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Ian A Wilson

Publications and source records attributed to Ian A Wilson.

At least 19 recordsLinked to original sources
PubMed2007

Biodistribution and radiation dosimetry of the amyloid imaging agent 11C-PIB in humans.

UNLABELLED: We investigated the biodistribution and radiation dosimetry of the PET amyloid imaging agent (11)C-PIB ((11)C-6-OH-BTA-1) (where BTA is benzothiazole) in humans. Previous radiation exposure estimates have been based on animal experiments. A dosimetry study in humans is essential for a balanced risk-benefit assessment of (11)C-PIB PET studies. METHODS: We used data from 16 different (11)C-PIB PET scans on healthy volunteers to estimate radiation exposure. Six of these scans were dynamic imaging over the abdominal region: 3 covering the upper abdomen and 3 covering the middle abdomen. On average, 489 MBq of (11)C-PIB (range, 416-606 MBq) were injected intravenously, and dynamic emission scans were recorded for up to 40 min. Two subjects had whole-body imaging over the entire body to illustrate the biodistribution. PET brain scans and blood and urine radioactivity measurements from our previous (11)C-PIB studies were also analyzed. Thirteen source organs and the remainder of the body were studied to estimate residence times and mean radiation-absorbed doses. The MIRD method was used to calculate the radiation exposure of selected target organs and the body as a whole. RESULTS: There is a high degree of consistency between our human data and previous biodistribution information based on baboons. In our study, the highest radiation-absorbed doses were received by the gallbladder wall (41.5 microGy/MBq), liver (19.0 microGy/MBq), urinary bladder wall (16.6 microGy/MBq), kidneys (12.6 microGy/MBq), and upper large intestine wall (9.0 microGy/MBq). The hepatobiliary and renal systems were the major routes of clearance and excretion, with approximately 20% of the injected radioactivity being excreted into urine. The effective radiation dose was 4.74 microSv/MBq. CONCLUSION: The established clinical dose of (11)C-PIB required for 3-dimensional PET amyloid imaging has an acceptable effective radiation dose. This dose is comparable with the average exposure expected in other PET brain receptor tracer studies. (11)C-PIB is rapidly cleared from the body, largely by the kidneys. From the viewpoint of radiation safety, these results support the use of (11)C-PIB in clinical PET studies.

Adult↗
PubMed2006

Comparative structural analysis of a novel glutathioneS-transferase (ATU5508) from Agrobacterium tumefaciens at 2.0 A resolution.

Glutathione S-transferases (GSTs) comprise a diverse superfamily of enzymes found in organisms from all kingdoms of life. GSTs are involved in diverse processes, notably small-molecule biosynthesis or detoxification, and are frequently also used in protein engineering studies or as biotechnology tools. Here, we report the high-resolution X-ray structure of Atu5508 from the pathogenic soil bacterium Agrobacterium tumefaciens (atGST1). Through use of comparative sequence and structural analysis of the GST superfamily, we identified local sequence and structural signatures, which allowed us to distinguish between different GST classes. This approach enables GST classification based on structure, without requiring additional biochemical or immunological data. Consequently, analysis of the atGST1 crystal structure suggests a new GST class, distinct from previously characterized GSTs, which would make it an attractive target for further biochemical studies.

Agrobacterium tumefaciens↗
PubMed2006

Structural basis of enhanced binding of extended and helically constrained peptide epitopes of the broadly neutralizing HIV-1 antibody 4E10.

Potent, broadly HIV-1 neutralizing antibodies (nAbs) may be invaluable for the design of an AIDS vaccine. 4E10 is the broadest HIV-1 nAb known to date and recognizes a contiguous and highly conserved helical epitope in the membrane-proximal region of gp41. The 4E10 epitope is thus an excellent target for vaccine design as it is also highly amenable to peptide engineering to enhance its helical character. To investigate the structural effect of both increasing the peptide length and of introducing helix-promoting constraints in the 4E10 epitope, we have determined crystal structures of Fab 4E10 bound to an optimized peptide epitope (NWFDITNWLWYIKKKK-NH(2)), an Aib-constrained peptide epitope (NWFDITNAibLWRR-NH(2)), and a thioether-linked peptide (NWFCITOWLWKKKK-NH(2)) to resolutions of 1.7 A, 2.1 A, and 2.2 A, respectively. The thioether-linked peptide is the first reported structure of a cyclic tethered helical peptide bound to an antibody. The introduced helix constraints limit the conformational flexibility of the peptides without affecting interactions with 4E10. The substantial increase in affinity (10 nM versus 10(4) nM of the IC(50) of the original KGND peptide template) is largely realized by 4E10 interaction with an additional helical turn at the peptide C terminus that includes Leu679 and Trp680. Thus, the core 4E10 epitope was extended and modified to a WFX(I/L)(T/S)XX(L/I)W motif, where X does not play a major role in 4E10 binding and can be used to introduce helical-promoting constraints in the peptide epitope.

