Recombinantly fused two single-chain variable fragments (scFv) of the TfR antibody 8D3 to the light chains of mAb158, an antibody selectively binding to Abeta protofibrils, which are involved in the pathogenesis of AD, markedly increasing mAb158 brain uptake, which makes it a strong candidate for improved Abeta immunotherapy and as a PET radioligand for early diagnosis and evaluation of treatment effect in AD [65]. The gene discussed is APP; the disease is Alzheimer disease.