Jiayu Wan

Isolation and characterisation of a new antimicrobial peptide from the skin of Xenopus laevis

A new antimicrobial peptide (AMP) named PGLa-H has been isolated from the skin of the African clawed frog (Xenopus laevis) using gel filtration and reverse-phase high-performance liquid chromatography (RP-HPLC). Its amino acid sequence was determined as KIAKVALKAL by Edman degradation, with a molecular weight of 1053.727 Da as analysed by matrix-assisted laser desorption/ionisation time-of-flight mass spectrometry (MALDI-TOF/TOF-MS). No similar AMP was found by BLAST search. Purified PGLa-H demonstrated antimicrobial ability against the reference bacteria Escherichia coli ATCC 25922 [minimum inhibitory concentration (MIC)=23.6 μg/mL], Staphylococcus aureus ATCC 25923 (MIC=8.7 μg/mL) and Bacillus subtilis (MIC=14.4μg/mL) and was active against multidrug-resistant meticillin-resistant S. aureus (MRSA) (MIC=67.8 μg/mL). The antimicrobial mechanism for this new peptide was further investigated by transmission electron microscopy. PGLa-H killed cells by destroying the cell membrane.

Genomic analysis of Newcastle disease virus strain NA-1 isolated from geese in China

Newcastle disease virus (NDV) has been thought to infect only domestic avian species, with waterfowl such as geese either not being infected, even by virulent strains, or developing only in apparent infection. In 1997, a new infectious disease producing high morbidity and mortality among geese broke out in many provinces of China, which was caused by a serotype I avian paramyxovirus (APMV-1)—NDV. To investigate how NDV spreads between chickens and geese, the complete genome of one NDV strain isolated from a goose was cloned and analyzed. The results indicate that there is conservation in NDV structural genetic evolution but that there are also considerable differences between goose and chicken NDV strains. Separate patterns of NDV evolution exist among wild bird species. Meanwhile, there is evidence indicating that the goose NDV may have evolved from chicken NDV strain Herts/33. In addition, the possibility was investigated that this new strain of NDV may bind to different sialic acid receptor binding sites than the normal NDV strains that have been investigated so far. This might provide clues to the evolution of the goose NDV.

Morphological changes of ricin toxin-induced apoptosis in human cervical cancer cells

The morphological changes of ricin-induced apoptosis in a human cervical cancer cell line were studied. To shed light on the mechanism of action of ricin toxin (RT) at the cellular level, we examined cell growth, apoptosis, changes of mitochondrial membrane potential (MMP) and cytochrome C translocation in HeLa cells by exposing these cells to RT for indicated times. The effect of RT on cell proliferation was measured by 3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium (MTS), inner salt; MTS assay and apoptosis were measured using flow cytometry, fluorescence microscopy and electron microscopy. Changes in MMP were monitored using flow cytometry. Western blot analysis was used to evaluate the release of mitochondrial cytochrome C. RT noticeably inhibited the proliferation of HeLa cells, and the half maximal inhibitory concentration dose was about 100 ng/ml. HeLa cells treated with RT showed typical characteristics of apoptosis rather than necrosis, including phosphatidylserine exposed from the inner to the outer leaflet of the plasma membrane, abnormal cell morphology, chromatin condensation and nuclear fragmentation. In contrast, during the process of cellular apoptosis, the messenger RNA (mRNA) and protein expression of cytochrome C in treated and untreated Hela cells were not significantly changed (data not shown). However, when cells were treated with RT, the massive translocation of cytochrome C to the nucleus was evident. Our results indicate that RT-induced HeLa cell apoptosis, especially for cytochrome C translocation, may play an important role in apoptosis induced by RT.

Overexpression of Shadoo protein in transgenic mice does not impact the pathogenesis of scrapie.

Shadoo is a glycoprotein expressed in the adult brain that is an interacting protein of prion protein; however, its function remains to be determined. To elucidate its role in prion pathogenesis, we generated transgenic mice overexpressing wild-type (wt) Shadoo driven by the murine PrP promoter. Expression of the murine Sprn transgene significantly increased brain Shadoo protein levels in all three mouse lines generated. Following infection with mouse-adapted scrapie strain 22L, all transgenic mice tested exhibited characteristics of scrapie disease. Importantly, there was no correlation between the expression level or incubation time of Shadoo with disease phenotype. We therefore conclude that Shadoo has little or no influence on the outcome of transmissible spongiform encephalopathy (TSE) disease in transgenic mice.

Detection of ricin intoxication in mice using serum peptide profiling by MALDI-TOF/MS.

