An analysis of the structural and functional similarities of insect hemocytes and mammalian phagocytes

Cellular immune senescence in mosquitoes accelerates when the temperature is warmer

Mosquitoes are poikilotherms and ectotherms, so their body temperature is predicated by the temperature of their environment. As the temperature rises, development and metabolism quicken. At the same time, immune strength weakens with aging, a process called senescence. Aging can be characterized as a function of time (chronological age) or as a function of how well the body operates (physiological age), and we predict that warmer temperature decouples chronological and physiological aging, accelerating immune senescence. We evaluated how warmer temperature and aging interact to alter cellular immunity in the mosquito, Anopheles gambiae, by rearing them at three temperatures and quantifying the number of immune cells, called hemocytes, and their phagocytic activity at four ages. We discovered that the number of circulating hemocytes decreases with warmer temperature and aging, and that the aging-dependent decrease occurs faster when the temperature is warmer. However, the number of sessile hemocytes attached to the dorsal abdominal wall increases with infection and warmer temperature but decreases with aging. When a mosquito is infected, the aging-dependent decrease in the number of sessile hemocytes occurs faster when the temperature is warmer. Although the number of hemocytes decreases with aging, the phagocytic activity of individual hemocytes increases, with the aging-dependent increase occurring earlier when the temperature is warmer. Overall, warmer temperature accelerates senescence of the cellular immune response in mosquitoes, which has implications for how poikilotherms and ectotherms fight infections as they age in our warming world.

Mycobacterium marinum as a model for understanding principles of mycobacterial pathogenesis

Mycobacterium marinum is a fish pathogen that has become a powerful and well-established model that has accelerated our understanding of the mechanisms of mycobacterial disease. M. marinum is a versatile surrogate for understanding the closely related human pathogen M. tuberculosis, which causes tuberculosis in humans. M. marinum has defined key mechanisms of pathogenesis, both shared with M. tuberculosis and unique to this species. In this review, we discuss the discovery of M. marinum as an occasional human pathogen, the shared aspects of pathogenesis with M. tuberculosis, and how M. marinum has been exploited as a model to define the molecular mechanisms of mycobacterial pathogenesis across several phases of infection.

Characterization of temporal expression of immune genes in female locust challenged by fungal pathogen, Aspergillus sp

Introduction

The innate immune system provides defense against invading pathogens in insects and mammals.

Methods

We conducted transcriptomic analyses of the locust Locusta migratoria under Aspergillus oryzae infection to clarify temporal variation in its molecular immune response.

Results

We found that fat body cells and hemocytes play different roles in the immune response of locusts to Aspergillus infection at different time points after inoculation, and melanization was the main process underlying the immune response of female locusts. Most pattern recognition receptors (PRR) genes were up-regulated in fat body cells and down-regulated in hemocytes from 24 h to 72 h after inoculation. This means that fat body cells, but not hemocytes, would be able to precisely recognize invading pathogens. Most serine protease inhibitors (SERPINs) genes and clip domain serine proteinase (CLIP) genes were up-regulated in fat body cells. However, most SERPINs were down-regulated in hemocytes, which indicated that serine proteinases may be inhibited to activate downstream reactions involving the prophenoloxidase (PPO), peroxidase (POD), and Toll pathways. Most lysozymes, PPOs, and peroxiredoxin (PRDX) are effectors that were up-regulated in fat body cells 24 h after inoculation but down-regulated 48 h and 72 h after inoculation. Similar patterns were observed for effectors in hemocytes, which indicates that locust immune genes expression was suppressed by A. oryzae 72 h after inoculation, and might result in the weak melanization of locusts in response to Aspergillus infection.

Discussion

Our findings enhance our understanding of insect-fungi interactions, as well as have implications for the development of more effective microbial control strategies for the management of locust populations.

In Vivo Antimicrobial Activity of Nisin Z Against S. aureus and Polyurea Pharmadendrimer PUREG4OEI48 Against P. aeruginosa from Diabetic Foot Infections

BACKGROUND/OBJECTIVES

Diabetic foot infections (DFIs) are commonly associated with frequent hospitalizations, limb amputations, and premature death due to the profile of the bacteria infecting foot ulcers. DFIs are generally colonized by a polymicrobial net of bacteria that grows in biofilms, developing an increased antimicrobial resistance to multiple antibiotics. DFI treatment is a hurdle, and the need to develop new therapies that do not promote resistance is urgent. Therefore, the antibacterial efficacy of Nisin Z (antimicrobial peptide), a core-shell polycationic polyurea pharmadendrimer (PUREG4OEI48) (antimicrobial polymer), and amlodipine (antihypertensive drug) was evaluated against S. aureus and P. aeruginosa isolated from a DFI and previously characterized.

METHODS

The antibacterial activity was analyzed in vitro by determining the minimal inhibitory concentration (MIC) and in vivo in a Galleria mellonella model by assessing the larvae survival and health index.

RESULTS

The results indicate that Nisin Z exhibited antibacterial activity against S. aureus in vivo, allowing larvae full survival, and no antibacterial activity against P. aeruginosa. Nisin Z may have reduced the antibacterial effectiveness of both PUREG4OEI48 and amlodipine. PUREG4OEI48 significantly increased the survival of the larvae infected with P. aeruginosa, while amlodipine showed no activity against both bacteria in vivo.

CONCLUSIONS

These findings suggest that both Nisin Z and PUREG4OEI48 could potentially be used individually as adjunct treatments for mild DFIs. However, further studies are needed to confirm these findings and assess the potential toxicity and efficacy of PUREG4OEI48 in more complex models.

The Klebsiella pneumoniae tellurium resistance gene terC contributes to both tellurite and zinc resistance

Klebsiella pneumoniae is widely recognized as a pathogen responsible for hospital-acquired infections and community-acquired invasive infections. It has rapidly become a significant global public health threat due to the emergence of hypervirulent and multidrug-resistant strains, which have increased the challenges associated with treating life-threatening infections. Tellurium resistance genes are widespread on virulence plasmids in K. pneumoniae isolates. However, the core function of the ter operon (terZABCDEF) in K. pneumoniae remains unclear. In this study, the multidrug-resistant K. pneumoniae P1927 strain was isolated from the sputum of a hospitalized pneumonia patient. The ter operon, along with antimicrobial resistance and virulence genes, was identified on a large hybrid plasmid in K. pneumoniae P1927. We generated a terC deletion mutant and demonstrated that this mutant exhibited reduced virulence in a Galleria mellonella larva infection model. Further physiological functional analysis revealed that terC is not only important for Te(IV) resistance but also for resistance to Zn(II), Mn(II), and phage infection. All genes of the ter operon were highly inducible by Zn(II), which is a stronger inducer than Te(IV), and the terBCDE genes were also induced by Mn(II). Collectively, our study demonstrates novel physiological functions of TerC in Zn(II) resistance and virulence in K. pneumoniae.IMPORTANCEKlebsiella pneumoniae has rapidly become a global threat to public health. Although the ter operon is widely identified in clinical isolates, its physiological function remains unclear. It has been proposed that proteins encoded by the ter operon form a multi-site metal-binding complex, but its exact function is still unknown. TerC, a central component of the tellurium resistance determinant, was previously shown to interact with outer membrane proteins OmpA and KpsD in Escherichia coli, suggesting potential changes in outer membrane structure and properties. Here, we report that TerC confers resistance to Zn(II), Mn(II), and phage infection, and Zn(II) was shown to be a strong inducer of the ter operon. Furthermore, TerC was identified as a novel virulence factor. Taken together, our results expand our understanding of the physiological functions encoded by the ter operon and its role in the virulence of K. pneumoniae, providing deeper insights into the link between heavy metal(loid) resistance determinants and virulence in pathogenic bacteria.

Transcriptome study reveals tick immune genes restrict Babesia microti infection

A systems biology approach was employed to gain insight into tick biology and interactions between vectors and pathogens. Haemaphysalis longicornis serves as one of the primary vectors of Babesia microti, significantly impacting human and animal health. Obtaining more information about their relationship is crucial for a comprehensive understanding of tick and pathogen biology, pathogen transmission dynamics, and potential control strategies. RNA sequencing of uninfected and B. microti-infected ticks resulted in the identification of 15 056 unigenes. Among these, 1 051 were found to be differentially expressed, with 796 being upregulated and 255 downregulated (P < 0.05). Integrated transcriptomics datasets revealed the pivotal role of immune-related pathways, including the Toll, Janus kinase/signal transducer and activator of transcription (JAK-STAT), immunodeficiency, and RNA interference (RNAi) pathways, in response to infection. Consequently, 3 genes encoding critical transcriptional factor Dorsal, Relish, and STAT were selected for RNAi experiments. The knockdown of Dorsal, Relish, and STAT resulted in a substantial increase in Babesia infection levels compared to the respective controls. These findings significantly advanced our understanding of tick-Babesia molecular interactions and proposed novel tick antigens as potential vaccine targets against tick infestations and pathogen transmission.

