Name: Phagocytosis Kinetics and Trichoderma stromaticum Conidial Viability Assay Using Human Peripheral Blood Mononuclear-Derived Macrophages
Uploaded: 2023-10-20T13:10:00
Description: Watch this Scientific Journal Video about Phagocytosis Kinetics and Trichoderma stromaticum Conidial Viability Assay Using Human Peripheral Blood Mononuclear-Derived Macrophages at JoVE.com

phagocytosis kinetics and trichoderma stromaticum conidial viability assay using human peripheral blood mononuclear-derived macrophages

Fungal Clearance Efficiency of Macrophages

The Trichoderma genus (Order: Hypocreales, Family: Hypocreaceae) is composed of ubiquitous, saprophytic fungi that are parasites of other fungal species and are capable of producing a range of commercially useful enzymes1. These fungal species are used for the production of heterologous proteins2, the production of cellulose3, ethanol, beer, wine, and paper4, in the textile industry5, food industry6, and in agriculture as biological control agents7,8. In addition to the industrial interest in these fungal species, the increasing number of infections in humans has given some Trichoderma species the status of opportunistic pathogens9.
Trichoderma spp. grow rapidly in culture, with initially white and cottony colonies that turn greenish yellow to dark green10. They are adapted to live in a wide range of pH and temperature conditions, and the opportunistic species are able to survive at physiological pH and temperatures and, thus, colonize different human tissues11,12,13. Importantly, the rise in the infection rate of Trichoderma spp. may be associated with virulence factors, and these are not well studied. In addition, studies focusing on understanding the immune response against opportunistic Trichoderma species are still rare.
During an infection, along with neutrophils, macrophages represent the line of defense responsible for phagocytosis, and, thus, prevent the growth and colonization of pathogens in different tissues. Using pattern recognition receptors, such as Toll-like receptors and C-type lectin receptors, macrophages phagocytose fungi and process them into phagolysosomes, thus promoting a respiratory burst, the release of pro-inflammatory cytokines, and the destruction of the phagocytosed microorganisms14. The mechanism of phagocytosis, however, can be affected and evaded by different microbial strategies, such as the size and shape of the fungal cells; the presence of capsules that hinder phagocytosis; decreasing the number of phagocytosis-inducing receptors; the remodeling of the structure of actin fibers in the cytoplasm; hindering the formation of pseudopodia; and phagosome or phagolysosome escape after the phagocytosis process14.
Many pathogens, including Cryptococcus neoformans, use macrophages as a niche to survive in the host, disseminate, and induce infection15. The phagocytosis and clearance assay is used to evaluate the immune response against pathogens and to identify the microbial strategies employed to evade the innate immune system15,16,17. This type of technique can also be used to examine the differential kinetics of phagocytosis, delayed phagosome acidification, and oxidative burst that result in reduced fungal killing18.
Different methods can be used to evaluate phagocytosis, fungal survival, and the evasion of the phagosome maturation process. These include fluorescence microscopy, which is used to observe phagocytosis, the cellular location, and the molecules produced during phagocytosis19; flow cytometry, which provides quantitative data on phagocytosis and is used to evaluate the different markers involved in the process20,21; intravital microscopy, which is used to assess microbial capture and phagosome maturation22; antibody-mediated phagocytosis, which is used to assess the specificity of the phagocytosis process for a pathogen23; and others24,25,26,27.
The protocol presented here employs a common, low-cost, and direct method using an optical microscope and plate growth assay to assess the phagocytosis and killing of fungal conidia. This protocol will provide the readers with step-by-step instructions for performing the phagocytosis and clearance assay using human peripheral blood mononuclear-derived macrophages exposed to T. stromaticum. PBMCs were used because Trichoderma conidia are applied as a biocontrol against phytopathogens and a biofertilizer for plant crops worldwide and have caused several human infections, called Trichodermosis. Besides that, there are only two previous works focusing on the interaction between Trichoderma conidia and the human immune system, in which we examined neutrophils28 and autophagy in macrophages29. This article shows first how the phagocytosis of the conidia of T. stromaticum by PBMC-derived macrophages can be studied, and then how the viability of the engulfed conidia can be assessed using simple microscopy-based techniques. This protocol may further facilitate investigations on macrophage-associated immune response or immune system modulation-related mechanisms.

