Infection and Immunity最新文献

Combating multidrug-resistant Acinetobacter baumannii is considered a priority by the World Health Organization. Virulence mechanisms, such as biofilm formation, multidrug resistance, and high adherence to both biotic and abiotic surfaces, underscore the urgency of exploring approaches to control this pathogen. The search for new antibiotic compounds and alternative strategies like immunotherapies and vaccination offers potential solutions to address this pressing health concern. In this context, adhesins play a crucial role in the pathogenicity and virulence of A. baumannii, making them potential targets for therapeutic interventions. To address this, we conducted a systematic review of A. baumannii adhesin research from the last decade (2013-2023). We reviewed 24 papers: 6 utilizing reverse vaccinology bioinformatic tools to predict adhesin targets for vaccine construction, 17 employing DNA recombinant techniques for in vivo active and passive immunization or in vitro antibody-mediated therapy assays, and 1 paper exploring the impact of pyrogallol therapy on A. baumannii virulence mechanisms. Our review identified over 20 potential targets with significant findings. We screened and summarized these targets to aid in further exploration of therapies and prevention.

Bacteria exhibit distinct behaviors in laboratory settings compared to infection environments. The presence of host cells induces changes in bacterial activity, while pathogens trigger immune responses that shape the microenvironment. Studying infection dynamics by microscopy, cytokine screening, and dual RNA sequencing in an air-liquid interface model, we found that prolonged Pseudomonas aeruginosa colonization of airway epithelium led to a pro-inflammatory response, consistent across P. aeruginosa strains, despite differences in the dynamics of this response. Concurrently, P. aeruginosa formed non-attached aggregates on the apical side of the cell layer and upregulated genes involved in biofilm formation and virulence. Notably, there was remarkable resemblance between the P. aeruginosa transcriptional profile in our model and that previously reported upon host cell contact. Developing a platform that replicates host microenvironments is vital not only for gaining deeper insights into the interplay between host and pathogen but also for evaluating therapeutic strategies in conditions that closely mirror clinical environments.

The lack of effective adaptive immunity against Chlamydia trachomatis leads to chronic or repeated infection and serious disease sequelae. Dendritic cells (DCs) are professional antigen-presenting cells that are crucial for the activation of T cells during C. trachomatis infection. cDC1s and cDC2s are the two main DC subsets responsible for T cell priming, but little is known about how C. trachomatis affects their ability to prime T cells. Using a mouse model of infection, we found that C. trachomatis uptake reduced the viability of cDC1s and cDC2s both in vitro and in vivo, with cDC1s experiencing more death. DC death was mainly due to apoptosis and is alleviated in Casp3/7 or Bak1/Bax knockout DCs. In addition, we observed that C. trachomatis-specific CD8+ T cells were preferentially activated by cDC1s. Reduction in DC viability by C. trachomatis impaired the ability of infected DCs to activate T cells upon co-culture, although in the case of CD8+ T cell priming, controlling for viability was insufficient to fully rescue the defect. RNA sequencing of DCs from infected mice showed upregulation of cell death pathways, supporting our observations of DC death caused by C. trachomatis. Finally, we validated our findings with human DCs in vitro, observing C. trachomatis-induced cell death. These results indicate that C. trachomatis may evade the adaptive immune system by directly inducing cell death in DCs.

Salmonella infections pose significant public health challenges worldwide. The diversity of Salmonella strains, particularly those isolated from environmental and clinical sources, necessitates innovative approaches to prevention and treatment. Previous research has shown that small extracellular vesicles (sEVs) produced by macrophages during Salmonella Typhimurium infection can induce robust immune responses when used as a vaccine, offering complete protection in systemic infection models. In this study, we isolated 120 Salmonella strains from qPCR invA-positive wastewater samples collected in Gainesville, FL. These strains underwent enrichment, selection, and biochemical confirmation, followed by serotyping and whole genome sequencing. Two isolates, Salmonella enterica subsp. diarizonae (Diarizonae) and S. enterica serovar Enteritidis, were selected for further analysis based on community prevalence and clinical severity. We also assessed the ability of sEVs produced by S. Typhimurium-infected macrophages to induce immune responses against these heterologous and circulating strains in mice. Immunization with sEVs induced robust antigen-specific SIgA and IgG responses against S. Typhimurium, Enteritidis, and Diarizonae, with high titers observed in sera and fecal samples. Proteomic analysis revealed differential expression of proteins in these strains, including antigenic proteins present in sEVs such as OmpA, FliC, or OmpD. Moreover, this study highlights the role of wastewater-based epidemiology (WBE) as a tool for environmental surveillance, offering a complementary perspective on Salmonella dynamics within a population. Integrating WBE with traditional surveillance methods, along with the promising results of sEV-based vaccination, provides a pragmatic strategy for developing effective preventative measures against Salmonella infections, addressing the diversity of non-typhoidal Salmonella strains.

