Structure, dynamics and immunogenicity of a catalytically inactive CXC chemokine-degrading protease SpyCEP from Streptococcus pyogenes

Over 18 million disease cases and half a million deaths worldwide are estimated to be caused annually by Group A Streptococcus. A vaccine to prevent GAS disease is urgently needed. SpyCEP (Streptococcus pyogenes Cell-Envelope Proteinase) is a surface-exposed serine protease that inactivates chemokines, impairing neutrophil recruitment and bacterial clearance, and has shown promising immunogenicity in preclinical models. Although SpyCEP structure has been partially characterized, a more complete and higher resolution understanding of its antigenic features would be desirable prior to large scale manufacturing. To address these gaps and facilitate development of this globally important vaccine, we performed immunogenicity studies with a safety-engineered SpyCEP mutant, and comprehensively characterized its structure by combining X-ray crystallography, NMR spectroscopy and molecular dynamics simulations. We found that the catalytically-inactive SpyCEP antigen conferred protection similar to wild-type SpyCEP in a mouse infection model. Further, a new higher-resolution crystal structure of the inactive SpyCEP mutant provided new insights into this large chemokine protease comprising nine domains derived from two non-covalently linked fragments. NMR spectroscopy and molecular simulation analyses revealed conformational flexibility that is likely important for optimal substrate recognition and overall function. These combined immunogenicity and structural data demonstrate that the full-length SpyCEP inactive mutant is a strong candidate human vaccine antigen. These findings show how a multi-disciplinary study was used to overcome obstacles in the development of a GAS vaccine, an approach applicable to other future vaccine programs. Moreover, the information provided may also facilitate the structure-based discovery of small-molecule therapeutics targeting SpyCEP protease inhibition.

Molecular requirements for inhibition of the chemokine receptor CCR8--probe-dependent allosteric interactions

BACKGROUND AND PURPOSE

Here we present a novel series of CCR8 antagonists based on a naphthalene-sulfonamide structure. This structure differs from the predominant pharmacophore for most small-molecule CC-chemokine receptor antagonists, which in fact activate CCR8, suggesting that CCR8 inhibition requires alternative structural probes.

EXPERIMENTAL APPROACH

The compounds were tested as inverse agonists and as antagonists against CCL1-induced activity in Gα(i) signalling and chemotaxis. Furthermore, they were assessed by heterologous competition binding against two radiolabelled receptor ligands: the endogenous agonist CCL1 and the virus-encoded antagonist MC148.

KEY RESULTS

All compounds were highly potent inverse agonists with EC(50) values from 1.7 to 23 nM. Their potencies as antagonists were more widely spread (EC(50) values from 5.9 to 1572 nM). Some compounds were balanced antagonists/inverse agonists whereas others were predominantly inverse agonists with >100-fold lower potency as antagonists. A correspondingly broad range of affinities, which followed the antagonist potencies, was disclosed by competition with [(125)I]-CCL1 (K(i) 3.4-842 nM), whereas the affinities measured against [(125)I]-MC148 were less widely spread (K(i) 0.37-27 nM), and matched the inverse agonist potencies.

CONCLUSION AND IMPLICATIONS

Despite highly potent and direct effects as inverse agonists, competition-binding experiments against radiolabelled agonist and tests for antagonism revealed a probe-dependent allosteric effect of these compounds. Thus, minor chemical changes affected the ability to modify chemokine binding and action, and divided the compounds into two groups: predominantly inverse agonists and balanced antagonists/inverse agonists. These studies have important implications for the design of new inverse agonists with or without antagonist properties.

Community DECISIONS: stakeholder focused watershed planning

Successful watershed planning can be enhanced by stakeholder involvement in developing and implementing plans that reflect community goals and resource limitations. Community DECISIONS (Community Decision Support for Integrated, On-the-ground Nutrient Reduction Strategies) is a structured decision process to help stakeholders evaluate strategies that reduce watershed nutrient imbalances. A nutrient accounting algorithm and nutrient treatment database provide information on nutrient loadings and costs of alternative strategies to reduce loadings. Stakeholders were asked to formulate goals for the North Fork Shenandoah River Watershed in Virginia and select among strategies to achieve those goals. The Vector Analytic Hierarchy Process was used to rank strategies. Stakeholders preferred a Maximum strategy that included point source upgrades, riparian buffers, no-till corn silage, wheat cover, and bioretention filters in developed areas. Participants generally agreed that the process helped improve communication among stakeholders, was helpful for watershed planning, and should be used for TMDL (Total Maximum Daily Load) planning. Participants suggested more attention be paid to ensuring that all relevant issues are addressed and all information needed to make decisions is available. Watershed planning should provide stakeholders with clear scientific information about physical and socioeconomic processes. However, planning processes must give stakeholders adequate time to consider issues that may not have been addressed by existing scientific models and datasets.

