In situ Hg2+ improved the peroxidase-like activity and triggered "ON" the oxidase-like activity of yolk-shell Co3S4 microspheres for the detection of Hg2.

Exploring highly active nanozymes is an important task to realize the real-time detection of some heavy metal ions in water. In this work, yolk-shell Co3S4 microspheres have been verified to possess excellent peroxidase-like activity, which can be further improved by adding Hg2+. Very interestingly, Hg2+ can trigger "ON" the oxidase-like activity of Co3S4 microspheres. The dual peroxidase-/oxidase-like activity of the yolk-shell Co3S4 microspheres is evaluated by using the chromogenic substrate 3,3',5,5'-tetramethylbenzidine (TMB). Furthermore, comprehensive studies verify that the enhanced peroxidase-like activity, together with the "ON" oxidase-like activity of the yolk-shell Co3S4 microspheres, is attributed to the in situ generation of HgS on the surface of Co3S4 microspheres and then the release of more active sites. Importantly, the in situ generated HgS on the surface of Co3S4 microspheres can form a heterojunction, which also accelerates the catalytic process. During the catalytic reaction, some active species (O2- and h+) can be detected by ESR. Thus, a colorimetric sensing platform based on Hg2+-triggered signal amplification has been successfully constructed, which can be validated by the detection of Hg2+ residue in environmental water.

Solar X-ray and EUV imager on board the FY-3E satellite.

The solar X-ray and Extreme Ultraviolet Imager (X-EUVI), developed by the Changchun Institute of Optics, Fine Mechanics and Physics, Chinese Academy of Sciences (CIOMP), is the first space-based solar X-ray and Extreme ultraviolet (EUV) imager of China loaded on the Fengyun-3E (FY-3E) satellite supported by the China Meteorological Administration (CMA) for solar observation. Since started work on July 11, 2021, X-EUVI has obtained many solar images. The instrument employs an innovative dual-band design to monitor a much larger temperature range on the Sun, which covers 0.6-8.0 nm in the X-ray region with six channels and 19.5 nm in the EUV region. X-EUVI has a field of view of 42', an angular resolution of 2.5″ per pixel in the EUV band and an angular resolution of 4.1″ per pixel in the X-ray band. The instrument also includes an X-ray and EUV irradiance sensor (X-EUVS) with the same bands as its imaging optics, which measures the solar irradiance and regularly calibrates the solar images. The radiometric calibration of X-EUVS on the ground has been completed, with a calibration accuracy of 12%. X-EUVI is loaded on the FY-3E satellite and rotates relative to the Sun at a uniform rate. Flat-field calibration is conducted by utilizing successive rotation solar images. The agreement between preliminarily processed X-EUVI images and SDO/AIA and Hinode/XRT images indicates that X-EUVI and the data processing algorithm operate properly and that the data from X-EUVI can be applied to the space weather forecast system of CMA and scientific investigations on solar activity.

FY-3D MERSI On-Orbit Radiometric Calibration from the Lunar View.

Limited by the on-orbital calibration capability, scaling the measured radiance in accuracy and stability is challenging for the Earth observation satellites in the reflective solar bands (RSBs). Although the lunar calibration is a well-developed technique in the RSBs, limited work has been done for Chinese Earth observation satellites. To improve the on-orbital calibration performance, the advanced MEdium Resolution Spectral Imager (MERSI II), which is the primary payload of the fourth satellite of the Fengyun 3 Series (FY-3D), expands the space view angle of the imager in order to capture better lunar images. In this study, we propose an absolute radiometric calibration method based on the FY-3D/MERSI lunar observation data. A lunar irradiance model named ROLO/GIRO has been used together with the necessary data procedures, including dark current count estimation, single pixel irradiance calculation, and full disk lunar irradiance calculation. The calibration coefficients obtained by the lunar calibration are compared with the pre-launch laboratory calibration. The results show that the deviations between the two calibration procedures are in a reasonable range in general. However, a relatively high non-linear response was found in the low energy incidence for some detectors, which leads to the large deviation in the corresponding bands. This study explored an ideal and independent method to validate MERSI on-orbit radiometric performance. The lunar calibration practiced for MERSI also gave a valuable example that can be recommended to the other Chinese Earth observation satellites.

