Phagocytosis of yeast: a method for concurrent quantification of binding and internalization using differential interference contrast microscopy

Enhancing impact of dietary nano formulated quercetin on laying performance: egg quality, oxidative stability of stored eggs, intestinal immune and antioxidants related genes expression

BACKGROUND

Nutritional interventions with natural antioxidants can provide a pragmatic solution for modifying hens' performance and maintaining oxidative stability of eggs during storage. Quercetin is the most abundant flavonoids with potent antioxidant and immune stimulant activities. The concept of incorporating of quercetin, as potent antioxidant and immunostimulant, into effective nano-carriers (QNPs) has promoted their bioavailability and stability thus, their effectiveness for the first time were assessed on laying hens' performance and immunity, eggs quality during storage. Four hundred 12-weeks-old Hy-line brown laying hens were distributed to four experimental groups: control group fed basal diets, and other 3 groups fed basal diets fortified with 100, 200 and 300 mg/kg QNPs for 60 weeks.

RESULTS

Laying performance and quality of laid eggs were improved as expressed by elevated laying rate, egg mass %, eggs weight and yolk weight in QNPs200 and 300. Fortification of QNPs300 remarkably decreased layers serum total cholesterol concurrently with decreased egg yolk saturated fatty acids and cholesterol while increased polyunsaturated fatty acids. Over- 45 days storage period, QNPs enhanced phospholipids, total phenolics and flavonoids, total antioxidant activity (T-AOC) simultaneous with decreased MDA content in eggs. Furthermore, enhanced immune response was detected in both in serum and intestine of QNPs fed hens as reflected by higher lysozymes activity, IgM, IgG and phagocytic index and demotion of NO together with AvBD 6-12, IL-10, IgM and ATg 5-7-12 upregulation and downregulation of IL-1β and TNF-α especially at QNPs200 and 300. Intestinal redox balance was modified via decreasing H2O2 and MDA simultaneous with upregulation of catalase, SOD, GSH-Px, HO-1 and NQO1 in groups fed higher doses of QNPs.

CONCLUSIONS

QNPs supplementation provides a new nutritional strategy towards increasing hen performance, fortification of eggs with natural antioxidants that prevents egg quality deterioration during storage.

Detection and Quantification of Cryptococcus Uptake by Phagocytic Cells Using Imaging Flow Cytometry

Cryptococcus neoformans, the predominant etiological agent of cryptococcosis, is an encapsulated fungal pathogen found ubiquitously in the environment that causes pneumonia and life-threatening infections of the central nervous system. Following inhalation of yeasts or desiccated basidiospores into the lung alveoli, resident pulmonary phagocytic cells aid in the identification and eradication of Cryptococcus yeast through their arsenal of pattern recognition receptors (PRRs). PRRs recognize conserved pathogen-associated molecular patterns (PAMPs), such as branched mannans, β-glucans, and chitins that are the major components of the fungal cell wall. However, the key receptors/ligand interactions required for cryptococcal recognition and eventual fungal clearance have yet to be elucidated. Here we present an imaging flow cytometer (IFC) method that offers a novel quantitative cellular imaging and population statistics tool to accurately measure phagocytosis of fungal cells. It has the capacity to measure two distinct steps of phagocytosis: association/attachment and internalization in a high-throughput and quantitative manner that is difficult to achieve with other technologies. Results from these IFC studies allow for the potential to identify PRRs required for recognition, uptake, and subsequent activation of cytokine production, as well as other effector cell responses required for fungal clearance.

Dietary Curcumin Modulating Effect on Performance, Antioxidant Status, and Immune-Related Response of Broiler Chickens Exposed to Imidacloprid Insecticide

