Infection Model Research Articles

Universal antibacterial and anti-inflammatory treatment using chitosan-prussian blue nanozyme

Bacterial infections are a growing global public health problem, exacerbated by the widespread and often inappropriate use of antibiotics, leading to the emergence of non-antibiotic pathogens. Herein, we synthesized a chitosan-Prussian blue nanozyme (CS@PB), a non-antibiotic agent, for universal antibacterial and anti-inflammatory treatment of bacterial infections. Confocal microscopy images showed that CS@PB significantly enhanced the physical interaction between chitosan and bacteria, thereby increasing the antibacterial ability. Moreover, these nanozymes exhibited potent antioxidant and anti-inflammatory properties, promoting macrophage polarization toward the M2-like phenotype, reducing oxidative stress, and alleviating inflammation. This dual-action approach effectively accelerates the healing of bacteria-infected inflammatory wounds. The synergistic bactericidal and anti-inflammatory properties of CS@PBs inhibited wound infection and promoted the healing of skin infections in a mouse model. In addition, CS@PB displayed remarkable lung retention and potent bactericidal effects, resulting in significantly improved survival rates in mouse models of acute pulmonary bacterial infections. In conclusion, CS@PBs exhibited exceptional bactericidal capabilities, anti-inflammatory properties, and minimal toxicity, suggesting that they are promising candidates for a new generation of non-antibiotic antimicrobial agents for the treatment of bacterial infections.

Preclinical evaluation of combined therapy with amiodarone and low-dose benznidazole in a mouse model of chronic Trypanosoma cruzi infection

Chagasic chronic cardiomyopathy (CCC) is the primary clinical manifestation of Chagas disease (CD), caused by Trypanosoma cruzi. Current therapeutic options for CD are limited to benznidazole (Bz) and nifurtimox. Amiodarone (AMD) has emerged as most effective drug for treating the arrhythmic form of CCC. To address the effects of Bz and AMD we used a preclinical model of CCC. Female C57BL/6 mice were infected with T. cruzi and subjected to oral treatment for 30 consecutive days, either as monotherapy or in combination. AMD in monotherapy decreased the prolonged QTc interval, the incidence of atrioventricular conduction disorders and cardiac hypertrophy. However, AMD monotherapy did not impact parasitemia, parasite load, TNF concentration and production of reactive oxygen species (ROS) in cardiac tissue. Alike Bz therapy, the combination of Bz and AMD (Bz/AMD), improved cardiac electric abnormalities detected T. cruzi-infected mice such as decrease in heart rates, enlargement of PR and QTc intervals and increased incidence of atrioventricular block and sinus arrhythmia. Further, Bz/AMD therapy ameliorated the ventricular function and reduced parasite burden in the cardiac tissue and parasitemia to a degree comparable to Bz monotherapy. Importantly, Bz/AMD treatment efficiently reduced TNF concentration in the cardiac tissue and plasma and had beneficial effects on immunological abnormalities. Moreover, in the cardiac tissue Bz/AMD therapy reduced fibronectin and collagen deposition, mitochondrial damage and production of ROS, and improved sarcomeric and gap junction integrity. Our study underlines the potential of the Bz/AMD therapy, as we have shown that combination increased efficacy in the treatment of CCC.

Theranostic antibacterial hydrogel based on biopolymers cross-linked and doped with phytic acid from rice bran for wound healing

Theranostic antibacterial wound dressing is highly recommended in practical applications. The conventional methods of integrating diagnostic and therapeutic functions have the disadvantages of complicated preparation, mutual interference, inability to effectively broad spectrum antibacterial property, and easy to induce drug-resistant bacteria. Herein, a pH and light-responsive theranostic antibacterial hydrogel is developed by biopolymers polyvinyl alcohol (PVA) and polyaniline (PANI), and cross-linking with phytic acid (PA), which is widely present in rice bran. The biological polymer-based conductive hydrogel enables timely diagnosis and photothermal sterilization in-situ for wound healing. Because PANI is highly sensitive to pH changes in the bacterial microenvironment, the hydrogel can detect bacterial infections at concentrations as low as 103 CFU/mL. Subsequently, PANI absorbs near-infrared light to achieve on-demand exothermic sterilization (under 808 nm irradiation for 20 min, the killing ratios for Staphylococcus aureus and Escherichia coli reached almost 100 %). In addition, the hydrogel can monitor the intensity of joint movement to avoid wound re-tearing sensitively. In vitro cytotoxicity and hemocompatibility experiments and in vivo full-thickness infected wound model indicate that the hydrogel has good biocompatibility, antibacterial ability, and can accelerate the wound healing effectively. This work will promote the development of wearable electronic devices and precision medicine.