Amino Acid Sequence↗
PubMed2006

Glycan microarray technologies: tools to survey host specificity of influenza viruses.

New technologies are urgently required for rapid surveillance of the current H5N1 avian influenza A outbreaks to gauge the potential for adaptation of the virus to the human population, a crucial step in the emergence of pandemic influenza virus strains. Owing to the species-specific nature of the interaction between the virus and host glycans, attention has recently focused on novel glycan array technologies that can rapidly assess virus receptor specificity and the potential emergence of human-adapted H5N1 viruses.

Animals↗
PubMed2006

Structural characterization of mycobacterial phosphatidylinositol mannoside binding to mouse CD1d.

Mycobacterial phosphatidylinositol tetramannosides (PIM4) are agonists for a distinct population of invariant human (Valpha24) and mouse (Valpha14) NKT cells, when presented by CD1d. We determined the crystal structure at 2.6-A resolution of mouse CD1d bound to a synthetic dipalmitoyl-PIM2. Natural PIM2, which differs in its fatty acid composition is a biosynthetic precursor of PIM4, PIM6, lipomannan, and lipoarabinomannan. The PIM2 headgroup (inositol-dimannoside) is the most complex to date among all the crystallized CD1d ligands and is remarkably ordered in the CD1d binding groove. A specific hydrogen-bonding network between PIM2 and CD1d orients the headgroup in the center of the binding groove and above the A' pocket. A central cluster of hydrophilic CD1d residues (Asp(153), Thr(156), Ser(76), Arg(79)) interacts with the phosphate, inositol, and alpha1-alpha6-linked mannose of the headgroup, whereas additional specificity for the alpha1- and alpha2-linked mannose is conferred by Thr(159). The additional two mannoses in PIM4, relative to PIM2, are located at the distal 6' carbon of the alpha1-alpha6-linked mannose and would project away from the CD1d binding groove for interaction with the TCR. Compared with other CD1d-sphingolipid structures, PIM2 has an increased number of polar interactions between its headgroup and CD1, but reduced specificity for the diacylglycerol backbone. Thus, novel NKT cell agonists can be designed that focus on substitutions of the headgroup rather than on reducing lipid chain length, as in OCH and PBS-25, two potent variants of the highly stimulatory invariant NKT cell agonist alpha-galactosylceramide.

Animals↗
PubMed2006

Rapid and robust protection against cocaine-induced lethality in rats by the bacterial cocaine esterase.

There is no approved means to prevent the toxic actions of cocaine. Cocaine esterase (CocE) is found in a rhodococcal strain of bacteria that grows in the rhizosphere soil around the coca plant and has been found to hydrolyze cocaine in vitro. The esteratic activity of CocE (0.1-1.0 mg, i.v.) was characterized and confirmed in vivo by assessing its ability to prevent cocaine-induced convulsions and lethality in the rat. The therapeutic efficiency of the enzyme was demonstrated by the increasing dose of cocaine (100-1000 mg/kg, i.p.) required to produce toxic effects after a single intravenous injection of CocE. The enzyme demonstrated rapid kinetics for cocaine degradation in rat and human serum. Two catalytically inactive mutants of CocE (S117A or Y44F) failed to protect rats from the toxic effects of cocaine, confirming the protective effects are due to hydrolytic activity. However, butyrylcholinesterase, an endogenous cocaine-hydrolyzing enzyme, was inactive (1.3-13 mg, i.v.) in this rat toxicity procedure. Furthermore, CocE did not block the lethality of WIN-35065-2 (560 mg/kg, i.p.), a cocaine analog that lacks the benzoyl ester moiety targeted by CocE. This characterization of CocE provides preliminary evidence that the enzyme could serve as a suitable antidote to cocaine toxicity in humans.

