Effect of glycoPEGylation on factor VIIa binding and internalization

SUMMARY

Recombinant coagulation factor VIIa (rFVIIa), which is widely used for treatment of bleeding episodes in haemophilia patients with inhibitors, is cleared from the circulation relatively fast with a plasma half-life of 2-4 h. PEGylation is an established and clinically proven strategy for prolonging the circulatory life-time of bio-therapeutic proteins. The aim of this study was to investigate the effect of glycoPEGylation of rFVIIa on rFVIIa binding to its cellular receptors and its subsequent internalization. rFVIIa and glycoPEGylated rFVIIa were labeled with (125)I and the radio-iodinated proteins were used to monitor rFVIIa binding and uptake in endothelial cells and fibroblasts. FVIIa-TF activity at the cell surface was analyzed by a factor X activation assay. Modification of rFVIIa with PEG impaired rFVIIa binding to both endothelial cell protein C receptor and tissue factor (TF) on cell surfaces. The internalization of PEGylated rFVIIa in endothelial cells and fibroblasts was markedly lower compared to the internalization of rFVIIa in these cells. PEGylated rFVIIa was able to activate factor X on TF expressing cell surfaces at a rate similar to that of unmodified rFVIIa when the cells were not subjected to multiple washings to remove the free ligand. General effects such as steric hindrance or changes in electrostatic binding properties of the modified rFVIIa to its receptors are probably responsible for this impairment rather than a loss of specific recognition of the receptors, which could explain near normal activation of factor X by glycoPEGylated rFVIIa on TF expressing cells while its uptake is reduced.

Activity and regulation of glycoPEGylated factor VIIa analogs

BACKGROUND

Recombinant coagulation factor VIIa (rFVIIa) has proven to be a safe and effective drug for treatment of bleeding episodes in hemophilic patients with inhibitors. However, rFVIIa is cleared from the circulation relatively quickly. Protein modification with poly(ethylene glycol) (PEG) can prolong the circulatory lifetime of proteins but it could also impair protein function by molecular shielding of the protein surface.

OBJECTIVES

To characterize the interaction of glycoPEGylated rFVIIa - rFVIIa-10K PEG and rFVIIa-40K PEG - with tissue factor (TF), factor X (FX) and plasma inhibitors, tissue factor pathway inhibitor (TFPI) and antithrombin (AT).

METHODS

The amidolytic and FX activation assays were employed to investigate the interaction of glycoPEGylated rFVIIa with its macromolecular substrate and inhibitors.

RESULTS

Both the glycoPEGylated rFVIIa analogs exhibited similar amidolytic activity as that of rFVIIa in the absence or the presence of relipidated TF. The analogs were as effective as rFVIIa in activating FX in the absence of TF. In the presence of TF, the glycoPEGylated rFVIIa variants, relative to rFVIIa, were slightly less effective at lower concentrations, but no significant differences were found among them in activating FX at saturating concentrations. Both AT/heparin and TFPI effectively inhibited the glycoPEGylated rFVIIa bound to relipidated TF or TF on stimulated endothelial cells. In contrast to their normal interaction with TF, the glycoPEGylated rFVIIa variants appeared to interact poorly with phospholipids.

CONCLUSIONS

The glycoPEGylated rFVIIa variants retained their catalytic activity and interacted efficiently with TF, FX and the plasma inhibitors. Further work with appropriate in vitro and in vivo model systems is needed to determine the feasibility of using glycoPEGylated rFVIIa to improve therapeutic options for bleeding disorders.

Comparison of nested-polymerase chain reaction and virus culture for the diagnosis of genital herpes simplex virus infection

INTRODUCTION

This study was performed to compare nested-polymerase chain reaction (PCR) with viral culture as a diagnostic tool for genital herpes simplex virus (HSV) infection in a sexually transmitted infection (STI) clinic in Singapore.

METHODS

103 consecutive patients presenting with clinical features suggestive of genital herpes were enrolled in the study. Two swabs were obtained from each patient. On one swab, cell culture and typing was performed, and on the second swab, nested-PCR was performed and the infecting viral type was determined by using type-specific primers.

