James A. R. Nicoll

Neuropathology of human Alzheimer disease after immunization with amyloid-β peptide: a case report

Amyloid-β peptide (Aβ) has a key role in the pathogenesis of Alzheimer disease (AD). Immunization with Aβ in a transgenic mouse model of AD reduces both age-related accumulation of Aβ in the brain and associated cognitive impairment. Here we present the first analysis of human neuropathology after immunization with Aβ (AN-1792). Comparison with unimmunized cases of AD (n = 7) revealed the following unusual features in the immunized case, despite diagnostic neuropathological features of AD: (i) there were extensive areas of neocortex with very few Aβ plaques; (ii) those areas of cortex that were devoid of Aβ plaques contained densities of tangles, neuropil threads and cerebral amyloid angiopathy (CAA) similar to unimmunized AD, but lacked plaque-associated dystrophic neurites and astrocyte clusters; (iii) in some regions devoid of plaques, Aβ-immunoreactivity was associated with microglia; (iv) T-lymphocyte meningoencephalitis was present; and (v) cerebral white matter showed infiltration by macrophages. Findings (i)–(iii) strongly resemble the changes seen after Aβ immunotherapy in mouse models of AD and suggest that the immune response generated against the peptide elicited clearance of Aβ plaques in this patient. The T-lymphocyte meningoencephalitis is likely to correspond to the side effect seen in some other patients who received AN-1792 (refs. 7–9).

Long-term effects of Aβ42 immunisation in Alzheimer's disease: follow-up of a randomised, placebo-controlled phase I trial

BACKGROUND Immunisation of patients with Alzheimers disease with full-length amyloid-beta peptide (Abeta(42)) can clear amyloid plaques from the brain. Our aim was to assess the relation between Abeta(42) immune response, degree of plaque removal, and long-term clinical outcomes. METHODS In June, 2003, consent for long-term clinical follow-up, post-mortem neuropathological examination, or both, was sought from 80 patients (or their carers) who had entered a phase I randomised, placebo-controlled trial of immunisation with Abeta(42) (AN1792, Elan Pharmaceuticals) in September, 2000. The follow-up study was completed in September, 2006. Plaques were assessed in terms of the percentage area of the cortex with Abeta immunostaining (Abeta load) and in terms of characteristic histological features reflecting plaque removal. Survival of all 80 individuals until severe dementia or death was assessed with a Cox proportional hazard model. FINDINGS 20 participants--15 in the AN1792 group, five in the placebo group--died before follow-up started. A further 22 patients--19 in the AN1792 group, three in the placebo group--died during follow-up. Nine of the deceased patients, all in the AN1792 group, had given consent for post-mortem analysis; one of these who did not die with Alzheimers disease was excluded. In the remaining eight participants who received immunisation and who were examined neuropathologically, mean Abeta load was lower than in an unimmunised control group that was matched for age at death (2.1% [SE 0.7] in treated participants vs 5.1% [0.9] in controls; mean difference 3.0%, 95% CI 0.6-5.4; p=0.02). Although there was considerable variation in Abeta load and degree of plaque removal among immunised participants, the degree of plaque removal varied significantly with mean antibody response attained during the treatment study period (Kruskal-Wallis p=0.02). Seven of the eight immunised patients who underwent post-mortem assessment, including those with virtually complete plaque removal, had severe end stage dementia before death. In the whole cohort, there was no evidence of improved survival (hazard ratio 0.93, 95% CI 0.43-3.11; p=0.86) or of an improvement in the time to severe dementia (1.18, 0.45-3.11; p=0.73) in the AN1792 group versus the placebo group. INTERPRETATION Although immunisation with Abeta(42) resulted in clearance of amyloid plaques in patients with Alzheimers disease, this clearance did not prevent progressive neurodegeneration.

Microglia in neurodegenerative disease

Microglia, the resident macrophages of the CNS, are exquisitely sensitive to brain injury and disease, altering their morphology and phenotype to adopt a so-called activated state in response to pathophysiological brain insults. Morphologically activated microglia, like other tissue macrophages, exist as many different phenotypes, depending on the nature of the tissue injury. Microglial responsiveness to injury suggests that these cells have the potential to act as diagnostic markers of disease onset or progression, and could contribute to the outcome of neurodegenerative diseases. The persistence of activated microglia long after acute injury and in chronic disease suggests that these cells have an innate immune memory of tissue injury and degeneration. Microglial phenotype is also modified by systemic infection or inflammation. Evidence from some preclinical models shows that systemic manipulations can ameliorate disease progression, although data from other models indicates that systemic inflammation exacerbates disease progression. Systemic inflammation is associated with a decline in function in patients with chronic neurodegenerative disease, both acutely and in the long term. The fact that diseases with a chronic systemic inflammatory component are risk factors for Alzheimer disease implies that crosstalk occurs between systemic inflammation and microglia in the CNS.

