Structure of antibody molecules

Membrane-anchored DNA nanojunctions enable closer antigen-presenting cell-T-cell contact in elevated T-cell receptor triggering

How the engagement of a T-cell receptor to antigenic peptide-loaded major histocompatibility complex on antigen-presenting cells (APCs) initiates intracellular signalling cascades in T cells is not well understood. In particular, the dimension of the cellular contact zone is regarded as a determinant, but its influence remains controversial. This is due to the need for appropriate strategies for manipulating intermembrane spacing between the APC-T-cell interfaces without involving protein modification. Here we describe a membrane-anchored DNA nanojunction with distinct sizes to extend, maintain and shorten the APC-T-cell interface down to 10 nm. Our results suggest that the axial distance of the contact zone is critical in T-cell activation, presumably by modulating protein reorganization and mechanical force. Notably, we observe the promotion of T-cell signalling by shortening the intermembrane distance.

Site-Specific Antibody Assembly on Nanoparticles via a Versatile Coating Method for Improved Cell Targeting

Antibody-nanoparticle conjugates are promising candidates for precision medicine. However, developing a controllable method for conjugating antibodies to nanoparticles without compromising the antibody activity represents a critical challenge. Here, a facile and generalizable film-coating method is presented using zeolitic imidazole framework-8 (ZIF-8) to immobilize antibodies on various nanoparticles in a favorable orientation for enhanced cell targeting. Different model and therapeutic antibodies (e.g., Herceptin) are assembled on nanoparticles via a biomineralized film-coating method and exhibited high antibody loading and targeting efficiencies. Importantly, the antibodies selectively bind to ZIF-8 via their Fc regions, which favorably exposes the functional Fab regions to the biological target, thus improving the cell targeting ability of antibody-coated nanoparticles. In combination, molecular dynamics simulations and experimental studies on antibody immobilization, orientation efficiency, and biofunctionality collectively demonstrate that this versatile site-specific antibody conjugation method provides effective control over antibody orientation and leads to improved cell targeting for a variety of nanoparticles.

Central Nervous System Delivery of Antibodies and Their Single-Domain Antibodies and Variable Fragment Derivatives with Focus on Intranasal Nose to Brain Administration

IgG antibodies are some of the most important biopharmaceutical molecules with a high market volume. In spite of the fact that clinical therapies with antibodies are broadly utilized in oncology, immunology and hematology, their delivery strategies and biodistribution need improvement, their limitations being due to their size and poor ability to penetrate into tissues. In view of their small size, there is a rising interest in derivatives, such as single-domain antibodies and single-chain variable fragments, for clinical diagnostic but also therapeutic applications. Smaller antibody formats combine several benefits for clinical applications and can be manufactured at reduced production costs compared with full-length IgGs. Moreover, such formats have a relevant potential for targeted drug delivery that directs drug cargo to a specific tissue or across the blood–brain barrier. In this review, we give an overview of the challenges for antibody drug delivery in general and focus on intranasal delivery to the central nervous system with antibody formats of different sizes.

Comprehensive Molecular Characterization of a Cisplatin-Specific Monoclonal Antibody

Despite their immense and rapidly increasing importance as analytical tools or therapeutic drugs, the detailed structural features of particular monoclonal antibodies are widely unknown. Here, an antibody already in use for diagnostic purposes and for molecular dosimetry studies in cancer therapy with very high affinity and specificity for cisplatin-induced DNA modifications was studied extensively. The molecular structure and modifications as well as the antigen specificity were investigated mainly by mass spectrometry. Using nano electrospray ionization mass spectrometry, it was possible to characterize the antibody in its native state. Tandem-MS experiments not only revealed specific fragments but also gave information on the molecular structure. The detailed primary structure was further elucidated by proteolytic treatment with a selection of enzymes and high resolution tandem-MS. The data were validated by comparison with known antibody sequences. Then, the complex glycan structures bound to the antibody were characterized in all detail. The Fc-bound oligosaccharides were released enzymatically and studied by matrix-assisted laser desorption/ionization mass spectrometry. Overall 16 different major glycan structures were identified. The binding specificity of the antibody was investigated by applying synthetic single and double stranded DNA oligomers harboring distinct Pt adducts. The antibody-antigen complexes were analyzed by mass spectrometry under native conditions. The stability of the complex with double stranded DNA was also investigated.

