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Biomedical subjects

Peter G E Kennedy

Publications and source records attributed to Peter G E Kennedy.

At least 19 recordsLinked to original sources
PubMed2006

Varicella-Zoster virus gene expression at variable periods following death in a rat model of ganglionic infection.

We used a rat model of Varicella-Zoster virus (VZV) ganglionic infection, which mirrors some of the features of VZV latency in humans, to determine the temporal pattern of expression of a VZV immediate-early gene (63) and a VZV late gene (40) at 0, 24 and 48 h after death of the animal. The immediate-early VZV gene 63 is known to be abundantly expressed during human ganglionic latency, while the late VZV gene 40 is not expressed during human latency. Using both RNA in situ hybridisation (ISH) and nested RT-PCR, it was found that at all time points in both thoracic and lumbar ganglia, the number of ganglia positive for VZV gene 63 was higher than for gene 40. The expression of gene 40 did not increase with time postmortem (pm) These results provide indirect support for the hypothesis that patterns of expression of VZV genes detected in human tissue at even 48 h pm reflect the pattern of expression during human ganglionic latency.

Animals↗
PubMed2006

Human African trypanosomiasis-neurological aspects.

Human African Trypanosomiasis (HAT),which is also known as sleeping sickness, is a major cause of death and disability in 36 countries in sub-Saharan Africa. The disease is caused by the protozoan parasite of the Trypanosoma genus which is transmitted by the bite of the tsetse fly. The two types of HAT, the East African form due to Trypanosoma b.rhodesiensei (T. b.rhodesiensi) and the West African form due to T. b.gambiense, differ in their tempo of infection but in both cases the disease is always fatal if untreated. As well as multiple systemic features seen in the early (haemolymphatic) stage of disease, the late (encephalitic stage) stage, is associated with a wide range of neurological features including neuropsychiatric, motor and sensory abnormalities. Accurate staging of the disease is absolutely essential because of the potentially fatal complications of melarsoprol treatment of late-stage disease, the most important of which is a severe post-treatment reactive encephalopathy (PTRE) the pathogenesis of which is not fully understood. However, there is not a universal consensus as to how late-stage disease should be diagnosed using CSF criteria, and this has been very problematic in HAT. A more recent alternative drug for late stage gambiense disease is eflornithine (DFMO). There is a pressing need for a non-toxic oral drug for both early and late stage disease that would obviate many of the problems of staging, and various possible strategies to achieve this goal are currently underway. However, control of the disease will also require more effective measures of reducing man/fly contact and also the allocation of much greater financial and infrastructural resources than are currently available in Africa.

Central Nervous System↗
PubMed2006

Diagnostic and neuropathogenesis issues in human African trypanosomiasis.

Human African trypanosomiasis, also known as sleeping sickness, is caused by protozoan parasites of the genus Trypanosoma, and is a major cause of human mortality and morbidity. The East African and West African variants, caused by Trypanosma brucei rhodesiense and Trypanosoma brucei gambiense, respectively, differ in their presentation but the disease is fatal if untreated. Accurate staging of the disease into the early haemolymphatic stage and the late encephalitic stage is critical as the treatment for the two stages is different. The only effective drug for late stage disease, melarsoprol, which crosses the blood-brain barrier, is followed by a severe post-treatment reactive encephalopathy in 10% of cases of which half die. There is no current consensus on the diagnostic criteria for CNS involvement and the specific indications for melarsoprol therapy also differ. There is a pressing need for a quick, simple, cheap and reliable diagnostic test to diagnose Human African trypanosomiasis in the field and also to determine CNS invasion. Cerebrospinal fluid and plasma analyses in patients with Human African trypanosomiasis have indicated a role for both pro-inflammatory and counter-inflammatory cytokines in determining the severity of the meningoencephalitis of late stage disease, and, at least in T. b. rhodesiense infection, the balance of these opposing cytokines may be critical. Rodent models of Human African trypanosomiasis have proved very useful in modelling the post-treatment reactive encephalopathy of humans and have demonstrated the central role of astrocyte activation and cytokine balances in determining CNS disease. Such animal models have also allowed a greater understanding of the more direct mechanisms of trypanosome infection on CNS function including the disruption of circadian rhythms, as well as the immunological determinants of passage of trypanosomes across the blood-brain barrier.

