Intravenous immunoglobulin (
IVIg) has been a candidate as a potential anti-
amyloid immunotherapy for
Alzheimer disease (AD) because it contains anti-
amyloid β (Aβ)
antibodies. Although several studies with
IVIg in AD have been published, changing levels of Aβ efflux from the brain, or disaggregation of Aβ species induced by
immunotherapy, have not been properly investigated. Here, we carried out an open label study of
therapy with
IVIg in five patients with AD. We collected plasma from a peripheral vein (peripheral-plasma) and from the internal jugular vein (jugular-plasma) to estimate directly the efflux of soluble Aβ from the brain. We also measured high molecular weight (HMW) Aβ oligomers in CSF as a marker to detect disaggregated Aβ.
IVIg infusions were well tolerated in the majority of cases. However, one study subject had epileptic
seizures after
IVIg. Levels of HMW CSF Aβ oligomers in all participants were significantly increased after
IVIg. Aβ40 and Aβ42 levels in jugular-plasma were continuously or temporarily elevated
after treatment in three of five patients who showed preserved cognitive function, whereas levels of those in peripheral-plasma did not correlate with reactivity to the treatment. Other conventional
biomarkers including 11C-Pittsburgh compound B retention were not altered after the treatment. These findings imply that HMW Aβ oligomer levels could be a better
biomarker to reflect the anti-
amyloid effects of
IVIg than conventional Aβ species; moreover, Aβ in jugular-plasma seems to be a more direct and precise
biomarker to estimate clearance of Aβ from the brain rather than Aβ in peripheral-plasma.
TRIAL REGISTRATION: UMIN000022319.