Association of apolipoprotein E polymorphism with outcome after head injury

BACKGROUND Variation in outcome after head injury is not fully explained by known prognostic features. Polymorphism of the apolipoprotein E gene (APOE) influences neuropathological findings in patients who die from head injuries. More people who die from head injuries than non-head-injured controls have deposits of amyloid beta-protein in the cerebral cortex, with amyloid beta-protein deposits present predominantly in patients with the APOE epsilon4 allele. We report a prospective clinical study to test the hypothesis that patients with APOE epsilon4 have a worse clinical outcome 6 months after head injury than those without APOE epsilon4. METHODS We studied a prospectively recruited series of patients admitted after a head injury to a neurosurgical unit (n=93). Assessment of severity of the initial injury was by means of the Glasgow Coma Score (GCS). Outcome 6 months after injury was assessed by means of the Glasgow Outcome Scale. APOE genotypes were determined from blood samples by standard methods. FINDINGS Detailed information on outcome was available for 89 patients. 17 (57%) of 30 patients with APOE epsilon4 had an unfavourable outcome (dead, vegetative state, or severe disability) compared with 16 (27%) of the 59 patients without APOE epsilon4 (p=0.006). The association remained significant when adjustment was made to control for age, GCS, and computed tomography scan findings (p=0.024). INTERPRETATION Our findings show a significant genetic association of APOE polymorphism with outcome after head injury supporting the hypothesis of a genetically determined influence. Patients with APOE epsilon4 are more than twice as likely as those without APOE epsilon4 to have an unfavourable outcome 6 months after head injury. Further studies are under way to confirm and further evaluate this association.

Toxicity evaluation of replication-competent herpes simplex virus (ICP 34.5 null mutant 1716) in patients with recurrent malignant glioma

The herpes simplex virus (HSV) ICP34.5 null mutant 1716 replicates selectively in actively dividing cells and has been proposed as a potential treatment for cancer, particularly brain tumours. We present a clinical study to evaluate the safety of 1716 in patients with relapsed malignant glioma. Following intratumoural inoculation of doses up to l05 p.f.u., there was no induction of encephalitis, no adverse clinical symptoms, and no reactivation of latent HSV. Of nine patients treated, four are currently alive and well 14–24 months after 1716 administration. This study demonstrates the feasibility of using replication-competent HSV in human therapy.

Association of interleukin-1 gene polymorphisms with Alzheimer's disease.

Interleukin‐1 (IL‐1) is markedly overexpressed in Alzheimers disease. We found the IL‐1A 2,2 genotype in 12.9% of 232 neuropathologically confirmed Alzheimers disease patients and 6.6% of 167 controls from four centers in the United Kingdom and United States (odds ratio, 3.0; controlled for age and for ApoE [apolipoprotein E] genotype). Homozygosity for both allele 2 of IL‐1A and allele 2 of IL‐1B conferred even greater risk (odds ratio, 10.8). IL‐1 genotypes may confer risk for Alzheimers disease through IL‐1 overexpression and IL‐1–driven neurodegenerative cascades. Ann Neurol 2000;47:365–368

Review: Activation patterns of microglia and their identification in the human brain

Microglia in the central nervous system are usually maintained in a quiescent state. When activated, they can perform many diverse functions which may be either beneficial or harmful depending on the situation. Although microglial activation may be accompanied by changes in morphology, morphological changes cannot accurately predict the function being undertaken by a microglial cell. Studies of peripheral macrophages and in vitro and animal studies of microglia have resulted in the definition of specific activation states: M1 (classical activation) and M2 (sometimes subdivided into alternative activation and acquired deactivation). Some authors have suggested that these might be an overlapping continuum of functions rather than discrete categories. In this review, we consider translational aspects of our knowledge of microglia: specifically, we discuss the question as to what extent different activation states of microglia exist in the human central nervous system, which tools can be used to identify them and emerging evidence for such changes in ageing and in Alzheimers disease.

