Antibody Neutralization of CXCL10 in Vivo Is Dependent on Binding to Free and Not Endothelial-bound Chemokine: IMPLICATIONS FOR THE DESIGN OF A NEW GENERATION OF ANTI-CHEMOKINE THERAPEUTIC ANTIBODIES

To improve our understanding of properties that confer successful inhibition of chemokines in vivo, we analyzed anti-murine CXCL10 monoclonal antibodies (mAb) having different characteristics. 1B6 displayed potent inhibition of cell recruitment in vitro with an IC50 of 0.5 nm but demonstrated little efficacy in various animal models of human disease. On the contrary, 1F11 showed efficacy in several models of inflammation yet was less potent at inhibiting chemotaxis in vitro with an IC50 of 21 nm Furthermore, we observed that 1B6 displayed a rapid dose-dependent clearance (t½ 10-60 h) in contrast to 1F11, which presented a dose-proportional pharmacokinetic profile and a half-life of 12 days. Moreover, 1B6 recognized glycosaminoglycan (GAG)-bound CXCL10, resulting in target-mediated clearance, which was corroborated using CXCL10-deficient mice. In contrast to 1B6, 1F11 inhibited the interaction of CXCL10 with GAGs, did not recognize GAG-bound CXCL10, and did not display target-mediated drug disposition. Confirming previous animal studies, 1B6 was poor at reversing glycemia in a model of type 1 diabetes, whereas 1F11 induced early and prolonged control of diabetes. Furthermore, when using 1A4, a subsequently generated anti-mCXCL10 mAb that shares the property with 1F11 of being unable to recognize CXCL10 immobilized on GAG, we observed a similar superior control of diabetes as compared with 1B6. We therefore concluded that targeting chemokines with antibodies such as 1B6 that recognize the more abundant GAG-bound form of the chemokine may not be the optimal strategy to achieve disease control.

Evasins: Therapeutic Potential of a New Family of Chemokine-Binding Proteins from Ticks

Blood-sucking parasites, such as ticks, remain attached to their hosts for relatively long periods of time in order to obtain their blood meal without eliciting an immune response. One mechanism used to avoid rejection is the inhibition of the recruitment of immune cells, which can be achieved by a class of chemokine-binding proteins (CKBPs) known as Evasins. We have identified three distinct Evasins produced by the salivary glands of the common brown dog tick, Rhipicephalus sanguineus. They display different selectivities for chemokines, the first two identified show a narrow selectivity profile, while the third has a broader binding spectrum. The Evasins showed efficacy in animal models of inflammatory disease. Here, we will discuss the potential of their development for therapeutic use, addressing both the advantages and disadvantages that this entails.

De novo isolation of antibodies with pH-dependent binding properties

pH-dependent antibodies are engineered to release their target at a slightly acidic pH, a property making them suitable for clinical as well as biotechnological applications. Such antibodies were previously obtained by histidine scanning of pre-existing antibodies, a labor-intensive strategy resulting in antibodies that displayed residual binding to their target at pH 6.0. We report here the de novo isolation of pH-dependent antibodies selected by phage display from libraries enriched in histidines. Strongly pH-dependent clones with various affinity profiles against CXCL10 were isolated by this method. Our best candidate has nanomolar affinity for CXCL10 at pH 7.2, but no residual binding was detected at pH 6.0. We therefore propose that this new process is an efficient strategy to generate pH-dependent antibodies.

Targeting chemokines: Pathogens can, why can't we?

Chemoattractant cytokines, or chemokines, are the largest sub-family of cytokines. About 50 distinct chemokines have been identified in humans. Their principal role is to stimulate the directional migration of leukocytes, which they achieve through activation of their receptors, following immobilization on cell surface glycosaminoglycans (GAGs). Chemokine receptors belong to the G protein-coupled 7-transmembrane receptor family, and hence their identification brought great promise to the pharmaceutical industry, since this receptor class is the target for a large percentage of marketed drugs. Unfortunately, the development of potent and efficacious inhibitors of chemokine receptors has not lived up to the early expectations. Several approaches to targeting this system will be described here, which have been instrumental in establishing paradigms in chemokine biology. Whilst drug discovery programs have not yet elucidated how to make successful drugs targeting the chemokine system, it is now known that certain parasites have evolved anti-chemokine strategies in order to remain undetected by their hosts. What can we learn from them?

