Virulence最新文献

Fusobacterium nucleatum was long regarded as a single species and later subdivided into four subspecies (nucleatum, polymorphum, animalis, vincentii/fusiforme). In 2022, these subspecies were validated as separate species and further members of the F. nucleatum complex have been proposed (F. watanabei, F. paranimalis sp. nov.). Given the increasing evidence linking F. nucleatum to various diseases, identifying (sub-)species-specific virulence factors has become essential. Infection in mammalian hosts depends on virulence factors that can be surface-exposed, released into the extracellular environment, or injected directly into host cells. This narrative review aims to address the different pathogenic potentials of each former subspecies. These differences range from adhesin diversity and metabolic adaptations, the repertoire of ABC transporters, lyases and type IV conjugative pili to the capability to invade tissues, evade the immune system and form biofilms and outer membrane vesicles.

Classical swine fever virus (CSFV) remains a major threat to the global swine industry, yet the involvement of host miRNAs in its pathogenic mechanisms is not fully understood. In this study, we demonstrate for the first time that miR-17-5p inhibits CSFV replication through an autophagy-dependent mechanism by targeting polycystin-2 (PKD2), a key calcium channel protein that regulates the AMPK/mTOR signaling pathway. Using the PK-15 cell model, we found that CSFV infection significantly upregulates miR-17-5p expression. Functional assays revealed that miR-17-5p exerts antiviral effects by directly binding to the 3'-UTR of PKD2, as confirmed by bioinformatics prediction and dual-luciferase reporter assays. Silencing of PKD2 recapitulated the antiviral effect of miR-17-5p overexpression, while PKD2 reconstitution restored viral replication by activating AMPK signaling and suppressing mTOR activity, thereby significantly enhancing autophagic flux - as evidenced by increased LC3-II/I ratio and decreased p62 levels. Mechanistically, PKD2 regulates intracellular calcium dynamics, modulating the AMPK/mTOR-autophagy axis to promote CSFV proliferation. This work uncovers a novel host antiviral mechanism in which a miRNA controls virus-induced autophagy via calcium signaling. To our knowledge, this is the first report to establish the pivotal role of miRNA-mediated calcium signaling modulation in flavivirus-host interactions. These findings provide a mechanistic framework and potential therapeutic targets for anti-CSFV interventions focused on PKD2 or autophagy regulation.

Porcine reproductive and respiratory syndrome virus(PRRSV) is an economically important pathogen for global pork industry. As a positive-strand RNA virus, lacking exonuclease-mediated proofreading, its RNA-dependent RNA polymerase (RdRP) domain within the nonstructural protein 9(nsp9) plays a vital role in maintaining replication accuracy. To identify the residues of PRRSV that regulates replication fidelity, its RdRP structure was predicted by using Alpha Fold 2 and aligned with the solved structure of coxsackievirus B3 (CVB3) RdRP. This comparison identified conserved residues in PRRSV RdRP that are potentially involved in fidelity. Using site-directed mutagenesis, nucleoside analog sensitivity tests, and next-generation sequencing(NGS), it was found that the nsp9 K541R mutation enhances fidelity, as increasing viral resistance to mutagens like ribavirin, 5-Fluorouracil(5-FU), and 5-Azacytidine(5-AZC), as well as generating lower rate of non-contiguous junctions. In contrast, mutations at other positions, including A394G, L396S, and R401A, reduced fidelity and elevated frequency of recombination and mutation accumulation. Structural modeling revealed that the highly conserved residue K336 is spatially adjacent to the key fidelity site K541 but situated on the opposite side of the RNA channel. We found that K336R exhibits a dissociated "resistance-high recombination" phenotype. The findings reveal the importance of specific residues in PRRSV RdRP for replication fidelity and provide insights into the potential for improving the stability and safety of live attenuated vaccines through targeted modifications. Furthermore, the study emphasizes the structural conservation of fidelity determinants across RNA viruses, despite low sequence similarity, which can offer a framework for identifying fidelity key sites in other viral RdRPs.

Acute gastroenteritis (AGE) exerts a substantial healthcare burden and economic loss annually, mainly due to viral infections. The objective of the study was to elucidate the impact of the interactions between the AGE virus and gut microbiota on patient clinical symptoms, thereby facilitating the early diagnosis and treatment of AGE. Clinical information and fecal samples were collected from 289 AGE patients (exclude fungal, parasitic, and bacterial infections), of whom 23.5% were infected with AGE viruses. A scoring method was developed to assess the severity of virus-induced AGE in patients. The results indicate significant differences (p < 0.05 indicates a significant difference, as determined by Kruskal-Wallis test, p = 0.03) in clinical symptom scores among the None-virus, Single-virus, and Dual-virus group. The Single-virus (14.82) and Dual-virus (15.33) groups exhibited more severe clinical symptom, with scoring values higher than None-virus group (12.40). Although significant differences in microbial community composition were observed between the Single-virus and Dual-virus groups (as determined by Adonis analysis, Variation = 0.11, p = 0.034), the diversity index (e.g. Chao1) did not significantly differ among the None-virus (288.14), Single-virus (345.74), and Dual-virus (282.70) groups. Notably, the patients with a higher Prevotella/Bacteroides index displayed more severe clinical symptom, as the index in the Single-virus and Dual-virus groups was over 10-times greater than in the None-virus group. In summary, this study shows that clinical symptoms of patients with viral AGE could be exacerbated through promoting bacterial competitions, and this understanding would facilitate the early diagnosis and treatment of viral AGE.

