Infection and Immunity最新文献

Ticks are obligate hematophagous parasites and pathogen vectors responsible for morbidity and mortality worldwide. Ixodes scapularis is a vector for at least seven pathogens relevant to human and animal health, including the Lyme disease microbe, Borrelia burgdorferi, and the causative agent of anaplasmosis, Anaplasma phagocytophilum. Tick-host interactions affect the maintenance of tick-borne pathogens in a population. Here, we report that repeated I. scapularis larval infestations on the wild host species Peromyscus leucopus lead to immune-mediated rejection of the tick, a phenomenon termed acquired tick resistance (ATR). On previously infested mice, we observed that larval feeding success was reduced by over 50%, and fed larvae had decreased blood meal weights compared to larvae fed on naïve hosts. Over sequential infestations, mice exhibited increasingly severe inflammation at tick bite sites characterized by an influx of basophils, eosinophils, neutrophils, and T lymphocytes. Larvae fed on sensitized mice ingested higher quantities of host leukocytes when compared to ticks fed on naïve hosts, which rarely ingested nucleated cells. When challenged with B. burgdorferi or A. phagocytophilum, larvae fed on sensitized mice ingested more bacteria. Altogether, we demonstrate that reservoir host species develop ATR against larval I. scapularis, which reduces tick feeding success and affects pathogen ingestion by larvae. These results indicate that ATR could impact Ixodes population dynamics, prevalence of infected ticks, and pathogen circulation in the wild.

Chlamydiaceae is a family of obligate intracellular bacteria that infect a wide range of human and animal hosts. Chlamydia muridarum is a murine-specific species that has been leveraged as an efficacious model of disease mediated by human-specific Chlamydia trachomatis. Genes within the plasticity zone, a region of the chromosome with increased genetic variation across species and serovars, are speculated to contribute to species-specific pathogenesis. C. muridarum expresses three homologous proteins (TC0437-0439) that show similarity to large clostridial cytotoxins. The putative chlamydial cytotoxins have been proposed to mediate immediate toxicity in highly infected epithelial cells by interfering with actin polymerization. We utilized FRAEM mutagenesis to delete all three putative cytotoxins (tc0437-0439). The null strain retained immediate cytotoxicity but exhibited decreased invasion efficiency in tissue culture. During murine infections of the female genital tract, the absence of the putative cytotoxins caused decreased oviduct pathology and did not impact bacterial burden in the upper genital tract. These results indicate that the putative cytotoxins contribute to infection at the cellular level and in the female genital tract of mice.

In a healthy lung, the airway epithelium regulates glucose transport to maintain low glucose concentrations in the airway surface liquid (ASL). However, hyperglycemia and chronic lung diseases, such as cystic fibrosis (CF), can result in increased glucose in bronchial aspirates. People with CF are also at increased risk of lung infections caused by bacterial pathogens, including methicillin-resistant Staphylococcus aureus. Yet, it is not known how increased airway glucose availability affects bacteria in chronic CF lung infections or impacts treatment outcomes. To model the CF airways, we cultured immortalized CF (CFBE41o-) and non-CF (16HBE) human bronchial epithelial cells at the air-liquid interface (ALI). Glucose concentrations in the basolateral media were maintained at 5.5 or 12.5 mM to mimic a normal and hyperglycemic milieu, respectively. We found that glucose concentrations in the ASL of ALI cultures maintained in normal or high glucose mimicked levels measured in breath condensate assays from people with CF and hyperglycemia. Additionally, we found hyperglycemia increased S. aureus aggregation and antibiotic resistance during infection of cells maintained in high glucose compared to normal glucose conditions. Heightened antibiotic resistance was not observed during in vitro growth with elevated glucose. Limiting glucose with 2-deoxyglucose both decreased aggregation and reduced antibiotic resistance back to levels comparable to non-hyperglycemic conditions. These data indicate that hyperglycemia alters S. aureus growth during infection and may reduce efficacy of antibiotic treatment. Glucose restriction is a potential option that could be explored to limit bacterial growth and improve treatment outcomes in chronic airway infections.

