Neural Transplantation in Huntington's Disease: The NEST-UK Donor Tissue Microbiological Screening Program and Review of the Literature

Neural transplantation of human fetal tissue for Huntington's disease (HD) is now entering the clinical arena. The safety of the procedure has now been demonstrated in a number of studies, although the efficacy of such an approach is still being investigated. Stringent but practicable screening of the donor tissue for potential pathogens is an essential prerequisite for successful implementation of any novel transplant program that uses human fetal tissue. In this article we summarize the UK-NEST protocol for the screening of human fetal tissue being grafted to patients with mild to moderate HD. We describe the results of microbiological screening of 87 potential tissue donors in a pilot study, and of the first four donor–recipient patients included in the UK-NEST series. The rationale for the adoption and interpretation of the various tests is described and our methodology is compared with those previously used by other centers. This article therefore presents a comprehensive, logical yet pragmatic screening program that could be employed in any clinical studies that use human fetal tissue for neurotransplantation.

Ethnic diversity and patterns of infection of a UK HIV-positive patient population outwith major conurbations

We surveyed the HIV-positive population attending a major teaching hospital sited outwith a major conurbation. Eighty-five percent of homosexually acquired infections were contracted within the UK and 91% of heterosexually acquired infections were contracted outside of the UK. A strikingly wide range of nationalities (45) and countries of origin of infection were represented within a relatively small patient population. Most patients were non-UK-born immigrants. A high proportion of illegal immigrants were identified within which there was a high proportion lost to follow-up. This degree of ethnic diversity and domiciliary instability is rarely a feature of non-HIV populations in this setting and imposes additional demands on delivery of care and health-care planning.

Rev: beyond nuclear export

Rev remains a hot topic. In this review, we revisit the insights that have been gained into the control of gene expression by the retroviral protein Rev and speculate on where current research is leading. We outline what is known about the role of Rev in translation and encapsidation and how these are linked to its more traditional role of nuclear export, underlining the multifaceted nature of this small viral protein. We discuss what more is to be learned in these fields and why continuing research on these 116 amino acids and understanding their function is still important in devising methods to combat AIDS.

Candidaemia in a large teaching hospital: a clinical audit

BACKGROUND

Candidaemias are associated with significant morbidity and mortality. The British Society of Medical Mycology and Infectious Diseases Society of America recently published audit standards, to address the changing epidemiology of candidaemia and to improve outcomes.

AIM

To investigate the local epidemiology of candidaemia and the standard of care in a large teaching hospital.

DESIGN

Retrospective audit.

METHODS

Data were obtained for all candidaemia episodes over the 4-year period ending July 2004, from the medical and nursing notes, laboratory computer and patient administration system.

RESULTS

We identified 92 episodes in 90 patients. The main predisposing factors were being on an intensive care unit, having a central venous catheter, and (for neonates) prematurity. Central venous catheters were removed at a mean 1.8 days following candidaemia; 79% (37/47) were removed within 48 h (the audit standard). Identification and susceptibility tests were performed for 94.7% of isolates. All were susceptible to amphotericin B; 87% were susceptible to fluconazole. Antifungal treatment was started within 24 h of a positive blood culture in 84% of episodes. Initial antifungal therapy was appropriate in 95% (61/64) of treated cases. Most patients (81%) who survived or completed their intended course of treatment before death received at least 2 weeks treatment. However, only 45% of those transferred to other hospitals had accompanying guidance on the intended further duration of therapy. Thirty-day mortality was 41%. After adjustment for age, the presence of Candida-related complications was associated with an odds ratio for mortality of 6.5 (95% CI 1.2-36.5, p = 0.03).

DISCUSSION

Overall the audit standards set by the BSMM and IDSA were met, and discrepancies did not lead to a change in outcome. Improved intravenous catheter care, a more pro-active approach to searching for complications, and improvement in the inter-hospital transfer process, will assist in reducing morbidity and mortality.

