Tritrichomonas foetus induces apoptotic cell death in bovine vaginal epithelial cells

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.

Dysbiosis of fecal microbiota in cats with naturally occurring and experimentally induced Tritrichomonas foetus infection

The protozoal pathogen Tritrichomonas foetus infects the colon of domestic cats and is a major cause of chronic colitis and diarrhea. Treatment failure is common, but antibiotics may improve clinical signs in a subset of cats, leading researchers to question involvement of the colonic microbiota in disease pathogenesis. Studies performed in women with venereal Trichomonas vaginalis infections have revealed that dysbiosis of host microbiota contributes to pathogenicity with similar findings also found in mice with intestinal Tritrichomonas musculis The aim of this study was to characterize differences in the fecal microbiota of cats with and without naturally occurring T. foetus infection and in a group of kittens prior to and after experimentally induced infection. Archived fecal DNA from cats undergoing testing for T. foetus infection (n = 89) and experimentally infected kittens (n = 4; at pre-, 2 weeks, and 9 weeks post-infection) were analyzed by sequencing of 16S rRNA genes. Amongst the naturally infected population, the genera Megamonas and Helicobacter were significantly increased in prevalence and abundance in cats testing positive for T. foetus infection. In the group of four experimentally infected kittens, fecal samples post-infection had significantly lower abundance of genus Dialister and Megamonas and greater abundance of the class Betaproteobacteria and family Succinivibrionaceae. We hypothesize that T. foetus promotes dysbiosis by competition for fermentable substrates used by these bacteria and that metabolic byproducts may contribute to the pathogenesis of colonic inflammation and diarrhea. Future studies are warranted for the measurement of fecal concentrations of microbial and protozoal metabolites in cats with T. foetus infection for the identification of potential therapeutic targets.

Tritrichomonas Foetus as a Causative Agent of Tritrichomonosis in Different Animal Hosts

Tritrichomonas foetus is a protozoan parasite that has been traditionally identified as a cause of reproductive tract disease in cattle and gastrointestinal tract infection in cats. Moreover, T. foetus is also well known as a commensal of the nasal cavity, intestines, and stomach in swine. In this review we describe T. foetus as a pathogen dangerous to more than one animal host, diagnostic and taxonomic aspects of this infection, and the extent to which isolates from different hosts share genetic identity.

Mechanisms of Tritrichomonas foetus Pathogenicity in Cats with Insights from Venereal Trichomonosis

Almost 20 years has passed since trichomonosis was first recognized as a potential cause of diarrhea in domestic cats. Despite progress in confirming disease causation, developing means for diagnosis, and identifying approaches to treatment of the infection, we still know very little about how this parasite causes diarrhea. With increasing recognition of resistance of trichomonosis to treatment with 5‐nitroimidazole drugs, new treatment strategies based on an understanding of disease pathogenesis are needed. In this review, lessons learned from the pathogenesis of venereal trichomonosis in people and cattle are applied to clinical observations of trichomonosis in cats in effort to generate insight into areas where further research may be beneficial.

Tritrichomonas foetus infection, a cause of chronic diarrhea in the domestic cat

Tritrichomonas foetus is a very intriguing trichomonad protozoan with respect to its varied choice of residence in the different host species. It is an obligate parasite of the reproductive and the gastrointestinal tract of bovine and feline host respectively, leading to trichomonosis. Bovine trichomonosis is a sexually transmitted disease whereas feline trichomonosis is a disease with a purported fecal-oral route of spread. Further, the trichomonad is a commensal in the nasal passages, stomach, cecum and colon of swine host. Advances have been exponential in understanding the trichomonad biology and specifically feline trichomonosis since late 1990s and early 2000s when T. foetus was soundly determined to be a causative agent of chronic diarrhea in the domestic cat. It is a challenging task, even for a skilled investigator not to mention the busy clinical veterinarian, to keep up with the vast volume of information. Here we comprehensively reviewed the trichomonad biology, clinical manifestations, pathogenesis, host immunity, world map of distribution, risk factors, diagnosis and treatment. Risk factors associated with T. foetus-positive status in the domestic cat include young age, purebred, history of diarrhea, co-infections with other enteral pathogens. In addition, molecular similarity of bovine and feline isolates of T. foetus in DNA sequence was concisely discussed. The data presented serve as an information source for veterinarians, and investigators who are interested in biology of T. foetus and feline trichomonosis.

Is Trichomonas tenax a Parasite or a Commensal?

