Dosage thresholds for AAV2 and AAV8 photoreceptor gene therapy in monkey

Gene therapy is emerging as a therapeutic modality for treating disorders of the retina. Photoreceptor cells are the primary cell type affected in many inherited diseases of retinal degeneration. Successfully treating these diseases with gene therapy requires the identification of efficient and safe targeting vectors that can transduce photoreceptor cells. One serotype of adeno-associated virus, AAV2, has been used successfully in clinical trials to treat a form of congenital blindness that requires transduction of the supporting cells of the retina in the retinal pigment epithelium (RPE). Here, we determined the dose required to achieve targeting of AAV2 and AAV8 vectors to photoreceptors in nonhuman primates. Transgene expression in animals injected subretinally with various doses of AAV2 or AAV8 vectors carrying a green fluorescent protein transgene was correlated with surgical, clinical, and immunological observations. Both AAV2 and AAV8 demonstrated efficient transduction of RPE, but AAV8 was markedly better at targeting photoreceptor cells. These preclinical results provide guidance for optimal vector and dose selection in future human gene therapy trials to treat retinal diseases caused by loss of photoreceptors.

Trends in classification, referral and treatment and the effect on outcome of patients with glioma: a 20 year cohort

This retrospective audit was conducted to examine the changes in patient characteristics, referral, treatment and outcome over a 20-year period in a large regional neuro-oncology centre, focusing on the impact of the changes in pathological classification of gliomas. Using the Edinburgh Cancer Centre (ECC) database all cases of glioma were identified and patient, tumour and treatment characteristics noted. Survival was calculated from date of surgery or, if no operation was performed, the date of referral. Comparison was made between four periods 1988-1992 (c1), 1993-1997(c2), 1998-2002(c3) and 2003-2007 (c4). During the 20 years, 1175 patients with a glioma were referred to ECC. The median age increased from 53 years to 57 years (p < 0.001) but the proportion without pathology remained unchanged (10%). The distribution of pathological grades changed over time Grade I-II: 24, 6, 6, and 6%, Grade III: 42, 27, 17, and 13% and Grade IV: 24, 61, 68, and 68% in c1, c2, c3 and c4, respectively (p < 0.001). Immediate RT was given to 68% (c1), 70% (c2), 78% (c3) and 79% (c4). Median interval from resection to RT reduced from 43 days (c1) to 36 days (c4) (p < 0.001). 5-year overall survival for patients with Grade III lesions increased: 21% (c1), 35% (c2), 37% (c3), 33% (c4) as did 1-year overall survival for Grade IV lesions: 18% (c1), 26% (c2), 29% (c3), 27% (c4)). This improvement probably reflects the change in pathological classification rather than a change in management. Proportional hazards analysis of grade IV 1993-2007 only (to reduce pathological variation) showed that younger age, frontal lesions, excision, higher RT dose had reduced hazard of death. Interval from surgery to RT had no impact on survival in this series.

Neuropathic Nav1.3-mediated sensitization to P2X activation is regulated by protein kinase C

Background

Increased neuronal excitability and spontaneous firing are hallmark characteristics of injured sensory neurons. Changes in expression of various voltage-gated Na⁺ channels (VGSCs) have been observed under neuropathic conditions and there is evidence for the involvement of protein kinase C (PKC) in sensory hyperexcitability. Here we demonstrate the contribution of PKC to P2X-evoked VGSC activation in dorsal root ganglion (DRG) neurons in neuropathic conditions.

Results

Using the spinal nerve ligation (SNL) model of neuropathic pain and whole-cell patch clamp recordings of dissociated DRG neurons, we examined changes in excitability of sensory neurons after nerve injury and observed that P2X3 purinoceptor-mediated currents induced by α,β-meATP triggered activation of TTX-sensitive VGSCs in neuropathic nociceptors only. Treatment of neuropathic DRGs with the PKC blocker staurosporine or calphostin C decreased the α,β-meATP-induced Na⁺ channels activity and reversed neuronal hypersensitivity. In current clamp mode, α,β-meATP was able to evoke action-potentials more frequently in neuropathic neurons than in controls. Pretreatment with calphostin C significantly decreased the proportion of sensitized neurons that generated action potentials in response to α,β-meATP. Recordings measuring VGSC activity in neuropathic neurons show significant change in amplitude and voltage dependence of sodium currents. In situ hybridization data indicate a dramatic increase in expression of embryonic Na_v1.3 channels in neuropathic DRG neurons. In a CHO cell line stably expressing the Na_v1.3 subunit, PKC inhibition caused both a significant shift in voltage-dependence of the channel in the depolarizing direction and a decrease in current amplitude.