Wide-field auroral imager onboard the Fengyun satellite.

The newly launched Fengyun-3D (FY-3D) satellite carried a wide-field auroral imager (WAI) that was developed by Changchun Institute of Optics, Fine Mechanics and Physics, Chinese Academy of Sciences (CIOMP), which will provide a large field of view (FOV), high spatial resolution, and broadband ultraviolet images of the aurora and the ionosphere by imaging the N2 LBH bands of emissions. The WAI consists of two identical cameras, each with an FOV of 68° in the along-track direction and 10° in the cross-track direction. The two cameras are tilted relative to each other to cover a fan-shaped field of size 130° × 10°. Each camera consists of an unobstructed four-mirror anastigmatic optical system, a BaF2 filter, and a photon-counting imaging detector. The spatial resolution of WAI is ~10 km at the nadir point at a reference height of 110 km above the Earth's surface. The sensitivity is >0.01 counts s-1 Rayleigh-1 pixel-1 (140-180 nm) for both cameras, which is sufficient for mapping the boundaries and the fine structures of the auroral oval during storms/substorms. Based on the tests and calibrations that were conducted prior to launch, the data processing algorithm includes photon signal decoding, geometric distortion correction, photometric correction, flat-field correction, line-of-sight projection and correction, and normalization between the two cameras. Preliminarily processed images are compared with DMSP SSUSI images. The agreement between the images that were captured by two instruments demonstrates that the WAI and the data processing algorithm operate normally and can provide high-quality scientific data for future studies on auroral dynamics.

The long-term immunogenicity of an inactivated split-virion 2009 pandemic influenza A H1N1 vaccine: Randomized, observer-masked, single-center clinical study.

The aim of this study is to investigate the long-term immunogenicity of inactivated split-virion 2009 pandemic influenza A H1N1 vaccine after a single immunization. We recruited 480 adults, aged 18-60 years, for a placebo-controlled, observer-masked, single-center clinical study. We randomly assigned subjects into four groups: 15 µg, 30 µg and 45 µg of hemagglutinin (HA) dosage groups, and a placebo control group. Finally, 259 subjects completed the entire study. The rates of seroconversion and seroprotection and the geometric mean increase (GMI) fulfilled the criteria of the European Medicines Agency (EMEA) for influenza vaccine for 180 days after vaccination in all three dosage groups. However, the seroprotection rates of all dosage groups were below 70% at day 360 post vaccination, while the seroconversion rates and the GMI continued to meet the licensure criteria at this time point. In conclusion, a single dose of 15 µg HA vaccine could induce a protective immune response persisting for at least six months in adults. This study could be beneficial for the future development of influenza vaccines conferring long-term immunity.

Protection against multiple influenza A virus subtypes by intranasal administration of recombinant nucleoprotein.

Vaccination is a cost-effective way to control the influenza epidemic. Vaccines based on highly conserved antigens can provide protection against different influenza A strains and subtypes. In this study, the recombinant nucleoprotein (rNP) of the A/PR/8/34 (H1N1) influenza virus strain was effectively expressed using a prokaryotic expression system and then purified with a nickel-charged Sepharose affinity column as a candidate component for an influenza vaccine. The rNP was administered intranasally three times at 3-week intervals to female BALB/c mice in combination with an adjuvant (cholera toxin B subunit containing 0.2% of the whole toxin). Twenty-one days after the last immunization, the mice were challenged with homologous or heterologous influenza viruses at a lethal dose. The results showed that intranasal immunization of 10 µg rNP with adjuvant completely protected the immunized mice against the homologous influenza virus, and immunization with 100 µg rNP in combination with adjuvant provided good cross-protection against heterologous H5N1 and H9N2 avian influenza viruses. The results indicate that such a vaccine administered intranasally can induce mucosal and cell-mediated immunity, thus having the potential to control epidemics caused by new emerging influenza viruses.

