Immunohistochemical and in situ hybridisation detection of adenovirus early region 1A (E1A) gene in the microglia of human brain tissue

Emerging roles of pathogens in Alzheimer disease

Chronic spirochetal infection can cause slowly progressive dementia, cortical atrophy and amyloid deposition in the atrophic form of general paresis. There is a significant association between Alzheimer disease (AD) and various types of spirochete (including the periodontal pathogen Treponemas and Borrelia burgdorferi), and other pathogens such as Chlamydophyla pneumoniae and herpes simplex virus type-1 (HSV-1). Exposure of mammalian neuronal and glial cells and organotypic cultures to spirochetes reproduces the biological and pathological hallmarks of AD. Senile-plaque-like beta amyloid (Aβ) deposits are also observed in mice following inhalation of C. pneumoniae in vivo, and Aβ accumulation and phosphorylation of tau is induced in neurons by HSV-1 in vitro and in vivo. Specific bacterial ligands, and bacterial and viral DNA and RNA all increase the expression of proinflammatory molecules, which activates the innate and adaptive immune systems. Evasion of pathogens from destruction by the host immune reactions leads to persistent infection, chronic inflammation, neuronal destruction and Aβ deposition. Aβ has been shown to be a pore-forming antimicrobial peptide, indicating that Aβ accumulation might be a response to infection. Global attention and action is needed to support this emerging field of research because dementia might be prevented by combined antibiotic, antiviral and anti-inflammatory therapy.

In vivo adenovirus-mediated gene transfer for Parkinson's disease

Gene therapy is a potentially powerful approach to the treatment of neurological diseases. Neurotransmitter synthesizing enzymes and neurotrophic factors inhibiting neurodegenerative processes provide the basis for current development of gene therapy strategies for Parkinson's disease. Recently, in vivo gene transfer to the brain has been developed using adenovirus vectors. One of the advantages of recombinant adenovirus is that it can transduce both quiescent and actively dividing cells, thereby allowing both direct in vivo gene transfer and ex vivo gene transfer to neural cells. The expression of adenoviral vectors persists for several months with little inflammation, probably because the brain is partially protected from the immune system. Recombinant adenoviruses are currently being improved, particularly by inactivating viral genes controlling the expression of immunodominant viral proteins. Novel therapeutic tools such as vectors for gene therapy have to be evaluated in terms of efficacy and safety for future clinical trials. These vectors still need to be improved to allow long-term and possibly regulatable expression of the transgene.

Gene therapy for Parkinson's disease

Gene therapy is a potentially powerful approach to the treatment of neurological diseases. The discovery of neurotrophic factors inhibiting neurodegenerative processes and neurotransmitter-synthesizing enzymes provides the basis for current gene therapy strategies for Parkinson's disease. Genes can be transferred by viral or nonviral vectors. Of the various possible vectors, recombinant retroviruses are the most efficient for genetic modification of cells in vitro that can thereafter be used for transplantation (ex vivo gene therapy approach). Recently, in vivo gene transfer to the brain has been developed using adenovirus vectors. One of the advantages of recombinant adenovirus is that it can transduce both quiescent and actively dividing cells, thereby allowing both direct in vivo gene transfer and ex vivo gene transfer to neural cells. Probably because the brain is partially protected from the immune system, the expression of adenoviral vectors persists for several months with little inflammation. Novel therapeutic tools, such as vectors for gene therapy have to be evaluated in terms of efficacy and safety for future clinical trials. These vectors still need to be improved to allow long-term and possibly regulatable expression of the transgene.

Adenovirus-mediated gene transfer to the central nervous system for Parkinson's disease

Gene therapy is a potentially powerful approach to the treatment of neurological diseases. The discovery of neurotrophic factors inhibiting neurodegenerative processes and the isolation of genes encoding neurotransmitter synthesizing enzymes provide the basis for current gene therapy strategies for Parkinson's disease. Adenovirus vectors have been shown recently to allow efficient gene transfer to the brain. One of the advantages of recombinant adenovirus is that it can transduce both quiescent and actively dividing cells. Thus expression of transgenes in neurons using adenoviruses is possible after either direct in vivo gene transfer or ex vivo gene transfer. In vivo gene transfer, consisting of the direct intracerebral injection of genetic material, is a novel method that is particularly efficient with the adenoviral vector. Ex vivo gene transfer, combining gene transduction with intracerebral transplantation, is a way to improve the classical grafts which are limited by poor cell survival in Parkinson's disease. Probably because the brain is a partially immunologically privileged site, the expression of adenoviral vectors persists for several months with little inflammation. Recombinant adenoviruses are currently being improved, particularly by inactivating viral genes controlling the expression of immunodominant viral proteins.

Adenovirus gene transfer causes inflammation in the brain

We report that injecting an E1-deleted, non-replicating, human adenovirus type 5 vector into the brain leads to an inflammatory response. Much of this inflammation is induced directly by the virion particles themselves rather than through the expression of new proteins from the vector. The severity of inflammation was found to depend on the strain of inbred rat used: PVG rats have less inflammation than AO rats in response to a vector injection. Twelve hours after injection of adenovirus vectors into the striatum of AO rats, leukocytes were seen marginating to the walls of nearby blood vessels. By two days there was a large increase in major histocompatibility complex class I expression and a heavy infiltration of leukocytes, mainly macrophages and T cells. Retrograde transport of adenovirus to neurons of the substantia nigra was associated with a delayed and less intense inflammation at this distant site. Although AO and PVG rats showed comparable responses in the striatum up to six days, at later times PVG rats had less intense inflammation. In spite of the inflammatory response, vector-driven expression of the marker protein beta-galactosidase and an adenovirus early protein was seen for at least two months following the injection, although expression declined with time. The observation that adenovirus gene transfer leads to an inflammatory response in the brain must be taken into account when planning and interpreting experiments with these vectors. Furthermore, we conclude that using an appropriate strain of rat can diminish some aspects of the inflammation.