Trichomonas vaginalis triggers neutrophil extracellular traps reducing parasite integrity and growth

Giardia duodenalis triggered neutrophil extracellular traps in goats

Giardia duodenalis is a globally distributed zoonotic parasite primarily transmitted through the fecal-oral route, infecting various vertebrates, and the infection of which is prevalent in goats. Immune cells play a crucial role in pathogens invasion, and neutrophil extracellular traps (NETs) released by neutrophils serve as a non-specific defense mechanism against pathogens including parasites. In this study, we investigated the characteristics, components, and molecular mechanisms of goat NETs upon stimulation with G. duodenalis trophozoites. This study demonstrates that G. duodenalis trigger dose-dependent NETs formation in goat neutrophils, composed of DNA, citrullinated histone H3 (CitH3), and neutrophil elastase (NE). Reactive oxygen species (ROS) accumulation synchronizes with NETosis during G. duodenalis infection. Inhibitor experiments confirmed that G. duodenalis-induced NETs and ROS production depend on TLR2/4 signaling and require NADPH oxidase (NOX), ERK1/2, and p38 MAPK activation. This work identifies TLR2/4, NOX, ERK1/2, and p38 MAPK pathways as key regulators of NETs/ROS coordination during G. duodenalis infection, providing the first evidence of G. duodenalis-triggered NETs in goats. The findings highlight NETs as critical components of anti-G. duodenalis immunity and suggest potential for NETs-targeted therapeutic strategies.

Entamoeba histolytica-induced NETs are highly cytotoxic on hepatic and colonic cells due to serine proteases and myeloperoxidase activities

During intestinal and liver invasion by the protozoan parasite Entamoeba histolytica, extensive tissue destruction linked to large neutrophil infiltrates is observed. It has been proposed that microbicidal components of neutrophils are responsible for the damage, however, the mechanism by which they are released and act in the extracellular space remains unknown. In previous studies, we have shown that E. histolytica trophozoites induce NET formation, leading to the release of neutrophil granule content into extruded DNA. In this work, we evaluate the possible participation of NETs in the development of amoeba-associated pathology and analyze the contribution of anti-microbial components of the associated granules. E. histolytica-induced NETs were isolated and their effect on the viability and integrity of HCT 116 colonic and Hep G2 liver cultures were evaluated. The results showed that simple incubation of cell monolayers with purified NETs for 24 h resulted in cell detachment and death in a dose-dependent manner. The effect was thermolabile and correlated with the amount of DNA and protein present in NETs. Pretreatment of NETs with specific inhibitors of some microbicidal components suggested that serine proteases, are mostly responsible for the damage caused by NETs on HCT 116 cells, while the MPO activity was the most related to Hep G2 cells damage. Our study also points to a very important role of DNA as a scaffold for the activity of these proteins. We show evidence of the development of NETs in amoebic liver abscesses in hamsters as a preamble to evaluate their participation in tissue damage. In conclusion, these studies demonstrate that amoebic-induced NETs have potent cytotoxic effects on target cells and, therefore, may be responsible for the intense damage associated with tissue invasion by this parasite.

Extracellular Traps in Patients Diagnosed With Bacterial Vaginosis, Trichomoniasis, Candidiasis, Noninfectious Vaginitis and Cytolytic Vaginosis

Vaginal infections are a public health problem associated with serious health complications due to the exacerbated inflammation they generate. Vaginal inflammation may also occur in some noninfectious processes, such as noninfectious vaginitis and cytolytic vaginosis. Immune system cells respond to infections through various mechanisms, such as the formation of extracellular traps (ETs), which are DNA networks associated with effector proteins. Many pathogens induce ETs formation in vitro, as occurs in some natural infections. A recent report indicates that human vaginal infections in vivo generate ETs. Therefore, in this study, we aimed to identify ETs in samples from 40 donors who were diagnosed with infectious (i.e., bacterial vaginosis, candidiasis and trichomoniasis) and noninfectious (i.e., noninfectious vaginitis and cytolytic vaginosis) vaginal inflammation. We were able to observe ETs by identifying the LL-37 peptide, which is associated with DNA networks. In seven vaginal swabs from the control group (formed by 19 donors without vaginal infection symptoms), we detected at least one pathogen per sample and observed ETs; thus, these donors were considered asymptomatic. The remaining 12 donors were confirmed to be healthy, as their exudates did not present any tested pathogens, sign of inflammation or ETs. ETs in vaginal inflammatory processes can worsen inflammation but may also help control infection.

Bovine neutrophils kill the sexually-transmitted parasite Tritrichomonas foetus using trogocytosis

The protozoan parasite Tritrichomonas foetus (T. foetus) is the causative organism of bovine trichomonosis (also referred to as trichomoniasis), a sexually-transmitted infection that reduces fertility in cattle. Efforts to control trichomonosis on cattle farms are hindered by the discouragement of antibiotic use in agriculture, and the incomplete, short-lived protection conferred by the current vaccines. A more complete mechanistic understanding of what effective immunity to T. foetus entails could enable the development of more robust infection control strategies. While neutrophils, the primary responders to infection, are present in infected tissues and have been shown to kill the parasite in vitro, the mechanism they use for parasite killing has not been established. Here, we show that primary bovine neutrophils isolated from peripheral blood rapidly kill T. foetus in vitro in a dose-dependent manner, and that optimal parasite killing is reduced by inhibitors of trogocytosis. We also use imaging to show that bovine neutrophils surround T. foetus and trogocytose its membrane. These findings are consistent with killing via trogocytosis, a recently described novel neutrophil antimicrobial mechanism.