Yaba-like disease virus chemokine receptor 7L, a CCR8 orthologue

Yaba-like disease virus (YLDV) gene 7L encodes a seven-transmembrane G protein-coupled receptor with 53 % amino acid identity to human CC chemokine receptor 8 (CCR8). Initial characterization of 7L showed that this 56 kDa cell-surface glycoprotein binds human CCL1 with high affinity (K d=0·6 nM) and induces signal transduction by activation of heterotrimeric G proteins and downstream protein kinases. Further characterization of YLDV 7L is presented here and shows that murine CC chemokines can induce G-protein activation via the 7L receptor, despite having a low binding affinity for this receptor. In addition, when expressed by recombinant vaccinia virus (VACV), YLDV 7L was found on the outer envelope of VACV extracellular enveloped virus. The contribution of 7L to poxvirus pathogenesis was investigated by infection of mice with a recombinant VACV expressing 7L (vΔB8R-7L) and was compared with the outcome of infection by parental and revertant control viruses. In both intranasal and intradermal models, expression of 7L caused attenuation of VACV. The role of this protein in viral virulence is discussed.

9α,11β-PGF2and its stereoisomer PGF2αare novel agonists of the chemoattractant receptor, CRTH2

CRTH2 is a recently described chemoattractant receptor for the prostaglandin, PGD(2), expressed by Th2 cells, eosinophils and basophils, and believed to play a role in allergic inflammation. Here we describe the potency of several PGD(2) metabolites at the receptor to induce cell migration and activation. We report for the first time that the PGD(2) metabolite, 9alpha,11beta-PGF(2), and its stereoisomer, PGF(2alpha), are CRTH2 agonists. 9alpha,11beta-PGF(2) is a major metabolite produced in vivo following allergen challenge, whilst PGF(2alpha) is generated independently of PGD synthetase, with implications for CRTH2 signalling in the presence or absence of PGD(2) production.

Yaba-like disease virus protein 7L is a cell-surface receptor for chemokine CCL1

Yaba-like disease virus (YLDV) genes7Land145Rare located on opposite ends of the genome and are predicted to encode 7-transmembrane proteins (7-TM) that share 53 and 44 % amino acid identity, respectively, to human CC chemokine receptor 8 (hCCR8). In this report, we demonstrate that early after infection with YLDV, cells acquire the ability to bind human CCL1. By expression of genes7Land145Rin vaccinia virus, we demonstrated that each protein is glycosylated and is exposed on the cell surface with the N terminus outside the cell. Protein 7L, but not 145R, is able to bind hCCL1 (Kd=0·6±0·13 nM) and couple to heterotrimeric G-proteins and to activate the extracellular signal-regulated kinases (ERK1/2). 7L binds several chemokines including the viral chemokines vMIPI and vMIPII and hCCL7/MCP3. This binding seems species-specific as 7L does not bind the murine orthologues of CCL1 and CCL7 in the assays used. This represents the first example of a poxviral 7-TM chemokine receptor that has functional interactions with a human chemokine.

The evaluation of a precordial ECG BELT: technologist satisfaction and accuracy of recording

The standard method for performing electrocardiogram (ECG) recordings presents a challenge to technicians because of the need to correctly position the individual precordial electrodes according to 6 bony thoracic landmarks. A proposed new method using a 6-lead ECG BELT for precordial application was compared to the standard method to determine the level of agreement among automated interpretations. A comparison of automated interpretations from repeat standard recordings served as the control. Results indicate that BELT and standard automated interpretations disagreed significantly more frequently than repeat standard recording automated interpretations of the cardiac rhythm. The BELT's most obvious weakness was the inability to obtain a recording with a stable ECG baseline, triggering automated detection of "baseline artifact or wander," and requiring a repeat recording. These findings suggest that the ECG BELT is not adequate for clinical application in its current form.

Quantification of DNA using the luminescent oxygen channeling assay

BACKGROUND

Simplified and cost-effective methods for the detection and quantification of nucleic acid targets are still a challenge in molecular diagnostics.