Trichomonas tenax is considered a commensal organism found under poor oral hygiene conditions. T. tenax presents morphological similarities with T. vaginalis, and there are doubts concerning whether this protist is a parasite and whether it is a genetic variant of T. vaginalis. This study aimed to investigate the capacity of T. tenax to cause mammalian cell damage and compare its cytotoxicity with that of T. vaginalis. Protozoan-host cell interaction assays were performed with Madin-Darby canine kidney, HeLa, and gum cells and 3D spheroids, which were examined by scanning electron and transmission electron microscopy. Cellular viability experiments were also performed. T. tenax attached and had different forms when interacting with mammalian cells and caused damage with time-dependent host-cell viability. We observed that T. tenax produced plasma membrane projections and phagocytosed portions of the mammalian cells. In addition, T. tenax caused membrane blebbing and apoptotic bodies in HeLa cells, thus inducing cell death. Spheroids were also used in interaction assays with T. tenax and they were damaged by these cells. This study shows that T. tenax fulfills the requisites of a parasite, causing damage to different mammalian cells and behaving similarly to T. vaginalis when in contact with target cells in vitro.

Delineating cellular interactions between ciliates and fish by co-culturing Tetrahymena thermophila with fish cells

Although several species of Tetrahymena are often described as histophagous and opportunistic pathogens of fish, little is known about ciliate/fish cell interactions, but one approach for studying these is in vitro with cell lines. In this study, T. thermophila, B1975 (wild type) and NP1 (temperature sensitive mutant for phagocytosis) were cultured on monolayers of 3 fish epithelial cell lines, CHSE-214, RTgill-W1, and ZEB2J, and the rabbit kidney epithelial cell line, RK-13. Generally the ciliates flourished, whereas the monolayers died, being completely consumed over several days. The destruction of monolayers required that the ciliates could make contact with the animal cells through swimming, which appeared to dislodge or loosen cells so that they could be phagocytosed. The ciliates internalized into food vacuoles ZEB2J from cell monolayers as well as from cell suspensions. Phagocytosis was essential for monolayer destruction as monolayers remained intact under conditions where phagocytosis was impeded, such as 37°C for NP1 and 4°C for B1975. Monolayers of fish cells supported the proliferation of ciliates. Thus T. thermophila can 'eat' animal cells or be histophagous in vitro, with the potential to be histophagous in vivo.

Cysteine protease activity of feline Tritrichomonas foetus promotes adhesion-dependent cytotoxicity to intestinal epithelial cells

Trichomonads are obligate protozoan parasites most renowned as venereal pathogens of the reproductive tract of humans and cattle. Recently, a trichomonad highly similar to bovine venereal Tritrichomonas foetus but having a unique tropism for the intestinal tract was recognized as a significant cause of colitis in domestic cats. Despite a high prevalence, worldwide distribution, and lack of consistently effective drugs for treatment of the infection, the cellular mechanisms of T. foetus pathogenicity in the intestinal tract have not been examined. The aims of this study were to determine the pathogenic effect of feline T. foetus on porcine intestinal epithelial cells, the dependence of T. foetus pathogenicity on adhesion of T. foetus to the intestinal epithelium, and the identity of mediators responsible for these effects. Using an in vitro coculture approach to model feline T. foetus infection of the intestinal epithelium, these studies demonstrate that T. foetus promotes a direct contact-dependent activation of intestinal epithelial cell apoptosis signaling and progressive monolayer destruction. Moreover, these pathological effects were demonstrated to be largely dependent on T. foetus cell-associated cysteine protease activity. Finally, T. foetus cysteine proteases were identified as enabling cytopathic effects by promoting adhesion of T. foetus to the intestinal epithelium. The present studies are the first to examine the cellular mechanisms of pathogenicity of T. foetus toward the intestinal epithelium and support further investigation of the cysteine proteases as virulence factors in vivo and as potential therapeutic targets for ameliorating the pathological effects of intestinal trichomonosis.

Comparative analysis of Tritrichomonas foetus (Riedmüller, 1928) cat genotype, T. foetus (Riedmüller, 1928) cattle genotype and Tritrichomonas suis (Davaine, 1875) at 10 DNA loci

