Small symptomatic anterior communicating artery aneurysms: report of three cases and literature review.

PURPOSE: Given the anatomical relationship between the ACom complex and the optic nerve, small aneurysms of the ACom can present with visual symptoms. CASE REPORTS: We summarize and illustrate the clinical course of three patients with symptomatic small ACom aneurysms and collect similar other cases reported. RESULTS: Ten patients with small unruptured visually symptomatic anterior communicating artery aneurysms were found in the literature. Including three patients herein reported, the mean age at presentation was 56. The most common visual symptoms were bitemporal vision loss and/or a decrease in visual acuity. CONCLUSION: Unruptured aneurysms of the anterior communicating artery can present with visual symptoms due to compression of optic pathways, even at a small size. Prompt recognition and treatment of such a condition are paramount as new onset of visual symptoms can signify impending rupture akin to small PCom aneurysms compressing the third nerve. We discuss a few pitfalls of clipping small ACom aneurysms compressing the optic nerve.

PD-L1+ neutrophils contribute to injury-induced infection susceptibility.

The underlying mechanisms contributing to injury-induced infection susceptibility remain poorly understood. Here, we describe a rapid increase in neutrophil cell numbers in the lungs following induction of thermal injury. These neutrophils expressed elevated levels of programmed death ligand 1 (PD-L1) and exhibited altered gene expression profiles indicative of a reparative population. Upon injury, neutrophils migrate from the bone marrow to the skin but transiently arrest in the lung vasculature. Arrested neutrophils interact with programmed cell death protein 1 (PD-1) on lung endothelial cells. A period of susceptibility to infection is linked to PD-L1+ neutrophil accumulation in the lung. Systemic treatment of injured animals with an anti-PD-L1 antibody prevented neutrophil accumulation in the lung and reduced susceptibility to infection but augmented skin healing, resulting in increased epidermal growth. This work provides evidence that injury promotes changes to neutrophils that are important for wound healing but contribute to infection susceptibility.

Functional mimetic of the G-protein coupled receptor CXCR4 on a soluble antibody scaffold.

G-protein coupled receptors (GPCRs) constitute major drug targets due to their involvement in critical biological functions and pathophysiological disorders. The leading challenge in their structural and functional characterization has been the need for a lipid environment to accommodate their hydrophobic cores. Here, we report an antibody scaffold mimetic (ASM) platform where we have recapitulated the extracellular functional domains of the GPCR, C-X-C chemokine receptor 4 (CXCR4) on a soluble antibody framework. The engineered ASM molecule can accommodate the N-terminal loop and all three extracellular loops of CXCR4. These extracellular features are important players in ligand recruitment and interaction for allostery and signal transduction. Our study shows that ASMCXCR4 can be recognized by the anti-CXCR4 antibodies, MEDI3185, 2B11, and 12G5, and that ASMCXCR4 can bind the HIV-1 glycoprotein ligand gp120, and the natural chemokine ligand SDF-1α. Further, we show that ASMCXCR4 can competitively inhibit the SDF-1α signaling pathway, and be used as an immunogen to generate CXCR4-specific antibodies. This platform will be useful in the study of GPCR biology in a soluble receptor context for evaluating its extracellular ligand interactions.

Ligand- and cation-induced structural alterations of the leukocyte integrin LFA-1.

In αI integrins, including leukocyte function-associated antigen 1 (LFA-1), ligand-binding function is delegated to the αI domain, requiring extra steps in the relay of signals that activate ligand binding and coordinate it with cytoplasmic signals. Crystal structures reveal great variation in orientation between the αI domain and the remainder of the integrin head. Here, we investigated the mechanisms involved in signal relay to the αI domain, including whether binding of the ligand intercellular adhesion molecule-1 (ICAM-1) to the αI domain is linked to headpiece opening and engenders a preferred αI domain orientation. Using small-angle X-ray scattering and negative-stain EM, we define structures of ICAM-1, LFA-1, and their complex, and the effect of activation by Mn2+ Headpiece opening was substantially stabilized by substitution of Mg2+ with Mn2+ and became complete upon ICAM-1 addition. These agents stabilized αI-headpiece orientation, resulting in a well-defined orientation of ICAM-1 such that its tandem Ig-like domains pointed in the opposite direction from the ß-subunit leg of LFA-1. Mutations in the integrin ßI domain α1/α1' helix stabilizing either the open or the closed ßI-domain conformation indicated that α1/α1' helix movements are linked to ICAM-1 binding by the αI domain and to the extended-open conformation of the ectodomain. The LFA-1-ICAM-1 orientation described here with ICAM-1 pointing anti-parallel to the LFA-1 ß-subunit leg is the same orientation that would be stabilized by tensile force transmitted between the ligand and the actin cytoskeleton and is consistent with the cytoskeletal force model of integrin activation.

