A Van de Voorde

Development of a Specific Diagnostic Test for Measurement of β-Amyloid (1-42) [βA4(l-42)] in CSF

Alzheimer’s disease (AD) is considered as the most important of all neurodegenerative diseases, due to its frequent occurrence and devastating consequences. AD appears to be a very heterogeneous group of disorders sharing clinical characteristics and pathological hallmarks. Neuropathologically, the brains of AD patients are characterized by the presence of intracellular accumulations of neurofibrillary tangles (primarily composed of a hyperphosphorylated form of the microtubule associated protein tau) in the hippocampus and temporal lobe of the cerebral cortex, the extracellular deposition of amyloid fibrils in the senile plaques, and the degeneration of neurons and their synapses. Neither plaques or tangles are restricted to AD (Selkoe, 1991).

Radiolocalisation and imaging of stably HPLAP-transfected MO4 tumours with monoclonal antibodies and fragments

Immunotargeting of PLAP-expressing tumours was studied for two radioiodinated, highly specific anti-PLAP monoclonal antibodies, 7E8 and 17E3, differing 10-fold in affinity, as well as for 7E8 F(ab)2 fragments. An anti-CEA monoclonal antibody or anti-CD3 F(ab)2 fragments were used as controls. Specific and non-specific targeting was examined in nude mice simultaneously grafted with PLAP-positive tumours derived from MO4 1-4 cells, and CEA-positive tumours, derived from 5583-S cells. Results indicated that (1) MO4 1-4 tumours, with a stable expression of PLAP on the plasma membrane, represent a useful new in vivo model for immunodirected tumour targeting; (2) differences in antibody affinity for PLAP in vitro are not reflected in antibody avidity for tumour cells in vivo; and (3) excellent selective and specific localisation of the PLAP-positive tumours is achieved when 7E8 F(ab)2 fragments are used. The high tumour/blood ratios (10.7 +/- 3.9 at 46 h after injection) were due to a much faster blood clearance of 7E8 F(ab)2 fragments. At this time point, the mean tumour/non-tumour tissue ratio was as high as 34.5, and the mean specific localisation index was 29.0. As expected, the F(ab)2 fragments provided high tumour imaging efficiency on gamma camera recording. These data imply important potentials of the PLAP/anti-PLAP system for immunolocalisation and therapy in patients, but also emphasise that in vitro criteria alone are not reflected in in vivo tumour localisation capacities of antibodies.

Specific monoclonal antibodies against normal microtubule-associated protein-2 (MAP2) epitopes present in Alzheimer pathological structures do not recognize paired helical filaments

SummaryWe have developed monoclonal antibodies that detect normal microtubule-associated protein-2 (MAP2) epitopes in routinely fixed, paraffin-embedded tissue. The somatodendritic distribution of MAP2 in bovine and human nervous tissue was confirmed with several of these antibodies. Furthermore, some of these antibodies immunohistochemically labeled certain pathological structures in Alzheimer brain, especially neurites in senile plaques. Electron microscopic observations, however, indicate that these MAP2 epitopes are not located in the Alzheimer paired helical filaments themselves, but in amorphous granular structures coexistent with them. While the pathological nature of these structures is undetermined, they may represent artefactual modifications of normal cytoskeletal components.

Magnetic beads in suspension enable a rapid and sensitive immunodetection of human placental alkaline phosphatase

The kinetics and efficiency of the interaction between placental alkaline phosphatase and a monoclonal antibody (laboratory number 327) were determined by immunoassay using microtitre plates or magnetic beads. While only up to 45% of placental alkaline phosphatase was bound to microwells precoated with this antibody, even after prolonged incubation, no less than 60% and 100% binding were reached using magnetic beads after 1 and 3 h incubations, respectively. High-molecular-mass placental alkaline phosphatase and complexed placental alkaline phosphatase forms were also completely bound to magnetic beads in the presence of deoxycholate (up to 9 g/l for serum samples). The assay sensitivity was improved up to 4-fold. In addition, 100% binding of the antigen was achieved during simultaneous incubation of magnetic beads, monoclonal antibody (125 micrograms/l), and placental alkaline phosphatase. This one-step enzymatic assay, based on magnetic beads, is an attractive alternative to the classic assay performed in microtitre plates, enabling rapid, precise, and sensitive antigen detection, and only necessitating a minimum of laboratory equipment.

Tailoring of an Anti-Human Placental Alkaline Phosphatase Immunoglobulin Using Genetic Engineering

Human placental alkaline phosphatase (hPLAP; E.C.3.1.3.1.) is a member of a group of enzymes named according to the organ in which they predominate. Other members of this group include an intestinal isoenzyme (IAP) and a tissue non- specific isoenzyme found in liver, bone and kidney (LAP).