This work was supported by FMM-2008; FEDER (FISPI10-00975, -00265 and -00283); SGR2009-00761 and -42271. G.R-H is supported by a MAEC-AECI fellowship (Spanish government) and M.M-A by a PIF (UAB, Spain) fellowship.

The single-chain variable fragment, scFv-h3D6, has been shown to prevent in vitro toxicity induced by the amyloid β (Aβ) peptide in neuroblastoma cell cultures by withdrawing Aβ oligomers from the amyloid pathway. Present study examined the in vivo effects of scFv-h3D6 in the triple-transgenic 3xTg-AD mouse model of Alzheimer disease. Prior to the treatment, five-month-old female animals, corresponding to early stages of the disease, showed the first behavioral and psychological symptoms of dementia -like behaviors. Cognitive deficits included long- and short-term learning and memory deficits and high swimming navigation speed. After a single intraperitoneal dose of scFv-h3D6, the swimming speed was reversed to normal levels and the learning and memory deficits were ameliorated. Brain tissues of these animals revealed a global decrease of Aβ oligomers in the cortex and olfactory bulb after treatment, but this was not seen in the hippocampus and cerebellum. In the untreated 3xTg-AD animals, we observed an increase of both apoJ and apoE concentrations in the cortex, as well as an increase of apoE in the hippocampus. Treatment significantly recovered the non-pathological levels of these apolipoproteins. Our results suggest that the benefit of scFv-h3D6 occurs at both behavioral and molecular levels.