Enhancement of antibody functions through Fc multiplications.

Antibodies carry out a plethora of functions through their crystallizable fragment (Fc) regions, which can be naturally tuned by the adoption of several isotypes and post-translational modifications. Protein engineering enables further Fc function modulations through modifications of the interactions between the Fc and its functional partners, including FcγR, FcRn, complement complex, and additions of auxiliary functional units. Due to the many functions embedded within the confinement of an Fc, a suitable balance must be maintained for a therapeutic antibody to be effective and safe. The outcome of any Fc engineering depends on the interplay among all the effector molecules involved. In this report, we assessed the effects of Fc multiplication (or tandem Fc) on antibody functions. Using IgG1 as a test case, we found that, depending on the specifically designed linker, Fc multiplication led to differentially folded, stable molecules with unique pharmacokinetic profiles. Interestingly, the variants with 3 copies of Fc improved in vitro opsonophagocytic killing activity and displayed significantly improved protective efficacies in a Klebsiella pneumoniae mouse therapeutic model despite faster clearance compared with its IgG1 counterpart. There was no adverse effect observed or pro-inflammatory cytokine release when the Fc variants were administered to animals. We further elucidated that enhanced binding to various effector molecules by IgG-3Fc created a "sink" leading to the rapid clearance of the 3Fc variants, and identified the increased FcRn binding as one strategy to facilitate "sink" escape. These findings reveal new opportunities for novel Fc engineering to further expand our abilities to manipulate and improve antibody therapeutics.

Anti-MrkA Monoclonal Antibodies Reveal Distinct Structural and Antigenic Features of MrkA.

Antibody therapy against antibiotics resistant Klebsiella pneumoniae infections represents a promising strategy, the success of which depends critically on the ability to identify appropriate antibody targets. Using a target-agnostic strategy, we recently discovered MrkA as a potential antibody target and vaccine antigen. Interestingly, the anti-MrkA monoclonal antibodies isolated through phage display and hybridoma platforms all recognize an overlapping epitope, which opens up important questions including whether monoclonal antibodies targeting different MrkA epitopes can be generated and if they possess different protective profiles. In this study we generated four anti-MrkA antibodies targeting different epitopes through phage library panning against recombinant MrkA protein. These anti-MrkA antibodies elicited strong in vitro and in vivo protections against a multi-drug resistant Klebsiella pneumoniae strain. Furthermore, mutational and epitope analysis suggest that the two cysteine residues may play essential roles in maintaining a MrkA structure that is highly compacted and exposes limited antibody binding/neutralizing epitopes. These results suggest the need for further in-depth understandings of the structure of MrkA, the role of MrkA in the pathogenesis of Klebsiella pneumoniae and the protective mechanism adopted by anti-MrkA antibodies to fully explore the potential of MrkA as an efficient therapeutic target and vaccine antigen.

Force interacts with macromolecular structure in activation of TGF-ß.

Integrins are adhesion receptors that transmit force across the plasma membrane between extracellular ligands and the actin cytoskeleton. In activation of the transforming growth factor-ß1 precursor (pro-TGF-ß1), integrins bind to the prodomain, apply force, and release the TGF-ß growth factor. However, we know little about how integrins bind macromolecular ligands in the extracellular matrix or transmit force to them. Here we show how integrin αVß6 binds pro-TGF-ß1 in an orientation biologically relevant for force-dependent release of TGF-ß from latency. The conformation of the prodomain integrin-binding motif differs in the presence and absence of integrin binding; differences extend well outside the interface and illustrate how integrins can remodel extracellular matrix. Remodelled residues outside the interface stabilize the integrin-bound conformation, adopt a conformation similar to earlier-evolving family members, and show how macromolecular components outside the binding motif contribute to integrin recognition. Regions in and outside the highly interdigitated interface stabilize a specific integrin/pro-TGF-ß orientation that defines the pathway through these macromolecules which actin-cytoskeleton-generated tensile force takes when applied through the integrin ß-subunit. Simulations of force-dependent activation of TGF-ß demonstrate evolutionary specializations for force application through the TGF-ß prodomain and through the ß- and not α-subunit of the integrin.

A novel antibody discovery platform identifies anti-influenza A broadly neutralizing antibodies from human memory B cells.