Comparative Extracellular Vesicles Proteomics unravels host-pathogen interactions: New insights in bacterial and fungal endophthalmitis in murine models

PurposeEndophthalmitis, an intraocular infection, often results in devastating outcomes due to frequent misdiagnosis and delayed treatment initiation. Extracellular Vesicles (EVs) have long been lauded for its potential as a biomarker in several infections. Previously, we have profiled EVs in bacterial and fungal infected murine model of endophthalmitis. In this study, we reported a comparative analysis of bacterial and fungal endophthalmitis to understand the disease pathobiology and identify a potential signature molecule for diagnosis of infectious endophthalmitis. MethodsEndophthalmitis was induced by intravitreal injection of bacteria (S. aureus and P. aeruginosa) and fungus (A. flavus and C. albicans) in C57BL/6 mice followed by enucleation at 24 hours. EVs were isolated by ultracentrifugation and total proteins were subjected to LC-MS/MS. A comparative analysis of the EV protein cargo during bacterial and fungal endophthalmitis was performed in this study along with the pathway assessment by Kyoto Encyclopedia of Genes and Genomes (KEGG) and Gene Ontology. ResultsProteome analysis of EVs revealed the presence of over 1500 proteins in each of the infected and control groups. Comparative (bacteria versus fungal) study revealed that the protein cargo of the EVs was very distinct among the infected sets with a very few common proteins. Crucial differentially expressed proteins (DEPs) common to both infections were Complement Cascade 8-alpha (C8α), chymase, sorting nexin-29 and glutathione-S-transferase and common pathways were metabolic pathways, Staphylococcus aureus infection, PPAR signalling pathway, cAMP signalling pathway, TGFβ signalling pathway and HIF-1 signalling pathway. ConclusionThis study comprehensively investigates the global proteome of EVs derived from mice model of bacterial and fungal endophthalmitis. Proteomic analysis reveals the disparate EV protein cargo underlining the differences in the pathogenesis of bacterial and fungal endophthalmitis with C8α, chymase, sorting nexin 29 and glutathione-S-transferase common to both infections.

Dust sprinkling as an effective method for infecting layer chickens with wild-type Salmonella Typhimurium and changes in host gut microbiota.

Role of dust in Salmonella transmission on chicken farms is not well characterised. Salmonella Typhimurium (ST) infection of commercial layer chickens was investigated using a novel sprinkling method of chicken dust spiked with ST and the uptake compared to a conventional oral infection. While both inoculation methods resulted in colonisation of the intestines, the Salmonella load in liver samples was significantly higher at 7 dpi after exposing chicks to sprinkled dust compared to the oral infection group. Infection of chickens using the sprinkling method at a range of doses showed a threshold for colonisation of the gut and organs as low as 1000 CFU/g of dust. Caecal content microbiota analysis post-challenge showed that the profiles of chickens infected by the sprinkling and oral routes were not significantly different; however, both challenges induced differences when compared to the uninfected negative controls. Overall, the study showed that dust sprinkling was an effective way to experimentally colonise chickens with Salmonella and alter the gut microbiota than oral gavage at levels as low as 1000 CFU/g dust. This infection model mimics the field scenario of Salmonella infection in poultry sheds. The model can be used for future challenge studies for effective Salmonella control.

Analyzing a Dynamical System with Harmonic Mean Incidence Rate Using Volterra–Lyapunov Matrices and Fractal-Fractional Operators

This paper investigates the dynamics of the SIR infectious disease model, with a specific emphasis on utilizing a harmonic mean-type incidence rate. It thoroughly analyzes the model’s equilibrium points, computes the basic reproductive rate, and evaluates the stability of the model at disease-free and endemic equilibrium states, both locally and globally. Additionally, sensitivity analysis is carried out. A sophisticated stability theory, primarily focusing on the characteristics of the Volterra–Lyapunov (V-L) matrices, is developed to examine the overall trajectory of the model globally. In addition to that, we describe the transmission of infectious disease through a mathematical model using fractal-fractional differential operators. We prove the existence and uniqueness of solutions in the SIR model framework with a harmonic mean-type incidence rate by using the Banach contraction approach. Functional analysis is used together with the Ulam–Hyers (UH) stability approach to perform stability analysis. We simulate the numerical results by using a computational scheme with the help of MATLAB. This study advances our knowledge of the dynamics of epidemic dissemination and facilitates the development of disease prevention and mitigation tactics.