Author Spotlight: Unraveling the Interplay Between Trichoderma stromaticum and the Mammalian Immune System

Viability Assay of Trichoderma stromaticum Conidia Inside Human Peripheral Blood Mononuclear-Derived Macrophages

Our research is focused on understand the interaction between the Trichoderma fungi and the mammalian immune system. How do some Trichoderma species cause disease, how can they modulate the immune system, and how can this modulation impact the development of the disease? To answer this question, we use in vitro randomized models.We show that Trichoderma species modulates macrophages and neutrophils by targeting receptors involved in the phagocytosis process. These receptors include toll-like receptors and lectin receptors. When there is a decrease in phagocyte capacity of immune cells, susceptibility to pathogens, especially intracellular pathogens does increase.Ongoing, have many invasion mechanism to survive in the host. This include avoiding phagocytosis and survive inside macrophage. Pathogenic species use macrophage as Trojan horses to survive in disseminating the host.Here, we propose that to know if Trichoderma can survive inside macrophage, and for how long they survive.

Watch this Scientific Journal Video about Phagocytosis Kinetics and Trichoderma stromaticum Conidial Viability Assay Using Human Peripheral Blood Mononuclear-Derived Macrophages at JoVE.com

Phagocytosis Kinetics and Trichoderma stromaticum Conidial Viability Assay Using Human Peripheral Blood Mononuclear-Derived Macrophages

To treat human-derived macrophages with Trichoderma stromaticum conidia using sterile tweezers, add a round glass cover slip to each well of a 24 well plate. Count the PBMC suspension isolated from human blood and adjust the volume to plate eight times 10 to fifth cells per well to a final volume of one milliliter with R10 medium. After plating, use an inverted microscope.Observe the cell morphology. Incubate the cells at 37 degrees Celsius in 5%carbon dioxide for seven days, replacing the medium with fresh R10 medium every two days for the differentiation of the monocytes into macrophages. After seven days, observe the cell morphology using an inverted microscope.Then remove the medium from each well and wash the cells with one milliliter of PBS to remove debris and non-adherent cells. Next, prepare T.stromaticum conidia suspension at a final concentration of eight times 10 to the fourth conidia per milliliter in R10 medium. Add one milliliter of suspension to each well to obtain a multiplicity of infection of one to 10.Challenge the macrophages for three hours at 37 degrees Celsius under 5%carbon dioxide. After incubation, remove the medium and wash the cells with PBS to remove the nonphagocetized conidia. Then add one milliliter of R10 medium to each well and incubate the plate at different times.After the corresponding incubation, remove the medium and add one milliliter of PBS to that well. Then using tweezers and a needle, remove the round glass cover slips from the wells. Next, stain the cover slips using the components of the staining kit.Once the cover slips are dry, fix them on a glass slide using a mounting agent. For conidial viability assay, challenge the macrophages with T.stromaticum conidia and incubate the plate for different times at 37 degrees Celsius under 5%carbon dioxide. After each incubation, wash the cells twice with PBS to remove the unphagocytosed conidia.Then add 0.5 milliliters of sterile distilled water and incubate for 30 minutes. After confirming the cells are lysed, collect the suspension into a 1.5 milliliter tube. Centrifuge the suspension at 6, 000 times G for five minutes at room temperature and discard the supernatant carefully before resuspending the pellet in 10 microliters of sterile distilled water.Inoculate 10 microliters of the suspension onto the PDA plate and incubate at 28 degrees Celsius in the dark. At the beginning of the phagocytosis process, free conidia, conidia attached to the outer membrane of macrophages or completely internalized by macrophages were observed. With increased phagocytosis time, free and conidia attached to the outer membrane were completely internalized by the macrophages.The conidia were also observed in an upper plane compared to the macrophages, and more than one conidium was found in the same macrophage. After long periods, phagocytosed conidia germinate inside the macrophages and free conidia germinate in the R10 medium forming hyphae at 37 degrees Celsius. The phagocytosed conidia remained viable even after 120 hours of interaction with the macrophages.After phagocytosis, growth was monitored in terms of the time required for the culture to occupy the entire plate and to form colored green conidia.

Research

JoVE Journal

Immunology and Infection

Macrophages represent a crucial line of defense and are responsible for preventing the growth and colonization of pathogens in different tissues. Conidial ...