Abstract: A diagnostic test for preclinical and clinical Alzheimer's disease is based on plasma levels of A&bgr;40, A&bgr;42, their ratio, or their rate of entry following administration of antibodies that sequester A&bgr;. Alterations of any of these parameters from control values identifies preclinical or clinical Alzheimer's disease.

Abstract: This invention provides variant 266 antibodies that are engineered to lack an N-glycosylation site within the CDR2 of the heavy chain, pharmaceutical compositions thereof, and polynucleotide sequences, vectors, and transformed cells useful to express the variant antibodies. The variants sequester soluble A&bgr; peptide from human biological fluids and specifically bind an epitope contained within position 13-28 of the amyloid beta peptide A&bgr; with significantly greater affinity than either mouse antibody 266 or humanized 266 antibodies retaining N-glycosylation sites. The variant antibodies are useful for treatment or prevention of conditions and diseases associated with A&bgr;, including Alzheimer's disease, Down's syndrome, cerebral amyloid angiopathy, mild cognitive impairment, and the like.