Birds appear to be especially vulnerable to adverse impacts from insecticides. This is especially true for imidacloprid (IMI), which is considered the most toxic to avian species. Recently, prospective studies aimed at including natural alternative products to alleviate the toxic impact that comes from insecticides have been increased. Focusing on herbal growth promoters and antioxidative medicament for the poultry industry, this ongoing experiment was conducted to examine the curcumin role (CUR) in mitigating IMI-prompted detrimental effects on broilers' performance, immunity, and antioxidant status. A total number of one hundred and fifty commercial meat-type Ross 308 broilers chicks (one-day-old) were randomly allocated into equal five groups (30 chicks/group and 10 birds/replicate). The first group (C) was the control; the second group (CUR) was fed a diet containing CUR at the level of 450 mg/kg; the third group (IMI) was fed control diet for 14 days and then was fed a diet containing IMI at the level of 50 mg/kg; the fourth group (CUR+IMI co-treated) was fed a diet containing CUR+IMI; and the fifth group (CUR+IMI pro/co-treated) was fed a diet containing CUR for 14 days as protective and then a diet containing CUR+IMI for the rest of the trial. CUR supplementation either in the (CUR pro/co-treated) or (CUR co-treated) groups significantly (p < 0.05) improved final body weight and total body weight gain while decreasing the total feed intake and feed conversion ratio when compared to the IMI-exposed and non-treated birds. CUR induced a significant (p < 0.05) enhancement in hematological indices, phagocytosis %, phagocytic index, intracellular killing capacity, total proteins, globulin, liver function enzymes, lysozyme activity, and immunoglobulin-G levels compared to IMI-exposed and non-treated birds. In addition, dietary supplementation of CUR significantly (p < 0.05) modulated oxidative stress-related biomarkers in splenic tissues (total antioxidant capacity, superoxide dismutase, catalase, and glutathione peroxidase) and decreased malondialdehyde levels (p < 0.05) when compared to IMI-exposed and non-treated birds. CUR significantly down-regulated mRNA levels expression of IL-1β, TNF-α, and TLR4 and up-regulated IL-10 mRNA expression levels in spleens of birds when compared to those exposed to IMI-and non-treated. Finally, our results provided new insight into IMI-induced immuno-toxicity in broiler chickens. Furthermore, for the first time, our study informed that CUR can cause an in vivo protective effect against IMI toxicity, principally as a protective and/or as concurrent supplementation during the exposure to IMI toxicity.

Black Pepper or Radish Seed Oils in a New Combination of Essential Oils Modulated Broiler Chickens’ Performance and Expression of Digestive Enzymes, Lipogenesis, Immunity, and Autophagy-Related Genes

Optimal combinations of essential oils (EOs) can enhance performance and maintain poultry productivity. The effects of EOs with black pepper oil (BPO) or radish seed oil (RSO) on performance and the expression of digestive enzymes, lipogenesis, immunity, and autophagy-related genes in broiler chickens were explored. Six dietary treatments for 300 one-day-old chicks were allocated as follows: controls were fed a basal diet, one group was fed an EO-supplemented diet (1.5 g/kg diet of parsley, mint, and carrot seed oils (1:1:1)), and other groups received Eos + BPO0.25, Eos + BPO0.5, Eos + RSO0.25, and Eos + RSO0.5 treatments, with a basal diet containing EOs plus BPO or RSO at the level of 0.25 or 0.5 g/kg, respectively. Supplementation with 0.5 g/kg of EOs plus BPO or RSO resulted in the most improved maximum BWG and FCR in broiler chickens. The lactobacilli population was increased in Eos + BPO0.5, followed by EOs + RSO0.5, unlike in the control. The highest expression of the CCK and PNLIP genes was identified in the Eos + BPO group. The FAS and ACC genes were upregulated, while the IgA and IL-10 genes were downregulated, with EOs plus RSO or BPO. The group that received Eos + BPO0.5, followed by Eos + RSO0.5, displayed patterns of higher expression for atg5, atg7, and atg12, with lower expression of mTOR. In summary, a new combination of EOs with 0.5 g/kg BPO had potential growth-promoting and immune-boosting effects in broiler chickens.

Yeasts as a promising delivery platform for DNA and RNA vaccines

Yeasts are considered a useful system for the development of vaccines for human and veterinary health. Species such as Saccharomyces cerevisiae and Pichia pastoris have been used successfully as host organisms for the production of subunit vaccines. These organisms have been also explored as vaccine vehicles enabling the delivery of antigens such as proteins and nucleic acids. The employed species possess a GRAS status (Generally Recognized as Safe) for the production of therapeutic proteins, besides promoting immunostimulation due to the properties of their wall cell composition. This strategy allows the administration of nucleic acids orally and a specific delivery to professional antigen-presenting cells (APCs). In this review, we seek to outline the development of whole yeast vaccines (WYV) carrying nucleic acids in different approaches in the medical field, as well as the immunological aspects of this vaccine strategy. The data presented here reveal the application of this platform in promoting effective immune responses in the context of prophylactic and therapeutic approaches.

