Infection and Immunity最新文献

Lymphotoxin β receptor (LTβR/TNFRSF3) signaling plays a crucial role in immune defense. Notably, LTβR-deficient (LTβR^-/-) mice exhibit severe defects in innate and adaptive immunity against various pathogens and succumb to Toxoplasma gondii infection. Here, we investigated the bone marrow (BM) and peritoneal cavity (PerC) compartments of LTβR^-/- mice during T. gondii infection, demonstrating perturbed B-cell and T-cell subpopulations in the absence of LTβR signaling. T. gondii infection disrupted BM lymphopoiesis, depleting early and mature B cells in WT mice, whereas mature B cells remained present in LTβR^-/- BM. LTβR^-/- BM also exhibited reduced MHCII⁺ monocytes and a plasma cell compartment skewed toward IgM⁺ rather than IgA⁺ cells. In addition, BM Tcell subsets were altered, exhibiting decreased double-negative (CD4^-/CD8^-) and increased CD4⁺ and CD8⁺ T-cell frequencies. Analysis of the BM transcriptome revealed diminished interferon responses but an upregulated TNFα-NF-κB signaling signature in uninfected and infected LTβR^-/- mice, potentially compensating for the absence of LTβR signaling. LTβR^-/- mice displayed an altered B-1a to B-1b ratio and a predominant presence of neutrophils in the PerC. In summary, we identified novel immunological alterations in the BM and PerC compartments of LTβR^-/- mice, which suggest new roles for LTβR signaling in B- and T-cell homeostasis, migration, and pathogen defense.

Contagious bovine pleuropneumonia (CBPP), caused by Mycoplasma mycoides subsp. mycoides (Mmm), is a devastating cattle disease with high morbidity and mortality, threatening cattle productivity in Sub-Saharan Africa and potentially in parts of Asia. Cross-border livestock trade increases the risk of CBPP introduction or reintroduction. Current vaccines were developed from attenuated Mmm strains in the last century and face limitations regarding animal welfare, immunity duration, and adverse reactions, necessitating new vaccine strategies. Subunit vaccines offer a promising alternative, but identifying effective antigens is critical. Given the key role of cellular immunity in CBPP control, we focused on antigen identification that elicits a host cellular immune response. This study explores antigen candidates based on Ben-181, a vaccine that successfully eradicated CBPP in China. Ben-181 specifically induces interferon-γ (IFN-γ)-dependent IRG-47 expression, and IFN-γ correlates with cellular immune responses. We propose IRG-47 as a potential marker for Mmm antigen screening. Comparative genomic analysis between Ben-181 and the non-immunoprotective strain Ben-468 identified 35 proteins potentially linked to IRG-47 expression. Further screening revealed Mmm604, Mmm605, and Mmm606 as inducers of IRG-47 release. Intranasal immunization with these proteins in mice enhanced splenic lymphocyte proliferation, CD8 +T cell activation, a mixed Th1/Th2/Th17 response, and humoral antibody production. Mmm604 and Mmm606 also trigger mucosal antibody responses in mice. These proteins effectively stimulate cellular and humoral responses, making them promising candidates for Mmm subunit vaccine development. Our study highlights the potential of IRG-47 in Mmm antigen screening.

The stomach bacterium Helicobacter pylori is estimated to infect half of the world's population, and the health implications are affected by the age at infection. Neonatal H. pylori infection of mice is a relevant model to investigate metabolic and immunological effects. We performed an explorative study at the dynamic 1st month of life to compare the composition of the gastrointestinal tract microbiome and stomach gene expression of mice neonatally infected with H. pylori with that of uninfected mice. We found that H. pylori was present only in the stomach, and that H. pylori loads increase with age from 1 week after infection and onward, especially after weaning. Stomach and colon microbiome composition was strikingly similar between sites at the same sampling time but changed significantly over 1 week, with increased diversity at both sites. Despite the fact that the relative abundance of H. pylori in the stomach was low and never exceeded 3%, the composition and alpha diversity of the gastrointestinal microbiome was significantly affected by infection. In a pathway enrichment analysis, we found that stomach gene expression related to the extracellular matrix, muscle contraction, and metabolism was affected by infection. Expression of these key processes was, in infected mice, shifted away from that of control mice toward that of all mice sampled the subsequent week, which we speculate represents accelerated development in infected mice.