Acinetobacter baumannii is an opportunistic human pathogen that acquires nutrient metals from the vertebrate host amid infection. During zinc (Zn) scarcity, A. baumannii upregulates the expression of the predicted Zn metallochaperone, zigA. Loss of zigA compromises fitness during Zn deficiency, highlighting its role in this condition. To assess the contribution of ZigA to Zn-deficient A. baumannii, a multiparallel transposon sequencing and genetic interaction mapping approach was used. Transposon insertions in A1S_3027, encoding a predicted soluble lytic transglycosylase that tailors the bacterial cell wall, were enriched in the Zn-starved ΔzigA transposon library. Based on previous studies as well as structural and sequence homology, we designated A1S_3027 as soluble lytic transglycosylase B (SltB). Further analyses revealed that inactivating sltB rescued ΔzigA fitness defects during Zn starvation. An A. baumannii ΔzigAΔsltB mutant demonstrated altered cell envelope structures and increased cellular permeability, highlighting the roles of ZigA and SltB in maintaining cell envelope integrity. Furthermore, these mutants exhibited heightened resistance to β-lactam antibiotics and other cell wall-targeting agents. Alterations in cell envelope integrity in the ΔzigAΔsltB mutant improved fitness in a murine pneumonia infection model, emphasizing the contribution of ZigA and SltB to A. baumannii pathogenesis. This study elucidates how functional interactions between ZigA and SltB modulate cell envelope integrity and pathogenesis of A. baumannii during Zn depletion. These findings reveal an interplay between metal homeostasis and cell envelope integrity, offering insights into how A. baumannii ZigA contributes to these critical cellular processes.

The virulence plasmid of the obligate intracellular bacterium Chlamydia encodes eight proteins. Among these, Pgp3 is crucial for pathogenicity, and Pgp4 functions as a transcriptional regulator of both plasmid and chromosomal genes. The remaining proteins, Pgp1, Pgp5, Pgp6, Pgp7, and Pgp8, are predicted to play various roles in plasmid replication or maintenance based on their amino acid sequences. However, the function of Pgp2 remains unknown, even though it is required for transformation. In this study, we utilized AlphaFold to predict the three-dimensional (3-D) structure of Chlamydia trachomatis Pgp2. Despite a lack of apparent sequence homology, the AlphaFold structure exhibited high similarity to experimentally determined structures of several plasmid replication initiators. Notably, Pgp2 features a unique β-hairpin motif near the DNA-binding domain, absent in other plasmid replication initiators with overall 3-D structures similar to Pgp2. This β-hairpin motif is also present in AlphaFold models of Pgp2s across all 13 Chlamydia species. To assess its significance, we engineered a plasmid lacking the 11 amino acids constituting the β-hairpin motif in C. trachomatis Pgp2. Although this deletion did not alter the overall structure of Pgp2, the mutated plasmid failed to transform plasmid-free C. trachomatis. These findings reveal that Pgp2 is a plasmid replication initiator, with the β-hairpin motif playing a critical role in binding to its cognate iteron sequences in the replication origin of the chlamydial plasmid.

Widespread use of fluconazole has led to the emergence of fluconazole-resistant (FR) Candida spp. causing challenges in clinical treatment. Iron, an essential nutrient, affects the levels of ergosterol (a fluconazole target) in fungal membranes. Our lab-generated FR strain (fluconazole minimum inhibitory concentration [MIC] >125 µg/mL) showed a twofold lower MIC (4.66 µg/mL) for the iron chelator deferasirox (DFX), compared to its patent strain CAI4 (DFX MIC 9.34 µg/mL), suggesting a greater sensitivity to iron chelation. A sublethal dose of DFX (2.33 µg/mL) was able to effectively synergize with 125 µg/mL fluconazole to kill the FR strain. Iron estimation revealed significantly enhanced intracellular iron accumulation in the FR strain compared to CAI4. Expression of iron-uptake genes (FRP1, FRE10, and RBT5) was also significantly upregulated in the FR strain, particularly under high iron. FR strain also showed an increase in the levels of cellular ergosterol, along with an increase in the expression of ergosterol biosynthesis genes (ERG11 and ERG9), compared to CAI4, under both low and high iron. The strain further showed increased β-glucan levels and exposure. Additionally, FR strain showed significantly higher survival in high-iron mice compared to low-iron mice, during fluconazole treatment. Finally, we observed a synergistic fungicidal response between 2.33 µg/mL DFX and 125 µg/mL fluconazole, for FR clinical strains. Overall, this suggests that FR C. albicans actively uptakes more iron to maintain cellular conditions needed to support its resistance against fluconazole; and that DFX alone or in conjugation with fluconazole has the potential to overcome fluconazole drug resistance.