM. (Reprinted with permission from Ref. 27. Copyright 1997 Academic Press.)... 

Extracellular antigens are detected by APCs, such as lymphocytes, macrophages, and dendritic cells in interstitial fluid and blood. These detect the hapten and engulf the whole antigenic complex. Then, when inside the APC, the complex is partly dismantled and peptides attached to proteins similar to immunoglobulins, known as MHC II. The modified peptide-hapten complex is moved to the surface of the APC and presented as a complex with MHC to T-helper cells (CD4+), which activates and instructs the APC to make antibodies to the hapten and also B cells (memory cells with "memory" of the hapten) to proliferate. These events lead to types I to III responses. 

Boado et al. [28] devised delivery systems based on conjugates of streptavidin and the 0X26 monoclonal antibody directed to the transferrin receptor as a carrier for the transport of ASO. These delivery systems were found to transport peptide nucleic acid antisense molecules, but not ASO, across the BBB. These authors attributed this difference to preferential binding of phosphorothioate oligonucleotide to plasma protein instead of the antibody complex, which reduced their transport. 

To avoid high cytotoxicity and molecular heterogeneity of poly(L-lysine), molecularly homogenous lysine-rich synthetic peptides have been used for gene transfer. It is known that the active sites of enzymes, receptor ligands and antibodies usually involve about 5 to 20 amino acids. Thus, it should be possible to design small synthetic peptides to mimic the active sites of viral proteins and formulate synthetic peptide/DNA complexes that are as efficient as vimses, but do not have their limitations. The major components of a peptide-based delivery systems are ... 

To further examine the interactions between FMDV and neutralizing antibodies, the atomic structures of peptide—Fab complexes and the cryo-TEM structures of the Fab—virus complexes were determined [136]. In the image reconstructions, SD6 has a well-defined orientation on the virion surface whereas the density for 4C4 is extremely diffuse. One possible reason for this difference is that, while the RGD loop is in an extended conformation in the SD6 complex, a hinge rotation at the base of the loop may bring it closer to the capsid surface and stabilize the orientation. 

Tormo, J., Blaas, D., Parry, N. R., Rowlands, D., Stuart, D., and Fita, 1. (1994). Crystal structure of a human rhinovirus neutralizing antibody complexed with a peptide derived from viral capsid protein VP2. EMBO J. 13, 2247-2256. 

EL-4 cells (3 x 10 ) were lysed with N,N-dimethyl-N-(3-sulfopropyl)-3-[[(3a,5 P,7a, 12a)-3,7,12-trihydroxy-24-oxocholan-24-y 1]-amino]-l-propanaminium hydroxide (CHAPS). The nuclei and membranes were pelleted and the supematent lysate filtered to remove lipids. The lysate was sequentially passed over sepharose columns containing a) normal mouse serum b) Y-3 which is an anti-K monoclonal antibody. Both columns were washed with 45 coliunn volumes of progressively lower molarity salt solutions. The beads were then treated with acetic acid to release antigen-antibody complexes and the complex was denatured by boiling in 10% acetic acid. The mixture was filtered through a 3 kDa pore-size membrane and the filtrate containing MHC class I peptides subjected to reversed phase HPLC. 

Increased values of AH and AS for the mAh 4-4-20/monofluoresceinated peptide complexes relative to the mAh 4-4-20/fluorescein complex decay were interpreted as resulting from inclusion of the carrier peptides. Increased enthalpic contributions may have resulted from actual binding interactions between the surface accessible complementarity determining regions (CDRs) surrounding the mouth of the antibody active site and the amino acids of the peptides. Whitlow etal. (15) reported that a significant percentage of the amino acids that compose the mAb 4-4-20 CDRs were solvent accessible when fluorescein was in the active site. The increased values for AH also may have been due to differences in hydration of the antibody complexes. 

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