Animals↗
PubMed2006

Natural killer T cells recognize diacylglycerol antigens from pathogenic bacteria.

Natural killer T (NKT) cells recognize glycosphingolipids presented by CD1d molecules and have been linked to defense against microbial infections. Previously defined foreign glycosphingolipids recognized by NKT cells are uniquely found in nonpathogenic sphingomonas bacteria. Here we show that mouse and human NKT cells also recognized glycolipids, specifically a diacylglycerol, from Borrelia burgdorferi, which causes Lyme disease. The B. burgdorferi-derived, glycolipid-induced NKT cell proliferation and cytokine production and the antigenic potency of this glycolipid was dependent on acyl chain length and saturation. These data indicate that NKT cells recognize categories of glycolipids beyond those in sphingomonas and suggest that NKT cell responses driven by T cell receptor-mediated glycolipid recognition may provide protection against diverse pathogens.

Animals↗
PubMed2006

Details of Toll-like receptor:adapter interaction revealed by germ-line mutagenesis.

The immunovariant N-ethyl-N-nitrosourea-induced mutations Pococurante (Poc) and Lackadaisical were found to alter MyD88, creating striking receptor-selective effects. Poc, in particular, prevented sensing of all MyD88-dependent Toll-like receptor (TLR) ligands except diacyl lipopeptides. Furthermore, Poc-site and classical BB loop mutations caused equivalent phenotypes when engrafted into any TLR/IL-1 receptor/resistance (TIR) domain. These observations, complemented by data from docking studies and site-directed mutagenesis, revealed that BB loops and Poc sites interact homotypically across the receptor:adapter signaling interface, whereas the C-terminal alpha(E)-helices support adapter:adapter and receptor:receptor oligomerization. We have thus defined the TIR domain surface that mediates association between TLRs and MyD88 and the surface required for MyD88 or TLR oligomerization. Moreover, MyD88 engages individual TLRs differently, suggesting the feasibility of selective pharmacologic TIR domain receptor blockade.

Adaptor Proteins, Signal Transducing↗
PubMed2006

Inhibition of HIV Env binding to cellular receptors by monoclonal antibody 2G12 as probed by Fc-tagged gp120.

During natural HIV infection, an array of host receptors are thought to influence virus attachment and the kinetics of infection. In this study, to probe the interactions of HIV envelope (Env) with various receptors, we assessed the inhibitory properties of various anti-Env monoclonal antibodies (mAbs) in binding assays. To assist in detecting Env in attachment assays, we generated Fc fusions of full-length wild-type gp120 and several variable loop-deleted gp120s. Through investigation of the inhibition of Env binding to cell lines expressing CD4, CCR5, DC-SIGN, syndecans or combinations thereof, we found that the broadly neutralizing mAb, 2G12, directed to a unique carbohydrate epitope of gp120, inhibited Env-CCR5 binding, partially inhibited Env-DC-SIGN binding, but had no effect on Env-syndecan association. Furthermore, 2G12 inhibited Env attachment to primary monocyte-derived dendritic cells, that expressed CD4 and CCR5 primary HIV receptors, as well as DC-SIGN, and suggested that the dual activities of 2G12 could be valuable in vivo for inhibiting initial virus dissemination and propagation.

Animals↗
PubMed2006

Role of lipid trimming and CD1 groove size in cellular antigen presentation.

Cellular CD1 proteins bind lipids that differ in length (C(12-80)), including antigens that exceed the capacity of the CD1 groove. This could be accomplished by trimming lipids to a uniform length before loading or by inserting each lipid so that it penetrates the groove to a varying extent. New assays to detect antigen fragments generated within human dendritic cells showed that bacterial antigens remained intact, even after delivery to lysosomes, where control lipids were cleaved. Further, recombinant CD1b proteins could bind and present C(80) lipid antigens using a mechanism that did not involve cellular enzymes or lipid cleavage, but was regulated by pH in the physiologic range. We conclude that endosomal acidification acts directly, rather than through enzymatic trimming, to insert lipids into CD1b. Lipids are loaded in an intact form, so that they likely protrude through a portal near the bottom of the groove, which represents an escape hatch for long lipids from mycobacterial pathogens.

Antigen Presentation↗