Showing papers by "Guy's and St Thomas' NHS Foundation Trust published in 2001"

In vivo visualization of activated glia by[11C] (R)-PK11195-PET following herpes encephalitis reveals projected neuronal damage beyond the primary focal lesion

Abstract: A major challenge in the assessment of brain injury and its relationship to the ensuing functional deficits is the accurate delineation of the areas of damage. Here, we test the hypothesis that the anatomical distribution pattern of activated microglia, a normally dormant population of resident brain macrophages, can be used as a surrogate marker of neuronal injury not only at the primary lesion site but also in the antero- and retrograde projection areas of the lesioned neurones. Two patients with asymmetrical herpes simplex encephalitis were serially scanned 6 and 12 months after the acute illness using PET with [11C] (R)-PK11195, a marker of activated microglia/brain macrophages. The evolving structural changes in the brain were measured by volumetric MRI and compared with the pattern of [11C](R)-PK11195 binding. Corresponding to the clinically observed cognitive deficits, quantitative [11C](R)-PK11195-PET revealed highly significant signal increases within the affected limbic system and additionally in areas connected to the limbic system by neural pathways, including the lingual gyrus in the occipital lobe and the inferior parietal lobe, which had normal morphology on structural MRI. The increased [11C](R)-PK11195 binding, signifying the presence of activated microglia, persisted many months (>12) after antiviral treatment. Cortical areas that showed early high [11C](R)-PK11195 binding subsequently underwent atrophy. These observations demonstrate that in vivo imaging of activated microglia/brain macrophages provides a dynamic measure of active tissue changes following an acute focal lesion. Importantly, the glial tissue response in the wake of neuronal damage is protracted and widespread within the confines of the affected distributed neural system and can be related to the long-term functional deficits.

High-affinity anti-ganglioside IgG antibodies raised in complex ganglioside knockout mice: reexamination of GD1a immunolocalization.

Abstract: Gangliosides, sialic acid-bearing glycosphingolipids, are highly enriched in the vertebrate nervous system. Anti-ganglioside antibodies are associated with various human neuropathies, although the pathogenicity of these antibodies remains unproven. Testing the pathogenic role of anti-ganglioside antibodies will be facilitated by developing high-affinity IgG-class complement-fixing monoclonal anti-bodies against major brain gangliosides, a goal that has been difficult to achieve. In this study, mice lacking complex gangliosides were used as immune-naive hosts to raise anti-ganglioside antibodies. Wild-type mice and knockout mice with a disrupted gene for GM2/GD2 synthase (UDP-N-acetyl-D-galactosamine : GM3/GD3 N-acetyl-D-glactosaminyltransferase) were immunized with GD1a conjugated to keyhole limpet hemocyanin. The knockout mice produced a vigorous anti-GD1a IgG response, whereas wildtype littermates failed to do so. Fusion of spleen cells from an immunized knockout mouse with myeloma cells yielded numerous IgG anti-GD1a antibody-producing colonies. Ganglioside binding studies revealed two specificity classes; one colony representing each class was cloned and characterized. High-affinity monoclonal antibody was produced by each hybridoma : an IgG1 that bound nearly exclusively to GD1a and an IgG2b that bound GD1a, GT1b, and GT1aalpha. Both antibodies readily readily detected gangliosides via ELISA, TLC immune overlay, immunohistochemistry, and immunocytochemistry. In contrast to prior reports using anti-GD1a and anti-GT1b IgM class monoclonal antibodies, the new antibodies bound avidly to granule neurons in brain tissue sections and cell cultures. Mice lacking complex gangliosides are improved hosts for raising high-affinity, high-titer anti-ganglioside IgG antibodies for probing for the distribution and physiology of gangliosides and the pathophysiology of anti-ganglioside antibodies.