Animals↗
PubMed2005

Investigating the presence of human herpesvirus 7 and 8 in multiple sclerosis and normal control brain tissue.

Multiple sclerosis (MS) is an important demyelinating disease of the central nervous system, the aetiology of which is thought to have a possible viral component. In this study we investigated the possible involvement in MS of two herpes viruses: the neurotropic human herpesvirus 7 (HHV-7) and the related human herpesvirus 8 (HHV-8). Utilising fluorescent in situ hybridisation (FISH) techniques, we examined human post mortem tissues for the presence of immediate early and late viral gene or protein expression in MS patient normal appearing white matter (NAWM), lesional tissue and normal control brain samples. HHV-7 and/or HHV-8 mRNA or protein was detected in some individuals in all three sample categories and was restricted to oligodendrocytes, as determined by double mRNA FISH analysis or immuno fluorescence (IF). No samples showed evidence of viral mRNA when subjected to RT-PCR on extracted ribonucleic acid. We therefore conclude that there is little evidence in our particular sample cohort to suggest involvement of either HHV-7 or HHV-8 in MS.

Aged↗
PubMed2005

Viral encephalitis.

Acute viral encephalitis may be caused by a wide range of viruses but the most important is herpes simplex encephalitis (HSE) because of its severity, especially if untreated, and its good response to specific treatment with acyclovir. The outcome of any CNS viral infection is dependent on both the immune status of the host and the virulence of the infecting virus. In evaluating a patient with suspected viral encephalitis there are 3 essential steps, namely the identification of a true parenchymal virus infection of the brain rather than a non-infective encephalopathy, the distinction of an infectious viral encephalitis from an acute disseminated encephalomyelitis (ADEM), and then the determination, where possible, of the specific virus involved. In practice, the precise viral cause of the encephalitis may never be established. Analysis of the CSF for herpes simplex virus (HSV) DNA using the Polymerase Chain Reaction (PCR) has been a significant advance in the diagnosis of HSE as this test has a very high sensitivity and specificity especially with appropriate sample timing. It is essential to commence early treatment with intravenous acyclovir in patients suspected of having HSE because of the remarkable safety and efficacy of this drug and the dangers of delaying potentially effective treatment of life threatening disease. This review outlines the general management approach in patients suspected of having viral encephalitis.

Encephalitis, Herpes Simplex↗
PubMed2005

Early and late HHV-6 gene transcripts in multiple sclerosis lesions and normal appearing white matter.

Multiple sclerosis is an inflammatory demyelinating disease of the CNS, the aetiology of which is believed to have both genetic and environmental components. We have investigated one of the candidate viruses for the environmental component of multiple sclerosis, the neurotropic human herpesvirus 6 (HHV-6). Utilizing fluorescent in situ hybridization (FISH) techniques, we have examined human post-mortem tissues for the presence of immediate early and late viral gene expression in multiple sclerosis patient normal appearing white matter (NAWM), lesional tissue and normal control brain samples. HHV-6 gene transcription was detected in all tissue samples and was restricted to oligodendrocytes, as determined by double mRNA FISH analysis. Quantitative analysis of viral mRNA expression indicated that both NAWM and lesional multiple sclerosis samples exhibited significantly higher levels of HHV-6 expression compared with the normal control samples. Lesional samples exhibited the highest levels of viral gene expression, with NAWM exhibiting an intermediate level between lesional and control tissues. Immunofluorescence against early and late HHV-6 proteins verified active translation of HHV-6 viral mRNA in oligodendrocytes. Southern blot analysis of nested polymerase chain reactions using extracted genomic DNA and cDNA confirmed the presence of the HHV-6 genome in all individuals, with the active expression profile mirroring the FISH results. The frequent high level of HHV-6 infection in multiple sclerosis samples suggests a possible role in pathogenesis.

Adult↗
PubMed2005

Meningoencephalitic African trypanosomiasis: Brain IL-10 and IL-6 are associated with protection from neuro-inflammatory pathology.

