Zymography and reverse zymography for detecting MMPs and TIMPs.

Zymography is the electrophoretic separation of proteins through a polyacrylamide gel containing a proteolytic substrate. After denaturing (but nonreducing) electrophoresis, proteins are renatured and incubated in an appropriate buffer for proteolytic activity. Clear zones of lysis in the stained gel indicated active proteinases. Reverse zymography is a similar technique to detect proteinase inhibitors. After renaturing of proteins, the gel is incubated with metalloproteinases which digest the substrate incorporated into the gel. Inhibitors are shown as dark zones of inhibition against a clear background upon staining.

Development, validation, and clinical implementation of an assay to measure total antibody response to naglazyme (galsulfase).

Naglazyme (galsulfase, rhASB) was developed as enzyme replacement therapy for mucopolysaccharidosis type VI. Naglazyme generated an IgG antibody response in most patients. To better characterize Naglazyme immunogenicity, a solution phase bridged immunoassay was developed to measure total antibody response regardless of isotype. Overnight incubation of serum dilutions with rhASB labeled with biotin and ruthenium-based tags allowed antibody-antigen complexes to form prior to capture on a streptavidin plate. Neat serum was tolerated in the assay, with a 1:10 screening dilution implemented for testing. At this dilution, the assay was sensitive to 75 ng/ml anti-rhASB. Titers were reported as the highest dilution factor with signal above a 95% confidence interval from naïve individual sera. Precise measurement of titers, within two consecutive dilution factors, was observed across analysts and days. Clinical samples showed similar positive/negative results between the IgG ELISA and the total antibody ECLA, although with an imperfect correlation. Improvements in assay performance and implementation strategy altered some positive clinical samples to negative and vice versa. Comparison of the titer readout for clinical samples with the screening signal illustrates a range of relationships for signal versus sample dilution factor, confirming that signal from a screening dilution cannot directly predict the reported titer.