Nonmagnetic γ″-FeN thin films epitaxially grown on Cu(001): Electronic structure and thermal stability

6 págs.; 7 figs. ; PACS number s : 73.20. r, 71.20. b, 71.15.Mb, 68.37.EfWe report on a theoretical and experimental study of the growth, electronic structure, and thermal stability of ultrathin films of nonmagnetic iron nitride. The films are grown by evaporation of Fe, in a flux of atomic N produced by a plasma source, onto a Cu(001) surface kept at 300 K and characterized by x-ray photoelectron spectroscopy, ultraviolet photoelectron spectroscopy, and x-ray diffraction. The compound formed is identified as γ″ -FeN (001) growing epitaxially on the substrate. Its electronic structure and thermal stability has been studied and compared with first-principles calculations. This nitride film transforms to magnetic γ′ -Fe4 N phase by annealing above 650 K, opening new perspectives for applications of these films in functional magnetic nanostructures. © 2008 The American Physical Society.This work was supported by the Spanish CICyT under Grants No. FIS 2007-61114, No. MAT2004-05865, No. NAN2004-08881-C02-01, and CONSOLIDER on Molecular Nanoscience, the Comunidad de Madrid under Grant No. S-0505/MAT-0194, and the EU under the PF6 “Structuring the European Research Area” program Contract No. RII3- CT-2004-506008.Peer Reviewe

Recombinant AAV Vectors for Enhanced Expression of Authentic IgG

Adeno-associated virus (AAV) has become a vector of choice for the treatment of a variety of genetic diseases that require safe and long-term delivery of a missing protein. Muscle-directed gene transfer for delivery of protective antibodies against AIDS viruses and other pathogens has been used experimentally in mice and monkeys. Here we examined a number of variations to AAV vector design for the ability to produce authentic immunoglobulin G (IgG) molecules. Expression of rhesus IgG from a single single-stranded AAV (ssAAV) vector (one vector approach) was compared to expression from two self-complementary AAV (scAAV) vectors, one for heavy chain and one for light chain (two vector approach). Both the one vector and the two vector approaches yielded considerable levels of expressed full-length IgG. A number of modifications to the ssAAV expression system were then examined for their ability to increase the efficiency of IgG expression. Inclusion of a furin cleavage sequence with a linker peptide just upstream of the 2A self-cleaving sequence from foot-and-mouth disease virus (F2A) increased IgG expression approximately 2 fold. Inclusion of these sequences also helped to ensure a proper sequence at the C-terminal end of the heavy chain. Inclusion of the post-transcriptional regulatory element from woodchuck hepatitis virus (WPRE) further increased IgG expression 1.5-2.0 fold. IgG1 versions of the two rhesus IgGs that were examined consistently expressed better than the IgG2 forms. In contrast to what has been reported for AAV2-mediated expression of other proteins, introduction of capsid mutations Y445F and Y731F did not increase ssAAV1-mediated expression of IgG as determined by transduction experiments in cell culture. Our findings provide a rational basis for AAV vector design for expression of authentic IgG

Liver-Directed but Not Muscle-Directed AAV-Antibody Gene Transfer Limits Humoral Immune Responses in Rhesus Monkeys

A number of publications have described the use of adeno-associated virus (AAV) for the delivery of anti-HIV and anti-simian immunodeficiency virus (SIV) monoclonal antibodies (mAbs) to rhesus monkeys. Anti-drug antibodies (ADAs) have been frequently observed, and long-term AAV-mediated delivery has been inconsistent. Here, we investigated different AAV vector strategies and delivery schemes to rhesus monkeys using the rhesus monkey mAb 4L6. We compared 4L6 immunoglobulin G1 (IgG1) delivery using the AAV1 versus the AAV8 serotype with a cytomegalovirus (CMV) promoter and the use of a muscle-specific versus a liver-specific promoter. Long-term expression levels of 4L6 IgG1 following AAV8-mediated gene transfer were comparable to those following AAV1-mediated gene transfer. AAV1-mediated gene transfer, using a muscle-specific promoter, showed robust ADAs and transiently low 4L6 IgG1 levels that ultimately declined to below detectable levels. Intravenous AAV8-mediated gene transfer, using a liver-specific promoter, also resulted in low levels of delivered 4L6 IgG1, but those low levels were maintained in the absence of any detectable ADAs. Booster injections using AAV1-CMV allowed for increased 4L6 IgG1 serum levels in animals that were primed with AAV8 but not with AAV1. Our results suggest that liver-directed expression may help to limit ADAs and that re-administration of AAV of a different serotype can result in successful long-term delivery of an immunogenic antibody

AAV-Delivered Antibody Mediates Significant Protective Effects against SIVmac239 Challenge in the Absence of Neutralizing Activity