The parasitic protists in the genus Tritrichomonas cause significant disease in domestic cattle and cats. To assess the genetic diversity of feline and bovine isolates of Tritrichomonas foetus (Riedmüller, 1928) Wenrich and Emmerson, 1933, we used 10 different genetic regions, namely the protein coding genes of cysteine proteases 1, 2 and 4-9 (CP1, 2, 4-9) involved in the pathogenesis of the disease caused by the parasite. The cytosolic malate dehydrogenase 1 (MDH1) and internal transcribed spacer region 2 of the rDNA unit (ITS2) were included as additional markers. The gene sequences were compared with those of Tritrichomonas suis (Davaine, 1875) Morgan and Hawkins, 1948 and Tritrichomonas mobilensisCulberson et al., 1986. The study revealed 100% identity for all 10 genes among all feline isolates (=T. foetus cat genotype), 100% identity among all bovine isolates (=T. foetus cattle genotype) and a genetic distinctness of 1% between the cat and cattle genotypes of T. foetus. The cattle genotype of T. foetus was 100% identical to T. suis at nine loci (CP1, 2, 4-8, ITS2, MDH1). At CP9, three out of four T. suis isolates were identical to the T. foetus cattle genotype, while the T. suis isolate SUI-H3B sequence contained a single unique nucleotide substitution. Tritrichomonas mobilensis was 0.4% and 0.7% distinct from the cat and cattle genotypes of T. foetus, respectively. The genetic differences resulted in amino acid changes in the CP genes, most pronouncedly in CP2, potentially providing a platform for elucidation of genotype-specific host-pathogen interactions of T. foetus. On the basis of this data we judge T. suis and T. foetus to be subjective synonyms. For the first time, on objective nomenclatural grounds, the authority of T. suis is given to Davaine, 1875, rather than the commonly cited Gruby and Delafond, 1843. To maintain prevailing usage of T. foetus, we are suppressing the senior synomym T. suisDavaine, 1875 according to Article 23.9, because it has never been used as a valid name after 1899 and T. foetus is widely discussed as the cause of bovine trichomonosis. Thus bovine, feline and porcine isolates should all be given the name T. foetus. This promotes the stability of T. foetus for the veterinary and economically significant venereal parasite causing bovine trichomonosis.

Determination of presence of Tritrichomonas foetus in uterine lavages from cows with reproductive problems

The aim of this study was to determine the presence of Tritrichomonasfoetus in two dairy herds on the Altiplano Cundiboyacense. Twenty-one low-volume uterine lavages from cows with a history of reproductive problems in two dairy herds located in the municipality of Sibaté (Cundinamarca) and Ventaquemada (Boyacá) were evaluated. In the first herd, 10 cows were sampled and in the second, 11 cows, based on three inclusion criteria. The uterine lavages were obtained through infusion of physiological saline solution into the uterine body. The samples were centrifuged and seeded in Tritrichomonas basal medium for 10-15 days at 37 ºC. The protozoa were evaluated on the day of sampling and 10 and 15 days after incubation by means of direct viewing under a dark-field microscope. Positive samples were stained with Wright and Lugol to identify the morphological characteristics. This study showed that T. foetus was present in 61.8% of the animals sampled. The determination that T. foetus was present in 61.8% of the samples analyzed is a significant finding given that in the herds evaluated, this agent had not previously been diagnosed.

Cysteine peptidases, secreted by Trichomonas gallinae, are involved in the cytopathogenic effects on a permanent chicken liver cell culture

Trichomonas gallinae, the aetiological agent of avian trichomonosis, was shown to secrete soluble factors involved in cytopathogenic effect on a permanent chicken liver (LMH) cell culture. The present study focused on the characterization of these molecules. The addition of specific peptidase inhibitors to the cell-free filtrate partially inhibited the monolayer destruction, which implied the presence of peptidases in the filtrate and their involvement in the cytopathogenic effect. One-dimensional substrate (gelatin) SDS-PAGE confirmed the proteolytic character of the filtrate by demonstrating the proteolytic activity within the molecular weight range from 38 to 110 kDa. In addition, the proteolytic activity was specifically inhibited by addition of TLCK and E-64 cysteine peptidase inhibitors implying their cysteine peptidase nature. Furthermore, variations in the intensity and the number of proteolytic bands were observed between cell-free filtrates of low and high passages of the same T. gallinae clonal culture. Two-dimensional substrate gel electrophoresis of concentrated T. gallinae cell-free filtrate identified at least six proteolytic spots. The mass spectrometric analysis of spots from 2-D gels identified the presence of at least two different Clan CA, family C1, cathepsin L-like cysteine peptidases in the cell-free filtrate of T. gallinae. In parallel, a PCR approach using degenerated primers based on the conserved amino acid sequence region of cysteine peptidases from Trichomonas vaginalis identified the coding sequences for four different Clan CA, family C1, cathepsin L-like cysteine peptidases. Finally, this is the first report analyzing molecules secreted by T. gallinae and demonstrating the ubiquity of peptidases secreted by this protozoon.

