African swine fever (ASF) is a fatal infectious disease of swine caused by the African swine fever virus (ASFV). Currently, the disease is listed as a legally notifiable disease that must be reported to the World Organization for Animal Health (WOAH). The economic losses to the global pig industry have been insurmountable since the outbreak of ASF. Control and eradication of ASF are very critical during the current pandemic. Vaccination is the optimal strategy to prevent and control the ASF epidemic, but since inactivated ASFV vaccines have poor immune protection and there aren’t enough cell lines for efficient in vitro ASFV replication, an ASF vaccine with high immunoprotective potential still remains to be explored. Knowledge of the course of disease evolution, the way of virus transmission, and the breakthrough point of vaccine design will facilitate the development of an ASF vaccine. In this review, the paper aims to highlight the recent advances and breakthroughs in the epidemic and transmission of ASF, virus mutation, and the development of vaccines in recent years, focusing on future directions and trends.

Gram-negative bacteria utilize N-acylhomoserine lactones (AHLs) as quorum sensing (QS) signaling molecules for intercellular communication. Cell-to-cell communication depends on cell population density, and AHL-dependent QS is related to the production of multiple genes including virulence factors. Quorum quenching (QQ), signal inactivation by enzymatic degradation, is a potential strategy for attenuating QS regulated bacterial infections. Both Gram-positive and -negative bacteria have QQ enzymes that can degrade AHLs. In our previous study, strain Ruegeria mobilis YJ3, isolated from healthy shrimp, showed strong AHLs degradative activity. In the current study, an AHL lactonase (designated RmmL) was cloned and characterized from Ruegeria mobilis YJ3. Amino acid sequence analysis showed that RmmL has a conserved “HXHXDH” motif and clusters together with lactonase AidC that belongs to the metallo-β-lactamase superfamily. Recombinant RmmL could degrade either short- or long-chain AHLs in vitro. High-performance liquid chromatography analysis indicated that RmmL works as an AHL lactonase catalyzing AHL ring-opening by hydrolyzing lactones. Furthermore, RmmL can reduce the production of pyocyanin by Pseudomonas aeruginosa PAO1, while for the violacein and the extracellular protease activities by Chromobacterium violaceum CV026 and Vibrio anguillarum VIB72, no significant reduction was observed. This study suggests that RmmL might be used as a therapeutic agent in aquaculture.

African swine fever (ASF) is a highly contagious, acute, febrile disease caused by the African swine fever virus (ASFV), with morbidity and mortality rates approaching 100% in domestic and wild swine, resulting in massive economic losses to the pig industry worldwide. This study aimed to express the p30, p54, and p72 proteins encoded by ASFV in vitro using the Lactobacillus lactis (L. lactis) expression system. Here, six new functional recombinant L. lactis were constructed, and the expression of the p30 protein, p54 protein, p72 protein, p30-LTB (heat-labile enterotoxin B, LTB) fusion protein, p54-LTB fusion protein, and the p72-LTB fusion protein was successfully detected by Western blot analysis. Following oral immunization of rabbits with recombinant L. lactis, serum IgG, intestinal mucosal sIgA, cytokines (IL-4 and INF-γ), and splenocyte viability were higher than in the control group via ELISA. Notably, without the LTB adjuvant group, humoral and Th1 cellular immunity were promoted, whereas, with the LTB adjuvant group, local mucosal immunity, humoral immunity, and Th2 cellular immunity were promoted, providing new insights into the design and development of an ASFV subunit vaccine.

Introduction: Pseudorabies virus (PRV) is a herpesvirus that can infect domestic animals, such as pigs, cattle and sheep, and cause fever, itching (except pigs), and encephalomyelitis. In particular, the emergence of PRV variants in 2011 have resulted in serious economic losses to the Chinese pig industry. However, the signaling pathways mediated by PRV variants and their related mechanisms are not fully understood.Methods: Here, we performed RNA-seq to compare the gene expression profiling between PRV virulent SD2017-infected PK15 cells and Bartha-K/61-infected PK15 cells.Results: The results showed that 5,030 genes had significantly different expression levels, with 2,239 upregulated and 2,791 downregulated. GO enrichment analysis showed that SD2017 significantly up-regulated differentially expressed genes (DEGs) were mainly enriched in the binding of cell cycle, protein and chromatin, while down-regulated DEGs were mainly enriched in ribosomes. KEGG enrichment analysis revealed that the pathways most enriched for upregulated DEGs were pathways in cancer, cell cycle, microRNAs in cancer, mTOR signaling pathway and autophagy-animal. The most down-regulated pathways of DEGs enrichment were ribosome, oxidative phosphorylation, and thermogenesis. These KEGG pathways were involved in cell cycle, signal transduction, autophagy, and virus-host cell interactions.Discussion: Our study provides a general overview of host cell responses to PRV virulent infection and lays a foundation for further study of the infection mechanism of PRV variant strain.