Solutes, but not cells, drain from the brain parenchyma along basement membranes of capillaries and arteries: significance for cerebral amyloid angiopathy and neuroimmunology

Elimination of interstitial fluid and solutes plays a role in homeostasis in the brain, but the pathways are unclear. Previous work suggests that interstitial fluid drains along the walls of arteries. Aims: to define the pathways within the walls of capillaries and arteries for drainage of fluid and solutes out of the brain. Methods: Fluorescent soluble tracers, dextran (3 kDa) and ovalbumin (40 kDa), and particulate fluospheres (0.02 μm and 1.0 μm in diameter) were injected into the corpus striatum of mice. Brains were examined from 5 min to 7 days by immunocytochemistry and confocal microscopy. Results: soluble tracers initially spread diffusely through brain parenchyma and then drain out of the brain along basement membranes of capillaries and arteries. Some tracer is taken up by vascular smooth muscle cells and by perivascular macrophages. No perivascular drainage was observed when dextran was injected into mouse brains following cardiac arrest. Fluospheres expand perivascular spaces between vessel walls and surrounding brain, are ingested by perivascular macrophages but do not appear to leave the brain even following an inflammatory challenge with lipopolysaccharide or kainate. Conclusions: capillary and artery basement membranes act as ‘lymphatics of the brain’ for drainage of fluid and solutes; such drainage appears to require continued cardiac output as it ceases following cardiac arrest. This drainage pathway does not permit migration of cells from brain parenchyma to the periphery. Amyloid‐β is deposited in basement membrane drainage pathways in cerebral amyloid angiopathy, and may impede elimination of amyloid‐β and interstitial fluid from the brain in Alzheimers disease. Soluble antigens, but not cells, drain from the brain by perivascular pathways. This atypical pattern of drainage may contribute to partial immune privilege of the brain and play a role in neuroimmunological diseases such as multiple sclerosis.

The potential for efficacy of the modified (ICP 34.5 − ) herpes simplex virus HSV1716 following intratumoural injection into human malignant glioma: a proof of principle study

We have previously demonstrated the safety of intratumoural administration of the selectively replication-competent herpes simplex virus mutant HSV1716 in patients with high-grade glioma (HGG). Here we show its potential for efficacy by demonstrating that the virus survives and replicates when injected into the tumours of patients. Since HSV replication is a cytolytic process it must result in tumour cell killing. Twelve patients with biopsy-verified HGG received an intratumoural injection of 105 plaque-forming units (p.f.u.) of HSV1716. Four to 9 days after inoculation, tumours were removed and assayed for evidence of viral replication. In two patients, HSV1716, in excess of the input dose was recovered from the injection site. HSV DNA was detected by PCR at the sites of inoculation in 10 patients and at distal tumour sites in four. HSV-specific antigen was detected in tumour tissue from two patients. In five patients an immunological response to HSV1716, as detected by changes in levels of IgG and IgM, was demonstrated. This study demonstrates that HSV1716 replicates in HGG without causing toxicity in both HSV-seropositive and -seronegative patients.

Consequence of Aβ immunization on the vasculature of human Alzheimer's disease brain

A major feature of Alzheimers disease is the accumulation of amyloid-beta peptide (Abeta) in the brain both in the form of plaques in the cerebral cortex and in blood vessel as cerebral amyloid angiopathy (CAA). Experimental models and human clinical trials have shown that accumulation of Abeta plaques can be reversed by immunotherapy. In this study, we hypothesized that Abeta in plaques is solubilized by antibodies generated by immunization and drains via the perivascular pathway, detectable as an increase in cerebrovascular Abeta. We have performed a follow up study of Alzheimers disease patients immunized against Abeta42. Neuropathological examination was performed on nine patients who died between four months and five years after their first immunization. Immunostaining for Abeta40 and Abeta42 was quantified and compared with that in unimmunized Alzheimers disease controls (n = 11). Overall, compared with these controls, the group of immunized patients had approximately 14 times as many blood vessels containing Abeta42 in the cerebral cortex (P<0.001) and seven times more in the leptomeninges (P = 0.013); among the affected blood vessels in the immunized cases, most of them had full thickness and full circumference involvement of the vessel wall in the cortex (P = 0.001), and in the leptomeninges (P = 0.015). There was also a significantly higher level of cerebrovascular Abeta40 in the immunized cases than in the unimmunized cases (cortex: P = 0.009 and leptomeninges: P = 0.002). In addition, the immunized patients showed a higher density of cortical microhaemorrhages and microvascular lesions than the unimmunized controls, though none had major CAA-related intracerebral haemorrhages. The changes in cerebral vascular Abeta load did not appear to substantially influence the structural proteins of the blood vessels. Unlike most of the immunized patients, two of the longest survivors, four to five years after first immunization, had virtually complete absence of both plaques and CAA, raising the possibility that, given time, Abeta is eventually cleared from the cerebral vasculature. The findings are consistent with the hypothesis that Abeta immunization results in solubilization of plaque Abeta42 which, at least in part, exits the brain via the perivascular pathway, causing a transient increase in the severity of CAA. The extent to which these vascular alterations following Abeta immunization in Alzheimers disease are reflected in changes in cognitive function remains to be determined.