Virulence最新文献

Torovirus (ToV), while resembling coronavirus (CoV), belongs to a distinct family Tobaniviridae in the order Nidovirales. Porcine ToV (PToV) is widespread in pig populations across many countries, yet its potential pathogenicity in pigs remains poorly understood. The viral 3C-like protease (3CLP) plays a crucial role in processing viral polyproteins and manipulating the host antiviral immune response by targeting cellular proteins through its catalytic activity. In this study, we focused on PToV 3CLP due to its unique catalytic dyad characteristics and substrate recognition properties, which are distinct from those of CoV 3CLPs. We revealed that PToV 3CLP induces pyroptosis in porcine small intestinal IPEC-J2 cells and further demonstrated that porcine gasdermin D (pGSDMD) is a cleavage substrate for PToV 3CLP associated with this process. The catalytic residues, histidine 53 and serine 160, essential for the protease activity of PToV 3CLP, were required for the cleavage of pGSDMD at two distinct sites, glutamine 193 (Q193) and glutamine 277 (Q277). One of fragments produced by PToV 3CLP cleavage, pGSDMD_1-277, mimicked the activity of the N-terminal domain of pGSDMD (pGSDMD_1-279) in forming pores and ultimately triggering pyroptosis. Intriguingly, these results contrast with the inhibitory effect of CoV 3CLPs on pyroptosis, previously reported to target pGSDMD at the Q193 site. The study provides additional evidence of the distinct nature of 3CLP between ToV and CoV, which may partly explain the divergent clinical manifestations and pathogenesis observed in pigs infected by these nidoviruses.

Fowl adenoviruses (FAdVs) are widely distributed in poultry populations around the world, and many diseases are associated with FAdV infection in chickens. This study documented the first characterization of coinfection with fowl adenovirus serotypes 1 and 4 (FAdV-1 and -4) associated with hydropericardium hepatitis syndrome (HHS) in Chinese layer flocks, revealing a novel viral cooperation mechanism. Two novel strains (CH/SX/201805-1 and -4) were identified and isolated, with whole-genome sequencing showing CH/SX/201805-1 clustering with FAdV-1 (99.7% identity to FAdV-A-61/11z), whereas CH/SX/201805-4 displayed characteristic ORF19/27/29 deletions mirroring emergent Chinese FAdV-4 variants. Experimental coinfection in SPF chickens resulted in 87.5% mortality, which was 16.7% greater than that resulting from infection alone, with exacerbated pathology. In vitro coinfection experiments demonstrated concurrent viral replication within same LMH cells, a previously unreported phenomenon, where FAdV-1 increased FAdV-4 replication efficiency 21-fold (p < 0.001). Transcriptomic profiling revealed heat shock protein A2 (HSPA2) as the most differentially expressed gene, which was upregulated 2.8-fold during coinfection compared with infection with FAdV-4 alone. Functional validation through HSPA2 knockdown reduced FAdV-4 replication, establishing that FAdV-1 potentiates FAdV-4 through HSPA2-mediated host modulation. These findings provide the first evidence of HSPA2-dependent interserotype synergy in FAdV and can be used to develop a cellular model for FAdV coinfection studies. These insights redefine the understanding of FAdV pathogenesis and create new avenues for targeted intervention strategies against emerging FAdV coinfections.

Critical metabolic enzymes and pathways specific to bacterial adaptation in different host microenvironments directly contribute to bacterial pathogenicity. In this study, a virulent strain of the important zoonotic pathogen Streptococcus suis was found to show enhanced growth under anaerobic conditions compared to aerobic conditions. Transcriptomic analysis found a significant suppression of many central metabolic genes during anaerobic growth of S. suis. The transcriptomic data were used to reconstruct a genome-scale metabolic network to assess the distribution of metabolic fluxes in S. suis under different conditions. Significant activation of the arginine deiminase (ADI) and branched-chain amino acid (BCAA) biosynthesis pathways was identified. Gene deletion mutants of arcB and ilvC participating in these two pathways, respectively, were constructed. Compared to the wild-type strain, the ΔarcB mutant showed more significant growth deficiency under anaerobic conditions than under aerobic conditions. Accumulation of ATP and NH₃, the metabolites of the ADI pathway, was significantly higher when S. suis was cultured under anaerobic conditions, and this effect was attenuated in the ΔarcB mutant. The knockout of IlvC of the BCAA pathway disrupted the normal growth of S. suis in valine- and isoleucine-limited medium under anaerobic conditions. Both ΔarcB and ΔilvC showed attenuation in mice with decreased lethality, bacterial loads in tissues, and cytokine levels in serum, with the hypoxia-induced gene up-regulated in tissues. Therefore, ADI and BCAA pathways are critical for S. suis survival in response to hypoxia and infection in vivo, with ArcB and IlvC being promising drug targets.

