The I226R protein of African swine fever virus inhibits the cGAS-STING-mediated innate immune response / 生物工程学报

This study aimed to explore the mechanism of how African swine fever virus (ASFV) I226R protein inhibits the cGAS-STING signaling pathway. We observed that I226R protein (pI226R) significantly inhibited the cGAS-STING-mediated type Ⅰ interferons and the interferon-stimulated genes production by dual-luciferase reporter assay system and real-time quantitative PCR. The results of co-immunoprecipitation assay and confocal microscopy showed that pI226R interacted with cGAS. Furthermore, pI226R promoted cGAS degradation through autophagy-lysosome pathway. Moreover, we found that pI226R decreased the binding of cGAS to E3 ligase tripartite motif protein 56 (TRIM56), resulting in the weakened monoubiquitination of cGAS, thus inhibiting the activation of cGAS and cGAS-STING signaling. In conclusion, ASFV pI226R suppresses the antiviral innate immune response by antagonizing cGAS, which contributes to an in-depth understanding of the immune escape mechanism of ASFV and provides a theoretical basis for the development of vaccines.

The E248R protein of African swine fever virus inhibits the cGAS-STING-mediated innate immunity / 生物工程学报

We researched the mechanism of African swine fever virus (ASFV) protein E248R in regulating the cGAS-STING pathway. First, we verified via the dual-luciferase reporter assay system that E248R protein inhibited the secretion of IFN-β induced by cGAS-STING or HT-DNA in a dose-dependent manner. The relative quantitative PCR analysis indicated that the overexpression of E248R inhibited HT-DNA-induced transcription of IFN-b1, RANTES, IL-6, and TNF-α in PK-15 cells. Next, we found that E248R interacted with STING by co-immunoprecipitation assay and laser confocal microscopy. Finally, we demonstrated that E248R inhibited the expression of STING protein by using Western blotting. We demonstrated for the first time that the E248R protein of ASFV suppressed the host innate immune response via inhibiting STING expression. The results are pivotal in extending the understanding of the ASFV immune escape and can guide the design of vaccines against ASFV.

Development of a Recombinase-aided Amplification Combined With Lateral Flow Dipstick Assay for the Rapid Detection of the African Swine Fever Virus / 生物医学与环境科学（英文）

OBJECTIVE@#To establish a sensitive, simple and rapid detection method for African swine fever virus (ASFV) B646L gene.@*METHODS@#A recombinase-aided amplification-lateral flow dipstick (RAA-LFD) assay was developed in this study. Recombinase-aided amplification (RAA) is used to amplify template DNA, and lateral flow dipstick (LFD) is used to interpret the results after the amplification is completed. The lower limits of detection and specificity of the RAA assay were verified using recombinant plasmid and pathogenic nucleic acid. In addition, 30 clinical samples were tested to evaluate the performance of the RAA assay.@*RESULTS@#The RAA-LFD assay was completed within 15 min at 37 °C, including 10 min for nucleic acid amplification and 5 minutes for LFD reading results. The detection limit of this assay was found to be 200 copies per reaction. And there was no cross-reactivity with other swine viruses.@*CONCLUSION@#A highly sensitive, specific, and simple RAA-LFD method was developed for the rapid detection of the ASFV.

Comparison of the antigenicity of African swine fever virus p35 protein as diagnostic antigen / 生物工程学报

In order to screen African swine fever virus (ASFV) diagnostic antigen with the best enzyme linked immunosorbent assay (ELISA) reactivity. By establishing the ELISA method, the diagnostic antigen of ASFV p30 protein expressed by baculovirus-insect cell expression system as reference, we explored the antigenic properties and diagnostic potential of ASFV p35 protein expressed by prokaryotic expression system as a diagnostic antigen. The results of Western blotting and immunofluorescence show that the molecular weight of the recombinant p35 protein and p30 protein obtained was 40 kDa and 30 kDa, respectively, and these two proteins had good immuno-reactivity with ASFV positive serum. Recombinant p30 and p35 proteins were used as diagnostic antigens to establish ELISA, and the sensitivity and repeatability of these methods were tested. The results show that although the detection sensitivity of the p30-ELISA established in this study was higher than that of the p35-ELISA, the sensitivity of p35-ELISA was 95.8%, and variations in intra- and inter-assay repeatability of the two methods were less than 10%. The coincidence rate between the p35-ELISA and the imported kit was 97.2%. Results show that p35-ELISA was sensitive and stable, and could detect specific antibodies against ASFV.

Prevention, control and vaccine development of African swine fever: challenges and countermeasures / 生物工程学报

African swine fever (ASF) is a hemorrhagic and devastating infectious disease of pigs caused by African swine fever virus (ASFV), with mortality up to 100%. The first ASF outbreak occurred in China in August 2018, followed by 69 cases of ASF in 18 provinces in more than three months, causing a heavy burden to the pig industry. Based on the global epidemic situation of ASF and the experience of prevention and control in other countries, the ASF control and eradication situation in China is extremely complex and serious. The availability of effective and safe ASF vaccines is an urgent requirement to reinforce control and eradication strategies. Therefore, this article starts with the latest findings of ASFV, summarizes the progress in prevention and control strategies and vaccine approaches for ASFV. We also discuss the challenges of preventing and controlling ASF, focusing on current vaccine strategies, the gaps, future research directions, and key scientific issues in commercial applications. We hope to provide basic information for the development of vaccines and prevention control strategies against this disease in China.

Ubiquitin-proteasome pathway and virus infection / 生物工程学报

Ubiquitin is highly conserved 76 amino acid protein found in all eukaryotic organisms and ubiquitin-proteasome pathway (UPP) plays a very important role in regulated non-lysosomal ATP dependent protein degradation. This pathway participates in or regulates numerous cellular processes, such as selective protein degradation, cell cycle progression, apoptosis, signal transduction, transcriptional regulation, receptor control by endocytosis, immune response and the processing of antigens. Nevertheless, roles of UPP in virus infection are only beginning to be clarified. Ubiquitin homology has also been found in insect viruses. All viral ubiquitin genes encode an N-terminal ubiquitin sequence and 3-256 amino acids C-terminal peptides. Most of the residues known to be essential for ubiquitin function have been conserved in the viral variant. In Autographa californica nucleopolyhedrovirus (AcMNPV), viral ubiquitin is attached to the inner surface of budded viron membrane by a covalently linked phospholipid and is not essential for viral replication. Currently, insect viruses are the only viruses known to encode ubiquitin. However, ubiquitin also plays a role in the life cycle of other viruses. Host ubiquitin molecules have been found in some plant viruses and other animal viruses. Additionally, Africa swine fever virus (ASFV) encodes a ubiquitin-conjugating enzyme (E2) and a putative causal link between human immunodeficiency virus type 1 (HIV-1) and ubiquitin was established by showing that depletion of the intracellular pool of free ubiquitin inhibits the virus budding. Further analyses indicated that many retroviruses proteins which are required for efficient pinching off the virus bud contain a late domain. The core element of the late domain is a proline-rich motif (PPXY) which mediates the late domain to be ubiquitinated by cellular proteins. Recently, it has been shown that many retroviruses have developed mechanisms to escape the cellular immune response, to facilitate virus replication and to promote virus assembly and budding via host UPP.