Identification of the pharmacophore of the CC chemokine-binding proteins Evasin-1 and -4 using phage display

To elucidate the ligand-binding surface of the CC chemokine-binding proteins Evasin-1 and Evasin-4, produced by the tick Rhipicephalus sanguineus, we sought to identify the key determinants responsible for their different chemokine selectivities by expressing Evasin mutants using phage display. We first designed alanine mutants based on the Evasin-1·CCL3 complex structure and an in silico model of Evasin-4 bound to CCL3. The mutants were displayed on M13 phage particles, and binding to chemokine was assessed by ELISA. Selected variants were then produced as purified proteins and characterized by surface plasmon resonance analysis and inhibition of chemotaxis. The method was validated by confirming the importance of Phe-14 and Trp-89 to the inhibitory properties of Evasin-1 and led to the identification of a third crucial residue, Asn-88. Two amino acids, Glu-16 and Tyr-19, were identified as key residues for binding and inhibition of Evasin-4. In a parallel approach, we identified one clone (Y28Q/N60D) that showed a clear reduction in binding to CCL3, CCL5, and CCL8. It therefore appears that Evasin-1 and -4 use different pharmacophores to bind CC chemokines, with the principal binding occurring through the C terminus of Evasin-1, but through the N-terminal region of Evasin-4. However, both proteins appear to target chemokine N termini, presumably because these domains are key to receptor signaling. The results also suggest that phage display may offer a useful approach for rapid investigation of the pharmacophores of small inhibitory binding proteins.

Evasin-4, a tick-derived chemokine-binding protein with broad selectivity can be modified for use in preclinical disease models

Rhipicephalus sanguineus, the common brown dog tick, produces several chemokine-binding proteins which are secreted into the host in its saliva to modulate the host response during feeding. Two of these demonstrate very restricted selectivity profiles. Here, we describe the characterization of the third, which we named Evasin-4. Evasin-4 was difficult to produce recombinantly using its native signal peptide in HEK cells, but expressed very well using the urokinase-type plasminogen activator signal peptide. Using SPR, Evasin-4 was shown to bind most CC chemokines. Investigation of the neutralization properties by inhibition of chemokine-induced chemotaxis showed that binding and neutralization did not correlate in all cases. Two major anomalies were observed: no binding was observed to CCL2 and CCL13, yet Evasin-4 was able to inhibit chemotaxis induced by these chemokines. Conversely, binding to CCL25 was observed, but Evasin-4 did not inhibit CCL25-induced chemotaxis. Size-exclusion chromatography confirmed that Evasin-4 forms a complex with CCL2 and CCL18. In accordance with the standard properties of unmodified small proteins, Evasin-4 was rapidly cleared following in vivo administration. To enhance the in vivo half-life and optimize its potential as a therapeutic agent, Fc fusions of Evasin-4 were created. Both the N- and C-terminal fusions were shown to retain binding activity, with the C-terminal fusion showing a modest reduction in potency.

Juvenile nasopharyngeal angiofibromas in Denmark 1981-2003: diagnosis, incidence, and treatment

CONCLUSIONS

Juvenile nasopharyngeal angiofibroma (JNA) is a rare tumor in young males, with a non-negligible potential for recurrence. Preoperative embolization is a safe procedure that diminishes the peroperative blood loss and the need for blood transfusion. The endoscopic approach was used with good results in JNA stage I and II (Chandler).

OBJECTIVES

To estimate the incidence rate of JNA in the Danish population and to describe symptoms and treatment.

PATIENTS AND METHODS

This was a national retrospective cohort study. All cases of JNA diagnosed in Denmark from 1981 to 2003 were identified. Data were extracted from medical records.

RESULTS

Forty-five male (no female) JNA cases were identified. In 43 cases, clinical data were recovered. Median age was 15 years. The incidence rate in Denmark was 0.4 cases per million inhabitants per year and 3.7 cases per million males (aged 10-24) per year. All patients underwent surgery, and the endoscopic approach was increasingly being used. The embolization procedure proved to be safe and decreased the intraoperative blood loss statistically to 650 ml in the embolized group from an average of 1200 ml in the non-embolized group (p<0.05). Similarly, the need for peroperative blood transfusion was reduced (p<0.005). The primary recurrence rate was 23% and no patients died.