Conclusion

Neuropathic injury causes primary sensory neurons to become hyperexcitable to ATP-evoked P2X receptor-mediated depolarization, a phenotypic switch sensitive to PKC modulation and mediated by increased activity of TTX-sensitive VGSCs. Upregulation in VGSC activity after injury is likely mediated by increased expression of the Na_v1.3 subunit, and the function of the Na_v1.3 channel is regulated by PKC.

Stroke thrombolysis in England, Wales and Northern Ireland: how much do we do and how much do we need?

BACKGROUND

Data are limited on the proportion of stroke patients nationally appropriate for thrombolysis either within the 3 h time window or the recently tested 4.5 h. This information is important for the redesign of services.

METHODS

Data on case mix, eligibility for thrombolysis, treatment and outcomes were extracted from the National Sentinel Stroke 2008 Audit dataset. This contains retrospective data on up to 60 consecutive stroke admissions from each acute hospital in England, Wales and Northern Ireland between 1 April and 30 June 2008.

FINDINGS

All relevant hospitals participated, submitting data on 11,262 acute stroke patients. 2118 patients arrived within 2 h and 2596 within 3 h of the onset of symptoms and 587 people were already in hospital. Therefore, 28% (3183) were potentially eligible for thrombolysis based on a 3 h time criterion. Of these, 1914 were under 80 years and 2632 had infarction with 14% (1605) meeting all three National Institute of Neurological Disorders and Stroke study criteria and so being potentially eligible for thrombolysis. If the time window is increased to 4.5 h then only another 2% became eligible. If the age limit was removed for treatment, the percentage potentially appropriate for tissue plasminogen activator increased to 23% within 3 h and 26% within 4.5 h. Overall, 1.4% (160) of patients were thrombolysed.

INTERPRETATION

Thrombolysis rates are currently low in the UK. 14% of patients in this sample were potentially suitable for thrombolysis using the 3 h time window. This would only increase marginally if thrombolysis was extended to include those up to 4.5 h. The greatest impact on increasing the proportion of patients suitable for thrombolysis would be to increase the number of patients presenting early and by demonstrating that the treatment is safe and effective in patients over 80 years of age.

Adeno-associated virus-mediated gene transfer to nonhuman primate liver can elicit destructive transgene-specific T cell responses

Gene transfer to murine liver with vectors based on novel adeno-associated virus (AAV) serotypes is efficient, stable, and safe even in the setting of antigenic transgene products. We undertook a study in cynomolgus macaques to evaluate the relevance of these findings to primates. The vectors were based on AAV serotype 7 and expressed green fluorescence protein (GFP) from the cytomegalovirus enhanced beta-actin promoter in both single-stranded and self-complementary genomes. Transduction efficiencies from the single-stranded vectors were similar to those observed in mice, although there was no advantage in primates with the self-complementary vectors. Primates elicited vibrant cytotoxic T cell responses to GFP that correlated with hepatitis and loss of transgene expression. There was no evidence of T cell activation in response to the AAV capsid. These studies indicate that under some conditions primates may activate more robust T cell responses to transgene products than is observed in mice.

