Both Murine SAA1 and SAA2 Yield AA Amyloid in Alveolar Hydatid Cyst‐Infected Mice

Amyloid susceptible C57BL/6 and partially amyloid resistant A/J mice, infected intraperitoneally with 250 alveolar hydatid cyst (AHC), the larval stage of a cestode parasite Echinococcus multilocularis , develop multiple organ amyloid deposits at approximately 1 and 4 weeks post infection (p.i.), respectively. Pooled spleens and livers from each mouse strain, at 8 and 10 weeks p.i., were used for the purification of protein AA utilizing a HiLoad Superdex 200 column equilibrated with 5 M guanidine‐HCl. Protein AA from each mouse strain was separated on 16% Tris‐tricine SDS‐PAGE gels and immunoblotted with monospecific rabbit anti‐mouse AA IgG; five and six immunoreactive AA subspecies were detected in the C57BL/6 and A/J materials, respectively. N‐Terminal amino acid sequence analysis was performed on the bulk column‐purified protein AA as well as on the electroblotted AA subspecies from each mouse strain. The results show a mixture of serum amyloid A 1 (SAA 1 ) and (SAA 2 )‐derived AA protein from each mouse strain; SAA 1 ‐derived AA, although alluded to, has never been demonstrated as tissue deposits in mice. These findings suggest that the intense and persistent inflammatory processes in AHC‐infected mice may have induced conversion of weakly amyloidogenic SAA 1 to AA. This conversion could be detected by amino acid sequencing of electrophoretically separated AA subspecies.