Thrombomodulin (TM) is a membrane protein with significant roles in coagulation hemostasis and immune response. Its soluble form (sTM) has recently emerged as a key biomarker for severe invasive bacterial infections, including Necrotizing Soft Tissue Infections (NSTI). While various mechanical, chemical, and enzymatic mechanisms have been linked to TM shedding, this study investigates the direct impact of bacterial stimuli on soft tissue cells as primary sources of TM release. We stimulated organotypic models, composed of fibroblast and endothelial cells, with NSTI clinical isolates and found that while Group A Streptococcus and Escherichia coli had minimal effect on TM release, Staphylococcus aureus infection triggered a significant increase of sTM levels. We further assessed whether the secreted proteins of S. aureus led to higher TM levels by increased expression, increased cell toxicity, or direct cleavage of TM from the endothelial cell membrane. To investigate these mechanisms, we performed in vitro stimulations of endothelial monolayers with secreted proteins of two S. aureus isolates differing in their agr-system functionality. Our results indicate that S. aureus agr-regulated proteins induce TM shedding by direct cleavage from the cell membrane, an effect that was inhibited by metalloproteinase inhibitors. Stimulation with the pore-forming protein α-toxin showed similar results, suggesting a potential involvement of ADAM10 in TM cleavage. Additionally, we observed that other agr-regulated proteins can cleave TM directly. Altogether, this study reveals a pathogen-specific mechanism for TM release during S. aureus invasive infection, contributing to its elevated plasma levels and providing deeper insights into the pathophysiology of NSTI.

Recent reports have highlighted the increasing frequency of influenza A virus (IAV) spillover events from other species to dogs and cats. IAV, particularly the H3 subtype, exhibits a broad host range and a propensity for interspecies transmission, as exemplified by the sustained circulation of H3N2 and H3N8 canine influenza viruses in dog populations. This raises concerns about the potential role of companion animals as intermediate hosts in influenza virus transmission. To evaluate the susceptibility of dogs and cats to the prevalent H3 subtype influenza viruses, we experimentally inoculated groups of both species with three prevalent influenza viruses: H3N2 avian influenza virus (AIV), H3N8 avian influenza virus, and H3N2 swine influenza virus (SIV). Results showed that while all inoculated dogs exhibited seroconversion to all three viruses at 7, 14, and 21 days post-inoculation (dpi), they displayed no clinical signs, viral shedding, or evidence of viral replication in their organ tissues. In contrast, despite the cats did not exhibit apparent clinical signs, all inoculated cats exhibited seroconversion to all viruses at 7, 14 and 21 dpi, sustained nasal viral shedding for approximately one week, and demonstrated viral replication in their lungs, trachea, and nasal turbinate. Our findings underscore the higher susceptibility of cats compared to dogs to H3 subtype influenza viruses. These results emphasize the critical need for enhanced surveillance of cats within the influenza virus transmission network.

Malassezia globosa plays a crucial role as part of the human skin's mycobiome. However, this yeast has been detected in other niches, such as the gut. Despite being commensal, the pathogenic link in several dermatological conditions, but recently, chronic diseases such as cancer, Crohn's disease, and Parkinson's disease, among others, have been explored. Lipids can be involved in fungal pathogenesis, and this yeast is characterized by a significant lipid metabolic versatility, with a lack of the complex fatty acid synthase (FAS) required for the de novo synthesis of fatty acids, as it relies on lipase-releasing enzymes. Here, we assess lipid dynamics (lipids consumed vs. lipids secreted) using lipidomic analysis in the supernatant of mDixon media during two growth phases. 87 lipids within 17 classes of lipids were identified in three different lipid uptake-secretion patterns. Some lipids were characteristic, including the presence of glycochenodeoxycholic acid, glycerophospholipids (such as phosphocholine), cardiolipins, and sphingolipids (such as Cer-PI). Interestingly, sterols, bile acids, cholic acid and its derivates, some phosphocholines, fatty acyls, and cardiolipins were lipids consumed over time. The dynamic consumption of these lipids could presume an intriguing role in the metabolism of lipid processes in this yeast that could determine the interaction process and its pathogenic role.