Effect of vinyl sulfone inhibitors of cysteine proteinases on Tritrichomonas foetus infection

Tritrichomonas foetus is a sexually transmitted protozoon that causes genital inflammation and adverse pregnancy outcomes in cattle. Cysteine proteinases (CPs) released by T. foetus degrade immunoglobulin G (IgG) antibodies, complement component 3 and matrix proteins as well as inducing apoptosis of bovine genital epithelial cells. In this study, the efficacies of the vinyl sulfone CP inhibitors K11777 and WRR-483 were tested against CPs of T. foetus. The activity of secreted T. foetus CPs in culture supernatants was decreased in the presence of vinyl sulfone inhibitors. Inhibitor K11777 reduced the in vitro cytopathogenic effects of T. foetus in bovine foetal trophoblast cells, which are relevant target cells since this pathogen interferes with pregnancy. Pre-treatment of T. foetus prior to intravaginal inoculation diminished genital infection in a murine model. Therefore, vinyl sulfone CP inhibitors reduce several effects of T. foetus-secreted CPs, including cytotoxicity on relevant target host cells and genital infection in a murine model. These inhibitors have potential as chemotherapeutic agents against bovine trichomoniasis. Generalisation to human trichomoniasis requires further study.

The role of the P2X₇ receptor in infectious diseases

ATP is an extracellular signal for the immune system, particularly during an inflammatory response. It is sensed by the P2X₇ receptor, the expression of which is upregulated by pro-inflammatory cytokines. Activation of the P2X₇ receptor opens a cation-specific channel that alters the ionic environment of the cell, activating several pathways, including (i) the inflammasome, leading to production of IL-1β and IL-18; (ii) the stress-activated protein kinase pathway, resulting in apoptosis; (iii) the mitogen-activated protein kinase pathway, leading to generation of reactive oxygen and nitrogen intermediates; and (iv) phospholipase D, stimulating phagosome-lysosome fusion. The P2X₇ receptor can initiate host mechanisms to remove pathogens, most particularly those that parasitise macrophages. At the same time, the P2X₇ receptor may be subverted by pathogens to modulate host responses. Moreover, recent genetic studies have demonstrated significant associations between susceptibility or resistance to parasites and bacteria, and loss-of-function or gain-of-function polymorphisms in the P2X₇ receptor, underscoring its importance in infectious disease.

Trichomonas vaginaliskills and eats – evidence for phagocytic activity as a cytopathic effect

This study reports that the cytopathic effect ofTrichomonas vaginalis, an important human parasite of the urogenital tract, occurs due to mechanical stress and subsequent phagocytosis of the necrotic cells. The investigation was done using a primary culture of bovine oviduct epithelial cells (BOECs), grown either in monolayers or as floating cells. Trophozoites displaying different virulence levels were co-incubated with BOECs for times varying between 1 min and 48 h. Analyses were performed using videomicroscopy, scanning and transmission electron microscopy, colourimetric assays and cytochemistry. Injury was observed as early as 1 h after incubation, while after 12 h the host cells were severely damaged when a fresh trichomonad isolate was used. Trichomonads attack the host cells by clustering around them. Mechanical stress on the microvilli of the host cells was observed and appeared to induce plasma membrane damage and cell death. After membrane injury and lysis, fragments of the necrotic cells were ingested by trichomonads. Phagocytosis occurred by trichomonads avidly eating large portions of epithelial cells containing the nucleus and other organelles, but living or intact cells were not ingested. Necrotic fragments were rapidly digested in lysosomes, as shown by acid phosphatase and ruthenium red assays where only the BOECs were labelled. The lytic capacity of the trichomonads was more pronounced in host cell suspensions.

Characterization of a cysteine protease from Tritrichomonas foetus that induces host-cell apoptosis

Tritrichomonas foetus is a serious veterinary pathogen, causing bovine trichomoniasis and affecting cattle herds world-wide, resulting in inflammation of the genital tract, infertility and huge economic losses. The parasite secretes a cysteine protease (CP8), which induces cytotoxicity and apoptosis in bovine vaginal and uterine epithelial cells. Mallinson et al. [D.J. Mallinson, J. Livingstone, K.M. Appleton, S.J. Lees, G.H. Coombs, M.J. North, Microbiology 1995, 141 (12) 3077-3085.] originally reported a partial DNA sequence of T. foetus CP8 based on PCR cloning of T. foetus genomic DNA. Here we report the biochemical properties of the CP8 enzyme. Kinetic properties and the substrate specificity profile of T. foetus CP8 were studied using positional scanning synthetic combinatorial libraries and Michaelis-Menten kinetic analysis of three synthetic fluorogenic substrates. The preferred substrate Z-Leu-Arg-MCA prevented host-cell death/apoptosis induced by CP8. In addition, the DNA sequence was completed by 3' and 5' rapid amplification of cDNA ends (RACE) and the full-length amino acid sequence was obtained.

