Alan Solomon

Thermodynamic Modulation of Light Chain Amyloid Fibril Formation

To obtain further insight into the pathogenesis of amyloidosis and develop therapeutic strategies to inhibit fibril formation we investigated: 1) the relationship between intrinsic physical properties (thermodynamic stability and hydrogen-deuterium (H-D) exchange rates) and the propensity of human immunoglobulin light chains to form amyloid fibrils in vitro; and 2) the effects of extrinsically modulating these properties on fibril formation. An amyloid-associated protein readily formed amyloid fibrils in vitro and had a lower free energy of unfolding than a homologous nonpathological protein, which did not form fibrils in vitro. H-D exchange was much faster for the pathological protein, suggesting it had a greater fraction of partially folded molecules. The thermodynamic stabilizer sucrose completely inhibited fibril formation by the pathological protein and shifted the values for its physical parameters to those measured for the nonpathological protein in buffer alone. Conversely, urea sufficiently destabilized the nonpathological protein such that its measured physical properties were equivalent to those of the pathological protein in buffer, and it formed fibrils. Thus, fibril formation by light chains is predominantly controlled by thermodynamic stability; and a rational strategy to inhibit amyloidosis is to design high affinity ligands that specifically increase the stability of the native protein.

Quantitative analysis of amyloid mass by segmentation of microPET and CT images

Immunoglobulin light chain amyloidosis (AL) is characterized by the deposition of light chain components as insoluble fibrils in tissues and organs leading to dysfunction and death and is the most common form of peripheral amyloid disease in humans. Presently, there are no means available in the USA to image specifically these deposits and thus ascertain the presence or extent of disease. To this end we have developed an experimental murine model of localized AL and used this to evaluate a radioiodinated amyloid fibril-reactive antibody, 11-1F4. The goal of the present study was to validate the experimental model by correlating the accumulation of 124I-11-1F4 antibody in the amyloid, using segmented PET and CT images, with lesion mass, volume, and tissue activity.