Type I interferons (IFNs) play complex roles during bacterial infections. We previously found that type I IFNs were induced in Bordetella pertussis-infected adult mice but not in infant mice, a potentially relevant clinical dichotomy, since pertussis can be fatal in human infants. We investigated the role of type I IFNs and their cross-regulation with type III IFNs (IFN-λ) in B. pertussis infection across developmental stages. In contrast to global IFNAR1 knockout adult mice, in which lung inflammation was equivalent to that in wild-type mice, myeloid cell-specific deficiency of the type I IFN receptor protein IFNAR1 (LysM^CreIFNAR1^fl/fl) resulted in significantly reduced lung inflammation and pro-inflammatory cytokine production, despite elevated pulmonary IFN-λ levels. Mechanistically, we found that, in contrast to WT macrophages, IFNAR1-deficient macrophages produced IFN-λ in response to B. pertussis or pertussis toxin, a process dependent on the G protein-coupled receptor lysophosphatidic acid receptor 1 (LPAR1). IFNAR1 deficiency did not affect type I IFN expression or killing capacity by macrophages and neutrophils. In striking contrast to WT infant mice, which developed resistance to lethal B. pertussis infection by postnatal day 10 (P10), LysM^CreIFNAR1^fl/fl infant mice remained highly susceptible to lethal infection through P21, exhibiting increased lung bacterial burden and inflammation, as well as increased bacterial dissemination compared to WT infant mice. These findings reveal a critical age- and cell-specific interplay between type I and III IFNs during B. pertussis infection and highlight a novel LPAR1-dependent pathway for IFN-λ induction in the absence of type I IFN signaling.

Staphylococcus aureus is an important cause of human infections globally and ranks among the top causes of death by bacteria. In addition, the microbe is notorious for developing resistance to antibiotics. Methicillin-resistant S. aureus is endemic in healthcare facilities and the community in many regions of the world. Although our understanding of S. aureus as a human commensal organism and opportunistic pathogen remains incomplete, the use of genomics and transcriptomics approaches for S. aureus research has advanced this knowledge significantly over the past 20 years. This article reviews genomics approaches, with special emphasis on transcriptomics and single-cell sequencing, used to study S. aureus, past and present, and highlights selected discoveries made with these methods and new applications moving forward.

Listeria monocytogenes is a facultative intracellular pathogen that has garnered attention as a potential cancer therapeutic due to its ability to induce robust cell-mediated immunity. To ensure safe clinical administration, deletion of certain genes, such as actA, has been used to attenuate L. monocytogenes-based vaccine strains while preserving immunogenicity. Here we explored the potential inclusion of a purA gene deletion to enhance the development of L. monocytogenes-based immunotherapy. The purA gene encodes adenylosuccinate synthetase, which catalyzes the conversion of inosine monophosphate to adenosine monophosphate (AMP), a critical step in the de novo biosynthesis of purines. Since nucleotide biosynthesis is critical for the survival and pathogenesis of many bacterial pathogens, we examined the requirements of L. monocytogenes AMP synthesis in tissue culture and animal infection models. The purA mutants were able to escape from phagosomes of bone marrow-derived macrophages but were highly defective for subsequent growth in the host cell cytosol. In contrast to wild-type bacteria, the mutants did not grow in human serum or sheep blood. In intravenously infected mice, purA mutants were highly attenuated, similar to actA mutants, but displayed distinct growth kinetics during the course of infection. Remarkably, the purA mutants exhibited different localization patterns across splenic immune cells and elicited a more potent CD8⁺ T-cell response compared to actA mutants. These results underscore the essentiality of AMP biosynthesis for L. monocytogenes pathogenesis and provide new avenues for developing safe L. monocytogenes-based vaccines and therapeutics.

Klebsiella pneumoniae (Kp) is a major human pathogen causing hospital-acquired and community-acquired infections with emerging hypervirulent strains (hvKp) posing a significant threat due to its ability to cause severe invasive infections in healthy individuals. In addition to antimicrobial resistance, virulence factors including capsule production, biofilm formation, and iron acquisition systems are critical for hvKp pathogenesis. In this study, we investigated how resistance-nodulation-division (RND)-family efflux systems contribute to antimicrobial resistance and virulence in hvKp strain KPPR1 using the RND-specific inhibitor phenyl-arginine β-naphthylamide (PAβN). We found that PAβN treatment rendered KPPR1 more susceptible to multiple antibiotics while simultaneously attenuating virulence factor production. PAβN significantly reduced capsule biosynthetic gene expression, resulting in decreased uronic acid levels, hypermucoviscosity, and biofilm formation. PAβN also impaired growth under iron-limited conditions, suggesting RND-mediated efflux contributes to iron acquisition. PAβN-dependent virulence attenuation was demonstrated through reduced KPPR1 adherence to cultured intestinal enterocytes and decreased pathogenicity in the Galleria mellonella infection model compared to untreated controls. Collectively, these results demonstrate that RND-mediated efflux is critical for both antimicrobial resistance and virulence in hvKp strain KPPR1. Our findings establish RND efflux inhibitors as promising dual-target therapeutics that can simultaneously combat antibiotic resistance and attenuate virulence in hvKp infections.

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.