Faculty Bibliography

We have reported that an amyloid-beta derivative, K6Abeta1-30-NH2 reduces amyloid burden in mice to a similar extent as previously shown for Abeta1-42 (Am J Pathol 159:439-47,2001). This derivative may be a safer alternative to Alzheimer's vaccination with Abeta1-42 because it has a low beta-sheet content while maintaining the main antigenic sites of Abeta. To determine the in vivo effect of other derivatives with similar in vitro properties, we immunized Tg2576 mice with Abeta1-30-NH2, in which amino acids 18 and 19 were substituted with glutamate (Abeta1-30E18E19). In a parallel study, mice were immunized with K6Abeta1-30E18E19. Freund's adjuvant was used to allow a comparison with our findings with K6Abeta1-30-NH2. Antibody titers were detectable, but much lower than we had observed for K6Abeta1-30-NH2 or Abeta1-42, indicating that the central hydrophobic region of Abeta may have an epitope important for modulating humoral response. Cognitive performance was assessed in a radial arm maze before sacrifice at 19-21 months. Control Tg mice had more errors than their wild-type littermates (p<0.01), and the Abeta1-30E18E19-treated mice (p<0.05). Mice receiving K6Abeta1-30E18E19 also performed better than their Tg controls (p<0.05). Histologically, no difference was observed in brain amyloid plaque burden in 6E10 stained brain sections from the Abeta1-30E18E19-vaccinated mice, compared to vehicle treated mice. Furthermore, amyloid burden did not correlate with cognitive performance. Analysis of plaque burden in the K6Abeta1-30E18E19-immunized mice is underway, as well as measurements of brain levels of Abeta to determine if these values will provide a better correlation with cognitive performance. A robust antibody response and a diminished plaque burden may not be necessary for a therapeutic effect of Abeta derived vaccines

The prion protein (PrP) is a copper binding protein; however, the role of copper in prion infection is unclear. Under some conditions copper facilitates refolding of denatured PrPSc into a protease resistant and infectious form. Hence copper may enhance the infectivity of the prion protein. To determine the feasibility of copper targeted therapy for prion disease, we treated mice (n=10 per group) with d-penicillamine (d-PEN; 100 mg/kg, i.p.), immediately following scrapie inoculation (139A strain, i.p.). Subsequent drug injections were daily, five days per week. d-PEN delayed the onset of prion disease in the mice (p=0.002). The effect was more pronounced at the 1000-fold dilution of agent (d-PEN=179 +- 3 days, VEH=165 +- 4, p=0.006), but a trend for a delay was observed at the 10-fold dilution (d-PEN=153 +- 2, VEH=146 +- 3, p=0.1). As expected, d-PEN reduced brain copper levels (p<0.01) by 26% (10-fold dil.; p=0.04) and 32% (1000-fold dil.; p=0.02), compared to control animals. Brain levels of iron and zinc were not reduced. To further support the notion that the therapeutic effect of d-PEN was mediated through its copper chelating properties, brain homogenates from terminally ill 139A infected mice were incubated with copper and d-PEN. Following a 72 h incubation, copper sulfate increased aggregation of the prion protein in a dose dependent manner, resulting in an enhanced resistance to proteinase K. This effect was counteracted by co-incubation with d-PEN. These findings support the proposed in vivo effect of d-PEN in delaying the onset of prion disease in these mice. Copper chelator-based therapy may benefit those incubating prion disease but this approach may be more effective at higher doses and/or in a multi-targeted combinational therapy