The relationship of neuropathology to CNS inflammatory and counter-inflammatory cytokine production in African trypanosome-infected mice was studied using an infection model with a defined disease progression. The initial phase of CNS infection by trypanosomes, where only mild neuropathology is evident, was characterised by high levels of IL-10 and IL-6. In the later phase of CNS infection and in a post-drug treatment model, moderate to severe neuropathology was associated with high levels of IFN-gamma and TNF-alpha. The relationship of these cytokines to neuropathological grade suggests that IL-10 and IL-6 protect the CNS from inflammatory pathology when parasites first enter the brain and the data reconcile previously contradictory clinical measurements of CSF cytokines in meningoencephalitic patients with post-mortem histopathology observations.

Animals↗
PubMed2005

Transcriptomal analysis of varicella-zoster virus infection using long oligonucleotide-based microarrays.

Varicella-zoster virus (VZV) is a human herpes virus that causes varicella as a primary infection and herpes zoster following reactivation of the virus from a latent state in trigeminal and spinal ganglia. In order to study the global pattern of VZV gene transcription, VZV microarrays using 75-base oligomers to 71 VZV open reading frames (ORFs) were designed and validated. The long-oligonucleotide approach maximizes the stringency of detection and polarity of gene expression. To optimize sensitivity, microarrays were hybridized to target RNA and the extent of hybridization measured using resonance light scattering. Microarray data were normalized to a subset of invariant ranked host-encoded positive-control genes and the data subjected to robust formal statistical analysis. The programme of viral gene expression was determined for VZV (Dumas strain)-infected MeWo cells and SVG cells (an immortalized human astrocyte cell line) 72 h post-infection. Marked quantitative and qualitative differences in the viral transcriptome were observed between the two different cell types using the Dumas laboratory-adapted strain. Oligonucleotide-based VZV arrays have considerable promise as a valuable tool in the analysis of viral gene transcription during both lytic and latent infections, and the observed heterogeneity in the global pattern of viral gene transcription may also have diagnostic potential.

Animals↗
PubMed2004

Varicella-Zoster virus proteins encoded by open reading frames 14 and 67 are both dispensable for the establishment of latency in a rat model.

A rat model of Varicella-Zoster virus (VZV) provides a system in which to investigate the molecular determinants of viral latency in dorsal root ganglia (DRG). In this study, we determined whether the VZV glycoproteins gC and gI, corresponding to VZV open reading frames (ORFs) 14 and 67, respectively, were required for the establishment of latency in this model. A VZV gI deletion mutant (DeltagI) derived from a recombinant Oka (rOka) cosmid and a gC null mutant obtained from a clinical isolate were inoculated into the footpads of 6-week-old rats, and the presence of viral DNA and eight different VZV RNA transcripts corresponding to the three classes of genes was investigated by in situ RT-PCR amplification and in situ hybridization (ISH) in the DRG at 1 week, 1 month, and 18-24 months after infection. VZV DNA and restricted RNA expression was established with both deletion mutants as well as the parental rOka virus. Both VZV DNA and RNA were detected in neurons and non-neuronal cells. The pattern of viral RNA expression detected with both gC and gI mutants was restricted with transcripts for VZV genes 62 and 63 most frequently expressed 18-24 months after infection. Transcripts for VZV genes 18, 28, and 29 were also detected at these time points but at a slightly lower frequency. Transcripts for the late gene 40 were never detected. We conclude that VZV ORFs 14 and 67 are dispensable for the establishment of a latent infection in this model.

Animals↗
PubMed2004

Translation of varicella-zoster virus genes during human ganglionic latency.

Immunohistochemical analysis of fixed tissue sections of human trigeminal ganglia (TG) and dorsal root ganglia (DRG) revealed the neuronal expression of proteins encoded by Varicella-zoster virus (VZV) genes 21, 29, 62 and 63. These proteins were detected mainly in the neuronal cytoplasm, are likely to be present in low abundance during VZV latency, and mirror the profile of VZV gene transcription.

Cytoplasm↗
PubMed2004

Human African trypanosomiasis of the CNS: current issues and challenges.

Human African trypanosomiasis (HAT), also known as sleeping sickness, is a major cause of mortality and morbidity in sub-Saharan Africa. Current therapy with melarsoprol for CNS HAT has unacceptable side-effects with an overall mortality of 5%. This review discusses the issues of diagnosis and staging of CNS disease, its neuropathogenesis, and the possibility of new therapies for treating late-stage disease.

Africa↗
PubMed2003

Absence of detection of varicella-zoster virus DNA in temporal artery biopsies obtained from patients with giant cell arteritis.