Low-level LASER therapy accelerates fungal lesions cicatrization by increasing the production of Th1 and Th2 cytokines.

Our study focused on the resolution of lesions caused by fungal infection using a subcutaneous air pouch model of infection. We evaluated cell profile and cytokines, fungi viability, and the presence of fibroblasts and fibrocytes at the site of infection. Inoculation of P. brasiliensis (Pb) was performed using a subcutaneous air pouch model and the LLLT irradiation was performed on alternate days on the rear paws of mice for 10days, after which the cells from the air pouch were collected and analyzed. In animals irradiated with LLLT, the influx of cells to the air pouch was reduced, but they were more activated and produced pro-inflammatory (IL-12, IL-17 and TNF-α) and neutrophil (PMN) activating cytokines (IL-8, GM-CSF and γ-IFN). A better resolution of the infection, evidenced by the reduction in the number of viable fungi with preserved morphology in the air pouch, and an increase in the number of fibrocytes, indicating a healing profile were also observed. LLLT decreased the influx of PMN, but those presents were highly activated, with increased fungicidal activity. LLLT irradiation also resulted in earlier cicatrization at the site of infection, leading to a better outcome of the infection. These data are favorable to the use of LLLT as a complementary therapy in PCM.

The interplay of Pseudomonas aeruginosa and Staphylococcus aureus in dual-species biofilms impacts development, antibiotic resistance and virulence of biofilms in in vitro wound infection models.

Due to high tolerance to antibiotics and pronounced virulence, bacterial biofilms are considered a key factor and major clinical challenge in persistent wound infections. They are typically composed of multiple species, whose interactions determine the biofilm's structural development, functional properties and thus the progression of wound infections. However, most attempts to study bacterial biofilms in vitro solely rely on mono-species populations, since cultivating multi-species biofilms, especially for prolonged periods of time, poses significant challenges. To address this, the present study examined the influence of bacterial composition on structural biofilm development, morphology and spatial organization, as well as antibiotic tolerance and virulence on human skin cells in the context of persistent wound infections. By creating a wound-mimetic microenvironment, the successful cultivation of dual-species biofilms of two of the most prevalent wound pathogens, Pseudomonas aeruginosa and Staphylococcus aureus, was realized over a period of 72 h. Combining quantitative analysis with electron microscopy and label-free imaging enabled a comprehensive evaluation of the dynamics of biofilm formation and matrix secretion, revealing a twofold increased maturation of dual-species biofilms. Antibiotic tolerance was comparable for both mono-species cultures, however, dual-species communities showed a 50% increase in tolerance, mediated by a significantly reduced penetration of the applied antibiotic into the biofilm matrix. Further synergistic effects were observed, where dual-species biofilms exacerbated wound healing beyond the effects observed from either Pseudomonas or Staphylococcus. Consequently, predicting biofilm development, antimicrobial tolerance and virulence for multi-species biofilms based solely on the results from mono-species biofilms is unreliable. This study underscores the substantial impact of a multi-species composition on biofilm functional properties and emphasizes the need to tailor future studies reflecting the bacterial composition of the respective in vivo situation, leading to a more comprehensive understanding of microbial communities in the context of basic microbiology and the development of effective treatments.

Glucans: A Therapeutic Alternative for Sepsis Treatment

Sepsis treatment is a challenging condition due to its complexity, which involves host inflammatory responses to a severe and potentially fatal infection, associated with organ dysfunction. The aim of this study was to analyze the scientific literature on the immunomodulatory effects of glucans in a murine model of systemic infection induced by cecal ligation and puncture. This study comprises an integrative literature review based on systematic steps, with searches carried out in the PubMed, ScienceDirect, Scopus, Web of Science, and Embase databases. In most studies, the main type of glucan investigated was β-glucan, at 50 mg/kg, and a reduction of inflammatory responses was identified, minimizing the occurrence of tissue damage leading to increased animal survival. Based on the data obtained and discussed in this review, glucans represent a promising biotechnological alternative to modulate the immune response and could potentially be used in the clinical management of septic individuals.