The pleiotropic effects of natural AAV infections on liver-directed gene transfer in macaques

Adeno-associated viral (AAV) vectors hold great potential for liver-directed gene therapy. Stable and high levels of transgene expression have been achieved in many murine models. Systemic delivery of AAV vectors in nonhuman primates (NHPs) that are natural hosts of AAVs appear to be challenging due to the high prevalence of pre-existing neutralizing antibodies (NAbs). This study evaluates the performance of AAV8, hu.37, and rh.8 vectors expressing green fluorescent protein (GFP) from a liver-specific promoter in rhesus macaques. Two of the animals that received AAV8 showed transduction of 24 and 40% of hepatocytes 7 days after systemic vector delivery. Importantly, expression was detected in several animals after 35 days despite the elevation of liver enzymes and development of transgene-specific T cells in liver. Pre-existing low levels of NAbs profoundly impacted the outcome of gene transfer and redirected vector DNA to spleen. We developed a sensitive in vivo passive transfer assay to detect low levels of NAbs to these novel AAV serotypes. Other strategies need to be developed to reduce immune response to the transgene in order to maintain long-term gene expression.

Estimating the economic impact of a half-day reduction in length of hospital stay among patients with community-acquired pneumonia in the US

BACKGROUND

A recent study suggested that levofloxacin significantly reduces the hospital length of stay (LOS), by 0.5 days (p = 0.02), relative to moxifloxacin in patients with community-acquired pneumonia (CAP). The current analysis evaluated the potential economic impact of this half-day reduction in LOS.

METHODS

A cost model was developed to estimate the impact of a half-day reduction in LOS for CAP hospitalizations in the US. CAP incidence, hospitalization rate, and costs were obtained from published studies in PubMed and from publicly available government sources. The average daily cost of hospitalization was estimated for fixed costs, which comprise 59% of total inpatient costs. Costs from prior years were inflated to 2007 US dollars using the consumer price index. A range of cost savings, calculated using inpatient CAP costs from several studies, was extrapolated to the US CAP population.

RESULTS

Using the Centers for Disease Control National Hospital Discharge estimate of 5.3 days LOS for CAP, and an average cost (2007 $US) of $13,009 per CAP hospitalization, a daily fixed cost of $1448 was estimated. The resultant half-day reduction in costs associated with LOS was $724/hospitalization (range $457 to $846/hospitalization). When fixed and variable costs were considered, the estimated savings were $1227.27/episode. The incidence of CAP was estimated to be 1.9% (5.7 million cases/year based on current population census), and the estimated rate of CAP hospitalization was 19.6% (1.1 million annual hospitalizations). At $13,009/CAP-related hospitalization, total fixed inpatient costs of $8.6 billion annually were projected. The half-day reduction in LOS would therefore generate potential annual savings of approximately $813 million (range $513 million to $950 million). When total costs (fixed plus variable) were estimated, the mean savings for a half-day reduction would be approximately $1227/episode (range of $775 to $1434) or $1.37 billion annually in the US CAP population (range of $871 million to $1.6 billion). Limitations include the use of a single study for the estimation of fixed costs but a diversity of sources used for estimates of other variables, and lack of data with respect to the effects on costs of diagnostic-related groups, discounted contracts, and capitated payments.

CONCLUSIONS

A relatively small decrease in LOS in CAP can have a substantial cost impact, with estimated savings of $457 to $846 per episode or $500-$900 million annually. Additional evaluation is warranted for interpreting these cost-savings in the context of current antibiotic prescribing patterns.

Isolation and characterization of adenoviruses persistently shed from the gastrointestinal tract of non-human primates

Adenoviruses are important human pathogens that have been developed as vectors for gene therapies and genetic vaccines. Previous studies indicated that human infections with adenoviruses are self-limiting in immunocompetent hosts with evidence of some persistence in adenoid tissue. We sought to better understand the natural history of adenovirus infections in various non-human primates and discovered that healthy populations of great apes (chimpanzees, bonobos, gorillas, and orangutans) and macaques shed substantial quantities of infectious adenoviruses in stool. Shedding in stools from asymptomatic humans was found to be much less frequent, comparable to frequencies reported before. We purified and fully sequenced 30 novel adenoviruses from apes and 3 novel adenoviruses from macaques. Analyses of the new ape adenovirus sequences (as well as the 4 chimpanzee adenovirus sequences we have previously reported) together with 22 complete adenovirus genomes available from GenBank revealed that (a) the ape adenoviruses could clearly be classified into species corresponding to human adenovirus species B, C, and E, (b) there was evidence for intraspecies recombination between adenoviruses, and (c) the high degree of phylogenetic relatedness of adenoviruses across their various primate hosts provided evidence for cross species transmission events to have occurred in the natural history of B and E viruses. The high degree of asymptomatic shedding of live adenovirus in non-human primates and evidence for zoonotic transmissions warrants caution for primate handling and housing. Furthermore, the presence of persistent and/or latent adenovirus infections in the gut should be considered in the design and interpretation of human and non-human primate studies with adenovirus vectors.

