A fully human anti-Ep-CAM scFv-beta-glucuronidase fusion protein for selective chemotherapy with a glucuronide prodrug

Monoclonal antibodies against tumour-associated antigens could be useful to deliver enzymes selectively to the site of a tumour for activation of a non-toxic prodrug. A completely human fusion protein may be advantageous for repeated administration, as host immune responses may be avoided. We have constructed a fusion protein consisting of a human single chain Fv antibody, C28, against the epithelial cell adhesion molecule and the human enzyme β-glucuronidase. The sequences encoding C28 and human enzyme β-glucuronidase were joined by a sequence encoding a flexible linker, and were preceded by the IgGκ signal sequence for secretion of the fusion protein. A CHO cell line was engineered to secrete C28-β-glucuronidase fusion protein. Antibody specificity and enzyme activity were retained in the secreted fusion protein that had an apparent molecular mass of 100 kDa under denaturing conditions. The fusion protein was able to convert a non-toxic prodrug of doxorubicin, N-[4-doxorubicin-N-carbonyl(oxymethyl)phenyl]-O-β-glucuronyl carbamate to doxorubicin, resulting in cytotoxicity. A bystander effect was demonstrated, as doxorubicin was detected in all cells after N-[4-doxorubicin-N-carbonyl(oxymethyl)phenyl]-O-β-glucuronyl carbamate administration when only 10% of the cells expressed the fusion protein. This is the first fully human and functional fusion protein consisting of an scFv against epithelial cell adhesion molecule and human enzyme β-glucuronidase for future use in tumour-specific activation of a non-toxic glucuronide prodrug

Adenoviral vector-mediated expression of a gene encoding secreted, EpCAM-targeted carboxylesterase-2 sensitises colon cancer spheroids to CPT-11

CPT-11 (irinotecan or 7-ethyl-10[4-(1-piperidino)-1-piperidino] carbonyloxycamptothecin) is an anticancer agent in use for the treatment of colon cancer. In order to be fully active, CPT-11 needs to be converted into SN-38 (7-ethyl-10-hydroxycamptothecin) by the enzyme carboxylesterase (CE). In humans, only a minority of CPT-11 is converted to SN-38. To increase the antitumour effect of CPT-11 by gene-directed enzyme prodrug therapy, we constructed a replication-deficient adenoviral vector Ad.C28-sCE2 containing a fusion gene encoding a secreted form of human liver CE2 targeted to the surface antigen epithelial cell adhesion molecule (EpCAM) that is highly expressed on most colon carcinoma cells. By targeting CE2 to EpCAM, the enzyme should accumulate specifically in tumours and leakage into the circulation should be minimised. Ad.C28-sCE2-transduced colon carcinoma cells expressed and secreted active CE that bound specifically to EpCAM-expressing cells. In sections of three-dimensional colon carcinoma spheroids transduced with Ad.C28-sCE2, it was shown that C28-sCE2 was capable of binding untransduced cells. Most importantly, treatment of these spheroids with nontoxic concentrations of CPT-11 resulted in growth inhibition comparable to treatment with SN-38. Therefore, Ad.C28-sCE2 holds promise in gene therapy approaches for the treatment of colon carcinoma

Anti-tumour activity and toxicity of the new prodrug9-aminocamptothecin glucuronide (9ACG) in mice

Cancer chemotherapy is limited by the modest therapeutic index of most antineoplastic drugs. Some glucuronide prodrugs may display selective anti-tumour activity against tumours that accumulate β-glucuronidase. We examined the toxicity and anti-tumour activity of 9-aminocamptothecin glucuronide, a new glucuronide prodrug of 9-aminocamptothecin, to evaluate its potential clinical utility. 9-aminocamptothecin glucuronide was 25–60 times less toxic than 9-aminocamptothecin to five human cancer cell lines. β-glucuronidase activated 9-aminocamptothecin glucuronide to produce similar cell killing as 9-aminocamptothecin or topotecan. The in vivo toxicity of 9-aminocamptothecin glucuronide in BALB/c mice was dose-, route-, sex- and age-dependent. 9-aminocamptothecin glucuronide was significantly less toxic to female than to male mice but the difference decreased with age. 9-aminocamptothecin glucuronide and 9-aminocamptothecin produced similar inhibition (∼80%) of LS174T human colorectal carcinoma tumours. 9-aminocamptothecin glucuronide cured a high percentage of CL1-5 human lung cancer xenografts with efficacy that was similar to or greater than 9-aminocamptothecin, irinotecan and topotecan. The potent anti-tumour activity of 9-aminocamptothecin glucuronide suggests that this prodrug should be further evaluated for cancer treatment