Perinatal thymic-derived CD8αβ-expressing γδ T cells are innate IFN-γ producers that expand in IL-7R-STAT5B-driven neoplasms.

The contribution of γδ T cells to immune responses is associated with rapid secretion of interferon-γ (IFN-γ). Here, we show a perinatal thymic wave of innate IFN-γ-producing γδ T cells that express CD8αβ heterodimers and expand in preclinical models of infection and cancer. Optimal CD8αβ+ γδ T cell development is directed by low T cell receptor signaling and through provision of interleukin (IL)-4 and IL-7. This population is pathologically relevant as overactive, or constitutive, IL-7R-STAT5B signaling promotes a supraphysiological accumulation of CD8αβ+ γδ T cells in the thymus and peripheral lymphoid organs in two mouse models of T cell neoplasia. Likewise, CD8αβ+ γδ T cells define a distinct subset of human T cell acute lymphoblastic leukemia pediatric patients. This work characterizes the normal and malignant development of CD8αβ+ γδ T cells that are enriched in early life and contribute to innate IFN-γ responses to infection and cancer.

Organic acids mitigate Streptococcus agalactiae virulence in Tilapia fish gut primary cells and in a gut infection model

BackgroundStreptococcus agalactiae, a Gram-positive bacterium, has emerged as an important pathogen for the aquaculture industry worldwide, due to its increased induced mortality rates in cultured fish. Developing interventions to cure or prevent infections based on natural alternatives to antibiotics has become a priority, however, given the absence of scientific evidence regarding their mode of action progress has been slow.MethodsIn this study we aimed to investigate the effect of a mixture of organic acids (natural antimicrobials), AuraAqua (Aq), on the virulence of S. agalactiae using Tilapia gut primary epithelial cells and an in vitro Tilapia gut culture model. Our results show that Aq was able to reduce significantly, in vitro, the S. agalactiae levels of infection in Tilapia gut primary epithelial cells (TGP) when the MIC concentration of 0.125% was tested.Results and discussionAt bacterial level, Aq was able to downregulate bacterial capsule polysaccharide (CPS) gene expression, capC, resulting in a significant decrease in bacterial surface capsule production. The decrease in CPS production was also associated with a reduction in the pro-inflammatory IFNγ, IL1β, TNFα, SOD and CAT gene expression and H2O2 production in the presence of 0.125% Aq (P < 0.0001). The antimicrobial mixture also reduced the levels of S. agalactiae infection in an in vitro gut culture model and significantly reduced the IFNγ, IL1β, TNFα, SOD, CAT gene expression and H2O2 production in infected tissue. Moreover, genes involved in Tilapia resistance to S. agalactiae induced disease, MCP-8 and Duo-1, were also downregulated by Aq, as a consequence of reduced bacterial levels of infection.ConclusionConclusively, our study shows that mixtures of organic acids can be considered as potential alternative treatments to antibiotics and prevent S. agalactiae infection and inflammation in the Tilapia fish digestive tract.

Nano‐Fat Actuated Lipometabolic Reprogramming of Macrophages for Intracellular Infections in Biofilm Microenvironment

AbstractMetabolic competition is a zero‐sum game between bacterial biofilms and host immune responses on the surface of medical implants. In an in vitro biofilm‐macrophages co‐culture system, it is found that suppressed lipid metabolic processes in host macrophages in the biofilm microenvironment correlates with immune tolerance and intracellular persistence. Reactivation of immune cells against bacterial infection by reprogramming lipid metabolism through the supply of lipids such as oleic acid (OA) is a promising strategy, but this cannot completely destroy the bacterial biofilms. Nanomaterial‐based zinc ion interference therapy in antibacterial field emerges relying on the outstanding benefits of nanomaterials. Therefore, a targeted nano‐fat HSA‐IR820@OA@ZIF‐8 (HIROZ) with near infrared‐II (NIR‐II) photothermal capacities is developed for the destrcution of the biofilms via zinc ion combined photothermal therapy. The improved cellular compatibility and enhanced intracellular uptake make HIROZ induce intracellular lipid droplets (LDs) formation in macrophages. Photothermal combined zinc ion‐induced metabolic interference augments the antimicrobial effect of LDs and activates lipometabolic reprogramming‐mediated antibacterial immune responses via mitochondrial stress. In the mouse wound biofilm infections model and subcutaneous implant‐associated biofilm infections (IABIs) model, HIROZ demonstrates sustained and thorough biofilm scavenging based on reprogramming of lipid metabolism, providing a new idea for metabolic interference‐centered therapeutic strategies for full‐scale IABIs eliminations.

