Fuzhou Xu

Background: Actinobacillus pleuropneumoniae (APP) is the causative agent of porcine contagious pleuropneumonia, which remains a major pathogen endangering the swine industry. However, the mechanisms underlying its colonization and pathogenesis in pigs remain largely unknown.Methods: An integrated analysis combining transcriptomic and proteomic profiling was employed to detect genetic and protein changes in APP under iron starvation.Results: In total, 458 differentially expressed genes (DEGs) from the transcriptome and 532 differentially expressed proteins (DEPs) from the proteome were identified. The comparative analysis showed that 137 differentially expressed genes/proteins were shared between DEGs and DEPs, with the majority exhibiting consistent regulatory changes at both transcription and protein levels. Functional enrichment analysis revealed that the downregulated genes were predominantly associated with the generation of precursor metabolites and energy (45/105, 42.86%), primary metabolic process (29/105, 27.62%), ion binding (20/105, 19.05%), and metal cluster binding (18/105, 17.14%), corresponding to pathways involved in primary metabolites and energy biosynthesis and cellular respiration. Conversely, the upregulated genes were primarily enriched in iron transport (11/30, 36.67%) and iron binding (9/30, 30%), which corresponded to the iron starvation conditions. The expression changes of iron utilization systems, including TonB-ExbB-ExbD and some TonB-dependent receptors, by qRT-PCR were consistent with the results in both transcriptome and proteome analyses.Conclusion: This study provided a global perspective on the response mechanisms employed by APP to iron starvation, characterized by suppressing electron transport and energy metabolism pathways and upregulating the pathways associated with the TonB-ExbB-ExbD energy transduction system for iron acquisition.

Canine Parvovirus (CPV) is a highly contagious virus that causes severe hemorrhagic enteritis and myocarditis, posing a major threat to the life and health of dogs. The molecular mechanism by which VP2, the major capsid protein of CPV, infects host cells and utilizes host cell proteins for self-replication remains poorly understood. In this study, 140 host proteins specifically binding to CPV VP2 protein were identified by immunoprecipitation combined with liquid chromatography–mass spectrometry (LC-MS/MS). Subsequently, the protein Interaction Network (PPI), the annotation of gene ontology (GO) and the database of Kyoto Encyclopedia of Genes and Genomes (KEGG) were constructed for in-depth analysis. The results showed that CPV VP2 protein participated mainly in cell metabolism, cell biosynthesis, protein folding and various signal transduction processes. According to the results of proteomics analysis, we randomly selected seven proteins for co-immunoprecipitation verification, and the experimental results were consistent with the LC-MS/MS data. In addition, our study found that the expression level of the VP2-interacting protein FHL2 mediated CPV replication. Preliminary studies have shown that knockdown of FHL2 promotes CPV replication by decreasing the expression of interferon β (IFN-β) and interferon-stimulated genes (ISGs), while overexpression of FHL2 can inhibit the replication of CPV by up-regulating the expression of IFN-β and related ISGs. This study lays the foundation for elucidating the potential function of CPV VP2 protein in the process of viral infection and proliferation which provides a theoretical basis for the design of antiviral agents and vaccines.

Canine parvovirus (CPV) is a single-stranded DNA virus that can cause typical hemorrhagic enteritis, and it is one of the common canine lethal viruses. In previous studies, we screened the Food and Drug Administration (FDA)’s drug library and identified nitazoxanide (NTZ), which has anti-CPV capabilities. To investigate the potential antiviral mechanisms, we first reconfirmed the inhibitory effect of NTZ on the CPV by inoculating with different doses and treating for different lengths of time. Then, the differences in the transcription levels between the 0.1%-DMSO-treated virus group and the NTZ-treated virus group were detected using RNA-seq, and a total of 758 differential expression genes (DEGs) were finally identified. Further Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analyses of the DEGs revealed that these genes are involved in a variety of biological processes and/or signaling pathways, such as cell cycle, mitosis and cell proliferation and differentiation. A protein–protein interaction (PPI) analysis further identified hub genes associated with cell cycle and division among the DEGs. In addition, the expression levels of some of the enriched genes were detected, which were consistent with the high-throughput sequencing results. Moreover, when the cell cycle was regulated with cell cycle checkpoint kinase 1 (Chk1) inhibitor MK-8776 or Prexasertib HCl, both inhibitors inhibited the CPV. In summary, the transcriptome differential analysis results presented in this paper lay the foundation for further research on the molecular mechanism and potential targets of NTZ anti-CPV.

Introduction: Actinobacillus pleuropneumoniae, the causative agent of porcine pleuropneumonia, poses a significant threat to global swine populations due to its high prevalence, mortality rates, and substantial economic ramifications. Understanding the pathogen's defense mechanisms against host-produced reactive oxygen species is crucial for its survival, with OxyR, a conserved bacterial transcription factor, being pivotal in oxidative stress response.Methods: This study investigated the presence and role of OxyR in A. pleuropneumoniae serovar 1-12 reference strains. Transcriptomic analysis was conducted on an oxyR disruption mutant to delineate the biological activities influenced by OxyR. Additionally, specific assays were employed to assess urease activity, catalase expression, ApxI toxin secretion, as well as adhesion and invasion abilities of the oxyR disruption mutant on porcine 3D4/21 and PT cells. A mice challenge experiment was also conducted to evaluate the impact of oxyR inactivation on A. pleuropneumoniae virulence.Results: OxyR was identified as a conserved regulator present in A. pleuropneumoniae serovar 1-12 reference strains. Transcriptomic analysis revealed the involvement of OxyR in multiple biological activities. The oxyR disruption resulted in decreased urease activity, elevated catalase expression, enhanced ApxI toxin secretion—attributed to OxyR binding to the apxIBD promoter—and reduced adhesion and invasion abilities on porcine cells. Furthermore, inactivation of oxyR reduced the virulence of A. pleuropneumoniae in a mice challenge experiment.Discussion: The findings highlight the pivotal role of OxyR in influencing the virulence mechanisms of A. pleuropneumoniae. The observed effects on various biological activities underscore OxyR as an essential factor contributing to the pathogenicity of this bacterium.