A live bivalent influenza vaccine based on a H9N2 virus strain.

The purpose of this study was to construct an H9N2 virus-based bivalent live vaccine expressing the protective antigen of a different subtype of influenza virus. Reverse genetics was used to generate an influenza virus containing nine gene segments derived from the A/Chicken/Jiangsu/11/2002 (H9N2) strain, including independent M1 and M2 matrix gene segments. A recombinant virus expressing the H1N1 HA1 hemagglutinin protein was produced on this framework by substituting the extracellular domain of the H9N2 M2 gene with the H1N1 HA1 fragment from A/PR/8/34 (PR8, H1N1). The resulting hybrid virus H9N2-PR8/HA1 was genetically stable and of low pathogenicity. Intra-nasal immunization of BALB/c mice with H9N2-PR8/HA1 virus induced both anti-H9N2 virus and anti-PR8 HA antibodies and conferred protection to mice against lethal challenge (40x LD(50)) with either H1N1 or H9N2 viruses. This study provides a new influenza H9N2 virus model for the expression and/or delivery of foreign antigens.

Characterization of highly pathogenic H5N1 avian influenza viruses isolated from poultry markets in central China.

H5N1 highly pathogenic avian influenza (HPAI) viruses have seriously affected the Asian poultry industry since their recurrence in 2003. While surveillance in southern China has revealed that H5N1 viruses underwent extensive genetic reassortment to generate many different viral genotype viruses, little is known concerning the genotypes of H5N1 virus that circulated in central China in recent years. In this study, 16 H5N1 influenza viruses were isolated from the poultry market in central China during late 2006 and early 2007, and the genotypes and pathogenicity of the viruses were identified and characterized. All eight segments of each virus were sequenced, and phylogenetic analysis showed that the two surface glycoprotein genes, hemagglutinin (HA) and neuraminidase (NA), of all the viruses were closely related to the H5N1 viruses isolated in poultry in southern China since 2006. Phylogenetic analysis of the internal protein genes indicated that four viral genotypes circulated in poultry markets in central China. The virulence of 7 of the 16 isolates was tested in chickens and mice. The results showed that the 7 isolates were highly pathogenic for SPF chickens, and had a varied virulence in mice. Our results indicate that the H5N1 viruses circulated in central China have diversified characteristics of genotype and virulence.

A single immunization with HA DNA vaccine by electroporation induces early protection against H5N1 avian influenza virus challenge in mice.

BACKGROUND: Developing vaccines for the prevention of human infection by H5N1 influenza viruses is an urgent task. DNA vaccines are a novel alternative to conventional vaccines and should contribute to the prophylaxis of emerging H5N1 virus. In this study, we assessed whether a single immunization with plasmid DNA expressing H5N1 hemagglutinin (HA) could provide early protection against lethal challenge in a mouse model. METHODS: Mice were immunized once with HA DNA at 3, 5, 7 days before a lethal challenge. The survival rate, virus titer in the lungs and change of body weight were assayed to evaluate the protective abilities of the vaccine. To test the humoral immune response induced by HA DNA, serum samples were collected through the eye canthus of mice on various days after immunization and examined for specific antibodies by ELISA and an HI assay. Splenocytes were isolated after the immunization to determine the antigen-specific T-cell response by the ELISPOT assay. RESULTS: Challenge experiments revealed that a single immunization of H5N1 virus HA DNA is effective in early protection against lethal homologous virus. Immunological analysis showed that an antigen-specific antibody and T-cell response could be elicited in mice shortly after the immunization. The protective abilities were correlated with the amount of injected DNA and the length of time after vaccination. CONCLUSION: A single immunization of 100 mug H5 HA DNA vaccine combined with electroporation was able to provide early protection in mice against homologous virus infection.

