Pathogenesis of experimental amyloid protein A amyloidosis in sore hocks-affected rabbits.

Although the experimental transmission of amyloid protein A (AA) amyloidosis with amyloid-enhancing factor has been studied intensively, its pathogenesis remains obscure. We previously found that rabbits affected with 'sore hocks' (SH) uniquely developed AA amyloidosis in response to primary inflammatory stimulation followed by the administration of bovine AA fibrils. However, it is unknown why only the rabbits with preexisting SH developed experimental AA amyloidosis. There may be hidden factors in the SH status that stimulate the mechanism of cross-species transmission of AA amyloidosis. To examine the essential factors in the development of experimental AA amyloidosis in SH-affected rabbits, we studied the etiology of SH in rabbits pathologically and bacteriologically. In addition, we developed artificial SH symptoms in normal rabbits by use of an adjuvant prepared from Staphylococcus aureus (StA) isolated from a spontaneous SH-affected rabbit, and we evaluated the incidence of AA amyloidosis in rabbits with or without experimental SH symptoms. We found that StA administration was extremely efficient at stimulating the induction of experimental AA amyloidosis, and the influence of SH was required. We found that the persistent S. aureus infection in SH facilitates the development of experimental AA amyloidosis in rabbits and that the inflammatory stimulation provided by SH acts as an additional accelerator in experimental AA amyloidosis.