, 2000). Finally, others have postulated that prevention of amyloid deposition may be due to antibodies binding to early amyloid CX 5461 seeds at a point in the cascade when these species are present at low abundance, thus preventing amyloid propagation (Golde, 2003). Thus far, investigators have focused mostly on N-terminal antibodies, which can bind either

soluble or insoluble forms of Aβ, for targeting plaque (Pul et al., 2011). Prior studies have shown that both active and passive immunotherapy are effective in reducing amyloid deposition in transgenic APP mice when performed as a preventative measure; however, when these approaches are performed in aged transgenic mice with pre-existing deposits, they showed diminished (Levites et al., 2006) or no (Das et al., 2001) efficacy. We hypothesized that the inability of the N-terminal antibodies to remove existing plaque was due to antibody saturation with soluble Aβ upon entering the CNS. Thus, nonselective

antibodies will lack sufficient target engagement of deposited plaque and will not efficiently opsonize NLG919 supplier the intended target. In order to test our hypothesis, we developed an antibody that selectively targets deposited plaque in AD brain. The deposits found in AD are comprised of a heterogeneous mixture of Aβ peptides (Saido et al., 1996). Although the majority of the Aβ peptides end in the 42nd amino acid, there is an extraordinary amount of heterogeneity at the amino terminus. One previously identified truncation is the Aβp3-42 (Iwatsubo et al., 1996; Kuo et al., 1997; Saido et al., 1995). The Aβp3-42 peptide arises due to amino-terminal proteases trimming the first two amino

acids from the peptide, followed by cyclization of the functional group to form a pyrol ring at the amino terminus (pyroglutamate). This latter modification can occur spontaneously or by the action of glutaminyl cyclase (Chelius et al., 2006; Cynis et al., 2006). Early studies demonstrated that the Aβp3-42 peptide accumulates early in the deposition found cascade (Iwatsubo et al., 1996; Saido et al., 1995) and the biophysical properties of the Aβp3-42 highlighted the aggressive aggregation properties of the peptide (Schilling et al., 2006; Schlenzig et al., 2009). Since no published study reported detectable Aβp3-42 peptide in a physiological fluid (i.e., CSF or plasma), this modified Aβ peptide is probably plaque specific and thus an ideal target for immunotherapy. We generated and engineered high-affinity murine monoclonal antibodies specific for Aβp3-x with either minimal (mE8-IgG1) or maximal (mE8-IgG2a) effector function. These antibodies robustly labeled deposited plaque in both AD and PDAPP brain sections and led to a significant reduction of deposited Aβ in an ex vivo phagocytosis assay.