Escherichia coli is a key pathogen in extraintestinal infections, including prosthetic joint infections (PJIs), which account for approximately 9% of all such cases. Despite its clinical relevance, the molecular pathogenesis of E. coli in PJIs remains poorly defined. This study investigated the clinical, phylogenetic, and virulence profiles of E. coli isolates from PJIs and compared them to isolates from bacteremic urinary tract infections (UTIs). A total of 13 isolates from each infection type were analyzed using whole-genome sequencing (WGS) to determine phylogenetic relationships, sequence types, and the presence of virulence genes. PJI isolates exhibited substantial genetic diversity, encompassing 10 sequence types, with ST131 and ST69 being the most frequent. Phylogroup B2 predominated (53.9%) among PJI isolates. Adhesion and biofilm-related genes, such as fimG/H, csg, and epaO, were highly prevalent in PJI isolates, supporting the role of biofilm formation in pathogenesis. Conversely, toxin-associated genes (e.g. pic and senB) were more frequently detected in UTI isolates. Notably, the matA gene, linked to biofilm enhancement, was significantly associated with microbiological failure in PJIs (75% vs. 0%, p = 0.02). Phylogenetic analyses revealed no clustering by infection type, suggesting that ExPEC strains share a versatile genomic background, enabling them to adapt to different infection environments. The study highlights the critical role of biofilm formation in PJIs and underscores the genetic adaptability of ExPEC strains, which lack distinct virulence profiles specific to PJIs. However, the small number of PJI isolates limits the generalizability of these findings and warrants confirmation in larger cohorts.

In the context of COVID-19, macrophages are primarily responsible for sensing and responding to the virus, significantly influencing disease outcomes. They are involved in early pathogen recognition, immune activation, and tissue repair. Heterogeneity and phenotypic plasticity of macrophages are dynamically shaped by microenvironmental cues, including metabolites, hypoxia, and pathogen-derived signals. Notably, emerging evidence underscores that cellular metabolism, particularly in macrophages, dictates immune responses to viral infection. This metabolic-immune crosstalk critically determines COVID-19 severity, ranging from viral clearance to hyperinflammation or fibrosis. In this review, we systematically dissect how cell-intrinsic metabolic nodes and extrinsic factors modulate macrophage effector functions, while illustrating the complications associated with macrophage metabolic dysregulation in SARS-CoV-2 infection. These mechanistic insights provide a rational foundation for therapeutic strategies targeting macrophage metabolism to rebalance immune responses and mitigate COVID-19 complications.

Camellia oleifera is an important economic woody oil plant in many Asian countries, and the anthracnose caused by Colletotrichum fructicola is prevalent in its cultivation regions, causing significant losses annually. We previously found that CfGcn5-mediated H3 acetylation governs virulence of C. fructicola. To further elucidate the regulatory mechanism of CfGcn5, we carried out mass spectrometry analysis for CfGcn5-interacting proteins and identified CfAda3 protein for functional analysis. We found that CfAda3 was mainly localized in nucleus and cooperated with CfGcn5 to acetylate H3K18 for global gene transcription. Targeted gene deletion revealed that CfAda3 is involved in growth and conidiation. Similar to ΔCfgcn5 mutant, the ΔCfada3 mutant is defective in conidial germination, appressorial formation, autophagy, and in the response to environmental stresses. These combined effects result in its non-virulence on C. oleifera. In addition, we provided evidence showing that both NLS region and ADA3 domain are required for the localization and function of CfAda3. Moreover, we indicated that the interaction with CfGcn5 is essential but not sufficient for the normal localization and full function of CfAda3. Taken together, our studies not only illustrate the prominent roles of CfAda3 in growth, development, and virulence but also highlight how CfAda3 functions together with CfGcn5 in C. fructicola.

Peronophythora litchii is an oomycete pathogen responsible for litchi downy blight, a significant threat to global litchi production. Autophagy, a conserved degradation pathway crucial for the growth, development, and pathogenicity of phytopathogenic organisms, remains an area of active investigation. In this study, we characterized the function of the Atg26 homolog PlAtg26b in P. litchii. Using the CRISPR/Cas9 genome editing system, we generated PlATG26b knockout mutants and determined that PlAtg26b localizes to mitochondria under stress conditions. Although deletion of PlATG26b did not impair selective autophagy, it markedly reduced Atg8-PE synthesis, vegetative hyphal growth, asexual and sexual reproduction, and zoospore release. Furthermore, PlATG26b-deficient mutants exhibited significantly reduced virulence on litchi fruits and leaves. Collectively, our findings demonstrate that PlAtg26b plays a pivotal role in the biological development and pathogenicity of P. litchii.