Enterococci are Gram-positive cocci that are considered to be one of the causative agents of hospital-acquired infections. CRISPR-Cas is an adaptive immune system with targeted defense functions against foreign invading nucleic acids and plays an important role in antibiotic resistance. In this study, we aimed to investigate II-A CRISPR-Cas-mediated immunity and the molecular mechanism underlying the horizontal transfer of drug resistance genes in Enterococcus faecalis. The mutant strains were constructed by the homologous recombination strategy. The interference of plasmid transformation by the Enterococcus faecalis CRISPR1/Cas system was confirmed through plasmid transformation efficiency. The different mutation positions in the protospacer sequence S1 and PAM region recombinant plasmids were constructed through enzyme digestion and sequencing verification to assess the impact of the CRISPR-encoded immunity. In the wild-type strain, the transformation efficiency of plasmids pAT28-S1-S9 containing protospacers and PAM sites decreased (p < 0.05). Single-base mutations at positions 25 and 28 of the protospacer region eliminated the ability of the wild-type strain to prevent plasmid transformation containing the protospacer and PAM sites (p > 0.05), whereas a single mismatch at protospacer positions 2,10,18,23 did not affect the ability of CRISPR-Cas system-positive strains to interfere with plasmid transformation (p < 0.05). There was no significant difference between the wild-type strain and the mutant strain in the transformation efficiency of the pS1-pΔPAM plasmid without PAM and plasmids containing single mutations (p > 0.05). In conclusion, the CRISPR-Cas system can block the transformation of matching protospacer sequences, and mutations near or within the protospacer adjacent motif (PAM) allow the plasmid to escape CRISPR-encoded immunity.

The protozoan parasite T. gondii employs intricate mechanisms to exploit host cells while sustaining their viability, yet its interaction with ferroptosis - an iron-dependent cell death driven by lipid peroxidation - remains poorly defined. Here, we show T. gondii infection induces ferroptotic hallmarks in RAW264.7 macrophages, including elevated lactate dehydrogenase release, labile Fe^{2 +} accumulation, reactive oxygen species (ROS) generation, and lipid peroxidation. Molecular analyses revealed infection-induced downregulation of ferroptosis suppressor GPX4 and upregulation of pro-ferroptotic ACSL4 in macrophages and mice. Mechanistically, the SLC7A11/GPX4 axis governed parasite growth: knockdown of these genes promoted T. gondii replication, whereas overexpression restricted proliferation. Pharmacological studies showed ferroptosis inhibitor Fer-1 suppressed intracellular parasite proliferation. Notably, GPX4 inhibitor RSL3 exhibited context-dependent effects: pre-infection treatment enhanced replication, while post-infection administration inhibited growth. Direct RSL3 exposure induced time-dependent growth arrest in extracellular tachyzoites, associated with disrupted transcriptomes, increased lipid ROS, and downregulated parasite antioxidant genes (TgPRX2, TgTPX1/2, TgNXN), indicating redox homoeostasis impairment. In vivo murine studies corroborated this biphasic effect: therapeutic RSL3 administration post-infection significantly reduced parasite burdens across multiple organs (spleen, liver, kidney, brain) and improved survival rates, while prophylactic pretreatment exacerbated disease progression. We propose RSL3 exerts direct parasiticidal effects via oxidative damage but also enables early nutrient acquisition from ferroptosis-compromised host cells. These findings establish ferroptosis as a critical node in T. gondii pathogenesis, highlighting the parasite's hijacking of host iron-lipid metabolism. The dual role of ferroptosis regulators underscores the host-pathogen metabolic complexity and positions the SLC7A11/GPX4 axis as a promising therapeutic target.

Bacterial pathogens intricately modulate their response to a variety of stress and the virulence, particularly in light of the dynamic conditions both in natural habitat and within host organisms. Transfer-messenger RNA (tmRNA), which plays an important role in pathogenicity due to its major function in the trans-translation system for ribosome rescue, has been proved as a stress response molecule. Herein, our results indicate that the global regulator IscR acts as a crucial activator responsible for the expression of tmRNA in Aeromonas veronii, a bacterial pathogen posing significant challenges to both aquatic industry and public health. Bacterial one-hybrid and electrophoretic mobility shift assays (EMSA) confirm the direct binding of IscR to the promoter region of the ssrA gene which encodes tmRNA. Moreover, our phenotypic characterizations illustrate that the complementation of tmRNA can rescue the defects of iscR deletion in response to adverse stress, including nutrient deprivation, elevated temperatures, β-lactam antibiotics, and oxidative stress, as well as in establishing the pathogenicity characterized by motility, aggregation, adhesion, cytotoxicity, bacterial competition, and colonization in mice. Our findings offer insights into a potential model for strengthening bacterial survival in external environments, and provide an initial glimpse into the intricate interplay between the functional roles of IscR and tmRNA in the pathogenicity through the IscR-tmRNA regulatory axis.