Polymers for Improving the In Vivo Transduction Efficiency of AAV2 Vectors

Background: Adeno-associated virus has attracted great attention as vehicle for body-wide gene delivery. However, for the successful treatment of a disease such as Duchenne muscular dystrophy infusion of very large amounts of vectors is required. This not only raises questions about the technical feasibility of the large scale production but also about the overall safety of the approach. One way to overcome these problems would be to find strategies able to increase the in vivo efficiency. Methodology: Here, we investigated whether polymers can act as adjuvants to increase the in vivo efficiency of AAV2. Our strategy consisted in the pre-injection of polymers before intravenous administration of mice with AAV2 encoding a murine secreted alkaline phosphatase (mSeAP). The transgene expression, vector biodistribution and tissue transduction were studied by quantification of the mSeAP protein and real time PCR. The injection of polyinosinic acid and polylysine resulted in an increase of plasmatic mSeAP of 2- and 12-fold, respectively. Interestingly, polyinosinic acid pre-injection significantly reduced the neutralizing antibody titer raised against AAV2. Conclusions: Our results show that the pre-injection of polymers can improve the overall transduction efficiency of systemically administered AAV2 and reduce the humoral response against the capsid proteins

The implications of Methylphenidate use by healthy medical students and doctors in South Africa

Background: The use of medical stimulants to sustain attention, augment memory and enhance intellectual capacity is increasing in society. The use of Methylphenidate for cognitive enhancement is a subject that has received much attention in the literature and academic circles in recent times globally. Medical doctors and medical students appear to be equally involved in the off-label use of Methylphenidate. This presents a potential harm to society and the individual as the long-term side effect profile of this medication is unknown. Discussion: The implication of the use of Methylphenidate by medical students and doctors has not been fully explored. This article considers the impact of this use on the traditional role of medicine, society, the patient and suggests a way forward. We discuss the salient philosophy surrounding the use of cognitive enhancement. We query whether there are cognitive benefits to the use of Methylphenidate in healthy students and doctors and whether these benefits would outweigh the risks in taking the medication. Could these benefits lead to tangible outcomes for society and could the off label-use of Methylphenidate potentially undermine the medical profession and the treatment of patients? If cognitive benefits are proven then doctors may be coerced explicitly or implicitly to use the drug which may undermine their autonomy. The increased appeal of cognitive enhancement challenges the traditional role of medicine in society, and calls into question the role of a virtuous life as a contributing factor for achievement. In countries with vast economic disparity such as South Africa an enhancement of personal utility that can be bought may lead to greater inequities. Summary: Under the status quo the distribution of methylphenidate is unjust. Regulatory governmental policy must seek to remedy this while minimising the potential for competitive advantage for the enhanced. Public debate on the use of cognitive enhancement is long overdue and must be stimulated. The use of Methylphenidate for cognitive enhancement is philosophically defendable if long-term research can prove that the risks are negligible and the outcomes tangible

Rapid and Efficient Clearance of Blood-borne Virus by Liver Sinusoidal Endothelium

The liver removes quickly the great bulk of virus circulating in blood, leaving only a small fraction to infect the host, in a manner characteristic of each virus. The scavenger cells of the liver sinusoids are implicated, but the mechanism is entirely unknown. Here we show, borrowing a mouse model of adenovirus clearance, that nearly all infused adenovirus is cleared by the liver sinusoidal endothelial cell (LSEC). Using refined immunofluorescence microscopy techniques for distinguishing macrophages and endothelial cells in fixed liver, and identifying virus by two distinct physicochemical methods, we localized adenovirus 1 minute after infusion mainly to the LSEC (∼90%), finding ∼10% with Kupffer cells (KC) and none with hepatocytes. Electron microscopy confirmed our results. In contrast with much prior work claiming the main scavenger to be the KC, our results locate the clearance mechanism to the LSEC and identify this cell as a key site of antiviral activity

Health-related physical fitness of adolescents and young adults with myelomeningocele

To assess components of health-related physical fitness in adolescents and young adults with myelomeningocele (MMC), and to study relations between aerobic capacity and other health-related physical fitness components. This cross-sectional study included 50 adolescents and young adults with MMC, aged 16–30 years (25 males). Aerobic capacity was quantified by measuring peak oxygen uptake (peakVO2) during a maximal exercise test on a cycle or arm ergometer depending on the main mode of ambulation. Muscle strength of upper and lower extremity muscles was assessed using a hand-held dynamometer. Regarding flexibility, we assessed mobility of hip, knee and ankle joints. Body composition was assessed by measuring thickness of four skin-folds. Relations were studied using linear regression analyses. Average peakVO2 was 1.48 ± 0.52 l/min, 61% of the participants had subnormal muscle strength, 61% had mobility restrictions in at least one joint and average sum of four skin-folds was 74.8 ± 38.8 mm. PeakVO2 was significantly related to gender, ambulatory status and muscle strength, explaining 55% of its variance. Adolescents and young adults with MMC have poor health-related physical fitness. Gender and ambulatory status are important determinants of peakVO2. In addition, we found a small, but significant relationship between peakVO2 and muscle strength

