Biomedical subjects

Helena Persson

Publications and source records attributed to Helena Persson.

4 recordsLinked to original sources

PubMed2007

Exploring central and peripheral diversity in antibody evolution.

The antigen-binding site, the paratope, of an antibody can be seen as being composed of a central core and a more peripheral area situated at its rim. Naturally these regions acquire their diversity using different mechanisms and they also have dissimilar roles, as they contribute differently to the binding interaction. Also, antigens of different size utilize these regions differently; while haptens mainly interact with the central core, larger antigens have additional interactions in more peripheral regions. Since haptens do not occupy the entire available paratope we hypothesized that hapten-specific antibodies, as they develop naturally or in the laboratory, have an imprint of the carrier protein they were once selected on. By using combinatorial library and phage display technologies on a hapten-specific antibody we were able to demonstrate that a peripheral carrier imprint indeed exists. We further show that such an imprint can act as a seed in the evolution of binders that recognize the carrier protein even in the absence of the hapten modification. The observed results provide a plausible mechanism for how haptenization of self-antigens can lead to the development of autoimmunity.

Antibodies↗

PubMed2006

A focused antibody library for improved hapten recognition.

The topography of the antigen-binding site as well as the number and the positioning of the antigen contact residues are strongly correlated with the size of the antigen with which the antibody interacts. On the basis of these considerations, we have designed a focused scFv repertoire biased for haptens, designated the cavity library. The hapten-specific scFv, FITC8, was used as a scaffold for library construction. FITC8, like other hapten binders, displays a characteristic cavity in its paratope into which the hapten binds. In five of the six complementarity-determining regions, diversity-carrying residues were selected rationally on the basis of a model structure of FITC8 and on known antibody structure-function relationships, resulting in variation of 11 centrally located, cavity-lining residues. L3 was allowed to carry a more complex type of diversity. In addition, length variation was introduced into H2, as longer versions of this loop have been shown to correlate with increased hapten binding. The library was screened, using phage display, against a panel of five different haptens, yielding diverse and highly specific binders to four of the antigens. Parallel selections were performed with a library having diversity spread onto a greater area, including more peripherally located residues. This resulted in the isolation of binders, which, in contrast to the clones selected from the cavity library, were not able to bind to the soluble hapten in the absence of the carrier protein. Thus, we have shown that by focusing diversity to the hotspots of interaction a library with improved hapten-binding ability can be created. The study supports the notion that it is possible to create antibody libraries that are biased for the recognition of antigens of pre-defined size.

Animals↗

PubMed2006

Lactadherin binds to elastin--a starting point for medin amyloid formation?

Medin amyloid is found in the medial layer of the aorta in almost 100% of the Caucasian population over 50 years of age. The medin fragment is 5.5 kDa and derives from the C2-like domain of the precursor protein lactadherin. We have previously reported immunohistochemical findings showing that medin amyloid co-localizes with elastic fibers of arteries and herein we show that lactadherin also is associated with elastic structures of human aortic material. In addition, results from in vitro binding assays demonstrate that both medin and lactadherin bind to tropoelastin in a concentration-dependent fashion, suggesting that the lactadherin-tropoelastin interaction is mediated via the medin domain. It is possible that lactadherin, which is a cell adhesion protein, in this way connects smooth muscle cells to the elastic fibers of arteries. Given that both medin and lactadherin interact with elastic fibers, elastin is probably an important component in the formation of medin amyloid.

Amyloid↗

PubMed2004

Characterisation of Mal d 1-related genes in Malus.

It has been suggested that there are at least 15 Mal d 1-related (PR10) genes in one genotype of apple (Malus x domestica Borkh). We sequenced cDNA libraries of cultivar 'Royal Gala' and identified 12 members of the Mal d 1 family, including the previously reported Mal d 1b and Mal d 1d, an allelic variant of the previously reported Mal d 1a. Eight Mal d 1 gene products were expressed in tree-ripened fruit, in either the cortex or the skin, and most of these were also expressed in leaves in response to challenge with Venturia inaequalis -a fungal disease of apple. Mal d 1 gene products were identified from a large number of different tissues. Degree of ripeness as measured by standard parameters was shown not to predict either the amount of protein able to bind to a specific monoclonal antibody 5H8, previously shown to bind to an allergenic epitope in Mal d 1b and a/d, or the amount of Mal d 1 mRNA present. Mal d 1d and Mal d 1b were the most highly expressed isoforms in 'Royal Gala', particularly in the skin of fruit, and these isoforms were also predominant in other cultivars and species of apple. Genotypes, however, differed in relative predominance of Mal d 1b and Mal d 1d. The predominantly expressed Mal d 1 genes in ripe apple fruit were translated in vivo into proteins and proteins binding to the antibody were found in all cultivars and species examined. New Mal d 1 proteins were identified that bound to the 5H8 antibody. At least two new subfamilies have been identified, and while some structural differences are predicted between groups of isoforms, the P-loop motif is identical in all except two isoforms. A role in intracellular signalling in plants is suggested and in vitro expression of the isoforms should help in assessing their relative roles in disease, allergic responses, senescence and nucleotide-, cytokinin- and brassinosteroid-binding.

Allergens↗