The flavouring agent, 2-octenoic acid kills Galleria mellonella (Lepidoptera: Pyralidae) by affecting their immunocompetent cells and cuticular FFA profiles

This study investigates the effects of the naturally occurring flavouring agent, trans-2-octenoic acid, on the insect model Galleria mellonella by examining its impact on immunocompetent cells and free fatty acid (FFA) profiles in the cuticle. The value of LD50 for 2-octenoic acid has been calculated as 9.66 µg/mg of insect body mass, this value is outside the GHS scale, indicating that the compound is unlikely to cause acute toxicity after dermal application and is safe for humans and mammals. Thetreatment with 2-octenoic acid caused several changes in the insect defence mechanismes, viz. changes in cuticular FFA profiles and death of immunocompetent cells. In larvae, topical treatment of 2-octenoic acid increased the concentration of cuticular FFAs, particularly C6:0 (245 times higher), C15:0 (110 times higher), and C16:1 (1608 times higher), and 2-octenoic acid (C8:1) accumulated significantly on the surface of the cuticle. In adults, treatment resulted in lower cuticular C8:1concentrations than in larvae, which might indicate that 2-octenoic acid penetrates more effectively through the adult cuticle. The 2-octenoic acid application demonstrated considerable cytotoxicity against insect cell line Sf9 and G. mellonella hemocytes, with both in vivo and in vitro treatment. Our findings contribute to the broader understanding of how synthetic and naturally occurring chemicals may interact with the immune and physiological systems of insects, particularly focusing on G. mellonella as a model organism for toxicological studies. Given the increasing interest in the ecological and physiological impacts of food additives, our research provides novel insights into the biological interactions of 2-octenoic acid and its potential role as an insecticide.

Targeting the G-quadruplex as a novel strategy for developing antibiotics against hypervirulent drug-resistant Staphylococcus aureus

BACKGROUND

The rapid emergence of multiple drug-resistant (MDR) bacterial pathogens and the lack of a novel antibiotic pipeline pose a serious threat to global healthcare. The limited number of established targets further restricts the identification of novel antibiotics to treat life-threatening MDR infections caused by Staphylococcus aureus strains. Therefore, novel targets for developing antibiotics are urgently required. In this study, we hypothesized that the G-quadruplex (G4)-binding ligands can be used as novel antibiotics as their binding can possibly downregulate/block the expression of vital genes.

METHODS

To test this, first we screened the antibiotic properties of representative G4-binding ligands against hypervirulent and MDR S. aureus USA300 and determined the in vitro and in vivo antibacterial activity; and proposed the mechanism of action by applying various microbiological, infection, microscopic, and biophysicochemical techniques.

RESULTS

Herein, among screened G4-binding ligands, N-methyl mesoporphyrin IX (NMM) showed the highest antibacterial activity against S. aureus USA300. NMM exhibited a minimum inhibitory concentration (MIC) of 5 μM against S. aureus USA300, impacting cell division and the cell wall by repressing the expressions of genes in the division cell wall (dcw) gene cluster. Genome-wide bioinformatics analysis of G4 motifs and their mapping on S. aureus genome, identified the presence of G4-motif in the promoter of mraZ, a conserved master regulator of the dcw cluster regulating the coordinated cell division and cell wall synthesis. Physicochemical assessments using UV-visible, circular dichroism, and nuclear magnetic resonance spectroscopy confirmed that the G4-motif present in the mraZ promoter formed an intramolecular parallel G4 structure, interacting with NMM. In vivo reporter followed by coupled in vitro transcription/translation (IVT) assays confirmed the role of mraZ G4 as a target interacting NMM to impose extreme antibacterial activity against both the gram-positive and -negative bacteria. In-cell and in vivo validation of NMM using RAW264.7 cells and Galleria mellonella; respectively, demonstrated that NMM exhibited superior antibiotic activity compared to well-established antibiotics, with no observed cytotoxicity.

CONCLUSIONS

In summary, the current study identified NMM as a broad-spectrum potent antibacterial agent and elucidated its plausible mechanism of action primarily by targeting G4-motif in the mraZ promoter of the dcw gene cluster.

Refined methodology for quantifying Pseudomonas aeruginosa virulence using Galleria mellonella

Larvae of Galleria mellonella (the greater wax moth) are being increasingly used as a model to study microbial pathogenesis. In this model, bacterial virulence is typically measured by determining the 50% lethal dose (LD50) of a bacterial strain or mutant. The use of G. mellonella to study Pseudomonas aeruginosa pathogenesis, however, is challenging because of the extreme sensitivity of larvae to this bacterium. For some P. aeruginosa strains, as few as 1-5 colony-forming units are sufficient to kill G. mellonella, which poses challenges for determining LD50 values. For this reason, some groups have used time-to-death as a measure of P. aeruginosa virulence, but methodologies have not been standardized. We provide a detailed protocol for using the time at which 50% of larvae have died (LT50) at a particular inoculum as a measure of P. aeruginosa virulence. We also describe a quality control metric for enhancing the reproducibility of LT50 values. This approach provides an accurate and reproducible methodology for using G. mellonella larvae to measure and compare the virulence of P. aeruginosa strains.IMPORTANCEPseudomonas aeruginosa is a significant cause of morbidity and mortality. The invertebrate Galleria mellonella is used as a model to determine the virulence of P. aeruginosa strains. We provide a protocol and analytical approach for using a time-to-death metric to accurately quantify the virulence of P. aeruginosa strains in G. mellonella larvae. This methodology, which has several advantages over 50% lethal dose approaches, is a useful resource for the study of P. aeruginosa pathogenicity.

The flavouring agent, 2-octenoic acid kills Galleria mellonella larvae by affecting the cellular and humoral elements of insect immunological system

Larvae of Galleria mellonella are well known for their parasitisation of honeybees, so developing new methods of controlling the pest population is an important issue. The present research examined the immunotoxic effects of 2-octenoic acid against wax moth larvae. The last instar larvae were used for all experimental analyses. The tested fatty acid doses LD50 and LD100 (9.66 µg/mg and 11.72 µg/mg of body mass) were applied topically to insects under in vivo conditions and the hemolymph was collected after 24 and 48 h. To check the in vitro impact of the 2-octenoic acid, the examined fatty acid was given directly to the cultured hemocytes (to a final concentration: 0.33 and 0.16 µg/µl) and incubated for 24 and 48 h. Current research using fluorescence microscopy and spectrofluorimetric measurements indicates the death of immunocompetent cells via the apoptosis pathway. Moreover, it shows the activation of caspases and an increase in the level of reactive oxygen/nitrogen damage after both in vivo and in vitro treatment of 2-octenoic acid. This points to the impact of both cellular and humoral elements on the immunological response to the toxic compound. Hence, 2-octenoic acid seems to have significant potential as an insecticide while being safe for humans and the environment. Therefore, further research into its potential is warranted.

Synergistic activity between conventional antifungals and chalcone-derived compound against dermatophyte fungi and Candida spp

The scarce antifungal arsenal, changes in the susceptibility profile of fungal agents, and lack of adherence to treatment have contributed to the increase of cases of dermatomycoses. In this context, new antimicrobial substances have gained importance. Chalcones are precursors of the flavonoid family that have multiple biological activities, have high tolerability by humans, and easy synthesis. In this study, we evaluated the in vitro antifungal activity, alone and in combination with conventional antifungal drugs, of the VS02-4'ethyl chalcone-derived compound against dermatophytes and Candida spp. Susceptibility testing was carried out by broth microdilution. Experiments for determination of the target of the compound on the fungal cell, time-kill kinetics, and toxicity tests in Galleria mellonella model were also performed. Combinatory effects were evaluated by the checkerboard method. Results showed high activity of the compound VS02-4'ethyl against dermatophytes (MIC of 7.81-31.25 μg/ml). The compound targeted the cell membrane, and the time-kill test showed the compound continues to exert gradual activity after 5 days on dermatophytes, but no significant activity on Candida. Low toxicity was observed at 250 mg/kg. Excellent results were observed in the combinatory test, where VS02-4'ethyl showed synergistic interactions with itraconazole, fluconazole, terbinafine, and griseofulvin, against all isolates tested. Although further investigation is needed, these results revealed the great potential of chalcone-derived compounds against fungal infections for which treatments are long and laborious.

Streptococcus anginosus orchestrates antibacterial potential of NETs facilitating survival of accompanying pathogens

Streptococcus anginosus is considered an emerging opportunistic pathogen causing life-threatening infections, including abscesses and empyema. Noticeably, clinical data revealed that S. anginosus also constitutes an important component of polymicrobial infections. Here, we showed for the first time that S. anginosus inactivates the antibacterial potential of neutrophil extracellular traps (NETs). The process is determined by a cell wall-anchored nuclease referred to as SanA, which high expression dominates in clinical strains isolated from severe infections. Nuclease activity protects S. anginosus against the antibacterial activity of NETs, supporting at the same time the survival of coexisting highly pathogenic species of Enterobacteriales. Obtained data suggest that SanA nuclease should be recognized as a critical S. anginosus virulence factor determining severe monospecies purulent infections but also shielding other pathogens promoting the development of polymicrobial infections.