It has been suggested that Varicella-Zoster virus (VZV) may play a role in the pathogenesis of giant cell arteritis (GCA). We therefore used both in situ hybridisation and in situ Polymerase Chain Reaction amplification techniques in an attempt to identify VZV DNA in 15 temporal arteries from histologically proven GCA. We did not detect evidence of VZV DNA in the arteries of any of these subjects, nor in temporal arteries obtained from seven normal control subjects. VZV was detected, however, in neurons in a human trigeminal ganglion. While sampling variation and sensitivity issues are likely to play a role in the discrepancies observed in different studies of VZV in GCA, this study does not provide further support for the notion that VZV is playing a significant part in causing GCA.

DNA, Viral↗
PubMed2003

Clinical and neuroinflammatory responses to meningoencephalitis in substance P receptor knockout mice.

Human African trypanosomiasis, also known as sleeping sickness, affects the CNS at the late stage of the disease. Untreated the disease is invariably fatal, and melarsoprol, the only available and effective treatment for CNS disease, is associated in up to 10% of cases with a severe post-treatment reactive encephalopathy (PTRE), which can itself cause death. We used a reproducible mouse model of the PTRE to investigate the pathogenesis and treatment of this condition. Mice infected with Trypanosoma brucei brucei and treated subcuratively with diminazene aceturate develop a severe meningoencephalitis that closely resembles PTRE. We previously reported that substance P plays an important role in PTRE. We investigated the effect of disrupting the gene encoding for the NK1 receptor in mice on the clinical and neuroinflammatory response in this model. After induction of PTRE, NK1-/- mice showed a significant reduction in clinical impairment compared with NK1+/+ mice, but the severity of the neuroinflammatory response was significantly greater in NK1-/- mice. To explore the mechanisms of this dissociated phenotype, we treated infected NK1-/- mice with antagonists to NK2 and NK3 receptors, either singly or in combination. While none of these antagonist treatments altered the clinical score, combined treatment with the NK2 and NK3 antagonists significantly reduced the neuroinflammatory grading score in the NK1-/- mice. Thus, the clinical and neuroinflammatory responses to parasite invasion can be mediated by different pathways, and, importantly, the neuroinflammatory response is altered by alternative tachykinin receptor usage. These findings could be exploited to develop novel anti-inflammatory therapies in Human African trypanosomiasis by modulating the NK1 receptor as well as the parasite.

Animals↗
PubMed2003

Herpes simplex virus-1 and varicella-zoster virus latency in ganglia.

Two human alpha-herpesviruses, herpes simplex virus (HSV)-1 and varicella zoster virus (VZV), account for the most frequent and serious neurologic disease caused by any of the eight human herpesviruses. Both HSV-1 and VZV become latent in ganglia. In this review, the authors describe features of latency for these viruses, such as distribution, prevalence, abundance, and configuration of viral DNA in latently infected human ganglia, as well as transcription, translation, and cell type infected. Studies of viral latency in animal models are also discussed. For each virus, remaining questions and future studies to understand the mechanism of latency are discussed with respect to prevention of serious cutaneous, ocular, and neurologic disease produced by virus reactivation.

Animals↗
PubMed2003

Varicella-zoster virus gene 66 transcription and translation in latently infected human Ganglia.

Latent infection with varicella-zoster virus (VZV) is characterized by restricted virus gene expression and the absence of virus production. Of the approximately 70 predicted VZV genes, only five (genes 4, 21, 29, 62, and 63) have been shown by multiple techniques to be transcribed during latency. IE62, the protein product of VZV gene 62, is the major immediate-early (IE) virus-encoded transactivator of viral gene transcription and plays a pivotal role in transactivating viral genes during lytic infection. The protein kinase (66-pk) encoded by VZV gene 66 phosphorylates IE62, resulting in cytoplasmic accumulation of IE62 that mitigates nuclear IE62-induced gene activation. Analysis of latently infected human trigeminal ganglia for 66-pk expression by reverse transcriptase-dependent nested PCR, including DNA sequence analysis, in situ hybridization, and immunohistochemistry, revealed VZV open reading frame 66 to be a previously unrecognized latently expressed virus gene and suggests that prevention of IE62 import to the nucleus by VZV 66-pk phosphorylation is one possible mechanism by which VZV latency is maintained.

Base Sequence↗