Monoclonal antibody isolation directly from circulating human B cells is a powerful tool to delineate humoral responses to pathological conditions and discover antibody therapeutics. We have developed a platform aimed at improving the efficiencies of B cell selection and V gene recovery. Here, memory B cells are activated and amplified using Epstein-Barr virus infection, co-cultured with CHO-muCD40L cells, and then assessed by functional screenings. An in vitro transcription and translation (IVTT) approach was used to analyze variable (V) genes recovered from each B cell sample and identify the relevant heavy/light chain pair(s). We achieved efficient amplification and activation of memory B cells, and eliminated the need to: 1) seed B cells at clonal level (≤1 cell/well) or perform limited dilution cloning; 2) immortalize B cells; or 3) assemble V genes into an IgG expression vector to confirm the relevant heavy/light chain pairing. Cross-reactive antibodies targeting a conserved epitope on influenza A hemagglutinin were successfully isolated from a healthy donor. In-depth analysis of the isolated antibodies suggested their potential uses as anti-influenza A antibody therapeutics and uncovered a distinct affinity maturation pathway. Importantly, our results showed that cognate heavy/light chain pairings contributed to both the expression level and binding abilities of our newly isolated VH1-69 family, influenza A neutralizing antibodies, contrasting with previous observations that light chains do not significantly contribute to the function of this group of antibodies. Our results further suggest the potential use of the IVTT as a powerful antibody developability assessment tool.

Dimeric quaternary structure of human laforin.

The phosphatase laforin removes phosphate groups from glycogen during biosynthetic activity. Loss-of-function mutations in the gene encoding laforin is the predominant cause of Lafora disease, a fatal form of progressive myoclonic epilepsy. Here, we used hybrid structural methods to determine the molecular architecture of human laforin. We found that laforin adopts a dimeric quaternary structure, topologically similar to the prototypical dual specificity phosphatase VH1. The interface between the laforin carbohydrate-binding module and the dual specificity phosphatase domain generates an intimate substrate-binding crevice that allows for recognition and dephosphorylation of phosphomonoesters of glucose. We identify novel molecular determinants in the laforin active site that help decipher the mechanism of glucan phosphatase activity.

A procedure to construct exact solutions of nonlinear fractional differential equations.

We use the fractional transformation to convert the nonlinear partial fractional differential equations with the nonlinear ordinary differential equations. The Exp-function method is extended to solve fractional partial differential equations in the sense of the modified Riemann-Liouville derivative. We apply the Exp-function method to the time fractional Sharma-Tasso-Olver equation, the space fractional Burgers equation, and the time fractional fmKdV equation. As a result, we obtain some new exact solutions.

Shape change in the receptor for gliding motility in Plasmodium sporozoites.

Sporozoite gliding motility and invasion of mosquito and vertebrate host cells in malaria is mediated by thrombospondin repeat anonymous protein (TRAP). Tandem von Willebrand factor A (VWA) and thrombospondin type I repeat (TSR) domains in TRAP connect through proline-rich stalk, transmembrane, and cytoplasmic domains to the parasite actin-dependent motility apparatus. We crystallized fragments containing the VWA and TSR domains from Plasmodium vivax and Plasmodium falciparum in different crystal lattices. TRAP VWA domains adopt closed and open conformations, and bind a Mg(2+) ion at a metal ion-dependent adhesion site implicated in ligand binding. Metal ion coordination in the open state is identical to that seen in the open high-affinity state of integrin I domains. The closed VWA conformation associates with a disordered TSR domain. In contrast, the open VWA conformation crystallizes with an extensible ß ribbon and ordered TSR domain. The extensible ß ribbon is composed of disulfide-bonded segments N- and C-terminal to the VWA domain that are largely drawn out of the closed VWA domain in a 15 Å movement to the open conformation. The extensible ß ribbon and TSR domain overlap at a conserved interface. The VWA, extensible ß ribbon, and TSR domains adopt a highly elongated overall orientation that would be stabilized by tensile force exerted across a ligand-receptor complex by the actin motility apparatus of the sporozoite. Our results provide insights into regulation of "stick-and-slip" parasite motility and for development of sporozoite subunit vaccines.

Unexpected fold in the circumsporozoite protein target of malaria vaccines.