Nanotherapy delivery of c-myc inhibitor targets Protumor Macrophages and preserves Antitumor Macrophages in Breast Cancer

Tumor-associated macrophages (TAMs) enhance tumor growth in mice and are correlated with a worse prognosis for breast cancer patients. While early therapies sought to deplete all macrophages, current therapeutics aim to reprogram pro-tumor macrophages (M2) and preserve those necessary for anti-tumor immune responses (M1). Recent studies have shown that c-MYC (MYC) is induced in M2 macrophages in vitro and in vivo where it regulates the expression of tumor-promoting genes. In a myeloid lineage MYC KO mouse model, MYC had important roles in macrophage maturation and function leading to reduced tumor growth. We therefore hypothesized that targeted delivery of a MYC inhibitor to established M2 TAMs could reduce polarization toward an M2 phenotype in breast cancer models.

Methods: In this study, we developed a MYC inhibitor prodrug (MI3-PD) for encapsulation within perfluorocarbon nanoparticles, which can deliver drugs directly to the cytosol of the target cell through a phagocytosis independent mechanism. We have previously shown that M2-like TAMs express significant levels of the vitronectin receptor, integrin β3, and in vivo targeting and therapeutic potential was evaluated using αvβ3 integrin targeted rhodamine-labeled nanoparticles (NP) or integrin αvβ3-MI3-PD nanoparticles.

Results: We observed that rhodamine, delivered by αvβ3-rhodamine NP, was incorporated into M2 tumor promoting macrophages through both phagocytosis-independent and dependent mechanisms, while NP uptake in tumor suppressing M1 macrophages was almost exclusively through phagocytosis. In a mouse model of breast cancer (4T1-GFP-FL), M2-like TAMs were significantly reduced with αvβ3-MI3-PD NP treatment. To validate this effect was independent of drug delivery to tumor cells and was specific to the MYC inhibitor, mice with integrin β3 knock out tumors (PyMT-Bo1 β3KO) were treated with αvβ3-NP or αvβ3-MI3-PD NP. M2 macrophages were significantly reduced with αvβ3-MI3-PD nanoparticle therapy but not αvβ3-NP treatment.

Conclusion: These data suggest αvβ3-NP-mediated drug delivery of a c-MYC inhibitor can reduce protumor M2-like macrophages while preserving antitumor M1-like macrophages in breast cancer.

Hemin-bound cysteinyl bolaamphiphile self-assembly as a horseradish peroxidase-mimetic catalyst

A horseradish peroxidase (HRP) mimetic catalyst was constructed by tethering hemin to the cysteinyl bolaamphiphile assembly through thiol–Fe bond. The prepared catalyst showed high catalytic activity comparable to HRP even at the high temperature.

Cryptococcus gattii is killed by dendritic cells, but evades adaptive immunity by failing to induce dendritic cell maturation

During adaptive immunity to pathogens, dendritic cells (DCs) capture, kill, process, and present microbial Ags to T cells. Ag presentation is accompanied by DC maturation driven by appropriate costimulatory signals. However, current understanding of the intricate regulation of these processes remains limited. Cryptococcus gattii, an emerging fungal pathogen in the Pacific Northwest of Canada and the United States, fails to stimulate an effective immune response in otherwise healthy hosts leading to morbidity or death. Because immunity to fungal pathogens requires intact cell-mediated immunity initiated by DCs, we asked whether C. gattii causes dysregulation of DC functions. C. gattii was efficiently bound and internalized by human monocyte-derived DCs, trafficked to late phagolysosomes, and killed. Yet, even with this degree of DC activation, the organism evaded pathways leading to DC maturation. Despite the ability to recognize and kill C. gattii, immature DCs failed to mature; there was no increased expression of MHC class II, CD86, CD83, CD80, and CCR7, or decrease of CD11c and CD32, which resulted in suboptimal T cell responses. Remarkably, no increase in TNF-α was observed in the presence of C. gattii. However, addition of recombinant TNF-α or stimulation that led to TNF-α production restored DC maturation and restored T cell responses. Thus, despite early killing, C. gattii evades DC maturation, providing a potential explanation for its ability to infect immunocompetent individuals. We have also established that DCs retain the ability to recognize and kill C. gattii without triggering TNF-α, suggesting independent or divergent activation pathways among essential DC functions.