METHODS

Luminescent oxygen channeling assay (LOCI(TM)) latex particles can be conjugated to synthetic oligodeoxynucleotides and hybridized, via linking probes, to different DNA targets. These oligomer-conjugated LOCI particles survive thermocycling in a PCR reaction and allow quantified detection of DNA targets in both real-time and endpoint formats. The endpoint DNA quantification format utilized two sensitizer bead types that are sensitive to separate illumination wavelengths. These two bead types were uniquely annealed to target or control amplicons, and separate illuminations generated time-resolved chemiluminescence, which distinguished the two amplicon types.

RESULTS

In the endpoint method, ratios of the two signals allowed determination of the target DNA concentration over a three-log range. The real-time format allowed quantification of the DNA target over a six-log range with a linear relationship between threshold cycle and log of the number of DNA targets.

CONCLUSIONS

This is the first report of the use of an oligomer-labeled latex particle assay capable of producing DNA quantification and sequence-specific chemiluminescent signals in a homogeneous format. It is also the first report of the generation of two signals from a LOCI assay. The methods described here have been shown to be easily adaptable to new DNA targets because of the generic nature of the oligomer-labeled LOCI particles.

Identification of residues in the monocyte chemotactic protein-1 that contact the MCP-1 receptor, CCR2

The CC chemokine, MCP-1, has been identified as a major chemoattractant for T cells and monocytes, and plays a significant role in the pathology of inflammatory diseases. To identify the regions of MCP-1 that contact its receptor, CCR2, we substituted all surface-exposed residues with alanine. Some residues were also mutated to other amino acids to identify the importance of charge, hydrophobicity, or aromaticity at specific positions. The binding affinity of each mutant for CCR2 was assayed with THP-1 and CCR2-transfected CHL cells. The majority of point mutations had no effect. Residues at the N-terminus of the protein, known to be crucial for signaling, contribute less than a factor of 10 to the binding affinity. However, two clusters of primarily basic residues (R24, K35, K38, K49, and Y13), separated by a 35 A hydrophobic groove, reduced the level of binding by 15-100-fold. A peptide fragment encompassing residues 13-35 recapitulated some of the mutational data derived from the intact protein. It exhibited modest binding as a linear peptide and dramatically improved affinity when the region which adopts a single turn of a 3(10)-helix in the protein, which includes R24, was constrained by a disulfide bond. Additional constraints at the ends of the peptide, corresponding to the disulfide between the first and third cysteines in MCP-1, yielded further improvements in affinity. Together, these data suggest a model in which a large surface area of MCP-1 contacts the receptor, and the accumulation of a number of weak interactions results in the 35 pM affinity observed for the wild-type (WT) protein. The receptor binding site of MCP-1 also is significantly different from the binding sites of RANTES and IL-8, providing insight into the issue of receptor specificity. It was previously shown that the N-terminus of CCR2 is critical for binding MCP-1 [Monteclaro, F. S., and Charo, I. F. (1996) J. Biol. Chem. 271, 19084-92; Monteclaro, F. S., and Charo, I. F. (1997) J. Biol. Chem. 272, 23186-90]. Point mutations of six acidic residues in this region of the receptor were made to test their role in ligand binding. This identified D25 and D27 of the DYDY motif as being important. On the basis of our data, we propose a model in which the receptor N-terminus lies along the hydrophobic groove in an extended fashion, placing the DYDY motif near the basic cluster involving R24 and K49 of MCP-1. This in turn orients the signaling residues (Y13 and the N-terminus) for productive interaction with the receptor.

Using technology to move beyond customer satisfaction

If you don't deliver service your customers value, someone else will. Access to information is the foundation of customer satisfaction and retention. Here's how one organization determined that the efficiencies of a document-to-data information management system could pay for itself in the first year.

Identification of CCR8: a human monocyte and thymus receptor for the CC chemokine I-309

The human CC chemokine I-309 is a potent monocyte chemoattractant and inhibits apoptosis in thymic cell lines. Here, we identify a specific human I-309 receptor, and name it CCR8 according to an accepted nomenclature system. The receptor has seven predicted transmembrane domains, is expressed constitutively in monocytes and thymus, and is encoded by a previously reported gene of previously unknown function named, alternatively, CY6, TER1, and CKR-L1. After transfection with the CY6 open reading frame, a mouse pre-B cell line exhibited calcium flux and chemotaxis in response to I-309 (EC50 = 2 nM for each), whereas 20 other chemokines were inactive. Signaling was sensitive to pertussis toxin, suggesting coupling to a Gi-type G protein. These properties parallel those of endogenous I-309 receptors expressed in an HL-60 clone 15 cell line model. The apparent monogamous relationship between I-309 and CCR8 is unusual among known CC chemokines and known CC chemokine receptors. CCR8 may regulate monocyte chemotaxis and thymic cell line apoptosis.