Helicobacter pylori is the most common gastric pathogen. H. pylori is prone to develop antibiotic resistance and recurrence after therapy makes treatment problematic. H. pylori can be detected attached to the gastric epithelial cells; however, it is mostly found within the gastric mucus. Helicobacter species infections impair the mucus barrier by decreasing the binding ability of the mucins, decreasing the growth-limiting activity of mucins and decreasing mucin production. The current study aimed to restore mucin production in the male C57BL/6 mouse H. pylori (SS1) infection model and evaluate its effects on H. pylori density. Mice infected with SS1 were treated with (R)-α-methylhistamine (RαMH) or interleukin-4 (IL4). Treatment with RαMH or IL4 restored mucin production and decreased gastric H. pylori density compared to mock-treated infected mice. Treatment with RαMH and IL4 did not affect serum anti-H. pylori IgG levels, expression of antimicrobial peptides or H. pylori virulence factors. Further, RαMH did not have cytotoxic effects on H. pylori. However, the expression of cytokines (Tnf and Il4), factors related to mucus production (Tff1, Spedf, Stat6, and Ptgs1), and mucin O-glycan sialylation levels differed between mice treated with RαMH and IL4. This suggests that increased mucus production can have similar effects on pathogen density in spite of differences in the local niche. In conclusion, agents that stimulate mucin production in the gastric mucosa have the potential to aid in the removal of pathogens from the gastric niche.

The increasing incidence of infections attributed to hypervirulent carbapenem-resistant Klebsiella pneumoniae (Hv-CRKp) is of considerable concern. Bacteriophages, also known as phages, are viruses that specifically infect bacteria; thus, phage-based therapies offer promising alternatives to antibiotic treatments targeting Hv-CRKp infections. In this study, two isolated bacteriophages, Kpph1 and Kpph9, were characterized for their specificity against the Hv-CRKp K. pneumoniae NUHL30457 strain that possesses a K2 capsule serotype. Both phages exhibit remarkable environmental tolerance, displaying stability over a range of pH values (4-11) and temperatures (up to 50°C). The phages demonstrate potent antibacterial and antibiofilm efficacy, as indicated by their capacity to inhibit biofilm formation and to disrupt established biofilms of Hv-CRKp. Through phylogenetic analysis, it has been revealed that Kpph1 belongs to the new species of Webervirus genus, and Kpph9 to the Drulisvirus genus. Comparative genomic analysis suggests that the tail fiber protein region exhibits the greatest diversity in the genomes of phages within the same genus, which implies distinct co-evolution histories between phages and their corresponding hosts. Interestingly, both phages have been found to contain two tail fiber proteins that may exhibit potential depolymerase activities. However, the exact role of depolymerase in the interaction between phages and their hosts warrants further investigation. In summary, our findings emphasize the therapeutic promise of phages Kpph1 and Kpph9, as well as their encoded proteins, in the context of research on phage therapy targeting hypervirulent carbapenem-resistant Klebsiella pneumoniae.

Multiple porcine reproductive and respiratory syndrome virus (PRRSV) subtypes coinfect numerous pig farms in China, and commercial PRRSV vaccines offer limited cross-protection against heterologous strains. Our previous research confirmed that a PRRSV lineage 1 branch attenuated live vaccine (SD-R) provides cross-protection against HP-PRRSV, NADC30-like PRRSV and NADC34-like PRRSV. HP-PRRSV has undergone significant genetic variation following nearly two decades of evolution and has transformed into a subtype referred to as HP-like PRRSV, which also exhibits high pathogenicity. The effectiveness of immunising piglets with the SD-R strain to provide protection against infection with HP-like PRRSV remains uncertain. In the present study, we evaluated the protective effects of SD-R vaccine strains on DLF-challenged piglets. The results revealed that piglets challenged with DLF presented clinical symptoms such as continuous high fever and an obvious decrease in daily weight gain. Importantly, the piglets immunised with SD-R exhibited notable reductions in pathological damage, especially of decreases in DLF-induced thymic atrophy. Moreover, the serum of SD-R-immunised piglets strongly neutralised DLF, and the number of SD-R-vaccinated piglets demonstrating viraemia was greatly reduced. These results suggest that the PRRSV lineage 1 branch live vaccine candidate provides broad cross-protection against HP-like PRRSV in piglets.