[Cerebrospinal fluid proteins: III. Normal values of immunoglobulins G, A and M (variations related to race, sex and age)]

Detection methods for neural autoantibodies

Antibodies are part of the adaptive immune response that provides protection against microorganisms. In rare instances individuals can develop antibodies that bind to normal central nervous system structures. These antibodies have been classified into two groups depending on the subcellular location of their target antigens. Biomarker antibodies bind to cytosolic or nuclear targets. They do not impact on the normal function of the cell, but are most often paraneoplastic biomarkers that may suggest screening for different cancers. The second, more recently discovered group of antibodies recognize the three-dimensional structure of native proteins that are accessible on the cell surface. Understanding of this important difference is reflected in the nature of assays used to detect antibodies in these two groups. Western blots and, more recently, line blots, both of which use linear, denatured targets, are used to detect antibodies to intracellular targets. Newer assays have been developed that maintain the native structure of protein targets to permit detection of antibodies that recognize extracellular targets. In this chapter we describe the methods used to detect both antibody types, and discuss assay cut-offs, sample handling, and which biologic fluid to test.

Intramembranous fragment of amyloid-beta: A potential immunogen for Alzheimer's disease immunotherapy

Immunotherapy holds great promise for Alzheimer's disease (AD), but meningoencephalitis observed in the first AD vaccination trial, which accompanied T-lymphocytic infiltration, needs to be overcome. This study was aimed to investigate alternative approaches for a safer vaccine to treat AD. We used intramembranous fragment of amyloid-beta (IF-Abeta) to immunize Kunming mice for up to 2.5 months and then evaluated the immunization efficacy and potential adverse effects. Immunization of mice with IF-Abeta plus Freund's adjuvant resulted in moderate levels of Abeta antibodies (IgG), and the anti-sera were able to neutralize Abeta1-42-neurotoxicity in cultured primary cortical neurons. IF-Abeta itself did not show neurotoxicity, and immunization with IF-Abeta did not cause behavioral deficits in Morris water maze or any abnormalities by histological examinations of major organs including the brain. We conclude that vaccination with IF-Abeta may be a potentially safe and effective treatment for AD.

Antibody response and plasma Abeta1-40 levels in young Microcebus murinus primates immunized with Abeta1-42 and its derivatives

We have been developing Abeta derivative vaccines with the objective to improve the safety of Abeta targeting immunotherapy. Our Abeta homologs are designed to have less direct toxicity and to produce a modified immune response compared to Abeta. In extensive mouse studies, all our vaccines have improved cognition in transgenic mice while eliciting different immune responses and reducing brain amyloid burden to a variable degree. While we are continuing to characterize these vaccines in mice, in preparation for studies in old primates and for human trials we assessed their effect in young lemur primates (n=25) that with age develop Abeta plaques and tau aggregates as seen in Alzheimer's disease. In the primates, all the peptides administered with alum adjuvant elicited a moderate to robust anti-Abeta IgM response. Abeta1-42, K6Abeta1-30 and K6Abeta1-30[E(18)E(19)] resulted in a high anti-Abeta IgG response, whereas Abeta1-30[E(18)E(19)] produced a weaker more variable IgG titer. Notably, 22 weeks after the 3rd immunization, IgM and IgG levels in derivative-vaccinated primates were similar to preimmune values whereas Abeta1-42 treated primates maintained a moderate IgG titer. The increase in antibodies that recognized Abeta1-40 often correlated with increase in Abeta1-40 in plasma, which suggests that the antibodies were binding to Abeta in vivo. Interestingly, significant transient weight gain was observed (K6Abeta1-30-, Abeta1-30[E(18)E(19)]- and Abeta1-42-treated) or a trend in the same direction (K6Abeta1-30[E(18)E(19)]-treated, adjuvant controls) following the injections. Based on these findings, we have chosen K6Abeta1-30 for immunizations in old primates as the antibody response to this vaccine was less variable compared to other Abeta derivatives. Our present findings indicate that most of our Abeta derivatives elicit a substantial antibody response in primates, and importantly this effect is reversible which enhances the safety profile of our approach.

An attenuated immune response is sufficient to enhance cognition in an Alzheimer's disease mouse model immunized with amyloid-beta derivatives

Immunization with amyloid-beta (Abeta) 1-42 has been shown to reduce amyloid burden and improve cognition in Alzheimer's disease (AD) model mice. In a human trial, possible cognitive benefit was found but in association with significant toxicity in a minority of patients. We proposed that immunization with nonfibrillogenic Abeta derivatives is much less likely to produce toxicity and have previously shown that one such derivative (K6Abeta1-30) can reduce amyloid burden in mice to a similar extent as Abeta1-42. Here, we immunized AD model mice (Tg2576) with Abeta1-30[E18E19] or with K6Abeta1-30[E18E19]. These peptides were designed to be nontoxic and to produce less T-cell response, which has been linked to toxicity. K6Abeta1-30[E18E19] induced primarily an IgM response, whereas Abeta1-30[E18E19] induced an IgG titer that was lower than previously seen with K6Abeta1-30 or Abeta1-42. However, both treated animal groups performed better than Tg controls in the radial arm maze. Amyloid burden was similar in Abeta1-30[E18E19]-vaccinated mice and their Tg controls, whereas the number of medium and small sized plaques was reduced (29-34%) in K6Abeta1-30[E18E19]-immunized mice compared with Tg controls. Amyloid burden in these mice correlated inversely with plasma IgM levels. The cognitive benefit and amyloid reduction in the K6Abeta1-30[E18E19]-vaccinated mice are likely to be related to peripheral clearance of Abeta, because IgM does not cross the blood-brain barrier because of its large size. Our results indicate that these nontoxic Abeta derivatives produce an attenuated antibody response, which is less likely to be associated with negative side effects while having cognitive benefits.

A safer vaccine for Alzheimer's disease?

Recent reports indicate that amyloid-beta (Abeta) vaccine-based therapy for Alzheimer's disease (AD) may be on the horizon. There are, however, concerns about the safety of this approach. Immunization with Abeta1-42 may not be appropriate in humans because it crosses the blood-brain barrier, can seed fibril formation, and is highly fibrillogenic. Abeta1-42 fibrils can in turn cause inflammation and neurotoxicity. This issue is of a particular concern in the elderly who often do not mount an adequate immune response to vaccines. Our findings show that vaccination with nonamyloidogenic/nontoxic Abeta derivative may be a safer therapeutic approach to impede the progression of Abeta-related histopathology in AD. Although the site of action of the anti-Abeta antibodies has been suggested to be within the brain, peripheral clearance of Abeta may have a greater role in reducing cerebral amyloid plaques in these animals and eventually in AD patients. Antibodies in general are predominantly found outside the central nervous system (CNS) and will, therefore, primarily clear systemic Abeta compared to brain Abeta. This disruption of the equilibrium between central and peripheral Abeta should then result in efflux of Abeta out of the brain, and subsequent removal of plaques. Abeta therapy can be targeted to the periphery, which may result in fewer CNS side effects, such as inflammation. Future Abeta derived vaccines should include T(h) epitopes, carriers and/or lipid moieties to enhance antibody production in the elderly, the population predominantly affected by AD.