Inactivation of amyloid-enhancing factor (AEF): study on experimental murine AA amyloidosis

It is known that amyloid-enhancing factor (AEF) shortens the preamyloid phase in experimentally induced AA amyloidosis in mice. Because it is reported that AEF serves as both a nidus and a template for amyloid formation, AA amyloidosis may have transmissibility by a prion-like mechanism. It has been shown that amyloid fibrils also have AEF activity, and amyloid fibrils with AEF activity were named fibril-amyloid enhancing factor (F-AEF). In this study, we investigated methods to inactivate the AEF activity. AEF was extracted from the thyroid gland obtained at autopsy of a patient with AA amyloidosis. Before injection into mice, AEF was treated with several methods for inactivation. Of all the tested treatments, 1 N NaOH, 0.1 N NaOH, and autoclaving consistently demonstrated complete inactivation of AEF. Heat treatment led to incomplete inactivation, but 0.01 N NaOH, 0.001 N NaOH, pepsin, trypsin, pronase, and proteinase K treatment had no effect on AEF activity. By analysis with transmission electron microscopy, the AEF preparation contains amyloid fibrils, and a change of ultrastructure was shown after 1 N NaOH, 0.1 N NaOH, and autoclaving treatment. Furthermore, immunoblotting of AEF with antihuman AA antibody revealed that the protein band was scarcely found after autoclaving, 1 N NaOH, and 0.1 N NaOH treatment. Our results suggest that, similar to Creutzfeldt-Jakob disease (CJD), amyloidosis may require chemical or autoclaving decontamination.