Study on the Solutions of Impulsive Integrodifferential Equations of Mixed Type Based on Infectious Disease Dynamical Systems

Since ancient times, infectious diseases have been a major source of harm to human health. Therefore, scientists have established many mathematical models in the history of fighting infectious diseases to study the law of infection and then analyzed the practicability and effectiveness of various prevention and control measures, providing a scientific basis for human prevention and research of infectious diseases. However, due to the great differences in the transmission mechanisms and modes of many diseases, there are many kinds of infectious disease dynamic models, which make the research more and more difficult. With the continuous progress of infectious disease research technology, people have adopted more ways to prevent and interfere with the derivation and spread of infectious disease, which will make the state of infectious disease system change in an instant. The mutation of this state can be described more scientifically and reasonably by the mathematical impulse dynamic system, which makes the research more practical. Based on this, a time-delay differential system model of infectious disease under impulse effect was established by means of impulse differential equation theory. A class of periodic boundary value problems for impulsive integrodifferential equations of mixed type with integral boundary conditions was studied. The existence of periodic solutions of these equations was obtained by using the comparison theorem, upper and lower solution methods, and the monotone iteration technique. Finally, combined with the practical application, the established time-delay differential system model was applied to the prediction of the stability and persistence of the infectious disease dynamic system, and the correctness of the conclusion was further verified. This study provides some reference for the prevention and treatment of infectious diseases.

PET imaging of Aspergillus infection using Zirconium-89 labeled anti-β-glucan antibody fragments.

Invasive fungal diseases, such as pulmonary aspergillosis, are common life-threatening infections in immunocompromised patients and effective treatment is often hampered by delays in timely and specific diagnosis. Fungal-specific molecular imaging ligands can provide non-invasive readouts of deep-seated fungal pathologies. In this study, the utility of antibodies and antibody fragments (Fab) targeting β-glucans in the fungal cell wall to detect Aspergillus infections was evaluated both in vitro and in preclinical mouse models. The binding characteristics of two commercially available β-glucan antibody clones and their respective antigen-binding Fabs were tested using biolayer interferometry (BLI) assays and immunofluorescence staining. In vivo binding of the Zirconium-89 labeled antibodies/Fabs to fungal pathogens was then evaluated using PET/CT imaging in mouse models of fungal infection, bacterial infection and sterile inflammation. One of the evaluated antibodies (HA-βG-Ab) and its Fab (HA-βG-Fab) bound to β-glucans with high affinity (KD = 0.056 & 21.5nM respectively). Binding to the fungal cell wall was validated by immunofluorescence staining and in vitro binding assays. ImmunoPET imaging with intact antibodies however showed slow clearance and high background signal as well as nonspecific accumulation in sites of infection/inflammation. Conversely, specific binding of [89Zr]Zr-DFO-HA-βG-Fab to sites of fungal infection was observed when compared to the isotype control Fab and was significantly higher in fungal infection than in bacterial infection or sterile inflammation. [89Zr]Zr-DFO-HA-βG-Fab can be used to detect fungal infections in vivo. Targeting distinct components of the fungal cell wall is a viable approach to developing fungal-specific PET tracers.

Dysfunction of type 1 and type 2 immune cells: a lesson from exhausted-like ILC2s and their activation-induced cell death.