The multifunctional role of IFN-γ in Galleria mellonella (Lepidoptera) immunocompetent cells

Cytokines are highly conserved between mammals and insects. The present study examines the multiple effects of interferon-gamma (IFN-γ) application on the immunological defence mechanisms of Galleria mellonella larvae, invertebrates which are gaining popularity as a replacement for mammalian research models in immunological studies. G. mellonella hemolymph is known to contain an IFN-γ homolog that shares 33 % similarity with its mammalian analogue, and its level in insect hemocytes increases during exposition to entomopathogenic fungus Conidiobolus coronatus. The present research examines the impact of IFN-γ on larval development, the effectiveness of fungal infection, and the morphology and physiology of wax moth immunocompetent cells. Treatment with IFN-γ enhanced wound healing, chemotaxis activity and hemocyte impedance, while reducing hemocyte phagocytosis and oxidative stress in cultured immunocompetent cells; it also appears to increase the levels of Jak-2- and NF-κB-like molecules in hemocytes. Our findings suggest that IFN-γ demonstrated considerable similarity between mammals and humans, thus further demonstrating the evolutionary conservatism of cytokines.

The potential virulence of Listeria monocytogenes strains isolated from fresh produce processing facilities as determined by an invertebrate Galleria mellonella model

Listeria monocytogenes, a bacterium responsible for listeriosis, is an environmental and food-borne pathogen that poses a particular risk to pregnant women and the elderly. While traditionally associated with animal products, ready-to-eat salads are increasingly recognised as a source of Listeria outbreaks. However, little is known about the potential virulence of Listeria isolates from the fresh produce environment. This study assessed the virulence potential of nine L. monocytogenes strains from the fresh produce chain using the Galleria mellonella invertebrate infection model. Larvae were infected with 106 CFU of each strain via their circulatory system and compared to a reference strain L. monocytogenes (EGD-e) and Listeria ivanovii. Virulence was evaluated by measuring mortality rates, health index score of larvae, viable bacterial counts in the larvae, and the larvae's immune. Significant differences in larval mortality were observed among strains. Strains NLmo4 and NLmo5 caused the highest mortality rates (98.8% and 96.7%, respectively at 7 days post-infection), while strain NLmo20 had a significantly lower mortality rate of 65% at the same time point (p<0.05). Six isolates that caused varied mortality rates were then selected and tested for their ability to replicate both in vitro and in vivo and their impact on larval haemocyte density. In vitro growth rates were not significantly different among L. monocytogenes strains or compared to Listeria ivanovii. However, L. monocytogenes strains persisted and replicated in larvae up to 7d days post-infection, whereas Listeria ivanovii was reduced by 5 logs CFU by day 7. The presence of these L. monocytogenes strains caused organ damage in larvae, indicated by increased melanisation and subsequent larval death. Haemocyte density showed insignificant fluctuations following infection. In conclusion, the results of this study suggest L. monocytogenes strains from fresh produce food chain have varying pathogenicity levels and can pose potential risk to human health.

Galleria mellonella larvae as an alternative model to determine the pathogenicity of avian pathogenic Escherichia coli

RESEARCH HIGHLIGHTS

Galleria mellonella larvae are a viable model for determining APEC pathogenicity.Larval disease score is the main variable for determining APEC pathogenicity.Response variables should be evaluated up to 24 h post-inoculation.

Evaluating the Antimicrobial Efficacy of a Designed Synthetic peptide against Pathogenic Bacteria

Recent research has focused on discovering peptides that effectively target multidrug-resistant bacteria while leaving healthy cells unharmed. In this work, we describe the antimicrobial properties of RK8, a peptide composed of eight amino acid residues. Its activity was tested against multidrug-resistant Gram-negative and Gram-positive bacteria. RK8's efficacy in eradicating mature biofilm and increasing membrane permeability was assessed using Sytox Green. Cytotoxicity assays were conducted both in vitro and in vivo models. Circular dichroism analysis revealed that RK8 adopted an extended structure in water and sodium dodecyl sulfate (SDS). RK8 exhibited MICs of 8-64 μM and MBCs of 4-64 μM against various bacteria, with higher effectiveness observed in Methicillin-resistant Staphylococcus aureus (MRSA) and E. coli KPC+ strains than others. Ciprofloxacin and Vancomycin showed varying MIC and MBC values lower than RK8 for Gram-positive bacteria, but competitive for Gram-negative bacteria. The combination of RK8 and ciprofloxacin showed a synergistic effect. The RK8 peptides could reduce 38% of the mature Acinetobacter baumannii biofilm. Sytox Green reagent achieved 100% membrane permeation of Gram-positive and Gram-negative bacteria. The RK8 peptide did not show cytotoxic effects against murine macrophages (64 μM), erythrocytes (100 μM) or Galleria mellanella larvae (960 μM). In the stability test against peptidases, the RK8 peptide was stable, maintaining around 60% of the molecule intact after 120 min of incubation. These results highlight the potential of RK8 to be a promising strategy for developing a new antimicrobial and antibiofilm agent, inspiring and motivating further research in antimicrobial peptides.

Immunomodulation and Protective Effects of Cordyceps militaris Extract Against Candida albicans Infection in Galleria mellonella Larvae

Cordyceps militaris-derived formulations are currently used for multiple purposes because of their medical properties, especially immune system modulation. This study analyzes the inhibitory effects of C. militaris aqueous extract on Candida albicans infections and the immune response in larvae of the greater wax moth Galleria mellonella (Lepidoptera: Pyralidae). Larvae exhibited melanization within 1 h of being infected with C. albicans inoculum at a concentration of 106 cells/larvae, and died within 24 h from a lethal dose. Aqueous extract of C. militaris proved to be nontoxic at concentrations of 0.25 and 0.125 mg/larvae, and had the greatest ability to prolong the survival of larvae infected with a sublethal dose of C. albicans at a concentration of 105 cells/larvae. Moreover, the number of hemocytes in the hemolymph of G. mellonella increased after infection with C. albicans and treatment with the aqueous extract of C. militaris at 1, 24, and 48 h by 1.21 × 107, 1.23 × 107, and 1.4 × 107 cells/100 µL, respectively. The highest number of hemocytes was recorded after treatment of infected G. mellonella with the extract for 48 h. Transcriptional upregulation of the immune system was observed in certain antimicrobial peptides (AMPs), showing that the relative expression of galiomicin, gallerimycin, and lysozyme genes were upregulated as early as 1 h after infection. Therefore, we conclude that C. militaris aqueous extract can modulate the immune system of G. mellonella and protect against infection from C. albicans.

Back to the future: Forgotten protocols for optimizing the isolation of arthropod haemocytes

Consideration is given to previous and more recent protocols for harvesting arthropod haemocytes from Galleria, Drosophila, mosquitoes, Limulus and crustaceans. The optimal harvesting of these cells is essential for meaningful studies of invertebrate immunity in vitro. The results of such experiments, however, have often been flawed due to a lack of understanding of the fragile nature of arthropod haemocytes on exposure to bacterial lipopolysaccharides, resulting in the aggregation and loss of cell types during haemolymph clotting. This article emphasizes that although there are similarities between mammalian neutrophils and arthropod haemocytes, the protocols required for the successful harvesting of these cells vary significantly. The various stages for the successful harvesting of arthropod haemocytes are described in detail and should provide invaluable advice to those requiring both high cell viability and recovery of the different cell types for subsequent experimentation.

Killing of xenogenous and virally infected homogenous target cells by shrimp lymphocyte-like haemocytes

Haemocytes play a crucial role in the invertebrate's immune system. In our lab, five subpopulations of shrimp haemocytes were identified in the past: hyalinocytes, granulocytes, semi-granulocytes and two subpopulations of non-phagocytic cells. In the latter two subpopulations, their characteristics such as having small cytoplasmic rims and not adhering to plastic cell-culture plates are very similar to those of mammalian lymphocytes. Therefore, they were designated lymphocyte-like haemocytes. Although little is known about their function, we hypothesize, based on their morphology, that they may have a cytotoxic activity like natural killer cells, with the ability to recognize and kill target cells. In our study, K562 cells and Sf9 cells were used as xenogenous target cells to detect the cytotoxic activity of the shrimp non-adherent lymphocyte-like haemocytes. Non-adherent haemocytes were collected and mixed with K562 cells and Sf9 cells at a 5:1 ratio and the binding activity was examined under a microscope. The binding rate of non-adherent haemocytes to K562 cells and Sf9 cells reached 6.6 % and 2.4 % after 240 min of culture, respectively. Then, the killing activity of non-adherent haemocytes was detected by an EMA staining (fluorescence microscopy), which showed 3.75 % dead K562 cells and 1.025 % dead Sf9 cells, and by Sytox® blue staining (flow cytometry), which showed 4.97 % of dead K562 cells. Next, a killing assay was developed to visualize the killing activity of shrimp non-adherent haemocytes. Non-adherent haemocytes were pre-labeled in blue (CellTracker blue) and K562/Sf9 cells in green (CFSE); dead cells were differentially stained red with ethidium bromide. The cytotoxic activity increased and reached a level of 2.59 % in K562 cells and 0.925 % in Sf9 cells at 120 min after co-culture. Furthermore, in the co-cultures of non-adherent haemocytes with K562 cells and Sf9 cells, upregulation of the gene and protein expression of the cytotoxic molecules torso-like protein and granzyme B was observed by RT-qPCR at 240 min and western blotting at 180 min. Additionally, non-adherent haemocytes were co-cultured with WSSV-inoculated shrimp ovary and lymphoid organ cells to detect the cytotoxicity to homogenous target cells. The binding activity started at 60 min in both the ovary and lymphoid organ cultures and reached at 240 min 50.62 % and 40.7 %, respectively. The killing activity was detected by EMA staining and the percentage of dead ovary and lymphoid organ cells increased respectively from 10.84 % to 6.89 % at 0 min to 13.09 % and 8.37 % at 240 min. In conclusion, we demonstrated the existence of cytotoxic activity of shrimp lymphocyte-like haemocytes against xenogenous cells from mammals and insects and against WSSV-infected homogenous shrimp cells.

