Vincent Marchesi, MD, PhD

Alzheimer’s dementia is the result of a cascade of pathological processes that work in concert over many decades to reduce the number of functioning neurons of the human brain that are responsible for memory and other executive actions. Neuronal cell death is believed to be due to the accumulation of potentially toxic amyloid related peptides, referred to as Abeta 40 and 42, through either their excessive production or reduced clearance. Amyloid deposits can be removed from animal and human brains by specific antibody treatments, and clinical trials using this approach are now under way. Antibodies to fragments of amyloid abeta peptides are now recognized as biological agents with great therapeutic potential.

Two recent reports present evidence that naturally occurring auto-antibodies to abeta might be neuro-protective. In one study auto-antibodies to an aggregated form of abeta were found to be depressed in AD patients, but, paradoxically, elevated in normal, young adults. A second report describes a decrease in the incidence of AD in people treated with intravenous immunoglobulin preparations Both results are consistent with the idea that natural antibodies to abeta exist in all people and are depleted in advanced AD.

Contrary to these results, we have found that there is no clear correlation with levels of anti-abeta antibodies and the clinical status of the donor. Antibodies to a peptide fragment (p16-34) of abeta are elevated in many but not all individuals with advanced AD. We have found that intravenous immunoglobulin preparations also react with the p16-34 abeta fragment. If naturally occurring antibodies to abeta are indeed neuro-protective, as the available evidence suggests, it will be important to determine which epitopes of abeta induce the protective response, and, equally important, to identify the epitopes that might confer toxicity. The patho-physiological significance of auto-antibodies to amyloid abeta peptides is clearly a complicated question that deserves further study. auto-antibodies to amyloid abeta peptides
neuro-protective antibodies