The concept of immune cell exhaustion/dysfunction has developed mainly to understand impaired type 1 immune responses especially by CD8 T cells against tumors or virus-infected cells and has been applied to other lymphocytes. Natural killer (NK) cells and CD4 T cells support the efficient activation of CD8 T cells but exhibit a dysfunctional phenotype in tumor microenvironments and in chronic virus infections. In contrast, the concept of type 2 immune cell exhaustion/dysfunction is poorly established. Group 2 innate lymphoid cells (ILC2s) and T-helper 2 (Th2) cells are the major lymphocyte subsets that initiate and expand type 2 immune responses for antiparasitic immunity or allergy. In mouse models of chronic parasitic worm infections, Th2 cells display impaired type 2 immune responses. Chronic airway allergy induces exhausted-like ILC2s that quickly fall into activation-induced cell death to suppress exaggerated inflammation. Thus, the modes of exhaustion/dysfunction are quite diverse and rely on the types of inflammation and the cells. In this review, we summarize current knowledge of lymphocyte exhaustion/dysfunction in the context of type 1 and type 2 immune responses and discuss ILC2-specific regulatory mechanisms during chronic allergy.

A Promising Amphotericin B Derivative Induces Morphological Alterations, Mitochondrial Damage, and Oxidative Stress In Vitro and Prevents Mice from Death Produced by a Virulent Strain of Trypanosoma cruzi

Chagas Disease is a neglected tropical disease caused by the protozoan parasite Trypanosoma cruzi, affecting 6–8 million people, mainly in Latin America. The medical treatment is based on two compounds, benznidazole and nifurtimox, with limited effectiveness and that produce severe side effects; consequently, there is an urgent need to develop new, safe, and effective drugs. Amphotericin B is the most potent antimycotic known to date. A21 is a derivative of this compound with the property of binding to ergosterol present in cell membranes of some organisms. In the search for a new therapeutic drug against T. cruzi, the objective of this work was to study the in vitro and in vivo effects of A21 derivative on T. cruzi. Our results show that the A21 increased the reactive oxygen species and reduced the mitochondrial membrane potential, affecting the morphology, metabolism, and cell membrane permeability of T. cruzi in vitro. Even more important was finding that in an in vivo murine model of infection, A21 in combination with benznidazole was able to reduce blood parasitemia, diminish the immune inflammatory infiltrate in skeletal muscle and rescue all the mice from death due to a virulent T. cruzi strain.

Bioactivity-Based Molecular Networking-Guided Isolation of Epicolidines A-C from the Endophytic Fungus Epicoccum sp. 1-042.

Bioactivity-based molecular networking-guided fractionation enabled the isolation of three new polycyclic tetramic acids bearing cis-decalin, epicolidines A-C (1-3), along with one known compound, PF 1052 (4), from the endophytic fungus Epicoccum sp. 1-042 collected in Tibet, China. Their structures were assigned on the basis of extensive spectroscopic data, partial hydrolysis, advanced Marfey's method, quantum chemistry calculations, and X-ray diffraction analysis. Compounds 2-4 displayed promising activities against Gram-positive bacteria in vitro. Particularly, compound 4 displayed remarkable potential against vancomycin-resistant Enterococcus faecium (VRE) with an MIC value of 0.25 μg/mL, lower than the MIC (0.5 μg/mL) of the antibiotic combination quinupristin/dalfopristin (Q/D). In a further in vivo study, compound 4 increased the survival rate to 100% in the VRE-G. mellonella infection model at a concentration of 10 mg/kg.

Salmonella pathogenicity island-14 is a critical virulence factor responsible for systemic infection in chickens caused by Salmonella gallinarum

Salmonella enterica serovar Gallinarum (S. gallinarum) is an important host-specific pathogen that causes fowl typhoid, a severe systemic, septicemic, and fatal infection, in chickens. S. gallinarum causes high morbidity and mortality in chickens and poses a significant burden and economic losses to the poultry industry in many developing countries. However, the virulence factors and mechanisms of S. gallinarum-induced systemic infection in chickens remain poorly understood. In this study, we constructed a Salmonella pathogenicity island-14 (SPI-14) mutant strain (mSPI-14) of S. gallinarum and evaluated the pathogenicity of mSPI-14 in the chicken systemic infection model. The mSPI-14 exhibited the same level of bacterial growth and morphological characteristics but significantly reduced resistance to bile acids compared with the wild-type (WT) strain in vitro. The virulence of mSPI-14 was significantly attenuated in the chicken oral infection model in vivo. Chickens infected with WT showed typical clinical symptoms of fowl typhoid, with all birds succumbing to the infection within 6 to 9 days post-inoculation, and substantial increases in bacterial counts and significant pathological changes in the liver and spleen were observed. In contrast, all mSPI-14-infected chickens survived, the bacterial counts in the organs were significantly lower, and no significant pathological changes were observed in the liver and spleen. The expression of interleukin (IL)-1β, IL-12, CXCLi1, tumor necrosis factor (TNF)-α, and interferon (IFN)-γ in the liver of mSPI-14-infected chickens were significantly lower than those in the WT-infected chickens. These results indicate that SPI-14 is a crucial virulence factor in systemic infection of chickens, and avirulent mSPI-14 could be used to develop a new attenuated live vaccine to prevent S. gallinarum infection in chickens.