Circumsporozoite (CS) protein is the major surface component of Plasmodium falciparum sporozoites and is essential for host cell invasion. A vaccine containing tandem repeats, region III, and thrombospondin type-I repeat (TSR) of CS is efficacious in phase III trials but gives only a 35% reduction in severe malaria in the first year postimmunization. We solved crystal structures showing that region III and TSR fold into a single unit, an "αTSR" domain. The αTSR domain possesses a hydrophobic pocket and core, missing in TSR domains. CS binds heparin, but αTSR does not. Interestingly, polymorphic T-cell epitopes map to specialized αTSR regions. The N and C termini are unexpectedly close, providing clues for sporozoite sheath organization. Elucidation of a unique structure of a domain within CS enables rational design of next-generation subunit vaccines and functional and medicinal chemical investigation of the conserved hydrophobic pocket.

Dimerization of Vaccinia virus VH1 is essential for dephosphorylation of STAT1 at tyrosine 701.

The gene product of Vaccinia virus gene H1, VH1, is the first identified dual specificity phosphatase (DSP). The human genome encodes 38 different VH1-like DSPs, which include major regulators of signaling pathways, highly dysregulated in disease states. VH1 down-regulates cellular antiviral response by dephosphorylating activated STAT1 in the IFN-γ/STAT1 signaling pathway. In this report, we have investigated the molecular basis for VH1 catalytic activity. Using small-angle x-ray scattering (SAXS), we determined that VH1 exists in solution as a boomerang-shaped dimer. Targeted alanine mutations in the dimerization domain (aa 1-27) decrease phosphatase activity while leaving the dimer intact. Deletion of the N-terminal dimer swapped helix (aa 1-20) completely abolishes dimerization and severely reduces phosphatase activity. An engineered chimera of VH1 that contains only one active site retains wild-type levels of catalytic activity. Thus, a dimeric quaternary structure, as opposed to two cooperative active sites within the same dimer is essential for VH1 catalytic activity. Together with laforin, VH1 is the second DSP reported in literature for which dimerization via an N-terminal dimerization domain is necessary for optimal catalytic activity. We propose that dimerization may represent a common mechanism to regulate the activity and substrate recognition of DSPs, often assumed to function as monomers.

Dimeric quaternary structure of the prototypical dual specificity phosphatase VH1.

The Vaccinia virus H1 gene product, VH1, is a dual specificity phosphatase that down-regulates the cellular antiviral response by dephosphorylating STAT1. The crystal structure of VH1, determined at 1.32 A resolution, reveals a novel dimeric quaternary structure, which exposes two active sites spaced approximately 39 A away from each other. VH1 forms a stable dimer via an extensive domain swap of the N-terminal helix (residues 1-20). In vitro, VH1 can dephosphorylate activated STAT1, in a reaction that is competed by the nuclear transport adapter importin alpha5. Interestingly, VH1 is inactive with respect to STAT1 bound to DNA, suggesting that the viral phosphatase acts predominantly on the cytoplasmic pool of activated STAT1. We propose that the dimeric quaternary structure of VH1 is essential for specific recognition of activated STAT1, which prevents its nuclear translocation, thus blocking interferon-gamma signal transduction and antiviral response.

[Pancreatic peritoneal fistula with bisalbuminemia]. / Fistule pancréatico-péritonéale avec bisalbuminémie.

INTRODUCTION: Pancreatic fistulas are a complication that occur in 3 to 15% of cases during the progression of chronic or acute pancreatitis, usually alcohol-induced. Bisalbuminemia is characterised by two albumin fractions on serum protein electrophoresis. The presence of Bisalbuminemia is inconsistent and has only rarely been reported. OBSERVATION: A 42 year-old man, excessive drinker, developed pancreatic ascites related to a pancreatic-peritoneal fistula and associated with transitory bisalbuminemia. Treatment was medical with good short term results. DISCUSSION: Ascites was secondary to a pancreatic-peritoneal fistula. It can be constitutional or acquired and transitory, and secondary to prolonged treatment with b-lactamines in a patient with kidney failure or a pancreatic fistula.

The dural tail sign--beyond meningioma.

There have been somewhat conflicting reports published about the significance of linear meningeal thickening and enhancement adjacent to peripherally located cranial mass lesions on contrast-enhanced magnetic resonance (MR) images. Most of the authors consider this so-called "dural tail sign" or "flare sign" almost specific for meningioma. This review illustrates the MR imaging findings of a wide spectrum of disorders that show this dural sign. Causes include other extra-axial lesions and also peripherally located intra-axial lesions such as neuromas, chloromas, metastases, lymphoma, gliomas, pituitary diseases, granulomatous disorders, and also cerebral Erdheim-Chester disease. The dural tail sign is not specific to a particular pathological process. Nevertheless, useful conclusions can be drawn from the morphology of the lesion, its enhancement pattern, and its solitary or multifocal presentation. The final diagnosis must be based on cerebrospinal fluid studies or histological studies after biopsy.

