Generation and interrogation of a pure nuclear spin state by parahydrogen-enhanced NMR spectroscopy: a defined initial state for quantum computation.

We describe a number of studies used to establish that parahydrogen can be used to prepare a two-spin system in a pure state, which is suitable for implementing NMR quantum computation. States are generated by pulsed and continuous-wave (CW) UV laser initiation of a chemical reaction between Ru(CO)(3)(L(2)) [where L(2) = dppe = 1,2-bis(diphenylphosphino)ethane or L(2) = dpae = 1,2-bis(diphenylarsino)ethane] with pure parahydrogen (generated at 18 K). This process forms Ru(CO)(2)(dppe)(H)(2) and Ru(CO)(2)(dpae)(H)(2) on a sub-microsecond time-scale. With the pulsed laser, the spin state of the hydride nuclei in Ru(CO)(2)(dppe)(H)(2) has a purity of 89.8 +/- 2.6% (from 12 measurements). To achieve comparable results by cooling would require a temperature of 6.6 mK, which is unmanageable in the liquid state, or an impractical magnetic field of 0.44 MT at room temperature. In the case of CW initiation, reduced state purities are observed due to natural signal relaxation even when a spin-lock is used to prevent dephasing. When Ru(CO)(3)(dpae) and pulsed laser excitation are utilized, the corresponding dihydride product spin state purity was determined as 106 +/- 4% of the theoretical maximum. In other words, the state prepared using Ru(CO)(3)(dpae) as the precursor is indistinguishable from a pure state

Dengue Viruses Are Enhanced by Distinct Populations of Serotype Cross-Reactive Antibodies in Human Immune Sera

<div><p>Dengue viruses (DENV) are mosquito-borne flaviviruses of global importance. DENV exist as four serotypes, DENV1-DENV4. Following a primary infection, individuals produce DENV-specific antibodies that bind only to the serotype of infection and other antibodies that cross-react with two or more serotypes. People exposed to a secondary DENV infection with another serotype are at greater risk of developing more severe forms of dengue disease. The increased risk of severe dengue in people experiencing repeat DENV infections appear to be due, at least in part, to the ability of pre-existing serotype cross-reactive antibodies to form virus-antibody complexes that can productively infect Fcγ receptor-bearing target cells. While the theory of antibody-dependent enhancement (ADE) is supported by several human and small animal model studies, the specific viral antigens and epitopes recognized by enhancing human antibodies after natural infections have not been fully defined. We used antibody-depletion techniques to remove DENV-specific antibody sub-populations from primary DENV-immune human sera. The effects of removing specific antibody populations on ADE were tested both <i>in vitro</i> using K562 cells and <i>in vivo</i> using the AG129 mouse model. Removal of serotype cross-reactive antibodies ablated enhancement of heterotypic virus infection <i>in vitro</i> and antibody-enhanced mortality <i>in vivo</i>. Further depletion studies using recombinant viral antigens showed that although the removal of DENV E-specific antibodies using recombinant E (rE) protein resulted in a partial reduction in DENV enhancement, there was a significant residual enhancement remaining. Competition ADE studies using prM-specific Fab fragments in human immune sera showed that both rE-specific and prM-specific antibodies in primary DENV-immune sera significantly contribute to enhancement of heterotypic DENV infection <i>in vitro</i>. Identification of the targets of DENV-enhancing antibodies should contribute to the development of safe, non-enhancing vaccines against dengue.</p></div

Performance of indirect immunofluorescence assay, immunochromatography assay and reverse transcription-polymerase chain reaction for detecting human respiratory syncytial virus in nasopharyngeal aspirate samples

Comparison of the use of indirect immunofluorescence assay (IFA), immunochromatography assay (ICA-BD) and reverse transcription-polymerase chain reaction (RT-PCR) for detecting human respiratory syncytial virus (HRSV) in 306 nasopharyngeal aspirates samples (NPA) was performed in order to assess their analytical performance. By comparing the results obtained using ICA-BD with those using IFA, we found relative indices of 85.0% for sensitivity and 91.2% for specificity, and the positive (PPV) and negative (NPV) predictive values were 85.0% and 91.2%, respectively. The relative indices for sensitivity and specificity as well as the PPV and NPV for RT-PCR were 98.0%, 89.0%, 84.0% and 99.0%, respectively, when compared to the results of IFA. In addition, comparison of the results of ICA-BD and those of RT-PCR yielded relative indices of 79.5% for sensitivity and 95.4% for specificity, as well as PPV and NPV of 92.9% and 86.0%, respectively. Although RT-PCR has shown the best performance, the substantial agreement between the ICA-BD and IFA results suggests that ICA-BD, also in addition to being a rapid and facile assay, could be suitable as an alternative diagnostic screening for HRSV infection in children