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* Paul-Ehrlich-Institut, Div. of Immunology, Langen, Germany;
Institute for Pharmacy and Molecular Biotechnology, Heidelberg University, Heidelberg, Germany;
Paul-Ehrlich-Institut, Division of Medical Biotechnology, Langen, Germany;
Novartis Institutes for BioMedical Research Basel, Basel, Switzerland;
¶ Twincore, Center for Experimental and Clinical Infection Research, Hannover, Germany;
|| Institute for Neuropathology, University Hospital Freiburg, Freiburg, Germany; and
# Institute of Clinical Neuroanatomy, Neuroscience Center, Goethe-University, Frankfurt am Main, Germany
In transgenic animal models, humoral immunity directed against the β-amyloid peptide (Aβ), which is deposited in the brains of AD patients, can reduce Aβ plaques and restore memory. However, initial clinical trials using active immunization with Aβ1–42 (plus adjuvant) had to be stopped as a subset of patients developed meningoencephalitis, likely due to cytotoxic T cell reactions against Aβ. Previously, we demonstrated that retrovirus-like particles displaying on their surface repetitive arrays of self and foreign Ags can serve as potent immunogens. In this study, we generated retrovirus-like particles that display the 15 N-terminal residues of human Aβ (lacking known T cell epitopes) fused to the transmembrane domain of platelet-derived growth factor receptor (Aβ retroparticles). Western blot analysis, ELISA, and immunogold electron microscopy revealed efficient incorporation of the fusion proteins into the particle membrane. Without the use of adjuvants, single immunization of WT mice with Aβ retroparticles evoked high and long-lived Aβ-specific IgG titers of noninflammatory Th2 isotypes (IgG1 and IgG2b) and led to restimulatable B cell memory. Likewise, immunization of transgenic APP23 model mice induced comparable Ab levels. The CNS of immunized wild-type mice revealed neither infiltrating lymphocytes nor activated microglia, and no peripheral autoreactive T cells were detectable. Importantly, vaccination not only reduced Aβ plaque load to
60% of controls and lowered both insoluble Aβ40 as well as Aβ42 in APP23 brain, but also significantly reduced cerebral soluble Aβ species. In summary, Aβ retroparticle vaccination may thus hold promise as a novel efficient future candidate vaccine for active immunotherapy of Alzheimers disease.
The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked advertisement in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.
1 This work was supported by a grant from the Hans und Ilse Breuer Stiftung (to U.C.M.) and a grant from Alzheimer Forschungs-Initiative eV (to T.D.).
2 Address correspondence and reprint requests to Dr. Ulrike C. Müller, Heidelberg University, Institute for Pharmacy and Molecular Biotechnology, Bioinformatics and Functional Genomics, Im Neuenheimer Feld 364, D-69120 Heidelberg, Germany. E-mail address: u.mueller{at}urz.uni-hd.de
3 Abbreviations used in this paper: AD, Alzheimers disease; Aβ, β-amyloid peptide; EGF, epidermal growth factor; FA, formic acid; MLV, murine leukemia virus; PDGFR, platelet-derived growth factor receptor; THB, tissue homogenization buffer; VLP, virus-like particle; VSV, vesicular stomatitis virus.
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