Long-term delivery of potent broadly-neutralizing antibodies is a promising approach for the prevention of HIV-1 infection. We used AAV vector intramuscularly to deliver anti-SIV monoclonal antibodies (mAbs) in IgG1 form to rhesus monkeys. Persisting levels of delivered mAb as high as 270 mug/ml were achieved. However, host antibody responses to the delivered antibody were observed in 9 of the 12 monkeys and these appeared to limit the concentration of delivered antibody that could be achieved. This is reflected in the wide range of delivered mAb concentrations that were achieved: 1-270 mug/ml. Following repeated, marginal dose, intravenous challenge with the difficult-to-neutralize SIVmac239, the six monkeys in the AAV-5L7 IgG1 mAb group showed clear protective effects despite the absence of detectable neutralizing activity against the challenge virus. The protective effects included: lowering of viral load at peak height; lowering of viral load at set point; delay in the time to peak viral load from the time of the infectious virus exposure. All of these effects were statistically significant. In addition, the monkey with the highest level of delivered 5L7 mAb completely resisted six successive SIVmac239 i.v. challenges, including a final challenge with a dose of 10 i.v. infectious units. Our results demonstrate the continued promise of this approach for the prevention of HIV-1 infection in people. However, the problem of anti-antibody responses will need to be understood and overcome for the promise of this approach to be effectively realized

Au nanoparticle-functionalised WO3 nanoneedles and their application in high sensitivity gas sensor devices

A new method of synthesising nanoparticle-functionalised nanostructured materials via Aerosol Assisted Chemical Vapour Deposition (AACVD) has been developed. Co-deposition of Au nanoparticles with WO3 nanoneedles has been used to deposit a sensing layer directly onto gas sensor substrates providing devices with a six-fold increase in response to low concentrations of a test analyte (ethanol)

Inorganically coated colloidal quantum dots in polar solvents using a microemulsion-assisted method

The dielectric nature of organic ligands capping semiconductor colloidal nanocrystals (NCs) makes them incompatible with optoelectronic applications. For this reason, these ligands are regularly substituted through ligand-exchange processes by shorter (even atomic) or inorganic ones. In this work, an alternative path is proposed to obtain inorganically coated NCs. Differently to regular ligand exchange processes, the method reported here produces core-shell NCs and the removal of the original organic shell in a single step. This procedure leads to the formation of connected NCs resembling 1D worm-like networks with improved optical properties and polar solubility, in comparison with the initial CdSe NCs. The nature of the inorganic shell has been elucidated by X-ray Absorption Near Edge Structure (XANES), Extended X-ray Absorption Fine Structure (EXAFS) and X-ray Photoelectron Spectroscopy (XPS). The 1D morphology along with the lack of long insulating organic ligands and the higher solubility in polar media turns these structures very attractive for their further integration into optoelectronic devices

Anti-drug Antibody Responses Impair Prophylaxis Mediated by AAV-Delivered HIV-1 Broadly Neutralizing Antibodies

Adeno-associated virus (AAV) delivery of potent and broadly neutralizing antibodies (bNAbs is a promising approach for the prevention of HIV-1 infection. The immunoglobulin G (IgG)1 subtype is usually selected for this application, because it efficiently mediates antibody effector functions and has a somewhat longer half-life. However, the use of IgG1-Fc has been associated with the generation of anti-drug antibodies (ADAs) that correlate with loss of antibody expression. In contrast, we have shown that expression of the antibody-like molecule eCD4-Ig bearing a rhesus IgG2-Fc domain showed reduced immunogenicity and completely protected rhesus macaques from simian-HIV (SHIV)-AD8 challenges. To directly compare the performance of the IgG1-Fc and the IgG2-Fc domains in a prophylactic setting, we compared AAV1 expression of rhesus IgG1 and IgG2 forms of four anti-HIV bNAbs: 3BNC117, NIH45-46, 10-1074, and PGT121. Interestingly, IgG2-isotyped bNAbs elicited significantly lower ADA than their IgG1 counterparts. We also observed significant protection from two SHIV-AD8 challenges in macaques expressing IgG2-isotyped bNAbs, but not from those expressing IgG1. Our data suggest that monoclonal antibodies isotyped with IgG2-Fc domains are less immunogenic than their IgG1 counterparts, and they highlight ADAs as a key barrier to the use of AAV1-expressed bNAbs

Journeys to tuberculosis treatment: a qualitative study of patients, families and communities in Jogjakarta, Indonesia

<p>Abstract</p> <p>Background</p> <p>Many tuberculosis (TB) patients in Indonesia are diagnosed late. We seek to document patient journeys toward TB diagnosis and treatment and factors that influence health care seeking behavior.</p> <p>Methods</p> <p>TB patients in Jogjakarta municipality (urban) and Kulon Progo district (rural) were recruited from health care facilities participating in the DOTS strategy and health care facilities not participating in the DOTS strategy, using purposive sampling methods. Data were collected through in-depth interviews with TB patients and members of their family and through Focus Group Discussions (FGD) with community members.</p> <p>Results</p> <p>In total, 67 TB patients and 22 family members were interviewed and 6 FGDs were performed. According to their care seeking behavior patients were categorized into National TB program's (NTP) dream cases (18%), 'slow-but-sure patients' (34%), 'shopaholics' (45%), and the NTP's nightmare case (3%). Care seeking behavior patterns did not seem to be influenced by gender, place of residence and educational level. Factors that influenced care seeking behavior include income and advice from household members or friends. Family members based their recommendation on previous experience and affordability. FGD results suggest that the majority of people in the urban area preferred the hospital or chest clinic for diagnosis and treatment of TB whereas in the rural area private practitioners were preferred. Knowledge about TB treatment being free of charge was better in the urban area. Many community members from the rural area doubted whether TB treatment would be available free of charge.</p> <p>Conclusion</p> <p>Most TB patients took over a month to reach a DOTS facility after symptoms appeared and had consulted a number of providers. Their income and advice from household members and friends were factors that influenced their care seeking behavior most.</p