RESULTS

63 patients (61.2 percent) had a positive PCR test for HSV. Of these, 13 patients (20.6 percent) had HSV type 1 (HSV-1), 50 patients (79.4 percent) had HSV type 2 (HSV-2). HSV-1 and HSV-2 were detected by viral culture in only six patients and 24 patients, respectively. The sensitivity of cell culture compared to PCR was 46.1 percent for HSV-1 infection and 48 percent for HSV-2 infection. PCR further detected an additional 52.4 percent of HSV cases. The specificity of PCR was 100 percent.

CONCLUSION

Nested-PCR has been shown in this study to be an effective diagnostic and typing method for HSV infection in a STI clinic in Singapore with its higher sensitivity and specificity to routine viral isolation in cell culture.

Human placental extract offers protection against experimental visceral leishmaniasis: a pilot study for a phase-I clinical trial

An aqueous extract of human placenta (HPE) was found to offer protection against established experimental visceral leishmaniasis in BALB/c mice and hamsters, whether the Leishmania donovani strain involved was one that was sensitive or resistant to pentavalent antimony. Intraperitoneal administration of the extract, into mice or hamsters that had been infected 2 months previously, led to antileishmanial T-cell proliferation among splenic mononuclear cells, the generation of host-protective cytokines (interferon-gamma, tumour necrosis factor and interleukin-12) and the upregulation of the expression of inducible nitric oxide synthase (and subsequent NO generation) in splenocytes. Furthermore, splenic macrophages from the HPE-treated mice showed increased generation of reactive oxygen species and enhanced surface expression of antigens of major histocompatibility complex class II (MHCII), and the extract restored the otherwise-defective antigen-presenting ability of the macrophages. Thus, in mice and hamsters infected with L. donovani, HPE therapy can stimulate both arms of the host's immune system and favour the complete resolution of the leishmanial infection. Among five human cases of visceral leishmaniasis, 30 daily intramuscular injections of HPE, at doses much lower than those used in the experimental infections, also gave very promising results. Based on the results of this pilot study, a further evaluation of the efficacy of HPE therapy, which may offer a cost-effective way of improving the treatment of antimony-resistant cases of visceral leishmaniasis, is being undertaken.

Fluorescence properties of Ag nanoparticles in water

Ag nanoparticles in water phase have been synthesized employing the electro-exploding wire technique. A surface plasmon peak is observed at 400nm, characteristic of the Ag nanoparticles. A fluorescence emission peak is recorded at 300nm for excitation wavelengths in two different ranges 215-230 and 255-280nm. The position of the fluorescence peak remains fixed, irrespective of the excitation wavelength employed. These are assigned to electronic transition from different higher excited states to d levels of the Ag nanoparticles. In concomitant with these, there are two resonant absorptions at 5.76 and 4.59eV as evident from the fluorescence excitation spectra.

Intraoral Spitz naevus: a case report

Intraoral occurrences of Spitz naevus are very rare, there being only one previously documented case in the literature. Here is reported a case of a young male who presented with a pigmented lesion of the upper labial mucosa which had the clinical appearance of a simple naevus. Excision biopsy confirmed this to be a Spitz naevus. This lesion shares histopathological similarities with malignant melanoma. Spitz naevus is a benign lesion, but malignant transformation has been reported and close monitoring is recommended.

A systematic review of the role of proton pump inhibitors for symptoms of laryngopharyngeal reflux

. Proton pump inhibitors are currently used widely for the treatment of laryngopharyngeal reflux. . This systematic review assessed the efficacy of proton pump inhibitors in the treatment of symptoms of laryngopharyngeal reflux. . Outcome measures used to assess efficacy of proton pump inhibitors included endoscopic laryngeal signs and pH recordings. .Only two small randomized-controlled trials included patients with objective evidence of reflux in the 24-h ambulatory oesophageal pH monitoring. . Pooled analysis of these two randomized-controlled trials failed to show any effect in favour of treatment with proton pump inhibitors. .Further randomized-controlled trials are required to ascertain the role of proton pump inhibitors in the treatment of laryngopharyngeal reflux.