[Cerebral Erdheim-Chester disease]. / Maladie d'Erdheim-Chester cérébrale.

We report the case of a 26-old-year man hospitalized for first partial complex epileptic seizure. Brain MRI showed an asymptomatic pseudo-tumor lesion in the brainstem. Diabetes insipidus, hypophyseal gonadotropic deficiency and osteosclerosis of long bones strongly suggested Erdheim-Chester disease, a rare histiocytosis, confirmed after tibial biopsy. Six months later, the patient remained stable. A persistent, and even increased, enhancement with Gd-DTPA on brain MR images was noted as previously described. The review of the literature collected 64 cases, and only 7 cases of cerebral "tumor".

Primary breast sarcoma: clinicopathologic series from the Mayo Clinic and review of the literature.

Primary sarcomas of the breast are extremely rare, with less than 0.1% of all malignant tumours of the breast. Mayo Clinic Surgical Pathology database was searched for all breast sarcoma from 1910 to 2000. Pathology reports and slides were reviewed and tumour types were determined. Metaplastic carcinomas and phyllodes tumours were excluded. There were 25 women ranging in age 24-81 years (mean 45 years). All but one patient presented with a palpable lump. Mastectomy was performed in 19 patients and lumpectomy in five patients. Histopathological diagnoses were fibrosarcoma (six), angiosarcoma (six), pleomorphic sarcoma (six), leiomyosarcoma (two), myxofibrosarcoma (three), hemangiopericytoma (one) and osteosarcoma (one). Tumour size ranged from 0.3 to 12 cm (mean 5.7). Low-grade lesions were observed in 10 cases and high-grade in 15. Overall, mean follow-up was 10.5 years. Local recurrence was observed in 11 patients and ranged from 2 to 36 months (mean 15 m), while distant metastasis was observed in 10 patients (40%) affecting lungs, bones, liver, spleen, and skin. Of the 25 patients, 12 have died of disease and six of other causes. Five-year overall (OS) and cause-specific survival (CSS) were 66 and 70%, respectively. OS and DFS at 5 years were 91% for tumours < or =5 cm and 50% for tumours >5 cm. Tumour size was significantly associated with OS (risk ratio=1.3 per 1 cm increase; 95% CI, 1.02-1.7; P=0.036). There was no significant difference in OS or CSS between low- and high-grade lesions. In this series, tumour size was a more valuable prognostic factor than tumour grade.

[Intradiploic parietal meningoencephalocele]. / Méningoencéphalocèle intradiploïque pariétale.

Intradiploic meningoencephalocele is rarely found in adulthood. It is thought to be postraumatic and must be differenciated from congenital encephalocele. Imaging findings, particularly with Magnetic Resonance Imaging, are useful in determining the various linings and contents of this intradiploic defect.

[Diagnosis of periventricular ependymal enhancement in MRI in adults]. / Diagnostic d'un rehaussement épendymaire et périventriculaire en irm chez l'adulte.

Periventricular enhancement in adults at MRI is a significant finding since it often indicates the presence of an underlying disease requiring prompt medical attention. From a review of patients with periventricular enhancement, the main imaging features based on the underlying infectious or tumoral etiology will be described. The presented differential diagnosis is based on the immune status of the patient, type of enhancement, and response to a trial therapy. In immunocompromised patients, the main considerations are lymphoma and viral ependymitis. The pattern of enhancement is important. The presence of thin linear enhancement suggests a viral etiology (cytomegalovirus or varicella-zoster virus) that can be confirmed at CSF evaluation whereas the presence of nodular enhancement suggests a diagnosis of primary CNS lymphoma that can be confirmed by the presence of lymphomatous cells in the CSF or, more frequently, at stereotactic surgical biopsy performed after failure of response to anti-toxoplasmosis treatment. The presence of band enhancement is less specific and can be seen with viral, lymphomatous and even tuberculous involvement. In immunocompetent patients, a clinical context of infection will suggest bacterial or tuberculous ventriculitis and the presence of cystic lesions will suggest cysticercosis; in the absence of constitutional symptoms, the presence of nodular enhancement will suggest a tumoral process (lymphoma, ependymoma, germ cell tumor, or metastases). Rarely, linear enhancement will be due to sarcoidosis or Whipple's disease.