Cryptosporidium infects the intestine in a wide variety of vertebrates, and intestinal epithelial cells provide the first line of defense against Cryptosporidium infection. Interferon gamma (IFN-γ) from immune cells infiltrated at the site of infection plays a key role in the epithelial cell-intrinsic defense. Nevertheless, the success of the parasite is the result of its ability to evade the host immune responses. Increasing evidence suggests that long noncoding RNAs (lncRNA) participate in host-pathogen interactions, but the underlying mechanisms are not fully understood. We previously demonstrated that lncRNA U90926 is upregulated in response to infection but appears to be playing a pro-parasitic role given its ability to repress transcription of defense genes and aid the parasite during infection. We show here that inhibition of U90926 during Cryptosporidium infection increased expressions of Irgm2, Igtp, and Iigp1, which are known IFN-γ-stimulated genes, in a gene-specific manner. Depletion of U90926 results in an increase in histone modifications associated with gene transactivation in the promoter regions of Irgm2, Igtp, and Ilgp1, suggesting U90926 is regulating defense gene expression via epigenetic modifications. U90926 can interact with Ehmt2, a potent euchromatic methyltransferase, in the promoter region of these defense genes to alter histone modifications. Knockout of U90926 enhances IFN-γ-mediated inhibition of Cryptosporidium infection, suggesting that U90926 may modulate IFN-γ-induced gene expression to suppress cell-intrinsic antimicrobial defenses. The data highlight a strategy Cryptosporidium has evolved to hijack host cell lncRNA machinery to suppress the immune response and allow for a robust infection.

Chronic infections with Pseudomonas aeruginosa are a major contributor of lung decline in persons with cystic fibrosis (pwCF). P. aeruginosa establishes life-long infections in the CF airway by utilizing various adaptation strategies to persist, including altering the expression of metabolic genes to acquire nutrients that are abundant in the CF airway. Glycerol, which is readily available in the airway, is imported and metabolized by genes in the glp regulon, which is under the control of the GlpR repressor. Previously, it has been shown that the loss of GlpR results in increased biofilm development in a CF-adapted isolate of P. aeruginosa compared to a wound isolate. Based on the increased biofilm phenotype previously observed and because biofilms are associated with reduced antibiotic susceptibility, we questioned whether GlpR plays a role in mediating antibiotic susceptibility of P. aeruginosa. In this report, we show that loss of GlpR reduces tobramycin susceptibility of a CF-adapted isolate in synthetic sputum and in airway epithelial cell and Drosophila melanogaster colonization models. Furthermore, transcriptomics analysis revealed that CF-adapted mutants of glpR overexpress genes involved in multidrug resistance and chronic infection phenotypes such as alginate. In summary, our study illustrates that the activation of the glycerol (glp) regulon may promote P. aeruginosa persistence in the CF airway.

Clostridioides difficile is a spore-forming, Gram-positive bacterium that can cause infections in subjects with weakened immune system or following antibiotic treatment. These infections may lead to pseudomembranous colitis and antibiotic-associated diarrhea in humans. As such, C. difficile is a major cause of nosocomial illness worldwide. Major virulence factors of the bacterium are the large clostridium toxins A (TcdA) and B (TcdB)-high molecular mass proteins with intrinsic glucosyltransferase activity. Toxins bind to the intestinal epithelium and undergo endocytosis by the epithelial cells, followed by a conformational change triggered by the low pH of early endosomes. This conformational change leads to the exposure of hydrophobic segments, followed by membrane insertion, formation of pores, and translocation of the glucosyltransferase domain into the cellular cytoplasm. Once in the cytoplasm, the glucosyltransferase domain inactivates small GTPases of the Rho family of proteins, leading to the disruption of the cytoskeleton. In the current work, we describe the discovery and characterization of a panel of neutralizing mouse monoclonal antibodies capable of interfering with several steps of cellular intoxication by the toxins. The antibodies were produced using hybridoma technology. Neutralizing activity of the antibodies was confirmed using toxin neutralization assays, and functional assays were used to identify specific neutralization mechanisms. Binding epitopes of the antibodies were identified by hydrogen-deuterium exchange mass spectrometry and confirmed through negative-stain and cryo-electron microscopy. Together, our results show that full-length toxins and/or genetically- and chemically-modified toxoids can induce a wide spectrum of antibodies capable of neutralizing the toxins via a variety of mechanisms.

Chronic infections involving bacterial biofilms are a major clinical challenge due to the ability of biofilm to resist antimicrobial treatments and host immune responses. The resulting persistent infections are often accompanied by collateral damage mainly executed by activated components of the innate immune system in response to the infectious biofilm. The innate immune system responds to the recognition of pathogen-associated molecular patterns (PAMPs), which are broadly expressed by both planktonic and biofilm-forming bacteria. However, the expression of special PAMPs in association with biofilms remains poorly defined. Here, we review prior studies that provide experimental evidence of the existence of immune-activating molecular patterns that are expressed at immunostimulatory levels in biofilms but not in planktonic bacteria. Accordingly, we introduce the concept of biofilm-associated molecular patterns (BAMPs) as a subset of PAMPs that are expressed in biofilms. Identifying BAMPs and elucidating their role in innate immune activation may inform the development of targeted therapies to reduce collateral tissue damage in biofilm-associated infections.