Ovarian follicular cells have innate immune capabilities that modulate their endocrine function

Oestrogens are pivotal in ovarian follicular growth, development and function, with fundamental roles in steroidogenesis, nurturing the oocyte and ovulation. Infections with bacteria such as Escherichia coli cause infertility in mammals at least in part by perturbing ovarian follicle function, characterised by suppression of oestradiol production. Ovarian follicle granulosa cells produce oestradiol by aromatisation of androstenedione from the theca cells, under the regulation of gonadotrophins such as FSH. Many of the effects of E. coli are mediated by its surface molecule lipopolysaccharide (LPS) binding to the Toll-like receptor-4 (TLR4), CD14, MD-2 receptor complex on immune cells, but immune cells are not present inside ovarian follicles. The present study tested the hypothesis that granulosa cells express the TLR4 complex and LPS directly perturbs their secretion of oestradiol. Granulosa cells from recruited or dominant follicles are exposed to LPS in vivo and when they were cultured in the absence of immune cell contamination in vitro they produced less oestradiol when challenged with LPS, although theca cell androstenedione production was unchanged. The suppression of oestradiol production by LPS was associated with down-regulation of transcripts for aromatase in granulosa cells, and did not affect cell survival. Furthermore, these cells expressed TLR4, CD14 and MD-2 transcripts throughout the key stages of follicle growth and development. It appears that granulosa cells have an immune capability to detect bacterial infection, which perturbs follicle steroidogenesis, and this is a likely mechanism by which ovarian follicle growth and function is perturbed during bacterial infection.

Trichomonas adhere and phagocytose sperm cells: adhesion seems to be a prominent stage during interaction

Tritrichomonas foetus and Trichomonas vaginalis are extracellular parasites of the urogenital tract of cattle and humans, respectively. They cause infertility and abortion, but there is no documented information on the susceptibility of bovine sperm cells to this cattle parasite. The aim of this present work was to study the effects provoked by T. foetus and T. vaginalis when in interaction with bovine and human sperm cells. The bovine and human spermatozoa were obtained from uninfected bulls and men, respectively, and were exposed to living trichomonads over different periods of time. Light microscopy, video microscopy, scanning, and transmission electron microscopy first revealed a tropism, then a close proximity followed by a tight adhesion between these two different cells. A decrease in the spermatozoa motility was observed as well intense semen agglutination. The adhesion between trichomonads to the sperm cell occurred either by the flagella or sperm head. Motile parasites were observed during the next 12 h, whereas sperm cells in contact with the parasites rapidly became immotile. The parasites were able to maintain the sperm cells attached to their cell surface, followed by phagocytosis. This process began with a tight membrane-membrane adhesion and the incorporation of the sperm cell within an intracellular vacuole. Afterwards, the sperm cell was gradually digested in lysosomes. Many trichomonads were injured and/or died on making contact with the spermatozoa possibly due to necrosis. Results from this study demonstrated that both T. foetus and T. vaginalis interact with sperm cells provoking damage and death of these reproductive cells. Differences in the behavior of both trichomonads were evident, showing that T. vaginalis was much more virulent than T. foetus. The possible role of trichomonads in reproductive failure is discussed.

Pulmonary Superinfection by Trichomonads in the Course of Acute Respiratory Distress Syndrome

The finding of trichomonads in bronchoalveolar lavage fluid (BALF) samples from an acute respiratory distress syndrome (ARDS) patient, never previously reported, incited us to search for these parasites retrospectively in the BALF of patients with ARDS or related pathologies. Eighty-four consecutive BALF samples have been reviewed. Results were compared with data from clinical files of patients included in this study. Detection and identification of trichomonads were based on cytologic characteristics. Subsequently, immunocytochemistry and in situ hybridization were performed in the last case of the series. Our results were as follows: (1) Trichomonads were detected in 25/84 BALFs (20/77 patients). Among the patients testing positive, 17 suffered from ARDS, about 30% of the ARDS patients included in the study. (2) Trichomonads were detected more frequently at a late ARDS stage. (3) No correlation was found between trichomonad detection and other data. (4) Within the group of trichomonad-infected ARDS patients, density of infection correlated with higher mortality. The late detection of these microorganisms in the course of ARDS suggested that trichomonad development is a secondary event. As BALFs obtained early in the course of ARDS were also included in the study, trichomonad incidence could be underestimated. The significance of trichomonad lung colonization in ARDS and its potential pathogenic role are unclear. Nevertheless, the question of an active role of trichomonads in the extension of alveolar lesions or in the limitation of recovery is clearly raised.