Water precautions and ear surgery: evidence and practice in the UK

BACKGROUND

Patients are traditionally advised to refrain from exposing their ears to water after most otological procedures. However, recent evidence suggests that water does not adversely affect the outcome for children with tympanostomy tubes. The evidence behind the potential harmful effects of water on the outcome of other otological procedures is scarce.

OBJECTIVE

The study was done to determine the current practice of otolaryngology consultants in the UK on the advice given to patients regarding swimming, diving and bathing in soapy water after myringotomy and tympanostomy tube insertion, mastoidectomy and myringoplasty.

METHOD

Questionnaire based survey mailed to 382 members (consultants only) of the British Association of Otolaryngologists--Head & Neck Surgeons in the UK.

RESULTS

A total of 195 responses were received (reply rate 51 per cent). In all, 95.6 per cent of the respondents allowed their patients to swim after insertion of tympanostomy tubes, with 32.9 per cent insisting on the use of earplugs until extrusion of the tympanostomy tubes. However, 61.6 per cent of the respondents restricted diving in these patients. In comparison, the respondents were more conservative with water precautions following myringoplasty and mastoidectomy. More than half the respondents recommended earplugs for bathing after all three operations.

CONCLUSION

This study reveals current national practice among UK otolaryngologists. There is no general consensus in post-operative advice following otolaryngological procedures, indicating a need for national guidelines.

Does the slow compression technique of hyperbaric oxygen therapy decrease the incidence of middle-ear barotrauma?

OBJECTIVE

To note the incidence of middle-ear barotrauma following standard and slow compression during hyperbaric oxygen therapy (HBOT). The standards used were: (1) less than 40 per cent of the cohort should develop barotraumas, and (2) the incidence of barotrauma following the slow technique should be less than that caused by the standard technique.

DESIGN

Prospective clinical audit.

MATERIAL AND METHODS

Forty-two consecutive patients who received either standard compression or slow compression HBOT were included. Pre- and post-treatment otoscopy (graded according to a modified Teed's scale), tympanometry, audiometry and subjective ear complaints were compared between the groups and also compared with the set standard.

RESULTS

Significantly less middle-ear barotrauma was noted when using the slow compression technique compared with the standard compression technique (p < 0.05). The incidence of barotrauma when using standard compression failed to meet the set standard of less than 40 per cent.

CONCLUSION

The slow compression method of HBOT proved to be both safe and superior to the standard compression technique.

Culture, ethnicity, and paranoia

This paper defines concepts of culture, ethnicity, and paranoia. It then explores the relationship between culture and ethnicity and the development of paranoia both in mental health settings and in the wider world. The importance of cultural awareness training while dealing with an ethnic population in any multicultural setting is emphasized. When exploring paranoia, proper exploration of its genesis is essential to distinguish between pathological and nonpathological paranoia.

Endoscopic stapling of pharyngeal pouch

The relatively new technique of endoscopic stapling in the surgical management of pharyngeal pouch has gained widespread popularity over the last few years. The technique seems to be the procedure of choice as it is easier and quicker to perform and has a lower morbidity compared with open techniques. We present here an overview of the current evidence provided by a literature search performed by Ovid MEDLINE on literature published between January 1993 and May 2003 on endoscopic stapling of pharyngeal pouch. Several case series have been reported on various aspects of the surgery. The modifications in technique, peri-operative care, success rate, complications and recurrence are summarized, based on observational analytical case series. There were no randomized controlled trials comparing this approach to any other endoscopic or open surgical techniques for pharyngeal pouch.

Ectopic meningioma: a case report with a literature review

Ectopic (extradural) meningiomas that do not originate from either the optic fascicle or the intracranial meninges are exceedingly rare. A patient with an ectopic meningioma in the external auditory canal and mastoid was treated in our unit. The world literature of the last 20 years was reviewed.