A Haemophilus ducreyi strain lacking the yfeABCD iron transport system is virulent in human volunteers.

Haemophilus ducreyi causes the genital ulcer disease chancroid and painful cutaneous ulcers in children who live in the tropics. To acquire heme from the host, H. ducreyi expresses a TonB-dependent hemoglobin receptor, HgbA, which is necessary and sufficient for H. ducreyi to progress to the pustular stage of disease in a controlled human infection model. HgbA transports hemoglobin across the outer membrane; how heme is transported across the cytoplasmic membrane is unclear. In previous studies, transcripts encoding the YfeABCD heme transporter were upregulated in experimental lesions caused by H. ducreyi in human volunteers, suggesting the latter may have a role in virulence. Here we constructed a double deletion mutant, 35000HPΔyfeABΔyfeCD, which exhibited growth defects relative to its parent 35000HP in media containing human hemoglobin as an iron source. Five human volunteers were inoculated at three sites on the skin overlying the deltoid with each strain. The results of the trial showed that papules formed at 100% (95% CI, 71.5, 100) at both 35000HP and 35000HPΔyfeABΔyfeCD-inoculated sites (P = 1.0). Pustules formed at 60% (95% CI, 25.9, 94.1) at parent-inoculated sites and 53% (95% CI, 18.3, 88.4) at mutant-inoculated sites (P = 0.79). Thus, the ABC transporter encoded by yfeAB and yfeCD was dispensable for H. ducreyi virulence in humans. In the absence of YfeABCD, H. ducreyi likely utilizes other periplasmic binding proteins and ABC-transporters such as HbpA, SapABCDF, and DppBCDF to shuttle heme from the periplasm into the cytoplasm, underscoring the importance of redundancy of such systems in gram-negative pathogens.

#1902 Remdesivir ameliorates ferroptotic renal injury in hamster after SARS-CoV-2 infection

Abstract Background and Aims The purpose of this study was to see how remdesivir affected renal ferroptotic damage in hamsters following a human Severe Acute Respiratory Syndrome Coronavirus-2 (SARS-CoV-2) infection. We evaluated the inhibitory effects of remdesivir on the ferroptosis of SARS-CoV-2 infection in a hamster infection model and in in vivo assays. Method To investigate the effect of SARS-CoV-2 on renal ferroptosis, we administered 2.5 × 104 p.f.u. SARS-CoV-2 via intranasal to hamster. In the initial study, animals were treated with remdesivir subcutaneously (s.c.) for 7 days beginning at various times in relation to virus challenge. After 5 days, kidney tissues were harvested. The effect of REMDESIVIR on SARS-CoV-2 infection and ferroptosis were evaluated by immunohistochemistry. Next, ferroptosis-related markers, glutathione peroxidase 4 (Gpx4), 4-hydroxynonenal (4-HNE), Acyl-CoA synthetase long chain family member 4 (Acsl4), nuclear factor erythroid-2-related factor 2 (Nrf2), heme oxygenase-1 (Ho-1) were evaluated by quantitative PCR. Results In hamsters, SARS-CoV-2 resulted in high viral protein expression in the renal tubules and decreased renal tubular luminal diameter in periodic acid-Schiff (PAS) stained kidney sections. Remdesivir treatment decreased SARS-CoV-2-induced viral spike protein, HO-1, ferritin heavy chain1 (FTH1), ferritin light chain (FTL), and 4-HNE expression in renal tubular epithelial cells of hamsters in a dose-dependent manner. GPX4 expression suppression after infection was ameliorated by remdesivir administration. Increased ferroptosis-related mRNA marker (Gpx4, 4-HNE, Acsl4, Nrf2, Ho-1) expression in hamster kidneys was suppressed by remdesivir treatment. Conclusion All of our data suggest that remdesivir treatment ameliorated SARS-CoV-2 infection-induced ferroptosis in the kidney in a hamster model.