Virulence最新文献

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.

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.

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.

We studied the viromes of three dominant mosquito species in Wenzhou, a coastal city in Zhejiang Province, using metavirome sequencing, with 18 viral families identified. Viral sequences were verified by RT-PCR. The JEV E gene was most closely related to the 1988 Korean strain. DENV sequences were most closely related to the 1997 Australian strain. CHIKV-E1-1 was most closely related to the 1983 Senegal strain and belonged to West African genotype CHIKV. Remarkably, this is the first time that a West African genotype of CHIKV has been detected in Zhejiang Province. Mutations in the CHIKV-E1-1 protein A226V may increase infectivity in Ae. albopictus. Three non-conservative mutations of CHIKV-E1-1 (D45H, D70H and V290D) may have an impact on the function. In conclusion, our study reveals the diversity of mosquito-borne viruses and potential emerging outbreaks in the southeast coastal region of China, providing new perspectives for mining the ecological characterization of other important arboviruses.

Porcine deltacoronavirus (PDCoV) is increasingly prevalent in newborn piglets with diarrhea. With the development of research on the virus and the feasibility of PDCoV cross-species transmission, the biosafety and the development of pig industry have been greatly affected. In this study, a PDCoV strain CH/LNFX/2022 was isolated from diarrheal newborn piglets at a farm in China. A genome-wide based phylogenetic analysis suggests that 97.5% to 99.2% homology existed in the whole genomes of other strains. Five amino acid mutations are seen for the first time in the S protein. By constructing 3D models, it was found that the S1-NTD/CTD and S2-HR-C regions produced structural alterations. Protein functional analysis showed that the structural changes of the three regions changed the epitope of S protein, the O-GalNAc glycosylation site and the 3C-like protease cleavage site. In addition, oral administration of 10⁷ TCID₅₀ CH/LNFX/2022 to newborn piglets successfully reproduced obvious clinical signs of piglets, such as diarrhea and dehydration. Meanwhile, PDCoV antigen was detected by immunofluorescence in the small intestine, and microscopic lesions and intestinal mucosal barrier destruction were detected by histological observation and scanning electron microscopy. Our study confirmed that porcine coronavirus strains increased pathogenicity through evolution, damaged the intestinal barrier of newborn piglets, and caused diarrhea in pigs. This study provided the candidate strains and theoretical basis for establishing the prevention and control system of vaccine and diagnostic methods for piglet diarrhea.

Actinobacillus pleuropneumoniae (APP) is a significant pathogen in the swine industry, leading to substantial economic losses and highlighting the need for effective vaccines. This study evaluates the potential of APP-derived extracellular vesicles (APP-EVs) as a vaccine candidate compared to the commercial Coglapix vaccine. APP-EVs, isolated using tangential flow filtration (TFF) and cushioned ultracentrifugation, exhibited an average size of 105 nm and a zeta potential of -17.4 mV. These EVs demonstrated stability under external stressors, such as pH changes and enzymatic exposure and were found to contain 86 major metabolites. Additionally, APP-EVs induced dendritic cell (DC) maturation in a Toll-like receptor 4 (TLR4)-dependent manner without cytotoxicity. APP-EVs predominantly elicited Th1-mediated IgG responses in immunized mice without significant liver and kidney toxicity. Contrarily, unlike Coglapix, which induced stronger Th2-mediated responses and notable toxicity. In addition, APP-EVs triggered APP-specific Th1, Th17, and cytotoxic T lymphocyte (CTL) responses and promoted the activation of multifunctional T-cells. Notably, APP-EV immunization enhanced macrophage phagocytosis and improved survival rates in mice challenged with APP infection compared to those treated with Coglapix. These findings suggest that APP-EVs are promising vaccine candidates, capable of inducing potent APP-specific T-cell responses, particularly Th1, Th17, CTL, and multifunctional T-cells, thereby enhancing the protective immune response against APP infection.