Rates of inclusion of teenagers and young adults in England into National Cancer Research Network clinical trials: report from the National Cancer Research Institute (NCRI) Teenage and Young Adult Clinical Studies Development Group

Poor inclusion rates into clinical trials for teenagers and young adults (TYA; aged 13-24 years) have been assumed but not systematically investigated in England. We analysed accrual rates (AR) from 1 April 2005 up to 31 March 2007 to National Cancer Research Network (NCRN) Phase III trials for the commonest tumour types occurring in TYA and children: leukaemia, lymphoma, brain and central nervous system, bone sarcomas and male germ cell tumours. AR for 2005-2007 were 43.2% for patients aged 10-14 years, 25.2% for patients aged 15-19 years, and 13.1% for patients aged 20-24 years in the tumour types analysed. Compared with accrual from 1 April 2005 to 31 March 2006, AR between 1 April 2006 and 31 March 2007 increased for those aged 10-14 and 15-19 years, but fell for those aged 20-24 years. AR varied considerably among cancer types. Despite four trials being available, patients over 16 years with central nervous system tumours were not recruited. Rates of participation in clinical trials in England from 2005 to 2007 were much lower for TYA older than 15 years compared with children and younger teenagers. The variations in open trials, trial age eligibility criteria and extent of trial activation in treatment centres in part explain this observation. Other possible influences, such as difficulties associated with the consent of TYA require further evaluation. Closer dialogue between those involved in planning and running trials for children and for adults is necessary to improve trial availability and recruitment. Further research is required to identify trends in trial availability and accrual for those tumours constituting the remaining 26% of TYA cancers.

Randomized Phase III controlled trials of therapy in malignant glioma: where are we after 40 years?

The objective of this study was to review the results of randomized Phase III controlled trials (RCTs) that involve initial treatments of malignant glioma and determine changes in median survival times (MST) over the last 40 years. An electronic database search identified RCTs for patients undergoing initial treatment for supratentorial high-grade malignant glioma. MSTs were analysed with respect to the date that patient accrual to the trial started, to identify the time course of changes in MST. Linear regression was used for statistical analysis. The review included 44 clinical trials that recruited patients between 1966 and 2004. Overall, there was a steady significant improvement in MST for the novel treatment cohorts over this period (r(2) = 0.43, p < 0.001), with MST increasing from around 8 to 15 months. There was also consistent improvement in the MST of the control cohorts, from around 7 months to 14 months, that reached statistical significance (r(2) = 0.41, p < 0.001). However, analysis including a quadratic term revealed a trend towards the rate of improvement in MST decreasing in the last two decades in the control, but not novel treatment, groups. The differences, either positive or negative, in MSTs between the control and novel treatment cohorts, and number of trials performed have all decreased with time. Subgroup analysis of the three most recent clinical trials report statistically significant better outcomes in MST after either >90% or 'complete' tumour resection. Despite tremendous advances in both the understanding of the biology of malignant gliomas and treatments in neuro-oncology, the prognosis for patients with malignant gliomas, although improved, remains very poor. The limitations of this type of analysis, including how trial design can bias outcomes and militate against comparison of trials are discussed.

Equivalent-Forms Reliability of Printed and Spoken Versions of the NASA-TLX

Sixty-four participants provided subjective workload assessments after each of 15 trials of selected laparoscopic training tasks, including cannulation, ring transfer, and rope inspection. Half of the participants responded to the NASA-TLX using the traditional printed format with manual (written) responses. The remainder listened to auditory scale cues and made vocal responses. A comparison of the two formats revealed strong (r > .80) correlations and equivalent sensitivity to task and training effects, indicating that the vocal format may be a suitable substitute for traditional administration methods in the evaluation of surgical technology.