Allotype-related sequence variation of the heavy chain of rabbit immunoglobulin G

The heavy chain of rabbit immunoglobulin G exists in three major allotypic patterns, Aa1-Aa3. A comparison of the amino acid compositions of the heavy chains isolated from immunoglobulin IgG homozygous for each allotypic determinant revealed the presence of an additional methionine residue per chain in the Aa3 allotype relative to the Aa1 and Aa2 allotypes. The position of the additional methionine residue was determined by cyanogen bromide cleavage and by tryptic digestion of the gamma-chains; it coincided with the inter-Fd-Fc area of the chain. Isolation and characterization of the corresponding tryptic peptides of 31 amino acid residues from each of the allotypes showed the presence of a methionine-for-threonine replacement in the Aa3 allotype, but only in about 70-80% of the molecules. No other allotypic variations were seen in this tryptic peptide. Allotypically related variations in composition were also detected in the N-terminal cyanogen bromide-cleavage peptide.

Amino acid sequence restriction in rabbit antibody light chains

Light chains were obtained from IgG rabbit antibodies to the group-specific carbohydrates of groups A and C streptococci. An analysis of the amino acid alternatives which exist at the first three positions of the N-terminus in both light-chain preparations shows a marked restriction in amino acid sequence heterogeneity when compared with preimmune light chains. Both of these related, but immunologically distinct, antigenic determinants select the same uncommon subpopulation of rabbit light chains.

Genetics of immunoglobulin kappa-chains: chemical analysis of normal human light chains of differing Inv types

The relationship between Inv phenotype and the amino acid residue at position 191 in kappa-type light polypeptide chains derived from the immunoglobulins of ten normal human sera was investigated. In each case, the amino acid present at position 191 correlated with the Inv phenotype of the individual. Kappa chains of seven Inv (-1,3) homozygotes had valine, while those of three Inv (1,3) heterozygotes had some chains with leucine and some with valine at this position. Genes encoding the Inv (1) and Inv (3) variants appear to be expressed equally in the heterozygous state, since approximately equal amounts of each gene product was recovered from heterozygotes. The correlation between Inv phenotype and the amino acid residue present at position 191 is identical to that previously established for kappa-type Bence-Jones proteins and myeloma protein light chains. These observations support the hypothesis that the valine-leucine interchange is encoded by two allelic forms of a single kappa-chain common region gene.

Genetic implications of common region sequence comparisons of lambda immunoglobulin chains differing at position 190

The common regions of two lambda chains (amino acid residues 109 to 213) have been partially sequenced. These two human immunoglobulin chains have lysine at position 190, but are otherwise identical in their common-region sequence to four reported lambda chains that have arginine at position 190. The single amino acid interchange at position 190 may be explained either by an ambiguous codon at this position or by a gene duplication so recent that only a single mutational event has occured.

Studies on the competence of single cells to produce antibodies of two specificities

Two series of experiments were performed, utilizing a modification of the hemolysin plaque technique which registers 19S antibody, in an attempt to determine the frequency of cells capable of simultaneously producing antibody to two non-cross-reacting antigens. Mice were immunized i.v. with rabbit and camel RBC and their spleens assayed for cells producing antibody against both antigens. 16,904 cells producing antibody of one or the other specificity, from 26 mice, were counted. Not one cell was detected which produced antibody of two specificities. Rabbits were immunized intradermally with HSA to which polyalanyl and p-azobenzenearsonate groups were chemically attached. The individual haptens, polyalanyl, and p-azobenzenearsonate groups were coupled to separate aliquots of SRBC, and the lymph nodes of immunized rabbits were assayed for cells releasing antibody against both haptens. In a study of 11 rabbits, after counting 27,845 cells producing antibody, we detected no "double" plaques.

The structure of the heavy chain of immunoglobulin and its relevance to the nature of the antibody-combining site. The Second CIBA Medal Lecture

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Antibody variability. Somatic recombination between the elements of "antibody gene pairs" may explain antibody variability

I have analyzed the available amino acid sequence data from 30 myelomatosis-derived proteins. Several types of variation are apparent. I conclude that a major and genetically predetermined contribution to the variability of these proteins and of antibodies could be provided by chromosomal rearrangements resulting from somatic recombination between similar but not identical genes in antibody gene pairs. My hypothesis suggests many new types of experiment and can be tested (31).