Ricin toxin has been regarded as one of the most potent poisons in the plant kingdom, and there is no effective therapeutic countermeasure or licensed vaccine against it. Consequently, early detection of ricin intoxication is necessary. In this study, we took mice as test subjects, and used the technique of Matrix-assisted laser desorption/ionization time of flight mass spectrometry (MALDI-TOF/MS) and ClinProt™ microparticle beads to set up an effective detection model with an accuracy of almost 100%. Eighty-two peaks in the mass range 1000–10,000 m/z were detected by ClinProTools software, and five different peaks with m/z of 4982.49, 1333.25, 1537.86, 4285.05 and 2738.88 had the greatest contribution to the accuracy and sensitivity of this model. They may therefore provide biomarkers for ricin intoxication.

Analysis of intestinal injuries induced by ricin in vitro using SPR technology and MS identification.

The present study found that ricin toxicity did not only manifest itself as inhibition of protein synthesis, but also induced apoptosis of immune cells and played an extremely significant role in intestinal injury. In this report, we describe a novel method to estimate binding events occurring on intestinal brush border membranes (BBM) based on SPR technology in an attempt to mimic the real intestinal surface capable of interacting physically and/or actively with certain biological molecules. Combined with HPCE-ESI-MS indentification, we obtained 28 kinds of proteins in BBM that interacted with ricin.

Immunomodulatory activity of recombinant Ricin toxin binding Subunit B (RTB).

Ricin toxin binding subunit B (RTB) is one of the subunits of the ricin protein. RTB has been used as adjuvant, but little is known about its mechanism. In this study, we found that RTB increased not only nitric oxide (NO) release, but also tumor necrosis factor (TNF)-α and interleukin (IL)-6 production in mouse macrophage cell line RAW264.7 cells. They subsequently exhibited enhanced ConA-induced T-cell and LPS-induced B-cell proliferative responses. We also examined the cytokines that were produced from splenocytes following in vitro RTB administration. Increased levels of IL-2, interferon (IFN)-γ and TNF-α were observed, while IL-4 and IL-5 were unaffected. These results demonstrate that recombinant RTB can act on the immune system and activate T-cells by introducing a Th1 immune response. Th1 cells might be the primary cellular target affected by RTB. Our results suggest that the recombinant RTB can promote the activation of macrophages and has a beneficial effect on immunomodulatory activity.

Polymorphism of prion protein gene in Arctic fox (Vulpes lagopus).

Prion diseases are fatal neurodegenerative disorders of humans and certain other mammals. Prion protein gene (Prnp) is associated with susceptibility and species barrier to prion diseases. No natural and experimental prion diseases have been documented to date in Arctic fox. In the present study, coding region of Prnp from 135 Arctic foxes were cloned and screened for polymorphisms. Our results indicated that the Arctic fox Prnp open reading frame (ORF) contains 771 nucleotides encoding 257 amino acids. Four single nucleotide polymorphisms (SNPs) (G312C, A337G, C541T, and A723G) were identified. SNPs G312C and A723G produced silent mutations, but SNPs A337G and C541T resulted in a M–V change at codon 113 and R–C at codon 181, respectively. The Arctic fox Prnp amino acid sequence was similar to that of the dog (XM 542906). In short, this study provides preliminary information about genotypes of Prnp in Arctic fox.

Proteomic study of differential protein expression in mouse lung tissues after aerosolized ricin poisoning.

Ricin is one of the most poisonous natural toxins from plants and is classified as a Class B biological threat pathogen by the Centers for Disease Control and Prevention (CDC) of U.S.A. Ricin exposure can occur through oral or aerosol routes. Ricin poisoning has a rapid onset and a short incubation period. There is no effective treatment for ricin poisoning. In this study, an aerosolized ricin-exposed mouse model was developed and the pathology was investigated. The protein expression profile in the ricin-poisoned mouse lung tissue was analyzed using proteomic techniques to determine the proteins that were closely related to the toxicity of ricin. 2D gel electrophoresis, mass spectrometry and subsequent biological functional analysis revealed that six proteins including Apoa1 apolipoprotein, Ywhaz 14-3-3 protein, Prdx6 Uncharacterized Protein, Selenium-binding protein 1, HMGB1, and DPYL-2, were highly related to ricin poisoning.

Unchanged survival rates of Shadoo knockout mice after infection with mouse-adapted scrapie

Previous studies have demonstrated that Shadoo (Sho), a GPI-linked glycoprotein encoded by the Sprn gene with a membrane localization similar to PrPC, is reduced in the brains of rodents with terminal prion disease. To determine the functional significance of Sho in prion disease pathogenesis, Sho-deficient mice were generated by gene targeting. Sho knockout and control wild-type (WT) mice were infected with themouse-adapted scrapie strains 22L or RML. No significant differences in survival, the incubation period of prion disease or other disease features were observed between Sho mutant and WT mice. In this model of prion disease, Sho removal had no effect on disease pathogenesis.