A new ventilation tube for long-term middle ear ventilation

OBJECTIVES

The treatment of secretory otitis media often requires repeated tubulation of the tympanic membrane as the standard ventilation tubes are extruded before the disease of the middle ear has remitted. The T-tube and its modification have been developed to remain longer in situ, often requiring surgical removal. The rates of subsequent persisting tympanic membrane perforations and granulations around the tube have been unacceptably high. In the search for a long-term ventilation tube with fewer complications, the Duravent tube (Smith and Nephew) has been developed. The aim of the study was to estimate duration in situ and observe complications in using the Duravent tube compared with standard tubes and T- tubes.

STUDY DESIGN

Retrospective study.

METHODS

In all, 51 patients have been treated with the Duravent tube over a 2-year period. In all, 72 Duravent tubes have been inserted. All patients were subsequently invited for a follow-up examination at a median time of 28 months (range, 11-43 mo) after the tube insertion and were followed up for 5 years.

RESULTS

The duration in situ was optimal with a median duration of 17 months. The Duravent tube was extruded spontaneously in all but four cases in which surgical removal was necessary. The rate of persisting perforations of the tympanic membrane was low (4.2%) compared with 24% after the use of the T-tube. Likewise, the usual complications connected with long-term ventilation tubes were less frequent (14% compared with 35% when using the T-tube).

CONCLUSIONS

In the present study, the Duravent tube has proved superior to other known long-term ventilation tubes. The problem of granulations, otorrhoea, and tube occlusion was significantly less than reported in other studies using the T-tube.

Brain abscess caused by Salmonella enteritidis in an immunocompetent adult patient: successful treatment with cefotaxime and ciprofloxacin

A previously healthy 43-y-old man, who had spent 2 weeks in northern India, was admitted to hospital after a 2-day history of pyrexia, confusion and frontal headache. Cranial computerized tomography (CT) showed an abscess in the right parietal lobe. Spinal fluid and blood cultures gave growth of Salmonella enteritidis within 24 h. Treatment with cefotaxime was initiated, but ceased after 3 weeks due to drug fever, and ciprofloxacin was then given orally for 4 months. After 6 months, the patient was considered cured. Cases of salmonella brain abscesses are reviewed.

Rapid and precise in vivo measurement of human corneal thickness with optical low-coherence reflectometry in normal human eyes

An optical low-coherence reflectometer is used for rapid noncontact measurements of the human corneal thickness in vivo. Thickness measurements on ten volunteers show a standard deviation of 3.4 μm. The experiments reveal that the optical reflectometer benefits from a 2.5 fold enhancement of the measurement precision and a 2.8 fold reduction in measurement time compared to a standard clinical ultrasonic pachometer. © 1998 Society of Photo-Optical Instrumentation Engineers.

[Measuring corneal thickness in photo-keratectomy with a reflectometry incorporated into the laser beam of the excimer laser]

PURPOSE

To integrate a newly developed OLCR instrument into the optical system of the excimer laser. The instrument is designed to perform corneal pachymetry before, during, and after corneal photoablation and thus allow for a precise and continuous on-line measurement of the corneal photoablation process.

METHODS

The conditions required to integrate the OLCR instrument into the excimer laser optics were investigated. With a technical setting providing on-line data of corneal thickness, three groups of 8-10 corneae received central keratectomies of 27 (group 1), 82 (group 2) and 163 (group 3) microns calculated central depth and 7.38 mm diameter. All measurements were performed with OLCR and ultrasound.

RESULTS

The OLCR instrument was coupled into the optical system of the excimer laser and a useful signal obtained at SLD power levels of 40 microW incident on the cornea. Individual corneal thickness measurements were obtained before, during and after the photoablation procedure. In group 1, the ablation was 50.3 (40-68) microns measured with ultrasound and 30.2 (27-38) microns measured with OLCR. In group 2, the ablation was 101.1 (80-113) microns measured with ultrasound and 93.3 (76-109) microns measured with OLCR. In group 3, the ablation was 210.6 (190-227) microns measured with ultrasound and 188.4 (181-197) microns measured with OLCR. The precision (standard deviation) for measurements of individual corneas was 1-2 microns with OLCR and up to 12 mm in Ultrasound measurements.

CONCLUSION

With this interferometric method, continuous, non-contact measurement of corneal thickness before, during and after excimer laser photoablation were performed. By establishing a feed-back control between the pachymetric measurements and the photoablation process, the precision of excimer ablation may possibly be further increased.