Antifungal activity of indolicidin-derived peptide In-58 against Sporothrix globosa in vitro and in vivo

In-58, a peptide derived from indolicidin, shows extraordinary antibacterial activity and lower toxicity than indolicidin toward mammalian cells. Here, we investigated the antifungal activity of In-58 against the human pathogen Sporothrix globosa in vitro and in vivo. In-58 markedly inhibited the growth of Sporothrix globosa isolates in microdilution assays and showed no antagonism with any tested antifungal agent (itraconazole, terbinafine or amphotericin B). Scanning electron microscopy and propidium iodide staining indicated that In-58 alters the cell wall integrity and interacts with DNA, leading to disruption of S. globosa in a dose-dependent manner. In S. globosa, the mitochondrial membrane potential decreased and reactive oxygen species increased after treatment with In-58. In vivo experiments in the Galleria mellonella (greater wax moth) larval infection model revealed the effectiveness of In-58 against S. globosa infection with low toxicity. Our results indicate that In-58 possesses remarkable antifungal activity against S. globosa in vitro and in vivo. It has potential as a novel drug for the treatment of sporotrichosis.

The Future Exploring of Gut Microbiome-Immunity Interactions: From In Vivo/Vitro Models to In Silico Innovations

Investigating the complex interactions between microbiota and immunity is crucial for a fruitful understanding progress of human health and disease. This review assesses animal models, next-generation in vitro models, and in silico approaches that are used to decipher the microbiome-immunity axis, evaluating their strengths and limitations. While animal models provide a comprehensive biological context, they also raise ethical and practical concerns. Conversely, modern in vitro models reduce animal involvement but require specific costs and materials. When considering the environmental impact of these models, in silico approaches emerge as promising for resource reduction, but they require robust experimental validation and ongoing refinement. Their potential is significant, paving the way for a more sustainable and ethical future in microbiome-immunity research.

Role of eicosanoids in insect immunity: new insights and recent advances

Viruses, bacteria, fungus, protozoans, and different metazoan parasites and parasitoids present a constant threat to insects. Insect immunity has two components: humoral and cell mediated. Humoral immunity can be achieved by various antimicrobial proteins, namely, cecropins, sarcotoxin, defensin, attacin, etc. The cell-mediated immunity comprises various cells having immune functions fostering nodulation, phagocytosis, microaggregation, encapsulation etc. Eicosanoids play a crucial role in insect immunity comparable to other animals. The above-mentioned are signaling molecules derived from polyunsaturated fatty acids and they exert numerous physiological effects, namely, inflammation, immune modulation, and regulation of cellular processes. The review article elucidates various roles of eicosanoids, namely, nodulation reaction, Toll signaling pathway, nitric oxide (NO) generation, Ca2+ mobilization, production of reactive oxygen species (ROS), actin polymerization and aquaporin activation. Eicosanoids can function in immune priming in insects drawing hemocytes. An agent named Duox was also identified serving as ROS generator in insect gut. Moreover, role of Repat gene in insect immunity was also studied. However, recently the role of prostacyclin (PGI2) was found to be negative as it inhibits platelet aggregation. In this brief review, we have tried to shed light on the various functions of eicosanoids in immunity of insect those have been discovered recently. This concise study will allow to decipher eicosanoids' function in insect immunity in a nutshell, and it will pave the way for more researches to understand the key players of insect immunity which may eventually help to develop novel vector and pest control strategies in near future.

Characterization of Aspergillus fumigatus secretome during sublethal infection of Galleria mellonella larvae

Introduction. The fungal pathogen Aspergillus fumigatus can induce prolonged colonization of the lungs of susceptible patients, resulting in conditions such as allergic bronchopulmonary aspergillosis and chronic pulmonary aspergillosis.Hypothesis. Analysis of the A. fumigatus secretome released during sub-lethal infection of G. mellonella larvae may give an insight into products released during prolonged human colonisation.Methodology. Galleria mellonella larvae were infected with A. fumigatus, and the metabolism of host carbohydrate and proteins and production of fungal virulence factors were analysed. Label-free qualitative proteomic analysis was performed to identify fungal proteins in larvae at 96 hours post-infection and also to identify changes in the Galleria proteome as a result of infection.Results. Infected larvae demonstrated increasing concentrations of gliotoxin and siderophore and displayed reduced amounts of haemolymph carbohydrate and protein. Fungal proteins (399) were detected by qualitative proteomic analysis in cell-free haemolymph at 96 hours and could be categorized into seven groups, including virulence (n = 25), stress response (n = 34), DNA repair and replication (n = 39), translation (n = 22), metabolism (n = 42), released intracellular (n = 28) and cellular development and cell cycle (n = 53). Analysis of the Gallerial proteome at 96 hours post-infection revealed changes in the abundance of proteins associated with immune function, metabolism, cellular structure, insect development, transcription/translation and detoxification.Conclusion. Characterizing the impact of the fungal secretome on the host may provide an insight into how A. fumigatus damages tissue and suppresses the immune response during long-term pulmonary colonization.

Synthesis, Antibacterial Effects, and Toxicity of Licochalcone C

Drug-resistant bacteria constitute a big barrier against current pharmacotherapy. Efforts are urgent to discover antibacterial drugs with novel chemical and biological features. Our work aimed at the synthesis, evaluation of antibacterial effects, and toxicity of licochalcone C (LCC), a naturally occurring chalcone. The synthetic route included six steps, affording a 10% overall yield. LCC showed effects against Gram-positive bacteria (MIC = 6.2-50.0 µg/mL), Mycobacterium species (MIC = 36.2-125 µg/mL), and Helicobacter pylori (MIC = 25 µg/mL). LCC inhibited the biofilm formation of MSSA and MRSA, demonstrating MBIC50 values of 6.25 μg/mL for both strains. The investigations by fluorescence microscopy, using PI and SYTO9 as fluorophores, indicated that LCC was able to disrupt the S. aureus membrane, similarly to nisin. Systemic toxicity assays using Galleria mellonella larvae showed that LCC was not lethal at 100 µg/mL after 80 h treatment. These data suggest new uses for LCC as a compound with potential applications in antibacterial drug discovery and medical device coating.

The effect of infection with the entomopathogenic fungus Conidiobolus coronatus (Entomopthorales) on eighteen cytokine-like proteins in Galleria mellonella (Lepidoptera) larvae

Background

In response to the replace mammal research models with insects in preliminary immunological studies, interest has grown in invertebrate defense systems. The immunological response is regulated by cytokines; however, while their role in mammals is well understood, little is known of their function in insects. A suitable target for studies into insect immunology is Galleria mellonella (Lepidoptera), the wax moth: a common host for human fungal and bacterial pathogens. G. mellonella is also a perfect subject for studies into the presence of cytokine-like proteins.

Specific objectives

The main goal of present research was detection in insect immunocompetent cells the 18 mammalian cytokines (IL-1α, IL-1β, IL-2, IL-3, IL-6, IL-7, IL-8, IL-12, IL-13, IL-15, IL-17, IL-19, IFN-γ, TNF-α, TNF-β, GM-CSF, M-CSF, G-CSF), which play important role in immunological response and indication how their level change after fungal infection.

Methodology

The changes of cytokine-like proteins level were detected in hemocytes taken from G. mellonella larvae infected with entomopathogenic fungus, C. coronatus. The presence of cytokine-proteins was confirmed with using fluorescence microscopy (in cultured hemocytes) and flow cytometry (in freshly collected hemolymph). The ELISA test was used to detect changes in concentration of examined cytokine-like proteins.

