N-terminal truncated amyloid beta (Aβ) derivatives, especially the forms having pyroglutamate at the 3 position (AβpE3) or at the 11 position (AβpE11) have become the topic of considerable study. AβpE3 is known to make up a substantial portion of the Aβ species in senile plaques while AβpE11 has received less attention. We have generated very specific polyclonal antibodies against both species. Each antibody recognizes only the antigen against which it was generated on Western blots and neither recognizes full length Aβ. Both anti-AβpE3 and anti-AβpE11 stain senile plaques specifically in Alzheimer’s disease cerebral cortex and colocalize with Aβ, as shown by confocal microscopy. In a majority of plaques examined, AβpE11 was observed to be the dominant form in the innermost core. These data suggest that AβpE11 may serve as a generating site for senile plaque formation.

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SummaryInbred strains of mice provide a model for studies of the pathogenesis of amyloid A (AA) amyloidosis. All susceptible strains of mice described to date codominantly express two serum amyloid A (apoSAA) isoforms, apoSAA1 and apoSAA2, of which only apoSAA2 serves as a precursor for amyloid fibrils. In previous studies, we have shown that the CE/J strain, which produces a single, novel apoSAA isoform, apoSAAcE/j, is amyloid resistant. In the present study amyloidresistant CE/J females were mated with amyloid-susceptible CBA/J males to produce F1 hybrid offspring which were then backcrossed to the parental CBA/J mouse strain. Amyloid susceptibility was determined in 30 backcrossed mice 72 h after injection of murine amyloid enhancing factor and silver nitrate. ApoSAA isoforms in plasma were separated by isoelectric focusing gel electrophoresis and visualized after immunoblotting with anti-AA antiserum. Amyloid A fibrils in spleen homogenates were denatured by formic acid and AA protein was quantified by ELISA using anti-mouse apoSAA antibodies. Values <5 apoSAA equivalent units were considered negative. 13 mice expressed an apoSAA1 and apoSAA2 doublet characteristic of CBA/J mice, whereas 17 mice, expressed the apoSAAcE/j isoform codominantly with apoSAA1 and apoSAA2. The correlation of amyloid resistance to expression of the apoSAAcE/j isoform was absolute (17/17 were negative; mean score 2.6 _ 0.17 [standard error of the mean] apoSAA equivalent units) and the correlation between amyloid susceptibility and the expression of apoSAAz/apoSAA1 was also striking (12/13 were amyloid positive; mean score 47.9 _+ 9.0 [standard error of the mean] apoSAA equivalent units (P ~0.001). This is not significantly different from the 50% segregation of apoSAA phenotypes expected for linkage to a single gene. These results indicate that a single gene governs apoSAAcE/j expression and thus confers protection against amyloid deposition even in the presence of apoSAA1 and apoSAA2 isoforms and show for the first time that resistance to AA

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