Characterization of H5N1 influenza A viruses isolated from domestic green-winged teal.

Two avian influenza virus strains, A/domestic green-winged teal/Hunan/67/2005 (H5N1) (D-GWT/67) and A/domestic green-winged teal/Hunan/79/2005 (H5N1) (D-GWT/79), were isolated from healthy domestic green-winged teals (Anas crecca) in Hunan Province, South China. Genomic analysis showed that both isolates were reassortants. The hemagglutinin (HA) genes of the two isolates were closely related to that of an H5N1 strain isolated from tree sparrow (A/tree sparrow/Henan/1/04). The neuraminidase (NA) genes and the internal protein genes of both isolates were closely related to those from A/chicken/Shantou/4231/2003-like (H5N1) viruses, with exception of the matrix (M) gene of D-GWT/79, which was closely related to that of the H7N3 strain A/mallard/Netherlands/12/2000 isolated from wild mallard duck. The virulence of the two isolates was examined in chickens, ducks, and mice. Both strains were found to be highly pathogenic in chickens and ducks, but showed low pathogenicity in mice. These findings contribute to the realization that domestic green-winged teals carrying the H5N1 virus may play an important role in transmitting the virus among birds.

Comparing the ability of a series of viral protein-expressing plasmid DNAs to protect against H5N1 influenza virus.

Avian influenza has been regarded as a human health threat. A major measure to prevent its outbreak is vaccination. In this study, a series of expression plasmids carrying the hemagglutinin (HA), neuraminidase (NA), nucleoprotein (NP), matrix protein 1 (M1), and matrix protein 2 (M2) genes, respectively, of the avian influenza virus (AIV) A/Chicken/Henan/12/2004(H5N1) strain were constructed. These plasmids were administered to mice by electroporation (50 mug for each per administration, 1-5 times, at an interval of 2 weeks), and the mice were challenged with the homologous virus later. The mice immunized with HA plasmid once and the NA plasmid twice survived 100%, and those with NP plasmid showed 60-80% survival rate with at least three immunizations. The mice immunized with M1 plasmid survived 25% with five immunizations, while M2 plasmid had no protection even with five immunizations. The mixture of M1 and NP plasmids protected 95% of the mice against the homologous virus, and 80% of the mice against a challenge with heterologous H1N1 (PR8) virus. Moreover, the homologous protection lasted at least 6 months. Our data provided a basis for selecting multiple-component AIV vaccines.

Electroporation at low voltages enables DNA vaccine to provide protection against a lethal H5N1 avian influenza virus challenge in mice.

OBJECTIVE: Electroporation has been proved to enhance the efficacy of intramuscular delivery of DNA. However, the process of electroporation causes pain and discomfort to the patient receiving the treatment. Higher the electroporation voltages inflict greater pain, and this limits the circumstances in which the technique can be used clinically. The voltages generally used for electroporation in animals range from 100 to 1,200 V/cm. We studied the effect of DNA vaccination when electroporation was performed at lower voltages. METHODS: BALB/c mice were immunized twice by electroporation, at a 3-week interval, with H5N1 virus hemagglutinin (HA) DNA. One week after the booster had been given, the mice were challenged with a lethal dose of mouse-adapted H5N1 virus. The immune effects of HA DNA were evaluated by the survival rate, lung virus titer, bodyweight change and antibody titer of the mice. RESULTS: The higher the voltage used, the more able were the mice to survive the challenge. However, a significant degree of protection could also be achieved with a voltage as low as 5 V. When electroporation was performed at a voltage of 10 V, an immunization amount of 5 microg is enough for HA DNA to provide effective protection. CONCLUSION: Low-voltage electroporation can induce immunity and protect mice effectively. There is, therefore, the potential to reduce the voltages currently used for DNA electroporation.