TLR2 signaling subpathways regulate TLR9 signaling for the effective induction of IL-12 upon stimulation by heat-killed Brucella abortus

Brucella abortus is a Gram-negative intracellular bacterium that induces MyD88-dependent IL-12 production in dentritic cells (DCs) and a subsequent protective Th1 immune response. Previous studies have shown that the Toll-like receptor 2 (TLR2) is required for tumor-necrosis factor (TNF) production, whereas TLR9 is responsible for IL-12 induction in DCs after exposure to heat-killed Brucella abortus (HKBA). TLR2 is located on the cell surface and is required for optimal microorganism-induced phagocytosis by innate immune cells; thus, phagocytosis is an indispensable preliminary step for bacterial genomic DNA recognition by TLR9 in late-endosomal compartments. Here, we hypothesized that TLR2-triggered signals after HKBA stimulation might cross-regulate TLR9 signaling through the indirect modulation of the phagocytic function of DCs or the direct modulation of cytokine gene expression. Our results indicate that HKBA phagocytosis was TLR2-dependent and an essential step for IL-12p40 induction. In addition, HKBA exposure triggered the TLR2-mediated activation of both p38 and extracellular signal-regulated kinase 1/2 (ERK1/2). Interestingly, although p38 was required for HKBA phagocytosis and phagosome maturation, ERK1/2 did not affect these processes but negatively regulated IL-12 production. Although p38 inhibitors tempered both TNF and IL-12 responses to HKBA, pre-treatment with an ERK1/2 inhibitor significantly increased IL-12p40 and abrogated TNF production in HKBA-stimulated DCs. Further experiments showed that the signaling events that mediated ERK1/2 activation after TLR2 triggering also required HKBA-induced Ras activation. Furthermore, Ras-guanine nucleotide-releasing protein 1 (RasGRP1) mediated the TLR2-induced ERK1/2 activation and inhibition of IL-12p40 production. Taken together, our results demonstrated that HKBA-mediated TLR2-triggering activates both the p38 and ERK1/2 signaling subpathways, which divergently regulate TLR9 activation at several levels to induce an appropriate protective IL-12 response.

Staphylococcus aureus synthesizes adenosine to escape host immune responses

Staphylococcus aureus infects hospitalized or healthy individuals and represents the most frequent cause of bacteremia, treatment of which is complicated by the emergence of methicillin-resistant S. aureus. We examined the ability of S. aureus to escape phagocytic clearance in blood and identified adenosine synthase A (AdsA), a cell wall–anchored enzyme that converts adenosine monophosphate to adenosine, as a critical virulence factor. Staphylococcal synthesis of adenosine in blood, escape from phagocytic clearance, and subsequent formation of organ abscesses were all dependent on adsA and could be rescued by an exogenous supply of adenosine. An AdsA homologue was identified in the anthrax pathogen, and adenosine synthesis also enabled escape of Bacillus anthracis from phagocytic clearance. Collectively, these results suggest that staphylococci and other bacterial pathogens exploit the immunomodulatory attributes of adenosine to escape host immune responses.

Exogenous heat shock protein 70 binds macrophage lipid raft microdomain and stimulates phagocytosis, processing, and MHC-II presentation of antigens

The extracellular presence of endotoxin-free heat shock protein 70 (HSP70) enhances the rate and capacity of macrophage-mediated phagocytosis at 6 times the basal rate. It is protein-specific, dose- and time-dependent and involves the internalization of inert microspheres, Gram-positive and -negative bacteria and fungi. Structurally, exogenous HSP70 binds the macrophage plasma membrane, specifically on its lipid raft-microdomain. Disruption of lipid rafts, HSP70-LR interaction, or denaturing HSP70 abrogates the HSP-mediated increase in phagocytosis. Further, HSP70-mediated phagocytosis directly enhances the processing and presentation of internalized antigens via the endocytic MHC class-II pathway to CD4+ T lymphocytes. Modulating the HSP70-LR interaction presents an opportunity to intervene at the level of host-pathogen interface: a therapeutic tool for emerging infections, especially when conventional treatment with antibiotics is ineffective (antibiotic resistance) or unavailable (rapidly spreading, endemic). These results identify a new role for HSP70, a highly conserved molecule in stimulating phagocytosis: a primordial macrophage function, thereby influencing both innate and adaptive immune responses.

