The glycosyltransferase ST3GAL2 modulates virus proliferation and the inflammation response in porcine reproductive and respiratory syndrome virus infection.

ß-galactoside α-2,3-sialyltransferase 2 (ST3GAL2) is a member of the sialyltransferase family that mediates terminal modification of glycoproteins and glycolipids. ST3GAL2 has been found to play a role in obesity, aging, and malignant diseases. In this study, we cloned porcine ST3GAL2 (pST3GAL2) from porcine alveolar macrophages (PAMs), and its role in porcine reproductive and respiratory syndrome virus (PRRSV) infection was investigated by transcriptome analysis. pST3GAL2 was found to be located in the Golgi apparatus, and it was expressed at high levels in PRRSV-infected PAMs. Overexpression of pST3GAL2 resulted in a slight increase in PRRSV proliferation, and the interaction between pST3GAL2 and GP2a of PRRSV was detected by coimmunoprecipitation and confocal microscopy. The expression of pro-inflammatory cytokines (IFN-ß, IL-2, IL-6, IL-18, IL-1ß and TNF-α) was significantly inhibited in pST3GAL2-overexpressing, PRRSV-infected cells and upregulated in PRRSV-infected pST3GAL2-knockout cells, while the pattern of expression of anti-inflammatory cytokines (IL-4 and IL-10) was diametrically opposite. Our results demonstrate that the regulation of pST3GAL2 plays an important role in PRRSV proliferation and functional alterations in virus-infected cells. These results contribute to our understanding of the role of ß-galactoside α-2,3-sialyltransferase 2 in antiviral immunity.

RBM39 Alters Phosphorylation of c-Jun and Binds to Viral RNA to Promote PRRSV Proliferation.

As transcriptional co-activator of AP-1/Jun, estrogen receptors and NF-κB, nuclear protein RBM39 also involves precursor mRNA (pre-mRNA) splicing. Porcine reproductive and respiratory syndrome virus (PRRSV) causes sow reproductive disorders and piglet respiratory diseases, which resulted in serious economic losses worldwide. In this study, the up-regulated expression of RBM39 and down-regulated of inflammatory cytokines (IFN-ß, TNFα, NF-κB, IL-1ß, IL-6) were determined in PRRSV-infected 3D4/21 cells, and accompanied with the PRRSV proliferation. The roles of RBM39 altering phosphorylation of c-Jun to inhibit the AP-1 pathway to promote PRRSV proliferation were further verified. In addition, the nucleocytoplasmic translocation of RBM39 and c-Jun from the nucleus to cytoplasm was enhanced in PRRSV-infected cells. The three RRM domain of RBM39 are crucial to support the proliferation of PRRSV. Several PRRSV RNA (nsp4, nsp5, nsp7, nsp10-12, M and N) binding with RBM39 were determined, which may also contribute to the PRRSV proliferation. Our results revealed a complex mechanism of RBM39 by altering c-Jun phosphorylation and nucleocytoplasmic translocation, and regulating binding of RBM39 with viral RNA to prompt PRRSV proliferation. The results provide new viewpoints to understand the immune escape mechanism of PRRSV infection.

Development of IMBs-qPCR detection method for Yersinia enterocolitica based on the foxA gene.

Yersinia enterocolitica is an important zoonotic pathogen, which seriously endangers food-safety risk. In this study, the recombinant outer membrane protein OmpF and its antibody were prepared and coupled with immunomagnetic beads (IMBs) to capture Y. enterocolitica in food samples, combining the quantitative PCR detection with primers of virulence factor gene foxA for Yersinia enterocolitica contamination. The results showed that the capture efficiency of approximately 80% using anti-OmpF antibody-immunomagnetic beads and linearly dependent capture under 101-105 CFU/mL Y. enterocolitica compared with less than 10% capture of other bacteria. The detection limit of 64 CFU/mL was obtained based on foxA gene PCR detection combined with capture of the anti-OmpF antibody-immunomagnetic beads to detect Yersinia enterocolitica in artificially contaminated milk and pork samples. Compared to the culture method, the developed IMBs-qPCR method has higher consistency, was less time consuming, which taken together provides an effective alternative method for rapid detection of Y. enterocolitica in food.

Visual Detection of Clostridium perfringens Alpha Toxin by Combining Nanometer Microspheres with Smart Phones.

Clostridium perfringens α toxin (CPA) is an important virulence factor that causes livestock hemorrhagic enteritis and food poisoning by contaminated meat products. In this study, the nano-silica microspheres combined with smartphone image processing technology was developed to realize real-time CPA detection. First, the N-terminal and C-terminal domain of the CPA toxin (CPAC3 and CPAN) and their anti-sera were prepared. The silica microspheres coupled with the antibody of CPAC3 was prepared to capture the toxin that existed in the detection sample and the fluorescent-labeled antibody of CPAN was incubated. Moreover, the fluorescent pictures of gray value were performed in a cell phone app, corresponding to toxin concentration. The new assay takes 90 min to perform and can detect CPA as little as 32.8 ng/mL. Our results showed a sensitive, stable, and convenient CPA detection system, which provides a novel detection method of native CPA in foods.

E3 ubiquitin ligase ASB8 negatively regulates interferon via regulating TBK1/IKKi homeostasis.

Cells recognize virus nucleic acid by pattern recognition receptors (PRRs), virus involve in the activation of signaling cascade of variable adaptor proteins, TANK-binding kinase1(TBK1)/ inhibitor of nuclear factor kappa-B kinase subunit epsilon(IKKi) complex, IκB kinase(IKKs) to trigger activation of transcription factor, interferon regulatory factor 3/7(IRF3/7), ultimately, leading to the production of type I interferon and exert anti-viral effects. In this study, E3 ubiquitin ligase ankyrin repeat and SOCS box-containing 8(ASB8) interacted with TBK1/IKKi and phosphorylation modification of ASB8 at site of Ser17 to further strengthen its ubiquitination activity were verified. Conversely, phosphorylated ASB8 accelerate K48-linked ubiquitination and degradation of TBK1/IKKi, which further reduces phosphorylation level of IRF3 and inhibits production of IFN-ß. At the same time, a new bridge molecule Leucine-rich repeat containing protein 10B(LRRC10B) upregulated after viral infection are involved in the formation and interaction with ASB8-TBK1/IKKi complex was reported. Our study reveals a new mechanism of ubiquitin ligase ASB8 modulating antiviral innate immunity by altering stability of TBK1/IKKi kinase complex.