Anti-ADDL antibodies differentially block oligomer binding to hippocampal neurons.

Abeta-derived diffusible ligands (ADDLs) are abundant in AD brain, bind to hippocampal neurons and induce deficits in rodent cognition. To further investigate ADDL binding to neurons and identify antibodies that block this association, a panel of anti-Abeta and anti-ADDL antibodies was characterized for their ability to immuno-detect neuronally bound ADDLs and attenuate the binding of ADDLs to neurons. The results showed that anti-Abeta and anti-ADDL antibodies were able to abate ADDLs binding to hippocampal neurons, but to different degrees. Quantitative assessment of binding showed that one antibody, ACU-954 was markedly more effective at blocking ADDL binding than other antibodies assessed. ACU-954 was also found to block ADDL binding to hippocampal slice cultures, attenuate the ADDL-induced loss of dendritic spines and detect "natural ADDLs" in human AD tissue. These results demonstrated that antibodies that bind to and block ADDL binding to neurons can be identified, although their efficacy is conformationally specific since it is not readily apparent or predictable based on the core linear epitope or affinity for monomeric Abeta.

The in vitro neuronal toxicity of pentraxins associated with Alzheimer's disease brain lesions.

Serum amyloid P component (AP) and C-reactive protein (CRP) are normal serum components which belong to the pentraxin family of proteins. These proteins have been previously localized by immunohistochemical method to the brain lesions of Alzheimer's disease (AD). AP is a constant constituent of amyloid deposits including those found in AD. Both AP and CRP have been localized to AD neurofibrillary tangles. An indirect role for these proteins has been previously suggested in the etiology of AD. We studied the effects of serum AP and CRP on a human-derived neuronal cell line (hNT). In treated cell cultures, AP and CRP were detected immunohistochemically within hNT neurons, indicating cellular uptake of these proteins. Serum AP at the lowest serum physiological concentration (8 microgram/ml) showed a marked toxicity to hNT neurons. CRP also displayed toxicity to the hNT neurons but at a level compatible with inflammatory states (50 microgram/ml). These results suggest a more direct role for serum AP and CRP in the pathogenesis of AD.

C-reactive protein-like immunoreactivity in the neurofibrillary tangles of Alzheimer's disease.

C-reactive protein (CRP) is a plasma acute-phase protein, normally not found in the brain. Previous studies have demonstrated the presence of CRP in the senile plaques of Alzheimer's disease (AD). In this study, the presence of CRP-like immunoreactivity in AD neurofibrillary tangles (NFT) was demonstrated following pre-treatment of tissue sections with formic acid. CRP-like immunoreactivity was observed in both extracellular and intracellular NFT and was co-localized with the NFT marker PHF-1 and the amyloid P component (AP). The CRP-like immunoreactive NFT were less numerous and more limited in their distribution than PHF-1 or AP-immunoreactive NFT. The present results further support an involvement of inflammatory processes in the etiology of AD.