Human endogenous retrovirus-W envelope (syncytin) is expressed in both villous and extravillous trophoblast populations

The placenta is unique amongst normal tissues in transcribing numerous different human endogenous retroviruses at high levels. In this study, RT-PCR and immunohistochemistry were used to investigate the expression of syncytin in human trophoblast. Syncytin transcripts were found in first-trimester trophoblast cells with both villous and extravillous phenotypes and also in the JAR and JEG-3 choriocarcinoma cell lines. Syncytin protein was detected in villous trophoblast and in all extravillous trophoblast subpopulations of first- and second-trimester placental tissues. It was also present in ectopic trophoblast from tubal implantations. This study confirms that syncytin is expressed widely by a variety of normal human trophoblast populations, as well as choriocarcinoma cell lines.

Inhibition of hepatitis B virus by lentiviral vector delivered antisense RNA and hammerhead ribozymes

Chronic hepatitis B virus (HBV) infection is an important cause of cirrhosis and hepatocellular carcinoma. Current treatments are limited and may be ineffective. Nucleic acid-mediated targeting of viral mRNA is an attractive and specific approach for viral infection and lentiviral vectors provide a means to express antisense sequences or ribozymes stably in target cells permitting continuous production within that cell and its progeny. To demonstrate long-term gene expression by lentiviral vectors in hepatocytes and to introduce lentiviral vectors expressing anti-HBV genes to assess their effect against HBV, lentiviral vectors expressing a reporter gene were assessed for longevity of gene expression in hepatocytes in vitro. Hammerhead ribozymes and antisense sequences targeting the HBV encapsidation signal (epsilon), X or surface antigen on mRNAs were cloned into lentiviral vectors and used to transduce HBV expressing hepatocytes where the effect on HBV mRNA level was assessed using ribonuclease protection. Gene expression in hepatocytes from integrated vectors continued for over 4 months without selection. Antisense RNA targeting HBs mRNA reduced this transcript, whilst antisense RNA to HBX mRNA was ineffective. Sense RNAs corresponding to epsilon and HBX mRNA also reduced HBV mRNA levels. Ribozymes targeting HBs and HBX mRNA effectively reduced HBV mRNA levels compared with inactive constructs indicating their effect to be enzymatic rather than antisense. Lentiviral vectors can produce long-term gene expression in hepatocytes and thus permit prolonged expression of antiviral genes targeting the HBV encapsidation signal, surface and X mRNAs as treatments for chronic HBV infection.

Lentivirus-mediated gene transfer of viral interleukin-10 delays but does not prevent cardiac allograft rejection

Human immunodeficiency virus (HIV)-based lentiviral vectors expressing viral interleukin-10 (vIL-10) were used to transduce rat cardiac allografts with the aim of extending graft survival. vIL-10 expression was first shown, by RT-PCR, to persist in transduced heart isografts for at least 28 days after transduction. Cardiac transplants were performed in a fully allogeneic rat strain combination (Lewis to DA); allografts transduced by vectors expressing vIL-10 showed significantly prolonged survival (14.5 vs 7.5 days median survival time). Mixed lymphocyte reactions (MLRs) were used to determine the influence, in vitro, of vIL-10 on alloantigen-induced T-cell proliferation. Bioactive vIL-10, produced by DA rat aortic endothelial cells transduced with HIV-PGK-vIL-10, was added to MLRs at different time points and lymphocyte proliferation was assessed by uptake of [3H]thymidine. T-cell proliferation was inhibited by >80% when vIL-10 was added to the MLR at day 1, 2 or 3 of coculture. The inhibitory effect was significantly decreased when addition of vIL-10 was delayed until day 4 or 5 (47 and 35% inhibition, respectively). The extended graft survival time is comparable to that using adenoviral vectors delivering vIL-10 in a similar rat strain combination. The limited improvement in survival may be due to lack of inhibition of the early phase of the alloimmune response as suggested by in vitro studies confirming that maximum suppression of the MLR by vIL-10 can only be achieved if the cytokine is present at the initiation of alloimmune recognition. The delay in expression of vIL-10 from the lentiviral vector means that protocols must be developed to suppress the early stages of alloimmune stimulation before vIL-10 is produced.

