BackgroundPorcine circovirus type 2 (PCV2) is considered to be the primary causative agent of postweaning multisystemic wasting syndrome (PMWS), which has become a serious economic problem for the swine industry worldwide. The major genotypes, PCV2a and PCV2b, are highly prevalent in the pig population and are present worldwide. However, another newly emerging PCV2b genotype mutant, which has a mutation in its ORF2-encoded capsid protein, has been sporadically present in China, as well as in other countries. It is therefore important to determine the relative virulence of the newly emerging PCV2b genotype mutant, compared with the existing PCV2a and PCV2b genotypes, and to investigate whether the newly emerging mutant virus induces more severe illness.Methodology/Principal FindingsTwenty healthy, 30-day-old, commercial piglets served as controls or were challenged with PCV2a, PCV2b and the newly emerging mutant virus. A series of indexes representing different parameters were adopted to evaluate virulence, including clinical signs, serological detection, viral load and distribution, changes in immune cell subsets in the peripheral blood, and evaluation of pathological lesions. The newly emerging PCV2 mutant demonstrated more severe signs compatible with PMWS, characterized by wasting, coughing, dyspnea, diarrhea, rough hair-coat and depression. Moreover, the pathological lesions and viremia, as well as the viral loads in lymph nodes, tonsils and spleen, were significantly more severe (P<0.05) for piglets challenged with the newly emerging mutant compared with those in the groups challenged with PCV2a and PCV2b. In addition, a significantly lower average daily weight gain (P<0.05) was recorded in the group challenged with the newly emerging PCV2 mutant than in the groups challenged with the prevailing PCV2a and PCV2b.ConclusionsThis is believed to be the first report to confirm the enhanced virulence of the newly emerging PCV2 mutant in vivo.

Previous studies show that the metalnitrogen moieties with unsaturated nitrogen coordination numbers possess higher catalytic activities and the reported smallest nitrogen coordination number is confirmed to be ≈2 for Co-N 2 and Fe-N 2 moieties using extended X-ray absorption fine structure spectra analysis. [4][5][6] These results indeed give an in-depth insight at the atomic level into structural dependence of catalytic activity of metal nitride nanoparticles by closely correlating the average structural information with catalytic performances. However, the active metalnitrogen moieties confined at the surface layer of materials that host catalysis reactions still remain unclear.Building metal-nitrogen moieties with unsaturated nitrogen coordination numbers to enhance material's catalytic activity remains a fundamental challenge. The state-of-the-art pyrolysis technique of specific precursors is commonly used to construct metal-nitrogen moieties. However, the simultaneous presence of multiple metal species in most composite catalysts makes it highly complex to understand the nature of metal-nitrogen moieties. [7][8][9][10] The short length scale of nanostructured catalysts makes it extremely challenging to quantify metal-nitrogen moiety structure and distributions and to correspondingly elucidate the electronic structure features and unusual activity. The metal-nitrogen moieties are indeed a kind of active clusters at atomic level, which are strictly confined at lattice in local structures in crystalline composites. The polycrystalline or amorphous states of composites make it highly uncertain to construct resolved metal-nitrogen moieties and to accordingly expose these active centers on material's surfaces to host catalysis reactions. Another consideration should be given to the resolved structural feature and chemical composition of moieties that tailor electronic structures to facilitate catalysis functionalities.Single crystals with porosity, combining the advantages of long-range structural coherence of bulk crystals and large surface areas of porous materials, could provide opportunities to host the metal-nitrogen moieties with unsaturated nitrogen coordination on surface. The long-range structural coherence in single crystals offers the possibility to stabilize the metalnitrogen moieties in lattice of local structures on crystalline surfaces especially on the condition that the surface moieties have similar chemical compositions to bulk crystals. Porous Altering a material's catalytic properties would require identifying structural features that deliver electrochemically active surfaces. Single-crystalline porous materials, combining the advantages of long-range ordering of bulk crystals and large surface areas of porous materials, would create sufficient active surfaces by stabilizing 2D active moieties confined in lattice and may provide an alternative way to create high-energy surfaces for electrocatalysis that are kinetically trapped. Here, a radical concept of building active metalnitrogen moieties ...

A TiO2/Fe2O3 heterojunction with an internal electric field was constructed for enhancing photocatalytic reduction efficiency of Cr(vi).