Introduction: Quorum sensing (QS) is a bacterial intercellular communication system that can regulate the expression of various virulence genes coordinate the group behaviors of the bacteria by sensing the concentration of signaling molecules in the surrounding environment. An increase in bacterial drug-resistance has been caused by the widespread use of antibiotics, making it urgent to identify safe and effective alternatives to antibiotics. Quorum quenching (QQ) is a strategy to control bacterial infections by disrupting the QS system, which reduces pathogenicity or increases biofilm susceptibility to antibiotics. Several natural agents with QQ activity have been identified, including small molecular inhibitors and QQ enzymes that disrupt bacterial QS by degrading or modifying the QS signal molecules.Methods: In the present study, We performed heterologous recombinant expression of the potential QQ enzyme-encoding gene RmmLII from Tritonibacter mobilis YJ3. The degradation activity of RmmLII against AHLs was assessed in vitro using the A136 liquid X-Gal assay and a plate detection method. Furthermore, the degradation mechanism of RmmLII was analyzed via high-performance liquid chromatography-mass spectrometry (HPLC-MS). The effects of RmmLII on extracellular proteases production, pyocyanin synthesis, rhamnolipids secretion, biofilm formation, and motility of Pseudomonas aeruginosa PAO1 were evaluated in vitro. Additionally, a mouse infection model was established using P. aeruginosa PAO1 to investigate the impact of RmmLII on the production of inflammatory cytokines IL-1β, IL-6, and TNF-α, as well as mouse survival rates.Results: A novel N-acylhomoserine (AHL) lactonase RmmLII was identified and characterized from T. mobilis YJ3, which was isolated from healthy shrimp in our previous work. Through amino acid sequence alignment, a conserved “HXHXDH” domain was detected in RmmLII, indicating that RmmLII belongs to the phosphotriesterase (PTE) family. Recombinant RmmLII could effectively degrade AHLs in vitro, both long-chain and short-chain AHLs, ranging from C₆ to C₁₄. It exhibited the strongest quenching effect on C₆-HSL, C₈-HSL, C₁₀-HSL, 3-oxo-C₈-HSL, 3-oxo-C₁₀-HSL, 3-oxo-C₁₂-HSL, and 3-oxo-C₁₄-HSL, while the quenching effect on C14-HSL and 3-oxo-C₆-HSL was relatively weaker, especially with more notable degradation activity towards long-chain AHLs with a substitution of oxo-group at the C-3 position. HPLC-MS analysis revealed that RmmLII could hydrolyze the ester bond of AHLs. In addition, RmmLII significantly inhibited the production of extracellular proteases, pyocyanin, rhamnolipids, biofilm formation, as well as motility of P. aeruginosa PAO1 in vitro. It also reduced the production of inflammatory factors IL-1β, IL-6, and TNF-α, thereby improving the survival rates of mice infected with PAO1 in vivo.Discussion: This study demonstrates the potential application of RmmLII in controlling PAO1 infections, offering new insights for the development of novel antibiotic alternatives. RmmLII has the potential as a therapeutic agent for application in the mitigating PAO1 infections.

Corrigendum: Vaccines for African swine fever: an update Name of all authors as they appear in the published original article (INSERT ONLY IF correcting author names or adding authors. Insert the correct version of the author list)Affiliations of all authors as they appear in the published original version of the article (INSERT ONLY IF correcting affiliation(s) or adding affiliation(s). Insert the correct version of the affiliation(s))* Correspondence: shanhu67@163.com; xlcai_99@163.comKeywords: same as original articleCorrigendum on: Zhang H, Zhao S, Zhang H, Qin Z, Shan H and Cai X (2023). Vaccines for African swine fever: an update. Front. Microbiol. 14:1139494. doi: 10.3389/fmicb.2023.1139494Incorrect Funding In the published article, there was an error in the Funding statement. [The last funding no. is in- correct. This work is based upon research funded by the Shandong Provincial Key Research and Development Program (Major Scientific and Technological Innovation Project; No. 2020CXGC010801-02), the Shandong Province Agricultural Major Application Technology Innovation Project (No. SD2019XM003), the Project of Shandong Province Science and Technology Achievement Transfer Transformation Subsidy (No. 2021 LYXZ020), the Shandong Provincial Major Project of the New-Old Kinetic Energy Conversion [No. (2020)1220], and the Shandong Province Natural Science Foundation (No. ZR201910250090).]. The correct Funding statement appears below.FUNDING[This work is based upon research funded by the Shandong Provincial Key Research and Development Program (Major Scientific and Technological Innovation Project; No. 2020CXGC010801-02), the Shandong Province Agricultural Major Application Technology Innovation Project (No. SD2019XM003), the Project of Shandong Province Science and Technology Achievement Transfer Transformation Subsidy (No. 2021 LYXZ020), the Shandong Provincial Major Project of the New-Old Kinetic Energy Conversion [No. (2020)1220], and the Project ZR2020MC185 supported by Shandong Provincial Natural Science Foundation.).The authors apologize for this error and state that this does not change the scientific conclusions of the article in any way. The original article has been updated.