Current anti-doping policy: a critical appraisal

BACKGROUND: Current anti-doping in competitive sports is advocated for reasons of fair-play and concern for the athlete's health. With the inception of the World Anti Doping Agency (WADA), anti-doping effort has been considerably intensified. Resources invested in anti-doping are rising steeply and increasingly involve public funding. Most of the effort concerns elite athletes with much less impact on amateur sports and the general public. DISCUSSION: We review this recent development of increasingly severe anti-doping control measures and find them based on questionable ethical grounds. The ethical foundation of the war on doping consists of largely unsubstantiated assumptions about fairness in sports and the concept of a "level playing field". Moreover, it relies on dubious claims about the protection of an athlete's health and the value of the essentialist view that sports achievements reflect natural capacities. In addition, costly antidoping efforts in elite competitive sports concern only a small fraction of the population. From a public health perspective this is problematic since the high prevalence of uncontrolled, medically unsupervised doping practiced in amateur sports and doping-like behaviour in the general population (substance use for performance enhancement outside sport) exposes greater numbers of people to potential harm. In addition, anti-doping has pushed doping and doping-like behaviour underground, thus fostering dangerous practices such as sharing needles for injection. Finally, we argue that the involvement of the medical profession in doping and anti-doping challenges the principles of non-maleficience and of privacy protection. As such, current anti-doping measures potentially introduce problems of greater impact than are solved, and place physicians working with athletes or in anti-doping settings in an ethically difficult position. In response, we argue on behalf of enhancement practices in sports within a framework of medical supervision. SUMMARY: Current anti-doping strategy is aimed at eradication of doping in elite sports by means of all-out repression, buttressed by a war-like ideology similar to the public discourse sustaining international efforts against illicit drugs. Rather than striving for eradication of doping in sports, which appears to be an unattainable goal, a more pragmatic approach aimed at controlled use and harm reduction may be a viable alternative to cope with doping and doping-like behaviour

Derivation of a Myeloid Cell-Binding Adenovirus for Gene Therapy of Inflammation

The gene therapy field is currently limited by the lack of vehicles that permit efficient gene delivery to specific cell or tissue subsets. Native viral vector tropisms offer a powerful platform for transgene delivery but remain nonspecific, requiring elevated viral doses to achieve efficacy. In order to improve upon these strategies, our group has focused on genetically engineering targeting domains into viral capsid proteins, particularly those based on adenovirus serotype 5 (Ad5). Our primary strategy is based on deletion of the fiber knob domain, to eliminate broad tissue specificity through the human coxsackie-and-adenovirus receptor (hCAR), with seamless incorporation of ligands to re-direct Ad tropism to cell types that express the cognate receptors. Previously, our group and others have demonstrated successful implementation of this strategy in order to specifically target Ad to a number of surface molecules expressed on immortalized cell lines. Here, we utilized phage biopanning to identify a myeloid cell-binding peptide (MBP), with the sequence WTLDRGY, and demonstrated that MBP can be successfully incorporated into a knob-deleted Ad5. The resulting virus, Ad.MBP, results in specific binding to primary myeloid cell types, as well as significantly higher transduction of these target populations ex vivo, compared to unmodified Ad5. These data are the first step in demonstrating Ad targeting to cell types associated with inflammatory disease

Kupffer Cells Hasten Resolution of Liver Immunopathology in Mouse Models of Viral Hepatitis

Kupffer cells (KCs) are widely considered important contributors to liver injury during viral hepatitis due to their pro-inflammatory activity. Herein we utilized hepatitis B virus (HBV)-replication competent transgenic mice and wild-type mice infected with a hepatotropic adenovirus to demonstrate that KCs do not directly induce hepatocellular injury nor do they affect the pathogenic potential of virus-specific CD8 T cells. Instead, KCs limit the severity of liver immunopathology. Mechanistically, our results are most compatible with the hypothesis that KCs contain liver immunopathology by removing apoptotic hepatocytes in a manner largely dependent on scavenger receptors. Apoptotic hepatocytes not readily removed by KCs become secondarily necrotic and release high-mobility group box 1 (HMGB-1) protein, promoting organ infiltration by inflammatory cells, particularly neutrophils. Overall, these results indicate that KCs resolve rather than worsen liver immunopathology