Regulated recruitment of DC-SIGN to cell-cell contact regions during zymosan-induced human dendritic cell aggregation

Zymosan is a beta-glucan, mannan-rich yeast particle widely used to activate the inflammatory response of immune cells. We studied the zymosan-binding potential of human dendritic cells (hDCs) by using specific carbohydrate inhibitors and blocking monoclonal antibodies. We show that DC-specific intercellular adhesion molecule-grabbing nonintegrin (DC-SIGN) is a major nonopsonic recognition receptor for zymosan on hDCs. Indeed, blocking of DC-SIGN inhibited the inflammatory response of DCs to zymosan. We compared the zymosan-binding capacity of hDC-SIGN to that of Dectin-1 and complement receptor 3 (CR3), which are receptors involved in the nonopsonic recognition of these yeast-derived particles. Dectin-1- and DC-SIGN-K562 cells bound to zymosan particles, whereas CR3-K562 cells did not. DC-SIGN and Dectin-1 were also expressed in COS cells to compare their ability to trigger particle internalization in a nonphagocytic cell line. DC-SIGN transfectants were unable to internalize bound particles, indicating that DC-SIGN is primarily involved in recognition but not in particle internalization. Zymosan induced a rapid DC aggregation that was accompanied by a dramatic change of DC-SIGN distribution in the plasma membrane. Under resting conditions, DC-SIGN was diffusely distributed through the cell surface, displaying clusters at the free leading edge. Upon zymosan treatment, DC-SIGN was markedly redistributed to cell-cell contacts, supporting an adhesion role in DC-DC interactions. The mechanism(s) supporting DC-SIGN-mediated intercellular adhesion were further investigated by using DC-SIGN-K562 aggregation. DC-SIGN was highly concentrated at points of cell-cell contact, suggesting a role for enhanced avidity during DC-SIGN-mediated intercellular adhesion.

A single-step, sensitive flow cytofluorometric assay for the simultaneous assessment of membrane-bound and ingested Candida albicans in phagocytosing neutrophils

BACKGROUND

Distinguishing ingested particles from those attached to the cell surface is an essential requirement when performing quantitative studies of phagocytosis. In the present report, we describe a simple, sensitive and reliable flow cytofluorometric method that achieves this goal in a Candida albicans-human neutrophils (PMN) system.

METHODS

The assay is based on the observation that the vital dye trypan blue (TB), while quenching the green fluorescence of fluorescein-labeled C. albicans, causes them to fluoresce red. PMN were incubated with fluorescein-labeled yeast particles for the required time. Aliquots of the incubation mixtures were then promptly diluted with an equal volume of a TB solution at pH 4.0, and subsequently analyzed by flow cytometry for green and red fluorescence.

RESULTS

Since TB does not penetrate into the cells, ingested yeasts retain their green fluorescence, while membrane-bound particles display a red fluorescence.

CONCLUSIONS

Our fluorescence flow cytometric method enables to simultaneously distinguish, within the leukocyte population, cell subsets with attached and ingested yeast particles. Its major features are: (1) accuracy, sensitivity and reproducibility; (2) no further sample manipulations after completion of phagocytosis; (3) possibility of counting free, attached and internalized yeast particles; and (4) use of a nontoxic reagent (TB).

Phagocytosis and intracellular fate of Aspergillus fumigatus conidia in alveolar macrophages

Aspergillus fumigatus is the most prevalent airborne fungal pathogen responsible for fatal invasive aspergillosis in immunocompromised patients. Upon arrival in the lung alveolus, conidia of A. fumigatus are phagocytosed by alveolar macrophages, the major phagocytic cells of the lung. Engulfment and intracellular trafficking of A. fumigatus conidia in alveolar macrophages of two different origins, the murine cell line MH-S and human pulmonary alveolar macrophages, were analyzed by electron microscopy and immunofluorescence. Phagocytosis of A. fumigatus conidia required actin polymerization and phosphatidylinositol 3-kinase activity. Fusion of A. fumigatus phagosomes with early and late endosomes was shown by immunolabeling with specific markers for the transferrin receptor, early endosome antigen, and Rab7. Maturation of A. fumigatus phagolysosomes was monitored by using a fixable acidotropic probe, LysoTracker Red DND-99, and an anti-cathepsin D antibody. Bafilomycin A-induced inhibition of lysosomal acidification abolished the conidial killing by the macrophages. These data suggest that the maturation of A. fumigatus phagosomes results from fusion with the compartments of the endocytic pathway and that the killing of conidia depends on phagolysosome acidification. A model for the phagocytosis of A. fumigatus conidia by alveolar macrophages is proposed on the basis of these results.