Results

Our findings indicated the presence of eighteen cytokine-like molecules in G. mellonella hemocytes during infection with C. coronatus. The hemocytes taken from infected larvae demonstrated higher fluorescence intensity for six cytokine-like proteins (GM-CSF, M-CSF, IL-3, IL-15, IL-1β and IL-19) compared to untreated controls. ELISA test indicated significantly higher IL-3 and IL-15. M-CSF, IL-1α and IL-19 concentration in the hemolymph after fungal infection, and significantly lower TNF-β and G-CSF.

Conclusions

Our findings confirm that the selected cytokine-like molecules are present in insect hemocytes and that their concentrations change after fungal infection, which might suggest that they play a role in the anti-fungal immunological response.

Mechanistic insights on the antibacterial action of the kyotorphin peptide derivatives revealed by in vitro studies and Galleria mellonella proteomic analysis

OBJECTIVES

The selected kyotorphin derivatives were tested to improve their antimicrobial and antibiofilm activity. The antimicrobial screening of the KTP derivatives were ascertained in the representative strains of bacteria, including Streptococcus pneumoniae, Streptococcus pyogenes, Escherichia coli and Pseudomonas aeruginosa.

METHODS

Kyotorphin derivatives, KTP-NH2, KTP-NH2-DL, IbKTP, IbKTP-NH2, MetKTP-DL, MetKTP-LD, were designed and synthesized to improve lipophilicity and resistance to enzymatic degradation. Peptides were synthesized by standard solution or solid-phase peptide synthesis and purified using RP-HPLC, which resulted in >95 % purity, and were fully characterized by mass spectrometry and 1H NMR. The minimum inhibitory concentrations (MIC) determined for bacterial strains were between 20 and 419 μM. The direct effect of IbKTP-NH2 on bacterial cells was imaged using scanning electron microscopy. The absence of toxicity, high survival after infection and an increase in the hemocytes count was evaluated by injections of derivatives in Galleria mellonella larvae. Proteomics analyses of G. mellonella hemolymph were performed to investigate the underlying mechanism of antibacterial activity of IbKTP-NH2 at MIC.

RESULTS

IbKTP-NH2 induces morphological changes in bacterial cell, many differentially expressed proteins involved in DNA replication, synthesis of cell wall, and virulence were up-regulated after the treatment of G. mellonella with IbKTP-NH2.

CONCLUSION

We suggest that this derivative, in addition to its physical activity on the bacterial membranes, can elicit a cellular and humoral immune response, therefore, it could be considered for biomedical applications.

Antifungal potential of the new copper(II)-theophylline/1,10-phenanthroline complex against drug-resistant Candida species

Candida spp. are the commonest fungal pathogens worldwide. Antifungal resistance is a problem that has prompted the discovery of novel anti-Candida drugs. Herein, 25 compounds, some of them containing copper(II), cobalt(II) and manganese(II) ions, were initially evaluated for inhibiting the growth of reference strains of Candida albicans and Candida tropicalis. Eight (32%) of the compounds inhibited the proliferation of these yeasts, displaying minimum inhibitory concentrations (MICs) ranging from 31.25 to 250 μg/mL and minimum fungicidal concentration (MFCs) from 62.5 to 250 μg/mL. Drug-likeness/pharmacokinetic calculated by SwissADME indicated that the 8 selected compounds were suitable for use as topical drugs. The complex CTP, Cu(theo)2phen(H2O).5H2O (theo = theophylline; phen = 1,10-phenanthroline), was chosen for further testing against 10 medically relevant Candida species that were resistant to fluconazole/amphotericin B. CTP demonstrated a broad spectrum of action, inhibiting the growth of all 20 clinical fungal isolates, with MICs from 7.81 to 62.5 μg/mL and MFCs from 15.62 to 62.5 μg/mL. Conversely, CTP did not cause lysis in erythrocytes. The toxicity of CTP was evaluated in vivo using Galleria mellonella and Tenebrio molitor. CTP had no or low levels of toxicity at doses ranging from 31.25 to 250 μg/mL for 5 days. After 24 h of treatment, G. mellonella larvae exhibited high survival rates even when exposed to high doses of CTP (600 μg/mL), with the 50% cytotoxic concentration calculated as 776.2 μg/mL, generating selectivity indexes varying from 12.4 to 99.4 depending on each Candida species. These findings suggest that CTP could serve as a potential drug to treat infections caused by Candida species resistant to clinically available antifungals.

Single-cell RNA-seq revealed heterogeneous responses and functional differentiation of hemocytes against white spot syndrome virus infection in Litopenaeus vannamei

Shrimp hemocytes are the vital immune cells participating in innate immune response to defend against viruses. However, the lack of specific molecular markers for shrimp hemocyte hindered the insightful understanding of their functional clusters and differential roles in combating microbial infections. In this study, we used single-cell RNA sequencing to map the transcriptomic landscape of hemocytes from the white spot syndrome virus (WSSV)-infected Litopenaeus vannamei and conjointly analyzed with our previous published single-cell RNA sequencing technology data from the healthy hemocytes. A total of 16 transcriptionally distinct cell clusters were identified, which occupied different proportions in healthy and WSSV-infected hemocytes and exerted differential roles in antiviral immune response. Following mapping of the sequencing data to the WSSV genome, we found that all types of hemocytes could be invaded by WSSV virions, especially the cluster 8, which showed the highest transcriptional levels of WSSV genes and exhibited a cell type-specific antiviral response to the viral infection. Further evaluation of the cell clusters revealed the delicate dynamic balance between hemocyte immune response and viral infestation. Unsupervised pseudo-time analysis of hemocytes showed that the hemocytes in immune-resting state could be significantly activated upon WSSV infection and then functionally differentiated to different hemocyte subsets. Collectively, our results revealed the differential responses of shrimp hemocytes and the process of immune-functional differentiation post-WSSV infection, providing essential resource for the systematic insight into the synergistic immune response mechanism against viral infection among hemocyte subtypes.

IMPORTANCE

Current knowledge of shrimp hemocyte classification mainly comes from morphology, which hinder in-depth characterization of cell lineage development, functional differentiation, and different immune response of hemocyte types during pathogenic infections. Here, single-cell RNA sequencing was used for mapping hemocytes during white spot syndrome virus (WSSV) infection in Litopenaeus vannamei, identifying 16 cell clusters and evaluating their potential antiviral functional characteristics. We have described the dynamic balance between viral infestation and hemocyte immunity. And the functional differentiation of hemocytes under WSSV stimulation was further characterized. Our results provided a comprehensive transcriptional landscape and revealed the heterogeneous immune response in shrimp hemocytes during WSSV infection.

Galleria mellonella as a Model for the Study of Fungal Pathogens: Advantages and Disadvantages

The study of pathogenicity and virulence of fungal strains, in vivo in the preclinical phase, is carried out through the use of animal models belonging to various classes of mammals (rodents, leproids, etc.). Although animals are functionally more similar to humans, these studies have some limitations in terms of ethics (animal suffering), user-friendliness, cost-effectiveness, timing (physiological response time) and logistics (need for adequately equipped laboratories). A good in vivo model must possess some optimal characteristics to be used, such as rapid growth, small size and short life cycle. For this reason, insects, such as Galleria mellonella (Lepidoptera), Drosophila melanogaster (Diptera) and Bombyx mori (Lepidoptera), have been widely used as alternative non-mammalian models. Due to their simplicity of use and low cost, the larvae of G. mellonella represent an optimal model above all to evaluate the virulence of fungal pathogens and the use of antifungal treatments (either single or in combination with biologically active compounds). A further advantage is also represented by their simple neuronal system limiting the suffering of the animal itself, their ability to survive at near-body ambient temperatures as well as the expression of proteins able to recognise combined pathogens following the three R principles (replacement, refinement and reduction). This review aims to assess the validity as well as the advantages and disadvantages of replacing mammalian classes with G. mellonella as an in vivo study model for preclinical experimentation.

Thwarting resistance: MgrA inhibition with methylophiopogonanone a unveils a new battlefront against S. aureus

Limitations in the clinical treatment of Staphylococcus aureus (S. aureus) infections have arisen due to the advent of antibiotic-resistant strains. Given the immense potential of therapeutic strategies targeting bacterial virulence, the role of MgrA as a pivotal virulence determinant in S. aureus-orchestrating resistance, adherence, and hundreds of virulence targets-becomes indispensable. In this investigation, leveraging advanced virtual screening and fluorescence anisotropy assays, we discerned methylophiopogonanone A (Mo-A), a flavonoid derivative, as a potent disruptor of the MgrA-DNA interaction nexus. Subsequent analysis revealed that Mo-A effectively inhibits the expression of virulence factors such as Hla and Pvl in S. aureus and markedly reduces its adhesion capability to fibrinogen. On a cellular landscape, Mo-A exerts a mitigating influence on the deleterious effects inflicted by S. aureus USA300 on A549 cells. Furthermore, our data indicate that Mo-A downregulates the transcription of genes associated with immune evasion, such as nucleases (nuc), Staphylococcal Chemotaxis Inhibitory Protein (chips), and Staphylococcal Complement Inhibitor (scin), thereby undermining immune escape and amplifying neutrophil chemotaxis. Upon application in an in vivo setting, Mo-A assumes a protective persona in a murine model of S. aureus USA300-induced pneumonia and demonstrates efficacy in the Galleria mellonella infection model. Of note, S. aureus displayed no swift acquisition of resistance to Mo-A, and the effect was synergistically enhanced when used in combination with vancomycin. Our findings add substantive weight to the expanding field of virulence-targeted therapeutic strategies and set the stage for more comprehensive exploration of Mo-A potential in combating antibiotic-resistant S. aureus.