Protozoan parasites: programmed cell death as a mechanism of parasitism

Programmed cell death (PCD) is a potent mechanism to remove parasitized cells, but it has also been shown that protozoan parasites can induce or inhibit apoptosis in host cells. In recent years, it has become clear that unicellular parasites can also undergo PCD, meaning that they commit suicide in response to various stimuli. This review focuses on the role of protozoan PCD and on the interaction between protozoan parasites and the host cell death machinery from the perspective of parasite survival strategies.

Tritrichomonas foetus damages bovine oocytes in vitro

Tritrichomonas foetus is an extracellular parasite of the urogenital tract in cattle. It causes infertility and abortion, but there is no documented information on the susceptibility of bovine oocytes to the parasite, except by one article that claimed no effects of T. foetus on oocytes or embryos. The aim of the present study was to study the effects provoked by T. foetus when in interaction with bovine oocytes. Oocytes were obtained from cow ovaries and divided into two groups: (1) one group contained cumulus cells, whereas (2) a second group was denuded from these cells. Light microscopy, video microscopy and scanning electron microscopy (SEM) revealed that exposure of oocytes to T. foetus caused rapid adhesion of the trichomonads to cumulus cells and to the zona pellucida (ZP). Motile parasites were observed for 12 h. The ZP was completely damaged, and the parasites were able to infiltrate beneath the ZP and reached the oocytes directly when the oocytes were denuded of the cumulus cells. Both the oocytes and the cumulus cells exhibited morphological characteristics compatible with apoptosis after interaction with T. foetus, such as chromatin condensation, the presence of several cytoplasmic vacuoles, with intact cellular membranes and organelles. The results from this study demonstrate that when a large number of T. foetus interacts with oocytes in vitro damage and apoptosis are provoked in the cow's reproductive cells. The behavior of this parasite as one of the causes of cattle infertility is discussed.

Tritrichomonas foetus: Pathogenesis of acute infection in normal, estradiol-treated, and stressed mice

Environmental stress and endocrine control can affect pathogenesis of sexually transmitted diseases such as trichomoniasis. Acute Tritrichomonas foetus infection was compared in female BALB/c mice to infections in mice treated with high doses of estradiol or housed in constant bright illumination (stressed). In untreated mice, T. foetus readily colonized the reproductive tract, causing minimal epithelial damage and inflammation. Several fold increases of IFN-gamma, TNF-alpha, MCP-1, and IL-6 cytokines were detected after estradiol-treatment of mice, resulting in greatly enhanced inflammation and tissue damage throughout the reproductive tract. Interestingly, estradiol-treatment of mice resulted in reduced T. foetus colonization compared to untreated mice. Infection in stressed mice resulted in increased tissue damage, inflammation, and inflammatory cytokine expression, although parasite colonization within the reproductive tract was similar to that in untreated mice. These results indicate that either estradiol-treatment or stress result in pathogenesis often observed during severe disease. Alternatively, infection in non-treated mice results in chronic colonization, with little inflammation or pathology.

Trichomonas vaginalis lipophosphoglycan triggers a selective upregulation of cytokines by human female reproductive tract epithelial cells

Trichomonas vaginalis is one of the most common nonviral sexually transmitted human infections and, worldwide, has been linked to increased incidence of human immunodeficiency virus type 1 transmission, preterm delivery, low birth weight, cervical cancer, and vaginitis. The molecular pathways that are important in initiating host inflammatory and immune responses to T. vaginalis are poorly understood. Here we report interactions of human cervicovaginal epithelial cells with the most abundant cell surface glycoconjugate of the parasite, the T. vaginalis lipophosphoglycan (LPG). Purified LPG mediated the adhesion of parasites to human vaginal epithelial cells in a dose-dependent manner. Furthermore, T. vaginalis LPG (but not LPG from Tritrichomonas foetus, the causative agent of bovine trichomoniasis) induced a selective upregulation of chemotactic cytokines by human endocervical, ectocervical, and vaginal epithelial cells, which do not express Toll-like receptor 4/MD2. The T. vaginalis LPG triggered interleukin 8 (IL-8), which promotes the adhesion and transmigration of neutrophils across the endothelium, and macrophage inflammatory protein 3alpha, which is a chemoattractant for immune cells and is essential for dendritic cell maturation. These effects were dose dependent and sustained in the absence of cytotoxicity and IL-1beta release and utilized, at least in part, a signaling pathway independent from the Toll-like/IL-1 receptor adaptor protein MyD88.