Mobile genetic elements play an essential part in the infectious process of major pathogens, yet the role of prophage dynamics in Staphylococcus aureus pathogenesis is still not well understood. Here, we studied the impact of the Φ13 hlb-converting prophage, whose integration inactivates the hlb β-toxin gene, on staphylococcal pathogenesis. We showed that prophage Φ13 is lost in approximately half the bacterial population during the course of infection. Inactivation of the Φ13 int recombinase gene, essential for insertion/excision, locked the prophage in the bacterial chromosome, leading to a significant loss of virulence in a murine systemic infection model. In contrast, the non-lysogen strain (ΔΦ13), where the hlb beta-hemolysin gene is reconstituted, displayed strongly increased virulence. Accordingly, histopathological analyses revealed more severe nephritis in mice infected with bacteria lacking prophage Φ13 (ΔΦ13), compared to infection with the parental strain. Infection with the ∆int mutant, where beta-hemolysin production is abolished, led to the least severe renal lesions. Cytokine induction in a human neutrophil model showed significantly increased IL-6 expression following infection with the beta-hemolysin producing strain (ΔΦ13). Our results indicate that timely in vivo excision of the Φ13 prophage is essential for progression of the S. aureus infectious process: early excision leads to rapid host death, whereas the inability to excise the prophage significantly reduces staphylococcal virulence.IMPORTANCEThis study highlights prophage Φ13 excision as a critical factor in Staphylococcus aureus pathogenesis, influencing infection outcomes by balancing rapid host killing with reduced bacterial virulence. This mechanism may represent a bet-hedging strategy in genetic regulation, resulting in a mixed bacterial population capable of rapidly switching between two processes: bacterial colonization and host damage. Unraveling this dynamic opens new possibilities for developing targeted therapies to disrupt or modulate prophage activity, offering a novel approach to mitigating S. aureus infections.

Chlamydia trachomatis (CT) infection can lead to pelvic inflammatory disease, infertility, and other reproductive sequelae when it ascends to the upper genital tract. Factors including chlamydial burden, coinfection with other sexually transmitted bacterial pathogens, and oral contraceptive use influence risk for upper genital tract spread. Cervicovaginal microbiome composition influences CT susceptibility, and we investigated if it contributes to spread by analyzing amplicon sequence variants (ASVs) derived from the V4 region of 16S rRNA genes in vaginal samples collected from women at high risk for CT infection and for whom endometrial infection had been determined. Participants were classified as CT negative (CT-, n = 70), CT positive at the cervix (Endo-, n = 79), or CT positive at both cervix and endometrium (Endo+, n = 68). Although we were unable to identify many significant differences between CT-infected and -uninfected women, differences in abundance of ASVs representing Lactobacillus iners and Lactobacillus crispatus subspecies but not dominant lactobacilli were detected. Thirteen informative ASVs predicted endometrial chlamydial infection (area under the curve = 0.72), with CT ASV abundance emerging as a key predictor. We also observed a positive correlation between levels of cervically secreted cytokines previously associated with CT ascension and abundance of the informative ASVs. Our findings suggest that vaginal microbial community members may influence chlamydial spread directly by nutrient limitation and/or disrupting endocervical epithelial integrity and indirectly by modulating proinflammatory signaling and/or homeostasis of adaptive immunity. Further investigation of these predictive microbial factors may lead to cervicovaginal microbiome biomarkers useful for identifying women at increased risk for disease.

Preterm infants are highly susceptible to bacterial infections and inflammatory diseases. These vulnerabilities arise from disruptions in gut microbiome structure and function, immune system immaturity, and underdeveloped organ systems. In this review, we explore the role of the gut microbiome in neonatal health. With a specific focus on preterm infants, we outline how microbiome disruption contributes to negative clinical outcomes. First, we provide an overview of infant gut microbiome development, highlighting key factors that influence its trajectory. Next, we examine the interplay between the infant gut microbiome and the development of systemic and intestinal immune systems, with emphasis on how microbiome perturbations related to preterm birth alter host-microbiome interactions and the overall immune landscape. We then discuss the role of altered gut composition in disease states common to preterm infants, such as sepsis, bacterial infections, and necrotizing enterocolitis. Finally, we discuss current and future diagnostics and treatments and offer our perspective on future research to untangle the host-microbiome interface in early life.