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Avian hepatitis E virus (avian HEV) increases poultry mortality and decreases egg production, leading to huge economic losses worldwide. However, there is no effective serological test for avian HEV. Researchers previously created a testing platform using the nanobody (Nb)-horseradish peroxidase (HRP) fusion protein as an ultrasensitive probe to develop competitive ELISA (cELISA) to detect antibodies against different animal viruses. In this study, a rapid and reliable cELISA was developed to test for antibodies against avian HEV using the same platform. Six anti-avian HEV capsid protein nanobodies were selected from an immunized Bactrian camel using phage display technology. The avian HEV-Nb49-HRP fusion protein was expressed and used as a probe for developing a cELISA assay to test for avian HEV antibodies. The cut-off value of the developed cELISA was 22.0%. There was no cross-reaction with other anti-avian virus antibodies, suggesting that the cELISA had good specificity. The coefficients of variation were 0.91% to 4.21% (intra-assay) and 1.52% to 6.35% (inter-assay). Both cELISA and indirect ELISA showed a consistency of 86.7% (kappa = 0.738) for clinical chicken serum samples, and coincidence between cELISA and Western blot was 96.0% (kappa = 0.919). The epitope recognized by Nb49 was located in aa 593-604 of the avian HEV capsid protein, and the peptide (TFPS) in aa 601-604 was essential for binding. The novel cELISA is a saving cost, rapid, useful, and reliable assay for the serological investigation of avian HEV. More importantly, the peptide TFPS may be crucial to immunodominant antigen composition and protection. [ABSTRACT FROM AUTHOR]

Purpose: The particle-size distribution of runoff sediment is important in understanding, characterizing and modeling the transport behavior of sediment and sediment-associated chemicals. The objective of this study was to investigate the particle-size distribution of sediments eroded from three soils in China under natural rainfall. Materials and methods: Each of the three soils was packed to a depth of 30 cm in a 20 × 2.1 m runoff plot. Sediments yielded in nine natural rainfall events were analyzed for their particle-size distribution prior to and following dispersion. Results and discussion: The sediment size measured in the undispersed condition was always larger than the one determined after chemical dispersion, indicating that part of the sediment was eroded in aggregated form. The degree of sediment aggregation depended on the clay content and the organic matter content of the sources. The mean sediment size quantified by mean weight diameter linearly increased with sediment yield for the two soils with relatively high clay content. The rate of increase was greater in the undispersed condition than that in the dispersed condition for these two soils. Comparing sediments to the corresponding source soil, the results of mean weight diameter and enrichment ratio both revealed that aggregate-size distribution was more sensitive to soil erosion than the primary particle-size distribution. Small aggregates, rather than the primary particles, were selectively eroded in the rainfall events. Conclusions: These findings support the use of both dispersed and undispersed sediment-size distributions for the characterization of sediment transport and the associated sediment-bound nutrients and contaminants. [ABSTRACT FROM AUTHOR]

Background: Avian hepatitis E virus (HEV) is the main causative agent of big liver and spleen disease, as well as hepatitis-splenomegaly syndrome in chickens. To date, conventional reverse transcriptase polymerase chain reaction (RT-PCR) and nested RT-PCR methods have been used for the diagnosis of avian HEV infection in chickens. However, these assays are time consuming, inconvenient, and cannot detect the virus quantitatively. In this study, a rapid and sensitive SYBR Green real-time RT-PCR assay was developed to detect avian HEV RNA quantitatively in serum, liver, spleen, and fecal samples from chickens. Results: Based on the sequence of the most conserved HEV gene, ORF3, the primers for the assay were designed, and the standard plasmid was constructed. The detection limit of the assay was shown to be 10 copies/µl of standard plasmid/reaction, with a corresponding cycle-threshold value of 29.3. The standard curve exhibited a dynamic linear range across at least 7 log units of DNA copy number. The specificity and reproducibility of this assay was high, showing that the assay detected avian HEV RNA specifically and with little variability. Compared to conventional RT-PCR, the current assay is more sensitive for detecting avian HEV in serum, liver, spleen, and fecal samples from chickens. Conclusions: A rapid, specific, and reproducible SYBR Green real-time RT-PCR assay was developed for the diagnosis of avian HEV infection in chickens. This assay can accurately detect avian HEV RNA in serum, liver, spleen, and fecal samples with more sensitivity than conventional RT-PCR. [ABSTRACT FROM AUTHOR]

The topography (slope gradient and slope length) has an important effect on soil erosion by water. Slope gradient and slope length factor are the parameters of the universal soil loss equation that is commonly used to predict soil erosion. These factors are usually extracted from the digital elevation model (DEM). Thus the DEM grid size will influence topographic factors and therefore soil loss calculation. The purpose of this study was to investigate the effect of DEM grid size on the topographic factors and therefore soil loss prediction on a typical watershed in northeast of China. The site for the case study was Dontaigou watershed which is located at Huairou district, Beijing, China. Contour lines of 2 m interval digitized from 1:2,000 scale of topographic maps were used to generate DEM with grid size of 2 m. The DEMs with grid sizes of 3-30 m, at 1 m intervals, were created using the nearest neighbor resampling method. In total, 29 DEMs with different grid sizes were obtained. Four different scenarios of the channel initiation threshold were used to extract the drainage channel and let the slope length cutoff. Chinese soil loss equation was used to predict the soil loss. The results show that DEM grid size had different effects on the topographic factor. The average calculated slope steepness factor decreased with the increase of the DEM grid size in a linear decay function. The average slope length factor increased with DEM grid size when the drainage channel was not considered. It slightly decreased with DEM grid size and then increased when the drainage channel suitable for DEM grid size was used. However, comparing different grid sizes, the LS factor and the soil loss prediction of DEM grid size less than or equal to 10 m were close to those of 2 m DEM. The channel initiation threshold had effects on the extraction of slope length and then slope length factor. We found that the effect of DEM grid size on predicting soil loss depends on selection of suitable channel initiation threshold. [ABSTRACT FROM AUTHOR]

Highlights: [•] We develop a bELISA for detection of antibodies against avian hepatitis E virus. [•] Cut-off value of bELISA is 20.7%. [•] The bELISA had a sensitivity of 98.3%. [•] The compliance rates of the bELISA with iELISA and Western blot were 83.7% and 93.3%, respectively. [•] The bELISA shows high reproducibility compared with iELISA and Western blot. [ABSTRACT FROM AUTHOR]