Interaction of Tritrichomonas foetus and the bovine oviduct in an organ culture model

Tritrichomonas foetus is an extracellular parasite of the reproductive tract in cattle. The mechanism by which T. foetus causes abortion in cattle is largely unknown. There are no studies of infection in the cow oviducts, almost all published papers are related to vagina infection and few articles focusing on the uterus. The aim of the present study was to establish a working model of bovine oviduct epithelial cells and submit these cells to Tritrichomonas foetus interaction. Twenty bovine oviducts were obtained from cows at a commercial abattoir and T. foetus was injected through the isthmus into the oviduct lumen. The whole oviduct was analyzed by scanning and transmission electron microscopy. The results reported here demonstrate that: (1) fresh whole oviducts can be used as a good model to study parasite-host cell interaction; (2) cow oviduct epithelium has been shown to consist of two cell types: ciliated and nonciliated secretory cells, and T. foetus displayed great specificity for the nonciliated cells localized in the deeper oviduct folds; (3) T. foetus adheres as single separate cells, and maintains the flagella externalized; (4) differently from T. vaginalis, T. foetus does not change its shape during the adhesion process; and (5) oviduct cells exhibited morphological characteristics of apoptosis after trichomonadal interaction.

Use of the cow as a large animal model of uterine infection and immunity

For most of the reproductive cycle in both humans and animals, the uterus is clear of pathogenic bacteria. However, it is readily contaminated with pathogens, such as Escherichia and Tritichomonas species, during sexual intercourse and after parturition. Uterine infection is particularly common after parturition in cattle (Bos taurus), causing clinical disease and infertility. The endocrine and immune responses to uterine infection in cattle have been investigated in vivo and using tissue culture. Cattle are of sufficient size to permit monitoring of reproductive and immune function throughout uterine infections, and primary cell cultures are readily established. In the whole animal, uterine infections suppress GnRH and LH secretion, and inhibit the growth of ovarian follicles and their estradiol secretion. The immune response is characterized by an influx of neutrophils into the uterus and increased concentrations of acute phase proteins in peripheral plasma. In vitro, the endometrial and ovarian cell function is modified by challenge with bacteria, their products such as lipopolysaccharide or pro-inflammatory cytokines. However, it is interesting to note that the susceptibility to uterine infection and the immune response are partially regulated by the ovarian steroid hormone mileu. In conclusion, the ease of working with cattle, the availability of tissues and the similarity of uterine infection between mammals, make Bos taurus a good model for studying uterine infection and immunity.

In vitro cytopathic effects of a cysteine protease of Tritrichomonas foetus on cultured bovine uterine epithelial cells

OBJECTIVE

To evaluate the cytopathic effects of Tritrichomonas foetus and a purified cysteine protease (ie, CP30) of T foetus on cultured bovine uterine epithelial cells (BUECs) in vitro.

SAMPLE POPULATION

10 reproductive tracts were obtained from late-term bovine fetuses at a commercial abattoir.

PROCEDURE

An in vitro culture system of BUECs was developed to study the cytopathic effects of T foetus and purified CP30 of T foetus on host cells. Cytotoxicity of T foetus or CP30 on exposed BUECs was determined. Fluorescence microscopy and flow cytometry analyses were used to detect apoptosis. A fluorometric assay was used to detect BUEC caspase 3 activation. The CP inhibitor E-64 and a caspase inhibitor were used to inhibit apoptosis.

RESULTS

Cytopathic effects were observed in BUECs treated with parasites or CP30 and were concentration and time dependent. The BUECs underwent apoptosis in the presence of parasites or CP30. The specific CP inhibitor E-64 abolished the induction of apoptosis in BUECs by CP30. The caspase inhibitor reduced the amount of apoptosis in BUECs.

CONCLUSIONS AND CLINICAL RELEVANCE

T foetus and its CP30 induce apoptosis in cultured BUECs in vitro. Induction of apoptosis by CP30 is correlated with protease activity. Endometrial cell death as a result of a T foetus infection is likely to be more important in mediating infertility than a direct effect on the conceptus. Provoking an apoptotic reaction in the host may mitigate an inflammatory reaction or immune response and therefore favor survival of the parasite in a chronic infection.