Response of the mosquito immune system and symbiotic bacteria to pathogen infection

Mosquitoes are the deadliest animal in the word, transmitting a variety of insect-borne infectious diseases, such as malaria, dengue fever, yellow fever, and Zika, causing more deaths than any other vector-borne pathogen. Moreover, in the absence of effective drugs and vaccines to prevent and treat insect-borne diseases, mosquito control is particularly important as the primary measure. In recent decades, due to the gradual increase in mosquito resistance, increasing attention has fallen on the mechanisms and effects associated with pathogen infection. This review provides an overview of mosquito innate immune mechanisms in terms of physical and physiological barriers, pattern recognition receptors, signalling pathways, and cellular and humoral immunity, as well as the antipathogenic effects of mosquito symbiotic bacteria. This review contributes to an in-depth understanding of the interaction process between mosquitoes and pathogens and provides a theoretical basis for biological defence strategies against mosquito-borne infectious diseases.

Klebsiella pneumoniae DedA family proteins have redundant roles in divalent cation homeostasis and resistance to phagocytosis

The DedA superfamily is a highly conserved family of membrane proteins. Deletion of Escherichia coli yqjA and yghB, encoding related DedA family proteins, results in sensitivity to elevated temperature, antibiotics, and alkaline pH. The human pathogen Klebsiella pneumoniae possesses genes encoding DedA family proteins with >90% amino acid identity to E. coli YqjA and YghB. We hypothesized that the deletion of K. pneumoniae yqjA and yghB will impact its physiology and may reduce its virulence. The K. pneumoniae ΔyqjA ΔyghB mutant (strain VT101) displayed a growth defect at 42°C and alkaline pH sensitivity, not unlike its E. coli counterpart. However, VT101 retained mostly wild-type resistance to antibiotics. We found VT101 was sensitive to the chelating agent EDTA, the anionic detergent SDS, and agents capable of alkalizing the bacterial cytoplasm such as bicarbonate or chloroquine. We could restore growth at alkaline pH and at elevated temperature by addition of 0.5-2 mM Ca2+ or Mg2+ to the culture media. VT101 displayed a slower uptake of calcium, which was dependent upon calcium channel activity. VT201, with similar deletions as VT101 but derived from a virulent K. pneumoniae strain, was highly susceptible to phagocytosis by alveolar macrophages and displayed a defect in the production of capsule. These findings suggest divalent cation homeostasis and virulence are interlinked by common functions of the DedA family.IMPORTANCEKlebsiella pneumoniae is a dangerous human pathogen. The DedA protein family is found in all bacteria and is a membrane transporter often required for virulence and antibiotic resistance. K. pneumoniae possesses homologs of E. coli YqjA and YghB, with 60% amino acid identity and redundant functions, which we have previously shown to be required for tolerance to biocides and alkaline pH. A K. pneumoniae strain lacking yqjA and yghB was found to be sensitive to alkaline pH, elevated temperature, and EDTA/SDS and displayed a defect in calcium uptake. Sensitivity to these conditions was reversed by addition of calcium or magnesium to the growth medium. Introduction of ΔyqjA and ΔyghB mutations into virulent K. pneumoniae resulted in the loss of capsule, increased phagocytosis by macrophages, and a partial loss of virulence. These results show that targeting the Klebsiella DedA family results in impaired divalent cation transport and, in turn, loss of virulence.

Safety Assessment of the Potential Probiotic Bacterium Limosilactobacillus fermentum J23 Using the Mexican Fruit Fly (Anastrepha ludens Loew, Diptera: Tephritidae) as a Novel In Vivo Model

Safety assessment of probiotics is difficult but essential. In this work, the Mexican fruit fly, Anastrepha ludens (Loew) (Diptera: Tephritidae), was used as in vivo model to assess the biosafety of Limosilactobacillus fermentum J23. In the first set of experiments, the strain was orally administered to adult flies through direct feeding, whereas in the second set of experiments, it was supplemented through the larval rearing medium. Data showed that L. fermentum J23 did not lead to increased mortality or treatment-related toxicity signs in adult female and male flies. Ingestion of L. fermentum J23 by adult female flies led to a statistically significant improvement in locomotor activity compared to the control groups (ca. 59% decrease in climbing time, p < 0.0001). A positive trend in lifespan extension under stress (maximum lifespan = 144 h) was also observed. When L. fermentum J23 was administered to the larvae, the adult emergence (p = 0.0099), sex ratio (p = 0.0043), and flight ability (p = 0.0009) increased significantly by 7%, 31%, and 8%, respectively, compared to the control diet. No statistical effect between the control diet and the L. fermentum J23-based diet for the number of pupae recovered, pupal weight, duration of the pupal stage, lifespan under stress, and morphological development was observed. We conclude that feeding L. fermentum J23 to the novel experimental model A. ludens had no toxic effects and could be safely considered a potential probiotic for food supplements; however, further studies are still needed to establish its biosafety in humans.

Effect of the polysaccharide capsule and its heptose on the resistance of Campylobacter jejuni to innate immune defenses

Campylobacter jejuni is a commensal in many animals but causes diarrhea in humans. Its polysaccharide capsule contributes to host colonization and virulence in a strain- and model-specific manner. We investigated if the capsule and its heptose are important for interactions of strain NCTC 11168 with various hosts and their innate immune defenses. We determined that they support bacterial survival in Drosophila melanogaster and enhance virulence in Galleria mellonella. We showed that the capsule had limited antiphagocytic activity in human and chicken macrophages, decreased adherence to chicken macrophages, and decreased intracellular survival in both macrophages. In contrast, the heptose increased uptake by chicken macrophages and supported adherence to human macrophages and survival within them. While the capsule triggered nitric oxide production in chicken macrophages, the heptose mitigated this and protected against nitrosative assault. Finally, the C. jejuni strain NCTC 11168 elicited strong cytokine production in both macrophages but quenched ROS production independently from capsule and heptose, and while the capsule and heptose did not protect against oxidative assault, they favored growth in biofilms under oxidative stress. This study shows that the wild-type capsule with its heptose is optimized to resist innate defenses in strain NCTC 11168 often via antagonistic effects of the capsule and its heptose.

Polystyrene Microplastics Exacerbate Candida albicans Infection Ability In Vitro and In Vivo

Plastic pollution is an important environmental problem, and microplastics have been shown to have harmful effects on human and animal health, affecting immune and metabolic physiological functions. Further, microplastics can interfere with commensal microorganisms and exert deleterious effects on exposure to pathogens. Here, we compared the effects of 1 µm diameter polystyrene microplastic (PSMPs) on Candida albicans infection in both in vitro and in vivo models by using HT29 cells and Galleria mellonella larvae, respectively. The results demonstrated that PSMPs could promote Candida infection in HT29 cells and larvae of G. mellonella, which show immune responses similar to vertebrates. In this study, we provide new experimental evidence for the risk to human health posed by PSMPs in conjunction with Candida infections.

Establishing Galleria mellonella as an invertebrate model for the emerging multi-host pathogen Helcococcus ovis

Helcococcus ovis (H. ovis) can cause disease in a broad range of animal hosts, including humans, and has been described as an emerging bacterial pathogen in bovine metritis, mastitis, and endocarditis. In this study, we developed an infection model that showed H. ovis can proliferate in the hemolymph and induce dose-dependent mortality in the invertebrate model organism Galleria mellonella (G. mellonella). We applied the model and identified H. ovis isolates with attenuated virulence originating from the uterus of a healthy post-partum dairy cow (KG38) and hypervirulent isolates (KG37, KG106) originating from the uterus of cows with metritis. Medium virulence isolates were also isolated (KG36, KG104) from the uterus of cows with metritis. A major advantage of this model is that a clear differentiation in induced mortality between H. ovis isolates was detected in just 48 h, resulting in an effective infection model able to identify virulence differences between H. ovis isolates with a short turnaround time. Histopathology showed G. mellonella employs hemocyte-mediated immune responses to H. ovis infection, which are analogous to the innate immune response in cows. In summary, G. mellonella can be used as an invertebrate infection model for the emerging multi-host pathogen Helcococcus ovis.