Impaired neutrophil extracellular trap-forming capacity contributes to susceptibility to chronic vaginitis in a mouse model of vulvovaginal candidiasis

Vulvovaginal candidiasis (VVC), caused by Candida albicans, is characterized by aberrant inflammation by polymorphonuclear neutrophils (PMNs) in the vaginal lumen. Data from the established murine model shows that despite potent antifungal properties, PMNs fail to clear C. albicans due to local heparan sulfate that inhibits the interaction between PMNs and C. albicans, resulting in chronic vaginal immunopathology. To understand the role of neutrophil extracellular traps (NETs) in defense against C. albicans at the vaginal mucosa, we investigated the NET-forming capacity of PMNs in chronic VVC-susceptible (CVVC-S/C3H) and -resistant (CVVC-R/CD-1) mouse strains. Immunofluorescence revealed the formation of NETs (release of DNA with PMN-derived antimicrobial proteins) in PMN-C. albicans cocultures using vaginal conditioned medium (VCM) generated from CVVC-R/CD-1 mice, similar to NET-inducing positive controls. Under these NETotic conditions, PMNs released high levels of double-stranded DNA bound with NET-associated proteins, concomitant with substantial C. albicans killing activity. In contrast, PMN-C. albicans cocultures in VCM from CVVC-S/C3H mice lacked NET formation together with reduced antifungal activity. Similar results were observed in vivo: active NET-C. albicans interaction followed by fungal clearance in inoculated CVVC-R/CD-1 mice, and sustained high vaginal fungal burden and no evidence of NETs in inoculated CVVC-S/C3H mice. Furthermore, the level of Ki67 expression, a putative NETotic PMN marker, was significantly reduced in vaginal lavage fluid from CVVC-S/C3H mice compared to CVVC-R/CD-1 mice. Finally, scanning electron microscopy revealed that PMNs in CVVC-R, but not CVVC-S, conditions exhibited NETs in direct contact with C. albicans hyphae in vitro and in vivo. These results suggest that VVC-associated immunopathology includes impaired NET-mediated antifungal activity.

NETosis in Parasitic Infections: A Puzzle That Remains Unsolved

Neutrophils are the key players in the innate immune system, being weaponized with numerous strategies to eliminate pathogens. The production of extracellular traps is one of the effector mechanisms operated by neutrophils in a process called NETosis. Neutrophil extracellular traps (NETs) are complex webs of extracellular DNA studded with histones and cytoplasmic granular proteins. Since their first description in 2004, NETs have been widely investigated in different infectious processes. Bacteria, viruses, and fungi have been shown to induce the generation of NETs. Knowledge is only beginning to emerge about the participation of DNA webs in the host's battle against parasitic infections. Referring to helminthic infections, we ought to look beyond the scope of confining the roles of NETs solely to parasitic ensnarement or immobilization. Hence, this review provides detailed insights into the less-explored activities of NETs against invading helminths. In addition, most of the studies that have addressed the implications of NETs in protozoan infections have chiefly focused on their protective side, either through trapping or killing. Challenging this belief, we propose several limitations regarding protozoan-NETs interaction. One of many is the duality in the functional responses of NETs, in which both the positive and pathological aspects seem to be closely intertwined.

Infinity war: Trichomonas vaginalis and interactions with host immune response

Trichomonas vaginalis is the pathological agent of human trichomoniasis. The incidence is 156 million cases worldwide. Due to the increasing resistance of isolates to approved drugs and clinical complications that include increased risk in the acquisition and transmission of HIV, cervical and prostate cancer, and adverse outcomes during pregnancy, increasing our understanding of the pathogen's interaction with the host immune response is essential. Production of cytokines and cells of innate immunity: Neutrophils and macrophages are the main cells involved in the fight against the parasite, while IL-8, IL-6 and TNF-α are the most produced cytokines in response to this infection. Clinical complications: T. vaginalis increases the acquisition of HIV, stimulates the invasiveness and growth of prostate cells, and generates an inflammatory environment that may lead to preterm birth. Endosymbiosis: Mycoplasma hominis increased cytotoxicity, growth, and survival rate of the parasite. Purinergic signaling: NTPD-ases and ecto-5'-nucleotidase helps in parasite survival by modulating the nucleotides levels in the microenvironment. Antibodies: IgG was detected in serum samples of rodents infected with isolates from symptomatic patients as well as patients with symptoms. However, antibody production does not protect against a reinfection. Vaccine candidate targets: The transient receptor potential- like channel of T. vaginalis (TvTRPV), cysteine peptidase, and α-actinin are currently cited as candidate targets for vaccine development. In this context, the understanding of mechanisms involved in the host-T. vaginalis interaction that elicit the immune response may contribute to the development of new targets to combat trichomoniasis.