Several viruses, including influenza A virus (IAV), encode viral factors to hijack cellular RNA biogenesis processes to direct the degradation of host mRNAs, termed "host shutoff." Host shutoff enables viruses to simultaneously reduce antiviral responses and provides preferential access for viral mRNAs to cellular translation machinery. IAV PA-X is one of these factors that selectively shuts off the global host genes. However, the specific role of PA-X host shutoff activity in viral fitness of IAV remains poorly understood. Herein, we successfully mapped PA-X 100 V as a novel site important for host shutoff of the H7N9 and H5N1 viruses. By analysing the polymorphism of this residue in various subtype viruses, we found that PA-X 100 was highly variable in H7N9 viruses. Structural analysis revealed that 100 V was generally close to the PA-X endonuclease active site, which may account for its host shutoff activity. By generating the corresponding mutant viruses derived from the parental H7N9 virus and the PA-X-deficient H7N9 virus, we determined that PA-X 100 V significantly enhanced viral fitness in mice while diminishing viral virulence in chickens. Mechanistically, PA-X 100 V significantly increased viral polymerase activity and viral replication in mammalian cells. Furthermore, PA-X 100 V highly blunted the global host response in 293T cells, particularly restraining genes involved in energy metabolism and inflammatory response. Collectively, our data provided information about the intricate role of the PA-X host shutoff site in regulating the viral fitness of the H7N9 influenza virus, which furthers our understanding of the complicated pathogenesis of the influenza A virus.

Klebsiella pneumoniae is a gram-negative pathogen that can cause multiple diseases including sepsis, urinary tract infections, and pneumonia. The escalating detections of hypervirulent and antibiotic-resistant isolates are giving rise to growing public concerns. Outer membrane vesicles (OMVs) are spherical vesicles containing bioactive substances including lipopolysaccharides, peptidoglycans, periplasmic and cytoplasmic proteins, and nucleic acids. Emerging studies have reported various roles of OMVs in bacterial virulence, antibiotic resistance, stress adaptation, and host interactions, whereas knowledge on their roles in K. pneumoniae is currently unclear. In this review, we summarized recent progress on the biogenesis, components, and biological function of K. pneumoniae OMVs, the impact and action mechanism in virulence, antibiotic resistance, and host immune response. We also deliberated on the potential of K. pneumoniae OMVs in vaccine development, as diagnostic biomarkers, and as drug nanocarriers. In conclusion, K. pneumoniae OMVs hold great promise in the prevention and control of infectious diseases, which merits further investigation.

The resistance of commonly used clinical antibiotics, such as daptomycin (DAP), has become increasingly serious in the fight against Staphylococcus aureus (S. aureus) infection. It is essential to explore key pathogenicity-driven genes/proteins in bacterial infection and antibiotics resistance, which contributes to develop novel therapeutic strategies against S. aureus infections. The nt5 gene of S. aureus, encoding 5'-nucleotidase (NT5), is nearly unknown for its function in drug resistance and bacterial infection. Herein, to reveal nt5 gene role in drug resistance and infection ability of S. aureus, we performed nt5^C166T gene mutation using a clustered regulatory interspaced short palindromic repeat ribonucleic acid (RNA)-guided base editing system to investigate the lose-of-function of NT5 protein. Subsequent transcriptome sequencing of the mutant strain revealed that nt5 inactivation caused changes in cell membrane integrity and inhibited nucleotide metabolism, suggesting the nt5 gene may be involved in bacterial drug resistance and virulence. The mutant strain exhibited enhanced tolerance to DAP treatment by attenuating cell membrane potential dissipation and slowing deoxyribonucleic acid release. Moreover, the nt5 mutation alleviated abscess degree of mouse kidneys caused by S. aureus infection byreducing the expression of IL-1β, IL-6, and IL-18. The nt5 mutant strain was easily swallowed by host immune cells, resulting in weak bacterial toxicity of the S. aureus mutant in the bacterial infection process. In summary, nt5 gene mutation confers tolerance to DAP and a lower bacterial capacity to form kidney abscesses through phagocytosis of host immune cells, which indicates the targeted inhibition of NT5 protein would offer a potential new therapeutic strategy against S. aureus infection.