Sporothrix brasiliensis Infection Modulates Antimicrobial Peptides and Stress Management Gene Expression in the Invertebrate Biomodel Galleria mellonella

Sporothrix brasiliensis is the most pathogenic species, responsible for the Brazilian cat-transmitted sporotrichosis hyperendemic. In this scenario, an investigation of the pathogen-host interaction can provide relevant information for future treatment strategies. To this end, the invertebrate Galleria mellonella has proven to be a suitable alternative for evaluating the virulence of pathogenic fungi, since the insect immune system is similar to the mammalian innate immune response. The aim of this work was to investigate phenotypic and molecular aspects of the immune response of G. mellonella throughout the S. brasiliensis infection. Hemocyte density and the evolution of the fungal load were evaluated. In parallel, RT-qPCR expression analysis of genes encoding antimicrobial peptides (Gallerimycin and Galiomycin) and stress management genes (C7 Contig 15362 and C8 Contig 19101) was conducted. The fungal load and hemocyte densities increased simultaneously and proportionally to the deleterious morphological events and larvae mortality. Gallerimycin, C7 Contig 15362 and C8 Contig 19101 genes were positively regulated (p < 0.05) at distinct moments of S. brasiliensis infection, characterizing a time-dependent and alternately modulated profile. Galiomycin gene expression remained unchanged. Our results contribute to the future proposal of potential alternative pathways for treating and consequently controlling S. brasiliensis zoonosis, a major public health issue in Latin America.

Traversing the Cell Wall: The Chitinolytic Activity of Histoplasma capsulatum Extracellular Vesicles Facilitates Their Release

Histoplasma capsulatum is the causative agent of histoplasmosis. Treating this fungal infection conventionally has significant limitations, prompting the search for alternative therapies. In this context, fungal extracellular vesicles (EVs) hold relevant potential as both therapeutic agents and targets for the treatment of fungal infections. To explore this further, we conducted a study using pharmacological inhibitors of chitinase (methylxanthines) to investigate their potential to reduce EV release and its subsequent impact on fungal virulence in an in vivo invertebrate model. Our findings revealed that a subinhibitory concentration of the methylxanthine, caffeine, effectively reduces EV release, leading to a modulation of H. capsulatum virulence. To the best of our knowledge, this is the first reported instance of a pharmacological inhibitor that reduces fungal EV release without any observed fungicidal effects.

Sensor histidine kinases kdpD and aauS regulate biofilm and virulence in Pseudomonas aeruginosa PA14

Pseudomonas aeruginosa is a multidrug-resistant opportunistic human pathogen that utilizes two-component systems (TCSs) to sense pathophysiological signals and coordinate virulence. P. aeruginosa contains 64 sensor histidine kinases (HKs) and 72 response regulators (RRs) that play important roles in metabolism, bacterial physiology, and virulence. However, the role of some TCSs in virulence remains uncharacterized. In this study, we evaluated the virulence potential of some uncharacterized sensor HK and RR knockouts in P. aeruginosa using a Galleria mellonella infection model. Furthermore, we demonstrated that KdpD and AauS HKs regulate virulence by affecting P. aeruginosa biofilm formation and motility. Both ΔkdpD and ΔaauS showed reduced biofilm and motility which were confirmed by restored phenotypes upon complementation. Moreover, ΔkdpD and ΔaauS exhibited increased survival of HeLa cells and G. mellonella during in vivo infection. Altered expression of the transcriptional regulators anR and lasR, along with the virulence genes lasA, pelA, cupA, pqsA, pqsB, pqsC, and pqsD in the mutant strains elucidated the mechanism by which ΔkdpD and ΔaauS affect virulence. These findings confirm that kdpD and aauS play important roles in P. aeruginosa pathogenesis by regulating biofilm formation and motility.

Polypeptides Targeting Paracoccidioides brasiliensis Drk1

Considering the toxicity of conventional therapeutic approaches and the importance of precise mechanistic targets, it is important to explore signaling pathways implicated in fungal pathobiology. Moreover, treatment of paracoccidioidomycosis, a systemic mycosis caused by a dimorphic fungus, requires prolonged therapeutic regimens. Among the numerous factors underpinning the establishment of Paracoccidioides spp. infection, the capacity to transition from the mycelial to the yeast form is of pivotal importance. The Drk1 protein of Paracoccidioides brasiliensis likely plays a decisive role in this morphological shift and subsequent virulence. We identified peptides with affinity for the PbDrk1 protein using the phage-display method and assessed the effects of these peptides on P. brasiliensis. The peptides were found to inhibit the phase transition of P. brasiliensis. Furthermore, a substantial proportion of these peptides prevented adhesion to pneumocytes. Although these peptides may not possess inherent antifungal properties, they can augment the effects of certain antifungal agents. Notably, the cell wall architecture of P. brasiliensis appears to be modulated by peptide intervention, resulting in a reduced abundance of glycosylated proteins and lipids. These peptides were also evaluated for their efficacy in a Galleria mellonella model and shown to contribute to enhanced larval survival rates. The role of PbDrk1, which is notably absent in mammals, should be further investigated to improve the understanding of its functional role in P. brasiliensis, which may be helpful for designing novel therapeutic modalities.

Alternative Non-Mammalian Animal and Cellular Methods for the Study of Host-Fungal Interactions

In the study of fungal pathogenesis, alternative methods have gained prominence due to recent global legislation restricting the use of mammalian animals in research. The principle of the 3 Rs (replacement, reduction, and refinement) is integrated into regulations and guidelines governing animal experimentation in nearly all countries. This principle advocates substituting vertebrate animals with other invertebrate organisms, embryos, microorganisms, or cell cultures. This review addresses host-fungus interactions by employing three-dimensional (3D) cultures, which offer more faithful replication of the in vivo environment, and by utilizing alternative animal models to replace traditional mammals. Among these alternative models, species like Caenorhabditis elegans and Danio rerio share approximately 75% of their genes with humans. Furthermore, models such as Galleria mellonella and Tenebrio molitor demonstrate similarities in their innate immune systems as well as anatomical and physiological barriers, resembling those found in mammalian organisms.

Hypervirulent Klebsiella pneumoniae detection methods: a minireview

Hypervirulent Klebsiella pneumoniae (hvKp), characterized by high virulence and epidemic potential, has become a global public health challenge. Therefore, improving the identification of hvKp and enabling earlier and faster detection in the community to support subsequent effective treatment and prevention of hvKp are an urgent issue. To address these issues, a number of assays have emerged, such as String test, Galleria mellonella infection test, PCR, isothermal exponential amplification, and so on. In this paper, we have collected articles on the detection methods of hvKp and conducted a retrospective review based on two aspects: traditional detection technology and biomarker-based detection technology. We summarize the advantages and limitations of these detection methods and discuss the challenges as well as future directions, hoping to provide new insights and references for the rapid detection of hvKp in the future. The aim of this study is to focus on the research papers related to Hypervirulent Klebsiella pneumoniae involving the period from 2012 to 2022. We conducted searches using the keywords "Hypervirulent Klebsiella pneumoniae, biomarkers, detection techniques" on ScienceDirect and Google Scholar. Additionally, we also searched on PubMed, using MeSH terms associated with the keywords (such as Klebsiella pneumoniae, Klebsiella Infections, Virulence, Biomarkers, diagnosis, etc.).

Induced expression modes of genes related to Toll, Imd, and JAK/STAT signaling pathway-mediated immune response in Spodoptera frugiperda infected with Beauveria bassiana

Spodoptera frugiperda is one of the most harmful pests that attack maize and other major food crops and causes huge economic loss every year in China and other countries and regions. Beauveria bassiana, a kind of entomological fungus that is highly pathogenic to pests, is harmless to the environment and human beings. However, at present, S. frugiperda has gradually developed resistance to many pesticides and microbial insecticides. In this study, transcriptome sequencing was conducted to analyze the differences in gene expression between B. bassiana-infected and -uninfected S. frugiperda. More than 160 Gb of clean data were obtained as 150-bp paired-end reads using the Illumina HiSeq™ 4000 platform, and 2,767 and 2,892 DEGs were identified in LH36vsCK36 and LH144vsCK144, respectively. In order to explore the roles of JAK/STAT, Toll, and Imd signaling pathways in antifungal immune response in S. frugiperda against B. bassiana infection, the expression patterns of those signaling pathway-related genes in B. bassiana-infected S. frugiperda were analyzed by quantitative real-time PCR. In addition, antifungal activity experiments revealed that the suppression of JAK/STAT, Toll, and Imd signaling pathways by inhibitors could inhibit the antifungal activity to a large extent and lead to increased sensitivity of S. frugiperda to B. bassiana infection, indicating that JAK/STAT, Toll, and Imd signaling pathways and their associated genes might be involved in the synthesis and secretion of antifungal substances. This study implied that JAK/STAT, Toll, and Imd signaling pathways played crucial roles in the antifungal immune response of the S. frugiperda larvae, in which the related genes of these signaling pathways could play special regulatory roles in signal transduction. This study would improve our understanding of the molecular mechanisms underlying innate immunity and provide the basis for a wide spectrum of strategies against antifungal resistance of S. frugiperda.

