Virulence最新文献

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.

Vulvovaginal candidiasis (VVC) is one of the most common infections caused by Candida albicans. VVC is characterized by an inadequate hyperinflammatory response and clinical symptoms associated with Candida colonization of the vaginal mucosa. Compared to other host niches in which C. albicans can cause infection, the vaginal environment is extremely rich in lactic acid that is produced by the vaginal microbiota. We examined how lactic acid abundance in the vaginal niche impacts the interaction between C. albicans and the human immune system using an in vitro culture in vaginal simulative medium (VSM). The presence of lactic acid in VSM (VSM+LA) increased C. albicans proliferation, hyphal length, and its ability to cause damage during subsequent infection of vaginal epithelial cells. The cell wall of C. albicans cells grown in VSM+LA displayed a robust mannan fibrillar structure, β-glucan exposure, and low chitin content. These cell wall changes were associated with altered immune responses and an increased ability of the fungus to induce trained immunity. Neutrophils were compromised in clearing C. albicans grown in VSM+LA conditions, despite mounting stronger oxidative responses. Collectively, we found that fungal adaptation to lactic acid in a vaginal simulative context increases its immunogenicity favouring a pro-inflammatory state. This potentially contributes to the immune response dysregulation and neutrophil recruitment observed during recurrent VVC.

Chronic kidney and urinary tract diseases, including glomerulonephritis, nephrotic syndrome, and chronic kidney disease (CKD), present significant global health challenges. Recent studies suggest a complex interplay between infectious pathogens and immune-mediated kidney damage. This study employs Generalized Summary data-based Mendelian Randomization (GSMR) to explore causal relationships between pathogen-derived antibodies and major urinary and kidney diseases.We conducted a two-sample MR analysis using summary statistics from large-scale Genome-Wide Association Studies (GWAS) to assess associations between 46 pathogen-specific antibodies and seven urinary system diseases. We utilized robust statistical methods, including inverse variance weighting, to ascertain causal effects while controlling for potential confounders.Significant associations were identified between several pathogen-specific antibodies and disease risk. Notably, Epstein-Barr virus (EBNA-1) antibody levels were inversely associated with glomerulonephritis and nephrotic syndrome, indicating a potential protective effect. Conversely, Anti-Merkel cell polyomavirus IgG seropositivity was linked to increased risks of CKD and glomerulonephritis. Additionally, immune-mediated mechanisms were highlighted, with certain antibodies exhibiting dual roles as risk factors or protective agents.This study underscores the complex role of pathogen antibodies in the pathogenesis of kidney and urinary tract diseases, revealing significant implications for future research and potential therapeutic strategies. The findings advocate for further investigation into specific pathogen interactions with the immune system, aiming to inform targeted interventions.

Severe dengue often presents as shock syndrome with enhanced vascular permeability and plasma leakage into tissue spaces. In vitro studies have documented the role of Src family kinases (SFKs) and RhoA-kinases (ROCK) in dengue virus serotype 2 (DENV2)-induced endothelial permeability. Here, we show that the FDA-approved SFK inhibitors Bosutinib, Vandetanib and Ponatinib, as well as the ROCK inhibitors, Netarsudil and Ripasudil significantly inhibit DENV2-induced endothelial permeability. In cultured telomerase immortalized human microvascular endothelial cells (HMEC-1), treatment with these inhibitors reduced the phosphorylation of VE-Cadherin, Src and myosin light chain 2 (MLC2) proteins that were upregulated during DENV2 infection. It also prevented the loss of VE-Cadherin from the inter-endothelial cell junctions induced by viral infection. In in-vivo studies using DENV2-infected AG129 IFN receptor-α/β/γ deficient mice, ponatinib, when administered 24 h post-infection onwards, demonstrated significant benefits in improving body weight, clinical outcomes, and survival rates. While all virus-infected, untreated mice died by day-10 post-infection, 80% of the ponatinib-treated mice survived, and approximately 60% were still alive at the end of the 15-day observation period. The treatment also significantly reduced disease severity factors such as vascular leakage, thrombocytopenia; mRNA transcript levels of proinflammatory cytokines such as IL-1β and TNF-α; and restored liver function. Comparable effects were observed even when ponatinib treatment was initiated after symptom onset. The results highlight ponatinib as an effective therapeutic option in severe dengue; and also a similar potential for other FDA- approved SFK and ROCK inhibitors.

One of the most common hospital-acquired infections is caused by toxigenic Clostridioides difficile. Although C. difficile ST37 only produces a functional toxin B, it causes disease as severe as that caused by hypervirulent ST1. We aim to compare the differences in virulence and drug resistance between ST37 and ST1 isolates. We conducted whole-genome sequencing on ST37 and ST1 isolates, analyzing their type-specific genes, and the distribution and mutation of genes related to virulence and antibiotic resistance. We compared the in vitro virulence-related phenotypes of ST37 and ST1 isolates, including: TcdB concentration, number of spores formed, aggregation rate, biofilm formation, swimming diameter in semi-solid medium, motility diameter on the surface of solid medium, and their resistance to 14 CDI-related antibiotics. We detected 4 ST37-specific genes related to adherence, including lytC, cbpA, CD3246, and srtB. We detected 97 virulence-related genes in ST37 isolates that exhibit genomic differences compared to ST1. ST37 isolates showed increased aggregation, biofilm formation, and surface motility compared to ST1 in vitro. Chloramphenicol resistance gene catQ and tetracycline resistance gene tetM are present in ST37 but absent in ST1 strains. The resistance rates of ST37 to chloramphenicol and tetracycline were 45.4% and 81.8%, respectively, whereas ST1 isolates were sensitive to both antibiotics. ST1 was more resistant to rifaximin than ST37. ST37 isolates showed stronger aggregation, biofilm formation and surface motility, and had higher resistance rates to chloramphenicol and tetracycline. ST1 isolates showed stronger ability to produce toxin and sporulation, and was highly resistant to rifaximin.