Trichomonas vaginalis adherence mediates differential gene expression in human vaginal epithelial cells

Trichomonas vaginalis, an ancient protist, colonizes the vaginal mucosa causing trichomonosis, a vaginitis that sometimes leads to severe health complications. Preparatory to colonization of the vagina is the adhesion to vaginal epithelial cells (VECs) by trichomonads. We hypothesized that VECs alter the gene expression to form a complex signalling cascade in response to trichomonal adherence. In order to identify the genes that are upregulated, we constructed a subtraction cDNA library after contact with parasites that is enriched for differentially expressed genes from the immortalized MS-74 VECs. Sixty cDNA clones were sequenced and to our knowledge for the first time, differentially regulated genes were identified in response to early trichomonal infection. The identified genes were found to encode functional proteins with specific functions associated with cell structure maintenance and extracellular matrix components, proinflammatory molecules and apoptosis. Semi-quantitative reverse transcription polymerase chain reaction (RT-PCR) confirmed expression of selected genes. Further, cyclooxygenase 2 (COX-2) protein expression was analysed using Western blot and immunofluorescence assays. Data suggest that p38 mitogen-activated protein (MAP) kinase and tyrosine kinases play a role in COX-2 induction. Finally, T. vaginalis and Tritrichomonas foetus but not Pentatrichomonas hominis induce expression of COX-2. This is a first attempt at elucidating the basis of interaction of trichomonads with host cells and the corresponding host responses triggered by the parasites.

Identification of Trichomonas vaginalis cysteine proteases that induce apoptosis in human vaginal epithelial cells

A secreted cysteine protease (CP) fraction from Trichomonas vaginalis is shown here to induce apoptosis in human vaginal epithelial cells (HVEC) and is analyzed by mass spectrometry. The trichomonad parasite T. vaginalis causes one of the most common non-viral sexually transmitted infection in humans, trichomoniasis. The parasite as well as a secreted cysteine protease (CP) fraction, isolated by affinity chromatography followed by Bio-Gel P-60 column chromatography, are shown to induce HVEC apoptosis, as demonstrated by the Cell Death Detection ELISA(PLUS) assay and annexin V-fluorescein isothiocyanate flow cytometry analyses. Initiation of apoptosis is correlated with protease activity because the specific CP inhibitor E-64 inhibits both activities. SDS-PAGE analysis of the CP fraction reveals triplet bands around 30 kDa, and matrix-assisted laser desorption ionization time-of-flight MS indicates two closely associated peaks of molecular mass 23.6 and 23.8 kDa. Mass spectral peptide sequencing of the proteolytically digested CPs results in matches to previously reported cDNA clones, CP2, CP3, and CP4 (Mallinson, D. J., Lockwood, B. C., Coombs, G. H., and North, M. J. (1994) Microbiology 140, 2725-2735), as well as another sequence with high homology to CP4 (www.tigr.org). These last two species are the most abundant components of the CP fraction. The present results, suggesting that CP-induced programmed cell death may be involved in the pathogenesis of T. vaginalis infection in vivo, may have important implications for therapeutic intervention.

Heterologous expression in Tritrichomonas foetus of functional Trichomonas vaginalis AP65 adhesin

Background

Trichomonosis, caused by Trichomonas vaginalis, is the number one, nonviral sexually transmitted infection that has adverse consequences for the health of women and children. The interaction of T. vaginalis with vaginal epithelial cells (VECs), a step preparatory to infection, is mediated in part by the prominent surface protein AP65. The bovine trichomonad, Tritrichomonas foetus, adheres poorly to human VECs. Thus, we established a transfection system for heterologous expression of the T. vaginalis AP65 in T. foetus, as an alternative approach to confirm adhesin function for this virulence factor.

Results

In this study, we show stable transfection and expression of the T. vaginalis ap65 gene in T. foetus from an episomal pBS-ap65-neo plasmid. Expression of the gene and protein was confirmed by RT-PCR and immunoblots, respectively. AP65 in transformed T. foetus bound to host cells. Specific mAbs revealed episomally-expressed AP65 targeted to the parasite surface and hydrogenosome organelles. Importantly, surface-expression of AP65 in T. foetus paralleled increased levels of adherence of transfected bovine trichomonads to human VECs.

Conclusion

The T. vaginalis AP65 adhesin was stably expressed in T. foetus, and the data obtained using this heterologous system strongly supports the role of AP65 as a prominent adhesin for T. vaginalis. In addition, the heterologous expression in T. foetus of a T. vaginalis gene offers an important, new approach for confirming and characterizing virulence factors.