The use of thalidomide in the treatment of intracranial tuberculomas in adults: two case reports

We present two cases of tuberculous meningitis (TBM) in adults complicated by focal neurological deficits which showed progression whilst on steroids. In case 1 an MRI demonstrated multiple ring-enhancing lesions compressing the optic chiasm leading to a bitemporal hemianopia. After the introduction of thalidomide serial imaging and field perimetry at 6, 9, 12 and 24 months into treatment showed progressive improvement. In case 2, two months into anti-tuberculous treatment with steroids, the patient developed fluctuating right sided paralysis with the MRI demonstrating a large ring-enhancing mass encasing the left internal carotid and middle cerebral arteries. Thalidomide was introduced as an immunomodulatory adjunct and subsequently the patient made a complete neurological recovery. The immunomodulatory effects of thalidomide may have a role in the acute and chronic management of TBM complicated by intracranial tuberculomas.

The packaging signal of simian immunodeficiency virus is upstream of the major splice donor at a distance from the RNA cap site similar to that of human immunodeficiency virus types 1 and 2

Deletion mutation of the RNA 5' leader sequence of simian immunodeficiency virus (SIV) was used to localize the virus packaging signal. Deletion of sequences upstream of the major splice donor (SD) site produced a phenotype most consistent with a packaging defect when analysed by both RNase protection assay and RT-PCR. Sequences downstream of the SD were deleted and produced varying effects but did not affect packaging: a large downstream deletion had little effect on function, whereas a nested deletion produced a profound replication defect characterized by reduced protein production. Secondary structure analysis provided a potential explanation for this. The major packaging signal of SIV appears to be upstream of the SD in a region similar to that of human immunodeficiency virus type 2 (HIV-2) but unlike that of HIV-1; however, the packaging signal of all three viruses are at a similar distance from their respective cap sites. This conserved positioning suggests that it is more important in the virus life cycle than the position of the signal relative to the SD.

Prolonged survival in AIDS-related progressive multifocal leucoencephalopathy following anti-retroviral therapy and cidofovir

We describe the case of a 44-year-old man who developed sub-acute cerebellar ataxia due to AIDS-related progressive multifocal leucoencephalopathy (PML) caused by JC virus. Following treatment with highly active anti-retroviral therapy (HAART) and cidofovir, he made a marked neurological improvement and is leading an independent life 18 months after the diagnosis of PML. Early recognition of AIDS-related PML and treatment with HAART improves prognosis. Cidofovir, an inhibitor of viral DNA polymerase, appears to have an additive beneficial effect and should be considered especially in patients who fail to improve despite treatment with HAART and in patients who have a high JC virus load in CSF.

The impact of new diagnostic methodologies in the management of meningitis in adults at a teaching hospital

BACKGROUND

Suspected meningitis is a frequent reason for admission to hospital in the UK. While bacterial meningitis requires prompt antibiotic therapy to reduce mortality and morbidity, enteroviral meningitis, the most frequent viral cause, is almost invariably a benign disease.

AIM

To determine the clinical presentation, laboratory findings and outcome of meningitis by microbiological aetiology and patient age, and to assess the clinical management of adults presenting with meningitis, with reference to national guidelines.

DESIGN

Retrospective case-note review.

METHODS

Adult (>14 years) admissions to Addenbrooke's Hospital with meningitis or meningococcal septicaemia March 1996-September 2001 were audited retrospectively. The case definition was: symptoms compatible with meningitis, and either abnormal CSF (leukocytes >5x10(9)/ml) or meningococcal disease. The only exclusion criterion was the presence of a ventricular shunt.

RESULTS

Only 30% of patients seen by a General Practitioner were given pre-admission antibiotics. In a substantial number of cases, including those with bacterial meningitis, antibiotic administration was delayed either because patients were sent for CT head scans (delaying a lumbar puncture) or because the diagnosis was not considered, especially in elderly patients with reduced conscious levels. There were no confirmed cases of H. influenzae meningitis. Overall outcomes in terms of mortality and disability were similar to UK national data. A surprising number of patients (40%) were afebrile on admission.

DISCUSSION

The proportion of patients with meningitis given pre-hospital antibiotics by GPs is still worryingly low, although early hospital management has improved. Improved diagnostic facilities, particularly viral PCR assays, reduce antibiotic usage and hospital stay, with considerable financial savings.