Luminescent oxygen channeling assay (LOCI): sensitive, broadly applicable homogeneous immunoassay method

Luminescent oxygen channeling assay (LOCI) is a homogeneous immunoassay method capable of rapid, quantitative determination of a wide range of analytes--including high and very low concentrations of large and small molecules, free (unbound) drugs, DNA, and specific IgM. Assays have been carried out in serum and in lysed blood. Reliable detection of 1.25 microU/L thyrotropin (TSH) and 5 ng/L hepatitis B surface antigen (HBsAg) corresponds to detection limits approximately 3- and approximately 20-fold lower, respectively, than those of the best commercially available assays. An assay of chorionic gonadotropin is capable of quantification over a 10(6)-fold range of concentrations without a biphasic response. Latex particle pairs are formed in the assay through specific binding interactions by sequentially combining the sample and two reagents. One particle contains a photosensitizer, the other a chemiluminescer. Irradiation causes photosensitized formation of singlet oxygen, which migrates to a bound particle and activates the chemiluminescer, thereby initiating a delayed luminescence emission. Assay times range from 1 to 25 min.

Luminescent oxygen channeling assay (LOCI): sensitive, broadly applicable homogeneous immunoassay method

Luminescent oxygen channeling assay (LOCI) is a homogeneous immunoassay method capable of rapid, quantitative determination of a wide range of analytes--including high and very low concentrations of large and small molecules, free (unbound) drugs, DNA, and specific IgM. Assays have been carried out in serum and in lysed blood. Reliable detection of 1.25 microU/L thyrotropin (TSH) and 5 ng/L hepatitis B surface antigen (HBsAg) corresponds to detection limits approximately 3- and approximately 20-fold lower, respectively, than those of the best commercially available assays. An assay of chorionic gonadotropin is capable of quantification over a 10(6)-fold range of concentrations without a biphasic response. Latex particle pairs are formed in the assay through specific binding interactions by sequentially combining the sample and two reagents. One particle contains a photosensitizer, the other a chemiluminescer. Irradiation causes photosensitized formation of singlet oxygen, which migrates to a bound particle and activates the chemiluminescer, thereby initiating a delayed luminescence emission. Assay times range from 1 to 25 min.

Myocarditis: a clinical perspective

Myocarditis can have many diverse presentations ranging from ventricular arrhythmias to congestive heart failure, secondary to dilated cardiomyopathy. The recent resurgence of endomyocardial biopsy has greatly enhanced our ability to diagnose this intriguing entity. The biopsy has shown that unexplained arrhythmias have a 15% to 29% incidence of myocarditis, while those with an idiopathic congestive cardiomyopathy have a biopsy-proved range of 9% to 63%. The cause of this process has, at times, been blamed on viruses, but definite cause-and-effect relationships are mostly conjecture and anecdotal. The current role of immunosuppressive therapy in myocarditis is potentially promising, and may alter the subsequent course of the illness.

A non-flow cytometric system for detecting antibodies and cellular antigens in blood

The system described here can distinguish between single and agglutinated erythrocytes by use of a non-flow fiber optic fluorometer. The method is capable of detecting cell-surface antigens and antibodies to cell-surface antigens present in blood. Significant features include high-efficiency fluorescent dyes that intercalate into cell membranes, a stretching membrane for transport and mixing of samples, charged colloidal magnetite for magnetic separation of erythrocytes, and an immersible fiber optic probe for measuring fluorescence associated with cells in a 1-nL volume of a bulk solution. We describe the application of the system to automation of ABO/Rh grouping and antibody screening.

A residents' training program for the development of smoking intervention skills

This article describes the results of a three-hour training program that teaches residents a patient-centered counseling approach to smoking cessation, emphasizing questioning and exploring feelings, rather than providing information. Fifty internal medicine and family practice residents affiliated with a university medical center were assessed before and after training using questionnaires and videotape documenting changes in their knowledge about smoking, attitudes concerning intervention, and intervention skills. The residents showed a significant increase in knowledge and perceived themselves as having significantly more influence on their patients who smoke after completion of the training program. Counseling skills improved significantly in the use of questions and exploring feelings as judged by blind evaluation of videotapes. The results of this three-hour training program suggest that physicians in training are responsive to the teaching of specialized skills deemed important for promoting health behavior changes in their patients.