Insect-pathogen crosstalk and the cellular-molecular mechanisms of insect immunity: uncovering the underlying signaling pathways and immune regulatory function of non-coding RNAs

Multicellular organisms are constantly subjected to pathogens that might be harmful. Although insects lack an adaptive immune system, they possess highly effective anti-infective mechanisms. Bacterial phagocytosis and parasite encapsulation are some forms of cellular responses. Insects often defend themselves against infections through a humoral response. This phenomenon includes the secretion of antimicrobial peptides into the hemolymph. Specific receptors for detecting infection are required for the recognition of foreign pathogens such as the proteins that recognize glucans and peptidoglycans, together referred to as PGRPs and βGRPs. Activation of these receptors leads to the stimulation of signaling pathways which further activates the genes encoding for antimicrobial peptides. Some instances of such pathways are the JAK-STAT, Imd, and Toll. The host immune response that frequently accompanies infections has, however, been circumvented by diseases, which may have assisted insects evolve their own complicated immune systems. The role of ncRNAs in insect immunology has been discussed in several notable studies and reviews. This paper examines the most recent research on the immune regulatory function of ncRNAs during insect-pathogen crosstalk, including insect- and pathogen-encoded miRNAs and lncRNAs, and provides an overview of the important insect signaling pathways and effector mechanisms activated by diverse pathogen invaders.

In vivo study on borophene nanoflakes interaction with Tenebrio molitor beetle: viability of hemocytes and short-term immunity effect

The family of graphene-based materials welcomed a new member, borophene, in 2014. Research on synthesis routes and experimental study on physicochemical and biological (especially in vivo) properties still is strongly desired in order to evaluate its practical potential as a drug delivery-system. The effect of two-dimensional borophene nanoflakes on cells, systems and the entire animal organism has not been studied so far. Therefore, we investigated in vivo its biocompatibility with hemocytes in the Tenebrio molitor as a model organism. Short-term studies demonstrated that borophene nanoflakes at doses of 0.5, 1 or 2 µg of nanoflakes per insect did not induce hemocytotoxicity. Hemocytes exposed to nanoflakes showed morphology, adhesiveness and ability to form filopodia as in the control hemocytes. A detailed study indicates that borophene nanoflakes do not: (i) generate intracellular reactive oxygen species in hemocytes, (ii) affect the mitochondrial membrane potential and (iii) interfere with phagocytosis. Therefore, this contribution presents new in vivo insights into the group of two-dimensional materials which are one of the most promising materials for biomedical applications owing to their special structure and unique properties. However, long-term studies in insects and other animals are still necessary to confirm that borophene is biocompatible and biologically safe.

Single-Cell Atlas Reveals the Hemocyte Subpopulations and Stress Responses in Asian Giant Softshell Turtle during Hibernation

Hibernation in turtle species is an adaptive survival strategy to colder winter conditions or food restrictions. However, the mechanisms underlying seasonal adaptions remain unclear. In the present study, we collected hemocytes from Pelochelys cantorii and compared the molecular signature of these cells between the active state and hibernation period based on single-cell RNA sequencing (scRNA-seq) analysis. We found six cell types and identified a list of new marker genes for each cell subpopulation. Moreover, several heat shock genes, including the Hsp40 family chaperone gene (DNAJ) and HSP temperature-responsive genes (HSPs), were upregulated during the hibernation period, which predicted these genes may play crucial roles in the stress response during hibernation. Additionally, compared to hemocytes in the active state, several upregulated differentially expressed immune-related genes, such as stat1, traf3, and socs6, were identified in hemocytes during the hibernation period, thus indicating the important immune function of hemocytes. Therefore, our findings provide a unified classification of P. cantorii hemocytes and identify the genes related to the stress response, thereby providing a better understanding of the adaptive mechanisms of hibernation.

Low dose γ-radiation induced effects on wax moth (Galleria mellonella) larvae

Larvae of the greater wax moth Galleria mellonella are common pests of beehives and commercial apiaries, and in more applied settings, these insects act as alternative in vivo bioassays to rodents for studying microbial virulence, antibiotic development, and toxicology. In the current study, our aim was to assess the putative adverse effects of background gamma radiation levels on G. mellonella. To achieve this, we exposed larvae to low (0.014 mGy/h), medium (0.056 mGy/h), and high (1.33 mGy/h) doses of caesium-137 and measured larval pupation events, weight, faecal discharge, susceptibility to bacterial and fungal challenges, immune cell counts, activity, and viability (i.e., haemocyte encapsulation) and melanisation levels. The effects of low and medium levels of radiation were distinguishable from the highest dose rates used - the latter insects weighed the least and pupated earlier. In general, radiation exposure modulated cellular and humoral immunity over time, with larvae showing heightened encapsulation/melanisation levels at the higher dose rates but were more susceptible to bacterial (Photorhabdus luminescens) infection. There were few signs of radiation impacts after 7 days exposure, whereas marked changes were recorded between 14 and 28 days. Our data suggest that G. mellonella demonstrates plasticity at the whole organism and cellular levels when irradiated and offers insight into how such animals may cope in radiologically contaminated environments (e.g. Chornobyl Exclusion Zone).

Lipids as a key element of insect defense systems

The relationship between insect pathogenic fungi and their insect hosts is a classic example of a co-evolutionary arms race between pathogen and target host: parasites evolve towards mechanisms that increase their advantage over the host, and the host increasingly strengthens its defenses. The present review summarizes the literature data describing the direct and indirect role of lipids as an important defense mechanism during fungal infection. Insect defense mechanisms comprise anatomical and physiological barriers, and cellular and humoral response mechanisms. The entomopathogenic fungi have the unique ability to digest the insect cuticle by producing hydrolytic enzymes with chitin-, lipo- and proteolytic activity; besides the oral tract, cuticle pays the way for fungal entry within the host. The key factor in insect resistance to fungal infection is the presence of certain types of lipids (free fatty acids, waxes or hydrocarbons) which can promote or inhibit fungal attachment to cuticle, and might also have antifungal activity. Lipids are considered as an important source of energy, and as triglycerides are stored in the fat body, a structure analogous to the liver and adipose tissue in vertebrates. In addition, the fat body plays a key role in innate humoral immunity by producing a range of bactericidal proteins and polypeptides, one of which is lysozyme. Energy derived from lipid metabolism is used by hemocytes to migrate to the site of fungal infection, and for phagocytosis, nodulation and encapsulation. One polyunsaturated fatty acid, arachidonic acid, is used in the synthesis of eicosanoids, which play several crucial roles in insect physiology and immunology. Apolipoprotein III is important compound with antifungal activity, which can modulate insect cellular response and is considered as important signal molecule.

Galleria mellonella-A Model for the Study of aPDT-Prospects and Drawbacks

Galleria mellonella is a promising in vivo model insect used for microbiological, medical, and pharmacological research. It provides a platform for testing the biocompatibility of various compounds and the kinetics of survival after an infection followed by subsequent treatment, and for the evaluation of various parameters during treatment, including the host-pathogen interaction. There are some similarities in the development of pathologies with mammals. However, a limitation is the lack of adaptive immune response. Antimicrobial photodynamic therapy (aPDT) is an alternative approach for combating microbial infections, including biofilm-associated ones. aPDT is effective against Gram-positive and Gram-negative bacteria, viruses, fungi, and parasites, regardless of whether they are resistant to conventional treatment. The main idea of this comprehensive review was to collect information on the use of G. mellonella in aPDT. It provides a collection of references published in the last 10 years from this area of research, complemented by some practical experiences of the authors of this review. Additionally, the review summarizes in brief information on the G. mellonella model, its advantages and methods used in the processing of material from these larvae, as well as basic knowledge of the principles of aPDT.

Studies of Streptococcus anginosus Virulence in Dictyostelium discoideum and Galleria mellonella Models

For many years, Streptococcus anginosus has been considered a commensal colonizing the oral cavity, as well as the gastrointestinal and genitourinary tracts. However, recent epidemiological and clinical data designate this bacterium as an emerging opportunistic pathogen. Despite the reported pathogenicity of S. anginosus, the molecular mechanism underpinning its virulence is poorly described. Therefore, our goal was to develop and optimize efficient and simple infection models that can be applied to examine the virulence of S. anginosus and to study host-pathogen interactions. Using 23 S. anginosus isolates collected from different infections, including severe and superficial infections, as well as an attenuated strain devoid of CppA, we demonstrate for the first time that Dictyostelium discoideum is a suitable model for initial, fast, and large-scale screening of virulence. Furthermore, we found that another nonvertebrate animal model, Galleria mellonella, can be used to study the pathogenesis of S. anginosus infection, with an emphasis on the interactions between the pathogen and host innate immunity. Examining the profile of immune defense genes, including antimicrobial peptides, opsonins, regulators of nodulation, and inhibitors of proteases, by quantitative PCR (qPCR) we identified different immune response profiles depending on the S. anginosus strain. Using these models, we show that S. anginosus is resistant to the bactericidal activity of phagocytes, a phenomenon confirmed using human neutrophils. Notably, since we found that the data from these models corresponded to the clinical severity of infection, we propose their further application to studies of the virulence of S. anginosus.